JPH01150575A - Multicolor thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a multicolor thermal recording material excellent in the preservability of recording capacity before printing and the stability of recording after printing, by incorporating a basic dye precursor, an acidic substance generating the color forming reaction with the basic dye precursor at the time of heating and a base precursor generating a base upon the decarbonation at the time of heating. CONSTITUTION:A multicolor thermal recording material contains a basic dye precursor, an acidic substance generating the color forming reaction with the basic dye precursor at the time of heating and a base precursor generating a base upon the decarbonation at the time of heating and prepared by forming a thermal color forming layer consisting of at least two color forming systems having different color forming temps. and developing colors in different hues on a support. A high temp. thermal color forming layer forming a color at relatively high temp. is set to a lower layer and a low temp. thermal color forming layer forming a color at relatively low temp. is set to an upper layer and the base precursor generating a base upon the decarbonation at the time of heating is contained in the intermediate layer between both layers or in the low temp. thermal color forming layer. For example, a blue color is developed at the time of heating at relatively low temp. but erased by the generated base at the time of heating at relatively high temp. and only a red color formed at high temp. is developed.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a multicolor heat-sensitive recording material,
In particular, the present invention relates to a multicolor heat-sensitive recording material that has excellent storage stability before thermal recording and recording stability after thermal recording, and has high color density during thermal recording.

(Prior art) As a multicolor heat-sensitive recording material, for example, a colorless or light-colored basic dye precursor, an acidic substance that is solid at room temperature that reacts with the basic dye precursor when heated, and a basic substance that is solid at room temperature. A multicolor color-forming heat-sensitive recording material containing a combination of a substance and a dispersion of a color-forming substance that reacts with the basic substance to form a color when heated is described in Japanese Patent Publication No. Shoj/-57j4-. There is.

The heat-sensitive recording material takes advantage of the 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, and when the phenolic substance melts during heating, a coloring reaction occurs with the phenolic substance (crystal pi-olet). When the organic base melts, the environment of the entire system becomes basic, so either the coloring of the coloring substance that causes a coloring reaction with the phenolic substance is suppressed, or the coloring is already done. In addition to fading or erasing this color, the base causes the color-forming substances that can develop a different color to develop, thereby selectively melting each color-forming substance depending on the heating temperature and producing color. A reaction occurs to develop color and a multicolor thermosensitive recording material is obtained.

The multicolor heat-sensitive recording material is characterized in that a phenolic coloring substance that has been once colored is bleached by an organic base, and then a coloring substance that can be colored by the basic substance is colored.

Color-forming heat-sensitive recording materials using basic colorless dye precursors (leuco dyes) are generally used as recording materials for heat-sensitive recording methods, but nuclear leuco dyes generally do not discolor or disappear when exposed to bases. Are known. If an acidic colorless dye precursor is used instead of such a basic colorless dye precursor, it is easy to imagine that the scales will decolor on contact with acid.

The multicolor heat-sensitive material uses the above-mentioned acid-base reaction to develop, fade, or erase color, and the color-forming substance and the basic substance are contained in the same layer in close proximity and in a dispersed state. Because of this, it is easy for the dispersions to come into contact with each other.
It is chemically unstable and has the disadvantage of causing undesirable discoloration when it is exposed to sweat from hands or oily substances during handling before and after recording, or when it comes into contact with adhesive tape or diazo copying paper.

(Problems to be Solved by the Invention) Therefore, the first object of the present invention is to provide a multicolor heat-sensitive recording material that has excellent storage performance of recording performance before printing and stability of recording after printing. It is in. The first object of the present invention is to provide a multicolor heat-sensitive material that has high color density and excellent manufacturing suitability.

(Means for Solving the Problem) As a result of intensive research, the present inventors found that a basic dye precursor, an acidic substance that causes a coloring reaction with the basic dye precursor when heated, and a The objective was achieved by a multicolor thermosensitive recording material characterized by containing a base precursor that generates . Typical examples of the multicolor development mechanism of the present invention will be outlined below.

