JPH02264216A - Liquid crystal device - Google Patents

Abstract

PURPOSE:To allow a time-divided driving with a low voltage and high contrast by constituting a dimming layer of a transparent solid material of a three- dimensional network structure having fine open pores and a specific liquid crystal material filling the above-mentioned fine open pores. CONSTITUTION:The dimming layer supported between two sheets of substrates which have electrode layers and at least one of which is transparent consists of the transparent solid material of the three-dimensional network structure having the fine open pores and the liquid crystal material filling the fine open pores. The liquid crystal material is a nematic liquid crystal material contg. two kinds of the compds. expressed by formulas I, II and forms a continuous layer in the dimming layer and the transparent solid material is distributed in the form of three-dimensional network in the liquid crystal material. In the formulas I, II, R<1> denotes 1 to 10C straight chain alkyl group; m, n respectively independently denote 0 or 1; X<1>, X<2> respectively independently denote a hydrogen atom, fluorine atom, etc.; R<2> denotes 1 to 10C straight chain alkyl group or straight chain alkoxyl group. The time-divided driving with the low voltage and the high contrast is possible in this way.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a thin film containing a liquid crystal that can be formed over a large area. , blocking, and transmitting can be controlled electrically, and are used as screens to block the view in building windows and show windows, as well as curtains for lighting control, as well as to display characters and figures, and to provide high-speed response. Therefore, by electrically switching the display,
Used as display devices such as advertising boards, information boards, decorative display boards, etc.

(Prior art) Liquid crystal display elements have conventionally been TN using nematic liquid crystal.
type and STN type are in practical use.

Also, devices using ferroelectric liquid crystals have been proposed. These require polarizing plates and also require alignment treatment. On the other hand, as a method for manufacturing large, inexpensive liquid crystal devices that are bright and have good contrast without requiring these devices, a method is known in which liquid crystal encapsulation is used to disperse liquid crystal droplets in a polymer and then turn the polymer into a film. It is being Here, gelatin, gum arabic, polyvinyl alcohol, etc. have been proposed as encapsulating substances (Japanese Patent Publication No. 58-501631, USP 443).
No. 5047).

In the technology disclosed in the above specification, if the liquid crystal molecules encapsulated with polyvinyl alcohol have positive dielectric constant anisotropy in a thin layer, the liquid crystal molecules can be encapsulated in the presence of an electric field. are aligned in the direction of the electric field, and when the refractive index n0 of the liquid crystal and the refractive index np of the polymer are equal, transparency is exhibited. When the electric field is removed, the liquid crystal molecules return to their random alignment and the refractive index of the liquid crystal droplet deviates from 00, so the liquid crystal droplet scatters light at its interface and blocks the transmission of light, making the thin layer cloudy. do. In addition to the above-mentioned techniques, there are several other known techniques for making thin films of polymers containing dispersed encapsulated liquid crystals.
No. 1-502128 discloses a method in which liquid crystal is dispersed in an epoxy resin, JP-A No. 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 No. 62-1988 discloses a method in which the phase separation between a liquid crystal and a photocured product is fixed by light exposure. No. 2231 discloses a liquid crystal dispersed in a special ultraviolet curable polymer.

(Problems to be Solved by the Invention) Important characteristics required for the practical use of large-sized liquid crystal devices such as those described above include: 1) ability to be driven at low voltage; 2) sufficient contrast; and 2) ability to perform time-division driving.

In particular, ■ ensures safety and lower power consumption when using building windows and show windows; This is necessary to advance the display performance of billboards, etc.

However, Special Publication No. 58-501631, Special Publication No. 6
1502128 and Japanese Patent Application Laid-Open No. 62-2231, it takes 25V or more to obtain sufficient transparency, and in most cases 50V to 20V.
It is said that it will be driven at a high voltage of 0.
No. 5528 and JP-A No. 64-62615, the best contrast ratio is at most 10, but in many cases it is less than 8. To date, it has not been possible to create a liquid crystal device that simultaneously has the above properties (1) and (2). Not yet. Furthermore, these patents do not have threshold characteristics and steepness characteristics that are indicators for the practical use of time-division driving, and therefore are inferior to conventional liquid crystal display elements whose operating principle is light scattering.

Furthermore, in order to obtain the necessary dimming properties, the respective refractive indices must be selected sufficiently to optimize the mismatch between the individual refractive indices of the liquid crystal material and the refractive index of the photocured material. There is.

As a result of intensive study on the preferred combination of the structure of a liquid crystal device and the physicochemical structure of the liquid crystal material used in the device, the inventors of the present invention have developed a time-sharing method with lower voltage and higher contrast than conventional large-sized liquid crystal devices. We succeeded in producing a large-sized liquid crystal device that can be driven and does not require the use of polarizing plates.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a liquid crystal device described below.

