JP3223455B2 - Method for producing liquid crystal / polymer composite film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal / polymer composite film having an electric field or thermal response and capable of displaying and recording information, and a method for producing the same.
The polymer composite film can be widely applied to light control panels, displays, recording media, and the like.

[0002]

2. Description of the Related Art Conventionally, liquid crystal displays have characteristics such as low power consumption, light weight, and thinness, and are widely used as wristwatches, calculators, personal computers, televisions, and the like as display media for characters and images. . In general TN and STN-liquid crystal displays, liquid crystal is sealed in a liquid crystal cell in which a predetermined seal or the like is provided between glass plates having transparent electrodes, and sandwiched by polarizing plates from both sides. However, the conventional liquid crystal display requires (1) a narrow viewing angle because two polarizing plates are required, and a lack of luminance, so that a backlight with high power consumption is required. (2) The cell thickness dependency is large, and it is difficult to increase the area. (3) Since the structure is complicated and it is difficult to enclose the liquid crystal in the cell,
There are problems such as high manufacturing cost, and there is a limit to the weight reduction, thinning, large area, low power consumption, and low cost of the liquid crystal display.

As a liquid crystal display medium for solving such problems, application of a liquid crystal / polymer composite film in which liquid crystal is dispersed in a polymer matrix is expected, and research and development thereof have been activated. The following techniques have already been disclosed. The method for producing a liquid crystal / polymer composite film can be mainly classified into an emulsion method and a phase separation method. The emulsion method includes a method of preparing an aqueous solution in which liquid crystal is emulsified using polyvinyl alcohol (PVA) as a protective colloid.
-501631), a method of mixing a liquid crystal emulsion with latex to prepare an aqueous solution (JP-A-60-252687), and the like. On the other hand, the phase separation method can be further classified into a method of fixing the phase separation state of the liquid crystal and the matrix resin, and a method of separating the liquid crystal from the matrix resin during film formation.

As a method of fixing the phase separation state, a method of dispersing a liquid crystal in an epoxy resin and then curing the liquid crystal (Japanese Patent Application Laid-Open No.
No. 61-502128) and a method of dispersing liquid crystal in a UV-curable resin and then curing the liquid crystal (Japanese Patent Publication No. 622-2231) has been proposed. As a method of separating the liquid crystal during film formation,
A method of performing phase separation during curing of the film, a method of performing phase separation during solvent evaporation, and a method of performing phase separation during the cooling process of the thermoplastic resin are disclosed in JP-T-63-501512, but further improvements have been made. Various techniques have been reported. As a method of performing phase separation during curing, a method of separating a liquid crystal during UV curing in a mixed system of a liquid crystal and a UV-curable resin (JP-A-63-271233, JP-A-1-252689),
In a mixed system of a liquid crystal and a thermosetting epoxy resin, there is a method of separating a liquid crystal during heat curing (JP-A-63-287820, JP-A-1-299022). As a method for phase separation during solvent evaporation, an acrylic resin having an active hydrogen group is used as a matrix (Japanese Patent Application Laid-Open No. 1-230693) and a cellulose acetate is used as a matrix (Japanese Patent Application Laid-Open No. 63-124025). And those using a resin incompatible with liquid crystal as a matrix (JP-A-63-43993).

[0005]

The above-mentioned prior art relating to the liquid crystal / polymer composite film has problems such as seepage of liquid crystal, high driving voltage, low contrast, and low coating suitability. In particular, Japanese Patent Application Laid-Open Nos. 1-252689 and 1-309025 disclose a technique characterized in that the liquid crystal is in a continuous phase for the purpose of lowering the driving voltage. However, JP-A-58-501631, which is a typical example of the emulsion method, "liquid crystal encapsulated"
Also, in JP-A-62-48789, "Encapsulated liquid crystal having a smectic phase", it is not considered that the liquid crystal exists as a completely independent phase. For that reason, Japanese Patent Application Laid-Open No. 62-48789 states that "encapsulated liquid crystals are defined as individual capsules or individual volumes of a capsule medium, such as in a solid medium, such as a dry, stable emulsion. It refers to an amount of liquid crystal material contained or contained.
However, individual volumes may be interconnected by one or more passages. The liquid crystals are preferably present in both the individual volumes and the connecting passages. Is described.

