JPH10264525A - Heat sensitive recording body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sensitive recording body, reduced in the fog of skin under a high temperature atmosphere and high in the sensitivity of recording. SOLUTION: In a heat sensitive recording body, provided with a prime coat layer and a heat sensitive recording layer, containing leuco dye and coloring agent, sequentially on a bearer, 10 wt.% or more of organic pigment, whose oil absorption is 100 ml/100 g or more and which is provided with through holes, is contained in the prime coat layer while at least one kind of 3-(N-thyl-N- isoamylamino)-7-(o-chroloanilino)fluoran, 3-diethylamino-7-(o-chroloanilino)fluoran and the like is contained in the leuco dye and at least one kind of 4,4- dihydroxydiphenylsulfone, 2,4-dihydroxydiphenylsulfone and the like is contained in the coloring agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material utilizing a color-forming reaction between a leuco dye and a color former, and more particularly to a heat-sensitive recording material excellent in recording sensitivity and recording running property.

[0002]

2. Description of the Related Art A thermosensitive recording material is known in which a leuco dye and a color former are brought into contact with heat to obtain a recorded image by utilizing a color development reaction between a colorless or pale leuco dye and a color former. I have. Such a thermosensitive recording medium is relatively inexpensive, and the recording apparatus is compact and easy to maintain.
It is used not only as a recording medium for facsimile and various computers but also in a wide range of fields.

Accordingly, the environment in which the thermosensitive recording medium is used has been diversified. For example, POS (point of sales)
System use has been used in various manufacturing processes,
Accordingly, the thermal recording medium is required to have low background fog even when used under severe conditions such as an environmental temperature of 100 ° C. On the other hand, in recent years, the speed of recording devices has been increased, and higher recording sensitivity of thermosensitive recording media has also been required.

[0004] In a heat-sensitive recording medium utilizing a color-forming reaction between a leuco dye and a color former, heat resistance and recording sensitivity are characteristics that contradict each other. That is, a thermosensitive recording medium having good recording sensitivity is
There was a drawback that background fog was easily generated by heat. For the purpose of improving such disadvantages, a heat-sensitive recording material containing an organic pigment having a through hole in an undercoat layer of the heat-sensitive recording material is described in JP-A-5-222108, but in terms of background fog, At present, sufficient effects have not been obtained.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-sensitive recording medium which is free from background fog in a high-temperature environment and is excellent in recording sensitivity and recording running performance.

[0006]

[MEANS FOR SOLVING THE PROBLEMS] An undercoat layer,
And a heat-sensitive recording medium in which a heat-sensitive recording layer containing a leuco dye and a color former is sequentially provided, and the oil absorption in the undercoat layer is 10%.
An organic pigment having 0 ml / 100 g or more and having a through hole is contained in an amount of 10% by weight or more based on the total solid content of the undercoat layer, and 3- (N) as a leuco dye is contained in the heat-sensitive recording layer.
-Ethyl-N-isoamylamino) -7- (o-chloroanilino) fluoran, 3-diethylamino-7- (o
-Chloroanilino) fluoran, 3-di (n-butyl)
Amino-7- (o-chloroanilino) fluoran, 3-
Diethylamino-7- (o-fluoroanilino) fluoran, 3-di (n-butyl) amino-7- (o-fluoroanilino) fluoran, 3- (N-ethyl-p-toluidino) -6-methyl- 7-anilinofluoran, 3-
(N-ethyl-p-toluidino) -6-methyl-7-
At least one of (p-toluidino) fluorane is contained, or 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 1,1-bis (4-hydroxyphenyl) is used as a colorant.
The above-mentioned problem was solved by including at least one of -1-phenylethane, 4,4′-cyclohexylidenediphenol, and bis (3-allyl-4-hydroxyphenyl) sulfone.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, 3- (N-ethyl-N-isoamylamino) -7- (o-chloroanilino) fluoran and 3-diethylamino-7- ( o-chloroanilino) fluoran, 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran, 3-diethylamino-7- (o-
Fluoroanilino) fluoran, 3-di (n-butyl)
Amino-7- (o-fluoroanilino) fluoran, 3
-(N-ethyl-p-toluidino) -6-methyl-7-
Anilinofluoran or at least one of 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluoran (hereinafter, referred to as a specific leuco dye) is contained or colored. As an agent, 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 4,4'-cyclohexylidenediphenol, bis ( At least one of 3-allyl-4-hydroxyphenyl) sulfone (hereinafter, referred to as a specific colorant) is contained. However, when such a specific leuco dye or a specific colorant is used, high temperature conditions However, although the occurrence of background fog is suppressed, there is a problem that the sensitivity at the time of recording is low. However,
The oil absorption between the support and the heat-sensitive recording layer is 100 ml / 1.
An organic pigment having through holes of 00 g or more (hereinafter referred to as a specific organic pigment) is 10% by weight or more, more preferably 3% by weight or more.
It has been found that by providing an undercoat layer containing 0% by weight to 90% by weight, even under a high temperature condition of 90 ° C. to 110 ° C., it is possible to obtain a thermosensitive recording medium having less background fog and high recording sensitivity. It is.