The multicolor heat-sensitive recording material of the present invention is one in which a heat-sensitive coloring layer consisting of at least λ coloring systems having different coloring temperatures and different color tones is formed on a support. As a system, the lower layer is a high-temperature thermosensitive coloring layer that develops color at a relatively high temperature, the upper layer is a low-temperature thermosensitive coloring layer that develops color at a relatively low temperature, and between these layers or the low-temperature thermosensitive coloring layer is a layer that is decarboxylated when heated. Examples include those containing a base precursor that generates a base.

In this case, for example, when heated at a relatively low temperature, a blue color develops, and when the color is developed at a relatively high temperature, this blue color is erased by the generated base, and a red color develops at a higher temperature. Only the color develops.

Conventionally, solid crystals whose melting points are higher than the coloring temperature of the low-temperature coloring layer, such as certain alcohols, polyethers, polyethylene glycols, and guanidine derivatives, have been used as decolorizing agents. Since coloring agents are hygroscopic, if they are incorporated in the heat-sensitive layer in this form, they will absorb moisture from the air during the storage period of the recording material, causing fogging or discoloration in the recording material, causing the image to deteriorate. It had the disadvantage of making it unclear.

The point of the present invention lies in the discovery of an innovative decolorizing agent that overcomes these drawbacks.

That is, the decolorizing agent of the present invention is itself neutral;
When heated, decarboxylation occurs for the first time to generate a base, and this base exhibits the effect of decoloring the colored product of the basic dye precursor and the acidic substance.

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

% Kaisho is a major improvement on this problem! Tar/A
F, the sulfonylacetate base precursor described in the specification of 4tlA1 and JP-A-Sho! There is a propiolate base precursor described in Patent No. 137/10゜137,
Both can be used as a decolorizing agent in the present invention. However, in the present invention, a base precursor with an even higher decomposition rate is desired, and as a result of intensive studies, we have developed a group of base precursors that have an extremely high decomposition rate and good stability over time.

These base precursors are characterized by extremely low solubility in water, and when added to heat-sensitive materials, they are usually added in the form of a suspension of finely dispersed crystals, and are extremely stable below the melting point (or decomposition point) of the compound itself. It also has the physical property of rapidly decomposing above its melting point and producing a base. Therefore, long-term storage of heat-sensitive materials has almost no adverse effects.

The base precursor preferably used in the present invention is represented by the following general formula (1).

B-X-B-λR8OCHCOH()) In the above formula, B
represents a group representing an organic base, X represents a divalent organic group, and R represents an aliphatic group, an aromatic group, or a heterocyclic group.

Particularly useful base precursors in the present invention include general formula (1), where B is an amidino group or a guanidino group, and R
is an aryl group.

Preferred specific examples of the base precursor are listed below, but the BA of the present invention is not limited thereto.

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These decolorizing agents can be used in finely dispersed form using a ball mill or the like in the presence of an appropriate protective colloid such as Poval, and can be used in the color forming layer or between the color forming layers. It can be used as a layer or included in a subbing layer or a protective layer. Furthermore, the decolorizing agent used in the present invention is neutral at room temperature and has almost no chemical effect on either low-temperature or high-temperature coloring systems under storage conditions. It is also possible to have a high-temperature coloring system and a color erasing agent exist in exactly the same layer.

This can also be said to be extremely useful in terms of manufacturing costs. The color erasing agent used in the present invention has a color erasing effect on the coloring system of a basic dye precursor and an acidic substance when heated,
Therefore, a thermosensitive coloring system that develops color at low temperatures needs to be a coloring system consisting of a basic dye precursor (typically a leuco dye) and an acidic substance (typically a phenolic substance). On the other hand, since a thermosensitive coloring system that develops color at a high temperature does not need to be decolored, a conventionally known thermosensitive coloring system can be used as appropriate.

In particular, diazonium salts and couplers are used as high-temperature coloring systems.
When using a color system consisting of a base or a color system consisting of an acidic dye precursor and a base, the base, which is an oil coloring agent for low temperature systems, generated during high temperature color development will not have a negative effect on the color development of the high temperature system. Useful.

Some of these known thermosensitive coloring systems are described below, but the present invention is not limited thereto.

