Light Modulation Device

Abstract

The present application relates to a light modulating device and an eyewear. The present application can provide a light modulation device having both excellent mechanical properties and optical properties by applying a polymer film that is also optically anisotropic and mechanically anisotropic to a substrate.

Claims

1. A light modulation device comprising: a first polymer film substrate and a second polymer film substrate disposed opposite to each other and a light modulation film layer having a light modulation layer between the first polymer film substrate and the second polymer film substrate, wherein each of the first polymer film substrate and the second polymer film substrate has an in-plane retardation of 4,000 nm or more for light having a wavelength of 550 nm, wherein each of the first and second polymer film substrates are stretched films, wherein the stretched films having been stretched in a machine direction and in a transverse direction, wherein the machine direction is perpendicular to the transverse direction, wherein the machine direction and the transverse direction are in-plane directions, wherein the first polymer film substrate and the second polymer film substrate are disposed so that an angle formed by the transverse direction of the first polymer film substrate and the transverse direction of the second polymer film substrate is in a range of 0 degrees to 10 degrees.

2. The light modulation device according to claim 1, wherein each of the first polymer substrate and second polymer film substrate is an electrode film substrate in which an electrode layer is formed on one side, and the first polymer substrate and second polymer film substrate are disposed so that the electrode layer of the first polymer substrate and the electrode layer of the second polymer substrate face each other.

3. The light modulation device according to claim 1, wherein the first polymer substrate and second polymer film substrate are polyester film substrates.

4. The light modulation device according to claim 18, E1 in each of the first and second polymer film substrates is 15% or more.

5. The light modulation device according to claim 18, wherein each of the first polymer substrate and the second polymer film substrate is stretched to an elongation (E3) in a third direction, wherein an angle formed with both the machine direction and the transverse direction is within a range of 40 degrees to 50 degrees, wherein the third direction is an in-plane direction, wherein E3 is larger than E1, and wherein a ratio of E3 to E2 is 5 or more.

6. The light modulation device according to claim 1, wherein each of the first polymer substrate and the second polymer film substrate has a ratio (CTE2/CTE1) of a coefficient of thermal expansion (CTE2) in the machine direction to a coefficient of thermal expansion (CTE1) in the first transverse direction of 1.5 or more.

7. The light modulation device according to claim 6, wherein CTE2 is in a range of 5 to 150 ppm/ C.

8. The light modulation device according to claim 1, wherein each of the first polymer substrate and the second polymer film substrate has a ratio (YM1/YM2) of an elastic modulus (YM1) in the transverse direction to an elastic modulus (YM2) in the machine direction of 1.5 or more.

9. The light modulation device according to claim 8, wherein YM1 is in a range of 4 to 10 GPa.

10. The light modulation device according to claim 1, wherein each of the first polymer substrate and second polymer film substrate has a ratio (MS1/MS2) of a maximum stress (MS1) in the transverse direction to a maximum stress (MS2) in the machine direction of 1.5 or more.

11. The light modulation device according to claim 10, wherein MS1 is in a range of 150 to 250 MPa.

12. The light modulation device according to claim 1, further comprising a polarizer disposed on at least one side of the light modulation film layer.

13. The light modulation device according to claim 12, wherein an angle formed by a transmission axis of the polarizer and the transverse direction of the first polymer film substrate and the second polymer film substrate is in a range of 0 degrees to 10 degrees.

14. The light modulation device according to claim 1, comprising two light modulation film layers, wherein an angle formed by the transverse directions of all of the first polymer film substrate and the second polymer film substrate included in each of the light modulation film layers is in a range of 0 degrees to 10 degrees.

15. The light modulation device according to claim 1, wherein the light modulation layer is a liquid crystal layer, an electrochromic material layer, a photochromic material layer or an electrophoretic material layer, a dispersed particle orientation layer or a guest host liquid crystal layer.

16. An eyewear comprising a left eye lens, a right eye lens, and a frame for supporting the left eye lens and the right eye lens, wherein each of the left eye lens and the right eye lens comprises the light modulation device of claim 1.

17. The light modulation device according to claim 12, wherein an angle formed by a transmission axis of the polarizer and the transverse direction of the first polymer film substrate and the second polymer film substrate is in a range of 80 degrees to 100 degrees.

18. The light modulation device according to claim 1, wherein the first and second polymer substrates are stretched in the transverse direction to an elongation (E1) and stretched in the machine direction to an elongation (E2), wherein a ratio of E1 to E2 is 3 or more.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0170] FIGS. 1 to 4 are schematic diagrams of exemplary light modulation devices of the present application.

[0171] FIG. 5 shows light axes of the first and second light modulation layers in a horizontal orientation state.

