Optical device and use thereof

Abstract

An optical device and a use thereof are provided. The optical device is capable of suppressing external bubble inflow by eliminating negative pressures that can occur due to shape deformation of a base material in an environment changing between a high temperature and a low temperature and generating a positive pressure. Such optical device can be used as various transmittance-variable devices.

Claims

1. An optical device comprising a first base layer, a liquid crystal layer and a second base layer sequentially and a sealant disposed between the first and the second base layers and the sealant surrounds the liquid crystal layer between the first and the second base layers, wherein at least one of the first base layer or the second base layer is a heat shrinkable base layer, wherein the optical device has a positive pressure higher than an atmospheric pressure therein upon changing a temperature from a high temperature of 90° C. to 100° C. to a low temperature of −30° C. to −40° C., wherein the heat shrinkable base layer is shrinkable in a MD direction and is expandable in a TD direction, wherein a shrinkage rate in the MD direction is in a range of 0.01% or more and 5% or less and an expansion rate in the TD direction is of 0.01 times to 0.5 times, wherein the first and the second base layers are configured to block external bubble inflow.

2. The optical device according to claim 1, wherein each of the first base layer and the second base layer is the heat shrinkable base layer.

3. The optical device according to claim 1, wherein the heat shrinkable base layer has a length change rate (ΔL) of a negative number in the following equation 1: $\begin{array}{cc}\Delta L=\frac{L-L_0}{L_0}\times 100& \left[\mathrm{Equation}1\right]\end{array}$ wherein, L.sub.0 is a length of the base layer in one direction at 25° C. and L is a length of the base layer in the MD direction after heat treatment at a temperature range of 80° C. to 150° C. for a time period of 1 minute to 180 minutes.

4. The optical device according to claim 3, wherein the heat shrinkable base layer has an absolute value of a length change rate of 0.001% or more.

5. The optical device according to claim 3, wherein the heat shrinkable base layer has an absolute value of a length change rate of 5% or less.

6. The optical device according to claim 1, wherein the heat shrinkable base layer is a retardation film having an in-plane retardation value of 3000 nm or more for light having a wavelength of 550 nm.

7. The optical device according to claim 1, wherein the heat shrinkable base layer is a polyethylene terephthalate (PET) film or a triacetyl cellulose (TAC) film.

8. The optical device according to claim 1, further comprising a first electrode layer and a second electrode layer formed on the first base layer and the second base layer, respectively.

9. The optical device according to claim 8, further comprising a first alignment film and a second alignment film formed on the first electrode layer and the second electrode layer, respectively.

10. The optical device according to claim 1, wherein the liquid crystal layer switches between a transparent mode having transmittance of 40% or more and a non-transparent mode having transmittance of less than 40% depending on voltage application.

11. The optical device according to claim 1, wherein the liquid crystal layer comprises a smectic liquid crystal compound, a nematic liquid crystal compound or a cholesteric liquid crystal compound.

12. The optical device according to claim 1, wherein the liquid crystal layer further comprises an anisotropic dye.

13. The optical device according to claim 1, wherein the liquid crystal layer further comprises the sealant on sides thereof.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a diagram illustratively showing an optical device according to one example of the present application.

(2) FIG. 2 is an exemplary diagram for explaining a case where a positive pressure is generated inside an optical device in the present application.

(3) FIG. 3 is an exemplary diagram for explaining a case where a negative pressure is generated inside an optical device in the present application.

(4) FIG. 4 is an image photographing the initial state of the optical device in Example 1 before heat treatment using a digital camera.

(5) FIG. 5 is an image photographing a state of the optical device in Example 1 after repeated heat treatment using a digital camera.

(6) FIG. 6 is an image photographing the initial state of the optical device in Comparative Example 1 before heat treatment using a digital camera.

(7) FIG. 7 is an image photographing a state of the optical device in Comparative Example 1 after repeated heat treatment using a digital camera.

(8) FIG. 8 is an image photographing the initial state of the optical device in Comparative Example 2 before heat treatment using a digital camera.

(9) FIG. 9 is an image photographing a state of the optical device in Comparative Example 2 after repeated heat treatment using a digital camera.

(10) FIG. 10 is a detailed diagram of TMA equipment.

MODE FOR INVENTION

(11) 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.

Measurement Example 1. Shrinkage Rate Measurement of Base Layer after Heat Treatment

(12) For a base layer, a heat shrinkage rate was measured by a method of measuring length changes of a sample that appear while changing a temperature of 5° C. under the conditions of 25° C. to 120° C., using a TMA (thermomechanical analysis) apparatus under the trade name of Q400 manufactured by TA instruments. The heat shrinkage rate is based on length changes of the sample, where in Examples and Comparative Examples, the length change rate means a length change rate measured after being left at 120° C. for 1 hour. The sample of the base layer was prepared so as to have an area of 600 mm×300 mm and a thickness of 80 μm.

