JPH09277704A - Thermal recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording medium which shows high recording sensitivity and also superior recording run smoothness almost without generated refuse from a recording head. SOLUTION: This thermal recording medium consists of an undercoat and a thermal recording layer containing leuco dye and a coloring agent which are sequentially laminated on a support. The undercoat contains an organic pigment with an oil absorption amount of at least, 100ml/100g (based on JIS K 5101) and also a through hole.

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-developing reaction between a leuco dye and a color former, and more particularly to a heat-sensitive recording material having excellent recording sensitivity and recording running property.

[0002]

2. Description of the Related Art A thermosensitive recording medium is known in which a coloring image of a colorless or pale leuco dye and a coloring agent is utilized to bring a recording image by bringing both coloring substances into contact with each other by heat. Since such a thermosensitive recording medium is relatively inexpensive, the recording device is compact, and its maintenance is easy, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields.

Particularly in recent years, the improvement of facsimile printer devices has progressed, and in the heat-sensitive fax, the size of A4 is 1
Recording speeds of 0 seconds or less and 120 characters / second or more are possible with a thermal printer, and there is a further demand for higher sensitivity of thermal recording materials. Conventionally, in order to obtain a high-sensitivity heat-sensitive recording material, the materials for constituting the heat-sensitive recording layer such as a leuco dye, a coloring agent and a sensitizer, and the support have been improved.
0142, JP-A-54-115255, JP-A-53-1
Although disclosed in Japanese Patent No. 56086, satisfactory results are not always obtained because new defects are accompanied by improvements.

Further, in order to enhance the recording sensitivity of the thermosensitive recording medium, the heat insulating property of the support is important. In order to enhance the heat insulating property of the support, a hydrophobic organic polymer compound granular material having a low thermal conductivity is contained between the support and the heat-sensitive recording layer (JP-A-59-171685 and JP-A-59-171685). 60
No. 2397), or containing fine particles of a hollow organic polymer compound in the undercoat layer in order to add air barrier properties (JP-A-59-171685 and JP-A-59-225987). ) Etc. have been proposed. However, since these organic polymer compound granules have lower oil absorbency than inorganic pigments, they have a drawback that deposits (head residue) on the thermal head are likely to occur during recording.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosensitive recording medium which is excellent in recording sensitivity and recording runability with less head residue.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a thermosensitive recording medium in which an undercoat layer and a thermosensitive recording layer containing a leuco dye and a color former are sequentially provided on a support to solve the above problems. As one means, 1) Oil absorption of 100 ml / 100 g (J
(Based on IS K 5101) and above, and contains an organic pigment having a through hole. As another means, an oil absorption amount of 100 ml / 100 g (JI
SK5101) or more and an organic pigment having a through hole is contained, and 2) an organic pigment having a through hole is further contained in an amount of 40% by weight or more based on the total solid amount of the undercoat layer, 3) The organic pigment having a through hole has a volume average particle size of 0.1 to 5.0 μm, and 4) the organic pigment having a through hole is a styrene-acrylic copolymer. .

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, an organic pigment having an oil absorption amount of 100 ml / 100 g (based on JIS K 5101) or more and having through holes (hereinafter referred to as a specific organic pigment) is contained in an undercoat layer. Characterized by containing,
When the oil absorption amount is less than 100 ml / 100 g, the recording sensitivity and the head residue reduce the recording running property.
In order to obtain a specific organic pigment exceeding 100 ml / ml, the volume ratio of the through holes to the specific organic pigment particles is 90%.
%, And therefore, after forming the undercoat layer, there is a risk that specific organic pigment particles are destroyed and the recording sensitivity is lowered. Oil absorption is 100-200ml / 10
About 0 g is more preferable. The volume ratio of the through holes in the specific organic pigment particles is about 10 to 80%.

The material of the specific organic pigment is not particularly limited, but for example, resins such as polystyrene, polymethyl (meth) acrylate, polyvinyl chloride, polyurethane, polyvinylidene chloride, poly (meth) acrylonitrile, or resin components thereof. And a copolymer having styrene, such as a styrene-acrylic copolymer. Of these, a styrene-acrylic copolymer is preferable because it is less likely to cause background fog and deterioration of a recorded image with time.

