JP2002187351A - Heat-sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-sensitive recording material having a high color developing density, small fogging, excellent preservability, chemical resistance and sticking resistance of an image part. SOLUTION: The heat-sensitive recording material comprises a heat-sensitive color developing layer containing an electron donative colorless dye and an electron acceptive compound on a support. The color developing layer contains N-(4-hydroxyphenyl)-p-toluenesulfonamide as the acceptive compound and a 2-benzyloxynaphthalene (x) and amide N-stearylstearate (y) in a range of a content ratio (mass ratio: x/y) of 95/5 to 40/60 as a sensitizer.

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, and more particularly to a heat-sensitive recording material having high color density, background fog, image preservability,
The present invention relates to a heat-sensitive recording material having excellent chemical resistance and sticking property.

[0002]

2. Description of the Related Art In general, heat-sensitive recording materials are relatively inexpensive, and their recording devices are compact and maintenance-free, so that they are widely used.
Under such circumstances, in recent years, competition for sales of heat-sensitive recording materials has intensified, and there is a demand for heat-sensitive recording materials to have higher functions which are differentiated from conventional functions. To respond to such demands,
Research on the color density, image storability, and the like of heat-sensitive recording materials has been earnestly conducted.

In conventional thermal recording materials, 2,2-bis (4-hydroxyphenyl) propane (so-called "bisphenol A") is widely used as an electron-accepting compound which reacts with an electron-donating colorless dye to form a color. Have been. However, in this heat-sensitive recording material, a material which can simultaneously satisfy each of sensitivity, background fog, image storability, chemical resistance and sticking property has not been obtained.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and achieve the following objects. That is, an object of the present invention is to provide a heat-sensitive recording material having high color density, low background fog, and excellent in storage stability (density stability), chemical resistance and sticking property of an image area.

[0005]

Means for Solving the Problems In order to improve various properties of a heat-sensitive recording material, the present inventors have intensively studied and pursued each of an electron-accepting compound, a sensitizer, an image stabilizer and the like, and pursued the present invention. It was completed. Specific means for solving the above problems are as follows. That is,

<1> A heat-sensitive recording material having a thermosensitive coloring layer containing an electron-donating colorless dye and an electron-accepting compound on a support, wherein the thermosensitive coloring layer comprises N as the electron-accepting compound. -(4-hydroxyphenyl) -p-
Toluenesulfonamide further containing 2-benzyloxynaphthalene (x) and N-stearylstearic acid amide (y) as sensitizers, and the 2-benzyloxynaphthalene and the N-stearylstearic acid amide The ratio (mass ratio: x / y) is 95/5 to 40/60.
Is a heat-sensitive recording material.

<2> The heat-sensitive coloring layer is composed of 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane and 1,1,3-tris as an image stabilizer.
The heat-sensitive recording material according to <1>, further including at least one of 3-tris (2-methyl-4-hydroxy-5-cyclohexyl) butane. <3> When the content of the image stabilizer is electron-donating colorless dye 1
10 to 100 parts by mass with respect to 00 parts by mass.
2>.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The heat-sensitive recording material of the present invention has a heat-sensitive coloring layer containing an electron-donating colorless dye and an electron-accepting compound on a support. N- (4-hydroxyphenyl)-as a compound
p-toluenesulfonamide, and 2-benzyloxynaphthalene (x) and N-stearylstearic acid amide (y) as a sensitizer in a mass ratio (x / y) of 95 /
Included in the range of 5-40 / 60. Hereinafter, the heat-sensitive recording material of the present invention will be described in detail.

<Thermosensitive Coloring Layer> In the present invention, the thermosensitive coloring layer formed on the support contains at least an electron-donating colorless dye, an electron-accepting compound, and a sensitizer. From the viewpoint of further improving the storage stability, it is preferable that the thermosensitive coloring layer contains an image stabilizer. Further, if necessary, it may contain a pigment, an adhesive or an ultraviolet absorber.

(Electron-donating colorless dye) Examples of the electron-donating colorless dye include 2-anilino-3-methyl-
6-diethylaminofluoran, 2-anilino-3-methyl-6- (N-ethyl-N-isoamylamino) fluoran, 2-anilino-3-methyl-6- (N-ethyl-N-propylamino) fluoran, 3-di (n-butylamino) -6-methyl-7-anilinofluoran, 2
-Anilino-3-methyl-6-N-ethyl-N-sec
-Butylaminofluoran, 3-di (n-pentylamino) -6-methyl-7-anilinofluoran, 3- (N
-N-hexyl-N-ethylamino) -6-methyl-7
-Anilinofluoran, 3- [N- (3-ethoxypropyl) -N-ethylamino) -6-methyl-7-anilinofluoran, 3-di (n-butylamino) -7- (2
-Chloroanilino) fluoran, 3-diethylamino-
7- (2-chloroanilino) fluoran, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-
Anilinofluoran and the like. These may be used alone or in combination of two or more.

Among the above, the color density, the storage stability of the image area and the chemical resistance can be further improved.
Anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6- (N-ethyl-N
-Isoamylamino) fluoran and 2-anilino-3
It preferably contains at least one selected from -methyl-6- (N-ethyl-N-propylamino) fluoran.

The amount of the electron-donating colorless dye to be applied is
Is a dry mass of 0.1 to 1.0 g / m ^TwoIs preferred, and
From the viewpoint of further improving the color density and the background fog, 0.
2 to 0.5 g / m^TwoIs particularly preferred.

