Illumination device having multiple LED elements with varying color temperatures

Abstract

An illumination device is provided with an arrangement for reducing color unevenness. A plurality of light-emitting devices are provided, each of which includes a transparent enclosure sealing a light-emitting element and further including a phosphor excited by light emitted from the light-emitting element. A substrate is provided upon which the plurality of light-emitting devices are mounted. The light-emitting devices are provided with predetermined color temperatures that vary in accordance with their position along the substrate to reduce color unevenness, for example increasing in a phased manner from the center of the substrate toward the outer circumference thereof.

Claims

1. An illumination device comprising: a planar substrate; a plurality of first light-emitting devices of a first color temperature arranged on a first direction of the planar substrate and separated from each other by a first distance; a plurality of second light-emitting devices of a second color temperature arranged on the planar substrate and circumferentially disposed about the plurality of first light-emitting devices and separated from each other by a second distance without any additional light-emitting device disposed in the second distance; wherein the second color temperature is higher than the first color temperature; wherein at least two of the plurality of second light-emitting devices are disposed in the first distance; wherein each of the plurality of first light-emitting devices and the plurality of second light emitting devices further independently comprising: a light emitting element, and a resin including a phosphor sealing the light emitting element.

2. The illumination device of claim 1, wherein the light emitting element is a blue light emitting element.

3. An illumination device comprising: a planar substrate including an inner portion and an outer portion circumferentially disposed about the inner portion; a plurality of first light-emitting devices of a first color temperature arranged in the inner portion; a plurality of second light-emitting devices of a second color temperature arranged in the outer portion and separated from each other by a second distance without any additional light-emitting device disposed in the second distance; wherein the second color temperature is higher than the first color temperature.

4. The illumination device of claim 3, wherein each of the plurality of first light-emitting devices and the plurality of second light-emitting devices further comprising: a light-emitting element; and a resin including a phosphor sealing the light-emitting element.

5. The illumination device of claim 3, wherein the plurality of first light-emitting devices are separated from each other by a first distance, and wherein at least two of the plurality of second light-emitting devices are disposed in the first distance.

6. The illumination device of claim 4, wherein the light emitting element is a blue light emitting element.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) FIG. 1 is a top view of an illumination device in accordance with a first embodiment of the present invention.

(2) FIG. 2 is a sectional side view of the illumination device of FIG. 1.

(3) FIG. 3 is a sectional side view of a light-emitting device of the illumination device of FIG. 1.

(4) FIG. 4 is a top view of an illumination device in accordance with a second embodiment of the present invention.

(5) FIG. 5 is a top view of an illumination device in accordance with a third embodiment of the present invention.

(6) FIG. 6 is a top view of an illumination device in accordance with a fourth embodiment of the present invention.

(7) FIG. 7 is a top view of an illumination device in accordance with a fifth embodiment of the present invention.

(8) FIG. 8 is a top view of an illumination device in accordance with a sixth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(9) Throughout the specification and claims, the following terms take at least the meanings explicitly associated herein, unless the context dictates otherwise. The meanings identified below do not necessarily limit the terms, but merely provide illustrative examples for the terms. The meaning of “a,” “an,” and “the” may include plural references, and the meaning of “in” may include “in” and “on.” The phrase “in one embodiment,” as used herein does not necessarily refer to the same embodiment, although it may.

(10) Hereinafter, preferred embodiments of the present invention may be described with reference to the accompanying drawings.

(11) Referring to FIG. 1, in an embodiment an illumination device 10 is provided with a substrate 12 formed into a disc-like shape and a plurality of light-emitting devices 14 mounted on the substrate 12.

(12) The substrate 12 as shown is a component on which the plurality of light-emitting devices 14 are mounted concentrically at predetermined intervals. More specifically, the substrate 12 has a disk-like shape with a center position (center) 12a, a middle position 12b outside of the center position 12a, and an outer circumferential position (outer circumference) 12c outside of the middle position 12b, on which the plurality of light-emitting devices 14 are mounted.

(13) The plurality of light-emitting devices 14 are provided with: one center light-emitting device (light-emitting device) 14a mounted at the center position 12a of the substrate 12; a plurality of middle light-emitting devices (light-emitting devices) 14b mounted at the middle position 12b outside of the center light-emitting device 14a at predetermined intervals; and a plurality of outer light-emitting devices (light-emitting devices) 14c mounted at the outer circumferential position 12c outside of the middle light-emitting devices 14b at predetermined intervals.

(14) As shown in FIG. 2, the center light-emitting device 14a, the middle light-emitting devices 14b, and the outer light-emitting devices 14c each include an LED (light-emitting element) 16 that emits blue light in a wavelength range of approximately 380 to 480 nm; and an enclosure 18 that seals the LED 16.

