JP3182695B2 - Light scattering liquid crystal two-layer panel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal device which can achieve high brightness and high contrast. The present invention relates to a decorative display board such as a public notice board or the like by electrically switching its display with high-speed response. It is used as a variety of display devices such as a watch calculator computer terminal that requires a bright screen.

[0002]

2. Description of the Related Art Conventionally, a TN type or STN type liquid crystal display element using a nematic liquid crystal has been put to practical use. Further, a device using a ferroelectric liquid crystal has been proposed.

[0003] Since these require a polarizing plate, there is a limit to brightening the surface.

On the other hand, as a method of manufacturing a large and inexpensive liquid crystal device which does not require a polarizing plate or an alignment treatment, and which is bright, has good contrast, and disperses liquid crystal droplets in a polymer by encapsulating the liquid crystal, the polymer is dispersed. A method of forming a film is known. JP-T-58-501631 JP,
U.S. Pat. No. 4,435,047 proposes gelatin, gum arabic, polyvinyl alcohol, and the like as an encapsulating material. In addition to these, for example, Japanese Patent Application Laid-Open No. 61-502128 discloses a liquid crystal. Are dispersed in an epoxy resin, JP-A-61-305528 discloses a method in which the phase separation between a liquid crystal and a photocured product is fixed by light exposure, and JP-A-62-2231 discloses a special product. Liquid crystal dispersed in a transparent ultraviolet curable polymer,
JP-A-144321 discloses a method of mixing polyester, liquid crystal, and a solvent in a solvent to form a film.

However, Japanese Patent Publication No. Sho 58-501631
JP, JP-T-61-502128 and JP-A-6-128128
In a liquid crystal device obtained by the technique disclosed in Japanese Patent Application Laid-Open No. 1-2231, a high voltage drive of 25 V or more, in many cases 50 V to 200 V is used to obtain sufficient transparency. And JP-A-1-6
The contrast ratio of the liquid crystal device disclosed in Japanese Patent No. 2615 is 10 at most, and is 8 in most cases.
This is the case, and did not have the characteristics required for practical use of the liquid crystal device.

Further, in order to enable low-voltage drivability, high-contrast, and time-division drivability, which are important characteristics required for practical use of a liquid crystal device as described above, JP-A-1-11-1
Japanese Patent No. 98725 discloses a liquid crystal device having a structure in which a liquid crystal material forms a continuous layer, and a polymer substance is distributed in a three-dimensional network in the continuous layer.

[0007]

However, when the light-scattering type liquid crystal device as described above is used as a display panel, black or other colors installed behind the panel apply a voltage or the like because light scattering is used. There is a major drawback in that even when not performed, the image is not cut off and appears faintly on the cloudy portion. This makes direct-view display difficult, and in particular, full-color display has been impossible.

An object of the present invention is to provide a light scattering capable of direct-view type full-color display in which black or other colors provided behind the panel are not faintly reflected in a cloudy portion even when no voltage or the like is applied. It is an object of the present invention to provide a liquid crystal device.

[0009]

The present inventors have established a new liquid crystal device which solves the above-mentioned problem by combining the above-mentioned light-scattering type liquid crystal display technology with a conventionally known liquid crystal display technology. .

That is, in order to solve the above problems, the present invention has two light control layers sandwiched between two transparent substrates having a transparent electrode layer, and the light control layer is formed of a liquid crystal. The polyvinyl
Layer encapsulated with alcohol, liquid in epoxy resin
Layer in which crystal droplets are dispersed, layer in which liquid crystal droplets are dispersed in a photocured product, and
Layers of liquid crystals in polymer materials distributed in a three-dimensional network
A light scattering type liquid crystal display panel, which is one kind selected from a layer having : and a guest-host type liquid crystal display panel containing a dichroic dye dissolved in a liquid crystal material. A liquid crystal two-layer panel is provided.

FIG. 1 shows an example of the structure of the black-and-white type liquid crystal two-layer panel of the present invention.

When the liquid crystal light control layer of the panel A is not applied with the voltage of (a), the light incident from the front is scattered and becomes cloudy, but the light traveling straight enters the panel B. At this time, the panel B is set so that a voltage is applied, and the incident light is transmitted without being absorbed by the black dichroic dye, is reflected by the white reflector at the back, and becomes white when viewed from the front.

