JP2002187356A - 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 and excellent prsservability or the like 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, 2- benzyloxynaphthalene and amide methylolstearate as a sensitizer and 1,1,3-tris(2- methyl-4-hydroxy-5-tert-butylphenyl)butane and/or 1,1,3-tris(2-methyl-4-hydroxy-5- cyclohexyl)butane as an image stabilizer so that a mass ratio (x/y) of the 2- benzyloxynaphthalene (x) to the amide methylolstearate (y) is in a range of 95/5 to 40/60.

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 storability, and the like.
The present invention relates to a heat-sensitive recording material having excellent chemical resistance and sticking properties.

[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, none of these heat-sensitive recording materials could simultaneously satisfy each of sensitivity, background fog, image storability, chemical resistance, and sticking property.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material having a high color density, a low background fog, and excellent image area preservability, chemical resistance and sticking properties. is there.

[0005]

Means for Solving the Problems The present inventors have intensively studied each of an electron-accepting compound, a sensitizer, an image stabilizer and the like, pursued the development of a good heat-sensitive recording material, and completed the present invention. did. That is, the present invention

<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-
Toluene sulfonamide, 2-benzyloxynaphthalene and methylol stearamide as sensitizers, and 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butyl) as image stabilizers Phenyl) butane and / or 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexyl)
Butane, and the mass ratio (x / y) of the 2-benzyloxynaphthalene (x) to the methylol stearamide (y) is in the range of 95/5 to 40/60. It is a heat-sensitive recording material that is characterized.

<2> The content of the image stabilizer is 10 to 10 with respect to 100 parts by mass of the electron-donating colorless dye.
The thermosensitive recording material according to <1>, wherein the amount is 0 parts by mass.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Thermosensitive Recording Material The thermosensitive recording material of the present invention is a thermosensitive recording material having a thermosensitive coloring layer containing a colorless electron-donating dye and an electron-accepting compound on a support. The thermosensitive coloring layer contains N- (4-hydroxyphenyl) -p-toluenesulfonamide as the electron-accepting compound, 2-benzyloxynaphthalene and methylol stearamide as sensitizers, and 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) as a stabilizer
Butane and / or 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexyl) butane; and the above-mentioned 2-benzyloxynaphthalene (x) and the above-mentioned methylol stearamide (y). Mass ratio (x
/ Y) is in the range of 95/5 to 40/60. Hereinafter, the thermosensitive recording material of the present invention will be described in the order of the thermosensitive coloring layer and the support.

<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, a sensitizer, and an image stabilizer. It is characterized by doing. Further, the heat-sensitive recording material of the present invention may contain a pigment, an adhesive, an ultraviolet absorber, or the like, if necessary.

(Electron-donating colorless dye) Examples of the electron-donating colorless dye include 2-anilino-3-methyl-6-diethylaminofluoran and 2-anilino-3-methyl-6.
-(N-ethyl-N-isoamylamino) fluoran and 2-anilino-3-methyl-6- (N-ethyl-N
It is preferably at least one selected from -propylamino) fluorane. These may be used alone or in combination of two or more. 2-anilino-3-methyl-6-diethylaminofluoran, 2-
Electron donation of at least one selected from anilino-3-methyl-6- (N-ethyl-N-isoamylamino) fluoran and 2-anilino-3-methyl-6- (N-ethyl-N-propylamino) fluoran When used as a neutral colorless dye, the color density, the storage stability of the image area, and the chemical resistance can be further improved.

The electron-donating colorless dye according to the present invention may be, for example, 3-di (n-butylamino) -6-methyl-7-anilinofluoran or 2-anilino-3 in addition to those described above. -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 may be used.

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 color density and background fog
0.2-0.5 g / m^TwoIs particularly preferred.

(Electron-Accepting Compound) The heat-sensitive recording material of the present invention is characterized by containing N- (4-hydroxyphenyl) -p-toluenesulfonamide as an electron-accepting compound. The heat-sensitive recording material of the present invention comprises the above-mentioned N- (4
-Hydroxyphenyl) -p-toluenesulfonamide as an electron-accepting compound can increase the coloring density, suppress background fog, and improve chemical resistance. The content of the electron-accepting compound is preferably from 50 to 400% by mass, particularly preferably from 100 to 300% by mass, based on the color of the electron-donating colorless dye.

The electron accepting compound of the present invention includes N- (4-
In addition to (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.

