JPH05116452A - Reversibvle thermal recording material, production thereof, and image indication method using the same material - Google Patents

Abstract

PURPOSE:To obtain a reversible thermal recording material which is hardly lowered in opaque degree, even if an image is repeatedly formed/erased thereon using a heating means, such as a thermal head, applying heat and pressure at the same time, and is improved in repeated-use durability, the production thereof, and an image indication method using the material. CONSTITUTION:A reversible thermal recording material is provides with a heat-sensitive layer on a substrate. The heat-sensitive layer mainly composed of a resin matrix (esp. thermoset or radiation-curing resin) and micro-capsules of an organic low-molecular substance as a core substance dispersed in the resin matrix reversibly changes in transparency depending on a temperature. In the production of the reversible thermal recording material, the micro-capsules are produced using the organic low-molecular substance as a core substance by an air suspension method, a spray granulation method, or the like, and the heat-sensitive layer is provided using the micro-capsules. Furthermore, in an image indication method, an image is formed and/or erased on the reversible thermal recording material using a thermal head.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention utilizes a reversible change in transparency depending on the temperature of a heat-sensitive layer so that an image can be formed and erased repeatedly, and a reversible heat-sensitive recording material. And an image display method using the same.

[0002]

2. Description of the Related Art In recent years, reversible thermosensitive recording materials have been attracting attention because they enable temporary image formation and can erase the image when it is no longer needed. As a typical example, the glass transition temperature (Tg) is from 50 to 60 ° C. to 8
The transparent state and the cloudy state are reversibly changed by the heat of dispersing an organic low molecular weight substance such as a higher fatty acid in a resin matrix such as a vinyl chloride-vinyl acetate copolymer having a low glass transition temperature of less than 0 ° C. Reversible thermosensitive recording materials are known (JP-A-54-119377 and JP-A-55-1541).
Bulletins such as No. 98).

When a heat roller, a hot pen or the like is used as a heating method during image formation and erasing, and only heat is applied without applying much pressure, repeated image formation-
Even if it is erased, there is no problem in durability. However, when pressure is applied using a thermal head, etc., and heating is performed at the same time, the resin base material around the organic low molecular weight material particles deforms as the image is repeatedly formed and erased, resulting in finely dispersed organic low molecular weight material. There is a drawback that the particles gradually become larger in diameter, the effect of scattering light is lessened, the white turbidity is lowered, and the image and the contrast are lowered.

Further, in order to reduce the deformation of the resin base material,
When the resin base material is a heat- or radiation-curable resin, there are drawbacks that the turbidity is lowered and the transparent state does not change to the opaque state.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks, and in a reversible thermosensitive recording material in which the transparent state and the cloudy state reversibly change depending on the temperature, it is A reversible thermosensitive recording material having a reduced white turbidity even when repeatedly image-formed and erased by using a heating means which applies pressure at the same time and having improved repeated durability.
It is an object of the present invention to provide a manufacturing method thereof and an image display method using the same.

[0006]

According to the present invention, a resin base material and microcapsules containing an organic low molecular weight substance dispersed in the resin base material as a core substance are contained as a main component on a support and are dependent on temperature. And a reversible thermosensitive recording material having a heat-sensitive layer whose transparency reversibly changes, and the resin matrix is a heat- or radiation-curable resin. Provided is a thermosensitive recording material, and the reversible thermosensitive recording material is characterized in that the wall film substance of the microcapsules is cured.
Furthermore, in the method for producing the reversible thermosensitive recording material, an organic low molecular weight substance is used as a core substance, and an air suspension method, a spray granulation method, a pan coating method, an electrostatic coalescence method, a vacuum deposition method, an interfacial polymerization method, and an in situ method are used. Polymerization method, complex coacervation method, phase separation method from organic solution system, in-liquid drying method, melt dispersion cooling method, in-liquid curing coating method, to produce a microcapsule, then the microcapsules There is provided a method for producing the reversible thermosensitive recording material, which comprises dispersing a capsule in a resin base material to prepare a thermosensitive layer forming liquid, and providing a thermosensitive layer on a support, and further, the reversible thermosensitive recording. There is provided an image display method characterized in that a material is used and an image is formed and / or erased by using a thermal head.

That is, the inventors of the present invention have made earnest studies, and as a result,
Durability against repeated image formation-erasing by heating means such as applying pressure from a thermal head and heating at the same time by using microcapsules with organic low molecular weight material as core material and resin base material as main components It has been found that a reversible thermosensitive recording material having improved temperature can be obtained.