[0172] FIG. 6 shows pretilt directions of the first to fourth vertical alignment films.

[0173] FIG. 7 illustratively shows eyewear.

[0174] FIGS. 8 and 9 show durability evaluation results for Examples and Comparative Examples.

[0175] FIGS. 10 to 12 are the results of observing appearances of light modulation devices of Examples.

MODE FOR INVENTION

[0176] Hereinafter, the present application will be specifically described by way of Examples, but the scope of the present application is not limited by the following examples.

[0177] The polymer film substrates used in Examples or Comparative Examples are a PC (polycarbonate) film substrate (PC substrate, thickness: 100 m, manufacturer: Teijin, product name: PFC100-D150), which is an isotropic film substrate usually applied as a substrate, and a PET (polyethylene terephthalate) film substrate (SRF substrate, thickness: 80 m, manufacturer: Toyobo, product name: TA044), which is an asymmetric substrate according to the present application, and the following physical properties are the results of measurement in a state where an ITO (indium tin oxide) film having a thickness of about 20 nm is formed on one side of each film substrate.

[0178] 1. Phase Retardation Evaluation of Polymer Film Substrate

[0179] The in-plane retardation value (Rin) of the polymer film substrate was measured for light having a wavelength of 550 nm using a UV/VIS spectroscope 8453 instrument from Agilent Co., Ltd. according to the following method. Two sheets of polarizers were installed in the UV/VIS spectroscope so that their transmission axes were orthogonal to each other, and a polymer film was installed between the two sheets of polarizers so that its slow axis formed 45 degrees with the transmission axes of the two polarizers, respectively, and then the transmittance according to wavelengths was measured. The phase retardation order of each peak is obtained from the transmittance graph according to wavelengths. Specifically, a waveform in the transmittance graph according to wavelengths satisfies Equation A below, and the maximum peak (Tmax) condition in the sine waveform satisfies Equation B below. In the case of max in Equation A, since the T of Equation A and the T of Equation B are the same, the equations are expanded. As the equations are also expanded for n+1, n+2 and n+3, arranged for n and n+1 equations to eliminate R, and arranged for n into n and n+1 equations, the following Equation C is derived. Since n and can be known based on the fact that T of Equation A and T of Equation B are the same, R for each of n, n+1, n+2 and n+3 is obtained. A linear trend line of R values according to wavelengths for 4 points is obtained and the R value for the equation 550 nm is calculated. The function of the linear trend line is Y=ax+b, where a and b are constants. The Y value when 550 nm has been substituted for x of the function is the Rin value for light having a wavelength of 550 nm.

T=sin.sup.2[(2R/)][Equation A]

T=sin.sup.2[((2n+1)/2)][Equation B]

n=(n3n+1)/(2n+1+12n)[Equation C]

[0180] In the above, R denotes in-plane retardation (Rin), denotes a wavelength, and n denotes a nodal degree of a sine waveform.

[0181] 2. Evaluation of Tensile Property and Coefficient of Thermal Expansion of Polymer Film Substrate

[0182] A tensile strength test was conducted according to the standard by applying a force at a tensile speed of 10 mm/min at room temperature (25 C.) using UTM (Universal Testing Machine) equipment (Instron 3342) to measure the elastic modulus (Young's modulus), elongation and maximum stress of the polymer film substrate. In this case, each specimen was prepared by tailoring it to have a width of about 10 mm and a length of about 30 mm, and both ends in the longitudinal direction were each taped by 10 mm and fixed to the equipment, and then the evaluation was performed.

[0183] A length expansion test was conducted according to the standard while elevating the temperature from 40 C. to 80 C. at a rate of 10 C./min using TMA (thermomechanical analysis) equipment (Metteler toledo, SDTA840) to measure the coefficient of thermal expansion. Upon the measurement, the measurement direction length of the specimen was set to 10 mm and the load was set to 0.02 N.

[0184] The evaluation results of physical properties of each film substrate measured in the above manner are shown in Table 1 below.

[0185] In Table 1 below, MD and TD are MD (machine direction) and TD (transverse direction) directions of the PC substrate and the SRF substrate which are stretched films, respectively, and 45 is the direction forming 45 degrees with both the MD and TD directions.

