Display device

Abstract

A display device in which an image with a wide color reproduction range and bright red can be displayed is provided. The display device is a display device such as, for example, a liquid crystal display device, a cathode ray tube, an organic electroluminescent display device, a plasma display panel, and a field emission display. The display device includes a display surface including a pixel having red, green, blue, and yellow sub-pixels, wherein the red sub-pixel preferably has the largest aperture area.

Claims

1. A display device comprising: a display surface including a plurality of pixels each including at least four color sub-pixels; wherein the at least four color sub-pixels includes a red sub-pixel, a green sub-pixel, and a magenta sub-pixel; a red of the red sub-pixel is a color having a dominant wavelength of 595 nm or more and 650 nm or less; a color purity of the red of the red sub-pixel is 75% or more and 97% or less, a green of the green sub-pixel is a color having a dominant wavelength of 490 nm or more and 555 nm or less; a color purity of the green of the green sub-pixel is 50% or more and 80% or less; a magenta of the magenta sub-pixel is a color having a dominant wavelength of 495 nm or more and 560 nm or less; and a color purity of the magenta of the magenta sub-pixel is 60% or more and 80% or less.

2. The display device according to claim 1, wherein the red sub-pixel has a largest aperture area of the plurality of pixels.

3. The display device according to claim 1, wherein the at least four color sub-pixels includes a blue sub-pixel; and the blue sub-pixel has a largest aperture area of the plurality of pixels.

4. The display device according to claim 1, wherein the at least four color sub-pixels includes a blue sub-pixel; and the red sub-pixel and the blue sub-pixel have a same size and the red sub-pixel and the blue sub-pixel have a largest aperture area of the plurality of pixels.

5. The display device according to claim 1, wherein a lightness value of red light displayed by at least one of the plurality of pixels is between 12% and 25% of a lightness value of white light displayed by the at least one of the plurality of pixels.

6. The display device according to claim 1, wherein the at least four color sub-pixels includes a blue sub-pixel; a blue of the blue sub-pixel is a color having a dominant wavelength of 450 nm or more and 490 nm or less; and a color purity of the blue of the blue sub-pixel is 50% or more and 95% or less.

7. The display device according to claim 1, wherein the at least four color sub-pixels includes a yellow sub-pixel; a yellow of the yellow sub-pixel is a color having a dominant wavelength of 565 nm or more and 580 nm or less; and a color purity of the yellow of the yellow sub-pixel is 90% or more and 97% or less.

8. The display device according to claim 1, wherein the at least four color sub-pixels includes blue and yellow sub-pixels.

9. The display device according to claim 1, wherein the at least four color sub-pixels consists of four color sub-pixels.

10. A display device comprising: a display surface including a plurality of pixels each including at least four color sub-pixels; wherein the at least four color sub-pixels includes a red sub-pixel and a magenta sub-pixel; a red of the red sub-pixel is a color having a dominant wavelength of 595 nm or more and 650 nm or less; a color purity of the red of the red sub-pixel is 75% or more and 97% or less; a magenta of the magenta sub-pixel is a color having a dominant wavelength of 495 nm or more and 560 nm or less; and a color purity of the magenta of the magenta sub-pixel is 60% or more and 80% or less.

11. The display device according to claim 10, wherein the red sub-pixel has a largest aperture area of the plurality of pixels.

12. The display device according to claim 10, wherein the at least four color sub-pixels includes a blue sub-pixel; and the blue sub-pixel has a largest aperture area of the plurality of pixels.

13. The display device according to claim 10, wherein the at least four color sub-pixels includes a blue sub-pixel; and the red sub-pixel and the blue sub-pixel have a same size and the red sub-pixel and the blue sub-pixel have a largest aperture area of the plurality of pixels.

14. The display device according to claim 10, wherein a lightness value of red light displayed by at least one of the plurality of pixels is between 12% and 25% of a lightness value of white light displayed by the at least one of the plurality of pixels.

15. The display device according to claim 10, wherein the at least four color sub-pixels includes a blue sub-pixel; a blue of the blue sub-pixel is a color having a dominant wavelength of 450 nm or more and 490 nm or less; and a color purity of the blue of the blue sub-pixel is 50% or more and 95% or less.

16. The display device according to claim 10, wherein the at least four color sub-pixels includes a yellow sub-pixel; a yellow of the yellow sub-pixel is a color having a dominant wavelength of 565 nm or more and 580 nm or less; and a color purity of the yellow of the yellow sub-pixel is 90% or more and 97% or less.

17. The display device according to claim 10, wherein the at least four color sub-pixels includes blue, green, and yellow sub-pixels.

18. The display device according to claim 10, wherein the at least four color sub-pixels consists of four color sub-pixels.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a planar view schematically showing the TFT substrate in the liquid crystal display device in accordance with a preferred embodiment 1 of the present invention.

(2) FIG. 2 is a planar view schematically showing the counter substrate in the liquid crystal display device in accordance with preferred embodiment 1 of the present invention.

(3) FIG. 3 is a cross-sectional view schematically showing the liquid crystal display device in accordance with preferred embodiment 1 of the present invention.

(4) FIG. 4 is a view showing spectral transmittance characteristics of a liquid crystal layer.

(5) FIG. 5 is a planar view schematically showing a display surface of the liquid crystal display device in accordance with preferred embodiment 1 of the present invention.

(6) FIG. 6 is a planar view schematically showing a display surface of the liquid crystal display device in accordance with preferred embodiment 1 of the present invention.

(7) FIG. 7 is a diagram showing spectral transmittance characteristics of the color filters.

(8) FIG. 8 is a diagram showing spectral characteristics of a light source of a back light, used in the liquid crystal display device (the liquid crystal display device A6 in Table 3) in accordance with preferred embodiment 1 of the present invention.

(9) FIG. 9 is a diagram showing spectral characteristics of a light source of a backlight, used in a conventional three-primary-color liquid crystal display device.

(10) FIG. 10 is a diagram showing a relationship between a lightness of red and a lightness of white displayed by the liquid crystal display device in accordance with preferred embodiment 1 of the present invention.

(11) FIG. 11 is a view schematically showing a modified example of the display surface of the liquid crystal display device in accordance with preferred embodiment 1 of the present invention.

(12) FIG. 12 is a view schematically showing a modified example of the display surface of the liquid crystal display device in accordance with preferred embodiment 1 of the present invention.

(13) FIG. 13 is a diagram showing spectral transmittance characteristics of the color filters.

(14) FIG. 14 is a view schematically showing a display surface of the liquid crystal display device in accordance with a preferred embodiment 2 of the present invention.

(15) FIG. 15 is a view schematically showing a display surface of the liquid crystal display device in accordance with preferred embodiment 2 of the present invention.

(16) FIG. 16 is a diagram schematically showing a relationship between a lightness of red and a lightness of white displayed by the liquid crystal display device in accordance with preferred embodiment 2 of the present invention.

(17) FIG. 17 is a view schematically showing a display surface of the liquid crystal display device in accordance with a preferred embodiment 3 of the present invention.

(18) FIG. 18 is a view schematically showing a display surface of the liquid crystal display device in accordance with preferred embodiment 3 of the present invention.

(19) FIG. 19 is a diagram showing a relationship between a lightness of red and a lightness of white displayed by the liquid crystal display device in accordance with preferred embodiment 3 of the present invention.

(20) FIG. 20 is a view schematically showing a modified example of the display surface of the liquid crystal display device in accordance with preferred embodiment 3 of the present invention.

(21) FIG. 21 is a view schematically showing a modified example of the display surface of the liquid crystal display device in accordance with preferred embodiment 3 of the present invention.

(22) FIG. 22 is a diagram schematically showing spectral transmittance characteristics of the color filters used in the liquid crystal display device in FIG. 21.

(23) FIG. 23 is a view schematically showing a modified example of the display surface of the liquid crystal display device in accordance with preferred embodiment 3 of the present invention.

(24) FIG. 24 is a view schematically showing a modified example of the display surface of the liquid crystal display device in accordance with preferred embodiment 3 of the present invention.

(25) FIG. 25 is a view schematically showing a display surface of the liquid crystal display device in accordance with a preferred embodiment 4 of the present invention.

(26) FIG. 26 is a view schematically showing a display surface of the liquid crystal display device in accordance with preferred embodiment 4 of the present invention.

(27) FIG. 27 is a diagram showing a relationship between a lightness of red and a lightness of white displayed by the liquid crystal display device in accordance with preferred embodiment 4 of the present invention.

(28) FIG. 28 is a view schematically showing a display surface of the liquid crystal display device in accordance with a preferred embodiment 5 of the present invention.

(29) FIG. 29 is a view schematically showing a display surface of the liquid crystal display device in accordance with preferred embodiment 5 of the present invention.

(30) FIG. 30 is a diagram showing a relationship between a lightness of red and a lightness of white displayed by the liquid crystal display device in accordance with preferred embodiment 5 of the present invention.

(31) FIG. 31 is a view schematically showing a modified example of the display surface of the liquid crystal display device in accordance with preferred embodiment 5 of the present invention.

(32) FIG. 32 is a view schematically showing a modified example of the display surface of the liquid crystal display device in accordance with preferred embodiment 5 of the present invention.

(33) FIG. 33 is a view schematically showing a display surface of the liquid crystal display device in accordance with a preferred embodiment 6 of the present invention.