Although it is not clear why the microcapsules containing an organic low molecular weight substance as a core substance in the present invention improve the durability against repeated image formation and erasing by a heating means such as a thermal head, it is not clear. By using a microcapsule having a substance as a core substance, it becomes possible to use any resin base material, and as the resin base material, a highly heat-resistant thermoplastic resin having a high glass transition point, or further heat or By using a resin that is cured by radiation such as ultraviolet rays and electron beams, the heating of the thermal head and the like that applies heat and pressure at the same time causes little deformation of the resin base material even when recording and erasing are repeated. It is considered that the durability is improved because the organic low molecular weight substance inside remains as fine particles.

Further, even if the recording and erasing are repeatedly performed by using a heating means for simultaneously applying heat and pressure by curing the wall film of the microcapsule, the organic low-molecular-weight organic molecule does not deform. It is considered that the material particles are maintained as fine particles and the durability is improved.

The reversible thermosensitive recording material of the present invention utilizes the transparency change (transparent state, cloudy opaque state) as described above, and the difference between the transparent state and the cloudy opaque state is presumed as follows. .. That is, in the case of (i) transparent, the particles of the organic low molecular weight substance in the microcapsule are composed of large particles of the organic low molecular weight substance, and the light incident from one side is transmitted to the other side without being scattered. Therefore, in the case of (ii) white turbidity, the particles of the organic low molecular weight substance are composed of polycrystals of fine crystals of the organic low molecular weight substance, and the crystal axes of the individual crystals are in various directions. This is because the light entering from one side is refracted many times at the crystal interface of the organic low molecular weight substance particles and is scattered and thus appears white.

In FIG. 1 (representing the change in transparency due to heat), a heat-sensitive layer mainly composed of a resin base material and microcapsules having an organic low molecular weight substance as a core substance is, for example, at room temperature of T ₀ or lower. Then it is cloudy and opaque. When it is heated to a temperature T ₂ , it becomes transparent, and even if it is returned to room temperature below T _{0 in} this state, it remains transparent. It is considered that this is because the organic low-molecular-weight substance undergoes a semi-molten state from the temperature T ₂ to T ₀ or less and the crystal grows from a polycrystal to a single crystal. Further heating to a temperature of T ₃ or higher results in a semitransparent state between the maximum transparency and the maximum opacity. Next, when this temperature is lowered, the initial cloudy opaque state is restored without taking the transparent state again. It is considered that this is because the organic low molecular weight substance is melted at a temperature of T ₃ or higher and is then cooled to precipitate polycrystals. It should be noted that when this opaque state is heated to a temperature between T _{1 and} T ₂ and then cooled to room temperature, that is, a temperature of T ₀ or lower, an intermediate state between transparent and opaque can be obtained. In addition, if the transparent material at room temperature is heated to a temperature of T ₃ or higher and then returned to room temperature,
It returns to cloudy and opaque state again. That is, it can take both opaque and transparent forms at room temperature and intermediate forms thereof.

Therefore, the heat-sensitive layer can be selectively heated by selectively applying heat to form a cloudy image on a transparent background and a transparent image on a cloudy background, and the change can be repeated many times. It is possible. By arranging a coloring sheet on the back surface of such a heat-sensitive body, it is possible to form an image of the color of the coloring sheet on a white background or an image of the white background on the background of the color of the coloring sheet. Further, when projected by an OHP (overhead projector) or the like, the cloudy portion becomes a dark portion, the transparent portion transmits light, and becomes a bright portion on the screen.

In order to form and erase an image using such a reversible thermosensitive recording material, it is necessary to have two thermal heads for image formation and image erasure, or to change the applied energy conditions. Therefore, it is effective to use a thermal head having a single thermal head for image formation and image deletion. In the former case, the cost of the apparatus increases because two thermal heads are required, but if the reversible heat-sensitive recording material is passed once with different energy application conditions for each thermal head, image formation and erasure can be performed. You can do it. In the latter case, an image is formed and erased by one thermal head. Therefore, the conditions for applying energy to the thermal head at one time when the thermal recording material passes are adjusted according to the image forming portion and the erasing portion. The operation is complicated, but the operation is complicated, such as changing finely, or once erasing the image on the thermosensitive recording material and then running the thermosensitive recording material in the reverse direction again to form an image under different energy conditions. Therefore, the equipment cost is reduced.

