JP2002258259A - Polymer dispersion type liquid crystal element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To apply a polymer dispersion type liquid crystal element using a two-frequency driving liquid crystal to a paper-like display by improving scattering strength in an opaque state. SOLUTION: A mixture of a precursor of a polymer compound, a two- frequency driving liquid crystal, and an amphiphilic gelling agent is encapsulated in a cell. The precursor is then polymerized to disperse liquid crystal drops of the two-frequency driving liquid crystal in a polymer matrix in a droplet state. At the same time, coagulation of the amphiphilic gelling agent is contained in both the polymer matrix and the liquid crystal drops to provide a paper-like opaque state by a light scattering effect caused by the coagulation of the amphiphilic gelling agent, in addition to the difference of refractive index between the polymer compound and the liquid crystal, in an opaque state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal device such as a display device and an optical shutter constituting various displays, and more particularly to a liquid crystal device having a memory property.

[0002]

2. Description of the Related Art In recent years, a polymer-dispersed liquid crystal (Pol) which does not require a polarizing plate and utilizes a difference in refractive index between a liquid crystal and a polymer compound has been used.
ymer Dispersed Liquid Cry
sta) devices have been developed. This polymer-dispersed liquid crystal element is a precursor of a liquid crystal and a polymer compound (hereinafter, referred to as a “polymer precursor”; for example, an ultraviolet-curable monomer).
Are mixed and dissolved in a predetermined ratio to prepare a solution having liquid crystallinity. Next, the above-mentioned solution is sealed between a pair of transparent substrates in a state where an interval is maintained at a predetermined distance. In this state, ultraviolet rays are irradiated from one or both of the substrates to polymerize and cure the polymer precursor, and at the same time, phase separate the liquid crystal and the polymer compound. As a result, a polymer / liquid crystal composite layer in which liquid crystal droplets are dispersed and arranged in the polymer compound layer is formed.

The operation principle of the polymer dispersed liquid crystal device is as follows.

The polymer / liquid crystal composite layer exhibits an optically opaque state (scattering state) because the optical anisotropy of the liquid crystal is randomly arranged in a state where no electric field is applied. When a voltage is applied to the polymer / liquid crystal composite layer exhibiting this state, the optical anisotropy of the liquid crystal changes to a fixed arrangement, so that the liquid crystal becomes an optically transparent state. By utilizing this principle, a bright display with a wide viewing angle can be achieved without using a polarizing plate. At this time, in order to maintain the transparent state, usually,
It is necessary to continuously apply a voltage to the polymer / liquid crystal composite layer. That is, when the applied voltage is removed after the transparent state is formed, the state returns to the original optically opaque state.

As a method for producing the above-mentioned polymer-dispersed liquid crystal device, a monofunctional monomer having a hydroxyl group, for example, 2-hydroxyethyl methacrylate is often used as a polymer precursor (see Japanese Patent Application Laid-Open No. H8-15675). ). In a conventional polymer-dispersed liquid crystal device, an attempt is made to use a so-called "hysteresis" phenomenon as a memory, in which the transparent state does not return to the original opaque state even when the voltage is removed after the transparent state is applied by applying a voltage. Has been made. However, once the conventional liquid crystal element transitions to the transparent state, in order to return to the opaque state, a step of heating the element to gradually cool the polymer / liquid crystal composite layer to a molten state is essential, which is inconvenient for practical use. It is.

Therefore, as an example of solving the above problem,
The so-called dual-frequency driving liquid crystal, which has a different sign of dielectric anisotropy depending on the frequency of the applied voltage, is combined with a specific polymer material to produce a polymer-dispersed liquid crystal device. There is known a liquid crystal element which has a memory function that can be performed only by switching the applied voltage and that can maintain the transparent state and the opaque state even after the applied voltage is removed (JP-A-9-120058,
The 22nd Liquid Crystal Symposium Lecture 3D10).

