JP2012245630A - Thermosensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermosensitive recording material having higher color optical density, where a color development part and a non-color development part with a pattern formed thereon is in an appropriate range, while reducing deposits on a thermal head, and to provide a method for forming patterns using the same.SOLUTION: The thermosensitive recording material includes a thermosensitive coloring layer containing, on a support: an electron-donating dye precursor; an electron-accepting compound that reacts with the electron-donating dye precursor to develop a color; a calcium carbonate aggregate; and colloid calcium carbonate.

Description

  The present invention relates to a heat-sensitive recording material.

  In general, a heat-sensitive recording material is used in a wide range because it is relatively inexpensive, its recording device is compact, and maintenance-free. As such a heat-sensitive recording material, a material provided with a heat-sensitive coloring layer containing an electron-donating dye precursor and an electron-accepting compound that develops a colorless dye on a support is generally widely used. Under such circumstances, recently, the sales competition of the heat-sensitive recording material has intensified, and the heat-sensitive recording material is required to have a higher function that is differentiated from the conventional function. In order to meet these requirements, the sensitivity is high, the color density is high, and the glossiness of the color-formed and non-color-developed areas after pattern formation is in an appropriate range that does not become too high. Research on improvement of a heat-sensitive recording material with less adhesion (hereinafter also referred to as “head dirt”) has been conducted earnestly.

For example, a thermal recording material in which columnar calcium carbonate and fine particle calcium carbonate bundles are contained in a specific amount in the thermal coloring layer to reduce IC pen head wear and adhesion of debris to the line thermal head (Patent Document) 1), and a heat-sensitive recording material in which an aggregate of amorphous silica and a basic pigment such as light calcium carbonate are contained to prevent head contamination is known (see Patent Document 2).
However, these heat-sensitive recording materials are not satisfactory in all of sensitivity, color density of the recorded pattern, glossiness of the colored and non-colored areas after pattern formation, and head contamination.

Japanese Patent No. 3060630 International Patent Publication No. WO2006 / 070594

  An object of the present invention is a high sensitivity, a high color density of a pattern recorded by a thermal head, an appropriate range in which the glossiness of a color-development portion and a non-color-development portion after pattern formation is not too high, and It is an object of the present invention to provide a heat-sensitive recording material with less residue attached to a thermal head and a pattern forming method.

The present invention for solving the above problems is as follows.
<1> A thermosensitive material comprising an electron donating dye precursor, an electron accepting compound that reacts with the electron donating dye precursor to develop a color, a calcium carbonate aggregate, and colloidal calcium carbonate on a support. A heat-sensitive recording material provided with a coloring layer.
<2> The heat-sensitive recording material according to <1>, wherein the calcium carbonate aggregate is an aggregate having a volume average particle size of 1.0 μm to 5.0 μm and an oil absorption of 40 ml / 100 g to 80 ml / 100 g.
<3> The thermosensitive recording material according to <1> or <2>, wherein the colloidal calcium carbonate has a volume average primary particle size of 30 nm to 300 nm and a specific surface area of 10 m ² / g to 30 m ² / g.

<4> The heat-sensitive recording material according to any one of claims 1 to 3, wherein a particle shape of the calcium carbonate aggregation is a spindle shape or a granular shape.
<5> The heat-sensitive recording material according to any one of <1> to <4>, wherein the primary particle shape of the colloidal calcium carbonate is a cubic shape.
<6> The ratio of the calcium carbonate aggregate to the colloidal calcium carbonate is in the range of 20/80 to 80/20 in terms of mass ratio, and the total content of both is 25% by mass in the thermosensitive coloring layer. The thermosensitive recording material according to any one of <1> to <5>, which is in the range of -75% by mass.
<7> The electron donating dye precursor according to any one of <1> to <6>, comprising at least one compound selected from fluoran compounds represented by the following general formula (I): Thermal recording material.
Formula (I):

In the general formula (I), R _{1 to} R ₅ each independently represents a hydrogen atom, an alkyl group, an allyl group, or a phenyl group. These groups may be further substituted with at least one substituent selected from halogen, alkyl group, allyl group, hydroxy group, alkoxy group, acyl group, amino group, substituted amino group and nitro group. R ₁ and R ₂ , or R ₄ and R ₅ may be bonded to each other to form a ring.

<8> The heat-sensitive recording material according to any one of <1> to <7>, wherein the electron-accepting compound is at least one selected from compounds represented by the following general formula (II).
Formula _{(II): R 6 -Ph-} SO 2 R 7
In the general formula (II), R ₆ represents a hydroxyl group or an alkyl group, and R ₇ represents —Ph, —NH—Ph, —Ph—OR _8, or —NH—CO—NH—Ph. R ₈ represents an alkyl group. Ph represents a phenyl group which may be substituted with a substituent containing —SO ₂ R ₇ .
<9> The heat-sensitive recording material according to any one of <1> to <8>, wherein the electron-accepting compound is 4-hydroxybenzenesulfonanilide.
<10> The thermosensitive recording material according to any one of <1> to <9>, wherein the thermosensitive coloring layer further contains a binder.
<11> The thermosensitive recording material according to any one of <1> to <10>, wherein the thermosensitive coloring layer further contains a sensitizer.

<12> Pattern formation in which the heat-sensitive color forming layer of the heat-sensitive recording material according to any one of <1> to <11> is heated in a pattern with a thermal head, and the heat-sensitive color developing layer in the heated portion is colored. Method.

  According to the present invention, the sensitivity is high, the color density of the pattern recorded by the thermal head is high, the glossiness of the color development part and the non-color development part after pattern formation is in an appropriate range that is not too high, and Provided are a heat-sensitive recording material and a pattern forming method with less residue attached to a thermal head.

  A heat-sensitive recording material according to the present invention comprises an electron donating dye precursor, an electron accepting compound that causes the electron donating dye precursor to develop color when heated, a calcium carbonate aggregate, and colloidal calcium carbonate on a support. And a thermosensitive coloring layer. These will be described below.

