JPH0455831A - Liquid crystal display device - 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 [Field of Industrial Application] The present invention relates to a matrix-type liquid crystal display device comprising a polymer-dispersed liquid crystal layer.

The liquid crystal display device manufactured according to the present invention can be used for various displays, optical shutters, control devices, etc., and can be particularly suitably used as a large screen liquid crystal display device.

[Prior art and its problems]

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

As a polymer-dispersed liquid crystal, NCAP (Nematic
Curvilinear Aligned Phas
e: Nematic curve type aligned phase) liquid crystal (Special publication 1985-5)
01631), latex-incorporated liquid crystal (Japanese Unexamined Patent Publication No. 60-252687), a material in which liquid crystal microdroplets are dispersed in epoxy resin (Japanese Unexamined Patent Publication No. 61-502128), or a network structure prepared by a solvent casting method. liquid crystal composite film (Polymer Preprints,
Japan vol, 37+No, 8+2450 (1
988)) etc. are known.

This polymer-dispersed liquid crystal display panel has advantages such as no leakage of liquid crystal, no need for a polarizing plate, and quick response. However, when attempting to display color using dichroic dyes, there is a problem in that the contrast is poor because the dichroic dyes and liquid crystals dissolve in the polymer medium. When a water-soluble polymer is used as the polymer medium, the above-mentioned problems are improved, but there is a problem that the display performance deteriorates due to moisture absorption from the peripheral edge of the panel.

In order to prevent moisture absorption from the periphery, attempts have been made to seal with various adhesives, but so far no adhesive has been found that exhibits a sufficient moisture-proofing effect over a long period of time.

Means for Solving Problem C] The present inventors conducted intensive research to solve the above problems, and as a result, they arrived at the present invention.

The present invention utilizes the advantage that polymer-dispersed liquid crystal is solid, and a liquid crystal layer can be formed on each pixel electrode by a printing method.

That is, the present invention provides a first substrate having a pixel electrode, a signal electrode disposed at a distance from the pixel electrode and sending a signal to the pixel electrode, and a varistor connecting the pixel electrode and the signal electrode; A liquid crystal display device comprising: a second substrate provided with an electrode to face the pixel electrode; and a polymer-dispersed liquid crystal layer filled between the first substrate and the second substrate. The present invention relates to a liquid crystal display device characterized in that a dispersed liquid crystal layer is formed on each of the pixel electrodes, and a gap between an adjacent polymer dispersed liquid crystal layer is filled with saturated hydrocarbons.

The present invention will be explained below with reference to the drawings.

FIG. 1 shows an example of a liquid crystal display device 1 according to the present invention. It is a partially enlarged vertical cross-sectional view showing an aspect. On the first substrate 2, a pixel electrode 3 and a signal electrode 4 are arranged. The pixel electrode 3 and the signal electrode 4 are arranged with a gap between them, and are electrically connected by a varistor 5. A scanning electrode 7 is arranged on the second substrate 6 so as to face the pixel electrode 3 .

A polymer-dispersed liquid crystal layer 8 is disposed and sandwiched between the first substrate 2 and the second substrate 6 so as to correspond to the pixel electrode 3 . The gaps between each polymer-dispersed liquid crystal layer 8 are filled with saturated hydrocarbons 9.

Saturated hydrocarbons have a great moisture-proofing effect and do not adversely affect liquid crystals, dyes, etc. Furthermore, it also has the effect of increasing the insulation between the varistor and the scanning electrode.

Examples of the saturated hydrocarbons used in the present invention include paraffin wax, liquid paraffin, polyolefin polymers, and mixtures thereof.

Paraffin wax and polyolefin polymers have good fluidity when heated and molten, so they can be easily filled into the gaps in the polymer-dispersed liquid crystal layer by coating or injection. An adhesive such as a hot melt adhesive can also be added and mixed with the saturated hydrocarbon.

The peripheral edge of the substrate can be sealed using an epoxy resin adhesive, but it is also possible to seal the edge using a hot melt adhesive, an ultraviolet curable adhesive, or a mixture of paraffin wax and hot melt adhesive. By sealing, moisture resistance can be further improved.

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 Curvilin
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 Preprints, Japan vol.
, 37. No. 8.2450 (1988)).

The liquid crystal used in the present invention is not particularly limited, and suitable examples include nematic liquid crystal, smectic liquid crystal, and the like.