In a polymer-dispersed liquid crystal device using a dual-frequency drive liquid crystal, when displaying an opaque state, the orientation of liquid crystal molecules in the liquid crystal droplets is almost perpendicular to the direction in which an electric field is applied (with respect to the element substrate). (Horizontal) or a random alignment state. In this state, the average refractive index (n _c ) of the liquid crystal is set to be larger than the refractive index (n) of the polymer compound around the liquid crystal droplet. The opaque scattering state is realized by the mismatch of the refractive indices.

[0008]

In recent years, a “paper-like display” capable of displaying in a digital environment while maintaining the convenience of paper has been proposed (Motoya Shin: IEICE, EID97-160, 35, 1988). When the polymer-dispersed liquid crystal element described above is used for this paper-like display, it is necessary to realize a paper-like state, that is, a state as close as possible to the whiteness of paper.

However, there is a problem that the opaque state of the conventional polymer-dispersed liquid crystal element does not reach the whiteness of the paper, and the other side can be seen through. In order to improve the light scattering intensity in the opaque state, it is necessary to increase the difference in the refractive index between the above-described liquid crystal and the polymer compound, but the magnitude of the refractive index depends on the molecular structure of the material. It is difficult to change that value significantly.

An object of the present invention is to solve the above problems and realize a paper-like opaque state in a polymer-dispersed liquid crystal device having a memory property, thereby making it possible to apply the device to a paper-like display. Is to do.

[0011]

According to the present invention, a liquid crystal droplet of a two-frequency drive liquid crystal sandwiched between a pair of substrates and having different signs of dielectric anisotropy according to the frequency of an applied voltage is sandwiched between the substrates. A liquid crystal device comprising at least a polymer / liquid crystal composite layer dispersed in the form of droplets in a molecular compound layer and an electrode for applying a voltage to the polymer / liquid crystal composite layer. The molecule-liquid crystal composite layer has a hydrophobic group, a hydrophilic group,
And a polymer-dispersed liquid crystal device containing an amphiphilic gelling agent which is a self-organizing compound having at least a group that expresses an intermolecular interaction.

In the present invention, the following configuration is included as a preferred embodiment. The amphiphilic gelling agent has at least one selected from a hydroxyl group and a metal salt thereof, a carboxyl group and a metal salt thereof as a hydrophilic group. The amphiphilic gelling agent has at least one selected from an amide group, a carboxyl group, and an ammonium group as a group that expresses an intermolecular interaction. The amphiphilic gelling agent is an amino acid derivative having a hydrophobic group and a hydrophilic group. The liquid crystal element is in an opaque state in an initial state, and the liquid crystal element becomes optically transparent by applying a voltage of a first driving frequency to the polymer / liquid crystal composite layer, and the polymer / liquid crystal composite By applying a voltage of the second drive frequency to the body layer, the liquid crystal element becomes optically opaque. The first driving frequency is a frequency at which the two-frequency driving liquid crystal exhibits a positive dielectric anisotropy, and the second driving frequency is a frequency at which the two-frequency driving liquid crystal exhibits a negative dielectric anisotropy.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, an amphiphilic gelling agent is contained in a polymer / liquid crystal composite layer to improve the scattering intensity in an opaque state due to the aggregation effect of the gelling agent. Has features.

The amphiphilic gelling agent used in the present invention has a self-organizing property of forming a fibrous aggregate (aggregate) by using intermolecular force such as hydrogen bond or coordinate bond as a driving force, The liquid crystal can be gelled by adding a small amount. Further, it is considered that the fibrous aggregate forms a rod-shaped micelle by having amphiphilicity, that is, having hydrophilicity and hydrophobicity,
Good compatibility with compounds having many polar groups in the short axis direction of liquid crystal molecules, such as dual frequency driving.

In the liquid crystal device of the present invention, a two-frequency drive liquid crystal, a polymer precursor, and the above-mentioned amphiphilic gelling agent are mixed at a predetermined ratio and injected between substrates on which necessary members such as electrodes are formed.
It is formed by polymerizing the above polymer precursor. In this polymerization process, liquid crystal droplets composed of liquid crystal molecules are dispersed and arranged in a droplet form in a matrix composed of a polymer compound (hereinafter, referred to as a “polymer matrix”), and a polymer / liquid crystal composite layer is formed. . At this time, since the gelling agent has good compatibility with the dual-frequency driving liquid crystal, some gelling agent molecules mainly gather in the liquid crystal droplets to form an aggregate, and they are randomly dispersed. Conceivable. Also, the gelling agent naturally exists as an aggregate in the polymer matrix. As a result, in the liquid crystal device of the present invention, in addition to the difference in refractive index between the liquid crystal and the polymer compound, the light scattering effect of the aggregate of the gelling agent is added, and the paper is opaque (scattered). Like high scattering intensity is obtained.

