JPH02202986A - lcd device - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal device which can be driven at a low voltage and can be made in a large size without the necessity for a polarizing plate by forming a light-controlling layer which is held between two base plates and comprises a continuous layer of a nematic liquid crystal material containing two specified compounds and having a transparent solid substance dispersed therein. CONSTITUTION:A liquid crystal device having two base plates, which have an electrode layer and at least one of which is transparent, and a light- controlling layer held between these base plates, wherein the light-controlling layer comprises a continuous layer of a nematic liquid crystal material containing both a compound of formula I (wherein R<1> is 1-10C straight-chain alkyl) and a compound of formula II (wherein R<2> is 1-12C straight-chain alkyl) and having a transparent solid substance dispersed therein. Because of the constitution and the liquid crystal material used, this liquid crystal device can be driven at a much lower voltage than conventional large liquid crystal devices and, in addition, it can be made in a large size without the necessity for the use of a polarizing plate.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a liquid crystal per FJA thin film that can be formed over a large area. Restriction, blocking, and transmission can be controlled electrically, and it is used in building windows and sissy windows to block vision, as well as in curtains to control daylight, as well as to display text and graphics, with high-speed response. By electrically switching the display using the switch, it can be used as a display device for advertising boards, guide 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 the encapsulating substance (Japanese Patent Publication No. 58-501631, tlsP44
No. 35047).

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 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 technology, there are other technologies that use a thin film of a polymer containing dispersed encapsulated liquid crystals (some are known, for example,
No. 1-502128 discloses a liquid crystal dispersed in an epoxy resin, and JP-A-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 liquid crystal devices such as those described above are (i) ability to drive at low voltage (ii) sufficient contrast (iii)
) Time division driving may be possible.

In particular, (i) and (iii) are extremely important characteristics in order to make the driving part of the device inexpensive.

However, to date, (i) to (ui)
A liquid crystal device that does not require a polarizing plate with this property has not been fabricated.

The inventors of the present invention have conducted extensive studies on the preferred combination of the structure of a liquid crystal device and the chemical structure of the liquid crystal material used in the device, and have found that it can be driven at a much lower voltage than conventional large liquid crystal devices, and that it can be driven with a polarizing plate. We have succeeded in creating a liquid crystal device that can be made larger without the need for the use of.

(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 has two substrates each having an electrode layer and at least one of which is transparent, and a light control layer supported between the substrates, and this light control layer has the following general formula (I )
and a transparent solid substance, the liquid crystal material forming a continuous phase, and the transparent solid substance being dispersed in the liquid crystal material. It is a liquid crystal device characterized by:

A compound represented by general formula (I) (wherein R1 represents a linear alkyl group having 1 to 10 carbon atoms) (hereinafter referred to as a compound of formula (I)).

) A compound represented by the general formula (n) (wherein, RI represents a linear alkyl group having 1 to 12 carbon atoms) (hereinafter referred to as a compound of formula (II)).

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 ratio of the liquid crystal material forming a continuous phase between the two substrates is preferably 70% by weight or more, and even more preferably 70 to 90% by weight (hereinafter, % means % by weight). ).

The transparent solid component interposed in the continuous phase of this liquid crystal material is
It may be dispersed in the form of particles, but preferably has a three-dimensional network structure. In any case, it is essential to form an optical interface with the liquid crystal material and to cause light scattering to occur. Its transparency can be determined appropriately depending on the purpose of use of the device, and its solidity is not limited to being rigid, but has flexibility, flexibility, and elasticity as long as it can meet the purpose. If the particles are too large or too small compared to the wavelength of light, light scattering properties cannot be expected, but choose the appropriate size and shape depending on the purpose. be able to.

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 liquid crystal material forms a continuous phase 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 monomers or oligomers; This is a method for manufacturing a liquid crystal device in which a transparent solid synthetic resin component in the form of a dimensional network is dispersed in a continuous liquid crystal phase.

