JP5823086B1 - Thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-sensitive recording material excellent in heat discoloration resistance, particularly in a white paper portion. A support, an undercoat layer containing a pigment and a binder as main components provided on the support, a colorless to light-colored electron-donating leuco dye and an electron acceptor provided on the undercoat layer. In the heat-sensitive recording material comprising a heat-sensitive recording layer containing a color developer as a main component, the pigment contained in the undercoat layer is formed by agglomerating spindle-shaped primary particles radially to form secondary particles. A heat-sensitive recording material, characterized by being rosetta-type light calcium carbonate and having a bulk density of 240 g / L or less. [Selection] Figure 1

Description

  The present invention utilizes a coloring reaction between a colorless or light-colored electron-donating leuco dye (hereinafter also referred to as “leuco dye”) and an electron-accepting developer (hereinafter also referred to as “developer”). The present invention relates to a heat-sensitive recording material, which is excellent in heat discoloration resistance, particularly heat resistance discoloration property of a blank paper portion.

In general, a thermal recording material is usually a colorless or light leuco dye and a developer such as a phenolic compound, each of which is ground and dispersed into fine particles, and then mixed together to form a binder, a filler, a sensitivity improver, A coating liquid obtained by adding a lubricant and other auxiliary agents is coated on a support such as paper, synthetic paper, film, plastic, etc., and is widely used as various recording media.
In recent years, such heat-sensitive recording materials have been used in facsimiles, computer terminal printers, automatic ticket vending machines, measurement recorders, and the like. Furthermore, the use of thermal recording media has been expanded to various tickets, receipts, labels, bank ATMs, gas and electric meter readings, and car tickets, etc. There is a need to preserve the image area and the blank paper area under such conditions as, for example, an environment such as a high temperature in a car in midsummer. In order to solve such a problem, configurations of a developer, a dye, and a protective layer have been studied (Patent Documents 1 to 3, etc.).
It has also been proposed to improve the recording sensitivity and printing runnability by providing an undercoat layer containing an inorganic pigment or plastic particles between the support and the heat-sensitive recording layer (Patent Documents 4, 5, etc.).

JP-A-10-86529 JP2008-6739 JP 2010-94986 JP 05-162446 A JP2012-076228

Conventionally, in order to improve the heat discoloration resistance of the thermal recording material, particularly the heat discoloration resistance of the white paper portion, the constitution of the developer, the dye and the protective layer has been mainly studied as described above (Patent Literature). 1 to 3), the present inventors studied to provide an undercoat layer between the support and the thermosensitive recording layer, and to improve the heat discoloration of the thermosensitive recording medium by the constitution of the undercoat layer.
Accordingly, an object of the present invention is to provide a heat-sensitive recording material excellent in heat discoloration resistance, in particular, heat discoloration resistance of a blank paper portion.

As a result of intensive studies, the present inventors have provided an undercoat layer between the support of the heat-sensitive recording medium and the heat-sensitive recording layer, and spindle-shaped primary particles as a pigment aggregated radially into the undercoat layer as secondary particles. By adding light calcium carbonate having a characteristic rosetta shape and limiting the bulk density to a specific bulk density, the heat discoloration resistance of the thermal recording material, in particular, the heat discoloration resistance of the blank paper portion is improved. The present invention has been completed.
The rosette type light calcium carbonate used in the present invention has a specific shape and bulk density (see FIGS. 1 and 2), and the undercoat layer containing such a pigment is applied to the heat-sensitive recording layer from the support side. Therefore, it is considered that heat transfer to the heat-sensitive recording layer is reduced even when stored in a high temperature environment, and the heat discoloration is excellent.
Further, when the undercoat layer contains such a pigment, it is considered that the absorption performance peculiar to the material contained in the undercoat layer or the adjacent thermosensitive recording layer is exhibited. For example, after the coloring material contained in the heat-sensitive recording layer, particularly the developer, is melted by heating with a thermal head at the time of printing, it cannot participate in color development, i.e., there is no opportunity for chemical reaction with the leuco dye, resulting in surplus. It is considered that the developer was absorbed by the undercoat layer. As a result, it is considered that the thermal head is less likely to become scum and the printing running property (head scum resistance) is improved. Moreover, it is thought that it also affects the expression of the binder contained in such an undercoat layer.

  That is, the present invention relates to a support, an undercoat layer containing a pigment and a binder as main components provided on the support, and a colorless to light-colored electron-donating leuco dye provided on the undercoat layer. In a heat-sensitive recording material having a heat-sensitive recording layer containing an electron-accepting developer as a main component, the pigment contained in the undercoat layer forms secondary particles by agglomerating spindle-shaped primary particles radially. And a rosette-type light calcium carbonate having a bulk density of 240 g / L or less.

It is a photograph of Rosetta-type light calcium carbonate (Albuquerque LO). It is a photograph of rosetta type light calcium carbonate (TP221BM).

The heat-sensitive recording material of the present invention comprises a support, an undercoat layer provided on the support, and a heat-sensitive recording layer provided on the undercoat layer.
This undercoat layer contains a pigment and a binder as main components, and this pigment is rosetta-type light calcium carbonate formed by agglomerating spindle-shaped primary particles radially to form secondary particles.
The bulk density of the rosetta type light calcium carbonate is 240 g / L or less, preferably 150 to 220 g / L. This bulk density is measured in accordance with JIS-K-5101-12-1 (pigment test method-part 12: apparent density or apparent specific volume-section 1: stationary method).

