JPH03263014A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain an excellent display quality by using materials having the same refractive index as liquid crystal as spacer materials for gap adjustment. CONSTITUTION:Spacers having almost the same refractive index as liquid crystal enclosed between a pair of liquid crystal display substrates 11 and 12 facing each other are used as spacers 15 for gap adjustment which uniformly set the gap between liquid crystal display substrates with high precision. Consequently, refraction is suppressed as much as possible even when the back light for liquid crystal display is projected to spacers 15 for the gap adjustment in liquid crystal, and the image induced by the light refraction of spacers 15 is not projected on the display face, and the reflection of external light is prevented. Thus, the contrast is improved and the display quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is configured to seal a liquid crystal between two substrates of a liquid crystal display device with high accuracy in thickness interval.

This invention relates to the structure of a liquid crystal display device by applying gap control spacers.

[Conventional technology]

In a liquid crystal display device in which two substrates each having a pixel electrode are placed facing each other to form a pair, and a predetermined distance is maintained between the substrates and liquid crystal is sealed between the substrates, the distance between the substrates is too thick or uneven. If this occurs, interference lines will occur in the display of the liquid crystal display device, and color tone variations will occur due to single display response characteristics, switching voltage fluctuations, etc., and this is not desirable as a liquid crystal display device. Therefore, in order to improve the characteristics of the liquid crystal display device,
It was necessary to make the spacing between the liquid crystal display substrates thin and uniform with high accuracy.

For this purpose, spherical particles made of plastic, glass, etc. with a diameter of about 5 to 10 μm or
A fiber-shaped gap spacer with a length of about 10 μm and a length of several tens to several hundreds of μm is used.

Related devices of this type include Japanese Unexamined Patent Publication No. 62-1
No. 29819, JP-A-62-129820, JP-A-6
No. 4-91117 and the like.

[Problem to be solved by the invention]

Although the above-mentioned conventional technology sufficiently deals with gap adjustment, no consideration is given to the selection of the material of the spacer, leading to the problem of pixel failure. That is, when a liquid crystal display device assembled using only the conventional technology projects light along a solid line to display an image, the shadow of the gap adjustment spacer is displayed on one screen, making it difficult to see the image quality and lowering the contrast. In particular, in a projection type liquid crystal display device, the spacer is enlarged and projected, making it very noticeable and undesirable.

An object of the present invention is to solve the above-mentioned problems and provide a liquid crystal display device that can obtain excellent display quality by making the shadow of the gap adjustment spacer less noticeable and improving contrast. .

[Means to solve the problem]

In order to achieve the above objective, the refractive index of the spacer is used as a gap adjustment spacer to accurately and uniformly set the distance between the liquid crystal display substrates. The purpose is to use a spacer whose refractive index is approximately the same.

In addition, as a second method to achieve the above purpose,
The goal is to use a spacer with appropriate light transmittance.

In carrying out the present invention, the spacer may be made of spherical or fibrous inorganic or organic materials that are chemically stable with respect to liquid crystals, or composite materials thereof.

[Effect]

According to the above configuration, even if the light from the backlight for the liquid crystal display is projected onto the gap adjustment spacers in the liquid crystal, refraction is suppressed as much as possible, and the refraction of the light is induced by the spacers on the display surface. No image is projected, and reflection of external light can be prevented, improving contrast and display quality.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. still,
These figures are shown schematically to make the present invention easier to understand, and the relationships in shape, size, arrangement, etc. of each component are not limited to the illustrated examples.

FIG. 1 is a sectional view illustrating the structure of a liquid crystal display according to the present invention.

In FIG. 1, 11 indicates a first electrode substrate.

Reference numeral 12 indicates a second electrode substrate disposed opposite to the first electrode plate 11. In both cases, a pattern of a transparent electrode film is formed on a glass plate. Reference numeral 13 denotes a sealing material. Koji uses an ultraviolet curing adhesive, and the sealing material 13 seals the substrate 11 and the substrate 12 in a predetermined area (hereinafter referred to as the sealing part).
Paste it with

14 is a liquid crystal material, and 15 is a spherical gap adjustment spacer for adjusting the gap between both substrates 11 and 12 uniformly and accurately. The features of the present invention are realized by using a material whose refractive index matches the refractive index of the spacer 15 to that of the liquid crystal 14 encapsulating it.

