JPS62102225A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To inhibit generation of foams and fuluctuation in company with contraction of a polarizing plate and to permit stable liquid crystal display for a long time by enhancing adhesion of the polarizing plate by interposing a coupling agent between a transparent substrate and the polarizing plate. CONSTITUTION:A polarizing plate 17 is covered on a second principal plane 102, and 112 of a first and second transparent substrate 10, 11 of a liquid crystal display device interposing a coupling agent 16 such as alkylaminosilane, etc. By this constitution, the adhesion of a substrate glass to an adhesive material layer provided on the polarizing plate 17 is enhanced. As the result, generation of foams and fluctuation are prevented even if the polarizing plate 17 is contracted by the change of the environmetal conditions. Accordingly, liquid crystal display of stable quality is permitted for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a liquid crystal display device that displays numbers, characters, etc.

[Technical background of the invention]

FIG. 5 is a diagram showing an example of the structure of a polarizing plate used in a liquid crystal display device. As can be seen from the figure, this polarizing plate consists of two triacetate films (G) and a polyvinyl alcohol film (2) that has been stretched and dyed with iodine etc.
It has a four-layer structure, including a layer of adhesive for adhering to the glass substrate. In most liquid crystal display devices, one or two polarizing plates are provided in a liquid crystal cell, and display is performed using various electro-optic effects using the polarizing plates. Therefore, this polarizing plate attachment process is very important in manufacturing liquid crystal display devices.

Normally, the polarizing plate is attached by cleaning the surface of the assembled liquid crystal cell in which liquid crystal is injected to prevent bubbles, dirt, etc. from entering.

[Problems with background technology]

By the way, polarizing plates, depending on the material they are made of, are subject to elongation or contraction due to changes in the environment such as temperature and humidity. It contracts during change but does not elongate much.

As the polarizing plate shrinks due to environmental changes, bubbles and wavy fluctuations (hereinafter referred to as astigmatism) occur. This is thought to occur because the glass surface is usually a polar surface and has weak adhesion to the polarizing plate glue.

[Purpose of the invention]

The present invention has been made to solve these conventional drawbacks, and aims to provide a liquid crystal display device that can maintain stable quality for a long period of time.

[Summary of the invention]

That is, the present invention is a liquid crystal display device characterized in that a coupling agent is interposed when attaching a polarizing plate to a transparent substrate, thereby improving the adhesion between the polarizing plate and the transparent substrate and improving the adhesive strength of the polarizing plate. Generation of astigmatism and shrinkage bubbles due to shrinkage can be prevented 6 [Embodiments of the Invention] The details of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention. In the figure, a first transparent substrate (10), which is a glass plate, for example, and a second transparent substrate (10), which is a glass plate, for example.
The first main surface (101), (111) of the transparent substrate (11)
On top is a transparent electrode (12) made of, for example, IT○.

(13) is formed. The first and second transparent substrates (10) and (11) have first main surfaces (101) and (111).
) sides facing each other, and a liquid crystal layer (1
4) is held between adhesives (15). Also the first
and the second main surface (10) of the second transparent substrate (10), (11).
2) A polarizing plate (17) is attached to at least one, for example both, of (112) through a coupling agent (16) such as alkylaminosilane.

The coupling agent (16) can be formed by, for example, simply applying a 0.1% alkylaminosilane solution in ethanol with gauze or the like. When using the coating method,
The concentration of alkylaminosilane is insufficient at O and OS%, and at 0.2%, traces of silane will remain, so the appropriate concentration is about 0.1%. After silane coating, a polarizing plate (17) is attached and autoclaved for 20 minutes at a temperature of 60'C and a pressure of 5 kg/a#. Next, heat treatment is performed at a temperature of about 70° C. for 3 hours, and the attachment of the polarizing plate (17) is completed.

Next, changes in the surface state of the first and second transparent substrates (to) and (11) due to the coupling agent (16) will be explained. Figure 2 shows the coupling agent (16).

It is a schematic diagram of glass surface silane treatment when using a silane coupling agent which is an organic silane compound. As can be seen from the figure, the silane coupling agent is hydrolyzed in the presence of water, chemically adsorbed onto the glass surface, and hydrogen-bonded with each adjacent organic silane. When heated, the silane treatment is completed by dehydration polymerization. At this time, the surface of the glass is modified from hydrophilic to hydrophobic (oleophilic). This is due to the alkyl group or alkylamino group coordinating to the silicon atom. The glue on the polarizing plate is mostly organic compounds, which makes it more compatible with the hydrophobic groups on the glass surface, creating a stronger bond with the glass surface.

In fact, in this example, even when subjected to a 240-hour high temperature storage test at 85° C., almost no bubbles or astigmatism occur due to shrinkage of the polarizing plate (17). At this time, the polarizing plate (17) has shrunk by 0.2 to 0.45 an. Furthermore, Figures 3 and 4 show the life time and polarizing plate (17
) is a diagram showing the relationship between shrinkage (vertical or horizontal). As can be seen from these figures, the shrinkage of the polarizing plate (17) becomes almost constant over 24 hours in any of the conditions ① to m, so the generation of bubbles in the polarizing plate (17) occurs within these 24 hours. It turns out. Therefore, if the coupling agent (16) is heat-treated within these 24 hours to improve its adhesion to the glue of the polarizing plate (17), almost no bubbles will be generated. Further, as a result of a peel test, the adhesion strength of the polarizing plate (17) was improved by about 0.11 kg compared to the conventional plate without the coupling agent (16). It was found that when heat treatment was performed, the adhesion strength of the polarizing plate (17) was further improved by about 1.35 times.

Although alkylaminosilane was used as the coupling agent (16) in this example, a chromium complex having a linear alkyl group and a halogenated alkyl group at the terminal may also be used.

〔Effect of the invention〕

As explained above, in the liquid crystal display device of the present invention, since a coupling agent is provided between the transparent substrate and the polarizing plate, the adhesion of the polarizing plate is improved, and bubbles and astigmatism due to shrinkage occur. can be suppressed and high reliability can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a schematic diagram of glass surface silane treatment, FIGS. 3 and 4 are diagrams showing the relationship between life time and shrinkage of a polarizing plate, and FIG. The figure is a diagram showing an example of the structure of a polarizing plate used in a liquid crystal display device. (lO) First transparent substrate (11)...Second transparent substrate (12), (13)...Transparent electrode (14)...Liquid crystal layer (16), coupling agent (17), polarizing plate substitute Person Patent Attorney Noriyuki Ken Yudo Ogo Norio t' Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (3)

[Claims] (1) First and second surfaces with transparent electrodes formed on the first main surface
a transparent substrate, a liquid crystal layer sandwiched between the first and second transparent substrates, and polarized light adhered to at least one of the second main surfaces of the first and second transparent substrates via a coupling agent. A liquid crystal display device characterized by comprising a plate. (2) The liquid crystal display device according to claim 1, wherein the coupling agent is an organic silane compound. (3) The liquid crystal display device according to claim 1, wherein the coupling agent is a chromium complex having a linear alkyl group and a halogenated alkyl group at the end.