Rosetta-type light calcium carbonate used in the present invention is formed by agglomerating primary particles of spindle-shaped light calcium carbonate in a radial manner to form secondary particles. From the vicinity of the center, the primary particles are radially extended in the longitudinal direction.
Rosetta-type light calcium carbonate used in the present invention is, for example, Specialty Minerals Inc. It is available as Albuquer LO (bulk density: 210 g / L) manufactured by KK or TP221BM (bulk density 230 g / L) manufactured by Okutama Kogyo Co., Ltd.
Rosetta-type light calcium carbonate may be used after being pulverized by a known pulverizer such as a ball mill, an attritor, or a sand glider.

In the undercoat layer of the present invention, a pigment other than the rosetta-type light calcium carbonate of the present invention may be used. Examples of pigments other than rosetta-type light calcium carbonate include light calcium carbonate formed by forming irregularly shaped secondary particles, and light brown chestnut light formed by agglomerating needle-like primary particles radially to form secondary particles Calcium carbonate, light calcium carbonate, heavy calcium carbonate, primary calcium, spindle, columnar, square, spherical, etc., without forming secondary particles, (calcined) kaolin, clay, talc, silica , Aluminum oxide, zinc oxide, titanium oxide, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, aluminum silicate, magnesium silicate, calcium silicate and the like. These pigments can be used alone or in admixture of two or more.
When the undercoat layer contains a pigment other than the rosetta type light calcium carbonate of the present invention, the content of the rosetta type light calcium carbonate of the present invention is the same as the total pigment contained in the undercoat layer (the rosetta type light calcium carbonate of the present invention). Inclusive) is preferably 50% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight or more.

If the undercoat layer of the present invention further contains organic hollow particles, the heat discoloration of the white paper portion is further improved, the heat insulation of the undercoat layer is improved, and a thermosensitive recording material excellent in color development sensitivity is obtained. preferable.
The organic hollow particles used in the present invention are fine hollow particles that have a thermoplastic resin as a shell and contain air or other gas inside, and are already in a foamed state.
Examples of the thermoplastic resin include polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyacrylic acid ester, polyacrylonitrile, polybutadiene, and copolymers thereof. In particular, styrene resins such as polystyrene, acrylic resins such as polyacrylic acid esters and polyacrylonitrile, copolymers thereof, or copolymer resins mainly composed of polyvinylidene chloride and polyacrylonitrile are preferable. Specifically, such organic hollow particles are available under the trade name SX8782 manufactured by JSR Corporation, trade names MH5055 and MH8103K manufactured by Nippon Zeon Co., Ltd., and trade name Ropeke HP-91 manufactured by Rohm & Haas Japan.

The hollow ratio of the organic hollow particles is preferably 40 to 90%, more preferably 45 to 90%. When the hollow ratio is less than 40%, the heat insulation becomes insufficient, and heat energy from the thermal head or the like is easily released out of the heat-sensitive recording medium through the support. A sufficient effect may not be obtained.
Here, the hollow ratio is calculated from the outer diameter and inner diameter of the hollow particles, and is represented by the hollow ratio = (the inner diameter of the hollow particles / the outer diameter of the hollow particles) ³ × 100 (%).

The average particle diameter of the organic hollow particles is preferably 0.5 to 10 μm, more preferably 1 to 5 μm. When the average particle size is larger than 10 μm, the smoothness of the surface of the heat-sensitive recording layer formed on the undercoat layer is lowered, and the adhesion between the heat-sensitive recording material and the thermal head is lowered, so that a sufficient effect cannot be obtained. There is. On the other hand, when the average particle size is smaller than 0.5 μm, the amount of the gas contained in the hollow particles is small, and thus a sufficient effect may not be obtained.
Here, the average particle diameter is indicated by a median diameter d _{50 in} which the particles on the large side and the small side are equivalent (volume basis) when the particles are divided into two according to the diameter. It can be measured by the device.

As a binder used in the undercoat layer, polyvinyl alcohols such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, and terminal alkyl-modified polyvinyl alcohol, hydroxyethyl cellulose, Cellulose ethers and derivatives thereof such as methylcellulose, ethylcellulose, carboxymethylcellulose, acetylcellulose, starch, enzyme-modified starch, thermochemically modified starch, oxidized starch, esterified starch, etherified starch (for example, hydroxyethylated starch, etc.), cationization Starch and other starches, polyacrylamide, cationic polyacrylamide, anionic polyacrylamide, amphoteric polyacryl Water-soluble resins such as polyacrylamides such as amides; Urethane resins such as polyester polyurethane resins, polyether polyurethane resins, polyurethane ionomer resins, styrene-butadiene copolymers, styrene-butadiene-acrylonitrile copolymers, styrene -Styrene-butadiene resin such as butadiene-acrylic copolymer, acrylic resin composed of monomer components copolymerizable with (meth) acrylic acid and (meth) acrylic acid such as (meth) acrylonitrile, ethylene, Polyolefin resin, polyvinyl acetate, consisting of monomer components that can be copolymerized with olefins such as propylene and butylene, and olefins such as unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid, itaconic acid, and fumaric acid , Vinyl chloride-acetic acid Illustrative non-water-soluble resins such as nyl copolymers, polyvinyl chloride, polyvinylidene chloride, polyacrylates, polystyrose and their copolymers, silicone resins, petroleum resins, terpene resins, ketone resins, coumarone resins be able to.
Among these, as the water-soluble resin, polyvinyl alcohols, cellulose ethers and derivatives thereof, and starches are preferable, and polyvinyl alcohols are more preferable. The water-soluble resin can be used by dissolving in a solvent such as water.
Further, as the water-insoluble resin, styrene-butadiene resin, acrylic resin, and polyolefin resin are preferable, and styrene-butadiene resin is more preferable. The water-insoluble resin can be used as an emulsion dispersed in water or another medium in the form of an emulsification or paste.
Two or more kinds of these binders may be used in combination according to the required quality.

