JPH04368914A - Liquid crystal device - Google Patents

Abstract

PURPOSE:To prevent the degradation in a contrast ratio by equaling the ratios of a change in double refractive anisotropy with a temp. change of a liquid crystal panel and a high-polymer phase difference plate. CONSTITUTION:Transparent substrates 11a, 11b consisting of glass, plastic, etc., for crimping liquid crystal molecules are formed with transparent electrode layers 12a, 12b on the front surfaces and are further formed with thin films consisting of polyimide, 'Teflon(R)', etc., by printing, dipping, vapor deposition, etc., and provided with uniaxially oriented film layers 13a, 13b subjected to a rubbing treatment in one direction. The substrates 11a and 11b are so disposed that the oriented film layers thereof face each other. The liquid crystal 14 is crimped in the spacing therebetween. A liquid crystal driving voltage is held impressed to the transparent electrode layers 12a, 12b. The liquid crystal is sealed by sealing agents 15a, 15b. Further, the phase difference plate 16 having the double refractive anisotropy is provided and the ratios of the change in the double refractive anisotropy with the temp. change of the liquid crystal panel and the phase difference plate 16 are equalized.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electro-optical device using liquid crystal used in systems such as computer terminals, image display devices, and shutters.

0002

2. Description of the Related Art Conventionally, as shown in FIG. 5, 51 is a light source;
A known liquid crystal device includes a polarizer 52, a liquid crystal panel 53 to which a liquid crystal drive voltage is applied, a phase correction plate 54, and an analyzer 55. The light from the light source 51 passes through a polarizer 52 and becomes linearly polarized as 56, and is further polarized as 57 due to the birefringence anisotropy of the liquid crystal in the liquid crystal panel 53.
becomes elliptically polarized light. Since this birefringence anisotropy differs depending on the wavelength, the degree of elliptically polarized light that comes out differs, but when the phase correction plate 54 is laminated on the liquid crystal panel, this plays the role of phase compensation and the light of each wavelength returns to almost linearly polarized light 58. . If the analyzer 55 is set perpendicular to the polarization direction, almost no light will pass through it, resulting in a color close to black.

When a voltage is applied to the liquid crystal panel 53, the balance of elliptical polarization compensation is disrupted, so that light that cannot be compensated leaks from the analyzer, thereby producing a display.

0004

[Problems to be Solved by the Invention] However, in a conventionally configured liquid crystal device, the contrast ratio decreases at low temperatures such as 0°C or high temperatures such as 50°C, so it is difficult to use the liquid crystal device. The problem was that the possible temperature range became narrower. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a liquid crystal device whose contrast ratio does not decrease even with temperature changes, in order to solve these conventional problems.

[0005]

[Means for Solving the Problems] In order to solve the above problems, the present invention laminates a liquid crystal panel in which liquid crystal is sandwiched between a pair of transparent substrates and a polymer retardation plate having birefringence anisotropy. In a liquid crystal device including a pair of polarizing plates outside a liquid crystal panel and a retardation plate, the rate of change in birefringence anisotropy of the liquid crystal panel and the polymer retardation plate with respect to temperature change was made equal.

[0006]

[Operation] In the liquid crystal device configured as above,
Since the rate of change in birefringence anisotropy with respect to temperature change of the liquid crystal panel and the retardation plate is equal, phase compensation of the light transmitted through the liquid crystal panel is performed from low to high temperatures, and the light shielding performance of the liquid crystal device does not deteriorate. No reduction in contrast ratio.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. In FIG. 1, reference numerals 11a and 11b are transparent substrates made of glass, plastic, etc. for sandwiching liquid crystal molecules, and transparent electrode layers 12a, 12b are formed on the surface of the substrates, and polyimide, Teflon, etc. are formed by printing, dipping, vapor deposition, etc. Uniaxial alignment film layers 13a and 13b are provided, each having a thin film formed thereon and subjected to a rubbing treatment in one direction. Substrate 11a
and 11b have their alignment film layers facing each other, and a liquid crystal 14 is sandwiched between them. Transparent electrode layers 12a, 12
A liquid crystal driving voltage is applied to b. 15a and 15b are sealants for sealing the liquid crystal. 16 is a retardation plate having birefringence anisotropy, 17a is a polarizer, 17b is an analyzer, and 18 is a light source.

FIG. 2 is a diagram showing the temperature dependence of birefringence anisotropy, where the horizontal axis 21 is temperature in degrees Celsius, and the vertical axis 22 is birefringence anisotropy in nm. 23a shows the temperature dependence of birefringence anisotropy of a liquid crystal panel, 23b and 23c show the temperature dependence of birefringence anisotropy of a retardation plate having birefringence anisotropy, and the materials are polycarbonate and polycarbonate, respectively. It is acrylic. The birefringence anisotropy at 25°C is 8 for the liquid crystal panel.
00 nm, and the retardation plate is 570 nm. The rate of change in birefringence anisotropy with respect to temperature change is -1 nm for liquid crystal panels.
/℃, polycarbonate retardation plate +0.1nm/℃
, the acrylic retardation plate has a temperature of -1 nm/°C, which is the same as that of the liquid crystal panel.