When the liquid crystal light control layer of the panel A applies the voltage shown in FIG.
Incident on. At this time, the panel B is set so that no voltage is applied, and the incident light is absorbed by the black dichroic dye and becomes black when viewed from the front. Although this example is a reflection type, a transmission type in which a backlight is installed behind the panel B can be used in the same manner. Further, a polarizing plate may be inserted between the panel A and the panel B or behind the panel B in order to sharpen black.

FIG. 2 shows a structural example of a full-color liquid crystal two-layer panel of the present invention.

When the liquid crystal light control layer of the panel A is not applied with the voltage of (a), the light incident from the front is scattered and becomes cloudy, but the light traveling straight enters the panel B. At this time, the panel B is set so that no voltage is applied, and the incident light is absorbed by the black dichroic dye, so that the colors of the RGB color filters of the panel B cannot be seen from the front.

When the liquid crystal light control layer of the panel A is applied with the voltage shown in FIG.
Incident on. At this time, it is set so that a voltage is applied to the panel B, and the incident light is transmitted without being absorbed by the black dichroic dye, and is transmitted through the RGB color filter of the panel B. You can see the color. Although this example is a reflection type, a transmission type in which a backlight is installed can also be used like the monochrome type, and a polarizing plate may be inserted between the panel A and the panel B or behind the panel B.

The dimming layer of the light-scattering type liquid crystal display panel used in the present invention may be, for example, a layer in which liquid crystal is encapsulated with polyvinyl alcohol or the like as described in JP-A-58-501631. Tokio Sho 61-
Liquid crystal droplets dispersed in an epoxy resin as described in JP-A-502128 may be used.
Liquid crystal droplets may be dispersed in a photo-cured product by phase separation by light exposure as described in JP-A-305528, or a liquid crystal material may form a continuous layer as described in, for example, JP-A-1-198725. Alternatively, the continuous layer may have a structure in which the polymer substance is distributed in a three-dimensional network.

As the polymer substance giving the three-dimensional network structure, a thermosetting resin or an ultraviolet-curable resin obtained by polymerizing a polymer-forming monomer or oligomer is preferable. Further, a synthetic resin soluble in an organic solvent and a synthetic resin soluble in water are also suitable.

As a method of forming a light control layer containing a polymer substance having a uniform three-dimensional network structure on a substrate, for example, a liquid crystal material, a polymer-forming monomer or an oligomer, and A homogeneous solution with a photopolymerization initiator,
While being kept in an isotropic liquid state, it is sandwiched between transparent substrates having two transparent electrode layers, or a coater such as a spin coater is provided on a substrate having one transparent electrode layer. May be applied, and then the other substrate may be overlaid, which is irradiated with radiation such as ultraviolet rays or electron beams,
Alternatively, the resin is thermally polymerized and cured to form a three-dimensional network synthetic resin layer.

The method for uniformly forming a transparent solid substance having a three-dimensional network structure on a substrate is not limited to these methods.

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 liquid crystal compounds or a substance other than the liquid crystal compound. Any material which is generally recognized as a liquid crystal material in this technical field may be used, and a material having a positive dielectric anisotropy is preferable. As the liquid crystal used, a nematic liquid crystal, a smectic liquid crystal, and a cholesteric liquid crystal are preferable, and a nematic liquid crystal is particularly preferable. In order to improve the performance, a cholesteric liquid crystal, a chiral nematic liquid crystal, a chiral smectic liquid crystal, or the like, or a chiral compound may be appropriately contained.

The liquid crystal material used in the present invention is preferably a compounded composition comprising at least one compound selected from the following compound group. The properties of the liquid crystal material, that is, the phase of the isotropic liquid and the liquid crystal are preferable. For the purpose of improving the transition temperature, melting point, viscosity, Δn, Δε, solubility with the polymerizable composition and the like, they can be appropriately selected, blended and used.

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-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 and the like can be mentioned.

The proportion of the liquid crystal material in the light modulating layer having a structure in which the liquid crystal material forms a continuous layer and the polymer substance is distributed in a three-dimensional network in the continuous layer is preferably 60% by weight or more. Particularly preferred is a range of -90% by weight.