As the binder used in the undercoat layer of the present invention, it is preferable to use a water-soluble resin and a water-insoluble resin in combination at a certain ratio.
The weight ratio (solid content) of the water-soluble resin / water-insoluble resin is preferably 35/100 or less, more preferably 3/100 to 30/100, still more preferably 3/100 to 20/100.
When the weight ratio of the water-soluble resin / water-insoluble resin exceeds 35/100, the heat discoloration resistance, print image quality, and head residue resistance tend to be lowered (see Examples below).
Further, if the water-soluble resin is less than 3/100, the effect of suppressing migration described later cannot be sufficiently obtained, and the strength of the coating layer may be lowered.

Water-soluble resins such as polyvinyl alcohols generally have high viscosity and water retention and are easy to penetrate and fix in the voids of the undercoat layer containing the pigment having the specific shape and bulk density of the present invention. Therefore, it is considered that the gap in the undercoat layer is filled, and the heat discoloration resistance, the print image quality, and the head residue resistance are lowered.
On the other hand, water-insoluble resins such as styrene-butadiene resins generally have low viscosity and water retention, and pass through the undercoat layer containing a pigment having a specific shape and bulk density according to the present invention to the support. So-called migration that penetrates easily occurs.
By properly adjusting the mixing ratio of water-soluble resin and water-insoluble resin, the undercoat layer can be made bulky (low density) while suppressing migration. It is thought that the resistance to head scum can be obtained.

  In the present invention, a dispersant, a plasticizer, a thickener, a surfactant, an active agent, a pH adjuster, an antifoaming agent, a water retention agent, an antiseptic agent are used in the undercoat layer as long as the desired effect on the above-described problems is not impaired. Various auxiliary agents such as coloring dyes, ultraviolet absorbers, antioxidants, and water / oil repellents can be used.

  The amount of the pigment, organic hollow particles, and binder used in the undercoat layer is determined according to the required performance and recordability and is not particularly limited, but is usually 100 parts by weight of the total solid content of the undercoat layer. The pigment has a solid content of 50 to 95 parts by weight, preferably 70 to 90 parts by weight. Further, the content of the organic hollow particles with respect to 100 parts by weight of the total solid content of the undercoat layer is preferably 1 to 18 parts by weight, more preferably 3 to 15 parts by weight in terms of solids. Increasing the content of organic hollow particles tends to improve the color development sensitivity, but if the content exceeds 18 parts by weight, the residue adheres to the thermal head and the like, and the print running property (head residue resistance) decreases. There are things to do. The content of the binder is preferably 7 to 30 parts by weight, more preferably 10 to 25 parts by weight in terms of solid content.

In the present invention, the support and the means for applying an undercoat layer on the support are not particularly limited, and are well known and commonly used on a support made of an appropriate material such as paper, recycled paper, plastic film, and synthetic paper. Can be applied according to technique. For example, an air machine, a rod blade coater, a vent blade coater, a bevel blade coater, a roll coater, a curtain coater, etc. When using a blade coater such as a blade coater, vent blade coater, or bevel blade coater, high-concentration coating is possible, so that the undercoat layer coating solution does not easily penetrate into the support and forms a uniform undercoat layer. Therefore, it is preferable.
The coating amount of the undercoat layer is determined according to the required performance and recording suitability, and is not particularly limited, but the general coating amount is about 1 to 15 g / m ² in terms of solid content.

  Next, various materials used in the heat-sensitive recording layer of the heat-sensitive recording material of the present invention are exemplified, but a binder, a crosslinking agent, a pigment, and the like are provided as necessary as long as the desired effects on the above-described problems are not inhibited. It can also be used for each coating layer.

  As the developer, any known developer in the field of conventional pressure-sensitive or thermal recording paper can be used, and is not particularly limited. For example, activated clay, attapulgite, colloidal silica, aluminum silicate, etc. Inorganic acidic substance, 4,4′-isopropylidene diphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 4,4′-dihydroxy Diphenyl sulfide, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, 4,4′-dihydroxydiphenyl sulfone, 2,4′-dihydroxydiphenyl sulfone, 4-hydroxy-4′-isopropoxydiphenyl sulfone, 4-hydroxy-4 '-N-propoxydiphenylsulfone, bis (3 Allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4′-methyldiphenylsulfone, 4-hydroxyphenyl-4′-benzyloxyphenylsulfone, 3,4-dihydroxyphenyl-4′-methylphenylsulfone, 1- [ 4- (4-hydroxyphenylsulfonyl) phenoxy] -4- [4- (4-isopropoxyphenylsulfonyl) phenoxy] butane, a phenol condensation composition described in JP2003-154760, and JP8-59603A Aminobenzenesulfonamide derivatives, bis (4-hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-oxapentane, butyl bis (p-hydroxyphenyl) acetate, bis (p -Hydroxyphenyl) methyl acetate, 1 1-bis (4-hydroxyphenyl) -1-phenylethane, 1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 1,3-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, di (4-hydroxy-3-methylphenyl) sulfide, 2,2′-thiobis (3-tert-octylphenol), 2,2′-thiobis (4-tert-octylphenol) ), Phenolic compounds such as diphenylsulfone cross-linking compounds described in WO 97/16420, compounds described in WO 02/081229 or JP-A 2002-301873, and N, N′-di-m-chlorophenylthiourea, etc. Thiourea compound, p-chlorobenzoic acid, stearyl gallate, bis [4- (n-octyloxycarbonylamino) ) Zinc salicylate] dihydrate, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid, 5- [p- (2-p- Methoxyphenoxyethoxy) cumyl] aromatic carboxylic acids of salicylic acid, and salts of these aromatic carboxylic acids with polyvalent metal salts such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel, and thiocyanic acid Examples include zinc antipyrine complexes and complex zinc salts of terephthalaldehyde acid with other aromatic carboxylic acids. These developers can be used alone or in combination of two or more. 1- [4- (4-Hydroxyphenylsulfonyl) phenoxy] -4- [4- (4-isopropoxyphenylsulfonyl) phenoxy] butane is available, for example, under the trade name JKY-214 manufactured by API Corporation. Yes, the phenol condensation composition described in JP-A No. 2003-154760 is available, for example, under the trade name JKY-224 manufactured by API Corporation, and is a diphenylsulfone cross-linking compound described in International Publication No. WO 97/16420 Is available under the trade name D-90 manufactured by Nippon Soda Co., Ltd. Moreover, the compound as described in WO02 / 081229 etc. is available as Nippon Soda Co., Ltd. brand name NKK-395 and D-100. In addition, a metal chelate color-developing component such as a higher fatty acid metal double salt and a polyvalent hydroxyaromatic compound described in JP-A-10-258577 can also be contained.