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

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

As the resin which is not dissolved in alkaline water,
The thing which polymerized at least 1 type of the said hydrophobic monomer is mentioned. Of course, at least one of the above vinyl monomers of unsaturated carboxylic acid may be copolymerized as long as it is not dissolved in alkaline water.

The shape of the specific organic pigment particles is not particularly limited, but a spherical structure is preferred because a structure in which the particles are dense when the undercoat layer is formed improves the coating strength. The volume average particle diameter is not particularly limited either, but considering the thickness of the undercoat layer and the coating strength, it is 0.1 to 5.0 μm, more preferably 0.1 to 1.2 μm.
m.

The amount of the specific organic pigment used is not particularly limited, but is preferably 10% by weight or more based on the total solid amount of the undercoat layer. If it is less than 10% by weight, the recording sensitivity may be lowered, and if it exceeds 95% by weight, the surface strength of the undercoat layer may be lowered to make it difficult to form a heat-sensitive recording layer uniformly. The degree is more preferable.

Other known inorganic pigments or organic pigments may be used in combination within the range that does not impair the desired effects of the present invention. Specific examples of such pigments include, for example, calcium carbonate, magnesium carbonate, kaolin, calcined kaolin, talc, aluminum hydroxide, amorphous silica, inorganic pigments such as titanium oxide, polystyrene, polymethyl acrylate, polyvinyl chloride, and polychlorination. An organic pigment having a solid structure or a hollow structure, which is composed of vinylidene or urea-formaldehyde resin, may be mentioned.

For the undercoat layer, for example, a coating solution for an undercoat layer obtained by adding an adhesive to an aqueous dispersion containing a specific organic pigment while mixing and stirring is used for high-quality paper, neutral paper, coated paper, synthetic paper. It is formed by coating and drying it on a support such as paper, film or nonwoven fabric so that the coating amount after drying is about 1 to 20 g / m ² , 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,
Of etherified starch, methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, fully (or partially) saponified polyvinyl alcohol, carboxy modified polyvinyl alcohol, acetoacetyl group modified polyvinyl alcohol, silicon modified polyvinyl alcohol, acrylic acid amide-acrylic acid ester copolymer Salt, acrylic acid amide-acrylic acid ester / methacrylic acid copolymer salt, styrene-maleic anhydride copolymer salt, isobutylene-maleic anhydride copolymer salt, water-soluble adhesive such as casein, and natural Examples of water-dispersible adhesives include rubber latex, styrene-butadiene latex, acrylonitrile-butadiene latex, and methyl methacrylate-butyl acrylate latex. Of these, starch and starch derivatives such as oxidized starch, enzyme-modified starch, esterified starch, and etherified starch are preferably used because they have a great effect of improving head casks. The amount of adhesive used is 5 to the total solid amount of the undercoat layer.
It is about 35% by weight.

If necessary, various auxiliary agents such as a dispersant, a defoaming agent, a coloring dye, a fluorescent dye and a curing agent can be appropriately added to the undercoat layer coating liquid.

The coating liquid for the undercoat layer is prepared by using a coating device used for the production of general coated paper, for example, a blade coater, a roll coater, a reverse roll coater, a rod blade coater, a chanplex coater, a cartain coater. It is coated on a support.

A heat-sensitive recording layer is provided on the undercoating layer thus formed, and various known leuco dyes can be used as the leuco dye contained in the heat-sensitive recording layer. Specific examples thereof include 3,3- Bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3
-Diethylamino-7-anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-6-methyl-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-di (n-butyl) amino-7- (O-chloroanilino) fluorane, 3-diethylamino-7- (o-fluoroanilino) fluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane, 3-diethylamino-6. -Chloro-7-anilinofluorane,
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 can be mentioned. Of course, it is not limited to these, and two or more kinds may be used in combination as required.

