JP2002072180A - Liquid crystal element - Google Patents

Abstract

(57) Abstract: Provided is a liquid crystal element which can switch between two states having a memory property by a driving voltage of 100 V or less at room temperature. SOLUTION: A pair of substrates, a pair of electrodes, a composite comprising at least a low-molecular liquid crystal composition and a polymer composition sandwiched between the substrates, and voltage applying means for applying a voltage between the electrodes are provided. In the liquid crystal element provided, the composite contains an ionic compound, and the polymer composition has a network structure in which polymer linear chains are bonded to each other via a cross-linking agent. A liquid crystal element having a hydroxyl group-containing side chain whose free end is a polymer straight chain.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In recent years, a reflection type liquid crystal display element which does not require a polarizing plate or a backlight has attracted attention as a low power consumption type display element. Under such circumstances, reflection using a composite of a low-molecular liquid crystal composition and a polymer composition capable of electrically switching between two display states having a memory property (transparent state and light scattering state). Liquid crystal display devices have been reported. For example, JP-A-2-193115 and JP-A-6-0667165 disclose a method of realizing switching between the two states by changing the magnitude of an electric field frequency applied to a pixel portion of a display element. Is disclosed.

The display device disclosed in Japanese Patent Application Laid-Open No. 2-193115 has a composite comprising a low-molecular liquid crystal and a side-chain high-molecular liquid crystal sandwiched between electrodes. When a low frequency or direct current electric field is applied to the complex, ions are driven in the complex. As a result, the arrangement of the low-molecular liquid crystal is disturbed, and a scattering state in which incident light is strongly scattered is formed. On the other hand, when a high-frequency electric field is applied to the composite, the low-molecular liquid crystal in the composite is homeotropically aligned in the direction of the electric field. As a result, a transparent state that allows incident light to pass is formed. The two states (scattering state and transparent state) are maintained even after the application of the low-frequency and high-frequency electric fields is released. That is, the two states have a memory property.

A display device disclosed in Japanese Patent Application Laid-Open No. 6-067165 also has a composite composed of a low-molecular liquid crystal and a side-chain high-molecular liquid crystal sandwiched between electrodes. The polymer liquid crystal is characterized by having an ionic group. Further, the display element may be formed by applying a solution in which a low-molecular liquid crystal, a high-molecular liquid crystal, and an electrolyte are dissolved. When a DC electric field is applied to the complex, ions are driven in the complex. As a result, the arrangement of the low-molecular liquid crystal is disturbed, and a scattering state in which incident light is strongly scattered is formed. On the other hand, when a high-frequency electric field is applied to the composite, the low-molecular liquid crystal in the composite is homeotropically aligned in the direction of the electric field. as a result,
A transparent state that allows incident light to pass is formed. The two states (scattering state and transparent state) are maintained even after the application of the low-frequency and high-frequency electric fields is released. That is, the two states have a memory property. This memory property is attributed to the smectic orientation of the composite.

[0005]

However, the polymer-dispersed liquid crystal display device according to the above prior art has the following problems. As a first problem, the display element disclosed in the above-mentioned JP-A-2-193115 has a problem that the driving temperature is high. JP-A-2-193
In the embodiment of No. 115, switching between two states having a memory property is realized by heating the temperature of the display element to 87 ° C. Although the reason why such high-temperature heating is necessary is not specified, it is presumed that one of the reasons for heating is to lower the viscosity of the polymer liquid crystal.

As a second problem, the above-mentioned Japanese Patent Application Laid-Open No.
The display element disclosed in No. 7165 uses a polymer liquid crystal and realizes a transition between two states at room temperature. However, there is a problem that the drive voltage is unknown. That is, in the example of JP-A-6-0667165, the driving voltage of the display element is not specified. Since the polymer liquid crystal exhibiting a high viscosity and a smectic phase is driven at room temperature, it is presumed that a driving voltage of 100 V or more is required.

