JP2012206440A - Heat sensitive recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sensitive recording medium having superior recording sensitivity and storage stability of recording images, and having less texture fogging and less attachment of scum to a thermal head.SOLUTION: The heat sensitive recording medium has on a support medium, a thermosensitive recording layer containing a leuco dye, coloring agent and sensitizer. The recording medium contains as the coloring agent, at least one selected from 4,4'-(3-tosylureido)diphenylmethane, 4,4'-(3-tosylureido)diphenylether, N-(3-tosyl)-N'-phenylurea and butyl 4-(p-tosylureido)benzoate, and further contains as a sensitizer, diphenylsulfone of 50-200 mass% based on the total mass of the whole coloring agent contained in the recording medium.

Description

The present invention relates to a heat-sensitive recording material using a coloring reaction between a colorless or light-colored leuco dye and a color former, and relates to a heat-sensitive recording material excellent in recording sensitivity and storage stability of a recorded image.

A heat-sensitive recording material is known which utilizes a color reaction between a colorless or light-colored leuco dye and an organic or inorganic colorant to obtain a recorded image by bringing both coloring materials into contact with each other by heat. Such heat-sensitive recording materials are relatively inexpensive, and the recording equipment is compact and easy to maintain, so that they are used not only as recording media for facsimiles and various computers but also in a wide range of fields.

The fields of use include, for example, cash register paper and ticket paper for POS (point of sales) systems, but with the expansion of the system, the use environment and use methods are diversified, and use under severe conditions increases. Have been doing. In addition, the printing speed of printers is increasing year by year, and it is desired that printing can be performed with lower printing energy. Further, since it is also used as a receipt, it is necessary that the storage and the sealability with respect to various chemicals such as oil, plasticizer, office supplies, and hand cream in the recording section are good.

In a heat-sensitive recording material provided with a heat-sensitive recording layer mainly composed of a leuco dye and a colorant on a support, it is known that the color-development reaction is reversible, so that the color-development image disappears with time. It has been. This decolorization is accelerated under exposure, high temperature and high humidity atmosphere, and further proceeds rapidly by contact with a plasticizer, oil, etc., and the recorded image may be decolored until it cannot be read. In addition, when a thermal recording medium is used as a parking ticket sheet, it is left in the vehicle, and particularly in the summer, it is placed in a harsh and high temperature atmosphere. The contrast with the recorded image) is lost, and in extreme cases, reading may be impossible.

In order to improve the storability of the recorded image against such problems, a method of providing a protective layer on the heat-sensitive recording layer, a method of adding an epoxy compound to the heat-sensitive recording layer, and the like have been proposed. A sufficient effect of improving print storage stability with respect to oil and plasticizer is not obtained. Further, when the protective layer is provided, there is a disadvantage that the recording sensitivity is lowered. In recent years, development of colorants having high print storage stability has progressed, and the problems of exposure, high-temperature, decolorization under high-humidity atmospheres and low-contrast problems at high temperatures are being solved, but the recording sensitivity is low. There is a drawback.

In order to satisfy such requirements, various proposals have been made for colorants.

For example, 4,4 ′-(3-tosylureido) diphenylmethane, 4,4 ′-(3-tosylureido) diphenyl ether, or specific N as a new electron acceptor excellent in oil resistance and plasticizer resistance of the recording portion -Arylsulfonyl (thio) ureas have been proposed (see Patent Documents 1 and 2).
However, 4,4 ′-(3-tosylureido) diphenylmethane, 4,4 ′-(3-tosylureido) diphenyl ether, or the specific N-arylsulfonyl (thio) ureas described above are resistant to plasticizer and oil in the recording area. Although the performance is improved, it is difficult to obtain a high recording density, and in order to obtain a high recording density, it is necessary to increase the number of copies. In such a case, the color of the white paper portion (background portion) under high temperature and high humidity storage is observed. Etc. The heat and humidity resistance of the background is inferior.

