JP5151026B2 - Liquid crystal microcapsule, manufacturing method thereof, and liquid crystal display element using the same - Google Patents

Liquid crystal microcapsule, manufacturing method thereof, and liquid crystal display element using the same Download PDF

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JP5151026B2
JP5151026B2 JP2005348125A JP2005348125A JP5151026B2 JP 5151026 B2 JP5151026 B2 JP 5151026B2 JP 2005348125 A JP2005348125 A JP 2005348125A JP 2005348125 A JP2005348125 A JP 2005348125A JP 5151026 B2 JP5151026 B2 JP 5151026B2
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JP2006183046A (en
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直樹 氷治
滋 山本
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富士ゼロックス株式会社
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Description

  The present invention relates to a liquid crystal microcapsule used for a display element, an image / information recording element, an image / information recording medium, a spatial light modulator, a manufacturing method thereof, and a liquid crystal display element using the same.

  Liquid crystal is widely used as a display material. However, since it is a liquid, it is necessary to produce a cell composed of two substrates at a constant interval and to inject the liquid crystal into the cell. In this case, there are problems that it takes time to inject, and that when the cell is pushed or bent, the distance between the substrates changes and the display is modulated.

  This problem can be solved by covering the liquid crystal with a film to form liquid crystal microcapsules. The liquid crystal microcapsule is advantageous in that the liquid crystal is protected by the coating because it is protected by a film, and the liquid crystal microcapsule can be applied to the substrate to produce a cell, thereby eliminating the need for time-consuming liquid crystal injection. .

  By the way, in general, when liquid crystal is used as a display element, it is important to control the alignment of the liquid crystal in order to fully bring out its performance. For example, in Japanese Patent Laid-Open No. 2002-275471, a liquid crystal microcapsule in which a guest-host liquid crystal in which a dichroic dye is dissolved in a liquid crystal is microencapsulated, a liquid crystal molecule is formed on the inner surface of the film by using a specific film material. On the other hand, a technique for improving the display contrast by controlling the liquid crystal so as to be vertically oriented is disclosed.

  Such liquid crystal microcapsules that are not subjected to alignment control are colored when no voltage is applied, as shown in FIG. 4A, because the liquid crystal is aligned substantially parallel to the substrate surface. When a nematic liquid crystal having positive dielectric anisotropy is used as the liquid crystal and a voltage is applied between the two electrodes, the liquid crystal changes to be transparent because it is aligned perpendicular to the substrate as shown in FIG. Since the liquid crystal is curved and aligned along the interface at the interface with the coating, there is a portion where the liquid crystal is aligned standing with respect to the substrate surface, so that a sufficient color density cannot be obtained.

On the other hand, when the liquid crystal is controlled so as to be aligned perpendicularly to the coating surface, the liquid crystal is aligned substantially perpendicularly to the substrate surface as shown in FIG. When a voltage is applied between two electrodes using a nematic liquid crystal having negative dielectric anisotropy for the liquid crystal, the liquid crystal is colored because it is aligned parallel to the substrate surface as shown in FIG. In this case, since the liquid crystal is forcibly aligned parallel to the substrate surface by the action of voltage, the degree of parallelism can be made higher than in FIG. For this reason, the color density can be increased and the display contrast can be improved.
JP 2002-275471 A

  As another example of alignment control of liquid crystal microcapsules, in the application number FE03-04164, the authors used cholesteric liquid crystal microcapsules exhibiting selective reflection in the visible wavelength region, and the liquid crystal molecules were perpendicular to the inner surface of the film. Discloses a method for improving contrast by controlling to be oriented in the direction. As shown in FIG. 5, liquid crystal microcapsules are formed into a layer with a binder and are used as a display element by being sandwiched between a pair of electrodes (between substrates provided with electrodes).

  The cholesteric liquid crystal is composed of rod-like liquid crystal molecules aligned in a spiral shape, and interference-reflects (referred to as selective reflection) light having a wavelength corresponding to the spiral pitch. The cholesteric liquid crystal has a planar (P) orientation in which the direction of the helical axis is perpendicular to the substrate surface as shown in FIG. 5A and generates selective reflection, and a focal that is parallel and does not generate selective reflection as shown in FIG. 5B. It has two orientation states that are stable when no voltage is applied, that is, conic (F) orientation, and these can be used as a display element by applying a voltage to cause mutual transition. In the liquid crystal microcapsule, the liquid crystal molecules are oriented in parallel to the inner surface of the film, and as a result, the cholesteric layer (direction perpendicular to the helical axis) at the F orientation is distorted so as to bend along the inner surface of the film. For this reason, selective reflection is possible in part and the display contrast is lowered. On the other hand, when the inner surface of the film is oriented vertically, this distortion is reduced and the display contrast can be improved.

  As described above, making the inner surface of the coating vertically aligned is an important means for improving the display performance of the liquid crystal microcapsules.

  By the way, as a method of vertically aligning the inner surface of the liquid crystal microcapsule film, the above-mentioned JP-A No. 2002-275471, after mixing a radical polymerizable monomer having an alkyl group or a fluoroalkyl group with liquid crystal and dispersing in water, A method of forming a film by heat polymerization is disclosed.

  Since radical polymerization proceeds everywhere in the dispersed phase, in order for the generated polymer to form a uniform film, it must be devised so that the polymer moves to the interface between the liquid crystal and the aqueous phase. It is necessary to control so that the surface tension of the polymer is between the surface tension of the liquid crystal and the outer water phase, and to precipitate at an appropriate rate. Depending on the type of liquid crystal and the combination with the monomer used, this condition is not always satisfied, and there is a problem that a film cannot be formed, pinholes are generated, or a mechanically weak film can be formed. . With such a coating, only liquid crystal microcapsules with poor vertical alignment can be obtained.

  In order to avoid this problem, in this patent, the dispersion liquid in which the monomer is dispersed is added to the liquid crystal microcapsule dispersion liquid once formed, and the monomer is deposited on the previous film to cure it. A method of strengthening by duplicating is disclosed. However, this method has a problem that it takes time and effort.

  Accordingly, in view of the above problems, an object of the present invention is to provide a liquid crystal microcapsule having a film having a uniform film thickness and good vertical alignment, and a production method for easily obtaining the same. Moreover, the objective of this invention is providing the liquid crystal display element using this liquid crystal microcapsule.

The above problem is solved by the following means. That is,
The liquid crystal microcapsule according to the first aspect of the present invention includes a liquid crystal and a film made of polyurea containing the liquid crystal, and the polyurea has an alkyl group and / or a fluoroalkyl group directly or indirectly via a urethane bond. It is characterized by being combined.

The liquid crystal microcapsule of the present invention includes a liquid crystal and a film made of polyurea containing the liquid crystal, and the polyurea is represented by the following structural formula (I) as at least a polyisocyanate, water, and an alignment material. It is a polymer compound obtained by reacting at least one kind of compound.

Structural formula (I): C n F m H (2n + 1-m) -X-Y
(In the structural formula (I), X is - (OCH 2) p -, - (OCH 2 CH 2) p -, - (OCH 2 CH 2 CH 2) p -, - (COOCH 2 CH 2) p -, - (OCOCH 2 CH 2 ) p -, -. Ph-, or -O-Ph- (. here p is 0 to 5 integer) indicating a Y is -OH, -COO-CH ( CH 2 OH) 2 or —COO—CH (OH) CH 2 OH, wherein m is an integer of 0 or more and (2n + 1) or less, and n is an integer of 4 or more and 30 or less.