The basic colorless dye precursor used in the present invention includes:
For example, crystal violet lactone, 3-indolino-5-p-dimethylaminophenyl-ot-dimethylaminophthalide, 3-diethylamino-7-chlorofluorane, 3-diethylamine-7-cyclohexylaminofluorane, 3-diethylamine- one methyl-7-1
-butylfluorane, 3-diethylamine-2-methyl-7-anilinofluorane, 3-diethylamine-6-
Methyl-7-p-butylanilinofluorane, 5-(N
-phenyl-N-ethyl)aminofluorane, 3-diethylamine-7-sibenzylaminofluorane, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-t-methyl-7-xylidinofluorane,
λ-anilino 3-methyl-6-(N-ethyl-p-1
luidino) fluorane, 3-pyrrolidino-6-methyl-
7-anilinofluorane, 3-pyrrolidino-7-cyclohexylaminofluorane, 3-pyreno-6-methyl-toluidinofluorane, 3-pyrrolidino-6-
Methyl-7-(p-l luidino)fluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-N
Examples include, but are not limited to, -methylcyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-7-(m-trifluoromethylanilino)fluoran, and the like.

As the acidic substance that causes a coloring reaction with these basic dye precursors, phenol compounds, organic acids or metal salts thereof, oxybenzoic acid esters, etc. are used.

Especially the melting point! 00 to 2!0°C, particularly preferably 60° to 2!0°C, and phenols and organic acids that are sparingly soluble in water are desirable.

Examples of phenolic compounds include French, Hiro'-impropylidene diphenol (bisphenol A), p-te
rt-butylphenol, 2,4t-dinitrophenol, 3. ≠-dichlorophenol, Hiro, Hiro'-methylene bis (co, otsu-ji tert -7-thylphenol), p-phenylphenol, ≠, ≠-cyclohexylidene diphenol, j, 2'-methylene bis (1,t-tert-butylphenol), x, x'
-methylenebis(α-phenyl-p-cresol)thiodiphenol, ≠, μ′-thiobis(4-tert-butyl-m-cresol), sulfonyldiphenol, /
,/-bis(≠-hydroxyphenyl)-n-totican, μ, 4L-his(4L-hydroxyphenyl)-/-
In addition to pentanoic acid ethyl ester, there are p-tert-butylphenol-formalin compound, p-phenylphenol-formalin condensate, and the like.

Examples of the organic acid or its metal salt include J-tert-butylsalicylic acid, j, j-1crt-butylsalicylic acid, and
-L[Lj-α-methylbenzylsalicylic acid, 3. ! −
Di-α-methylbenzylsalicylic acid, 3-tert-octylsalicylic acid,! -α,γ-dimethyl-α-phenyl-r-phenylpropylsalicylic acid and the like and their zinc salts, lead salts, aluminum salts, magnesium salts, and nickel salts are useful.

Examples of the ox'/benzoate esters include ethyl p-oxybenzoate, butyl p-oxybenzoate, heptyl p-oxybenzoate, benzyl p-oxybenzoate, and the like.

Examples of acidic colorless dye precursors used in the present invention include evaphenolphthalein, fluorescein, 2',
≠/ , j/ , 7/-tetrabromo-3, ≠,! ,
t-tetra-fluorofluorescein, tetra-7゛lomophenol blue, μ, j, G.

Examples include, but are not limited to, 7-tetrabromophenolphthalein, nioquine, alarin cresol red, and conaphtholphenolphthalein.

As the basic substance that causes a color-forming reaction with the acidic dye precursor used in the heat-sensitive recording material of the present invention, there are used basic substances that are sparingly water-soluble or water-insoluble, and substances that generate dialkali when heated.

Basic substances include inorganic and organic ammonium salts, organic amines, amides, urea and thiourea and their derivatives, thiazoles, virols, 7 pyrimidis, piperazines, guanidines, indoles, imidazoles, imidacillins, Examples include nitrogen-containing compounds such as triazoles, morpholines, piperidines, amidines, formazines, and pyridines. Specific examples of these are:
Example ammonium acetate, tricyclohexylamine,
Tribenzylamine, octadecylbenzylamine, stearylamine, allyl urea, thiourea, methylthiourea, allylthiourea, ethylenethiourea, cobenzylimitasol, μm phenylimitasol, 2-phenyl-≠-methyl-imidazole, coundesyl Ruimidazoline, 2, II, j-trifuryl-2-imidacillins-1 diphenyl-≠1 μm dimethyl-coimidapurine, cophenylu-coimidazoline, /IJ, 3-
Triphenylguanidine, /, 2-ditolylguanidine, /2.2-dicyclohexylguanidine, /, 2-dicyclohexyl-3-7enylguanidine, l, 2.3
- Tricyclo to bovine silguanidine, guanidine trichloroacetate N.

