JP2002200849A - Thermal recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording medium which is free from the generation of a texture fog and shows outstanding image conservation properties, color development, chemical resistance and stickiness. SOLUTION: This thermal recording medium has a thermal color development layer containing an electron-donating colorless dye, an electron-receiving compound and a sensitizer, formed on a support. The thermal color development layer contains an N-(4-hydroxyphenyl)-p-toluenesulfonamide as an electron- receiving compound, a 2-benzyloxynaphthalene (X) and an ethylene-bis-amide behenate (Y) as the sensitizer. In addition, the mass ratio (X/Y) between the 2-benzyloxynaphthalene (X) and the ethylene-bis-amide behenate (Y) is within the 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 which does not cause background fogging and has an image storability.
The present invention relates to a heat-sensitive recording material having excellent color density, chemical resistance, and sticking.

[0002]

2. Description of the Related Art Conventionally, heat-sensitive recording materials have been used in a wide range of fields such as facsimile machines, printers, and labels because their recording devices are relatively inexpensive, and their recording devices are small and maintenance-free.

An electron-donating colorless dye and an electron-accepting compound are commonly used in this heat-sensitive recording material. For example, British Patent 2,140,449 and US Pat. No. 4,480,052
Nos. 4,436,920, JP-B-60-
23992, JP-A-57-179636 and 60-
Each of JP-A-123556 and JP-A-60-123557 describes these recording materials in detail.

[0004] However, in the heat-sensitive recording material, there are a problem that a fogging is caused by a solvent or the like, and a problem that a color forming body is discolored by a fat or oil or a chemical. For this reason, in the field of labels, slips, word processing paper, plotter paper, etc., thermal recording materials do not yet sufficiently satisfy the performance required in the market. Researches on improvements in color density and color sensitivity, storage stability of non-image areas and image areas, and the like have been actively conducted.

As the electron-accepting compound in the conventional recording material, various compounds such as bisphenol A, p-hydroxybenzoic acid esters, and bis- (4-hydroxyphenyl) sulfone are known. Also, there were problems in color density, color sensitivity, storage stability of non-image areas and image areas (weather resistance, chemical resistance, plasticizer resistance) and the like. For example, in the case of a heat-sensitive recording material using bis- (3-phenyl-4-hydroxyphenyl) sulfone, there is a problem that writing on a background portion of the recording material occurs when writing with a fluorescent pen.

[0006]

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 a high color density, a small amount of background fogging, excellent image storability, chemical resistance, and excellent production stability.

[0007]

Means for solving the above problems are as follows. That is, <1> a heat-sensitive recording material comprising a support provided with a thermosensitive coloring layer containing an electron-donating colorless dye, an electron-accepting compound and a sensitizer, wherein the thermosensitive coloring layer comprises the electron-accepting layer. N- (4-hydroxyphenyl) -p-toluenesulfonamide as the sensitizing compound, 2-benzyloxynaphthalene (X) and ethylenebisbehenamide (Y) as the sensitizer, And a mass ratio (X / Y) in the range of 95/5 to 40/60. <2> The thermosensitive coloring layer further includes an image stabilizer
1,1,3-tris (2-methyl-4-hydroxy-5
The heat-sensitive recording material according to <1>, containing at least one of -tert-butylphenyl) butane and 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexyl) butane. <3> With respect to 100 parts by mass of the electron-donating colorless dye,
<2> wherein the image stabilizer is used in an amount of 10 to 100 parts by mass.
The heat-sensitive recording material described in 1.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The heat-sensitive recording material of the present invention comprises a support provided with a thermosensitive coloring layer containing an electron-donating colorless dye, an electron-accepting compound and a sensitizer. Contains N- (4-hydroxyphenyl) -p-toluenesulfonamide as the electron accepting compound,
Further, it comprises 2-benzyloxynaphthalene (X) and ethylenebisbehenamide (Y) as a sensitizer in a mass ratio (X / Y) of 95/5 to 40/60. ing.

(Thermosensitive Coloring Layer) In the thermosensitive recording material of 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. I do. Further, the heat-sensitive recording material of the present invention preferably contains an image stabilizer in the heat-sensitive coloring layer in order to further improve the image storability, and if necessary, further contains a pigment, an adhesive, or an ultraviolet absorber. Etc. may be included.