Among the specific leuco dyes, 3-di (n
-Butyl) amino-7- (o-chloroanilino) fluoran, 3-di (n-butyl) amino-7- (o-fluoroanilino) fluoran or 3- (N-ethyl-p-
Toluidino) -6-methyl-7-anilinofluoran is particularly preferred since it reduces the occurrence of background fogging.

The amount of the specific leuco dye or the specific coloring agent is not particularly limited, but the specific leuco dye is 5 to 35% by weight based on the total solid content of the heat-sensitive recording layer.
The degree is preferred. In addition, the oil absorption of a specific organic pigment is 10
When the amount is less than 0 ml / 100 g, there is a possibility that the residue may adhere to the thermal head at the time of recording and the recording traveling property may be reduced, or the recording sensitivity may not be improved.

The material of the specific organic pigment is not particularly limited. For example, resins such as polystyrene, polymethyl (meth) acrylate, polyvinyl chloride, polyurethane, polyvinylidene chloride, poly (meth) acrylonitrile, and resin components thereof And a styrene-acrylic copolymer. Above all, a styrene-acrylic copolymer is preferable since the background fog and the deterioration of the recorded image with time are reduced.

It is sufficient that at least one or more through-holes are present in the specific organic pigment particles.
For example, using a resin particle dissolved in alkaline water such as sodium hydroxide, ammonium hydroxide, potassium hydroxide, and triethylamine as a core material to elute the core material with the alkaline water while synthesizing a resin that is not dissolved in the alkaline water. Is obtained by

The resin particles dissolved in the alkaline water include, for example, at least one of hydrophobic monomers such as styrene, methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate, and (meth) acrylic acid. And copolymers obtained by emulsion polymerization of at least one vinyl monomer of an unsaturated carboxylic acid such as itaconic acid and crotonic acid. The amount of the unsaturated carboxylic acid vinyl monomer is preferably 10 to 50% by weight based on all monomers.

[0013] Examples of resins that are not dissolved in alkaline water include:
Examples thereof include those obtained by polymerizing at least one of the above-mentioned hydrophobic monomers. Of course, as long as it is not dissolved in alkaline water, at least one of the above-mentioned unsaturated carboxylic acid vinyl monomers may be copolymerized.

The shape of the specific organic pigment is not particularly limited, but is preferably a slightly flat spherical shape so that the particles do not become too dense when the undercoat layer is formed and the strength of the coating film does not decrease. The flatness is preferably about 0 to 30%. The volume average particle size is not particularly limited, either, but is preferably 0.1 to 5.0 μm, more preferably 0.1 to 1.2 μm in consideration of the thickness of the undercoat layer and the strength of the coating film.
m.

Other known inorganic or organic pigments can be used in combination as long as the desired effects of the present invention are not impaired. Specific examples of such pigments include, for example, calcium carbonate, magnesium carbonate, kaolin, calcined kaolin,
Inorganic pigments such as talc, aluminum hydroxide, amorphous silica, titanium oxide, etc., and a solid or hollow structure composed of polystyrene, polymethyl acrylate, polyvinyl chloride, polyvinylidene chloride, and urea-formaldehyde resin And organic pigments.

