JP2003096454A - Microcapsule enclosing photosensitive liquid-crystal composition and reversible recording material comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microcapsule comprising a liquid-crystal composition having photosensitivity, and a reversible recording material comprising the microcapsule and capable of repeating recording/erasion of a color image. SOLUTION: This microcapsule encloses the photosensitive liquid crystal obtained by adding 0.5-10 pts.wt. of a photochromic compound having an azobenzene group based on 100 pts.wt. of the cholesteric liquid crystal having <=2,000 molecular weight and 30-150 deg.C glass transition temperature into a hollow wall membrane composed of a polymeric substance. The reversible recording material is prepared by forming a reversible recording layer containing the microcapsule on a support and is capable of writing information in a multicolor image display by irradiation with light during heating of the liquid crystal phase, fixing the image by quenching operation and further erasing the image by heating to an isotropic phase. Thereby, repetitive rewriting can be carried out.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a microcapsule containing a liquid crystal composition having photosensitivity, and a reversible recording material using the microcapsule. More specifically, by irradiating the liquid crystal phase with light when it is heated, it is possible to rewrite repeatedly by writing information in multicolor image display, fixing the color by a quenching operation, and erasing by heating the isotropic phase. Reversible recording material.

[0002]

2. Description of the Related Art Hitherto, as reversible recording materials, light-sensitive recording materials such as leuco dyes / developing / reducing agents, organic low molecular weight compounds / polymer resin matrix systems, and photochromic compounds such as spiropyran derivatives have been used. Recording materials are known.

When a leuco dye / developer / color-reducing agent type recording material is heated and then rapidly cooled, a color is developed by opening a lactone ring in the molecular structure of the leuco dye, and a coloured image is heated and then gradually cooled to give a lactone. The ring closes and disappears. Organic low molecular weight compound / polymer resin matrix recording materials, for example, recording materials using a combination of behenic acid and PVCA (vinyl chloride-vinyl acetate copolymer), switch between transparency / scattering of color image depending on heating temperature. be able to. However, none of these reversible recording materials can achieve both color recording and rewritable properties, since they can only display in a single color.

In recent years, a color thermosensitive recording material has been announced by a new method using a cholesteric liquid crystal compound (N. Tamaoki, et. Al., Advanced).
Materials, 9 (14), 1102 (199)
7)) This recording material is a recording material containing a cholesteric liquid crystalline compound having a molecular weight of 2000 or less and a glass transition temperature of 30 to 150 ° C., as described in JP-A-11-024027. The liquid crystal compound retains the reflected light based on the helical molecular arrangement in the cholesteric liquid crystal phase by rapidly cooling from the high temperature that forms the cholesteric liquid crystal to a temperature below its glass transition temperature. become. Therefore, it has been attracting attention as a color recording material that can be repeatedly rewritten.

Further, the same inventors as the above invention have proposed a rewritable full-color recording material in an optical mode and an image forming method in Japanese Patent Laid-Open No. 2000-89398. This is achieved by using a liquid crystalline composition having photosensitivity obtained by adding a photochromic compound such as an azobenzene derivative to the above cholesteric liquid crystalline compound. That is, in this recording material, when the cholesteric liquid crystalline compound in the recording layer exhibits a cholesteric liquid crystal phase at a temperature at which it is irradiated with image forming light, its reflection wavelength is continuously changed according to the irradiation light amount. The cholesteric liquid crystal compound is changed into a glass-like solid while keeping the reflected light by an operation of rapidly cooling the recording layer to a temperature not higher than the glass transition temperature of the cholesteric liquid crystal compound to form an image.

[0006]

In a recording material using such a cholesteric liquid crystal compound, when the liquid crystal compound is heated to a temperature at which its isotropic phase or liquid crystal phase is formed, the liquid crystal compound becomes a liquid crystal compound. Flowability occurs. Therefore, when this is used as a reversible recording material in which recording and erasing of images are repeatedly performed on the recording layer by a contact heating method such as a thermal head, the thickness of the recording layer is affected by pressure stress or the like. Problems such as unevenness and / or leakage of the liquid crystalline compound from the edges of the recording material occur. Further, the liquid crystal composition having photosensitivity may be decomposed or oxidized by ultraviolet rays and / or air to deteriorate its performance after long-term use. Furthermore, in the manufacturing process in which at least one of the transparent substrates is filled with the liquid crystalline compound, it is necessary to use an organic solvent and / or heat and melt to perform casting, which makes the manufacturing process complicated. there were.

The present invention makes microcapsules containing a liquid crystalline composition having photosensitivity in order to achieve both color recording and rewritable characteristics and to solve the above problems. Also, the present invention aims to provide a reversible recording material using the microcapsules.

[0008]

