JPH044959B2 - - Google Patents

Description

[Detailed description of the invention]

"Industrial Application Field" The present invention relates to a heat-sensitive recording material, and in particular to a new heat-sensitive paper that has excellent thermal responsiveness and can reproduce halftones. ``Prior art'' The thermal recording method has three advantages: (1) no development is required, (2) when the support is paper, the paper quality is similar to ordinary paper, (3) easy handling, and (4) color density. It has rapidly become popular in the field of facsimiles and printers in recent years due to its advantages such as (5) the recording device is simple and inexpensive, and (6) there is no noise during recording. As the heat-sensitive recording material, a leuco color-forming heat-sensitive recording material, which is excellent in color density and color development speed, is mainly used. In general, text recording is mainly performed in thermal recording, but in recent years there has been an increasing demand for image recording with gradation, such as hard copies of television images. There are two ways to express gradation: one is to keep the recording density constant and change the recording area, and the other is to keep the recording area constant and change the recording density. However, the former reduces resolution and is difficult to express halftones. The latter is better because of its limitations. However, while the former method is suitable for conventional thermal paper, the latter method is not so suitable. This is because the latter method requires intermediate density printing on thermal paper. That is, it is required that the applied energy changes with a certain degree of gentleness (the rate of change is not too large). However, conventional leuco color-forming thermal recording paper is made by finely dispersing a leuco dye and a phenolic color developer into micron-order sizes, mixing them, and applying the mixture to a paper support, which is then heated with a thermal head. The color forming components melt and mix with each other to form a color, but it is not easy to create differences in temperature characteristics between particles or between coated layer parts. "Problems to be Solved by the Invention" In conventional thermal paper, the rate of change in color density with respect to changes in applied energy (heat amount) is large, especially in low density areas, and stable gradation recording performance is poor. ``Object of the Invention'' Therefore, the first object of the present invention is to provide a recording material that is excellent in smooth gradation recording properties and has high thermochromic properties. A second object of the present invention is to provide a recording material with excellent manufacturing suitability and excellent image storage stability. "Means for Solving the Problems" As a result of intensive research, the present inventors have found that microcapsules containing at least one component that causes a color reaction and an organic solvent in the core react with the component that causes a color reaction. The heat-sensitive recording material is characterized in that it has two or more types of microcapsules having different glass transition points on the microcapsule walls as the microcapsules in the heat-sensitive material having the other component that develops color on the same side of the support. was achieved. "Operation" The microcapsules of the present invention can be destroyed by heat or pressure, as used in conventional recording materials, to separate the reactive substances contained in the core of the microcapsules and the reactive substances outside the microcapsules. This method does not cause a coloring reaction by contacting the microcapsules with each other, but by heating the reactive substance present in the core and outside of the microcapsules, it permeates through the microcapsule walls and causes a reaction. Until now, it has been known that when microcapsule walls are formed by a polymerization method, they do not become completely impermeable but have permeability. This permeability of the microcapsule wall was known as a phenomenon in which low-molecular substances gradually permeate over a long period of time, but a phenomenon in which they permeate instantaneously due to heating as in the present invention is unknown. Nakatsuta. Therefore, the microcapsule walls of the present invention do not necessarily need to be melted by heat. Even when the core substance of the microcapsule liquid used in the method of the present invention is removed and heated, the upper wall appears to hardly melt. However, if the glass transition points of the microcapsule walls are different, the printing density with respect to the applied energy will be different, so gradation reproducibility can be improved by using two or more types of microcapsules with different glass transition points. The difference in glass transition point of the microcapsules is preferably about 20 to 200°C,
Particularly preferred is about 20-150°C. The present invention will be explained in more detail. As for the organic solvent used in the present invention, low boiling point ones have evaporation loss during raw storage.