FIG. 1 is a schematic sectional view of the basic structure of the liquid crystal device of the present invention. In the figure, 10 and 11 are substrates, 12, 13
Is an electrode, 14 is a spacer, and 15 is a polymer / liquid crystal composite layer.

In the present invention, at least one of the substrates 10 and 11 is transparent, and is made of hard materials such as glass and quartz, as well as polyethylene terephthalate (PET), polyether sulfone (PES), and polycarbonate (P).
Flexible materials such as C) can also be used. Further, electrodes 12, 1 and 2 are provided on the inner surfaces of both substrates, respectively.
3 is formed in an appropriate shape by a vapor deposition method, a sputtering method, or the like. When the substrates 10 and 11 are transparent, the electrodes formed thereon are made of ITO (indium-tin-tin).
Oxide) or another transparent conductive material can be used. It is also possible to form one of the electrodes 12 and 13 with an opaque material, for example, Al, Pt, A
Metals such as u, Ti and alloys thereof.

In the liquid crystal device of the present invention, the surface of each substrate in contact with the polymer / liquid crystal composite layer 15 may be subjected to an alignment treatment. The method of the alignment treatment and the alignment treatment agent are not particularly limited.
A thin film made of polyimide, polyvinyl alcohol, or the like is formed on top of the films 2 and 13 and a rubbing treatment is applied to the surface of the thin film, or a thin film or oxidized film of a vertical alignment treatment agent made of an alkylammonium salt, polyimide, or the like is formed. A vertical alignment film such as a silicon thin film can be used as appropriate. Further, when the horizontal alignment process is performed, the angle formed by each alignment direction when a pair of substrates is formed is not limited.

The liquid crystal element of the present invention is arranged in a state where the above-mentioned pair of substrates are opposed to each other at a predetermined interval (for example, about 1 to 20 μm) via a spacer 14 made of an insulating film or spherical fine particles. The mixture of the polymer precursor, the two-frequency driven liquid crystal, and the amphiphilic gelling agent prepared in the manner described above is sealed, and the polymer precursor is polymerized to form the polymer / composite layer 15.

The amphiphilic gelling agent used in the present invention is a self-assembled compound, and has a hydrophilic group, a hydrophobic group, and a group that exhibits intermolecular interaction such as hydrogen bond and coordination bond in the molecule. At least have. The bonding mode of these groups and the number of each group are not specified. Assuming that the hydrophilic group is A, the group that expresses intermolecular interaction is B, and the hydrophobic group is C, for example, ABC, ABCB, ABCCA, AB
-CB, AB-AC, AB-A-BC, C-
BAC, CBABC, ABCBA
And the like. Preferably, one end of the molecule is A,
The other end is C.

Hereinafter, a hydrophilic group, a group that develops an intermolecular interaction, and a hydrophobic group will be described.

The hydrophilic group contained in the amphiphilic gelling agent used in the present invention is a group that generates an ionic bond, and specifically, a hydroxyl group, a carboxyl group, a hydroxide,
Examples thereof include a carboxyl salt, a sulfonate, an ammonium salt, and a phosphate, and among them, a hydroxyl group and a metal salt thereof, and a carboxyl group and a metal salt thereof are preferable. In addition, any ions may be used as long as they are ions contained in the electrolyte, and are not particularly limited.