A microcapsule encapsulating a photosensitive liquid crystalline composition of the present invention comprises a hollow wall membrane formed of a polymeric substance and an inner side thereof,
And a core material composed of a light-sensitive liquid crystalline composition, wherein the light-sensitive liquid crystalline composition has a molecular weight of 2000 or less and 3 or less.
Cholesteric liquid crystal compound having a glass transition temperature of 0 to 150 ° C. and 0.5 to 10 parts by weight thereof.
It is a mixture with a part by weight of a photochromic compound. In the microcapsule of the present invention, the cholesteric liquid crystal compound is a compound represented by the following formula (I): Z-O-CO-R-CO-OY (I) [Z in the formula (I) and Y's each independently represent a cholesteryl group, a hydrogen atom or an alkyl group, provided that at least one of Z and Y represents a cholesteryl group, and R is a divalent group having 2 to 30 carbon atoms. Represents an organic group of].
In the microcapsule of the present invention, the divalent organic group represented by R in the formula (I) is a hydrocarbon group represented by the following formula (II): — (CH ₂ ) _m —C≡C— C≡C- (CH ₂ ) _n- (II) [In the formula (II), m and n each independently represent an integer of 1 or more, provided that the sum of m and n is 30.
Does not exceed ] It is preferable to be selected from In the microcapsule of the present invention, the photochromic compound is preferably selected from azobenzene derivatives. In the microcapsule of the present invention, the azobenzene derivative is a compound represented by the following formula (III): Z ¹ -O-CO-R ¹ -CO-Y ¹ -A (III) [In the formula (III) , A is a hydrogen atom or 1 to 20
Represents an organic group having 4 carbon atoms, Y ¹ represents an azobenzene group, Z ¹ represents a cholesteryl group, and R ¹ represents a divalent organic group containing 2 to 30 carbon atoms.] It is preferably selected. In the microcapsule of the present invention, the divalent organic group represented by R ¹ in the formula (III) is a hydrocarbon group represented by the following formula (IV): — (CH ₂ ) _{m 1} —C≡C -C≡C- (CH _{2) n1} - in (IV) [the formula (IV), m1 and n1, mutually independently each represent an integer of 1 or more, provided that the sum of m1 and n1 is It does not exceed 30]. In the microcapsule of the present invention, it is preferable that the polymer material for hollow wall membrane contains at least one selected from polyurea and polyurethane. In the microcapsule of the present invention, the microcapsule contains the cholesteric liquid crystal compound, the photochromic compound, and a polymer-forming organic raw material forming at least one of polyurea and polyurethane by polymerization.
It is dissolved and mixed in a water-insoluble organic solvent having a boiling point of 100 ° C. or lower, the organic solvent solution is emulsified and dispersed in an aqueous medium, and the emulsified dispersion is heated to volatilize and remove the organic solvent, and then the It is preferably prepared by polymerizing a polymer-forming organic raw material. The reversible recording material of the present invention has a support and a reversible recording layer formed thereon, and the reversible recording layer contains the microcapsules of the present invention.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional explanatory view of an example of the constitution of a reversible recording material using the microcapsules according to the present invention. In FIG. 1, a reversible recording material 1 of the present invention has photosensitivity obtained by adding a photochromic compound to a cholesteric liquid crystal compound in an organic polymer compound as a capsule wall material on a support 2. A reversible recording layer 5 including a large number of microcapsules 3 containing a liquid crystal composition and a binder 4 binding the microcapsules 3 is provided. It is preferable that the support has a function of absorbing visible light in order to observe the reflection color derived from the pitch of the helical molecular arrangement of the cholesteric liquid crystal phase. Therefore, it is preferable to provide the protective layer 6 having high transparency thereon.

In the microcapsule of the present invention, a photochromic compound is added to the cholesteric liquid crystal compound contained in the microcapsule, and the obtained liquid crystal composition having photosensitivity is formed by a polymer substance. It is contained inside the shell wall. The reversible recording layer containing the microcapsules is heated according to a desired image to bring the cholesteric compound into a cholesteric liquid crystal phase,
By irradiating this with light through the transparent protective layer, the color of the reflected light is shifted to the short wavelength side in accordance with the amount of irradiation light. After that, when the recording layer is rapidly cooled to a temperature below the glass transition temperature of the cholesteric liquid crystal compound, it becomes a glassy solid (cholesteric glass phase) while maintaining the helical molecular arrangement of the cholesteric liquid crystal phase, and the helical shape of the cholesteric liquid crystal phase. It becomes possible to observe the reflection color derived from the pitch of the molecular arrangement.

The image information formed on the recording layer of the recording material of the present invention is recorded once and then erased by heating the whole or a part of the image information above the melting point of the liquid crystalline composition having photosensitivity. Further, new image information can be optically recorded on the recording layer from which the image has been erased by the above method, and this recording / erasing can be repeated any number of times.

In the reversible recording material of the present invention, the optical energy of the photochromic compound can be obtained by simply irradiating the photochromic compound mixed with the cholesteric liquid crystal compound with light having low energy for causing a photoisomerization reaction of the azobenzene group of the photochromic compound. Image information can be written by partially changing the properties, and the image information can be preserved by fixing its optical properties by a quenching operation.

For example, when a cholesteric liquid crystal compound having an optical property of selectively reflecting light of a certain wavelength in the visible region is in a liquid crystal state, if it is partially irradiated with light according to a desired image, The cholesteric liquid crystalline compound distributed in the portion not irradiated with is still retaining the selective reflectivity for light having a wavelength in the initial visible region, while the cholesteric liquid crystalline compound in the portion irradiated with light is retained. The compound changes so as to exhibit a reflection color having a shorter wavelength than that of the unirradiated portion, depending on the irradiation light amount. By rapidly cooling the liquid crystal state to a glass transition temperature or lower, the liquid crystal state can be fixed to the glass and the coloring state can be fixed. As an example of this, a color image in which the unirradiated portion is red and the light-irradiated portion is blue can be produced on the recording layer.

Further, if a recording layer containing a cholesteric liquid crystalline compound having a selective reflection characteristic in the infrared region is partially irradiated with light according to a desired image in its liquid crystal state,
The unirradiated part does not reflect visible light, so it is kept in a transparent state, and the irradiated part shows a reflection color of a shorter wavelength than the unirradiated part, that is, a visible color, depending on the irradiation light amount. Like When this colored state is fixed to glass by a rapid cooling operation, a color image with a colorless background can be obtained. At this time, when a black light absorbing layer is provided on the back surface of the recording layer, color image information with a black background can be recorded.

In particular, in the recording material of the present invention, the cholesteric liquid crystal compound and the photochromic compound encapsulated in the microcapsules have common properties such as molecular weight and functional groups, so that they are thermally stable in a glassy solid. Therefore, it is excellent in stability when the recorded image information is stored for a long period of time.

Further, in the reversible recording material of the present invention,
By heating the recording layer, the liquid crystal composition having photosensitivity is brought into a fluid state when it is in an isotropic phase or a liquid crystal phase. In such a fluid state, even when image recording and erasing are repeatedly performed, the liquid crystal composition having photosensitivity is contained in the microcapsules, and therefore the thickness of the recording layer is affected by pressure stress. There is no unevenness, and there is no problem such as leakage of the liquid crystalline composition having photosensitivity from the edge of the recording material.