In the liquid crystal microcapsule of the present invention, the polyisocyanate is a polyisocyanate represented by the following structural formulas (1) to (3) , and at least one of these adducts, isocyanurates, burettes, and allophanates. It is preferable that

In the liquid crystal microcapsule of the present invention, the polyurea is obtained by reacting at least polyisocyanate, water, at least one compound represented by the structural formula (I) as an alignment material, and polyamine. A molecular compound is preferred. Further, as the polyamine, polyallylamine is preferable, and polyallylamine having a weight average molecular weight of 300 to 30,000 is particularly preferable.

In the liquid crystal microcapsule of the present invention, a cholesteric liquid crystal, a nematic liquid crystal, or a smectic liquid crystal can be used as the liquid crystal. The cholesteric liquid crystal preferably has a selective reflection peak wavelength of 600 to 800 nm.

  On the other hand, the method for producing a liquid crystal microcapsule according to the present invention comprises reacting an alignment material composed of a compound having an alkyl group and / or a fluoroalkyl group and a hydroxyl group, a polyisocyanate, and water to produce the polyurea. The coating film is formed and liquid crystal is included in the coating film.

  More specifically, a step of preparing an oil phase by mixing the liquid crystal, the alignment material, and the polyisocyanate, a step of producing a dispersion by dispersing the oil phase in an aqueous phase, and the dispersion A step of heating the liquid and reacting the alignment material, the polyisocyanate, and the water to form the polyurea to form the coating film, and encapsulating the liquid crystal in the coating film. It is.

  In the method for producing liquid crystal microcapsules of the present invention, polyurea can also be produced by further reacting the polyamine together with the alignment material, the polyisocyanate, and the water. In this case, the step of mixing the liquid crystal, the alignment material, and the polyisocyanate to prepare an oil phase, the step of dispersing the oil phase in an aqueous phase to produce a dispersion, and the dispersion Adding the polyamine to the substrate, heating the dispersion, and reacting the alignment material, the polyisocyanate, the polyamine, and the water to form the polyurea to form the coating film. And including the liquid crystal.

In the manufacturing method of the liquid crystal microcapsules of the present invention, before Symbol polyamine is suitably a polyallylamine.

  The liquid crystal display element of the present invention is characterized in that the liquid crystal microcapsule of the present invention is sandwiched between a pair of electrodes.

  ADVANTAGE OF THE INVENTION According to this invention, the liquid-crystal microcapsule which has a film with a uniform film thickness and favorable vertical alignment property, and the manufacturing method which can obtain it simply can be provided. In addition, a liquid crystal display element using the liquid crystal microcapsule can be provided.

Hereinafter, the liquid crystal microcapsule of the present invention will be described together with its production method.
First, FIG. 1 schematically shows a configuration of a liquid crystal microcapsule of the present invention and a manufacturing method thereof. As shown in FIG. 1, the liquid crystal microcapsule of the present invention has a structure in which the liquid crystal is included in a film made of polyurea, and an alkyl group and / or a fluoroalkyl group is bonded to this polyurea as a vertical alignment group by a urethane bond. It is connected directly or indirectly via The inside of the coating made of polyurea is the oil phase, and the outside is the water phase.

And the liquid crystal microcapsule of the present invention comprises an alignment material comprising a compound having an alkyl group and / or a fluoroalkyl group and a hydroxyl group, polyisocyanate, water (H 2 O), and, if necessary, a polyamine. It is obtained by reacting to produce a polyurea having an alkyl group and / or a fluoroalkyl group as a vertical alignment group and including a liquid crystal with this polyurea.
However, in the present invention, as the alignment material, at least one compound represented by the following structural formula (I) is applied.

  First, as a first production method of the liquid crystal microcapsule of the present invention, polyurea is produced by reacting an alignment material composed of a compound having an alkyl group and / or a fluoroalkyl group and a hydroxyl group, polyisocyanate, and water. How to do will be described.

  Specifically, as the first production method, first, an oil phase is prepared by mixing liquid crystal, an alignment material, and polyisocyanate. Next, the oil phase is dispersed in the aqueous phase to produce a dispersion. Then, the dispersion is heated. Through this step, the alignment material, polyisocyanate, and water are reacted to form polyurea to form a film, and the liquid crystal can be included in the film.

  In the first production method, the polyisocyanate in the oil phase reacts with the water in the aqueous phase to produce carbamic acid, and further produces an amine with decarboxylation (formula A). Both carbamic acid and amine combine with other polyisocyanates to form polyurea coatings (formulas B and C).

Formula A: R 1 —NCO (polyisocyanate) + H 2 O → R 1 —NHCOOH (carbamic acid) → R 1 —NH 2 (amine) + CO 2
Formula B: R 1 -NCO + R 1 -NHCOOH → R 1 -NHCONH-R 1 ( polyurea) + CO 2
Formula C: R 1 —NCO + R 1 —NH 2 → R 1 —NHCONH—R 1 (polyurea)

Here, R 1 is a moiety other than one isocyanate group of polyisocyanate (for example, if polyisocyanate is xylene diisocyanate, R 1 is OCN—CH 2 —C 6 H 4 —CH 2 —, 1,6-hexane diisocyanate. OCN— (CH 2 ) 6 —, 4,4′-diphenylmethane diisocyanate is OCN—C 6 H 4 —CH 2 —C 6 H 4 — and the like).

  In the first method, only the reaction of one isocyanate group of the polyisocyanate is described in the formulas A to C, but since the polyisocyanate has a plurality of isocyanate groups, the second and third stages of the formulas A to C are described. The eye reaction produces a polymer. Since a series of reactions of the formulas A to C proceed at the interface between the oil phase and the water phase, a film is inevitably formed. Once the coating is formed, the reaction rate is greatly reduced because the contact between the polyisocyanate and water is cut off. Therefore, if there is a part where the film has not yet been formed, the reaction proceeds preferentially in that part, so that a uniform film is formed.

An alkyl group and / or a fluoroalkyl group (denoted as R 2 in the following formula D) is a vertical alignment group that aligns liquid crystal vertically with respect to the film surface, and an alignment material composed of this and a compound having a hydroxyl group is A hydroxyl group is taken into the film by urethane bonding with the polyisocyanate, and gives vertical alignment to the film (formula D below). In addition, when the alignment material has a bonding group between the vertical alignment group and the hydroxyl group, the alkyl group and / or fluoroalkyl group as the vertical alignment group is indirectly bonded to the urethane bond, and the And imparts vertical alignment to the coating (formula E below).

Formula D: R 2 —OH (alignment material) + OCN—R 1 (polyisocyanate) → R 2 —OCONH—R 1 (urethane bond)
Formula E: R 2 —X—OH (alignment material) + OCN—R 1 (polyisocyanate) → R 2 —X—OCONH—R 1 (urethane bond)

Here, R 1 is the same as above. R 2 is an alkyl group and / or a fluoroalkyl group as a vertical alignment group. X represents a linking group connecting an alkyl group and / or a fluoroalkyl group and a hydroxyl group (for example, a phenylene group -Ph-, an alkyl ester group -OCO- (CH 2 ) p- , an alkyl ether group -O- (CH 2 )). p -, - (OCH 2 CH 2) p -, - (OCH 2 CH 2 CH 2) p, phenyl ester group --OCO-Ph-, phenyl ether group -O-Ph- like any group: wherein p is It is 0 or more and 5 or less, and the case of 0 corresponds to the case of direct binding shown in Formula D). Although the degree varies depending on the type of bond group of X, generally, the vertical alignment property decreases as p increases. Therefore, p is preferably 5 or less.