(Electron-Accepting Compound) The heat-sensitive recording material of the present invention comprises N- (4-hydroxyphenyl) -p-toluenesulfonamide as an electron-accepting compound. In the heat-sensitive recording material of the present invention, the N- (4-
By containing (hydroxyphenyl) -p-toluenesulfonamide as an electron-accepting compound, it is possible to improve color density, suppress background fog, and improve chemical resistance. The content of the electron accepting compound is 50 to 50% based on the amount (mass) of the electron donating colorless dye.
400 mass% is preferable, and 100 to 300 mass% is particularly preferable.

In the present invention, in addition to the above-mentioned N- (4-hydroxyphenyl) -p-toluenesulfonamide, other known electron-accepting compounds may be used in combination as long as the effects of the present invention are not impaired. . The known electron-accepting compound can be appropriately selected from known ones and used. In particular, from the viewpoint of suppressing background fog, a phenolic compound, or a salicylic acid derivative and a polyvalent metal salt thereof are used. Is preferred.

Examples of the phenolic compound include 2,2'-bis (4-hydroxyphenol) propane (bisphenol A), 4-t-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, 1,1 '-Bis (4-hydroxyphenyl) cyclohexane, 1,1'-bis (3-chloro-4-hydroxyphenyl) cyclohexane, 1,1'-bis (3
-Chloro-4-hydroxyphenyl) -2-ethylbutane, 4,4'-sec-isooctylidenediphenol, 4,4'-sec-butylenediphenol, 4-
tert-octylphenol, 4-p-methylphenylphenol, 4,4′-methylcyclohexylidenephenol, 4,4′-isopentylidenephenol, 4
-Hydroxy-4-isopropyloxydiphenylsulfone, benzyl p-hydroxybenzoate, 4'4-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone and the like.

Examples of the salicylic acid derivative and its polyvalent metal salt include, for example, 4-pentadecylsalicylic acid,
5-di (α-methylbenzyl) salicylic acid, 3,5-di (tert-octyl) salicylic acid, 5-octadecylsalicylic acid, 5-α- (p-α-methylbenzylphenyl) ethylsalicylic acid, 3- α-methylbenzyl-5-
tert-octylsalicylic acid, 5-tetradecylsalicylic acid, 4-hexyloxysalicylic acid, 4-cyclohexyloxysalicylic acid, 4-decyloxysalicylic acid, 4-dodecyloxysalicylic acid, 4-pentadecyloxysalicylic acid, -Octadecyloxysalicylic acid and the like, zinc, aluminum, calcium, copper,
Lead salts and the like are also included.

When the above-mentioned known electron-accepting compound is used in combination, the N- (4-hydroxyphenyl) -p according to the present invention is used.
-The content of toluenesulfonamide is preferably 50% by mass or more, more preferably 70% by mass or more of the total content (mass) of the electron-accepting compound.

In the present invention, when preparing a coating solution for forming a thermosensitive coloring layer, the particle diameter of the electron-accepting compound is preferably 1.0 μm or less in terms of volume average particle diameter.
4 to 0.7 μm is more preferred. When the volume average particle size is 1.0 μm or less, the thermal sensitivity does not easily decrease.
The volume average particle diameter can be easily measured by a laser diffraction type particle size distribution analyzer (for example, LA500 (manufactured by Horiba)) or the like.

(Sensitizer) In the heat-sensitive recording material of the present invention, the heat-sensitive coloring layer contains 2-benzyloxynaphthalene and N-stearylstearic acid amide as sensitizers. In the present invention, by containing both 2-benzyloxynaphthalene and N-stearylstearic acid amide as sensitizers in the thermosensitive coloring layer, the sensitivity is greatly improved while the occurrence of background fog is suppressed. Can be.

The content ratio (mass ratio: x / y) of the 2-benzyloxynaphthalene (x) to N-stearylstearic amide (y) is 95/5 to 40 /
60. If the mass ratio is smaller than 95/5, the sensitivity is low, and if it is larger than 40/60, the sensitivity is low. Among the content ratios, 90/10 to 50/50 are more preferable, and 85/15 to 70/30 are particularly preferable.

The total content of the above sensitizers is determined by the electron accepting compound N- (4-hydroxyphenyl) -p-
75 to 100 parts by mass of toluenesulfonamide
200 parts by mass is preferable, and 100 to 150 parts by mass is more preferable. When the total content of the sensitizer is in the range of 75 to 200 parts by mass, the effect of improving the sensitivity is large and the image storability is excellent.

In the thermosensitive coloring layer, in addition to the above-mentioned 2-benzyloxynaphthalene and N-stearylstearic acid amide, other sensitizers may be used insofar as the effects of the present invention are not impaired. Examples of the other sensitizer include aliphatic monoamide, stearyl urea, p-benzylbiphenyl, di (2-methylphenoxy) ethane,
Di (2-methoxyphenoxy) ethane, β-naphthol- (p-methylbenzyl) ether, α-naphthylbenzylether, 1,4-butanediol-p-methylphenylether, 1,4-butanediol-p-isopropyl Phenyl ether, 1,4-butanediol-p
-Tert-octylphenyl ether, 1-phenoxy-2- (4-ethylphenoxy) ethane, 1-phenoxy-2- (chlorophenoxy) ethane, 1,4-butanediol phenyl ether, diethylene glycol bis (4-methoxyphenyl) Ether, m-terphenyl, methyl oxalate methyl benzyl ether, 1,2-diphenoxymethylbenzene, 1,2-bis (3-methylphenoxy) ethane, 1,4-bis (phenoxymethyl) benzene and the like.

