JPH08194208A - Liquid crystal optical element and its production - Google Patents

Abstract

PURPOSE: To produce a liquid crystal optical element with low driving voltage and little hysteresis even when the element is used for a display by constituting the capsule wall from a polymer material having urethane bonds in the molecule. CONSTITUTION: In this liquid crystal optical element, a liquid crystal/polymer composite film comprising encapsulated liquid crystal particles dispersed in a particulate state and a matrix material which includes these particles, the wall material of the capsule consists of a polymer material having urethane bonds in the molecule. The polymer material having urethane bonds in the molecule is prepared from urethane oligomers and has a low mol.wt. and good solubility with a liquid crystal or comonomers. The polymer is an extremely flexible material although it has no soft segment. These characteristics contribute to reducing the driving voltage of the element which is produced by using this polymer material. Moreover, since the polymer synthesized from urethane oligomers has proper crosslinks, it does not increase the hysteresis of the element produced by using the polymer.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a public display, a personal computer,
The present invention relates to a liquid crystal / polymer composite film type liquid crystal optical element useful as a display for portable information terminals and the like, OHP, cards and the like, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal / polymer composite film in which liquid crystal molecules are dispersed in the form of droplets in a polymer matrix, or a liquid crystal / polymer matrix in which a continuous phase is formed / high The molecular composite film turns on the applied voltage.
When turned off, it reversibly exhibits a transmission-scattering state and is used as a material for a liquid crystal optical element. As a technique for producing the liquid crystal / polymer composite film, a method of using PVA (polyvinyl alcohol) as a polymer matrix for holding liquid crystal particles in a dispersed state (Japanese Patent Publication No. 58-501631).
Japanese Patent Laid-Open Publication No. 61-5), a method using an epoxy resin (Tokusho Sho 61-5
No. 02128), a method using a UV-curable resin (JP-A-1-252689), and the like. Further, a solvent is removed from a uniform solution of a liquid crystal and a polymer matrix to form a liquid crystal / polymer composite film. Method for forming a film (JP-A 1-230
693).

[0003]

However, the liquid crystal optical element using the liquid crystal / polymer composite film obtained by the above-mentioned conventional method is unsatisfactory in that the driving voltage as the element is high and a large hysteresis is generated. It is sufficient and its application range is limited. Actually the above liquid crystal /
In order to apply the polymer composite film type liquid crystal optical element as a display, how to reduce the driving voltage and how to reduce the hysteresis is an important issue. It varies greatly depending on the material used to form the composite membrane, and as a material for the polymer matrix,
One using a polymer of an acrylic acid biphenyl ester derivative (JP-A-5-53096) and one using a fluorine-containing (meth) acrylic acid ester polymer (JP-A-5-53096).
Although many reports have been made recently, such as Japanese Patent Laid-Open No. 194955), none of them has sufficient characteristics. Therefore, an object of the present invention is to provide a liquid crystal optical element using a liquid crystal / polymer composite film having a low driving voltage and a small hysteresis even when applied as a display.

[0004]

The above object can be achieved by the present invention described below. That is, the present invention is a liquid crystal optical element using a liquid crystal / polymer composite film comprising granular encapsulated liquid crystal particles and a matrix material encapsulating the particles, wherein the capsule wall material is A liquid crystal optical element comprising a polymer material having a urethane bond in the molecule, a liquid crystal / polymer composite comprising liquid crystal particles dispersed in a granular form and a polymer matrix material encapsulating the liquid crystal particles. In a liquid crystal optical element using a film, a liquid crystal optical element characterized in that the polymer matrix material is a polymer material having a urethane bond in the molecule, and the liquid crystal and the polymer matrix material form a three-dimensional network. In a liquid crystal optical element using a liquid crystal / polymer composite film, the polymer matrix material comprises a polymer material having a urethane bond in the molecule. Liquid crystal optical element characterized the door, and a manufacturing method thereof.