For example, the refractive index of the liquid crystal sealed between both substrates is 1.59.
˜1.61, the features of the present invention can be realized by setting the refractive index of the spacer material to 1.58 to 1.62 accordingly.

Hereinafter, an example of a method for manufacturing a projection type liquid crystal display device will be described in detail in order to determine the assembly process of the present invention.

First, the first electrode substrate 11 is manufactured by the following steps. A dyeing material is applied onto a glass substrate with a thickness of 1.1 m, and patterned according to color through a photolithography process. Then,
After forming the protective film, a pixel electrode is formed and further patterned by photolithography.

ITO (indium oxide transparent electrode) was used as the pixel electrode. Next, an alignment film (polyimide varnish type) was formed on this glass substrate to a thickness of about 1oO by using a spin code.
It was coated so as to have an orientation of 100 nm, and after drying, it was rubbed to give it orientation.

On the other hand, the second electrode substrate 12 was manufactured through a normal semiconductor manufacturing process, particularly a thin film transistor (TPT) manufacturing process. Like the first electrode substrate, the second electrode substrate 12 is a glass substrate having a thickness of 1.1 mm, and thin film transistors are formed in a matrix in the plane of the substrate. Furthermore, the surface of the second electrode substrate was also treated in the same process as for forming the alignment film of the first electrode plate 11, and finally the second electrode substrate 12 was manufactured.

A liquid crystal display device in which a pair of first and second electrode substrates are integrated is manufactured by the following steps.

First, a sealing material 13 containing an ultraviolet curing adhesive as a main component is formed by a printing method on the substrate peripheral area (sealing area) of the surface on which the alignment film is formed of the first electrode substrate 11 (a portion of which is left as a frontage area). On the other hand, a sealing material is similarly formed on the second electrode substrate side so as to face the sealing material 13 formed on the first electrode substrate side. Now, the configuration of the features of the present invention is realized by the following process.

That is, beads as gap adjustment spacers 15 are scattered on the surface of the inner region on which the sealant is not formed, of the second electrode substrate on which the sealant 13 is formed. In this scattering method, beads are dispersed in pure water and dispersed by a spray method. The selection of beads at this time is a key feature of the present invention, and it lies in scattering beads having a refractive index equivalent to the refractive index of the encapsulating liquid crystal, which has been measured in advance. In this example, beads with a refractive index of 1.58 were dispersed while the liquid crystal had a refractive index of 1.60. The composition of the beads is 5iOz
A 42 z○3. zHO, Mg0tC
It contains ab, Bed, ZnO and 5isNa as additives, and is alkali-free glass beads.

By adjusting the amount of additives, the refractive index can be adjusted from 1.44 to 2.2.
5, the light transmittance can be controlled from 2.1 to 78%. The spherical diameter of the beads was 5.5 μm, and the amount of spraying was about 200 beads/approximately.

The first electrode substrate 11 and the second electrode substrate 12 configured in this manner are arranged so that the alignment film and sealant 13 sides face each other. In this state, heat and pressure bonding is performed to temporarily bond the sealing material 13 to form an integral piece.

Thereafter, the liquid crystal to be sealed (in a boat-shaped cup) and the liquid crystal display substrate formed integrally with each other are placed in a vacuum device and the pressure is reduced at the same time. The reduced pressure was about 10-3 Torr. At this time, a vacuum is drawn between the substrates and the substrates try to come into close contact with each other. However, since there are beads 15 scattered between the substrates, the adhesion is hindered, that is, the first electrode substrate 1
The gap between 1 and the second electrode substrate 12 is the bead diameter 5.5.
It is adjusted to about μm. Furthermore, liquid crystal encapsulation is performed by simultaneously placing an opening in a vacuum gap-adjusted substrate that does not form a seal into a liquid crystal.

Immediately after that, by gradually leaking the vacuum inside the vacuum device, the sealant flows between the substrates through the opening of the base. Immediately after the liquid crystal is filled between the substrates, apply adhesive of the same material as the sealing material 13 to the opening, irradiate the entire seal part with an ultraviolet irradiation device, and seal the liquid crystal between the substrates in the same manner as the final bonding. A liquid crystal display device of the present invention is obtained.