(Image Stabilizer) In the heat-sensitive recording material of the present invention, it is preferable that the thermosensitive coloring layer further contains an image stabilizer for the purpose of further improving image storability. As the image stabilizer, a phenol compound, particularly a hindered phenol compound, is effective.
Tris (2-methyl-4-hydroxy-5-tert-
Butylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexyl) butane,
1,1,3-tris (2-ethyl-4-hydroxy-5
-Cyclohexylphenyl) butane, 1,1,3-tris (3,5-di-tert-butyl-4-hydroxyphenyl) butane, 1,1,3-tris (2-methyl-4
-Hydroxy-5-tert-butylphenyl) propane, 2,2′-methylene-bis (6-tert-butyl-4-methylphenol), 2,2′-methylene-bis (6-tert-butyl-4-) Ethylphenol) 4,
4'-butylidene-bis (6-tert-butyl-3-
Methylphenol), 4,4′-thio-bis- (3-methyl-6-tert-butylphenol) and the like. Among the above, 1,1,3-tris (2-methyl-
It is preferred to include at least one of 4-hydroxy-5-tert-butylphenyl) butane and 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexyl) butane.

As the image stabilizer, in particular, 1,1,3-
Tris (2-methyl-4-hydroxy-5-tert-
Butylphenyl) butane and 1,1,3-tris (2-
When at least one of methyl-4-hydroxy-5-cyclohexyl) butane is contained in the thermosensitive coloring layer, N- (4-hydroxyphenyl) -p-toluenesulfonamide as the electron accepting compound and a sensitizer 2
-Interaction with benzyloxynaphthalene and N-stearylstearic acid amide can improve background fog and greatly improve the storage stability of the image area.

The 1,1,3-tris (2-methyl-4)
-Hydroxy-5-tert-butylphenyl) butane (α) and 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexyl) butane (β) may be used alone, You may use together. The mass ratio (α / β) when both are used is 20/80 to 8
0/20 is preferable, and 40/60 to 60/40 is more preferable.

Here, the 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane and 1,1,3-tris (2-methyl-4-butyl)
In addition to (hydroxy-5-cyclohexyl) butane, other image stabilizers other than the above may be used in combination. When other image stabilizers are used in combination, the 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane and / or 1,1,3-tris (2-
The total content of methyl-4-hydroxy-5-cyclohexyl) butane is preferably 50% by mass or more, more preferably 70% by mass or more of the total amount of the image stabilizer in the thermosensitive coloring layer.

The total content of the image stabilizer is preferably from 100 parts by mass of the electron-donating colorless dye from the viewpoint of efficiently exhibiting desired effects on background fog, image preservability, chemical resistance and sticking property. Thus, the amount is preferably 10 to 100 parts by mass, more preferably 20 to 60 parts by mass.

(Inorganic Pigment) In the heat-sensitive recording material of the present invention, the heat-sensitive coloring layer may contain an inorganic pigment, if necessary, as long as the effect of the present invention is not impaired. As the inorganic pigment, light calcium carbonate or aluminum hydroxide is preferably used alone or in combination. By including light calcium carbonate and / or aluminum hydroxide as the inorganic pigment, it is possible to reduce background fog and abrasion of the thermal head, and furthermore, it is possible to prevent scum adhesion to the thermal head and improve sticking properties. .

The content of the inorganic pigment is from 50 to 250 based on 100 parts by mass of the electron-accepting compound from the viewpoints of color density and adhesion of dregs to the thermal head.
A mass part is preferred, 70-170 mass parts is more preferred, and 90-140 mass parts is especially preferred. In addition, the particle diameter of the inorganic pigment, from the viewpoint of color density, and adhesion of scum to the thermal head, a volume average particle diameter of 0.6 to
2.5 μm, preferably 0.8 to 2.0 μm
Is more preferable, and particularly preferably 1.0 to 1.6 μm.

When the light calcium carbonate (c) and the aluminum hydroxide (a) are used in combination, the mass ratio (c / a) may be in the range of 80/20 to 20/80. More preferably, it is more preferably in the range of 60/40 to 40/60.

The light calcium carbonate generally has a crystal form such as calcite, aragonite, vaterite, etc., and the inorganic pigment used in the present invention is preferably a calcite-based light calcium carbonate from the viewpoints of absorption, hardness and the like. Further, it is preferable that the particles have a spindle shape or a triangular shape. As a method for producing the calcite-based light calcium carbonate, a known production method can be applied.

Examples of other inorganic pigments include calcium carbonate other than calcite-based light calcium carbonate, barium sulfate, lithopone, wax, kaolin, calcined kaolin, and amorphous silica. When the light calcium carbonate or the like and the other inorganic pigment are used in combination,
The ratio (v / w) of the total mass (v) of the light calcium carbonate or the like to the total mass (w) of the other inorganic pigment is 100 /
The range of 0-60 / 40 is preferable, and 100 / 0-80.
The range of / 20 is more preferable.

(Adhesive) In the heat-sensitive recording material of the present invention, an adhesive may be contained in the heat-sensitive coloring layer as long as the effects of the present invention are not impaired. In recent years, as heat-sensitive recording materials have been used in various fields, there have been cases where the heat-sensitive recording materials are used for offset printing. But,
Generally, heat-sensitive recording materials have poor surface strength, and thus have a problem of poor printability, such as causing troubles such as paper peeling during offset printing. In order to solve such a problem, the suitability for offset printing can be improved by including an adhesive in the thermosensitive coloring layer.

The adhesive may be a saponification degree of 85 to 99.
Polyvinyl alcohol having a molar percentage of 200 to 2000 is preferable. By containing the polyvinyl alcohol, while maintaining the color density of the heat-sensitive recording material, to increase the interlayer adhesion between the heat-sensitive coloring layer and the support, such as to prevent troubles such as peeling during offset printing and the like. So-called printability can be improved. Further, the saponification degree is preferably 85 to 99 mol%. When the saponification degree is in the range of 85 to 99 mol%, paper peeling due to insufficient water resistance to dampening water used for offset printing is prevented, and further, the coating liquid preparation At this time, it can be prevented that undissolved substances are generated and cause a defective portion.