The group that expresses intermolecular interaction contained in the amphiphilic gelling agent used in the present invention, which expresses at least intermolecular interaction between gelling agent molecules, has a property that a liquid crystal molecule and a gelling agent molecule are expressed. And an interaction may be developed between them. Preferably, it is a group having a hydrogen bonding property. Specifically, a group having at least one or more amide group, carboxyl group, and ammonium group is preferable, and more specifically, glycine, alanine, valine, leucine, and isoleucine. , Phenylalanine, aspartic acid, glutamic acid, asparagine, glutamine, serine, threonine,
Groups derived from amino acids such as cysteine, urea, glucoamide and the like are preferred. Among them, valine, leucine,
Glycine, aspartic acid, glutamic acid, and glucoamide are preferably used, and these may be the same or different dimers or more. Therefore, as the amphiphilic gelling agent used in the present invention, an amino acid derivative having a hydrophilic group and a hydrophobic group is preferably used.

Examples of the hydrophobic group contained in the amphiphilic gelling agent used in the present invention include hydrogen, a linear aliphatic hydrocarbon group having 1 to 29 carbon atoms and a branched aliphatic hydrocarbon group. Specifically, examples of the linear aliphatic hydrocarbon group include a nonyl group, a decyl group, an undecyl group, a lauryl group, a tridecyl group, a myristyl group, a pentadecyl group, a palmityl group, a heptadecyl group, a stearyl group, an arachidyl group, and a docosanoyl group. , A tricosyl group, a tetracosyl group, a hexacosyl group, a triaconsyl group, and the like, and as a branched aliphatic hydrocarbon group, a 3,5,5-trimethylhexyl group,
A hexyldecyl group, a 2-methylhexadecyl group and the like can be mentioned as examples, but are not limited thereto. In addition, it is sufficient that at least one of these substituents is provided, and another type of substituent may be provided (for example, when a dicarboxylic acid such as aspartic acid is bonded as a group that develops an intermolecular interaction). , An undecyl group and a stearyl group are bonded to the respective carboxylic acids).

Further, by bonding the hydrocarbon group between the hydrophilic group and the group that develops an intermolecular interaction, the distance between the group that develops an intermolecular interaction and the hydrophilic group is increased. Each function can be fully demonstrated. At the same time, the heat resistance is also improved by improving the intermolecular interaction.

In the present invention, the amphiphilic gelling agent to be added to the liquid crystal composition may be used alone or as a mixture of two or more. Specific examples of the amphiphilic gelling agent preferably used in the present invention are shown below.

[0027]

Embedded image

The two-frequency driving liquid crystal used in the present invention is a liquid crystal having a different sign of dielectric anisotropy (Δε) depending on the frequency of an applied voltage. For example, when a low-frequency voltage is applied, the liquid crystal is oriented in parallel with the direction of the electric field. Orientation is performed in a direction perpendicular to the direction of the electric field by applying a high-frequency voltage. Specific examples of the dual-frequency driving liquid crystal preferably used in the present invention include 2, 3
-Dicyano-4-pentyloxyphenyl-4- (trans-4-ethylcyclohexyl) benzoate, 2,
3-dicyano-4-pentyloxyphenyl-trans-4-propyl-1-cyclohexanecarboxylate, 2,3-dicyano-4-ethoxyphenyl-4-
(Trans-4-pentylcyclohexyl) benzoate, 2,3-dicyano-4-ethoxyphenyl-4-
(Trans-4-butylcyclohexyl) benzoate, 2,3-dicyano-4-butoxyphenyl-4-
Low molecular liquid crystals such as (trans-4-butylcyclohexyl) benzoate can be used alone or as a mixture of two or more. In addition, a liquid crystal material that exhibits nematic or cholesteric properties is preferably used, but a smectic material is also used in the present invention as long as the liquid crystal has a different sign of dielectric anisotropy depending on the frequency as described above. be able to.

In the present invention, the mixing ratio of the two-frequency driven liquid crystal and the amphiphilic gelling agent depends on the type of each material, but is based on 100 parts by weight of the two-frequency driven liquid crystal. 0.1 to 1.5 parts by weight of the agent is preferred. If the amount of the gelling agent is too large, the transmitted light intensity in the transparent state will be low, and sufficient contrast cannot be obtained. Conversely, if the amount of the gelling agent is too small, aggregation of the gelling agent becomes difficult to occur, and sufficient scattering intensity cannot be obtained in an opaque state.

