JPH08201780A - Liquid crystal display medium - Google Patents

Abstract

PURPOSE: To maintain the oriented state of liquid crystal molecules after the applied voltage is removed by using such a composite material that is divided into a region essentially comprising an aggregate of polymer material and a region essentially comprising a liquid crystal and that the polymer aggregate is locally dense near at least one substrate. CONSTITUTION: A polymer dispersion liquid crystal(PDLC) 1 as a composite material comprising a polymer 2 and a nematic liquid crystal 3 is sealed between a pair of glass substrates 4, 4. In this liquid crystal, layers essentially comprising the aggregate of the polymer 2 are separated from each other in such a manner that the layer on one of the substrates 4, 4 is made thick and two layers 2 are connected at several positions with columns of the polymer 2. A liquid crystal-rich layer essentially comprising the liquid crystal 3 is present between these layers. The polymer 2 acts as a capacitor, and since the polymer is locally dense on one side, an uneven electric field is produced which holds the oriented state on the interface between the liquid crystal 3 and the polymer 2. Therefore, even after the voltage is removed, the orientation can be easily maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display medium,
In particular, the present invention relates to a liquid crystal display medium having a property that liquid crystal molecules maintain alignment even after removal of an applied voltage, that is, a so-called memory property.

[0002]

2. Description of the Related Art Liquid crystals are located in an intermediate phase between solids and liquids, and although the substance is in the liquid state,
It exhibits optical anisotropy such as a solid crystal. Therefore, it is possible to make a liquid crystal having a thickness of several μm by utilizing the liquid state of the liquid crystal, and it is possible to change the direction of the molecular axis by a slight electric current as compared with a solid. Utilizing this property, a liquid crystal cell in which a liquid crystal is enclosed between electrode substrates to form a panel has characteristics of low voltage driving, low power consumption, passive type that does not emit light by itself, and flat type.

When the liquid crystal was first put into practical use, it was applied to the character display of a wristwatch by utilizing such characteristics of the liquid crystal, but since then, further research has progressed, and in recent years, color television and in-vehicle devices have been applied. It has been put to practical use as a display for navigation systems for automobiles and as a color panel for notebook computers.

As the field of application has expanded, it has become necessary to develop a new liquid crystal material having a performance satisfying the requirements according to the specifications of various displays. However, since it is difficult to realize all requirements with a single liquid crystal material, in reality, a mixed liquid crystal in which about 10 kinds of liquid crystal compounds are mixed is developed. Polymer dispersed liquid cryst is a composite of polymer and nematic liquid crystal.
al: Hereinafter, abbreviated as PDLC) has also been studied.

In this PDLC, nematic liquid crystals of spherical droplets are dispersed in a polymer, and the arrangement of liquid crystal molecules in the nematic liquid crystal is changed by applying a voltage, and the change in the refractive index due to the change is applied. It is a thing. In other words, in the off state when no voltage is applied, the optical axes of the liquid crystal droplets are irregularly oriented, so the refractive index of extraordinary light does not match the refractive index of the polymer, and the light is scattered to form an opaque white color. Indicates. On the other hand, in the ON state where a voltage is applied, the optical axes of the droplets are arranged in the voltage direction, and the refractive index of ordinary light substantially matches the refractive index of the polymer, so that light scattering is reduced and the liquid crystal becomes transparent.

Here, as a typical structure of the PDLC, schematic views of scanning electron microscope photographs are shown in FIGS. 14 and 15.
Shown in FIG. 14 shows a droplet type structure, and FIG. 15 shows a reverse type structure. Moreover, (a) is a peeling surface of the PDLC cell, and (b) is a cross-sectional view.

From FIG. 14, a droplet type PDLC 1 sandwiched between a pair of glass substrates 4 and 4 is
It can be seen that spherical small droplets of nematic liquid crystal 3 are uniformly dispersed in polymer 2.

Further, from FIG. 15, a reverse type PD
LC1 has a nematic liquid crystal 3 present in the gap between spherically gathered polymers 2. This reverse type PDL
C1 also has a uniform structure.

Since such a PDLC does not require a polarizing plate, a bright display can be obtained, good visual characteristics, flexibility and the like can be applied to a large area light control glass or a new display. It is attracting attention for its potential application.