  As the leuco dye, those known in the conventional pressure-sensitive or thermal recording paper field can be used, and are not particularly limited. However, triphenylmethane compounds, fluorane compounds, fluorene compounds, divinyl compounds are not limited. Compounds and the like are preferred. Specific examples of typical colorless or light-colored dyes (dye precursors) are shown below. These dye precursors may be used alone or in combination of two or more.

<Triphenylmethane leuco dye>
3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide (also known as malachite green lactone)

<Fluoran leuco dye>
3-diethylamino-6-methylfluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (o, p-dimethylanilino) fluorane, 3-diethylamino- 6-methyl-7-chlorofluorane, 3-diethylamino-6-methyl-7- (m-trifluoromethylanilino) fluorane, 3-diethylamino-6-methyl-7- (o-chloroanilino) fluorane, 3- Diethylamino-6-methyl-7- (p-chloroanilino) fluorane, 3-diethylamino-6-methyl-7- (o-fluoroanilino) fluorane, 3-diethylamino-6-methyl-7- (m-methylanilino) fluorane 3-diethylamino-6-methyl-7-n-octylanilinofluorane, 3-di Tilamino-6-methyl-7-n-octylaminofluorane, 3-diethylamino-6-methyl-7-benzylaminofluorane, 3-diethylamino-6-methyl-7-dibenzylaminofluorane, 3-diethylamino- 6-chloro-7-methylfluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-diethylamino-6-chloro-7-p-methylanilinofluorane, 3-diethylamino-6-ethoxy Ethyl-7-anilinofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7- (m-trifluoromethylanilino) fluorane, 3-diethylamino- 7- (o-chloroanilino) fluorane, 3-diethylamino-7- (p Chloroanilino) fluorane, 3-diethylamino-7- (o-fluoroanilino) fluorane, 3-diethylamino-benzo [a] fluorane, 3-diethylamino-benzo [c] fluorane, 3-dibutylamino-6-methyl-fluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7- (o, p-dimethylanilino) fluorane, 3-dibutylamino-6-methyl-7- ( o-chloroanilino) fluorane, 3-dibutylamino-6-methyl-7- (p-chloroanilino) fluorane, 3-dibutylamino-6-methyl-7- (o-fluoroanilino) fluorane, 3-dibutylamino-6 -Methyl-7- (m-trifluoromethylanilino) fluorane, 3-dibutylamino- 6-methyl-7-chlorofluorane, 3-dibutylamino-6-ethoxyethyl-7-anilinofluorane, 3-dibutylamino-6-chloro-7-anilinofluorane, 3-dibutylamino-6- Methyl-7-p-methylanilinofluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7- (o-fluoroanilino) fluorane, 3-di-n-pentylamino -6-methyl-7-anilinofluorane, 3-di-n-pentylamino-6-methyl-7- (p-chloroanilino) fluorane, 3-di-n-pentylamino-7- (m-trifluoro Methylanilino) fluorane, 3-di-n-pentylamino-6-chloro-7-anilinofluorane, 3-di-n-pentylamino-7- (p-chloro) Nilino) fluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-propylamino) -6-methyl -7-anilinofluorane, 3- (N-methyl-N-cyclohexylamino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-N-cyclohexylamino) -6-methyl-7 -Anilinofluorane, 3- (N-ethyl-N-xylamino) -6-methyl-7- (p-chloroanilino) fluorane, 3- (N-ethyl-p-toludino) -6-methyl-7-ani Linofluorane, 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isoamylamino) -6-chloro-7-a Linofluorane, 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isobutylamino) -6-methyl-7-anilinofur Oran, 3- (N-ethyl-N-ethoxypropylamino) -6-methyl-7-anilinofluorane, 3-cyclohexylamino-6-chlorofluorane, 2- (4-oxahexyl) -3-dimethyl Amino-6-methyl-7-anilinofluorane, 2- (4-oxahexyl) -3-diethylamino-6-methyl-7-anilinofluorane, 2- (4-oxahexyl) -3-dipropyl Amino-6-methyl-7-anilinofluorane, 2-methyl-6-p- (p-dimethylaminophenyl) aminoanilinofluorane, 2-methoxy-6-p -(P-dimethylaminophenyl) aminoanilinofluorane, 2-chloro-3-methyl-6-p- (p-phenylaminophenyl) aminoanilinofluorane, 2-chloro-6-p- (p- Dimethylaminophenyl) aminoanilinofluorane, 2-nitro-6-p- (p-diethylaminophenyl) aminoanilinofluorane, 2-amino-6-p- (p-diethylaminophenyl) aminoanilinofluorane, 2-diethylamino-6-p- (p-diethylaminophenyl) aminoanilinofluorane, 2-phenyl-6-methyl-6-p- (p-phenylaminophenyl) aminoanilinofluorane, 2-benzyl-6 -P- (p-phenylaminophenyl) aminoanilinofluorane, 2-hydroxy-6-p- (p-phenylamino) Nophenyl) aminoanilinofluorane, 3-methyl-6-p- (p-dimethylaminophenyl) aminoanilinofluorane, 3-diethylamino-6-p- (p-diethylaminophenyl) aminoanilinofluorane, 3 -Diethylamino-6-p- (p-dibutylaminophenyl) aminoanilinofluorane, 2,4-dimethyl-6-[(4-dimethylamino) anilino] -fluorane

