JP2011073386A - Thermal recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal recording material which improves the oil resistance and plasticizer resistance of a recording part, and has no problem with the generation of background fogging even at a high-temperature and high-humidity environment, and has excellent long-term preservability. <P>SOLUTION: The thermal recording material comprises a thermal recording layer containing leuco dye and a colorant on a base material where the colorant contains at least one selected from 4,4'-(3-(tosyl)ureide) diphenylmethane and 4,4'-(3-(tosyl)ureide) diphenyl ether and further contains 4-hydroxy-4'-benzyloxy-diphenylsulfone. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heat-sensitive recording material having a high recording density, excellent plasticizer resistance and oil resistance of a recording part, and having little background fog even under high temperature and high humidity.

  A heat-sensitive recording material is known in which a recording image is obtained by reacting a colorless or light-colored leuco dye and a color former capable of acting as an electron acceptor of the leuco dye with heat to cause color development.

As a colorant used for such a heat-sensitive recording material, a recording portion having a high recording density is obtained, while a background portion other than the recording portion has a so-called background fogging (a whiteness of the background portion is high). Desired.
Further, the recording part is required to have excellent oil resistance and plasticizer resistance because long-term storage stability in various environments is required.

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

  For example, 4,4 ′-(3- (tosyl) ureido) diphenylmethane, 4,4 ′-(3- (tosyl) ureido) are new electron acceptors excellent in oil resistance and plasticizer resistance of the recording portion. Diphenyl ether has been proposed (see Patent Document 1). However, in at least one selected from 4,4 ′-(3- (tosyl) ureido) diphenylmethane and 4,4 ′-(3- (tosyl) ureido) diphenyl ether, the plasticizer resistance and oil resistance of the recording area are as follows. Although improved, it is difficult to obtain a high recording density, and it is necessary to increase the number of dividends in order to obtain a high recording density. In such a case, coloring of the white paper part (background part) under high-temperature and high-humidity storage is observed. The heat and humidity resistance of the background is inferior.

Moreover, combined use (refer patent document 2) of 4-hydroxy-4'- benzyloxy diphenyl sulfone and hydrogenated bisphenol A type epoxy compound is described as a colorant or a part of colorant, and further, the said As a specific sensitizer used in combination with a color former, a thermal recording medium using N- (4-methylphenyl) acetamide (see Patent Document 3) is described. However, the present situation is that satisfactory characteristics regarding the recording sensitivity and the storage stability of the recorded image have not been obtained.

JP-A-5-147357 JP 2008-296427 A JP 2001-063220 A

  The present invention has been made in view of the circumstances as described above, and the object thereof is to improve the oil resistance and plasticizer resistance of the recording portion, and the problem of background fogging even under high temperature and high humidity storage. It is an object to provide a thermal recording material excellent in long-term storage stability.

  The heat-sensitive recording material of the present invention is a heat-sensitive recording material having a heat-sensitive recording layer containing a leuco dye and a colorant on a support, and 4,4 ′-(3- (tosyl) ureido as the colorant. ) Diphenylmethane and at least one selected from 4,4 ′-(3- (tosyl) ureido) diphenyl ether, further containing 4-hydroxy-4′-benzyloxydiphenyl sulfone, The content of at least one selected from-(3- (tosyl) ureido) diphenylmethane and 4,4 '-(3- (tosyl) ureido) diphenyl ether is 5 to 20% by mass with respect to the total solid content of the thermosensitive recording layer. More preferably, it is 6 to 20% by mass, most preferably 7 to 18% by mass, and the 4-hydroxy-4′-benzyloxydiphen Content of Rusuruhon is preferably from 1 to 15 wt% with respect to the heat-sensitive recording layer total solid content, more preferably 2 to 10 wt%, and most preferably 2-9 wt%.

  In addition, at least one selected from 4,4 ′-(3- (tosyl) ureido) diphenylmethane and 4,4 ′-(3- (tosyl) ureido) diphenyl ether and 4-hydroxy-4′-benzyloxydiphenylsulfone Is preferably 9 to 27 mass%, more preferably 10 to 25 mass%, based on the total solid content of the heat-sensitive recording layer. This is because if the content is less than 9% by mass, the recording density is low, and if it exceeds 27% by mass, the color developing component increases and head debris is likely to occur.