[0010]

An application example using the PDLC 1 as a light control material is, for example, Japanese Patent Application No. 1-3.
There are 9209 and Japanese Patent Application No. 1-130197, but in order to keep the transparent state from the white opaque state in any PDLC 1, voltage application must be continued and it is not efficient. .

Therefore, it is an object of the present invention to provide a liquid crystal display medium using PDLC, which overcomes the above-mentioned problems in the prior art and can maintain the alignment state of liquid crystal molecules even after the applied voltage is removed. .

[0012]

In order to achieve the above-mentioned object, a liquid crystal display medium according to claim 1 of the present invention comprises two substrates having electrodes and a nematic liquid crystal supported between the substrates. A liquid crystal display medium comprising a composite in which a polymer is dispersed, wherein the composite is divided into a region mainly composed of polymer aggregates and a region mainly composed of liquid crystals, and the polymer aggregates are It is characterized in that it is concentrated on at least one side of the substrate.

A liquid crystal display medium according to a second aspect of the present invention is characterized in that, in the first aspect, the polymer has a structure formed by a cross-linking reaction of a low molecular weight compound containing a hydroxyl group.

The liquid crystal display medium according to claim 3 of the present invention is the liquid crystal display medium according to claim 1 or 2, wherein the polymer is 7
It is characterized by having a surface energy of 0 erg / cm ² or more.

The liquid crystal display medium according to a fourth aspect of the present invention is the liquid crystal display medium according to any one of the first to third aspects, wherein the complex in which the polymer is dispersed in the nematic liquid crystal has a memory property. Is characterized by.

[0016]

In the liquid crystal display medium of the present invention, since the volume resistivity of the polymer is larger than the resistance of the nematic liquid crystal and the dielectric constant is small, the polymer functions as a capacitor, and further, the polymer is Since they are concentrated on one side, the electric field is biased. Furthermore, an interaction is attempted to maintain the alignment state at the interface between the liquid crystal and the polymer.
Further, the polymer has a higher surface energy than nematic liquid crystal, and is more likely to undergo phase separation due to the hydrophilicity of the hydroxyl group and the hydrophobicity of the liquid crystal. Therefore, even if the applied voltage is removed, it is easy to maintain the alignment at the interface between the polymer and the liquid crystal and the PD having a large scattering coefficient is used.
It has characteristics such as obtaining LC.

[0017]

The present invention will be described below with reference to the embodiments shown in the drawings.

FIG. 1 shows the structure of a liquid crystal display medium using a PDLC 1 which is an embodiment of the present invention.
2 is a schematic view of a photograph taken by a scanning electron microscope to clarify the structure of FIG.
Shown in cross-section.

The liquid crystal display medium has a thickness of about 1 mm.
On the inner surfaces of the pair of glass substrates 4 and 4, ITO films 5 each containing indium oxide as a main component are attached as transparent electrodes for applying a voltage to the liquid crystal molecules 3a, and are patterned according to the purpose. There is. The pair of glass substrates 4 and 4 are spaced apart by a distance of several μm, that is, the so-called PD.
It is bonded so as to keep the cell thickness which is the thickness of LC1. At this time, in order to obtain a constant cell thickness, fine particles having a uniform particle size such as silicon dioxide are used as the spacer 6. The spacers 6 are enclosed between the glass substrates 4 and 4 in a mixed solution in which a predetermined nematic liquid crystal 3 and polymer 2 are uniformly mixed.

Next, the PDL used in this embodiment
The structure of C1 will be described. In FIG. 2, in the PDLC 1 enclosed between the pair of glass substrates 4 and 4, a polymer 2 layer formed mainly of spherical polymers 2 is formed among the two glass substrates 4 and 4. One of the two substrates is separated so as to be thicker, and both polymer layers 2 are connected to each other by a columnar polymer 2 in some places, and a liquid crystal rich layer mainly composed of a liquid crystal 3 is provided between the polymer layers 2. It has a structure that exists so as to be sandwiched between.