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 can be extremely effective depending on the type of monomer or oligomer, and can prevent the resin from becoming too cross-linked, thereby making the liquid crystal material more responsive to electric fields. , low voltage drive performance is exhibited.Excellent examples of chain transfer agents include butanediol dithioprobionate, pentaerythritol tetrakis (β-thiopropionate), triethylene glycol dimercaptan, etc.Addition of chain transfer agent The amount depends on the type of monomer or oligomer used, but too little will have a weak effect, and too much will reduce the opacity of the device and reduce the contrast of the display.The 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.

The thickness of the light control layer is usually adjusted to a range of 5 microns to 30 microns.

A liquid crystal device configured in this manner enables time-division driving, which was not possible with conventional droplet dispersion type liquid crystal devices, and also has a lower driving voltage than conventional droplet dispersion type liquid crystal devices. High contrast and fast response speed. For example, while a conventional droplet dispersion type liquid crystal device requires a driving voltage of 60V or more in effective value, and in many cases 100V or more, the liquid crystal device of the present invention requires a rise response time of approximately 20V driving voltage. A response time of 3 to 4 msec and a falling response time of 4 to 30 msec are achieved.

(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 I-limethylolbroban triacrylate as a polymer-forming monomer (the same applies hereinafter), (1)
Liquid crystal (A) 2-hydroxy-2-methyl composition 1-phenylpropan-1-one 0.2 as a polymerization initiator
% and 80% of the liquid crystal (A) described below was mixed as a liquid crystal material, a small amount of alumina powder with an average particle size of 10 μm was added as a spacer, and the mixture was inserted between two ITO glass plates of 20 x 20 cm, and exposed to ultraviolet rays. The monomer was cured (polymerized) by irradiation. The curing conditions were: the liquid crystal device was heated under a metal halide lamp (80 W/cm) at 3.5 m/min;
UV rays were irradiated. 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 resulting liquid crystal device has a threshold voltage of V+o
-8,4V, V*o" 17. TV, :17Trust 1;19, rise response time 2.7ms, fall response time 20ms, number of time division lines N,, -2,5 there were.

Transition temperature 77 ℃ (N-1 point) 8 ℃ (C
-N point) Refractive index n, -1,716 n, -1,509 Δn -0,207 Threshold voltage (■) 1.21V Viscosity at 20°C 57.1 c, p.

(2) Number of time-division drive lines N,,X-((α”+1)/(α”-1))”However,
α-V,. / Vi.

(3) The light transmittance of the device when no voltage is applied is 0%,
When the light transmittance when the light transmittance does not change as the applied voltage increases is 100%, the applied voltage at which the light transmittance is 90% is 'l'91, and when the light transmittance is 10%. Let the applied voltage be Vl+).

(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 approximately 18V, and has a rise response time of 3 to 30V even at such a low voltage. 4m
It has a high response speed of 1/2 and a high response speed of about 1:19, has a threshold value, and is capable of 1/2 duty time-division driving.
y, it becomes extremely easy to produce large-sized displays for advertisements, etc., and the manufacture of such liquid crystal devices becomes extremely easy and inexpensive.

Claims (1)

[Claims] 1. Two substrates each having an electrode layer, at least one of which is transparent, and a light control layer supported between the substrates, wherein the light control layer has a general formula ▲ mathematical formula, chemical formula, or table. ▼ (In the formula, R^1 represents a linear alkyl group having 1 to 10 carbon atoms.) Compounds represented by the general formula ▲ Numerical formulas, chemical formulas, tables, etc. ▼ (In the formula, R ^2 represents a linear alkyl group having 1 to 12 carbon atoms. A liquid crystal device characterized in that a solid substance is dispersed in the liquid crystal material. 2. The liquid crystal device according to claim 1, wherein the liquid crystal material accounts for 70% 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 transparent solid substance is dispersed in the liquid crystal material in the form of particles or a three-dimensional network. 5. The liquid crystal device according to claim 1, wherein the light control layer has a thickness of 5 to 30 microns.