That is, the liquid crystal device according to the present invention includes two substrates each having an electrode layer and at least one of which is transparent, and a light control layer supported between the substrates, the light control layer having continuous fine pores. It consists of a transparent solid material with a three-dimensional network structure and a liquid crystal material that fills the continuous Vt micropores, and the liquid crystal material contains a compound represented by the following general formula (I) and a compound represented by the following general formula (II). A liquid crystal device, which is a nematic liquid crystal material, characterized in that the liquid crystal material forms a continuous layer in the light control layer, and the transparent solid substance is distributed in the liquid crystal material in a three-dimensional network. be.

General formula (I) (wherein R1 represents a linear alkyl group having 1 to 10 carbon atoms, m and n each independently represent 0 or 1,
Xl and Xt each independently represent a hydrogen atom, a fluorine atom, a chlorine atom or a cyano group. ) (hereinafter referred to as a compound of formula (I)).

) (wherein, R2 represents a linear alkyl group or a linear alkoxyl group having 1 to 10 carbon atoms) (hereinafter referred to as a compound of formula (n)) In this device, a substrate may be made of a rigid material such as glass or metal, or may be made of a flexible material such as a plastic film. Two substrates can be placed facing each other with an appropriate distance between them. Also, at least one of them is transparent, and the second one is transparent.
The light control layer supported between the layers must be visible from the outside world. However, complete transparency is not required. If the liquid crystal device is used to act on light passing from one side of the device to the other, both substrates are provided with suitable transparency. Appropriate transparent or opaque electrodes may be disposed on the entire surface or part of the substrate depending on the purpose.

A liquid crystal material and a transparent solid component are interposed between the two substrates. Incidentally, it is desirable to interpose a spacer for maintaining the distance between the two substrates according to a conventional method, as in well-known liquid crystal devices.

The light control layer requires that the liquid crystal material in continuous fine pores forms a continuous phase, and that the transparent solid material is distributed in the liquid crystal material in a three-dimensional network. If the ratio of the liquid crystal material component to the transparent solid substance is too small, it becomes difficult for the liquid crystal material to form a continuous layer, and when it is too large, the transparent solid substance tends to become difficult to form a three-dimensional network structure, which is not preferable.

The ratio of the liquid crystal material to the light control layer components is preferably 60
% by weight or more, and even more preferably from 70 to 90% by weight (hereinafter, % means % by weight).

The average diameter of the liquid crystal material in the continuous fine pores and the shape of the three-dimensional network structure is 0.2 to 2.
A range of 0 microns is preferred.

Three-dimensional network-like transparent solid in liquid crystal materials.

The material is not limited to being rigid, and may have flexibility, softness, and elasticity as long as it meets the purpose.

Synthetic resins are suitable as these transparent solid components. As a material that provides a three-dimensional network structure, an ultraviolet curing type heptamer or oligomer is preferable.

These liquid crystal devices can preferably be manufactured as follows.

That is, between two substrates each having an electrode layer and at least one of which is transparent, the above-mentioned liquid crystal material and an ultraviolet curable polymer-forming monomer or oligomer are placed as essential components, and a polymerization initiator and a chain are placed as optional components. The photochromic layer is made of a transparent solid material by irradiating ultraviolet light through a transparent substrate in the presence of a solution consisting of a transfer agent, photosensitizer, dye crosslinking agent, etc., thereby polymerizing the monomer or oligomer. This is a method for manufacturing a liquid crystal device comprising a three-dimensional network structure forming continuous fine pores, and a continuous layer of the liquid crystal material as an essential component in the continuous fine pores.

In this method, the ultraviolet curable polymer-forming monomer or oligomer that is an essential component may be one that forms a three-dimensional network in the continuous phase of the liquid crystal material by the irradiated ultraviolet rays. Good examples of molecule-forming monomers are trimethylolpropane triacrylate, tricyclodecane dimethylol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, hexanediol diacrylate, neopentyl glycol diacrylate,
Tris(acryloxyethyl)isocyanurate and the like.

Similarly, a good example of a polymer-forming oligomer is caprolactone-modified hydroxypivalic acid ester neopentyl glycol diacrylate.

Optional components include polymerization initiators, chain transfer agents, photosensitizers, dyes, crosslinking agents, etc., and can be appropriately selected depending on the types of monomers, oligomers, etc. and the performance of the desired liquid crystal device. can.

In particular, the combined use of a chain transfer agent is extremely effective depending on the type of monomer or oligomer, and prevents the resin from becoming too cross-linked, thereby making the liquid crystal material more responsive to electric fields. Demonstrates low voltage drive performance.

Examples of chain transfer agents include butanediol dithioprobionate, pentaerythritol tetrakis (β-thiopropionate), triethylene glycol dimercaptan, and the like. The amount of chain transfer agent added varies depending on the type of monomer or oligomer used, but if it is too small, the effect will be weak, and if it is too large, the opacity of the device will decrease and the contrast of the display will deteriorate. Its effective amount is 0.05-30% based on monomer or oligomer
However, 0.1 to 20% is suitable.

