JPH0821986A - Light scattered type liquid crystal display element - Google Patents

Abstract

PURPOSE:To make a liquid crystal display element have a large area and thin film-typed, to make the whiteness at the time of light-scattering bright and to make the visibility excellent. CONSTITUTION:In the light scattering type liquid crystal display element having two substrate which have electrode layer and at least either of which is transparent and a light control layer containing liquid crystal material and transparent solid material between the substrates, the transmissivity of the aperture part of the transparent substrate is >=82% at respective wavelengths in the wavelength region of 400-500nm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a liquid crystal device capable of forming a large area.
Transmission can be operated electrically or thermally, and by displaying characters and figures and switching the display electrically with high-speed response, it can be used for advertising boards, guide boards, decorative display boards, etc. The present invention relates to a light-scattering type liquid crystal display element used as a high information display body such as a display body and a display for OA equipment.

[0002]

2. Description of the Related Art A liquid crystal display device has a DS (dynamic
The scattering type was first applied as a liquid crystal display device, and was used for early LCD watches and calculators. At present, TN (twisted nematic) type and STN (super twisted nematic) type liquid crystal display devices using nematic liquid crystals have been put into practical use and are most widely used.

As a light-scattering type liquid crystal display device, a DS type liquid crystal display device generates turbulence due to an ionic current when a voltage is applied, and utilizes the principle of dynamic scattering to utilize the scattered light of light for display. It was used as a direct-viewing type liquid crystal display element that requires no polarizing plate.

However, since the light reflection plate is attached, the reflection type has a drawback that the display surface is a mirror surface and the displayed contents are difficult to see. Further, since this type is a current operation type, it has a short life and is not practical.

The light-scattering type liquid crystal display device, in which the light control layer is composed of a liquid crystal material and a transparent solid substance, controls transmission and scattering of light by an electric field effect, and the alignment of liquid crystal molecules when an electric field is not applied. Is randomized, and the display is recognized by switching between a scattering state in which light is scattered and becomes cloudy, and a transparent state in which liquid crystal molecules are aligned in the direction of the electric field when an electric field is applied and light is transmitted.

As a light-scattering liquid crystal display device, Japanese Patent Laid-Open No.
-198725 and JP-A-2-85822, a liquid crystal device having a dimming layer formed by forming a continuous layer of a liquid crystal material and forming a three-dimensional network polymer substance in the continuous layer. Is disclosed.

[0007]

A light-scattering type liquid crystal display device in which a light control layer is made of a liquid crystal material and a transparent solid substance is used as a light source in the same manner as a conventional TN type or STN type liquid crystal display device. When mounted on the side, the light-transmitting body becomes visible due to the light passing through the transparent portion, which makes it difficult to recognize the display.

Due to such a problem, in the direct-viewing type and light-scattering type liquid crystal display element, the display quality is remarkably deteriorated by the conventional method of providing the light source on the back side of the display.

Further, when the direct-view type reflection system which has been practically used for the TN type and the STN type is applied to the light-scattering type liquid crystal display element, the light scattered by the light control layer is generated in the light-scattering state when no voltage is applied. Since it is reflected and scattered again by the light control layer,
The white display is strengthened. However, when the light-scattering liquid crystal element is set to the light-transmitting state by applying a voltage, the ambient light incident on the element is directly reflected, so that the reflection plate looks like a mirror, and the display is uncomfortable unlike black and white display or color display. Becomes In particular, it is difficult to obtain a monochrome display with this method.

Therefore, when the light-scattering type liquid crystal display element is used as a direct-view type, a light absorbing plate is arranged on the back side of the element to display light scattering (white) when no voltage is applied and the color of the light absorbing plate when a voltage is applied. There is a way to do it.

By using this method, it is possible to display white and the color of the light absorbing plate. In order to further improve the visibility, it is desired to further improve the whiteness at the time of light scattering, improve the contrast, and improve the visibility.

An object of the present invention is to provide a light-scattering type liquid crystal display device which has a bright white when light is scattered, improves the contrast and improves the visibility.

[0013]

In order to solve the above-mentioned problems, the present invention has a structure in which at least one having an electrode layer is transparent.
In a light-scattering liquid crystal display element having a single substrate and a light control layer between these substrates, and the light control layer contains a liquid crystal material and a transparent solid substance, the transmittance of the opening portion of the transparent substrate is Four
82% at each wavelength in the wavelength range of 00 to 500 nm
Provided is a light-scattering liquid crystal display device characterized by the above.