In the present invention, the polymer / liquid crystal composite layer 1
As a precursor before polymerization of the polymer compound constituting 5,
It is preferably a mixture of at least one or more monofunctional monomers and one or more polyfunctional monomers.

The monofunctional monomers include light, heat,
A wide variety of materials can be used as long as they cause a polymerization reaction by application of voltage, radiation, etc. In the present invention, hydroxyalkyl (meth) acrylates represented by the following formulas (1) and (2) are preferably used. .

[0032]

Embedded image In the above formula, R has 1 to 3 carbon atoms having one or more hydroxyl groups.
And 0 represents an aliphatic hydrocarbon group.

Among them, 2-hydroxyethyl methacrylate is particularly preferred. In addition, hydroxyalkyl such as 2-ethylhexyl (meth) acrylate, 2-hydroxyethyl acrylate, hydroxypropyl (meth) acrylate and hydroxybutyl (meth) acrylate (Meth) acrylate is preferred. In this case, the number of carbon atoms of the alkyl group, the number of hydroxyl groups, and the bonding position of the hydroxyl group are not particularly limited. In addition, phenoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate and the like can be mentioned.

The polyfunctional monomer is a material having a functional group capable of binding to the monofunctional monomer.
Specifically, for example, bifunctional alkyl diol diglycidyl ether di (meth) acrylate [the following formulas (3) and (4)] and alkyl diol di (meth) acrylate [the following formulas (5) and (6)] Is preferred. Among them, alkyl diol diglycidyl ether di (meth)
Hexanediol diglycidyl ether di (meth) acrylate is particularly preferable as the acrylate, and 1,6-hexanediol diacrylate is particularly preferable as the alkyldiol di (meth) acrylate.

[0035]

Embedded image In the above formula, R has 1 to 3 carbon atoms having one or more hydroxyl groups.
And 0 represents an aliphatic hydrocarbon group. N represents 1 to 30.

In addition to the above, alkyl glycol di (meth) acrylates include ethylene glycol diglycidyl ether di (meth) acrylate, butanediol diglycidyl ether di (meth) acrylate, and ethylene glycol as alkyl diol di (meth) acrylate. Examples thereof include di (meth) acrylate and butanediol di (meth) acrylate, but the number of carbon atoms of these alkyl groups, the number of hydroxyl groups, and the bonding position of the hydroxyl groups are not particularly limited. Other than these, bisphenol-
AEO-modified di (meth) acrylate, isocyanuric acid E
O-modified di (meth) acrylate, tripropylene glycol di (meth) acrylate, pentaerythritol diacrylate monostearate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, "Kayara" manufactured by Nippon Kayaku Co., Ltd.
d R167, HX220, HX620, R684 "and the like.

In the present invention, the mixing weight ratio of the monofunctional monomer and the polyfunctional monomer in the polymer precursor is as follows:
Monofunctional monomer 1-1 to 5 parts of polyfunctional monomer
0 parts is preferable, and 2 to 6 parts is particularly preferable. The mixture weight ratio of the polymer precursor and the liquid crystal was 1
One part or more of the liquid crystal is preferable, and 1 to 4 parts is particularly preferable. If the liquid crystal is less than the above range, the optical characteristics of the element will be poor, and if the liquid crystal is too large,
A situation arises in which the polymer matrix cannot form all liquid crystals into liquid crystal droplets.

Further, a polymerization initiator may be added to the mixture of the polymer precursor and the liquid crystal, if necessary. When the polymer precursor is photopolymerized by irradiation with ultraviolet light, a photopolymerization initiator can be used as a polymerization initiator. For example, 1-hydroxycyclohexylphenyl ketone (for example, manufactured by Ciba Specialty Chemicals, Inc.) Irgacure 184), benzyl dimethyl ketal (Irgacure 651), 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropanone-1-one (Irgacure 90)
7 "), 2-hydroxy-2-methyl-1-phenylpropan-1-one (" Darocur 117 "manufactured by Merck Ltd.)
3 "), 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one (Darocure 1116), 2,4-diethylthioxanthone (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) ) And ethyl p-dimethylaminobenzoate ("Kayacure-" manufactured by Nippon Kayaku Co., Ltd.)
EPA "), isopropylthioxanthone (" Kantacure ITX "manufactured by Ward Prekinsop)
And ethyl p-dimethylaminobenzoate, acylphosphine oxide ("Lucillin TP" manufactured by BASF)
O "). The concentration of the photopolymerization initiator is preferably in the range of 0.1 to 5% by weight based on the total weight of the mixture of the polymer precursor, the liquid crystal and the amphiphilic gelling agent.