[0005]

The present inventors have conducted earnest research and development to develop a novel polymer encapsulating material for liquid crystal particles or a polymer matrix material for liquid crystal particles used in a liquid crystal optical element. It has been found that a polymer material obtained from a urethane oligomer having a is effective in reducing the driving voltage of a liquid crystal / polymer composite film type liquid crystal optical element. We also synthesized a novel urethane acrylate oligomer that has excellent solubility in liquid crystals and can improve the driving voltage and hysteresis of the resulting device. This urethane acrylate oligomer has a low molecular weight because a soft segment such as polypropylene oxide is not introduced, and therefore has good compatibility with liquid crystals and comonomers. In addition, it is a very flexible material in spite of the absence of soft segments, and this characteristic contributes to the reduction of the driving voltage of the device obtained by using the above material, and is synthesized from the above urethane oligomer. The polymer is reasonably crosslinked so that it does not increase the hysteresis of the device obtained using it.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to preferred embodiments. The liquid crystal optical element of the present invention,
A liquid crystal / polymer composite film comprising liquid crystal particles and a polymer matrix material is used, one example of which is an example in which liquid crystal particles are encapsulated by a polymer of urethane acrylate oligomer, and another example. Is an example of using a polymer composed of the above oligomer as a polymer matrix, and yet another example is a liquid crystal / polymer composite film in which a liquid crystal and a polymer matrix material form a three-dimensional network. In the liquid crystal optical element, the polymer matrix material comprises a polymer material having a urethane bond in the molecule. In the present invention, the first example is particularly preferable.

The liquid crystal referred to in the present invention is an organic mixture exhibiting a liquid crystal state near room temperature, and nematic liquid crystal or cholesteric liquid crystal is preferably used for display applications, and smectic liquid crystal is used for OHP or card applications. To be These liquid crystals may have positive or negative dielectric anisotropy. Incidentally, the liquid crystal mixture may contain a dichroic dye. When the dichroic dye is used, it is preferably used in the range of about 0.5 to 5 parts by weight per 100 parts by weight of the liquid crystal. In the first embodiment of the present invention, the above liquid crystal is finely dispersed and used by being encapsulated with a polymer having a urethane bond.

The novel urethane acrylate oligomer used as a wall material or a polymer matrix material for encapsulating liquid crystal particles in the present invention is a urethane oligomer obtained by using a bifunctional isocyanate having a melting point of 0 ° C. or less as a raw material. Is preferred. As the bifunctional diisocyanate, for example, 1,6-hexamethylene diisocyanate, 2,2,4 (2,4,
4) -trimethylhexamethylene diisocyanate, m
-Xylene diisocyanate, m-tetramethyl xylene diisocyanate (m-TMXDI), isophorone diisocyanate (IPDI), 2,6-toluene diisocyanate, lysine diisocyanate and the like, among which the flexibility of the polymer finally obtained Aliphatic diisocyanates that contribute to the properties are preferred.

Two radically polymerizable groups are introduced into the above bifunctional isocyanate. Preferred as the radically polymerizable group is (meth) acrylate having one hydroxyl group in the molecule, and examples thereof include 2-hydroxyethyl (meth) acrylate (2HEA), 2-hydroxypropyl (meth) acrylate, and 2-hydroxypropyl (meth) acrylate. Examples thereof include hydroxybutyl (meth) acrylate and N-methylol acrylamide. Also, those having a fluorine atom introduced into the molecule, for example, 3- (perfluoro-3-methylbutyl)
2-Hydroxypropyl (meth) acrylate, 3-perfluoro-2-hydroxypropyl (meth) acrylate and the like are also mentioned as preferable examples.