Moreover, it is preferable to contain 0.05-0.9 mass part of said 4-hydroxy-4'-benzyloxy diphenyl sulfone with respect to 1 mass part of said colorants.
Furthermore, it is preferable that an undercoat layer is provided between the support and the heat-sensitive recording material.

  The heat-sensitive recording material of the present invention contains at least one selected from 4,4 ′-(3- (tosyl) ureido) diphenylmethane and 4,4 ′-(3- (tosyl) ureido) diphenyl ether as a colorant. Further, by containing 4-hydroxy-4′-benzyloxydiphenyl sulfone, the recording portion has oil resistance and plasticizer resistance, and is excellent in recording density and heat and moisture resistance of the background portion.

  The heat-sensitive recording material of the present invention is a heat-sensitive recording material having a heat-sensitive recording layer containing a leuco dye and a colorant on a support, and 4,4 ′-(3- (tosyl) ureido as the colorant. ) It contains at least one selected from diphenylmethane and 4,4 ′-(3- (tosyl) ureido) diphenyl ether, and further contains 4-hydroxy-4′-benzyloxydiphenylsulfone.

[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, at least one selected from a leuco dye and 4,4 ′-(3- (tosyl) ureido) diphenylmethane and 4,4 ′-(3- (tosyl) ureido) diphenyl ether as a colorant. Seeds are contained, and further 4-hydroxy-4'-benzyloxydiphenylsulfone is contained.
Hereinafter, each will be described in order.

<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.

<4,4 ′-(3- (tosyl) ureido) diphenylmethane and 4,4 ′-(3- (tosyl) ureido) diphenyl ether>
4,4 ′-(3- (tosyl) ureido) diphenylmethane and 4,4 ′-(3- (tosyl) ureido) diphenyl ether are excellent in oil resistance and plasticizer resistance in the recording area, but the recording density, When an amount capable of ensuring a level that can satisfy oil resistance and plasticizer resistance is added, there is a problem that background fogging occurs due to high temperature and high humidity storage. However, in the present invention, by using in combination with 4-hydroxy-4′-benzyloxydiphenylsulfone, the background fog does not become a problem, and excellent recording density, oil resistance and plasticizer resistance of the recording portion are ensured. Can do.

  At least one selected from 4,4 ′-(3- (tosyl) ureido) diphenylmethane and 4,4 ′-(3- (tosyl) ureido) diphenyl ether is contained in the thermosensitive recording layer with respect to the solid content of the thermosensitive recording layer. The content is preferably 5 to 20% by mass, more preferably 6 to 20% by mass, and most preferably 7 to 18% by mass.

<4-Hydroxy-4′-benzyloxydiphenyl sulfone>
4-hydroxy-4'-benzyloxydiphenyl sulfone is used in combination with at least one selected from 4,4 '-(3- (tosyl) ureido) diphenylmethane and 4,4'-(3- (tosyl) ureido) diphenyl ether By doing so, it is possible to increase the color development sensitivity without affecting the unrecorded portion (background portion).

  4-hydroxy-4'-benzyloxydiphenyl sulfone is preferably contained in the thermosensitive recording layer in an amount of 1 to 15% by mass, more preferably 2 to 10% by mass, and most preferably 2 to 9% by mass.

  In addition, at least one selected from 4,4 ′-(3- (tosyl) ureido) diphenylmethane and 4,4 ′-(3- (tosyl) ureido) diphenyl ether and 4-hydroxy-4′-benzyloxydiphenylsulfone Is preferably 9 to 27% by mass, more preferably 10 to 25% by mass, based on the total solid content of the heat-sensitive recording layer.

  4-hydroxy-4'-benzyloxydiphenylsulfone preferably has an average particle size of 0.1 to 3.0 [mu] m, more preferably 0.3 to 1.5 [mu] m.