TABLE-US-00001 TABLE 1 Coefficient Elastic Maximum of Thermal Rin modulus Elongation Stress Expansion Direction (nm) (GPa) (%) (MPa) (ppm/ C.) PC MD 12.1 1.6 13.6 63.4 119.19 Substrate TD 1.6 11.6 62.3 127.8 SRF MD 14800 2.5 6.1 81.5 83.3 Substrate 45 15176 3.2 60.4 101.6 52.2 TD 15049 5.8 44.7 184.6 21.6

Example 1

[0186] Two SRF substrates were used to manufacture a light modulation device. An alignment film was formed on an ITO (indium tin oxide) film (electrode layer) of the SRF substrate (width: 15 cm, length: 5 cm) to prepare a first substrate. As the alignment film, one obtained by rubbing a polyimide-based horizontal alignment film (SE-7492, Nissan) having a thickness of 300 nm with a rubbing cloth was used. A second substrate was prepared in the same manner as the first substrate. The first and second substrates were disposed opposite to each other so that their alignment films faced each other, a composition in which a chiral dopant (S811, Merck) was formulated in a concentration of about 0.519 wt % to a GHLC mixture (MDA-16-1235, Merck) comprising a liquid crystal compound having a positive dielectric constant anisotropy with a refractive index anisotropy (N) of 0.13 and a dichroic dye was positioned therebetween, and then the frame was sealed to prepare a light modulation film layer. Here, the TD directions (slow axis directions) of the first and second substrates were each 0 degrees based on the rubbing axis of the first substrate alignment film, and the rubbing directions of the first and second alignment films were 90 degrees to each other. The obtained light modulation layer was an STN mode liquid crystal layer having a twisted angle of about 270 degrees, and the cell gap was 12 m. The light modulation film layer is a device having a linear light transmittance of about 28.0% upon no voltage application and a linear light transmittance of about 62.7% upon applying a voltage of about 15V, which can switch between the transmission and blocking modes. Here, the transmittance is a transmittance for light with a wavelength of about 550 nm as a transmittance using NDH5000SP (manufactured by Secos) equipment.

Comparative Example 1

[0187] A light modulation device was manufactured in the same manner as in Example 1, except that a PC substrate was applied as a substrate.

Test Example 1

[0188] Using the light modulation devices of Example 1 and Comparative Example 1, an eyewear element of the type shown in FIGS. 8 and 9 was manufactured, and a heat shock test was conducted in a state of bending the element. The heat shock test was performed by setting a step of raising the temperature of the eyewear from about 40 C. to 90 C. at a temperature increase rate of about 16.25 C./min and then maintaining it for 10 minutes, and again reducing the temperature from 90 C. to 40 C. at a temperature decrease rate of about 16.25 C./min and then maintaining it for 10 minutes as one cycle and repeating the cycle 500 times, where this test was conducted with the eyewear attached to a bending jig having a curvature radius of about 100R. FIG. 8 showed the case of Example 1 and FIG. 9 showed the case of Comparative Example 1, where in the case of Comparative Example 1, severe cracks were observed as in the drawing.

Comparative Example 2

[0189] A light modulation film layer was manufactured in the same manner as in Example 1, except that the first directions (TD directions) of the first and second substrates were set to 90 degrees to each other. At this time, based on the rubbing direction of the alignment film on the first substrate, the first direction of the first substrate was 0 degrees and the first direction of the second substrate was 90 degrees.

Comparative Example 3

[0190] A light modulation film layer was manufactured in the same manner as in Example 1, except that the first directions (TD directions) of the first and second substrates were set to 90 degrees to each other. At this time, based on the rubbing direction of the alignment film on the first substrate, the first direction of the first substrate was 45 degrees and the first direction of the second substrate was 135 degrees.

Test Example 2

[0191] The void generation was evaluated while the devices of Example 1, Comparative Examples 2 and 3 were each stored at 60 C. and 85% relative humidity, and the results were shown in Table 2 below. Specifically, it was evaluated whether or not the visually observed voids occurred in the light modulation layer while being kept under the above conditions. Generally, the size of the visually observed voids is about 10 m.

TABLE-US-00002 TABLE 2 First Number of occur- samples Number of Number of rence initially bad void good void Void time of introduced samples samples incidence void Compar- 2 12 12 0 100% 120 h ative 3 12 12 0 100% 144 h Example 1 12 1 11 8% 504 h

[0192] As results of Table 2, in the case of Comparative Examples 2 and 3, voids were observed within 500 hours in all of the initially introduced samples to show the void incidence of 100%, and the times when the voids were first observed were also within 120 hours and 144 hours, respectively.

[0193] On the other hand, in the case of Example 1, voids were not observed within 500 hours, and the time when the voids were first observed was also about 504 hours.

Example 2

[0194] A light modulation device having the structure of FIG. 4 was produced. As the first to fourth polymer film substrates (31, 33, 34, 36), the SRF substrate was used. A vertical alignment film (PVM-11 polyimide layer from HANCHEM, Co. Ltd.) was formed on the ITO film of the SRF substrate, and a guest host liquid crystal layer comprising liquid crystals and dichroic dyes was prepared as the light modulation layer, where HNG730200 (ne: 1.551, no: 1.476, //: 9.6, : 9.6, TNI:100, n: 0.075, : 5.7) from HCCH was prepared as the liquid crystal and X12 from BASF was prepared as the dichroic dye.

