JP2742573B2 - Polymer / liquid crystal composite film and manufacturing method thereof - Google Patents

Description

The present invention relates to a polymer / liquid crystal composite film in which liquid crystal particles are dispersed in a polymer material film, and a method for producing the same.

[Prior art] The conventional method for producing a polymer / liquid crystal composite film involves dissolving a liquid crystal and a polymer in a common solvent and dissolving the solution on the electrode side of the transparent conductive film so that the film thickness becomes constant. And then evaporate the solvent to obtain a polymer / liquid crystal composite film. A flexible liquid crystal film is obtained by attaching another transparent conductive film to the composite film from the electrode side.

Another production method is to mix and dissolve a polymer and liquid crystal in a mixed solvent of a good solvent and a poor solvent, develop this solution on the water surface, dissolve the good solvent in water, evaporate the poor solvent, and To obtain a polymer / liquid crystal composite film. This polymer
The liquid crystal composite film is sandwiched between two transparent conductive films with the electrode surface inside, thereby forming a flexible liquid crystal film.

[Problems to be Solved by the Invention] In the polymer / liquid crystal composite film, the conductivity of the polymer is σ _P , the conductivity of the liquid crystal is σ _LC , the voltage applied to the polymer is E _P ,
When E _LC a Ru voltage or a liquid crystal, at low frequencies the following equation holds (Kyushu University, polymer Proceedings, Vol.38, Nanba3,198
9).

Therefore, the electric field applied to the liquid crystal is determined by the ratio between the conductivity of the polymer and the liquid crystal. When the conductivity σ _LC of the liquid crystal is constant, the larger the conductivity σ _P of the polymer is, the larger the electric field is. Becomes possible.

However, the polymer material used in the conventional polymer / liquid crystal composite film is an insulating material having a low conductivity, for example, having a resistivity (the reciprocal of the conductivity) of about 10 ¹⁵ Ωcm. Has a drawback that the voltage applied to the liquid crystal is small, low-voltage driving cannot be performed, the change in transmittance is small when the electric field is turned on and off, a large contrast ratio cannot be obtained, and the device cannot be used.

Further, the conventional polymer / liquid crystal composite film has a relatively thick film thickness of about 5 to 10 μm, and thus requires a large driving voltage, and has a non-uniform film thickness and uneven transmittance. Furthermore, since the arrangement of the polymers was irregular, the liquid crystal molecules did not easily move with respect to the on / off of the electric field, resulting in poor responsiveness.

[Means for Solving the Problems] According to the present invention, the liquid crystal is filled in the holes from which the ions of the electrolytically polymerized film of the deionized monomer material have escaped.

Further, according to the present invention, a polymer film is formed by an electrolytic polymerization method, electrolyte ions are removed from the polymer film, and liquid crystal is impregnated into the holes of the polymer film from which ions have escaped.

Embodiment An embodiment of the present invention will be described with reference to the drawings. In the present invention, a polymer film is first formed by an electrolytic polymerization method. For example, as shown in FIG.
The solution 12 is a monomer material to be reacted to become a polymer,
For example, the monomer material is 3-methylthiophene, the electrolyte is lithium perchlorate, and the solvent is propylene carbonate. In addition, pyrrole and thiophene can be used as a monomer material, tetrabutylammonium perchlorate and the like can be used as an electrolyte, and acetonitrile and benzene can be used as a solvent.

The transparent conductive film 13 is put in the solution 12. The transparent conductive film 13 is formed, for example, by depositing a transparent electrode 15 such as ITO on one surface of a polyethylene terephthalate film. The counter electrode 16 faces the transparent conductive film 13.
Into solution 12. As the counter electrode 16, a platinum plate, a gold plate, a ferro plate, or the like is used. Transparent conductive film 13 and counter electrode 16
Is connected to the constant current DC power supply 17. At this time, power supply 17
The positive electrode is made the transparent conductive film 13 side. An ammeter 18 is inserted in series with the power supply 17 as necessary. Actually, the solution 12 is put in the container 11 with the transparent conductive film 13 and the counter electrode 16 set in the container 11.