When the reversible thermosensitive recording material of the present invention is prepared, the heat sensitive layer is provided by, for example, dissolving the resin base material in a solvent which dissolves only the resin base material and adding the organic low molecular weight substance to the core material. Disperse the microcapsules with various methods,
This can be carried out by a method of applying it on a support member and evaporating the solvent to form a film or sheet. The heat-sensitive layer forming solvent can be variously selected according to the type of microcapsules having a resin base material and an organic low molecular weight substance as a core substance, for example, tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, toluene, Examples thereof include benzene.
In the heat sensitive layer, the microcapsules containing the organic low molecular weight substance as the core substance exist in a dispersed state.

In the present invention, an organic low molecular weight substance is used as a core substance by being encapsulated in microcapsules. Microencapsulation, for example, as a physical or mechanical method, air suspension method, spray granulation method, pan coating method, electrostatic coalescence method, etc.
It can be used in the form of microcapsules having a particle size of about 0.1 to several tens of μm by a known technique such as a complex coacervation method, an interfacial polymerization method or an in situ polymerization method as a physical chemistry or a chemical method. The mechanical method is preferably such that the encapsulation film is apt to be porous due to its mechanism, and the protection and masking of the core substance are insufficient, and the physicochemical or chemical method based on the curing mechanism of the film is used. In the present invention, microencapsulation by interfacial polymerization method or in situ polymerization method is particularly preferable. Examples of the capsule wall polymer of the interfacial polymerization method include polyamide, polyurethane, polyester, polyurea, epoxy, polycarbonate, polysulfonamide, polysulfonate and the like. Preferred capsule wall polymers are polyamides, polyurethanes, polyesters, polyureas, polycarbonates. Examples of the capsule wall polymer in the in situ polymerization method include poly (meth) acrylic acid ester, polyvinyl acetate, styrene-divinylbenzene copolymer, polyurethane, polyurea, urea-formally condensate, melamine-formalin condensate, phenol-formalin condensation. Things etc. are mentioned. The size of the microcapsules is about 0.1 to 20 μm, preferably 0.1 to 5 μm, more preferably 0.1 to 2 μm.

On the other hand, as the organic low molecular weight substance, any substance that changes from polycrystal to single crystal by heat in the microcapsule (changes within the temperature range of T _{1 to} T ₃ shown in FIG. 1) may be used. Generally a melting point of 30 to 200 ° C., preferably 50
The thing of about 150 degreeC is used. Alkanols; alkane diols; halogen alkanols or halogen alkane diols;
Alkyl amines; Alkanes; Alkenes; Alkynes; Halogen alkanes; Halogen alkenes; Halogen alkynes;
Cycloalkanes; cycloalkenes; cycloalkynes; saturated or unsaturated mono- or dicarboxylic acids or their esters, amides or ammonium salts; saturated or unsaturated halogen fatty acids or their esters, amides or ammonium salts; allylcarboxylic acids or their esters , Amides or ammonium salts; halogenallylcarboxylic acids or their esters, amides or ammonium salts; thioalcohols; thiocarboxylic acids or their esters, amines or ammonium salts; carboxylic acid esters of thioalcohols and the like. These may be used alone or in admixture of two or more. The carbon number of these compounds is 10 to 60, preferably 10 to 38, and particularly 10 to 3
0 is preferred. The alcohol group portion in the ester may be saturated or unsaturated, and may be halogen-substituted. In any case, the organic low molecular weight substance has at least 1 of oxygen, nitrogen, sulfur and halogen in the molecule.
Species, such as -OH, -COOH, -CONH, -COO
_{R, -NH, -NH 2, -S} -, - S-S -, - O-,
A compound containing halogen or the like is preferable.

More specifically, these compounds include lauric acid, dodecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, henicosanoic acid, tricosanoic acid, lignoceric acid, pentacosanoic acid, cerotic acid, montanic acid, melicinic acid, stearin. Higher fatty acids such as acids, behenic acid, nonadecanoic acid, aragic acid, and oleic acid; esters of higher fatty acids such as methyl stearate, tetradecyl stearate, octadecyl stearate, octadecyl laurate, tetradecyl palmitate, dodecyl behenate; C _{16 H 33 -O-C 16 H 33} , C 16 H 33 -S-C
₁₆ H ₃₃ , C ₁₈ H ₃₇ -S-C ₁₈ H ₃₇ , C ₁₂ H ₂₅ -S
_{-C 12 H 25, C 19 H} 39 -S-C 19 H 39, C 12 H 25
_{-S-S-C 12 H 25} , Etc., such as ether or thioether. Among them, in the present invention, higher fatty acids, particularly palmitic acid, heneicosanoic acid, tricosanoic acid, lignoceric acid, pentadecanoic acid,
Higher fatty acids having 16 or more carbon atoms such as nonadecanoic acid, arachidic acid, stearic acid and behenic acid are preferable,
-24 higher fatty acids are more preferred.