(Electron-donating colorless dye) The electron-donating colorless dye of the present invention is not particularly limited, and any heat-sensitive coloring material generally known as a leuco dye can be arbitrarily applied. Among these electron donating colorless dyes, 2-anilino-3-methyl-6-diethylaminofluoran,
Be 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 Is preferred.
These may be used alone or in combination of two or more. The above 2-anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-
(N-ethyl-N-isoamylamino) fluoran and 2-anilino-3-methyl-6- (N-ethyl-N-
At least one selected from propylamino) fluoran
By using the seed as an electron-donating 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 needs to contain N- (4-hydroxyphenyl) -p-toluenesulfonamide as the 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, more 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.

The above-mentioned known electron-accepting compounds can be appropriately selected from known ones and used. In particular, from the viewpoint of suppressing background fogging, phenolic compounds or salicylic acid derivatives and polyvalent metal salts thereof are used. Is preferred. Examples of the phenolic compound include, for example, 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 -Ethyl butane, 4,
4'-sec-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.

[0016] The salicylic acid derivatives include 4-
Pantadecyl salicylic acid, 3-5-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, -Decyloxysalicylic acid, 4-dodecyloxysalicylic acid, 4-pentadecyloxysalicylic acid,
Octadecyloxysalicylic acid and the like, and 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. The volume average particle diameter is 1.0
It is preferable that the particle diameter is not more than μm, since the decrease in thermal sensitivity is suppressed. The volume average particle size can be easily measured by a laser diffraction type particle size distribution analyzer (for example, LA500 manufactured by Horiba, Ltd.) or the like.

(Sensitizer) The heat-sensitive recording material of the present invention requires that the above-mentioned thermosensitive coloring layer contains 2-benzyloxynaphthalene and ethylenebisbehenamide as sensitizers. The heat-sensitive recording material of the present invention has the heat-sensitive coloring layer,
By containing 2-benzyloxynaphthalene and ethylenebisbehenamide as sensitizers, the sensitivity can be significantly improved while suppressing the occurrence of background fog. Further, the mass ratio (X / Y) of the above-mentioned 2-benzyloxynaphthalene (X) to ethylenebisbehenamide (Y) is in the range of 95/5 to 40/60.
If the mass ratio is greater than 95/5, the sensitivity will be low, and if it is less 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 two sensitizers of the present invention is determined by the electron accepting compound N- (4-hydroxyphenyl).
It is preferably 75 to 200 parts by mass per 100 parts by mass of p-toluenesulfonamide, and 100 to 15 parts by mass.
More preferably, it is 0 parts by mass. 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 good.

In the heat-sensitive coloring layer according to the present invention, in addition to the above-mentioned 2-benzyloxynaphthalene and ethylenebisbehenamide, other sensitizers may be used in combination as long as the effects of the present invention are not impaired. As the other sensitizers described above,
Aliphatic monoamide, stearyl urea, p-benzylbiphenyl, di (2-methylphenoxy) ethane, di (2-methoxyphenoxy) ethane, β-naphthol-
(P-methylbenzyl) ether, α-naphthylbenzyl ether, 1,4-butanediol-p-methylphenyl ether, 1,4-butanediol-p-isopropylphenyl 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 methylbenzyl 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:
In order to further improve the image storability, it is preferable to include an image stabilizer in the thermosensitive coloring layer. Image stabilizers for this purpose include 1,1,3-tris (2-methyl-4-
Hydroxy-5-tert-butylphenyl) butane and 1,1,3-tris (2-methyl-4-hydroxy-5)
-Cyclohexyl) butane is preferably contained. When the image stabilizer is contained in the thermosensitive coloring layer, N- (4-hydroxyphenyl) -p-toluenesulfonamide as the electron accepting compound, 2-benzyloxynaphthalene and ethylenebisbehenic acid as sensitizers By interacting with the amide, it is possible to significantly improve the storage stability of the image area without deteriorating the background fog. The above 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 or in combination. When both are used, the mass ratio (α / β) is 80/20 to 80/20.
It is preferably in the range of 20/80, 60/40
More preferably, it is in the range of 40/60.

The total amount of the above two types of image stabilizers used in the present invention is preferably from the viewpoint of efficiently exhibiting the desired effects on background fog, image storability, chemical resistance and sticking properties. For 100 parts by mass, 1
The amount is preferably from 0 to 100 parts by mass, more preferably from 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
In addition to ert-butylphenyl) butane or 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexyl) butane, a known image stabilizer may be used in combination. 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 known image stabilizer,
Phenol compounds, especially hindered phenol compounds, are effective, for example, 1,1,3-tris (2-methyl-
4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-
Tris (2-methyl-4-hydroxy-tert-butylphenyl) 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.