The reaction of the above-mentioned diisocyanate with the (meth) acrylic acid ester to form the urethane oligomer is preferably carried out in a molar ratio of the former: latter = about 1: 2. In the reaction, a solvent may or may not be used, but it is preferable to use an inert organic solvent such as methyl ethyl ketone or toluene in consideration of temperature control, reaction yield, product purity and the like. Reaction temperature is room temperature to 100 ℃
It takes about 30 minutes to 3 hours to complete. Next, a typical method for synthesizing a urethane oligomer will be illustrated. (1) 2HEA (dehydrated, containing 400 ppm methylethylhydroquinone) 100 g (2) m-TMXDI 105 g (3) methylethylketone (dehydrated) 100 g (4) benzoquinone 20 mg (5) dibutyltin dilaurate (catalyst) 50 mg

The above components (1), (3), (4) and (5) were charged into a four-necked flask and kept at 60 ° C. with stirring under a nitrogen atmosphere, and then the component (2) was taken for 1 hour. Dropped. Then, the temperature was raised to 70 ° C., and the reaction was allowed to proceed until the absorption based on the isocyanate disappeared by infrared spectroscopy. After completion of the reaction, the solvent was removed by distillation under reduced pressure to obtain an oily urethane oligomer.

The encapsulation of the liquid crystal with the urethane oligomer is carried out by mixing the liquid crystal and the urethane oligomer, and adding a suitable type and amount of a monomer and a polymerization initiator thereto to form a solution. At this time, the liquid crystal and the oligomer are excellent in compatibility and form a uniform solution. Heat if necessary. Next, the mixture thus obtained is emulsified and dispersed in an aqueous medium by using an appropriate emulsifier, surfactant or protective colloid, and then ultrasonically or mechanically stirred, and then at a temperature of about 50 to 95 ° C for 1 to 24 hours. By heat-polymerizing, liquid crystal particles encapsulated with a polymer having a urethane bond can be obtained. In this case, the amount of the liquid crystal and the oligomer (+ monomer) is about 5 to 50 per 100 parts by weight of the former.
A range of parts by weight is preferred. If the amount of the oligomer (+ monomer) used is too small, encapsulation of the liquid crystal particles will be insufficient and the exudation of the liquid crystal and the strength of the particles will be insufficient. On the other hand, if the amount of the oligomer (+ monomer) used is too large, the electric field responsiveness of the device is reduced. Further, the diameter of the obtained encapsulated particles varies depending on the degree of dispersion of the liquid crystal before the polymerization, but in the present invention, the encapsulated particles having an average particle diameter of about 1 to 4 μm are preferable.

As the monomer to be copolymerized with the urethane acrylate oligomer, various (meth) acrylates and monomers having a vinyl group can be used. For example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, phenoxyethyl (meth) acrylate, styrene, vinyl acetate, trifluoroethyl ( Examples thereof include (meth) acrylate and 2,2,3,3,3-pentafluoropropyl (meth) acrylate. or,
A polyfunctional monomer (oligomer) having two or more polymerization active groups can also be used. For example, divinylbenzene, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate,
Dipentaneerythritol hexa (meth) acrylate, 2,2-bis [4- (methacryloylpolyoxyethyl) phenyl] propane, polydimethylsiloxane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetra ( Examples thereof include (meth) acrylate.

In the encapsulated liquid crystal dispersion liquid obtained as described above, a polymer matrix material is added to the encapsulated liquid crystal as needed to form a liquid crystal / polymer composite film without once separating the encapsulated liquid crystal. It can be used as a coating liquid for forming. The protective colloid such as polyvinyl alcohol used at the time of encapsulation may be used as it is as a polymer matrix. Further, in order to remove impurities generated during polymerization, the generated encapsulated liquid crystal is once separated by centrifugation or the like, and this is dispersed in an aqueous medium containing an appropriate amount of polymer matrix to prepare a coating solution. Preference is given to using. The amount of the encapsulated liquid crystal and the polymer matrix used is such that the mixture ratio (weight ratio) of polymer matrix / liquid crystal is 5/95 to 50/50 in the case of display use, and in the case of OHP or card use. Is 55/45 to 35/65. If the amount of the liquid crystal used is too small, not only is the transparency insufficient when a voltage is applied, but also a large amount of voltage is required to bring the film into a transparent state. If the amount used is too large, not only the scattering (turbidity) at the time of voltage application becomes insufficient, but also the strength of the film decreases, which is not preferable. or,
A dichroic dye can be added to the liquid crystal in order to improve the contrast and color tone of the liquid crystal / polymer composite film. Light absorption (coloring) due to the guest-host effect of the dye in this case
-It is possible to obtain a liquid crystal / polymer composite film that switches in the transparent state.

