JPH0419709A - Production of high-polymer/liquid crystal composite - Google Patents

Abstract

PURPOSE:To obtain a high change in light transmittance and good contrast with a low driving voltage by adding a polymn. initiator and peroxide to a uniform soln. mixed with a nematic type liquid crystal, bifunctional polyester oligomer and acrylic monomer at prescribed ratios, then irradiating the mixture with UV rays to cause a phase sepn. CONSTITUTION:The high-polymer/liquid crystal composite formed by dispersing and holding the liquid crystal into a high-polymer matrix of a monomer oligomer system is obtd. by adding the polymn. initiator at a prescribed concn. to the uniform soln. mixed with the liquid crystal of a nematic type which exhibits a nematic phase at room temp. and the bifunctional polyester oligomer, the acrylic monomer at the prescribed ratios of the liquid crystal and the oligomer/monomer. Further, the peroxide is added to the mixture and thereafter, the mixture is irradiated with the UV rays to cause the phase sepn. The high- polymer/liquid crystal composite with which the high change in the light transmittance and the good contrast are obtainable even with the low driving voltage and which is low in viscosity, allows easy handling and has good productivity is easily obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a polymer/liquid crystal composite in which liquid crystal is dispersed and held in a polymer matrix.
In particular, it relates to improvements in its electrical and optical properties.

(Prior Art) A polymer/liquid crystal composite is one in which very fine liquid crystals are dispersed and held in a polymer matrix, and the alignment state of the liquid crystals changes depending on the presence or absence of an electric field. For example, when there is no electric field, the liquid crystal is in a random state, so light is scattered due to spatial differences in refractive index. On the other hand, when an electric field is applied, the liquid crystals become aligned in the direction of the electric field.

As a result, the refractive index of the liquid crystal portion and the polymer matrix portion match, resulting in a transparent state allowing light to pass through.

Such polymer/liquid crystal composites do not require polarizing plates, so they have very good light transmission, and they can be made into large areas, making them suitable for use in photosensitive films and various display devices. Its application to nato is being extensively studied.

Incidentally, known methods for producing such a polymer/liquid crystal composite include (1) solvent evaporation from an emulsified state, (2) phase separation by solvent evaporation, (2) phase separation by quenching, and (2) phase separation by polymerization. Among these, structural stability, productivity,
Phase separation by polymerization (2) is attracting attention because of the possibility of structural control.

In addition, the types of liquid crystals and polymer matrices include:
Liquid crystals, monomers, and oligomers are attracting attention due to the above-mentioned structural stability (Proceedings of the 38th Polymer Symposium, p. 2151;
prints japanv o 1.38
No. 7 (1989) 'Polymer-liquid crystal composites (1) to (II)'').

For this, BDH's product name E-8 (cyano biphenyl type) was used as the liquid crystal, 2-ethylhexyl acrylate was used as the monomer, and bifunctional urethane acrylate (molecule jl 2000) was used as the oligomer. : Oligomer-6:2.4 :1.6 (
A polymer/liquid crystal composite is disclosed in which a homogeneous solution mixed at a ratio of 1 to 10% by weight is polymerized and phase separated by ultraviolet irradiation.

(Problems to be Solved by the Invention) The relationship between the drive voltage and light transmittance of such a conventional polymer/liquid crystal composite film is shown in FIG.

As is clear from the second figure, the driving voltage is as high as approximately 20V, and the change in transmittance with respect to this driving voltage is approximately 70%.
However, it is not possible to obtain a sufficiently satisfactory contrast. Furthermore, the viscosity of a homogeneous solution containing liquid crystals, monomers, and oligomers is high, making it difficult to handle.
There is also the disadvantage that productivity is poor.

The present invention has been developed in view of these points, and it is possible to obtain a high change in light transmittance and good contrast with a low driving voltage, a low viscosity, easy handling, and a highly productive high-speed The object is to provide a manufacturing method for obtaining a molecule-liquid crystal composite.

(Means for Solving the Problems) The present invention provides a polymer/liquid crystal composite in which a liquid crystal is dispersed and held in a monomer/oligomer based polymer matrix. After adding a polymerization initiator at a predetermined concentration and further adding peroxide to a homogeneous liquid crystal solution containing a functional polyester oligomer and an acrylic acid monomer and a mixture of oligomer/monomer at a predetermined ratio, It is characterized by phase separation by irradiation with ultraviolet rays.

(Function) In the present invention, a cyanobiphenyl nematic type liquid crystal is used as the liquid crystal. Further, a bifunctional polystyl is used as the oligomer, and an acrylic acid type monomer is used.

Then, after adding a polymerization initiator at a predetermined concentration and further adding peroxide to a homogeneous solution of these mixtures, ultraviolet rays are irradiated to perform homopolymerization of bifunctional polyester oligomers, homopolymerization of acrylic acid monomers, or Copolymerization of both is caused to produce a polymer matrix in which these homopolymers and copolymers are mixed. At this time, phase separation occurs between the polymer matrix and the liquid crystal, and a polymer-liquid crystal composite is produced.

The light transmission characteristics of this polymer-liquid crystal composite are extremely low, with a driving voltage of about IOV, as shown in Examples below. Further, the change in light transmittance with respect to this driving voltage is as large as about 95% or more, and the contrast is also high.

Note that when the mixing ratio of the liquid crystal in the above-mentioned homogeneous solution is more than 75% by weight, the driving voltage becomes high and the change in light transmittance with respect to this driving voltage becomes small. Further, since the alignment state of the liquid crystal does not change satisfactorily, the contrast is also poor. The viscosity also becomes too high. The mixing ratio of liquid crystal is 65
The same applies when the amount is less than 75% by weight, and therefore, in the present invention, the mixing ratio of the liquid crystal is set to 75 to 65% by weight.

