JPH01265228A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To realize the extremely bright liquid crystal display element by providing a specific optical function layer consisting of three layers on a light- incidence side transparent substrate. CONSTITUTION:On one of a couple of transparent substrates, i.e. 109, the optical function layers consisting of three layers or a birefringent layer 102, a microlens layer 105, and a lambda/2 phase difference layer 107 is provided from the incidence side of light. The incident light is separated by the birefringent layer 102 into an ordinary light beam 103 and an extraordinary light beam 104, which are converged by the microlens layer 105 so that both light beams are put one over the other spatially. Then either of the ordinary light beam 103 and extraordinary light beam 104 is rotated by the lambda/2 phase difference layer 107 to the plane of polarization of the other and then the incident light beam is converted into luminous flux which has a specific polarizing direction without being absorbed, so an extremely bright display which is essentially free from light absorption is made.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a liquid crystal display element.

[Conventional technology]

FIG. 2 shows the structure of a twisted nematic (TN) type liquid crystal display element, which is a typical example of a liquid crystal display element. Two polarizers are placed before and after a liquid crystal cell, which is made up of a liquid crystal cell held between a pair of transparent substrates having transparent electrode coatings, so that their polarization directions differ by 90@ from each other. A polarizer aligns the polarization direction of incident light, and has the function of selectively transmitting only light with a specific polarization component. Liquid crystals have the effect of rotating the plane of polarization of light passing through the liquid crystal layer depending on how the liquid crystal molecules are arranged, so by combining two polarizers and a liquid crystal layer, the amount of transmitted light can be controlled. For more information about liquid crystal display elements, see, for example, "Fundamentals and Applications of Liquid Crystal Electronics" edited by Sasaki, Ohmsha (1993).
79).

[The problem that the invention attempts to solve]

However, sheet polarizers used in conventional liquid crystal display devices are made by uniaxially stretching and aligning organic polymer materials, so they are easy to mass produce and are inexpensive. As a result, the polarizer itself absorbs a portion of the incident light, resulting in poor light transmittance.Furthermore, the polarizer itself may be thermally destroyed due to the heat generation effect associated with light absorption when exposed to strong light. There were some problems. SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and its purpose is to provide a bright liquid crystal display element that essentially does not absorb light and has high light transmittance.

[Means to solve the problem]

In order to solve the above problems, the liquid crystal display element of the present invention is a liquid crystal display element that holds a liquid crystal between a pair of transparent substrates and displays image information by controlling the amount of light transmitted through the electro-optic effect of the liquid crystal. , on one of the transparent substrates located on the light incident side, there is a layer that separates the incident light beam into two linearly polarized light components whose polarization planes are orthogonal to each other, and a layer that spatially separates the two separated linearly polarized light components. It is characterized by forming a layer that focuses light at different positions and a layer that rotates the plane of polarization of one linearly polarized light component obtained by the light focusing means.

[Effect]

When natural light emitted from a normal light source is incident on an optically anisotropic medium such as calcite or a uniaxially oriented polymer, two light beams (
It is separated into ordinary light and extraordinary light). This phenomenon occurs because the refractive power of the medium is different between the two beam axes.

FIG. 1 is a cross-sectional view of the structure of a liquid crystal display element according to the present invention, and the present invention will be explained in detail based on FIG. In a conventional liquid crystal display element, an optically functional layer consisting of three layers is formed on a transparent substrate located at a position where a polarizer is placed, that is, located on the light source side.

First, a birefringent layer (102
), the incident light is divided into an ordinary ray (103) and an extraordinary ray (
104) and are focused using lenses (105) at different positions so that the two light beams do not spatially overlap. Next, by rotating the plane of polarization of either the ordinary ray or the extraordinary ray (extraordinary ray in Figure 1) and aligning it with the plane of polarization of the other (ordinary ray in Figure 1), the incident ray will be absorbed. All of the light is converted into a light beam having a specific polarization direction (the vibration direction in FIG. 1 is the same as that of ordinary light), and reaches the transparent aperture of the liquid crystal display element.

Therefore, by configuring a polarizer similar to the conventional one on the side of the liquid crystal display element that does not face the light source, it can have the same display function as a normal liquid crystal display element, and also improve the efficiency of light use because there is no light absorption. This results in an expensive, or extremely bright, liquid crystal display element.

〔Example〕

Hereinafter, the present invention will be explained in detail based on Examples.

However, the present invention is not limited to the following examples.

[Example 1] FIG. 1 is a cross-sectional view of the structure of a TN type liquid crystal display element. A ^/2 retardation layer (107) was formed on the first substrate (109) of a pair of transparent glass substrates on which a transparent common electrode i (110) was formed, with a spacer interposed therebetween.

This retardation layer has a striped retardation shoulder part (107) with a width of 100 μm and an air layer part (107) with a width of 100 μm.
106) are arranged alternately.

A transparent glass plate is placed on top of it as a spacer, and the width is 20mm.
A microlens layer (105) consisting of lenticular lenses with a pitch of 0 μm and a pitch of 200 μm was formed. At this time, the optical axis of the microlens was positioned on the boundary between the phase difference shoulder and the air layer.

For this microlens layer, a methacrylate negative resist was spin-coded on a glass plate, exposed and developed using photolithography, and the negative resist was over-etched to form a lenticular lens array. Furthermore, a birefringent layer (102) was formed thereon via a spacer. The birefringent layer was obtained by unidirectionally stretching a sheet-like polyimide polymer material and then press-molding it.