These include N'-dibenzylpiperazine, 4t,p'-dithiomorpholine, morpholinium trichloroacetate, co-aminohenzothiazole, and cobenzoylhydrazinopenzothiazole. Two or more of these basic substances can also be used in combination.

The diazo compound used in the heat-sensitive material of the present invention is a diazonium salt represented by the general formula A r N 2 +X-, and can develop a color by causing a coupling reaction with a coupling agent. It is a compound that can be decomposed. (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 diazonium compounds that form salts include μ
m diazo°-/-dimethylaminebenzene, ≠-diazo/-diethylaminobenzene, Hiro-diazo-/-dipropylaminobenzene, μm diazo, f-/-methylbenzylaminobenzene, ≠-diazo/-dibenzylamino Benzene, μm diazo-7-ethylhydroxyethylaminebenzene, gudiazo-/-diethylamino-
3-Methoxybenzene, μm diazo-/-dimethylamino-comethylbenzene, Hiro-diazo-/-benzoylamino-2,j-shedkin benzene, Kudiazo-
/-morpholinobenzene, Hiro-diazo-/-morpholino-co,! -jethoxybenzene, goodiazo-/-morpholino-co, j-dibutoxybenzene, dadiazo/
-Anilinobenzene, Hiro-diazo-/-tolylmercapto-j, j-jethoxybenzene, Gudiazo-/,
Examples include 4t-methoxybenzoylaminoco, j-jethoxybenzene, and the like.

Specific examples of acid anions include CF C00-n
2n+1 (n is an integer from 3 to ri), CmF2m+□SO3- (m is an integer from 2 to ♂), (CIF2g+, 5O2)2CH-(
(l is an integer of /~/♂), C(CH3)H (n is an integer of 3~2) (n is an integer of 3~2) BF-1pF6-, and the like.

In particular, among the acid anions, those containing a monofluoroalkyl group or perfluoroalkenyl group or PF
6- is preferable because the increase in capri during raw storage is small.

Specific examples of the diazo compound (diazonium salt) include the following examples.

0C4H0 0C4H0OH QC4)1°C2H5 C2H5 QC4H8 OC4H9 C2H5 0C4H8 C4H9 C4H9 The coupling agent used in the heat-sensitive recording material of the present invention is one that forms a dye by coupling with a diazo compound (diazonium salt) in a basic atmosphere. Specific examples include resorcinol, 70 glucine, sodium 3-dihydroxynaphthalene-t-sulfonate, /-hydroxy-! - naphthoic acid morpholinopropylamide,
/, j-dihydroxynaphthalene, 3-dihydroxynaphthalene, Naphthoic acid-1-methylanilide, λ-hydroxy-3-naphthoic acid ethanolamide, λ-hydroxy-3-naphthoic acid octylamide, 2-hydroxy-3-naphthoic acid-hedodecyloxypropylamide, 2-hydroac-3 -Naphthoic acid tetratecylamide, acetanilide, acetoacetanilide, benzoylacetanilide, l-phenyl-3-methyl-j-pyrazolone, /-(2', 4!
',A'-)lichlorophenyl)-3-benzamide-! -pyrazolone, /-(2'.

u', 6'-)-lichlorophenyl)-3-anilino-y-pyrazolone, l-phenyl-3-7 2-2-ylacetamidoj-pyrazolone, and the like.

Among these diazonium salts, those encapsulated in thermoresponsive microcapsules by the method described in JP-A-60-6-23 and the like are particularly preferably used.