When a light-scattering type liquid crystal display element having a light control layer containing a liquid crystal material and a transparent solid substance is used as a direct-view type, when a light absorbing plate is arranged on the back surface side of the element, no voltage is applied. The light incident on the device is scattered by the light control layer. The intensity of the backscattered light at this time has a larger value in the visible light region on the short wavelength side than on the long wavelength side.

Therefore, if the transmittance of the transparent substrate on the surface side on the short wavelength side in the visible light region is high, the whiteness at the time of light scattering increases and the device becomes brighter. As a result, the contrast is improved and the visibility is improved. It is a light-scattering type liquid crystal display device having excellent characteristics.

The substrate used in the present invention has four openings.
The transmittance may be 82% or more at each wavelength in the wavelength range of 00 to 500 nm.

The transmittance of the substrate is affected by the respective transmittances of a transparent plate such as a glass plate and a film and ITO and the like.

In the transparent plate, the transmittance depends on the material, thickness and the like. Therefore, when the transmittance is not so high due to the material of the transparent plate, it is necessary to increase the transmittance by using a method such as thinning the transparent plate.

Also in the case of ITO, the transmittance depends on its resistivity, film thickness and the like. Therefore, in order to obtain high transmittance, it is necessary to select the optimum range of the resistivity and the film thickness.

As described above, the material and thickness of the transparent plate and I
By selecting the resistivity and film thickness of TO, 400-
The transmittance is 82 at each wavelength in the wavelength range of 500 nm.
% Or more of the substrate can be obtained.

The transparent plate may be a rigid material such as glass or the like, or may be a flexible material such as a plastic film.

As a concrete example of a transparent plate, soda lime glass plate, silica-coated soda lime glass plate, borosilicate glass plate, non-alkali glass plate, polycarbonate plate and the like can be mentioned as a solid material. Examples of the flexible material include a polyether sulfone film, a polyethylene terephthalate film, a polyarylate film, a phenoxy ether film and the like.

The two substrates are opposed to each other and are separated by an appropriate distance. The two substrates are transparent, and the liquid crystal layer and the transparent polymer sandwiched between the two substrates are provided. It must be possible to make the light control layer, which is a layer containing a substance, visible from the outside. In addition, a transparent electrode is arranged on the entire surface or a part of the substrate according to the purpose.

In order to control the thickness of the transparent solid substance uniformly attached to the substrates, it is desirable to interpose a spacer for holding a gap between the two substrates, as in a commonly known liquid crystal device.

As the spacer, for example, Mylar,
Alumina, rod-type glass fiber, glass beads, polymer beads, and other various liquid crystal cells can be used.

The transparent polymer substance formed in the light control layer may be one in which a liquid crystal material is dispersed in the form of liquid drops in the polymer, but one having a three-dimensional network structure is more preferable.

It is preferable that a liquid crystal material is filled in the three-dimensional network portion of the transparent polymer material and that the liquid crystal material forms a continuous layer. By forming a disordered state of the liquid crystal material, It is essential for forming an optical boundary surface and expressing light scattering.

As the transparent polymer substance used in the present invention, a photocurable synthetic resin is suitable. A photo-curable resin obtained by polymerizing a polymer-forming monomer or oligomer is preferable as a polymer that gives a three-dimensional network structure.

As a method of forming a three-dimensional network structure by a transparent polymer substance formed between substrates, for example, (a) liquid crystal material and (b) polymer sandwiched between two substrates are used. A method of polymerizing the photopolymerizable composition by irradiating it with an actinic ray while maintaining the light control layer forming material containing the forming monomer or oligomer and the polymerization initiator in an isotropic liquid state can be mentioned.

The average distance between the meshes of the three-dimensional mesh structure formed of the transparent solid substance is preferably in the range of 0.2 to 5 μm. In addition, the layer thickness of the layer having a transparent solid substance is set to 1 to obtain a sufficient contrast between the opacity due to light scattering and the transparency achieved electrically or thermally depending on the purpose of use. The range of 30 μm is preferable.