An object of the present invention is to provide a liquid crystal device which can solve the above-mentioned problems of the prior art. That is, a liquid crystal display element using a composite comprising at least a low-molecular liquid crystal composition, a polymer composition, and an ionic component,
An object of the present invention is to provide a liquid crystal element which can switch between two states having memory properties by using a driving voltage of 100 V or less at room temperature without using a polymer liquid crystal as the polymer composition.

[0008]

That is, the present invention provides a composite comprising a pair of substrates, a pair of electrodes, at least a low-molecular liquid crystal composition and a polymer composition sandwiched between the substrates, In a liquid crystal device having a voltage applying means for applying a voltage between electrodes, an ionic compound is contained in the composite, and the polymer composition is such that polymer straight chains are bonded to each other via a crosslinking agent. A liquid crystal element having a network structure as described above, and wherein the polymer linear chain has a hydroxyl group-containing side chain having a free end.

Preferably, the ionic compound is an organic salt. Preferably, the organic salt is an ammonium salt. Preferably, the ammonium salt is tetraethylammonium iodide. Preferably, the organic salt is a bile salt. Preferably, the bile salt is sodium deoxycholate.

It is preferable that the polymer composition is a photopolymer of a monofunctional composition and a polyfunctional composition. The photopolymerization is preferably performed in a coexistence state of the low-molecular liquid crystal composition and the ionic compound, in addition to the monofunctional composition and the polyfunctional composition. It is preferable that the crosslinking agent contains a hydroxyl group.

The polymer composition is a photopolymer of a monofunctional composition and a polyfunctional composition, and the monofunctional composition preferably comprises at least two kinds of monofunctional compounds. When an electrical signal of a first frequency is applied between the electrodes, the complex develops a transparent state, and when an electrical signal of a second frequency is applied between the electrodes, the complex becomes non-transparent. It is preferable to express a state.

It is preferable that the transparent state and the non-transparent state be maintained even when the application of the first electric signal and the second electric signal is cancelled. Preferably, the magnitude of the first frequency is greater than the magnitude of the second frequency. Preferably, the magnitude of the second frequency is less than 100 Hz.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The present invention provides a pair of substrates, a pair of electrodes, a composite comprising at least a low-molecular liquid crystal composition and a polymer composition sandwiched between the substrates, and a voltage application unit for applying a voltage between the electrodes. A liquid crystal element comprising an ionic compound added to the composite, the polymer composition has a network structure in which polymer linear chains are bonded to each other via a cross-linking agent, Further, the polymer straight chain is characterized in that it has a hydroxyl group-containing side chain whose terminal is a free end.

Further, in the present invention, when an electric signal of a first frequency is applied between the electrodes, the complex develops a transparent state. On the other hand, when an electric signal of the second frequency is applied between the electrodes, the composite develops a non-transparent state.

[0015] The second frequency drives an ion derived from the ionic compound in the liquid crystal composition in an electric field,
The frequency is set to a value that can destroy the molecular orientation of the liquid crystal composition corresponding to the transparent state. That is, the magnitude of the second frequency is set such that the force for breaking the molecular orientation of the liquid crystal composition corresponding to the transparent state is larger than the electric field torque acting on the low-molecular liquid crystal composition. I do. Similarly, in order to reduce the magnitude of the electric field torque, it is preferable to set the magnitude of the absolute value of the dielectric anisotropy of the low-molecular liquid crystal composition to be small. The low-molecular liquid crystal composition according to the present invention will be described later. The second
The preferred magnitude of the frequency varies depending on the configuration of the liquid crystal element, but can exhibit a frequency of less than 100 Hz.
The first frequency is set to a frequency at which ions derived from the ionic compound do not break the molecular orientation of the liquid crystal composition. That is, the magnitude of the first frequency needs to be set to a magnitude that does not allow ions to move following changes in the electric field. Generally, the magnitude of the first frequency is greater than the magnitude of the second frequency.

