JP2003094806A - Heat sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sensitive recording material, which has high sensitivity and high color developing density and excellent water resistance. SOLUTION: In the heat sensitive recording material having a heat sensitive recording layer mainly made of a leuco dye and a developer developing the color in the leuco dye under heat on a support, the heat sensitive recording layer includes a copolymer of a (monomer I) or a vinyl monomer having a heterocyclic group with a basic nitrogen in the heterocycle and a (monomer II) or an ethylenic vinyl monomer having an α,β-saturated double bond.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material excellent in color developing sensitivity and water resistance.

[0002]

2. Description of the Related Art In recent years, various recording materials have been researched, developed and put into practical use in the information recording field with the diversification of information and the expansion of needs. Among them, thermal recording materials include (1) heating. The information processing field () has the advantages that simple image recording is possible only by the process, and (2) the necessary device mechanism is simple and compact, and the recording material is easy to handle and inexpensive. Desk calculator, output of computer etc.), medical measurement recorder field, low speed or high speed facsimile field, automatic ticket vending machine field (tickets, entrance tickets, etc.), thermal copying machine field, PO
It is used in various fields such as the label field of S system.

As such a heat-sensitive recording material, there is a demand for a material which rapidly develops a high density color and has a high fastness to the color image and the background. Therefore, as a low-melting-point developer or sensitizer, a material that is eutectic with a leuco dye or a developer and causes a melting point drop is added. Since the temperature decreases, there is a problem that the sensitivity is improved and the background fog is generated at a low temperature.

There have been various proposals for making a leuco dye into fine particles to make a heat-sensitive recording material highly sensitive. For example, a leuco dye having a volume average particle size of 2 μm or less is used (JP-A-57 / 57).
No. 47693), two or more kinds of leuco dyes are pulverized at the same time so as to have an average particle size of 2 μm or less (JP-A-7-223375), and the average particle size is 0.1.
A heat-sensitive recording material (JP-A-7-186527), which contains a leuco dye and a color-developing agent of μm to 0.8 μm, and colloidal silica having an average particle size of 5 to 20 nm, has been proposed.

These leuco dyes are made into fine particles by using a water-soluble polymer such as cellulose or polyvinyl alcohol as a dispersant, and bring the particles to a predetermined particle size in water by a dispersing machine such as a ball mill, sand mill, high speed jet mill or attritor. However, the proportion of the fine particle component increases as the average particle diameter is made smaller, and particularly those having an average particle diameter of 0.3 μm or less deteriorate the heat-resistant storage of the heat-sensitive recording material. Further, when polyvinyl alcohol is used as a dispersant to form fine particles, coloring (liquid fog) of the dispersion liquid occurs, so that the background density of the heat-sensitive recording material is increased.

Further, a method of making fine particles of a leuco dye by an emulsion method has been proposed. For example, JP-A-61-2
No. 187283 describes a method of emulsifying a solution in which a leuco dye is dissolved in an organic solvent in water, but a step of removing the organic solvent after emulsification is necessary, and background fog occurs due to residual organic solvent. There are drawbacks. JP-A-56-
No. 164890 proposes a method in which a leuco dye is emulsified with a heat-fusible substance, but the heat-fusible substance lowers the melting point and heat-resistant storage. JP-A-7-18653
No. 1 proposes a heat-sensitive recording material in which the volume average particle diameter of the leuco dye is 0.3 μm or less and contains an ultraviolet absorber. A method of emulsifying with a high pressure homogenizer using an emulsifier is described. In addition, JP-A-7-22337
No. 9 proposes an emulsion-dispersed leuco dye having an average particle diameter of 1.0 μm or less. The emulsion-dispersion method in this proposal is a method in which a leuco dye is heated and melted at high speed using an emulsifier. A method of emulsifying and dispersing by high-pressure spray from a stirrer or a nozzle is described. The melting point of leuco dye is usually 150 ° C. or higher.
In order to heat-melt the leuco dye and emulsify it in water as described in JP-A No. 7-223379, a special apparatus such as a high pressure container is required, and it is difficult to industrially mass-produce it. Further, the method of emulsifying the leuco dye uses a low molecular weight emulsifier, and thus has a drawback that the water resistance of the heat-sensitive recording material is lowered.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a heat-sensitive recording material which is improved in the drawbacks of the prior art and has a high color density, high sensitivity, low background fog and excellent water resistance.

