JPH0333824A - Film formation of liquid crystal material - Google Patents

Abstract

PURPOSE:To produce a liquid crystal film having a large area and uniform film thickness with good productivity by liquefying a liquid crystal material in the form of mists and depositing the resulted liquid drops on a substrate and thereby forming the film. CONSTITUTION:The container of a spray 11 is so formed that the inside thereof can be pressurized by an air pressure 13. A soln. 12 of the liquid crystal material is put into the spray 11 and while 1.5kg/cm<2> air pressure is sent therein the liquid drops 1 in the form of the mists are sprayed in the state of parting by about 50cm from a glass substrate 3 (150mmX200mmX0.8mm) with an ITO film used as the substrate. The liquid drops 1 are deposited on the ITO film and the film is formed thereon while the spray is moved in one direction along the longitudinal direction of the substrate 3 at v=2.5cm/sec speed. The liquid crystal film having the large area and uniform film thickness is produced with the good productivity in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a film of a liquid crystal material used for liquid crystal optical elements, liquid crystal storage elements, liquid crystal acoustic elements, etc.

[Conventional technology]

Various methods have been devised as methods for forming films of liquid crystal materials. For example, ■ A method in which liquid crystal is applied to a substrate on which electrodes are formed using an offset printing method, and then the opposing substrates are pressed and bonded with the liquid crystal in between (Japanese Patent Application Laid-open No. 75817/1983); ■ A method in which a spacer material is mixed. There is a method of forming a liquid crystal layer by applying liquid crystal to a substrate on which electrodes are formed using a spin code method or a roll coat method (Japanese Patent Laid-Open No. 133122/1983). However, since method (2) uses offset printing, it is difficult to obtain a thin film of several μm or less, the quality of the obtained liquid crystal film is not smooth, and when the liquid crystal is dissolved in a solvent to obtain a thin film, the viscosity increases. Since it becomes very small, there is a problem that it flows on the offset convex plate, making it impossible to print well. In addition, method (2) requires the incorporation of a spacer material in order to make the film thickness uniform, and has the problem of being complicated and requiring equipment and processes to obtain uniform dispersion.

[Problem to be solved by the invention]

SUMMARY OF THE INVENTION The present invention aims to provide a method for forming a liquid crystal material that can produce a liquid crystal film having a large area and a uniform thickness with good productivity, and has a high manufacturing yield without contaminating the liquid crystal film with dust. It is something to do. Furthermore, it is an object of the present invention to provide a method for forming a film of a liquid crystal material, which makes it possible to obtain a liquid crystal element with good high-speed response to changes in electric field.

[Means to solve the problem]

The present inventors have conducted intensive research to solve the above-mentioned problems, and as a result, they have found that the object can be achieved by forming a film by forming liquid crystal material into droplets, and have completed the present invention.

That is, the present invention provides a method for forming a film of a liquid crystal material, in which a liquid crystal material is atomized into droplets, and the resulting droplets are deposited on a substrate to form a film.

Examples of the liquid crystal material used in the present invention include low-molecular liquid crystals, polymer liquid crystals, or mixtures thereof that exhibit a nematic phase, cholesteric phase, or smectic phase. Preferably, a ferroelectric liquid crystal material exhibiting a ferroelectric phase such as a chiral smectic C phase with good high-speed response to electric field changes is used. Such ferroelectric liquid crystal materials include, for example, low-molecular ferroelectric liquid crystal compounds, ferroelectric polymer liquid crystals, or liquid crystal materials made of compositions thereof;
Furthermore, a low-molecular or high-molecular non-ferroelectric non-liquid crystal substance or a low-molecular or high-molecular non-ferroelectric liquid crystal substance, and a low-molecular or high-molecular non-liquid crystal substance having chiral properties, or a low-molecular or high-molecular non-liquid crystal substance Examples include liquid crystal materials in which a liquid crystal substance having chiral properties is combined to exhibit a ferroelectric phase such as a chiral smectic C phase.