(Support)
A conventionally known support can be used as the support. Specific examples include a paper support such as high-quality paper, a support such as a coated paper obtained by applying a resin or a pigment to paper, a resin-laminated paper, an undercoat base paper having an undercoat layer, a synthetic paper, or a plastic film. From the viewpoint of thermal head matching characteristics, an undercoat base paper having an undercoat layer is preferred, and an undercoat base paper provided with an undercoat layer containing an oil-absorbing pigment using a blade coater is particularly preferred.

  As the support, a smooth support having a smoothness defined by JIS-P8119 of 300 seconds or more is preferable from the viewpoint of dot reproducibility.

It is preferable to have an undercoat layer between the support and the thermosensitive coloring layer. As such an undercoat layer, a layer mainly composed of a pigment and a binder is preferable.
As the pigment, all of general inorganic and organic pigments can be used, and an oil-absorbing pigment having an oil absorption specified by JIS-K5101 of 40 ml / 100 g (cc / 100 g) or more is particularly preferable. Examples of the oil-absorbing pigment include calcined kaolin, aluminum oxide, magnesium carbonate, calcium carbonate, amorphous silica, calcined diatomaceous earth, aluminum silicate, aluminomagnesium silicate, aluminum hydroxide and the like. Particularly preferred is calcined kaolin having an oil absorption of 70 to 80 ml / 100 g.

Examples of the binder used for the undercoat layer include water-soluble polymers and aqueous binders.
Examples of the water-soluble polymer include starch, polyvinyl alcohol, polyacrylamide, carboxymethyl alcohol, methyl cellulose, and casein.
Synthetic rubber latex or synthetic resin emulsion is generally used as the aqueous binder, and examples thereof include styrene-butadiene rubber latex (SBR), acrylonitrile-butadiene rubber latex, methyl acrylate-butadiene rubber latex, and vinyl acetate emulsion. .
These may be used singly or in combination of two or more.
The amount of the binder used is determined in consideration of the film strength of the coating layer and the thermal sensitivity of the thermosensitive coloring layer, but is 3 to 100% by mass, preferably 5 to 50%, based on the pigment added to the undercoat layer. % By mass, particularly preferably 8 to 15% by mass. In addition, a wax, a decoloring inhibitor, a surfactant and the like may be added to the undercoat layer.

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 blade coating using a blade coater is particularly preferable. Furthermore, you may use it, performing a smoothing process, such as a calendar, as needed.
The method using the blade coater is not limited to the coating method using a bevel type or bent type blade, but also includes a rod blade coating method and a bill blade coating method, and is not limited to an off-machine coater. You may apply with the installed on-machine coater. In addition, in order to give the fluidity | liquidity at the time of blade coating and to obtain the outstanding smoothness and surface shape, the etherification degree is 0.6-0.8 and the weight average molecular weight is 20000-200000 in the coating liquid for undercoat layers. Carboxymethyl cellulose may be added in an amount of 1 to 5% by mass, preferably 1 to 3% by mass, based on the pigment.

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

(Electron-donating dye precursor)
The electron donating dye precursor is a substantially colorless compound, and has a property of coloring by donating electrons or accepting protons such as acids.
Examples of the electron-donating dye precursor used as the color forming component of the heat-sensitive recording material of the present invention include phthalide compounds, fluoran compounds, phenothiazine compounds, indolyl phthalide compounds, which are known for thermal paper and pressure-sensitive paper, Various compounds such as leucooramine compounds, rhodamine lactam compounds, triphenylmethane compounds, triazene compounds, spiropyran compounds, pyridine compounds, pyrazine compounds, fluorene compounds, and the like can be mentioned. System compounds are preferred.

  Examples of the fluoran compound include U.S. Pat. Nos. 3,624,107, 3,627,787, 3,641,011, and 3,462,828. No. 3,681,390, 3,920,510, 3959,571, and the like.

As the electron-donating dye precursor of the present invention, it is particularly preferable to use at least one fluoran compound represented by the following general formula (I) to increase color density and suppress background fogging, and to maintain image storability and resistance. It is preferable for improving chemical properties.
Formula (I)

In general formula (I), R < ₁ > -R < ₅ > represents a hydrogen atom, an alkyl group, an allyl group, or a phenyl group each independently. These groups may be further substituted with at least one substituent selected from halogen, alkyl group, allyl group, hydroxy group, alkoxy group, acyl group, amino group, substituted amino group and nitro group. R ₁ and R ₂ , or R ₄ and R ₅ may be bonded to each other to form a ring.

  Specific examples of the fluorane compound represented by the general formula (I) include 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-dibutylaminofluorane, 2- (2,4-Xylidino) -3-methyl-6-diethylaminofluorane, 2- (2,6-xylidino) -3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-N- Ethyl-N-isopentylaminofluorane, 2-anilino-3-methyl-6-dipentylaminofluorane, 2-anilino-3-methyl-6- (N-ethyl-Np-tolylamino) fluorane, 2- Anilino-3-methyl-6- (N-ethyl-N-ethoxypropylamino) fluorane, 2-m-trifluoromethylanilino-6-diethylamino Oran, 2- (3-Toluidino) -3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-N-tetrahydrofurfurylaminofluorane, 2-anilino-3-methyl -6-N-cyclohexyl-N-methylaminofluorane, 2-anilino-3-methyl-6-Nn-propyl-N-methylaminofluorane, 2-anilino-3-methyl-6- (N- And ethyl-N-isoamylamino) fluorane, 2-anilino-3-methyl-6- (N-ethyl-N-propylamino) fluorane, and the like. These fluoran compounds may be used alone or in combination of two or more.

In the heat-sensitive recording layer of the present invention, a fluoran compound other than the fluoran compound represented by the general formula (I) may be used.
Examples of other fluorane compounds include 3-di (n-butylamino) -6-methyl-7-anilinofluorane and 3-di (n-pentylamino) -6-methyl-7-anilinofluor. Oran, 3- (Nn-hexyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3- [N- (3-ethoxypropyl) -N-ethylamino) -6-methyl- 7-anilinofluorane, 3-di (n-butylamino) -7- (2-chloroanilino) fluorane, 3-diethylamino-7- (2-chloroanilino) fluorane, 3- (N-cyclohexyl-N-methylamino) ) -6-methyl-7-anilinofluorane and the like, and these may be used in combination with those of the general formula (I).