A mixture obtained by adding the above polymer precursor and a dual frequency drive and adding an amphiphilic gelling agent is mixed between the substrates and irradiated with ultraviolet rays, whereby the polymer precursor undergoes a polymerization reaction and is cured. Then, the liquid crystal phase-separates from the polymer compound to form liquid crystal droplets. The polymerization reaction is performed at a temperature higher than the phase transition temperature at which the liquid crystal changes from a liquid crystal state to an isotropic liquid phase. By this operation, it is possible to form the polymer / liquid crystal composite layer 15 in a state where the liquid crystal droplets are dispersed in the polymer matrix.

Further, in the present invention, a post-baking step of holding the element at an arbitrary temperature for an arbitrary time after the polymerization of the polymer precursor is performed, whereby a more uniform form and more stable driving characteristics are obtained. It can be a liquid crystal element.

In the liquid crystal device of the present invention, for example, in the state where no voltage is applied, the directors of the liquid crystal molecules in the liquid crystal droplets are random, and the light is scattered to be opaque. In the polymer / liquid crystal composite layer in this state, the first driving frequency, that is, the low frequency at which the two-frequency driving liquid crystal constituting the liquid crystal droplet shows a positive dielectric anisotropy (the sign of the dielectric anisotropy changes) By applying a voltage having a frequency lower than the crossover frequency, the directors of the liquid crystal molecules are aligned in the direction in which the voltage is applied, so that light is transmitted and the liquid crystal molecules become transparent. This transparent state is maintained even after the applied voltage is removed. Next, a second driving frequency, that is, a high frequency (higher than the crossover frequency) voltage at which the liquid crystal exhibits negative dielectric anisotropy is applied to the polymer / liquid crystal composite layer in the transparent state. As a result, the directors of the liquid crystal molecules are aligned perpendicularly to the voltage application direction, and an opaque state is caused by the effect of the aggregate of the amphiphilic gelling agent contained in the polymer / liquid crystal composite layer. When the applied voltage is removed,
The director of the liquid crystal molecules becomes perpendicular or random to the voltage application direction, and the light is scattered, so that the opaque state continues.

FIG. 2 schematically shows an apparatus for evaluating the light transmission characteristics of the liquid crystal element of the present invention. This apparatus is an example of an evaluation apparatus when the liquid crystal element is of a transmission type. In the figure,
20 is a liquid crystal element of the present invention, 21 is a voltage applying means, 22 is a voltage amplifying means, 23 is a light source, 24 is a light transmission amount detecting means,
25 is a display output means. In the device, a voltage of an appropriate frequency output from the voltage applying unit 21 is applied to the liquid crystal element 20 through the voltage amplifying unit 22. The optical characteristics of the element 20 are changed by applying a series of voltages as described above. A light source 23 is placed on one side with the element 20 interposed therebetween. Light from the light source 23 passes through the element 20, and light enters the light transmission amount detecting means 24. The signal output from the means 24 is transferred to the display output means 25, where it is output, displayed and analyzed as appropriate.

FIG. 3 is a diagram schematically showing an example of a display device constituted by using the liquid crystal element of the present invention. In the figure, 30
Is a liquid crystal element of the present invention, 31 and 32 are substrate ends of the element 30, 33 is a driver for driving, and 34 is a driving control means. In this configuration, a matrix electrode as shown in FIG. 4 is formed on each of the substrates constituting the liquid crystal element 30. In FIG. 4, 40 is a substrate, 41 is an electrode pattern, and 42 is an electrode lead portion. The electrode lead-out part 42 is drawn out to the substrate ends 31 and 32, is connected to the driving driver 33, and receives a driving signal from the driving control means 34.