Examples of ferroelectric polymer liquid crystals include acrylate main chain polymer liquid crystals, methacrylate main chain polymer liquid crystals, chloroacrylate main chain polymer liquid crystals, oxirane main chain polymer liquid crystals, and siloxane main chain polymer liquid crystals. Includes liquid crystals, ester main chain polymer liquid crystals, etc.

Examples of repeating units of the acrylate main chain polymer liquid crystal include (A) and (B).

Examples of the repeating unit of the methacrylate main chain polymer liquid crystal include (C) CH3 (D).

Examples of the repeating unit of the chloroacrylate main chain polymer liquid crystal include (E).

The repeating unit of the oxirane main chain-based molecular liquid crystal is as follows: for example, (F) Examples include.

The repeating unit of the siloxane main chain polymer liquid crystal is as follows: for example, (G) CH3 Examples include.

As a repeating unit of ester main chain polymer liquid crystal, for example, (H) (I) (J) Examples include.

In addition, in the repeating unit of the above-mentioned ferroelectric polymer liquid crystal, the side chain skeleton may be replaced with a biphenyl skeleton, a phenylbenzoate skeleton, a biphenylbenzoate skeleton, or a phenyl 4-phenylbenzoate skeleton, and benzene in these skeletons The ring may be substituted with a pyrimidine ring, pyridine ring, pyridazine ring, pyrazine ring, tetrazine ring, cyclohexane ring, dioxane ring, dioxaborinane ring, or may be substituted with a halogen group such as fluorine or chlorine, or a cyano group, 1-methylalkyl group, 2-
Fluoroalkyl group, 2-chloroalkyl group, 2-chloro-3-methylalkyl group, 2-trifluoromethylalkyl group, 1-alkoxycarbonylethyl group, 2-alkoxy-1-methylethyl group, 2-alkoxypropyl group , 2-chloro-1-methylalkyl group, 2-alkoxycarbonyl-1-trifluoromethylpropyl group, etc., or may be substituted with these optically active groups via an ester bond or an ether bond. The length of the spacer may vary from 1 to 30 methylene chain lengths.

Further, the above ferroelectric polymer liquid crystal has a number average molecular weight of 1.0
00 to 400.000 can be used.

Examples of ferroelectric low-molecular liquid crystal compounds include Schiff base-based ferroelectric low-molecular liquid crystal compounds, azo and azoxy-based ferroelectric low-molecular liquid crystal compounds, biphenyl and aromatifux ester-based ferroelectric low-molecular liquid crystal compounds, and halogen-based ferroelectric low-molecular liquid crystal compounds. , a ferroelectric low-molecular liquid crystal compound into which a ring substituent such as a cyano group has been introduced, a ferroelectric low-molecular liquid crystal compound having a heterocycle, and the like.

As a thick basic ferroelectric low molecular weight liquid crystal compound, for example, Compound (1) shown below ~ (4) is raised can be lost.

(1) 113 5-10. 12, 4 (2) 7-10, 1 (3) n=7. 8, 4 (4) 2 4. 8.2 Examples of the azo and azoxy-based ferroelectric low-molecular liquid crystal compounds include the following (5) and (6).

(5) n:': 4, (6) n=16 Examples of biphenyl and aromatics ester-based ferroelectric low-molecular liquid crystal compounds include the following compounds (7
) and (8).

(7) n" (8) n=8 Examples of ferroelectric low-molecular liquid crystal compounds into which ring substituents such as halogen and cyano groups are introduced include the following compounds (9
) to (11).

(9) n 7, 8.10 (10) n 冑 (11) n = 4, 6 Examples of ferroelectric low-molecular liquid crystal compounds having a heterocycle include the following compounds (12), (■3 ).

(12) (13) n = 7, 8.11 The above compound is a typical compound of a ferroelectric low-molecular liquid crystal compound, and the ferroelectric low-molecular liquid crystal compound of the present invention does not have any of these structures. It is not limited to the formula.

Furthermore, 0 to 60% by weight of a non-liquid crystal polymer may be added to the above-mentioned liquid crystal material in order to improve the mechanical strength of the liquid crystal element and the alignment properties against bending alignment treatment. As the polymer to be added, thermoplastic resins and crosslinkable resins are used, and adhesives are particularly suitable.