The use of 4-allyloxy-4′-hydroxydiphenylsulfone (see Patent Document 3) is described as a colorant or a part of the colorant, and the colorant used in combination with the colorant. As an oligomer type colorant (see Patent Document 4), 4,4′-dihydroxydiphenylsulfone (see Patent Document 5), or 2,4′-dihydroxydiphenylsulfone (see Patent Document 6). In addition to 4-allyloxy-4′-hydroxydiphenylsulfone, a urea urethane compound (see Patent Document 7), p-acetylbiphenyl (see Patent Document 8) as a specific sensitizer, and a specific preservative improver Describes a heat-sensitive recording material using a methylated methylol melamine condensate (see Patent Document 9). Furthermore, in addition to 4-allyloxy-4′-hydroxydiphenylsulfone, there is described a thermal recording material (see Patent Document 10) in which a leuco dye, a colorant, and various storage stabilizers are used in combination. Even in the case of a human body, no satisfactory characteristics have been obtained with respect to recording sensitivity and storability of recorded images.

JP-A-5-147357 Japanese Patent Laid-Open No. 5-32061 JP 2001-310561 A Japanese Patent Laid-Open No. 2002-283741 JP 2004-130539 A JP 2004-195747 A JP 2004-255842 A JP 2002-052842 A JP 2004-237476 A JP 2004009593 A

An object of the present invention is to provide a heat-sensitive recording material that is excellent in recording sensitivity and storage stability of a recorded image, has less background fogging, and has less residue on a thermal head.

(1) In a heat-sensitive recording material having a heat-sensitive recording layer containing a leuco dye, a colorant and a sensitizer on the support, 4,4 ′-(3-tosylureido) diphenylmethane, 4, It contains at least one selected from 4 '-(3- (tosylureido) diphenyl ether, N- (3-tosyl) -N'-phenylurea, and butyl 4- (p-tosylureido) benzoate, and diphenyl as a sensitizer A heat-sensitive recording material comprising 50 to 200% by mass of sulfone with respect to the colorant.

(2) The heat-sensitive recording material according to (1), wherein the heat-sensitive recording layer further contains 4-allyloxy-4'-hydroxydiphenylsulfone as a colorant.

(3) The content of the 4-allyloxy-4′-hydroxydiphenylsulfone in the heat-sensitive recording layer is such that the 4,4 ′-(3-tosylureido) diphenylmethane, 4,4 ′-(3- (tosylureido) diphenylether, 5 to 90% by mass based on the total mass in at least one thermosensitive recording layer selected from N- (p-tosyl) -N′-phenylurea and butyl 4- (3-tosylureido) benzoate (1 ) Or (2).

The heat-sensitive recording material of the present invention has an effect excellent in recording sensitivity and storage stability of a recorded image, and it is possible to provide a heat-sensitive recording material with less background fogging and less debris adhesion to the thermal head. .

[Support]
The support used in the heat-sensitive recording material of the present invention is not particularly limited, and examples thereof include neutral or acidic high-quality paper, synthetic paper, transparent or translucent plastic film, and white plastic film. Although the thickness of a support body is not specifically limited, Usually, it is about 20-200 micrometers.

(Thermosensitive recording layer)
In the heat-sensitive recording layer, leuco dye and, as a colorant, 4,4 ′-(3-tosylureido) diphenylmethane, 4,4 ′-(3-tosylureido) diphenyl ether, N- (p-tosyl) -N ′ -It contains at least one selected from phenylurea and butyl 4- (3-tosylureido) benzoate, and contains diphenyl sulfone as a sensitizer in an amount of 50 to 200% by mass with respect to the colorant.

Hereinafter, each will be described in order.
(Coloring agent)
The colorants used in the present invention are 4,4 ′-(3-tosylureido) diphenylmethane, 4,4 ′-(3- (tosylureido) diphenyl ether, N- (p-tosyl) -N′-phenylurea, and Butyl 4- (3-tosylureido) benzoate is at least one selected from 4-benzoyloxy-4′-hydroxydiphenyl sulfone.

When 4-allyloxy-4′-hydroxydiphenylsulfone is used in combination, the content in the thermosensitive recording layer is 4,4 ′-(3-tosylureido) diphenylmethane, 4,4 ′-(3- (tosylureido) diphenylether. , N- (p-tosyl) -N′-phenylurea, and butyl 4- (3-tosylureido) benzoate, 5 to 90% by mass with respect to the total mass in the heat-sensitive recording layer. When the content is 5% by mass or more, desired recording sensitivity is easily obtained, and when the content is 90% by mass or less, the storage stability (oil resistance and plasticizer resistance) of the recording portion is prevented from being lowered. be able to.