[0195] The vertical alignment film was coated on the ITO layer of the polymer film substrate by bar coating and then baked at 120 C. for 1 hour to obtain an alignment film having a thickness of 300 nm. The alignment film was rubbed with a rubbing cloth to produce a first polymer film substrate. Subsequently, column spacers having a height of 10 m and a diameter of 15 m were arranged at intervals of 250 m on the ITO layer of the same polymer film substrate as above, and a vertical alignment film was coated on the ITO film by bar coating and rubbed to produce a second polymer film substrate. 28 mg of the dichroic dye was dissolved in 2 g of the liquid crystal, and the suspension was removed with a syringe filter made of 0.2 m PP (polypropylene). A sealant was drawn on the edge of the alignment film surface of the second polymer film substrate with a seal dispenser. After the liquid crystal-dye mixed liquid was sprayed on the alignment film of the second polymer film substrate, a first light modulation layer was formed and the first polymer film substrate was covered and laminated to produce a first light modulation layer. At this time, the lamination was subjected so that the first directions (TD directions, slow axis directions) of the first and second substrates were parallel to each other and the rubbing directions of the alignment films of the first substrate and the second substrate were 180 degrees to each other. The third polymer film substrate (34), the fourth polymer film substrate (36) and the second light modulation layer (35) of FIG. 4 were formed in the same manner to produce a second light modulation film layer. Subsequently, the light modulation device of Example 2 was produced by attaching the first light modulation film layer and the second light modulation film layer so that the rubbing directions of their alignment films were orthogonal to each other at 90 degrees.

[0196] The thickness (cell gap) of each of the first and second light modulation layers (32, 35) is 12 m. In the produced light modulation device, when the direction (TD direction, slow axis direction) of the first substrate is 0 degrees, the first directions (TD directions, slow axis directions) of the second to fourth substrates are also 0 degrees, the light axis of the first light modulation layer upon horizontal orientation is 0 degrees, and the light axis of the second light modulation layer upon horizontal orientation is 90 degrees.

Example 3

[0197] A light modulation device was produced in the same manner as in Example 1, except that the substrates were disposed so that in Example 2, the first directions (TD directions, slow axis directions) of the second and third substrates were 90 degrees when the first direction (TD direction, slow axis direction) of the first substrate was 0 degrees.

Example 4

[0198] A light modulation device was produced in the same manner as in Example 1, except that in Example 2, the light axis of the first light modulation layer upon horizontal orientation was changed to be +45 degrees and the light axis of the second light modulation layer upon horizontal orientation was changed to be 45 degrees.

Test Example 3

[0199] For the devices of Examples 2 to 4, rainbow characteristics at the front (tilt angle of 0 degrees) and viewing angle (tilt angle of 23 degrees), and electro-optical characteristics were evaluated, and the results were shown in the drawings and the following Table 3.

[0200] FIGS. 10 to 11 are each the results of observing the rainbow characteristics at the tilt angles for Examples 2 to 4, and even when a plurality of light modulation film layers were overlapped as shown in the drawing, optical defects such as a rainbow phenomenon did not occur.

[0201] The electro-optical characteristics were evaluated by placing the light modulation device on the backlight after connecting the electrode layers of the first and third polymer film substrates among the electrode layers of the first to fourth polymer film substrates of the light modulation device to one terminal and connecting the electrode layers of the second and third polymer film substrates to one terminal, connecting the two electrode terminals to the terminals of the function generator, and measuring luminance values with photodiode while applying the voltage from 0 Vrms to 28 Vrms to measure the transmittance. The initial luminance value of the backlight was measured and converted to a percentage to record the transmittance value.

[0202] The contrast ratio (CR) is a ratio (Tc/T) of the transmittance (Tc) in a state of no voltage application to the transmittance (T) upon applying a voltage of 28V. dC* is a color difference for values of color coordinates a and b when measuring an actual sample based on color coordinates (a, b)=(0, 0) of the D65 light source upon using Lab color coordinates, and means a color difference index converted by Equation SQRT (a{circumflex over ()}+b{circumflex over ()}2).

TABLE-US-00003 TABLE 3 Example 1 Example 2 Example 3 Rainbow No No No Transmittance (0 V) 44.4% 44.3% 45.6% Transmittance (28 V) 2.42% 2.17% 12.44% CR 19.3:1 20.4:1 3.7:1 dC* 13.8 14.3 8.3