Further, the degree of polymerization of polyvinyl alcohol is 2
When the amount is in the range of 00 to 2000, it is not necessary to increase the amount of addition, so that an increase in the amount of addition does not cause a decrease in image density. Furthermore, since polyvinyl alcohol is easily dissolved in the solvent and the viscosity of the coating solution does not increase,
Its preparation and application are easy. In addition, the said polymerization degree means the average polymerization degree calculated | required by the method of JIS-K6726 (1994).

The content of the polyvinyl alcohol in the thermosensitive coloring layer is from 30 to 300% by mass, based on 100 parts by mass of the electron-donating colorless dye, from the viewpoint of color density and suitability for offset printing (paper peeling, etc.). Is preferably 70 to 200% by mass, more preferably 100 to 1% by mass.
70% by mass is particularly preferred. The polyvinyl alcohol contained in the heat-sensitive coloring layer can also serve as a dispersant, a binder, and the like, in addition to the purpose of an adhesive for enhancing interlayer adhesion.

As described above, the polyvinyl alcohol includes a saponification degree of 85 to 99 mol% and a polymerization degree of 200 to
Any one that satisfies the condition of 2000 is suitable, but from the viewpoint of the color density in recording with a thermal head, at least one selected from sulfo-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol and acetoacetyl-modified vinyl alcohol is used. Is preferred.

The sulfo-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol and acetoacetyl-modified vinyl alcohol may be used alone, in combination, or in combination with another polyvinyl alcohol. When the other polyvinyl alcohol is used in combination, the total content of the sulfo-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, and acetoacetyl-modified vinyl alcohol is 10% by mass or more of the total amount (mass) of polyvinyl alcohol in the thermosensitive coloring layer. Is preferable, and 20 mass% or more is more preferable.

The sulfo-modified polyvinyl alcohol is
Saponify a polymer obtained by polymerizing an olefin sulfonic acid such as ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid or a salt thereof with a vinyl ester such as vinyl acetate in an alcohol or an alcohol / water mixed solvent. Method, a method of copolymerizing a sodium ester of a sodium salt of a amide and a vinyl ester such as vinyl acetate, and a method of saponifying the obtained copolymer, and treating polyvinyl alcohol with bromine, iodine, etc., in an aqueous sodium acid sulfite solution. It can be produced by a method of heating, a method of heating polyvinyl alcohol in a concentrated aqueous solution of sulfuric acid, or a method of acetalizing polyvinyl alcohol with an aldehyde compound containing a sulfonic acid group.

The diacetone-modified polyvinyl alcohol is a partially or completely saponified copolymer of a monomer having a diacetone group and a vinyl ester, and is obtained by copolymerizing a monomer having a diacetone group with a vinyl ester. It is produced by saponifying the obtained resin. In the diacetone-modified polyvinyl alcohol, the content of the monomer having a diacetone group (repeating unit structure) is not particularly limited.

The acetoacetyl-modified polyvinyl alcohol is generally used as a solution of a polyvinyl alcohol-based resin,
It can be produced by adding and reacting liquid or gaseous diketene to a dispersion or powder. The acetylation degree of the acetoacetyl-modified polyvinyl alcohol can be appropriately selected depending on the intended quality of the heat-sensitive recording material.

(Ultraviolet Absorber) The heat-sensitive recording material of the present invention may contain an ultraviolet absorber in the heat-sensitive coloring layer as long as the effects of the present invention are not impaired. Examples of the ultraviolet absorber that can be used in the present invention include the following.

[0043]

Embedded image

(Binder) In the present invention, the dispersion of the electron-donating colorless dye, the electron-accepting compound and the sensitizer may be carried out in a water-soluble binder. The water-soluble binder used in this case is preferably a compound that dissolves in water at 25 ° C. in an amount of 5% by mass or more.

As specific examples of the water-soluble binder,
Polyvinyl alcohol, methylcellulose, carboxymethylcellulose, starches (including modified starch), gelatin, gum arabic, casein, styrene
Saponified maleic anhydride copolymers and the like can be mentioned.

These binders are used not only at the time of dispersion but also at the time of dispersion.
It is also used for the purpose of improving the coating strength of the thermosensitive coloring layer. For this purpose, styrene-butadiene copolymer, vinyl acetate copolymer, acrylonitrile-butadiene copolymer, methyl acrylate-butadiene copolymer are used. Polymer,
Synthetic polymer latex binders such as polyvinylidene chloride can also be used in combination.

The colorless electron-donating dye, the electron-accepting compound, the sensitizer, and the like are dispersed simultaneously or separately by a stirring / pulverizer such as a ball mill, an attritor, or a sand mill to prepare a coating liquid. In the coating solution, if necessary, various pigments, metal soaps, waxes, surfactants, and the like may be added, and further, an antistatic agent, the ultraviolet absorber, an antifoaming agent, a fluorescent dye, and the like. It may be added.

The pigments include, for example, calcium carbonate, barium sulfate, lithopone, wax, kaolin, calcined kaolin, amorphous silica and aluminum hydroxide. The metal soaps include higher fatty acid metal salts. For example, zinc stearate, calcium stearate, aluminum stearate and the like can be used.

Examples of the wax include paraffin wax, microcrystalline wax, carnauba wax, methylol stearamide, polyethylene wax, polystyrene wax and fatty acid amide wax, and these can be used alone or in combination. Examples of the surfactant include a sulfosuccinic acid-based alkali metal salt and a fluorine-containing surfactant.

