JPS6147931A - Liquid crystal display element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to a liquid crystal display element.

[Prior art]

The alignment film used in liquid crystal display elements has the function of adhering well to a substrate having a patterned transparent electrode on one surface, aligning the liquid crystal sandwiched between opposing electrodes in a predetermined direction, and being compatible with the usage environment. must be stable over a long period of time.

Traditionally, twisted field effect (TN) liquid crystal display systems have been used.
There are various types, such as type), guest-host type (GH type), and phase change type, and various types of alignment film materials have also been proposed. The liquid crystal is aligned horizontally to the substrate. As a so-called horizontal alignment film material.

For example, in addition to silicon dioxide, various organic polymer materials are known. Among organic polymer materials, imide-based materials such as polyesterimide, polyamideimide, and polyimide have the advantage that they have good uniformity in liquid crystal alignment and that the alignment uniformity is maintained over a long period of time. However, such imide-based polymer materials require heating for 20 minutes or more at a temperature of 300°C or higher to form an alignment film, so they are not suitable for regular continuous production of liquid crystal display devices. On the other hand, there are various horizontal alignment film materials that cannot be applied to plastic substrates, but can be formed at temperatures below 150°C.1 For example, amide resin/isocyanate/organotitanate compositions ( However, in many cases, liquid crystal display elements obtained using such low-temperature film-forming film materials are subjected to high-temperature, high-humidity conditions, such as 80°C,
If left in an environment with a humidity of 90%, the alignment film will be affected by moisture that enters from the surface of the polymer substrate or the sealing layer, and the alignment film will not perform its original function, resulting in poor alignment and the like.

〔the purpose〕

The present invention provides an alignment film material that has excellent low-temperature film formation properties, adheres well to substrates with patterned transparent electrodes on its surface, has excellent uniform alignment performance for liquid crystals, and is highly stable during long-term use. The purpose of the present invention is to provide a liquid crystal display element with excellent reliability under high temperature and high humidity environments.

〔composition〕

According to the present invention, there is provided a liquid crystal display element characterized by having an alignment film mainly composed of vinylidene chloride/vinyl chloride copolymer.

The liquid crystal display element of the present invention is characterized by using an alignment film mainly composed of vinylidene chloride/vinyl chloride copolymer. In this case, vinylidene chloride/vinyl chloride copolymer is
It is a conventionally known substance, and in the case of the present invention, the vinylidene chloride content is 95% by weight.

It is advantageous to use preferably 90-95% by weight.

In order to form an alignment film on a substrate using the alignment film material of the present invention, a solution prepared by dispersing vinylidene chloride/vinyl chloride copolymer in a splitting ether type solvent such as dioxane or tetrahydrofuran is prepared using conventional methods. It may be applied by the method described above, dried, heat treated, and then rubbed. in this case,
Heat treatment temperature is 60-100℃, preferably 80-90℃
It is.

The substrate used in the present invention has a patterned transparent electrode on one surface, and conventionally known substrates are used.For example, in addition to glass, polyester such as polyethylene terephthalate and polyethylene terephthalate, epoxy resin, phenol resin, etc. .

Heat-resistant resins such as polyimide, polycarbonate, polysulfone, polyethersulfone, polyetherimide, acetylcellulose, polyamino acid ester, aromatic polyamide, polystyrene, polyacrylic acid ester, polymethacrylic acid ester, polyacrylamide, polyethylene, polypropylene, etc. Examples include plastic films formed from vinyl polymers, fluorine-containing resins such as polyvinylidene fluoride, modified products thereof, and the like.

The substrate may be used with a protective layer provided on its surface, if necessary, but in this case, the adhesive force between the alignment film and the Wi-retaining layer may be insufficient.

In such a case, first, the surface of the substrate having the protective layer is subjected to an appropriate base treatment (e.g., isocyanate treatment, phenol/chloroprene sesame treatment, etc.), and then
An alignment film may be formed.

Vinylidene chloride used as alignment film material in the present invention/
The adhesion of vinyl chloride copolymers can generally be improved by blending them with organic titanium compounds. In this case, the organic titanium compound used is one represented by the following general formula.

Ti(ORn.

In the formula, R is an alkyl group, an alkenyl group, or an acyl group, and the number of carbon atoms thereof is 1, usually 1 to 40, preferably 2 to 1.
It is O. Specific examples of R include alkyl groups such as ethyl, propyl, butylhexyl, and octyl, as well as alkenyl groups such as allyl group.

Examples include acyl groups such as acetylacetyl group.

The organic titanium compound is blended in an amount of 1 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the vinylidene chloride/vinyl chloride copolymer.

Further, the inclination (tilt angle) of the liquid crystal alignment can be changed by changing the amount of the organic titanium compound.

Furthermore, a plasticizer can be added to the vinylidene chloride/vinyl chloride copolymer used in the present invention to impart plasticity, thereby increasing the rubbing effect and adhesive strength. In this case, commonly used plasticizers such as acetyl tributyl citrate and dibutyl sepacate can be used. In addition, in the case of vinylidene chloride/vinyl chloride copolymer, if the coating liquid is applied and then heated to 80°C or higher during the drying process, chlorine is released from the copolymer and the transparent electrode becomes black. In addition to the fear,
When a liquid crystal display element is stored for a long period of time, there is a risk that chlorine will be liberated. Therefore, in the case of the present invention, prior to preparing the alignment film coating solution, the vinylidene chloride/vinyl chloride copolymer is heat-treated at a temperature of 100°C or higher for 1 hour or more to remove chlorine that is easily released. It is preferable to leave it there. Furthermore, the influence of free chlorine can also be minimized by adding a small amount of epoxidized higher fatty acid ester.