(34) FIG. 34 is a view schematically showing a display surface of the liquid crystal display device in accordance with preferred embodiment 6 of the present invention.

(35) FIG. 35 is a diagram showing a relationship between a lightness of red and a lightness of white displayed by the liquid crystal display device in accordance with preferred embodiment 6 of the present invention.

(36) FIG. 36 is a view schematically showing a display surface of a conventional four-primary-color liquid crystal display device.

(37) FIG. 37 is a view schematically showing a display surface of a conventional three-primary-color liquid crystal display device.

(38) FIG. 38 is a diagram showing spectral characteristics of a light source of a backlight used in a conventional four-primary-color display device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(39) The present invention is mentioned in more detail below with reference to preferred embodiments, but it is not limited to only these preferred embodiments. Configurations and measurement values and the like in the following preferred embodiments are based on a simulation which is performed using a computer program. In the following preferred embodiments, a transmissive liquid crystal display device is exemplified to explain the present invention.

(40) Preferred Embodiment 1

(41) A configuration of a liquid crystal display device in accordance with preferred embodiment 1 of the present invention is mentioned below. The configuration of the liquid crystal display device of the present invention is not limited to this configuration.

(42) FIG. 1 is a planar view schematically showing a configuration of a TFT substrate 200 in a transmissive liquid crystal display device in accordance with preferred embodiment 1 of the present invention. As shown in FIG. 1, the TFT substrate 200 has the following configuration. Matrix wirings defined by scanning lines 4 and signal lines 6 are arranged on a glass substrate, for example. In each intersection of the matrix wirings, a thin film transistor (TFT) 8 is arranged. In each region surrounded by the matrix wirings, a transmissive electrode 35 (including transmissive electrodes 35R, 35G, 35Y, and 35B) made of a transparent conductive material such as indium tin oxide (ITO) is arranged. A gate electrode of the TFT 8 is connected to the scanning line 4, and a source electrode of the TFT 8 is connected to the signal line 6. The drain electrode of the TFT 8 is connected to the transmissive electrode 35 through a drain-extracting wiring 9. The transmissive electrodes 35R, 35G, 35Y, and 35B are arranged to oppose a red color filter 10R, a green color filter 10G, a blue color filter 10B, and a yellow color filter 10Y, respectively. The red, green, blue, and yellow color filters 10R, 10G, 10B, and 10Y are arranged in the below-mentioned color filter substrate 11 of the liquid crystal display device. According to the present preferred embodiment, as shown in FIG. 1, the scanning line 4 and the signal line 6 are arranged in such a way that the transmissive electrode 35R opposing the red color filter 10R is large and the transmissive electrodes 35G, 35Y, and 35R opposing the other color filters are equivalently small. A storage capacitor wiring 7 is arranged in parallel to the scanning line 4 to maintain a voltage applied to the transmissive electrode 35. The storage capacitor wiring 7 opposes the end of the drain-extracting wiring 9 with an insulating film therebetween to define a storage capacitance 3.

(43) FIG. 2 is a planar view schematically showing a configuration of the color filter substrate (counter substrate) 100 in the transmissive liquid crystal display device in accordance with preferred embodiment 1 of the present invention.

(44) According to the color filter substrate 100, as shown in FIG. 2, the red color filter 10R, the green color filter 10G, the yellow color filter 10Y, and the blue color filter 10B are arranged in a stripe pattern in this order, and a black matrix 10BM is arranged around each filter and between the filters. Each of the color filters 10R, 10G, 10B, and 10Y selectively transmits light. The red color filter 10R mainly transmits a red component of incident light. The green color filter 10G mainly transmits a green component of incident light. The blue color filter 10B mainly transmits a blue component of incident light. The yellow color filter 10Y mainly transmits both of a red component and a green component of incident light. In the present preferred embodiment, as shown in FIG. 2, the color filters 10R, 10B, 10G, and 10Y are arrayed in the same pattern among all of the pixels, but may be arrayed in a different pattern among the pixels. The configuration of the pixel in the present invention is not especially limited. The color filters 10R, 10B, 10G, and 10R are arranged to oppose the transmissive electrodes 35R, 35G, 35Y, and 35B, respectively, arranged in the above-mentioned TFT substrate 200 of the liquid crystal display device. The black matrix 10BM is arranged to oppose the scanning line 4 and the signal line 6 in the liquid crystal display device. According to the present preferred embodiment, as shown in FIG. 2, the area of the red color filter 1OR is large, and other color filters 10B, 10G, and 10Y are equivalently small.

(45) FIG. 3 is a cross-sectional view schematically showing the transmissive liquid crystal display device in accordance with preferred embodiment 1 of the present invention.

(46) As shown in FIG. 3, a transmissive liquid crystal display device 500 in accordance with preferred embodiment 1 of the present invention includes a liquid crystal layer 300 between the above-mentioned color filter substrate 100 and the above-mentioned TFT substrate 200. The color filter substrate 100 includes a retarder 22 and a polarizer 23 on an outer surface side (observation surface side) of the glass substrate 21, and further includes the red color filter 10R, the green color filter 10G, the blue color filter 10B, and the yellow color filter 10Y, the black matrix 10BM, and an overcoat layer 25, a counter electrode 26, and an alignment film 27 on an inner surface side (back surface side) of the glass substrate 21.

(47) The retarder 22 adjusts a polarization state of light which passes through the retarder 22. The polarizer 23 transmits only light having a specific polarization component. According to the present preferred embodiment, the arrangement and configuration of the retarder 22 and the polarizer 23 are adjusted in such a way that the retarder 22 and the polarizer 23 function as circular polarizers.

(48) The overcoat layer 25 prevents elution of a contaminant from the red, green, blue, and yellow filters 10R, 10G, 10B, and 10Y into the liquid crystal layer 300. Further, the overcoat layer 25 flattens the surface of the color filter substrate 100. The counter electrode 26 opposes the transparent electrodes 35R, 35G, 35B, and 35Y arranged on the TFT substrate 200 side with the liquid crystal layer 300 therebetween. The counter electrode 26 is used to drive liquid crystal molecules by applying a voltage to the liquid crystal layer 300. The counter electrode 26 is made of a transparent conductive material such as, for example, indium tin oxide (ITO). The alignment film 27 controls alignment of liquid crystal molecules in the liquid crystal layer 300.

(49) The TFT substrate 200 includes a retarder 32 and a polarizer 33 on an outer surface side (back surface side) of the glass substrate 31, and further includes the thin film transistor (TFT) 8, an interlayer insulating film 34, the transparent electrode 35 (defined of the transparent electrodes 35R, 35G, 35B, and 35Y), and an alignment film 38 on an inner surface side (observation surface side) of the glass substrate 31.

(50) The retarder 32 adjusts a polarization state of light which passes through the retarder 32, similarly to the retarder 22. The polarizer 33 transmits only light having a specific polarization component, similarly to the polarizer 23. According to the present preferred embodiment, this polarizer 33 is arranged to be optically perpendicular or substantially optically perpendicular to the circular polarizer arranged on the color filter substrate 100 side.

(51) The transparent electrode 35 (defined of the transparent electrodes 35R, 35G, 35B, and 35Y) is arranged in each color filter on the color filter substrate 100 side. In each color filter region, a voltage is applied to the liquid crystal layer 300 to drive liquid crystal molecules. The alignment film 38 controls alignment of the liquid crystal molecules in the liquid crystal layer 300, similarly to the alignment film 27.

(52) On the rear surface side (back surface side) of the TFT substrate 200, a backlight 36 is arranged to be used for display. Spectral characteristics and the like of a light source of the backlight are mentioned below. FIG. 4 is a view showing spectral characteristics of the liquid crystal layer 300. According to the present preferred embodiment, a nematic liquid crystal with a negative dielectric anisotropy is used as a material for the liquid crystal layer 300.

(53) FIG. 5 is a planar view schematically showing a configuration of the pixel of the liquid crystal display device 500 in accordance with preferred embodiment 1 of the present invention. According to the present preferred embodiment, the liquid crystal display device 500 has the above-mentioned configuration. Therefore, as shown in FIG. 5, the red sub-pixel 5Ra has the largest aperture area. The green, blue, and yellow sub-pixels 5Ga, 5Ba, and 5Ya are equivalently small. Such a preferred embodiment is mentioned below. The aperture area means an area of a region which is actually used in displaying an image, and it does not include an area of a region which is shielded by the thin film transistors (TFT) 8, the scanning lines 4, the signal lines 6, and storage capacitances 3, and black matrixes 10BM. The liquid crystal display device 500 in accordance with the present preferred embodiment includes a plurality of pixels 11a arrayed in a matrix pattern. The shaded portion in FIG. 5 corresponds to one pixel. In FIG. 5, four pixels among the plurality of pixels 11a defining the display surface 500a in the liquid crystal display device 500 are shown.

(54) As shown in FIG. 5, the pixel 11a is defined by a plurality of sub-pixels. According to the present preferred embodiment, the four sub-pixels defining the pixel 11a are a sub-pixel 5Ra for displaying red, a sub-pixel 5Ga for displaying green, and a sub-pixel 5Ba for displaying blue, and a sub-pixel 5Ya for displaying yellow. FIG. 5 shows a configuration in which these four sub-pixels are arranged in one row and four columns in the pixel 11a. FIG. 6 shows another configuration of a pixel defining a screen surface 500b of the liquid crystal display device and shows a configuration in which four sub-pixels 5Rb, 5Gb, 5Bb, and 5Yb are arranged in two rows and two columns in the pixel 11b. According to the present preferred embodiment, the array of the red, green, blue, and yellow sub-pixels is not especially limited to the arrays shown in FIGS. 5 and 6. Attributed to the aperture area ratio among the respective sub-pixels, the effects can be obtained.