The coating amount of the electron donating dye precursor is preferably 0.1 to 1.0 g / m ² in terms of dry mass, and 0.2 to 0.5 g / m ² from the viewpoint of further improving the color density and the background covering. m ² is more preferable.

(Electron-accepting compound)
The thermosensitive coloring layer according to the present invention contains at least one electron-accepting compound that reacts with the electron-donating dye precursor to cause color development. As an electron-accepting compound, it can select suitably from a conventionally well-known thing, For example, a phenolic compound, a salicylic acid derivative, and its polyvalent metal salt are preferable.
As an electron-accepting compound in the present invention, in addition to excellent gradation reproducibility, it is possible to increase sensitivity while maintaining low background fogging and suppressing print tailing, and long-term storability of image formation (image storability) ), Chemical resistance, ink jet suitability, and thermal head head matching properties can be improved at the same time, it is preferably at least one compound represented by the following general formula (II).

Formula _{(II): R 6 -Ph-} SO 2 R 7
In the general formula (II), R ₆ represents a hydroxyl group or an alkyl group, and R ₇ represents —Ph, —NH—Ph, —Ph—OR _8, or —NH—CO—NH—Ph. R ₈ represents an alkyl group. Ph represents a phenyl group which may be substituted with a substituent containing —SO ₂ R ₇ .

As the alkyl group represented above, an alkyl group having 1 to 3 carbon atoms is preferable, and for example, a methyl group, an ethyl group, an isopropyl group, and the like are preferable. Among these, as R ₆ , a hydroxyl group is particularly preferable.

R ₈ represents an alkyl group, and the alkyl group is preferably an alkyl group having 1 to 4 carbon atoms, and particularly preferably an isopropyl group. Ph may be a substituted phenyl group in which the phenyl group is substituted with “substituent containing —SO ₂ R ₇ ”, and R ₇ of the substituent is further substituted with a methyl group, a halogen atom, or the like. May be. Examples of the substituent include —CH ₂ —C ₆ H ₅ —NHCONH—SO ₂ —C ₆ H ₅ , —SO ₂ —C ₆ H ₅ , —SO ₂ —C ₆ H ₄ —CH ₃ , —SO ₂ —. C ₆ H ₄ -Cl, and the like. Among these, as R ₇ , —NHPh is preferable, and —NH—C ₆ H ₅ is particularly preferable.

  Preferable specific examples of the compound represented by the general formula (II) include 4-hydroxybenzenesulfonanilide (= pN-phenylsulfamoylphenol) and pN- (2-chlorophenyl) sulfamoylphenol. P-N-3-tolylsulfamoylphenol, pN-2-tolylsulfamoylphenol, pN- (3-methoxyphenyl) sulfamoylphenol, pN- (3-hydroxyphenyl) Sulfamoylphenol, pN- (4-hydroxyphenyl) sulfamoylphenol, 2-chloro-4-N-phenylsulfamoylphenol, 2-chloro-4-N- (3-hydroxyphenyl) sulfa Moylphenol, 4'-hydroxy-p-toluenesulfonanilide, 4,4'-bis (p-tolu Emissions sulfonylamino carbonylamino) diphenylmethane (= BTUM), 4- hydroxy-4'-isopropoxydiphenylsulfone, 2,4-bis (phenylsulfonyl) phenol, and the like. However, the present invention is not limited to these.

  Among the electron-accepting compounds represented by the general formula (II), 2,4-bis (phenylsulfonyl) phenol, 4-hydroxybenzenesulfonanilide, 4- in terms of the balance between image storability and background fogging. Hydroxy-4'-isopropoxydiphenyl sulfone is preferred.

The electron-accepting compound is also preferably any one selected from salicylic acid derivatives and polyvalent metal salts thereof.
Examples of the salicylic acid derivative include 4-pentadecylsalicylic 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-cyclohexyloxysartyl Acid, 4-decyloxysalicylic acid, 4-dodecyloxysalicylic acid, 4-pentadecyloxysalicylic acid, 4-octadecyloxysalicylic acid,

4- (n-pentanoylamino) salicylic acid, 4- (n-hexanoylamino) salicylic acid, 4- (n-octanoylamino) salicylic acid, 4- (hexadecanoylamino) salicylic acid, 4- (N′-n) -Butylcarbamoylamino) salicylic acid, 4- (N'-n-hexylcarbamoylamino) salicylic acid, 4- (N'-n-octylcarbamoylamino) salicylic acid, 4- (N'-hexadecylcarbamoylamino) salicylic acid, 4- (N-octyloxycarbonylamino) salicylic acid, 4- (n-nonyloxycarbonylamino) salicylic acid, 4- (n-decyloxycarbonylamino) salicylic acid, 4- (n-undecyloxycarbonylamino) salicylic acid, 4- ( n-dodecyloxycarbonylamino) salicylic acid, 4- (n-tri Decyloxycarbonylamino) salicylic acid, 4- (n-tetradecyloxycarbonylamino) salicylic acid, 4- (n-pentadecyloxycarbonylamino) salicylic acid, 4- (n-hexadecyloxycarbonylamino) salicylic acid, 4- (n -Octadecyloxycarbonylamino) salicylic acid, 3- (n-octyloxycarbonylamino) salicylic acid, 3- (n-nonyloxycarbonylamino) salicylic acid, 3- (n-decyloxycarbonylamino) salicylic acid, 3-
(N-undecyloxycarbonylamino) salicylic acid, 3- (n-dodecyloxycarbonylamino) salicylic acid, 3- (n-tridecyloxycarbonylamino) salicylic acid, 3- (n-tetradecyloxycarbonylamino) salicylic acid, 3 -(N-pentadecyloxycarbonylamino) salicylic acid, 3- (n-hexadecyloxycarbonylamino) salicylic acid, 3- (n-octadecyloxycarbonylamino) salicylic acid, 5- (n-octyloxycarbonylamino) salicylic acid, 5 -(N-nonyloxycarbonylamino) salicylic acid, 5- (n-decyloxycarbonylamino) salicylic acid, 5- (n-undecyloxycarbonylamino) salicylic acid, 5- (n-dodecyloxycarbonylamino) salicylic acid, 5- n-tridecyloxycarbonylamino) salicylic acid, 5- (n-tetradecyloxycarbonylamino) salicylic acid, 5- (n-pentadecyloxycarbonylamino) salicylic acid, 5- (n-hexadecyloxycarbonylamino) salicylic acid, 5 Examples include-(n-octadecyloxycarbonylamino) salicylic acid.