[0006] Thus, there is a description that "the internal volume of each capsule is fluidly connected to one or more via a connecting passage", and PSDrzaic <J. Appl.
s., 60 (5), 2142 (1986)>, "It is more accurate to describe that a liquid crystal forms a network in a polymer matrix than a liquid crystal is encapsulated.
However, the physical properties can be described by a model in which the liquid crystal is considered as a discontinuous capsule. Is shown.
On the other hand, JP-T-61-502128 disclosed as a phase separation method
JP-A-62-2231 and JP-A-63-501512, it is described that "the liquid crystal microdroplets are of uniform size and spacing". In the case where the mixing ratio is small, a high driving voltage is required, and the mixing ratio of the liquid crystal is large, it is easily presumed that the liquid crystal does not exist independently. Therefore, the technology characterized by the fact that the liquid crystal is in a continuous phase is not considered to have novelty, and discloses a specific technology that does not exude the liquid crystal and lowers the driving voltage. It can not be said.

Therefore, in order to lower the driving voltage, it is necessary to lower the content of the polymer. However, in the conventional method, the content of the polymer is reduced and the liquid crystal becomes a continuous phase. Create problems. or,
In the method of lowering the driving voltage by reducing the film thickness, there is a problem that it is difficult to obtain contrast. Further, in the conventional method, since the size of the liquid crystal particles cannot be controlled, the particle size distribution is large, the driving voltage differs depending on the particles, and a steep rise cannot be expected. In addition, there is a problem that the area of the interface between the liquid crystal and the polymer matrix, which greatly affects the contrast, is small, and the contrast ratio is reduced by the decrease in the film thickness. In addition, when the conventional polymer matrix is used as a device, such as a polyvinyl alcohol resin, an epoxy resin, a polyurethane resin, a polycarbonate resin, a UV-curable resin of polythiol, or the like, it has poor water resistance and thermal stability, or has a high molecular mobility. Not only lacks reliability and stability, but also has a problem with the electro-optic effect (eg, responsiveness). Furthermore, as one of the scattering mechanisms of the liquid crystal / polymer composite film, there is a mismatch between the refractive indices of the liquid crystal and the matrix polymer, but the difference in the refractive index between the polymer matrix and the liquid crystal is not sufficient. This is one of the causes of a decrease in contrast.

[0008] Regarding coating aptitude, it is difficult to control the viscosity because the liquid crystal is not completely contained by the polymer, that is, it is not an emulsion.
The wettability to the transparent electrode is poor, and a stable film cannot be formed. As a method for solving these problems, Japanese Patent Application Laid-Open No. 1-203494 discloses microencapsulation of liquid crystal. Here, it is described that the following general chemical preparation method, physical preparation method, and physical / mechanical preparation method can be used. Chemical preparation methods include interfacial polymerization method, in situ polymerization method, in-liquid curing coating method (orifice method), etc. Physical preparation methods include coacervation method, interfacial precipitation method (liquid concentration method) ,
(In-liquid drying method, secondary elution method), melt dispersion method, inclusion exchange method, and powder pressure method. Physical / mechanical preparation methods include spray-drying, air suspension coating, vacuum evaporation coating, inorganic material wall encapsulation, electrostatic coalescence,
High-speed airflow impact method and the like can be mentioned.

The interfacial polymerization method is a method in which water-soluble and oil-soluble monomers are selected as two kinds of monomers that undergo polycondensation or polyaddition reaction, and one of them is dispersed and reacted at the interface. is there. The in situ polymerization method is a method in which a reactant (monono, initiator) is supplied from one of the inside and the outside of a core material and reacted on the surface of the core. The in-liquid curing coating method is a method in which a core material is encapsulated in advance with a wall film agent, and then the wall film is cured in a curing liquid. The coacervation method can be used in an aqueous solution system or an organic solvent system. In an aqueous solution system, a simple coacervation method in which phase separation occurs due to a decrease in solubility, and a complex coacervation method in which phase separation is performed by electrical interaction can be used. In an organic solvent system, a phase separation phenomenon caused by a change in solubility or temperature is used. The interface precipitation method is a method that can be encapsulated under mild conditions without vigorous reaction or sudden pH change,
For example, after the aqueous solution of the core material is dispersed in the hydrophobic polymer solution, it is further dispersed in the protective colloid solution.
The melting dispersion method uses a wax material such as wax or polyethylene as a wall film material, and is a method in which a nucleus material is dispersed in a liquid with a wax material under heating and then cooled.

