JPH078595B2 - Multicolor thermal recording material - Google Patents

Description

The present invention relates to a multicolor color-developing heat-sensitive recording material,
In particular, the present invention relates to a multicolor color-developing heat-sensitive recording material which is excellent in storability before heat recording and safety in recording after heat recording and has a high color density during heat recording.

(Prior Art) As a multicolor color-developing heat-sensitive recording material, for example, a colorless or light-colored basic dye precursor, an acidic substance that is solid at room temperature to cause a reaction with the basic dye precursor at the time of heating, and a basic solid that is solid at room temperature. JP-B-51-37542 discloses a multicolor type color-forming heat-sensitive recording material containing a substance and a dispersion of a color-forming substance which develops a color upon reaction with the basic substance in combination.

The heat-sensitive recording material utilizes a difference in melting point between a phenolic acidic substance that is solid at room temperature and an organic base that is solid at room temperature to cause a color reaction with the phenolic substance when the phenolic substance melts during heating (crystal bio-leptlactone). When the organic base melts, the environment of the entire system becomes basic, so the color development of the color forming substance that causes a color forming reaction with the phenolic substance is suppressed or already developed. When this occurs, it discolors or erases color, and by causing the base to develop a color-forming substance capable of forming a different color, the respective color-forming substances are selectively melted by the heating temperature. A multicolor coloring thermosensitive recording material is obtained by causing a coloring reaction to develop a color.

The multicolor color-developing heat-sensitive recording material is characterized in that a phenolic color-developing material that bears a color is fading with an organic base, and a color-developing substance capable of developing color with the basic substance is developed therein.

Generally, a basic colorless dye precursor (leuco dye) color-developing thermal recording material is used as a recording material used in a thermal recording method. However, it is common that the leuco dye is faded or erased by a base. Known to be. When an acidic colorless dye precursor is used instead of such a basic colorless dye precursor, it is easily conceivable that the acid colorless dye precursor can be decolored by contact with an acid.

The multicolor coloring type heat-sensitive material is used for color development or fading or erasing by utilizing the above-mentioned acid-base reaction. However, the color-forming substance and the basic substance are closely dispersed in the same layer. Since it is contained, it is easy for the dispersions to come into contact with each other,
It is chemically unstable, and has the drawback that sweat and oily substances adhere to the hands before and after recording, and undesired decoloring occurs when it comes into contact with adhesive tape or diazo copy paper.

(Problems to be Solved by the Invention) Therefore, a first object of the present invention is to provide a multicolor thermosensitive recording material which is excellent in preservability of recording performance before printing and stability of recording after printing. It is in. A second object of the present invention is to provide a multicolor coloring heat-sensitive material having a high color density and excellent manufacturability.

(Means for Solving the Problem) An object of the present invention is to provide a high-temperature color-forming layer and a low-temperature color-forming layer containing a basic dye precursor and an acidic substance that causes a color-developing reaction upon heating with the basic dye precursor on a support. In a multicolor heat-sensitive recording material having a structure in which these layers are provided in this order, and an intermediate layer is provided between both layers as necessary, a base precursor represented by the following general formula (I) is added to the low-temperature color-forming layer or the intermediate layer. It was achieved by a multicolor thermosensitive recording material characterized in that

B—X—B.2RSO ₂ CH ₂ CO ₂ H (I) In the above formula, B represents a group representing an organic base, X represents a divalent organic group, R represents an aliphatic group, an aromatic group and a heterocyclic group. Represents

To give an example of the multicolor thermosensitive recording material according to the present invention, when it is heated at a relatively low temperature, it develops blue, and when it is developed at a relatively high temperature, this blue color is erased by the generated base, Only the red color, which is colored at higher temperature, will be colored.

Conventionally, solid crystals having a melting point higher than the coloring temperature of the low temperature coloring layer, for example, specific alcohols, polyethers, polyethylene glycols, guanidine derivatives, etc. have been used as the decoloring agents. Since the agent is hygroscopic, if it is contained in the heat-sensitive layer as it is, it absorbs moisture in the air during the storage period of the recording material, which causes fogging or fading phenomenon in the recording material and makes the image unclear. There was a drawback that

The point of the present invention is to find an epoch-making decoloring agent that overcomes such drawbacks.

That is, the decolorizing agent of the present invention is itself neutral,
When heated, it decarboxylates for the first time to generate a base, and this base exerts the effect of decoloring the color formed product of the basic dye precursor and the acidic substance for the first time.

