Thermosensitive recording composition

Abstract

To provide a thermal recording material that has superior thermal responsiveness, retains whiteness and surface storage stability, and yet excels in the storage stability of a printed part, particularly stability to oil, plasticizer, and water.SOLUTION: A thermal recording composition contains a coloring agent and a developer. The developer contains a first color-developing compound, [3-(3-phenylureido)phenyl]=4-methylbenzenesulfonate or N-[2-(3-phenylureido)phenyl]benzenesulfonamide, and a second color-developing compound, 4,4'-bis(3-tosylureido)diphenylmethane.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a heat-sensitive recording composition containing a color-developing compound having a specific structure, and a heat-sensitive recording material having a heat-sensitive recording layer made of the composition on a support material, which has excellent storage stability of a printed portion and a background.

Background Art

[0002] A heat-sensitive recording material is generally obtained by dispersing a normally colorless or light-colored leuco dye and a color-developing compound such as a phenolic compound in particulate form, mixing the two, and adding additives such as a binder, a sensitizer, a filler, and a lubricant to the mixture to obtain a coating solution, which is then applied to paper, film, synthetic paper, etc. and used. By heating the coating obtained above using a thermal printer or the like having a built-in thermal head, color recording (printing) is obtained by a chemical reaction in which one or both of the leuco dye and the color-developing compound melt and come into contact with each other. Compared with other recording methods, the heat-sensitive recording method has advantages such as (1) no noise during recording, (2) no need for development and fixing, (3) maintenance-free, and (4) relatively inexpensive machinery, and thus is widely used in the fields of facsimile, computer output, printers such as calculators, recorders for medical measurement, automatic ticket vending machines, heat-sensitive recording type labels, etc.

[0003] In recent years, the applications of heat-sensitive recording materials have been increasing in the fields of labels, tickets, and multiple-ride tickets, etc. associated with the POS systemization in retail stores and supermarkets, and the automation of transportation systems. In these applications, the resistance of the recorded images (printing, images, patterns) to water, alcohol, etc., and the storage stability of the coating material before color development recording are essential conditions. In addition, the demand for high-speed recording to improve productivity has been further increasing, and the development of a heat-sensitive recording material with excellent heat responsiveness that can fully cope with high-speed recording is strongly desired. In order to enhance the heat responsiveness, generally, a color-developing compound with a low melting point and a small heat of fusion is required. However, when such a color-developing compound is used, the unprinted part (background) of the heat-sensitive recording material tends to turn black during production, use, or storage, a phenomenon called background fogging, so improvement in the stability of the background is desired.

[0004] Generally, color-developing compounds having phenolic hydroxyl groups have high color-developing ability. Among them, bisphenol-based compounds have been reported many times due to their high color density. 2,2-Bis(4-hydroxyphenyl)propane (bisphenol A) (Patent Document 1) and 4,4'-dihydroxydiphenyl sulfone (bisphenol S) (Patent Document 2) etc. have been proposed. However, these compounds have disadvantages of poor heat responsiveness due to their high melting points, and the printed parts are poor in water resistance. Moreover, phenolic compounds such as bisphenol A have been pointed out as a problem in terms of their use due to endocrine problems, and non-phenolic color-developing compounds that do not contain a phenol structure are desired.

[0005] In response to such demands, as non-phenolic color-developing compounds, Patent Document 3 discloses [3-(3-phenylureido)phenyl]=4-methylbenzenesulfonate, Patent Document 4 discloses N-[2-(3-phenylureido)phenyl]benzenesulfonamide, Patent Document 5 discloses 5-(N-3-methylphenyl-sulfonylamide)-(N',N''-bis-(3-methylphenyl)-isophthalic acid diamide, and Patent Document 6 discloses 4,4'-bis(3-tosylureido)diphenylmethane respectively.