Further, the present invention is characterized in that the transparent state and the non-transparent state are maintained even when the application of the first electric signal and the second electric signal is cancelled. The type and composition of the low-molecular liquid crystal composition are not particularly limited. For example, a low-molecular liquid crystal exhibiting a nematic phase or a cholesteric phase at around room temperature where driving of a liquid crystal element is assumed can be given.

Further, the sign (positive or negative) of the dielectric anisotropy of the preferred low-molecular liquid crystal composition varies depending on the type of the composite, the electrode configuration, and the like, and thus it is difficult to determine uniformly. However, the sign of the dielectric anisotropy is preferably positive. This is because when the dielectric anisotropy is positive, the contrast between the two states (the transparent state and the non-transparent state) can often be increased. On the other hand, the absolute value of the dielectric anisotropy is preferably not too large. The reason will be described. Even when the electric signal of the second frequency is applied to the composite, an electric field torque acts on the low-molecular liquid crystal composition to develop a molecular orientation corresponding to the transparent state. At the same time, a force due to the electric field driving of the ions acts on the low-molecular liquid crystal composition to break the molecular orientation corresponding to the transparent state. If the value of the dielectric anisotropy is too large, the electric field torque may be larger than the force caused by the electric field driving of the ions. In this case, even if the electric signal of the second frequency is applied, a non-transparent state cannot be formed or a sufficient non-transparent state cannot be formed. In the present invention, the absolute value of the dielectric anisotropy can be a value smaller than 18. As a low-molecular liquid crystal composition satisfying the above-mentioned conditions, for example, BL009 manufactured by Merck Ltd. can be mentioned. BL009 exhibits a nematic phase (isotropic phase transition temperature: 108 ° C) at room temperature, and has a dielectric anisotropy of +15.
5 is a low-molecular liquid crystal.

The ionic compound is not limited in principle. For example, an organic salt, a metal salt, or the like can be used. Examples of the organic salt include an ammonium salt. A quaternary ammonium salt represented by (R ₄ ) NX is typical. The above R represents a linear, branched, saturated or unsaturated hydrocarbon having 1 to 30 carbon atoms, and the four Rs may be the same or different. X represents a halogen atom of iodine, bromine, chlorine, fluorine or other negative ions. When X is a halogen, it may form a complex with a liquid crystal molecule and become an ionic component in the liquid crystal composition. Examples of such ammonium salts include tetraethylammonium iodide and tetra-n-butylammonium tetrafluoroborate.

In the present invention, bile salts can be used as the organic salt. Examples of the bile salt include sodium deoxycholate. When a bile salt is used, the liquid crystal composition becomes a chiral nematic liquid crystal exhibiting a cholesteric phase.

Further, in the present invention, room temperature molten salts can be used as the organic salts. 1-ethyl-3 as a room temperature molten salt
Methyl-1H-imidazolium tetrafluoroborate can be mentioned. In the present invention, not only one kind of ionic compound but also two or more kinds of ionic compounds may be used in combination.

Since the preferred weight concentration of the ionic compound in the composite varies depending on the type of the liquid crystal composition or the polymer composition, it is difficult to determine uniformly. For example, the amount can be about 0.00001% by weight to 10% by weight based on the liquid crystal composition.

As described above, the polymer composition according to the present invention has a network structure in which linear polymer chains are bonded to each other via a crosslinking agent. In order to form such a structure, in the present invention, a polymer of a polymer precursor composed of a monofunctional composition and a polyfunctional composition is used as the polymer composition according to the present invention.

The monofunctional composition can be used irrespective of its type as long as it is a photopolymerizable material. For example,
2-ethylhexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, butanediol mono (meth) acrylate, hexanediol (meth) acrylate, Phenoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, 4-hydroxybutyl acrylate, polyethylene glycol monomethacrylate (eg, Blemmer PE series manufactured by NOF), polyethylene glycol monoacrylate (eg, Blemmer AE manufactured by NOF) Series) and so on. Alternatively, a liquid crystalline monoacrylate (for example,
UV curable liquid crystal manufactured by Dainippon Ink and Chemicals, Inc.) can also be used. One or a mixture of two or more of these monofunctional compounds can be used as the monofunctional composition.