In order to widen the range of temperature at which the material can be made transparent, the organic low molecular weight substances described in this specification may be appropriately combined, or such organic low molecular weight substances may be combined with other materials having different melting points. Good. These are disclosed in, for example, JP-A-63-39378 and JP-A-63-130380, and the specifications such as Japanese Patent Application No. 1-140109, but the invention is not limited thereto.

The weight ratio of the organic low molecular weight substance to the resin base material in the heat sensitive layer is preferably about 2: 1 to 1:16, more preferably 1: 2 to 1: 6. When the ratio of the resin base material is less than this, it becomes difficult to form a film in which the organic low molecular weight substance is retained in the resin base material, and when it exceeds the ratio, the amount of the organic low molecular weight substance is small, so that it becomes opaque. Becomes difficult.

The thickness of the heat sensitive layer is preferably 1 to 30 μm,
2 to 20 μm is more preferable. If the heat-sensitive portion is too thick, heat distribution will occur in the layer of the heat-sensitive portion, and it will be difficult to achieve uniform transparency. On the other hand, if the heat-sensitive layer is too thin, the white turbidity is lowered and the contrast is lowered. Further, the white turbidity can be increased by increasing the amount of the organic low molecular weight substance in the heat sensitive layer.

In the microcapsules, in addition to the above components, a surfactant, in order to facilitate the formation of a transparent image,
Additives such as high boiling point solvents can be added. Specific examples of these additives are as follows. Examples of high boiling point solvents: tributyl phosphate, tri-2-phosphate
Ethylhexyl, triphenyl phosphate, tricresyl phosphate, butyl oleate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, di-n-octyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate , Dioctyldecyl phthalate, diisodecyl phthalate, butylbenzyl phthalate,
Dibutyl adipate, di-n-hexyl adipate, di-2-ethylhexyl adipate, di-2 azelaate
-Ethylhexyl, dibutyl sebacate, di-2-ethylhexyl sebacate, diethylene glycol dibenzoate, triethylene glycol di-2-ethyl butyrate, methyl acetylricinoleate, butyl acetylricinoleate, butylphthalylbutyl glycolate, acetylcitric acid Tributyl.

Examples of surfactants and other additives: polyhydric alcohol higher fatty acid ester; polyhydric alcohol higher alkyl ether; polyhydric alcohol higher fatty acid ester, higher alcohol, higher alkylphenol, higher fatty acid higher alkylamine, higher fatty acid amide , Lower olefin oxide adducts of fats and oils or polypropylene glycol; acetylene glycol; Na, Ca, Ba or Mg salt of higher alkylbenzene sulfonic acid; higher fatty acid, aromatic carboxylic acid, higher fatty acid sulfonic acid, aromatic sulfonic acid, sulfuric acid monoester Or Ca, Ba or Mg salt of phosphoric acid mono- or di-ester; low degree of sulfated oil; poly long chain alkyl acrylate; acrylic orgomer; poly long chain alkyl methacrylate; long chain alkyl methacrylate to amine-containing mono Chromatography copolymers; styrene-maleic anhydride copolymer; olefin-maleic anhydride copolymer.

In the present invention, the resin used as the resin base material includes, but is not limited to, the following resins. For example, ionomer resin, isobutylene-maleic anhydride copolymer resin, AAS resin, AE
S resin, AS resin, ABS resin, ACS resin, MBS resin, ethylene-vinyl chloride copolymer resin, ethylene-vinyl acetate copolymer resin, vinylidene chloride resin, vinyl chloride resin, chlorinated vinyl chloride resin, chlorinated polyethylene, chlorinated Polypropylene, coumarone resin, ketone resin, vinyl acetate resin, phenoxy resin, butadiene resin, fluororesin, vinyl propionate resin, polyacetal, polyamide,
Polyamideimide, polyarylate, thermoplastic polyimide, polyetherimide, polyetheretherketone, polyethylene, polyethylene oxide, polyethylene terephthalate, polycarbonate, polystyrene, polysulfone, polyparamethylstyrene polyvinyl alcohol, polyvinyl ether, polyvinyl butyral, polyvinyl formal, poly Thermoplastic resin such as butylene terephthalate, polypropylene, polymethylpentene, methacrylic resin, liquid crystal polymer, DFK resin,
Epoxy resin, xylene resin, guanamine resin, diallyl phthalate resin, vinyl ester resin, phenol resin, unsaturated polyester resin, furan resin, polyimide, poly-p-hydroxybenzoic acid, polyurethane, maleic acid resin, melamine resin, urea resin, etc. The thermosetting resin of is mentioned.