℃ or higher, and phosphoric acid esters, phthalic acid esters, other carboxylic acid esters, fatty acid amides, alkylated biphenyl, alkylated terphenyl, chlorinated paraffin, alkylated naphthalene, diarylethane, etc. are used. Specific examples include tricresyl phosphate, trioctyl phosphate, octyl diphenyl phosphate, tricyclohexyl phosphate, dibutyl phthalate, dioctyl phthalate, dilaurate phthalate, dicyclohexyl phthalate, butyl oleate, diethylene glycol dibenzoate, and dioctyl sebacate. , dibutyl sebacate, dioctyl adipate, trioctyl trimellistate, acetyltriethyl citrate, octyl maleate, dibutyl maleate, isopropylbiphenyl, isoamyl biphenyl, chlorinated paraffin, diisopropylnaphthalene, 1,1'-ditolylethane, 2, 4
- ditertiaryaminophenol, N,N-dibutyl-2-butoxy-5-tertiaryoctylaniline, and the like. Among the synthetic resins, polyurea, polyurethane, polyester, polyamide,
Particularly good results are obtained when using urea-formalin resins or mixtures thereof. Capsule walls can be made by polymerizing reactants from inside oil droplets, or by polymer precipitation, which provide dense walls and excellent storage stability.
Capsule size and wall thickness can be easily controlled and preferred capsules can be obtained. This method and specific examples of compounds are described in the specifications of US Pat. No. 3,726,804 and US Pat. No. 3,796,669. For example, when polyurethane is used as the capsule wall material, a polyvalent isocyanate and a second substance that reacts with it to form the capsule wall (such as a polyol) are mixed into the oily liquid to be encapsulated, emulsified and dispersed in water, and then heated to a temperature. By rising, a polymer formation reaction occurs at the oil droplet interface, forming a capsule wall. At this time, an auxiliary solvent with a low boiling point and strong dissolving power can be used in the oil droplet liquid. In this case, regarding the polyisocyanate to be used and the polyol and polyamine that react with it, US Pat.
No. 379268, Special Publication No. 48-40347, No. 49-24159,
It is disclosed in JP-A-48-80191 and JP-A-48-84086, and they can also be used. Examples of the polyvalent isocyanate that is the first wall film-forming substance 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'-dimethoxy-4,4'-biphenyl-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, xylene-1,4-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1 , 2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, etc., 4,4',4''-triphenylmethane triisocyanate, toluene-2,4,6-
Triisocyanates such as triisocyanate, 4,4'-dimethyldiphenylmethane-2,
Tetraisocyanates such as 2',5,5'-tetraisocyanate, adducts of hexamethylene diisocyanate and trimethylolpropane, 2,4
- Isocyanate prepolymers such as adducts of tolylene diisocyanate and trimethylolpropane, adducts of xylylene diisocyanate and trimethylolpropane, and adducts of tolylene diisocyanate and hexanetriol. Examples of the polyol, which is one of the second wall-forming substances, include aliphatic and aromatic polyhydric alcohols, hydroxy polyesters, and hydroxy polyalkylene ethers. Preferred polyols include the following () between two hydroxyl groups:
Examples include polyhydroxy compounds having a molecular weight of 5,000 or less and having groups of (), (), or () in their molecular structure. () Aliphatic hydrocarbon group having 2 to 8 carbon atoms Here, Ar in (), (), and () represents a substituted or unsubstituted aromatic moiety, and the aliphatic hydrocarbon group in () has −CnH _2o − as its basic skeleton,
Hydrogen groups may be substituted with other elements. To give a concrete example, as an example of (),
Ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-
heptandinol, 1,8-octanediol,
Propylene glycol, 2,3-dihydroxybutane, 1,2-dihydroxybutane, 1,3-dihydroxybutane, 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,
Examples include 1,1-trimethylolpropane, hexanetriol, pentaerythritol, and glycerin. Examples of () include condensation products of aromatic polyhydric alcohols and alkylene oxides such as 1,4-di(2-hydroxyethoxy)benzene and resorcinol dihydroxyethyl ether. Examples of () include p-xylylene glycol, m-xylylene glycol, α,α'-dihydroxy-p-diisopropylbenzene, and the like. An example of () is 4,4'-dihydroxy-