The polyfunctional composition is characterized in that it is a material having a functional group capable of binding to the monofunctional composition. Examples of the bifunctional composition which is one kind of the multifunctional composition include, for example, bisphenol-AEO modified diacrylate, isocyanuric acid EO modified diacrylate, tripropylene glycol diacrylate, pentaerythritol diacrylate monostearate, polyethylene glycol diacrylate. Acrylate, polypropylene glycol diacrylate, 1,4 butanediol diacrylate,
1,6 hexanediol diacrylate, Kayara
d R167, HX220, HX620, R684 (all manufactured by Nippon Kayaku) and the like. As trifunctional compositions, and even more multifunctional compositions,
Trimethylolpropane triacrylate, trimethylolpropane triethoxyacrylate, modified glycerin triacrylate, pentaerythritol triacrylate, modified trimethylolpropane triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol Hexaacrylate, tris (2-hydroxyethyl) isocyanurate (meth) acrylate, dipentaerythritol caprolactam-modified acrylate (trade name: DPCA-20, 30, 60, 12 manufactured by Nippon Kayaku)
0 "). One or a mixture of two or more of these polyfunctional compounds can be used as the polyfunctional composition.

The polymer composition according to the present invention preferably has a hydroxyl-containing side chain having a free end. Therefore, it is preferable to use a monofunctional compound capable of forming such a side chain. As such a monofunctional compound, the above-mentioned 4-hydroxybutyl acrylate can be mentioned. In the present invention, a polymer composition may be formed using two types of monofunctional compounds. In this case, it is preferable that at least one kind of monofunctional compound can form a hydroxyl group-containing side chain having a free end.
On the other hand, the crosslinking agent according to the present invention preferably contains a hydroxyl group. Examples of such a crosslinking agent include the aforementioned Kay.
A polyfunctional compound having a hydroxyl group in the molecule, such as arad R167, can be mentioned.

Further, in the polymer composition according to the present invention, (the length of the hydroxyl-containing side chain whose free end is the free end) / (the length of the polyfunctional compound residue) is 0.05.
It is preferably larger than 2 and smaller than 2.

Next, a method of manufacturing a liquid crystal device according to the present invention will be described. The method for manufacturing a liquid crystal element according to the present invention includes a step of forming a state in which a mixture of at least the liquid crystal composition, the polymer precursor, and the ionic compound is filled between the substrates. And then forming the composite by polymerizing the polymer precursor.

The concentration of the monofunctional compound in the polymer precursor according to the present invention is 40% by weight or more. Preferably, it is in the range of 50 wt% to 90 wt%. The concentration of the liquid crystal composition in the mixture is from 30 wt% to 90 wt%, preferably 40 wt%.
It is in the range of wt% to 80 wt%.

In the method for manufacturing a liquid crystal element according to the present invention,
During the polymerization, the mixture is heated to a temperature equal to or higher than the isotropic phase transition temperature of the liquid crystal composition, and the polymer precursor is polymerized in the heated state. The polymerization of the polymer precursor may be performed with a polymerization initiator added to the mixture. For example, in the case where the polymerization of the precursor is performed by photopolymerization by ultraviolet irradiation, a photopolymerization initiator can be used as the polymerization initiator. Examples of the photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone (“Irgacure 184” manufactured by Ciba-Geigy), benzyl dimethyl ketal (“Irgacure 651”) and the like.
The concentration of the photopolymerization initiator is 0.1 to 5 watts based on the total weight of the mixture of the polymer precursor and the liquid crystal composition.
It is preferably in the range of t%.

