JPH0436721A - lcd display panel - Google Patents

Abstract

PURPOSE:To seal the peripheral edges of substrates at a short period of time and to lessen the influence on a liquid crystal by heating in a sealing stage by hermetically sealing the peripheral edges with a mixture composed of paraffin wax and hot melt adhesive. CONSTITUTION:The paraffin wax having 60 to 75 deg. m.p. is preferable. The hot melt adhesive is exemplified by hydrocarbon resin, etc., essentially consisting of polyolefins. A packing material having electrical insulating and moistureproofing characteristics are further added and mixed to and with the sealing material and this material is applied to the sealing part, by which the deterioration in the performance of the panel is further prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polymer-dispersed liquid crystal display panel with excellent water resistance.

The liquid crystal display panel of the present invention can be used for various displays, optical shutters, control devices, etc., and can be particularly suitably used as a liquid crystal display panel for large screens.

[Prior art and its problems]

Recently, a polymer-dispersed liquid crystal display panel comprising a medium layer in which liquid crystals are dispersed has been proposed in Japanese Patent Publication No. 58-501631.

The conventional method for sealing this polymer-dispersed liquid crystal display panel is to seal the peripheral edges of two substrates with a sealant in advance, fill the liquid crystal through the injection hole, and then
It is not possible to use a method of sealing the injection port.

Therefore, in order to seal this polymer-dispersed liquid crystal display panel, a method has been adopted in which the polymer-dispersed liquid crystal is sandwiched between two substrates, and then the periphery of the substrates is sealed using an epoxy resin.

In this case, there was a problem in that the epoxy resin could not be sufficiently cured in order to prevent the liquid crystal inside the cell from being deteriorated by heat. As a result, the sealing becomes insufficient, moisture easily enters the inside, and the performance of the liquid crystal display panel deteriorates during long-term use.

[Means for solving problems]

The present inventors conducted extensive research in order to solve the above problems, and as a result, they arrived at the present invention.

The present invention consists of two substrates on which transparent electrodes are disposed, and a medium layer in which liquid crystal is dispersed in the medium, and the medium layer is
In a liquid crystal display panel sandwiched between two substrates with transparent electrode surfaces facing each other, the sealing material for sealing the peripheral edge of the substrate is a mixture of paraffin wax and hot melt adhesive. Related to liquid crystal display panels.

As the sealing material in the present invention, a mixture of paraffin wax and hot melt adhesive is used. The paraffin wax is not particularly limited, but one having a melting point of 60-75°C is preferable. In addition, the hot melt adhesive is not particularly limited, but suitable examples include hydrocarbon resins containing polyolefins as a main component, fluororesins, and the like. Specific examples of hydrocarbon resins mainly composed of polyolefins include ethylene homopolymers, or binary or random block or random polymers of ethylene and other α-olefins such as propylene, butene, pentene, hexene, heptene, etc. Copolymers can be mentioned. Furthermore, homopolymers of propylene, or propylene and ethylene, butene, pentene, hexene,
Two or more block or random copolymers with other α-olefins such as heptene can be mentioned.

Specific examples of fluororesins include polytetrafluoroethylene resin, ethylene-tetrafluoroethylene copolymer resin,
Examples include vinylidene fluoride resin, trifluorochloroethylene resin, vinyl fluoride resin, and tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin.

In the present invention, the mixing ratio of paraffin and hot melt adhesive is such that if there is too much paraffin, the sealant may crack partially if excessive impact is applied during handling; If the ratio is too small, the performance will deteriorate when the panel is used for a long period of time, so a ratio of 95:5 to 20:80 (weight ratio) is usually preferable.

These sealing materials are applied to the sealing portion at the peripheral edge of the substrate in a heated and molten state.

In addition, by further adding and mixing an electrically insulating and moisture-proof filler to the sealing material and applying it to the sealing part,
Furthermore, deterioration of panel performance can be prevented. Specific examples of fillers include powdered, flaky, or fibrous glass, calcium carbonate, talc, mica, and the like.

The medium layer of the present invention is a medium layer in which liquid crystal is dispersed in the medium, and a specific example thereof is a polymer-dispersed liquid crystal, such as N CA P (N CA P ( Nematic curve
ear Aligned Phase: Nematic curve aligned phase) liquid crystal (Special Publication No. 58-501631)
, latex-incorporated liquid crystal (Japanese Patent Application Laid-Open No. 60-252687
), a material in which liquid crystal microdroplets are dispersed in epoxy resin (Japanese Patent Publication No. 61-502128), or a liquid crystal composite film with a network structure prepared by a solvent casting method (Po
lymer t”reprints, Japan vo
l, 37. No. 8.2450 (1988)).

〔Example〕

EXAMPLES The present invention will be explained in further detail by way of Examples below.

Example 1 10% PVA aqueous solution, liquid crystal, dichroic dye (PVA:liquid crystal = 1:3.5 (weight ratio), dichroic dye is 3% by weight of liquid crystal)
] was thoroughly mixed, and this was coated and dried using a doctor blade on a substrate of a transparent electrode material that had been patterned into a predetermined electrode pattern using ITO or the like (thickness: 15 μm). A liquid crystal display panel was fabricated by bonding this substrate to another substrate on which predetermined electrodes had been patterned using ITO or the like in advance so as to match each other at a predetermined position.

As a sealant, melted paraffin wax (melting point 68-7
0°C) and 80 parts by weight of propylene-ethylene random copolymer (APAO-RT230 manufactured by Rexene, USA).
2) 20 parts by weight of the mixture was applied to the peripheral edge of the substrate to seal the liquid crystal display panel.

The above liquid crystal display panel was subjected to a humidity resistance test for 500 hours at 60° C. and 195% humidity.

The resistance value when 50V was applied was 4.3×io” before the test.
Ω, 2 after the test. I x 109Ω, and did not change much.

Example 2 In addition to the sealing material used in Example 1, glass peas (manufactured by Toshiba Parodi, GB210, average particle size 1) were added as a filler.
Panels were prepared in the same manner at 60°C and 95% humidity, except that 100 parts by weight of 7μm) were used.
A moisture resistance test was conducted for 00 hours.

The resistance value when 50V is applied is 4.2 x 10" before the test.
Ω was 2.9XIO'Ω after the test, and did not change at all.

Comparative Example 1 A liquid crystal display panel was manufactured in the same manner as in Example 1 except that only a conventionally known two-component epoxy resin adhesive was used as the sealing material.
A time moisture resistance test was conducted.

The resistance value when 50V was applied was 5.4 x 109 before the test.
The resistance was 2.3×10'Ω after the test, and the resistance decreased significantly.

〔Effect of the invention〕

Since the liquid crystal display panel of the present invention is sealed with a mixture of paraffin wax and true melt adhesive, it has low hygroscopicity and can improve long-term reliability.

Further, when the sealing material of the present invention is used, the peripheral edge of the substrate can be sealed in a short time, and the adverse effect on the liquid crystal due to heating in the sealing process is small.

Patent applicant: Ube Industries Co., Ltd.

Claims (1)

[Claims] A liquid crystal display panel consisting of two substrates provided with transparent electrodes and a medium layer in which liquid crystal is dispersed in the medium, the medium layer being sandwiched between the two substrates so that the transparent electrode surfaces face each other. A liquid crystal display panel characterized in that a sealing material for sealing a peripheral portion of a substrate is a mixture of paraffin wax and a hot melt adhesive.