JPS6167830A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To prevent a liquid crystal display element from separation, movement and condensation and to improve its reliability by filling the gap between a pair of plastic substrates with spacers consisting of an organic insulating material and restricting their diameters smaller than the gap so that the specific number of spacers are uniformly dispersed and fixed in orientation films. CONSTITUTION:A pair of plastic substrates 1 on which transparent conductive films and orientation films 5 are laminated respectively are opposed through spacers 6 and a liquid crystal is sealed up within the gap between the substrates 1. The spacers 6 are made of an organic insulating material and restricted at their diameters smaller than the gap so that the spacers 6 are uniformly dispersed and fixed in the orientation films 5 within the range of 10 pieces/mm<2> - 60 pieces/mm<2>. Since the spacers 6 made of the organic insulating material are familiar with the precuser solution of the orientation films 5, they are prevented from separation from the orientation films 5, movement and condensation. Since the diameters of the spacers 6 are smaller than the thickness of the cell, the pressure-reduced status in the element is loosened under high temperature and high humidity and no bubble is generated. Since many spacers are uniformly dispersed and fixed on the orientation films as shown above, the thickness of the cell can be kept uniformly, the orientation films 5 can be prevented from damage and the formation of an induced domain can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a liquid crystal display element using a plastic film as a substrate.

(Prior art) A liquid crystal display element consists of two glass substrates with a transparent conductive film and an alignment film laminated thereon facing each other with a spacer interposed between them, liquid crystal injected into the gap between these glass substrates, and the surrounding area covered with a sealant. In addition to sealing, a polarizing plate is provided on the outside of these glass substrates.

Incidentally, in recent years, liquid crystal display elements have become increasingly lighter, smaller, and thinner, but liquid crystal display elements that use glass as a substrate as described above naturally have limitations due to mechanical strength, manufacturing constraints, etc. There is.

It is not possible to adequately respond to such trends.

Glass also has the disadvantage that it has poor impact resistance, so there is a risk of breakage.

Therefore, Plasti is an alternative to glass.

A liquid crystal display element using a film as a substrate has been proposed. An example is shown in FIG.

A substrate made of a plastic film (hereinafter referred to as a plastic substrate) a, a layer with an anchor on its inner surface, b
, transparent conductive films c, c and alignment films d, d-1)
The periphery of the two plastic substrates a and a is pasted together with a sealing material through a spacer e, and a liquid crystal g is placed between the two plastic substrates a and
is injected.

Furthermore, a gas barrier layer h and polarizing plates i and i are provided on the outer surfaces of the plastic substrates a and a.

(Problems to be Solved by the Invention) However, since plastic substrates have higher flexibility than glass substrates, the following problems arise.

In other words, when two plastic substrates are bonded together via a spacer, even if the gap between the plastic substrates (hereinafter referred to as cell thickness) is uniform, when liquid crystal is injected, the cell thickness will exceed the set value, and the spacer will be scattered. If this happens, the spacers may move or agglomerate in some areas, which is undesirable in terms of display quality. In addition, it is easily affected by external forces2.
For example, when the surface of a liquid crystal display element is rubbed with a knife, in the case of dispersed spacers, the spacers move and agglomerate in some areas. Furthermore, if you rub it strongly with your fingers, there will be areas where the spacers are not distributed, and as a result, the upper and lower plastic substrates will come into contact with each other in those areas, damaging the alignment film provided on the inner surface and disrupting the alignment rules of the liquid crystal.

Furthermore, there is a serious problem that the transparent conductive film is damaged, leading to disconnection.

Attempts have therefore been made to solve the above problem by either stopping the use of spacers or by significantly reducing the amount of spacers used.

However, if no spacer is used at all, it becomes difficult to make the cell thickness uniform, which is not desirable in terms of display quality. In addition, the alignment film may be easily damaged by external force, or the liquid crystal may become stuck during liquid crystal injection. Movement and uniform cell thickness.

There are still problems in terms of damage to the alignment film due to external forces.

Therefore, none of the above methods can be said to be a desirable solution.

Furthermore, in addition to the above-mentioned problems, plastic substrates also have the following problems.

In other words, plastic substrates have significantly higher gas permeability and water vapor permeability than glass substrates, so if a liquid crystal display element is left in a high-temperature, high-humidity atmosphere, the inside of the liquid crystal display element may temporarily expand as the plastic substrate expands. The pressure is reduced, and gas or water vapor in the air permeates through the plastic substrate.

It happens that a 1M product gets into the liquid crystal display element. At this time, there is a problem in that when an external force or thermal shock is applied, gas etc. accumulated in the liquid crystal display element appear as bubbles, and these bubbles have a significant adverse effect on display quality. In order to solve this problem, the above phenomenon is noticeable when the spacer diameter and cell thickness are the same.

It is desirable to make the diameter of the spacer smaller than the cell thickness to ease the depressurized state, but if the diameter of the spacer is made smaller than the cell thickness, in the case of dispersed spacers, the spacer itself will be fixed between the plastic substrates.

The spacer is not retained, and the spacer easily moves and aggregates.

As a result, various problems such as damage to the alignment film as described above occur.

(Means for Solving the Problems) In the liquid crystal display element of the present invention, the spacers are formed from an organic insulating material, and the diameter thereof is smaller than the gap between the plastic substrates. It is uniformly dispersed and fixed in the alignment film.

(effect) This is because the spacer is made of an organic insulating material.

The compatibility between the spacer and the alignment film precursor solution becomes good, and the spacer detaches from the alignment film and moves.

Agglomeration is prevented. Also, by making the diameter of the spacer smaller than the cell thickness.