The type of the substrate according to the present invention is not particularly limited. For example, a glass substrate, a plastic substrate, or the like can be given. On the other hand, the electrode surface and the substrate surface according to the present invention may be provided with an alignment treatment layer such as a vertical alignment treatment or a horizontal alignment treatment for liquid crystal. Vertical alignment treatment is cetyltrimethylammonium bromide,
Gas phase adsorption and immersion using octadecylethoxysilane etc.
It can be performed by a method such as spin coating. The horizontal alignment treatment can be formed by providing a thin film made of polyimide, polyvinyl alcohol, or the like on the electrode and rubbing the thin film. Further, if not necessary, the alignment treatment may not be performed.

FIG. 1 shows an example of a schematic view of a liquid crystal element according to the present invention. In FIG. 1, reference numerals 11 and 12 are transparent substrates. 13 and 14 are transparent electrodes. Reference numeral 15 denotes a composite comprising a polymer composition, a liquid crystal composition, and an ionic compound. Reference numeral 16 denotes voltage applying means. Reference numeral 17 denotes a spacer for maintaining a gap between the substrate 11 and the substrate 12. The cell gap according to the present invention is preferably selected between 1 and 20 μm.

The liquid crystal device according to the present invention is capable of suppressing the driving temperature and the driving voltage, which are problems in the prior art.
The inventor has found out. It is presumed that one reason that the driving temperature and the driving voltage of the liquid crystal element according to the present invention are suppressed is that no polymer liquid crystal is used in the polymer composition.

By utilizing the transparent state and the non-transparent state of the composite, the liquid crystal device according to the present invention can be applied to a display device or an optical shutter device.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to embodiments.

Example 1 In this example, polyethylene glycol monomethacrylate PE90 (10 parts by weight) manufactured by NOF Corporation and K
A mixture consisting of Ayarad R167 (4 parts by weight) and 1,6-hexanediol diacrylate (1 part by weight) was used as a polymer precursor. Next, 10 parts by weight of the polymer precursor, 27 parts by weight of a p-type nematic liquid crystal having a dielectric anisotropy value of +15.5 (BL009, manufactured by Merck), 1 part by weight of tetraethylammonium iodide, 1 part by weight of a polymerization initiator (Irgacure 184, manufactured by Ciba Geigy) was mixed. The mixture is liquid, and hereinafter, a mixed solution 1
I will call it.

The mixed solution 1 was poured into a hollow portion of a liquid crystal cell placed on a hot plate whose surface temperature was maintained at 115 ° C. Note that the liquid crystal cell has a structure in which a pair of glass substrates provided with ITO electrodes are opposed to each other via a 7 μm spacer. The glass substrate surface and the ITO electrode surface facing the hollow portion of the liquid crystal cell were subjected to a vertical alignment treatment with cetyltrimethylammonium bromide before the injection of the mixed solution 1.

Next, the liquid crystal cell was irradiated with ultraviolet rays having an intensity of 0.3 mW / cm ² for 10 minutes while maintaining the hot plate temperature at 115 ° C. The polymer precursor was polymerized by the irradiation of ultraviolet rays to form a composite of a polymer and a liquid crystal composition in the hollow portion. After stopping the ultraviolet irradiation, the heating of the hot plate was also stopped. Thereafter, with the liquid crystal cell placed on a hot plate, cooling was performed until the cell temperature reached 27 ° C. After the cooling was completed, the obtained liquid crystal element exhibited cloudiness due to light scattering. The light transmittance of the liquid crystal element in this light scattering state was 19%. The light transmittance in a state where the hollow portion of the liquid crystal cell was empty was set to 100%.