Examples include diphenylmethane, 2-(p,p'-dihydroxydiphenylmethyl)benzyl alcohol, an adduct of ethylene oxide to bisphenol A, and an adduct of propylene oxide to bisphenol A. The polyol is preferably used in a ratio of 0.02 to 2 moles of hydroxyl groups per mole of isocyanenate groups. Examples of polyamines that are other second wall-forming substances include ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, p-phenylenediamine, m-phenylenediamine, piperazine, 2- Examples include methylpiperazine, 2,5-dimethylpiperazine, 2-hydroxytrimethylenediamine, diethylenetriamine, triethylenetriamine, triethylenetetramine, diethylaminopropylamine, tetraethylenepentamine, and amine adducts of epoxy compounds. By varying the amount of polyisocyanate, polyol, or polyamine added, the wall thickness will vary, other things being equal. By varying the agitation during emulsification dispersion, the particle size and, therefore, the wall thickness, other things being equal, can be varied. Additionally, polyisocyanate can react with water to form a polymer film. Water-soluble polymers can be used when making microcapsules, but water-soluble polymers include water-soluble anionic polymers, nonionic polymers, and amphoteric polymers. Can be used both natural and synthetic
For example, those having -COO ^- , -SO ^- ₃ groups, etc. can be mentioned. Specific anionic natural polymers include gum arabic and alginic acid, while semi-synthetic products include carboxymethyl cellulose, phthalated gelatin, sulfated starch, sulfated cellulose, and lignin sulfonic acid. Synthetic products include maleic anhydride-based (including hydrolyzed) copolymers, acrylic acid-based (including methacrylic acid-based) polymers and copolymers, vinylbenzenesulfonic acid-based polymers and copolymers, Examples include carboxy-modified polyvinyl alcohol. Examples of nonionic polymers include polyvinyl alcohol, hydroxyethyl cellulose, and methyl cellulose. Examples of amphoteric compounds include gelatin. These water-soluble polymers are used as a 0.01 to 10 wt% aqueous solution. The glass transition point of the capsule wall of the present invention is the glass transition point "as a system" including the effects of couplers, basic substances, color development accelerators, and the like. In other words, the glass transition point itself inherent to the capsule wall, or the substance outside the capsule (particularly the glass transition point adjusting agent) was heated and melted during thermal printing, diffused into the capsule wall, and caused an interaction. What is the glass transition point in the state? The former method of controlling the glass transition point specific to the capsule wall is to change the type of capsule wall forming agent. In the case of polyurea, polyurethane, and mixed polyurea/urethane capsules, it is particularly advantageous because the glass transition point can be changed widely by changing the type of isocyanate used, and by changing the type and amount of polyol and polyamine used together. The glass transition point in the state where the latter interaction occurs can be changed by placing a glass transition point adjusting agent outside the capsule. Especially melting point 50
Hydroxy compounds, carbamate esters, aromatic methoxy compounds, etc. at ~170°C are effective. This glass transition point is determined by measuring the capsule wall or the interaction substance (capsule wall/glass transition point adjusting agent outside the capsule) using a Vibron PPV-type (manufactured by Toyo Baldwin Co., Ltd.), and measuring the tan δ peak. It means temperature and is the dynamic loss modulus subtracted by the storage modulus. The temperature at which thermal paper using capsules can develop color is determined when the glass transition point of the capsule wall "as a system" is determined. The reason for this is that when the capsule wall changes from a glass state to a rubber state, substances diffuse between the inside and outside of the capsule and a coloring reaction occurs. The capsule wall or the interaction product of the capsule wall and the heat-fusible substance to be subjected to the measurement of the glass transition point is prepared, for example, as follows. 20 parts of xylylene diisocyanate/trimethylolpropane (3:1 adduct) as a capsule wall component was dissolved in 30 parts of ethyl acetate, coated with a bar on a polyethylene sheet, reacted in water at 40 to 60°C, peeled off, and then dried for 24 hours. Air dry for 1 day at ℃, 64%RH, 10
A polyurea film with a thickness of ~20μ was obtained. This is the sample for measuring the glass transition point of the capsule wall alone. As a method for preparing an interaction product between a heat-fusible substance and a capsule wall, the above polyurea film is
After immersing in a 20% methanol solution of benzyloxyphenol for 30 hours, air drying at 24℃ and 64%RH for 1 day.