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 a group such as 3-chloro-2-hydroxypropyl, dimethylaminoethyl, diethylaminoethyl or the like; ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-butylene glycol, tetramethylene glycol, Mono (meth) acrylate or poly (meth) acrylate such as hexamethylene glycol, neopentyl glycol, trimethylolpropane, glycerin and pentaerythritol; vinyl acetate, vinyl butyrate or vinyl benzoate, acrylonitrile, cetyl vinyl ether, limonene, cyclohexene, diallyl Phthalate, diallyl isophthalate, 2-, 3- or 4-vinylpyridine, acrylic acid, methacrylic acid, Rylamide, methacrylamide, N-hydroxymethylacrylamide or N-hydroxyethylmethacrylamide and alkyl ether compounds thereof; di (meth) of diol obtained by adding 2 mol or more of ethylene oxide or propylene oxide to 1 mol of neopentyl glycol ) Acrylates;
Diol or tri (meth) acrylate of triol obtained by adding 3 mol or more of ethylene oxide or propylene oxide to 1 mol of trimethylolpropane; obtained by adding 2 mol or more of ethylene oxide or propylene oxide to 1 mol of bisphenol A Di (meth) acrylate of diol; reaction product of 1 mol of 2-hydroxyethyl (meth) acrylate and 1 mol of phenyl isocyanate or n-butyl isocyanate;
Examples thereof include poly (meth) acrylate of dipentaerythritol, and include trimethylolpropane triacrylate, tricyclodecane dimethylol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, hexanediol diacrylate, and neopentyl glycol diacrylate. Acrylate and tris- (acryloxyethyl) isocyanurate are particularly preferred.

Examples of the polymer-forming oligomer include caprolactone-modified hydroxypivalic acid ester neopentyl glycol diacrylate.

In order to control the thickness of the transparent solid substance uniformly attached to the substrate, a spacer may be mixed with a solution of a liquid crystal material and a monomer or oligomer, or a solution of an organic solvent and a monomer or oligomer,
A spacer may be applied on one of the substrates.

Examples of the polymerization initiator include 2-hydroxy-2-methyl-1-phenylpropan-1-one ("Darocur 1173" manufactured by Merck) and 1-hydroxycyclohexylphenyl ketone ("Ciba Geigy"). Irgacure 184 "), 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropane-1-
ON (“Darocure 1116” manufactured by Merck), benzyldimethyl ketal (“Irgacure 651” manufactured by Ciba-Geigy), 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropanone-1 (Ciba -"Irgacure 907" manufactured by Geigy Corporation), 2,4-diethylthioxanthone ("Kayacure DET" manufactured by Nippon Kayaku Co., Ltd.)
X ") and ethyl p-dimethylaminobenzoate (" Kayacure-EPA "manufactured by Nippon Kayaku Co., Ltd.), isopropylthioxanthone (" Kantacure ITX "manufactured by Ward Prekinsopp) and ethyl p-dimethylaminobenzoate Of 2-hydroxy-2-methyl-1-phenylpropan-1-one, which is a liquid, is particularly preferable in view of compatibility with a liquid crystal material, a polymer-forming monomer or an oligomer.

When the average diameter of the shape of the three-dimensional network structure formed from the transparent solid material is too large or too small compared to the wavelength of light, the light scattering property tends to decrease. Therefore, the range of 0.2 to 2 μm is preferable. In addition, the thickness of the layer having the transparent solid material is set to 2 depending on the purpose of use in order to obtain a sufficient contrast between opacity due to light scattering and transparency achieved electrically.
It is preferably in the range of 15 to 15 μm.

The substrate spacing of the light scattering type liquid crystal display panel manufactured by such a method is preferably in the range of 2 to 30 μm, and particularly preferably in the range of 5 to 20 μm.

As the liquid crystal material used in the guest-host type liquid crystal display panel, any liquid crystal material that can be used in a light scattering type liquid crystal display panel can be used without any particular limitation.

The dichroic dye used in the guest-host type liquid crystal display panel can be used without particular limitation as long as it is a dichroic dye for liquid crystal use. For example, anthraquinone dyes,
Examples include dichroic dyes such as azo dyes, quinophthalone dyes, perylene dyes, coumarin dyes, thioindigo dyes, merocyanine dyes, styryl dyes, and oxonol dyes.