As the above-mentioned known electron accepting compounds, known ones can be appropriately selected and used, and particularly from the viewpoint of suppressing background fogging, phenolic compounds or
Salicylic acid derivatives and polyvalent metal salts thereof are preferred. Examples of the phenolic compound include 2,2′-bis (4-hydroxyphenol) propane (bisphenol A), 4-t-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, and 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′-se
c-isooctylidene diphenol, 4,4'-sec
-Butylene diphenol, 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.

The salicylic acid derivatives and polyvalent metal salts thereof include 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 in the present invention, N- (4-hydroxyphenyl) -p-toluenesulfonamide according to the present invention is used with respect to the total amount of all electron-accepting compounds. , 50% by mass or more, more preferably 70% by mass or more.

In the present invention, when preparing a coating solution for the thermosensitive coloring layer, the particle diameter of the electron-accepting compound is preferably not more than 1.0 μm in terms of volume average particle diameter, and is preferably from 0.4 to 0.
7 μm is more preferred. When the volume average particle size is 1.
When the thickness is 0 μm or less, the thermal sensitivity does not easily decrease. The volume average particle diameter is measured by a laser diffraction particle size distribution analyzer (for example, L
It can be easily measured by A500 (manufactured by Horiba).

(Sensitizer) The heat-sensitive recording material of the present invention is characterized in that the heat-sensitive color-forming layer contains 2-benzyloxynaphthalene and methylol stearamide as sensitizers. The heat-sensitive recording material of the present invention contains 2-benzyloxynaphthalene and methylol stearamide as sensitizers in the heat-sensitive coloring layer, thereby greatly improving the sensitivity while suppressing the occurrence of background fog. Can be. Further, the mass ratio (x / y) of the above-mentioned 2-benzyloxynaphthalene (x) to methylol stearamide (y) is in the range of 95/5 to 40/60. If the mass ratio is less than 95/5, the sensitivity becomes low,
Also, if it is larger than 40/60, the sensitivity will be low. The mass ratio is preferably 90/10 to 50/50, and more preferably 85/15 to 70/30.

The total content of the sensitizer is preferably from 75 to 200 parts by mass based on 100 parts by mass of N- (4-hydroxyphenyl) -p-toluenesulfonamide which is an electron accepting compound. More preferably, it is 100 to 150 parts by mass. The total content of the sensitizer is 75 to 200.
When the amount is within the range of parts by mass, the effect of improving sensitivity is large and the image storability is good.

In the heat-sensitive coloring layer according to the present invention, in addition to the above-mentioned 2-benzyloxynaphthalene and methylolstearic acid amide, the heat-sensitive coloring layer may be formed in a range that does not impair the effects of the present invention.
Other sensitizers may be used in combination. Other sensitizers include aliphatic monoamides, stearyl ureas, p-benzyl biphenyl, 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) The heat-sensitive recording material of the present invention comprises:
As an image stabilizer, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane and 1,1,3-tris (2-
It is characterized by containing at least one of methyl-4-hydroxy-5-cyclohexyl) butane. When the above-mentioned image stabilizer is contained in the thermosensitive coloring layer, N- (4-hydroxyphenyl)-as the above-mentioned electron accepting compound is obtained.
Interaction of p-toluenesulfonamide with 2-benzyloxynaphthalene and methylol stearamide as sensitizers can improve background fog and greatly improve the storage stability of the image area. The above 1,
1,3-tris (2-methyl-4-hydroxy-5-t
tert-butylphenyl) butane (α) and 1,1,
3-Tris (2-methyl-4-hydroxy-5-cyclohexyl) butane (β) may be used alone or in combination, and when both are used in combination, the mass ratio (α / β) is preferably in the range of 20/80 to 80/20, and more preferably in the range of 40/60 to 60/40.

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

Further, the heat-sensitive recording material of the present invention comprises
1,3-tris (2-methyl-4-hydroxy-5-t
Known image stabilizers may be used in addition to ert-butylphenyl) butane or 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexyl) butane. When a known image stabilizer is used in combination, the above 1,1,3
-Tris (2-methyl-4-hydroxy-5-tert
-Butylphenyl) butane or 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexyl)
Butane is preferably contained in an amount of 50% by mass or more, more preferably 70% by mass or more, based on the total amount of the image stabilizer. As the above-mentioned known image stabilizer, a phenol compound, particularly a hindered phenol compound, is effective. For example, 1,1,3-tris (2-
Ethyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (3,5-di-ter
t-butyl-4-hydroxyphenyl) butane, 1,
1,3-tris (2-methyl-4-hydroxy-5-t
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.

