JPH0247628A - Processing method of liquid crystal - Google Patents

Abstract

PURPOSE:To easily obtain a uniformly oriented film by subjecting a liquid crystal to an electric field orientation then to crosslinking. CONSTITUTION:The liquid crystal is subjected to the electric field orientation, then to the crosslinking. The liquid crystal to be subjected to the electric field orientation is exemplified by a crosslinkable liquid crystal compds., mixture composed of a non-crosslinkable liquid crystal compd. and a crosslinkable non- liquid crystal compd., and mixture composed of the crosslinkable liquid crystal compd. and the crosslinkable non-liquid crystal compd. The liquid crystal may be a ferroelectric liquid crystal and a low polymer compd. contg. a chiral alkyl group and tolanes contg. a chiral alkyl group are usable as well. Further, a ferroelectric high-polymer liquid crystalline compd. is usable as well. The oriented film which is uniform and has excellent dynamical strength is obtd. in this way.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a method for processing liquid crystals.

[Prior Art] In recent years, in contrast to low-molecular liquid crystal compounds that are widely used in the electronics application field, active development has been carried out to apply high-molecular liquid crystal compounds to recording and display elements. An electric field is used as a method for aligning polymeric liquid crystals.

[Problems to be solved by the invention] However, even if an attempt is made to align using a liquid crystal polymer with a molecular weight of several hundred thousand or more and sufficient film-forming properties, the inherent high viscosity of the polymer Therefore, it is difficult to obtain a sufficiently uniform alignment film.

[Means for Solving the Problems] The present inventors have arrived at the present invention as a result of intensive studies on processing methods for obtaining monodomain film-forming liquid crystal aligning films.

That is, the present invention is a method for processing a liquid crystal characterized by subjecting the liquid crystal to electric field alignment and then crosslinking the liquid crystal.

In the present invention, as the liquid crystal to be aligned by electric field, (1)
Examples include a crosslinkable liquid crystal compound, (2) a mixture of a non-crosslinkable liquid crystal compound and a crosslinkable non-liquid crystal compound, and (3) a mixture of a crosslinkable liquid crystal compound and a crosslinkable non-liquid crystal compound.

Examples of the crosslinkable liquid crystal compound include compounds obtained by chemically adding or substituting a crosslinking group to a conventionally known liquid crystal compound.

Such liquid crystal compounds include phenylbenzoic acid esters, biphenyl and its esters, phenylcyclohexane and its esters, cyclohexylcyclohexane and its esters, phenyldioxane and its esters, and phenylpyrimidine. and its esters.

Further, a polymeric liquid crystal compound having a large molecular weight can also be used.

Examples of polymer liquid crystal compounds include main chain type polymer liquid crystal compounds,
Examples include side chain type polymer liquid crystal compounds.

A main chain polymer liquid crystal compound is a polymer compound in which a mesogen is contained in the main chain, and may contain a visible group (hereinafter referred to as a spacer) as required.As a mesogen, Q
-X-0 may be mentioned. Here, as X, CH=CH.

C-C, CH=CH-Go, Co-0, Go-NH.

CH=N, N=N, N=, N, Q, 0
etc.

Examples of the spacer include methylene chains, oxyethylene chains, oxypropylene pyrene chains, and dimethylsiloxane chains of CI to CL2.

Examples of main chain polymeric liquid crystal compounds include those with the following structure described in Macromolecular Φ Hemie, Vol. 184, p. 253 (1983).

[-(CH2)11-0-c>Coo-Q-Coo-]
(1) Cellulose derivatives such as poly(γ-benzylglutamate hydroxypropyl cellulose) can also be used as other main chain polymeric liquid crystal compounds.

A side chain type polymeric liquid crystal compound is one in which a mesogen is included in the side chain, and a spacer may be interposed between the main chain and the mesogen. In addition to those mentioned above, mesogens include those containing a cholesteryl group or a chiral nematic group. Examples of the main chain used in the side chain type polymeric liquid crystal compound include a c-C bond, a Sl-0 bond, and the like. An example of the former is Macromolecule Hemi-17.
9, p. 254 (1978), the chemical structures shown below are listed.