The energy for polymerization is ultraviolet light, visible light,
An electron beam or the like can be used, but ultraviolet rays are preferable. In the polymerization of the polymerizable composition by ultraviolet irradiation in the liquid crystal material, the light irradiation intensity and the irradiation amount also require a certain intensity or more, which depends on the reactivity of the polymerizable composition and the type and concentration of the polymerization initiator. Depending on the light intensity, it is possible to form a three-dimensional mesh and uniformize the size of the mesh by selecting an appropriate light intensity. More preferably, as the method of irradiating light, uniform irradiation in time and plane allows the polymerizable composition interposed between the substrates to be instantaneously irradiated with strong light to proceed with the polymerization. It is effective in making the size of the uniform. That is, by irradiating in a pulsed manner with an appropriate light intensity, a uniform three-dimensional network polymer can be realized during continuous liquid crystal feeding.

The network-forming polymerizable composition includes optional components such as a polymer-forming monomer, an oligomer and a polymerization initiator.

As the polymer-forming monomer, for example,
Styrene, chlorostyrene, α-methylstyrene, divinylbenzene; as a substituent, methyl, ethyl, propyl, butyl, amyl, 2-ethylhexyl, octyl,
Nonyl, dodecyl, hexadecyl, octadecyl, cyclohexyl, benzyl, methoxyethyl, butoxyethyl, phenoxyethyl, allyl, methallyl, glycidyl, 2-hydroxyethyl, 2-hydroxypropyl,
Acrylate, methacrylate or fumarate having groups such as 3-chloro-2-hydroxypropyl, dimethylaminoethyl, diethylaminoethyl; ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-butylene glycol, tetramethylene glycol, hexa Poly (meth) acrylates or poly (meth) acrylates such as methylene glycol, neopentyl glycol, trimethylolpropane, glycerin and pentaerythritol;
Vinyl acetate, vinyl butyrate or vinyl benzoate, acrylonitrile, cetyl vinyl ether, limonene, cyclohexene, diallyl phthalate, 2-, 3- or 4-vinyl pyridine, acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-hydroxymethyl acrylamide or N-hydroxyethyl methacrylamide and alkyl ether compounds thereof; di- or tri (meth) acrylate of triol obtained by adding 3 mol or more of ethylene oxide or propylene oxide to 1 mol of trimethylolpropane; to 1 mol of neopentyl glycol Di (meth) diol obtained by adding 2 moles or more of ethylene oxide or propylene oxide
Acrylate; Reaction product of 1 mol of 2-hydroxyethyl (meth) acrylate and 1 mol of phenyl isocyanate or n-butyl isocyanate; Poly (meth) acrylate of dipentaerythritol; Poly (tris- (hydroxyethyl) -isocyanuric acid poly ( (Meth) acrylate; poly (meth) acrylate of tris- (hydroxyethyl) -phosphoric acid; di- (hydroxyethyl)-
Dicyclopentadiene mono (meth) acrylate or di (meth) acrylate; pivalate neopentyl glycol diacrylate; caprolactone modified hydroxypivalate neopentyl glycol diacrylate; linear aliphatic diacrylate; polyolefin modified neopentyl glycol di An acrylate etc. can be mentioned.

Examples of the polymer-forming oligomer include epoxy (meth) acrylate and polyester (meth).
Various acrylate oligomers such as acrylate, polyurethane (meth) acrylate, and polyether (meth) acrylate can be used.

The transparent solid substance having this three-dimensional network structure is not limited to a solid substance, but is flexible as long as it can be used according to the purpose.
It may have elasticity.

Examples of the polymerization initiator include 2-hydroxy-2-methyl-1-phenylpropan-1-one (“Darocur 1173” manufactured by Merck) and 1-hydroxycyclohexyl phenyl ketone (“Ciba Geigy” manufactured by Ciba Geigy). Irgacure 184 "), 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropane-1-
On (Merck "Darocur 1116"), benzyl dimethyl ketal (Ciba Geigy "Irgacure 651"), 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropanone-1 (Ciba) -Geigy "Irgacure 907"), 2,4-diethylthioxanthone (Nippon Kayaku "Kayakyu DET
X)) and ethyl p-dimethylaminobenzoate (“Kayacure EPA” manufactured by Nippon Kayaku Co., Ltd.), isopropyl thioxanthone (“Cantcure ITX” manufactured by Ward Prekinsop) and ethyl p-dimethylaminobenzoate. And a mixture thereof.