[0006] However, [3-(3-phenylureido)phenyl]=4-methylbenzenesulfonate and N-[2-(3-phenylureido)phenyl]benzenesulfonamide are excellent in heat resistance and have very good ground color coverage, but the storage stability of the printed area is not necessarily satisfactory compared to existing color-developing compounds having phenolic hydroxyl groups, and in particular, improvement in the storage stability of the printed area against oil and plasticizers is desired. In addition, 5-(N-3-methylphenyl-sulfonylamide)-(N’,N’’-bis-(3-methylphenyl)-isophthalic acid diamide and 4,4’-bis(3-tosylureido)diphenylmethane have low thermal responsiveness and are not practical as color-developing compounds for general thermal paper. Moreover, although 4,4’-bis(3-tosylureido)diphenylmethane is characterized by good storage properties, the printed area significantly fades in warm water at about 40°C, so there are limitations in its use for food applications, logistics applications, etc.

[0007] As a measure to improve the storage stability of the printed area, it is generally practiced to add a hindered phenol-based compound as an antioxidant, but it is not preferable due to endocrine problems and the like. Also, there are various antioxidants other than hindered phenol-based ones, but there are problems such as a decrease in whiteness and deterioration in heat resistance, and they do not satisfy the required characteristics for thermal recording applications regardless of whether they are phenolic or non-phenolic.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

[0009] An object of the present invention is to solve the problems of the above-described conventional technologies. More specifically, an object of the present invention is to provide a heat-sensitive recording material that is excellent in heat responsiveness, maintains whiteness and storage stability of the texture, and has excellent storage stability of the printed portion, particularly excellent stability against oil, plasticizer, and water. [Means for Solving the Problems]

[0010] As a result of intensive studies, the present inventors have newly found that a heat-sensitive recording composition containing a color former and a color developer containing a plurality of color-developing compounds having a specific structure as essential components solves the above problems, and have thus completed the present invention. That is, the present invention provides: [1] A heat-sensitive recording composition containing a color former and a color developer, wherein the color developer contains [3-(3-phenylureido)phenyl]=4-methylbenzenesulfonate or N-[2-(3-phenylureido)phenyl]benzenesulfonamide, which is a first color-developing compound, and 4,4'-bis(3-tosylureido)diphenylmethane, which is a second color-developing compound. [2] The heat-sensitive recording composition according to [1] above, wherein the color former contains a compound selected from the group consisting of triarylmethane compounds, fluoran compounds, azaphthalide compounds, and fluorene compounds. [3] The color former is selected from the group consisting of 3 - diethylamino - 6 - methyl - 7 - anilinofluoran, 3 - (N - ethyl - p - toluidino) - 6 - methyl - 7 - anilinofluoran, 3 - (N - ethyl - N - isoamylamino) - 6 - methyl - 7 - anilinofluoran, 3 - diethylamino - 6 - methyl - 7 - (o,p - dimethylanilino)fluoran, 3 - pyrrolidino - 6 - methyl - 7 - anilinofluoran, 3 - (cyclohexyl - N - methylamino) - 6 - methyl - 7 - anilinofluoran, 3 - diethylamino - 7 - (m - trifluoromethylanilino)fluoran, 3 - N - n - dibutylamino - 6 - methyl - 7 - anilinofluoran, 3 - diethylamino - 6 - methyl - 7 - (m - methylanilino)fluoran, 3 - N - n - dibutylamino - 7 - (o - chloroanilino)fluoran, 3 - (N - ethyl - N - tetrahydrofurfurylamino) - 6 - methyl - 7 - anilinofluoran, 3 - (N - ethyl - N - ethoxypropylamino) - 6 - methyl - 7 - anilinofluoran, 3 - (N - ethyl - N - isobutylamino) - 6 - methyl - 7 - anilinofluoran, and 3 - dipentylamino - 6 - methyl - 7 - anilinofluoran. The heat - sensitive recording composition according to the previous item [2] contains a fluoran compound. [4] The heat - sensitive recording composition according to any one of the previous items [1] to [3], wherein the content of the developer is 100 to 500% by mass of the content of the color former. [5] The heat - sensitive recording composition according to any one of the previous items [1] to [4], wherein the content ratio of the first color - developing compound to the second color - developing compound is 95:5 to 60:40. [6] A heat - sensitive recording material having a heat - sensitive recording layer composed of the heat - sensitive recording composition according to any one of the previous items [1] to [5] on a support. [7] The heat - sensitive recording material according to the previous item [6], wherein the support is high - quality paper, synthetic paper, or a plastic film. [8] The heat - sensitive recording layer is 1 to 20 g / m 2 The heat - sensitive recording material according to the previous item [6] or [7]. [9] The heat - sensitive recording material according to any one of [6] to [8], further having an undercoat layer containing an organic pigment and / or an inorganic pigment between the support and the heat - sensitive recording layer.