(Inorganic Pigment) The heat-sensitive recording material of the present invention may contain an inorganic pigment in the heat-sensitive coloring layer if necessary, as long as the effects of the present invention are not impaired. As the inorganic pigment,
It is preferable to use light calcium carbonate or aluminum hydroxide alone or in combination. By containing light calcium carbonate and / or aluminum hydroxide as the inorganic pigment, background fogging and abrasion of the thermal head can be reduced, and further, adhesion of scum to the thermal head and prevention of sticking can be improved. .

The content of the inorganic pigment is preferably from 50 to 250 parts by mass, more preferably from 70 to 170 parts by mass, based on 100 parts by mass of the electron-accepting compound from the viewpoint of color density and adhesion of scum to a thermal head. Is more preferably 90 to 140 parts by mass. Further, the particle diameter of the inorganic pigment is preferably from 0.6 to 2.5 μm, preferably 0.8 to 2.0 μm in terms of volume average particle diameter, from the viewpoint of color density and adhesion of dregs to the thermal head. More preferably,
It is particularly preferred that the thickness be 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) is 80 /
It is preferably in the range of 20 to 20/80, and 60
More preferably, it is within the range of / 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 used.

Other inorganic pigments include calcium carbonate other than calcite-based light calcium carbonate, barium sulfate, lithopone, wax, kaolin, calcined kaolin, amorphous silica and the like. When the light calcium carbonate or the like is used in combination with another inorganic pigment, 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 used. Is 100 / 0-60
/ 40, preferably 100/0 to 8
More preferably, it is within the range of 0/20.

(Adhesive) The heat-sensitive recording material of the present invention may contain an adhesive 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. However, heat-sensitive recording materials generally 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.

As the above adhesive, a saponification degree of 85 to 99 is used.
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. The saponification degree is preferably 85 to 99 mol%. The saponification degree is 8
When the content is within the range of 5 to 99 mol%, paper peeling due to insufficient water resistance to fountain solution used for offset printing is prevented, and furthermore, undissolved water is prevented during preparation of a coating liquid. It is possible to prevent an object from being generated and causing a defective portion. Further, it is preferable to use polyvinyl alcohol having a degree of polymerization in the range of 200 to 2,000. When the polymerization degree is in the range of 200 to 2,000, it is not necessary to increase the amount of addition, so that the increase in the amount of addition does not cause a decrease in image density. Further, 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 degree of polymerization refers to an average degree of polymerization determined by the method described in JIS-K6726 (1994).

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

The polyvinyl alcohol includes a saponification degree of 85 to 99 mol% and a polymerization degree of 200 to 20.
Any condition that satisfies the condition of 00 is preferable, 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 another polyvinyl alcohol is used in combination, the above-mentioned sulfo-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, and acetoacetyl-modified vinyl alcohol are added in an amount of 1 to the total mass of the polyvinyl alcohol.
0% by mass or more, preferably 20% by mass
More preferably, it is included.

The above sulfo-modified polyvinyl alcohol is
Saponify a polymer obtained by polymerizing an olefinsulfonic acid such as ethylenesulfonic acid, allylsulfonic acid, and methallylsulfonic 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 thermosensitive 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.

[0037]

Embedded image

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

Specific examples of the above water-soluble binder include:
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 above colorless electron-donating dye, electron-accepting compound and sensitizer are dispersed simultaneously or separately by a stirrer / pulverizer such as a ball mill, an attritor or a sand mill to prepare a coating liquid. . In the coating liquid, various pigments, metal soaps, waxes, and surfactants may be further added as necessary, and further, an antistatic agent, the ultraviolet absorber, the defoaming agent, a fluorescent dye, and the like. May be added.

Examples of the pigments include calcium carbonate, barium sulfate, lithopone, wax stone, kaolin, calcined kaolin,
Amorphous silica and aluminum hydroxide are used. As the metal soap, higher fatty acid metal salts are used, for example, zinc stearate, calcium stearate, aluminum stearate and the like.