Here, the ordinary ray (103) and the extraordinary ray (104) separated by the birefringent layer were aligned using the aforementioned microlens so that they were focused on the phase base layer and the air layer, respectively. In the configuration of this embodiment, a microlens layer (108) is formed on the first transparent glass substrate, and this lens is provided to effectively guide light to the liquid crystal layer. It's a thing, but it's not necessarily a necessity. Unlike conventional polarizing plates that utilize dichroism of light absorption, the polarizing element obtained with the above configuration is capable of aligning the plane of polarization in a fixed direction without essentially absorbing light at all.

Then, a liquid crystal cell was assembled between the above substrate and a second transparent glass substrate (112) via a spacer and a gap material so that the common electrodes were perpendicular to each other, and liquid crystal was sealed. Then the first
A conventional polarizing plate (1
13) was placed.

The brightness of the TN liquid crystal display element equipped with the polarizing element obtained with the above structure was approximately twice as high as that of the conventional one. In addition, even if the intensity of the incident light is significantly increased, the polarizing element formed on the first substrate does not have a light absorption effect, so it has been confirmed that it does not cause thermal damage and functions stably for a long time. Ta.

[Example 2] FIG. 2 is a cross-sectional view of the structure of a TPT liquid crystal display element. A polysilicon thin film transistor (T
PT) (203) was formed into a matrix. On the other hand, a polarizing element and a transparent common electrode were formed on the counter substrate (2Q1) by the same means as in Example 1 above. Then, a liquid crystal cell was assembled using the above-mentioned pair of substrates via a spacer and a gap material, and liquid crystal was sealed therein. Furthermore, as in Example 1, a conventional polarizing plate (113) was placed on the back surface of the quartz substrate to form a TPT liquid crystal display element.

In the present TPT liquid crystal display element, a significant improvement in brightness was confirmed as in the case of the above-mentioned TN type liquid crystal display element.

Since TPT liquid crystal display elements can finely control the amount of transmitted light in multiple stages, they are used in liquid crystal televisions, liquid crystal projectors, etc., and their applications are rapidly expanding in the fields of video and image processing.

Furthermore, a liquid crystal display element using a metal-insulator-metal structure diode element (MIM) as a switching element for liquid crystal control has been developed, and this MIM liquid crystal display element also uses the polarized light of the present invention. It is possible to significantly improve the brightness of the display element by incorporating the display element.

〔Effect of the invention〕

As explained above, in the liquid crystal display element of the present invention, instead of the conventional polarizing plate placed on the light incidence side of the liquid crystal display element, the incident light is placed on one of the transparent substrates located on the light incidence side. A layer that separates light into two linearly polarized light components whose planes of polarization are orthogonal to each other, a layer that focuses the two separated linearly polarized light components at spatially different positions, and a layer that is obtained by the light focusing means. By configuring a layer that rotates the polarization plane of the linearly polarized light component, light absorption is essentially very low, and the polarization direction of all light is aligned in one direction, and the liquid crystal pixel area is Therefore, it is possible to create an extremely bright liquid crystal display element that has never been seen before. Furthermore, since a conventional polarizing plate is not used on the light incident side of the liquid crystal display element, even when strong light is incident, the liquid crystal display element functions stably for a long time without causing self-destruction due to heat generation. Liquid crystal display elements are widely used due to their low voltage drive and low power consumption, but one of their drawbacks is that they have low light utilization efficiency and dark display surfaces because they transmit information by controlling polarization components. there were. However, compared to the conventional liquid crystal display element, the liquid crystal display element of the present invention has
The brightness on the display surface is approximately doubled, making it an extremely bright display element. Therefore, it can be said that it is an optimal liquid crystal display element for liquid crystal televisions, liquid crystal glow projectors, and the like.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the structure of a TN type liquid crystal display element of the present invention. FIG. 2 is a cross-sectional view of the structure of the TFT type liquid crystal display element of the present invention. 101... Incident light 102... Birefringent layer 103... Ordinary ray 104... Extraordinary ray 105... Microlens layer 106... Air layer portion 107... Phase base layer portion 108... Microlens layer 109...First transparent glass substrate 110...Common electrode 111...Liquid crystal layer portion 112...Second transparent glass substrate 113...Polarizing plate 114...Emitted light 115...・Polarization direction of light passing through the λ/2 retardation layer (
116...Polarization direction of the polarizing plate 113 (perpendicular to the page) 201...Counter substrate 20.2...Pixel electrode 203...TFT element 204...Quartz substrate or above Applicant: Seiko Epson Co., Ltd. Agent Patent Attorney Kizobe Suzuki (1 person) 0no01 Figure 1 0ν101 Figure 2

Claims (1)

[Claims] In a liquid crystal display element that displays image information by holding a liquid crystal between a pair of transparent substrates and controlling the amount of light transmission through the electro-optical effect of the liquid crystal, one of the transparent substrates located on the light incident side is , a layer that separates an incident light beam into two linearly polarized light components whose polarization planes are orthogonal to each other, a layer that focuses the two separated linearly polarized light components at spatially different positions, and a means for focusing the light. A liquid crystal display element comprising a layer that rotates the plane of polarization of one of the obtained linearly polarized light components.