As described above, the structure of the PDLC 1 of this embodiment is different from that of the conventional PDLC 1 shown in FIGS. 14 and 15 in that the PDLC 1 has a reverse type structure. The structure is characterized by having a liquid crystal rich layer, and is characterized by having a non-uniform structure in which the polymer layer 2 is abundant on the upper side of the substrate and the liquid crystal layer 3 is abundant on the lower side of the substrate. Such a structure results from the fact that the polymerization reaction for forming the polymer 2 proceeds from the direction of irradiation with ultraviolet rays, as shown in FIG. That is, when the ultraviolet rays are irradiated from above, the polymerization reaction proceeds from above, and accordingly, the liquid crystal 3 is phase-separated, is expelled to the outside of the polymer 2, and moves downward.

Therefore, the position of the liquid crystal rich layer can be controlled by the irradiation direction of ultraviolet rays. For example, when ultraviolet rays are irradiated from both directions, as shown in FIG. 4, the polymer layer 2 exists on both substrate sides and the liquid crystal is present at the center. There will be a rich layer.

Here, the reason why the PDLC 1 of this embodiment having such a structure has a so-called memory property in which the liquid crystal molecules 3a maintain the alignment state even after the applied voltage is removed will be described.

This is due to the influence of the bias of the electric field and the liquid crystal 3.
It is considered that this is due to the interaction between each molecule at the interface between the polymer and the polymer layer 2. That is, the volume resistivity value of the polymer layer 2 is 10 ¹⁴ for a general methacrylate polymer 2.
(Ω · cm) or more, the dielectric constant is 2 to 5, and in the nematic liquid crystal E7, 10 ¹⁰ to 10 ¹² (Ω · cm), the dielectric constant is 10 or more, and the polymer layer 2 is larger than the liquid crystal layer 3. The polymer layer 2 functions as a capacitor because it has a volume resistivity. Further, since the polymer layer 2 has a volume specific resistance larger than that of the liquid crystal layer 3 and has a small dielectric constant, the impedance changes depending on the frequency, and an electric field difference occurs at the interface between the polymer layer 2 and the liquid crystal layer 3. Further, as described above, in the structure of the PDLC 1 of this embodiment, since the upper and lower polymer layers 2 have different thicknesses, a large electric field is generated on the thick polymer layer 2 side and a small electric field is generated on the thin polymer layer 2 side. Occurs, and there is a bias in the electric field. Therefore, it is considered that this electric field difference remains after the application.

Further, as shown in FIG. 5 (a) voltage applied state and (b) voltage removed state of the PDLC, the polymer layer 2 exists above and below with the liquid crystal layer 3 interposed therebetween.
Further, since a pillar of the polymer 2 exists so as to connect the upper and lower polymers 2 so as to partition the liquid crystal layer 3, (a) of FIG.
In the voltage applied state, when a voltage is applied and an electric field is applied in the vertical direction of the liquid crystal display medium, the liquid crystal molecules 3a are oriented according to this direction and become transparent. However, even if the voltage is removed thereafter, the interface between the polymer layer 2 and the liquid crystal layer 3 existing above and below or the interface between the column of the polymer 2 and the liquid crystal 3 as shown by the voltage removal state in FIG. 5B. In the above, it is considered that there is a so-called memory property in which there is an effect of mutually maintaining the alignment state, and in cooperation with the bias of the electric field described above, the alignment state is maintained even after the voltage is removed.

Next, it was examined how the difference in structure between the PDLC 1 of this embodiment and the conventional droplet type PDLC 1 affects the light scattering coefficient. The scattering coefficient represents how much light can be scattered without irradiating the light when it is irradiated, and the magnitude of the voltage applied when the PDLC 1 is applied to a display or the like. On the other hand, it is one of the factors to judge how much the amount of light displayed on the screen can be obtained. Therefore, the larger the light scattering coefficient, the larger the amount of received light can be secured with a smaller voltage.