[0008]

SUMMARY OF THE INVENTION The present invention has been made as a result of studying a resin and a leuco dye dispersant in a thermal recording material.
It is achieved by (1) to (6).

(1) In a heat-sensitive recording material having a heat-sensitive recording layer containing a leuco dye and a color developer capable of coloring the leuco dye on heating as a main component, a basic nitrogen ring is formed in the heat-sensitive recording layer. A vinyl monomer having a heterocyclic group within it (referred to as monomer I) and an ethylenic vinyl monomer having an α, β saturated double bond (referred to as monomer II)
A heat-sensitive recording material containing a copolymer of

(2) The heat-sensitive recording material as described in (1) above, wherein a copolymer of monomer I and monomer II is used as a dispersant for the leuco dye.

(3) The heat-sensitive recording material as described in (1) or (2) above, wherein the monomer I is vinylimidazole and / or vinylpyrrolidone.

(4) The composition according to any one of the above (1) to (3), wherein the proportion of the monomer I contained in the copolymer of the monomer I and the monomer II is 5 to 95% by weight. Thermal recording material.

(5) The heat-sensitive recording material as described in any of (1) to (4) above, wherein a copolymer of monomer I and monomer II is used as a dispersant for the color developer.

(6) The heat-sensitive recording material as described in any of (1) to (5) above, wherein an intermediate layer containing thermoplastic hollow resin particles is provided between the support and the heat-sensitive color forming layer. .

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the heat-sensitive recording material of the present invention is characterized by containing a copolymer of monomer I and monomer II in the heat-sensitive recording layer. This copolymer can be obtained by a known radical polymerization using a vinyl monomer having a heterocyclic group having a basic nitrogen in the ring and an ethylenic vinyl monomer having an α, β saturated double bond. When used as a material, solution polymerization in water, a water-soluble solvent, or a mixture of water and a water-soluble solvent is preferable.

Examples of the monomer I include vinyl pyridine, vinyl imidazole, 2-methyl-N vinyl imidazole, vinyl pyrrolidone and the like.

Examples of the monomer II include methyl (meth)
Acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate,
2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, furfuryl (meth) acrylate, benzyl (meth) acrylate, stearyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) ) Crylate, cyclohexyl (meth) acrylate,
Isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, polypropylene glycol mono (meth) acrylate, polyethylene glycol (meth)
Examples thereof include acrylate, EO-PO-mono (meth) acrylate, vinyl acetate, styrene, P-vinyltoluene and butadiene.

The content of the monomer I in the copolymer is 5 to 9
It is 5% by weight, preferably 30 to 90% by weight.
If it is less than 5%, the stability of the copolymer itself is poor, and if it is 95% or more, the water resistance of the thermal recording material paper is poor.

The copolymer of the present invention can be used as an underlayer of a heat-sensitive recording material, a binder of the heat-sensitive recording layer, and if necessary, an overcoat layer formed on the heat-sensitive recording layer, a leuco dye dispersion liquid. It is preferably used as a dispersant for a dispersion liquid containing a and a color developer. In particular, when the copolymer of the present invention is used as a dispersant for a leuco dye dispersion, it is possible to form fine particles in a short time, the leuco dye dispersion is less colored, and a low molecular weight surfactant is used. The water resistance of the heat-sensitive recording material is excellent as compared with the case of dispersion.

The leuco dyes used in the heat-sensitive recording color-forming layer of the present invention may be used alone or in admixture of two or more, and as such leuco dyes, those applied to this type of heat-sensitive recording material are arbitrary. And leuco compounds of dyes such as triphenylmethane type, fluorane type, phenothiazine type, auramine type, spiropyran type, indolinophtalide type dyes are preferably used. Specific examples of such leuco dyes include those shown below.