The various components contained in the thermosensitive coloring layer are mixed and prepared into a coating liquid. The heat-sensitive coloring layer can be formed by applying the prepared coating solution (coating solution for forming the heat-sensitive coloring layer) on a support by, for example, a known coating method. Examples of the known coating method include a method using an air knife coater, a roll coater, a blade coater, a curtain coater, and the like. The heat-sensitive recording material of the present invention is dried after coating a coating solution on a support, and thereafter subjected to a smoothing treatment with a calender or the like, and then used. As the coating method, a method using a curtain coater is particularly preferable from the viewpoint that the thermosensitive coloring layer can be uniformly coated and the sensitivity and the image storability are efficiently improved. The coating amount of the coating solution for forming the thermosensitive coloring layer is not particularly limited, and is usually 2 parts by dry weight.
About 7 g / m ² is preferred.

<Support> As the support used in the present invention, a conventionally known support can be used. Specific examples include paper supports such as high-quality paper, coated paper obtained by applying a resin or pigment to paper, resin-laminated paper, basecoat base paper having an undercoat layer, synthetic paper, and supports such as plastic films. From the viewpoint of thermal head matching characteristics, an undercoat base paper having an undercoat layer is preferable, and an undercoat base paper having an undercoat layer containing an oil-absorbing pigment using a blade coater is particularly preferable.

As the support, JIS-P8119 is used.
From the viewpoint of dot reproducibility, a smooth support having a smoothness of 300 seconds or more as defined by is preferred.

As described above, the support used in the present invention preferably has an undercoat layer.
The undercoat layer preferably contains a pigment and a binder as main components. As the pigment, any of general inorganic and organic pigments can be used. In particular, the oil absorption degree specified by JIS-K5101 is 40 ml / 100 g (cc / 100 g).
g) or more oil-absorbing pigments are preferred. Examples of the oil-absorbing pigment include calcined kaolin, aluminum oxide, magnesium carbonate, calcium carbonate, amorphous silica, calcined diatomaceous earth, aluminum silicate, magnesium aluminosilicate, and aluminum hydroxide. Among them, JIS- The oil absorption specified by K5101 is 70-80m
1/100 g of calcined kaolin is particularly preferred.

Examples of the binder used in the undercoat layer include a water-soluble polymer and an aqueous binder. These may be used alone or as a mixture of two or more. Examples of the water-soluble polymer include starch, polyvinyl alcohol, polyacrylamide, carboxymethyl alcohol, methyl cellulose, casein, and the like. As the aqueous binder, for example, synthetic rubber latex and synthetic resin emulsion are generally used. For example, styrene-butadiene rubber latex (SBR), acrylonitrile-butadiene rubber latex, methyl acrylate-butadiene rubber latex, vinyl acetate emulsion and the like are used. Is mentioned.

The content of the binder is determined in consideration of the film strength of the layer and the thermal sensitivity of the heat-sensitive coloring layer.
100 mass% is preferable, 5 to 50 mass% is more preferable, and 8 to 15 mass% is particularly preferable. Further, a wax, a decoloring inhibitor, a surfactant and the like may be added to the undercoat layer.

For the application of the undercoat layer, a known coating method can be used. Specifically, for example, a method using an air knife coater, a roll coater, a blade coater, a gravure coater, a curtain coater, or the like can be used. Among them, blade coating using a blade coater is preferable. Further, if necessary, a smoothing treatment such as a calender may be performed before use. The method using the blade coater is not limited to a coating method using a bevel-type or vent-type blade, including a rod blade coating method and a bill blade coating method, and is not limited to an off-machine coater, and may be applied to a paper machine. Coating may be performed with an on-machine coater installed. In addition, in order to obtain excellent smoothness and surface state by imparting fluidity during blade coating,
The degree of etherification of the undercoat layer coating solution is 0.6-
0.8, carboxymethyl cellulose having a weight average molecular weight of 20,000 to 200,000
% By mass, preferably 1 to 3% by mass.

The coating amount of the undercoat layer is not particularly limited, but is 2 g / m ² or more, preferably 4 g / m ² or more, and 7 g / m ^{2 to} 12 g, depending on the characteristics of the heat-sensitive recording material.
g / m ² is particularly preferred.

<Protective Layer> A protective layer can be provided on the thermosensitive coloring layer, if necessary. The protective layer contains a binder, a surfactant, an organic or inorganic pigment, a heat-fusible substance, and the like. As the binder, for example, polyvinyl alcohol or modified polyvinyl alcohol, starch or oxidized starch, modified starch such as urea phosphorylated ester, styrene-maleic anhydride copolymer, styrene-maleic anhydride copolymer alkyl ester , A carboxyl group-containing polymer such as a styrene-acrylic acid copolymer, a vinyl acetate-acrylamide copolymer, methylcellulose, carboxymethylcellulose,
Hydroxymethyl cellulose, gelatins, gum arabic, casein, polyacrylamide derivatives, polyvinylpyrrolidone, and styrene-butadiene rubber latex, acrylonitrile-butadiene rubber latex, methyl acrylate-butadiene rubber latex, vinyl acetate emulsion, and the like, among which water-soluble The conductive polymer is preferred.

As the water-soluble polymer, for example, polyvinyl alcohol, oxidized starch and urea-phosphorylated starch are preferable, and the polyvinyl alcohol (v)
And oxidized starch and / or urea phosphorylated ester (w) in a mass ratio of 90/10 to 10/90 (v /
It is further preferred to mix in w). Further, when oxidized starch and urea phosphate esterified starch are used in combination, that is, when three are used in combination with polyvinyl alcohol,
The oxidized starch (W ¹ ) and the urea phosphate esterified starch (W ² ) have a mass ratio (W ¹ /
W ² ) is preferably used.