As a method for producing a liquid crystal / polymer composite film using the above coating solution, a coating method and an electrodeposition method which are particularly easy to cope with a large area, a light weight by a film electrode and the like are desirable. Without using the coating liquid, for example, a phase separation method by light, heat curing, a phase separation method by solvent evaporation, a phase separation method by temperature change, or the like using a solution or the like is not excluded. As a coating method, for example, an electrodeposition coating method, screen printing, stencil printing using a metal mask, brush coating, spray coating, blade coating, doctor coating or the like is applied to one surface of the element substrate. By drying this, a liquid crystal / polymer composite film can be formed. The thickness of the formed liquid crystal / polymer composite film is about 3 to 15
The range of μm is preferable, and when the composite film is too thin, there are problems in that the scattering intensity in the light scattering state is lowered, the contrast of scattering-transmission is lowered, and the like, and when it is too thick, the obtained element is driven. There is a problem in that the voltage becomes high.

As a method of applying the coating solution, an electrodeposition coating method is preferable in addition to the coating method. The electrodeposition coating here means that a main electrode and a counter electrode, which are coating substrates, are placed in a coating liquid containing liquid crystal particles and an electric current is applied thereto, so that the liquid crystal particles and the polymer matrix material are electrically deposited on the substrate. Liquid crystal / polymer composite film is formed by adsorbing or depositing on the substrate, then taking out the electrodeposited substrate and drying and removing the solvent. The electrodeposition coating includes an anion electrodeposition method in which a liquid crystal and a polymer material are projected on the anode and a cation electrodeposition method in which a liquid crystal and a polymer material are projected on the cathode. However, a transparent metal oxide such as ITO serves as an electrode. Since a substrate having a different thickness is usually used as a coating substrate, the anion electrodeposition method is preferably used in order to avoid coloring of the transparent electrode due to reduction. Examples of the anionic resin preferably used as the polymer matrix used in the electrodeposition method include maleated oil resin, anion-modified polybutadiene resin, polyester resin, and acrylic resin.

The coating liquid used for preparing the liquid crystal / polymer composite film by electrodeposition coating can be prepared by emulsifying and dispersing the liquid crystal in an aqueous solution of the anionic resin. or,
In order to optimize the coating film structure of the formed liquid crystal / polymer composite film and to optimize the voltage distribution to the liquid crystal / polymer composite film,
As described above, it is particularly preferable to use the coating liquid in which the liquid crystal is encapsulated in advance and is dispersed in the anionic resin aqueous solution. An organic solvent is usually added to the electrodeposition bath in order to improve the solubility of the polymer matrix material and obtain a smooth coating film. As the organic solvent used here, alcohols such as ethanol, methanol, and isopropanol,
Cellosolves such as methyl cellosolve and ethyl cellnolub, hydrophilic organic solvents such as glycol and carbitol are preferably used, but hydrophobic solvents such as xylol and toluol can also be used depending on the case.

Examples of the auxiliaries which can be used include a surfactant for imparting dispersion stability of liquid crystal particles, a leveling agent for improving smoothness of a coating film, an antifoaming agent and the like.
When the encapsulated liquid crystal has an anionic group such as a carboxyl group, the capsule itself has a capability of electrophoresing and depositing on the substrate, so that the anionic resin can be used without using an anionic resin. Can be worn. The film thus deposited and formed on the electrode is heated and dried to remove volatile components such as water and organic solvent, and becomes a desired liquid crystal / polymer composite film.

The element substrate used for forming the above liquid crystal / polymer composite film is one that is generally used in conventionally known liquid crystal optical elements, for example, ITO-based, SnO ₂
Examples of the transparent electrode substrate include a transparent conductive material such as glass and ZnO based on a transparent substrate such as glass or polymer film. When an opaque conductive substrate is used as one of the substrates, its electrode is used. It is also possible to use a reflection type electrode having a surface irregularity made of a metal having a high reflectance, such as aluminum, silver, chromium or nickel. The substrate itself may be glass, polymer film or others.