Other examples of materials used in high-temperature coloring systems include (υ long-chain fatty acid iron salts such as ferric stearate and ferric myristylate, 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, and silver bases such as acetic acid, stearic acid, and palmitic acid, and alkalis such as calcium sulfide, strontium sulfide, and vanium sulfide. A combination with an earth metal sulfide, or a combination of the organic acid heavy metal salt and an organic chelating agent such as S-diphenylcarbazide or diphenylcarbazone; (3) oxalic acid of silver, lead, mercury, or thorium; (4) combinations of heavy metal oxalates such as salts with sulfur compounds such as Na-tetrathionate, sodium thiosulfate, thiourea; (4) fatty acid ferrous salts such as ferric stearate;
．． (5) A combination with an aromatic polyhydroxy compound such as Hiroshi-dihydroxytetraphenylmethane, (5) A noble metal salt of an organic acid such as oxalate, mercuric oxalate, and an organic polyhydroxo compound such as polyhydroxy alcohol, glycerin, or glycol. (6) a combination of an organic acid noble metal salt such as silver behenate or silver stearate and an aromatic organic reducing agent such as protocatechuic acid, spiroindane, or hydroquinone; (7) ferric pelargonic acid; , combinations of fatty acid ferric salts such as ferric laurate and thiosemicarbamide or inthiosemicarbamide derivatives, (8) organic acid lead salts such as lead caproate, lead pelargonate, lead behenate. (9) Combination of higher fatty acid heavy metal salts such as ferric stearate and copper stearate with zinc sialyldithiocarbamate, 00 Examples include those forming oxazine dyes, such as a combination of resorcinol and a nitroso compound.

A coloring aid can be used in the coloring layer of the present invention. In particular, it is preferable to use an appropriate heat sensitizer for low-temperature coloring systems. Known sensitizers can be used, including waxes such as higher fatty acid amides such as stearic acid amide, erucic acid amide, palmitic acid amide, ethylene bisstearamide or higher fatty acid esters, or benzoic acid amide. Acid phenyl derivatives or urea derivatives such as /-phenylurea, /-methyl-3-phenylurea, /-ethyl-3-phenylurea, /.

/-diethyl-3-phenylurea, /-phenyl-3
-propylurea, 3-phenyl-/, /-dipropylurea, /-isopropyl-3-phenylurea, /-
Isopropyl-3-phenyl-/-propylurea, /
, l-diisopropyl-/-dicyclohexyl-3-phenylurea, /-(J-methoxy-propyl)-3-
Phenylurea, /-(J-cyclohexylpropyl)
-3-phenylurea, /-(p-methoxyphenyl)
-3-bunalureido, /=(S-phenoxyethyl)
-3-phenylurea, /-benzyl-3-phenylurea, /-(≠-octadenyloxyphenyl)-3
-phenylurea, / -octadecyl urea, /-dodecyl-3-butyl urea, /-benzyl-3-butyl urea, /.

/-diisobutyl-5-(/-naphthyl)urea, /,
3-Dioctadecylurea, l,/-dimethyl-5-(
Ko, Hiro-xylyl) urea, μ, lIt'-bis(J-
butylureido) diphenylmethane, λ, Hiro-bis[3
-(+2-butoxyethyl)ureido]toluene, /,
tr-His(3-benzylureido)hexane or urethane derivatives such as phenylcarbamoyloxytoticane, phenylcarbamoyloxyoctadecane, phenylcar-3-phenylurea, /-phthyl-3-phenylurea, /, /-dibutyl-3-phenyl urea,
l-isobutyl-3-phenylurea, /-tert-butyl-3-phenylurea, /-tert-butyl-
/-methyl-3-phenylurea, /-henthyl-3-
Phenylurea, /, /-cybenthyl-3-phenylurea, /-tertiary is phenyl-3-phenylurea,
/-isobenthyl-3-phenylurea, /-phenyl-5-(/,j,2-1-limethylbrobyl)urea, 1
-(/-ethyl-3-methylbutyl)-3-phenylurea, /-(l-ethyl-2,2-dimethylphthyl)-
3-phenylurea, /-phenylurea-(/, /, 3
．． ．． 3-tetramethylbutyl)urea,/-decyl-3
-phenylurea, /-(/-butylhexyl)-3-
Phenylurea, /-(/-butyl-/-ethylpentyl)-3-phenylurea, /-dodecyl-3-phenylurea, /-octadecyl-3-phenylurea, /
-cyclohexyl-3-phenylurea, al or naphthol derivatives, such as λ-benzyloxyj-p-t-butylphenoxycarbonylnaphthalene, /-benzyloxynaphthalene, codedecyloxynaphthalene, 2-p-chlorobenzyloxynaphthalene , λ-p-isozolopylbenzyloxynaphthalene, codedecyloxynaphthalene,
codedecyloxynaphthalene, commyristoyloxinaphthalene, 2-pt-butylbenzoyloxynaphthalene, λ-benzoyloxynaphthalene,! -benzyloxy-J-N- (j-dodecyloxyprobyl)
Carbamoylnaphthalene, copenzyloxy-5-N
-octylcarbamoylnaphthalene, 2-benzyloxy-3-dodecyloxycarbonylnaphthalene, and the like.