3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis ( p-dimethylaminophenyl) -6-diethylaminophthalide,
3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-chlorofluorane, 3-dimethylamino-5,7 -Dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-
Diethylamino-7,8-benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-
(Np-tolyl-N-ethylamino) -6-methyl-
7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluorane, 2- {3. 6-bis (diethylamino)-
9- (o-chloroanilino) xanthyl benzoate lactam}, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-di- n-Butylamino-7- (o-chloroanilino) fluorane, 3-N-methyl-N, n-amylamino-6-
Methyl-7-anilinofluorane, 3-N-methyl-N
-Cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3- (N, N-diethylamino) -5
-Methyl-7- (N, N-dibenzylamino) fluorane, benzoyl leuco methylene blue, 6'-chloro-
8'-methoxy-benzoindolino-spiropyran,
6'-bromo-3'-methoxy-benzoindolino-spiropyran, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2'-methoxy-5'-chlorophenyl) phthalide, 3- (2'-hydroxy-4 '
-Dimethylaminophenyl) -3- (2'-methoxy-
5'-nitrophenyl) phthalide, 3- (2'-hydroxy-4'-diethylaminophenyl) -3- (2'-
Methoxy-5'-methylphenyl) phthalide, 3-
(2'-methoxy-4'-dimethylaminophenyl)-
3- (2'-hydroxy-4'-chloro-5'-methylphenyl) phthalide, 3- (N-ethyl-N-tetrahydrofurfuryl) amino-6-methyl-7-anilinofluorane, 3-N -Ethyl-N- (2-ethoxypropyl) amino-6-methyl-7-anilinofluorane, 3
-N-methyl-N-isobutyl-6-methyl-7-anilinofluorane 3-morpholino-7- (N-propyl-
Trifluoromethylanilino) fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3
-Diethylamino-5-chloro-7- (N-benzyl-
Trifluoromethylanilino) fluorane, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluorane, 3-diethylamino-5-chloro-7- (α
-Phenylethylamino) fluorane, 3- (N-ethyl-p-toluidino) -7- (α-phenylethylamino) fluorane, 3-diethylamino-7- (o-methoxycarbonylphenylamino) fluorane, 3-diethylamino- 5-methyl-7- (α-phenylethylamino) fluorane, 3-diethylamino-7-piperidinofluorane, 2-chloro-3- (N-methyltoluidino) -7- (pn-butylanilino) fluorane, Three
-Di-n-butylamino-6-methyl-7-anilinofluorane, 3,6-bis (dimethylamino) fluorenspiro (9,3 ')-6'-dimethylaminophthalide,
3- (N-benzyl-N-cyclohexylamino)-
5,6-benzo-7-α-naphthylamino-4′-bromofluorane, 3-diethylamino-6-chloro-7-
Anilinofluorane, 3-diethylamino-6-methyl-7-mesitidino-4 ', 5'-benzofluorane, 3
-N-methyl-N-isopropyl-6-methyl-7-anilinofluorane, 3-N-ethyl-N-isoamyl-
6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (2 ', 4'-dimethylanilino) fluorane, 3-morpholino-7- (N-propyl-trifluoromethylanilino) ) Fluoran, 3-pyrrolidino-7-trifluoromethylanilinofluorane,
3-diethylamino-5-chloro-7- (N-benzyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluorane, 3-diethylamino-5-chloro- (Α-
Phenylethylamino) fluorane, 3- (N-ethyl-p-toluidino) -7- (α-phenylethylamino) fluorane, 3-diethylamino-7- (o-methoxycarbonylphenylamino) fluorane, 3-diethylamino-5 -Methyl-7- (α-phenylethylamino) fluorane, 3-diethylamino-7-piperidinofluorane, 2-chloro-3- (N-methyltoluidino) -7- (p-N-butylanilino) fluorane 3,
6-bis (dimethylamino) fluorene spiro (9,
3 ')-6'-dimethylaminophthalide, 3- (N-benzyl-N-cyclohexylamino) -5,6-benzo-7-α-naphthylamino-4'-bromofluorane,
3-diethylamino-6-chloro-7-anilinofluorane, 3-N-ethyl-N-(-2-ethoxypropyl) amino-6-methyl-7-anilinofluorane, 3
-N-ethyl-N-tetrahydrofurfurylamino-6
-Methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-mesitidino-4 ', 5'-benzofluorane, 3-p-dimethylaminophenyl) -3-
{1,1-bis (p-dimethylaminophenyl) ethylene-2-yl} phthalide, 3- (p-dimethylaminophenyl) -3- {1,1-bis (p-dimethylaminophenyl) ethylene-2- Il} -6-dimethylaminophthalide, 3- (p-dimethylaminophenyl) -3-
(1-p-Dimethylaminophenyl-1-phenylethylene-2-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (1-p-dimethylaminophenyl-
1-p-chlorophenylethylene-2-yl) -6-dimethylaminophthalide, 3- (4'-dimethylamino-
2'-methoxy) -3- (1 "-p-dimethylaminophenyl-1" -p-chlorophenyl-1 ", 3" -butadiene-4 "-yl) benzophthalide, 3- (4'-dimethylamino-2) '-Benzyloxy) -3- (1 "-
p-dimethylaminophenyl-1 "-phenyl-1",
3 "-butadiene 4" -yl) benzophthalide 3-dimethylamino-6-dimethylamino-fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide, 3,
3-bis {2- (p-dimethylaminophenyl) -2-
p-methoxyphenyl) ethenyl} -4,5,6,7-
Tetrachlorophthalide, 3-bis {1,1-bis (4-
Pyrrolidinophenyl) ethylene-2-yl} -5,6-
Examples include dichloro-4,7-dibromophthalide, bis (p-dimethylaminostyryl) -1-naphthalenesulfonylmethane, and bis (p-dimethylaminostyryl) -1-p-tolylsulfonylmethane.