When a constant current, for example, 5 mA / cm ² is passed between the transparent conductive film 13 and the counter electrode 16 through the solution 12 to cause an electrolytic polymerization reaction, a polymer film (electropolymerized film) is applied to the electrode 15 of the transparent conductive film 13. 19) is formed with a uniform film thickness. Polymer membrane
The electropolymerization reaction is stopped when the film thickness of 19 becomes about 5000 °.

Next, electrolyte ions are removed from the obtained polymer film 19. For example, as shown in FIG. 2 by attaching the same reference numerals to parts corresponding to FIG. 1, a transparent conductive film 13 having a polymer film 19 formed thereon and a counter electrode 16 are set in a container 11, and The solution 21 is charged, and a constant current is supplied between the transparent conductive film 13 and the counter electrode 16 by the power supply 17. In this case, a solution obtained by removing the monomer material from the solution 12 at the time of the electrolytic polymerization is used as the solution 21, and the positive electrode of the power supply 17 is connected to the counter electrode 16, and a current flows in the opposite direction to that at the time of the electrolytic polymerization. Thereby, the electrolyte ions in the polymer film 19 are removed. The current supply time is, for example, about 1 to 2 hours. Thereafter, in order to complete deionization as necessary, the transparent conductive film 13 with the polymer film 19 is immersed in methyl alcohol for about 24 hours. For the above-mentioned electrolytic polymerization and deionization, a conventionally known technique can be applied.

Next, a transparent conductive film provided with a deionized polymer film is put into a liquid crystal, and the liquid crystal is impregnated into the pores of the polymer film from which ions have escaped. At this time, pressure can be applied to speed up and ensure the impregnation. In this way, the polymer
A liquid crystal composite film is obtained. Another transparent conductive film is adhered to the polymer film impregnated with the liquid crystal from the electrode side to obtain a flexible liquid crystal film.

In the above description, if the thickness of the polymer film 19 is larger than 5000 Å, the adhesive strength with the transparent conductive film 13 is reduced, and there is a tendency that the polymer film 19 is easily peeled off. The amount of liquid crystal impregnated in the film 19 decreases, and the ON / OFF ratio of the transmittance cannot be increased. When lithium perchlorate is used as the electrolyte, the ions are large, many liquid crystals can be impregnated, the ions easily move in the polymer film 19, and deionization can be easily performed.

[Effects of the Invention] As described above, according to the present invention, the deionized electrolytic polymerized film is impregnated with liquid crystal, and the conductivity of the deionized electrolytic polymerized film is a conventional polymer film. Since the conductivity is higher than that of the liquid crystal, for example, the resistivity is about 10 ¹⁰ Ωcm, the conductivity is about five digits higher, and a large voltage is applied to the liquid crystal at a low frequency, low voltage driving is possible.

Further, as described above, the thickness of the electrolytic polymer film (polymer film) of about 0.5 μm is sufficient, and may be thinner than the conventional one, so that low voltage driving is possible. Moreover, the thickness of the electropolymerized film is more uniform than that of the conventional one, and there is no unevenness in contrast. A large number of fine holes are densely formed in the polymer film by deionization, and the holes are filled with liquid crystal, so that a high contrast ratio can be obtained even if the film thickness is small. Further, since the electrolytic polymer film is formed by regularly arranging the monomer molecules, when an electric field is applied, the liquid crystal molecules easily move so as to be aligned with the arrangement of the monomer molecules, and a high-speed responsive one can be obtained.

[Brief description of the drawings]

FIG. 1 is a view schematically showing an electrolytic polymerized film production apparatus, and FIG. 2 is a view schematically showing a deionization apparatus.

Claims (2)

(57) [Claims] 1. A polymer in which liquid crystal is filled into pores from which ions of an electrolytic polymerized film of a deionized monomer material have escaped.
Liquid crystal composite film. 2. A polymer / liquid crystal composite film in which a polymer film is formed by an electrolytic polymerization method, electrolyte ions are removed from the polymer film, and liquid crystal is impregnated into pores of the polymer film from which ions have escaped. Method.