JPS6115128A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent the generation of bubbles by using substrates each formed by laminating base films having superior resistance to heat and a liq. crystal on both sides of a barrier film having low gas permeability as flexible plastic substrates in a liq. crystal display device. CONSTITUTION:Base films 1 of plastics having superior resistance to heat and a liq. crystal such as polyether sulfone or polyimide resin are laminated on both sides of a barrier film 2 of plastics having low gas permeability such as polyvinylidene chloride or nylon with an adhesive 3 such as a urethane adhesive in- between to form a substrate having a sandwich structure. A transparent electrode 4 and an orienting film 5 are formed on the substrate. Such two substrates are assembled into a cell, and a liq. crystal is injected into the cell to obtain a liq. crystal display device. This display device can maintain its reliability for a long period because bubbles are hardly generated in the liq. crystal layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a liquid crystal display device using a flexible plastic film substrate.

[Prior art]

Conventionally, flexible liquid crystal display devices have been manufactured using plastic substrates, but they can withstand the process of manufacturing liquid crystal display devices and are also cheap for liquid crystal materials.

Generally, fixed substrate materials are easily permeable to air, and therefore, when a completed liquid crystal display is subjected to a durability test, air bubbles may occur within the cells. When viewed through polarizing plates from above and below, these air bubbles become black spots and significantly deteriorate the appearance.

[Purpose of the invention]

The present invention solves this drawback and aims to prevent bubbles in a liquid crystal display device using a flexible substrate.

〔composition〕

The liquid crystal display device of the present invention has heat resistance and solvent resistance.

A paste film made of plastic with excellent liquid crystal resistance and a barrier film with low air permeability are laminated together by laminate, sand inch, etc. and used as a substrate. Those with a laminate structure are thin and bonded at low cost, and those with a sand inch structure are characterized by being easy to manufacture with less deformation such as curling during processing.

The plastic film in contact with the liquid crystal layer is made of polyethersulfone, polysulfone, cellulose triacetate, polycarbonate, polyetherimide, polyetheretherketone, phenoxyurethane resin, epoxy resin film, or polyimide resin with a thickness of 15 to 100 μm. use something The heat resistance temperature of these resins is 150~2
00°C, and has excellent solvent resistance and liquid crystal resistance, and can be used alone as a substrate for liquid crystal displays, but its air permeability is relatively high.

The barrier film laminated to improve the permeability is made of polyvinylidene chloride, polyvinylidene chloride-polyvinylidene chloride mixture, polyacrylontrile, polyvinyl alcohol, polyvinyl alcohol-polyethylene copolymer, nylon, or the like. 5 with excellent ventilation prevention properties
A material having a thickness of ~50 μm is used, and urethane-based, epoxy-based, or polyester-based adhesives can be used as the bonding adhesive.

The thickness of the thus laminated substrates is cL025 to α6, and a thickness of α1 to α2 makes it easy to manufacture a liquid crystal display.

〔Example〕

(Example 1) A 35 μm thick polyether sulfone film was used as the base film, and this was used as a barrier film of 15 μm thick.
A substrate with a sandwich structure was fabricated by laminating a μ-thick polyvinylidene chloride film with urethane adhesive on both sides.

This is shown in FIG. In the figure, number 1 indicates the base film, number 2 indicates the barrier film, and number 5 indicates the adhesive.

The thickness of the adhesive was 5 μm, resulting in a substrate with a total thickness of 95 μm. The oxygen permeability of this substrate is 10ccO,/αtm
・It is less than 24H, and the oxygen permeability of a simple 100 μm thick polyether sulfon film is 200 to 500 α.
The barrier properties were significantly improved compared to /αtm-24'H.

Tin oxide-indium oxide (ratio 5) was added to this as a transparent electrode.
:95) was formed to have a thickness of 200 mm by sputtering, and processed into a predetermined electrode shape using a photolithography trap. After applying a polyimide resin as a submerged alignment agent, alignment treatment was performed by rubbing in one direction with gauze. After screen-printing an epoxy sealant, spraying a gap agent, and performing a vertical conduction process, the upper and lower substrates were assembled, and the sealant was cured under pressure. Liquid crystal was injected into this using a vacuum injection method, and the injection port was sealed with epoxy adhesive to complete the liquid crystal cell. A cross-sectional view of this liquid crystal cell is shown in FIG. In the figure, numbers 1 to 6 indicate the sandwich substrates shown in FIG. 1, number 4 indicates the transparent T1 pole, and number 5
indicates an alignment agent, number 6 indicates a sealing agent, and number 7 indicates a gap agent.

A liquid crystal display was completed by attaching polarizing plates to the top and bottom of this liquid crystal cell. This liquid crystal display had a high reliability as a product, as it took more than 10 times longer for bubbles to start forming in the cells than one made using a simple polyether sulfon substrate.

(Example 2) A uniaxially stretched polyester film was used as the base film.
A substrate having a thickness of 5 .mu.m was used, and in the same manner as in Example 1, a sandwich structure substrate was produced by sandwiching a polyvinylidene chloride film having an i s tt ma+ thickness as a barrier film. Using this, a liquid crystal cell was manufactured in the same manner as in Example 1.

(Example 5) A uniaxially stretched polyester film with a thickness of 50 μm was used as a base film, and this was laminated to a polyvinylidene chloride film with a thickness of 15 μm using a urethane adhesive. This section [iI diagram is shown in FIG. In the figure, number 8 indicates the base film, number 9 indicates the barrier film, and number 10 indicates the contact layer. This substrate had a thickness of 70 μm, and was used to fabricate a liquid crystal cell as in Example 1. Note that since polyvinylidene chloride has a possessive effect on liquid crystals, a liquid crystal display was manufactured with the surface laminated with polyvinylidene chloride on the outside.

(Example 4) A liquid crystal display device was constructed by using the liquid crystal display bodies of Examples 1 to 5 and combining them with a driving section.

〔Effect of the invention〕

As explained above, in the liquid crystal display used in the liquid crystal display device of the present invention, the substrate has the properties of a base film with excellent heat resistance, solvent resistance, liquid crystal resistance, and barrier film with excellent air permeation prevention effect. A liquid crystal display device constructed using the liquid crystal layer has the advantage that bubbles are not generated in the liquid crystal layer, and reliability as a product can be ensured over a long period of time.

[Brief explanation of the drawing]

FIG. 1 shows a sectional view of a laminated structure of a flexible substrate used in a liquid crystal display device of the present invention. FIG. 2 shows a cross-sectional view of a liquid crystal display manufactured using the substrate of FIG. 1. FIG. 5 shows a cross-sectional view of a substrate in Example 5. FIG. 4 shows a cross-sectional view of a liquid crystal display manufactured using the substrate of Example 5. 1...Base film 2...Barrier film 5...Adhesive layer 4.11...Transparent conductive film 5.12...・Alignment film 6.13... Sealing agent 7.14... Gap agent 8... Base film 9... Barrier film 10... Adhesive layer or above

Claims (1)

[Claims] 1. A liquid crystal display device comprising at least a liquid crystal layer and a pair of flexible substrates sandwiching the liquid crystal layer, wherein the substrate is a plastic film having excellent heat resistance and liquid crystal resistance. 1. A liquid crystal display device characterized by having a substrate formed by laminating a plastic film with low air permeability. 2. In the plastic film with low air permeability as described in claim 1, the plastic film with low air permeability has an oxygen permeability coefficient of 20c. c. /m^2・24
A liquid crystal display device characterized in that it is ^H or less.