(Inorganic Pigment) The thermosensitive coloring layer may contain an inorganic pigment, if necessary, as long as the effects of the present invention are 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 fogging and wear of the thermal head, and furthermore, it is possible to prevent adhesion of scum to the thermal head and improve sticking properties.

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 in 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. In this case, the saponification degree is preferably from 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, 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 a solvent and the viscosity of the coating solution does not increase, the preparation and coating are easy. In addition, the said degree of polymerization refers to the average degree of polymerization obtained 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 other polyvinyl alcohol is used in combination, the sulfo-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, and acetoacetyl-modified vinyl alcohol are preferably contained in an amount of 10% by mass or more based on the total mass of each polyvinyl alcohol. More preferably, the content is 20% by mass or more.

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

In the present invention, the dispersion of the colorless electron-donating 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 preferably a compound that dissolves in water at 25 ° C. in an amount of 5% 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. The coating amount of the thermosensitive coloring layer is not particularly limited, but is usually preferably about ² to 7 g / m ² in terms of dry mass.

<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 is preferably provided on a support, and preferably has a pigment and a binder as main components. As the pigment, any of general inorganic and organic pigments can be used. In particular, an oil-absorbing pigment having an oil absorption of 40 ml / 100 g (cc / 100 g) or more specified in JIS-K5101 is preferable. 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-K5101 Calcined kaolin having a prescribed oil absorption of 70 to 80 ml / 100 g 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, 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, 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 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 to 0.8,
Carboxymethyl cellulose having a weight average molecular weight of 20,000 to 200,000 is 1 to 5% by mass based on the pigment,
Preferably, 1 to 3% by mass may be added.

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 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 -Carboxyl group-containing polymers such as acrylic acid copolymers, vinyl acetate-acrylamide copolymers, methyl cellulose, carboxymethyl cellulose, hydroxymethyl cellulose, gelatins, arabic gum, casein, polyacrylamide derivatives, polyvinylpyrrolidone, and styrene-butadiene rubber latex , Acrylonitrile-butadiene rubber latex, methyl acrylate-butadiene rubber latex,
A vinyl acetate emulsion or the like is 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.

Thus, in the present invention, chemical resistance and image storability are improved by adding a surfactant to the coating solution for the protective layer. 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 0.1 to the solid content of the coating solution for the protective layer.
1-5 mass% is preferable, and 0.5-3 mass% is more preferable. In addition, the coating liquid for the protective layer includes a lubricant, an antifoaming agent,
A fluorescent whitening agent, a colored organic pigment, and the like can be added within a range that does not impair the effects of the present invention. 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]

The present invention will be described in detail with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, “parts” and “%” in the examples 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.

<Preparation of Thermosensitive Recording Material> (Example 1) (1) Preparation of Solution A 10 parts of 2-anilino-3-methyl-6-diethylaminofluoran (an electron-donating colorless dye) and polyvinyl alcohol ( PVA-105, manufactured by Kuraray Co., Ltd.) 2.5
% Solution was mixed while being dispersed by a sand mill to obtain a dispersion A having an average particle diameter of 0.7 μm.

(2) Preparation of Solution B 20 parts of N- (4-hydroxyphenyl) -p-toluenesulfonamide (electron accepting compound) and 100 parts of a 2.5% solution of polyvinyl alcohol (PVA-105) Were mixed while being dispersed by a sand mill, to obtain a dispersion B having an average particle diameter of 0.7 μm.

(3) Preparation of Solution C 20 parts of 2-benzyloxynaphthalene (sensitizer),
100 parts of a 2.5% solution of polyvinyl alcohol (PVA-105) was mixed while being dispersed with a ball mill,
A dispersion C having an average particle size of 0.7 μm was obtained.

(4) Preparation of Solution D 10 parts of ethylenebisbehenamide (sensitizer) and 40 parts of a 2.5% solution of polyvinyl alcohol (PVA-105) were mixed while being dispersed by a sand mill. A dispersion D having an average particle diameter of 0.7 μm was obtained.

(5) Preparation of Solution E 1,1,3-tris (2-methyl-4-hydroxy-5
-Tert-butylphenyl) butane (image stabilizer) and polyvinyl alcohol (PVA-105) 2.
25 parts of the 5% solution were mixed while being dispersed by a sand mill to obtain a dispersion D having an average particle diameter of 0.7 μm.