It was used as a sample. Preferred embodiments for use in the heat-sensitive recording material of the present invention include the following. (1) A heat-sensitive recording material that has a capsule containing a leuco dye and an organic solvent as a core substance, and a color developer that develops the color of the leuco dye on the same side of a support. (Use the same leuco dye for each microcapsule with a different glass transition point, or use several types of leuco dyes at the same composition ratio.) (2) In (1), at least a portion of the organic solvent is replaced by a vinyl compound, Contains photopolymerization initiator/
or no heat-sensitive recording material. (3) Among diazo compounds, coupling agents capable of coupling with diazo compounds, and basic substances,
A heat-sensitive recording material having a capsule containing at least a diazo compound as a core substance, a coupling agent, and a basic substance on the same side of a support. Examples of the leuco dye used in the heat-sensitive recording material (1) of the present invention include crystal violet lactone, 3-indolino-3-p-dimethylaminophenyl-6-dimethylaminophthalide, 3-diethylamino-7-chloro Fluoran, 3-diethylamino-7-cyclohexylaminofluorane, 3-diethylamino-5-methyl-7-t-
Butylfluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-p-butylanilinofluorane, 2-(N-phenyl-N-ethyl)aminofluoran Orane, 3-diethylamino-7-dibenzylaminofluorane, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 2-
Anilino-3-methyl-6-(N-ethyl-p-
toluidino) fluorane, 3-pyrrolidino-6-
Methyl-7-anilinofluorane, 3-pyrrolidino-cyclohexylaminofluorane, 3-piperidino-6-methyl-7-toluidinofluorane, 3-pyrrolidino-6-methyl-7-(p-toluidino)fluorane , 3-piperidino-6-methyl-7-anilinofluorane, 3-N-methylcyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-7-(m-
Examples include, but are not limited to, trifluoromethylaniline) fluorane. As a color developer for these color formers, a phenol compound, an organic acid or a metal salt thereof, an oxybenzoic acid ester, etc. are used. In particular, the melting point is 50° to 25°C, particularly preferably
Phenols and organic acids that are sparingly soluble in water at temperatures between 60° and 200°C are preferable. Examples of phenolic compounds include 4,4'-isopropylidene-diphenol (bisphenol A), P-tert-butylphenol, 2,4-dinitrophenol, 3,4-dichlorophenol, and 4,4'-methylene. -bis(2,6-di-tert)
-butylphenol), p-phenylphenol,
4,4-cyclohexylidene diphenol, 2,
2'-methylenebis(4-tert-butylphenol), 2,2'-methylenebis(α-phenyl-p
-cresol)thiodiphenol, 4,4'-thiobis(6-tert-butyl-m-cresol), sulfonyldiphenol, 1,1-bis(4-hydroxyphenyl)-n-dodecane, 4,4- In addition to bis(4-hydroxyphenyl)-1-pentanoic acid ethyl ester, p-tert-butylphenol-formalin condensate, p-phenylphenol-
Formalin condensates, etc. As the organic acid or its metal salt, 3-tert
-butylsalicylic acid, 3,5-tert-butylsalicylic acid, 5-α-methylbenzylsalicylic acid,
3,5-di-α-methylbenzylsalicylic acid, 3
-tert-octylsalicylic acid, 5-α,γ-dimethyl-α-phenyl-γ-phenylpropylsalicylic acid, etc., and their zinc salts, lead salts, aluminum salts, magnesium salts, and nickel salts are useful. Examples of oxybenzoic acid esters include ethyl p-oxybenzoate, butyl p-oxybenzoate, and p-oxybenzoate.
-heptyl oxybenzoate, benzyl p-oxybenzoate, etc. The vinyl compound used in the heat-sensitive recording material (2) of the present invention is a compound having one or more vinyl or vinylidene groups, preferably a plurality, such as an acryloyl group, a methacryloyl group, an allyl group, an unsaturated polyester group, a vinyloxy group, Examples include compounds having an acrylamide group. The most typical examples include reaction products of polyols, polyamines, amino alcohols, etc. and unsaturated carboxylic acids, and reaction products of acrylates or methacrylates having hydroxyl groups and polyisocyanates. For example, representative compounds include polyethylene glycol diacrylate, propylene glycol dimethacrylate, pentaerythritol triacrylate, trimethylolpropane diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate,
Hexanediol diacrylate, 1,2-butanediol diacrylate, tetrakis β-acryloxyethyl ethylene diamine, reaction product of epoxy resin and acrylic acid, reaction product of methacrylic acid, pentaerythritol and acrylic acid, maleic acid and diethylene glycol These include condensates of acrylic acid, methyl methacrylate, butyl methacrylate, styrene, divinylbenzene, and diarylnaphthalene. A plurality of these can be used in combination depending on the purpose. The photopolymerization initiator used in the heat-sensitive recording material (2) of the present invention includes one or a combination of organic or inorganic compounds having the ability to initiate polymerization of a vinyl compound by irradiation with light. These materials are already well-documented in detail.