The undercoat layer is prepared, for example, by adding an adhesive to an aqueous dispersion containing a specific organic pigment while mixing and stirring, and applying a coating liquid for the undercoat layer to, for example, a blade coater, a roll coater, or a reverse roll coater. Using a rod blade coater, champlex coater, cartean coater, etc., the coated amount after drying on a support such as high quality paper, neutral paper, coat paper, synthetic paper, film, nonwoven fabric, etc. is 1 to 20 g / m ² , and preferably about ² to 10 g / m ² .

Examples of the adhesive used in the undercoat layer include starch, oxidized starch, enzyme-modified starch, esterified starch,
Etherified starch, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, completely (or partially) saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, acrylic acid amide-acrylate copolymer Water-soluble adhesives such as coalesced salts, acrylic acid amide-acrylic acid ester-methacrylic acid copolymer salts, styrene-maleic anhydride copolymer salts, isobutylene-maleic anhydride copolymer salts, and casein; And water-dispersible adhesives such as natural rubber latex, styrene-butadiene latex, acrylonitrile-butadiene latex, and methyl methacrylate-butyl acrylate latex. Of course, it is not limited to these. The amount of the adhesive used is about 5 to 35% by weight based on the total solid content of the undercoat layer.

In the undercoat layer coating liquid, various auxiliaries such as a dispersant, an antifoaming agent, a coloring dye, a fluorescent dye and a curing agent can be appropriately added, if necessary.

The heat-sensitive recording layer is provided on the undercoat layer thus formed. The heat-sensitive recording layer contains at least one specific leuco dye or at least one specific colorant. Other known leuco dyes or other known colorants can be used in combination as long as the desired effect is not inhibited. Specific examples of other leuco dyes include, for example, 3- (N-ethyl-N-isoamylamino)
-6-methyl-7-anilinofluoran, 3-dimethylamino-7- (m-trifluoromethyl) anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-di ( n-butyl) amino-6-methyl-7-anilinofluoran, 3- (Nn-hexyl-N-ethyl) amino-6-methyl-7-anilinofluoran, 3- (N-ethyl- N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluoran, 3
-Diethylamino-6-chloro-7-anilinofluoran, 3-diethylamino-6-methyl-7-p-ethoxyanilinofluoran, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7 -Anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3- (N-methyl-NN-propylamino)-
6-methyl-7-anilinofluoran, 3,3-bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6
7-tetrachlorophthalide, 3,3-bis [1- (4-
Methoxyphenyl) -1- (4-pyrrolidinophenyl)
Ethylene-2-yl] -4,5,6,7-tetrachlorophthalide and the like.

Other colorants include, for example, 4,4'-isopropylidenediphenol, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, benzyl 4-hydroxybenzoate, 4-hydroxy- 4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxyphenyl-
4'-benzyloxyphenylsulfone, 3,4-dihydroxyphenyl-4'-methylphenylsulfone, bis (p-hydroxyphenyl) butyl acetate, bis (p-
Phenolic compounds such as methyl hydroxyphenyl) acetate; thiourea compounds such as N, N'-di-m-chlorophenylthiourea; p-cumylphenyl N- (p-tolylsulfonyl) carbamoylate; p-tolylsulfonyl) -N '-(p-tolyl) urea, 4,4'
- bis (p- tolylsulfonyl aminocarbonylamino) having a -SO ₂ NH- bond in the molecule of diphenylmethane, p- chlorobenzoic acid zinc 4- [3-
Zinc (p-tolylsulfonyl) propyloxy] salicylate and zinc of aromatic carboxylic acid such as 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] zinc salicylate.

The ratio of the specific leuco dye to the color former or the leuco dye to the specific color former is generally 1 to 10 parts by weight, preferably 1 to 10 parts by weight, per part by weight of the specific leuco dye or leuco dye. About 2 to 5 parts by weight of a coloring agent or a specific coloring agent is used.

The heat-sensitive recording layer may contain a sensitizer for further increasing the recording sensitivity and a storability improving agent for improving the storability of the recorded image. Such sensitizers include, for example, stearic acid amide, N-benzoyl stearic acid amide, ethylenebisstearic acid amide, N-methylol stearic acid amide, dibenzyl terephthalate, dimethyl terephthalate, benzyl p-benzyloxybenzoate, 1-hydroxy-2-naphthoic acid phenyl, 2-naphthylbenzyl ether, m-tert-phenyl, p-benzylbiphenyl, 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, 1,2-di (2-naphthoxyethane), 1- (2-naphthoxy ) -2-phenoxyethane, dibenzyl oxalate, di-p-methylbenzyl oxalate, di-p-chlorobenzyl oxalate, p-acetophenethidide, N-acetoacetyl-
p-Toluidine, di (β-biphenylethoxybenzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane and the like.

