JP3021261B2 - Manufacturing method of plastic substrate liquid crystal display element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal display device having a plastic substrate.
Personal, such as electronic notebooks, personal computers, word processors, etc., with strong demands for light weight and impact resistance
The present invention relates to a method for manufacturing a plastic substrate liquid crystal display element suitably used as a display for OA equipment.

[0002]

2. Description of the Related Art Conventionally, it is generally known to use polyimide as an alignment film material. However, since polyimide is solvent-insoluble, it is difficult to form a film on a substrate by a printing method. After printing in the form of a polyamic acid solvent at the stage before the polymerization, it was necessary to cyclize by heating to obtain a polyimide structure. In this case, since the cyclization by heating requires a high-temperature treatment of about 250 ° C. to 350 ° C.,
A plastic substrate having a heat resistance temperature of at most about 200 ° C. is difficult to apply because of its heat resistance.
When baking is performed at a temperature of 00 ° C. or less, the electro-optical characteristics of the device, that is, the display quality are adversely affected, and the electro-optical characteristics such as the contrast of the liquid crystal display device obtained on the original glass substrate may be obtained. No, it had a fatal effect on display quality.

In order to solve these problems, Japanese Patent Publication No.
Japanese Patent Publication No. 37292/1993, Japanese Patent Publication No. 5-39288, and Japanese Patent Publication No. 5-39287 have proposed a method. First, Japanese Patent Publication No. 5-37292 describes a liquid crystal display device having an alignment film composed of a film containing polyimide as a main component. this is,
As a polymer, it is characterized in that an alignment film is formed by dissolving a specially heat-stable polyimide in a solvent, which enables low-temperature sintering of the alignment film forming process only at the temperature at which the solvent is removed. And

Further, Japanese Patent Publication No. 5-39288 discloses that
A liquid crystal display device having an alignment film composed of a coating containing polyamide as a main component is described. This is also characterized by forming an alignment film after dissolving a specially heat-stable polyamide as a polymer in a solvent.
This enables low-temperature firing at only the temperature at which the solvent is removed in the process of forming the alignment film.

Further, Japanese Patent Publication No. 5-39287 discloses a liquid crystal display device having an alignment film composed of a film containing a polyamide ester as a main component. This is also characterized in that, as a polymer, a specially heat-resistant polyamide ester is dissolved in a solvent and then the alignment film is formed, whereby the process of forming the alignment film is performed at a low temperature only at the temperature at which the solvent is blown off. Sintering is possible.

[0006]

However, as described above, Japanese Patent Publication No. 5-39288 and Japanese Patent Publication No. 5-39
No. 287, Japanese Patent Publication No. 5-37292, etc., with respect to the material technology for forming an alignment film, although it is possible to perform a lower-temperature baking treatment than before,
As an alignment film of a plastic substrate liquid crystal display element, the alignment of liquid crystal molecules on a polyimide alignment film after formation is insufficient, so that it is impossible to maintain a constant liquid crystal molecule alignment state, and a d / p margin (liquid crystal It has no molecular twist, d: cell gap, and p: pitch of liquid crystal molecules), and is not particularly suitable for STN (super twisted nematic) mode, etc., and it is difficult to obtain electro-optical characteristics, so that the degree is not so high. That was enough.

The present invention is intended to further solve the above problems which could not be obtained conventionally.
Capable of forming an alignment film of a plastic substrate heat-resistant temperature (200 ° C.) below the heating (baking) process, producing child excellent plastic substrate liquid crystal display device characteristics
It is an object of the present invention to provide a method for manufacturing a plastic substrate liquid crystal display element that can be used .

[0008]

[0009]

According to the present invention, there is provided a method of manufacturing a plastic substrate liquid crystal display device, comprising: a pair of translucent plastic substrates; and transparent electrodes formed on opposing surfaces of the pair of plastic substrates. And an alignment film, wherein a liquid crystal layer is interposed between the pair of plastic substrates, and the liquid crystal display element has a polyether amide or a derivative thereof in an amount of 3 to 10 wt%.
N-methylpyrrolidone (NMP) and γ-butyl
Lactone (GBL) and butyl cellosolve acetate
After being dissolved in a solvent mixed at a ratio of 4: 3: 3 , printing is performed on the plastic substrate, only the solvent is removed by heating and / or heating under reduced pressure, and the plastic substrate is baked at a temperature lower than the heat resistance temperature. The feature is that an alignment film is formed, thereby achieving the above object.