<Fluorene leuco dye>
3,6,6′-tris (dimethylamino) spiro [fluorene-9,3′-phthalide], 3,6,6′-tris (diethylamino) spiro [fluorene-9,3′-phthalide]

<Divinyl leuco dye>
3,3-bis- [2- (p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrabromophthalide, 3,3-bis- [2- (P-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide, 3,3-bis- [1,1-bis (4-pyrrolidinophenyl) ) Ethylene-2-yl] -4,5,6,7-tetrabromophthalide, 3,3-bis- [1- (4-methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2- Yl] -4,5,6,7-tetrachlorophthalide

<Others>
3- (4-Diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- ( 1-octyl-2-methylindol-3-yl) -4-azaphthalide, 3- (4-cyclohexylethylamino-2-methoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl)- 4-azaphthalide, 3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide, 3,6-bis (diethylamino) fluorane-γ- (3′-nitro) anilinolactam, 3,6 -Bis (diethylamino) fluorane-γ- (4′-nitro) anilinolactam, 1,1-bis- [2 ′, 2 ′, 2 ″, 2 ″ -tetrakis- (p-dimethylamino) Enyl) -ethenyl] -2,2-dinitrileethane, 1,1-bis- [2 ′, 2 ′, 2 ″, 2 ″ -tetrakis- (p-dimethylaminophenyl) -ethenyl] -2- β-naphthoylethane, 1,1-bis- [2 ′, 2 ′, 2 ″, 2 ″ -tetrakis- (p-dimethylaminophenyl) -ethenyl] -2,2-diacetylethane, bis- [2, 2,2 ′, 2′-Tetrakis- (p-dimethylaminophenyl) -ethenyl] -methylmalonic acid dimethyl ester

  A conventionally well-known sensitizer can be used as a sensitizer. Examples of the sensitizer include fatty acid amides such as stearamide and palmitic acid amide, ethylene bisamide, montanic acid wax, polyethylene wax, 1,2-bis- (3-methylphenoxy) ethane, p-benzylbiphenyl, β- Benzyloxynaphthalene, 4-biphenyl-p-tolyl ether, m-terphenyl, 1,2-diphenoxyethane, dibenzyl oxalate, di (p-chlorobenzyl) oxalate, di (p-methylbenzyl) oxalate, Dibenzyl terephthalate, benzyl p-benzyloxybenzoate, di-p-tolyl carbonate, phenyl-α-naphthyl carbonate, 1,4-diethoxynaphthalene, 1-hydroxy-2-naphthoic acid phenyl ester, o-xylene-bis -(Phenyl ether), 4- (m-me Tilphenoxymethyl) biphenyl, 4,4′-ethylenedioxy-bis-benzoic acid dibenzyl ester, dibenzoyloxymethane, 1,2-di (3-methylphenoxy) ethylene, bis [2- (4-methoxy- Phenoxy) ethyl] ether, methyl p-nitrobenzoate, phenyl p-toluenesulfonate, o-toluenesulfonamide, p-toluenesulfonamide and the like. These sensitizers may be used alone or in combination of two or more.

  Examples of the pigment include kaolin, calcined kaolin, calcium carbonate, aluminum oxide, titanium oxide, magnesium carbonate, aluminum silicate, magnesium silicate, calcium silicate, aluminum hydroxide, silica and the like, and can be used in combination according to the required quality. .

  As the binder, fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetyl modified polyvinyl alcohol, carboxy modified polyvinyl alcohol, amide modified polyvinyl alcohol, sulfonic acid modified polyvinyl alcohol, butyral modified polyvinyl alcohol, olefin modified polyvinyl alcohol, Nitrile-modified polyvinyl alcohol, pyrrolidone-modified polyvinyl alcohol, silicone-modified polyvinyl alcohol, other modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer, styrene-butadiene copolymer and ethyl cellulose, acetyl Cellulose derivatives such as cellulose Casein, arabic gum, oxidized starch, etherified starch, dialdehyde starch, esterified starch, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylic ester, polyvinyl butyral, polystyrose and copolymers thereof, polyamide resin, Silicone resin, petroleum resin, terpene resin, ketone resin, coumarone resin and the like can be exemplified. These polymer substances are used by dissolving them in solvents such as water, alcohol, ketones, esters, hydrocarbons, etc., and are used in the state of being emulsified or pasted in water or other media to achieve the required quality. It can also be used in combination.