Examples of such a preservability improver include, for example, 2,
2′-methylenebis (4-methyl-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-butylphenyl) butane, 2,2
-Bis (4-hydroxy-3,5-dichlorophenyl)
Hindered phenol compounds such as propane and 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 1,4-diglycidyloxybenzene, 4,4 ′
Epoxy compounds such as -diglycidyloxydiphenylsulfone, 4-benzyloxy-4 '-(2-methylglycidyloxy) diphenylsulfone, diglycidyl terephthalate, cresol novolak type epoxy resin, phenol novolak type epoxy resin, and bisphenol A type epoxy resin , N, N'-di-2-naphthyl-p-phenylenediamine, sodium or polyvalent metal salt of 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate, bis (4-ethyleneimino Carbonylaminophenyl) methane and the like

The heat-sensitive recording layer generally uses water as a dispersion medium,
A leuco dye (a specific leuco dye), a coloring agent (a specific coloring agent), and if necessary, a sensitizer, a preservative improver, etc., together with a stirring / crushing machine such as a ball mill, an attritor, or a sand mill, or After separately dispersing, the coating liquid for the heat-sensitive recording layer obtained by adding the adhesive while mixing and stirring is applied onto the undercoat layer after drying to 1 to 15 g / m ² , preferably 2 to 6 g / m 2. It is formed by coating and drying so as to be about ² .

As the adhesive used for the heat-sensitive recording layer,
What was illustrated by the undercoat layer is mentioned. The amount of the adhesive used is about 5 to 35% by weight based on the total solid content of the heat-sensitive recording layer.

Furthermore, various auxiliaries can be added to the coating solution for the heat-sensitive recording layer, if necessary, for example, kaolin,
Pigments such as talc, calcium carbonate, aluminum hydroxide, titanium oxide, barium sulfate, amorphous silica, zinc oxide, calcined kaolin, urea / formalin resin filler, sodium dioctyl sulfosuccinate, sodium dodecylbenzene sulfonate, lauryl alcohol sulfate Dispersants such as sodium and fatty acid metal salts; lubricants such as zinc stearate and calcium stearate; waxes such as polyethylene wax, carnauba wax, paraffin wax, and ester wax; antifoaming agents; fluorescent dyes, coloring dyes, and curing agents. Can be Further, specific organic pigments can be added.

The coating solution for the heat-sensitive recording layer includes, for example, bar coating, air knife coating, rod blade coating, pure blade coating, and short coating.
It is applied onto the undercoat layer by a well-known coating method such as dwell coating, barber blade coating, curtain coating, and die coating. The coating amount of the heat-sensitive recording layer coating liquid is not particularly limited, and is usually ² to 12 g / m ² , preferably 3 to 8 g / m ² in dry weight.
^{About 2} .

If necessary, a protective layer may be provided on the heat-sensitive recording layer or on the back surface of the support to enhance the storability, or after coating each layer, it may be subjected to a smoothing treatment such as super calendaring. Further, a heat-sensitive recording material, such as applying a pressure-sensitive adhesive treatment to the back surface of the support to process it into an adhesive label, providing a rewetting adhesive layer, or providing a magnetic recording layer, a printing coating layer, and a thermal transfer recording layer. Various known techniques in the manufacturing field can be added as necessary.

[0029]

The present invention will be described in more detail with reference to the following Examples, but it should be understood that the present invention is by no means restricted to such specific Examples. In the examples, "parts" and "%" indicate parts by weight and% by weight, respectively, unless otherwise specified.

Example 1 Preparation of Coating Solution for Undercoat Layer The volume average particle diameter was 0.6 μm and the oil absorption was 150 ml /
500 parts of a 20% dispersion of a styrene-methyl methacrylate copolymer organic pigment having 100 g of through-holes, and 10 parts of a styrene-butadiene latex having a solid concentration of 48% (trade name: L-1571, manufactured by Asahi Kasei Corporation); A composition comprising 50 parts of a 20% aqueous solution of polyvinyl alcohol (trade name: PVA-205, manufactured by Kuraray Co., Ltd.) was mixed and stirred to obtain a coating liquid for an undercoat layer.