  Examples of the polyvalent metal salt of the salicylic acid derivative include zinc, aluminum, calcium, copper, and lead salts of the salicylic acid derivative.

  The content of the electron-accepting compound in the heat-sensitive recording layer is preferably 50% by mass to 400% by mass and more preferably 100% by mass to 300% by mass with respect to the mass of the electron donating dye precursor.

  The electron-accepting compound is contained in a particle-dispersed state in the thermosensitive coloring layer. The particle diameter of the dispersed particles in such a particle dispersion state is preferably 2.0 μm or less in terms of volume average particle diameter, and more preferably 0.5 μm to 1.2 μm. It is preferable that the volume average particle size is 2.0 μm or less because a heat-sensitive recording material having high heat sensitivity can be obtained. Note that the lower limit of the volume average particle size is preferably 0.5 μm or more because a heat-sensitive recording material free from the occurrence of background fogging can be obtained. Here, the volume average particle diameter can be easily measured by a laser diffraction / scattering particle size distribution analyzer (for example, “LA500” manufactured by Horiba, Ltd.).

(Calcium carbonate aggregate)
The calcium carbonate aggregate is formed by collecting a large number (at least 50) of primary particles of calcium carbonate, and the aggregate has a spindle shape (here, the spindle shape is a cylindrical shape with both ends narrowed). Shape means) or granular (here, granular means hexahedron or sphere) is excellent in the property of adsorbing the colored product of the electron-donating dye precursor and has a high definition image. It is preferable from the standpoint of obtaining the effect of being obtained.
Moreover, it is preferable also from the point that the printing ink in the case of additionally printing on a thermosensitive recording layer is absorbed, and the printing image without a blur is obtained.
The aggregate is preferably obtained by chemically aggregating primary particles of calcium carbonate. Here, the chemical agglomeration specifically means an agglomeration obtained by adjusting the reaction conditions at the time of calcium carbonate production.
The average particle diameter of the primary particles forming the aggregate (hereinafter also referred to as “average primary particle diameter”) is suitably in the range of 50 nm to 500 nm in terms of volume average.
The calcium carbonate aggregate is selected from a range in which the volume average particle diameter of the secondary particles is 1.0 μm or more and 5.0 μm or less, and the color development density is high, and the glossiness in the color development part and the non-color development part is in an appropriate range. It is preferable because it is easy to.
Further, the calcium carbonate aggregate preferably has an oil absorption amount (oil absorption amount of boiled linseed oil) of 40 ml / 100 g or more and 80 ml / 100 g or less because of its excellent property of adsorbing the colored product of the electron donating dye precursor. .
Further, it is preferable from the viewpoint that a printing-free image can be obtained on the heat-sensitive recording layer by absorbing printing ink in the case of additionally printing.
The shape of the aggregate, the average particle diameter, and the average primary particle diameter can be specified, measured, and calculated from an electron micrograph.
Such a calcium carbonate aggregate can be obtained as a commercial product. For example, Shiraishi Hana PZ (cubic calcium carbonate aggregate), Tunex-E (spindle-shaped calcium carbonate aggregate), Universe 70 (spindle-shaped calcium carbonate aggregate), Tunex FF (spindle shape) Calcium carbonate aggregates).

  The calcium carbonate aggregate is contained in the thermosensitive coloring layer in the range of 10% by mass to 80% by mass with respect to the total weight, so that the coloring density is high and the glossiness in the color developing part and the non-color developing part is appropriate. It is preferable from the viewpoint that it is easy to be within the range and the head is less dirty.

(Colloidal calcium carbonate)
Colloidal calcium carbonate having a primary particle size of 30 nm to 300 nm in terms of volume average is suitable, and the aggregation of primary particles is extremely small (the number of aggregates of 20 or more primary particles is 30% or less of the total number). ) Is appropriate. Further, colloidal calcium carbonate is preferable in the range where the specific surface area is 10 m ² / g or more and 30 m ² / g or less because a heat sensitive recording material with high sensitivity and less head contamination can be obtained. Such colloidal calcium carbonate can be obtained as a commercial product. For example, (a primary particle is cubic shape, an average primary particle diameter of 150 nm, a specific surface area of ^{10.0m 2 /g~14.0m 2 / g) Brilliant} -15 manufactured by Shiraishi Kogyo Co., Ltd., include Brilliant-1500, etc. It is done.
The average primary particle diameter of colloidal calcium carbonate can be measured and calculated from an electron micrograph.

The ratio of the calcium carbonate aggregate to the colloidal calcium carbonate is suitably in the range of 20/80 to 80/20 by mass ratio. In particular, the range of 35/65 to 65/35 is preferable in terms of high sensitivity and high density.
Moreover, it is suitable for the total amount of these both content to exist in the range of 25 mass%-75 mass% in the said thermosensitive coloring layer, and it exists in the range of 35 mass%-65 mass%. As a result, a heat-sensitive recording material is obtained that is less likely to cause head contamination.
Further, it is also preferable from the viewpoint that an image without bleeding can be obtained by absorbing printing ink in the case of additionally performing printing on the heat-sensitive recording layer.
Since the heat-sensitive recording material according to the present invention contains calcium carbonate aggregates and colloidal calcium carbonate in the heat-sensitive color developing layer, the space between the former aggregates fills the space between the latter colloidal calcium carbonates in the heat-sensitive color developing layer. As a result, it is considered that a heat-sensitive recording material having high sensitivity, high color density, and little head contamination can be obtained.

