JPH02269310A - Liquid crystal device - Google Patents

Abstract

PURPOSE:To allow a time-divided driving with a low voltage and high contrast and the formation of the device to a larger size by forming a continuous layer in a dimming layer by a nematic liquid crystal material which contains a specific compd. and other specific compd. and distributing a transparent solid material in the form of three-dimensional network into the liquid crystal material. CONSTITUTION:This device has the dimming layer supported between substrates and the dimming layer consists of the transparent solid material of the three-dimensional network structure having fine open pores and the liquid crystal material filling the fine open pores. The liquid crystal material is the nematic liquid crystal material contg. the compd. expressed by formula I and the compd. expressed by formula II and the continuous layer is formed in the dimming layer by this liquid crystal material. The transparent solid material is distributed in the form of the three-dimensional network into the liquid crystal material. In the formula I, R<1> denotes 1 to 10C straight chain alkyl group. In the formula II, R<2> denotes 1 to 10C straight chain alkyl group or straight chain alkoxyl group. The liquid crystal device which allows the time-divided driving with the low driving voltage and the high contrast and the easy display in the large size 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 in building windows and shutter windows to block visibility and curtains to control daylight, as well as to display text and graphics and provide high-speed response. By electrically switching the display depending on the
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)-0 In the technology disclosed in the above specification, liquid crystal molecules encapsulated with polyvinyl alcohol can be used in the presence of an electric field if they have positive dielectric constant anisotropy in a thin layer. When the liquid crystal molecules below are aligned in the direction of the electric field and the refractive index n0 of the liquid crystal is equal to the refractive index n0 of the polymer, 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, and ■ provides improved visibility and improved opening performance, as well as excellent visibility of character displays. ■ 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 to be driven at a high voltage of 0V, and is
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 there. 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, to obtain the necessary dimming properties, each refractive index must be selected sufficiently to optimize the match between the individual refractive indices of the liquid crystal material and the refractive index of the photocured material. There are some unavoidable annoyances.

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 (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.

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

) A compound represented by general formula (II) (wherein R2 represents a linear alkyl group or a linear alkoxyl group having 1 to 1 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, the two substrates Both provide appropriate 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
It is not limited to rigidity, but also dance, flexibility, and
It can have flexibility and elasticity.

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 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 highly crosslinked, thereby making the liquid crystal material more responsive to electric fields. Demonstrates low voltage drive performance.

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 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, it is possible to inject this solution between the substrates, but it is also possible to apply it 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 of 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 material 80% of the liquid crystal (A) described below was mixed as a spacer, and an average particle size of 1 was added as a spacer.
Add a small amount of 0μm alumina powder, 20C11X20C!
The curing conditions were as follows: The monomer was inserted between two ITO glass plates and irradiated with ultraviolet rays to cure (polymerize) the monomer.
The liquid crystal device was heated using a metal halide lamp (80W/cm
) at a speed of 3.5 m/min, and was irradiated with ultraviolet rays. The energy given was 500…J/cm”
corresponds to 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
=8.8 V, V? @= 18.3 V, :I
7 Trust = 1819, rising response time 2.5 ms, falling response time 11.3 ms, number of time division lines N...
=2.6.

Liquid day day day (A) Composition transition temperature 83.4°C (N-1 point) °C (C-N point) Refractive index n, = 1.703 n, = 1.506 Δn = o, 197 Threshold Value voltage (V) 1.43V Viscosity at 20°C 59.1 c, p.

(2) Number of time-division drive lines N,,, = ((α!+1)/(α”-1)]”However, α=V, ./V l.

(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 V. , 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 . From the value of , T l , I"1. Rise response time is 3 to 12 seconds even at moderately low voltages.
It has a high response speed of milliseconds, a high transparent-opaque contrast of approximately 1=19, has a threshold value, and is capable of time-division driving of 1/2 deity. 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) and general formula (II) ▲ Numerical formulas, chemical formulas, tables, etc. are available▼ (In the formula, R^2 represents a linear alkyl group having 1 to 10 carbon atoms. (representing an alkyl group or a linear alkoxyl group), the liquid crystal material forms a continuous layer in the light control layer, and the transparent solid substance is a nematic liquid crystal material containing a compound represented by A liquid crystal device characterized by a three-dimensional network distribution inside the 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.