[-CHaCH-co
(2) C O −0 − (
C H2) 6o -0-Q-o C H3 Examples of the latter include those represented by the following chemical structure described in JP-A-56-79173.

Further, in the present invention, the liquid crystal may be a ferroelectric liquid crystal, and such a liquid crystal may be a low-molecular compound containing a chiral alkyl group, specifically, Chapter 7 of "Liquid Crystals - Fundamentals" co-edited by Mitsuharu Okano and Shunsuke Kobayashi. (Baifukan, published in 1985) can be used. Tolans containing a xylalkyl group (eg, Japanese Patent Application No. 81-438H) can also be used. Furthermore, it is also possible to use a ferroelectric polymeric liquid crystal compound as shown in the following formula.

[-CH2CH-Ko body O ch = cholesteryl group The crosslinkable groups added or substituted to the liquid crystal compound include groups that cause a reaction triggered by light irradiation, that is, photocrosslinking, and other groups (other than photocrosslinking). It can be roughly divided into groups that crosslink by the reaction of

Examples of the group that causes a photocrosslinking reaction include a radical polymerizable group, a photodimerizable group, an azide group, and a cationic polymerizable group.

Examples of the radically polymerizable group include an acrylate group, an α-chloroacrylate group, a methacrylate group, a styryl group, a vinyl group, a vinyl ester group, a vinyl ketone group, and an acrylamide group.

Examples of polymeric liquid crystal compounds containing such radically polymerizable groups include acrylic acid ester of hydroxypropylcellulose described in Molecular Crystals & Liquid Crystals: Letters, Vol. 102, p. 255 (1984) and Patent Application No. 1982. Mention may be made of polysiloxanes containing acrylic groups as described in Book No. 294857.

Examples of groups that cause other photocrosslinking reactions and groups that cause crosslinking by other reactions include Japanese Patent Application No. 82-294
Examples include those described in Ei57 specification.

Preferred crosslinkable groups are photocrosslinkable groups,
Particularly preferred are acrylate and methacrylate groups.

Examples of the non-crosslinkable liquid crystal compound include the above-mentioned liquid crystal compounds that have been used practically and known polymeric liquid crystal compounds.

As the crosslinkable non-liquid crystal compound in the present invention, various polymer compounds that are practically used as crosslinkable monomers and photocurable resins can be used.

The crosslinkable monomers include (1) a compound having two polymerizable double bonds and (2) a compound having at least one polymerizable double bond and having at least one functional group reactive with the monomer. Examples include compounds that have individual properties.

Examples of compound (1) include ■bis(meth)acrylamide ■di- or polyester of polyols and unsaturated mono- or polycarboxylic acid ■carbamyl ester ■di- or polyvinyl compound ■di- or poly- of polyols
(Meth)allyl ether ■Polycarboxylic acid Dimata 4
-Poly-allyl ester■Ester of unsaturated mono- or poly-carboxylic acid and mono(meth)allyl ether of polyol■Examples of allyloxyalkane compounds (2) include (meth)acrylic acid and/or
or ethylenically unsaturated compounds containing groups reactive with other copolymerizable monomers, such as carboxyl groups and groups reactive with carboxylic anhydride groups (hydroxyl groups, epoxy groups, cationic groups, etc.). .

Preferred crosslinking monomers are bis(meth)acrylamide, di- or polyesters of polyols and unsaturated monocarboxylic acids, and allyloxyalkanes, and particularly preferred are N,N'-methylene. Bisacrylamide, ethylene glycol diacrylate,
trimethylolpropane triacrylate and tetraallyloxyethane.

In the present invention, the weight average molecular weight of the liquid crystal is usually 1.