In addition to the above, the thermosensitive coloring layer may further include a binder, a sensitizer, an inorganic pigment other than the two types of calcium carbonate (hereinafter referred to as “other inorganic pigment”), an image stabilizer, an adhesive, an ultraviolet ray. At least one additive such as an absorbent may be contained depending on the purpose.
Hereinafter, these additives will be described.

(binder)
In general, the electron-donating dye precursor and the electron-accepting compound are both contained in the thermosensitive coloring layer in the form of particles dispersed. In order to maintain such a dispersed form stably and to facilitate the preparation of the coating solution for the thermosensitive coloring layer in such a dispersed state, and further to improve the film strength of the thermosensitive coloring layer, a binder is used. It is advantageous to use.

  Specific examples of the water-soluble binder include polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, starches (including modified starch), gelatin, gum arabic, casein, and saponified styrene-maleic anhydride copolymer.

  In addition, styrene-butadiene copolymer, vinyl acetate copolymer, acrylonitrile-butadiene copolymer, methyl acrylate-butadiene copolymer, synthetic polymer latex binder such as polyvinylidene chloride, etc. are mentioned. These water-soluble binders can also be used in combination.

  In order to disperse the electron-donating dye precursor and the electron-accepting compound in the form of particles, they are dispersed together with a dispersing agent and an aqueous binder solution by agitating / pulverizing machine such as a ball mill, an attritor, and a sand mill, and then mixed. The dispersion liquid and a separately prepared dispersion liquid of calcium carbonate aggregate and colloidal calcium carbonate are mixed to prepare a coating liquid for the thermosensitive coloring layer. In the coating solution, a binder and various additives are further added as necessary.

(Sensitizer)
The heat-sensitive recording material of the present invention may contain a known sensitizer in the heat-sensitive coloring layer. As a result, it is possible to obtain a high color image density while suppressing the background covering.
Sensitizers include aliphatic monoamides, stearyl urea, p-benzylbiphenyl, di (2-methylphenoxy) ethane, di (2-methoxyphenoxy) ethane, β-naphthol- (p-methylbenzyl) ether, α- Naphthyl benzyl 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, oxalic acid methylbenzyl ether 1,2-diphenoxy Examples include methylbenzene, 1,2-bis (3-methylphenoxy) ethane, 1,4-bis (phenoxymethyl) benzene, 1,2-diphenoxyethane, 1,2-bis (3-methylphenoxy) ethane, and the like. It is done. Among them, 1,2-diphenoxyethane or 1,2-bis (3-methylphenoxy) ethane is preferable because it is excellent in the property of obtaining a high color image density while suppressing the background covering.
The sensitizer is suitably contained in an amount of 1.5 to 3.5 parts by mass with respect to 1.0 part by mass of the electron donating dye precursor.

(Other inorganic pigments)
The thermosensitive coloring layer contains inorganic pigments other than the above-mentioned calcium carbonate aggregate and colloidal calcium carbonate, and is used for various purposes such as further improving ink jet recording suitability, sheet resistance, and head matching properties. Preferable examples of such other inorganic pigments include light calcium carbonate, aluminum hydroxide or amorphous silica, which are used alone or in combination.
By including light calcium carbonate and / or aluminum hydroxide and / or amorphous silica, it is possible to reduce the surface covering and the wear of the thermal head, and further to improve the adhesion prevention and sticking property to the thermal head. Can do. In addition, by including amorphous silica, bleeding due to ink jet recording can be prevented.

  Similarly, the particle diameter of the other inorganic pigment is preferably 0.6 to 2.5 μm in terms of volume average particle diameter and 0.8 to 2.0 μm from the viewpoint of color density and adhesion of residue to the thermal head. Is more preferable, and it is especially preferable that it is 1.0-1.6 micrometers.

Light calcium carbonate generally has crystal forms such as calcite, aragonite, and vaterite, but the inorganic pigment used in the present invention is preferably calcite-based light calcium carbonate from the viewpoint of absorbability, hardness, etc. It is preferable that the shape is a spindle shape or a decentered triangular surface state.
As a method for producing the calcite light calcium carbonate, a known production method can be used.

Examples of inorganic pigments other than the above include calcium carbonate other than calcite-based light calcium carbonate, barium sulfate, lithopone, wax, kaolin, and calcined kaolin. 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 preferably in the range of 100/0 to 60/40, and more preferably in the range of 100/0 to 80/20. The thermosensitive coloring layer preferably contains 20 to 150 parts by mass of an inorganic pigment with respect to 100 parts by mass in total of the electron donating dye precursor, the electron accepting compound and the sensitizer.
The content of the inorganic pigment may be 30 to 130 parts by mass with respect to a total of 100 parts by mass of the electron donating dye precursor, the electron accepting compound, and the sensitizer in order to make the effect more remarkable. More preferably, it is particularly preferable to contain 40 to 110 parts by mass.

  Examples of inorganic pigments other than the above include calcium carbonate other than calcite-based light calcium carbonate, barium sulfate, lithopone, wax, kaolin, and calcined kaolin. 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 preferably in the range of 100/0 to 60/40, and more preferably in the range of 100/0 to 80/20.

(Image stabilizer)
The heat-sensitive recording material of the present invention preferably contains an image stabilizer in the heat-sensitive color developing layer in order to suppress the deterioration of the background covering and improve the storage stability and chemical resistance of the image area.
As such an image stabilizer, a phenol compound, particularly a hindered phenol compound is effective. For example, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) 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.

  In the heat-sensitive recording material of the present invention, among the above-mentioned image stabilizers, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane and / or 1,1,3 is particularly preferable. It is preferable to contain -tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane in the heat-sensitive color developing layer because the chemical resistance and storage stability of the image area can be further improved.