Further, in the microcapsule of the present invention, since the liquid crystal composition having photosensitivity is encapsulated by the wall material of the polymer substance, the direct contact with the outside air is blocked, and therefore, for a long period of time. Even when used, it hardly oxidizes, decomposes and deteriorates due to air or ultraviolet rays, and can exhibit excellent performance in terms of long-term durability of the reversible recording material. Moreover, in the recording material of the present invention, a liquid crystal composition having photosensitivity is encapsulated in microcapsules, so that a recorded image has a short wavelength of a selective reflection wavelength generated by observing the image obliquely with respect to the recording surface. There are advantages such that shift shift can be suppressed, and viewing angle dependence of a recorded image can be suppressed.

Further, the liquid crystal composition having photosensitivity used in the present invention can be treated as ordinary solid fine particles by encapsulating it in microcapsules. For this reason, it is not necessary to use an organic solvent or heat-melt and cast to form the reversible recording layer, and the reversible recording layer is formed by a general coating method using an aqueous paint. can do. Therefore, the manufacturing process of the reversible recording layer can be significantly simplified.

The types of cholesteric liquid crystal compounds that can be used in the present invention have a molecular weight of 2000 or less, preferably 500 to 1500, as long as they can fix the cholesteric reflection color.
And has a glass transition temperature of 30 to 150 ° C.,
There is no particular limitation as long as it is preferably 50 to 110 ° C.

In the reversible recording material of the present invention, when the molecular weight of the cholesteric liquid crystalline compound exceeds 2000,
There is an inconvenience that the time required for recording and erasing an image becomes long. If the glass transition temperature is lower than 30 ° C, the recorded image may be discolored with time.
If the temperature exceeds 150 ° C., there arises a disadvantage that excessive heat energy is required for recording or erasing an image.

The chemical structure of the cholesteric liquid crystalline compound preferably used in the present invention is not particularly limited, but when the compound represented by the following formula (I) is used,
A clear color recorded image can be obtained. Z-O-CO-R-CO-OY (I) [In the above formula (I), Z and Y are each independently,
Represents a cholesteryl group, a hydrogen atom or an alkyl group, provided that at least one of Z and Y represents a cholesteryl group, and R represents a divalent hydrocarbon group having 2 to 20 carbon atoms].

Further, the divalent hydrocarbon group represented by R in the above formula (I) is preferably selected from hydrocarbon groups represented by the following formula (II). _{- (CH 2) m -C≡C-} C≡C- (CH 2) n - (II) [In the formula (II), m and n are independently of one another each represent an integer of 1 or more, However, the sum of m and n is 3
It does not exceed 0. ]

Preferred examples of the cholesteric liquid crystal compound having the above chemical structure include 10,12-docosadiyne dicarboxylic acid dicholesteryl ester, 8,12.
-Eicosadiene dicarboxylic acid dicholesteryl ester, eicosane dicarboxylic acid dicholesteryl ester,
Mention may be made of 10,12-pentacosadiyne dicarboxylic acid cholesteryl ester, dodecadicarboxylic acid dicholesteryl ester, and 12,14-hexacosadiyne dicarboxylic acid dicholesteryl ester.

As the cholesteric liquid crystal compound used in the present invention, in addition to the above, main chain type liquid crystals such as polypeptides, polyesters and polyamides, side chain type liquid crystals such as polyacrylates and polysiloxanes, cellulose derivatives and the like. It is also possible to select and use from a rigid main chain type liquid crystal and the like. Further, the cholesteric liquid crystal compound used in the present invention may be used in a single kind, or
It is also possible to use a mixture of a plurality of types as appropriate.

In the present invention, a photochromic compound is added to the cholesteric liquid crystal compound to form a liquid crystal composition having photosensitivity. The addition amount of this photochromic compound is the cholesteric liquid crystal compound 1
0.5 to 10 parts by weight with respect to 00 parts by weight, and 0.
It is preferably 5 to 7.5% by weight. If the amount of the photochromic compound added is less than 0.5 parts by weight, the sufficient photosensitivity effect required by the recording material of the present invention cannot be obtained. On the other hand, if the amount of addition exceeds 10 parts by weight, the color developability of the cholesteric liquid crystalline compound may be hindered.

As the photochromic compound that can be used in the present invention, various conventionally known compounds can be used. Such photochromic compounds are
“Photochromism-techniques of Chemistry Vol. II
I ”, Glenn H. Brown, Wiley Interscience, 1971
Examples thereof include azobenzene derivatives, indigo derivatives, fluquid derivatives, spiropyrans, diallylethenes and the like. In particular, it is preferable to use a photochromic compound, such as an azobenzene derivative, whose molecular size and morphology greatly change before and after photoreaction.

When the cholesteric liquid crystal compound and the photochromic compound have commonalities in their molecular weights and functional groups, the composition has high thermal stability in a glassy solid and the recorded image information is Excellent stability when stored for a long time. Therefore, the most suitable photochromic compound in the present invention is selected from the azobenzene derivatives, particularly the compound represented by the following formula (III). ^{Z 1 -O-CO-R 1} -CO-Y 1 -A (III) In the above formula (III), A is or a hydrogen atom 20
Represents an organic group having a carbon atom (the organic group represented by A includes an aliphatic group, an aromatic group, or a hydrocarbonoxy group), Y ¹ represents an azobenzene group, and Z ¹
Represents a cholesteryl group, R ¹ represents a divalent organic group containing 2 to 30 carbon atoms, 2 represented by R ¹
Valuable organic groups include aliphatic groups and aromatic groups.

2 represented by R ¹ in the above formula (III)
The valent organic group is preferably a hydrocarbon group represented by the following formula (IV). _{- (CH 2) m1 -C≡C-} C≡C- (CH 2) n1 - in (IV) above formula (IV), m1 and n1 are the independently of one another each represent an integer of 1 or more, provided that , M1 and n1 do not exceed 30.

Specific examples of the photochromic compound in the present invention include compounds represented by the following formulas (V), (VI) and (VII).