  Further, 4-hydroxy-4′-benzyl for at least one selected from 4,4 ′-(3- (tosyl) ureido) diphenylmethane and 4,4 ′-(3- (tosyl) ureido) diphenyl ether in the thermosensitive recording layer. The content ratio (mass ratio) of oxydiphenyl sulfone is preferably 0.05 to 0.9, more preferably 0.1 to 0.8, and most preferably 0.2 to 0.7. . This is because as the proportion of 4,4 '-(3- (tosyl) ureido) diphenylmethane increases, background fogging under high temperature and high humidity storage tends to occur. On the other hand, if the proportion of 4,4 '-(3- (tosyl) ureido) diphenylmethane is too small, a sufficient improvement effect of oil resistance and plasticizer resistance in the recording area cannot be obtained.

The color former used in the present invention is at least one selected from 4,4 ′-(3- (tosyl) ureido) diphenylmethane and 4,4 ′-(3- (tosyl) ureido) diphenyl ether. -Hydroxy-4'-benzyloxydiphenylsulfone, but if necessary, various known materials, such as activated clay, attapulgite, colloidal silica, aluminum silicate, etc. -Isopropylidene diphenol, 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-phenoxycarbo Nylaminophenyl) ureido] diphenylsulfone, Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) phenylurea, 4,4′-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, 4-hydroxybenzoic acid Benzyl, 4,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4′-methyldiphenylsulfone, 4-allyloxy Phenolic compounds such as -4'-hydroxydiphenylsulfone and 3,4-dihydroxyphenyl-4'-methylphenylsulfone, thiourea compounds such as N, N'-di-m-chlorophenylthiourea, N- (p-toluene) Sulfonyl) carba Iuric acid p-cumylphenyl ester, N- (p-toluenesulfonyl) carbamoyl acid p-benzyloxyphenyl ester, N- (o-toluoyl) -p-toluenesulfoamide, N- (p-toluenesulfonyl) -N Organic compounds having a —SO ₂ NH— bond in the molecule such as'-(p-tolyl) urea, p-chlorobenzoic acid, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 4- [3- Aromatic carboxylic acids such as (p-tolylsulfonyl) propyloxy] salicylic acid, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid, and zinc, magnesium, aluminum, calcium of these aromatic carboxylic acids, Salts with polyvalent metals such as titanium, manganese, tin, nickel, and antipyrine of zinc thiocyanate Body, can be used in combination organic acidic substances such as composite zinc salt of terephthalaldehyde acid with other aromatic carboxylic acids.

Various resins are usually used as binders in the coating solution for the binder thermal recording layer. 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.

Other components In the heat-sensitive recording material of the present invention, the heat-sensitive recording layer further contains a sensitizer, a storage stability improver, and other various auxiliary agents in addition to the color former, leuco dye and binder. Also good.

<Sensitizer>
A sensitizer may be added to the heat-sensitive recording layer of the present invention, such as stearamide, methoxycarbonyl-N-stearic acid benzamyl, N-benzoyl stearamide, N-eicosanoic acid amide, ethylenebisstearic acid. Amides, behenic acid amides, methylenebisstearic acid amides, N-methylol stearic acid amides, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2 -Naphtylbenzyl ether, m-terphenyl, p-benzylbiphenyl, oxalic acid di-p-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-methylphenoxy) 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, etc. Can be used as long as there is no hindrance.
When a sensitizer is used, the amount used may be an effective amount for sensitization, but is usually about 2 to 40% by mass, particularly 5 to 5% by mass based on the total solid content of the heat-sensitive recording layer. It is preferable to mix in the range of about 25% by mass.

<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%.

  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.

Ingredients as described above for the thermosensitive recording layer , that is, leuco dye, 4,4 ′-(3- (tosyl) ureido) diphenylmethane, 4,4 ′-(3- (tosyl) ureido) diphenyl ether, 4-hydroxy A coating liquid (coating liquid for heat-sensitive recording layer) is prepared by dispersing -4'-benzyloxydiphenyl sulfone, a sensitizer, an adhesive component, and, if necessary, an additive to be added in an aqueous medium. In general, water is used as a dispersion medium, and materials obtained by dispersing leuco dyes, colorants, sensitizers, etc. together or separately with a stirring / pulverizing machine such as a ball mill, attritor, sand mill, etc. It is prepared by blending.