The thermoplastic resin used preferably has a Tg of 30°C or higher, more preferably 70°C or higher.

Specifically, polyvinyl chloride, polyvinyl bromide, polyvinyl fluoride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-ethylene copolymer, vinyl chloride-propylene copolymer, vinyl chloride-vinylidene chloride copolymer Coalescence, vinyl chloride-butadiene copolymer, vinyl chloride-acrylic acid ester copolymer! ! Polymer, vinyl chloride-acrylonitrile copolymer, vinyl chloride-styrene-acrylonitrile terpolymer, vinyl chloride-vinylidene chloride-vinyl acetate copolymer, polyvinylidene chloride, polytetrafluoroethylene, polytetrafluorochloroethylene, polyfluoroethylene Halogenated vinyl polymers or copolymers such as vinylidene chloride; Polymers or copolymers of unsaturated alcohols or ethers such as polyvinyl alcohol, polyallyl alcohol, polyvinyl ether, polyallyl ether; Unsaturated alcohols such as acrylic acid or methacrylic acid Polymers or copolymers of saturated carboxylic acids; Polymers or copolymers of polyvinyl esters such as polyvinyl acetate, polyallyl esters such as polyphthalic acid, etc. that have unsaturated bonds in their alcohol residues; Polyacrylic esters , polymethacrylic acid ester,
Polymers or copolymers of acid residues such as polymers of maleic acid esters or fumaric acid esters, or polymers or copolymers of acid residues and alcohol residues having unsaturated bonds; polymers or copolymers of acrylonitrile or methacrylonitrile; Unsaturated nitrile polymers or copolymers such as polyvinylidene cyanide, malononitrile or fumaronitrile polymers or copolymers; polystyrene, polyα-methylstyrene, polyp-methylstyrene, styrene-α-methylstyrene copolymers,
Polymers or copolymers of aromatic vinyl compounds such as styrene-p-methylstyrene co-11, polyvinylbenzene, polyhalogenated styrene; complexes such as polyvinylpyridine, poly-N-vinylpyrrolidine, poly-N-vinylpyrrolidone, etc. Polymers or copolymers of cyclic compounds; polyester condensates such as polycarbonate, nylon 7
, polyamide condensates such as nylon 6.6; polymers or copolymers containing maleic anhydride, fumaric anhydride, and imidized products thereof; polyamide-imide, polyetherimide, polyimide,
Examples include heat-resistant organic polymers such as polyphenylene oxide, polyphenylene sulfide, polysulfone, polyniterol, polyarylate, and the like.

The adhesive may be used alone or mixed into a liquid crystal material, and may be a polymeric substance commonly used as an adhesive, such as an epoxy adhesive, an acrylic adhesive, Examples include polyurethane adhesives, hot melt adhesives, and elastomer adhesives.

Furthermore, additives such as pleochroic dyes and viscosity reducing agents may be added.

Examples of pleochroic dyes include styryl, azomethine, azo, naphthoquinone, anthraquinone, merocyanine, benzoquinone, and tetrazine dyes.

In the present invention, a substrate on which electrodes are normally provided is used as the substrate.

As the base material of the substrate, preferably a transparent material is used. For example, glass or plastics such as crystalline polymers such as -axially or biaxially oriented polyethylene terephthalate, amorphous polymers such as polysulfone and polyethersulfone, polyolefins such as polyethylene and polypropylene, polycarbonate, and polyamides such as nylon are used. . Plastic flexible substrates are preferably used because they are suitable for continuous production. The electrode may be made of any metal, metal oxide, conductive material, etc., but transparent electrodes are preferred when used as a liquid crystal optical element. The transparent electrode is N coated with tin oxide.
E S A film, I' made of tin oxide and indium oxide
A l'O film or the like is used. These electrodes can be fabricated using various known methods such as sputtering, vapor deposition, printing,
It can be provided on the above-mentioned base material such as glass or plastic using a coating method, a plating method, an adhesive method, or a suitable combination of these methods. Furthermore, these electrodes may be patterned in advance into a desired shape.