[Chemical 1] (In the formula (V), n2 and m2 represent an integer of 4 to 10, preferably an integer of 8, and Z ¹ represents a cholesteryl group.)

[Chemical 2] (In the formula, n3 represents an integer of 10 to 22, preferably 20 and Z ¹ represents a cholesteryl group.)

[Chemical 3] (In the formula, R ² has 1 to 16 carbon atoms, preferably,
7 and 12 represent an alkyl group, n4 and m4 are
Each independently represents an integer of 4 to 10, preferably 8, and Z ¹ represents a cholesteryl group. )

The compounds represented by the above formulas (V), (VI) and (VII) can be produced by the method described in Japanese Patent Application No. 2000-42966.

In the microcapsule of the present invention, a liquid crystalline composition having a photofunctionality obtained by adding a photochromic compound to the above cholesteric liquid crystalline compound is provided inside a hollow wall film formed of a polymer substance. It is included.

The microcapsules according to the present invention can be prepared by various known methods. Generally, the above-mentioned photo-sensitive liquid crystalline composition is dissolved in an organic solvent, if necessary, to obtain a core agent. It is prepared by a method of emulsifying and dispersing a solution (oily liquid) in an aqueous medium to form a hollow wall membrane made of a polymer substance around oily droplets. Specific examples of the polymer substance that forms the hollow wall film of the microcapsule include, for example, polyurethane resin, polyurea resin, polyamide resin, polyester resin, polycarbonate resin, aminoaldehyde resin, melamine resin, polystyrene resin, styrene-methacrylate copolymer resin. , Styrene-acrylate resin, gelatin, polyvinyl alcohol and the like. Among these, microcapsules having a hollow wall membrane made of polyurethane and polyurea resin or aminoaldehyde resin are particularly preferably used because they have excellent heat resistance. More preferably, microcapsules having a hollow wall film made of polyurethane and polyurea resin are used.

A hollow wall film is formed from at least one polymer substance selected from polyurea and polyurethane used in the present invention, and microcapsules containing a liquid crystal composition having photosensitivity inside thereof are prepared. As a method, for example, a liquid crystalline composition having photosensitivity and a boiling point of 1
It is dissolved in a low boiling point water-insoluble organic solvent at a temperature of 00 ° C. or lower, and a polymer-forming raw material, for example, a polyvalent isocyanate compound alone, or a mixture of a polyvalent isocyanate and a polyol that reacts with the polyvalent isocyanate, or a polyvalent isocyanate is added to the solution. ,
Polyol, biuret, or an adduct with isocyanuric acid is added, and this mixture is emulsified and dispersed in an aqueous medium containing a protective colloid substance such as polyvinyl alcohol, and if necessary, reactivity such as polyamine is added. After mixing the substances, the emulsified dispersion is heated to volatilize and remove the organic solvent in the emulsified particles, and then the polymer-forming raw material is polymerized, for example, a wall film made of polyurea or polyurethane is emulsified particles It is possible to use a method of forming microcapsules by forming a liquid crystal composition having photosensitivity inside the hollow wall film.

In order to sufficiently volatilize and remove the organic solvent from the emulsified particles in the step of preparing the microcapsules,
The conditions may be experimentally set in consideration of the type of solvent, the emulsification and dispersion conditions, the compounding ratio of the liquid crystal composition having photosensitivity and the solvent, and the like.

As the polymer-forming raw material used for forming the microcapsules, a mixture of a polyamine compound forming a polyurea and a polyvalent isocyanate compound, a mixture of a polyamine compound and a carbonic acid ester compound, a mixture of a polyamine compound and bisurethane are used. , A mixture of polyamine and urea, a compound of a polyvalent isocyanate compound forming a polyurethane and a polyol, an adduct of a polyvalent isocyanate and a polyol, an isocyanurate body of a polyvalent isocyanate, and the like can be used.

Examples of the polyvalent isocyanate compound used as the polymer-forming raw material include m-phenylene diisocyanate, p-phenylene diisocyanate,
2,6-Tolylene diisocyanate, 2,4-Tolylene diisocyanate, Naphthalene-1,4-diisocyanate, Diphenylmethane-4,4'-diisocyanate, 3,3'-Dimethyldiphenylmethane-4,4'-
Diisocyanate, xylylene-1,4-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2- Diisocyanates such as diisocyanate and cyclohexylene-1,4-diisocyanate,
Triisocyanates such as 4,4 ', 4 "-triphenylmethane triisocyanate and toluene-2,4,6-triisocyanate, 4,4'-dimethyldiphenylmethane-2,2', 5,5'-tetraisocyanate And the like, etc. Examples of adducts of polyvalent isocyanates and polyols include trimethylolpropane adduct of hexamethylene diisocyanate, trimethylolpropane adduct of 2,4-tolylene diisocyanate, and xylylene diisocyanate. Isocyanate prepolymers such as trimethylolpropane adduct of styrene and tolylene diisocyanate of hexanetriol can be used, and addition of polyvalent isocyanate compounds such as hexamethylene diisocyanate with biuret. , Polyvalent isocyanate compound, for example hexamethylene diisocyanate, also adduct of isocyanuric acid, it may be used as a polymer-forming material of the present invention.

Examples of the polyol compound used as the polymer-forming raw material include ethylene glycol,
1,3-propanediol, 1,4-butanediol,
1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, propylene glycol, 2,3-dihydroxybutane, 1,2-dihydroxybutane, 1,3-dihydroxy Butane, 2,2-dimethyl-1,3-propanediol, 2,4-pentanediol, 2,5-hexanediol, 3-methyl-1,5-pentanediol, 1,
4-cyclohexanedimethanol, dihydroxycyclohexane, diethylene glycol, 1,2,6-trihydroxyhexane, phenylethylene glycol, 1,
Aliphatic polyols such as 1,1-trimethylolpropane, hexanetriol, pentaerythritol and glycerin, aromatic compounds such as 1,4-di (2-hydroxyethoxy) benzene and 1,3-di (2-hydroxyethoxy) benzene Condensation product of polyhydric alcohol and alkylene oxide, p-xylylene glycol, m-xylylene glycol, α, α′-dihydroxy-p-diisopropylbenzene, 4,4′-dihydroxydiphenylmethane, 2- (p, p ′ -Dihydroxydiphenylmethyl)
Benzyl alcohol, 4,4'-isopropylidene diphenol, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide,
Examples thereof include ethylene oxide adduct of 4,4'-isopropylidenediphenol, propylene oxide adduct of 4,4'-isopropylidenediphenol, and acrylate having a hydroxy group in the molecule such as 2-hydroxyacrylate.