Further, the following resins that are cured by radiation such as ultraviolet rays and electron beams can also be used. As the ultraviolet curable resin, any monomer or oligomer (or prepolymer) which undergoes a polymerization reaction upon irradiation with ultraviolet rays and is cured to be a resin can be used. Examples of such monomers or oligomers include (poly) ester acrylate, (poly) urethane acrylate, epoxy acrylate, polybutadiene acrylate, silicone acrylate, and melamine acrylate. The (poly) ester acrylate is obtained by reacting a polyhydric alcohol such as 1,6-hexanediol, propylene glycol (as propylene oxide) or diethylene glycol with a polybasic acid such as adipic acid, phthalic anhydride or trimellitic acid and acrylic acid. It is a thing. The structural examples are shown in (a) to (c). (a) Adipic acid / 1,6-hexanediol - acrylic acid _{CH 2 = CHCOO- (CH 2)} 6 _{[O-CO- (CH 2) 4} -COO- (CH 2) 6 ] n OCOCH = CH ₂ (b ) Phthalic anhydride / Propylene oxide / Acrylic acid

[Chemical 1] (c) trimellitic acid / diethylene glycol / acrylic acid

[Chemical 2] The (poly) urethane acrylate is obtained by reacting a compound having an isocyanate group such as tolylene diisocyanate (TDI) with an acrylate having a hydroxy group. An example of the structure is shown in (d). HEA is 2
-Hydroxyethyl acrylate, HDO is an abbreviation for 1,6-hexanediol, and ADA is an abbreviation for adipic acid. (d) HEA / TDI / ADA / HDO / TDI / HEA

[Chemical 3] Epoxy acrylates are roughly classified into bisphenol A type, novolac type, and fatty type, and the epoxy group of these epoxy resins is esterified with acrylic acid to make the functional group an acryloyl group. Examples of the structure are shown in (e) to (g). (e) Bisphenol A-epichlorohydrin type / acrylic acid

[Chemical 4] (f) Phenolvolac-epichlorohydrin type / acrylic acid

[Chemical 5] (g) Fat type / acrylic acid

[Chemical 6] Polybutadiene acrylate is a 1,2-containing terminal OH group
Polybutadiene is reacted with isocyanate, 2-mercaptoethanol or the like, and then further reacted with acrylic acid or the like. An example of the structure is shown in (h). (h)

[Chemical 7] The silicone acrylate is, for example, methacryl-modified by a condensation reaction (demethanol reaction) of an organofunctional trimethoxysilane and a silanol group-containing polysiloxane, and a structural example thereof is shown in (i). (i)

[Chemical 8] The resin used for these resin base materials is dissolved or emulsion in an organic solvent or a solvent such as water. on the other hand,
As the material for the electron beam curable resin, the ultraviolet curable resin can be used as it is.

Of these, a resin which is cured by heat or radiation is preferable because it is less likely to be deformed even when pressure is applied during heating and durability is improved. Among these, a resin that is particularly hardened by radiation has a high hardness and is more preferable.

Further, a protective layer may be provided on the heat-sensitive layer of the present invention in order to prevent the transparency of the transparent portion from being lowered by the deformation of the surface due to the heat and pressure of the heating means such as a thermal head by a writing method. good. A protective layer (thickness: 0.
(1 to 10 μm), silicone rubber, silicone resin (described in JP-A-63-221087), polysiloxane graft polymer (JP-A-63-210).
No. 317385), an ultraviolet curable resin, an electron beam curable resin (described in JP-A-2-566), and the like.
In any case, a solvent is used at the time of coating, but it is desirable that the solvent is difficult to dissolve the resin of the heat sensitive layer and the organic low molecular weight substance. Examples of the solvent that hardly dissolves the resin and the organic low molecular weight substance in the heat-sensitive layer include n-hexane, methyl alcohol, ethyl alcohol, isopropyl alcohol and the like, and the alcohol solvent is particularly preferable from the viewpoint of cost.