It is preferable to heat the above liquid crystal material or add a solvent to the liquid crystal material to reduce the viscosity of the liquid crystal material and form it into droplets. The liquid crystal material may be heated to a temperature such that the viscosity of the liquid crystal material becomes atomized, for example, the temperature at which the liquid crystal material exhibits various liquid crystal phases, a tomochic phase, or a mixed phase of a liquid crystal phase and a tomochic phase. Heat to temperature. Preferably, the mixture is heated to a temperature at which the viscosity becomes extremely low and exhibits an isotonic phase. Furthermore, when adding a solvent to the liquid crystal material, an appropriate amount of solvent is added depending on the required viscosity and film thickness of the liquid crystal material. The solvent to be added may be any solvent that can dissolve the liquid crystal material, such as dichloromethane, chloroform, methyl ethyl ketone, 1,1.1-)lichloroethane, toluene, or a mixture of different solvents.

It is preferable to form the liquid crystal material into droplets in the form of mist using a spray or an ultrasonic atomizer. At this time, the average diameter of the droplets is in the range of 0.2 μmm 3 IIlIn.

Normally, in a liquid crystal element, the liquid crystal material needs to be made into a relatively thin film of several tens of micrometers or less, so it is preferable that the atomized droplets be relatively small, particularly preferably an average diameter of 0.2 micrometers.
-1OOu range. If the average diameter is less than 0.2 μm, the efficiency of film formation may be low, and if it exceeds 3 m, it may be difficult to form a sufficiently thin film even after solvent evaporation.

The method of forming droplets into a mist by spraying is a method in which a gas such as air is brought into a high pressure state and the liquid crystal material or its solution is injected from a nozzle.

At this time, the shape and diameter of the nozzle are not particularly limited; conventional ones can be suitably used. There is no limit to the number of nozzles, and if you want to uniformly form a film on the substrate, you can line up multiple nozzles depending on the width of the substrate, or if you want to vary the film thickness as necessary, you can change the nozzle arrangement. For example, place more of them in areas where you want to make them thicker.

In order to make the average diameter of the droplets within the range of 0.2μmm3tm, the nozzle hole diameter should be less than a few degrees, and the gas pressure should be between normal pressure and 5K.
g/cd is preferred.

Also, when adding a solvent to the liquid crystal material, the amount of solvent is also taken into account. Preferably, it is added so that the solution concentration is 0.5 to 80% by weight. If the concentration is too low, the film forming efficiency may decrease, and if the concentration is too high, it may be difficult to obtain a thin film.

Furthermore, in order to form a film of liquid crystal material with high productivity, it is recommended to move the spray relative to the substrate or to deposit the droplets on the substrate without moving the substrate relative to the spray. Since the amount of droplets deposited per unit area is determined by the speed, the moving speed is appropriately set depending on the desired film thickness.

Figure 1(a) shows that when a single wafer substrate is used as the substrate, the first
Figure (b) is a schematic view showing an example of a method for forming a film of a liquid crystal material using a one-spray method when a long substrate is used as the substrate.

In the method shown in FIG. 1(a), atomized droplets 1 are ejected from a spray nozzle 2 and deposited on a substrate 3. In the method shown in FIG.

At this time, the substrate 3 is transported by the substrate transport belt 5 and is moving from left to right in the figure. The substrate 3 on which the droplets 1 have been deposited and the liquid crystal film 4 has been formed is conveyed as it is by the conveyor belt 5 to a drying and laminating step.

In the method of FIG. 1(b), an array of spray nozzles 6
The droplets l ejected from the elongated substrate 7 are deposited on the elongated substrate 7. At this time, the long substrate 7 is moving in the flow direction of the line from left to right in the figure, and after the liquid crystal film 4 is formed, it is transferred to a drying and layering process.