  Note that the alignment material is important because it is used after being dissolved in the liquid crystal. For this reason, it is preferable to use a linking group containing an ether group such as an alkyl ether group as the linking group because an alignment material having flexibility and excellent solubility can be obtained.

  Next, as a second production method of the liquid crystal microcapsule of the present invention, an alignment material composed of a compound having an alkyl group and / or a fluoroalkyl group and a hydroxyl group, a polyisocyanate, a polyamine, and water are reacted. A method for producing polyurea will be described.

  Specifically, as the second production method, first, an oil phase is prepared by mixing liquid crystal, an alignment material, and polyisocyanate. Next, the oil phase is dispersed in the aqueous phase to produce a dispersion. Next, the polyamine is added to the dispersion. Then, the dispersion is heated. Through this step, the alignment material, polyisocyanate, polyamine, and water are reacted to form polyurea to form a film, and the liquid crystal can be included in the film.

  In the second production method, in addition to the reaction of the above formulas A to C formed by the polyisocyanate, water, and the alignment material, a binding reaction between the polyisocyanate and the polyamine is added (formula F).

Formula F: R 1 —NCO + NH 2 —R 3 (polyamine) → R 1 —NHCONH—R 3

Here, R 1 is the same as above. R 3 is a moiety other than one amino group of the polyamine (for example, R 3 is H 2 N—CH 2 CH 2 — if the polyamine is ethylenediamine, or H 2 N—CH 2 CH 2 —NH—CH 2 CH 2 if the polyamine is diethylenetriamine. -Etc.)

  The polymer formed at the interface between the oil phase and the aqueous phase diffuses into the oil phase due to thermal motion at the initial stage where the degree of polymerization is low. desirable. In general, the reaction rate of Formula F is faster than the series of reaction rates of Formulas A to C, so that a uniform coating can be formed more reliably.

  From the viewpoint of rapidly increasing the degree of polymerization, a high molecular polyamine is desirable as the polyamine, and polyallylamine having a primary amino group having high reactivity is particularly preferable. Although this liquid crystal microcapsule gives a hard coating due to a high degree of crosslinking, the authors' research results have revealed that the harder the coating, the higher the vertical alignment tends to be. can get. The reason why the harder the coating is, the higher the vertical alignment is. In such a coating, the shrinkage stress in the coating surface is large, and the polymer main chain tends to be oriented in the coating surface. It is speculated that the orientation may be improved.

  In addition, in both the first and second production methods, when a compound having only one hydroxyl group is used as the alignment material, the crosslinking density is lowered and the glass transition temperature of the film is lowered, or the strength may be insufficient. As a means for preventing this, a method of introducing a plurality of hydroxyl groups into the alignment material is effective.

  Thus, the liquid crystal microcapsule of the present invention can have a film with a uniform film thickness and high vertical alignment. For this reason, when the liquid crystal microcapsule of the present invention is used as a display element, remarkably high display performance is exhibited.

Hereinafter, each material in the liquid crystal microcapsule of the present invention will be described in more detail.
First, polyurea refers to a polymer compound in which monomers are bonded by urea bond-NHCONH-, and specifically, polyisocyanate and water, or polyisocyanate and polyamine are used as monomers, and these are reacted to form.

  As polyisocyanates, 1) ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, 2,2,4-trimethylhexane diisocyanate, lysine diisocyanate, 2,6-diisocyanate methylcaproate, bis (2-isocyanate) Ethyl) fumarate, bis (2-isocyanatoethyl) carbonate, 2-isocyanatoethyl-2, 6-diisocyanatohexanoate and other aliphatic polyisocyanates, 2) isophorone diisocyanate, dicyclohexylmethane diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate Bis (2-isocyanatoethyl) -4-cyclohexene-1,2-di Alicyclic polyisocyanates such as Rubokishireto, 3) xylylene diisocyanate, aromatic aliphatic polyisocyanates such as diethylbenzene diisocyanate, 4) tolylene diisocyanate, diphenylmethane diisocyanate, aromatic polyisocyanates such as naphthylene diisocyanate, and the like.

  In addition, polyisocyanates having 3 or more functional groups can be particularly preferably used in order to quickly increase the degree of polymerization and from the viewpoint of obtaining high vertical alignment by increasing the crosslinking density of the polymer. Such polyisocyanates can be obtained in the form of adducts, isocyanurates, burettes, allophanates of the above-mentioned diisocyanates, and examples thereof include the following compounds.

    Here, commercially available products of the above compounds include Coronate HX (product of Nippon Polyurethane Co., Ltd.), Vernock D-750, Crisbon NX (Product of Dainippon Ink and Chemicals), Death Module L (Product of Sumitomo Bayer), Coronate L (Product of Nippon Polyurethane Co., Ltd.), Takenate D102 (product of Mitsui Takeda Chemical Co., Ltd.) and the like.

    Here, Burnock D-950 (Dainippon Ink Chemical Co., Ltd. product) is mentioned as a commercial item of the said compound.

  Here, Takenate D110N (product of Mitsui Takeda Chemical Company) is mentioned as a commercial item of the said compound.

  As a result of detailed examination, the polyisocyanate is represented by xylene diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, isophorone diisocyanate polyisocyanate, and derivatives thereof represented by the following structural formulas (1) to (3), respectively. It has been found that a particularly high vertical alignment property can be obtained when at least one kind is used. Here, the derivatives refer to adducts, isocyanurates, burettes, allophanates, and the like.

  For example, 1) a polyisocyanate having a benzene ring or a cyclohexane ring forms a relatively rigid polyurea; 2) a methylene group is present between the benzene ring and the isocyanate group and between the cyclohexane ring and the isocyanate group. Because of being sandwiched, the hydrogen bond between the formed urea bonds is less susceptible to steric hindrance by the benzene ring or cyclohexane ring. It is presumed that the orientation of the main chain is thereby increased, and the orientation of the side chain is improved accordingly.

  Moreover, the addition amount of polyisocyanate shall be 1-20 parts with respect to 100 (weight) liquid crystal. If it is 1 part or less, the strength of the film is insufficient and sufficient vertical alignment may not be obtained. If it is 20 parts or more, the ratio of the film to the liquid crystal microcapsules increases, so that the display performance may deteriorate.

  Moreover, as an orientation material, the compound shown by the following structural formula (I) can be utilized suitably.

Structural formula (I): C n F m H (2n + 1-m) -X-Y
(In the structural formula (I), X is - (OCH 2) p -, - (OCH 2 CH 2) p -, - (OCH 2 CH 2 CH 2) p -, - (COOCH 2 CH 2) p -, - (OCOCH 2 CH 2 ) p -, -. Ph-, or -O-Ph- (. here p is 0 to 5 integer) indicating a Y is -OH, -COO-CH ( CH 2 OH) 2 or —COO—CH (OH) CH 2 OH, wherein m is an integer of 0 or more and (2n + 1) or less, and n is an integer of 4 or more and 30 or less.

C n F m H (2n + 1-m) in Structural Formula (I) represents an alkyl group / or a fluoroalkyl group, and m = 0 corresponds to an alkyl group, and m ≠ 0 corresponds to a fluoroalkyl group. . The alkyl group and fluoroalkyl group as the vertical alignment group are represented by the following formula.