(55) Six liquid crystal display devices A1 to A6 shown in Table 3 are prepared in this preferred embodiment. In each of these liquid crystal display devices A1 to A6, the red sub-pixel is different in aperture area from the other sub-pixels. Specifically, the aperture area of the red sub-pixel is the largest and the aperture areas of the green, blue, and yellow sub-pixels are equivalently small.

(56) TABLE-US-00003 TABLE 3 The largest aperture Color filter Light-emitting Aperture area ratio area/The smallest Lightness Lightness transmittance efficiency of (red:green:blue:yellow) aperture area of red (%) of white (%) backlight A1 11:9.7:9.7:9.7 1.13 12.3 97.7 39.6 0.78 A2 12:9.3:9.3:9.3 1.29 12.9 96.0 38.7 0.79 A3 13:9:9:9 1.44 13.4 93.3 37.7 0.78 A4 14:8.7:8.7:8.7 1.61 14.2 91.0 36.8 0.78 A5 15:8.3:8.3:8.3 1.81 14.9 88.6 35.8 0.78 A6 16:8:8:8 2.00 15.6 86.1 34.7 0.78

(57) In all of the liquid crystal display devices A1 to A6, a color filter having a spectral transmittance shown in FIG. 7 is used. The aperture area ratio among the sub-pixels varies depending on the liquid crystal display devices, and therefore, the chromaticity of white displayed by the color filter also varies depending on the liquid crystal display devices. In the present preferred embodiment, in order to obtain a desired chromaticity of white, a spectrum of a light source of the backlight 36 is adjusted in each liquid crystal display device. Specifically, spectral characteristics of the light source of the backlight 36 used in the liquid crystal display devices A1 to A6 are property adjusted in such a way that white displayed by the liquid crystal display device shows chromaticity coordinates: x=0.313; and y=0.329 and that the color temperature is about 6500K. A cold cathode fluorescent tube (CCFT) is used as the light source of the backlight 36, for example. The mixing ratio among red, green, and blue fluorescent materials is varied to adjust spectral characteristics of the light source. Spectral characteristics of the light source of the backlight 36 used in the liquid crystal display device A6 in Table 3 are shown in FIG. 8, as one example.

(58) Table 3 shows an aperture area ratio among the respective sub-pixels, an aperture area ratio between the sub-pixel having the largest aperture area (red sub-pixel) and the sub-pixel having the smallest aperture area (green, blue, or yellow sub-pixel), a lightness of red, a lightness of white, an average transmittance of the color filters, and a light-emitting efficiency of the light source of the backlight, in the liquid crystal display devices A1 to A6. The lightness of red is a value relative to 100 of a lightness Y of white in each liquid crystal display device (a ratio relative to the lightness of white). The lightness of white is a value relative to 100 of a lightness of white displayed by the following conventional four-primary-color liquid crystal display device (shown in FIG. 36). According to the conventional four-primary-color liquid crystal display device, the sub-pixels of the respective colors have the same aperture area, a color filter having a spectral transmittance shown in FIG. 7 is used, and a CCFT having spectral characteristics shown in FIG. 38 is used as a light source of the backlight 36. Further, the average transmittance of the color filters is an average value of transmittances in the respective color filters used for displaying white using the light source of the backlight 36 arranged in each liquid crystal display device. The light-emitting efficiency of the light source of the backlight 36 is determined as follows. First, a light-emitting efficiency of a red fluorescent material used in a CCFT (light source), a light-emitting efficiency of a green fluorescent material used in a CCFT (light source), and a light-emitting efficiency of a blue fluorescent material used in a CCFT (light source) are individually measured. Then, on the basis of these measurement values, the mixing ratio among the red, green, and blue fluorescent materials is varied. Under such a condition, the light-emitting efficiency in the case where red, green, and blue are combined is calculated. The light-emitting efficiency of the light source of the backlight 36 is a ratio between a light-emitting efficiency in the case where red, green, and blue are combined, and a light-emitting efficiency in the case where red, green, and blue are combined in the conventional three-primary-color display device.

(59) FIG. 10 is a diagram showing a relationship between a lightness of red and a lightness of white displayed by the liquid crystal display devices A1 to A6 prepared in the present preferred embodiment.

(60) According to the liquid crystal display devices A1 to A6 in the present preferred embodiment, the red sub-pixel has the largest aperture area. Therefore, the lightness of red can be more improved and brighter red can be displayed in comparison to the conventional four-primary-color liquid crystal display device (Table 1) shown in FIG. 36. That is, red with excellent visibility can be displayed. An appropriate one among these liquid crystal display devices A1 to A6 may be selected depending on an application and the like.

(61) According to the present preferred embodiment, a common CCFT is used as a light source of the backlight 36. The chromaticity of white is adjusted by varying only the mixing ratio among the red, green, and blue fluorescent materials. The lightness of white displayed by the liquid crystal display device is calculated, also taking the variation of the light-emitting efficiency, in the case that in the light source of the backlight, the mixing ratio among the fluorescent materials of the respective colors is varied, into consideration. That is, the lightness of white is the lightness in the liquid crystal display device, taking not only an average transmittance (efficiency) of the color filters but also the light-emitting efficiency of the light source of the back light 36 into consideration. In the preferred embodiments of the present invention, the chromaticity of white is set to the above-mentioned value, but it is not limited thereto. The same effect can be obtained if the chromaticity of white is appropriately adjusted to an optimal chromaticity.

(62) The pixel configuration of the liquid crystal display device in the present preferred embodiment is not limited to those shown in FIGS. 5 and 6. For example, as shown in FIG. 11, the liquid crystal display device in the present preferred embodiment may have a configuration in which a pixel 11c defining a display surface 500c is divided into five sub-pixels and two red sub-pixels are arranged. In FIG. 11, with regard to the aperture area ratio among the red sub-pixel 5Rc, the green sub-pixel 5Gc, the blue sub-pixel 5Bc, and the yellow sub-pixel 5Yc, red:green:blue:yellow is 2:1:1:1. Thus, a plurality of red sub-pixels are arranged, and thereby an amount of modification of the pixel design and the driving circuit design can be minimized.

(63) As shown in FIG. 12, the liquid crystal display device in the present preferred embodiment may have a configuration in which a pixel 11d defining a display surface 500d is divided into five sub-pixels, and two red sub-pixels having different color characteristics are arranged. Spectral characteristics of the color filters are shown in FIG. 13. In this case, light having a dominant wavelength of about 612 nm passes through a red sub-pixel 5R.sub.1d, and light having a dominant wavelength of about 607 nm passes through a red sub-pixel 5R.sub.2d. Also in the case shown in FIG. 12, the aperture areas of the red sub-pixels 5R.sub.1d and 5R.sub.2d, the green sub-pixel 5Gd, the blue sub-pixel Bd, and the yellow sub-pixel 5Yd are equivalent. With regard to the aperture area ratio among the respective sub-pixels, red:green:blue:yellow is 2:1:1:1. Thus, the two red sub-pixels having different color characteristics are arranged, and thereby the color reproduction range can be further extended. These pixel configurations are just mentioned as one example, and the present preferred embodiment is not limited to these pixel configurations.

(64) Preferred Embodiment 2

(65) With regard to a transmittance level relationship among the respective color filters arranged in the red, green, blue, and yellow sub-pixels, and a transmittance of the color filters for displaying white (an average transmittance of the red, green, blue, and yellow sub-pixels), yellow, green, white, red, and blue are ranked in descending order of transmittance. In some cases, the red and blue are counterchanged, and yellow, green, white, blue, and red are ranked in descending order of transmittance.

(66) Accordingly, if the aperture area of the red sub-pixel is increased, the transmittance of the color filters for displaying white is decreased because the color filter arranged in the red sub-pixel has a smaller transmittance than that of the color filters for displaying white. In addition, if the aperture areas of the green and yellow sub-pixels are decreased, the transmittance of the color filters for displaying white is further decreased because the color filters arranged in the green and yellow sub-pixels have a larger transmittance than that of the color filters for displaying white. In contrast, if the aperture area of the blue sub-pixel is decreased, the reduction in transmittance of the color filters for displaying white is minimized and possibly improved because the color filter arranged in the blue sub-pixel has the smallest transmittance. However, this relationship is satisfied if only color filter is taken into consideration. Hence, in an actual liquid crystal display device, the light-emitting efficiency of the light source of the backlight needs to be taken into consideration.

(67) In preferred embodiment 1, a certain effect in which the lightness of red is increased is recognized if the aperture area of the red sub-pixel is the largest and the aperture areas of the green, blue, and yellow sub-pixels are equivalently small. However, in preferred embodiment 1, as shown in FIG. 10, the lightness of white is slightly reduced in all of the liquid crystal display devices A1 to A6 shown in Table 3. Accordingly, the display device in preferred embodiment 2 is superior to that in preferred embodiment 1, if the reduction in lightness of white can be minimized. In the present preferred embodiment, the lightness of white is also taken into consideration, and the aperture area of the red sub-pixel is increased, and the aperture area of any one of the green, blue, and yellow sub-pixels is reduced. Such a preferred embodiment is mentioned below.