As the color developer used in the present invention, 4,4'-isopropylidene bisphenol, 4,
4'-isopropylidene bis (o-methylphenol), 4,4'-secondary butylidene bisphenol 4,4'-isopropylidene bis (2-tert-butylphenol), 4,4'-methylenebis (oxyethylenethio) di Phenol, zinc p-nitrobenzoate, 1,3,5-tris (4-tert-butyl-3)
-Hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 2,2- (3,4'-dihydroxydiphenyl)
Propane, bis (4-hydroxy-3-methylphenyl) sulfide, 4- {β- (p-methoxyphenoxy) ethoxy} salicylic acid, 1,7-bis (4-hydroxyphenylthio) -3,5-dioxaheptane , 1,
5-bis (4-hydroxyphenylthio) -5-oxapentane, phthalic acid monobenzyl ester monocalcium salt, 4,4′-cyclohexylidene diphenol,
4,4'-isopropylidene bis (2-chlorophenol), 2,2'-methylene bis (4-methyl-6-tert-butylphenol), 4,4'-butylidene bis (6-tert-butyl-2-methyl) Phenol, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,
3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 4,4'-thiobis (6-
Tert-butyl-2-methyl) phenol, 4,
4'-diphenol sulfone, 4-isopropoxy-
4'-hydroxydiphenyl sulfone, 4-benzyloxy-4'-hydroxydiphenyl sulfone, 4,4'-
Diphenol sulfoxide, isopropyl P-hydroxybenzoate, benzyl P-hydroxybenzoate, benzyl protocatechuylate, stearyl gallate, lauryl gallate, octyl gallate, 1,3-bis (4-hydroxyphenylthio) -propane, N , N'-diphenylthiourea, N, N'-di (m-chlorophenyl) thiourea, salicylanilide, bis- (4-hydroxyphenyl) acetic acid methyl ester, bis- (4-hydroxyphenyl) acetic acid benzyl ester, 1 , 3-bis (4-hydroxycumyl) benzene, 1,4-bis (4-hydroxycumyl) benzene, 2,4'-diphenol sulfone, 2,2'-diallyl-4,4'-diphenol Sulfone, 3,4-dihydroxyphenyl-4'-methyldiphenyl sulfone, 1-acetate Aryloxy-2-naphthoic acid zinc, 2-acetyloxy-1-naphthoic acid zinc, 2
-Zinc acetyloxy-3-naphthoate, α, α-bis (4-hydroxyphenyl) -α-methyltoluene, antipyrine complex of zinc thiocyanate, tetrabromobisphenol A, tetrabromobisphenol S, 4,
4'-thiobis (2-methylphenol), 4,4'-
Thiobis (2-chlorophenol), International Patent WO99
(Poly) 4-hydroxybenzoic acid derivative described in US Pat. No. 5,511,544, urea urethane compound described in International Patent WO 00/14058, diphenyl sulfone derivative described in JP-A-08-333329, and a sulfonylaminocarbonylamide group It is a colorant or the like. These developers are used in an amount of 2 to 10 parts by weight based on 1 part by weight of the leuco dye.