The reduced pressure inside the liquid crystal display element in a high temperature and high humidity atmosphere is relaxed, and the generation of bubbles is prevented. Also.

By uniformly dispersing and fixing spacers in the alignment film in a range of 10 spacers/mm2 or more and less than 60 spacers/1 m2.

The uniformity of the cell thickness is maintained, the alignment film is prevented from being damaged by external force, and the formation of induced domains is prevented.

(Example) FIG. 1 shows an embodiment of the liquid crystal display element of the present invention.

Plastic substrate 1. A gas barrier layer 2, 2 is provided on the outer surface of (2), while a plastic substrate 1.2 is provided on the inner surface.
Anchor N3 for increasing the adhesion between 1 and the transparent conductive film
, 3 was formed.

As the plastic substrate 1.1, a polyether sulfone film with a thickness of 10011 m expressed by the first-order general formula was used.

Note that the plastic film used for the plastic substrates 1, 1 is not limited to those described above.

For example, polyethylene terephthalate film.

Polycarbonate film, polysulfono film.

Polyetheretherketone films, polyphenoxyether films, polyarylate films, etc. may also be used.

Next, after forming a transparent conductive film on the anchor layer 3.3, a desired snow plowing pattern 4 is formed by etching.
, 4... were formed.

Indium Tin Oxide containing a small amount of tin was used as the transparent conductive film.

Then, into the precursor solution of the organic polymer alignment film.

Spacers 6 made of an organic insulating material were added, stirred, and applied onto the inner surface of the plastic substrate 1.1, followed by firing to form alignment films 5, 5. Here, the diameter of the two spacers 6 is smaller than the gap between the positive substrates 1.1 after the liquid crystal is injected, which will be described later.

As the organic polymer alignment film, a polyimide organic polymer alignment film was used. In addition, as a spacer, polymer beads (manufactured by Sekisui Fine Chemical Co., Ltd., product name "Micro Pearl 5PJ") were used.

The amount added is 111% with respect to the precursor solution of the alignment film.
It was made into the range of °C% - 54%. In addition, the above firing is at 180℃
I went there for an hour.

By the way, by changing the amount of spacers added to the alignment film precursor solution within the above range, the number of spacers 6 to be dispersed and fixed in the alignment film 5 can be changed as shown in Table 1 below. I was able to do that.

In any case of distribution, the spacers 6 are uniformly dispersed and fixed, and even if rubbed strongly several times with cotton cloth, the alignment film 5
It did not fall off, and its adhesion was strong. On the other hand, alumina oxide powder was used for the spacer instead of the polymer beads mentioned above.

It came off easily after rubbing it with a cotton cloth a few times.

This is considered to be due to the difference in adhesion caused by the compatibility between the organic polymer alignment film and the organic insulating material.

Next, after forming the alignment films 5, 5 as described above, an alignment treatment was performed to align the liquid crystal molecules in a certain direction.

After applying the sealant 7 to the inner surface of one plastic substrate and the common transfer material to the inner surface of the other substrate,
These two plastic substrates 1°1 were bonded together.

At this time, the cell thickness between the two plastic substrates 1.1 was the same as the diameter of the spacers 6.

Next, after injecting the liquid crystal 8 between the plastic substrates 1.1, they are sealed with resin, and the plastic substrates 1.1
Polarizing plates 9, 9 were respectively provided on the gas barrier layer 2.2 provided on the outer surface of the liquid crystal display element shown in FIG.

In the manner described above, various liquid crystal display elements with spacer distributions within the ranges shown in Table 1 were produced.

For each, the uniformity of cell thickness, the presence or absence of induced domains, and the presence or absence of damage to the alignment film due to the pressure test were investigated.

The results are shown in Table 1.

As is clear from this table, it is dispersed in the alignment film.

The amount of spacer to be fixed is 10 (11fl/# or more 60
When the range was less than f circle/**2, a liquid crystal display element was obtained that was good in terms of uniformity of cell thickness, presence of induced domains, and presence or absence of damage to the alignment film in the pressure test.

Next, for a liquid crystal display element in which spacers are dispersed and fixed in the alignment film in a range of 40 pieces/J or more 5 (B solid/customer), the spacers have a diameter smaller than the cell thickness.

Acceleration tests were conducted by applying external force and thermal shock to cells with the same diameter as the cell thickness, and the time required for bubble generation was investigated.

The results are shown in Table 2.

When a spacer with a small diameter was used, no air bubbles were generated within the liquid crystal display element. Furthermore, even if the diameter of the spacer was smaller than the cell thickness, there was no movement or aggregation of the spacer because the spacer was firmly fixed and held in the alignment film as described above.

(Effects of the Invention) According to the present invention, it is possible to eliminate separation, movement, and aggregation of spacers, and it is also possible to prevent damage to the alignment film and disconnection of the transparent conductive film due to external force. Furthermore, generation of bubbles in a high temperature and high humidity atmosphere can be prevented, and high quality and high reliability can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the liquid crystal display element of the present invention, and FIG. 2 is a sectional view showing a conventional liquid crystal display element using a plastic film as a substrate. DESCRIPTION OF SYMBOLS 1...Substrate, 5...Alignment film, 6...Spacer 8.
・LCD and 1 other person

Claims (1)

[Claims] 1) A pair of substrates made of a plastic film laminated with a transparent conductive film and an alignment film are placed facing each other with a spacer interposed therebetween,
In a liquid crystal display element in which a liquid crystal is sealed in a gap between these substrates, the spacer is formed of an organic insulating material and has a diameter smaller than the gap between the substrates, not less than 10 pieces/mm^2 and less than 60 pieces/mm^2. A liquid crystal display element characterized in that the range is uniformly dispersed and fixed in the alignment film.