Further, an intermediate layer may be provided between the protective layer and the heat-sensitive layer in order to protect the heat-sensitive layer from the solvent and the monomer component of the protective layer-forming liquid (JP-A-1-13378).
No. publication). As the material for the intermediate layer, the following thermosetting resins and thermoreversible resins can be used in addition to those listed as the resin base material in the thermosensitive layer. That is, specifically, polyethylene, polypropylene, polystyrene, polyvinyl alcohol, polyvinyl butyral, polyurethane, saturated polyester, unsaturated polyester, epoxy resin, phenol resin, polycarbonate, polyamide and the like can be mentioned. The thickness of the intermediate layer varies depending on the use, but is preferably about 0.1 to 2 μm. Below this,
The protective effect decreases, and if it exceeds this, the thermal sensitivity decreases.

In order to improve the image contrast of this recording material, it is possible to provide a light reflecting layer on the back surface of the recording layer. In this case, high contrast can be obtained even if the thickness of the recording layer is reduced. Specifically, Al, Ni, Sn, A
Vapor deposition of u, Ag, etc. may be mentioned (JP-A-64-
14079).

[0029]

EXAMPLES The present invention will be specifically described below with reference to examples. The parts in the examples represent parts by weight. Example 1 As a core substance, 15 parts of behenic acid and 15 parts of eicosanoic acid are uniformly dissolved at about 80 ° C. The solution was added dropwise to 80 parts of a 3% aqueous solution of a styrene-maleic anhydride copolymer adjusted to pH 4.5 at 80 ° C., and a microdroplet having an average particle size of 3 μm was added using a mixer. Emulsify and disperse. Next, 7.0 g of a melamine-formalin pun polymer (manufactured by Sanwa Keimcal Co., Ltd., Nikalac MX-54) was added to the obtained emulsion with stirring, and the mixture was reacted at 80 ° C. for 2 hours to obtain a microcapsule slurry having an average particle diameter of 3.2 μm. Got The obtained microcapsule slurry was filtered through a 1 μm filter, centrifuged and vacuum dried for 10 hours to prepare microcapsule particles (1). Next, microcapsule particles (1) 10 parts Urethane acrylate-based UV curable resin 10 parts (Dainippon Ink and Chemicals, Inc. Unidick C-157 75% butyl acetate solution) Toluene 10 parts are mixed and uniformly dispersed. The solution was applied onto 100 μm thick transparent PET, heated and dried, and then cured with an 80 w / cm ultraviolet lamp to provide a 15 μm thick thermosensitive layer to prepare a reversible thermosensitive recording material.

Example 2 As a core substance, 15 parts of behenic acid and 15 parts of eicosanoic acid are uniformly dissolved at about 80 ° C. 8% gelatin aqueous solution 100
While the parts were heated to 80 ° C., the melt and the epoxy resin (Epicote 828, manufactured by Yuka Shell Epoxy Co., Ltd.) 3.5
Part of the mixture, and the resulting mixture is emulsified and dispersed using a mixer so that the average particle diameter becomes 3 μm. While stirring the obtained emulsion, 3.5 parts of an epoxy resin curing agent, aliphatic polyamine (Epicure U, manufactured by Yuka Shell Epoxy Co., Ltd.) was dissolved in 7 parts of water and gradually added, and the temperature was raised to 80 ° C. The mixture was kept stirring for 4 hours to obtain a microcapsule slurry having an epoxy resin wall with an average particle diameter of 3.5 μm. The obtained microcapsule slurry was filtered with a 1 μm filter and centrifuged to prepare microcapsule particles (2). Using the microcapsule particles (2) thus obtained, a reversible thermosensitive recording material was prepared in the same manner as in Example 1.

Example 3 As a core substance, 12 parts of behenic acid, 12 parts of eicosanoic acid and 7.2 parts of dioctyl phthalate were uniformly dissolved at about 70 ° C. While heating 150 parts of an aqueous solution of 5% polyvinyl alcohol (88% in the degree of fighting, 1,400 in the degree of polymerization) to 60 ° C., 2 parts of 2,4 tolylene diisocyanate and 2,6 tolylene diisocyanate were mixed in an 8: 2 mixture. Add and emulsify and disperse using a mixer to form fine droplets having an average particle size of 3 μm. Then add 40 parts of hexamethylenediamine separately.
Part of the solution dissolved in water was gradually added dropwise to the above liquid, the liquid temperature was maintained at 60 ° C, and stirring was continued for 5 hours to obtain an average particle diameter of 3.5μ.
A microcapsule slurry of m polyurea walls was obtained.
The obtained microcapsule slurry was filtered through a 1 μm filter and centrifuged to prepare microcapsule particles (3). Using the microcapsule particles (3) thus obtained, a reversible thermosensitive recording material was prepared in the same manner as in Example 1.