In the physical / mechanical manufacturing method, since the liquid crystal as a core material is liquid at room temperature, an air suspension coating method and a vacuum evaporation coating method which can be applied only to a solid cannot be used. However, since the liquid crystal is liquid at room temperature, it is difficult to divert the above-described general method as it is, particularly for controlling the particle size and the distribution that greatly affect the driving voltage, contrast, and coating suitability. It is. Accordingly, it is an object of the present invention to solve the above-mentioned problems of the prior art, and to easily provide a liquid crystal / polymer composite film having an electric field and thermal response and capable of displaying and recording information. .

[0011]

The above object is achieved by the present invention described below. That is, the present invention relates to a water-soluble electron beam-curable monomer, oligomer, polymer or a mixture thereof.
A method for producing a liquid crystal / polymer composite film, comprising: dispersing a liquid crystal using an electron beam-curable compound having a surfactant activity in a mixture composed of at least one kind of a liquid crystal; and irradiating the mixture with an electron beam. .

[0012]

According to the present invention, a liquid crystal is dispersed in a water-soluble electron beam-curable resin composition using an electron beam-curable surfactant compound, and then irradiated with an electron beam. Thus, it is possible to easily provide a liquid crystal / polymer composite film having electric field and thermal responsiveness and capable of displaying and recording information. The liquid crystal / polymer composite film of the present invention can be widely applied to light control panels, displays, recording media, and the like.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to preferred embodiments. As the electron beam-curable surfactant used in the present invention, commercially available ionic or nonionic reactive surfactants can be used. For example, as specific examples of these, New Frontier N-177E, N-250Z, N-280A, A-229E or H-3355N, H-3
355S (manufactured by Daiichi Kogyo Seiyaku), sodium styrenesulfonate, 2-sulfoethyl methacrylate, diallyldimethylammonium chloride, 2-acyloxyethyltrimethylammonium chloride, 2-methacryloxyethyltrimethylammonium methoxysulfate, polyethylene glycol di (Meth) acrylate,
Examples thereof include polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polyethylene glycol polytetramethylene glycol (meth) acrylate, and polypropylene glycol polytetramethylene glycol (meth) acrylate. Preferably, a bifunctional or more functional surfactant is mixed. In addition, a radical-reactive protective colloid as an electron beam-curable surfactant compound is a polymer having a hydrophilic group and a hydrophobic group and a radical-reactive group introduced into a side chain of the polymer, for example, (partially saponified) polyvinyl alcohol. Any compound having an addition-polymerizable double bond, such as a compound having a (meth) acryloyl group introduced into a hydroxyl group, can be used.

As the water-soluble electron beam-curable monomers, oligomers and polymers used in the present invention, all commercially available ones can be used. In consideration of the stability and durability of the polymer matrix, it is desirable to use a bifunctional or higher functional one, more preferably a trifunctional or higher functional one. or,
When used in a display device using a light scattering mechanism based on the difference in the refractive index between the liquid crystal and the polymer matrix, the difference between the extraordinary light refractive index of the liquid crystal is large, and the polarity of the liquid crystal and silicon is significantly different. It is preferable to use a system electron beam-curable resin from the viewpoint of improving the contrast and forming stable liquid crystal oil droplets.

