JPH0436720A - Liquid crystal display panel - Google Patents

Abstract

PURPOSE:To expand a visual field without the need for providing color filters by incorporating dichromatic dyes into a liquid crystal and incorporating coloring agents therein. CONSTITUTION:The liquid crystal 5 dispersed in a medium 6 which is a light transparent high-polymer compd. is held in place by two sheets of substrates 1, 3 disposed with transparent electrodes 2, 4. The black dichromatic dye and the coloring agent are incorporated into the liquid crystal 5. The greater part of incident light is absorbed by the black dichromatic dye and, therefore, the liquid crystal display panel appears dark red in the stage of a voltage off. The greater part of the incident light is transmitted and, therefore, the liquid crystal display panel appears bright red in the stage of a voltage on.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polymer-dispersed liquid crystal display panel that can control the amount of light transmitted.

[Prior art and its problems]

In recent years, a new liquid crystal film technology called polymer-dispersed liquid crystal has been developed, and its use is progressing in film-like large-area optical shutters and large-area display members.

When a polymer-dispersed liquid crystal layer made using a liquid crystal with positive dielectric anisotropy and a normal refractive index almost equal to the refractive index of the polymer is sandwiched between two electrode substrates, light will be scattered when the electric field is off. However, when the electric field is ON, light can be transmitted.

As a polymer-dispersed liquid crystal, NCAP (Nematic
Curvilfnear 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), liquid crystal microdroplets dispersed in epoxy resin V (Japanese Unexamined Patent Publication No. 61-502128), or a mesh prepared by a solvent casting method. Structured liquid crystal composite film (Polymer Preprints+
Japan vol, 37+No, 82450 (19
88) ) etc. are known.

However, when a conventional polymer-dispersed liquid crystal is used as a liquid crystal display panel that can display color, a color filter is usually required. There were problems in that color shift was likely to occur due to the thickness of the screen, and the viewing angle was narrow.

To prevent this, it is necessary to
It is sufficient to form a color filter just below the OI pole, but
Driving voltage increases significantly, ITO! There was a problem in that manufacturing such as forming the poles was difficult.

On the other hand, there are liquid crystal compositions in which liquid crystals are encapsulated in microcapsules in a colored polymer and dispersed in a binder, or liquid crystals are encapsulated in microcapsules and dispersed in a colored binder. A color liquid crystal display using a liquid crystal composition was published in JP-A-62-287.
No. 11 and JP-A No. 62-28712.

In the case of the above-mentioned publication, when the voltage is OFF, the light is colored and transmitted, and when the voltage is ON, the light is not very colored and is transmitted almost colorless.

In other words, it is difficult to shut off light completely or to a level close to it. Therefore, a color liquid crystal display device made using a three-color liquid crystal composition of red, blue, and green has the disadvantage that the contrast is not very good and the vividness of the colors is also impaired.

On the other hand, Japanese Unexamined Patent Publication No. 64-91125 describes a liquid crystal display device characterized in that liquid crystal is dispersed in a light-absorbing medium in the form of microcapsules. In this case, light is absorbed when the voltage is OFF, it looks dark (black), and the voltage is OFF.
In the N state, most of the light passes through and it looks bright. If a color filter is attached to this, color display with good contrast is possible, but there are the same problems as mentioned above.

[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
A polymer-dispersed liquid crystal display panel sandwiched between two substrates with transparent electrode surfaces facing each other, characterized in that the liquid crystal contains a dichroic dye, and the liquid crystal and/or the medium contains a colorant. This invention relates to a liquid crystal display panel.

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

FIG. 1 is a longitudinal cross-sectional view showing one embodiment of a liquid crystal display panel made of a polymer-dispersed liquid crystal according to the present invention.

A liquid crystal 5 dispersed in a medium 6 such as a light-transmitting polymer compound is sandwiched between two substrates 1.3 on which transparent electrodes 2 and 4 are provided. The liquid crystal 5 contains a dichroic dye such as a black dichroic dye and a colorant. As the colorant, a non-dichroic dye or pigment is used.

In this case, when the voltage is off, the liquid crystal display panel appears dark red because most of the incident light is absorbed by the black dichroic dye. When the voltage is on, most of the incident light is transmitted, so it appears bright red.

Furthermore, the liquid crystal 5 can be colored with green and blue dichroic dyes and red non-dichroic dye so that it appears black (dark) when the voltage is off and red when the voltage is on.

FIG. 2 is a longitudinal cross-sectional view showing an embodiment of a full-color liquid crystal display panel made of a polymer-dispersed liquid crystal according to the present invention.

A transparent pixel electrode 10 and a signal electrode 11 are provided on the first substrate 7.
are formed by a known method such as patterning, and the varistor film 12 that connects the picture electrodes is formed by a known method such as screen printing.

Further, liquid crystals 13, 14, 15 colored with a black dichroic dye and red, green, and blue non-dichroic dyes are dispersed in a medium 16 such as a light-transmitting polymer compound to form a medium layer. ing.

On the other hand, a scanning electrode 9 is disposed on the second substrate 8, and the medium layer is sandwiched between the substrates 7 and 8 on each pixel electrode corresponding to R, G, and B so that the electrode surfaces face each other. The polymer-dispersed liquid crystal of the present invention having such a structure is NCA P (
Nematic Curvilinear Ali
gned Phase (nematic curve aligned phase) liquid crystal (Japanese Patent Publication No. 58-501631), latex-incorporated liquid crystal (Japanese Patent Publication No. 60-252687), material in which liquid crystal microdroplets are dispersed in epoxy resin (Japanese Patent Publication No. 58-501631), 6
1-502128) or a liquid crystal composite film with a network structure (Polymer Preprints, Japan).
n vol, 37. No. 8.2450 (1988),
JP-A-1-198725], etc. can be used.