As described above, the other device substrate is laminated on the surface of the liquid crystal / polymer composite film formed on one device substrate by a conventional method, and necessary sealing and wiring are performed to realize the present invention. A liquid crystal optical element is obtained. In the above description, an example in which a liquid crystal is encapsulated has been described, but in the present invention, as shown in the examples below, the liquid crystal is not encapsulated in the polymer matrix composed of the urethane oligomer. Even when the liquid crystal particles are dispersed and included, a liquid crystal optical element having similarly excellent properties can be obtained. When the device of the present invention is used for OHP or a card, only one electrode is used, a liquid crystal / polymer composite film is formed on the electrode, and a protective layer is further formed as necessary to form the device. Can be used to drive the liquid crystal / polymer composite film. In the case of a card, it is preferable to use a reflective electrode as the electrode, and in addition to the reflective electrode, an electrode in which the transparent electrode material is adhered on a white PET film can be used.

[0021]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. Example 1 Halogen-based liquid crystal (TL-205, manufactured by Merck Ltd.) 2.
0 g, 2-hydroxyethyl acrylate (2HE) per 1 mol of isophorone diisocyanate (IPDI)
A) 0.1 g with 2 mol added (Oligomer 1), 2
A uniform mixture of 0.4 g of ethylhexyl acrylate (EHA) and 0.01 g of azobisisobutyronitrile (AIBN) was prepared. To the above mixed solution, 10 g of a 2% aqueous solution of polyvinyl alcohol (EG-05, manufactured by Nippon Gosei Co., Ltd.) was added, ultrasonically dispersed, and then polymerized at 85 ° C. for 20 hours to encapsulate liquid crystal particles. This was centrifuged to remove free EG-05, and an aqueous medium was added to adjust the viscosity to an appropriate level to prepare a coating ink.

The above ink was applied onto ITO glass by a stencil printing method at a ratio of a film thickness after drying of 10 μm and dried to form a liquid crystal / polymer composite film, and an ITO-PET film was used as a counter electrode. The liquid crystal optical element of the present invention was obtained by pasting together. The electro-optical characteristics of the above element were measured, and it was found that when the difference between the transmittance (T ₀ ) when no voltage was applied and the saturated transmittance (T ₀₀ ) when voltage was applied was 100%, the application at 10% transmittance Voltage (V ₁₀ ) is 9.2V, 90
The applied voltage (V ₉₀ ) at the time of% transmittance was 16.3V.
Incidentally, T ₀ was 2% and T ₁₀₀ was 84%. The fall relaxation time (τ _off ) after applying 50 V to the cell for 2 minutes was 35 milliseconds. A voltage holding ratio (V _hr ) of 16 V after applying a pulse of 10 V for 30 μs was 93%.

Example 2 The oligomer in Example 1 was prepared by mixing 2 mol of 2HEA with 1 mol of a 1: 1 mixture of 2,2,4-trimethylhexamethylene diisocyanate and 2,4,4-trimethylhexamethylene isocyanate (TMDI). A liquid crystal optical element of the present invention was produced in the same manner as in Example 1 in place of the added one (oligomer 2). Its characteristic is V ₁₀ = 7.
8V, V ₉₀ = 15.4V, T ₀ = 2%, T ₁₀₀ = 84
%, Τ _off = 33 milliseconds, V _hr = 93%. Example 3 The oligomer 1 in Example 1 was added to 2 mol of 1 mol of m-tetramethylxylene diisocyanate (m-TMXDI).
A liquid crystal optical element of the present invention was produced in the same manner as in Example 1 except that 2 mol of HEA was added (Oligomer 3). The characteristics are V ₁₀ = 11.3V, V ₉₀ = 2
3.4V, T ₀ = 2%, T ₁₀₀ = 85%, τ _off = 27
Millisecond, V _hr = 87%.