Solution A Preparation A composition comprising 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran, 30 parts, 5 parts of a 5% aqueous solution of methylcellulose and 65 parts of water was subjected to sand milling to obtain an average particle size. The solution A was obtained by pulverizing until the diameter became 0.9 μm.

Solution B Preparation A composition comprising 30 parts of 2,4'-dihydroxydiphenylsulfone, 5 parts of a 5% aqueous solution of methylcellulose and 65 parts of water is pulverized by a sand mill until the average particle diameter becomes 1.0 μm. Liquid B was obtained.

Solution C Preparation of a composition comprising 15 parts of oxalic acid di-p-chlorobenzyl ester, 15 parts of oxalic acid di-p-methylbenzyl ester, 5 parts of a 5% aqueous solution of methylcellulose, and 65 parts of water by a sand mill. Liquid C was obtained by pulverizing until the average particle diameter became 0.9 μm.

Preparation of Coating Solution for Thermosensitive Recording Layer 30 parts of solution A, 70 parts of solution B, 70 parts of solution C, 15 parts of light calcium carbonate, 10 parts of a 30% dispersion of zinc stearate,
A composition comprising 100 parts of a 10% aqueous solution of polyvinyl alcohol and 10 parts of water was mixed and stirred to obtain a coating liquid for a heat-sensitive recording layer.

Preparation of Thermosensitive Recording Material A coating solution for an undercoat layer and a coating solution for a thermosensitive recording layer were dried on one side of a neutral paper-made high-quality paper containing an alkyl ketene dimer as a sizing agent having a basis weight of 50 g / m ² , respectively. An undercoat layer and a heat-sensitive recording layer were formed by sequentially applying and drying using a rod blade so that the subsequent coating amounts were 7 g / m ² and 6 g / m ^2, and then subjected to a supercalender treatment to obtain a heat-sensitive recording material. .

Example 2 A thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following undercoat layer coating liquid was used in place of the undercoat layer coating liquid used in the preparation of the thermosensitive recording medium of Example 1. A recording was obtained.

Preparation of Coating Solution for Undercoat Layer The volume average particle diameter is 0.6 μm and the oil absorption is 150 ml /
250 parts of a 20% dispersion of a styrene-methyl methacrylate copolymer organic pigment having 100 g of through-holes, a volume average particle diameter of 2.4 μm, and an oil absorption of 110 ml / 10
0g 20% dispersion of secondary coagulated light calcium carbonate 250
Parts, a styrene-butadiene-based latex having a solid concentration of 48% (trade name: L-1571, manufactured by Asahi Kasei Corporation), and polyvinyl alcohol (trade name: PVA-205,
A composition consisting of 50 parts of a 20% aqueous solution of Kuraray Co., Ltd.) was mixed and stirred to obtain a coating liquid for an undercoat layer.

Example 3 In the preparation of solution A in Example 1, 3-diethylamino-7 was used instead of 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran.
Except for using-(o-chloroanilino) fluoran,
A thermosensitive recording medium was obtained in the same manner as in Example 1.

Example 4 In the preparation of solution A of Example 1, 3-diethylamino-7 was used instead of 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran.
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that-(o-fluoroanilino) fluorane was used.

Example 5 In the preparation of solution A of Example 1, 3- (N-ethyl-p-) was used instead of 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran.
A thermosensitive recording material was obtained in the same manner as in Example 1 except that toluidino) -6-methyl-7-anilinofluoran was used.

Example 6 In the preparation of Solution A of Example 1, 3- (N-ethyl-p-) was used instead of 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran.
A thermosensitive recording medium was obtained in the same manner as in Example 1, except that toluidino) -6-methyl-7- (p-toluidino) fluoran was used.

Example 7 In the preparation of solution A in Example 1, 3- (N-ethyl-N-ethyl-N-butyl-amino-7- (o-chloroanilino) fluoran was used instead of 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran.
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that isoamylamino) -7- (o-chloroanilino) fluoran was used.