Of course, the polyvalent isocyanate compound, the adduct of polyvalent isocyanate and polyol, the polyol compound and the like are not limited to the above compounds,
Further, these may be used alone or in combination of two or more, if necessary. Among the polyvalent isocyanate compounds used in the present invention or the adducts of the polyvalent isocyanate compounds and the polyol compounds, it is particularly preferable to use one having three or more isocyanate groups in the molecule.

Examples of the polyamine compound used as the polymer-forming raw material of the present invention include ethylenediamine, trimethylenediamine, tetramethylenediamine,
Pentamethylenediamine, hexamethylenediamine, p
-Phenylenediamine, m-phenylenediamine, piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 2-hydroxytrimethylenediamine, diethylenetriamine, triethylenetriamine, triethylenetetramine, diethylaminopropylamine, tetraethylenepentamine, epoxy Examples thereof include amine adducts of compounds. Further, within the range that does not impair the object of the present invention,
A polymer substance other than the above may be contained.

The organic solvent used for preparing the microcapsules preferably has a boiling point of 100 ° C. or lower, more preferably 80 ° C. or lower, and is hydrophobic. For example, such low-boiling point hydrophobic (water-insoluble) organic solvents include butyl chloride (boiling point 78 ° C.) and ethylidene chloride (see
7 ° C.), propyl chloride (46 ° C. same), methylene chloride (42 ° C. same), ethyl acetate (77 ° C. same), methyl acetate (5 same)
7 ° C) and the like. Acetone (56
C.), methanol (at 65.degree. C.) and the like have high compatibility with water, and thus the emulsified state of the obtained emulsion may be unstable, which is not preferable.

There are no particular restrictions on the amount of the organic solvent used, which should be adjusted in a timely manner depending on the type and amount of the liquid-crystalline composition having photosensitivity to be used, and the type of organic solvent. Since it is preferable that the emulsion-dispersed droplets are in a sufficiently stable state, when forming a polyurethane or a polyurea resin, an organic solvent, a liquid crystal composition having photosensitivity, and a microcapsule wall film material are added together. On the other hand, it is preferable that the proportion of the organic solvent is generally adjusted within the range of about 10 to 95% by weight.

The weight ratio of the liquid crystalline composition having photosensitivity to the polymer in the microcapsules does not deteriorate the storage stability of the liquid crystalline composition having photosensitivity in the microcapsules due to long-term storage. In addition, since the shape of the reversible recording material is not deformed by repeated use, it is preferable to use a large amount of the wall film forming material as compared with a normal microcapsule. From these points, the total weight of the microcapsule, The content of the liquid crystal composition having photosensitivity is preferably 10 to 95% by weight, and 50
It is more preferably ˜95 wt%.

In the present invention, as the emulsifier (protective colloid agent) used for preparing the microcapsules, polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, modified polyvinyl alcohol such as sulfo group-modified polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, styrene- Water-soluble synthetic polymer compounds such as maleic anhydride copolymer salts and their derivatives can be used. Other surfactants, defoaming agents and the like may be used together with the emulsifier. The amount of the emulsifier used in preparing the microcapsules is not particularly limited, but generally 1 to 50 with respect to the weight of the microcapsules.
The amount is preferably wt%, more preferably about 3 to 30 wt%.

In the microcapsules used in the present invention, in addition to the liquid crystal composition having photosensitivity, an ultraviolet absorber, an antioxidant, an oil-soluble fluorescent dye, a release agent, etc. may be added if necessary. It may be added. Moreover, when polymerizing in the preparation of microcapsules, a tin compound, a polyamide compound, an epoxy compound, a polyamine compound or the like may be used in combination as a reaction accelerator. In addition, when using a polyamine compound, it is preferable to use an aliphatic polyamine compound from the viewpoint that light resistance is not deteriorated.

The particle size of the microcapsules in the present invention is preferably about 0.5 to 100 μm, more preferably 5 to 50 μm. If the average particle size is too small, it becomes difficult to form a helical molecular arrangement in the cholesteric liquid crystal phase,
This leads to a decrease in color density and color purity. On the other hand, the giant particles deteriorate the surface property of the recording material, which causes a decrease in color development sensitivity.

The reversible recording layer contains a binder in addition to the above-mentioned microcapsules of the liquid crystal composition having photosensitivity. Examples of the binder include polyvinyl alcohol and its derivatives, starch and its derivatives, hydroxymethyl cellulose and hydroxy. Cellulose derivatives such as ethyl cellulose, hydroxypropyl cellulose, methyl cellulose, ethyl cellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acrylic acid ester copolymer, acrylamide-acrylic acid ester-methacrylic acid ester copolymer, styrene-maleic anhydride. Water-soluble polymer materials such as copolymers, isobutylene-maleic anhydride copolymers, casein, gelatin and their derivatives, and polyvinyl acetate, polyurethane, polyacrylic , Polyacrylic acid ester, vinyl chloride-vinyl acetate copolymer, polybutylmethacrylate, ethylene-vinyl acetate copolymer emulsion, styrene-butadiene copolymer, styrene-butadiene-acrylic copolymer water-insoluble Polymer latex or the like can be used. In the reversible recording layer, organic and inorganic pigments, spacer particles, cross-linking agents, waxes, metal soaps, organic dyes, colored pigments, fluorescent dyes, oil repellents, defoamers, and viscosity, as long as the effects of the present invention are not impaired. Various additives such as regulators and antioxidants can be used. However, it is desirable that these materials have no absorption in the wavelength region of the selective reflection light to be recorded. The content of the liquid crystal composition microcapsules having photosensitivity in the reversible recording layer is preferably 50% by weight or more, and 6
It is more preferably 0 to 90% by weight. The content of the microcapsules of the liquid crystal composition having photosensitivity is 50.
When the content is less than the weight%, the reflectance of the recorded image decreases.
The content of the binder in the reversible recording layer is preferably 10 to 40% by weight.