(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 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, starch, 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 coating liquid for the protective layer, surfactants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, and surfactants 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.

The method for forming the undercoat layer, the thermal recording layer and the protective layer of the present invention is not particularly limited. For example, air knife coating, varibar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die A method of applying and drying the coating solution for the undercoat layer on the support by an appropriate coating method such as coating, and then applying and drying the coating solution for the heat sensitive recording layer and further the coating solution for the protective layer on the undercoat layer. Formed with.

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 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 Spherical resin particle dispersion (trade name: Grosdale 130S, composition: styrene, average particle size: 0.8 μm, manufactured by Mitsui Chemicals, solid content concentration 53 mass%) 90 parts, 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.

Preparation of solution A 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-based A composition (suspension) consisting of 20 parts of a 5% emulsion of foaming agent and 80 parts of water was subjected to a sand mill so that the median diameter by a laser diffraction particle size analyzer SALD2200 (manufactured by Shimadzu Corporation) was 0.5 μm. A liquid A was obtained.

-Preparation of liquid B 100 parts of 4,4 '-(3- (tosyl) ureido) diphenylmethane, 50 parts of a 20% aqueous solution of sulfone-modified polyvinyl alcohol (trade name: Gocelan L-3266, manufactured by Nippon Synthetic Chemical), natural fats and oils A composition (suspension) consisting of 10 parts of a 5% emulsion of an antifoaming agent and 90 parts of water is 1.0 μm in median diameter by a laser diffraction particle size measuring device SALD2200 (manufactured by Shimadzu Corporation) using a sand mill. The liquid B was obtained by processing in the same manner.

-Solution C preparation 4-hydroxy-4'-benzyloxydiphenylsulfone 100 parts, sulfone-modified polyvinyl alcohol (trade name: Go-Selan L-3266, manufactured by Nippon Synthetic Chemical Co., Ltd.) A composition (suspension) composed of 10 parts of a 5% emulsion of an antifoaming agent and 90 parts of water is sand milled to give a median diameter of 1.0 μm using a laser diffraction particle size analyzer SALD2200 (manufactured by Shimadzu Corporation). The liquid C was obtained by the same treatment.

-Preparation of solution D 100 parts of di-p-methylbenzyl oxalate, 50 parts of a 20% aqueous solution of sulfone-modified polyvinyl alcohol (trade name: Gocelan L-3266, supra), 5% emulsion 2 of natural fat and oil antifoaming agent 2 Part D and 98 parts of water were treated with a sand mill so that the median diameter by a laser diffraction particle size measuring instrument SALD2200 (manufactured by Shimadzu Corporation) was 1.0 μm to obtain a liquid D.

-Preparation of coating solution for heat-sensitive recording layer A solution 25.0 parts, solution B 37.5 parts, solution C 12.5 parts, solution D 37.5 parts, particulate amorphous silica (trade name: Mizukaseal P-527, 10 parts by Mizusawa Chemical Industry Co., Ltd., 20 parts by aluminum hydroxide (trade name: Hygielite H-42, Showa Light Metal Industry Co., Ltd.), 125 parts by weight of a 12% aqueous solution of polyvinyl alcohol having a saponification degree of 98 mol% and a polymerization degree of 1000 Zinc stearate dispersion (trade name: Hydrin Z-8-36, solid content concentration 36%, manufactured by Chukyo Yushi Co., Ltd.) 13.9 parts and water 18.6 parts were mixed and stirred to prepare a thermal recording layer coating solution. Prepared.

- 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 heat-sensitive recording material was obtained in the same manner as in Example 1 except that the amount of liquid C was changed to 2.5 parts in the preparation of the heat-sensitive 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 liquid B was changed to 20 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 the amount of liquid B was changed to 87.5 parts in the preparation of the heat-sensitive recording layer coating liquid of Example 1.