(68) Table 4 shows an aperture area ratio among the respective sub-pixels, an aperture area ratio between the sub-pixel having the largest aperture area (red sub-pixel) and the sub-pixel having the smallest aperture area (green sub-pixel), a lightness of red, a lightness of white, an average transmittance of the color filters, and a light-emitting efficiency of the light source of the backlight, in liquid crystal display devices B1 to B6 prepared in the present preferred embodiment in the case that the red sub-pixel has a large aperture area and the blue sub-pixel has a small aperture area.

(69) TABLE-US-00004 TABLE 4 The largest aperture Color filter Light-emitting Aperture area ratio area/The smallest Lightness Lightness transmittance efficiency of (red:green:blue:yellow) aperture area of red (%) of white (%) backlight B1 11:9:10:10 1.22 11.7 99.7 39.5 0.80 B2 12:8:10:10 1.50 12.3 98.3 38.4 0.81 B3 13:7:10:10 1.86 12.8 97.3 37.2 0.83 B4 14:6:10:10 2.33 13.3 95.9 36.0 0.84 B5 15:5:10:10 3.00 14.0 94.7 34.8 0.86

(70) Table 5 shows an aperture area ratio among the respective sub-pixels, an aperture area ratio between the sub-pixel having the largest aperture area (red sub-pixel) and the sub-pixel having the smallest aperture area (blue sub-pixel), a lightness of red, a lightness of white, an average transmittance of the color filters, and a light-emitting efficiency of the light source of the backlight, in liquid crystal display devices C1 to C3 prepared in the present preferred embodiment in the case that the red sub-pixel has a large aperture area and the blue sub-pixel has a small aperture area.

(71) TABLE-US-00005 TABLE 5 The largest aperture Color filter Light-emitting Aperture area ratio area/The smallest Lightness Lightness transmittance efficiency of (red:green:blue:yellow) aperture area of red (%) of white (%) backlight C1 11:10:9:10 1.22 11.6 95.7 40.2 0.75 C2 12:10:8:10 1.50 12.1 90.8 39.8 0.72 C3 13:10:7:10 1.86 12.9 84.3 39.3 0.68

(72) Table 6 shows an aperture area ratio among the respective sub-pixels, an aperture area ratio between the sub-pixel having the largest aperture area (red sub-pixel) and the sub-pixel having the smallest aperture area (yellow sub-pixel), a lightness of red, a lightness of white, an average transmittance of the color filters, and a light-emitting efficiency of the light source of the backlight, in liquid crystal display devices D1 to D6 prepared in the present Preferred embodiment in the case that the red sub-pixel has a large aperture area and the yellow sub-pixel has a small aperture area.

(73) TABLE-US-00006 TABLE 6 The largest aperture Color filter Light-emitting Aperture area ratio area/The smallest Lightness Lightness transmittance efficiency of (red:green:blue:yellow) aperture area of red (%) of white (%) backlight D1 11:10:10:9 1.22 12.4 98.4 39.0 0.80 D2 12:10:10:8 1.50 13.8 96.9 37.5 0.82 D3 13:10:10:7 1.86 15.2 94.8 36.0 0.83 D4 14:10:10:6 2.33 16.4 92.7 34.4 0.85 D5 15:10:10:5 3.00 17.8 91.3 32.8 0.88 D6 16:10:10:4 4.00 19.5 88.9 31.2 0.90

(74) Each of FIGS. 14 and 15 shows a schematic view of the liquid crystal display device in Table 6. FIG. 14 shows a configuration of a pixel 11e defining a display surface 500e of the liquid crystal display device, and the pixel 11e includes four sub-pixels 5Re, 5Ge, 5Be, and 5Ye arranged in a stripe pattern. FIG. 15 shows a configuration of a pixel 11f defining a display surface 500f of the liquid crystal display device, and the pixel 11f includes four sub-pixels 5Rf, 5Gf, 5Bf, and 5Yf arranged in two rows and two columns.

(75) FIG. 16 shows a relationship between a lightness of red and a lightness of white displayed by the respective liquid crystal displays shown in Tables 4, 5, and 6. In FIG. 16, ⋄ corresponds to the liquid crystal display devices B1 to B5 in Table 4; Δ corresponds to the liquid crystal display devices C1 to C3 in Table 5; and ∘ corresponds to the liquid crystal display devices D1 to D6 in Table 6. For comparison, □ shows the liquid crystal display devices A1 to A6 in accordance with preferred embodiment 1.

(76) As shown in FIG. 16, according to the liquid crystal display devices in Tables 4 to 6, the effect of improving the lightness of red can be observed in comparison to the conventional four-primary-color liquid crystal display device (see Table 1) shown in FIG. 36. Particularly in the liquid crystal display device D6 in Table 6, red having a lightness of as high as 19.5% can be displayed. As shown in Tables 4 and 6, the average transmittance of the color filters is reduced in comparison to the liquid crystal display devices A1 to A6 in preferred embodiment 1 if the green or yellow sub-pixel has a small aperture area. However, the spectral characteristics of the light source of the backlight are adjusted in order to maximize the chromaticity of white. As a result, the light-emitting efficiency of the light source is increased. Therefore, as shown in FIG. 16, the reduction in lightness of white can be minimized with the increase in the light-emitting efficiency of the light source of the backlight, in comparison to the liquid crystal display devices A1 to A6 in preferred embodiment 1. Particularly in the liquid crystal display devices D1 to D6 in Table 6, if the sub-pixel having a small aperture area is a yellow sub-pixel having a color filter with the highest transmittance, the average transmittance of the color filters is reduced, but the light-emitting efficiency of the light source of the backlight is increased. As a result, the reduction in lightness of white is decreased with the increase in the light source of the backlight.

(77) As shown in the liquid crystal display devices C1 to C3 in Table 5, it is not preferable to reduce the aperture area of the blue sub-pixel because the lightness of white is largely reduced. That is, if the sub-pixel having a small aperture area is a blue sub-pixel, the average transmittance of the color filters is increased because the color filter arranged in the blue sub-pixel has the smallest transmittance. However, the spectral characteristics of the light source of the backlight are adjusted in order to maximize the chromaticity of white. As a result, the light-emitting efficiency of the light source is reduced. Hence, the reduction in lightness of white is increased with the decrease in the light-emitting efficiency of the light source of the backlight.

(78) As mentioned above, the preferred embodiment in which the yellow sub-pixel has a small aperture area is the most effective preferred embodiment, followed by the preferred embodiment in which the green sub-pixel has a small aperture area and the preferred embodiment in which the blue sub-pixel has a small aperture area.

(79) The pixel design and the driving circuit design needs to be changed if the sub-pixels are largely different in aperture area. Therefore, it is preferable that an aperture area ratio among the sub-pixels is as small as possible. From viewpoint of this aperture area ratio, in the liquid crystal display device A4 in Table 3 in accordance with preferred embodiment 1, an aperture area ratio between the red sub-pixel having the largest aperture area, and the green, blue, and yellow sub-pixels having the smallest aperture areas is 1.61:1. In this case, the lightness of red is 14.2%; the lightness of white is 91.0%. The liquid crystal display device B5 in Table 4 in accordance with the present preferred embodiment can provide a lightness equivalent to 14.2% of red. According to this liquid crystal display device B5, the lightness of white is 94.7%. Therefore, the liquid crystal display device B5 is superior to the liquid crystal display device A4 in terms of the lightness of white. Further, the liquid crystal display device D3 in Table 6 in accordance with the present preferred embodiment also can provide a lightness equivalent to 14.2% of red. According to this liquid crystal display device D3, the lightness of white is 94.8%. Therefore, the liquid crystal display device D3 is also superior to the liquid crystal display device A4 in terms of the lightness of white.

(80) However, the aperture area ratio is 3:1 in the liquid crystal display device B5 in Table 4, and it is 1.86:1 in the liquid crystal display device D3 in Table 6. The ratio in each device is larger than that of the liquid crystal display device A4 in Table 3 in accordance with preferred embodiment 1. As mentioned above, it is preferable that the liquid crystal display device A4 in Table 3 in accordance with preferred embodiment 1 is selected depending on the pixel design and the driving circuit device. That is, in some cases, preferred embodiment 1 is better than preferred embodiment 2.

(81) Preferred Embodiment 3

(82) As mentioned in preferred embodiment 2, the preferred embodiment in which the red sub-pixel has the largest aperture area and the green or yellow sub-pixel has the smallest aperture area is advantage in that the reduction in lightness of white can be minimized. In the present preferred embodiment, the following preferred embodiment is mentioned as a more preferable preferred embodiment: the aperture areas of the blue sub-pixel as well as the red sub-pixel are equivalently large and the aperture areas of the green and yellow sub-pixels are equivalently small.

(83) In the present preferred embodiments, six liquid crystal display devices E1 to E6 shown in Table 7 were prepared. In each case, the aperture areas of the red and blue sub-pixels are equivalently large and the aperture areas of the green and yellow sub-pixels are equivalently small. Table 7 shows an aperture area ratio among the respective sub-pixels, an aperture area ratio between the sub-pixel having the largest aperture area (red or blue sub-pixel) and the sub-pixel having the smallest aperture area (green or yellow sub-pixel), a lightness of red, a lightness of white, an average transmittance of the color filters, and a light-emitting efficiency of the light source of the backlight, in the liquid crystal display devices E1 to E6 prepared in the present preferred embodiment.