(15) The enclosure 18 may be formed of resin (for example, silicon or epoxy, or the like) and further include a phosphor about the LED 16. The phosphor is excited by the blue light (in a wavelength range of approximately 380 to 480 nm) emitted from the LED 16 and converts the blue light into light in a wavelength range of approximately 480 to 780 nm. Such a phosphor may be of a white type including a yellow color. A combination ratio of this phosphor may be adjusted to vary the plurality of light-emitting devices 14 in a color temperature.

(16) With the plurality of light-emitting devices 14 as described, a portion of the blue light emitted from the LED 16 excites a light-emitter and is converted into light within a wavelength range of approximately 480 to 780 nm, and the rest of the blue light remains unconverted and is transmitted through the resin case 18.

(17) Through combining of the light in a wavelength range of approximately 480 to 780 nm obtained through the conversion and the blue light in a wavelength range of approximately 380 to 480 nm, conversion into a desired light color (for example a pseudo white) is made.

(18) Referring now to FIG. 3, the plurality of light-emitting devices 14 may have different tints depending on an irradiation direction.

(19) More specifically, in the plurality of light-emitting devices 14, emitted light 15 turns into bluish-white light 15a in the vicinity of a center 22a of an irradiation surface 22 and turns into more yellowish light 15b with a distance from the center 22a. Thus, the plurality of light-emitting devices 14 each appear to have a yellow ring generated at the outer circumference of the light-emitting devices 14 (or of the resin case 18).

(20) In other words, the plurality of light-emitting devices 14 each have a high color temperature associated with the vicinity of the center 22a of the irradiation surface 22 and have a lower color temperature associated with a distance from the center 22a.

(21) The light-emitting devices 14 as shown in FIG. 2 are arranged with the color temperature varied (more specifically, increased) in a phased manner from the center of the substrate 12 toward the outer circumference thereof (and with a corresponding distance from the center thereof) by adjusting a combination ratio of the light-emitter included in the resin case 18.

(22) More specifically, the color temperature of the middle light emitting devices 14b of the plurality of light emitting devices 14 is set higher than the color temperature of the center light emitting device 14a of the plurality of light emitting devices 14 and the color temperature of the outer light emitting devices 14c of the plurality of light emitting devices 14 is set higher than the color temperature of the middle light emitting devices 14b.

(23) Consequently, on an irradiation surface 24 (see FIG. 2) of the illumination device 10, a color temperature at an outer circumferential portion 24b can be brought closer to a color temperature at a more central portion 24a. Bringing the color temperature at the outer circumferential portion 24b of the irradiation surface 24 of the illumination device 10 closer to the color temperature at the center portion 24a thereof in this manner can reduce an appearance of color unevenness on the irradiation surface 24. In addition, bringing the color temperature at the outer circumferential portion 24b of the irradiation surface 24 closer to the color temperature at a center portion thereof to reduce the color unevenness may eliminate a need for subjecting light emitted from the plurality of light emitting devices 14 to diffusion processing with a reflection plate or a lens. In this case, a decrease in light extraction efficiency may be avoided.

(24) Additional embodiments may further be described with reference to FIGS. 4 to 8. Similar features for the additional embodiments may be shown and provided with the same numerals as shown in FIG. 1, and thus they are omitted from the description.

(25) Referring now to FIG. 4, an alternative embodiment of an illumination device 30 has a reflection plate 32 provided in what otherwise is equivalent to the illumination device 10 as shown in FIG. 1. The reflection plate 32 has a reflection surface 32a which is provided on a surface facing a plurality of light emitting devices 14 and which performs a light distribution control of light emitted from the plurality of light emitting devices 14.

(26) Consequently, light emitted from the plurality of light emitting devices 14 can be subjected to the light distribution control in a desired direction with the reflection surface 32a, thus providing high illumination intensity, which facilitates achieving a higher output.

(27) It may be assumed that, when the reflection plate 32 is used for obtaining high illumination intensity, a problem of appearance of color unevenness becomes more prominent. However, as is the case with the previously described embodiment of the illumination device 10, varying the plurality of light emitting devices 14 in a color temperature can reduce an appearance of color unevenness on an irradiation surface 22 and also can avoid a decrease in light extraction efficiency.

(28) Referring now to FIG. 5, in another embodiment an illumination device 40 is provided with a substrate 42 formed into a rectangular shape, and a plurality of light emitting devices 14 mounted on the substrate 42.

