JPS6231824A - Reflecting type liquid crystal displaying element - Google Patents

Abstract

PURPOSE:To eliminate the blur of the projecting image and to enhance the contrast ratio even when the element is used for the reflecting type OHP by enclosing the liquid crystal between substrates to provided with an insulating film and a transparent electrode and forming the reflecting film between one side substrate and the insulating film. CONSTITUTION:On a glass substrate 6, an SiO2 type insulating film 7 and a stripe-shaped transparent electrode 8 are formed, a reflecting film 10 of Al is vapor-deposited between one side substrate 6 and the film 7, a phase change type liquid crystal is enclosed between the substrates and the liquid crystal panel is formed. Even when the panel is sued for the reflecting type OHP, the light path difference of the reflecting light comes to be sufficiently small to the wavelength of the light, the blur of the projecting image to occur at the Fresnel lens part is eliminated, and the displaying with a high contrast ratio can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] A liquid crystal display element having a simple matrix panel configuration and having a reflective film between one glass substrate and an insulating film.

[Industrial application field]

The present invention relates to a reflective liquid crystal display element capable of providing stable display with high contrast.

2. Description of the Related Art Video projectors, overhead projectors (abbreviated as OHP), liquid crystal panels that use a laser writing method, and the like are known as projection displays that enlarge characters, figures, etc. and display them on a screen.

Video projectors are not common because they are expensive, and they also have the disadvantage of having a dark screen.

Further, OHPs are inexpensive and have bright screens, but the display screen is only a hard copy, and it is not possible to display images using a communication system.

In addition, LCD panels that use laser writing method heat the liquid crystal locally by irradiating it with laser light, causing a phase transition and changing the light transmittance, which is then enlarged and projected using a separate light source for projection. be.

However, this method requires a high-power laser light source for writing, and requires an expensive optical system to focus the laser light into a minute spot, making the device large and expensive, making it difficult to use in general. isn't it.

In contrast, the inventors
proposed a projection display using phase-change liquid crystal.

(Patent application 1986-37654 filed February 28, 1985)
(Projection type liquid crystal display device, its method and application) In other words, nematic-cholesteric phase change type liquid crystal display can display a large capacity, and unlike twisted nematic liquid crystal display, it is not necessary to use a polarizing plate, so the screen is bright and It is inexpensive and allows images to be transferred and displayed using a communication system.

The present invention relates to improvements in such phase change type liquid crystal display elements.

[Conventional technology]

The projection type phase change type liquid crystal display method proposed by the inventors uses an existing reflective OHP to enlarge and project a liquid crystal panel onto a screen.

First, consider the case where a transmissive OHP is used, a liquid crystal panel is placed in place of a hard copy, the screen is illuminated by a light source provided in the lower housing, and the screen is enlarged and projected onto the screen through a projector.

Here, a phase change type liquid crystal display performs display by utilizing whether the liquid crystal interposed between transparent matrix electrodes takes a transparent state or a cloudy state, and when the cloudy part is irradiated, light is scattered. It would not reach the screen, so a black and white image would be projected.

However, there is a problem in that the projected image appears gray because the light scattering in the cloudy part is not sufficient and some light is partially transmitted.

Therefore, in order to sufficiently scatter light in the cloudy part, it is necessary to use a reflective OHP.

FIG. 3 shows the cross-sectional structure of the reflective type 0f(P).

That is, among the light projected from the light source 2 of the projector 1, the light projected onto the transparent part of the liquid crystal panel 3 passes through the Fresnel lens 4 provided below, reaches the reflection plate 5, is reflected there, and is reflected again into the liquid crystal panel 3. The light passes through the panel 3 and reaches the projector 1, where it is reflected by a mirror, magnified by a lens, and projected onto a screen.

On the other hand, the light projected onto the cloudy part is scattered by the liquid crystal part and the Fresnel lens 4, and therefore black and white is improved compared to the case where a transmission type OHP is used, but the path difference between the projected light and the reflected light is Since there are 3 to 4 MM, there is a problem that the projected image is blurred, and improvements have been desired.

[Problem that the invention seeks to solve]

As explained above, when projecting an image drawn on a liquid crystal panel onto a screen using a commercially available OHP, reflective OHP
When HP is used, the problem is that the projected image becomes blurred because light scattering occurs between the liquid crystal part and the Fresnel lens part.