000-10,000, preferably 1,000-3,
It is 000.

If it is less than t, ooo, the film forming property is insufficient and 10,00
If it exceeds 0, electric field orientation becomes difficult.

In the present invention, intermediate phases taken by the liquid crystal include smectic phase (smectic A phase, chiral smectic C phase, etc.), nematic phase, cholesteric phase, etc. If a short response time is required, chiral smectic C phase is preferable. stomach.

In the present invention, the temperature at which the liquid crystal transitions from a liquid crystal phase to an isotropic liquid, that is, the clearing point, is usually 0°C or higher, but preferably 50°C or higher.

The crosslinkable group may be included in either the main chain or the side chain of the liquid crystal polymer compound or the non-liquid crystal polymer compound.

In the present invention, the liquid crystal may exhibit a nonlinear optical response. A group having such physical properties may be contained in any of a crosslinkable liquid crystal compound, a non-crosslinkable liquid crystal compound, or a crosslinkable non-liquid crystal compound.

As a basis for showing nonlinear optical response, Applied Physics Volume 57, 17
Examples include residues of nonlinear optical organic substances described on page 4 (1988). Examples of photocrosslinkable polymeric liquid crystal compounds containing such groups include copolymers containing structural units represented by the following general formula.

[-CH2CH-co
(5)C0-0-(CH2)go-Q
-Q-R [wherein R is NO2, OCO-CH=CH2. If necessary, various auxiliary agents as described below can be added to the liquid crystal in advance as long as they do not interfere with the liquid crystal properties.

Examples of photoinitiators for photocrosslinking include compounds described on page 12 of ``Optical radiation curing technology'' (Taiseisha, 1980), such as acetophenone, benzophenone, Michler's ketone, benzyl, benzoin, benzoin ether, benzyl ether, Mention may be made of benzyl dimethyl ketal, thioxanthone and derivatives thereof.

The liquid crystal is necessary for displaying or reading out the records on the liquid crystal.
It is also possible to contain dichroic dyes. Examples of dichroic dyes include merocyanine dyes, anthraquinone dyes, azo dyes, styryl dyes, azomethine dyes, and squalirium dyes.

The liquid crystal can contain a light-absorbing dye, which can be selected depending on the wavelength of the recording light. When using a semiconductor laser, it is best to use a near-infrared absorbing dye.
He-Ne laser, Ar laser, tungsten lamp,
When using a halogen lamp or the like, it is preferable to use a visible light absorbing dye.

Various near-infrared absorbing dyes have been developed in recent years, such as those described in Organic Synthetic Chemistry, Vol. 43, No. 4, pp. 36-45 (1985), such as phthalocyanines, tetradehydrocholine, benzenedithiol nickel complexes, and naphthoquinones. etc. are fried.

Further, the liquid crystal can contain a non-liquid crystal liquid in order to shorten the response time or lower the driving threshold voltage. Examples of such compounds include 2-oxazolidinones, propylene carbonate, dialkylbisufkenols, and alkylcyclohexylcyclohexanes.

In the present invention, an example of a liquid crystal formulation is as follows. % is by weight.

Normal Preferably crosslinkable liquid crystal compound 30-100% 50-99
%Non-crosslinkable liquid crystal compound θ~700~7θCrosslinkable non-liquid crystal compound θ~50 0~30 Photoinitiator
0-10 0-2 dichroic dye
θ~10 0~5 Recording light absorption dye
0~201-10 Non-liquid crystal liquid θ~2
00-10 In the present invention, the liquid crystal is supported on a substrate.

The substrate is selected in consideration of thermal conductivity, mechanical strength, optical properties, flatness accuracy, etc., depending on the purpose of use.

Specifically, glass, ceramics, plastics,
Commonly used substrates include (acrylic resin, methacrylic resin, polycarbonate resin, polyolefin resin) and metal (aluminum, etc.).

