JPH0327094B2 - - Google Patents

Description

[Detailed description of the invention]

<Technical Field> The present invention relates to a liquid crystal display element in which a base film is formed on a plastic film. <Prior art> Generally, a liquid crystal display element has a structure as shown in Fig. 1.
Transparent electrodes 2, 2 made of tin oxide, indium oxide, etc. are formed on the inner surfaces of a pair of opposing glass substrates 1, 1.
Then, alignment films 3, 3 made of metal oxide films or organic polymer films are layered, respectively, and these glass substrates 1, 1 are layered.
A liquid crystal 5 is disposed in between, and its peripheral portion is sealed with a sealing material 6, and furthermore, polarizing plates 7, 7 are disposed on the outer surfaces of the glass substrates 1, 1. On the other hand, as shown in FIG. 2, there is a liquid crystal display device that uses substrates 11, 11 made of plastic film instead of the glass substrates 1, 1. In this liquid crystal display device, the plastic film substrates 11, 11 themselves are inferior to the glass substrates 1, 1 in terms of moisture resistance, heat resistance, light exposure, liquid crystal resistance, solvent resistance, and scratch resistance. Since the adhesiveness and adhesion with other materials are poor, the constituent materials of the liquid crystal display element using the plastic film substrate 11 are often different from those of the liquid crystal display element using the glass substrate 1. However, as shown in FIG. 2, a liquid crystal display element using a plastic film substrate 11 is equipped with a transparent conductive film 2, an alignment film 3, a liquid crystal 5, a sealing material 6, and a polarizing plate 7. There is basically no difference from the previous liquid crystal display element. However, in a liquid crystal display device using a plastic film substrate 11, a base film 12 is usually provided on the plastic film substrate 11. This is because the plastic film substrate 11 has scratch resistance, solvent resistance,
This improves liquid crystal resistance and moisture resistance, and also improves adhesion to the transparent conductive film 2 formed on the plastic film substrate 11. This base film 1
The general requirement 2 is that the film be a hard film in order to particularly improve the scratch resistance of the plastic film substrate 11 and the adhesion with the transparent conductive film 2. As a general hard film, a silicone film formed by applying a silicone-based hard coating agent is often used, but with the exception of some base materials such as polycarbonate and acrylic, this silicone film is The adhesion to the base material is weak, and the adhesion is usually improved by roughening the surface of the base material using a substrate surface treatment agent called a primer or by creating a coupling effect. However, even if the adhesion is improved using a primer, the adhesion is weak to many plastic film substrates 11, 11 made of, for example, epoxy, polyethylene terephthalate, polyether sulfon, etc. If the plastic film substrates 11, 11 were left in a high temperature and high humidity atmosphere, the silicone film would peel off, making them unsuitable for practical use as liquid crystal display elements. Therefore, in order to ensure adhesion that can withstand practical use as a base film for liquid crystal display elements having plastic film substrates and hardness suitable for forming transparent conductive films, the present inventor developed two types of resins each having their own characteristics. We proposed a mixture of them to compensate for each other's shortcomings. That is, a polymer blend obtained by mixing a melamine resin and a silicone resin is used as a base film of a liquid crystal display element having a plastic film substrate. This improves the adhesion between the plastic film substrate and the underlying film.
Furthermore, the scratch resistance, solvent resistance, liquid crystal resistance, and moisture resistance of the plastic film substrate were also improved. Furthermore, since it was a hard film, it was possible to easily form a transparent conductive film on the base film and improve its adhesion. However, when a plastic film substrate on which a transparent conductive film is formed is left in a high-temperature, high-humidity atmosphere, the base film sometimes whitens or cracks. Moreover, this phenomenon was similarly observed when a liquid crystal display element of a plastic film having this base film was left in a high-temperature, high-humidity atmosphere. As a result, even if the lighting was good initially, after being left in a high temperature, high humidity atmosphere, a portion of the transparent conductive film would break, causing serious problems in terms of quality as a liquid crystal display element. <Object of the Invention> Therefore, the object of the present invention is to improve the adhesion between the plastic film substrate and the base film, improve the scratch resistance, solvent resistance, liquid crystal resistance, and moisture resistance of the plastic film substrate itself, and An object of the present invention is to provide a liquid crystal display element that can improve adhesion to a transparent conductive film formed on a base film, and can prevent whitening and disconnection of the transparent conductive film in a high temperature and high humidity atmosphere. <Configuration of the invention> In order to achieve the above object, the configuration of this invention is as follows:
In a liquid crystal display device in which a base film made of a polymer blend obtained by mixing a melamine resin and a silicone resin is formed on a plastic film substrate, the nonvolatile solid content of the silicone resin is reduced to one half of the nonvolatile solid content of the melamine resin. It is characterized by the following. <Effects of the Invention> According to the present invention, it is possible to improve the adhesion between the plastic film substrate and the base film, the scratch resistance, solvent resistance, liquid crystal resistance, and moisture resistance of the plastic film itself, and also to improve the adhesion between the plastic film substrate and the base film. It is possible to obtain a high-quality liquid crystal display element that has good adhesion to the base film and can prevent whitening of the base film and disconnection of the transparent conductive film in a high-temperature, high-humidity atmosphere. <Examples> The present invention will be described in detail below with reference to illustrated examples. A polymer blend is prepared by mixing a butyl methylol melamine coating agent SM-67 (hereinafter referred to as liquid A) manufactured by Teijin Kasei Ltd. with a silicone varnish hard coating agent Tosgard 510 (hereinafter referred to as liquid B) manufactured by Toshiba Silicone Co., Ltd. Created. At this time, the blend ratio is non-volatile solid content, (a) A liquid: B liquid = 1:
3. (b) A liquid: B liquid = 1:2, (c) A liquid: B liquid = 1:
1, (d) A liquid: B liquid = 2:1, (e) A liquid: B liquid = 3:
1. (F) Six types of blended polymers were prepared with a ratio of liquid A: liquid B = 5:1. On the other hand, the plastic film substrate for the liquid crystal display is made of polyethylene terephthalate, polycarbonate, 100 μm thick,
polysulfone, polyether sulfone,
Plastic film substrates made of polyether ether ketone, phenoxy ether type polymer, and polyarylate were prepared and thoroughly washed and degreased. Thereafter, the above polymer blend was applied to each of the above plastic film substrates using a dipping method, air-dried for 15 minutes, and then baked at 120°C for about 1 hour to form a cured coating film, which was used as a base film. . A transparent conductive film was formed on this base film. When the initial stage of the plastic film substrate on which the base film and transparent conductive film were formed, the adhesion between the base film and the transparent conductive film and the plastic film substrate was investigated using a cellophane tape peel test. As shown in Table 1, the results were good regardless of the type of plastic film.