From 4,4 ′-(3-tosylureido) diphenylmethane, 4,4 ′-(3- (tosylureido) diphenyl ether, N- (p-tosyl) -N′-phenylurea, and butyl 4- (3-tosylureido) benzoate In addition to at least one selected and 4-allyloxy-4′-hydroxydiphenylsulfone, various known colorants such as activated clay, attapulgite, colloidal silica, aluminum silicate and the like can be used as long as necessary. Inorganic acidic substance, 4,4′-isopropylidenediphenol, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis ( 4-hydroxyphenyl) -4-methylpentane, 2,4′-dihydroxydiphenylsulfone 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) phenylurea, 4,4 '-Dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, 4,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) Phenolic compounds such as sulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxyphenyl-4'-benzyloxyphenylsulfone, 3,4-dihydroxyphenyl-4'-methylphenylsulfone, N, N'- Di-m-chlorophenylthio Thiourea compounds such as a, N- (p-toluenesulfonyl) carbamoyl acid p-cumylphenyl ester, N- (p-toluenesulfonyl) carbamoyl acid p-benzyloxyphenyl ester, N- (o-toluoyl) -p Organic compounds having a —SO ₂ NH— bond in the molecule such as toluenesulfoamide, N- (p-toluenesulfonyl) -N ′-(p-tolyl) urea, p-chlorobenzoic acid, 4- [2- Aromatic carboxylic acids such as (p-methoxyphenoxy) ethyloxy] salicylic acid, 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid, And these aromatic carboxylic acids such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel Salts with polyvalent metals such as Le, and more may be used in combination with organic acid substance such as complex zinc salt of antipyrine complex of zinc thiocyanate, and terephthalaldehyde acid with other aromatic carboxylic acids.

(Sensitizer)
In the present invention, diphenyl sulfone is contained as a sensitizer in the heat-sensitive recording layer in an amount of 50 to 200% by mass, more preferably 70%, based on the total solid content of the colorant used in the heat-sensitive recording layer. -150 mass% is contained.

By containing diphenyl sulfone in the above range in the heat-sensitive recording layer, high sensitivity can be achieved while suppressing the occurrence of blank sheet fog and the generation of head debris during printing.

The reason why white paper fog is suppressed is not clear, but it is considered that the change in diphenyl sulfone due to storage temperature and humidity is suppressed under the above conditions.

  Further, although the reason why generation of head debris during printing is suppressed is not clear, dyes, colorants (4,4 ′-(3-tosylureido) diphenylmethane, 4,4 ′-(3- (tosylureido) diphenylether) , N- (p-tosyl) -N′-phenylurea, and at least one selected from butyl 4- (3-tosylureido) benzoate) and diphenylsulfone in a range where the viscosity of the molten head is difficult to adhere to the thermal head It is estimated that

If the diphenylsulfone content is less than 50% by mass, it is difficult to obtain a sufficient recording density. If the content exceeds 200% by mass, blank paper fog occurs when stored in a high temperature or high humidity environment, or during printing. The head debris is likely to occur.

Further, other sensitizers can be used in combination as long as the desired effects of the present invention are not hindered. Specifically, stearic acid amide, methoxycarbonyl-N-stearic acid benzamylide, N-benzoyl stearic acid amide, N-eicosanoic acid amide, ethylene bis stearic acid amide, behenic acid amide, methylene bis stearic acid amide, N-methylol Stearic acid amide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, m-terphenyl, p-benzylbiphenyl, di-p-oxalate Chlorobenzyl ester, oxalic acid di-p-methylbenzyl ester, p-tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ether, 1,2-di (3-methylphenoxy) ethane, 1,2-di (4 -Methylfe Xyl) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-di (4-chlorophenoxy) ethane, 1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- ( 3-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-acetoluidide, p-acetophenetide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) ) Benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane and the like.