  Examples of the crosslinking agent include epichlorohydrin resins such as polyamine epichlorohydrin resins and polyamide epichlorohydrin resins, polyamide urea resins, polyalkylene polyamine resins, polyalkylene polyamide resins, polyamine polyurea resins, and modified polyamines. Polyamine / polyamide resins such as resins, modified polyamide resins, polyalkylene polyamine urea formalin resins, or polyalkylene polyamine polyamide polyurea resins, glyoxal, methylol melamine, melamine formaldehyde resin, melamine urea resin, potassium persulfate, ammonium persulfate, persulfate Examples thereof include sodium sulfate, ferric chloride, magnesium chloride, borax, boric acid, alum, and ammonium chloride.

  Examples of the lubricant include fatty acid metal salts such as zinc stearate and calcium stearate, waxes, and silicone resins.

  In the present invention, 4,4′-butylidene (6-tert-butyl-3-methylphenol), 2 as a stabilizer for improving the oil resistance and the like of the image area as long as the desired effect on the above problems is not impaired. 2,2'-di-t-butyl-5,5'-dimethyl-4,4'-sulfonyldiphenol, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane and the like can also be added. In addition, benzophenone and triazole ultraviolet absorbers, dispersants, antifoaming agents, antioxidants, fluorescent dyes, and the like can be used.

  The types and amounts of the leuco dye, developer, sensitizer, and other various components used in the heat-sensitive recording layer of the present invention are determined according to the required performance and recording suitability, and are not particularly limited. Usually, 0.5 to 10 parts by weight of developer, 0.1 to 10 parts by weight of sensitizer, 0.5 to 20 parts by weight of pigment, and 0.01 to 10 parts by weight of stabilizer for 1 part by weight of leuco dye. Parts and other components of about 0.01 to 10 parts by weight. The binder is suitably about 5 to 25% by weight based on the solid content of the heat-sensitive recording layer.

  In the present invention, the leuco dye, the developer, and the material to be added as necessary are finely divided to a particle size of several microns or less by a pulverizer such as a ball mill, an attritor, or a sand glider, or an appropriate emulsifying device, and a binder. Depending on the purpose, various additive materials are added to obtain a coating solution. As a solvent used for this coating liquid, water or alcohol can be used, and its solid content is about 20 to 40% by weight.

  The heat-sensitive recording material of the present invention has an undercoat layer on the support and a heat-sensitive recording layer provided on the undercoat layer, but a layer other than the undercoat layer and the heat-sensitive recording layer may be provided as appropriate. For example, a protective layer can be provided on the heat-sensitive recording layer, and a backcoat layer can be provided on the opposite side of the support from the heat-sensitive recording layer.

In the present invention, means for applying a coating layer other than the undercoat layer, that is, a heat-sensitive recording layer, a protective layer, a backcoat layer, and the like are not particularly limited, and can be applied according to a well-known common technique. For example, an off-machine coating machine or an on-machine coating machine equipped with various coaters such as an air knife coater, a rod blade coater, a vent blade coater, a bevel blade coater, a roll coater, and a curtain coater is appropriately selected and used.
The coating amount of the coating layer other than the undercoat layer is determined according to the required performance and recording suitability, and is not particularly limited, but the general coating amount of the heat-sensitive recording layer is 2 to 12 g in solid content. / ^m is about ^2, the coating amount of the protective layer is 0.5 to 5.0 g / ^{m 2} is preferred solids.
Further, various known techniques in the heat-sensitive recording material field can be added as appropriate, such as applying a smoothing process such as supercalendering after coating each coating layer.

  The following examples illustrate the invention but are not intended to limit the invention. In Examples and Comparative Examples, “parts” represents “parts by weight” and “%” represents “% by weight” unless otherwise specified. Various dispersions or coating solutions were prepared as follows.

[Example 1]
A composition comprising the following composition was stirred and dispersed to prepare an undercoat layer coating solution.
<Undercoat layer coating solution 1>
Rosetta type light calcium carbonate (Specialty Minerals
Inc. Product name: Albuquer LO, bulk density: 210 g / L, FIG. 1)
100.0 parts Styrene-butadiene copolymer latex (manufactured by Zeon Corporation, trade name:
ST5526, solid content 48%) 40.0 parts Completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., trade name: PVA)
117, solid content 10%) 30.0 parts water 100.0 parts

Next, the undercoat layer coating solution 1 was applied to one side of a support (high-quality paper having a basis weight of 60 g / m ² ) with a vent blade coater so that the coating amount was 10.0 g / m ² in terms of solid content. Thereafter, drying was performed to obtain an undercoat layer-coated paper.

The developer dispersion (liquid A) and the leuco dye dispersion (liquid B) having the following composition were separately wet-ground with a sand grinder until the average particle size became 0.5 μm.
Developer dispersion (liquid A)
4-hydroxy-4'-isopropoxydiphenylsulfone (manufactured by API Corporation, trade name: NYDS) 6.0 parts fully saponified polyvinyl alcohol aqueous solution (trade name: PVA, manufactured by Kuraray Co., Ltd.)
117, solid content 10%) 18.8 parts water 11.2 parts
Leuco dye dispersion (liquid B)
3-dibutylamino-6-methyl-7-anilinofluorane (manufactured by Yamamoto Kasei Co., Ltd., trade name: ODB-2) 6.0 parts complete saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., trade name: PVA)
117, solid content 10%) 4.6 parts water 2.6 parts

Subsequently, each dispersion liquid was mixed in the following ratio to prepare a thermosensitive recording layer coating liquid.
<Thermosensitive recording layer coating solution 1>
Developer dispersion (liquid A) 36.0 parts Leuco dye dispersion (liquid B) 13.2 parts Completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., trade name: PVA)
117, solid content 10%) 25.0 parts Aluminum hydroxide (made by Showa Denko KK, trade name: Heidilite H-32,
50% dispersion) 12.0 parts

Next, on the undercoat layer of the undercoat layer-coated paper, the thermal recording layer coating solution 1 is applied with a rod blade coater so that the coating amount is 2.5 g / m ^{2 in} solid content, and then dried. And a heat-sensitive recording material was obtained by processing with a super calendar so that the smoothness was 500 to 1000 seconds.