For example, Kosar “Light Sensitive Systems”
John Wiley & Sons, Warashina et al. “Photosensitive resin”
It has been disclosed by Nikkan Kogyo Shimbun, Tsunoda et al.'s "Photosensitive Resin" Society of Printing, etc. Specific examples of photopolymerization initiators include aromatic ketones, quinone compounds, ether compounds, and nitro compounds. Specifically, benzoquinone, phenanthrenequinone, naphthoquinone, diisopropylphenanthrenequinone, benzoin butyl ether, benzoin, furoinbutyl ether, Michler's ketone, Michler's thioketone, tetraphenyllovhine dimer, fluorenone, trinitrofluorenone, β- Contains benzoylaminonaphthalene. These amounts range from 0.1% by weight to the vinyl compound.
It is added in an amount of about 30% by weight. The amount of compound added per unit area is leuco dye.
0.05 to 1.5 g, preferably 0.05 to 0.8 g, and the color developer is 0.3 to 8 g, preferably 0.5 to 5 g,
The organic solvent in the core material is 0.1-15g, preferably 0.1
~8g, and the organic solvent can be replaced with the vinyl compound in any proportion. The diazo compound used in ^the heat-sensitive material 3 of the present invention is a diazonium salt represented by the general formula ArN ₂ ⁺ It is a compound that can. (In the formula, Ar
represents a substituted or unsubstituted aromatic moiety,
N ₂ ⁺ represents a diazonium group and X ^- represents an acid anion. ) Specific examples of diazonium compounds that form salts include 4-diazo-1-dimethylaminobenzene, 4-diazo-1-diethylaminobenzene,
4-Diazo-1-dipropylaminobenzene, 4
-diazo-1-methylbenzylaminobenzene,
4-Diazo-1-dibenzylaminobenzene, 4
-Diazo-1-ethylhydroxyethylaminobenzene, 4-diazo-1-diethylamino-3-
Methoxybenzene, 4-diazo-1-dimethylamino-2-methylbenzene, 4-diazo-1-benzoylamino-2,5-diethoxybenzene,
4-Diazo-1-morpholino-2,5-diethoxybenzene, 4-diazo-1-morpholino-2,5-dibutoxybenzene, 4-diazo-1-anilinobenzene , 4-diazo-1-tolylmercapto-
2,5-diethoxybenzene, 4-diazo-1,
Examples include 4-methoxybenzoylamino-2,5-diethoxybenzene. A specific example of an acid anion is CnF ₂ n ₊₁ COO ^-
(n is an integer from 3 to 9), CmF ₂ m ₊₁ SO ₃ ^- (m is from 2 to
(ClF ₂ l ₊₁ SO ₂ ) ₂ CH ^- (l is an integer from 1 to 18), (n is an integer from 3 to 9) (n is an integer from 3 to 9)

[Formula] Examples include BR ₄ ^- and PF ₆ ^- . In particular, among the acid anions, those containing a perfluoroalkyl group or perfluoroalkenyl group, or PF ₆ ^- are preferable because they cause less increase in fog during raw storage. Specific examples of the diazo compound (diazonium salt) include the following examples. The coupling agent used in the thermal recording material 3 of the present invention is one that forms a dye by coupling with a diazo compound (diazonium salt) in a basic atmosphere, and specific examples include resorcin, phloroglucin, and 2,3-dihydroxynaphthalene. −
Sodium 6-sulfonate, 1-hydroxy-2
-Naphthoic acid morpholinopropylamide, 1,5
-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,3-dihydroxy-6-sulfanylnaphthalene, 2-hydroxy-3-naphthoic acid morpholinopropylamide, 2-hydroxy-3-naphthoic acid anilide, 2-hydroxy-
3-naphthoic acid-2'-methylanilide, 2-hydroxy-3-naphthoic acid ethanolamide, 2-
Hydroxy-3-naphthoic acid-N-dodecyl-oxy-propylamide, 2-hydroxy-3-naphthoic acid tetradecylamide, acetanilide,
Acetoacetanilide, benzoylacetanilide, 1-phenyl-3-methyl-5-pyrazolone, 1-(2',4',6'-trichlorophenyl)-3
-benzamide-5-pyrazolone, 1-(2',4',
6′-Trichlorophenyl)-3-anilino-5-
Examples include pyrazolone, 1-phenyl-3-phenylacetamido-5-pyrazolone, and the like. Furthermore, by using two or more of these coupling agents in combination, an image of any color tone can be obtained. As the basic substance used in the heat-sensitive recording material 3 of the present invention, a poorly water-soluble or water-insoluble basic substance or a substance that generates an alkali when heated is used. Basic substances include inorganic and organic ammonium salts, organic amines, amides, urea and thiourea and their derivatives, thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indoles, imidazoles, imidazolines, and triazoles. Examples include nitrogen-containing compounds such as morpholines, piperidines, amidines, formazines, and pyridines. Specific examples of these are:
