Light modulation device

Abstract

The present application relates to a light modulation device and a use thereof. 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 second polymer film substrate disposed opposite to each other, and an active liquid crystal film layer having an active liquid crystal layer which is disposed between the first polymer film substrate and the second polymer film substrate, wherein the active liquid crystal film layer contains a liquid crystal host and a dichroic dye guest, wherein the active liquid crystal layer is configured to switch between a horizontal orientation state and a vertical orientation state, 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, each of the polymer film substrates has a ratio (E1/E2) of an elongation (E1) in a first direction to an elongation (E2) in a second direction perpendicular to the first direction of 3 or more, and the first polymer film substrate and the second polymer film substrate are disposed so that an angle formed by the first direction of the first polymer film substrate and the first 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 film 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 film substrate and second polymer film substrate are disposed so that the electrode layers of the first polymer film substrate and the electrode layer of the second polymer film substrate face each other.

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

4. The light modulation device according to claim 1, wherein each of the first polymer film substrate and second polymer film substrate has the elongation (E1) in the first direction of 20% or more.

5. The light modulation device according to claim 1, wherein each of the first polymer film substrate and second polymer film substrate has an elongation (E3) in a third direction, wherein an angle formed with both the first and second directions is in a range of 40 degrees to 50 degrees, the elongation (E3) in a third direction is larger than the elongation (E1) in the first direction, and a ratio (E3/E2) of the elongation (E3) in the third direction to the elongation (E2) in the second direction is 5 or more.

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

7. The light modulation device according to claim 6, wherein the coefficient of thermal expansion (CTE2) in the second direction is in a range of 50 to 100 ppm/ C.

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

9. The light modulation device according to claim 8, wherein the elastic modulus (YM1) in the first direction is in a range of 2 to 10 GPa.

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

11. The light modulation device according to claim 10, wherein the maximum stress (MS1) in the first direction is in a range of 150 to 250 MPa.

12. 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 the left eye lens and the right eye lens each comprise the light modulation device of claim 1.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic diagram of an exemplary light modulation device of the present application.

(2) FIG. 2 illustratively shows eyewear.

(3) FIGS. 3 and 4 show durability evaluation results for Examples and Comparative Examples.

MODE FOR INVENTION

(4) 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.

(5) 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.

(6) 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.

(7) 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.

(8) 1. Phase Retardation Evaluation of Polymer Film Substrate

(9) 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]

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

(11) 2. Evaluation of Tensile Property and Coefficient of Thermal Expansion of Polymer Film Substrate

(12) 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.

(13) 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.

(14) The evaluation results of physical properties of each film substrate measured in the above manner are shown in Table 1 below.

(15) 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.

(16) TABLE-US-00001 TABLE 1 Coefficient Elastic Maximum of Thermal Rin modulus Stress Expansion Direction (nm) (GPa) Elongation (%) (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

(17) Two SRF substrates were used to manufacture a light modulation device. An alignment film was formed on an ITO (indium tin oxide) 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 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 device. 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 horizontal to each other, but were anti-horizontal, that is, the rubbing direction of the first alignment film and the rubbing direction of the second alignment film were opposite to each other. The obtained light modulation layer was a guest host liquid crystal layer in an ECB (electrically controllable birefringence) mode, and the cell gap was 12 m.

Comparative Example 1

(18) 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

(19) Using the light modulation devices of Example 1 and Comparative Example 1, an eyewear element of the type shown in FIGS. 3 and 4 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. 3 showed the case of Example 1 and FIG. 4 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

(20) A light modulation device 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

(21) A light modulation device 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

(22) 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.

(23) TABLE-US-00002 TABLE 2 Number of Number of Number of First samples initially bad void good void Void occurrence introduced samples samples incidence time of void Comparative 2 12 12 0 100% 120 h Example 3 12 12 0 100% 144 h Example 1 12 1 11 8% 504 h

(24) 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.

(25) 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.

Test Example 3

(26) An electro-optical characteristic and occurrence of a rainbow phenomenon were evaluated for the light modulation device produced in Example 1. The electro-optical characteristic was evaluated for the light modulation device by measuring a change in transmittance depending on whether or not a voltage was applied. Specifically, the transmittance according to the applied voltage was measured using a haze meter (NDH5000SP, Secos) while an AC power was connected to the electrode layers of the electrode film substrates and driven. The transmittance is average transmittance for light having a wavelength of 380 nm to 780 nm.

(27) The evaluation of the rainbow phenomenon is a cognitive evaluation, and it has been evaluated that the rainbow phenomenon occurs when two or more patterns representing different luminance rather than the same luminance in the sample are generated.

(28) As a result of the evaluation, no rainbow phenomenon was observed in the samples of Example 1, and it was confirmed that the transmittance upon no voltage application was about 33.6% and the transmittance upon voltage application (15V) was about 62.6%.