JPH02266324A - Liquid crystal device - Google Patents

Abstract

PURPOSE:To facilitate a large-sized display by using a nematic liquid crystal material which contains specific compds. and forms a continuous layer in a light control layer and distributing transparent solid materials in the form of three-dimensional network into the liquid crystal material. CONSTITUTION:The nematic liquid crystal material which contains the compds. expressed by formula I and formula II forms the continuous layer in the light control layer and the transparent solid materials are distributed in the form of the three-dimensional network in the liquid crystal material. In the formulas, R<1> denotes a straight chain alkyl group of 1 to 10C; m and n respectively in dependently denote 0 or 1; X<1> and X<2> respectively independently denote a hydro gen atom, fluorine atom, chlorine atom or cyano group. R<2> denotes 1 to 10 straight chain alkyl group. The liquid crystal device which allows the time divided driving with a low voltage and high contrast, does not require the use of polarizing plates and can be made into a larger size is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention provides a liquid crystal envelope i! which can be formed over a large area. The liquid crystal device of the present invention relates to a thin film, and is capable of electrically controlling the blocking and opening of a visual field, and the restriction, blocking, and transmission of light or illumination light, and is capable of electrically controlling the blocking and opening of a visual field, and the blocking, blocking, and transmitting of light or illumination light. It is used for screens and lighting control curtains, as well as for displaying advertising boards, information boards, decorative display boards, etc. by displaying characters and figures and switching the display electrically with high-speed response. It is used as a device for

(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 the encapsulating material (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. 1-5021.28 discloses a method in which liquid crystal is dispersed in an epoxy resin, and JP-A-61-305528 discloses a method in which the phase separation between a liquid crystal and a photocured material is fixed by light exposure. No. 62-2231 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 modulator required to obtain sufficient transparency requires a voltage of 25 V or more, and in many cases 50 V or more.
It is said to be driven at a high voltage of 00V, and is published 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 characteristics and 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 a time-sharing method that provides a warmer, 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. 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 <1) 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 R' represents a linear alkyl group having 1 to 10 carbon atoms, m and n each independently represent O or 1,
Xl and X2 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))
) A compound represented by the general formula (n) (wherein R2 represents a linear alkyl group having 1 to 10 carbon atoms) (hereinafter referred to as the compound of formula (II)) In this device, the substrate is The substrates may be made of a rigid material such as glass, metal, etc., or a flexible material such as a plastic film, and the substrates may be two sheets facing each other with an appropriate distance between them. be. 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 rays through a transparent substrate in the presence of a solution consisting of a transfer agent, a photosensitizer, a dye crosslinking agent, etc., thereby polymerizing the heptamer 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 polymer 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 polymer-forming materials 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.

Examples of optional components include polymerization initiators, chain transfer agents, photosensitizers, dyes, crosslinking agents, etc., which are selected as appropriate depending on the type of the seven polymers, oligomers, etc., and the performance of the desired liquid crystal device. be able to.

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 dithiopropionate, pentaerythritol tetrakis (β-thiopropionate), triethylene glycol dimercaptan, and the like. The amount of 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 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 20c11×20c
! It was inserted between two fTo glass plates No. 11 and irradiated with ultraviolet rays to harden (polymerize) the monomer. The curing conditions were as follows: The liquid crystal device was heated with a metal halide lamp (80W/
cm) at a speed of 3.5 m/min, and was irradiated with ultraviolet light. The energy given is 500 niJ/
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 VIo
= 8. OV, Vq. =14. OV, contrast -1:18, rising response time 3.4 ms, falling response time 12.2 ms, number of time division lines N, , = 3.9
Met.

(I) Liquid crystal (A) Composition 5% by weight 0% by weight Transition temperature 63.6°C (N-1 point) 1°C (
C-N point) Refractive index n, = 1.723 n, = 1.522 Δn = 0.201 Threshold voltage (Vth) 0.99 V Viscosity at 20°C 79.9 c, p.

(2) Number of time-division drive lines N,,, = ((α''+1)/(α2-1))'', where 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 V shown in (3) above. , Vl
. The respective light transmittances T, obtained by . , T from the value of T1°.

(Effects of the Invention) As described above, the present invention is a large-area, thin-film liquid crystal device that can be driven at a low voltage of about 14 V, and has a rise response time of 3 to 30 volts even at such a low voltage. 13
It has a high response speed of milliseconds, a high transparent-opaque contrast of approximately 1:18, has a threshold value, and is capable of time-division driving with a duty of 1/3. 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 represented by the formula (II) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R^2 represents a linear alkyl group having 1 to 10 carbon atoms.) Compounds represented by the formula (II) , wherein the liquid crystal material forms a continuous layer in the light control layer, and the transparent solid substance is distributed in a three-dimensional network in the liquid crystal material. LCD device. 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.