The temperature of the obtained liquid crystal element was maintained at 27 ° C.
A rectangular wave (± 80) as shown in FIG.
V, 2 kHz) (voltage application time = 100 ms)
ec). During voltage application, the liquid crystal element is in a transparent state (light transmittance =
95%). Even when the voltage application was released, the liquid crystal element maintained a transparent state (light transmittance = 85%). Next, a rectangular wave (± 8) as shown in FIG.
0 V, 50 Hz) (voltage application time = 100 m)
sec). During the voltage application, the liquid crystal element was in a light scattering state (light transmittance = 20%). Even when the voltage application was released, the liquid crystal element maintained the light scattering state (light transmittance = 20%).

Further, by applying the rectangular waves shown in FIGS. 2 and 3 alternately to the liquid crystal element (at the time of voltage application = 100 msec), a transparent state having a memory property (light transmittance after voltage release = 85%) is obtained. Light scattering state (light transmittance after voltage release =
20%) could be formed alternately. Figure 4 shows this situation.
Shown in

Example 2 In this example, the following processing was applied to the liquid crystal element prepared in Example 1. That is, a black light absorbing layer was provided on the back side of one substrate of the liquid crystal element. FIG. 5 shows a schematic view of the liquid crystal element in this embodiment. In FIG. 5, reference numerals 11 and 12 are transparent substrates. 13 and 14 are transparent electrodes. Reference numeral 15 denotes a composite of a polymer and a liquid crystal composition. The surfaces of the substrates 11 and 12 and the surfaces of the electrodes 13 and 14 which are in contact with the composite 15 are subjected to a vertical alignment treatment for the liquid crystal composition. Reference numeral 16 denotes voltage applying means. Reference numeral 17 denotes a spacer for maintaining a gap between the substrate 11 and the substrate 12. Reference numeral 18 denotes a black light absorbing layer provided on the back side of the substrate 12.

A rectangular wave (± 80 V, 2 kHz) as shown in FIG. 2 was applied between the electrodes of the obtained liquid crystal element (voltage application time = 100 msec). When the liquid crystal display element was observed from the upper surface of the substrate 11 during the application of the voltage, it was found that the color of the light absorbing layer was black. Even when the voltage application was released, the liquid crystal element showed black. Next, a rectangular wave (± 80 V, 50 Hz) as shown in FIG. 3 was applied between the electrodes of the liquid crystal element (voltage application time = 100 msec). When the liquid crystal element was observed from the upper surface of the substrate 11 during application of the voltage, the liquid crystal element exhibited a light scattering state, that is, a white color. Even when the voltage application was released, the liquid crystal element maintained white. Further, by alternately applying the rectangular waves shown in FIGS. 2 and 3 (at the time of voltage application = 100 msec),
It was possible to alternately form a black state and a white state having memory properties.

Example 3 In this example, polyethylene glycol monomethacrylate PE90 (5 parts by weight) manufactured by NOF Corporation and 4-
Hydroxybutyl acrylate (5 parts by weight) and Kaya
A mixture of rad R167 (4 parts by weight) and 1,6-hexanediol diacrylate (1 part by weight) was used as a polymer precursor. Next, 10 parts by weight of the polymer precursor,
27 parts by weight of a p-type nematic liquid crystal (BL009, manufactured by Merck), 1 part by weight of tetraethylammonium iodide, and 1 part by weight of a photopolymerization initiator (Irgacure 184, manufactured by Ciba Geigy) were mixed. The mixture is liquid,
Hereinafter, it is referred to as a mixed solution 2.

The mixed solution 2 was injected into a hollow portion of a liquid crystal cell placed on a hot plate whose surface temperature was maintained at 115 ° C. Note that the liquid crystal cell has a structure in which a pair of glass substrates provided with ITO electrodes are opposed to each other via a 7 μm spacer. The surface of the glass substrate and the surface of the ITO electrode facing the hollow portion of the liquid crystal cell are subjected to a vertical alignment treatment with cetyltrimethylammonium bromide before the injection of the mixed solution 2.