(84) TABLE-US-00007 TABLE 7 The largest aperture Color filter Light-emitting Aperture area ratio area/The smallest Lightness Lightness transmittance efficiency of (red:green:blue:yellow) aperture area of red (%) of white (%) backlight E1 11:9:11:9 1.22 12.1 102 38.1 0.85 E2 12:8:12:8 1.50 13.9 101 35.5 0.90 E3 13:7:13:7 1.86 15.3 100 32.7 0.97 E4 14:6:14:6 2.33 17.0 97 29.6 1.04 E5 15:5:15:5 3.00 18.7 92 26.2 1.11 E6 16:4:16:4 4.00 20.5 85 22.6 1.19

(85) Each of FIGS. 17 and 18 shows a schematic view of the liquid crystal display device in Table 7. FIG. 17 shows a configuration of a pixel 11g defining a display surface 500g of the liquid crystal display device, and the pixel 11g includes four sub-pixels 5Rg, 5Gg, 5Bg, and 5Yg arranged in a stripe pattern. FIG. 18 shows a configuration of a pixel 11h defining a display surface 500h of the liquid crystal display device, and the pixel 11h includes four sub-pixels 5Rh, 5Gh, 5Bh, and 5Yh arranged in two rows and two columns.

(86) FIG. 19 shows a relationship between a lightness of red and a lightness of white displayed by the respective liquid crystal displays E1 to E6 shown in Table 7. In FIG. 19, □ corresponds to the liquid crystal display devices E1 to E5 in Table 7. For comparison, ⋄ shows the liquid crystal display devices D1 to D6 in which the reduction in lightness of white is small in accordance with preferred embodiment 2.

(87) According to the present preferred embodiment, the liquid crystal display devices D1 to D6 in preferred embodiment 2 are further advantageous in terms of lightness of white, and especially in the liquid crystal display devices E1 to E3 in Table 7, the lightness of white is higher than that in the conventional four-primary-color liquid crystal display device (FIG. 36) in which four sub-pixels have the same aperture area. In order to maximize the chromaticity of white, a yellow component of light from the backlight needs to be increased as the blue sub-pixel has a larger aperture area. Therefore, the light-emitting efficiency can be improved. If the lightness of red is 19% or more, specifically if the liquid crystal display device E6 in Table 7 in the present preferred embodiment is compared with the liquid crystal display device D6 in Table 6 in preferred embodiment 2, the present preferred embodiment is disadvantageous in terms of display of white, in some cases.

(88) The pixel configuration of the liquid crystal display device in the present preferred embodiment is not limited to the configurations shown in FIGS. 17 and 18. For example, as shown in FIG. 20, a pixel 11i defining a display surface 500i is divided into six sub-pixels and two red sub-pixels 5R and two blue pixels 5B may be arranged. In FIG. 20, with regard to an aperture area ratio among respective sub-pixels 5Ri, 5Gi, 5Bi, and 5Yi, red:green:blue:yellow is 2:1:2:1. Thus, a plurality of red sub-pixels and a plurality of blue sub-pixels are arranged, and thereby modification of the pixel design and the driving circuit design can be minimized.

(89) As shown in FIG. 21, a pixel 11j defining a display surface 500j is divided into six sub-pixels, and two red sub-pixels and two blue sub-pixel having different color characteristics are arranged. FIG. 22 shows spectral characteristics of a color filter in this case. In this case, light having a dominant wavelength of about 460 nm passes through a blue sub-pixel 5B.sub.1j, and light having a dominant wavelength of about 488 nm passes through and a blue sub-pixel 5B.sub.2j. Also in the case shown in FIG. 21, a red sub-pixel 5Rj, a green sub-pixel 5Gj, the blue sub-pixels 5B.sub.1j and 5B.sub.2j, and a yellow sub-pixel 5Yj have equivalent aperture areas. With regard to an aperture area ratio among the respective sub-pixels, red:green:blue:yellow is 2:1:1:2. Thus, two blue sub-pixels having different color characteristics are arranged, and thereby the color reproduction range can be further extended.

(90) As shown in FIG. 23, a pixel 11k defining a display surface 500k is divided into six sub-pixels, and two red sub-pixels having different color characteristics and two blue sub-pixels are arranged. FIG. 13 shows spectral characteristics of a color filter in this case. In this case, light having a dominant wavelength of about 612 nm passes through a red sub-pixel 5R.sub.1k, and light having a dominant wavelength of about 607 nm passes through a red sub-pixel 5R.sub.2k. Also in the case shown in FIG. 23, the aperture areas of the red sub-pixels 5R.sub.1k and 5R.sub.2k, a green sub-pixel 5Gk, a blue sub-pixel 5Bk, and a yellow sub-pixel 5Yk are equivalent. With regard to an aperture area ratio among the respective sub-pixels, red:green:blue:yellow is 2:1:1:2. Thus, even by arranging the red sub-pixels having different color characteristics, the color reproduction range can be further extended.

(91) Further, as shown in FIG. 24, a pixel 11m defining a display surface about 500m is divided into six sub-pixels, and two red sub-pixels having different color characteristics and two blue sub-pixels having different color characteristics are arranged. Each of FIGS. 13 and 22 shows spectral characteristics of a color filter in this case. Also in the case shown in FIG. 24, the aperture areas of red sub-pixels 5R.sub.1m and 5R.sub.2m, a green sub-pixel 5Gm, blue sub-pixels 5B.sub.1m and 5B.sub.2m, and a yellow sub-pixel 5Ym are equivalent. With regard to an aperture area ratio among the respective sub-pixels, red:green:blue:yellow is 2:1:1:2. Thus, even by arranging the red sub-pixels having different color characteristics and the blue sub-pixels having different color characteristics, the color reproduction range can be further extended. These pixel configurations are just mentioned as one example, and the present preferred embodiment is not limited to these pixel configurations.

(92) Preferred Embodiment 4

(93) According to preferred embodiment 3, the preferred embodiment in which the aperture areas of the red and blue sub-pixels are equivalently large and the aperture areas of the green and yellow sub-pixels are equivalently small is mentioned. According to the present preferred embodiment, an preferred embodiment in which green and yellow sub-pixels which have small aperture areas are arranged to be different in aperture area ratio.

(94) Table 8 shows an aperture area ratio among the respective sub-pixels, an aperture area ratio between the sub-pixel having the largest aperture area (red or blue sub-pixel) and the sub-pixel having the smallest aperture area (green sub-pixel), a lightness of red, a lightness of white, an average transmittance of the color filters, and a light-emitting efficiency of the light source of the backlight, in liquid crystal display devices F1 to F4 prepared in the present preferred embodiment, in the case that aperture areas of the red and blue sub-pixel are equivalently large and an aperture area of the green sub-pixel is small.

(95) TABLE-US-00008 TABLE 8 The largest aperture Color filter Light-emitting Aperture area ratio area/The smallest Lightness Lightness transmittance efficiency of (red:green:blue:yellow) aperture area of red (%) of white (%) backlight F1 11:8:11:10 1.38 11.8 103 38.6 0.84 F2 12:6:12:10 2.00 12.3 103 36.4 0.90 F3 13:4:13:10 3.25 13.0 103 33.9 0.96 F4 14:2:14:10 7.00 13.9 101 31.2 1.03

(96) Each of FIGS. 25 and 26 schematically shows a liquid crystal display device in Table 8. FIG. 25 shows a configuration of a pixel 11n defining a display surface 500n of the liquid crystal display device, and the pixel 11n includes four sub-pixels 5Rn, 5Gn, 5Bn, and 5Yn arranged in a stripe pattern. FIG. 26 shows a configuration of a pixel 11p defining a display surface 500p of the liquid crystal display device, and the pixel 11p includes four sub-pixels 5Rp, 5Gp, 5Bp, and 5Yp arranged in two rows and two columns. These pixel configurations are just mentioned as one example. The present preferred embodiment is not especially limited to these pixel configurations.

(97) Table 9 shows an aperture area ratio among the respective sub-pixels, an aperture area ratio between the sub-pixel having the largest aperture area (red or blue sub-pixel) and the sub-pixel having the smallest aperture area (yellow sub-pixel), a lightness of red, a lightness of white, an average transmittance of the color filters, and a light-emitting efficiency of the light source of the backlight, in liquid crystal display devices G1 to G3 prepared in the present preferred embodiment, in the case that aperture areas of the red and blue sub-pixel are equivalently large and an aperture area of the yellow sub-pixel is small.

(98) TABLE-US-00009 TABLE 9 The largest aperture Color filter Light-emitting Aperture area ratio area/The smallest Lightness Lightness transmittance efficiency of (red:green:blue:yellow) aperture area of red (%) of white (%) backlight G1 11:10:11:8 1.38 13.0 100 37.5 0.84 G2 12:10:12:6 2.00 15.2 99 34.4 0.91 G3 13:10:13:4 3.25 18.0 96 31.1 0.98

(99) FIG. 27 shows a relationship between a lightness of red and a lightness of white displayed by the liquid crystal displays shown in Tables 8 and 9. In FIG. 27, Δ corresponds to the liquid crystal display device in Table 8; and ∘ corresponds to the liquid crystal display device in Table 9. For comparison, □ shows the liquid crystal display devices E1 to E6 in Table 7 in accordance with the preferred embodiment 3 in which the aperture areas of the red and blue sub-pixels are equivalently large and the aperture areas of the green and yellow sub-pixels are equivalently small.