Alkyl group: C n H 2n + 1
Fluoroalkyl groups: C n F m H 2n- m + 1 - (m ≦ 2n + 1)

  Here, n representing the chain length is preferably 4 or more and 30 or less, and more preferably 10 or more and 20 or less. If n is less than 4, sufficient vertical alignment may not be exhibited. When n is 20 or more, the strength of the film may be extremely reduced. Since the vertical alignment becomes stronger as the chain length is longer, n is preferably larger in this range. In general, an alignment material having an alkyl group has higher compatibility with a liquid crystal than an alignment material having a fluoroalkyl group, but this is not limited to this in a low-polarity liquid crystal such as a fluorine-based liquid crystal, and it is desirable to select appropriately.

In the structural formula (I), X is, - (OCH 2) p - , - (OCH 2 CH 2) p -, - (OCH 2 CH 2 CH 2) p -, - COOCH 2 CH 2 -, - Ph- , —O—Ph— and the like, and p is 0 or more and 5 or less. Although the degree varies depending on the type of bonding group of X, it is desirable that p is 5 or less because vertical alignment decreases as p increases. Among them, the linking group having an ether group (— (OCH 2 ) p —, — (OCH 2 CH 2 ) p —, — (OCH 2 CH 2 CH 2 ) p —) is a liquid crystal because it gives flexibility to the alignment material molecules. And can be suitably used with a wide variety of liquid crystal material types.

In Structural Formula (I), Y is a functional group for bonding with an isocyanate group, and is a hydroxyl group —OH, glycerol monoester —COO—CH (CH 2 OH) 2 , or —COO—CH (OH) CH. 2 OH can be suitably used.

  Moreover, it is preferable to use the addition amount of an orientation material in the range whose hydroxyl group number of the orientation material with respect to 100 isocyanate groups is 5-70, More preferably, it is the range of 20-50. When the amount is less than this range, sufficient vertical alignment cannot be obtained, and when the amount is too large, unreacted alignment material may remain or the crosslink density may be extremely lowered, which is not preferable.

  Next, polyamines include low molecular weight polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and hexamethylenediamine, and polymers such as chitosan, polylysine, Hoffman modified polyacrylamide, polyvinylamine, polyamidine, and polyallylamine. Polyamine is preferred.

  The polyamine is preferably a polymer polyamine, particularly polyallylamine, from the viewpoint of quickly increasing the degree of polymerization and increasing the crosslink density of the polymer to obtain high vertical alignment. High molecular weight polyamines, particularly polyallylamine, are also preferred from the standpoint that unreacted residues are difficult to dissolve in the liquid crystal and are difficult to degrade the electrical properties of the liquid crystal. Polyallylamine is commercially available in hydrochloride and free form, but is preferably free from the viewpoint of electrical characteristics.

  The polyamine preferably has a highly reactive primary amino group. A secondary or higher polyamine has a low reactivity, and it is difficult to obtain a good film. The weight average molecular weight of the polymer polyamine, particularly polyallylamine, is preferably from 300 to 1,000,000, more preferably from 300 to 30,000. When the weight average molecular weight is 300 or less, a sufficient effect of improving the vertical alignment is not observed. The higher the weight average molecular weight is, the higher the vertical alignment is. However, if the weight average molecular weight is too high, capsule aggregation tends to occur at the time of polymerization.

  As the polyamine, polyallylamine having a large number of primary amino groups is particularly suitable from the above viewpoint. For example, a compound represented by the following formula can be suitably used as the polyallylamine.

  Here, n represents an integer of 15 to 20,000.

  The addition amount of the polyamine is desirably in the range of 1 to 100 amino groups with respect to 100 isocyanate groups. Below this range, a sufficient film cannot be formed, so that a sufficient vertical alignment effect may not be obtained. Further, since the polyamine reacts only in an amount covering the surface of the dispersed phase, a large amount of unreacted polyamine may be generated even if it is added excessively, resulting in a lot of waste.

  Here, among the polyureas obtained by reacting the above materials, particularly preferred is a reaction of at least polyisocyanate, water, and at least one compound represented by the structural formula (I) as an alignment material. A polymer compound obtained by reacting at least a polyisocyanate, water, at least one compound represented by the structural formula (I) as an alignment material, and a polyamine. is there.

  Next, rod-like liquid crystal is used as the liquid crystal, and for example, any of nematic liquid crystal, cholesteric liquid crystal, and smectic liquid crystal can be used. As these liquid crystals, known liquid crystals can be used. As liquid crystal constituent materials, known liquid crystalline compounds such as cyanobiphenyl, phenylcyclohexane, phenylbenzoate, cyclohexylbenzoate, azomethine, azobenzene, pyrimidine, dioxane, cyclohexylcyclohexane, stilbene, and tolan Is available. Generally, these liquid crystal compounds are used in combination as a liquid crystal composition.

  A cholesteric liquid crystal is an optically active liquid crystal composition, and 1) an optically active compound called a chiral agent is added to the nematic liquid crystal composition, or 2) an optically active liquid crystal composition itself such as a cholesterol derivative. It is obtained by using. As the chiral agent, cholesterol derivatives such as cholesteryl nonanoate, compounds having an optically active group such as 2-methylbutyl group, and the like can be used.

  The helical pitch of the cholesteric liquid crystal can be changed depending on the type and amount of the chiral agent and the material of the liquid crystal. In order to develop a helical structure, the helical pitch needs to be equal to or smaller than the diameter of the liquid crystal microcapsule.

  When used as a display element using selective reflection, cholesteric liquid crystal macrocapsules generally have a reflection spectrum that spreads to a shorter wavelength side than the selective reflection wavelength band of uniformly cholesteric bulk cholesteric liquid crystal due to the orientation effect of the film. There are features to show. Therefore, when the selective reflection wavelength of the cholesteric liquid crystal is set to 600 to 800 nm, the reflection spectrum of the liquid crystal microcapsule can be applied to the entire visible wavelength region, and a whitened appearance can be given.

  Further, additives such as pigments and fine particles may be added to the liquid crystal. Further, it may be gelled using a crosslinkable polymer or a hydrogen bonding gelling agent, and the molecular weight of the liquid crystal may be any of a polymer, a medium molecule and a low molecule, or a mixture thereof.

Hereinafter, the first and second production methods will be described in detail.
First, the first production method includes A1) a step of preparing an oil phase by mixing a liquid crystal, an alignment material, and a polyisocyanate; A2) a step of dispersing the oil phase in an aqueous phase to produce a dispersion; A3) It consists of a series of steps of heating the dispersion.

  In step A1), a solvent (for example, ethyl acetate, butyl acetate, methyl ethyl ketone, toluene, etc.) for assisting mutual dissolution of the liquid crystal, the alignment material, and the polyisocyanate may be added to the oil phase. The oil phase may be heated. The former also has an effect of facilitating dispersion by lowering the viscosity of the oil phase.

  The dispersion in the step A2) is carried out by using a rotary blade type stirring device such as a propeller type, screw type, paddle type or internal tooth type, an ultrasonic stirring device, a jet type stirring device, a membrane emulsification device or the like.

  In order to prevent coalescence of the dispersed oil phase, an emulsion stabilizer may be added into the aqueous phase. As the emulsion stabilizer, surfactants: alkylbenzene sulfonates, polyethylene oxide alkyl esters and the like, and protective colloids: for example, polyvinyl alcohol, alkyl cellulose, hydroxy cellulose, gelatin and the like can be used.