(Leuco dye)
As the colorless or light-colored leuco dye used in the heat-sensitive recording layer, various known ones can be used. Specifically, for example, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide Blue coloring dyes such as 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide and fluorane, 3- (N-ethyl-Np- Tolyl) amino-7-N-methylanilinofluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, etc., green coloring dye, 3,6-bis (diethylamino) ) Fluorane-γ-anilinolactam, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane Red coloring dyes such as 3-diethylamino-7-chlorofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-cyclohexyl) ) Amino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-7- (o-chlorophenylamino) fluorane, 3- (N-ethyl-p-toluidino) -6-methyl -7-anilinofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluorane, 3- (N-ethyl-N-tetrahydrofurfuryl) Amino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-dimethylamino-6-methyl-7-anilinofluorane, 3-pyrrolidino-6 -Methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 2,2-bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3' Black coloring dyes such as methyl spiro [phthalide-3,9′-xanthen-2′-ylamino] phenyl} propane, 3-diethylamino-7- (3′-trifluoromethylphenyl) aminofluorane, 3,3- Bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1- ( -Methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3-p- (p-dimethylaminoanilino) anilino-6 Methyl-7-chlorofluorane, 3-p- (p-chloroanilino) anilino-6-methyl-7-chlorofluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6' A dye having an absorption wavelength in the near infrared region such as dimethylamino) phthalide; Of course, it is not limited to these, Moreover, 2 or more types can also be used together as needed.

(binder)
Various resins are usually used as binders in the thermal recording layer coating solution. Such binders include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy modified polyvinyl alcohol, acetoacetyl modified polyvinyl alcohol, silicon modified polyvinyl alcohol, diisobutylene / maleic anhydride copolymer. Compound salt, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion, urea resin, melamine resin, amide resin, polyurethane resin Are blended in a range of about 5 to 50% by mass, particularly about 10 to 40% by mass, based on the total solid content of the thermosensitive recording layer.

(Preservation improver)
In the heat-sensitive recording layer of the present invention, a storability improving agent may be added, for example, 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,2′-methylenebis (4-ethyl-). 6-tert-butylphenol), 2,2′-ethylidenebis (4,6-di-tert-butylphenol), 4,4′-thiobis (2-methyl-6-tert-butylphenol), 4,4′-butylidenebis (6-tert-butyl-m-cresol), 1- [α-methyl-α- (4′-hydroxyphenyl) ethyl] -4- [α ′, α′-bis (4′-hydroxyphenyl) ethyl] Benzene, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butyl) Enyl) butane, 4,4′-thiobis (3-methylphenol), 4,4′-dihydroxy-3,3 ′, 5,5′-tetrabromodiphenylsulfone, 4,4′-dihydroxy-3,3 ′ , 5,5'-tetramethyldiphenylsulfone, 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2, Hindered phenol compounds such as 2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 1,4-diglycidyloxybenzene, 4,4′-diglycidyloxydiphenylsulfone, 4-benzyloxy-4 ′ -(2-methylglycidyloxy) diphenylsulfone, diglycidyl terephthalate, cresol novolac epoxy resin, phenol novola Type epoxy resin, epoxy compound such as bisphenol A type epoxy resin, N, N′-di-2-naphthyl-p-phenylenediamine, 2,2′-methylenebis (4,6-di-tert-butylphenyl) Examples include sodium or polyvalent metal salts of phosphate, bis (4-ethyleneiminocarbonylaminophenyl) methane, and the like.
When a preservability improver is used, the amount used may be an effective amount for improving the preservability, but it is usually about 1 to 30% by mass with respect to the total solid content of the thermosensitive recording layer. It is preferable to mix | blend in the range of about 5-20 mass%.

(Other ingredients)
In the heat-sensitive recording material of the present invention, the heat-sensitive recording layer may further contain various other auxiliaries in addition to the color former, leuco dye, sensitizer, binder and preservability improver.

(Coating liquid for thermal recording layer)
The thermosensitive recording layer coating liquid containing the above-mentioned various components generally uses water as a dispersion medium, and a leuco dye, a colorant, a sensitizer, etc. together or separately by a stirring / pulverizing machine such as a ball mill, an attritor, or a sand mill. It is prepared by blending materials obtained by dispersing or the like.
In addition, various auxiliary agents can be added to the heat-sensitive recording layer coating liquid as necessary. For example, sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salt, etc. Agents, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax and other waxes, antifoaming agents, colored dyes, pigments and the like are added as appropriate. Examples of pigments include inorganic pigments such as kaolin, clay, calcium carbonate, calcined clay, calcined kaolin, titanium oxide, aluminum hydroxide, diatomaceous earth, particulate anhydrous silica, activated clay, styrene microballs, nylon powder, polyethylene powder, Examples include urea / formalin resin filler, organic pigments such as raw starch particles.