[0044]

[Examples] The present invention will be described in more detail with reference to the following examples, which do not limit the present invention in any way.

[Preparation of Mixture of Polymer Precursor, Dual Frequency Driven Liquid Crystal, and Amphiphilic Gelling Agent]
Hydroxymethyl methacrylate (HEMA), 2
"KAYARAD" manufactured by Nippon Kayaku Co., Ltd.
R-167 "and 1,6-hexanediol diacrylate (HDDA), HEMA: R-167: HDDA
= 5: 4: 1 to obtain a polymer precursor. As the amphiphilic gelling agent, a compound in which X = Br in the compound (1) shown above was used, and "DF01XX" manufactured by Chisso Corporation was used as the dual frequency driving liquid crystal. The polymer precursor, the amphiphilic gelling agent, and the dual-frequency driven liquid crystal were mixed at the weight ratio shown in Table 1 below, and 100 parts by weight of the mixture was mixed with a photopolymerization initiator (manufactured by Ciba Specialty Chemicals). "Irgacure 184") was added by 1 part by weight.

[Preparation of Liquid Crystal Element] A pair of substrates formed by forming a 0.03 μm-thick ITO film as an electrode on a glass substrate and further forming a vertical alignment film using cetyltrimethylammonium bromide on the glass substrate, Is 0.7 μm
The above mixture was sealed in a cell (manufactured by ehE Co., Ltd.) which was attached so as to face each other. At that time, the entire cell was placed on a hot plate maintained at 105 ° C. or higher. Then, the ultraviolet rays were irradiated at an intensity of 10 mW / cm ² for 10 minutes.
Irradiated for 30 minutes, allowed to stand for 30 minutes, and then gradually cooled to room temperature to obtain a device. At this stage (initial state), the device was clouded due to light scattering.

Further, as shown in Table 1, a liquid crystal device was produced in the same manner as in the above example except that no amphiphilic gelling agent was used, as shown in Table 1.

[Evaluation of Light Transmission Characteristics] The obtained liquid crystal element was set in the apparatus shown in FIG. An arbitrary waveform generator ("AWG2005" manufactured by Tektronix) was connected as a voltage applying means 21 to the electrode lead portion of the element through a voltage amplifier ("4010 high-speed amplifier" manufactured by NF) serving as voltage amplifying means 22. A mercury lamp (manufactured by Ushio Inc.) is provided as one of the elements 20 as a light source 23,
The ND filter group (not shown) and the photomultiplier tube ("H5784-03" manufactured by Hamamatsu Photonics, Inc.) as the light transmission amount detecting means 24 are driven on the opposite side of the light source 23 across the light source 23 by a dedicated high-voltage power supply (not shown). ) Was installed. This allows
The amount of light transmitted through the liquid crystal element 20 by the application of a voltage is detected by a photomultiplier tube, and the detection signal is output from an oscilloscope (“2445” manufactured by Tektronix, Inc.) as a display output unit 25.
Type)) and displayed.

The change in the light transmission state of the liquid crystal element in this example was evaluated by the following steps using the above-described evaluation apparatus. FIG. 5 shows the light transmission characteristics of the liquid crystal element of this example based on the evaluation.

Step (a) The initial state of the device was opaque.

Step (b) A voltage of 80 V / 2.5 kHz is applied to the element in the initial state by t =
0 was applied. As a result, the display portion (the region where the ITO film exists on both substrates) in the device became transparent, and the light transmittance increased. The light transmittance at this time is T.

Step (c) After less than one second from the start of the voltage application, the voltage was removed. As a result, the light transmittance of the display portion was slightly reduced, but the transparent state was maintained. This state was maintained after an arbitrary time had elapsed.

Step (d) A voltage of 80 V / 100 kHz was applied to the transparent element. As a result, the display portion of the device became opaque.