  The heating step of step 3) is a step of reacting polyisocyanate and water, and polyisocyanate and alignment material. The heating temperature and time must be appropriately selected so that the reaction proceeds sufficiently according to the material used, but generally the heating temperature is 50 to 100 ° C. and the overheating time is about 1 to 20 hours.

  Next, the second production method includes B1) a step of preparing an oil phase by mixing liquid crystal, an alignment material and polyisocyanate, and B2) a step of dispersing the oil phase in an aqueous phase to produce a dispersion. And B3) a step of adding the polyamine to the dispersion, and B4) a step of heating the dispersion.

  Of these, steps B1), B2) and B4) are the same as steps A1), A2) and A3), respectively. In the polyamine addition step of step B3), the reaction between the polyamine and the polyisocyanate is very fast. Therefore, the reaction should be performed with good stirring so that the reaction does not become non-uniform, and care must be taken to remove the exotherm.

  The liquid crystal microcapsules of the present invention described above can be used as a liquid crystal microcapsule film formed by being dispersed in a binder resin (its solution) and coated on a substrate. Binder resins include polyvinyl alcohol, alkylcellulose, gelatin, polyester, polyacrylate, polymethacrylate, polyvinyl, polyurethane, epoxy, polycarbonate, polyolefin, silicone, and other polymers, and metal produced by sol-gel reaction of metal alkoxides. Oxides can be used.

  Examples of the method for forming the liquid crystal microcapsule film include printing methods such as screen printing, letterpress printing, intaglio printing, flat plate printing, flexographic printing, spin coating methods, bar coating methods, dip coating methods, roll coating methods, A coating method such as a knife coating method or a die coating method can be used.

  The liquid crystal microcapsules of the present invention can be used for display elements, image / information recording elements, spatial light modulators, and the like. In particular, it is preferably used for a display element, that is, a liquid crystal display element. Hereinafter, the liquid crystal display element of the present invention will be described.

  The liquid crystal display element of the present invention has a configuration in which the liquid crystal microcapsule of the present invention is sandwiched between a pair of electrodes. Specifically, for example, as shown in FIG. 2, a liquid crystal microcapsule film in which liquid crystal microcapsules 4 are dispersed in a binder 3 is sandwiched between a pair of substrates 1 each provided with an electrode 2 to apply a voltage. A configuration may be adopted in which voltage pulses are given by means 5 and displayed. As a display background, a light absorbing member may be provided between the microcapsule film and the electrode 2 or on the back surface of the substrate 1. As the substrate 1, for example, glass or resin (transparent dielectric such as polyethylene terephthalate, polyethersulfone, polycarbonate, polyolefin, etc.) can be used. As the electrode 2, for example, a transparent conductive film such as an indium tin oxide alloy or zinc oxide can be used.

  As a display mode of the liquid crystal display element of the present invention, a light scattering-transmission mode or a birefringence mode may be used in addition to the guest / host mode and the selective reflection mode. Moreover, you may utilize a polarizing plate and a phase difference plate as an auxiliary member for that.

  As a driving method of the liquid crystal display element of the present invention, 1) a segment driving method in which the electrode is sandwiched between electrodes patterned in a display shape, and 2) a polymer / cholesteric liquid crystal dispersion between a pair of orthogonal stripe electrode substrates 3) Simple matrix driving method in which an image is written by scanning line-sequentially 3) Active elements such as thin film transistors, thin film diodes, MIM (metal-insulator-metal) elements are provided for each individual pixel, and these active elements are passed through. 4) An optical matrix driving method in which a photoconductor is stacked and sandwiched between a pair of electrodes, and an image is written by applying a voltage while projecting an optical image. 5] Between a pair of electrodes The polymer / cholesteric liquid crystal dispersion sandwiched between two layers is changed to the P orientation by applying a voltage, and then phase transition is performed with a laser or thermal head. 6) a known driving method such as an electrostatic driving method in which a polymer / cholesteric liquid crystal dispersion is applied onto an electrode substrate and an image is written with a stylus head or an ion head. Is applicable.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, these examples do not limit the present invention.

<Example 1>
Nematic liquid crystal E7 (manufactured by Merck Japan), chiral agent R811 (manufactured by Merck) and chiral agent R1011 (manufactured by Merck) are mixed at a weight ratio of 86.3 to 11.0 to 2.8 to obtain a wavelength. A cholesteric liquid crystal selectively reflecting at 620 nm was obtained.

Next, the following composition was mixed to obtain an oil phase.
・ Cholesteric liquid crystal: 1g
Polyisocyanate: Takenate D-110N (manufactured by Takeda Pharmaceutical Company Limited): 0.13 g
- alignment material: diethylene hexadecane ether (C 16 H 33 - (OCH 2 CH 2) 2 -OH): 0.05g
Solvent: ethyl acetate: 10g

  The obtained oil phase was put into 100 g of a 1% polyvinyl alcohol aqueous solution and dispersed with a propeller rotary stirrer to prepare a dispersion having an average particle size of 7 μm. The dispersion was placed in a container and reacted in a water bath at 85 ° C. for 2 hours. As a result of observation with a microscope, a uniform film was obtained.

  Next, the dispersion was centrifuged to settle the liquid crystal microcapsules, and the supernatant was discarded to concentrate the dispersion. The liquid crystal microcapsules were washed by repeating the operation of adding pure water to this, stirring, and concentrating the dispersion in the same manner twice. A liquid crystal microcapsule coating solution was prepared by adding a polyvinyl alcohol solution as a binder to the concentrated dispersion. The liquid crystal microcapsule and polyvinyl alcohol were 75 to 25 by weight.

This liquid crystal microcapsule coating solution was applied on a polyethylene terephthalate (PET) substrate with an indium tin oxide (ITO) electrode with an applicator to obtain a liquid crystal microcapsule film having a dry film thickness of 32 μm. Another electrode-attached substrate was prepared as a counter substrate, and a black paint obtained by adding carbon black to a polyvinyl alcohol aqueous solution was applied thereon so that the dry film thickness was 3 μm. further,
On top of this, a two-component urethane adhesive was applied to a thickness of 3 μm and bonded onto a liquid crystal microcapsule film to obtain a liquid crystal display element.

  A burst pulse composed of a symmetric rectangular wave having a frequency of 1 KHz and a length of 200 ms was applied between the upper and lower electrodes of the liquid crystal display element, and the reflectance at the selective reflection wavelength after the pulse application was measured. The reflectance characteristics were measured while changing the pulse voltage to obtain the maximum reflectance and the minimum reflectance, and the contrast ratio defined by these ratios was obtained. The contrast ratio was as good as 15.7: 1.

<Example 2>
In Example 1, after preparing the dispersion, liquid crystal microcapsules were similarly prepared except that 2.5 g of a 2% aqueous solution of polyallylamine (PAA-H10C manufactured by Nittobo Co., Ltd .: weight average molecular weight 100,000) was added. A display element was obtained. The contrast ratio of the liquid crystal display device using this liquid crystal microcapsule was as good as 30.4: 1, and a marked improvement was seen from Example 1.

  FIG. 3 shows the reflection spectrum of the cholesteric liquid crystal (LC) used and the reflection spectrum of the liquid crystal display element during bright display (dark) and dark display (dark). As shown in FIG. 3, in Example 2, the cholesteric liquid crystal used showed red selective reflection having a peak at a wavelength of 620 nm, whereas the reflection spectrum of the liquid crystal microcapsule broadly spreads to the shorter wavelength side. A good white display could be obtained.