(Undercoat layer)
In the present invention, if necessary, an undercoat layer is preferably provided between the support and the thermosensitive recording layer in order to further increase the recording sensitivity. The undercoat layer is for an undercoat layer mainly composed of an oil-absorbing pigment and / or organic hollow particles and / or thermally expandable particles having an oil absorption amount of 70 ml / 100 g or more, particularly about 80 to 150 ml / 100 g, and an adhesive. It is preferably formed by applying and drying a coating liquid on a support. Here, the oil absorption is a value determined according to the method described in JIS K 5101.

Various types of oil-absorbing pigments can be used, and specific examples thereof include inorganic pigments such as calcined kaolin, amorphous silica, light calcium carbonate, and talc. The average particle diameter of the primary particles of these oil-absorbing pigments is preferably about 0.01 to 5 μm, particularly about 0.02 to 3 μm. The amount of the oil-absorbing pigment can be selected from a wide range, but generally it is preferably about 2 to 95% by mass, particularly preferably about 5 to 90% by mass with respect to the total solid content of the undercoat layer.

Moreover, as an organic hollow particle, a conventionally well-known thing, for example, the particle | grains whose hollow rate consists of an acrylic resin, a styrene resin, a vinylidene chloride resin etc. about 50-99% can be illustrated. Here, the hollowness is a value obtained by (d / D) × 100. In the formula, d represents the inner diameter of the organic hollow particles, and D represents the outer diameter of the organic hollow particles. The average particle diameter of the organic hollow particles is preferably about 0.5 to 10 μm, particularly preferably about 1 to 3 μm. The amount of the organic hollow particles used can be selected from a wide range, but generally it is preferably about 2 to 90% by mass, particularly preferably about 5 to 70% by mass, based on the total solid content of the undercoat layer.

When the oil-absorbing inorganic pigment is used in combination with the organic hollow particles, the oil-absorbing inorganic pigment and the organic hollow particles are used within the above-mentioned usage amount range, and the total amount of the oil-absorbing inorganic pigment and the organic hollow particles is the entire undercoat layer. The solid content is preferably about 5 to 90% by mass, and more preferably about 10 to 80% by mass.

The adhesive is preferably an adhesive used for the heat-sensitive recording layer, particularly starch-vinyl acetate graft copolymer, polyvinyl alcohol, styrene-butadiene latex and the like.
The use ratio of the adhesive can be selected within a wide range, but generally it is preferably used in an amount of about 5 to 30% by mass, particularly about 10 to 20% by mass, based on the total solid content of the undercoat layer.

[Protective layer]
In the heat-sensitive recording material of the present invention, a protective layer can be provided on the heat-sensitive recording layer for the purpose of improving the storage stability of the recorded image with respect to chemicals such as a plasticizer and oil, or the recording suitability.

The method for preparing the coating liquid for forming the protective layer is not particularly limited. Generally, water is used as a dispersion medium, and starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy-modified polyvinyl alcohol. It is prepared by mixing and stirring a binder such as acetoacetyl-modified polyvinyl alcohol and silicon-modified polyvinyl alcohol and, if necessary, a pigment such as kaolin, light calcium carbonate, and fine particle silica.

A protective layer can be formed using the said binder and 1 or more types of the various adjuvant mentioned later as needed, without using a pigment.
The protective layer can also be formed by using the binder and the pigment in combination. In this case, the amount of the binder used is not particularly limited and can be appropriately selected from a wide range. Is preferred. Further, the amount of the pigment used is not particularly limited and can be appropriately selected from a wide range. In general, it is about 1 to 95% by mass, particularly about 2 to 90% by mass with respect to the total solid content of the protective layer. preferable.

Furthermore, in the protective layer coating solution, a surfactant such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, or a surfactant such as sodium dioctylsulfosuccinate (dispersant, wetting) Agent), an antifoaming agent, and various auxiliary agents such as water-soluble polyvalent metal salts such as potassium alum and aluminum acetate can be appropriately added. Further, in order to further improve the water resistance, a curing agent such as glyoxal, boric acid, dialdehyde starch, and epoxy compound can be used in combination.

In particular, in the protective layer, microcapsules encapsulating an ultraviolet absorber that is liquid at room temperature, such as 2- (2′-hydroxy-3′-dodecyl-5′-methylphenyl) benzotriazole, are added to the total solid content of the protective layer. On the other hand, when the ultraviolet absorber is added so as to be about 10 to 40% by mass, particularly about 15 to 38% by mass, the yellowing of the background and the fading of the recorded image are remarkably improved with respect to light exposure.