Example 4 The same procedure as in Example 1 was carried out except that the oligomer 1 in Example 1 was replaced with 1 mole of 1,6-hexanemethylene diisocyanate (HDI) to which 2 moles of 2HEA was added (oligomer 4). A liquid crystal optical element of the present invention was produced. The characteristics are V ₁₀ = 11.5V, V ₉₀ = 25.0V, T ₀
= 2.0%, T ₁₀₀ = 85%, τ _off = 30 milliseconds, V
_hr was 93%. Example 5 The same procedure as in Example 1 was carried out in the same manner as in Example 1 except that the oligomer 1 in Example 1 was replaced with the one obtained by adding 2 moles of 2HEA to 1 mole of m-xylene diisocyanate (m-XDI). A liquid crystal optical element was produced. The characteristics are V ₁₀ = 11.5V, V ₉₀ = 25.0V, T ₀ = 2.
1%, T ₁₀₀ = 85%, τ _off = 30 ms, V _hr = 9
It was 3%.

Example 6 In the same manner as in Example 1 except that the oligomer 1 in Example 1 was replaced with 2 moles of 2HEA added to 1 mole of 2,6-toluene diisocyanate (TDI) (oligomer 6). A liquid crystal optical element of the present invention was produced. The characteristics are as follows: V ₁₀ = 8.0V, V ₉₀ = 20.0V, T ₀ = 2%,
T ₁₀₀ = 85%, τ _off = 50 milliseconds, and V _hr = 91%. Example 7 The liquid crystal optical element of the present invention was obtained in the same manner as in Example 1 except that the oligomer 1 in Example 1 was replaced with the one obtained by adding 2 mol of 2HEA to 1 mol of lysine diisocyanate (LDI) (oligomer 7). It was made. Its characteristic is V ₁₀ =
12.0V, V ₉₀ = 25.5V, T ₀ = 2%, T ₁₀₀ =
84%, τ _off = 24 milliseconds, V _hr = 91%.

Comparative Example 1 A liquid crystal optical element of Comparative Example was prepared in the same manner as in Example 1 except that 0.5 g of methyl methacrylate was used as the capsule wall material in Example 1. Its characteristic is that V ₁₀ = 35
V, V ₉₀ = 65V. Comparative Example 2 A liquid crystal optical element of a comparative example was produced in the same manner as in Example 1 except that the capsule material in Example 1 was replaced with 0.5 g of EHA. The characteristic was that V ₁₀ was 70 V or more, which was a very high driving voltage. Comparative Example 3 A liquid crystal optical element of Comparative Example was produced in the same manner as in Example 1 except that the oligomer 1 in Example 1 was replaced with 1,6-hexanediol diacrylate. Its characteristics are V
It was a very high driving voltage of ₁₀ = 65V.

Example 8 A dichroic dye compounded for liquid crystal (TL-205) for black color (manufactured by Mitsui Toatsu Chemicals, Inc., SI800: SI1486:
SI426 = 30: 7: 7) was dissolved by 3% to prepare an encapsulated liquid crystal with the same composition ratio as in Example 1. After the suspension of this capsule was centrifuged, anion-type electrodeposition resin neutralized at a ratio of 10% and water were added to the capsule to prepare an electrodeposition composition having a solid content concentration of 20%. A liquid crystal / polymer composite film having a film thickness of 6 μm was produced by electrodeposition using a white polyethylene terephthalate film vapor-deposited with aluminum as an electrodeposition electrode. The dichroic dye-containing liquid crystal is spin-coated on a thin film transistor substrate, then pressure-bonded to the liquid crystal / polymer composite film, excess liquid crystal is removed, and then sealed with an ultraviolet curable resin, to thereby obtain a liquid crystal optical element of the present invention. Got When this was driven, a reflectance of 40% was shown when a voltage of 15 V was applied. Further, the reflectance when no voltage was applied was 6%.
The display quality was good with no parallax and a wide viewing angle.