Conventionally, various compounds that generate a base by thermal decomposition have been known, but none of them has been able to achieve both a sufficient decomposition rate and stability over time.

As a solution to this problem, it is disclosed in JP-A-59-168,44.
There are sulfonylacetate-based base precursors described in Japanese Patent No. 1 and No. 59-180,537, and propiolate-based base precursors, both of which can be used as the decoloring agent of the present invention. However, in the present invention, a base precursor having a higher decomposition rate is desired, and as a result of earnest studies, a group of base precursors having a significantly high decomposition rate and good stability over time have been developed.

As a feature of these base precursors, their solubility in water is extremely low, and when added to heat-sensitive materials, they are usually added in the form of a suspension in which crystals are finely dispersed, and are extremely stable below the melting point (or decomposition point) of the compound itself. In addition, the physical properties of rapidly decomposing above the melting point to form a base can be mentioned. Therefore, even if the heat-sensitive material is stored for a long period of time, it has almost no adverse effect.

As a base precursor particularly useful in the present invention, in the general formula (I), B is an amidino group or a guanidino group and R is
Can be an aryl group.

Specific preferred examples of the base precursor are listed below, but the present invention is not limited thereto.

These decolorizers can be used in the form of finely dispersed by a ball mill or the like in the presence of a suitable protective colloid such as Povar, and also in the color forming layer or as an intermediate layer between the color forming layers, It is also possible to include it in the undercoat layer or the protective layer. Furthermore, the decolorizing agent used in the present invention is neutral at room temperature, and has little chemical action under storage conditions for both low-temperature and high-temperature color-developing systems.
It is also possible to allow the high temperature color-developing system and the decoloring agent to be present in the same layer.

This is also extremely useful in terms of manufacturing cost. The decolorizing agent used in the present invention has a decolorizing effect on the coloring system of the basic dye precursor and the acidic substance when heated.
Therefore, the thermosensitive coloring system that develops color at low temperature must be a coloring system composed of a basic dye precursor (typically a leuco dye) and an acidic substance (typically a phenolic substance). On the other hand, since the thermosensitive color developing system which develops color at high temperature does not need to be decolored, a conventionally known thermosensitive color developing system can be appropriately used.

In particular, as a high temperature coloring system, a diazonium salt and a coupler,
Use of a system consisting of a base or a color-forming system consisting of an acid dye precursor and a base is useful because the base, which is a decolorizing agent for low-temperature systems, does not adversely affect the color development of the high-temperature color-developing system during high-temperature color development. Is.

A part of these known thermosensitive coloring systems will be described below, but the present invention is not limited thereto.

As the basic colorless dye precursor used in the present invention,
For example, crystal bio-leptlactone, 3-indolino-3-p-dimethylaminophenyl-6-dimethylaminophthalide, 3-diethylamino-7-chlorofluorane, 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) aminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-cyclohexylamino-6-chlorofluoroane, 3-diethylamino-6-methyl-7-xylidinofluorane,
2-anilino-3-methyl-6- (N-ethyl-p-toluidino) fluorane, 3-pyrrolidino-6-methyl-
7-anilinofluorane, 3-pyrrolidino-7-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-trifluoromethylanilino) fluorane and the like, but not limited thereto.

As the acidic substance that causes a color reaction with these basic dye precursors, a phenol compound, an organic acid or a metal salt thereof, an oxybenzoic acid ester, or the like is used.

In particular, the melting point is 50 ° to 250 ° C, particularly preferably 60 ° to 2 °
Phenols and organic acids, which are sparingly soluble in water at 00 ° C, are desirable.

Examples of phenol compounds are 4,4'-isopropylidene-diphenol (bisphenol A), p-tert-
Butylphenol, 2,4-dinitrophenol, 3,4-dichlorophenol, 4,4'-methylene-bis (2,6-di-
tert-butylphenol), p-phenylphenol,
4,4-Cyclohexylidenediphenol, 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-bis (4-hydroxyphenyl) -1-pentanoic acid ethyl ester, p-tert-butylphenol-formalin condensate, p-phenylphenol-formalin There are condensates and the like. 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 and the like and their zinc salts, lead salts, aluminum salts, magnesium salts and nickel salts are useful. is there.

Examples of the oxybenzoic acid ester include ethyl p-oxybenzoate, butyl p-oxybenzoate, heptyl p-oxybenzoate, benzyl p-oxybenzoate and the like.