[10] The heat-sensitive recording material according to the previous item [9], wherein the inorganic pigment is an oil-absorbing inorganic pigment having an oil absorption of 70 to 150 ml / 100 g,

[11] The heat-sensitive recording material according to the previous item

[10] , wherein the inorganic pigment is calcined kaolin, and

[12] The heat-sensitive recording material according to the previous item [9], wherein the organic pigment is plastic hollow particles having a value of average inner diameter of the pigment / average outer diameter of the pigment of 0.5 to 0.99, relates to.

Effect of the Invention

[0011] According to the present invention, it is possible to provide a heat-sensitive recording material excellent in heat responsiveness, storage stability of the printed portion and the background.

Mode for Carrying Out the Invention

[0012] The present invention will be described in detail based on embodiments below, but the present invention is not limited by these embodiments.

[0013] The heat-sensitive recording composition of the present invention contains a color former. The color former used in the heat-sensitive recording composition of the present invention is not particularly limited as long as it is a color-forming compound generally used for pressure-sensitive recording paper or heat-sensitive recording paper. Specific examples of the color former (color-forming compound) include fluoran compounds, triarylmethane compounds, spiro compounds, diphenylmethane compounds, thiazine compounds, lactam compounds, fluorene compounds, vinyl phthalide compounds, etc. Triarylmethane compounds, fluoran compounds, azaphthalide compounds or fluorene compounds are preferred, and fluoran compounds are more preferred. These color-forming compounds can be used alone or in combination.

[0014] The fluoran compound used as the color former is not particularly limited as long as it is a compound having a fluoran skeleton generally used as a color former for heat-sensitive recording paper. Specific examples of fluoran compounds include 3 - diethylamino - 6 - methyl - 7 - anilinofluorane, 3 - dibutylamino - 6 - methyl - 7 - anilinofluorane, 3-(N - methyl - N - cyclohexylamino)-6 - methyl - 7 - anilinofluorane, 3-(N - ethyl - N - isopentylamino)-6 - methyl - 7 - anilinofluorane, 3-(N - ethyl - N - isobutylamino)-6 - methyl - 7 - anilinofluorane, 3-[N - ethyl - N-(3 - ethoxypropyl)amino]-6 - methyl - 7 - anilinofluorane, 3-(N - ethyl - N - hexylamino)-6 - methyl - 7 - anilinofluorane, 3 - dipentylamino - 6 - methyl - 7 - anilinofluorane, 3-(N - methyl - N - propylamino)-6 - methyl - 7 - anilinofluorane, 3-(N - ethyl - N - tetrahydrofurylamino)-6 - methyl - 7 - anilinofluorane, 3 - diethylamino - 6 - methyl - 7-(p - chloroanilino)fluorane, 3 - diethylamino - 6 - methyl - 7-(p - fluoroanilino)fluorane, 3-[N - ethyl - N-(p - tolyl)amino]-6 - methyl - 7 - anilinofluorane, 3 - diethylamino - 6 - methyl - 7-(p - toluidino)fluorane, 3 - diethylamino - 7-(o - chloroanilino)fluorane, 3 - dibutylamino - 7-(o - chloroanilino)fluorane, 3 - diethylamino - 7-(o - fluoroanilino)fluorane, 3 - dibutylamino - 7-(o - fluoroanilino)fluorane, 3 - diethylamino - 7-(3,4 - dichloroanilino)fluorane, 3 - pyrrolidino - 6 - methyl - 7 - anilinofluorane, 3 - diethylamino - 6 - chloro - 7 - ethoxyethylaminofluorane, 3 - diethylamino - 6 - chloro - 7 - anilinofluorane, 3 - diethylamino - 7 - chlorofluorane, 3 - diethylamino - 7 - methylfluorane, 3 - diethylamino - 7 - octylfluorane, 3-[N - ethyl - N-(p - tolyl)amino]-6 - methyl - 7 - phenethylfluorane, 2 - methyl - 6-(N - p - tolyl - N - ethylamino)fluorane (RED520), 9-(N - ethyl - N - isopentylamino)spiro[benzo[a]xanthene - 12,3'-phthalide (RED500), 2'-anilino-6'-(N-ethyl-N-isopentylamino)-3'-methylspiro[phthalide-3,9'-xanthene] (S-205), 2'-anilino-6'-(N,N-dipentan-1-ylamino)-3'-methyl-3H-spiro[isobenzofuran-1,9'-xanthene]-3-one (Black305), 2'-anilino-6'-(dibutylamino)-3'-methylspiro[phthalide-3,9'-xanthene] (Black400), 2'-anilino-6'-[N-ethyl-N-(4-tolyl)amino]-3'-methyl-3H-spiro[isobenzofuran-1,9'-xanthene]-3-one (ETAC), 6-(diethylamino)-2-[(3-trifluoromethyl)anilino]xanthene-9-spiro-3'-phthalide (Black100), 1-ethyl-8-[N-ethyl-N-(4-methylphenyl)amino]-2,2,4-trimethyl-1,2-dihydrospiro[11H-chromeno[2,3,-g]quinolin-11,3'-phthalide] (H-1046), 3-dibutylamino-6-methyl-7-bromofluoran, and 3-[4-(diethylamino)phenyl]-3-(1-ethyl-2-methyl-1H-indol-3-yl)-1(3H)-isobenzofuranone (Blue502), etc. may be mentioned, and 3-dibutylamino-6-methyl-7-anilinofluoran is preferred.,