(13) Specifically, the length change rate of the sample is measured by a thermal expansion coefficient meter (TMA). The TMA is a measurement method that measures deformation of a sample appearing under a given load as a function of temperature and time when the sample has been heated or cooled to a given temperature condition. As shown in FIG. 7, the force pressing the sample between the quartz stage and the probe, which have little thermal deformation depending on temperatures, is 0.05 N, which is adjustable. While controlling the temperature, the position change of the probe by the sample is measured by the electrical signal of the LVDT. Force application range: 0.001 N to 2 N Temperature range: −150 to 1000° C. Resolution: 15 nm Sensitivity: 20 nm or less

(14) According to the above method, the length change rates of the base layer after heat treatment were measured according to the following equation 1, and the results were shown in Table 1 below.

(15) $\begin{array}{cc}\Delta L=\frac{L-L_0}{L_0}\times 100& \left[\mathrm{Equation}1\right]\end{array}$

(16) In Equation 1 above, L.sub.0 is the length of the base layer in the MD direction at 25° C. and L is the length of the base layer in the MD direction after heat treatment at 120° C. for 1 hour.

Example 1

(17) As each of a first base layer and a second base layer, a heat shrinkable base layer having a length change rate of −0.62% in Evaluation Example 1 was prepared. The heat shrinkable base layer is a PET (polyethylene terephthalate) film (SRF (super retardation film), manufactured by Toyobo) having an in-plane retardation value of 9000 nm for light having a wavelength of 550 nm and a thickness of 80 μm.

(18) ITO (indium-tin-oxide) was deposited on the first base layer and the second base layer to a thickness of 200 nm, respectively, to form first and second electrode layers. A horizontal alignment film (SE-7492, manufactured by Nissan Chemical Co., Ltd.) was coated on the first electrode layer and the second electrode layer to a thickness of 300 μm, respectively, and cured to form first and second alignment films.

(19) An optical device was produced by applying a sealant to the outer periphery of the first alignment film, applying liquid crystals (MDA 14-4145, manufactured by Merck) to the inner area of the sealant and laminating the second alignment film thereto. The produced device has an area of 600 mm×300 mm and a cell gap of 12 μm.

Example 2

(20) An optical device was manufactured in the same manner as in Example 1, except that a TAC film (None, manufactured by FUJI) having a length change ratio of −0.01% in Evaluation Example 1 and a thickness of 80 μm was used as the first base layer and the second base layer, respectively.

Comparative Example 1

(21) An optical device was manufactured in the same manner as in Example 1, except that a PC1 (polycarbonate) film (manufactured by Teigin) having a length change ratio of +0.15% in Evaluation Example 1 and a thickness of 100 μm was used as the first base layer and the second base layer, respectively.

Comparative Example 2

(22) An optical device was manufactured in the same manner as in Example 1, except that a PC2 (polycarbonate) film (manufactured by Keiwa) having a length change ratio of +0.16% in Evaluation Example 1 and a thickness of 100 μm was used as the first base layer and the second base layer, respectively.

Comparative Example 3

(23) An optical device was manufactured in the same manner as in Example 1, except that a COP (cycloolefin copolymer) film (ZF14, manufactured by Zeon) having a length change ratio of +0.11% in Evaluation Example 1 and a thickness of 100 μm was used as the first base layer and the second base layer, respectively.

Evaluation Example 1. Evaluation of High Temperature Durability

(24) The optical devices of Examples and Comparative Examples were each subjected to a cycling test 10 times from a high temperature of 90° C. to a low temperature of −40° C. and then bubble occurrence was observed inside the optical device, and the results were shown in Table 1 below. The bubbles generated inside the optical device could also be observed with naked eyes, and the images photographing them with a digital camera were shown in FIGS. 4 to 9.

(25) As shown in Table 1 below, in the case of Examples 1 and 2 using the heat shrinkable base layer, no bubbles were generated inside the optical device, but in the case of Comparative Examples 1 to 3 using the heat expandable base layer, bubbles were generated inside the optical device.

(26) FIGS. 4 and 5 are images photographing the initial state of Example 1 before heat treatment and the state of Example 1 after 10 times of the cycling test, respectively, with a digital camera. FIGS. 6 and 7 are images photographing the initial state of Comparative Example 1 before heat treatment and the state of Comparative Example 1 after 10 times of the cycling test, respectively, with a digital camera. FIGS. 8 and 9 are images photographing the initial state of Comparative Example 2 before heat treatment and the state of Comparative Example 2 after 10 times of the cycling test, respectively, with a digital camera. As shown in FIGS. 4 and 5, in Example 1, no bubbles were observed with naked eyes even after the cycling test, but as shown in FIGS. 6 to 9, in Comparative Examples 1 and 2, bubbles observed with naked eyes after the cycling test were generated.

(27) TABLE-US-00001 TABLE 1 Example Comparative Example 1 2 1 2 3 Length change rate (%) −0.62 −0.01 0.15 0.16 0.11 Bubble occurrence X X ◯ ◯ ◯ ◯: bubbles were observed with naked eyes; X: bubbles were not observed with naked eyes

(28) <Explanation of Reference Numerals> 10: first base layer 20: liquid crystal layer 30: second base layer 40: sealant 101: load 102: LVDT (linear variable differential transformer) 103: signal related to position 104: thermocouple 105: probe 106: sample 107: furnace