The liquid crystal used in the present invention is not particularly limited, and includes a nematic liquid crystal, a smectic liquid crystal,
Cholesteric liquid crystal or the like can be used. Liquid crystals suitable for the required electro-optic effect can be used in combination with the matrix polymer and the wall film agent. As for these materials, the smaller the amount of the resin having the surface active ability or the amount of the reactive surfactant (and / or the protective colloid) per 100 parts by weight of the liquid crystal material, the more preferable. Is preferably used at a ratio of 5 to 100 parts by weight. Of these, the amount of the above-mentioned resin having surface activity, which varies greatly depending on the surface activity, can be used in a ratio of 0.1 to 50 parts by weight. After mixing and stirring with a composition suitable for the required electro-optical effect as described above to form liquid crystal droplets, the structure is fixed by electron beam irradiation. In addition, it is possible to dilute with a solvent in consideration of coating suitability, but from the viewpoint of residual solvent and laminating processability, it is preferable to dilute with a low-viscosity monomer without solvent. As a coating method, usual roll coating, gravure coating, blade coating, or the like can be used. The electron beam is emitted from various electron beam accelerators such as, for example, Cockloft-Walton type, Bande graph type, Resonant transformation type, Insulating core transformer type, Linear type, Dynamitron type, High frequency type, etc.
１，1,000 KeV, preferably 100-300 KeV
An electron beam having the following energy is used.

[0016]

Next, the present invention will be described more specifically with reference to examples. In the description, parts and% are based on weight unless otherwise specified. Example 1 A urethane acrylate having a dimethylsiloxane skeleton was synthesized as an electron beam curing resin as follows. Silicone having hydroxyl groups at both ends (KF-6001, manufactured by Shin-Etsu Chemical Co., Ltd.) while adding an appropriate amount of di-n-butyltin dilaurate to 2 mol of isophorone diisocyanate and maintaining the temperature at 60 ° C.
One mole was added dropwise. Next, 2.1 mol of 2-hydroxyethyl acrylate was added dropwise to obtain the desired water-soluble urethane acrylate (S-2). In 20 parts of this S-2, monofunctional silicon acrylate (X-22-5)
002, manufactured by Shin-Etsu Chemical Co., Ltd.), and 10 parts of a reactive surfactant (New Frontier A229A) was added. Thereto, 60 parts of nematic liquid crystal (E-44, manufactured by Merck Limited) was added and ultrasonically dispersed. By irradiating the thus obtained resin composition with an electron beam of 5 Mrad, a liquid crystal / polymer composite film in which liquid crystals were independently formed as particles in a silicon resin matrix could be produced. The composite film obtained above shows excellent electrochemical characteristics (transmittance-voltage curve), does not exude liquid crystal,
Excellent stability.

[0017]

According to the present invention, the liquid crystal is encapsulated in an extremely thin wall film, the particle size and the distribution thereof are controlled by using a surfactant, and the liquid crystal does not exude.
A film excellent in the function of modulating light by an electric field, heat, or the like, that is, having a low driving voltage, a high contrast ratio, and the like can be obtained by stable coating. Further, since the electron beam curable resin is a matrix polymer, the film is excellent in stability and durability, and from the viewpoint of productivity, it is excellent in that solventless instant curing is possible.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiromi Maeda 1-1-1, Ichigaya-Kagacho, Shinjuku-ku, Tokyo Inside Dai Nippon Printing Co., Ltd. (72) Inventor Masayuki Ando 1-1-1, Ichigaga-cho, Shinjuku-ku, Tokyo No. 1 Inside Dai Nippon Printing Co., Ltd. (56) References JP-A-3-91718 (JP, A) JP-A-2-81024 (JP, A) JP-A-63-151354 (JP, A) 2-280120 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02F 1/1333 G09F 9/35

Claims (4)

(57) [Claims] (1) A water-soluble electron beam-curable monomer, oligomer, polymer, or a mixture of two or more thereof, comprising an electron beam-curable compound having a surface-active ability,
A method for producing a liquid crystal / polymer composite film, comprising irradiating an electron beam after dispersing the liquid crystal. 2. The method for producing a liquid crystal / polymer composite film according to claim 1 , wherein the water-soluble electron beam-curable monomer, oligomer or polymer is a polyfunctional compound having two or more functional groups. 3. The method for producing a liquid crystal / polymer composite film according to claim 1, wherein at least one of the water-soluble electron beam-curable monomers, oligomers and polymers is a silicon-based or fluorine-based compound. 4. A water-soluble electron beam-curable monomer,
The method for producing a liquid crystal / polymer composite film according to claim 1, wherein a compound having three or more functions is used.