Further, in order to obtain a clear printed image, as the coating amount of the reversible recording layer, and more preferably about 5 to 50 g / m ² is preferably 5 to 30 g / m ^2. When the coating amount of the recording layer is less than 5 g / m ² , sufficient selective reflection cannot be obtained, so that the recorded image lacks sharpness. On the other hand, when the coating amount exceeds 50 g / m ² , white turbidity of the recording layer becomes strong, and the recorded image becomes blurry and turbid.

The type, shape and size of the support material used in the present invention are not particularly limited, and include paper, polyolefin synthetic paper, synthetic fiber paper, non-woven fabric, PET, PES,
It is a film made of a synthetic resin such as polyether imide, a sheet such as glass or a plate, and may be flat or curved, and may be flexible or rigid. However, by using a flexible sheet material, it is difficult to break even if it is bent, and it is possible to bind multiple sheets into a file and carry it easily like a paper, so it is possible to handle more like paper. It is preferably used.

In the present invention, the function of absorbing visible light transmitted through the recording layer is recorded in order to more clearly observe the reflected color derived from the pitch of the helical molecular arrangement of the cholesteric liquid crystal phase. It is effective to have it on the back side of the layer. For example, it can be achieved by applying a black paint between the recording layer and the support to provide a light absorbing layer. When a transparent support is used, a light absorption layer can be formed on the surface opposite to the recording layer. Further, a black pigment or the like may be mixed in the support to give the support itself a light absorbing function.

As such a light-absorbing layer, for example, a recording material of a combination of a leuco dye / developing agent is used to obtain a cholesteric reflection color of the recording layer by heating means, and at the same time, a recorded image is obtained. The back surface of the can have a function of absorbing visible light. That is, it is possible to form a recorded image of any color on a white background. In particular, by using a reversible thermosensitive recording type leuco dye / developing / reducing agent capable of repeating coloring and decoloring as the light absorbing layer, versatility as a reversible recording material is further widened.

If necessary, a light reflection layer, a heat reflection layer,
A light (laser beam) absorbing layer may be provided between the recording layer and the support.

In the present invention, a magnetic recording layer may be provided on the surface (back surface) of the support on which the recording layer is not provided, or between the support and the recording layer. As the magnetic recording layer, a magnetic recording layer conventionally used for a magnetic ticket, a prepaid card, a magnetic commuter pass, or the like can be used. The reversible recording material of the present invention is also suitable for use as a display medium for a card in which an IC chip or the like is embedded.

In the present invention, an undercoat layer used in known heat-sensitive recording materials can also be used. Particularly when paper is used as the support, it is desirable to provide an undercoat layer between the light absorbing layer and the paper base, for example. Incorporating a pigment having a high porosity such as silica or calcined kaolin, or a plastic pigment, hollow particles, or a foam into the undercoat layer is effective in improving thermal efficiency.

In the reversible recording material of the present invention, it is preferable to provide a protective layer on the recording layer. Such a protective layer is highly transparent and can be appropriately selected from materials that do not impair the storage stability of the recording layer, and the thickness thereof is 0.5 to 3.
It is preferably 0 μm, more preferably 1 to 10
μm.

In the present invention, a resin layer cured by electron beams or ultraviolet rays may be provided on the recording layer or on the protective layer. Examples of the resin cured by an electron beam include JP-A-58-177392 and JP-A-58-177392.
It is described in the official gazette. Into such a resin, a non-electron beam curable resin, a pigment, and additives such as a defoaming agent, a leveling agent, a lubricant, a surfactant, a plasticizer and the like can be appropriately added. The resin layer cured by electron beams or ultraviolet rays is preferably coated so that the coating amount after drying is 0.5 to 30 g / m ^2, and more preferably 1 to 10 g / m ^2. To apply.

Further, the protective layer of the recording material of the present invention is PE
A plastic film having excellent transparency and heat resistance such as T, PES, and polyetherimide may be laminated on the recording layer. In this case, the thickness of the plastic film should be 1 so as not to hinder the heat transfer to the recording layer.
It is preferably about 30 μm.

In the present invention, a recording material can be printed with UV ink, flexo ink, etc., for example, a tint block can be printed. In this case, the printing may be performed on any layer such as the recording layer, the protective layer, the electron beam curable resin layer, the ultraviolet curable resin layer, or the plastic film.

As a method for forming an image using the reversible recording material of the present invention, the temperature of the recording layer is adjusted to a temperature at which the liquid crystal composition encapsulated in microcapsules and having photosensitivity exhibits a cholesteric liquid crystal phase. An image can be formed by heating and irradiating the recording layer with light through the transparent protective layer, and then rapidly cooling to a glass transition temperature or lower to fix and store the image information.
On the other hand, photoirradiation at room temperature causes photoisomerization of the photochromic compound, and immediately thereafter, the liquid crystalline composition having photosensitivity is heated to a temperature at which it exhibits a liquid crystal phase, and then rapidly cooled to a temperature below the glass transition temperature It is also possible to write image information by doing so.

In the recording material of the present invention, the light source for causing the photoisomerization reaction of the azobenzene group of the photochromic compound is a mercury lamp, a xenon lamp, a tungsten lamp, a laser or the like, which is appropriately selected according to the absorption wavelength of the photochromic compound. can do.

The reversible recording material of the present invention is cooled rapidly from the liquid crystal phase of the liquid crystalline composition having the photosensitivity of the reversible recording layer to the glass transition temperature or lower by a quenching operation after heating to fix an image. The fixation of this image is believed to be due to the phase transition from the cholesteric liquid crystal phase to the glass phase.