Various kinds of color-developing agents which are used in combination with the above leuco dyes are known, and the following are exemplified. 4-hydroxyacetophenol, 2,2'-dihydroxydiphenol, 4,4'-
Isopropylidene bis (2-tert-butylphenol), 4,4'-sec-butylidene diphenol, 4-
Phenylphenol, 4,4'-isopropylidenediphenol, 2,2-bis (4-hydroxyphenyl)-
4-methylpentane, 4,4'-cyclohexylidene diphenol, 2,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfone, 4-
Hydroxy-4'-isopropoxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxyphenyl-4'-benzyloxyphenyl sulfone, 3,4 -Dihydroxyphenyl-4 '
-Methylphenyl sulfone, hydroquinone monobenzyl ether, 4-hydroxybenzophenone, benzyl 4-hydroxybenzoate, 4-hydroxybenzoic acid-p-
Methoxybenzyl, novolac type phenol resin, phenol polymer, zinc p-tert-butylbenzoate, zinc 3-cyclohexyl-4-hydroxybenzoate, 4- [2
Zinc-(p-methoxyphenoxy) ethyloxy] salicylate, zinc 4- [3- (p-tolylsulfonyl) propyloxy] salicylate, zinc 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylate, N-
p-tolylsulfonyl-N'-phenylurea, 4,4 '
-Bis (Np-tolylsulfonylaminocarbonylamino) diphenylmethane and the like. Among them, 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, and bis (3-allyl-4-hydroxyphenyl) sulfone are preferable because they cause less background fog.

The ratio of the leuco dye to the coloring agent used is appropriately selected according to the type of leuco dye or coloring agent used and is not particularly limited, but generally 1 part by weight of the leuco dye is used. 1 to 10 parts by weight, preferably 2 to
About 5 parts by weight of the coloring agent is used.

The thermal recording layer generally uses water as a dispersion medium,
A leuco dye and a coloring agent are finely dispersed together or separately with a stirring / pulverizing machine such as a ball mill, attritor, or sand mill, and then the adhesive is mixed and stirred to obtain a coating liquid for a heat-sensitive recording layer. coating amount after drying on the undercoat layer is 1 to 15 g / m ^2, it is preferably formed by coating and drying so as to 2 to 6 g / m ² approximately.

The adhesive used for the heat-sensitive recording layer is
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 amount of the thermosensitive recording layer.

If desired, various auxiliary agents may be added to the heat-sensitive recording layer coating liquid, such as kaolin,
Calcium carbonate, aluminum hydroxide, titanium oxide, diatomaceous earth, amorphous silica, pigments such as urea / formalin resin filler, sodium dioctyl sulfosuccinate, sodium dodecylbenzene sulfonate, sodium lauryl alcohol sulfate, dispersant such as fatty acid metal salt,
Waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, defoaming agents, fluorescent dyes, and coloring dye curing agents can be used. Further, a specific organic pigment can be added.

In the heat-sensitive recording layer, it is possible to use a sensitizer for further increasing the recording sensitivity and a storability improver for enhancing the storability of a recorded image. Specific examples of the sensitizer include stearic acid amide, ethylenebistearic acid amide, behenic acid amide, methylenebisstearic acid amide, dibenzyl terephthalate, 2-naphthylbenzyl ether, m-terphenyl, dibenzyl oxalate, and the like. Oxalic acid di-p-methylbenzyl, oxalic acid di-
p-chlorobenzyl, p-benzylbiphenyl, 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- (2-methylphenoxy)
Ethane, p-methylthiophenylbenzyl ether,
1,4-di (phenylthio) butane, p-acetotoluidide, p-acetophenetide, N-acetoacetyl-
Examples thereof include p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane and the like.