For example, ammonium acetate, tricyclohexylamine, tribenzylamine, octadecylbenzylamine, stearylamine, allyl urea, thiourea, methylthiourea, allylthiourea, ethylenethiourea, 2-benzylimidazole, 4-phenylimidazole, 2-phenyl-4 -Methyl-imidazole, 2-undecyl-imidazoline, 2,4,5-trifuryl-2-imidazoline, 1,2-diphenyl-4,4-dimethyl-2
-imidazoline, 2-phenyl-2-imidazoline, 1,2,3-triphenylguanidine, 1,
2-ditolylguanidine, 1,2-dicyclohexylguanidine, 1,2,3-tricyclohexylguanidine, guanidine trichloroacetate,
N,N'-dibenzylpiperazine, 4,4'-dithiomorpholine, morpholinium trichloroacetate,
These include 2-amino-benzothiazole and 2-benzoylhydrazino-benzothiazole. Two or more of these basic substances can also be used in combination. Substances not contained in microcapsules are preferably used after being dispersed in solid form using a sand mill or the like. 2
In the case of more than one species, each substance is usually dispersed separately in an aqueous polymer solution, but there is no limitation. Preferred water-soluble polymers include water-soluble polymers used when making microcapsules. At this time, the concentration of water-soluble polymer is 2~
30 wt%, and the amount of the material to be dispersed in this water-soluble polymer solution is 5 to 40 wt%. As for the layered structure of the heat-sensitive material of the present invention, one or more heat-sensitive layers can be provided. When the heat-sensitive layer is one layer, two or more types of capsules having different glass transition points can be mixed and used. In the case of two layers, a high-sensitivity heat-sensitive layer containing capsules with a low glass transition temperature "as a system" from the side farthest from the support, followed by a low-sensitivity heat-sensitive layer containing capsules with a high glass transition temperature "as a system" It is convenient to provide. The same can be done for three or more layers. It is also possible to combine the case of the capsule described above with a multilayer configuration. Furthermore, if the particle size of the substance outside the capsule is a finite value, it will not be completely melted by the heating of the thermal head, and will only be completely melted when the applied energy increases. In particular, when two or more substances in a solid dispersion state outside the capsule are eutectic, the above-mentioned phenomenon related to particle size is likely to occur, and this can be advantageously used when providing gradation. In addition, providing a distribution in the wall thickness of the capsule can also be advantageously used in combination with the above-mentioned factors. In the case of a multilayer structure, simultaneous multilayer coating is also possible in addition to sequential coating one layer at a time. The heat-sensitive recording materials 1, 2, and 3 of the present invention contain silica, barium sulfate, titanium oxide,
Pigments such as aluminum hydroxide, zinc oxide, and calcium carbonate, and fine powders such as styrene beads and urea-melamine resin can be used. Similarly, metal soaps can also be used to prevent statesking. The amount of these used is 0.2 to 7 g/m ² . Furthermore, the light and heat sensitive recording materials 1 and 2 of the present invention include:
Thermofusible materials can be used to increase thermal recording density. As a heat-melting substance, it is solid at room temperature and has a melting point that melts when heated with a thermal head.