[0010]

According to the present invention, as described above, polyetheramide is dissolved in a high-boiling solvent. At this time, the polyetheramide is already a polymer. It is possible to form an alignment film on a substrate.

That is, the firing and baking temperature is 15
A temperature of about 0 ° C. to 200 ° C. is sufficient, and further lowering the solvent boiling point by adding a reduced pressure treatment can realize further lower-temperature firing. Therefore, in the alignment film firing step which is the MAX temperature of the liquid crystal manufacturing step on the plastic substrate, Processing can be performed at a temperature lower than the heat resistance temperature of the plastic substrate, and the same electro-optical characteristics as those of a glass substrate liquid crystal display element can be secured.

[0012]

EXAMPLES The present invention will be described below in detail with reference to Examples, but the present invention is not limited to these Examples.

(Embodiment) FIG. 1 shows a typical schematic view of a plastic substrate liquid crystal display device. In the figure, reference numerals 1 are polarizing plates, 2 and 4 are hard coats, 3 is a substrate, 5 is a transparent electrode, 6 is a top coat, 7 is an alignment film, 8 is a seal, and 9 is a liquid crystal.

The polarizing plate 1 is provided for the purpose of transmitting only light that vibrates strongly in a specific direction. A general manufacturing method is to stretch a thin film of PVA while heating it and contain a large amount of iodine. In contact with a solution called H ink.
Then, a film having polarized light by absorbing iodine is formed.

The hard coats 2 and 4 are composed of a gas barrier and I
An acrylic, epoxy, or siloxane-based coating film is used as a TO undercoat film. For example, a film is formed using a dip or roll coater and baked at 100 ° C. for 30 minutes.

The substrate 3 is a transparent plastic resin plate.
It is made of epoxy or acrylic plastic resin, polyether sulfone (PES), polyether terephthalate (PET), polycarbonate (PC), or the like.

The transparent electrode 5 is made of an indium tin oxide (ITO) film having a thickness of
After depositing the deposited film at 2000 angstrom, it is patterned by a method such as photoetching or using a laser beam to form an electrode shape.

The top coat 6 (insulating film) is generally called an overcoat process, and is provided as a thin protective layer on the surface of the substrate electrode. An oxide of Ti or Si is used as a film, and a silica coating material (for example, MOF manufactured by Tokyo Ohka Kogyo Co., Ltd.)
(Ti-Si film) with a film thickness of 700 to 1400 angstroms to provide hardness and insulation. Further, it is preferable that a film obtained by combining an acrylic resin with the oxide of Ti or Si has flexibility in addition to hardness and insulating properties. Other top coat resins include:
An acrylic resin or an epoxy resin can be used, and as the inorganic substance, SiO ₂ , TiO ₂ , or a mixture thereof can be used in addition to SiOx.

The seal 8 seals by heat fusion. The material is glass as an inorganic material, and nylon, polyester, polyimide, thermosetting epoxy or the like is used as an organic material. Among these, it is preferable to use a thermosetting epoxy.

Many liquid crystals 9 have been proposed, such as nematic, cholesteric, and smectic liquid crystals. There are many representatives such as cholesterol nonanoate.

The alignment film 7 is used for aligning the orientation of liquid crystal molecules on the plastic substrate 3 in one direction. According to the above-described procedure, the hard coat films 2 and 4 and the transparent electrode 5 is formed after each is formed. In preparing the alignment film, polyetheramide having a basic chemical structure represented by the following chemical formula 1 is converted into a solid content of 3 to 10% by weight, and a high boiling solvent, N-methylpyrrolidone (NMP), γ-butyl lactone (GB)
L), an ink is prepared by mixing butyl cellosolve acetate at a ratio of 4: 3: 3.