[Means for solving problems]

The above problem occurs in liquid crystal display devices that have a simple matrix panel configuration in which two glass substrates equipped with striped transparent electrodes are placed facing each other with an insulating film interposed between them, and a liquid crystal is sealed between them. This problem can be solved by using a reflective liquid crystal display element having a reflective film between it and an insulating film.

[Effect]

When a reflective OHP is used to illuminate a liquid crystal panel containing a phase change liquid crystal, the projected light passes through the liquid crystal layer twice, so there is an advantage that very high contrast can be obtained.

However, when reflective projection is performed using a conventional reflective OHP, there is a problem in that the image on the screen becomes blurred due to the optical path difference between the light reflecting parts.

In order to solve this problem, it is possible to design an optical system to correct the optical path difference, but this not only requires the use of expensive lenses, but also makes it impossible to use existing OHPs as they are.

Therefore, the inventors devised a method of imparting a light reflection function to a liquid crystal panel substrate as a method of performing projection display at low cost while using the existing 0)IP as is.

Conventionally, in 7-segment type liquid crystal displays, reflective electrodes in which the segments of one substrate are made of a material with high reflectivity such as aluminum (AI) have been put into practical use.
In a dot matrix type liquid crystal display, if one of the electrodes is a reflective electrode, the projected light will be reflected by the reflective electrode, resulting in an unclear screen with a striped pattern.

Therefore, the present invention is applied to the lower glass substrate.

A reflective layer is provided by vapor-depositing a material with high reflectance such as chromium (Cr), and a conventional dot matrix diagram is provided thereon. FIG. 2 is a cross-sectional view of a conventional liquid crystal display element.

Here, in the conventional structure, striped transparent electrodes 8 are provided through an insulating film 7 provided on a glass substrate 6, and these transparent electrodes 8 are fixed using spacers 9 so as to be perpendicular to each other with a slight interval between them. , and a nematic-cholesteric liquid crystal is sealed therebetween.

The structure of the liquid crystal display element according to the present invention is the same as the conventional one, except that a reflective film 10 is provided between the lower glass substrate 6 and the insulating film 7.

By doing so, the optical path difference of the reflected light becomes sufficiently small relative to the wavelength of the light, and blurring of the image can be eliminated.

〔Example〕

On a cleaned glass substrate 6 with an area of 60 x 50 nm and a thickness of 3H, At is deposited to a thickness of 3000 nm to form a reflective film 1.
0, and then apply OCD, a silicon dioxide-based coating liquid, on top of this.
(Tokyo Ohka type) was coated to a thickness of approximately 1500 mm using a spin code method to form an insulating film 7.

Next, indium oxide tin oxide (
In203.Sn02 (abbreviated as ITO) was deposited to a thickness of 500 nm, and a conventional photolithography process was performed to form a striped transparent electrode 8.

Further, the same glass substrate 6 was subjected to exactly the same processing except that the reflective film 10 was not attached to form a transparent electrode 8, and a nematic-cholesteric phase change type liquid crystal was sealed thereinto to form a liquid crystal panel.

This was placed on a reflective OHP as shown in FIG. 3 for projection display, and a clear image without blur could be obtained on the screen.

In the example, AI was used as the material for the reflective film 10, but when Cr is used, a somewhat dark background can be created, and when gold (Au) is used, a yellowish background can be created. I can do it.

In addition to SiO□, other highly insulating metal oxides such as SiO or highly transparent organic films can also be used as the material for the insulating layer 7.

〔Effect of the invention〕

As described above, by carrying out the present invention, it is possible to perform projection display with no blur and a high contrast ratio using an existing OHP, thereby increasing the demand for liquid crystal displays.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a liquid crystal display element according to the present invention, FIG. 2 is a cross-sectional view of a conventional liquid crystal display element, and FIG. 3 is a cross-sectional view of a reflective over-seven gutter diector. In the figure, 3 is a liquid crystal panel, 4 is a Fresnel lens, 5 is a reflector, 6 is a glass substrate, 7 is an insulating film,
8 is a transparent electrode, and 10 is a reflective film.

Claims (1)

[Claims] In a liquid crystal display element that has a simple matrix panel configuration in which two glass substrates (6) equipped with striped transparent electrodes (8) are opposed to each other with an insulating film (7) in between, and a liquid crystal is sealed between them, one glass substrate (6) and insulating film (
7) A reflective liquid crystal display element comprising a reflective film (10) between the device and the device.