A substance with a temperature of 50 to 150℃, including leuco dye, color developer,
It is a substance that dissolves diazo compounds, coupling agents, or basic substances. Thermofusible substances are 0.1 to 10
It is used in an amount of 0.2 to 7 g/m ² of solids by dispersing it in the form of particles. Specific examples of the heat-melting substance include fatty acid amides, N-substituted fatty acid amides, ketone compounds, N-substituted carbamate compounds, urea compounds, and esters. The thermosensitive recording materials 1, 2, and 3 of the present invention can be coated with a suitable binder. As a binder, polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose,
Hydroxypropyl cellulose, gum arabic,
Various emulsions such as gelatin, polyvinylpyrrolidone, casein, styrene-butadiene latex, acrylonitrile-butadiene latex, polyvinyl acetate, polyacrylic ester, and ethylene-vinyl acetate copolymer can be used. The amount used is 0.5 to 5 g/m ² of solid content. In the present invention, in addition to the above materials, citric acid, tartaric acid, oxalic acid, boric acid, phosphoric acid, and pyrophosphoric acid can be added as acid stabilizers. Thermal recording materials 1, 2 and 3 of the present invention include microcapsules containing one of the components that causes a color reaction;
The other component is either solidly dispersed or dissolved as an aqueous solution and then mixed to create a coating solution, which is then applied onto a support such as paper or synthetic resin film by bar coating, blade coating, air knife coating, gravure coating, or roll coating. , applied by spray coating, dip coating, etc. and dried to a solid content of 2.5 to 25.
A heat-sensitive layer of g/m ² is provided. As the paper used for the support, heat-extracted neutral paper with a pH of 6 to 9 (described in JP-A-55-14281) sized with a neutral sizing agent such as alkyl ketene dimer (described in JP-A No. 55-14281) is recommended in terms of storage stability over time. It is advantageous. In addition, in order to prevent the coating liquid from penetrating the paper and to improve the contact between the recording heat head and the heat-sensitive recording layer, the Steckigt sizing degree/(meter basis weight) described in JP-A-57-116687 is used. ² ≧3×10 ⁻³ and paper with a Beck smoothness of 90 seconds or more is advantageous. Also, paper with an optical surface roughness of 8μ or less and a thickness of 40 to 75μ, described in JP-A-58-136492,
- Paper with a density of 0.9 g/cm ² or less and an optical contact ratio of 15% or more as described in No. 69091, with a Canadian standard water level (JiS P8121) of 400 c.c. or more as described in JP-A-58-69097. A paper made from beaten pulp to prevent coating liquid from seeping in. The glossy side of base paper made by a Yankee machine is used as the coating surface to improve color density and resolution, as described in Japanese Patent Application Laid-Open No. 58-65695. The paper described in Japanese Patent Application No. 57-145872, in which the base paper is subjected to corona discharge treatment to improve its coating suitability, can also be used in the present invention and give good results. In addition to these, any support commonly used in the field of heat-sensitive recording paper can be used as the support of the present invention. Thermal recording materials 1, 2, and 3 of the present invention have excellent gradation recording and can be used as printer paper for facsimiles and computer computers that require high-speed recording. Fixation can be achieved by photocuring the capsule to inactivate it or by decomposing the unreacted diazo compound. It is also possible to first imagewise expose and then uniformly heat the unexposed portions to thermally color them. In addition, it can also be used as a heat-developable copying paper. Examples are shown below, but the present invention is not limited thereto. Note that "parts" indicating the amount added represent "parts by weight.""Examples" Example 1 Two types of capsules were prepared using the following diazo compounds. diazo compound (Capsule liquid A) 2 parts of the diazo compound and 18 parts of a (3:1) adduct of xylylene diisocyanate and trimethylolpropane were added to and dissolved in a mixed solution of 24 parts of dibutyl phthalate and 5 parts of ethyl acetate. This diazo compound solution was mixed with an aqueous solution containing 3.5 parts of polyvinyl alcohol, 1.7 parts of gelatin, and 2.4 parts of 1,4-di(2-hydroxyethoxy)benzene dissolved in 58 parts of water, and emulsified and dispersed at 20°C. , average particle size 3μ
An emulsion was obtained. 100 parts of water was added to the obtained emulsion and heated to 60° C. while stirring, and after 2 hours, capsule liquid A containing a diazo compound in the core substance was obtained. (Capsule liquid B) In the preparation of capsule liquid A, the following changes were made to prepare capsule liquid B. Instead of 18 parts of the (3:1) adduct of xylylene diisocyanate and trimethylolpropane, 18 parts of the same compound and 6 parts of the (3:1) adduct of toluylene diisocyanate and trimethylolpropane were used. Capsule liquid B was also obtained by the same procedure as capsule liquid A, except that 2.4 parts of 1,4-di(2-hydroxyethoxy)benzene was removed from the aqueous solution composition. Next, 20 parts of 2-hydroxy-3-naphthoic acid anilide was added to 100 parts of a 5% polyvinyl alcohol aqueous solution and dispersed in a sand mill for about 24 hours.