(6) Preparation of Solution F 40 parts of light calcium carbonate, 1 part of sodium polyacrylate, and 60 parts of water were mixed while being dispersed by a sand mill, and a pigment having an average particle diameter of 2.0 μm was obtained. Dispersion F was obtained.

(7) Preparation of Thermosensitive Coloring Layer Solution 60 parts of Solution A, 120 parts of Solution B, 120 parts of Solution C, 50 parts of Solution D, 30 parts of Solution E, 101 parts of Solution F, zinc stearate (30% 15 parts of paraffin wax (30% dispersion)
Liquid), 15 parts of sodium dodecylbenzenesulfonate (25 parts)
% Solution) was prepared to prepare a coating solution for the thermosensitive coloring layer.

(8) Preparation of Coating Solution for Support Undercoat Layer The following components were mixed by stirring with a dissolver, and the mixture was mixed with SBR20.
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 110 parts

(9) Formation of heat-sensitive recording material The base undercoat layer coating solution was coated on a base paper weighing 50 g / m ² by a blade coater so that the coating amount after drying was 8 g / m ² . It dried and the undercoat base paper was produced. Then, the coating solution for a heat-sensitive coloring layer was applied to the surface of the undercoat layer by a curtain coater such that the coating amount after drying was 4.5 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) Example 2 was repeated in the same manner as in Example 1 except that the liquid C was changed to 150 parts and the liquid D was changed to 25 parts. The heat-sensitive recording material was obtained.

Example 3 Example 7 was repeated in the same manner as in Example 1 except that 165 parts of solution C and 12.5 parts of solution D were used in the preparation of (7) the thermosensitive coloring layer solution. 3 was obtained.

(Example 4) The procedure of Example 1 was repeated, except that (7) the thermosensitive coloring layer liquid was prepared in such a manner that the liquid C was 75 parts and the liquid D was 87.5 parts. A heat-sensitive recording material according to Example 4 was obtained.

Example 5 In the preparation of Solution (5) of Example 1, 1,1,3-tris (2-
Instead of methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-cyclohexyl)
A heat-sensitive recording material according to Example 5 was obtained in the same manner as in Example 1, except that butane was used.

Example 6 The heat-sensitive recording material according to Example 6 was prepared in the same manner as in Example 1 except that in Example (7), the preparation of the thermosensitive coloring layer liquid, the E solution was changed to 10 parts. Obtained.

Example 7 The heat-sensitive recording material according to Example 7 was prepared in the same manner as in Example 1 except that 70 parts of Solution E was used in the preparation of (7) Thermosensitive Coloring Layer Solution of Example 1. Obtained.

Example 8 A thermosensitive recording material according to Example 8 was obtained in the same manner as in Example 1 except that in the preparation of the thermosensitive coloring layer solution (7) of Example 1, the liquid E was not used. .

(Example 9) Example 9 was repeated in the same manner as in Example 1 except that in the formation of (8) the heat-sensitive recording material of Example 1, coating was performed with an air knife coater instead of using a curtain coater. Was obtained.

Example 10 In Example 6, before performing the calendering treatment on the formed heat-sensitive coloring layer, the following coating solution for a protective layer was further applied on the heat-sensitive 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) Comparative Example 1 was prepared in the same manner as in Example 1 except that in the preparation of (7) the thermosensitive coloring layer liquid of Example 1, the liquid C was removed and the liquid D was changed to 60 parts. The heat-sensitive recording material was obtained.

Comparative Example 2 Comparative Example 2 was carried out in the same manner as in Example 1 except that 36 parts of solution C and 120 parts of solution D were used in the preparation of (7) thermosensitive coloring layer solution of Example 1. Was obtained.

(Comparative Example 3) In the preparation of solution (2) B in Example 1, instead of the electron accepting compound N- (4-hydroxyphenyl) -p-toluenesulfonamide,
A heat-sensitive recording material according to Comparative Example 3 was obtained in the same manner as in Example 1, except that 2,2-bis (4-hydroxyphenyl) propane (so-called “bisphenol A”) was used.

(Comparative Example 4) In the same manner as in Example 1 except that the liquid C was changed from 120 parts to 170 parts without using the liquid D in the preparation of the thermosensitive coloring layer liquid of Example 1 (7). Thus, a heat-sensitive recording material according to Comparative Example 4 was obtained.

The following evaluation tests were carried out on the heat-sensitive recording materials obtained in Examples 1 to 10 and Comparative Examples 1 to 4, and the results are shown in Table 1.