Therefore, in FIG. 6, the cell thickness of each PDLC 1 (μ
The relationship of the light scattering coefficient (μm ⁻¹ ) with respect to m) is shown. In the figure, “●” represents the scattering coefficient with respect to the cell thickness of the PDLC1 of the present invention, and “▲” represents the scattering coefficient with respect to the cell thickness of the droplet type PDLC1. From this figure, the droplet type PD
LC1 showed almost constant scattering coefficient regardless of the change in cell thickness. It is considered that this has a structure in which the nematic liquid crystal 3 and the polymer 2 are uniformly dispersed, and therefore the light scattering by the liquid crystal molecules 3a is not affected even if the cell thickness is thick or thin. On the other hand, the PDLC of this embodiment
In No. 1, the scattering coefficient rapidly increased as the cell thickness decreased. This is because the PDLC 1 of this embodiment has a structure in which a liquid-phase rich layer exists so as to be sandwiched between the polymer layers 2, and therefore when the cell thickness is large, that is, when the polymer layer 2 is thick. , The irradiation light is absorbed by the polymer layer 2, and the light reaching the liquid crystal layer 3 becomes small,
Light scattering by the liquid crystal molecules 3a is suppressed.

However, when the cell thickness of the PDLC 1 becomes thin, the amount of light absorbed in the polymer layer 2 also decreases and the amount of light reaching the liquid crystal layer 3 increases, so that the light scattered by the liquid crystal molecules 3a increases and the scattering coefficient Also grows.

Therefore, according to the structure of the PDLC 1 used in the liquid crystal display medium of the present invention, the light scattering coefficient increases as the cell thickness decreases, so that even a small amount of light has a sufficient scattering effect. This has been achieved and is convenient for application to displays and the like, and since the cell thickness can be reduced, the applied voltage can also be reduced, leading to labor saving.

Next, a method for actually manufacturing the PDLC cell which constitutes the liquid crystal display medium of this embodiment will be described by showing concrete materials and numerical values.

As a first embodiment, a nematic liquid crystal E7
And 2-hydroxyethyl methacrylate (hereinafter abbreviated as HEMA), which is a monomer having a hydroxyl group, are mixed at a weight ratio of 1: 1 and 3 wt% of Irgacure 184 as a polymerization initiator is added thereto to form a uniform solution. . A liquid crystal spacer 6 having a diameter of 10 μm is mixed in this uniform solution, and then applied to one of the two glass substrates 4 and 4 having the ITO electrode 5 attached thereto, while the other electrode-attached glass is used. The substrate 4 is attached to form a PDLC cell. Then, ultraviolet light having a main wavelength of 365 nm and a light intensity of 60 mW / cm ² is applied to the PDLC cell on one glass substrate 4
Irradiation for several minutes to several tens of minutes from the side, phase separation of the polymer 2 generated by the polymerization reaction of the monomer and the nematic liquid crystal 3 gives an opaque white PDLC 1. This polymerization reaction is a crosslinking reaction in which the monomer has a hydroxyl group. By the above method, the thick polymer layer 2 is formed on the side of the glass substrate 4 irradiated with ultraviolet rays, and the thin polymer layer 2 is formed on the opposite side of the glass substrate 4.

The mixing of the above solutions and other processing are all performed at room temperature.

Next, as a second embodiment, first, the P
In producing DLC1, 2-
Hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate, which is a monomer having a hydroxyl group, were mixed in a weight ratio of 1: 1 and nematic liquid crystal 3 was mixed in a mixed solution of this monomer in a weight ratio of 1: 1 to prepare a uniform solution.
Then, a liquid crystal display medium exhibiting white opacity was prepared from the PDLC1 solution by the same method as in the first embodiment described above.

Further, in order to determine the effect of the hydroxyl groups of the monomers in the liquid crystal display media of the first and second embodiments, n-butyl methacrylate, which is a monomer having no hydroxyl group, and nematic liquid crystal 3 as the first comparison material. Were mixed at a weight ratio of 1: 1 and a liquid crystal display medium was prepared by a polymerization reaction.

However, in this liquid crystal display medium, the monomer and the nematic liquid crystal 3 were completely compatible with each other, and the liquid crystal cell thereof was in a transparent state.

As a second comparative material, 2-hydroxyethyl methacrylate, a monomer having a hydroxyl group, and n-butyl methacrylate, a monomer having no hydroxyl group, were mixed at a weight ratio of 1: 1 and the nematic liquid crystal 3 was added thereto.
Was mixed at a weight ratio of 1: 1 to prepare a uniform solution, and then a liquid crystal display medium was prepared by a polymerization reaction in the same manner as in Example 1. In this PDLC cell, the monomer having a hydroxyl group and the nematic liquid crystal 3 were phase-separated, but the monomer having no hydroxyl group and the nematic liquid crystal 3 were compatible with each other, and thus a semitransparent state was exhibited.