1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane (α) and 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) ) Butane (β) may be used alone or in combination, and when both are used together, the mass ratio (α / β) is within the range of 20/80 to 80/20. It is preferable that it exists, and it is more preferable that it exists in the range of 40 / 60-60 / 40.
The total content of the image stabilizers (α and β) is the electron donating dye from the viewpoint of efficiently exerting desired effects on the background covering, image storage stability, chemical resistance and head matching (sticking) property. It is preferable to set it as 0.1-1.0 mass part with respect to 1.0 mass part of a precursor, It is still more preferable to set it as 0.2-0.8 mass part, 0.3-0.6 mass part It is particularly preferable that

  In the present invention, the above 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane (α) or 1,1,3-tris (2-methyl-4-hydroxy) is also used. In addition to -5-cyclohexylphenyl) butane (β), other known image stabilizers may be used in combination. When other image stabilizers are used in combination, the total content of the image stabilizers (α and β) is preferably 50% by mass or more based on the total amount of all the image stabilizers, and 70% by mass. It is more preferable that it is contained above.

(adhesive)
Further, the heat-sensitive recording material of the present invention can contain an adhesive in the heat-sensitive color developing layer within a range not impairing the effects of the present invention.
In recent years, as heat-sensitive recording materials have been widely used, cases where the heat-sensitive recording materials are used for offset printing have also occurred. However, since heat-sensitive recording materials generally have a low surface strength, they have problems such as poor printability, such as problems such as paper peeling during offset printing. In order to solve such a problem, it is possible to improve printability for offset printing by including an adhesive in the thermosensitive coloring layer.

  As the adhesive, polyvinyl alcohol having a saponification degree of 85 to 99 mol% and a polymerization degree of 200 to 2000 is preferable. By containing the polyvinyl alcohol, while maintaining the color density of the heat-sensitive recording material, the interlayer adhesion between the heat-sensitive color-developing layer and the support is increased to prevent troubles such as paper peeling that occurs during offset printing, etc. So-called printability can be improved. The saponification degree is preferably 85 to 99 mol%. When the degree of saponification is in the range of 85 to 99 mol%, it prevents paper peeling due to insufficient water resistance against dampening water used for offset printing. In this case, it is possible to prevent undissolved matter from being generated and cause defective portions. Furthermore, it is preferable to use polyvinyl alcohol having a polymerization degree in the range of 200 to 2,000. When the degree of polymerization is in the range of 200 to 2,000, it is not necessary to increase the addition amount, so that the image density is not lowered due to the increase in the addition amount. Further, since polyvinyl alcohol is easily dissolved in a solvent and the viscosity of the coating solution does not increase, its preparation and coating are easy. In addition, the said polymerization degree means the average degree of polymerization calculated | required by the method as described in JIS-K6726 (1994).

  The content of the polyvinyl alcohol in the thermosensitive coloring layer is 30 to 300% by mass with respect to 100 parts by mass of the electron donating dye precursor from the viewpoints of color density and offset printing suitability (such as paper peeling). It is preferably 70 to 200% by mass, particularly preferably 100 to 170% by mass. The polyvinyl alcohol contained in the heat-sensitive color-developing layer can also serve the purpose as a dispersant, a binder and the like in addition to the purpose as an adhesive that increases interlayer adhesion.

The polyvinyl alcohol is suitable as long as it satisfies the conditions of a saponification degree of 85 to 99 mol% and a polymerization degree of 200 to 2000. From the viewpoint of color density in recording with a thermal head, sulfo-modified polyvinyl alcohol is preferable. It is preferable to use at least one selected from alcohol, diacetone-modified polyvinyl alcohol, and acetoacetyl-modified vinyl alcohol.
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 the polyvinyl alcohol. More preferably, it is contained by mass% or more.

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

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

  In general, the acetoacetyl-modified polyvinyl alcohol can be produced by adding and reacting a liquid or gaseous diketene to a solution, dispersion or powder of a polyvinyl alcohol resin. The degree of acetylation of the acetoacetyl-modified polyvinyl alcohol can be appropriately selected according to the quality of the target heat-sensitive recording material.

(UV absorber)
Further, the heat-sensitive recording material of the present invention may contain an ultraviolet absorber in the heat-sensitive color developing 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.

The materials contained in the thermosensitive coloring layer are mixed and then coated on the support. Examples of the coating 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 dried after being coated with a coating solution on a support, and then subjected to a smoothing treatment with a calendar or the like for use. As the coating method, a method using a curtain coater is particularly preferable in the present invention from the viewpoint of uniformly coating the thermosensitive coloring layer and efficiently improving sensitivity and image storage stability.
Further, the coating amount of the thermosensitive coloring layer is not particularly limited, and usually about ² to 7 g / m ² is preferable in terms of dry mass.

(Protective layer)
A protective layer can be provided on the thermosensitive coloring layer as necessary. By providing the protective layer, image storage stability 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 phosphated starch, styrene-maleic anhydride copolymer, styrene-maleic anhydride copolymer alkyl esterified product, and styrene. -A carboxyl group-containing polymer such as an acrylic acid copolymer, vinyl acetate-acrylamide copolymer, methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, gelatin, gum arabic, casein, polyacrylamide derivatives, polyvinylpyrrolidone, and styrene-butadiene rubber Latex, acrylonitrile-butadiene rubber latex, methyl acrylate-butadiene rubber latex, vinyl acetate emulsion, etc. are used. Sex polymer is preferred.

As the water-soluble polymer, polyvinyl alcohol, oxidized starch, and urea phosphate esterified starch are preferable, and the polyvinyl alcohol (v) and oxidized starch and / or urea phosphate esterified starch (w) are 90/10. It is more preferable to mix at a mass ratio (v / w) of 10/90. In addition, 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 ) It is preferably used at a mass ratio (W ¹ / W ² ) of 10/90 to 90/10.

Further, as the modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, amide-modified polyvinyl alcohol are preferably used. In addition, sulfo-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and the like are used. Used. These polyvinyl alcohols can obtain more preferable results by combining a cross-linking agent that reacts therewith.
10-90 mass% is preferable with respect to solid content of the coating liquid for protective layers, and, as for content of water-soluble polymer, 30-70 mass% is more preferable.