Example 4 As a core substance, 12 parts of behenic acid, 12 parts of eicosanoic acid and 7.2 parts of dioctyl phthalate were uniformly dissolved at about 70 ° C. The solution was added dropwise while heating 80 parts of a 3% aqueous solution of a styrene-maleic anhydride copolymer having a pH of 4.0 to 70 ° C., and the average particle size was 3 using a mixer.
Emulsify and disperse into fine droplets of μm. Next, while stirring the obtained emulsion, a solution prepared by dissolving 10 parts of urea and 1 part of resorcin in 40 parts of water was added, 25 parts of a 37% formalin aqueous solution was further added, and the temperature of the system was adjusted to 65 ° C. and stirred for 5 hours. Continuously, a microcapsule slurry having an average particle diameter of 3.7 μm was obtained. The obtained microcapsule slurry was filtered with a 1 μm filter and centrifuged to prepare microcapsule particles (4). Using the microcapsule particles (4) thus obtained, a reversible thermosensitive recording material was prepared in the same manner as in Example 1.

Example 5 As a core substance, 12 parts of behenic acid, 12 parts of eicosanoic acid and 7.2 parts of dioctyl phthalate were uniformly dissolved at about 70 ° C. While heating 100 parts of a 15% aqueous solution of gum arabic to 70 ° C., 5 parts of the above-mentioned dissolved substance and halogenated epoxy resin (tetraprobisphenol A / diglycidyl ether type, epoxy equivalent 340 to 380) were added dropwise, and a mixer was used. And emulsified and dispersed to form fine droplets having an average particle diameter of 3 μm. While stirring the obtained emulsion, 2 parts of an epoxy resin curing agent aliphatic polyamine was dissolved in 7 parts of water and added gradually, the temperature was kept at 80 ° C., and stirring was continued for 4 hours to obtain an average particle size of 3. A 5 μm microcapsule slurry was obtained. The obtained microcapsule slurry is filtered with a 1 μm filter and centrifuged to obtain microcapsule particles (5).
It was created. Using the microcapsule particles (5) thus obtained, a reversible thermosensitive recording material was prepared in the same manner as in Example 1.

Example 6 Microcapsule particles (1) 10 parts (prepared in Example 1) Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 10 parts (UCH, VAGH) Isocyanate 2 parts (Nippon Polyester Coronate) L 50% toluene solution) 80 parts of toluene was uniformly mixed and dispersed to obtain a dispersion liquid having a thickness of 100 μm of transparent PE.
A reversible thermosensitive recording material was prepared by coating on T, heating and drying to form a 15 μm thick thermosensitive layer, and then heating at 50 ° C. for 24 hours to cure the resin base material.

Example 7 Microcapsule particles (1) 10 parts (prepared in Example 1) Vinyl chloride-vinyl acetate-phosphate ester copolymer 80 parts (Denka vinyl # 1000P 10% MEK solution manufactured by Denki Kagaku Kogyo Co., Ltd.) Of 100 μm thick transparent PE
A heat-sensitive layer having a thickness of 15 μm is provided on T by heating and drying, and a solution of polyamide resin (Toray Co., CM8000) 10 parts methanol 90 parts is applied on the heat-sensitive layer, and heat-drying to a thickness of about 0.5 μm. A thick intermediate layer was provided. Furthermore, a solution of urethane acrylate-based UV-curable resin 75% 10 parts butyl acetate solution (Dainippon Ink and Chemicals, Unidick C7-157) toluene 10 parts was applied, and after heating and drying, 80 w / cm. And an overcoat layer having a thickness of about 2 μm was provided to prepare a reversible thermosensitive recording material.