[Example 2]
The same as in Example 1 except that the blending amount of the styrene / butadiene copolymer latex in the undercoat layer coating liquid 1 was 45.0 parts and the blending amount of the completely saponified polyvinyl alcohol aqueous solution was 7.0 parts. Thus, a heat-sensitive recording material was produced.
[Example 3]
The same as in Example 1 except that the blending amount of the styrene / butadiene copolymer latex in the undercoat layer coating solution 1 was 44.0 parts and the blending amount of the completely saponified polyvinyl alcohol aqueous solution was 11.0 parts. Thus, a heat-sensitive recording material was produced.
[Example 4]
The same as in Example 1 except that the blending amount of the styrene / butadiene copolymer latex in the undercoat layer coating liquid 1 was 39.0 parts and the blending amount of the completely saponified polyvinyl alcohol aqueous solution was 37.0 parts. Thus, a heat-sensitive recording material was produced.
[Example 5]
The same as in Example 1 except that the blending amount of the styrene / butadiene copolymer latex in the undercoat layer coating solution 1 was 36.0 parts and the blending amount of the completely saponified polyvinyl alcohol aqueous solution was 50.0 parts. Thus, a heat-sensitive recording material was produced.
[Example 6]
The same as in Example 1 except that the blending amount of the styrene / butadiene copolymer latex of the undercoat layer coating liquid 1 was 35.0 parts and the blending amount of the completely saponified polyvinyl alcohol aqueous solution was 55.0 parts. Thus, a heat-sensitive recording material was produced.

[Example 7]
The same as in Example 1 except that the blending amount of the styrene / butadiene copolymer latex in the undercoat layer coating liquid 1 was 23.5 parts and the blending amount of the completely saponified polyvinyl alcohol aqueous solution was 111.0 parts. Thus, a heat-sensitive recording material was produced.
[Example 8]
The same as in Example 1 except that the blending amount of the styrene / butadiene copolymer latex in the undercoat layer coating liquid 1 was 15.5 parts and the blending amount of the completely saponified polyvinyl alcohol aqueous solution was 148.0 parts. Thus, a heat-sensitive recording material was produced.
[Example 9]
Example 1 except that Rosetta-type light calcium carbonate (Albuquer LO) in the undercoat layer coating solution 1 was changed to Rosetta-type light calcium carbonate (trade name: TP221BM, bulk density 230 g / L, FIG. 2). A thermosensitive recording material was produced in the same manner as described above.

[Example 10]
A thermosensitive recording material was produced in the same manner as in Example 1 except that the undercoat layer coating solution 2 was used instead of the undercoat layer coating solution 1.
<Undercoat layer coating solution 2>
Rosetta-type light calcium carbonate (Albuquer LO) 100.0 parts Organic hollow particles (Rohm and Haas, trade name: HP1055,
Average particle diameter (d ₅₀ ) 1.0 μm, hollow ratio 50%) 20.0 parts Styrene-butadiene copolymer latex (manufactured by Nippon Zeon Co., Ltd.,
Product name: ST5526) 40.0 parts Completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., product name: PVA)
117) 30.0 parts water 100.0 parts

[Example 11]
A thermosensitive recording material was produced in the same manner as in Example 1 except that the undercoat layer coating solution 3 was used instead of the undercoat layer coating solution 1.
<Undercoat layer coating solution 3>
Rosetta-type light calcium carbonate (Albuquer LO) 80.0 parts Firing clay (manufactured by BASF, trade name: Ansilex 93,
Bulk density: 195 g / L) 20.0 parts Styrene-butadiene copolymer latex (manufactured by Nippon Zeon Co., Ltd.)
Product name: ST5526) 40.0 parts Completely saponified polyvinyl alcohol aqueous solution (manufactured by Kuraray Co., Ltd.,
Product name: PVA117) 30.0 parts Water 100.0 parts

[Comparative Example 1]
Other than using Rosetta-type light calcium carbonate (product of Specialty Minerals Inc., trade name: Albuquer 5970, bulk density: 250 g / L) instead of rosetta-type light calcium carbonate (Albuquer LO) in undercoat layer coating solution 1 Was the same as in Example 1 to produce a thermosensitive recording material.
[Comparative Example 2]
A thermosensitive recording material was produced in the same manner as in Example 10 except that rosetta-type light calcium carbonate (Albuquer 5970) was used instead of rosetta-type light calcium carbonate (Albuquer LO) in the undercoat layer coating solution 2.
[Comparative Example 3]
A thermosensitive recording material was produced in the same manner as in Example 1 except that the undercoat layer coating solution 4 was used instead of the undercoat layer coating solution 1.
<Undercoat layer coating solution 4>
Rosetta-type light calcium carbonate (Albuquer 5970) 80.0 parts Firing clay (manufactured by BASF, trade name: Ansilex 93) 20.0 parts Styrene-butadiene copolymer latex (manufactured by Nippon Zeon Co., Ltd.)
Product name: ST5526) 40.0 parts Completely saponified polyvinyl alcohol aqueous solution (manufactured by Kuraray Co., Ltd.,
Product name: PVA117) 30.0 parts Water 100.0 parts