Examples of the acidic colorless dye precursor used in the present invention include phenolphthalein, fluorescein, 2 ',
4 ', 5', 7'-Tetrabromo-3,4,5,6-tetrachlorofluorescein, Tetrabromophenol blue, 4,5,
6,7-Tetrabromophenolphthalein, Eoquine,
Examples include but are not limited to aurin cresol red and 2-naphthol phenolphthalein.

As the basic substance that causes a color reaction with the acidic dye precursor used in the heat-sensitive recording material of the present invention, a hardly water-soluble or water-insoluble basic substance or a substance that generates an alkali by heating is used.

As the basic substance, inorganic and organic ammonium salts, organic amines, amides, urea and thiourea and their derivatives, thiazoles, pyrroles, pyridines, piperazines,
Examples of the nitrogen-containing compounds include guanidines, indoles, imidazoles, imidazolines, triazoles, morpholines, piperidines, amidines, formsazines and pyridines. Specific examples thereof include ammonium acetate, tricyclohexylamine, tribenzylamine, octadecylbenzylamine, stearylamine, allylurea, thiourea, methylthiourea, allylthiourea, ethylenethiourea, 2-benzylimidazole, 4-phenyl. Imidazole, 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-dicyclohexyl-3-phenylguanidine, 1,2,3- Tricyclohexylguanidine, guanidine trichloroacetate, N, N'-dibenzylpiperazine, 4,4'-dithiomorpholine, morpholinium trichloroacetate, 2-amino-benzothiazole, 2-benzoylhydrazino-benzothiazole . These basic substances can be used in combination of two or more.

The diazo compound used in the heat-sensitive material of the present invention has the general formula
ArN ₂ ⁺ X ^- is a diazonium salt represented by, it can be colored undergoing a coupling agent and a coupling reaction and a compound capable of by connexion decomposed into light. (In the formula, Ar represents a substituted or unsubstituted aromatic moiety, Na ⁺ represents a diazonium group, and X ⁻ represents an acid anion.) Specific examples of the diazonium compound forming a salt include:
-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-morpholinobenzene, 4-diazo-1-morpholino-2,5-diethoxybenzene, 4-diazo- 1-morpholino-2,5
-Dibutoxybenzene, 4-diazo-1-anilinobenzene, 4-diazo-1-toluylmercapto-2,5-diethoxybenzene, 4-diazo-1,4-methoxybenzoylamino-2,5-diethoxy Examples thereof include benzene.

Specific examples of the acid anion include CnF ₂ n ₊₁ COO ⁻ (n is 3 to
9 _{integer), CmF 2 m +1 SO 3} - (m is 2-8 integer), (ClF
_{2 l +1 SO 2) 2 CH} - (l 1 to 18 integer), BF ₄ ^-, PF ₆ ^-, and the like.

In particular, acid anions containing perfluoroalkyl or perfluoroalkenyl groups or PF
₆ ^- is preferable because of 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 heat-sensitive recording material of the present invention is a coupling agent which 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 octylamide,
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-benzamido-5-pyrazolone, 1- (2 ', 4', 6'-trichlorophenyl) -3 −
Examples thereof include anilino-5-pyrazolone and 1-phenyl-3-phenylacetamido-5-pyrazolone.

As these diazonium salts, those encapsulated in thermoresponsive microcapsules by the method described in JP-A-60-6493 and the like are particularly preferably used.

Other examples of those used for high temperature color development system are: (1) long-chain fatty acid iron salts such as ferric stearate and ferric myristyrene; and phenols such as tannic acid, gallic acid and ammonium salicylate. (2) Organic acid heavy metal salts such as nickel, cobalt, lead, copper, iron, mercury, silver salts such as acetic acid, stearic acid, palmitic acid and calcium sulfide, strontium sulfide, vanium chloride A combination with an alkaline earth metal sulfide, or a combination of the organic acid heavy metal salt with an organic chelating agent such as S-diphenylcarbaside or diphenylcarbazone, (3) silver, lead, mercury, Combination of heavy metal oxalate such as thorium oxalate and sulfur compound such as Na-tetrathionate, sodium thiosulfate, thiourea, (4) stearic acid Fatty acids such as ferric iron and ferric salts
A combination with an aromatic polyhydroxy compound such as 3,4-dihydroxytetraphenylmethane, (5) Organic acid precious metal salts such as oxalate and mercury oxalate, and organic polyhydric alcohols such as polyhydroxy alcohol, glycerin and glycol. (6) A combination with a hydroxy compound, (6) A combination of an organic acid noble metal salt such as silver behenate and silver stearate, and an aromatic organic reducing agent such as protocatechuic acid, spiroindane, and hydroquinone, (7) Pelargonic acid (8) Lead caproate, lead pelargonate, lead behenate organic, in combination with a ferric acid ferric salt such as ferric and ferric laurate and a thiosemicarbamide or isothiosemicarbamide derivative. A combination of a lead acid salt and a thiourea derivative such as ethylene thiourea and N-dotecil thiourea, (9) stearic acid second Examples include combinations of higher fatty acid heavy metal salts such as iron and copper stearate with zinc dialkyldithiocarbamate, and (10) those that form an oxazine dye, such as a combination of resorcin and a nitroso compound.

