JPH02267520A - Liquid crystal device - Google Patents

Abstract

PURPOSE:To obtain a large-area liquid crystal which allows a low-voltage and time-division driving and has a high contrast by distributing a transparent solid material of a three-dimensional network structure having the fine open pores in a liquid crystal material satisfying the fine open pores expressed by specific formula, and thereby forming a light control layer. CONSTITUTION:The light control layer is supported by two sheets of substrates at least one of which is transparent. The light control layer is formed of the liquid crystal material which forms continuous phases in the fine open pores and the transparent solid material which is distributed in the form of three- dimensional network in the liquid crystal material. The liquid crystal material consists of the nematic liquid crystal material contg. the compd. expressed by the formula. The transparent solid component is preferably a monomer or oligomer of a UV curing type. The large-area thin-film liquid crystal device which allows the low-voltage driving and the time-division driving and has the high contrast is obtd. 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 n 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 no, so the liquid crystal droplet scatters light at its interface and blocks the transmission of light, so the thin layer becomes 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
1-502128 and Japanese Patent Application Laid-open No. 62-2231, the liquid crystal light modulation element obtained by the technology disclosed in JP-A No. 1-502128 and JP-A-62-2231 requires a voltage of 25 V or more to obtain sufficient transparency, and a voltage of 50 V to 2
It is said to be driven with a high voltage of θQV, and is disclosed in Japanese Patent Application Laid-open No. 61-3.
No. 05528 and JP-A No. 64-62615, the best contrast ratio is at most 10, and in many cases 8.
To date, it has not been possible to create a liquid crystal device that simultaneously has the above properties (1) and (2).In addition, these patents contain information on threshold characteristics and threshold characteristics that are indicators of the practical application of time-division driving. Because it does not have steep characteristics, it is 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 found that the present inventors can achieve high contrast and low voltage and high contrast at a much lower voltage and higher contrast than conventional large liquid crystal devices. We have succeeded in producing a liquid crystal device that can be divided into parts and that does not require the use of polarizing plates and can be made larger.

(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. A nematic comprising a transparent solid substance with a three-dimensional network structure and a liquid crystal material filling the continuous fine pores, the liquid crystal material containing a compound represented by the following general formula (I) and a compound represented by the following general formula (II). It is a liquid crystal material,
The liquid crystal device is characterized in that the liquid crystal material forms a continuous layer in the light control layer, and the transparent solid material is distributed in the liquid crystal material in a three-dimensional network.

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 Xz each independently represent a hydrogen atom, a fluorine atom, a chlorine atom or a cyan group. ) (hereinafter referred to as a compound of formula (I)).

) A compound represented by the general formula (If) (wherein R1 represents a linear alkyl group or a linear alkoxyl group having 1 to 10 carbon atoms) (hereinafter referred to as a compound of formula (IF)) ) In this device, the substrate may be a rigid material such as glass, metal, etc., or 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.

The three-dimensional network-like transparent solid substance in the liquid crystal material is
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. Ultraviolet curable monomers or oligomers are preferred as those that provide a three-dimensional network structure.

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 molecular forming agents include 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 can be extremely effective depending on the type of monomer or oligomer, preventing the resin from becoming too cross-linked, thereby making the liquid crystal material more responsive to electric fields, and lowering voltages. Drivability is demonstrated. Examples of chain transfer agents include butanediol dithioprobionate, pentaerythritol tetrakis (β-thiopropionate), triethylene glycol dimercaptan, and the like. The amount of the chain transfer agent added varies depending on the type of polymer 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
Possible amounts are 0.05-30%, based on monomer or oligomer, but 0.1-20% is preferred.

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 monomer or oligomer or optional components,
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 (the same applies hereinafter) as a polymer-forming monomer, and 0.2% and 2-hydroxy-2-methyl-1-phenylpropan-1-one as a polymerization initiator. Mix 80% of the liquid crystal (A) described below as a liquid crystal 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 liquid crystal device was inserted between two ITO glass plates, irradiated with ultraviolet rays, and the monomer was cured (polymerized).
) at a speed of 3.5 m/min, and was irradiated with ultraviolet rays. The applied energy corresponds to 500 sJ/am''. 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 Vl(
+= 8.2 V, V9+1= 14.9 V,
:) 7 trust=l:18, rise response time 3.4
milliseconds, fall response time 12.3 milliseconds, number of time division lines N
,,,=3.5.

(I) Liquid crystal (A) Composition 15% by weight 10% by weight 5% by weight 10% by weight Transition temperature refractive index 76.5°C (N-1 point) 15°C (C-N point) n, = 1.712 n, =1.522 Δn=0.190 L! (i Voltage (Vth) 0.97 V Viscosity at 20°C 83.5 c, p.

(2) Number of time-division drive lines N,,, = ((α” + 1)/ (α”-1)) “However, α = V 9 @ / 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 V shown in (3) above. , ■,
. The respective light transmittances T, obtained by . , it is possible to drive with a voltage from the 'rhoO value, and even at such a low voltage, the response speed is high with a rise response time of 3 to 13 milliseconds, and the transparent-opaque contrast is high at approximately 1:18, making it possible to exceed the threshold value. have,
Time-division driving of 1/3 duty is possible. 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 mesh 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. ~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. , ▲There are mathematical formulas, chemical formulas, tables, etc.▼ represents ▲There are mathematical formulas, chemical formulas, tables, etc.▼ or ▲There are mathematical formulas, chemical formulas, tables, etc.▼.) It is a nematic liquid crystal material containing a compound represented by A liquid crystal device, characterized in that the liquid crystal material forms a continuous layer in the light control layer, and the transparent solid material is distributed in the liquid crystal material in a three-dimensional network. 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.