Next, while maintaining the hot plate temperature at 115 ° C., the liquid crystal cell was irradiated with ultraviolet rays having an intensity of 0.3 mW / cm ² for 10 minutes. The polymer precursor was polymerized by the irradiation of ultraviolet rays to form a composite of a polymer and a liquid crystal composition in the hollow portion. After stopping the ultraviolet irradiation, the heating of the hot plate was also stopped. Thereafter, with the liquid crystal cell placed on a hot plate, cooling was performed until the cell temperature reached 27 ° C. After the cooling was completed, the obtained liquid crystal element exhibited cloudiness due to light scattering. The light transmittance of the liquid crystal element in this light scattering state was 15%. The light transmittance in a state where the hollow portion of the liquid crystal cell was empty was set to 100%.

The temperature of the obtained liquid crystal element was maintained at 27 ° C.
A rectangular wave (± 80) as shown in FIG.
V, 2 kHz) (voltage application time = 100 ms)
ec). During voltage application, the liquid crystal element is in a transparent state (light transmittance =
95%). Even when the voltage application was released, the liquid crystal element maintained a transparent state (light transmittance = 83%). Next, a rectangular wave (± 8) as shown in FIG.
0 V, 50 Hz) (voltage application time = 100 m)
sec). During the application of the voltage, the liquid crystal element was in a light scattering state (light transmittance = 16%). Even when the voltage application was released, the liquid crystal element maintained the light scattering state (light transmittance = 16%).

Further, by applying rectangular waves shown in FIGS. 2 and 3 alternately to the liquid crystal element (at the time of voltage application = 100 msec), a transparent state having memory properties (light transmittance after voltage release = 83%) is obtained. Light scattering state (light transmittance after voltage release =
16%) were alternately formed.

Example 4 In this example, a liquid crystal device was prepared in the same manner as in Example 1, except that tetraethylammonium iodide was completely replaced with sodium deoxycholate to give cholesteric properties to the liquid crystal. The obtained liquid crystal element exhibited cloudiness due to light scattering. The light transmittance of the liquid crystal element in this light scattering state was 19%. The light transmittance in a state where the hollow portion of the liquid crystal cell was empty was set to 100%.

The temperature of the liquid crystal element was kept at 27 ° C., and a rectangular wave (± 80 V, 2 kHz) as shown in FIG.
z) was applied (voltage application time = 100 msec). During the voltage application, the liquid crystal element was in a transparent state (light transmittance = 95%). Even when the voltage application was released, the liquid crystal element maintained a transparent state (light transmittance = 85%). Next, a rectangular wave (± 80 V, 50 V) as shown in FIG.
Hz) (voltage application time = 100 msec).
During voltage application, the liquid crystal element is in a light scattering state (light transmittance = 20).
%). Even when the voltage application was released, the liquid crystal element maintained the light scattering state (light transmittance = 20%).

Further, by applying the rectangular waves shown in FIGS. 2 and 3 alternately to the liquid crystal element (at the time of voltage application = 100 msec), a transparent state having memory properties (light transmittance after voltage release = 85%) is obtained. Light scattering state (light transmittance after voltage release =
20%) could be formed alternately.

Embodiment 5 In this embodiment, the liquid crystal is BL009 and the dielectric anisotropy is +
3.8 p-type nematic liquid crystal (MLC-6225-00)
0, manufactured by Merck Ltd.), except that the liquid crystal device was completely replaced with the same method as in Example 1. The obtained liquid crystal element exhibited cloudiness due to light scattering. The light transmittance of the liquid crystal element in this light scattering state was 19%. The light transmittance in a state where the hollow portion of the liquid crystal cell was empty was set to 100%.

The temperature of the liquid crystal element was maintained at 27 ° C., and a rectangular wave (± 80 V, 2 kHz) as shown in FIG.
z) was applied (voltage application time = 100 msec). During the voltage application, the liquid crystal element was in a transparent state (light transmittance = 95%). Even when the voltage application was released, the liquid crystal element maintained a transparent state (light transmittance = 85%). Next, a rectangular wave (± 80 V, 50 V) as shown in FIG.
Hz) (voltage application time = 100 msec).
During voltage application, the liquid crystal element is in a light scattering state (light transmittance = 20).
%). Even when the voltage application was released, the liquid crystal element maintained the light scattering state (light transmittance = 20%).