Example 5
Example 1 except that 4,4 ′-(3- (tosyl) ureido) diphenyl methane was used in place of 4,4 ′-(3- (tosyl) ureido) diphenylmethane in the preparation of the liquid B of Example 1. In the same manner, a heat-sensitive recording material was obtained.

Example 6
A thermosensitive recording material was obtained in the same manner as in Example 1 except that the amount of liquid B was changed to 20 parts and the amount of liquid C was changed to 20 parts in the preparation of the thermal recording layer coating liquid of Example 1.

Example 7
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the amount of liquid B was changed to 45 parts and the amount of liquid C was changed to 2 parts in the preparation of the heat-sensitive recording layer coating liquid of Example 1.

Comparative Example 1
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the liquid C was not used in the preparation of the heat-sensitive recording layer coating material of Example 1.

Comparative Example 2
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that in the preparation of the heat-sensitive recording layer coating material of Example 1, the amount of liquid B was changed to 100 parts and liquid C was not used.

Comparative Example 3
In the preparation of the liquid B of Example 1, 2,2 ′-[4- (4-hydroxyphenylsulfonyl) phenoxy] diethyl ether (trade name: in place of 4,4 ′-(3- (tosyl) ureido) diphenylmethane) A heat-sensitive recording material was obtained in the same manner as in Example 1 except that D-90 (manufactured by Nippon Soda Co., Ltd.) was used.

Comparative Example 4
In the preparation of solution C in Example 1, 4-hydroxy-4'-isopropoxydiphenylsulfone (trade name: D-8, manufactured by Nippon Soda) was used instead of 4-hydroxy-4'-benzyloxydiphenylsulfone. Except for the above, a heat-sensitive recording material was obtained in the same manner as in Example 1.

Comparative Example 5
In the preparation of the thermal recording layer coating liquid of Example 1, the thermal recording medium was prepared in the same manner as in Example 1 except that the liquid B was not used and the amount of the liquid C was changed from 12.5 parts to 50 parts. 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 was 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 the print. The recording portion is required to be 1.20 or more for practical use, while the lower the numerical value is preferable for the background portion. If it exceeds 2, background fog becomes a problem.

(2) Heat resistance Visual density of Macbeth densitometer (trade name: RD-914 type, Macbeth Co., Ltd.) after the thermal recording medium before recording was left for 24 hours in an atmosphere of 60 ° C. and 30% RH. Measured in mode.
The smaller the value, the better. When it exceeds 0.2, background fog becomes a problem.

(3) Moisture and heat resistance Visual density of Macbeth densitometer (trade name: RD-914 type, Macbeth Co., Ltd.) as the density of the background after leaving each thermosensitive recording medium before recording in an atmosphere of 40 ° C. and 80% RH for 24 hours. Measured in mode.
The smaller the value, the better. When it exceeds 0.2, background fog becomes a problem.

(4) Oil resistance Salad oil was applied on the surface of each heat-sensitive recording medium that was colored for recording density measurement, left for 24 hours, and then the surface of the recording area was wiped with gauze. Name: RD-914 type, Macbeth Co., Ltd.) 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) Plasticizer resistance Each heat sensitive material in which a wrap film (trade name: High Wrap KMA-W, manufactured by Mitsui Chemicals Co., Ltd.) is wrapped three times on a polycarbonate pipe (40 mmΦ), and then colored for recording density measurement. A recording medium is placed, and a wrap film is wrapped in three layers on the recording medium and allowed to stand at 40 ° C. for 24 hours, and then the density of the recording portion is set in a visual mode of a Macbeth densitometer (trade name: RD-914, Macbeth). It was measured. 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.

  As can be seen from the table, when 4,4 ′-(3- (tosyl) ureido) diphenylmethane is used alone, the recording density is low at 16% by mass in the thermosensitive recording layer (Comparative Example 1), and 30% by mass or more. Even if the recording density could be ensured by the inclusion, the heat resistance and heat-and-moisture resistance of the background portion were lowered to a problem level (Comparative Example 2).