(100) FIG. 27 shows that the liquid crystal display devices F1 to F4 in Table 8 in the present preferred embodiment are superior in lightness of white to the liquid crystal display devices E1 to E4 in Table 7 in preferred embodiment 3, although the lightness of red is small in the liquid crystal display devices F1 to F4. However, if two liquid crystal display devices that are the same in the aperture area ratio among the sub-pixels, i.e., the liquid crystal display device F3 in Table 8 and the liquid crystal display device G3 in Table 9, are compared, the lightness of white is high, but a large effect of improving the lightness of red cannot be obtained and the lightness of red cannot be increased to about 14% or more according to the liquid crystal display device F3 in Table 8. In contrast, according to the liquid crystal display device G3 in Table 9, the lightness of white is not so high, but a large effect of improving the lightness of red can be obtained. Also in this case, the preferred embodiment may be appropriately selected depending on a desired lightness of red. The liquid crystal display devices G1 to G3 in Table 9 in the present preferred embodiment are superior in lightness of red to the liquid crystal display devices E1 to E3 in Table 7 in preferred embodiment 3, although the lightness of white is small in the liquid crystal display devices G1 to G3.

(101) Preferred Embodiment 5

(102) As shown in preferred embodiments 1 and 4, if the aperture areas of both of the red and blue sub-pixels are large, the average transmittance of the color filters is reduced in comparison to the case that only the aperture area of the red sub-pixel is large. However, the proportion of the blue component which passes through the color filter is increased. Therefore, with regard to the wavelength characteristics of the backlight used, the blue component whose light-emitting efficiency is low can be decreased. Therefore, alight source having a high light-emitting efficiency can be used as the backlight. As a result, if the average transmittance of the color filters and the light-emitting efficiency of the light source of the backlight are taken into consideration, the light-emitting efficiency of the light source of the backlight can be high enough to compensate the reduction of the average transmittance of the color filter due to the increase in aperture area of the blue sub-pixel. According to preferred embodiments 1 to 4, the case where at least red sub-pixel has the largest aperture area is mentioned. In the present preferred embodiment, the case where the blue sub-pixel has the largest aperture area is mentioned.

(103) Table 10 shows an aperture area ratio among the respective sub-pixels, an aperture area ratio between the sub-pixel having the largest aperture area (blue sub-pixel) and the sub-pixel having the smallest aperture area (green or yellow sub-pixel), a lightness of red, a lightness of white, an average transmittance of the color filters, and a light-emitting efficiency of the light source of the backlight, in liquid crystal display devices H1 to H4 prepared in the present Preferred embodiment, in the case that an aperture area of the blue sub-pixel is large and aperture areas of the green and yellow sub-pixels are equivalently small.

(104) TABLE-US-00010 TABLE 10 The largest aperture Color filter Light-emitting Aperture area ratio area/The smallest Lightness Lightness transmittance efficiency of (red:green:blue:yellow) aperture area of red (%) of white (%) backlight H1 10:9:12:9 1.33 11.7 105 38.1 0.87 H2 10:8:14:8 1.75 12.6 106 35.4 0.95 H3 10:7:16:7 2.29 13.5 104 32.4 1.02 H4 10:6:18:6 3.00 14.8 101 29.2 1.09

(105) Each of FIGS. 28 and 29 schematically shows a liquid crystal display device in Table 10. FIG. 28 shows a configuration of a pixel 11q defining a display surface 500q of the liquid crystal display device, and the pixel 11q includes four sub-pixels 5Rq, 5Gq, 5Bq, and 5Yq arranged in a stripe pattern. FIG. 29 shows a configuration of a pixel 11r defining a display surface 500r of the liquid crystal display device, and the pixel 11r includes four sub-pixels 5Rr, 5Gn, 5Br, and 5Yr arranged in two rows and two columns. These pixel configurations are just mentioned as one example. The present preferred embodiment is not limited to these pixel configurations.

(106) Table 11 shows an aperture area ratio among the respective sub-pixels, an aperture area ratio between the sub-pixel having the largest aperture area (blue sub-pixel) and the sub-pixel having the smallest aperture area (green sub-pixel), a lightness of red, a lightness of white, an average transmittance of the color filters, and a light-emitting efficiency of the light source of the backlight, in liquid crystal display devices I1 to I4 prepared in the present Preferred embodiment, in the case that an aperture area of the blue sub-pixel is large and an aperture area of the green sub-pixel is small.

(107) TABLE-US-00011 TABLE 11 The largest aperture Color filter Light-emitting Aperture area ratio area/The smallest Lightness Lightness transmittance efficiency of (red:green:blue:yellow) aperture area of red (%) of white (%) backlight I1 10:9:11:10 1.33 11.1 103 39.0 0.83 I2 10:8:12:10 1.75 11.2 105 37.5 0.86 I3 10:7:13:10 2.29 11.3 107 35.9 0.90 I4 10:6:14:10 3.00 11.3 108 34.2 0.94

(108) Table 12 shows an aperture area ratio among the respective sub-pixels, an aperture area ratio between the sub-pixel having the largest aperture area (blue sub-pixel) and the sub-pixel having the smallest aperture area (yellow sub-pixel), a lightness of red, a lightness of white, an average transmittance of the color filters, and a light-emitting efficiency of the light source of the backlight, in liquid crystal display devices J1 to J4 prepared in the present preferred embodiment, in the case that an aperture area of the blue sub-pixel is large and an aperture area of the yellow sub-pixel is small.

(109) TABLE-US-00012 TABLE 12 The largest aperture Color filter Light-emitting Aperture area ratio area/The smallest Lightness Lightness transmittance efficiency of (red:green:blue:yellow) aperture area of red (%) of white (%) backlight J1 10:10:11:9 1.33 11.7 102 39.0 0.83 J2 10:10:12:8 1.75 12.5 103 37.5 0.87 J3 10:10:13:7 2.29 13.2 103 35.9 0.91 J4 10:10:14:6 3.00 14.2 102 34.2 0.95

(110) FIG. 30 shows a relationship between a lightness of red and a lightness of white displayed by the liquid crystal displays shown in Tables 10 to 12. In FIG. 30, ⋄ corresponds to the liquid crystal display device in Table 10; □ corresponds to the liquid crystal display device in Table 11; and Δ corresponds to the liquid crystal display device in Table 12. For comparison, ∘ shows the liquid crystal display devices E1 to E6 in Table 7 in accordance with the preferred embodiment 3 in which the aperture areas of the red and blue sub-pixels are equivalently large and the aperture areas of the green and yellow sub-pixels are equivalently small.

(111) According to the liquid crystal display devices I1 to I4 in Table 11, the effect of improving the lightness of white can be observed, but the effect of improving the lightness of red is hardly observed. In contrast, the lightness of white is about 106% when the lightness of red is about 12.6% in the liquid crystal display device H2 in Table 10; the lightness of white is about 103% when the lightness of red is about 12.5% in the liquid crystal display device J2 in Table 12. Thus, the liquid crystal display devices H2 and J2 are excellent in lightness of white. However, according to the present preferred embodiment, the lightness of red is not so increased. Therefore, if the lightness of red needs to be increased to about 15% or more, it is preferable that an appropriate liquid crystal display device is selected from those in preferred embodiments 1 to 4.

(112) The pixel configuration of the liquid crystal display device in the present preferred embodiment is not limited to those shown in FIGS. 28 and 29. For example, as shown in FIG. 31, a pixel 11s defining a display surface 500s is divided into five sub-pixels and two blue sub-pixels 5B may be arranged. In FIG. 31, with regard to an aperture area ratio among the respective sub-pixels 5Rs, 5Gs, 5Bs, and 5Ys, red:green:blue:yellow is 1:1:2:1. Thus, a plurality of blue sub-pixels are arranged, and thereby modification of the pixel design and the driving circuit design can be minimized.

(113) As shown in FIG. 32, a pixel 11t defining a display surface 500t is divided into five pixels, and two blue sub-pixels having different color characteristics may be arranged. FIG. 22 shows spectral characteristics of a color filter in this case. In this case, light having a dominant wavelength of about 460 nm passes through a blue sub-pixel 5B.sub.1t, and light having a dominant wavelength of about 488 nm passes through a blue sub-pixel 5B.sub.2t. Also in the case shown in FIG. 32, aperture areas of a red sub-pixel 5Rt, a green sub-pixel 5Gt, the blue sub-pixels 5B.sub.1t and 5B.sub.2t, and a yellow sub-pixel 5Yt are equivalent. With regard to an aperture area ratio among the respective sub-pixels, red:green:blue:yellow is 2:1:1:2. Thus, two blue sub-pixels having different color characteristics are arranged, and thereby the color reproduction range can be further extended. These pixel configurations are just mentioned as one example. The present preferred embodiment is not limited to these pixel configurations.

(114) Preferred Embodiment 6

(115) The present preferred embodiment shows a case where the yellow sub-pixel has the smallest aperture area.

(116) Table 13 shows an aperture area ratio among the respective sub-pixels, an aperture area ratio between the sub-pixel having the largest aperture area (red, green, or blue sub-pixel) and the sub-pixel having the smallest aperture area (yellow sub-pixel), a lightness of red, a lightness of white, an average transmittance of the color filters, and a light-emitting efficiency of the light source of the backlight, in liquid crystal display devices K1 to K5 prepared in the present preferred embodiment, in the case that an aperture area of the yellow sub-pixel is small and aperture areas of the other sub-pixels are equivalently large.