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

The color forming agent and the color developer are used, for example, in a dispersion medium, each singly or in combination, pulverized and dispersed to a particle size of several μm. The particle size at this time is the average particle size! It is pulverized to a particle size of less than μ, more preferably less than 3 μ. 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, imbutylene- Maleic anhydride copolymer, polyacrylic acid, polyacrylic acid amide, starch derivatives, casein, gelatin, etc. are used, and dispersion is carried out using a ball mill, sand mill, attritor, colloid mill, etc. These water-soluble polymers also act as binders after coating.

Water-resistant agents (gelling agents, cross-linking agents) are added to the coating solution as a binder for the purpose of imparting water resistance, or emulsions of hydrophobic polymers, specifically sterentadiene rubber latex, acrylic resin emulsions, etc. You can also add etc. Further, the coloring agent may be encapsulated in heat-responsive microcapsules.

Additives are further added to the heat-sensitive coating liquid thus obtained in order to meet various requirements. Examples of additives include adding oil-absorbing substances such as inorganic pigments to the heat-sensitive recording layer in order to prevent the recording head from becoming dirty during recording, and adding oil-absorbing substances such as inorganic pigments to the heat-sensitive recording layer to improve the releasability of the heat-sensitive head. Fatty acids, metal soaps, etc. are added.

Therefore, in general, a heat-sensitive recording sheet is constructed by coating a support with pigments, wax, additives, etc. in addition to a color forming agent and developer that directly contribute to color development.

Specifically, the pigments include kaolin, calcined kaolin,
Talc, waxite, diatomaceous earth, calcium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium carbonate, titanium oxide, barium carbonate, fine particulate anhydrous silica, activated clay, urea-formalin filler, cellulose filler, wax, etc. Examples include paraffin wax, carnauba wax, microcrystalline wax, polyethylene wax, and higher fatty acid esters.

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

The thermosensitive recording material of the present invention can perform multicolor recording and can be used as printer paper for facsimiles and computers that require high-speed recording, and as recording paper for electrocardiograms, recorders, and the like.

Example (Preparation of coating liquid A) Base precursor (BP-4) with the following structure! ,.

O? and/! % polyvinyl alcohol aqueous solution j, 2 t water r and ry were mixed and finely dispersed in a paint shaker for 3 hours.

(Preparation of coating liquid BO) The precursor contained in coating liquid A was added to the following BP-! The rest was obtained in the same way.

(Preparation of coating liquid C) Coating liquid A was obtained in the same manner except that the precursor contained in coating liquid A was changed to BP-3μ shown below.

(Preparation of coating liquid) Coating liquid A was prepared in the same manner except that a solid base, tricyclohexylguanidine, was used in place of the base precursor.

(Preparation of coating liquid E) Coating liquid E was obtained as a low-temperature black coloring thermosensitive system as follows.

Color development agent: noanilino-3-methyl-N-methyl-N-cyclohexylaminofluorane, color developer: bisphenol A, sensitizer: (44,4u-methoxyphenylthio)ethane, each 20 f/fl 00
f's! % polyvinyl alcohol (Kuraray PVA-7o
z) Dispersion was carried out in a ball mill with an aqueous solution overnight to reduce the volume average particle size to 3 μm or less. Using "th calcium carbonate (Unibur 70 Shiraishi Kogyo) as a pigment, r
oy'q Sodium hexametaphosphate O0j% solution/lO?
It was used after being dispersed with a homogenizer. Each of the dispersions prepared as described above is a 2-anilino-3-methyl-6-N-methyl-N-cyclohexylaminofluorane dispersion! 2, Bisphenol octadispersion 109, (4L,
4L'-methoxyphenylthio)xpn dispersion 109
, calcium carbonate dispersion ljt, and further ljt.
c! Obtained by adding the rumored Zinc Stearate Marujo/32.