Any heating means can be used for recording on the recording material of the present invention as long as it can heat the temperature of the reversible recording layer to the melting point temperature or higher of the liquid crystalline composition having photosensitivity. Can also be used. Examples thereof include various known heating means such as a thermal head, a heating roll, a heating stamp, a hot plate, and a laser beam.

On the other hand, as the cooling means, any means may be used as long as it can contact the recording material immediately after heating and radiate heat. For example, it can be carried out by immersion in a cooling liquid or a cooling gas atmosphere, or by contact with a cooling gas flow or a surface of a cooling solid. However,
The heating means and the cooling means are not limited to these.

The cooling rate for fixing the image is 1 ° C.
/ Sec or more, more preferably 10 ° C
/ Sec or more, more preferably 50 ° C / sec or more. 1
If the cooling rate is less than ° C / sec, the color of the image tends to change at the fixing stage. For the same reason, it is desirable to shorten the time from image formation to fixing. Depending on the ambient temperature and the type of cholesteric liquid crystal compound used, if left at room temperature for 10 seconds or longer, the color of the image may partially change before fixation.

[0064]

The present invention will be described in more detail with reference to the following examples, which should not be construed as limiting the invention. Unless otherwise specified, “part” and “%” indicate “part by weight” and “% by weight”, respectively.

Example 1 <Preparation of Microcapsule Dispersion Liquid (A) Encapsulating Liquid Crystalline Composition Having Photosensitivity> As a cholesteric liquid crystal compound, 10,12-docosadiyne dicarboxylic acid dicholesteryl ester (molecular weight: : 1099.8, glass transition temperature: 80 ° C.) 50 parts by weight, and as a photochromic compound, a compound of the following formula (VIII) (molecular weight: 10
80) 0.5 part by weight was used.

[Chemical 4] A mixture of the cholesteric liquid crystal compound and the photochromic compound is dissolved in 200 parts by weight of methylene chloride,
To this solution, a 3: 1 adduct of trimethylolpropane with xylene diisocyanate (Takenate D-110N, manufactured by Takeda Pharmaceutical Co., Ltd.) as a polymer substance for forming a wall film material 10
Parts by weight, and then gradually adding this solution to 500 parts by weight of a 3% aqueous polyvinyl alcohol solution,
This mixture is rotated with a homomixer at a rotation speed of 1000 rp.
It was emulsified and dispersed by stirring m. Then, the obtained emulsion was heated to a temperature of 45 ° C. and kept for 2 hours to evaporate and remove methylene chloride. The obtained emulsion is heated to 60 ° C. and the organic polymer is subjected to a curing reaction for 4 hours, thereby dispersing microcapsules containing a liquid crystalline composition having an average particle size of 15 μm and having photosensitivity. Liquid (A)
Got

Example 2 <Preparation of Microcapsule Dispersion Liquid (B) Encapsulating Liquid Crystalline Composition Having Photosensitivity> In Example 1 above,
As the photochromic compound, a liquid crystal composition having photosensitivity was obtained in the same manner as in Example 1 except that the addition amount of the compound of the formula (VIII) was changed to 2.5 parts by weight. A microcapsule dispersion liquid (B) having an average particle diameter of 16 μm was obtained.

Example 3 <Preparation of Microcapsule Dispersion Liquid (C) Encapsulating Liquid Crystalline Composition Having Photosensitivity> In Example 1 above,
As a photochromic compound, a liquid crystal composition having photosensitivity was prepared in the same manner as in Example 1 except that the addition amount of the compound of the formula (VIII) was changed to 5 parts by weight. An encapsulated microcapsule dispersion liquid (C) having an average particle size of 16 μm was obtained.

[Example 4] <Preparation of reversible recording material (D) using microcapsules> A black pigment was kneaded in as a support and had a thickness of 75 μm.
Polyetherimide (PEI) film (Sumilite FS-1401B (trademark), manufactured by Sumitomo Bakelite Co., Ltd.)
Was used. A coating material for a recording layer comprising 80 parts of the microcapsule dispersion liquid (A) (solid content concentration 15%) and 6 parts of styrene-butadiene latex (solid content concentration 50%) has a coating amount of 20 g / m after drying. ² was applied onto the surface of the support and dried to form a reversible recording layer. Further, an ultraviolet curable varnish was applied on the recording layer so that the coating amount was 3 g / m ^2, and this was irradiated with ultraviolet rays to form a transparent protective layer. Since the cholesteric liquid crystal compound in the microcapsules was translucent, a reversible recording material (D) having a black background color of the PEI film as a support was obtained.

[Example 5] <Preparation of reversible recording material (E) using microcapsules> In place of 80 parts of the microcapsule dispersion liquid (A) (solid content concentration 15%) in Example 4, the microcapsules were used. A reversible recording material (E) was obtained in the same procedure as in Example 4 except that 80 parts of the capsule dispersion liquid (B) (solid content concentration 15%) was used.

[Example 6] <Preparation of reversible recording material (F) using microcapsules> In place of 80 parts of the microcapsule dispersion liquid (A) (solid content concentration 15%) in Example 4 described above, microcapsules were used. A reversible recording material (F) was obtained in the same procedure as in Example 4 except that 80 parts of the capsule dispersion liquid (C) (solid content concentration 15%) was used.

<Evaluation of Image Formation> For the reversible recording materials (D) to (F) using the microcapsules containing the liquid crystalline composition having photosensitivity prepared in Examples 4 to 6, a reversible recording medium was used. After heating at 0 ° C. to melt the liquid crystalline composition in the microcapsules, subsequently, 9
The recording medium was placed on a hot stage kept at 5 ° C. Ultraviolet light from a mercury lamp was partially irradiated therethrough for 30 seconds through a mask (irradiation energy 100 mJ / c
m ² ), the cis-trans isomerization of the azobenzene group was changed until it reached a steady state. The unirradiated part remained as it was and no color change was observed, but the color tone of the irradiated part shifted to the shorter wavelength side. After the ultraviolet irradiation, the recording material was immersed in ice water and rapidly cooled to 0 ° C. to fix the color development. Table 1 shows the measurement results of the peak wavelength λmax of the reflection band of the ultraviolet-irradiated part and the unirradiated part of the obtained reversible recording material.