The heat-sensitive recording layer may optionally contain a sensitivity improver (heat-fusible substance), and specific examples thereof include the following. Fatty acids such as stearic acid and behenic acid, fatty acid amides such as stearic acid amide and palmitic acid amide, fatty acid metal salts such as zinc stearate, aluminum stearate, calcium stearate, zinc palmitate and zinc behenate, p-benzyl Biphenyl, terphenyl, triphenylmethane,
Benzyl p-benzyloxybenzoate, β-benzyloxynaphthalene, phenyl β-naphthoate, phenyl 1-hydroxy-2-naphthoate, methyl 1-hydroxy-2-naphthoate, diphenyl carbonate, glare coal carbonate, terephthalic acid Dibencil, dimethyl terephthalate, 1,4-dimethoxynaphthalene, 1,4-
Diethoxynaphthalene, 1,4-dibenzyloxynaphthalene, 1,2-diphenoxyethane, 1,2-bis (3
-Methylphenoxy) ethane, 1,2-bis (4-methylphenoxy) ethane, 1,4-diphenoxy-2-butene, 1,2-bis (4-methoxyphenylthio) ethane, dibenzoylmethane, 1,4 -Diphenylthiobutane, 1,4-diphenylthio-2-butene, 1,3-bis (2-vinyloxyethoxy) benzene, 1,4-bis (2-vinyloxyethoxy) benzene, p- (2-
Vinyloxyethoxy) biphenyl, acetylbiphenyl, p-aryloxypphenyl, p-propargyloxybiphenyl, dibenzoyloxymethane, dibenzoyloxypropane, dibenzyldisulfide, 1,1
-Diphenylethanol, 1,1-diphenylpropanol, p-benzyloxybenzyl alcohol, 1,3
-Phenoxy-2-propanol, N-octadecylcarbamoyl-p-methoxycarbonylbenzene, N-octadecylcarbamoylbenzene, 1,2-bis (4-
Methoxyphenoxy) propane, 1,5-bis (4-methoxyphenoxy) -3-oxapentane, dibenzyl oxalate, bis (4-methylbenzyl) oxalate, bis (4-chlorobenzyl) diphenyl sulfone oxalate and the like.

In order to produce the heat-sensitive recording material of the present invention,
When the above materials are bonded and supported on a support, various commonly used binders can be appropriately used, and specific examples thereof include the following.

Polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose and ethyl cellulose, polyacrylic acid sodium -Da, polyvinylpyrrolidone, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt , Water-soluble polymers such as polyacrylamide, sodium alginate, gelatin and casein, as well as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutylmethacrylate G, ethylene / vinyl acetate copolymer Emulsion and styrene / butadiene copolymers such as the body, styrene / butadiene / latex such as acrylic copolymer.

Further, in the present invention, if necessary,
Auxiliary additive components that are commonly used in this type of heat-sensitive recording material, such as fillers, surfactants, lubricants, pressure color-developing inhibitors and the like, can be used together.

In this case, examples of the filler include inorganic fine powders such as diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide and aluminum hydroxide, Urea-formalin resin, styrene / methacrylic acid copolymer,
Organic fine powders such as polystyrene resin and vinylidene chloride resin can be used, and can also be used in combination with a cross-linking material or the copolymer of the present invention.

As the lubricant, higher fatty acid and its metal salt,
Higher fatty acid amide, higher fatty acid ester, animal type,
Examples thereof include various vegetable or petroleum waxes.

As the support in the present invention, paper, synthetic paper,
Any of laminated paper and the like can be used.

In the present invention, for the purpose of increasing the sensitivity of the heat-sensitive recording material, it is preferable to provide an undercoat layer containing a binder and hollow particles as main components between the support and the heat-sensitive recording layer. As the binder, the binder resin used in the heat-sensitive recording layer can be used. The hollow particles include, for example, a thermoplastic resin as a shell and a hollow ratio of 30%.
Thus, those having a weight average particle diameter of 0.4 to 10 μm can be used. The hollow ratio here is the ratio of the outer diameter to the inner diameter of the hollow particles, and is (the inner diameter of the hollow particles / the outer diameter of the hollow particles) × 1
It is represented by 00%.

The undercoat layer has a dry weight of 2-1.
0 g / m ^2, preferably can be provided in a range of 2.5~7g / m ^2. The amount of hollow particles in the undercoat layer is 30 to 90% by weight, preferably 40 to 80% by weight
Is.

Further, in the present invention, a protective layer can be provided on the heat-sensitive recording layer as described above, and the protective layer is a binder and a filler (calcium carbonate, silica, aluminum hydroxide) which can be used in the heat-sensitive recording layer. Etc.) as the main component, as well as an ultraviolet curable resin or an electron beam curable resin.