A color forming auxiliary agent can be used in the color forming layer of the present invention. In particular, it is preferable to use an appropriate heat sensitizer for the low temperature color developing system. As these sensitizers, known compounds can be used, for example, higher fatty acid amides such as stearic acid amide, erucic acid amide, palmitic acid amide, waxes such as ethylene bis stearoamide or higher fatty acid ester, or benzoin. Acid phenyl derivative or urea derivative, for example, 1-phenylurea, 1-methyl-3-phenylurea, 1-ethyl-3-phenylurea, 1,1-diethyl-3-phenylurea, 1-phenyl-3-propylurea, 3- Phenyl-1,1-dipropylurea, 1-isopropyl-3-phenylurea, 1-isopropyl-
3-phenyl-1-propylurea, 1,1-diisopropyl-1-dicyclohexyl-3-phenylurea, 1
-(3-methoxy-propyl) -3-phenylurea,
1- (3-cyclohexylpropyl) -3-phenylurea, 1- (p-methoxyphenyl) -3-butylureido, 1- (2-phenoxyethyl) -3-phenylurea, 1-benzyl-3-phenylurea, 1- (4-
Octadecyloxyphenyl) -3-phenylurea, 1-octadecylurea, 1-dodecyl-3-butylurea, 1-benzyl-3-butylurea, 1,1-diisobutyl-3- (1-naphthyl) urea, 1,3 -Dioctadecylurea, 1,1-dimethyl-3- (2,4-xylyl) urea, 4,4'-bis (3-butylureido) diphenylmethane, 2,4-bis [3- (2-butoxyethyl) Ureido] toluene, 1,6-bis (3-benzylureido) hexane or urethane derivative, for example, phenylcarbamoyloxidedecane, phenylcarbamoyloxyoctadecane, phenylca-3-phenylurea, 1-butyl-3-phenylurea, 1,1 -Dibutyl-3-phenylurea, 1-isobutyl-3-phenylurea, 1-tert-butyl-3- Phenyl urea, 1-tert-butyl-1-methyl-3-phenyl urea, 1-penter-3-phenyl urea, 1,1-dipentyl-3-phenyl urea, 1-tert-pentyl-3-phenyl urea, 1-isopentyl-3- Phenylurea, 1-phenyl-3- (1,2,2-trimethylpropyl) urea, 1- (1-ethyl-3-methylbutyl) -3-phenylurea, 1- (1-ethyl-2,2-
Dimethylbutyl) -3-phenylurea, 1-phenyl-3- (1,1,3,3-tetramethylbutyl) urea, 1-
Decyl-3-phenylurea, 1- (1-butylhexyl) -3-phenylurea, 1- (1-butyl-1-ethylpenter) -3-phenylurea, 1-dodecyl-
3-phenylurea, 1-octadecyl-3-phenylurea, 1-cyclohexyl-3-phenylurea, or a naphthol derivative, for example, 2-benzyloxy-3-pt-butylphenoxycarbonylnaphthalene, 1-benzyloxynaphthalene,
2-benzyloxynaphthalene, 2-p-chlorobenzyloxynaphthalene, 2-p-isopropylbenzyloxynaphthalene, 2-dodecyloxynaphthalene, 2-
Decanoyloxynaphthalene, 2-myristoyloxynaphthalene, 2-pt-butylbenzoyloxynaphthalene, 2-benzoyloxynaphthalene, 2-benzyloxy-3-N- (3-dodecyloxypropyl) carbamoylnaphthalene, 2-benzyl Oxy-3-N-
Examples include octylcarbamoylnaphthalene and 2-benzyloxy-3-dodecyloxycarbonylnaphthalene.

When these low melting point compounds are used together with a color developer, they can be used alone or as a mixture.