The shape of the base body can be obtained in various ways depending on the purpose, for example,
Examples include a plate shape, a disk shape, and a drum shape.

When laminating on a substrate, an adhesive, an adhesive, or the like may be used to improve the adhesion between the film-forming liquid crystal and the substrate. As such, it is possible to use pressure-sensitive adhesives and adhesives commonly used for laminated films.

In the present invention, the liquid crystal is sandwiched between electrodes and an electric field is applied to it. The pair of electrodes is usually provided sandwiching the liquid crystal, but may take other forms.

In addition to metals such as aluminum and silver, transparent conductors such as indium tin oxide are preferably used as electrode materials.

The electric field typically has a strength of 1” lOMV/m and a frequency of 10
An alternating current of 0-10.0 QOHz is used.

When an electric field is applied, liquid crystals with positive dielectric anisotropy align perpendicularly to the electrodes, and liquid crystals with negative dielectric anisotropy align in parallel.

In the present invention, the liquid crystal is crosslinked after electric field alignment.

Preferably, crosslinking is carried out using light. As this light,
Although ultraviolet rays are usually used, radiation such as electron beams and alpha rays may also be used.

In the present invention, a desired pattern may be formed by interposing a photomask between the light source and the light source during light irradiation.

In such a case, the film is developed, washed, and dried using a suitable developer, for example, an organic solvent such as methyl ethyl ketone or xylene. In this way, a liquid crystal film having a desired shape can be formed at a desired position on the substrate.

In addition to the recording/displaying layer made of the liquid crystal film formed on the substrate in this way, layers having various functions for the purpose of recording/displaying can be provided. Examples of such a layer include a light absorbing layer, a reflective layer, an antireflection layer, and a protective layer.

The light-absorbing layer may be formed by coating the above-mentioned light-absorbing dye, or may be formed by vacuum deposition of carbon or metal (bismuth, tellurium, etc.). The reflective layer is usually provided by vacuum-depositing aluminum, silver, or the like.

The anti-reflection layer is described in the Thin Film Handbook, page 820 (1978).
A transparent inorganic compound such as magnesium fluoride, such as magnesium fluoride, can be installed by vapor deposition.

The liquid crystal obtained according to the processing method of the present invention can be used as a recording display element.

The device can be recorded using light. As recording light, semiconductor laser, Ar laser, 1[1e-Me
Recording light such as a laser is used.

An example of a laser beam irradiation method is generally to irradiate a beam narrowed to 1 to IO μmφ with a pulse width of 0.1 to 10 μs and an energy of 5 to 20 mW.

As recording light for this element, it is also possible to use conventional light sources, such as tungsten lamps, xenon lamps, high-pressure mercury lamps, and light sources from light-emitting diodes.

When using such a light source, a pattern can be placed and written between the light source and the element. Furthermore, an arrayed device such as a liquid crystal printer or a light emitting diode printer can also be used.

It is also possible to use a heat source such as a thermal printer head instead of light for recording.

Reading is generally performed using an optical head.

Furthermore, the liquid crystal obtained according to the processing method of the present invention can be used as a large-area display device, and in this case, 1.
If necessary, backlighting can be provided from the rear.

Erasing can be done by heat or light. If it is caused by heat, use an infrared lamp, nichrome wire heater, etc.
The recording layer is usually heated to 100-150°C. In the case of erasing with light, the same laser light used for recording can be used.

Recording and erasing can be performed repeatedly, for example, 10 to 100 times or more.

[Example] Hereinafter, the present invention will be further explained with reference to Examples, but the present invention is not limited thereto.

Example 1 To synthesize a photocrosslinkable liquid crystal compound, 4-allyloxybenzoic acid trityl ester was first obtained by reacting trityl chloride and 4-allyloxybenzoic acid in THF-)diethylamine. 0.84g of this trityl ester
2.23 g of 14-allyloxybenzoic acid-4'-Schiff/phenyltriester (CNSO-3) and 1,3,5
．． An intermediate obtained from 0.6 g of 7-titramethyltetrasiloxane was treated with water/acetic acid to remove the trityl group. Next, trifluoroacetic anhydride and hydroxyethyl acrylate were reacted in sequence to obtain a photolinkable polymeric liquid crystal compound containing about 20 mol% of acrylate groups based on mesogenic groups.