Example 8 In the preparation of solution A in Example 1, 3-di (n-butyl) amino-7- was used instead of 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that (o-fluoroanilino) fluorane was used.

Example 9 The procedure of Example 1 was repeated except that 4,4'-dihydroxydiphenylsulfone was used instead of 2,4'-dihydroxydiphenylsulfone in the preparation of solution B. A recording was obtained.

Example 10 In the preparation of solution B of Example 1, except that 1,1-bis (4-hydroxyphenyl) -1-phenylethane was used instead of 2,4′-dihydroxydiphenylsulfone. A thermosensitive recording medium was obtained in the same manner as in Example 1.

Example 11 The procedure of Example 1 was repeated, except that 4,4′-cyclohexylidenediphenol was used instead of 2,4′-dihydroxydiphenylsulfone in the preparation of solution B of Example 1. A thermosensitive recording medium was obtained.

Example 12 The procedure of Example 1 was repeated except that bis (3-allyl-4-hydroxyphenyl) sulfone was used instead of 2,4′-dihydroxydiphenylsulfone in the preparation of solution B of Example 1. A thermosensitive recording medium was obtained in the same manner.

Example 13 In the preparation of the solution A in Example 1, 3-di (n-butyl) amino-6-amino was used instead of 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that methyl-7-anilinofluoran was used.

Comparative Example 1 A thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following undercoat layer coating liquid was used in place of the undercoat layer coating liquid used in the preparation of the thermosensitive recording medium of Example 1. A recording was obtained.

Preparation of Coating Solution for Undercoat Layer The volume average particle diameter is 0.6 μm and the oil absorption is 150 ml /
50 parts of a 20% dispersion of a styrene-methyl methacrylate copolymer organic pigment having 100 g of through-holes, a volume average particle diameter of 2.4 μm, and an oil absorption of 110 ml / 100
g 20% dispersion of secondary coagulated light calcium carbonate 450
Parts, a styrene-butadiene-based latex having a solid concentration of 48% (trade name: L-1571, manufactured by Asahi Kasei Corporation), and polyvinyl alcohol (trade name: PVA-205,
A composition consisting of 50 parts of a 20% aqueous solution of Kuraray Co., Ltd.) was mixed and stirred to obtain a coating liquid for an undercoat layer.

Comparative Example 2 A thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following undercoat layer coating liquid was used in place of the undercoat layer coating liquid used in the preparation of the thermosensitive recording medium of Example 1. A recording was obtained.

Preparation of Coating Solution for Undercoat Layer The volume average particle diameter is 0.7 μm, and the oil absorption is 40 ml / 1.
00g of a polystyrene organic pigment having a solid structure
500 parts of a 0% dispersion, 10 parts of a styrene-butadiene latex having a solid concentration of 48% (trade name: L-1571, manufactured by Asahi Kasei Corporation), and polyvinyl alcohol (trade name:
A composition comprising 50 parts of a 20% aqueous solution of PVA-205 (manufactured by Kuraray Co., Ltd.) was mixed and stirred to obtain a coating liquid for an undercoat layer.

Comparative Example 3 A thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following undercoat layer coating liquid was used in place of the undercoat layer coating liquid used in the preparation of the thermosensitive recording medium of Example 1. A recording was obtained.

Preparation of Coating Solution for Undercoat Layer The volume average particle diameter is 0.6 μm, and the oil absorption is 80 ml / 1.
500 parts of a 20% dispersion of a styrene-methyl methacrylate copolymer organic pigment having a through-hole of 00 g, and 500 parts of a styrene-butadiene latex having a solid concentration of 48% (trade name: L-1571, manufactured by Asahi Kasei Corporation) , And a composition comprising 50 parts of a 20% aqueous solution of polyvinyl alcohol (trade name: PVA-205, manufactured by Kuraray Co., Ltd.) were mixed and stirred to obtain a coating liquid for an undercoat layer.

Comparative Example 4 A thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following undercoat layer coating liquid was used in place of the undercoat layer coating liquid used in the preparation of the thermosensitive recording medium of Example 1. A recording was obtained.