The color former and the color developer are used individually or in a dispersion medium by pulverizing them to a particle size of several μm and dispersing them. At this time, the particle size is crushed to an average particle size of 5 μm or less, more preferably 3 μm or less. The dispersion medium is generally a water-soluble polymer having a concentration of about 1 to 10%, such as polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, isobutylene-anhydrous. Maleic acid copolymer, polyacrylic acid, polyacrylic acid amide, starch derivative, casein, gelatin and the like are used, and the dispersion is performed using a ball mill, a sand mill, an attritor, a colloid mill and the like. Further, these water-soluble polymers also function as a binder after coating. For the purpose of imparting water resistance as a binder, a water resistant agent (gelling agent, cross-linking agent) is added to the coating liquid at the time of coating, or a hydrophobic polymer emulsion, specifically, styrene-butadiene rubber latex, acrylic resin emulsion, etc. Can also be added. Further, the color former may be included in the thermoresponsive microcapsules.

Additives are added to the heat-sensitive coating liquid thus obtained in order to satisfy various requirements. As an example of the additive, an oil-absorbing substance such as an inorganic pigment is added to the heat-sensitive recording layer in order to prevent the recording head from being soiled during recording, and in order to further enhance the releasability from the heat-sensitive head. Fatty acids, metal soaps, etc. are added.

Therefore, in general, a thermosensitive recording sheet is formed by coating a support with a pigment, a wax, an additive and the like in addition to a color former and a color developer that directly contribute to color development.

Specifically, as the pigment, kaolin, calcined kaolin,
Talc, wax, diatomaceous earth, calcium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium carbonate, titanium oxide, barium carbonate, fine anhydrous silica,
It is selected from activated clay, urea-formalin filler, cellulose filler and the like. Examples of waxes include paraffin wax, carnauba wax, microcrystalline wax, polyethylene wax and higher fatty acid ester.

Examples of the metal soap include higher fatty acid polyvalent metal salts such as zinc stearate, aluminum stearate, calcium stearate, and zinc oleate. These are dispersed in the aforementioned water-soluble polymer and applied.

The heat-sensitive recording material of the present invention can be used as recording paper for printers, electrocardiograms, recorders and the like for facsimiles and electronic calculators, which are capable of multicolor recording and require high-speed recording.

Example (Preparation of coating liquid A) 6.0 g of base precursor (BP-6) having the following structure A 15% polyvinyl alcohol aqueous solution (5.2 g) and water (8.8 g) were mixed and finely dispersed for 3 hours using a paint shaker.

(Preparation of coating liquid B) The precursor contained in coating liquid A was changed to BP-5 described below, and other components were obtained in the same manner.

(Preparation of coating liquid C) The precursor contained in coating liquid A was changed to BP-34 described below, and other components were obtained in the same manner.

(Preparation of coating liquid D) Tricyclohexylguanidine, which is a solid base, was used in place of the base precursor of coating liquid A, and the same procedure was followed.

(Preparation of Coating Liquid E) A coating liquid E was obtained as a low temperature black color heat-sensitive system as follows.

2-anilino-3-methyl-N-methyl- as a color former
N-cyclohexylaminofluorane, bisphenol A as a color developer, and 20 g of each of (4,4'-methoxyphenylthio) ethane as a sensitizer together with 100 g of an aqueous solution of 5% polyvinyl alcohol (Kuraray PVA-105) for 24 hours. The particles were dispersed by a ball mill to have a volume average particle diameter of 3 μm or less.
Calcium carbonate as a pigment (Unibur 70 Shiraishi Industry)
80 g was used together with 160 g of 0.5% sodium hexametaphosphate solution dispersed by a homogenizer. 2-anilino-3-methyl-6 was added to each dispersion liquid prepared as described above.
-N-Methyl-N-cyclohexylaminofluorane dispersion liquid 5g, bisphenol A dispersion liquid 10g, (4,4'-methoxyphenylthio) ethane dispersion liquid 10g, calcium carbonate dispersion liquid 15g were mixed in a ratio, and further mixed. Obtained by adding 3 g of 21% zinc stearate emulsion.

(Preparation of coating liquid F) A coating liquid F was prepared as follows as a high temperature heat-sensitive red coloring system.