Specific examples of such a storability improver include, for example, 2,2'-methylenebis (4-methyl-6-ter).
t-butylphenol), 2,2'-methylenebis (4,6-di-tert-butylphenol), 2,
2'-ethylidene bis (4,6-di-tert-butylphenol), 2,2 '-(2,2-propylidene) bis (4,6-di-tert-butylphenol), 4,
4'-thiobis (3-methyl-6-tert-butylphenol), 4,4'-thiobis (2-methyl-6-t
tert-butylphenol), 4,4′-thiobis (2
-Ethyl-6-tert-butylphenol), 4,
4'-butylidene bis (6-tert-butyl-m-cresol), 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,
3-tris (2-methyl-4-hydroxy-5-tert-
Butylphenyl) butane, 1,4-diglycidyloxybenzene, 4,4′-diglycidyloxydiphenylsulfone, 4-benzyloroxyphenyl-4 ′-(2-
Methyl-2,3-epoxypropyloxy) phenyl sulfone, diglucidyl terephthalate, N, N′-di-2
-Naphthyl-p-phenylenediamine, 2,2'-methylenebis (4,6-di-tert-butylphenyl) sodium phosphate, etc. may be mentioned.

The coating liquid for the heat-sensitive recording layer is, for example, bar coating, air knife coating, rod blade coating, pure blade coating, short dwell coating, varibar blade coating,
It is applied onto the undercoat layer by a known coating method such as curtain coating or die coating.

It is also possible to provide a protective layer on the heat-sensitive recording layer or on the back surface side so as to improve the storage stability and impart a strong gloss.
It is also possible to perform smoothing treatment such as super calendaring after forming each layer. Further, the back surface of the thermosensitive recording medium is treated with an adhesive to form an adhesive label, a rewetting adhesive layer is provided, or a magnetic recording layer, a coating layer for printing, or a thermal transfer recording layer is provided. Various known techniques in the field of recording material production can be added as necessary.

[0029]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" and "%" in the examples mean "parts by weight" and "% by weight", respectively, unless otherwise specified.

Example 1 Preparation of Coating Liquid for Undercoat Layer Volume average particle diameter is 0.6 μm and oil absorption is 150 ml /
500 parts of a 20% dispersion of a styrene-methyl methacrylate copolymer organic pigment having 100 g of through-holes, 10 parts of a styrene-butadiene latex having a solid concentration of 48% (trade name: L-1571, manufactured by Asahi Kasei), 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 undercoating.

Preparation of Solution A 30 parts of 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 5% aqueous solution of methylcellulose 5
Part and 65 parts of water were pulverized with a sand mill until the average particle size was 0.9 μm to obtain a liquid A.

Preparation of Solution B Solution B was prepared by pulverizing a composition comprising 30 parts of 2,4′-dihydroxydiphenyl sulfone, 5 parts of a 5% aqueous solution of methylcellulose, and 65 parts of water with a sand mill until the average particle diameter became 1.0 μm. Got

Preparation of Solution C A composition consisting of 30 parts of 1,2-di (3-methylphenoxy) ethane, 5 parts of a 5% aqueous solution of methylcellulose and 65 parts of water was pulverized with a sand mill until the average particle diameter became 1.0 μm. Then, a C liquid was obtained.

Preparation of coating liquid for heat-sensitive recording layer 33 parts of solution A, 70 parts of solution B, 70 parts of solution C, 15 parts of light calcium carbonate, 10 parts of 30% dispersion of zinc stearate,
100 parts of a 10% aqueous solution of polyvinyl alcohol and 10 parts of water were mixed and stirred to obtain a heat-sensitive recording layer coating liquid.

Preparation of thermosensitive recording medium An undercoat layer coating solution and a thermosensitive recording layer coating solution were applied to one side of 50 g / m ² of neutral paper at a coating amount of 7 g /
m ² and 6 g / m ² were sequentially applied and dried to form an undercoat layer and a heat-sensitive recording layer, and then super calendering was performed to obtain a heat-sensitive recording material.

Example 2 In the preparation of the coating liquid for the undercoat layer of Example 1, a styrene-methylmethacrylate copolymer organic pigment having a through hole with a volume average particle size of 0.6 μm and an oil absorption of 150 ml / 100 g. Instead of 500 parts of 20% dispersion liquid, the volume average particle diameter is 2.6 μm and the oil absorption is 180 ml / 10.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 500 parts of a 20% dispersion liquid of a styrene-methylmethacrylate copolymer organic pigment having 0 g of through holes was used.