Example 9 Halogen-based liquid crystal (TL-205, manufactured by Merck Ltd.) 80
%, 10% of the oligomer 1 used in Example 1 and EHA
The mixture was mixed at a ratio of 10%, and the photopolymerization initiator (ZLI-3331, Merck Co.
50 mW / cm ² while maintaining the whole substrate at 38 ° C. by sandwiching it between two ITO electrode glass substrates on which 11.0 μm glass fiber spacers are scattered.
Ultraviolet rays having the intensity of 1 were irradiated for 60 seconds to obtain a liquid crystal / polymer composite film. The structure of this film was such that the liquid crystal and the polymer matrix material mutually formed a three-dimensional network. The characteristics of the liquid crystal / polymer composite film are V ₁₀ = 5.8 V and V ₉₀ = 1.
The values were _0.0 V, T ₀ = 5%, T ₁₀₀ = 90%, τ _off = 30 milliseconds, and V _hr = 94%.

Example 10 Smectic liquid crystal (S-6, manufactured by Merck Ltd.) 2.0
g, dichroic dye (S-428, manufactured by Mitsui Toatsu Chemicals, Inc.)
0.04g, Oligomer 1 0.1g, HEA 0.4g
And a uniform mixture of AIBN 0.01 g was prepared. To the above mixture, 10 g of a 2% aqueous solution of EG-05 was added, ultrasonically dispersed, and then polymerized at 70 ° C. for 24 hours to encapsulate liquid crystal particles. To this liquid crystal microcapsule dispersion, KH-20 (manufactured by Nippon Gosei Co., Ltd.) was added as a thickener to prepare an ink. The proportion of liquid crystal in the solid content of this ink was adjusted to 50%. The above ink was coated on a white polyethylene terephthalate (PET) film with ITO by a stencil printing method and dried to form a liquid crystal / polymer composite film having a thickness of 8 μm. When a corona voltage of 5 kV was applied to this film, the film changed from black to light gray. The contrast between these two states is 2.
It was 5. Further, this contrast was kept good for one month or more at room temperature.

[0030]

According to the present invention as described above, by using the polymer material having a urethane bond, the driving voltage of the liquid crystal optical element can be remarkably reduced, and high contrast, high voltage holding ratio, A liquid crystal / polymer composite type liquid crystal optical element having low hysteresis and high reliability can be provided.

Claims (7)

[Claims] 1. A liquid crystal optical element using a liquid crystal / polymer composite film comprising granular encapsulated liquid crystal particles and a matrix material encapsulating the particles, wherein the capsule wall material is a molecule. A liquid crystal optical element comprising a polymer material having a urethane bond therein. 2. A liquid crystal optical element using a liquid crystal / polymer composite film comprising liquid crystal particles dispersed in a granular form and a polymer matrix material encapsulating the liquid crystal particles, wherein the polymer matrix material comprises: A liquid crystal optical element comprising a polymer material having a urethane bond in the molecule. 3. A liquid crystal optical element using a liquid crystal / polymer composite film in which a liquid crystal and a polymer matrix material form a three-dimensional network, wherein the polymer matrix material has a heavy bond having a urethane bond in the molecule. A liquid crystal optical element comprising a united material. 4. A polymer having a urethane bond is composed of a urethane oligomer having two urethane bonds in one molecule and two (meth) acryl groups.
3. The liquid crystal optical element according to any one of 3 to 3. 5. The liquid crystal optical element according to claim 4, wherein the urethane oligomer is prepared from diisocyanate having a melting point of 0 ° C. or lower. 6. The diisocyanate is 1,6-hexamethylene diisocyanate, 2,2,4 (2,4,4)-
Trimethylhexamethylene diisocyanate, m-xylene diisocyanate, m-tetramethyl xylene diisocyanate, isophorone diisocyanate, 2,6
-The liquid crystal optical element according to claim 5, which is selected from the group consisting of toluene diisocyanate and lysine diisocyanate. 7. A pair of electrodes is dipped in an electrodeposition bath, and an electric current is applied between the electrodes to form a liquid crystal / polymer composite film on one electrode surface by electrodeposition. In the method for producing a liquid crystal optical element to be used, the electrodeposition bath is in an aqueous medium,
A method for producing a liquid crystal optical element, which is an electrodeposition bath containing liquid crystal particles encapsulated by a polymer having a urethane bond and a polymer matrix material.