Regarding the blending ratio of oligomer and monomer at this time, if the oligomer/monomer weight ratio is larger than 7/3, the viscosity of the homogeneous solution will be too high, and conversely, if it is smaller than 2/8 weight ratio, the polymer matrix will be The effect is not good. Further, the characteristics also deteriorate near the intermediate value of 515. Therefore, in the present invention, the blending ratio of oligomer and monomer is 773 to 6.5/3.5 or 4/6 to 2/8.
(weight ratio). In addition, the particle size of the liquid crystal is preferably about 2 to 3 μm in order to obtain characteristics such as low voltage driving and high contrast.

Further, the molecular weight of the oligomer is 1000 or less in order to cause the above-mentioned homopolymerization and copolymerization to occur well and to obtain a good polymer matrix.

Preferably 650-850. In particular, it is preferably about 770.

(Example) As a cyanobiphenyl-based nematic type liquid crystal, the product name E-9 (which exhibits a nematic phase at room temperature) manufactured by BD 1 was used. As the bifunctional polyester oligomer, HX-820 (trade name) manufactured by KAYARAD (molecular weight 768) was used. Furthermore, 2-ethylhexyl acrylate was used as the acrylic acid monomer.

Such liquid crystal, oligomer, and monomer were mixed in a ratio of liquid crystal: oligomer: monomer -7: 1.8: 1.2 (weight ratio), and 3 weight of Darocurl 173 (trade name, manufactured by MERK) was added as a polymerization initiator. % was added to prepare a homogeneous solution.

Next, this homogeneous solution was injected into a 10 μm thick glass cell with a transparent electrode, and the wavelength was 400 nm and the intensity was 3 mW/cm2.
UV rays were irradiated for 3 to 4 minutes. As a result, a single or copolymerization reaction of the oligomer and monomer occurs, and a phase separation between the mixture of polymer compounds (polymer matrix) produced by this polymerization reaction and the liquid crystal is performed.

The light transmission characteristics of the polymer/liquid crystal composite obtained as described above are as shown by the broken line in FIG.

Note that the light source used at this time had a light wavelength of B33 nm, as in the case of FIG. 2 described above.

In the present invention, the liquid crystal, oligomer, and monomer described above were mixed in a predetermined ratio, a predetermined weight of a polymerization material was added, and then 3% by weight of benzoyl peroxide was added as an accelerator to prepare a homogeneous solution.

Next, this homogeneous solution was injected into a 10 μm thick glass cell with a transparent electrode, and the wavelength was 400 nm and the intensity was 3 mW/c.
m 2 of ultraviolet light was irradiated for 3 to 4 minutes. by this,
A single or copolymerization reaction of the oligomers and monomers occurs, and a phase separation between the mixture of polymer compounds (polymer matrix) produced by this polymerization reaction and the liquid crystal occurs.

The light transmission characteristics of the polymer/liquid crystal composite obtained as described above are as shown by the solid line in FIG.

Incidentally, as the light source at this time, a light source having a light wavelength of 6Hnm was used as in the case of FIG. 2 described above.

As is clear from this figure, the polymer and
According to the liquid crystal composite, driving is performed at an extremely low voltage of about 1OV, and the change in light transmittance with respect to this driving voltage is as large as about 90%. Furthermore, as described above, the viscosity of the homogeneous solution before the start of the polymerization reaction can be kept low.

(Effects of the Invention) As explained above, according to the method for producing a polymer/liquid crystal composite according to the present invention, a nematic type liquid crystal is used as the liquid crystal, and a liquid crystal whose main component is bifunctional polyester is used as the oligomer. Using acrylic acid as a monomer, a solution of them mixed in a predetermined ratio,
After adding a polymerization initiator at a predetermined concentration and further adding peroxide, we irradiated it with ultraviolet rays to cause phase separation, making it possible to obtain a high change in light transmittance and good contrast with a low driving voltage, as well as to reduce viscosity. This type of polymer/liquid crystal composite has the advantage of being easy to obtain, with a low oxidation rate, easy handling, and good productivity.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the light transmission characteristics of a polymer/liquid crystal composite according to the present invention, and FIG. 2 is a graph showing the light transmission characteristics of a conventional polymer/liquid crystal composite. Patent Applicant: Representative of Victor Japan Co., Ltd. Kunio Umiki ■ Ii (V) Procedural Amendment July 72, 1990 1. 2゜3゜ Display of the case 1990 Patent Application No. 124931, Name of the invention Relationship to the case of a person amending the manufacturing method of a polymer/liquid crystal composite Patent applicant address 3-chome Moriyamachi, Kanayō-ku, Yokohama-shi, Kanagawa Prefecture 12 number 5
゜Amendment target 6, contents of amendment (1) Molecular weight 2,000J on page 3, line 13 of the specification is corrected to "Molecular weight 2 (100J). (2) rKAYARADJ" Nippon Kayaku on page 7, line 12 of the specification. ” and above.

Claims (1)

[Claims] In a polymer/liquid crystal composite in which a liquid crystal is dispersed and held in a monomer/oligomer polymer matrix, a nematic type liquid crystal that exhibits a nematic phase at room temperature, a bifunctional polyester oligomer, and an acrylic acid monomer are used as liquid crystals. , and is characterized in that a polymerization initiator is added at a predetermined concentration to a homogeneous solution containing oligomers/monomers mixed at a predetermined ratio, and after further addition of peroxide, ultraviolet rays are irradiated to cause phase separation. A method for producing a polymer/liquid crystal composite.