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

Part λ of the following diazo compound and 11 parts of (J:/) adduct of xylyle/diisocyanate and 1-limeterolpropane were added to a mixed solvent of ≠ part of dibutyl heptalate and 5 parts of ethyl acetate and dissolved therein. Add this diazo compound solution to polyvinyl alcohol! .

Some of it is water! is mixed with an aqueous solution in which 1 part is dissolved, and 2o
Emulsification and dispersion was carried out at 0C to obtain an emulsion with an average particle size of 3μ. Add 100 parts of water to the obtained emulsion and add Ao while stirring.
After heating to 0C and 2 hours later, a microcapsule liquid containing a diazo compound in the core was obtained.

(Diazo Compound) Additionally, 10 parts of the following compound was added to 100 parts of a j% polyvinyl alcohol aqueous solution and dispersed in a sand mill for about 2 μm to obtain a dispersion of a red color-forming coupling agent having an average particle size of 3 μm.

The compound was added to 10 mt of r-dicyclohexyl-3-phenylguanidine and 100 parts of a z% polyvinyl alcohol aqueous solution and dispersed in a sand mill for about 10 hours to obtain an average particle size of 3μ/2. ! - A dispersion of triphenylguanidine was obtained.

Also, p-benzyloxyphenol 10FA! ,! % polyvinyl alcohol aqueous solution and dispersed in a sand mill for about λ≠ time to obtain a dispersion of p-benzyloxyphenol having an average particle size of 3μ.

30 parts of the capsule liquid obtained as above, 20 parts of the coupling agent dispersion, /2. 30 parts of the J-triphenylguanidine dispersion and 20 parts of the p-benzyloxyphenol dispersion were mixed to obtain a high-temperature red coloring heat-sensitive coating liquid F.

<Example-1> Coating liquid F was applied to smooth high-quality paper (j Oit/m) at a dry weight of 4'? /m, dry weight of coating liquid A is 2? /m2
A heat-sensitive recording material was obtained by sequentially coating and drying coating liquid E to a dry weight of 44 f/m. Printing energy/♂m was measured using a Kyocera thermal printing tester.
When printed at J/mm, a clear black colored image was obtained. On the other hand, when printing was performed at ≠o m J / m m , a clear red colored image was obtained.

In addition, as a test to accelerate stability over time, the coated paper was
When %RH was printed in the same way after aging for one day, it was black,
The red color was clear, there was almost no change in the background, and the product had good storage stability.

<Example 2> A heat-sensitive recording material was obtained in exactly the same manner as in Example 7 except that coating liquid B was used instead of coating liquid A. When this product was evaluated in the same manner, both the unaged sample and the aged sample showed clear black and red coloring, and there was no fogging on the background.

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

Comparative Example 1> A heat-sensitive recording material was obtained in exactly the same manner except that a coating liquid was used instead of coating liquid A in Example-/. When this product was evaluated in the same manner, the unaged sample showed clear black and red coloring, but the background had a dark fog. Furthermore, when printed after aging, the black color became faint and unclear, and the red color appeared clearly. Furthermore, there were more and more dark spots on the scalp.

<Example-4> Coating liquid F was applied and dried at a dry weight of 45 f/m2 on smooth high-quality paper (jot/m2), and a mixture of coating liquid E and coating liquid A in a weight ratio of 221 was dried on top of it. 6f/m in weight
A heat-sensitive recording material was obtained by coating and drying the coating to a ratio of 2. When this product was evaluated in the same manner as in Example 7, it showed clear black and red coloring, and there was no fogging on the background. Furthermore ao
'c. Even after printing with TaO%RH after aging, clear black and red colors were produced, and the fogging on the background did not worsen.

<Comparative Example 2> A heat-sensitive recording material was obtained in exactly the same manner except that the coating liquid A of Example DA was replaced with a coating liquid. When this product was evaluated in the same manner as Example-μ, black coloring hardly occurred, only red coloring occurred, and the background was darkened.

Claims (1)

[Claims] A multicolor thermosensitive recording material characterized by containing a basic dye precursor, an acidic substance that causes a coloring reaction when heated with the basic dye precursor, and a base precursor that decarboxylates when heated to generate a base.