Figure 1 shows methods (a) and 2) in which droplets fall from top to bottom, but in order to prevent dripping, droplets are sprayed from the bottom or side of the substrate and deposited on the substrate. The film may be formed by

Further, in order to improve the film quality of the liquid crystal material, the substrate may be heated with a heating plate, heating roller, etc. when or after the droplets are deposited on the substrate. A preferable heating temperature range is 25° C. to 150° C., and particularly preferably a temperature several degrees Celsius above the boiling point of the solvent, so that the film quality is hardly deteriorated by heating.

Furthermore, when depositing droplets of the liquid crystal material on the substrate, or when the solvent immediately evaporates and the liquid crystal material turns into microdomains and is deposited on the substrate, a magnetic field or an electric field is applied to the droplets or the microdomains. It is preferable to provide some degree of orientation.

This operation can facilitate the orientation treatment and the like in later steps. The preferred applied magnetic field is between 500 and 30,000 Gauss.

Further, a preferable applied electric field is 2 to 200 MV/m.

Further, a method of forming droplets into a mist using an ultrasonic atomizer is a method in which ultrasonic vibration is applied to a liquid crystal material or its solution, and the liquid crystal material or its solution is formed into droplets using the energy and then sprayed. The same method commonly used for humidifiers can be used. The preferred applied frequency is 20K
Hz to 10 MHz.

A method using an ultrasonic atomizer generally makes it easier to obtain fine droplets than a method using a spray.

Fine droplets stay in the air for a long time until they are deposited on the substrate, and when they are deposited on the substrate, a liquid crystal film with a uniform thickness is obtained. Therefore, it is particularly suitable for producing a thin liquid crystal film of several micrometers or less, such as when a ferroelectric liquid crystal material is used.

For the film forming method using this ultrasonic atomizer, it is preferable to replace the spray atomizers in FIGS. 1(a) and (c) with an ultrasonic atomizer, and otherwise use the same configuration as in FIG. 1(a) or (b). .

Alternatively, the method shown in FIG. 2 may also be suitably used.

In the method shown in FIG. 2, droplets 1 sprayed from the spray port 9 of the ultrasonic sprayer 8 are deposited on the base Fia.

Here, the substrate 3 is a single wafer substrate and is conveyed by a substrate conveyance belt 5, but in the case of a long substrate, it is shown in FIG. 1 (b).
Similarly, the substrate can be moved without using a conveyor belt. 10 is a protective cover.

The heating of the substrate and the application of a magnetic field or electric field to the droplets are the same as in the case of using a spray.

As described above, according to the present invention, a liquid crystal film having a large area and a uniform thickness can be manufactured with high productivity. Furthermore, since the film forming apparatus does not contact the film surface, it is possible to prevent dust from entering the liquid crystal film and improve manufacturing yield.

〔Example〕

Example 1 A liquid crystal polymer having the following structure and properties was dissolved in 1,1°1-trichloroethane to form a 3% by weight solution.

Polymer liquid crystal Mu-15゜O0 4 32 [gniglass state, SmA: smectic A phase, Is
o: Tokichi phase] In addition, a commercially available can-on spray was modified to produce the image shown in Figure 3 (a
), the inside of the container for sprayer 1 can be pressurized using pneumatic equipment 3. In this spray step, the liquid crystal material solution 12 described above was poured into the glass substrate with an ITO film (150 m x 200 m x 0.8 am), which was used as a substrate, at a distance of about 50 C11 while applying an air pressure of 1°5 kg/d. Atomized droplets are ejected at a speed of v
The film was formed by depositing droplets on the ITO film while moving in one direction along the longitudinal direction of the substrate at = 2.5 cm/sec (
Figure 3 (b)).

The average diameter of the droplets jetted at this time was about 30 μm as measured by light scattering. The thickness of the obtained film after solvent evaporation was about 9 μm. Also, unlike applying the solution to glass with an ITO film, there was no phenomenon such as repellency caused by poor wettability of the ITO film surface, so a uniform film could be formed over the entire surface of the substrate.