A mixture containing 0.5% of the photoinitiator Irganox 184 (manufactured by Ciba Geigy) was placed between two ITO glass plates so that the thickness of the liquid crystal layer was equal to 1θμ, and the temperature was maintained at 80°C at 1kHz and 20V. It was confirmed that the liquid crystal was oriented in a so-called homeotropic manner.

Next, the film was irradiated with ultraviolet rays (1, OJ/cm2) using an ultraviolet irradiation device (manufactured by Ushioni-Chikku Co., Ltd.).

The film of the crosslinked polymeric liquid crystal compound thus obtained was uniform throughout and had a high degree of orientation.

Example 2 Optically active 2-methylbutanol, 4'-oxyphenyl-4-benzoic acid, 1,12-dibromododecane and acrylic acid were used as starting materials according to the method described in Proceedings of the Liquid Crystal Conference, page 150 (1987). An optically active ferroelectric liquid crystal compound was synthesized. On the other hand, Sannix Boliol GP-300 (glycerin with an average of 3.6 moles of propylene oxide added, manufactured by Sanyo Chemical Industries, Ltd.) 300 g, isophorone diisocyanate) 625
g, put 300 g of cyclohexanone and 50 mg of dibutyltin dilaurate into a Kolben, and add 75 to 85 g.
After reacting at °C for 4 hours, 348 g of 2-hydroxyethyl acrylate and 0.1 g of hydroquinone monomethyl ether were charged, and the reaction was further carried out for 200 hours to obtain an oligomer having 3 acryloyl groups per molecule.

Ferroelectric liquid crystal compound 7.0g, oligomer 0.7g
After homogeneously mixing 0.1 g of benzoin methyl ether, the temperature that shows chiral smectic C! 5°C
Vacuum injected into a 10 μm thick liquid crystal cell while maintaining
z, an electric field of 50 V was applied. This was irradiated with ultraviolet rays and crosslinked in the same manner as in Example 1.

[Effects of invention The liquid crystal processing method of the present invention has the following effects.

(1) In the method of the present invention, the molecular weight is usually 1.000.
Since the liquid crystal having a molecular weight of about 10,000 to 10,000 is oriented by an electric field and then made to have a high molecular weight, it is possible to avoid the problem of high viscosity, which is an inherent property of polymers, which hinders uniform alignment.

It has been difficult to align conventional polymer liquid crystals with an electric field, which have a molecular weight of several hundred thousand or more and sufficient mechanical strength.

(2) Since high molecular weight occurs at a relatively low concentration of crosslinking groups, cracks are less likely to occur in the film.

When a low-molecular liquid crystal compound having a polymerizable group, such as a conventionally known monoacrylate liquid crystal compound, is polymerized after electric field alignment, it shrinks significantly and cracks occur.

(3) By crosslinking, the main chain can be fixed in a state where the mesogens are oriented, and an oriented film with excellent mechanical strength can be obtained.

Because of the above effects, the processing method of the present invention can be applied to recording and display elements.

Claims (1)

[Claims] 1. A method for processing liquid crystal, which comprises aligning the liquid crystal with an electric field and then crosslinking it. 2. The processing method according to claim 1, wherein the liquid crystal is a ferroelectric liquid crystal. 3. The processing method according to claim 1 or 2, wherein the liquid crystal exhibits a nonlinear optical response. 4. The weight average molecular weight of the liquid crystal is 1,000 to 10,0.
4. The processing method according to claim 1, wherein the processing method is 00. 5. The processing method according to any one of claims 1 to 4, wherein the crosslinking is photocrosslinking.