The present invention is particularly effective when using water-soluble or hygroscopic polymers such as polyvinylpyrrolidone or polyvinyl alcohol as a medium, but of course other polymers,
For example, the present invention is applicable when polystyrene, polyvinyl chloride, polycarbonate, butadiene rubber, polymethyl methacrylate, polybutyl methacrylate, ethyl cellulose, cyanoethyl cellulose, polyvinylidene fluoride, NBR (tolyl rubber), polyethylene, polypropylene, etc. are used as the medium. There is no problem with that.

〔Example〕

The present invention will be explained in more detail with reference to Examples below.

Example: 14 g of an aqueous solution containing 2 g of polyvinyl alcohol, 5 g of liquid crystal (Merck E-44), and black dichroic dye were placed on the portions of the second substrate 6 having transparent scan electrodes corresponding to pixels on the scanning electrode surface. An emulsion consisting of 0.2 g (Mitsui Toatsu Dye S-301) and 2 g of isobutyl alcohol was applied through a screen and dried to form a polymer-dispersed liquid crystal layer (thickness: 15 μm).

On the other hand, a varistor element was formed by a printing method between a signal electrode made of a transparent electrode on the first substrate 2 and a pixel electrode.

After bonding the first substrate and the second substrate together at a predetermined position, the substrates are heated to 80"C, and the peripheral edge of the substrate is immersed in molten paraffin wax (melting point 60-62"C) heated to BO"C. Paraffin wax was filled in the gap between the BoIJmer dispersed liquid crystal layers.

Next, the peripheral edge of the substrate was sealed using an ultraviolet curable adhesive to produce a liquid crystal display device. No discoloration due to penetration of the adhesive into the liquid crystal layer was observed.

±18 between the signal electrode and scanning electrode of this liquid crystal display device
When a 0V pulse (1/256 duty) was applied, the desired pixel area lit up (contrast ~30) without any cell talk.

The liquid crystal display device was heated for 50 minutes at 60°C and 95% humidity.
A 0 hour moisture resistance test was conducted.

The resistance value when 50V was applied was 6 x 109Ω before the test.
After the test, it was 5.5 X I O9, and there was almost no change.

Further, when a voltage was applied in the same manner as above, the contrast was ~28, and no deterioration was observed.

Example 2 In the same manner as in Example 1, the first substrate and the second substrate were bonded together at a predetermined position, and then the periphery was sealed with an epoxy adhesive except for the injection port.

Warmed to approximately 50°C and immersed the inlet in liquid paraffin in a vacuum chamber. After liquid paraffin was filled into the gap between the polymer-dispersed liquid crystal layers by capillary action, the injection port was sealed with an epoxy adhesive.

When a moisture resistance test was conducted in the same manner as in Example 1, there was no liquid leakage and no deterioration in display characteristics was observed.

Example 3 A first substrate produced in the same manner as Example 1 was heated to about 85°C.
Polyolefin hot melt (APAOR)
T-2315, REXENE Co., Ltd.) was sprinkled and melted. Next, the second substrate, which has been preheated to 85°C, is placed on top of the other in a predetermined position, and the inside of the panel is strongly pressed toward the periphery to squeeze out the excess hot melt, and then the injection port is closed. was sealed with epoxy adhesive.

A moisture resistance test was conducted in the same manner as in Example 1. No deterioration in display characteristics was observed before and after the moisture resistance test.

Note that in the above description, the scanning electrode over the signal electrode is specified, but the signal electrode may be used as the scanning electrode, and the scanning electrode may be driven as the signal electrode.

〔Effect of the invention〕

According to the present invention, since the gaps in the polymer-dispersed liquid crystal layer are filled with saturated hydrocarbons, it has excellent moisture resistance.
Long-term reliability can be improved.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a liquid crystal display device of the present invention. 1: Liquid crystal display device, 2: First substrate, 3: Pixel electrode, 4
: Signal electrode, 5: Varistor, 6: Second substrate, 7: Scanning electrode, 8: Polymer dispersed liquid crystal layer, 9: Saturated hydrocarbons

Claims (1)

[Claims] a first substrate having a pixel electrode, a signal electrode disposed at a distance from the pixel electrode and sending a signal to the pixel electrode, and a varistor connecting the pixel electrode and the signal electrode, facing the pixel electrode; In a liquid crystal display device comprising a second substrate provided with an electrode, and a polymer-dispersed liquid crystal layer filled between the first substrate and the second substrate, the polymer-dispersed liquid crystal layer formed on the electrode,
A liquid crystal display device characterized in that a gap between adjacent polymer-dispersed liquid crystal layers is filled with saturated hydrocarbons.