The proportion of the polymerization initiator used is preferably in the range of 0.1 to 10.0% of the polymerizable composition.

The liquid crystal material used in the present invention does not need to be a single liquid crystal compound, and may be a mixture containing two or more kinds of liquid crystal compounds or substances other than the liquid crystal compounds. Any material that is generally recognized as a liquid crystal material in this technical field is preferable, and one having a positive dielectric anisotropy is preferable, and if the manufactured liquid crystal device is a liquid crystal that can obtain good characteristics. good.

The liquid crystal used is preferably a nematic liquid crystal, a smectic liquid crystal or a cholesteric liquid crystal, particularly preferably a nematic liquid crystal. In order to improve its performance, cholesteric liquid crystals, chiral nematic liquid crystals, chiral smectic liquid crystals, chiral compounds and 2
A color dye or the like may be appropriately contained.

The liquid crystal material used in the present invention is preferably a blended composition comprising one or more compounds selected from the compound group shown below, and the characteristics of the liquid crystal material, that is, the phase of the isotropic liquid and the liquid crystal. For the purpose of improving the transition temperature, melting point, viscosity, Δn, Δε, solubility with a polymerizable composition and the like, they can be appropriately selected and blended for use.

Examples of the liquid crystal material include 4-substituted benzoic acid 4'-substituted phenyl ester, 4-substituted cyclohexanecarboxylic acid 4'-substituted phenyl ester, 4-substituted cyclohexanecarboxylic acid 4'-substituted biphenyl ester, 4- (4-substituted cyclohexanecarbonyloxy)
Benzoic acid 4'-substituted phenyl ester, 4- (4-substituted cyclohexyl) benzoic acid 4'-substituted phenyl ester, 4- (4-substituted cyclohexyl) benzoic acid 4'-substituted cyclohexyl ester, 4-substituted 4'-substituted Biphenyl, 4-substituted phenyl-4'-substituted cyclohexane,
4-substituted 4 ″ -substituted terphenyl, 4-substituted biphenyl 4′-substituted cyclohexane, 2- (4-substituted phenyl)
-5-substituted pyrimidine etc. can be mentioned.

The proportion of the liquid crystal material in the light control layer is 60% by weight.
The above is preferable, and the range of 70 to 90% by weight is particularly preferable. (Hereinafter, "%" means "% by weight")

[0043]

EXAMPLES The present invention will be described in more detail with reference to examples. However, the invention is not limited to these examples. In the following Examples and Comparative Examples, "%" represents "% by weight", and each of the evaluation characteristics means the following symbols and contents.

Further, the intensity of ultraviolet rays is as follows: Unimeter "UIT-101" manufactured by Ushio Inc. and light receiving element "UVD-3".
65 PD].

The transmittance of the substrate is a value measured using a spectrophotometer "U-3500" manufactured by Hitachi, Ltd.

The intensity of the backscattered light when the voltage of the light-scattering type liquid crystal display device is OFF is measured by the color difference meter “C” manufactured by Minolta Camera Co.
R-200b ”is used to measure the reflectance.

ROFF: Reflectance (%) when no voltage is applied RON: Reflectivity (%) when saturation voltage is applied CR: Contrast = ROFF / RON

(Example 1) "PN001" (nematic liquid crystal material manufactured by Rodick) 80.0%, lauryl acrylate 3.92%, "KAYARAD-HX-"
620 "(caprolactone-modified hydroxypivalic acid ester neopentyl glycol diacrylate manufactured by Nippon Kayaku Co., Ltd.) 15.68% and" Darocur 1173 "(polymerization initiator manufactured by Merck; 2-hydroxy-2-methyl-1-)
A dimming layer forming material composed of 0.4% of phenylpropan-1-one was prepared. A glass substrate with an ITO electrode having a transmittance of 82% or more at each wavelength in the wavelength region of 400 to 500 nm of the opening portion of one substrate as shown in FIG. After applying, the prepared light control layer forming material is sandwiched between two substrates, and the whole substrate is kept at 36 ° C.
It was manufactured by irradiating with 45 mW / cm ² of ultraviolet rays for 60 seconds, and the polymerizable composition was cured to obtain a light scattering type liquid crystal display device having a light control layer composed of a liquid crystal material and a transparent solid substance.

A black light-absorbing plate was placed behind this light-scattering type liquid crystal display element, and the reflectance at the time of light-scattering and at the time of light-transmitting was measured. ROFF = 18.5% RON = 7.7% CR = 2 Was 4.