<Example 2.1>
In Example 1, a liquid crystal microcapsule was prepared in the same manner except that 2.5 g of a 2% aqueous solution of polyallylamine (PAA-05L manufactured by Nittobo Co., Ltd .: weight average molecular weight 5,000) was added after preparing the dispersion. A liquid crystal display element was obtained. The contrast ratio of the liquid crystal display device using this liquid crystal microcapsule was as good as 25.7: 1, and was markedly improved over Example 1.

  In Example 2, aggregation of capsules was observed after heat polymerization, but in this example, the amount of aggregation was significantly reduced. When the amount of aggregation relative to the weight average molecular weight of polyallylamine (PAA) was examined, as shown in FIG. 6, there was a change point between molecular weights 10,000 and 100,000, and it was found that the aggregation was small below this.

<Example 3>
A liquid crystal microcapsule was prepared in the same manner as in Example 2 except that 1-octanol (C 8 H 17 OH) was used as the alignment material, to obtain a liquid crystal display element. The contrast ratio of the liquid crystal display element using this liquid crystal microcapsule was 8.8: 1.
<Example 4>
A liquid crystal microcapsule was produced in the same manner as in Example 2 except that 1-dodecanol (C 12 H 25 OH) was used as an alignment material to obtain a liquid crystal display element. The contrast ratio of the liquid crystal display device using this liquid crystal microcapsule was as good as 22.4: 1, and the effect of increasing the chain length as compared with Example 3 was prominent.

<Example 5>
A liquid crystal microcapsule was produced in the same manner as in Example 2 except that 1-pentadecanol (C 15 H 31 OH) was used as the alignment material to obtain a liquid crystal display element. The contrast ratio of the liquid crystal display element using this liquid crystal microcapsule was as good as 27.0: 1, and the effect of increasing the chain length further than in Example 4 appeared.

<Example 6>
A liquid crystal microcapsule was prepared in the same manner as in Example 2 except that perfluorodecylethanol having a fluoroalkyl group (C 10 F 21 CH 2 OH, ie, C 11 F 21 H 2 —OH) was used as the alignment material. A liquid crystal display element was obtained. The contrast ratio of the liquid crystal display device using the liquid crystal microcapsules was 8.3: 1.
<Example 6.1>
Liquid crystal microcapsules were prepared in the same manner as in Example 2 except that polyethylene glycol (10EO) hexadecane ether (C 16 H 33 — (OCH 2 CH 2 ) 10 —OH) was used as the alignment material to obtain a liquid crystal display element. It was. The difference from Example 2 is that the number of repeating ethylene oxide units was changed from 2 to 10. The contrast ratio of the liquid crystal display device using the liquid crystal microcapsules was 7.0: 1.

<Example 6.2>
A liquid crystal microcapsule was prepared in the same manner as in Example 2 except that polyethylene glycol (20EO) hexadecane ether (C 16 H 33 — (OCH 2 CH 2 ) 20 —OH) was used as the alignment material to obtain a liquid crystal display element. It was. The difference from Example 2 is that the number of repeating ethylene oxide units was changed from 2 to 20. The contrast ratio of the liquid crystal display element using this liquid crystal microcapsule was 6.5: 1.

<Example 6.3>
A liquid crystal microcapsule was produced in the same manner as in Example 2 except that ethylene glycol monostearate (C 17 H 35 — (COO—CH 2 CH 2 ) —OH) was used as the alignment material, and a liquid crystal display device was obtained. . The contrast ratio of the liquid crystal display device using the liquid crystal microcapsules was 14.7: 1.

<Example 7>
Liquid crystal microcapsules were produced in the same manner as in Example 2 except that glycerol monoisostearate (C 17 H 35 —COO—CH (CH 2 OH) 2 ) having two hydroxyl groups was used as the alignment material. The contrast ratio of the liquid crystal display device using this liquid crystal microcapsule was 18.5: 1.

<Comparative Example 1>
A liquid crystal microcapsule was produced in the same manner as in Example 2 except that no alignment material was added, to obtain a liquid crystal display element. The contrast ratio of the liquid crystal display device using the liquid crystal microcapsule was 6.1.

<Comparative example 2>
Nematic liquid crystal E7 (manufactured by Merck Japan), chiral agent R811 (manufactured by Merck) and chiral agent R1011 (manufactured by Merck) are mixed at a weight ratio of 86.3 to 11.0 to 2.8 to obtain a wavelength. A cholesteric liquid crystal selectively reflecting at 620 nm was obtained.

Next, the following composition was mixed to obtain an oil phase.
・ Cholesteric liquid crystal: 0.85g
Monomer: CH 2 ═C (CH 3 ) COOCH 2 (CH 2 ) 16 CH 3 : 0.060 g
Monomer: CH 2 = CHCOOCH 2 C 2 F 5 : 0.045 g
Monomer: C 2 H 5 C [CH 2 OCOCH═CH 2 ] 3 : 0.045 g
-Radical polymerization initiator: Azoisobutyronitrile: 0.003 g
Solvent: ethyl acetate: 10g

  The obtained oil phase was put into 100 g of a 1% aqueous polyvinyl alcohol solution and dispersed with a propeller rotary stirrer to prepare a dispersion having an average particle size of 10 μm. The dispersion was heated at 90 ° C. for 6 hours in a nitrogen atmosphere to radically polymerize the monomer, thereby producing a liquid crystal microcapsule.

  Next, the liquid dispersion microcapsules were settled by centrifuging the dispersion, and the supernatant was discarded to concentrate the dispersion. Pure water was added and stirred, and the operation of concentrating the dispersion was repeated twice to wash the liquid crystal microcapsules. A liquid crystal microcapsule coating solution was prepared by adding a polyvinyl alcohol solution as a binder to the concentrated dispersion. The liquid crystal microcapsule and polyvinyl alcohol were 75 to 25 by weight.

  This liquid crystal microcapsule coating solution was applied on a polyethylene terephthalate (PET) substrate with an indium tin oxide (ITO) electrode with a gap applicator to obtain a liquid crystal microcapsule film having a dry film thickness of 30 μm. This liquid crystal capsule had relatively many liquid crystal leaks. Next, another substrate with electrodes was prepared, and a two-component urethane-based adhesive was applied thereon to a thickness of 3 μm and bonded onto the liquid crystal microcapsule film to obtain a liquid crystal display element.

  The maximum reflectance and the minimum reflectance were obtained by applying a burst pulse consisting of a symmetric rectangular wave having a frequency of 1 KHz and a length of 200 ms between the upper and lower electrodes of the liquid crystal display element. The contrast ratio was as low as 5.0: 1.

  The results of Examples 1-7 and Comparative Examples 1-2 are summarized in Table 1. All the examples showed better contrast ratios than the comparative examples.

<Example 7.1>
The polyisocyanate D110N used in Example 2 is a trimethylolpropane adduct of xylene diisocyanate, which is converted to a trimethylolpropane adduct of 1,3-bis (isocyanatomethyl) cyclohexane represented by the following structural formula. A liquid crystal capsule was produced in the same manner as in Example 2 except that the replacement was performed. The contrast ratio of the liquid crystal display device using this liquid crystal microcapsule was 12.0: 1.

<Example 7.2>
A liquid crystal capsule was prepared in the same manner as in Example 2, except that the polyisocyanate of Example 2 was replaced with an isocyanurate of isophorone diisocyanate represented by the following structural formula. The contrast ratio of the liquid crystal display element using this liquid crystal microcapsule was 15.3: 1.