Example 8 γ-Fe ₂ O ₃ 10 parts Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 10 parts (UCC, VAGH) Isocyanate (Nippon Polyurethane, Coronate) on white PET having a thickness of about 188 μm. L 2 parts 50% toluene solution) Methyl ethyl ketone 40 parts Toluene 40 parts is applied with a wire bar and dried by heating to about 1
A magnetic recording layer having a thickness of 0 μm was provided. A special acrylic UV-curable resin (manufactured by Dainippon Ink and Chemicals, Inc. 10 parts Unidic C7-164, 49% butyl acetate solution) toluene 4 parts was applied with a wire bar, and after heating and drying, 8
Ultraviolet rays were irradiated for 5 seconds with a 0 w / cm ultraviolet lamp to provide a smoothing layer having a thickness of about 1.5 μm. About 40 A1 on it
It was vacuum-deposited so as to have a thickness of 0Å, and a light reflection layer was provided. Further, the same heat-sensitive layer dispersion as in Example 1 was applied thereon,
A heat-sensitive layer having a thickness of 5 μm was provided by heating and drying to prepare a reversible heat-sensitive recording material.

Comparative Example 1 Behenic acid 5 parts Eicosane diacid 5 parts Diisodecyl phthalate 3 parts Vinyl chloride-vinyl acetate-phosphate ester copolymer 40 parts (Denka vinyl # 1000P manufactured by Denki Kagaku Co.) on 100 μm thick transparent PET. A solution of 120 parts of THF and 80 parts of toluene was applied and dried by heating to provide a heat sensitive layer having a thickness of about 15 μm. Further, an intermediate layer and an overcoat layer were provided thereon in the same manner as in Example 7 to prepare a reversible thermosensitive recording material.

Comparative Example 2 Comparative Example 1 was repeated except that a magnetic recording layer, a smoothing layer and a light reflecting layer were provided on white PET in the same manner as in Example 8 and then the thickness of the heat sensitive layer was set to about 5 μm. Then, a thermosensitive layer, an intermediate layer and a protective layer were provided to prepare a reversible thermosensitive recording material.

The reversible thermosensitive recording material prepared as described above was used to form an image in a cloudy state using a thermal head of 8 dots / mm, and the image was formed by erasing it with a heat roller heated to 80 to 85 ° C. to make it transparent. -Erasing was repeated 100 times. Initial image density at that time and 100
Table 1 shows the image densities for the second time and their differences. The image density was measured using Macbeth reflection densitometer RD-914. Then, the one using transparent PET as a support was printed in black.
The density was measured with (O, D19) as the back surface.

[0040]

[Table 1]

[0041]

Since the reversible thermosensitive recording material of the present invention uses the microcapsules having the organic low molecular weight substance as the core substance, the heating means such as a thermal head for simultaneously applying heat and pressure is used to repeatedly form and erase images. Even if it is carried out, the white turbidity is not lowered so much and the repeating durability is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a change in transparency of a reversible thermosensitive recording material according to the present invention due to heat.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Makoto Kawaguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Fumito Masuchibuchi 1-3-6 Nakamagome, Ota-ku, Tokyo Shares Company Ricoh

Claims (5)

[Claims] 1. A heat-sensitive layer having microcapsules containing a resin base material and an organic low-molecular substance as a core substance as a main component and having a transparency reversibly changing depending on temperature is provided on a support. And a reversible thermosensitive recording material. 2. The reversible thermosensitive recording material according to claim 1, wherein the resin base material is a heat or radiation curable resin. 3. The reversible thermosensitive recording material according to claim 1, wherein the wall film material of the microcapsules is cured. 4. A reversible thermosensitive material comprising, on a support, a thermosensitive layer whose main component is a microcapsule containing a resin base material and an organic low-molecular substance as a core material, and whose transparency reversibly changes depending on temperature. In a method for producing a recording material, an organic low molecular weight substance is used as a core substance, and an air suspension method, a spray granulation method, a pan coating method, an electrostatic coalescence method, a vacuum deposition method, an interfacial polymerization method, ins
in situ polymerization method, complex coacervation method,
A microcapsule is produced by any one of a phase separation method from an organic solution system, a liquid drying method, a melt dispersion cooling method, a liquid hardening coating method, and then the microcapsule is dispersed in a resin base material. A method for producing the reversible thermosensitive recording material, comprising preparing a thermosensitive layer forming liquid and providing a thermosensitive layer on a support. 5. A heat-sensitive material comprising a support and a microcapsule containing a resin base material and an organic low-molecular substance dispersed in the resin base material as a core material as a main component, and a transparency reversibly changing depending on temperature. An image display method characterized in that a reversible thermosensitive recording material provided with a layer is used and an image is formed and / or erased by using a thermal head.