In the thermal recording material of the present invention, the method for forming the undercoat layer, the thermal recording layer and the protective layer is not particularly limited. For example, air knife coating, varibar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating After coating and drying the undercoat layer coating liquid on the support by an appropriate coating method such as die coating, the thermal recording layer coating liquid and further the protective layer coating liquid are coated and dried on the undercoat layer, etc. It is formed by the method.

If an undercoat layer, the coating amount of the undercoat layer coating solution 3 to 20 g / ^{m 2} approximately by dry weight, preferably 5~12g / ^{m 2} approximately. The coating amount of the heat-sensitive recording layer coating composition is 2~12g / ^{m 2} approximately by dry weight, preferably 3 to 10 g / ^{m 2} approximately. When the protective layer is provided, the coating amount of the protective layer coating solution is adjusted in the range of about 0.5 to 15 g / m ² , preferably about 1.0 to 8 g / m ² in terms of dry weight.

If necessary, a protective layer can also be provided on the back side of the heat-sensitive recording material to further improve the storage stability or give it a high gloss. Applying a smoothing process such as supercalendering after coating each layer, or applying an adhesive treatment to the back side of the thermal recording material to process it into an adhesive label, magnetic recording layer, printing coating layer, and thermal transfer recording layer Various known techniques in the heat-sensitive recording material manufacturing field, such as providing an ink jet recording layer, can be added as necessary.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the scope of the present invention is not limited to these examples. Unless otherwise specified, “part” and “%” in the examples represent “part by mass” and “% by mass”, respectively.

Example 1
Preparation of coating solution for undercoat layer 90 parts of spherical resin particle dispersion (trade name: Grosdale 130S, composition: styrene, average particle size: 0.8 μm, Mitsui Chemicals, solid content concentration 53 mass%), calcined kaolin 120 parts of 50% aqueous dispersion (trade name: Ansilex, Engelhard) (average particle size: 0.6 μm), styrene-butadiene latex (trade name: L-1571, manufactured by Asahi Kasei Chemicals, solid content A composition comprising 10 parts of a 48% by weight concentration, 50 parts of a 10% aqueous solution of oxidized starch, and 20 parts of water was mixed and stirred to obtain a coating solution for an undercoat layer.

Solution A preparation 3-di (n-butyl) amino-6-methyl-7-anilinofluorane 100 parts, saponification degree 60 mol%, polymerization degree 200 polyvinyl alcohol 20% aqueous solution 50 parts, natural fat and oil A composition (suspension) consisting of 20 parts of a 5% emulsion of foaming agent and 80 parts of water was treated with a sand mill so that the average particle size was 0.5 μm to obtain liquid A.

-B liquid preparation 4,4 '-(3-tosylureido) diphenylmethane 100 parts, sulfone modified polyvinyl alcohol (trade name: Gocelan L-3266, manufactured by Nippon Synthetic Chemical Co., Ltd.) 50% 20% aqueous solution, natural fat-based antifoaming agent A composition (suspension) comprising 10 parts of a 5% emulsion and 90 parts of water was treated with a sand mill so that the average particle size was 1.0 μm to obtain a liquid B.

-Solution C preparation 4-allyloxy-4'-hydroxydiphenyl sulfone (trade name: BPS-MAE, manufactured by Nikka Chemical Co., Ltd.), sulfone-modified polyvinyl alcohol (trade name: Go-Selan L-3266, Nihon Gosei) A composition (suspension) consisting of 50 parts of a 20% aqueous solution (made by Kagaku Co., Ltd.), 10 parts of a 5% emulsion of a natural fat and oil-based antifoaming agent, and 90 parts of water so that the average particle size is 1.0 μm by a sand mill To obtain a liquid C.

D solution preparation From 100 parts of diphenylsulfone, 50 parts of a 20% aqueous solution of sulfone-modified polyvinyl alcohol (trade name: Gocelan L-3266, supra), 2 parts of a 5% emulsion of natural fat and oil-based antifoaming agent, and 98 parts of water The resulting composition was treated with a sand mill so that the average particle size was 1.0 μm to obtain liquid D.

