JPS62244019A - Liquid crystal electro-optical device - Google Patents

Abstract

PURPOSE:To obtain the titled device which is excellent in its storage effect, steepness and orienting property, and has a high contrast ratio, by placing plural pieces of liquid crystal elements between two pieces of polarizing plates. CONSTITUTION:In a liquid crystal electro-optical device which has placed a liquid crystal element between two pieces of roughly orthogonal polarizing plates, two pieces of liquid crystal elements are superposed so that picture elements of the respective liquid crystal elements are superposed each other. As for a response speed and a threshold characteristic, a storage effect, and an orienting property, thickness (d) of a liquid crystal layer 11 is thinned to about 1mum, and the liquid crystal element of this thickness (d) is superposed by (n) pieces and placed between two pieces of polarizing plates 16. In this way, the screen can be brightened.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a liquid crystal electro-optical device.

[Conventional technology]

In a conventional liquid crystal electro-optical device, only one liquid crystal element is sandwiched between two polarizing plates.

[Problem that the invention seeks to solve]

There are no particular problems when using a twisted nematic type liquid crystal element. However, an attempt was made to use all ferroelectric liquid crystals, which respond in a few microseconds and have steep threshold characteristics and memory effects.

In order to develop the characteristic sound, the thickness t1 of the liquid crystal layer is
It must be made as thin as ~2 μm. However, 2
Intensity of transmitted light when sandwiched between two orthogonal polarizing plates! is s
As the thickness of the liquid crystal layer d'j is proportional to in''(2πd#n/λ), 1 decreases, and when used as a display, the screen becomes dark.On the contrary, d'! !
-As d increases, the threshold characteristics and memory effect worsen, resulting in a decrease in contrast ratio, and the response speed is inversely proportional to the applied electric field, so increasing d will slow down the response unless a higher voltage is applied. There is a problem. It seems that the brightness of the screen can be solved by increasing the birefringence of the liquid crystal, but it is not easy to increase it further than the current situation (<CL2).

Furthermore, it is much more difficult to align a strong fIs-conductive liquid crystal than in the case of a nematic liquid crystal, and the thicker the liquid crystal layer, the worse the alignment becomes. If the orientation deteriorates, light will pass through even in the OFF state, and the memory effect will also deteriorate, resulting in a decrease in contrast ratio.

SUMMARY OF THE INVENTION The object of the present invention is to solve these problems and provide a liquid crystal optical device that responds at high speed, has good orientation of liquid A, has a high contrast ratio, and has a bright display screen.

〔problem? Means to solve]

First, the response speed, threshold characteristics, memory effect, and orientation are ensured by reducing the thickness d of the liquid crystal 1'1# to 1 μmaK. Then, a total of n liquid crystal elements (m
≧2) Stacked and sandwiched between two polarizing plates. To do this (
(Thus, sin" (2πmdTh/λ) becomes larger and the screen can be made brighter. When used as a display device, it is usually necessary to use white light, so that the transmitted light does not have a shadow and is the brightest. The condition is that the retardation is 0.
Since it is about 25 μm in summer, main: [125
m depending on the +fi of the liquid crystal material used so that it becomes μm.
(!: Just choose dk.

〔Example〕

FIG. 1 is a cross-sectional view of a liquid crystal device according to the present invention. show. 11 is a liquid crystal layer, 12 is an alignment control film, 15 is glass!&, i4 is a scanning electrode, 15 is a signal electrode, 16 is an elemental layer, 17 is a spacer, and 18 is a single liquid crystal element. In Figure 1, two liquid crystal sweets (m=2) are laid down so that the pixels of each liquid crystal element overlap.

As a first actual example, Δn=[LCD material of L16? Figure 90 shows the contrast ratio for various liquid crystal layer thicknesses. d) At 1.5 μm, no memory effect is obtained and the contrast ratio is 1, but as the thickness is decreased by 5eL, the contrast ratio increases by lU. Therefore, mdΔnzI
m = 2, d = (L
All liquid crystal electro-optical devices were made with a thickness of 75 μm. m==
When comparing the display characteristics with the case where d=1.5 μm, the contrast ratio was improved from 1.5 to 27, and a good display was obtained. According to the second factor, m ” 1 , d ”:
(The contrast ratio when L is 75 μm is 20, and the liquid crystal;
) does not match the contrast ratio. That is, the transmission source strength factor ON in the ON state is sin'(2πmdAn/λ)
Therefore, by stacking two sheets, the QM increases and the contrast ratio increases.

As a second example, a liquid crystal material with Δn=12 was used. In this case, the contrast ratio was 1 when the liquid crystal layer thickness was 1 μm or more. Therefore, by setting m = 5 and d = α5 μm, a good display with a contrast of 20 can be obtained.

In the third example, a liquid crystal material with Δn=[Li2 was used. In this case, d=2. Although a contrast ratio of 6 was obtained even with Qμm, by setting m=2 and a=1.0μm, the contrast ratio could be increased to t26.

Since the voltage that can be applied to the liquid crystal (liquid crystal) - is limited to approximately 1/2 of the IO breakdown voltage, the applied voltage? It is not possible to increase the response speed any higher than that.

However, in any of the examples, dΔn:(L25
becomes e, a! - applied voltage versus thickness dO, IAn-KO
Then, m = 2 and 5, and the thickness of each liquid crystal element is d.
Since it is set to o/2 or dO/3, the electric field applied to each liquid crystal layer is 2Ko or 3Eo, making the response twice or three times faster.

〔Effect of the invention〕

According to the structure of the present invention, in the conventional technology, one liquid crystal element is sandwiched between two 41J quaternary sheets, but by dividing it into two or more sheets and reducing the thickness of each liquid crystal layer, the memory effect, It is possible to create a liquid crystal electro-optical length ifk with excellent steepness and orientation, a high contrast ratio, a bright display screen, and a fast response. The present invention can be applied to large displays, optical modulators, etc.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the liquid crystal ridge light bank according to the present invention, and FIG.
Does the figure show the dependence of contrast ratio on liquid crystal layer thickness? FIG. 11. Crystal No. 12. Orientation control film 15. Glass base 14. Scan' to E pole 1. Signal electrode 1 & polarizing plate 1Z. Spacer 1a. Crystal element. Above’31 Figure

Claims (2)

[Claims] (1) A liquid crystal electro-optical device in which a liquid crystal element is sandwiched between two substantially orthogonal polarizing plates, characterized in that a plurality of liquid crystal elements are sandwiched between the two polarizing plates. (2) The liquid crystal electro-optical device according to claim 1, wherein the liquid crystal elements are stacked so that the pixels of each of the plurality of liquid crystal elements overlap.