The heat-sensitive recording material of the present invention is produced by the following method using the above materials. That is, according to a conventional method, a leuco dye, a color developer, a sensitizer, etc. are separately and separately bound to a binder (leuco dye and / or color developer, at least one of which is a copolymer of monomer I and monomer II or, if necessary, A thermosensitive color developing layer coating liquid is prepared by pulverizing and dispersing with other additives in a disperser such as a ball mill, attritor, or sand mill (usually water is used as a medium when pulverizing and dispersing is performed in a wet state). Separately, a coating solution for the undercoat layer and a coating solution for the protective layer are separately prepared by using a binder and / or other additives as required. When an undercoat layer is provided on a support such as paper, the thermal recording material of the present invention is prepared by repeating coating and drying in the order of forming an undercoat layer, a thermosensitive coloring layer, and a protective layer if necessary. That. If necessary, it is possible to provide a magnetic recording layer on the opposite side of the support on the thermosensitive recording layer.

The recording method of the heat-sensitive recording material of the present invention is not particularly limited to a heating pen, a thermal head, laser heating and the like depending on the purpose of use.

[0035]

EXAMPLES Next, the present invention will be described in more detail by way of examples. The parts and% shown below are based on weight.

1. Preparation of Solution A A composition (30% dye content) comprising 30 parts of 3-dibutylamino-6-methyl-N-7-anilinofluorane and the dispersant shown in Table 1 below was dispersed by a sand mill.
(A-1, A-2, A-3, A-4, A-5, A-6) For comparison, a dye dispersion liquid was prepared in a system not using the dispersant of the present invention. (A-7, A-8)

[0037]

[Table 1] MMA; Methyl Methacrylate BA; Butyl Acrylate VP; Vinyl Pyrrolidone St; Styrene MA; Methyl Acrylate VIM; Vinyl Imidazole

2. Preparation of solution B (2) -1 20 parts of 4-isopropoxy 4′-hydroxydiphenyl sulfone, 10% aqueous solution of polyvinyl alcohol 20
Parts and 60 parts of water were dispersed in a sand mill to obtain a dispersion liquid. (2) -2 Similar to (2) -1, except that 20 parts of 10% MMA / VP (10/90 weight ratio) aqueous solution was used instead of 20 parts of 10% polyvinyl alcohol aqueous solution of (2) -1. A dispersion was obtained.

3. Preparation of thermosensitive color developing coating solution 20 parts of solution A, 60 parts of solution B, colloidal silica (solid content;
20%) 10 parts, styrene-butadiene latex (solid content; 50%) 20 parts, stearic acid amide dispersion (solid content; 20%) 15 parts, dioctylsulfosuccinic acid aqueous solution (solid content; 5%) 1 part The materials were mixed to prepare a heat-sensitive recording layer coating liquid.

4. Preparation of Undercoat Layer Forming Liquid (4) -1 Calcined Kaolin 20 parts Styrene / butadiene copolymer latex (solid content concentration 47.5%) 20 parts Water 60 parts The above mixture is stirred and dispersed to form an undercoat layer forming liquid. Was prepared. (4) -2 Hollow resin particles (hollowness 90%, weight average particle diameter 3.5 μm, solid content 40%) 25 parts Styrene / butadiene copolymer latex (solid content concentration 47.5%) 15 parts water 60 parts The mixture was stirred and dispersed to prepare an undercoat layer forming liquid.

5. Preparation of Overcoat Layer Forming Liquid A mixture of aluminum hydroxide 20 parts, 10% polyvinyl alcohol aqueous solution 20 parts and water 60 parts was dispersed by a ball mill for 24 hours to prepare an overcoat layer forming liquid.

(Example 1) A fine paper having a basis weight of 60 g / m ² was coated with the undercoat liquid of (4) -1 so that the dry coating amount was 3.0 g / m ² and dried. . Then, a thermosensitive recording layer coating solution using A-1 as solution A and (2) -1 as solution B was used, and the amount of dye deposited was 0.45 g.
/ M ² was applied and dried so as to further over liquid so that the resin dry coverage is 1.5 g / m ² thereon (5)
Was coated and dried. Then, it was processed in a super calender to obtain a heat-sensitive recording material of the present invention.