Examples of commercially available dichroic dyes include “SI-497” (blue) and “M-M” manufactured by Mitsui Toatsu Dye Co., Ltd.
137 "(blue)," SI-426 "(red),
"S-416" (black), "S-344" (black), Nippon Kayaku's "LCD-118" (blue),
"LCD-208" (red), "LCD-465"
(Black), “CLD-506” (blue) manufactured by Sumitomo Chemical Co., Ltd., and the like.

The content of the dichroic dye is based on the amount of the liquid crystal material.
The range of 0.01 to 10% by weight is preferred.

The guest-host type liquid crystal display panel is usually manufactured by a well-known method.

The light-scattering type liquid crystal two-layer panel of the present invention having such a configuration can provide a high contrast, bright, direct-view type liquid crystal device of monochrome and full-color display.

[0037]

EXAMPLES Examples of the present invention will be shown below, and the present invention will be described more specifically. However, the present invention is not limited to these examples.

Example 1 Trimethylolpropane triacrylate 1 was used as a monomer for forming a transparent solid substance.
9.8% by weight, 2-hydroxy-2- as a polymerization initiator
A mixture of 0.2% by weight of methyl-1-phenylpropan-1-one and 80% by weight of a liquid crystal (A) described later as a liquid crystal material, a small amount of alumina powder having an average particle diameter of 10 μm was added as a spacer, and two 20 cm × 20 cm sheets were used. Was inserted between the ITO glass plates and irradiated with ultraviolet rays to cure (polymerize) the monomers. The curing conditions were such that the liquid crystal device was passed under a metal halide lamp (80 W / cm) at a speed of 3.5 m / min, and irradiated with ultraviolet rays. The energy given is 500
It corresponds to mJ / cm ² . The electrode spacing of the liquid crystal device is 11
μm. When the cross section of the light control layer formed between the two glass plates was observed with a scanning electron microscope, a three-dimensional network of the polymer was observed.

[0039]

Embedded image

[0040]

The obtained liquid crystal device was connected to panel A of FIG.
Liquid crystal "RDX-5082" (Rodick)
General TN-L containing 98% by weight and 2% by weight of a black dichroic dye “S-416” (manufactured by Mitsui Toatsu Dye Co., Ltd.)
A two-layer panel was produced by stacking the CDs as panel B with panel A facing upward. When the panel A was turned off and the panel B was driven at 5 V (a), and when the panel A was driven at 20 V and the panel B was turned off (b), the contrast was 28: 1.

(Comparative Example 1) The contrast when a black back screen was installed behind panel A in the same manner as in Example 1 was 6: 1.

[0043]

The light scattering type two-layer panel of the present invention is a liquid crystal device having a much higher contrast than a conventional light scattering type liquid crystal device when it is of a direct viewing type.

Further, when a two-layer panel was manufactured using a TFT-TN-LCD with an RGB color filter as shown in FIG. 2, a clear direct-view type full-color liquid crystal device was manufactured. The light-scattering type two-layer panel enables a direct-view full-color display, which was not possible with the light-scattering type. The panel A on which the light scattering layer is formed does not have a liquid crystal continuous layer as in the embodiment of the present invention, but also has a liquid crystal droplet dispersed in a polymer such as NCAP. We were able to.

Therefore, the liquid crystal device of the present invention is useful as a direct-view display device such as a display device at the terminal of a computer.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of the structure of a light-scattering type liquid crystal two-layer panel of the present invention.

FIG. 2 is a schematic sectional view showing an example of the structure of a light-scattering type liquid crystal two-layer panel of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Transparent electrode 3 Liquid crystal material 4 Dichroic dye 5 Light control layer 6 Sealant 7 Reflector 8 RGB color filter

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-102326 (JP, A) JP-A-62-289934 (JP, A) JP-A-61-119129 (JP, U) (58) Survey Field (Int.Cl. ⁷ , DB name) G02F 1 / 1333,1 / 1347,1 / 137

Claims (1)

(57) [Claims] 1. A liquid crystal display device comprising: two light control layers sandwiched between two transparent substrates having a transparent electrode layer ;
Layer encapsulated with polyvinyl alcohol, epoxy
A layer in which liquid crystal droplets are dispersed in a resin.
Liquid in dispersed layers and polymer substances distributed in a three-dimensional network
A light-scattering type liquid crystal display panel, which is one kind selected from a layer having a continuous crystal layer , and a guest-host type liquid crystal display panel containing a dichroic dye dissolved in a liquid crystal material. Light scattering liquid crystal two-layer panel.