The electro-optical characteristics (on-memory characteristics) of the liquid crystal display medium thus prepared were measured in order to determine whether or not it had a memory characteristic. The results are shown in FIGS. Further, in order to examine how the memory property changes with time, the memory transmittance with respect to the time elapsed after removal of the applied voltage was measured. Of these, the results for the first embodiment are shown in FIG.

In these experiments, a high-speed power amplifier, a function generator, and a digital multimeter were used for frequency and voltage control in order to ensure high accuracy, and the transmittance was 632.8 wavelength.
It was measured with light of nm.

First, FIG. 7 shows the voltage / light transmission characteristics of the first embodiment. The vertical axis represents the transmittance (%), and the horizontal axis represents the voltage (V). Further, “◯” represents the on-characteristics showing the transmittance in the state where the voltage is applied, and “●” represents the memory characteristics showing the transmittance after removing the applied voltage. For these displays, the same display method is used for FIGS. 8 to 10 shown below.

As shown in FIG. 7, the on-characteristics of the liquid crystal display medium of the first embodiment show a transmittance of several% when the voltage is 0 (V), and thereafter, the transmittance increases with an increase in the voltage. , 50
90 when a voltage of (V) to 100 (V) is supplied
It showed a transmittance of%.

On the other hand, the memory characteristics show a transmittance of several% when the voltage is 0 (V), and the transmittance also increases with an increase in the voltage, and the transmittance changes from 50 (V) to 100 (V). When the voltage is applied, the transmittance is about 80%, which shows that the liquid crystal display medium of the first embodiment has a memory property.

Next, regarding the first embodiment, the relationship between the memory transmittance and the elapsed time after removal of the applied voltage is shown in FIG.
It is shown in FIG. The vertical axis represents the memory transmittance (%), and the horizontal axis represents the elapsed time after the electric field is removed. From FIG. 11, the initial memory transmittance after removal of the applied voltage was about 80%, but the memory transmittance decreased to about 75% one day later, but after that, there was almost no change. The transmittance was maintained at 75% even after a year, and the memory characteristics were extremely stable.

Next, FIG. 8 shows the voltage / transmittance characteristics of the liquid crystal display medium of the second embodiment. As shown in FIG. 8, the on-characteristic shows that the transmittance is several% when the voltage is 0 (V).
Then, the transmittance tends to increase as the voltage increases, and when a voltage of 50 (V) to 100 (V) is supplied, the transmittance of 90% is exhibited. It showed almost the same tendency as the voltage-transmittance characteristic.

On the other hand, the memory characteristic is that the transmittance is several% when the voltage is 0 (V), and the transmittance also increases as the voltage increases, from 50 (V) to 100 (V). When the voltage is applied, the transmittance is about 80%, which shows that the liquid crystal display medium of the second embodiment has a memory property.

On the other hand, as shown in FIG. 9, the voltage-transmittance characteristic of the liquid crystal display medium of the first comparative material is as shown in FIG. I couldn't do it.

Next, the ON characteristic of the second comparative material is 0.
The transmittance was about 25 (%) at the voltage of (V), and then gradually increased with the increase of the voltage, and the transmittance was about 60 (%) at the voltage of 100 (V). But,
Regarding the memory characteristics, the voltage was only slightly increased from 0 (V) to 100 (V), and no memory characteristic was observed.

From the above results, the polymer 2 in PDLC1
Paying attention to the hydroxyl group possessed by, the same experiment was conducted for the polymer 2 having another type of hydroxyl group and the polymer 2 having no hydroxyl group. FIG. 12 shows the chemical structure of the polymer 2 having a hydroxyl group used in this experiment, and FIG. 13 shows the chemical structure of the polymer 2 having no hydroxyl group. Further, the surface energies of the polymer 2 and the nematic liquid crystal 3 were measured in order to examine how the hydroxyl groups of the polymer 2 relate to the memory property. The results are shown in Tables 1 to 4 below together with the phase state of PDLC1 and the presence / absence of memory property.