-Preparation of coating solution for heat-sensitive recording layer 25.0 parts of liquid A, 37.5 parts of liquid B, 37.5 parts of liquid D, fine particle amorphous silica (trade name: Mizukaseal P-527, manufactured by Mizusawa Chemical Co., Ltd.) 10 Parts, 20 parts of aluminum hydroxide (trade name: Heidilite H-42, Showa Light Metal Industry Co., Ltd.), 125 parts of 12% aqueous solution of polyvinyl alcohol having a saponification degree of 98 mol% and a polymerization degree of 1000, zinc stearate dispersion (product) (Name: Hydrin Z-8-36, solid content concentration 36%, manufactured by Chukyo Yushi Co., Ltd.) 13.9 parts and 18.6 parts of water were mixed and stirred to prepare a thermal recording layer coating solution.

- on one surface of woodfree paper having produced 64 g / m ² (acid paper) of the heat-sensitive recording material, forming an undercoat layer, an undercoat layer coating solution weight after drying by coating and drying so that 8 g / m ² The heat-sensitive recording layer coating solution was applied and dried so that the weight after drying was 3.5 g / m ² to form a heat-sensitive recording layer, and then a super calender was applied to obtain a heat-sensitive recording material.

(Example 2)
A thermosensitive recording material was obtained in the same manner as in Example 1 except that the amount of the liquid D was reduced from 37.5 parts to 22.5 parts in the preparation of the thermosensitive recording layer coating liquid of Example 1.

(Example 3)
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the amount of the liquid D was increased from 37.5 parts to 60 parts in the preparation of the heat-sensitive recording layer coating liquid of Example 1.

Example 4
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 12.5 parts of liquid C was added in the preparation of the heat-sensitive recording layer coating liquid of Example 1.

(Example 5)
Thermosensitive recording was performed in the same manner as in Example 1, except that 4,4 ′-(3-tosylureido) diphenylmethane was used instead of 4,4 ′-(3-tosylureido) diphenylmethane in the preparation of Liquid B of Example 1. Got the body.

(Example 6)
In the preparation of the liquid B of Example 1, 4,4 ′-(3-tosylureido) diphenyl ether was used instead of 4,4 ′-(3-tosylureido) diphenylmethane, and the preparation of the thermal recording layer coating liquid of Example 1 was performed. In Example 1, a heat-sensitive recording material was obtained in the same manner as in Example 1 except that 12.5 parts of C liquid was added.

(Example 7)
In the preparation of the liquid B of Example 1, the same procedure as in Example 1 was performed except that N- (p-tosyl) -N′-phenylurea was used instead of 4,4 ′-(3-tosylureido) diphenylmethane. A heat-sensitive recording material was obtained.

(Example 8)
In the preparation of the liquid B of Example 1, N- (p-tosyl) -N′-phenylurea was used instead of 4,4 ′-(3-tosylureido) diphenylmethane, and the thermal recording layer coating liquid of Example 1 was used. A thermosensitive recording material was obtained in the same manner as in Example 1 except that 12.5 parts of liquid C was added.

Example 9
A thermosensitive recording material was prepared in the same manner as in Example 1 except that butyl 4- (3-tosylureido) benzoate was used in place of 4,4 ′-(3-tosylureido) diphenylmethane in the preparation of solution B of Example 1. Obtained.

(Example 10)
In the preparation of the liquid B of Example 1, butyl 4- (3-tosylureido) benzoate was used in place of 4,4 ′-(3-tosylureido) diphenylmethane, and in the preparation of the thermal recording layer coating liquid of Example 1. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 12.5 parts of liquid C was added.

(Comparative Example 1)
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the amount of the liquid D was reduced from 37.5 parts to 7.5 parts in the preparation of the heat-sensitive recording layer paint of Example 1.

(Comparative Example 2)
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the amount of liquid D was increased from 37.5 parts to 90 parts in the preparation of the heat-sensitive recording layer paint of Example 1.

(Comparative Example 3)
In the preparation of the liquid B of Example 1, 2,2 ′-[4- (4-hydroxyphenylsulfonyl) phenoxy] diethyl ether (trade name: D-90) was used instead of 4,4 ′-(3-tosylureido) diphenylmethane. Except for using Nippon Soda Co., Ltd.), a thermal recording material was obtained in the same manner as in Example 1.

(Comparative Example 4)
The same procedure as in Example 1 was performed except that 1,2-di (3-methylphenoxy) ethane (trade name: KS-232, manufactured by Sanko Co., Ltd.) was used instead of diphenylsulfone in the preparation of solution D in Example 1. A heat-sensitive recording material was obtained.