(117) TABLE-US-00013 TABLE 13 The largest aperture Color filter Light-emitting Aperture area ratio area/The smallest Lightness Lightness transmittance efficiency of (red:green:blue:yellow) aperture area of red (%) of white (%) backlight K1 10.5:10.5:10.5:8.5 1.24 12.2 100.0 38.7 1.00 K2 11:11:11:7 1.57 13.6 99.0 37.0 0.99 K3 11.5:11.5:11.5:5.5 2.09 15.2 98.2 35.2 0.98 K4 12:12:12:4 3.00 17.3 95.6 33.3 0.96 K5 12.5:12.5:12.5:2.5 5.00 19.3 93.5 31.3 0.94

(118) Each of FIGS. 33 and 34 schematically shows a liquid crystal display device in Table 13. FIG. 33 shows a configuration of a pixel 11u defining a display surface 500u of the liquid crystal display, and the pixel 11u includes four sub-pixels 5Ru, 5Gu, 5Bu, and 5Yu arranged in a stripe pattern. FIG. 34 shows a configuration of a pixel 11v defining a display surface 500v of the liquid crystal display, and the pixel 11v includes four sub-pixels 5Rv, 5Gv, 5Bv, and 5Yv arranged in two rows and two columns. These pixel configurations are just mentioned as one example. The present preferred embodiment is not limited to these pixel configurations.

(119) Table 14 shows an aperture area ratio among the respective sub-pixels, an aperture area ratio between the sub-pixel having the largest aperture area (red or green sub-pixel) and the sub-pixel having the smallest aperture area (yellow sub-pixel), a lightness of red, a lightness of white, an average transmittance of the color filters, and a light-emitting efficiency of the light source of the backlight, in liquid crystal display devices L1 to L4 prepared in the present preferred embodiment, in the case that an aperture area of the yellow sub-pixel is small and aperture areas of the red and green sub-pixels are equivalently large.

(120) TABLE-US-00014 TABLE 14 The largest aperture Color filter Light-emitting Aperture area ratio area/The smallest Lightness Lightness transmittance efficiency of (red:green:blue:yellow) aperture area of red (%) of white (%) backlight L1 11:11:10:8 1.24 13.0 100.6 37.6 0.85 L2 12:12:10:6 1.57 15.2 98.6 34.4 0.91 L3 13:13:10:4 3.25 18.0 95.9 31.1 0.98 L4 14:14:14:2 7.00 21.3 90.8 27.5 1.04

(121) FIG. 35 shows a relationship between a lightness of red and a lightness of white displayed by the liquid crystal displays shown in Tables 13 and 14. In FIG. 35, Δ corresponds to the liquid crystal display devices K1 to K5 in Table 13; and ⋄ corresponds to the liquid crystal display device in Table 14. For comparison, ∘ shows the liquid crystal display devices E1 to E6 in Table 7 in accordance with the preferred embodiment 3 in which the aperture areas of the red and blue sub-pixels are equivalently large and the aperture areas of the green and yellow sub-pixels are equivalently small.

(122) According to the liquid crystal display devices in Tables 13 and 14, the aperture area ratio needs to be increased, but the light-emitting efficiency of the light source of the backlight is increased. Therefore, such liquid crystal display devices are advantageously employed in order to increase the lightness of red.

(123) Preferred Embodiment 7

(124) The present preferred embodiment shows a case where red, blue, green, and yellow sub-pixels are ranked in descending order of aperture area.

(125) Table 15 shows an aperture area ratio among the respective sub-pixels, an aperture area ratio between the sub-pixel having the largest aperture area (red sub-pixel) and the sub-pixel having the smallest aperture area (yellow sub-pixel), a lightness of red, a lightness of white, an average transmittance of the color filters, and a light-emitting efficiency of the light source of the backlight, in liquid crystal display devices M1 and M2 prepared in the present preferred embodiment.

(126) TABLE-US-00015 TABLE 15 The largest aperture Color filter Light-emitting Aperture area ratio area/The smallest Lightness Lightness transmittance efficiency of (red:green:blue:yellow) aperture area of red (%) of white (%) backlight M1 10:8:9:7 1.42 13.2 92.5 37.4 0.84 M2 10:6:8:4 2.50 17.2 88.7 32.5 0.93

(127) According to the liquid crystal display device in Table 15, the aperture area of the red sub-pixel is relatively large and therefore the effect of improving the lightness of red is large. In addition, the blue sub-pixel has a relatively large aperture area, and the yellow sub-pixel has a small aperture area. Therefore, a light source having a high light-emitting efficiency can be used in order to maximize the chromaticity of white. Therefore, the lightness of red is increased at a relatively small aperture area ratio. As a result, the reduction in the lightness of white can be minimized.

(128) Preferred Embodiment 8

(129) The present preferred embodiment shows a case where red, blue, yellow, and green sub-pixels are ranked in descending order of aperture area.

(130) Table 16 shows an aperture area ratio among the respective sub-pixels, an aperture area ratio between the sub-pixel having the largest aperture area (red sub-pixel) and the sub-pixel having the smallest aperture area (green sub-pixel), a lightness of red, a lightness of white, an average transmittance of the color filters, and a light-emitting efficiency of the light source of the backlight, in liquid crystal display devices N1 to N3 prepared in the present preferred embodiment.

(131) TABLE-US-00016 TABLE 16 The largest aperture Color filter Light-emitting Aperture area ratio area/The smallest Lightness Lightness transmittance efficiency of (red:green:blue:yellow) aperture area of red (%) of white (%) backlight N1 12:9:11:10 1.33 12.2 100.3 38.3 0.83 N2 14:8:12:10 1.75 13.2 99.6 36.3 0.87 N3 16:8:14:10 2.00 14.1 99.5 34.4 0.92

(132) According to the liquid crystal display devices in Table 16, the red sub-pixel has the largest aperture area, and therefore the effect of improving the lightness of red is large. In addition, the blue sub-pixel has a relatively large aperture area and the yellow sub-pixel has a relatively small aperture area. Therefore, a light source having a high light-emitting efficiency can be used in order to maximize the chromaticity of white. Therefore, the lightness of red can be improved at a relatively small aperture area ratio. As a result, the reduction in lightness of white can be minimized.

(133) Preferred Embodiment 9

(134) The present preferred embodiment shows a case where red, green, blue, and yellow sub-pixels are ranked in descending order of aperture area.

(135) Table 17 shows an aperture area ratio among the respective sub-pixels, an aperture area ratio between the sub-pixel having the largest aperture area (red sub-pixel) and the sub-pixel having the smallest aperture area (yellow sub-pixel), a lightness of red, a lightness of white, an average transmittance of the color filters, and a light-emitting efficiency of the light source of the backlight, in liquid crystal display devices O1 to O6 prepared in the present preferred embodiment.

(136) TABLE-US-00017 TABLE 17 The largest aperture Color filter Light-emitting Aperture area ratio area/The smallest Lightness Lightness transmittance efficiency of (red:green:blue:yellow) aperture area of red (%) of white (%) backlight O1 12:11:10:9 1.33 13.0 96.3 38.7 0.79 O2 12:11:10:8 1.50 13.7 96.0 37.9 0.80 O3 14:12:10:8 1.75 14.5 92.5 37.2 0.79 O4 16:14:10:8 2.00 15.4 89.0 36.9 0.76 O5 14:13:12:7 2.00 15.2 95.9 35.9 0.84 O6 14:13:12:6 2.33 15.8 95.4 35.0 0.86

(137) According to the liquid crystal display devices in Table 17, the red sub-pixel has a large aperture area, and therefore the effect of improving the lightness of red is large. In addition, the yellow sub-pixel has a small aperture area. Therefore, a light source with a high light-emitting efficiency can be used in order to maximize the chromaticity of white. Therefore, the lightness of red can be improved at a relatively small aperture area ratio. As a result, the reduction in lightness of white can be minimized.

(138) Preferred Embodiment 10

(139) The present preferred embodiment shows a case where red, blue, yellow, and green sub-pixels are ranked in descending order of aperture area.

(140) Table 18 shows an aperture area ratio among the respective sub-pixels, an aperture area ratio between the sub-pixel having the largest aperture area (red sub-pixel) and the sub-pixel having the smallest aperture area (yellow or green sub-pixel), a lightness of red, a lightness of white, an average transmittance of the color filters, and a light-emitting efficiency of the light source of the backlight, in liquid crystal display devices P1 to P3 prepared in the present preferred embodiment.

(141) TABLE-US-00018 TABLE 18 The largest aperture Color filter Light-emitting Aperture area ratio area/The smallest Lightness Lightness transmittance efficiency of (red:green:blue:yellow) aperture area of red (%) of white (%) backlight P1 12:9:10:9 1.33 12.9 97.8 38.0 0.82 P2 14:8:10:8 1.75 14.8 94.5 35.3 0.85 P3 16:7:10:7 2.29 16.7 91.2 32.4 0.89

(142) According to the liquid crystal display devices in Table 18, the red sub-pixel has a large aperture area, and therefore the effect of improving the lightness of red is large. In addition, the aperture area of the blue sub-pixel is relatively large and the aperture areas of the yellow and green sub-pixels are small. Therefore, alight source with a high light-emitting efficiency can be used in order to maximize the chromaticity of white. Therefore, the lightness of red can be improved at a relatively small aperture area. As a result, the reduction in lightness of white can be minimized.