The gap size between the first electrode base and the second electrode base of the liquid crystal display device manufactured in this way was 61 mm in the sealing plane.
It was 5.3-0.015 μm in the range of 46 mm.

The effects of the liquid crystal display device manufactured by the method of the present invention as described above were evaluated as follows.

FIG. 2 schematically shows a projection type projection system for evaluating the effects of the present invention. From the left in the figure, light sources 2. Optical system 32 Projection type liquid crystal display substrate manufactured in this example 1. Projection lens 4. It consists of a video screen 5. As a result, the display area of the projection type liquid crystal display substrate 1 is 61 m x 46 cm.
is enlarged to approximately 110cs x 83a++ and projected on the screen 5. With conventional substrates, countless shadows that are not displayed by pixels are projected on the enlarged and projected image on the screen, which is one of the causes of poor image quality.

As already mentioned, this is the shadow of the spacer for gap adjustment. On the other hand, in the projection type liquid crystal display substrate having the structure described in Embodiment 1 of the present invention, this image was hardly seen, and the image quality on the screen was extremely good.

FIG. 3 shows the ratio of the refractive index of the spacer and the liquid crystal, the intensity of light transmitted through the spacer on the screen, especially the outline of the spacer, and the liquid without the spacer. The light intensity ratio is
Measurements were taken for each of the colors red, green, and blue. As a result, the refractive index of the spacer is 0.97 to 1 of that of the liquid crystal.
．． In the range of 12, the light intensity ratio becomes thicker (I'/I
o > 70%) and the variation was small, that is, there was little unevenness.

FIG. 4 shows the light transmittance of the spacer and the light intensity ratio between the spacer part and the part without the spacer and only liquid crystal on the screen. Using backlight illumination of 1051 ux, the light intensity ratio is shown when the liquid crystal is turned on 100% and when it is turned on to 10 N for halftone display. As a result, in the 100% ON state, that is, when the intensity of the projected light is strong, the spacer's light transmittance is 4% or more with less variation, and when the projected light intensity is weak, the spacer's light transmittance is 41% or less. There is less variation, and the shadow of the spacer becomes less noticeable.

In addition, reflection of external light is reduced and contrast is increased. The light transmittance of the spacer may be controlled by coating the surface of the glass beads with a coating material.

In this case, an amorphous Si film is deposited to a thickness of 75 to 220 nm while stirring glass beads using a low pressure CVD method.

〔Effect of the invention〕

According to the present invention, since the shadow caused by the spacer can be made less noticeable, a display device with good image quality can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of the liquid crystal display device of the present invention, FIG. 2 is a configuration diagram of a projection system for evaluating the liquid crystal display device of the present invention, and FIGS. 3 and 4 are refraction of the spacer of the present invention. FIG. 3 is a diagram illustrating variations in ratio, light transmittance, and projected image. DESCRIPTION OF SYMBOLS 1...Liquid crystal display base, 2...Light source, 3...Optical system, 4...Projection lens, and...Video screen, 11...
...First electrode substrate, 12...Second electrode substrate, 13...
- Sealing material, 14... Liquid crystal material, 15... Spacer for gap adjustment.

Claims (1)

[Claims] 1. In a liquid crystal display device in which liquid crystal is sealed between a pair of substrates disposed facing each other via a spacer for adjusting the gap between the substrates and the substrates are bonded together with a sealing material, the spacer material for adjusting the gap is provided. A liquid crystal display device characterized in that a material having a refractive index equivalent to that of the liquid crystal is used as the material. 2. The refractive index of the gap adjustment spacer is 0 of the refractive index of the liquid crystal.
．． 2. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is made of an inorganic material and an organic material in a range of 97 to 1.12 times. 3. In a liquid crystal display device in which liquid crystal is sealed between a pair of substrates disposed facing each other via a spacer for adjusting the gap between the substrates and the substrates are bonded together with a sealing material, the light transmittance of the spacer for adjusting the gap is 4 to 4. 41%. 4. The liquid crystal display device according to claim 1 or 3, characterized in that a spacer is used, which is formed by coating the surface of the base material with a film having an appropriate refractive index and/or light transmittance. LCD display device. 5. The liquid crystal display device according to claim 1 or 3, wherein the liquid crystal display device uses an enlarged image as a projection type of a light transmission type or a light reflection type.