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

The materials contained in these thermosensitive coloring layers are mixed and then applied onto a support. Examples of the application method include a method using an air knife coater, a roll coater, a blade coater, a curtain coater, or the like. The heat-sensitive recording material of the present invention is applied with a coating solution on a support, dried, and then subjected to a smoothing treatment with a calender or the like, and then used. As the above-mentioned coating method, a method using a curtain coater is particularly preferable in the present invention, from the viewpoint that the thermosensitive coloring layer can be uniformly coated and the sensitivity and the image storability are efficiently improved. Further, the coating amount of the thermosensitive coloring layer is not particularly limited, and is usually preferably about ² to 7 g / m ^{2 on} a dry mass basis.

<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, 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 above 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 in 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.
-The oil absorption specified by K5101 is 70 to 80 ml / 10
0 g of calcined kaolin is particularly preferred.

The binder used for the undercoat layer includes a water-soluble polymer and an aqueous binder. These may be used alone or as a mixture of two or more. As the water-soluble polymer,
Starch, polyvinyl alcohol, polyacrylamide, carboxymethyl alcohol, methylcellulose,
And casein. As the aqueous binder, a synthetic rubber latex or a synthetic resin emulsion is generally used, and styrene-butadiene rubber latex (SBR), acrylonitrile-butadiene rubber latex, methyl acrylate-butadiene rubber latex,
And vinyl acetate emulsion. The amount of these binders used is determined in consideration of the film strength of the coating layer, the thermal sensitivity of the thermosensitive coloring layer, etc., but is 3 to 100% by mass, preferably 5 to 100% by mass, based on the pigment added to the undercoat layer. It is 50% by mass, particularly preferably 8 to 15% by mass. The undercoat layer may contain a wax, a decoloring inhibitor, a surfactant and the like.

A known coating method can be used for coating the undercoat layer. Specifically, air knife coater, roll coater, blade coater,
A method using a gravure coater, a curtain coater, or the like can be used, and among them, blade coating using a blade coater is preferable. Further, it may be used after being subjected to a smoothing process such as a calender as required. The method using the blade coater is not limited to a coating method using a bevel type or a vent type blade, includes a rod blade coating method or a bill blade coating method, and is not limited to an off-machine coater, and is not limited to an off-machine coater. Coating may be performed with an on-machine coater installed. In addition, in order to impart fluidity during blade coating to obtain excellent smoothness and surface condition, the degree of etherification of the coating solution for the undercoat layer is 0.6 to 0.5.
8, carboxymethyl cellulose having a weight average molecular weight of 20,000 to 200,000 may be added to the pigment at 1 to 5% 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. By providing the protective layer, image storability and chemical resistance can be improved. The protective layer can contain a binder, a surfactant, an organic or inorganic pigment, a heat-fusible substance, and the like. Examples of the binder include polyvinyl alcohol or modified polyvinyl alcohol, starch or oxidized starch, modified starch such as urea phosphate esterified starch, styrene-maleic anhydride copolymer, styrene-maleic anhydride copolymer alkyl esterified product, styrene -A carboxyl group-containing polymer such as an acrylic acid copolymer,
Vinyl acetate-acrylamide copolymer, methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, gelatins, gum arabic, casein, polyacrylamide derivatives, polyvinylpyrrolidone, styrene-butadiene rubber latex, acrylonitrile-butadiene rubber latex, methyl acrylate-butadiene rubber Latex, vinyl acetate emulsion and the like are used, and among them, a water-soluble polymer is preferable.

As the water-soluble polymer, polyvinyl alcohol, oxidized starch, and urea phosphate esterified starch are preferred. The polyvinyl alcohol (v) and oxidized starch and / or urea phosphate esterified starch (w) are used. Mass ratio (v / w) of 90/10 to 10/90
It is more preferable to mix them. When oxidized starch and urea phosphated starch are used in combination, that is, when three are used in combination with polyvinyl alcohol, oxidized starch (W ¹ ) and urea phosphated starch (W ² ) , A mass ratio of 10/90 to 90/10 (W ¹ /
W ² ) is preferably used.

As the modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, and amide-modified polyvinyl alcohol are preferably used. In addition, sulfo-modified polyvinyl alcohol and carboxy-modified polyvinyl alcohol are used. Alcohol or the like is used. These polyvinyl alcohols can obtain more favorable results by combining a crosslinking agent that reacts with the polyvinyl alcohol. The content of the water-soluble polymer is preferably from 10 to 90% by mass, more preferably from 30 to 70% by mass, based on the solid content of the coating solution for the protective layer.