The following evaluation test was performed on the heat-sensitive recording material thus obtained, and the results are shown in Table 1.

(1) Recording density Using a thermal recording evaluation machine (trade name: TH-PMD, manufactured by Okura Electric Co., Ltd.), each thermal recording medium is printed at an applied energy of 0.34 mJ / dot, and a recorded portion and an unrecorded portion ( The density of the background portion was measured in a visual mode of a Macbeth densitometer (trade name: RD-914, Macbeth).
The larger the numerical value, the higher the density of printing, and the recording portion is required to be 1.20 or more practically. If it exceeds 2, background fog becomes a problem.

(2) The density of the background after leaving each thermosensitive recording medium before heat-resistant recording in an atmosphere of 60 ° C. and 30% RH for 24 hours was measured with a Macbeth densitometer (trade name: RD-914 type, Macbeth). Measured in visual mode.
The smaller the value, the better. When it exceeds 0.2, background fog becomes a problem.

(3) The density of the background after leaving each heat-sensitive recording material before moisture and heat resistance recording in an atmosphere of 40 ° C. and 90% RH for 24 hours was measured with a Macbeth densitometer (trade name: RD-914, Macbeth). Measured in visual mode.
The smaller the value, the better. When it exceeds 0.2, background fog becomes a problem.

(4) Salad oil was applied to the surface of the recording part of each thermal recording material developed for measuring the oil-resistant recording density, and the density of the recording part after wiping the surface with gauze after standing for 24 hours was measured with a Macbeth densitometer (trade name) : RD-914 type, Macbeth Co.) visual mode. Further, the storage ratio of the recording part was obtained by the following formula. There is no problem if the recording density after the salad oil coating treatment is 0.6 or more and the storage rate is 50% or more.
Storage rate (%) = measured value (recording density) ÷ recording density before processing × 100

(5) Each thermal recording in which a wrap film (trade name: High Wrap KMA-W, manufactured by Mitsui Chemicals Co., Ltd.) is wrapped three times on a plasticizer-resistant polycarbonate pipe (40 mmφ) and colored for recording density measurement. Put the body on it, wrap the wrap film in triplicate and let it stand at 40 ° C for 24 hours, then measure the density of the recording part in the Macbeth densitometer (trade name: RD-914, Macbeth) visual mode did. Further, the storage rate of the recording part was calculated based on the above formula, as in the case of oil resistance.
There is no problem if the recording density after processing is 0.6 or more and the storage rate is 50% or more.

(6) Using a debris adhesion test on a thermal head and a thermal recording evaluation machine (trade name: TH-PMD, manufactured by Okura Electric Co., Ltd.), 1 m is printed with a checkered pattern (the applied energy of the printing portion is 0.34 mJ / dot). The thermal head after printing and the printed matter were visually observed and evaluated as follows.
○: No adhesion of debris on the thermal head, no printing failure, and excellent printability.
Δ: A slight amount of residue is observed on the thermal head, but no printing trouble occurs and there is no practical problem.
X: The residue is attached to the thermal head and printing trouble occurs, which is not practical.

  As shown in the examples and comparative examples, the thermal recording material of the present invention has an effect excellent in recording sensitivity and storage stability of the recorded image, has less background fogging, and has less residue on the thermal head. Is the body.

Claims (3)

In a heat-sensitive recording material having a heat-sensitive recording layer containing a leuco dye, a colorant and a sensitizer on the support, 4,4 ′-(3-tosylureido) diphenylmethane, 4,4′- Containing at least one selected from (3- (tosylureido) diphenyl ether, N- (3-tosyl) -N′-phenylurea, and butyl 4- (p-tosylureido) benzoate, and diphenylsulfone as a sensitizer, A heat-sensitive recording material comprising 50 to 200% by mass with respect to the colorant. The heat-sensitive recording material according to claim 1, wherein the heat-sensitive recording layer further contains 4-allyloxy-4'-hydroxydiphenyl sulfone. The content of the 4-allyloxy-4′-hydroxydiphenylsulfone in the heat-sensitive recording layer is such that the 4,4 ′-(3-tosylureido) diphenylmethane, 4,4 ′-(3- (tosylureido) diphenylether, N- ( The content is 5 to 90% by mass with respect to the total mass in at least one thermosensitive recording layer selected from p-tosyl) -N′-phenylurea and butyl 4- (3-tosylureido) benzoate. A heat-sensitive recording material according to 1.