(29) The illumination device 40, as is the case with the embodiment of the illumination device 10 as shown in FIG. 1, is arranged with a color temperature varied (more specifically, increased) in a phased manner from a center of the substrate 42 toward an outer edge thereof (with distance from the center thereof) by adjusting a combination ratio of a light-emitter included in the resin case 18 of the plurality of light emitting devices 14. More specifically, the color temperature of outer light-emitting devices 14e of the plurality of light emitting devices 14 is set higher than a color temperature of center light-emitting devices 14d of the plurality of light emitting devices 14.

(30) Consequently, as is the case with the illumination device 10 as shown in FIG. 1, an appearance of color unevenness on an irradiation surface can be reduced, and a decrease in light extraction efficiency can be avoided.

(31) Referring now to FIG. 6, in another embodiment an illumination device 50 is provided with a substrate 52 formed into a square shape and a plurality of light emitting devices 14 mounted on the substrate 52.

(32) The illumination device 50, as is also the case with the illumination device 10 as shown in FIG. 1, is arranged with a color temperature varied (more specifically, increased) in a phased manner from a center of the substrate 52 toward an outer edge thereof (with a corresponding distance from the center thereof) by adjusting a combination ratio of a light-emitter included in the resin case 18 of the plurality of light emitting devices 14.

(33) More specifically, a color temperature of middle light-emitting devices 14b of the plurality of light emitting devices 14 is set higher than the color temperature of the center light-emitting device 14a of the plurality of light emitting devices 14, and a color temperature of outer light-emitting devices 14c of the plurality of light emitting devices 14 is set higher than the color temperature of the middle light-emitting devices 14b. Consequently, as is the case with the illumination device 10 as shown in FIG. 1, an appearance of color unevenness on an irradiation surface can be reduced, and a decrease in light extraction efficiency can be avoided.

(34) Referring now to FIG. 7, in another embodiment an illumination device 60 is provided with a substrate 62 formed into a rectangular shape and a plurality of light emitting devices 14 mounted on the substrate 62.

(35) The plurality of light emitting devices 14 are provided by providing in a continuous manner one or more light-emitting units 64 each having a plurality of outer light-emitting devices 14e with a high color temperature so arranged as to surround a center light-emitting device 14d.

(36) Note that the adjacent light-emitting units 64 share the outer light-emitting device 14e with the high color temperature. Since the light-emitting unit 64 has the plurality of outer light-emitting devices 14e with the high color temperature arranged around the center light-emitting device 14d, an appearance of color unevenness at the light-emitting unit 64 can be avoided.

(37) Providing light-emitting units 64 in a continuous manner, as is the case with the illumination device 10 shown in FIG. 1, can reduce an appearance of color unevenness on an irradiation surface, and can avoid a decrease in light extraction efficiency. In addition, providing the light-emitting units 64 in a continuous manner permits the illumination device 60 to be formed into any shape such as a rectangle, thus facilitating a broader scope of potential applications for the illumination device 60.

(38) Referring now to FIG. 8, in another embodiment an illumination device 70 is provided with a substrate 72 formed into a rectangular shape and a plurality of light emitting devices 14 mounted on the substrate 72.

(39) The plurality of light emitting devices 14 are provided by plurally providing in a continuous manner a light-emitting unit 74 having a plurality of outer light-emitting devices 14e with the high color temperature so arranged as to surround a center light-emitting device 14d. Since the light-emitting unit 74 has the plurality of outer light-emitting devices 14e with the high color temperature arranged around the center light-emitting device 14d, an appearance of color unevenness at the light-emitting unit 74 can be avoided.

(40) Providing this light-emitting unit 74 in a continuous manner, as is the case with the illumination device 10 as shown in FIG. 1, can reduce an appearance of color unevenness on an irradiation surface, and can avoid a decrease in light extraction efficiency. In addition, plurally providing the light-emitting unit 74 in a continuous manner permits the illumination device 70 to be formed into any shape such as a rectangle, thus widening its use.

(41) Note that the illumination devices of the present invention are not limited to the embodiments described above, and thus can be modified or improved when appropriate. For example, the LED 16 that emits blue light is illustrated as a light-emitter, but an LED of a different type can also be used.

(42) Moreover, the phosphor is of a white type including a yellow color, although it is not limited thereto.

(43) As an example of arranging the plurality of light emitting devices 14 with a color temperature varying in a phased manner from the center of the substrate toward an outer circumference thereof, the color temperature is increased in a phased manner, although it is not limited thereto.

(44) Furthermore, the shapes of the substrates 12, 42, 52, 62, and 72, the light emitting devices 14, the LED (light-emitter) 16, the resin case 18, etc. are not limited to those illustrated, and thus can be modified when appropriate.

(45) Thus, although there have been described particular embodiments of the present invention of a new and useful Illumination Device having Multiple LED Elements With Varying Color Temperatures it is not intended that such references be construed as limitations upon the scope of this invention except as set forth in the following claims.