FIG. 3 is a diagram showing the optical axis direction of the liquid crystal device using the retardation plate shown in FIG. 2, where 31a is the rubbing direction on the upper substrate, 31b is the rubbing direction on the lower substrate, and 32
a is the transmission axis direction of the upper polarizing plate, 32b is the transmission axis direction of the lower polarizing plate, and 33 is the maximum refractive index direction of the retardation plate, which is the stretching axis direction when the retardation plate is a uniaxially stretched film. 34 is the twist angle of the liquid crystal molecules, which is 240° in this embodiment. 35 is the angle between the rubbing direction 31a on the upper substrate and the transmission axis direction 32a of the upper polarizing plate, and in this example, 13
0°, 36 is the angle formed between the rubbing direction 31b on the lower substrate and the transmission axis direction 32b of the lower polarizing plate, which is 4 in this example.
5° and 37 are angles formed between the rubbing direction 31a on the upper substrate and the maximum refractive index direction 33 of the retardation plate, which is 80° in this embodiment.

FIG. 4 is a diagram showing the temperature dependence of the contrast ratio, where the horizontal axis 41 is temperature in degrees Celsius, and the vertical axis 42 is the contrast ratio. 43a and 43b indicate the temperature dependence of the contrast ratio when polycarbonate and acrylic retardation plates are laminated on a liquid crystal panel, respectively. Comparing 43a and 43b, at low temperature (0℃) and at high temperature (50℃)
It can be seen that the retardation plate 43b has a better contrast ratio.

By thus equalizing the rate of change in birefringence anisotropy with respect to temperature change between the liquid crystal panel and the retardation plate, it was possible to prevent the contrast ratio from decreasing at low temperatures and at high temperatures. If the rate of change in birefringence anisotropy with respect to temperature change is the same for the liquid crystal panel and the retardation plate, then
Similar effects can be obtained regardless of the material of the retardation plate.

Although the above embodiments show the results when the angle is fixed, the same effect can be obtained even if the angle in FIG. 3 is shifted from -30° to +30°. We also showed the results when the birefringence of the liquid crystal panel and retardation plate was fixed, but -10
Even when changing from 0 nm to +100 nm, the same effect can be obtained if the rate of change in birefringence anisotropy with respect to temperature change is the same.

[0013] In the example, in the case of 240° twist,
Similar effects can be obtained with other twist angles. In the example, the retardation plate was positioned below the upper polarizing plate and above the liquid crystal panel, but even if the retardation plate was positioned above the lower polarizing plate and below the liquid crystal panel, the direction of light traveling could be reversed. If you think about the direction, Figure 3
A similar effect can be obtained by setting the inner optical axis direction in the negative direction.

In the embodiment, as shown in FIG. 1, a light source is placed on the back of the liquid crystal device, but if a reflector is used instead of the light source, it can be used as a reflective liquid crystal display device. .

[0015]

Effects of the Invention As explained above, this invention has a liquid crystal panel in which a liquid crystal is sandwiched between a pair of transparent substrates, and a polymer retardation plate having birefringence anisotropy, which are laminated to form a liquid crystal panel and a retardation plate. In a liquid crystal device equipped with a pair of polarizing plates on the outside of the plate, the liquid crystal panel and polymer retardation plate are configured so that the rate of change in birefringence anisotropy with respect to temperature changes is the same, so that This has the effect of not reducing the contrast ratio.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a cross-sectional structure of a liquid crystal device of the present invention.

FIG. 2 is a diagram showing the temperature dependence of birefringence anisotropy of the liquid crystal device of the present invention.

FIG. 3 is a diagram showing the optical axis direction of the liquid crystal device of the present invention.

FIG. 4 is a diagram showing the temperature dependence of the contrast ratio of the liquid crystal device of the present invention.

FIG. 5 is an explanatory diagram showing a cross-sectional structure of a conventional liquid crystal device.

[Explanation of symbols]

11a, 11b Transparent substrate 12a, 12b Transparent electrode layer 13a, 13b Uniaxial alignment film layer 14 Liquid crystal 15a, 15b Sealant 16 Retardation plate 17a　Polarizer 17b Analyzer 18 Light source

Claims (1)

[Claims] 1. A liquid crystal panel in which a liquid crystal is sandwiched between a pair of transparent substrates and a polymer retardation plate having birefringence anisotropy are laminated, and a pair of polarizing plates is provided outside the liquid crystal panel and the retardation plate. 1. A liquid crystal device comprising: a liquid crystal device characterized in that the rate of change in birefringence anisotropy of the liquid crystal panel and the polymer retardation plate with respect to temperature change is approximately equal.