The surface energy was obtained by measuring the contact angle. That is, in the method of measuring the surface energy of the polymer 2, the polymer 2 whose surface energy is desired to be obtained is formed in a substrate shape, and polar pure water and non-polar jodhed methane are dropped on the polymer 2. Then, the contact angle between the two liquids and the polymer substrate is measured and substituted into a predetermined simultaneous equation to obtain the surface energy. On the other hand, as for the surface energy of the liquid crystal 3, the liquid crystal 3 is dropped on a substrate whose surface energy is required in advance, such as a glass substrate 4 and a Teflon substrate. Then, the contact angle between each substrate and the liquid crystal 3 is measured and substituted into a predetermined simultaneous equation to obtain the surface energy.

[0049] Table 1 corresponds to the liquid crystal display medium of the first embodiment, and PDLC made of a monomer having a hydroxyl group.
This is the result regarding 1. Each polymer 2 has a surface energy of 70 erg / cm ² or more, and the phase state of PDLC 1 causes phase separation to exhibit white opacity and has a memory property. The surface energy of 70 erg / cm ² or more means that the surface energy of water is usually about 72 erg / cm ^2.
Since it is cm ^2, it is considered that the value of the surface energy of water is approached by having a hydroxyl group.

In addition, Table 2 corresponds to the liquid crystal display medium of the second embodiment, in which the monomers having hydroxyl groups are mixed in a weight ratio of 1: 1 to produce polymer 2 PDLC.
2 shows the results for 1. Similar to the result of the first embodiment, the surface energy is 70 erg / cm ² or more, and the phase state of PDLC1 causes white opaque phase separation, and also has a memory property.

On the other hand, Table 3 corresponds to the first comparative material and shows the results when a monomer having no hydroxyl group is used. The surface energy of each polymer 2 is 27.7 to 6
2.3erg / cm ² and is varied, none of them exceeding 70erg / cm ² as in the first embodiment and the second embodiment. In addition, the phase state of PDLC1 was transparent because polymer 2 and liquid crystal 3 were compatible with each other in each sample, and no memory property was observed.

Further, Table 4 corresponds to the second comparative material, and shows the results when a monomer having a hydroxyl group and a monomer having no hydroxyl group are mixed. The surface energy of each sample is 70 as in the first and second embodiments.
erg / cm ² or more, it does not have a memory property, and the phase state of PDLC 1 was semitransparent because the polymer 2 and the liquid crystal display medium were partially compatible with each other. This causes phase separation in the monomer part having a hydroxyl group,
This is because the monomers having no hydroxyl group are compatible with each other.

As described above, the polymer 2 having a hydroxyl group is phase-separated from the liquid crystal 3, and the polymer 2 having no hydroxyl group is the liquid crystal 3.
It is considered that the compatibility with is due to the relationship between the chemical structure of the liquid crystal 3 and the chemical structure of the polymer 2. That is, since the liquid crystal 3 has a chemical structure having no hydroxyl group and has hydrophobicity, if the hydrophilic polymer 2 having a hydroxyl group is mixed therein, the liquid crystal 3 is miscible as if it were a relation between water and oil. Without this, phase separation is likely to occur. However, the polymer 2 having no hydroxyl group easily mixes because it is in a mixed state of hydrophobic substances.

Further, considering the surface energy, the surface energy of the liquid crystal 3 is 24 erg / cm ² , whereas the surface energy of the polymer 2 having a hydroxyl group is 70 er.
g / cm ² or more, the difference in surface energy is 46e
rg / cm ² or more.

On the other hand, since the surface energy of the polymer 2 having no hydroxyl group is about 60 erg / cm ² at the maximum, the difference in surface energy from the liquid crystal 3 is 36 erg / cm ^2.
In the case of a small polymer, the difference in surface energy from the liquid crystal 3 is 3.7 erg / cm ² .

Therefore, it is considered that the large difference in surface energy between the polymer 2 having a hydroxyl group and the liquid crystal 3 also affects the ease of phase separation.

From the above results, in order for the PDLC 1 to have a memory property, the phase state must be a phase-separated state, and the condition therefor is that the polymer 2 mixed with the nematic liquid crystal E7 is a monomer or dimer. That is, at the time of low molecular weight, it contains a hydroxyl group in the molecular structure and has a surface energy of 70 erg / cm ² or more after the polymerization reaction.