  On the other hand, by using 4,4 ′-(3- (tosyl) ureido) diphenylmethane or 4,4 ′-(3- (tosyl) ureido) diphenyl ether in combination with 4-hydroxy-4′-benzyloxydiphenylsulfone, It can be seen that the recording density, the oil resistance of the recording portion, and the plasticizer resistance can be improved without lowering the heat resistance and heat and moisture resistance of the background portion (Examples 1 to 7).

  Even when 4,4 ′-(3- (tosyl) ureido) diphenylmethane and 4-hydroxy-4′-benzyloxydiphenylsulfone are used in combination, 4,4 ′-(3- (tosyl) ureido ) When the content of diphenylmethane was as large as 29% by mass, the heat resistance and moist heat resistance of the background portion tended to decrease (Example 4).

  However, if the ratio of 4-hydroxy-4′-benzyloxydiphenylsulfone / 4,4 ′-(3- (tosyl) ureido) diphenylmethane exceeds 0.9, the effect of improving the oil resistance and plasticizer resistance of the recording area (Example 6) On the contrary, when the ratio is less than 0.05, the recording density tends to decrease (Example 7).

  From the above, at least one selected from 4,4 ′-(3- (tosyl) ureido) diphenylmethane and 4,4 ′-(3- (tosyl) ureido) diphenyl ether, and 4-hydroxy-4′-benzyloxydiphenyl Sulfone within a predetermined range (preferably 5-20% by weight of the former compound, 1-15% by weight of the latter compound, more preferably 6-20% by weight of the former compound, 2-10% by weight of the latter compound, most preferably The former compound is contained in an amount of 7 to 18% by mass and the latter compound is contained in an amount of 2 to 9% by mass. The compounding ratio of both compounds (4-hydroxy-4′-benzyloxydiphenylsulfone / 4,4 ′-(3- 0.05 to (tosyl) ureido) diphenylmethane and 4,4 ′-(3- (tosyl) ureido) diphenyl ether) It can be seen that it is preferable in the range of 0.9.

Claims (6)

  In a heat-sensitive recording material having a heat-sensitive recording layer containing a leuco dye and a colorant on a support, 4,4 ′-(3- (tosyl) ureido) diphenylmethane and 4,4′- A thermosensitive recording material comprising at least one selected from (3- (tosyl) ureido) diphenyl ether and further containing 4-hydroxy-4′-benzyloxydiphenylsulfone.   The thermosensitive recording layer is at least selected from 4,4 ′-(3- (tosyl) ureido) diphenylmethane and 4,4 ′-(3- (tosyl) ureido) diphenyl ether with respect to the total solid content of the thermosensitive recording layer. The heat-sensitive recording material according to claim 1, wherein 1 to 5% by mass and 1 to 15% by mass of 4-hydroxy-4′-benzyloxydiphenylsulfone are contained.   The thermosensitive recording layer is at least selected from 4,4 ′-(3- (tosyl) ureido) diphenylmethane and 4,4 ′-(3- (tosyl) ureido) diphenyl ether with respect to the total solid content of the thermosensitive recording layer. The heat-sensitive recording material according to claim 1 or 2, comprising 1 to 7 mass% of 1 type and 2 to 9 mass% of 4-hydroxy-4'-benzyloxydiphenylsulfone.   The thermosensitive recording layer comprises at least one selected from 4,4 ′-(3- (tosyl) ureido) diphenylmethane and 4,4 ′-(3- (tosyl) ureido) diphenyl ether and 4-hydroxy-4′-. The heat-sensitive recording material according to any one of claims 1 to 3, wherein the total content of benzyloxydiphenyl sulfone is 9 to 27 mass% with respect to the total solid content of the heat-sensitive recording layer.   Content ratio of 4-hydroxy-4'-benzyloxydiphenyl sulfone to at least one selected from 4,4 '-(3- (tosyl) ureido) diphenylmethane and 4,4'-(3- (tosyl) ureido) diphenyl ether Is a thermal recording medium according to any one of claims 1 to 4, which is 0.05 to 0.90.   The heat-sensitive recording material according to any one of claims 1 to 5, further comprising an undercoat layer between the support and the heat-sensitive recording material.