<Example 7.3>
A liquid crystal capsule was produced in the same manner as in Example 2 except that the polyisocyanate of Example 2 was replaced with a trimethylolpropane-adduct of hexamethylene diisocyanate represented by the following structural formula. The contrast ratio of the liquid crystal display element using this liquid crystal microcapsule was 7.8: 1.

<Example 7.4>
A liquid crystal capsule was produced in the same manner as in Example 2 except that the polyisocyanate of Example 2 was replaced with an isocyanurate of hexamethylene diisocyanate represented by the following structural formula. The contrast ratio of the liquid crystal display device using the liquid crystal microcapsules was 8.5: 1.

<Example 7.5>
A liquid crystal capsule was prepared in the same manner except that the polyisocyanate of Example 2 was replaced with a hexamethylene diisocyanate burette represented by the following structural formula. The contrast ratio of the liquid crystal display element using this liquid crystal microcapsule was 10.2: 1.

<Example 7.6>
A liquid crystal capsule was produced in the same manner as in Example 2 except that the polyisocyanate of Example 2 was replaced with an allophanate of hexamethylene diisocyanate represented by the following structural formula. The contrast ratio of the liquid crystal display element using this liquid crystal microcapsule was 8.2: 1.

  The results of Examples 7.1 to 7.6 are summarized in Table 2 together with the results of Comparative Example 1 above. All the examples showed better contrast ratios than the comparative examples.

<Example 8>
2 wt% of black dichroic dye S-344 (Mitsui Toatsu Chemical Co., Ltd.) was added to negative type nematic liquid crystal ZLI-2806 (Merck Japan Co., Ltd.) to obtain a guest / host liquid crystal.

Next, the following composition was mixed to obtain an oil phase.
・ Guest / Host LCD: 1g
Polyisocyanate: Takenate D-110N (manufactured by Takeda Pharmaceutical Company Limited): 0.13 g
Alignment material: Diethylene glycol hexadecane ether: 0.05 g
Solvent: ethyl acetate: 10g

  This oil phase was put into 100 g of a 1% aqueous polyvinyl alcohol solution and dispersed with a propeller rotary stirrer to prepare a dispersion having an average particle size of 7 μm. The dispersion was placed in a container and reacted in a water bath at 85 ° C. for 2 hours.

  Next, the dispersion was centrifuged to settle the liquid crystal microcapsules, and the supernatant was discarded to concentrate the dispersion. Pure water was added and stirred, and the operation of concentrating the dispersion was repeated twice to wash the liquid crystal microcapsules. A liquid crystal microcapsule coating solution was prepared by adding a polyvinyl alcohol solution as a binder to the concentrated dispersion. The liquid crystal microcapsule and polyvinyl alcohol were 75 to 25 by weight.

  This liquid crystal microcapsule coating solution was applied on a polyethylene terephthalate (PET) substrate with an indium tin oxide (ITO) electrode with a gap applicator to obtain a liquid crystal microcapsule film having a dry film thickness of 15 μm. Next, another substrate with electrodes was prepared, and a two-component urethane-based adhesive was applied thereon to a thickness of 3 μm and bonded onto a liquid crystal microcapsule film to obtain a liquid crystal display element.

When a symmetric rectangular wave having a frequency of 1 KHz was applied between the upper and lower electrodes of the liquid crystal display element on a white background, a good light-dark display could be obtained.
<Example 10>
First, the following composition was mixed to obtain an oil phase.
・ Nematic liquid crystal E7: 1g
Polyisocyanate: Takenate D-110N (manufactured by Takeda Pharmaceutical Company Limited): 0.13 g
Alignment material: Diethylene glycol hexadecane ether: 0.05 g
Solvent: ethyl acetate: 10g

  This oil phase was put into 100 g of a 1% aqueous polyvinyl alcohol solution and dispersed with a propeller rotary stirrer to prepare a dispersion having an average particle size of 1 μm. The dispersion was placed in a container and reacted in a water bath at 85 ° C. for 2 hours.

  Next, the dispersion was centrifuged to settle the liquid crystal microcapsules, and the supernatant was discarded to concentrate the dispersion. Pure water was added and stirred, and the operation of concentrating the dispersion was repeated twice to wash the liquid crystal microcapsules. A liquid crystal microcapsule coating solution was prepared by adding a polyvinyl alcohol solution as a binder to the concentrated dispersion. The liquid crystal microcapsule and polyvinyl alcohol were 75 to 25 by weight.

  This liquid crystal microcapsule coating solution was applied on a polyethylene terephthalate (PET) substrate with an indium tin oxide (ITO) electrode with a gap applicator to obtain a liquid crystal microcapsule film having a dry film thickness of 15 μm. Next, another substrate with electrodes was prepared, and a two-component urethane-based adhesive was applied thereon to a thickness of 3 μm and bonded onto a liquid crystal microcapsule film to obtain a liquid crystal display element.

  When a symmetric rectangular wave with a frequency of 1 KHz was applied between the upper and lower electrodes of the liquid crystal display element, a good scattering-transmission display could be obtained.

<Example 11>
In Example 8, after preparing the dispersion, liquid crystal microcapsules were similarly prepared except that 2.5 g of a 2% aqueous solution of polyallylamine PAA-H10C (manufactured by Nittobo Co., Ltd .: weight average molecular weight 100,000) was added. A display element was obtained. When a symmetric rectangular wave having a frequency of 1 KHz was applied between the upper and lower electrodes of a liquid crystal display element using this liquid crystal microcapsule, a better light-dark display than that in Example 8 could be obtained.

<Example 12>
In Example 10, a liquid crystal microcapsule was prepared in the same manner except that 2.5 g of a 2% aqueous solution of polyallylamine PAA-H10C (manufactured by Nittobo Co., Ltd .: weight average molecular weight 100,000) was added after preparing the dispersion. A display element was obtained. When a symmetric rectangular wave having a frequency of 1 KHz was applied between the upper and lower electrodes of the liquid crystal display element using the liquid crystal microcapsules, a better scattering-transmission display was obtained compared to Example 10.

<Example 13>
First, the following composition was mixed to obtain an oil phase.
Smectic A liquid crystal: S2 (Merck): 1g
Polyisocyanate: Takenate D-110N (manufactured by Takeda Pharmaceutical Company Limited): 0.13 g
Alignment material: Diethylene glycol hexadecane ether: 0.05 g
Solvent: ethyl acetate: 10g

  The obtained oil phase was put into 100 g of 1% polyvinyl alcohol aqueous solution, dispersed with a propeller rotary stirrer to prepare a dispersion having an average particle size of 1 μm, and reacted in a water bath at 85 ° C. for 2 hours. .

  Next, the liquid dispersion microcapsules were settled by centrifuging the dispersion, and the supernatant was discarded to concentrate the dispersion. Pure water was added and stirred, and the operation of concentrating the dispersion was repeated twice to wash the liquid crystal microcapsules. A liquid crystal microcapsule coating solution was prepared by adding a polyvinyl alcohol solution as a binder to the concentrated dispersion. The liquid crystal microcapsule and polyvinyl alcohol were 75 to 25 by weight.

  This liquid crystal microcapsule coating solution was applied on a polyethylene terephthalate (PET) substrate with an indium tin oxide (ITO) electrode with a gap applicator to obtain a liquid crystal microcapsule film having a dry film thickness of 20 μm. Next, another substrate with electrodes was prepared, and a two-component urethane-based adhesive was applied thereon to a thickness of 3 μm and bonded onto the liquid crystal microcapsule film to obtain a liquid crystal display element.