[0022]

Embedded image

The ink prepared as described above is letterpress-printed in a predetermined pattern by offset printing, and 3
The film is formed with a thickness of 00 to 800 angstroms.
Baking is performed in a hot air circulating oven at 150 to 200 ° C. for 2 hours to form a baked film. Further, after the above printing, 0.1 to 0.01 torr in a vacuum oven.
r, after 30 minutes of decompression, baking at 150 to 200 ° C. or during the decompression, 150 to 2
Performing calcination at 00 ° C. is preferable in terms of shortening the time. The details of the conditions are as follows: after leaving under a reduced pressure of 0.1 torr for 30 minutes, baking at 180 ° C. for 1 hour and 30 minutes to form an alignment film, or during the processing under a reduced pressure of 0.01 torr for 30 minutes. It was confirmed that baking at 150 ° C. to form an alignment film was favorable. After that, similar to the above-described procedure, the liquid crystal 9 is sealed between the two plastic substrates 3 and then sealed with the sealing material 8 to complete the plastic substrate liquid crystal display element of this embodiment. I do.

Comparative Example 1 In Comparative Example 1, an alignment film was formed by a conventional method. Among the constituent elements, the above-described embodiment was applied as it was except for the conditions for forming the alignment film. Using polyamic acid as the material of the alignment film,
The resultant was baked at 250 ° C. for 30 minutes to form an alignment film.

Comparative Example 2 In Comparative Example 2, an alignment film was formed by a conventional method. Among the constituent elements, the above-described embodiment was applied as it was except for the conditions for forming the alignment film. Using polyamic acid as the material of the alignment film,
Baking was performed at 150 ° C. for 30 minutes to form an alignment film.

FIG. 2 shows a comparison between the characteristics of the plastic substrate liquid crystal display device obtained according to the present embodiment and the plastic substrate liquid crystal display device obtained according to the prior art. However, a rubbing angle of 22
At 0 ° C., the substrate PES is 0.1 mmt, the cell thickness is 6 μm, and cyclohexane and tolan liquid crystals are used.

[0027]

As described above, according to the present invention,
It is possible to form an alignment film on a plastic substrate by dissolving polyetheramide in a high boiling point solvent, removing the solvent by evaporation, and baking the film only.

That is, the firing and baking temperature is 15
A temperature of about 0 ° C. to 200 ° C. is sufficient, and further lowering the solvent boiling point by adding a reduced pressure treatment can realize further lower-temperature firing. Therefore, in the alignment film firing step which is the MAX temperature of the liquid crystal manufacturing step on the plastic substrate, The plastic substrate liquid crystal display can be processed at a temperature not higher than the heat resistance temperature of the plastic substrate, and can produce a plastic liquid crystal display having the same electro-optical characteristics as a conventional glass substrate liquid crystal display.
It has become possible to provide a method for manufacturing the display element .

[Brief description of the drawings]

FIG. 1 is a sectional view of the most typical plastic substrate liquid crystal display device.

FIG. 2 is a diagram comparing the electro-optical characteristics of the device of the embodiment of the present invention and those of the prior art under various alignment film processing conditions.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polarizer 2 Hard coat 3 Substrate 4 Hard coat 5 Transparent electrode 6 Top coat 7 Alignment film 8 Seal 9 Liquid crystal

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/1337

Claims (1)

(57) [Claims] 1. A liquid crystal layer comprising a pair of translucent plastic substrates, a transparent electrode and an alignment film respectively formed on opposing surfaces of the pair of plastic substrates, and a liquid crystal layer interposed between the pair of plastic substrates. In a plastic substrate liquid crystal display element constituted by interposing a polyether amide or a derivative thereof, 3 to 10 wt%
N-methylpyrrolidone (NMP) and gamma
Cyllactone (GBL) and butyl cellosolve acetate
Are dissolved in a solvent mixed at a ratio of 4: 3: 3 ,
A method for manufacturing a plastic substrate liquid crystal display device, comprising printing on the plastic substrate, removing only the solvent by heating and / or heating under reduced pressure, and sintering the plastic substrate at a temperature not higher than the allowable temperature limit. Method.