Specific examples of the light-transmitting polymer compound used as a medium in the present invention include polyvinyl J real alcohol, polymethyl methacrylate, ultraviolet curing resin, polyvinyl chloride, vinylidene chloride resin, and the like.

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

The amount of liquid crystal used is 1 to 10 times that of the polymer compound.

In particular, it is preferable to use 2 to 5 times the amount.

The dichroic dye contained in the liquid crystal can be appropriately selected from ordinary dichroic dyes for liquid crystal displays.

In addition, the non-dichroic dye or pigment used as a coloring agent is not particularly limited, but for example, 5olvent
Red dyes such as Red 1 and 5olvent Red 3, green dyes such as 5olvent Green 3,
5olvent Blue 35, 5olvent
Blue dye such as Blue 11, chromophthal red A2
Examples include red pigments such as B (Ciba Geigy), green pigments such as Heliogen Green G (BASF), and blue pigments such as Heliogen Blue B (BASF). The ratio of the dichroic dye and colorant to the liquid crystal is preferably 0.1 to 10 parts by weight per 100 parts by weight of the liquid crystal.

Although FIGS. 1 and 2 show an example in which the liquid crystal contains a dichroic dye and a coloring agent, the coloring agent may also be contained in the liquid crystal and/or the medium.

〔Example〕

The liquid crystal display panel of the present invention can be manufactured using the above-mentioned polymer dispersed liquid crystal, for example, by the following method.

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

Example 1 Black dichroic dye 330 was added to 2.5 g of 12% PVA aqueous solution.
1 (Mitsui Toatsu Dye) 20■ and red dye 5olvent
Liquid crystal E-44 (B) containing 20 mg of Red 3
DH Co., Ltd.) was added and stirred at high speed to emulsify. The emulsion was applied to the electrode surface of a glass substrate with ITO using a doctor blade and dried (thickness: 15 μm). A liquid crystal display panel was produced by sandwiching the electrodes between ITO glass substrates so that their electrode surfaces faced each other.

When the voltage was OFF, the color was deep red, and when a voltage of 70 V was applied, it appeared bright red, and the ratio of the amount of transmitted light, that is, the contrast, was 46 at 610 nm.

Example 2 Black dichroic dye 5301 (
Mitsui Toatsu dye) 30■ and red dye 5olvent R
Liquid crystal with 20mg of ed 3 dissolved (BDHE-44)
1.5g was added. Emulsion R was obtained by stirring at high speed. Similarly, emulsion G was prepared using green dye 5olvent Green3, and blue dye 5olvent Blue
Emulsion B was prepared using No. 11.

The emulsion R is applied by screen printing to the area corresponding to the red display on the surface of the transparent scanning electrode 9 of the glass substrate 8, which has been covered with a mask 17 using a paste (ink) containing a black dye (pigment) in advance, and is dried. . Next, apply emulsion G to the part corresponding to the green display, dry it, and apply emulsion B to the part corresponding to the blue display.
was applied and dried to form a polymer-dispersed liquid crystal layer. The film thickness was 14 μm in all cases.

Thereafter, the polymer-dispersed liquid crystal layer was sandwiched between glass substrates 7 on which transparent pixel electrodes 10, signal electrodes 11, and varistor elements 12 were formed, to produce a liquid crystal display panel.

Example 3 80 mg of a red pigment Chromophthal Red A2B (manufactured by Ciba Geigy) was added to 4 g of a 10% PVA aqueous solution and mixed and dispersed. Next, 1 liquid crystal (BDHE-44) in which 30 μm of black dichroic dye 3201 (manufactured by Mitsui Toatsu Dye Co., Ltd.) was dissolved.
．． 5 g was added and stirred at high speed to obtain emulsion R. Similarly, emulsion G was obtained using 60 ml of green pigment Heliogen Green G (manufactured by BASF), and emulsion B was obtained using 50 ml of blue pigment Heliogen Blue B (manufactured by BASF).

A liquid crystal display panel was prepared in the same manner as in Example 2 using the above emulsions R, G, and B.

〔Effect of the invention〕

In the liquid crystal display panel of the present invention, since the dichroic dye is contained in the liquid crystal and the colorant is contained in the liquid crystal and/or the medium, colored light is transmitted through the medium layer when voltage is applied. It is characterized by a wide viewing angle and no need to provide a color filter, which was previously required.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing one embodiment of the liquid crystal display panel of the present invention. FIG. 2 is a longitudinal cross-sectional view showing an embodiment of a full-color liquid crystal display panel made of a polymer-dispersed liquid crystal according to the present invention. 1.3,7. 8: Substrate, 2, 4: Transparent electrode, 5: Liquid crystal colored with dichroic dye and non-dichroic dye, 6, 1.
6: Light-transmitting polymer compound, 7°9: Scanning electrode, 10:
Pixel electrode, 11: Signal electrode, 12: Varistor film, 13:
Liquid crystal colored with black dichroic dye and red non-dichroic dye, 14: Liquid crystal colored with black dichroic dye and green non-dichroic dye, 15: Black dichroic dye and blue Liquid crystal colored with non-dichroic dye, 17: Black mask Patent applicant Ube Industries, Ltd. Figure 2 Figure 1

Claims (1)

[Claims] A polymer-dispersed type consisting of two substrates on which transparent electrodes are arranged and a medium layer in which liquid crystal is dispersed in the medium, and the medium layer is sandwiched between the two substrates so that the transparent electrode surfaces face each other. A liquid crystal display panel characterized in that the liquid crystal contains a dichroic dye, and the liquid crystal and/or the medium contains a colorant.