  Examples of the crosslinking agent include polyvalent amine compounds such as ethylenediamine, polyhydric aldehyde compounds such as glyoxal, glutaraldehyde, and dialdehyde, dihydrazide compounds such as adipic acid dihydrazide and phthalic acid dihydrazide, and water-soluble methylol compounds (urea, melamine, and phenol). ), Polyfunctional epoxy compounds, polyvalent metal salts (Al, Ti, Zr, Mg, etc.), etc. are preferably used. When used in combination with the polyvinyl alcohol, the content of the crosslinking agent relative to the polyvinyl alcohol is preferably about 2 to 30% by mass, and more preferably 5 to 20% by mass. By using the cross-linking agent, film strength, water resistance and the like can be improved. As a crosslinking agent used for this invention, a polyhydric aldehyde compound, a dihydrazide compound, etc. are preferable.

  As the inorganic pigment, for example, aluminum hydroxide and kaolin are preferable, and aluminum hydroxide having an average particle diameter of 0.5 to 0.9 μm is preferable from the viewpoint of color density by recording with a thermal head. 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. As the organic pigment, urea-formalin resin, styrene-methacrylic acid copolymer, polystyrene, and the like can be used.

As content of the said inorganic pigment, 10-90 mass% is preferable with respect to solid content of the coating liquid for protective layers, and 30-70 mass% is further more preferable.
When the protective layer contains an inorganic pigment and a water-soluble polymer, the mixing ratio varies depending on the type of inorganic pigment, its particle diameter, the type of water-soluble polymer, etc. The functional polymer is preferably 50 to 400% by mass, and more preferably 100 to 250%. The total content of the inorganic pigment and the water-soluble polymer contained in the protective layer is preferably 50% by mass or more 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 alkylbenzene sulfonates such as sodium dodecylbenzene sulfonate, sulfosuccinic acid alkyl ester salts such as sodium dioctyl sulfosuccinate, polyoxyethylene alkyl ether phosphate, sodium hexametaphosphate, perfluoroalkyl carboxylate Etc., and sulfosuccinic acid alkyl ester salts are particularly preferable. 0.1-5 mass% is preferable with respect to solid content of the coating liquid for protective layers, and, as for content of surfactant, 0.5-3 mass% is more preferable.
In addition, a lubricant, an antifoaming agent, a fluorescent brightening agent, a colored organic pigment, and the like can be added to the protective layer coating solution 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, waxes such as paraffin wax, microcrystalline wax, carnauba wax and synthetic polymer wax.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “part” and “%” in the examples represent “part by mass” and “% by mass”, respectively. Further, “average particle diameter” in the examples represents “volume average particle diameter”, and represents a value measured using “LA500” manufactured by Horiba, Ltd.

Example 1
[Preparation of electron-donating colorless dye dispersion]
A sand mill mixed with 20 parts of 3-N, N-dibutylamino-6-methyl-7-anilinofluorane and 80 parts of a 5% aqueous solution of polyvinyl alcohol (trade name PVA-105, manufactured by Kuraray Co., Ltd.) Was used to prepare an electron donating colorless dye dispersion (A) having a volume average particle size of 0.6 μm.
[Preparation of sensitizer dispersion]
20 parts of 1,2-bis (3-methylphenoxy) ethane and 70 parts of a 5% strength polyvinyl alcohol (PVA-105) aqueous solution were mixed and pulverized using a sand mill to obtain a volume average particle size of 0.6 μm. A sensitizer dispersion was prepared.

[Preparation of electron-accepting compound dispersion]
20 parts of 4-hydroxybenzenesulfonanilide and 70 parts of a 5% strength polyvinyl alcohol (PVA-105) aqueous solution were mixed, pulverized using a sand mill, and a color developer dispersion (volume average particle diameter 0.6 μm) ( A) was prepared.
It was.
[Preparation of pigment dispersion]
Shiraka Hana PZ as calcium carbonate aggregate (particle shape: cubic shape, aggregated, boiled linseed oil absorption 48 ml / 100 g) (manufactured by Shiraishi Calcium Co., Ltd.) and brilliant 15 as colloidal calcium carbonate (particle shape: cubic shape, ratio) Surface area 13.8 g / m ² ) (manufactured by Shiraishi Calcium Co., Ltd.) 20 parts, Poise 520 (manufactured by Kao Co., Ltd.) 1 part, water 59 parts are mixed, dispersed with a dissolver and a volume average particle size of 2.1 μm. A pigment dispersion was prepared.

[Preparation of coating solution for thermosensitive recording layer]
10 parts of the above electron-donating colorless dye dispersion, 15 parts of sensitizer dispersion, 15 parts of developer dispersion (A), 25 parts of pigment dispersion, 31% concentration of Hydrin Z-7 (Chukyo Yushi Co., Ltd.) )) 1.2 parts, Hydrin D337 with a concentration of 31% (manufactured by Chukyo Yushi Co., Ltd.) 2.5 parts, 2% (2-ethylhexyl) sodium sulfosuccinate aqueous solution 1.0 part, and water 20 parts were mixed. Thus, a thermal recording layer coating solution (1) was obtained.

[Preparation of thermal recording material]
As a support, a high-quality paper having a smoothness of 300 seconds according to JIS-P8119 is prepared, and a wire bar is used so that the surface of the high-quality paper and the heat-sensitive recording layer mass after drying are 4.0 g / m ² . Then, the thermal recording layer coating solution (1) was applied, dried in an oven at 50 ° C., and then subjected to a calendar treatment to obtain a thermal recording material (1).

(Example 2)
A heat-sensitive recording material (2) was obtained in the same manner as in Example 1, except that the white glossy PZ of the pigment dispersion of Example 1 was changed to Tunex E (spindle shape / aggregation, boiled linseed oil absorption 53 ml / 100 g).

(Example 3)
A heat-sensitive recording material (3) was obtained in the same manner as in Example 1, except that the white glossy PZ of the pigment dispersion of Example 1 was changed to Tunex FF (spindle shape / aggregation, boiled linseed oil absorption 58 ml / 100 g).

Example 4
A heat-sensitive recording material (4) was obtained in the same manner as in Example 1 except that the brilliant 15 of the pigment dispersion of Example 1 was changed to brilliant 1500 (cubic, specific surface area 14.7 g / m ² ).