Further, by applying the rectangular waves shown in FIGS. 2 and 3 alternately to the liquid crystal element (at the time of voltage application = 100 msec), a transparent state having memory properties (light transmittance after voltage release = 85%) is obtained. Light scattering state (light transmittance after voltage release =
20%) could be formed alternately.

[0053]

As described above, the present invention has provided a liquid crystal element which can solve the above-mentioned problems of the prior art. That is, it is possible to switch between two states having memory properties, and this switching is performed at room temperature for 100 hours.
A liquid crystal element that can be realized with a driving voltage of V or less can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a liquid crystal element according to the present invention.

FIG. 2 is a diagram showing electric signals used for transition between states of a liquid crystal element in Examples 1 to 4 of the present invention.

FIG. 3 is a diagram showing electric signals used for transition between states of a liquid crystal element in Examples 1 to 4 of the present invention.

FIG. 4 is a diagram showing a change in transmittance of a liquid crystal element in Example 1.

FIG. 5 is a schematic view of a liquid crystal element in Example 2.

[Explanation of symbols]

 11, 12 Transparent substrate 13, 14 Transparent electrode 15 Composite 16 Voltage applying means 17 Spacer 18 Light absorbing layer

Claims (14)

[Claims] 1. A pair of substrates, a pair of electrodes, a composite comprising at least a low-molecular liquid crystal composition and a polymer composition sandwiched between the substrates, and a voltage applying means for applying a voltage between the electrodes. In the liquid crystal device comprising, the composite contains an ionic compound, the polymer composition has a network structure in which polymer linear chains are bonded to each other via a cross-linking agent, A liquid crystal device, wherein the polymer straight chain has a hydroxyl-containing side chain having a free end. 2. The liquid crystal device according to claim 1, wherein the ionic compound is an organic salt. 3. The liquid crystal device according to claim 2, wherein the organic salt is an ammonium salt. 4. The liquid crystal device according to claim 3, wherein said ammonium salt is tetraethylammonium iodide. 5. The liquid crystal device according to claim 2, wherein the organic salt is a bile salt. 6. The liquid crystal device according to claim 5, wherein the bile salt is sodium deoxycholate. 7. The liquid crystal device according to claim 1, wherein the polymer composition is a photopolymer of a monofunctional composition and a polyfunctional composition. 8. The method according to claim 1, wherein the photopolymerization is performed in a coexistence state of the low-molecular liquid crystal composition and the ionic compound, in addition to the monofunctional composition and the polyfunctional composition. The liquid crystal device according to claim 1 or 7. 9. The liquid crystal device according to claim 1, wherein said crosslinking agent contains a hydroxyl group. 10. The method according to claim 1, wherein the polymer composition is a photopolymer of a monofunctional composition and a polyfunctional composition, and the monofunctional composition comprises at least two kinds of monofunctional compounds. The liquid crystal device according to claim 7, wherein: 11. When an electrical signal of a first frequency is applied between the electrodes, the complex develops a transparent state, and when an electrical signal of a second frequency is applied between the electrodes,
2. The liquid crystal device according to claim 1, wherein the composite exhibits a non-transparent state. 12. The liquid crystal device according to claim 11, wherein the transparent state and the non-transparent state are maintained even when the application of the first electric signal and the second electric signal is cancelled. . 13. The method according to claim 13, wherein the magnitude of the first frequency is equal to the magnitude of the second frequency.
2. The frequency is greater than the magnitude of the frequency.
2. The liquid crystal device according to 1. 14. The magnitude of the second frequency is 100H
14. The liquid crystal device according to claim 13, wherein the value is less than z.