Preparation of Coating Solution for Undercoat Layer Hollow acrylic resin particles having an outer wall having a thickness of 0.1 μm (volume average particle diameter: 1.0 μm, oil absorption: 55 ml / 1
500 g of a 20% dispersion of 50 g, having a solids concentration of 48%
Styrene-butadiene-based latex (trade name: L-1)
571, 10 parts of Asahi Kasei Corporation) and 20% of polyvinyl alcohol (trade name: PVA-205, manufactured by Kuraray Co., Ltd.)
A composition comprising 50 parts of an aqueous solution was mixed and stirred to obtain a coating liquid for an undercoat layer.

[Comparative Example 5] In the preparation of the solution A of Example 1, 3- (N-ethyl-N-) was used instead of 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran.
(Isoamino) -6-methyl-7-anilinofluoran and, in the preparation of solution B, in the preparation of solution B of Example 1, 4,4'-isopropylidenediene was used instead of 2,4'-dihydroxydiphenylsulfone. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that phenol was used. A thermosensitive recording medium was obtained in the same manner as in Example 1 except for the above.

Comparative Example 6 In Comparative Example 5, 3- (N
-Ethyl-N-isoamino) -6-methyl-7-anilinofluoran except that 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluoran was used instead of A thermosensitive recording medium was obtained in the same manner as in Comparative Example 5.

[Comparative Example 7] In Comparative Example 5, 4,4 '
A heat-sensitive recording material was obtained in the same manner as in Comparative Example 5, except that 4-hydroxy-4'-isopropoxydiphenylsulfone was used instead of -isopropylidenediphenol.

The following evaluation tests were performed on the thermosensitive recording medium, and the obtained results are shown in Table 1.

Recording Sensitivity and Recording Runnability Using a thermosensitive recording medium evaluation machine (trade name: TH-PMD III type, Okura Electric Co., Ltd.), applied voltage 18 V, applied energy 0.
One meter was recorded on the thermosensitive recording medium under the condition of 30 mJ / dot. The recording sensitivity was evaluated by measuring the recorded density of each recorded portion and the unrecorded portion in a visual mode of a Macbeth densitometer (trade name: RD-914, Macbeth). Further, the recording runnability was determined from the degree of head residue adhering to the thermal head after recording. (Judgment criteria) ：: There is no head residue. ：: There is slight head residue. Δ: There is a little head residue. ×: A lot of head meal

The heat-sensitive recording medium recorded at the above “recording sensitivity” was
A recorded part and an unrecorded part (background fog) after being left for 1 hour in a thermostat at 100 ° C. are subjected to a Macbeth densitometer (trade name: RD)
-914 type, Macbeth).

[0063]

[Table 1]

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As is clear from the results shown in Table 1, all of the heat-sensitive recording media of the present invention are excellent in recording sensitivity and recording traveling property.
In addition, it was a heat-sensitive recording material which was less fogged by heat and had excellent heat resistance.

Claims (2)

[Claims] 1. A thermosensitive recording medium comprising a support, on which an undercoat layer and a thermosensitive recording layer containing a leuco dye and a colorant are sequentially provided, the undercoat layer having an oil absorption of 100 ml / 100 g.
An organic pigment having at least through holes (based on JIS K 5101) is contained in an amount of 10% by weight or more based on the total solid content of the undercoat layer. (O-chloroanilino) fluoran, 3-diethylamino-7- (o-chloroanilino)
Fluoran, 3-di (n-butyl) amino-7- (o-
Chloroanilino) fluoran, 3-diethylamino-7
-(O-fluoroanilino) fluoran, 3-di (n-
Butyl) amino-7- (o-fluoroanilino) fluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-p-
At least one of toluidino) -6-methyl-7- (p-toluidino) fluoran, or the colorant is 4,4′-dihydroxydiphenylsulfone, 2,4 ′
-Dihydroxydiphenyl sulfone, 1,1-bis (4
-Hydroxyphenyl) -1-phenylethane, 4,
A heat-sensitive recording material comprising at least one of 4'-cyclohexylidenediphenol and bis (3-allyl-4-hydroxyphenyl) sulfone. 2. A leuco dye comprising 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran and 3-di (n
The thermal recording according to claim 1, wherein the thermal recording is at least one of -butyl) amino-7- (o-fluoroanilino) fluoran and 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluoran. body.