(Example 5)
A thermosensitive recording material (5) was obtained in the same manner as in Example 1 except that the electron-donating colorless dye used in Example 1 was changed to 3-N, N-diethylamino-6-methyl-7-anilinofluorane. It was.

(Example 6)
A thermosensitive recording material (6) was obtained in the same manner as in Example 1 except that the electron accepting compound used in Example 1 was changed to 2,4-bis (phenylsulfonyl) phenol.

(Example 7)
A thermosensitive recording material (7) was obtained in the same manner as in Example 1 except that the electron-accepting compound used in Example 3 was changed to 4-hydroxy-4′-isopropoxydiphenylsulfone.

(Comparative Example 1)
A thermosensitive recording material (5) was obtained in the same manner as in Example 1 except that colloidal calcium carbonate was not used in the preparation of the pigment dispersion in Example 1.
(Comparative Example 2)
A thermosensitive recording material (6) was obtained in the same manner as in Example 3 except that colloidal calcium carbonate was not used in the preparation of the pigment dispersion in Example 2.
(Comparative Example 3)
A heat-sensitive recording material (7) was obtained in the same manner as in Example 1 except that the calcium carbonate aggregate was not used in the preparation of the pigment dispersion in Example 1.

<Measurement / Evaluation>
<Color development> About the heat-sensitive recording materials (1) to (7) of Examples 1 to 7 and Comparative Examples 1 to 3, the following three were used using a thermal printing tester (KLT head) (manufactured by Kyocera Corporation). Printing was performed with various types of printing energy, and the color density for each was measured with a Macbeth reflection densitometer (Macbeth RD-918).
・ Printing energy 1 ... 0.15mJ / dot
・ Printing energy 2 ... 0.20mJ / dot
・ Printing energy 3 ... 0.25mJ / dot

<Head Dirt> Using a thermal recording medium evaluator (trade name: TH-PMH, manufactured by Okura Electric Co., Ltd.), recording was performed at an applied energy of 0.25 mj / dot. From the degree of sticking or thermal head debris generated during recording The recording running property was determined as follows.
[Standard]
○: No residue was observed, and no white spots or the like were observed on the print.
Δ: The amount of residue attached was moderate, but no white spots were observed on the print.
X: A large amount of scum was adhered, and troubles such as white spots were observed in the print print.

<Whiteness> The whiteness of the unrecorded part was measured using a Hunter whiteness meter. As the filter, blue was used when the recorded image was black, and amber was used when the recorded image was blue.
<Glossiness> Using a glossmeter (trade name: GM-26D, manufactured by Murakami Color Research Laboratory), the glossiness of the unrecorded area and the recorded area (printing energy 0.25 mJ / dot) is measured at an incident angle of 60 degrees. did.

  From the results shown in Table 1, the heat-sensitive recording material according to the present invention has high recording sensitivity, an image having a high color density in the recording area is obtained, and there is little head contamination, and the whiteness of the unrecorded area after recording. It can be understood that the background of the unrecorded portion and the glossiness of the image of the recorded portion are within appropriate ranges.

Claims (12)

  A thermosensitive coloring layer containing an electron-donating dye precursor, an electron-accepting compound that reacts with the electron-donating dye precursor, develops color, a calcium carbonate aggregate, and colloidal calcium carbonate on a support. Thermal recording material provided.   The heat-sensitive recording material according to claim 1, wherein the calcium carbonate aggregate is an aggregate having a volume average particle diameter of 1.0 µm to 5.0 µm and an oil absorption of 40 ml / 100 g to 80 ml / 100 g. 3. The heat-sensitive recording material according to claim 1, wherein the colloidal calcium carbonate has a volume average primary particle size of 30 nm to 300 nm and a specific surface area of 10 m ² / g to 30 m ² / g.   The thermosensitive recording material according to any one of claims 1 to 3, wherein a particle shape of the calcium carbonate aggregate is a spindle shape or a granular shape.   The heat-sensitive recording material according to any one of claims 1 to 4, wherein a primary particle shape of the colloidal calcium carbonate is a cubic shape.   The ratio of the calcium carbonate aggregate to the colloidal calcium carbonate is in the range of 20/80 to 80/20 by mass ratio, and the total content of both is 25% by mass to 75% by mass in the thermosensitive coloring layer. The heat-sensitive recording material according to claim 1, which is in a range of%. The heat-sensitive recording material according to any one of claims 1 to 6, wherein the electron-donating dye precursor is at least one of fluoran compounds represented by the following general formula (I).
Formula (I):


In the general formula (I), R _{1 to} R ₅ each independently represents a hydrogen atom, an alkyl group, an allyl group, or a phenyl group. These groups may be further substituted with at least one substituent selected from halogen, alkyl group, allyl group, hydroxy group, alkoxy group, acyl group, amino group, substituted amino group and nitro group. R ₁ and R ₂ , or R ₄ and R ₅ may be bonded to each other to form a ring. The heat-sensitive recording material according to any one of claims 1 to 7, wherein the electron-accepting compound is at least one selected from compounds represented by the following general formula (II).
Formula _{(II): R 6 -Ph-} SO 2 R 7
In the general formula (II), R ₆ represents a hydroxyl group or an alkyl group, and R ₇ represents —Ph, —NH—Ph, —Ph—OR _8, or —NH—CO—NH—Ph. R ₈ represents an alkyl group. Ph represents a phenyl group which may be substituted with a substituent containing —SO ₂ R ₇ .     The heat-sensitive recording material according to any one of claims 1 to 8, wherein the electron-accepting compound is 4-hydroxybenzenesulfonanilide.   The thermosensitive recording material according to any one of claims 1 to 9, wherein the thermosensitive coloring layer further contains a binder.   The thermosensitive recording material according to any one of claims 1 to 10, wherein the thermosensitive coloring layer further contains a sensitizer.   A pattern forming method in which the heat-sensitive color forming layer of the heat-sensitive recording material according to any one of claims 1 to 11 is heated in a pattern with a thermal head, and the heat-sensitive color developing layer in the heated portion is colored.