2 parts of the following diazo compound and 18 parts of a (3: 1) adduct of xylylene diisocyanate and trimethylolpropane were added to a mixed solvent of 24 parts of dibutyl phthalate and 5 parts of ethyl acetate and dissolved. The solution of this diazo compound was mixed with an aqueous solution in which 5.2 parts of polyvinyl alcohol was dissolved in 58 parts of water and was emulsified and dispersed at 20 ° C. to obtain an emulsion having an average particle size of 3 μ. 100 parts of water is added to the obtained emulsion, and the mixture is stirred at 60
The mixture was heated to 0 ° C., and after 2 hours, a microcapsule liquid containing a diazo compound in the core was obtained.

Further, 10 parts of the following compound 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 liquid of a red coloring coupling agent having an average particle diameter of 3 μm.

Further, 10 parts of 1,2-dicyclohexyl-3-phenylguanidine was added to 100 parts of a 5% aqueous solution of polyvinyl alcohol and dispersed by a sand mill for about 24 hours to obtain 1,2,
A dispersion of 3-triphenylguanidine was obtained.

In addition, 10 parts of p-benzyloxyphenol was added to 100 parts of a 5% aqueous solution of polyvinyl alcohol, and a sand mill was used to obtain about 24 parts.
After time-dispersion, a dispersion liquid of p-benzyloxyphenol having an average particle size of 3 μ was obtained.

30 parts of the capsule liquid obtained as described above, 20 parts of the coupling agent dispersion, 1,2,3 triphenyl guanidine dispersion liquid 30
Parts and 20 parts of a dispersion liquid of p-benzyloxyphenol were mixed to obtain a high temperature red color heat-sensitive coating liquid F.

<Example-1> 6 g / dry weight of coating liquid F was applied onto smooth wood free paper (50 g / m ² ).
m ² and coating liquid A were applied in a dry weight of 2 g / m ² , and coating liquid E was applied and dried in order to give a dry weight of 4 g / m ² to obtain a heat-sensitive recording material. When this was printed using a thermal printing tester manufactured by Kyocera with a printing energy of 18 mJ / mm ² , a clear black color image was obtained. On the other hand, when printing was performed at 40 mJ / mm ² , a clear red color image was obtained this time. Also, as a stability test over time,
When the coated paper was aged at 40 ° C and 90% RH for one day and printed in the same way, it was clear that both black and red color development were clear, and that there was almost no change in the background, and it had good storability.

<Example-2> A thermosensitive recording material was obtained in the same manner as in Example-1, except that the coating liquid B was used in place of the coating liquid A. When this product was also evaluated in the same manner, it showed clear black and red colors in both the unaged sample and the aged sample, and there was no fog on the background.

<Example-3> A thermosensitive recording material was obtained in the same manner as in Example-1, except that the coating liquid C was used instead of the coating liquid A. When this product was also evaluated in the same manner, both unaged sample and aged sample showed clear black and red color development, and there was no fog on the background.

<Comparative Example-1> A thermosensitive recording material was obtained in the same manner except that the coating liquid D was used instead of the coating liquid A of Example-1. When this was similarly evaluated, the unaged sample showed clear black and red colors, but the background had a dark fog. Further, when printing was performed after aging, the black color was thin and unclear, and the red color was clear. In addition, the background had more dark fog.

<Example -4> smooth high-quality paper (50g / m ²⁾ on a dry weight coating liquid F on 6 g / m ²
After coating and drying, a mixture of coating liquid E and coating liquid A in a weight ratio of 2: 1 was coated and dried to a dry weight of 6 g / m ² to obtain a heat-sensitive recording material. When this product was evaluated by the same method as in Example-1, it showed clear black and red color development and no fog on the background. Furthermore, even after printing after aging at 40 ° C and 90% RH, clear black and red coloring was exhibited, and the fog on the background did not deteriorate.

<Comparative Example-2> A thermosensitive recording material was obtained in the same manner except that the coating liquid D was used in place of the coating liquid A of Example-4. When this product was evaluated in the same manner as in Example 4, almost no black coloration occurred, only red color was formed, and the background was darkened.

Claims (1)

[Claims] 1. A high-temperature color-developing layer and a low-temperature color-developing layer containing a basic dye precursor and an acidic substance which causes a color-developing reaction upon heating with the basic dye precursor are provided in this order on a support, and if necessary, both layers are provided. In a multicolor thermosensitive recording material having a structure in which an intermediate layer is provided between layers, a base precursor represented by the following general formula (I) is added in the low temperature color forming layer or in the intermediate layer. Recording material. B—X—B.2RSO ₂ CH ₂ CO ₂ H (I) In the above formula, B represents a group representing an organic base, X represents a divalent organic group, R represents an aliphatic group, an aromatic group and a heterocyclic group. Represents