(Example 2) The thermosensitive recording material of the present invention was prepared in the same manner as in Example 1 except that the coating liquid for the thermosensitive recording layer was prepared by using the liquid A-2 instead of the liquid A-1 in Example 1. Got

(Example 3) The thermosensitive recording material of the present invention was prepared in the same manner as in Example 1 except that the coating liquid for the thermosensitive recording layer was prepared by using the liquid A-3 in place of the liquid A-1 in Example 1. Got

(Example 4) The thermosensitive recording material of the present invention was prepared in the same manner as in Example 1 except that the liquid A-4 used in Example 1 was replaced by the liquid A-4. Got

(Example 5) The thermosensitive recording of the present invention was carried out in the same manner as in Example-1 except that the coating liquid for the thermosensitive recording layer using the liquid A-5 was used in place of the liquid A-1 in Example 1. Got the material.

Example 6 The thermosensitive recording material of the present invention was prepared in the same manner as in Example 1 except that the coating solution for the thermosensitive recording layer was prepared by using the solution A-6 instead of the solution A-1 in Example 1. Got

(Example 7) Example 1 was repeated except that the solution A-5 was used in place of the solution A-1 in Example 1 and the coating solution for the heat-sensitive recording layer used in (2) -1 was used as the solution B. A thermal recording material of the present invention was obtained in the same manner as in.

(Example 8) Example 8 was repeated except that (4) -2 was used as the under solution of Example 1 and the coating solution for the heat-sensitive recording layer using the solution A-5 was used in place of the solution A-1. A thermal recording material of the present invention was obtained in the same manner as in 1.

(Comparative Example 1) A comparative heat-sensitive recording material was obtained in the same manner as in Example 1 except that the liquid A-7 was used in place of the liquid A-1 in Example 1.

(Comparative Example 2) A comparative heat-sensitive recording material was obtained in the same manner as in Example 1 except that Solution A-8 was used in place of Solution A-1 in Example 1.

Table 2 shows the evaluation results of these thermal recording materials. <Evaluation Method> Sensitivity Magnification: The calendered product was measured with a thermal printing experimental device having a thin film head manufactured by Matsushita Electric Parts Co., Ltd., head power 0.45 W / dot, 1 line recording time 20 msec /
L, scanning density 8 × 385 dots / mm, 1 m
A pulse width of 0.0 to 0.7 mmsec was printed every sec, the print density was measured by a Macbeth densitometer RD-914, and the pulse width at which the density became 1.0 was calculated. Comparative Example 1
Is calculated as follows: (pulse width of Comparative Example 1) / (pulse width of measured sample) = sensitivity magnification. The larger the value, the better the sensitivity (thermal response).

Image density: A calendered product was printed with a pulse width of 0.5 mmsec using the above thermal printing experimental device.
The print density and background density were measured with a Macbeth densitometer RD-914.

Water resistance: Each sample printed under the above conditions was immersed in water at 20 ° C. for 15 hours, and then the density of the image area was measured.

[0055]

[Table 2]

[0056]

As is clear from the description of the examples, the thermosensitive recording material of the present invention has a high color density, high sensitivity, and excellent water resistance.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kunio Hayakawa             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Mitsuru Morita             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Yuichi Kawaguchi             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh F term (reference) 2H026 AA07 AA28 BB02 CC05 DD04                       DD14 DD48 DD53 EE03 FF01                       FF11 FF15

Claims (6)

[Claims] 1. A heat-sensitive recording material having a heat-sensitive recording layer containing, as a main component, a leuco dye and a developer capable of coloring the leuco dye when heated, the heat-sensitive recording layer comprising the following monomer I and monomer II. A heat-sensitive recording material containing a copolymer of (Monomer I) A vinyl monomer having a heterocyclic group having a basic nitrogen in the ring. (Monomer II) An ethylenic vinyl monomer having an α, β saturated double bond. 2. The heat-sensitive recording material according to claim 1, wherein the copolymer of the monomer I and the monomer II is used as a dispersant for a leuco dye. 3. The heat-sensitive recording material according to claim 1, wherein the monomer I is vinylimidazole and / or vinylpyrrolidone. 4. The heat-sensitive recording material according to claim 1, wherein the proportion of the monomer I in the copolymer of the monomer I and the monomer II is 5 to 95% by weight. . 5. The heat-sensitive recording material according to claim 1, wherein the copolymer of the monomer I and the monomer II is used as a dispersant for a dispersion liquid containing a color developer. . 6. The heat-sensitive recording material according to claim 1, wherein an intermediate layer containing thermoplastic hollow resin particles is provided between the support and the heat-sensitive recording layer.