  The obtained liquid crystal display element was white. When a symmetric rectangular wave having a frequency of 1 KHz and a voltage of 200 V was applied between the upper and lower electrodes, it turned transparent. When this was heated to an isotropic phase transition temperature of 48 ° C. or higher and cooled to room temperature, it returned to white again. Thus, an electric writing / thermal erasing type display medium could be obtained.

<Example 14>
In Example 13, after preparing the dispersion, liquid crystal microcapsules were similarly prepared except that 2.5 g of a 2% aqueous solution of polyallylamine PAA-H10C (manufactured by Nittobo Co., Ltd .: weight average molecular weight 100,000) was added. A display element was obtained. When a symmetric rectangular wave having a frequency of 1 KHz and a voltage of 200 V was applied between the upper and lower electrodes of the liquid crystal display element using the liquid crystal microcapsule, a better scattering-transmission display was obtained as compared with Example 13.

It is a schematic diagram which shows the structure of the liquid crystal microcapsule of this invention, and its manufacturing method. It is a schematic block diagram which shows an example of the liquid crystal display element of this invention. It is a figure which shows the reflection spectrum of the cholesteric liquid crystal (LC) in Example 2, and the reflection spectrum at the time of bright display (bright) and dark display (dark) of a liquid crystal display element. It is a figure which shows the orientation state of the liquid crystal in the liquid crystal microcapsule which is not orientation-controlled, and the orientation state of the liquid crystal in the liquid crystal microcapsule which was orientation-controlled. It is a figure which shows the orientation state of a cholesteric liquid crystal. It is a figure which shows the aggregation amount with respect to the weight average molecular weight of polyallylamine (PAA).

Explanation of symbols

1 Substrate 2 Electrode 3 Binder 4 Liquid Crystal Microcapsule 5 Voltage Application Means

Claims (19)

  1. A liquid crystal, and a coating made of polyurea containing the liquid crystal,
    The liquid crystal micro, wherein the polyurea is a polymer compound obtained by reacting at least a polyisocyanate, water, and at least one compound represented by the following structural formula (I) as an alignment material. capsule.
    Structural formula (I): C n F m H (2n + 1-m) -X-Y
    (In the structural formula (I), X is - (OCH 2) p -, - (OCH 2 CH 2) p -, - (OCH 2 CH 2 CH 2) p -, - (COOCH 2 CH 2) p -, - (OCOCH 2 CH 2 ) p -, -. Ph-, or -O-Ph- (. here p is 0 to 5 integer) indicating a Y is -OH, -COO-CH ( CH 2 OH) 2 or —COO—CH (OH) CH 2 OH, wherein m is an integer of 0 or more and (2n + 1) or less, and n is an integer of 4 or more and 30 or less.
  2. The polyisocyanate is at least one of polyisocyanates represented by the following structural formulas (1) to (3) and adducts, isocyanurates, burettes, and allophanates. Item 2. A liquid crystal microcapsule according to item 1.
  3.   The polyurea is a polymer compound obtained by reacting at least a polyisocyanate, water, at least one compound represented by the structural formula (I) as an alignment material, and a polyamine. The liquid crystal microcapsule according to claim 1.
  4. The liquid crystal microcapsule according to claim 3, wherein the polyamine is polyallylamine.
  5.   5. The liquid crystal microcapsule according to claim 4, wherein the polyallylamine has a weight average molecular weight of 300 or more and 30,000 or less.
  6.   The liquid crystal microcapsule according to claim 1, wherein the liquid crystal is a cholesteric liquid crystal.
  7.   The liquid crystal microcapsule according to claim 6, wherein a peak wavelength of selective reflection of the cholesteric liquid crystal is 600 to 800 nm.
  8.   The liquid crystal microcapsule according to claim 1, wherein the liquid crystal is a nematic liquid crystal.
  9.   The liquid crystal microcapsule according to claim 1, wherein the liquid crystal is a smectic liquid crystal.
  10. The alignment material comprising at least one of the compounds represented by the following structural formula (I), polyisocyanate, and water are reacted to form the polyurea to form the film, and the film includes liquid crystal. A method for producing a liquid crystal microcapsule, comprising:
    Structural formula (I): C n F m H (2n + 1-m) -X-Y
    (In the structural formula (I), X is - (OCH 2) p -, - (OCH 2 CH 2) p -, - (OCH 2 CH 2 CH 2) p -, - (COOCH 2 CH 2) p -, - (OCOCH 2 CH 2 ) p -, -. Ph-, or -O-Ph- (. here p is 0 to 5 integer) indicating a Y is -OH, -COO-CH ( CH 2 OH) 2 or —COO—CH (OH) CH 2 OH, wherein m is an integer of 0 or more and (2n + 1) or less, and n is an integer of 4 or more and 30 or less.
  11. Mixing the liquid crystal, the alignment material, and the polyisocyanate to prepare an oil phase;
    Dispersing the oil phase in an aqueous phase to produce a dispersion;
    Heating the dispersion, reacting the alignment material, the polyisocyanate, and the water to form the polyurea to form the coating, and encapsulating the liquid crystal with the coating;
    The manufacturing method of the liquid crystal microcapsule of Claim 10 which has these.
  12. The alignment material comprising at least one of the compounds represented by the following structural formula (I), polyisocyanate, polyamine, and water are reacted to form a polyurea to form a film, and a liquid crystal is formed by the film. A method for producing a liquid crystal microcapsule, comprising:
    Structural formula (I): C n F m H (2n + 1-m) -X-Y
    (In the structural formula (I), X is - (OCH 2) p -, - (OCH 2 CH 2) p -, - (OCH 2 CH 2 CH 2) p -, - (COOCH 2 CH 2) p -, - (OCOCH 2 CH 2 ) p -, -. Ph-, or -O-Ph- (. here p is 0 to 5 integer) indicating a Y is -OH, -COO-CH ( CH 2 OH) 2 or —COO—CH (OH) CH 2 OH, wherein m is an integer of 0 or more and (2n + 1) or less, and n is an integer of 4 or more and 30 or less.
  13. Mixing the liquid crystal, the alignment material, and the polyisocyanate to prepare an oil phase;
    Dispersing the oil phase in an aqueous phase to produce a dispersion;
    Adding the polyamine to the dispersion;
    Heating the dispersion, reacting the alignment material, the polyisocyanate, the polyamine, and the water to form the polyurea to form the coating, and encapsulating the liquid crystal with the coating;
    The manufacturing method of the liquid crystal microcapsule of Claim 12 which has these.
  14.   The method for producing liquid crystal microcapsules according to claim 12 or 13, wherein the polyamine is polyallylamine.
  15.   The method for producing liquid crystal microcapsules according to claim 10, wherein the liquid crystal is a cholesteric liquid crystal.
  16.   The method for producing a liquid crystal microcapsule according to claim 15, wherein a peak wavelength of selective reflection of the cholesteric liquid crystal is 600 to 800 nm.
  17.   The method for producing liquid crystal microcapsules according to claim 10, wherein the liquid crystal is a nematic liquid crystal.
  18.   The method for producing liquid crystal microcapsules according to claim 10, wherein the liquid crystal is a smectic liquid crystal.
  19.   A liquid crystal display element comprising the liquid crystal microcapsule according to claim 1 sandwiched between a pair of electrodes.
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