[Comparative Example 4]
A thermosensitive recording material was produced in the same manner as in Example 1 except that the undercoat layer coating solution 5 was used instead of the undercoat layer coating solution 1.
<Undercoat layer coating solution 5>
Baked clay (manufactured by BASF, trade name: Ansilex 93) 100.0 parts Styrene-butadiene copolymer latex (manufactured by Nippon Zeon,
Product name: ST5526) 40.0 parts Completely saponified polyvinyl alcohol aqueous solution (manufactured by Kuraray Co., Ltd.,
Product name: PVA117) 30.0 parts Water 100.0 parts

[Comparative Example 5]
A thermosensitive recording material was produced in the same manner as in Example 1 except that the undercoat layer coating solution 6 was used in place of the undercoat layer coating solution 1.
<Undercoat layer coating liquid 6>
Organic hollow particles (Rohm and Haas, trade name: HP1055)
20.0 parts Styrene-butadiene copolymer latex (manufactured by Nippon Zeon Co., Ltd.,
Product name: ST5526) 40.0 parts Completely saponified polyvinyl alcohol aqueous solution (manufactured by Kuraray Co., Ltd.,
Product name: PVA117) 30.0 parts Water 100.0 parts

The following evaluation was performed about the produced thermosensitive recording material.
<Color development sensitivity (print density)>
Using the TH-PMD manufactured by Okura Electric Co., Ltd. (with a thermal recording paper printing tester and a Kyocera thermal head), the produced thermal recording medium was solid printed at an applied energy of 0.27 mJ / dot and a printing speed of 50 mm / sec. did. The printing density of the solid printing part was measured with a Macbeth densitometer (RD-914, using an amber filter) to evaluate the color development sensitivity.

<Heat-resistant discoloration of blank paper>
The produced thermal recording material was treated in an environment of 80 ° C. for 1 hour and then allowed to stand in an environment of 23 ° C. and 50% RH for 3 hours.
Measure the density of the non-printing area (blank area) with a Macbeth densitometer (RD-914, using amber filter), calculate the ground color value from the difference between the values before and after processing, and heat resistance of the non-printing area (blank area) Sex was evaluated according to the following criteria. If the evaluation is good or acceptable, there is no practical problem.
Ground color development value = (density of non-printed part after processing)-(density of non-printed part before processing)
Good: Ground color development value is less than 0.3 Possible: Ground color development value is 0.3 or more and less than 0.4 Impossibility: Ground color development value is 0.4 or more

<Print quality>
Using the TH-PMD manufactured by Okura Electric Co., Ltd. (with a thermal recording paper printing tester and a Kyocera thermal head installed), the printed thermal recording medium was solid printed at an applied energy of 0.15 mJ / dot and a printing speed of 50 mm / sec. did. The solid print portion was visually observed, and the print image quality was evaluated according to the following criteria. If the evaluation is excellent, good, or acceptable, there is no practical problem.
Excellent: No white spots are observed.
Good: Some white spots are observed, but the whole is solid.
Good: A white portion is observed, but the whole is generally solid.
Impossible: There are many white areas.

<Printability (head residue resistance)>
The produced thermal recording material was solid-printed with an applied energy of 0.20 mJ / dot under an environment of −10 ° C. using a printing tester (manufactured by Canon Inc., HT180). The state of the thermal head deposit after 1 m printing was visually observed and evaluated according to the following criteria. If the evaluation is excellent, good, or acceptable, there is no practical problem.
Excellent: No deposits.
Good: Almost no deposits.
Yes: There are some deposits.
Impossible: There are many deposits.

＊表中、ＰＶＡ／ＳＢＲ（％）は、ＳＢＲ（スチレン・ブタジエン共重合体ラテックス）に対するＰＶＡ（完全ケン化型ポリビニルアルコール）の重量割合（固形分％）を表す。The evaluation results are shown in Table 1.

* In the table, PVA / SBR (%) represents a weight ratio (solid content%) of PVA (fully saponified polyvinyl alcohol) to SBR (styrene-butadiene copolymer latex).

Claims (7)

A support, an undercoat layer containing a pigment and a binder as main components provided on the support, a colorless to light-colored electron-donating leuco dye and an electron-accepting developer provided on the undercoat layer And a thermosensitive recording layer containing as a main component, the pigment contained in the undercoat layer is a rosette-type light carbon dioxide in which spindle-shaped primary particles are aggregated radially to form secondary particles. A heat-sensitive recording material that is calcium and has a bulk density of 240 g / L or less. The heat-sensitive recording material according to claim 1, wherein the bulk density is 150 to 220 g / L. The heat-sensitive recording material according to claim 1 or 2, wherein the binder contained in the undercoat layer comprises a water-soluble resin and a water-insoluble resin, and the weight ratio of water-soluble resin / water-insoluble resin is 35/100 or less. The heat-sensitive recording material according to claim 1 or 2, wherein the binder contained in the undercoat layer comprises a water-soluble resin and a water-insoluble resin, and the weight ratio of water-soluble resin / water-insoluble resin is 3 to 30/100. . The heat-sensitive recording material according to any one of claims 1 to 4, wherein the water-soluble resin is a polyvinyl alcohol. The heat-sensitive recording material according to any one of claims 1 to 5, wherein the water-insoluble resin is a styrene-butadiene resin. The heat-sensitive recording material according to claim 1, wherein the rosetta-type light calcium carbonate is 70% by weight or more of the total pigment contained in the undercoat layer.

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