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

(2) Background Coverage The heat-sensitive recording materials obtained in the above Examples and Comparative Examples were
The background after standing for 24 hours in an environment of 60 ° C. and a relative humidity of 20% was measured with a Macbeth reflection densitometer (RD-918). Here, the lower the numerical value, the better the background covering.

(3) Image Preservability The thermosensitive recording materials obtained in the above Examples and Comparative Examples 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 of 20 ° C. and 20% relative humidity. Thereafter, the image density was measured with a Macbeth reflection densitometer (RD-918), and the residual ratio with respect to the image density of the product before leaving the image recorded under the same apparatus and conditions as in the above (1) was calculated from the following equation. . Here, the higher the numerical value, the better the image storability. Image preservability (%) = (image density after standing / image density of product before standing) × 100

(4) Chemical resistance Under the same conditions as described above, printing was performed on the heat-sensitive recording materials obtained in Examples and Comparative Examples, and the printed and non-printed portions were marked with a yellow marker pen (manufactured by Zebra Corp., Name: PE
N2) was marked and left for 24 hours, then visually observed and evaluated according to the following criteria. …: No decoloration is observed, and the printed portion is clearly observed. Δ: A slight decrease in density is observed in the printed portion, but the printed portion can be read. ×: The printed portion is completely erased.

(5) Sticking property A FAX (SFX85) manufactured by Sanyo Electric Co., Ltd. Using the three charts, printing was performed on the heat-sensitive recording materials obtained in the above Examples and Comparative Examples. The printing sound at that time was observed, and the overexposed state was visually observed, and evaluated according to the following criteria. …: There is no noise other than the print sound, and no overexposure is observed. Δ: There is a slight noise sound, and overexposure is observed. ×: Clear noise (adhesion sound) is generated, and many overexposures are observed.

[0088]

[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 high in sensitivity, have less fogging, and are excellent in image preservability of color-formed images, chemical resistance and sticking properties. I understand. Examples 1, 6, 7, 8
From the comparison, it was found that when the image stabilizer was contained, the image storability was excellent. In particular, from a comparison between Examples 1 and 6, it was found that when the amount of the image stabilizer to be used is 20 parts by mass or more with respect to the electron-donating colorless dye, the image preservability and the chemical resistance are further excellent. Similarly, Examples 1 and 7
From the comparison, when the amount used is 100 parts by mass or less,
It was found that the background covering and the sticking property were further excellent. Further, from a comparison between Examples 1 and 9, it was found that the application of the heat-sensitive layer using a curtain coater was superior in sensitivity 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, Table 1 shows that Comparative Example 1 in which 2-benzyloxynaphthalene was not used and Comparative Example 4 in which ethylene bisbehenamide was not used showed sensitivity,
It turned out that image preservability and chemical resistance were inferior. 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 also inferior in sensitivity, background fogging, image preservability, and chemical resistance. . Further, Comparative Example 4 using bisphenol A as the electron-accepting compound was slightly inferior in image storability and sticking property, and remarkably inferior in chemical resistance.

[0091]

According to the present invention, it is possible to provide a heat-sensitive recording material which has little background fogging and is excellent in image storability, coloring, chemical resistance and sticking.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hirofumi Mitsuo 200 Nakanakazato, Fujinomiya-shi, Shizuoka Fuji Photo Film Co., Ltd. F-term (reference) 2H026 AA07 BB02 BB25 DD02 DD12 DD45 FF01

Claims (3)

[Claims] 1. A thermosensitive recording material comprising a support having thereon a thermosensitive coloring layer containing an electron-donating colorless dye, an electron-accepting compound and a sensitizer, wherein said thermosensitive coloring layer comprises: N- (4-hydroxyphenyl) -p-toluenesulfonamide as the hydrophilic compound; and 2-benzyloxynaphthalene (X) and ethylenebisbehenamide (Y) as the sensitizer. And the mass ratio (X / Y) is 95/5 to 40/60.
A heat-sensitive recording material. 2. The thermosensitive coloring layer further comprises 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane and 1,1,3,
2. The heat-sensitive recording material according to claim 1, which comprises at least one of 3-tris (2-methyl-4-hydroxy-5-cyclohexyl) butane. 3. The heat-sensitive recording material according to claim 2, wherein the image stabilizer is used in an amount of 10 to 100 parts by mass with respect to 100 parts by mass of the electron-donating colorless dye.