Step (e) After a lapse of less than one second from the start of the application of the voltage of 80 V / 100 kHz, the voltage was removed. As a result, although the degree of the opaque state was slightly reduced, the opaque state was substantially maintained. This state is maintained after a certain period of time (hereinafter,
This state is called a “scattering memory state”. The light transmittance at this time is defined as Sm.

Hereinafter, the contrast between the transparent state and the scattering memory state when the voltage is applied is defined as CR, and CR = T / Sm
Is defined. Sm indicates that the smaller the value, the higher the scattering intensity. The results are shown in Table 1 below. The temperature at the time of evaluation was 30 ° C.

[0056]

[Table 1]

As described above, the liquid crystal device of the example using the amphiphilic gelling agent has a smaller light transmittance (Sm) in the scattering memory state, that is, a lower scattering intensity than the device of the comparative example. It was found to be strong and the contrast improved.

[0058]

As described above, according to the present invention, in the polymer dispersion type liquid crystal device using the dual frequency driving liquid crystal, the scattering intensity in the opaque state can be increased and the contrast can be improved. Practical use as a display became possible.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a basic configuration of a liquid crystal element of the present invention.

FIG. 2 is a schematic diagram showing the configuration of an example of an apparatus for evaluating the light transmission characteristics of a liquid crystal element according to the present invention.

FIG. 3 is a schematic diagram illustrating a configuration of an example of a display device configured using the liquid crystal element of the present invention.

FIG. 4 is a diagram showing an example of an electrode pattern in the liquid crystal element of the present invention.

FIG. 5 is a diagram showing light transmission characteristics in an example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10, 11 Substrate 12, 13 Electrode 14 Spacer 15 Polymer / liquid crystal composite layer 20 Liquid crystal element 21 Voltage applying means 22 Voltage amplifying means 23 Light source 24 Light transmission amount detecting means 25 Display output means 30 Liquid crystal elements 31, 32 Substrate edge 33 drive driver 34 drive control means 40 substrate 41 electrode pattern 42 electrode lead-out part

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H089 HA04 JA03 QA16 TA07 2H093 NA17 ND01 ND24 NF11 4H027 BB11 BD24 BE07 DQ02 4J002 BG071 BQ001 CD191 EP016 EP036

Claims (6)

[Claims] 1. A pair of substrates, and sandwiched between the substrates,
A polymer-liquid crystal composite layer in which liquid crystal droplets of a dual-frequency driven liquid crystal having a different sign of dielectric anisotropy according to the frequency of an applied voltage are dispersed in a polymer compound layer in a droplet form; A liquid crystal device comprising at least an electrode for applying a voltage to the composite layer, wherein the polymer / liquid crystal composite layer is in both the liquid crystal droplet and the polymer compound layer,
A polymer-dispersed liquid crystal device comprising an amphiphilic gelling agent, which is a self-organizing compound having at least a hydrophobic group, a hydrophilic group, and a group that expresses an intermolecular interaction in a molecule. 2. The liquid crystal device according to claim 1, wherein the amphiphilic gelling agent has, as a hydrophilic group, at least one selected from a hydroxyl group and a metal salt thereof, a carboxyl group and a metal salt thereof. 3. The liquid crystal according to claim 1, wherein the amphiphilic gelling agent has at least one selected from an amide group, a carboxyl group, and an ammonium group as a group that expresses an intermolecular interaction. element. 4. The liquid crystal device according to claim 1, wherein the amphiphilic gelling agent is an amino acid derivative having a hydrophobic group and a hydrophilic group. 5. The liquid crystal element is in an opaque state in an initial state, and the liquid crystal element becomes optically transparent by applying a voltage of a first drive frequency to the polymer / liquid crystal composite layer. The liquid crystal device according to any one of claims 1 to 4, wherein the liquid crystal device becomes optically opaque by applying a voltage having a second drive frequency to the polymer / liquid crystal composite layer. 6. The first driving frequency is a frequency at which the two-frequency driving liquid crystal has a positive dielectric anisotropy, and the second driving frequency is a frequency at which the two-frequency driving liquid crystal has a negative dielectric anisotropy. 6. The liquid crystal device according to claim 5, wherein the frequency is the indicated frequency.