In order to support a solution containing each of these components between two substrates, this solution may be injected between the substrates, but it may be applied onto one substrate using a coater such as a spinner.
Then, the other substrate may be stacked.

Curing of the uncured solution can be accomplished by irradiating a suitable dose of ultraviolet light through the transparent substrate. Depending on the type of nanatsuma or oligomer or optional ingredients,
Heat or electron beams can also be used instead.

As the thickness of the light control layer becomes thinner, its light-shielding properties deteriorate;
Since the viewing angle for lighting tends to be narrow, a range of 5 to 30 microns is preferable.

A liquid crystal device configured in this way has lower driving voltage and higher contrast than conventional droplet dispersion type liquid crystal devices or devices with fixed phase separation between liquid crystal and photocured material, and is also useful for improving display performance. Split drive is possible.

(Example) Examples of the present invention will be shown below to further specifically explain the present invention. However, the present invention is not limited to these examples.

Example 1 19.8% by weight of trimethylolpropane triacrylate as a polymer-forming monomer (the same applies hereinafter), 0.2% of 2-hydroxy-2-methyl-1-phenylpropan-1-one as a polymerization initiator, and liquid crystal Mix 80% of the liquid crystal (A) described below as a material, add a small amount of alumina powder with an average particle size of 10 μm as a spacer, and make a 20 cm x 20 cm
The monomer was inserted between two ITO glass plates and irradiated with ultraviolet rays to harden (polymerize) the monomer. The curing conditions were as follows: The liquid crystal device was heated using a metal halide lamp (80W/c+s
) at a speed of 3.5 m/min, and was irradiated with ultraviolet rays. The applied energy corresponds to 500 mJ/cm''. The electrode spacing of the device is 11 μm.

When a cross section of the light control layer formed between two glass plates was observed using a scanning electron microscope, a three-dimensional polymer network was observed.

The obtained liquid crystal device has a threshold voltage of V16
= 8.3 V, V90 = 14.2 V, -7
contrast = 1:20, rising response time 3.4 microseconds, falling response time 13.8 milliseconds, number of time division lines N□, =
It was 4.2.

(I) Liquid crystal (A) Composition 15% by weight 103% by weight 7% by weight 8% by weight Transition temperature 75.3°C (N-I point) 15°C
(C-N point) Refractive index n, = 1.721 n, = 1.523 Δn = 0.198 Threshold voltage (VLh) 0.96 V Viscosity at 20°C 84.1 c, p.

(2) Number of time-division drive lines N+++ax = ((cx” + 1) / (α”
1)) “However, α=V,./V+.

(3) The light transmittance of the device when no voltage is applied is 0%,
When the light transmittance at which the light transmittance does not change as the applied voltage increases is 100%, the applied voltage at which the light transmittance becomes 90% is (2). , The applied voltage when the light transmittance becomes 10% is ■. shall be.

(4) With the device removed from the photometer, the light transmittance when the light source is on is 100%, and the light transmittance when the light source is off is 0.
%, the applied voltage shown in (3) above. , vl
. The respective light transmittances T, obtained by . , TIO values, the contrast between transparent and opaque is as high as about 1:20, and it has a threshold value, and is capable of time-division driving with a 1/4 duty. Therefore, it becomes extremely easy to adjust lighting, view, and display large-sized displays for advertisements, etc., and furthermore, manufacturing such a liquid crystal device is extremely easy and inexpensive.

Claims (1)

[Claims] 1. A three-dimensional device comprising two substrates, at least one of which is transparent, having an electrode layer, and a light control layer supported between the substrates, the light control layer having continuous fine pores. It consists of a transparent solid substance with a network structure and a liquid crystal material that fills the continuous fine pores, and the liquid crystal material has the general formula (I) ▲ Numerical formula, chemical formula, table, etc. ▼ (In the formula, R^1 is the number of carbon atoms 1 ~10 linear alkyl groups, m and n each independently represent 0 or 1, and X^1 and X^2 each independently represent a hydrogen atom, a fluorine atom, a chlorine atom, or a cyano group .) Compounds and general formula (II) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R^2 represents a linear alkyl group or a linear alkoxyl group having 1 to 10 carbon atoms. ), wherein the liquid crystal material forms a continuous layer in the light control layer, and the transparent solid substance is distributed in the liquid crystal material in a three-dimensional network. A liquid crystal device characterized by: 2. The liquid crystal device according to claim 1, wherein the liquid crystal material accounts for 60% by weight or more of the components of the light control layer. 3. The liquid crystal device according to claim 1, wherein the transparent solid material is made of synthetic resin. 4. The liquid crystal device according to claim 1, wherein the light control layer has a thickness of 5 to 30 microns.