Examples of the modified polyvinyl alcohol include acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, and amide-modified polyvinyl alcohol. In addition, sulfo-modified polyvinyl alcohol and carboxy-modified polyvinyl alcohol Polyvinyl alcohol and the like. These polyvinyl alcohols can obtain more favorable results by combining a crosslinking agent that reacts with the polyvinyl alcohol. As the content of the water-soluble polymer, a coating solution for forming a protective layer (hereinafter referred to as a “coating solution for protective layer”)
There is that. ) Of 10 to 90 of the total solid content (mass)
% By mass is preferable, and 30 to 70% by mass is more preferable.

Examples of the crosslinking agent include polyamine compounds such as ethylenediamine, polyhydric aldehyde compounds such as glyoxal, glutaraldehyde, and dialdehyde; dihydrazide compounds such as adipic dihydrazide and phthalic dihydrazide; and water-soluble methylol compounds ( Urea, melamine, phenol), polyfunctional epoxy compounds,
Preferable examples include polyvalent metal salts (such as Al, Ti, Zr, and Mg). When used in combination with the polyvinyl alcohol, the content of the crosslinking agent with respect to the polyvinyl alcohol is preferably about 2 to 30% by mass, and more preferably 5 to 20% by mass. By using the crosslinking agent,
The film strength and water resistance can be improved. Among the crosslinking agents, polyhydric aldehyde compounds, dihydrazide compounds and the like are particularly preferred.

As the inorganic pigment, for example, aluminum hydroxide and kaolin are preferable, and from the viewpoint of the color density obtained by recording with a thermal head, the average particle size is from 0.5 to 0.5.
0.9 μm aluminum hydroxide is preferred. In addition, as the inorganic pigment, calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, barium sulfate, zinc sulfate, talc, clay, calcined clay, colloidal silica, and the like can be used. Further, as the organic pigment, urea-formalin resin, styrene-methacrylic acid copolymer, polystyrene and the like can be used.

The content of the inorganic pigment is preferably from 10 to 90% by mass, more preferably from 30 to 70% by mass, based on the total solids (mass) of the coating solution for the protective layer. The mixing ratio when the inorganic pigment and the water-soluble polymer are contained in the protective layer varies depending on the type of the inorganic pigment, its particle diameter, the type of the water-soluble polymer, and the like. The content of the conductive polymer is preferably 50 to 400% by mass.
~ 250% is more preferred. The total content of the inorganic pigment and the water-soluble polymer contained in the protective layer is 50% of the protective layer.
It is preferable that the amount is at least mass%.

In the present invention, it is preferable to add a surfactant to the coating solution for the protective layer in view of chemical resistance and image storability. Examples of the surfactant include alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, alkyl sulfosuccinates such as dioctyl sodium sulfosuccinate, polyoxyethylene alkyl ether phosphate, sodium hexametaphosphate, and perfluoroalkyl carboxylate. And the like, and among them, a sulfosuccinic acid alkyl ester salt is particularly preferred. The content of the surfactant is preferably from 0.1 to 5% by mass, more preferably from 0.5 to 3% by mass, based on the total solids (mass) of the coating solution for the protective layer. In addition, a lubricant, an antifoaming agent, a fluorescent whitening agent, a colored organic pigment, and the like can be added to the coating solution for the protective layer as long as the effects of the present invention are not impaired. Examples of the lubricant include metal soaps such as zinc stearate and calcium stearate, and waxes such as paraffin wax, microcrystalline wax, carnauba wax and synthetic polymer wax.

[0065]

EXAMPLES The present invention will be described below in detail with reference to Examples, but the present invention is not limited to only the following Examples. In the examples, “parts” and “%” indicate “parts by mass” and “% by mass”, respectively, unless otherwise specified. Similarly, “average particle diameter” in the examples indicates “volume average particle diameter”, and indicates a value measured using LA500 (manufactured by Horiba, Ltd.).

Example 1 << Formation of Thermosensitive Recording Material >><Preparation of Coating Solution for Thermosensitive Coloring Layer> (Preparation of Dispersion A) The following components were mixed while being dispersed by a sand mill to have an average particle diameter of 0. A dispersion A of 0.7 μm was obtained. [Dispersion A composition]-2-anilino-3-methyl-6-diethylaminofluorane 10 parts (electron-donating colorless dye)-Polyvinyl alcohol 2.5% solution 50 parts (PVA-105, manufactured by Kuraray Co., Ltd.)

(Preparation of Dispersion B) A dispersion B having an average particle diameter of 0.7 μm was obtained by mixing the following components while dispersing them in a sand mill. [Dispersion B composition] N- (4-hydroxyphenyl) -p-toluenesulfonamide 20 parts (electron accepting compound) Polyvinyl alcohol 2.5% solution 100 parts (PVA-105, manufactured by Kuraray Co., Ltd.)

(Preparation of Dispersion C) The following components were dispersed and mixed by a sand mill to obtain a dispersion C having an average particle diameter of 0.7 μm. [Dispersion C Composition] 20 parts 2-benzyloxynaphthalene (sensitizer) 100 parts polyvinyl alcohol 2.5% solution (PVA-105, manufactured by Kuraray Co., Ltd.)

(Preparation of Dispersion D) The following components were mixed while being dispersed by a sand mill to obtain a dispersion D having an average particle diameter of 0.7 μm. [Dispersion D composition]-N-stearyl stearamide (sensitizer) 10 parts-Polyvinyl alcohol 2.5% solution 40 parts (PVA-105, manufactured by Kuraray Co., Ltd.)

(Preparation of Dispersion E) The following components were mixed while being dispersed by a sand mill to obtain a dispersion E having an average particle diameter of 0.7 μm. [Composition of dispersion E] 5 parts of 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane (image stabilizer) 25 parts of 2.5% polyvinyl alcohol solution (PVA) -105, manufactured by Kuraray Co., Ltd.)