Example 2 Using the same means as in Example 1, a long fTO film-attached PES (polyethersulfone) substrate was used as the substrate, and droplets were deposited on the ITO film to form a film. Here, instead of moving the spray, the long substrate is moved at a constant speed of 10
It was moved longitudinally at CII/sec. As with the glass substrate, the obtained film surface was smooth and the film thickness was 4.5μ.
It was uniform at m±0.3 am.

Example 3 A ferroelectric liquid crystal having the structure and characteristics shown below and an epoxy resin shown below were mixed in the ratio shown below, and 5M dichloromethane was mixed.
It was made into a volume% solution.

Ferroelectric liquid crystal (cry: crystalline phase, SmC" nichiral smectic C phase, N9: chiral nematic phase) made of epoxy resin oil shell epoxy ■ Epikote 834 (base material) / Evomate QX-12 (
A device as shown in FIG. 2 was prepared using a commercially available air humidifier as an ultrasonic atomizer. Using a uniaxially stretched PET substrate with ITOg (thickness 1ool1m, [300am) that had been coated with polyimide and rubbed in advance as a substrate, this I
A film was formed by depositing droplets sprayed from an ultrasonic atomizer onto the TO film.

At this time, the average diameter of the ejected droplets was 18 μm.

Next, the substrate on which the liquid crystal film was formed was passed through a drying oven heated to 50° C. to evaporate the solvent, and then a similar substrate was laminated onto the liquid crystal film using a pair of pressure rollers. Next, the substrate on which the liquid crystal film was formed was instantaneously heated to 180"C using a heating roller with a diameter of 10100a, and the temperature was increased to 180"C at a rate of about 20C/min.
Cooled to 60°C. Before the liquid crystal material crystallized, a square <5 cm was cut out and observed under crossed nicols, and an extremely uniform film with no color unevenness was obtained.

The film thickness of the liquid crystal material was found to be 4.2 μm as determined from spectrum measurement of coloring due to birefringence. Also, when we examined the film thickness of all the films cut out from other places, we found 4.
The thickness was in the range of 2 μm±0.2 μm, and it was clear that the film thickness uniformity was excellent.

〔Effect of the invention〕

According to the method for forming a liquid crystal material film of the present invention, a large-area, uniform, and thick liquid crystal film can be manufactured with high productivity. Furthermore, since the film forming apparatus does not contact the film surface, it is possible to prevent dust from entering the liquid crystal film and improve manufacturing yield.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are schematic diagrams showing an example of a method for forming a film of a liquid crystal material using a one-way spray method. FIG. 2 is a schematic diagram showing an example of a film forming method using an ultrasonic atomizer. FIG. 3(a) is a schematic illustration of a spray that can pressurize the inside of a container with air pressure, and FIG. 3(b) is a schematic illustration of an example of a film forming method using the spray. Symbol explanation Droplet 2 Spray nozzle board
4 Formed liquid crystal film substrate conveyor belt spray nozzle array long substrate ultrasonic atomizer spray nozzle 10 Protective cover spray 12 Solution air pressure

Claims (1)

[Scope of Claims] 1. A method for forming a film of a liquid crystal material by forming a liquid crystal material into droplets in the form of mist and depositing the resulting droplets on a substrate. 2. The method for forming a film of a liquid crystal material according to claim 1, wherein the liquid crystal material is atomized into droplets using a spray or an ultrasonic atomizer. 3. The method for forming a film of a liquid crystal material according to claim 1 or 2, wherein the liquid crystal material is heated or a solvent is added to the liquid crystal material to form droplets. 4. The method for forming a film of a liquid crystal material according to claim 1, 2 or 3, wherein the substrate is heated during or after depositing the droplets on the substrate. 6. The method for forming a film of a liquid crystal material according to claim 1, wherein the droplets are deposited on the substrate while moving the substrate. 7. The method for forming a film of a liquid crystal material according to any one of claims 1 to 6, wherein the average diameter of the droplets is in the range of 0.2 μm to 3 mm. 8. The method for forming a film of a liquid crystal material according to any one of claims 1 to 7, wherein the liquid crystal material exhibits ferroelectricity. 9. The method for forming a film of a liquid crystal material according to any one of claims 1 to 8, wherein the substrate is a flexible substrate.