〔effect〕

The alignment film mainly composed of vinylidene chloride/vinyl chloride copolymer according to the present invention has the ability to align liquid crystal in a predetermined direction, that is, horizontally or vertically, and has excellent liquid crystal resistance and high temperature and high humidity resistance. This provides a highly reliable liquid crystal display element.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 A thin film formed by applying a thin layer of alignment film material solution onto a transparent substrate and drying it was rubbed three times in a fixed direction with a sponge roll at an applied pressure of 100 g/cm. A TN type display liquid crystal is dropped onto the rubbed alignment film in the initial state, and a substrate having a similarly rubbed alignment film thereon is brought into relative contact so that the rubbing directions are perpendicular to each other.

This laminate is placed between two orthogonal polarizing plates, upper and lower, and after confirming that the area where the liquid crystal is present becomes a bright field due to the presence of the 90" twisted nematic liquid crystal, each substrate is separated and The rubbed alignment film was heated to 80°C.
Then, the alignment film is exposed in an atmosphere with a humidity of 90% and left for a predetermined period of time. After leaving the alignment film for a predetermined period of time, the moisture adhering to the alignment film is removed, and then the liquid crystal is sandwiched between the substrates again in the same manner as above, and the laminate is placed between two orthogonal polarizing plates, and the liquid crystal is placed between the two orthogonal polarizing plates. Observe the orientation state. In this case, if the alignment film has poor high temperature and high humidity resistance, the initial state alignment will be disturbed.

The high temperature and high humidity resistance of the alignment film can be evaluated based on the disturbance of the liquid crystal alignment.

Further, in the above, instead of leaving the alignment film in a high temperature and high humidity atmosphere, the liquid crystal resistance of the alignment film can be evaluated by leaving it immersed in liquid crystal at a high temperature (80° C.).

The results of tests conducted on various alignment film materials as described above are shown in the following table.

In Table 1, the vinylidene chloride/vinyl chloride copolymer (I) shown in Experiment No. 7 was manufactured by Dow Chemical Company, and the vinylidene chloride/vinyl chloride copolymer (I) shown in Experiment No. 8
Vinyl chloride copolymer (n) is saran wrap for household use and contains an ester plasticizer.

As is clear from the results shown in Table 1, the alignment films of vinylidene chloride/vinyl chloride copolymer used in the present invention (Experiments No. 7 and No. 8) are extremely excellent in both high temperature and high humidity resistance and liquid crystal resistance. It can be seen that it is something that On the other hand, the polymers shown in Experiments Nos. 1 to 6 and Experiments Nos. 8 to 1O for comparison do not show such good results.

Example 2 A transparent conductive film of isodium oxide/tin was provided on a uniaxially stretched transparent polyester film by a sputtering method so as to have a surface resistance of 300 Ω/hole, and then by a conventional method.
Create electrodes using photoetching method.

On the other hand, saran wrap for household use, which has been previously heat-treated at 120° C. for 1 hour, is added to tetrahydrofuran and heated to 60° C. to prepare a solution (A) having a polymer concentration of 2.5% by weight. Also, 0.6% by weight of tetraoctyl titanate
Next, an alignment film forming coating solution was prepared by mixing these solutions (A) and solution CB) at a weight ratio of 1:1.

This alignment film forming coating liquid was applied onto the previously prepared substrate using a 1 mil blade coater, and dried at 120° C. for 15 minutes to form an alignment film. As a result of a substrate peel test (JIS K-5400), it was confirmed that this alignment film had a sufficiently high adhesive strength to the substrate.

Next, a linear pressure of 100 g/c+ was applied to the two substrates having the alignment films obtained as described above using a sponge roll.

After applying a 1.5% by weight ethanol dispersion of 10 μm divinylbenzene polymer particles (Microvar, manufactured by Tanesui Kagaku Co., Ltd.) as a spacer onto one substrate using a spinner at 2000 rpm, the substrate was rubbed three times with , stack the other substrate on top of this so that the rubbing direction is perpendicular to this, bond it with a silicone adhesive, and heat it at 130°C for 30 minutes.
An empty cell was prepared by heating for 0 minutes. This empty cell was filled and sealed with a TN type liquid crystal by a conventional method to produce a liquid crystal display element.

Further, for comparison, a comparative liquid crystal display element was produced in the same manner as above except that vinylidene chloride resin for coating (vinylidene chloride/vinyl acetate/acrylonitrile copolymer) was used as the alignment film material.

The two types of liquid crystal display elements obtained above showed display performance with extremely good contrast in the initial state, but in a high-temperature resistance test in which they were left in an atmosphere of 60°C and 90% humidity, the comparative products showed that the sealing adhesive Misalignment starting from the periphery of the layer was observed after 24 hours. In contrast, it was confirmed that the present R-light product was stable for more than 500 hours.

Example 3 In Example 2, instead of the uniaxially stretched polyester film, the following am-retaining liquid was applied onto the polycarbonate film using a 1 mm blade, and the film was applied at 80 w/am.
A liquid crystal display element was produced in the same manner except that a protective layer was formed by irradiation for 5 seconds under an ultra-high pressure mercury lamp from a distance of 15 cm. This liquid crystal display element also has a temperature of 60°C.
It was stable for more than 500 hours at a humidity of 90%, and the adhesive strength between the alignment film and the substrate was also sufficiently high.

[Protective layer forming liquid]

Dipentaerythritol pentaacrylate = 40 parts by weight Dipentaerythritol tetra

Claims (1)

[Claims] (1) A liquid crystal display element characterized by having an alignment film mainly composed of vinylidene chloride/vinyl chloride copolymer.