(Preparation of Pigment Dispersion F) The following components were dispersed and mixed in a sand mill to give an average particle diameter of 2.0 μm.
m of pigment dispersion F was obtained. [Pigment dispersion F composition] ・ 40 parts of light calcium carbonate ・ 1 part of sodium polyacrylate ・ 60 parts of water

A compound having the following composition was mixed to obtain a coating solution for a thermosensitive coloring layer. [Coating liquid composition for thermosensitive coloring layer] 60 parts of dispersion A 120 parts of dispersion B 120 parts of dispersion C 50 parts of dispersion D 30 parts of dispersion E 101 parts of pigment dispersion F 101 parts of zinc stearate 15 parts of 30% dispersion ・ 15 parts of paraffin wax (30%) ・ 4 parts of sodium dodecylbenzenesulfonate (25%)

<Preparation of Coating Solution for Support Undercoat Layer> The following components were stirred and mixed with a dissolver,
20 parts of (styrene-butadiene latex) and 25 parts of oxidized starch (25%) were added to obtain a coating solution for a support undercoat layer. [Coating solution composition for support undercoat layer] 100 parts of calcined kaolin (oil absorption 75 ml / 100 g) 1 part of sodium hexametaphosphate 1 part of distilled water

<Formation of Thermal Recording Material> Weighing 50 g / m ²
The base undercoat layer is coated with the coating solution for the support undercoat layer by a blade coater so that the coating amount after drying is 8 g / m ^2. Was prepared. Next, the coating solution for a thermosensitive coloring layer was applied on the undercoat layer by a curtain coater so that the coating amount after drying was 4 g / m ^2, and then dried. The surface of the formed heat-sensitive coloring layer was subjected to a calendering treatment to obtain a heat-sensitive recording material of the present invention.

Example 2 Dispersion C in Example 1
From 120 parts to 150 parts and dispersion D from 50 parts to 25 parts.
The heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the composition was changed to parts.

Example 3 Dispersion C in Example 1
From 120 parts to 165 parts and the dispersion D from 50 parts to 1 part.
A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the amount was changed to 2.5 parts.

Example 4 Dispersion C in Example 1
From 120 parts to 75 parts and dispersion D from 50 parts to 87.
A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1, except that the amount was changed to 5 parts.

Example 5 The 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane used in the preparation of the dispersion E in Example 1 was
1,1,3-tris (2-methyl-4-hydroxy-5
Example 1 except that -cyclohexyl) butane was used.
In the same manner as in the above, a thermosensitive recording material of the present invention was obtained.

Example 6 Dispersion E in Example 1
Was changed from 30 parts to 10 parts to obtain a heat-sensitive recording material of the present invention in the same manner as in Example 1.

Example 7 Dispersion E in Example 1
Was changed from 30 parts to 70 parts to obtain a heat-sensitive recording material of the present invention in the same manner as in Example 1.

Example 8 In Example 1, dispersion E
Was used in the same manner as in Example 1 except that the heat-sensitive recording material of the present invention was obtained.

Example 9 The heat-sensitive recording material of the present invention was prepared in the same manner as in Example 1, except that the coating solution for the heat-sensitive coloring layer was applied by an air knife coater instead of a curtain coater. Obtained.

[Example 10] In Example 6, before applying the calendering treatment to the formed thermosensitive coloring layer, a coating liquid for a protective layer prepared in the following composition was further applied on the thermosensitive coloring layer by dry coating. A heat-sensitive material according to the present invention was prepared in the same manner as in Example 6, except that a protective layer was formed by coating and drying with a curtain coater so that the amount was 2 g / m ^2, and the surface of the protective layer was subjected to a calendering treatment. A recording material was obtained.

<Preparation of Coating Solution for Protective Layer> First, the following compounds were dispersed in a sand mill to prepare a pigment dispersion having an average particle diameter of 2 μm.・ 40 parts of aluminum hydroxide (average particle diameter 1 μm) (Heidilite H42, manufactured by Showa Denko KK) ・ 1 part of sodium polyacrylate ・ 60 parts of water Subsequently, a 15% aqueous solution of urea phosphate esterified starch (MS4600, 200 parts of Nippon Shokuhin Kako Co., Ltd.) and a 15% aqueous solution of polyvinyl alcohol (PVA-105,
60 parts of water were added to 200 parts of Kuraray Co., Ltd., and the pigment dispersion was further mixed. Further, 25 parts of emulsified dispersion of zinc stearate having an average particle diameter of 0.15 μm (Hydrin F115, manufactured by Chukyo Yushi Co., Ltd.) And 125 parts of a 2% aqueous solution of 2-ethylhexyl sulfosuccinate soda salt were mixed to obtain a coating solution for a protective layer.

[Comparative Example 1] In Example 1, the dispersion C
Was used, and a thermosensitive recording material of a comparative example was obtained in the same manner as in Example 1 except that the dispersion D was changed from 50 parts to 60 parts.

Comparative Example 2 Dispersion C in Example 1
From 120 parts to 36 parts, and Dispersion D from 50 parts to 120 parts.
In the same manner as in Example 1, except that the composition was changed to parts, a thermosensitive recording material of Comparative Example was obtained.

Comparative Example 3 N- (4-hydroxyphenyl) -p-toluenesulfonamide used for preparing dispersion B in Example 1 was replaced with 2,2-bis (4-hydroxyphenyl) propane [bisphenol A) A heat-sensitive recording material of Comparative Example was obtained in the same manner as in Example 1 except that A) was used.

[Comparative Example 4] In Example 1, the dispersion D
Was used, and a thermosensitive recording material of a comparative example was obtained in the same manner as in Example 1, except that the dispersion C was changed from 120 parts to 170 parts.