A 3μ coupling component dispersion was obtained. Next, 20 parts of triphenylguanidine was added to 100 parts of a 5% polyvinyl alcohol aqueous solution and dispersed in a sand mill for about 24 hours to obtain a dispersion of triphenylguanidine with an average particle size of 3 μm. Further, 20 parts of p-benzyloxyphenol was added to 100 parts of a 5% polyvinyl alcohol aqueous solution and dispersed in a sand mill for about 24 hours to obtain a dispersion of p-benzyloxyphenol having an average particle size of 3 μm. 30 parts of capsule liquid A obtained as above,
A coating solution was prepared by adding 20 parts of capsule liquid B, 15 parts of coupling compound, and 15 parts of triphenylguanidine.The coating solution was coated on smooth high-quality paper (50 g/m ² ) using a coating rod to give a dry weight of 14 g/m 2 . ² and dried at 45°C for 30 minutes to obtain a heat-sensitive recording material. The glass transition points of the capsule walls of capsule liquid A and capsule liquid B as a system are 120°C and 120°C, respectively.
It was 140℃. Example 2 Coupling composition dispersion added to 50 parts of capsule liquid B
15 parts of triphenylguanidine dispersion were added to prepare a first layer coating solution. Next, 15 parts of a coupling component dispersion, 15 parts of a triphenylguanidine dispersion, and 15 parts of p-benzyloxyphenol were added to 50 parts of capsule liquid A to prepare a coating liquid for the second layer. The coating liquid for the first layer and the coating liquid for the second layer were sequentially applied in layers on high-quality paper (50 g/m ² ) using a coating rod so that the dry weights were 6 g and 7 g, respectively.
A heat-sensitive recording material was obtained by drying at ℃ for 30 minutes. The glass transition point of the capsule wall used in the first coating solution was 140°C.
The glass transition temperature of the substance interacting with the capsule wall and p-benzyloxyphenol used in the second layer coating liquid was 80 to 90°C "as a system". Example 3 A heat-sensitive recording material was obtained in the same manner as in Example 2, except that an intermediate layer of polyvinyl alcohol (dry film thickness: 0.5μ) was provided between the first layer and the second layer. . Comparative Example A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 50 parts of Capsule Liquid A was used instead of 30 parts of Capsule Liquid A and 20 parts of Capsule Liquid B in Example 1. (Test method) The obtained heat-sensitive recording material was thermally recorded by changing the applied energy, and then the entire surface was exposed using Ricopy Super Dry 100 (manufactured by Ricoh Co., Ltd.) and fixed. The blue density of the obtained recorded image was measured using a Macbeth reflection densitometer. The results are shown in Figure 1. "Effects of the Invention" From FIG. 1, it is clear that Examples 1, 2, and 3 have smoother density changes and superior gradation expression, especially at low applied energy, compared to Comparative Examples.

[Brief explanation of drawings]

FIG. 1 shows the relationship between the energy applied to the heat-sensitive recording material and the print density. However, in FIG. 1, curves 1 to 4 represent the following. 1...Example 1, 2...Example 2, 3...Example 3, 4...Comparative example.

Claims (1)

[Claims] 1. A heat-sensitive material having microcapsules containing at least one component that causes a color reaction and an organic solvent in the core, and another component that develops a color by reacting with the component that causes a color reaction, on the same side of a support. A heat-sensitive recording material characterized in that two or more types of microcapsules whose walls have different glass transition points are used as microcapsules.