Example 3 In the preparation of the coating liquid for the undercoat layer of Example 1, instead of 50 parts of a 20% aqueous solution of polyvinyl alcohol (trade name: PVA-205, manufactured by Kuraray Co., Ltd.), an oxidized starch (trade name: ace) was used. A, made by Oji Corn Starch Co., Ltd.) 10% aqueous solution 10
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 0 part was used.

Example 4 In the preparation of the coating liquid for the undercoat layer of Example 1, instead of 50 parts of a 20% aqueous solution of polyvinyl alcohol (trade name: PVA-205, manufactured by Kuraray Co., Ltd.), 5 parts of corn starch were used.
% Aqueous solution 100 parts and 20% aqueous solution 25 of polyvinyl alcohol (trade name: PVA-205, manufactured by Kuraray Co., Ltd.)
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that parts were used.

Example 5 In the preparation of the coating liquid for the undercoat layer of Example 1, a styrene-methyl methacrylate copolymer organic pigment having a through-hole with a volume average particle size of 0.6 μm and an oil absorption of 150 ml / 100 g. Instead of 500 parts of 20% dispersion liquid, the volume average particle diameter is 0.6 μm and the oil absorption is 150 ml / 10.
Examples except that 200 parts of a 20% dispersion of polystyrene organic pigment having 0 g of through holes and 300 parts of a 20% dispersion of calcined kaolin (trade name: Ansilex, manufactured by EMC) having an oil absorption of 130 ml were used. A thermal recording material was obtained in the same manner as in 1.

Example 6 A thermosensitive recording medium was prepared in the same manner as in Example 1 except that 4,4'-dihydroxydiphenylsulfone was used instead of 2,4'-dihydroxydiphenylsulfone in the preparation of the liquid B of Example 1. Got

Example 7 In the preparation of solution B of Example 1, bis (3-allyl-4-) was used in place of 2,4'-dihydroxydiphenyl sulfone.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that hydroxyphenyl) sulfone was used.

Example 8 In the preparation of solution B of Example 1, 4-hydroxy-4'- was used instead of 2,4'-dihydroxydiphenyl sulfone.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that isopropoxydiphenyl sulfone was used.

Example 9 Thermal recording was carried out in the same manner as in Example 1 except that 4,4'-isopropylidenediphenol was used in place of 2,4'-dihydroxydiphenylsulfone in the preparation of solution B of Example 1. Got the body

Comparative Example 1 Preparation of Coating Liquid for Undercoat Layer 100 parts of calcined clay (trade name: Ansilex, manufactured by EMC, oil absorption 130 ml / 100 g), solid concentration 48%
Styrene-butadiene latex (trade name: L-1
571, manufactured by Asahi Kasei Co., Ltd., 50 parts of a 20% aqueous solution of polyvinyl alcohol (trade name: PVA-205, manufactured by Kuraray Co., Ltd.), and 250 parts of water were mixed and stirred to obtain an undercoating coating liquid.

Preparation of Thermosensitive Recording Medium Except that the above-mentioned undercoat layer coating solution was used in place of the undercoat layer coating solution used in the preparation of the thermal recording medium of Example 1,
A thermosensitive recording medium was obtained in the same manner as in Example 1.

Comparative Example 2 In the preparation of the coating liquid for the undercoat layer of Example 1, 500 parts of a 20% dispersion of an organic pigment having a through hole having a volume average particle diameter of 0.6 μm and an oil absorption of 150 ml / 100 g was used. Instead, the volume average particle size is 0.6 μm and the oil absorption is 80 m.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 500 parts of a 20% dispersion liquid of an organic pigment having 1/100 g of through holes was used.