<< Evaluation >> (1) Sensitivity A thermal head (KJT-216-8M) manufactured by Kyocera Corporation
PD1) and Examples 1 to 10 using a thermal printer having a pressure roll of 100 kg / cm ² immediately before the head.
Printing was performed on the heat-sensitive recording materials obtained in Comparative Examples 1 to 4.
The printing is performed with a pulse width of 2.1 ms using a pressure roll at a head voltage of 24 V and a pulse period of 10 ms, and the printing density is measured using a Macbeth reflection densitometer (RD-
918). Table 1 shows the results.

(2) Background fog The heat-sensitive recording materials obtained in the above Examples 1 to 10 and Comparative Examples 1 to 4 were treated at 60 ° C. and 20% relative humidity in an environment of 2%.
After standing for 4 hours, the surface of the skin was measured using a Macbeth reflection densitometer (RD).
-918). Table 1 shows the results. Note that the lower the numerical value, the better the result.

(3) Image Preservation The heat-sensitive recording materials obtained in Examples 1 to 10 and Comparative Examples 1 to 4 were recorded on the same apparatus and under the same conditions as in the above (1). It was left for 24 hours in an environment with a humidity of 20%. Thereafter, the image density was measured using a Macbeth reflection densitometer (RD-
918), and the residual ratio with respect to the image density of an unprocessed product (without standing) in which an image was recorded under the same apparatus and conditions as in (1) above was calculated from the following equation. Table 1 shows the results.
The higher the value, the better the image storability. Image storability (%) = (image density after standing / unprocessed image density) × 100

(4) Chemical resistance The surface of the heat-sensitive recording materials obtained in Examples 1 to 10 and Comparative Examples 1 to 4 was coated with a fluorescent pen (Zebra highlighter 2-pink,
Zebra Co., Ltd.), and after one day, the degree of background fogging of each heat-sensitive recording material and the stability of the image area were visually observed and evaluated according to the following criteria. Table 1 shows the results. [Criterion] カ: No fog was observed, and no change in the image area was observed. Δ: Some fogging was observed, and decoloring of the image area was slightly observed. X: Fogging was remarkably observed. Further, the color of the image portion was erased.

(5) Sticking property FAX (SFX85, manufactured by Sanyo Electric Co., Ltd.) and a test chart of IEEJ NO. Using the three charts, printing was performed on the heat-sensitive recording materials obtained in Examples 1 to 10 and Comparative Examples 1 to 4. The printing sound at that time and the overexposed state measured visually were evaluated according to the following criteria. Table 1 shows the results. [Criterion] ：: There was no noise other than the print sound, and no whiteout was observed. Δ: There was slight noise, and overexposure was observed. ×: Clear noise (adhesion sound) was generated, and many overexposures were observed.

[0094]

[Table 1]

From the results shown in Table 1 above, the heat-sensitive recording materials of the present invention obtained in Examples 1 to 10 show the sensitivity, background fog,
It was excellent in each of the image preservability, chemical resistance and sticking property of the color image. In addition, in comparison between Examples 1 and 5 and Example 8, the image storability was able to be further improved by including the image stabilizer. In particular, as shown in the comparison between Example 1 and Example 5, when the content of the image stabilizer with respect to the electron-donating colorless dye is 20 parts by mass or more, the image storability and chemical resistance are further improved. be able to. Example 1 and Example 7
From the comparison with the above, sticking property was able to be improved by setting the content of the image stabilizer to 100 parts by mass or less. Further, from a comparison between Example 1 and Example 9, it was found that the application of the thermosensitive coloring layer using a curtain coater was more excellent in sensitivity, background fog, and image storability. Comparison between Example 6 and Example 10 showed that the provision of the protective layer was more excellent in chemical resistance and image storability.

On the other hand, the heat-sensitive recording materials of Comparative Examples 1 and 4, which did not use either 2-benzyloxynaphthalene or N-stearylstearic amide, were particularly inferior in image storability. Further, in the heat-sensitive recording material of Comparative Example 2 in which the content ratio (mass ratio) of 2-benzyloxynaphthalene and N-stearylstearic amide was out of the range of 95/5 to 40/60, the background fog and image storability It was particularly inferior in terms of. Further, in the heat-sensitive recording material of Comparative Example 3 using bisphenol A as the electron-accepting compound, the image storability and the sticking property were slightly inferior, and the chemical resistance was remarkably inferior.

[0097]

According to the present invention, as compared with the conventional heat-sensitive recording material, the coloring density is higher, the background fog is less, and the storage stability (density stability) of the image area, the chemical resistance and the sticking property are excellent. A heat-sensitive recording material can be provided.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hirofumi Mitsuo 200 No. Onakazato, Fujinomiya City, Shizuoka Prefecture Fuji Photo Film Co., Ltd. F-term (reference) 2H026 AA07 BB25 DD02 DD12 DD13 DD34 DD43 DD45 DD53

Claims (3)

[Claims] 1. A thermosensitive recording material having a thermosensitive coloring layer containing an electron-donating colorless dye and an electron-accepting compound on a support, wherein the thermosensitive coloring layer comprises N- as the electron-accepting compound.
(4-hydroxyphenyl) -p-toluenesulfonamide, further containing 2-benzyloxynaphthalene (x) and N-stearylstearic acid amide (y) as sensitizers; Content ratio with N-stearyl stearamide (mass ratio: x / y)
Is in the range of 95/5 to 40/60. 2. The method according to claim 1, wherein the heat-sensitive coloring layer comprises 1,1 as an image stabilizer.
1,3-tris (2-methyl-4-hydroxy-5-t
The heat-sensitive recording material according to claim 1, further comprising at least one of tert-butylphenyl) butane and 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexyl) butane. 3. The heat-sensitive recording material according to claim 2, wherein the content of the image stabilizer is 10 to 100 parts by mass based on 100 parts by mass of the electron-donating colorless dye.