(143) Preferred Embodiment 11

(144) The present preferred embodiment shows a case where blue, red, green, and yellow sub-pixels are ranked in descending order of aperture area.

(145) Table 19 shows an aperture area ratio among the respective sub-pixels, an aperture area ratio between the sub-pixel having the largest aperture area (blue sub-pixel) and the sub-pixel having the smallest aperture area (red sub-pixel), a lightness of red, a lightness of white, an average transmittance of the color filters, and a light-emitting efficiency of the light source of the backlight, in liquid crystal display devices Q1 and Q2 prepared in the present preferred embodiment.

(146) TABLE-US-00019 TABLE 19 The largest aperture Color filter Light-emitting Aperture area ratio area/The smallest Lightness Lightness transmittance efficiency of (red:green:blue:yellow) aperture area of red (%) of white (%) backlight Q1 9:8:10:7 1.42 12.6 95.9 37.5 0.87 Q2 8:6:10:4 2.50 15.2 94.1 32.3 0.99

(147) According to the liquid crystal display devices in Table 19, the red sub-pixel has a relatively large aperture area and therefore the effect of improving the lightness of red is large. In addition, the aperture area of the blue sub-pixel is large and the aperture area of the yellow sub-pixel is small. Therefore, a light source having a high light-emitting efficiency can be used in order to maximize the chromaticity of white. Therefore, the lightness of red can be improved at a relatively small aperture area ratio. As a result, the reduction in lightness of white can be minimized.

(148) Preferred Embodiment 12

(149) The present embodiment shows a case where blue, red, yellow, and green sub-pixels are ranked in descending order of aperture area.

(150) Table 20 shows an aperture area ratio among the respective sub-pixels, an aperture area ratio between the sub-pixel having the largest aperture area (red sub-pixel) and the sub-pixel having the smallest aperture area (green sub-pixel), a lightness of red, a lightness of white, an average transmittance of the color filters, and a light-emitting efficiency of the light source of the backlight, in liquid crystal display devices R1 to R3 prepared in the present preferred embodiment.

(151) TABLE-US-00020 TABLE 20 The largest aperture Color filter Light-emitting Aperture area ratio area/The smallest Lightness Lightness transmittance efficiency of (red:green:blue:yellow) aperture area of red (%) of white (%) backlight R1 11:9:12:10 1.33 11.6 103.9 38.4 0.85 R2 12:8:14:10 1.75 12.2 105.1 36.4 0.91 R3 15:8:16:10 2.00 13.7 102.6 34.0 0.95

(152) According to the liquid crystal display devices in Table 20, the aperture area of the red sub-pixel is relatively large and therefore the effect of improving the lightness of red is large. Further, the aperture area of the blue sub-pixel is large and the aperture areas of the yellow sub-pixel are relatively small. Therefore, alight source with a high light-emitting efficiency can be used in order to maximize the chromaticity of white. Therefore, the lightness of red can be improved at a relatively small aperture area ratio. As a result, the reduction in lightness of white can be minimized.

(153) Preferred Embodiment 13

(154) The present preferred embodiment shows a case where blue, green, red, and yellow sub-pixels are ranked in descending order of aperture area.

(155) Table 21 shows an aperture area ratio among the respective sub-pixels, an aperture area ratio between the sub-pixel having the largest aperture area (red sub-pixel) and the sub-pixel having the smallest aperture area (yellow sub-pixel), a lightness of red, a lightness of white, an average transmittance of the color filters, and a light-emitting efficiency of the light source of the backlight, in liquid crystal display devices S1 to S7 prepared in the present preferred embodiment.

(156) TABLE-US-00021 TABLE 21 The largest aperture Color filter Light-emitting Aperture area ratio area/The smallest Lightness Lightness transmittance efficiency of (red:green:blue:yellow) aperture area of red (%) of white (%) backlight S1 10:11:12:8 1.50 12.3 102.5 37.9 0.86 S2 10:11:12:7 1.71 13.0 102.3 36.9 0.88 S3 10:11:12:7 1.71 13.3 101.9 36.9 0.87 S4 10:11:12:6 2.00 13.9 101.0 35.8 0.89 S5 10:11:12:5 2.40 15.0 99.8 34.7 0.91 S6 11:12:13:6 2.17 14.6 99.8 35.3 0.89 S7 13:14:15:6 2.50 15.5 98.9 34.4 0.91

(157) According to the liquid crystal display devices in Table 21, the aperture area of the yellow sub-pixel is particularly small. Therefore, a red component of light can be emitted at a high intensity from a backlight, and therefore, the effect of improving the lightness of red is large. In addition, the aperture area of the blue sub-pixel is large and the aperture area of the yellow sub-pixel is small. Therefore, a light source with a high light-emitting efficiency can be used in order to maximize the chromaticity of white. Therefore, the lightness of red can be improved at a relatively small aperture area ratio. As a result, the reduction in lightness of white can be minimized.

(158) Preferred Embodiment 14

(159) The present preferred embodiment shows a case where blue and green sub-pixels, followed by red and yellow sub-pixels, are ranked in descending order of aperture area.

(160) Table 22 shows an aperture area ratio among the respective sub-pixels, an aperture area ratio between the sub-pixel having the largest aperture area (blue or green sub-pixel) and the sub-pixel having the smallest aperture area (yellow sub-pixel), a lightness of red, a lightness of white, an average transmittance of the color filters, and a light-emitting efficiency of the light source of the backlight, in liquid crystal display devices T1 to T3 prepared in the present preferred embodiment.

(161) TABLE-US-00022 TABLE 22 The largest aperture Color filter Light-emitting Aperture area ratio area/The smallest Lightness Lightness transmittance efficiency of (red:green:blue:yellow) aperture area of red (%) of white (%) backlight T1 9:10:10:7 1.43 12.5 100.8 38.2 0.83 T2 9:10:10:5 2.00 14.4 99.9 35.9 0.88 T3 9:10:10:4 2.50 15.7 98.2 34.6 0.90

(162) According to the liquid crystal display in Table 22, the aperture area of the yellow sub-pixel is particularly small. Therefore, a red component of light can be emitted at a higher intensity from a backlight and the like. Therefore, the effect of improving the lightness of red is large. In addition, the aperture area of the blue sub-pixel is large and the aperture area of the yellow sub-pixel is small. Therefore, a light source with a high light-emitting efficiency can be used in order to maximize the chromaticity of white. Therefore, the lightness of red can be improved at a relatively small aperture area ratio. As a result, the reduction in lightness of white can be minimized.

(163) As mentioned above, preferred embodiments 1 to 14 show the case where the color filter having spectral characteristics in FIG. 7, 13, or 22 is used. However, the color filter is not limited thereto, and even using a color filter different in hue or chroma from that of these preferred embodiments, the effect of improving the lightness of red can be observed. Specifically, such a color filter can be applied to a display device in which light having a dominant wavelength of about 595 nm or more and about 650 nm or less passes through a red sub-pixel; light having a dominant wavelength of about 490 nm or more and about 555 nm or less passes through a green sub-pixel; light having a dominant wavelength of about 450 nm or more and about 490 nm or less passes through a blue sub-pixel; light having a dominant wavelength of about 565 nm or more and about 580 nm or less passes through a yellow sub-pixel. Preferred embodiments 1 to 14 show the configuration in which the pixel is defined by the red, green, blue, and yellow sub-pixels. The pixel configuration is not limited thereto. The same effect can be obtained even in the case where the pixel is defined by red, green, blue, yellow, and magenta sub-pixels.

(164) According to preferred embodiments 1 to 14, a common CCFT is used as the light source of the backlight, but the light source is not limited thereto. The above-mentioned effect of improving the lightness of red can be observed even using a backlight different from that used in preferred embodiments, such as a white light-emitting diode (a combination of a blue LED and a yellow fluorescence), RGB-LED, a hot cathode fluorescent tube (HCFT), an organic electroluminescence, and a field emission display (FED).

(165) In addition, according to preferred embodiments 1 to 14, the mixing ratio among the fluorescent materials of red, green, and blue, is varied to adjust spectral characteristics of the light source, and thereby the chromaticity of white displayed by the liquid crystal display device is maximized. However, the way of optimizing the chromaticity of white is not limited thereto. For example, the chromaticity of white displayed by the liquid crystal display device may be maximized by modifying an optical design of a liquid crystal layer or an optical film, or varying an applied voltage at the time of display of white.

(166) According to preferred embodiments 1 to 14, a transmissive liquid crystal display device which performs display using a backlight is used. However, in addition to the transmissive liquid crystal display device, the present invention can be preferably used in liquid crystal display devices in other display systems such as a transflective liquid crystal display device which performs transmissive display using a backlight and performs reflective display using external light and/or a front light and a reflective liquid crystal display device which performs display using a light source such as a front light, or used in various display devices such as a cathode ray tube (CRT), an organic electroluminescent display device (OELD), a plasma display panel (PDP), and a field emission displays (FED) such as a surface-conduction electron-emitter display (SED).

(167) In the present description, if the terms “or more” and “or less” are used, the value (boundary value) is included.

(168) The present application claims priority under the Paris Convention and the domestic law in the country to be entered into national phase on Patent Application No. 2006-169206 filed in Japan on Jun. 19, 2006, the entire contents of which are hereby incorporated by reference.

(169) While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.