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, polyvalent metal salts (such as Al, Ti, Zr, and Mg) are preferably used. When used in combination with the polyvinyl alcohol,
The content of the crosslinking agent with respect to the polyvinyl alcohol is 2 to
It is preferably about 30% by mass, more preferably 5 to 20% by mass. By using the crosslinking agent, the film strength, the water resistance, and the like can be improved. As the crosslinking agent used in the present invention, a polyhydric aldehyde compound, a dihydrazide compound and the like are preferable.

As the above-mentioned inorganic pigment, for example, aluminum hydroxide and kaolin are preferable, and from the viewpoint of color density by recording with a thermal head, the average particle size is 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 based on the solid content of the coating solution for the protective layer.
30-70 mass% is more preferable. When the protective layer contains an inorganic pigment and a water-soluble polymer, the mixing ratio 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, and 100 to 2% by mass.
50% is more preferred. Further, the total content of the inorganic pigment and the water-soluble polymer contained in the protective layer is preferably at least 50% by mass of the protective layer.

In the present invention, chemical resistance can be further improved by adding a surfactant to the coating solution for the protective layer. Examples of the surfactant include an alkylbenzene sulfonate such as sodium dodecylbenzenesulfonate;
Alkyl sulfosuccinates such as sodium dioctyl sulfosuccinate, polyoxyethylene alkyl ether phosphate, sodium hexametaphosphate, perfluoroalkyl carboxylate, and the like are preferred, and alkyl sulfosuccinate 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 solid content 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.

[0058]

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. Unless otherwise specified, “parts” and “%” in the examples indicate “parts by mass” and “% by mass”, respectively. 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, and the average particle diameter was reduced to 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) The following components were dispersed and mixed in a sand mill to obtain a dispersion B having an average particle diameter of 0.7 μm. [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 mixed while being dispersed 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] 10 parts of methylol stearamide (sensitizer) 40 parts of 2.5% polyvinyl alcohol solution (PVA-105, manufactured by Kuraray Co., Ltd.)

(Preparation of Dispersion E) A dispersion E having an average particle diameter of 0.7 μm was obtained by mixing the following components while dispersing them in a sand mill. [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 mixed while being dispersed 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 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 Thermosensitive Recording Material> Weighing 50 g / m ²
Was coated with the above coating solution for a support undercoat layer by a blade coater so that the coating amount after drying was 8 g / m ^2, and dried to prepare an undercoat base paper. Next, the coating amount after drying on the undercoat layer surface is 4.5.
The coating solution for the thermosensitive coloring layer was applied by a curtain coater so as to have a 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 according to Example 1.

Example 2 Dispersion C in Example 1
From 120 parts to 150 parts and dispersion D from 50 parts to 25 parts.
A thermosensitive recording material according to Example 2 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 thermosensitive recording material according to Example 3 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.
Example 4 was repeated in the same manner as in Example 1 except that the number of parts was changed to 5.
Was obtained.

Example 5 Dispersion E in Example 1
Of 1,1,3-tris (2-methyl-4-hydroxy-
5-tert-butylphenyl) butane is 1,1,3-
A thermosensitive recording material according to Example 5 was obtained in the same manner as in Example 1, except that tris (2-methyl-4-hydroxy-5-cyclohexyl) butane was used.

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

Example 7 Dispersion E in Example 1
Was changed from 30 parts to 50 parts to obtain a heat-sensitive recording material according to Example 7 in the same manner as in Example 1.

Example 8 Dispersion E in Example 1
Was changed to 30 parts from 30 parts to obtain a heat-sensitive recording material according to Example 8 in the same manner as in Example 1.

Example 9 A heat-sensitive recording material according to Example 9 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. I got

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

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

[Comparative Example 1] In Example 1, the dispersion C
Was used, and the heat-sensitive recording material according to Comparative Example 1 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.
A thermosensitive recording material according to Comparative Example 2 was obtained in the same manner as in Example 1 except that the composition was changed to parts.

[Comparative Example 3] In Example 1, the dispersion E
Was used in the same manner as in Example 1 except that no heat-sensitive recording material according to Comparative Example 3 was obtained.

Comparative Example 4 Dispersion B in Example 1
Of N- (4-hydroxyphenyl) -p-toluenesulfonamide to 2,2-bis (4-hydroxyphenyl)
A heat-sensitive recording material according to Comparative Example 4 was obtained in the same manner as in Example 1 except that propane [bisphenol A] was used.