As described above, according to the above-described present embodiment, the liquid crystal 3 and the polymer 2 can be easily phase-separated by the action of the hydroxyl group of the polymer 2, and the PDL at this time can be obtained.
A liquid crystal display medium having a large scattering coefficient and a memory property can be obtained from the structure of C1.

Therefore, when the liquid crystal display medium of the present embodiment is applied to a display or the like, a thinner display can be produced and the applied voltage can be reduced, leading to labor saving, so that it can be said that the liquid crystal display medium is highly practical. .

The present invention is not limited to the above embodiment, but can be modified as necessary.

For example, the liquid crystal display medium is PDLC.
1 was applied to one of the glass substrates 4 and 4, and the other glass substrate 4 was attached to the glass substrate 4, and this was prepared from the injection port or the like which was previously provided.
1 may be injected by a vacuum injection method or the like, and the injection port may be sealed with a sealing material.

In addition to glass, the substrate may be a plastic film and glass, or a combination of plastic films.

Further, the polymer 2 used in the preparation of the liquid crystal display medium may be produced by mixing two or more monomers as long as it finally has the constitution as in the present invention.

[0064]

As described above, according to the liquid crystal display medium of the present invention, the function of the hydroxyl group of the polymer allows the liquid crystal and the polymer to be easily phase-separated. A liquid crystal display medium having a large scattering coefficient and a memory property can be obtained from the structure of a composite of a nematic liquid crystal and a nematic liquid crystal.

Therefore, if the liquid crystal display medium of the present invention is applied to a display or the like, a thinner display can be produced, the applied voltage can be reduced, and labor can be saved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of the essential parts of a liquid crystal display medium according to an embodiment of the present invention.

2A and 2B are sectional views of a PDLC used in an embodiment of the present invention.

FIG. 3 is an explanatory diagram regarding a structure in which a PDLC solution is irradiated with ultraviolet light from one direction.

FIG. 4 is an explanatory diagram regarding the structure when the PDLC solution is irradiated with ultraviolet rays from both directions.

FIG. 5 is an explanatory diagram regarding (a) voltage application state and (b) voltage removal state of PDLC used in the embodiments of the present invention.

FIG. 6 is a graph showing the relationship between the cell thickness and the light scattering coefficient for the PDLC used in the example of the present invention and the conventional droplet type PDLC.

FIG. 7 is a diagram showing voltage / light transmission characteristics according to the first embodiment of the present invention.

FIG. 8 is a diagram showing voltage / light transmission characteristics according to the second embodiment of the present invention.

FIG. 9 is a diagram showing voltage / light transmission characteristics of a liquid crystal display medium as a first comparative material.

FIG. 10 is a diagram showing voltage / light transmission characteristics of a liquid crystal display medium as a second comparative material.

FIG. 11 is a diagram showing a change in memory transmittance with respect to elapsed time after removal of an applied voltage according to the first embodiment of the present invention.

FIG. 12 is a diagram showing a chemical molecular structure of a polymer having a hydroxyl group used in Examples of the present invention.

FIG. 13 is a diagram showing a chemical molecular structure of a polymer having no hydroxyl group used as a comparative material of the present invention.

14A and 14B are a cross-sectional view of a conventional droplet type PDLC.

FIG. 15A is a peeling side view of a conventional reverse type PDLC, and FIG.

[Explanation of symbols]

 1 PDLC (polymer dispersed liquid crystal) 2 polymer, polymer layer 3 liquid crystal, liquid crystal layer 4 glass substrate 5 ITO electrode 6 spacer

Claims (4)

[Claims] 1. A liquid crystal display medium comprising two substrates having electrodes and a composite material in which a polymer is dispersed in a nematic liquid crystal supported between the substrates, wherein the composite material is mainly an assembly of polymers. A liquid crystal display medium, characterized in that it is divided into a body region and a liquid crystal region, and the polymer aggregates are densely concentrated on at least one of the substrates. 2. The liquid crystal display medium according to claim 1, wherein the polymer has a structure formed by a crosslinking reaction of a low molecular weight compound containing a hydroxyl group. 3. The liquid crystal display medium according to claim 1, wherein the polymer has a surface energy of 70 erg / cm ² or more. 4. The liquid crystal display medium according to claim 1, wherein the composite has a memory property.