[0072]

[Table 1]

<Evaluation of Repeated Durability> A printing test was conducted on each of the reversible recording materials (E) to (F) of Examples 4 to 6.
And, the operation of heating the recording material to a temperature of 130 ° C. or higher to change the liquid crystalline composition to an isotropic phase and erase the liquid crystalline composition is performed.
Repeatedly applied. As a result, on the surface of the reversible recording material,
Almost no damage such as scratches and roughness was observed, and there was almost no change in the thickness of the recording material. In addition, deterioration of color development and decolorization was not observed.

[0074]

INDUSTRIAL APPLICABILITY The microcapsule of the present invention contains a liquid crystal composition having photosensitivity, which is obtained by adding a photochromic compound to a cholesteric liquid crystal compound, and the reversible recording material of the present invention is Including a capsule in the recording layer, by heating the liquid crystal composition and irradiating it with light when it is in the liquid crystal phase, multi-color image information can be written, and a rapid cooling operation is performed. By doing so, the image can be fixed.
Further, by heating a recording material having a fixed image to change the liquid crystalline composition to an isotropic state, the image can be erased, and thus rewriting can be repeated. Since the liquid crystalline composition is encapsulated in microcapsules, even if it is subjected to repeated printing and erasing operations, its performance is less likely to deteriorate, and the liquid crystalline composition is microencapsulated. Since it can be treated as ordinary solid fine particles, the recording layer can be formed by the coating method used in general water-based paints, and the manufacturing method thereof can be greatly simplified.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view of one embodiment of a reversible recording material containing a microcapsule of the present invention.

[Explanation of symbols]

1 ... Reversible recording material 2 ... Support 3 ... Microcapsules containing light-sensitive liquid crystalline composition 4 ... Binder 5 ... Reversible recording layer 6 ... Transparent protective layer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09K 9/02 B41M 5/18 101A 4H027 G02F 1/13 102 112 500 5/26 102 G03C 1/73 503 B01J 13/02 A (72) Inventor Nobuyuki Tamaki 1-1-1 East, Tsukuba City, Ibaraki Prefecture Independent Administrative Law Institute of Industrial Science and Technology Tsukuba Center (72) Inventor Hiroo Matsuda 1-1-1 East, Tsukuba City, Ibaraki Prefecture F-term in the Tsukuba Center of the National Institute of Advanced Industrial Science and Technology (reference) 2H026 AA01 2H088 EA62 GA03 GA10 MA20 2H111 HA07 HA09 HA13 HA35 2H123 AA00 AA01 AA04 4G005 AA01 BA01 BB08 BB09 BB12 BB13 BB13 BB25 DC11X DC41X DD38Z080X07 BE02 DM02

Claims (9)

[Claims] 1. A hollow wall film formed of a polymer substance, and a core material which is encapsulated inside the hollow wall film and is composed of a photosensitive liquid crystalline composition, wherein the photosensitive liquid crystalline composition is Cholesteric liquid crystalline compound having a molecular weight of 2000 or less and a glass transition temperature of 30 to 150 ° C., and 0.5 to 1 per 100 parts by weight thereof.
A mixture with 0 parts by weight of a photochromic compound,
A microcapsule encapsulating a light-sensitive liquid crystal composition characterized by the above. 2. The cholesteric liquid crystal compound is a compound represented by the following formula (I): Z—O—CO—R—CO—O—Y (I) [Z and Y in the above formula (I) are , Each independently represent a cholesteryl group, a hydrogen atom or an alkyl group, provided that at least one of Z and Y represents a cholesteryl group, and R represents a divalent organic group having 2 to 30 carbon atoms. Represents a group], The microcapsule according to claim 1. 3. The divalent organic group represented by R in the formula (I) is a hydrocarbon group represented by the following formula (II): — (CH ₂ ) _m —C≡C—C≡ _{C- (CH 2) n - (} II) [in the formula (II), m and n are independently of one another each represent an integer of 1 or more, provided that the sum of m and n is 30
Does not exceed ] The microcapsule of Claim 2 selected from these. 4. The microcapsule according to claim 1, wherein the photochromic compound is selected from azobenzene derivatives. 5. The azobenzene derivative is represented by the following formula (II
Compound represented by I): Z ¹ -O-CO-R ¹ -CO-Y ¹ -A (III) [In the formula (III), A is a hydrogen atom or 1 to 20]
Represents an organic group having 4 carbon atoms, Y ¹ represents an azobenzene group, Z ¹ represents a cholesteryl group, and R ¹ represents a divalent organic group containing 2 to 30 carbon atoms.] The microcapsule according to claim 4, which is selected. 6. The divalent organic group represented by R ¹ in the formula (III) is a hydrocarbon group represented by the following formula (IV): — (CH ₂ ) _m1 —C≡C—C ≡C- (CH _{2) n1} - in (IV) [the formula (IV), m1 and n1, mutually independently each represent an integer of 1 or more, provided that the total 30 of the m1 and n1 Do not exceed], The microcapsule according to claim 5. 7. The shell wall polymer is polyurea,
The microcapsule according to claim 1, containing at least one selected from the group consisting of: and polyurethane. 8. The cholesteric liquid crystal compound, the photochromic compound, and a polymer-forming organic raw material forming at least one of polyurea and polyurethane by polymerization are dissolved in a water-insoluble organic solvent having a boiling point of 100 ° C. or lower. Prepared by emulsifying and dispersing the organic solvent solution in an aqueous medium, heating the emulsion dispersion to volatilize and remove the organic solvent, and then polymerize the polymer-forming organic raw material. The microcapsule according to any one of claims 1 to 7, which is prepared. 9. A support and a reversible recording layer formed thereon, wherein the reversible recording layer contains the microcapsule according to any one of claims 1 to 8. Characteristic reversible recording material.