Comparative Example 3 Preparation of Coating Liquid for Undercoat Layer Organic pigment in the form of fine particles (trade name: Grosdale 110
M, manufactured by Mitsui Toatsu Chemicals, Inc., oil absorption 90 ml / 100 g), 285 parts of 35% dispersion, 10 parts of styrene-butadiene latex (trade name: L-1571, manufactured by Asahi Kasei) having a solid concentration of 48%, polyvinyl alcohol (Product name: PVA
-205, 50% 20% aqueous solution of Kuraray Co., Ltd., water 25
0 part was mixed and stirred to obtain a coating liquid for undercoat.

Preparation of Thermosensitive Recording Material The undercoat layer coating solution described above was used instead of the undercoat layer coating solution used in the preparation of the thermal recording material of Example 1.
A thermosensitive recording medium was prepared in the same manner as in Example 1.

Comparative Example 4 Preparation of Coating Liquid for Undercoat Layer 30% dispersion of organic hollow particles (trade name: MHG504
0, manufactured by Zeon Corporation, 330 parts, 48% styrene-butadiene latex (trade name: L-1571, manufactured by Asahi Kasei Co., Ltd.), 10 parts, polyvinyl alcohol (trade name: PVA-).
205, manufactured by Kuraray Co., Ltd.) 50% 20% aqueous solution, water 250
The parts were mixed and stirred to obtain a coating liquid for undercoat.

Preparation of Thermosensitive Recording Material The undercoat layer coating solution was used in place of the undercoat layer coating solution used in the preparation of the thermal recording material of Example 1, except that
A thermosensitive recording medium was obtained in the same manner as in Example 1.

The thermal recording materials thus obtained were evaluated as follows, and the results are shown in Table 1. [Recording sensitivity] Each thermosensitive recording medium was recorded at a voltage of 25 V and an energy of 0.24 mJ / dot by using a thermosensitive evaluation device [trade name: TH-PMD, manufactured by Okura Electric Co., Ltd.], and recorded areas and unrecorded areas. Macbeth Densitometer [RD-914
Type, manufactured by Macbeth Co.).

[Heat-Resistant Storage Property] The thermosensitive recording medium recorded in the above [Recording sensitivity] was left in a thermostat at 80 ° C. for 1 hour, and the recorded portion and unrecorded portion (background fog) were subjected to Macbeth densitometer [ RD-914 type, manufactured by Macbeth].

[Head residue] Using the heat-sensitive evaluation machine, 10 sheets of heat-sensitive recording material of A4 size were printed at an applied voltage of 25 V and an applied energy of 0.50 mj / dot, and the condition of the residue attached to the head was visually evaluated. To do.

[Surface Strength] Ink for evaluating pick strength (T
OKA Printing Ink Super Deluxe
T = 13) of 0.4 cc was used to perform a printing test with an RI type printing tester to visually evaluate the degree of peeling of the coating layer surface. ⊚: There is no peeling of the coating layer and good printability is exhibited. ◯: Peeling of the coating layer is slightly observed. Δ: Peeling of the coating layer is large, which is a practical problem. X: The coating layer was completely peeled off.

[0055]

[Table 1]

[0056]

As is clear from the results of [Table 1], all of the thermosensitive recording materials of the present invention were excellent in recording sensitivity and printability, and were excellent in recording running property with less head residue. .

Claims (5)

[Claims] 1. A heat-sensitive recording material comprising a support and an undercoat layer and a heat-sensitive recording layer containing a leuco dye and a colorant, which are sequentially provided on the support. The undercoat layer has an oil absorption of 100 ml / 100.
A thermosensitive recording material characterized by containing an organic pigment having a through hole and having a size of g (based on JIS K 5101) or more. 2. The thermal recording material according to claim 1, wherein the organic pigment having through holes is contained in an amount of 40% by weight or more based on the total solid amount of the undercoat layer. 3. The thermal recording material according to claim 1, wherein the organic pigment having through holes has a volume average particle diameter of 0.1 to 5.0 μm. 4. The thermal recording material according to claim 1, wherein the material of the organic pigment having through holes is a styrene-acrylic copolymer. 5. The thermosensitive recording medium according to claim 1, wherein starch or a derivative thereof is used as an adhesive in the undercoat layer.