As a result of observing the light control layer of the light-scattering type liquid crystal display device thus obtained with an electron microscope, a three-dimensional network polymer having an average void spacing of 1.2 μm was confirmed.

[0051]

(Example 2) 80.0% of "PN001",
3.92% lauryl acrylate, "KAYA Rad
A photochromic layer-forming material consisting of RAD) -HX-620 "15.68% and" Darocur 1173 "0.4% was prepared. As shown in FIG. 2, the opening portion of one substrate 400
11. A glass substrate with an ITO electrode having a transmittance of 82% or more at each wavelength in the wavelength range of ˜500 nm.
After applying a 0 micron glass fiber spacer, sandwich the prepared light control layer forming material between two substrates, and irradiate it with 45 mW / cm ² ultraviolet rays for 60 seconds while keeping the entire substrate at 36 ° C. A light-scattering liquid crystal display device having a dimming layer composed of a liquid crystal material and a transparent solid substance was obtained by manufacturing and curing the polymerizable composition.

A black light-absorbing plate was placed behind this light-scattering type liquid crystal display element, and the reflectance at the time of light-scattering and at the time of transmitting was measured. ROFF = 19.1% RON = 7.7% CR = 2 It was 0.5.

As a result of observing the light control layer of the light-scattering type liquid crystal display device thus obtained with an electron microscope, a three-dimensional network polymer having an average void spacing of 1.2 μm was confirmed.

(Comparative Example 1) "PN001" 80.0%,
3.92% lauryl acrylate, "KAYA Rad
RAD) -HX-620 "15.68% and" Darocur 1173 "(2-hydroxy-2-methyl- manufactured by Merck & Co., Inc.)
A dimming layer forming material consisting of 0.4% of 1-phenylpropan-1-one) was prepared. At each wavelength in the wavelength region of 400 to 500 nm of the opening portion of one substrate as shown in FIG. 3, a glass substrate with an ITO electrode that does not have a transmittance of 82% or more has a glass fiber of 11.0 microns. After applying the spacers made from the above, sandwich the prepared light control layer forming material between the two substrates and irradiate it with 45 mW / cm ² of ultraviolet rays for 60 seconds while keeping the entire substrate at 36 ° C to produce a polymer. The composition was cured to obtain a light-scattering liquid crystal display device having a light control layer composed of a liquid crystal material and a transparent solid substance.

A black light-absorbing plate was placed behind this light-scattering type liquid crystal display element, and the reflectance at the time of light-scattering and at the time of light-transmitting were measured. ROFF = 13.3% RON = 7.8% CR = 1 It was 0.7.

As a result of observing the light control layer of the light-scattering type liquid crystal display device thus obtained with an electron microscope, a three-dimensional network polymer having an average gap of 1.2 μm was confirmed.

As described above, it is clear that the light-scattering liquid crystal display device of the present invention is a light-scattering liquid crystal display device in which the white during light scattering is brighter and the contrast is higher than that of the comparative example. Is.

[0059]

The light-scattering liquid crystal display device of the present invention is a large-area, thin-film liquid crystal display device having a bright white when light is scattered and excellent visibility.

[Brief description of drawings]

FIG. 1 is a table showing the relationship between the wavelength of transmitted light and the transmittance at the opening of the substrate used in Example 1.

FIG. 2 is a chart showing the relationship between the wavelength of transmitted light and the transmittance at the opening of the substrate used in Example 2.

FIG. 3 is a chart showing the relationship between the wavelength of transmitted light and the transmittance at the opening of the substrate used in Comparative Example 1.

Claims (3)

[Claims] 1. A light scattering type in which at least one substrate having an electrode layer is transparent and two light control layers are provided between these substrates, and the light control layer contains a liquid crystal material and a transparent solid substance. In the liquid crystal display device, the transmittance of the opening of the transparent substrate is 82 at each wavelength in the wavelength range of 400 to 500 nm.
% Or more, a light scattering type liquid crystal display device. 2. The light-scattering liquid crystal display device according to claim 1, wherein the transparent solid substance is an ultraviolet curable resin. 3. The light-scattering liquid crystal display device according to claim 1, wherein the light control layer has a continuous layer of a liquid crystal material and a three-dimensional mesh-like transparent solid substance.