[Table] (Note) ○ indicates good quality.
Next, a plastic film substrate made of a phenoxy ether type polymer, which is considered to have the weakest adhesion among the seven types of plastic film substrates mentioned above, was placed in a high temperature, high humidity atmosphere at 80°C and 95%RH for 60 minutes.
After standing for a period of time, a cellophane tape peeling test was conducted in the same manner. Also, the appearance was examined. The results are shown in Table 2 below.

【table】

[Table] (Note) ○ indicates good quality, △ indicates fair quality, and × indicates poor quality.
As shown in Table 2 above, the adhesion, whitening, and crack occurrence vary depending on the ratio of the polymer blend. After producing a liquid crystal display element using a plastic film substrate having these base films, we investigated the lighting after leaving it in an atmosphere of 80°C and 95% RH for 120 hours, and found that the above (a), (b), At blend ratio (c), part of the transparent conductive film was disconnected and the lamp did not light up properly. On the other hand, those with blend ratios (d), (e), and (f) lit up normally. As can be seen from the above results, the plastic film liquid crystal display element having the base film according to the present invention has excellent adhesion between the plastic film substrate and the base film, scratch resistance of the plastic film itself, solvent resistance, and liquid crystal resistance. In addition, it is possible to improve the adhesion between the transparent conductive film and the base film, and prevent whitening of the base film and disconnection of the transparent conductive film in a high-temperature, high-humidity atmosphere.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a liquid crystal display element using a glass substrate, and FIG. 2 is a sectional view of a liquid crystal display element using a plastic film substrate. 2... Transparent conductive film, 3... Alignment film, 5... Liquid crystal, 6... Seal material, 7... Polarizing plate, 11... Plastic film substrate, 12... Base film.

Claims (1)

[Claims] 1. In a liquid crystal display element in which a base film made of a polymer blend obtained by mixing a melamine resin with a silicone resin is formed on a plastic film substrate, the non-volatile solid content of the silicone resin is reduced to half the non-volatile solid content of the melamine resin. 1 or less.