Comparative Example 5 Dispersion E in Example 1
Of 1,1,3-tris (2-methyl-4-hydroxy-
A heat-sensitive recording material according to Comparative Example 5 was obtained in the same manner as in Example 1, except that 5-tert-butylphenyl) butane was changed to 2,2'-methylenebis (4-methyl-6-tert-butylphenol). .

[Comparative Example 6] In Example 1, the dispersion D
Was used, and the heat-sensitive recording material according to Comparative Example 6 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 9 using a thermal printing apparatus 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 6. The printing was performed with a head voltage of 24 V and a pulse period of 10 m.
Pulse width 2.1m using pressure roll under the condition of s
s, and the print density is measured with a Macbeth reflection densitometer (R
D-918). Table 1 shows the results.

(2) Background Fogging The background of the heat-sensitive recording materials obtained in Examples 1 to 10 and Comparative Examples 1 to 6 was left for 24 hours in an environment of 60 ° C. and a relative humidity of 20%. Reflection densitometer (R
D-918). Table 1 shows the results. Note that the lower the numerical value, the better the result.

(3) Image preservability The heat-sensitive recording materials obtained in Examples 1 to 10 and Comparative Examples 1 to 6 were recorded with 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 (R
D-918), and the residual ratio with respect to the image density of an unprocessed product (with no standing) on 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 6 was written with a fluorescent pen (Zebra Highlighter 2-Pink, manufactured by Zebra Corp.). 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] A: No fog was observed, and no change in the image area was observed. Δ: Slight 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 A 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 6. The printing sound at that time and the overexposed state measured visually were comprehensively 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.

[0089]

[Table 1]

From Table 1, it can be seen that the heat-sensitive recording materials obtained in Examples 1 to 9 of the present invention are excellent in sensitivity, background fog, image storability of color images, chemical resistance and sticking properties. all right. From the comparison between Example 1 and Examples 6 and 8, when the content of the image stabilizer with respect to the electron-donating colorless dye is 10 parts by mass or more, particularly 20 parts by mass or more, image preservability and chemical resistance are obtained. Was found to be even better. Similarly, from a comparison between Example 1 and Example 7, it was found that the sticking property was further excellent when the content was 60 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 superior in sensitivity, background fogging, and image storability. Further, from the comparison between Examples 6 and 10, it was found that the provision of the protective layer improved the image storability and the chemical resistance.

On the other hand, from Table 1, it was found that Comparative Example 1 in which 2-benzyloxynaphthalene was not used was particularly poor in background fog and image preservability. Comparative Example 2 in which the mass ratio of 2-benzyloxynaphthalene to methylol stearamide was out of the range of 95/5 to 40/60 was particularly poor in image storability. Further, Comparative Example 3 in which no image stabilizer was used was particularly inferior in image storability. Comparative Example 4 using bisphenol A as the electron-accepting compound was slightly inferior in image storability and sticking properties and remarkably inferior in chemical resistance. Further, Comparative Example 5 using an image stabilizer other than the image stabilizer according to the present invention was particularly inferior in image storability and sticking property.

[0092]

As described above, according to the present invention,
It is possible to provide a heat-sensitive recording material having a higher color density, less background fog, and excellent image area storage stability, chemical resistance, and sticking properties as compared with conventional heat-sensitive recording materials.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hirofumi Mitsuo 200 No. Onakazato, Fujinomiya City, Shizuoka Prefecture F-Film Co., Ltd. F-term (reference) 2H026 AA07 BB25 DD02 DD12 DD13 DD17 DD23 DD43 DD45 EE00 FF00

Claims (2)

[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, and further, as a sensitizer, 2-benzyloxynaphthalene and methylol stearamide.
As an image stabilizer, 1,1,3-tris (2-methyl-4
-Hydroxy-5-tert-butylphenyl) butane and / or 1,1,3-tris (2-methyl-4-
(Hydroxy-5-cyclohexyl) butane, and the mass ratio (x / y) of the 2-benzyloxynaphthalene (x) to the methylol stearamide (y)
Is in the range of 95/5 to 40/60. 2. The heat-sensitive recording material according to claim 1, wherein the content of the image stabilizer is 10 to 100 parts by mass based on 100 parts by mass of the colorless electron-donating dye.