[0015] The triarylmethane compound used as a color former is not particularly limited as long as it is a compound having a triarylmethane skeleton generally used as a color former for thermal recording paper. Specific examples of the triarylmethane compound include 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as Crystal Violet Lactone or CVL), 3,3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3-(1,2-dimethylaminoindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2-phenylindol-3-yl)phthalide, 3,3-bis(1,2-dimethylindol-3-yl)-5-dimethylaminophthalide, 3,3-bis(1,2-dimethylindol-3-yl)-6-dimethylaminophthalide, 3,3-bis(9-ethylcarbazol-3-yl)-5-dimethylaminophthalide, 3,3-(2-phenylindol-3-yl)-5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-(1-methylpyrrol-2-yl)-6-dimethylaminophthalide, 3-(4-diethylamino-2-methylphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide (Blue200), 3-[4-(diethylamino)-2-hexyloxyphenyl]-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide (Blue203), 3-(4-diethylamino-2-methylphenyl)-3-(1-ethyl 2-methyl-1H-indol-3-yl)-4-azaphthalide (Blue220), and 7-(4-diethylamino-2-ethoxyphenyl)-7-(1-ethyl-2-methyl-1H-indol-3-yl)furo[3,4-b]pyridin-5(7H)-one (Blue63), etc.

[0016] The spiro compound used as a color former is not particularly limited as long as it is a compound having a spiro skeleton generally used as a color former for thermal recording paper. Specific examples of the spiro compound include 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3'-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-propylspirobenzopyran, 3-methylnaphtho-(3-methoxybenzene)spiropyran, 1,3,3-trimethyl-6-nitro-8'-methoxyspiro(indoline-2,2'-benzopyran), and the like.

[0017] The diphenylmethane compound used as a color former is not particularly limited as long as it is a compound having a diphenylmethane skeleton generally used as a color former for thermal recording paper. Specific examples of the diphenylmethane compound include N-halophenyl-leucoauramine, 4,4-bis-dimethylaminophenylbenzhydryl benzyl ether, N-2,4,5-trichlorophenylleucoauramine, and the like.

[0018] The thiazine compound used as a color former is not particularly limited as long as it is a compound having a thiazine skeleton generally used as a color former for thermal recording paper. Specific examples of the thiazine compound include benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, and the like.

[0019] The lactam compound used as a color former is not particularly limited as long as it is a compound having a lactam skeleton generally used as a color former for thermal recording paper. Specific examples of the lactam compound include rhodamine B anilinolactam, rhodamine B-p-chloroanilinolactam, and the like.

[0020] The fluorene compound used as a color former is not particularly limited as long as it is a compound having a fluorene skeleton generally used as a color former for thermal recording paper. Specific examples of the fluorene compound include 3,6-bis(dimethylamino)fluorene spiro(9,3’)-6’-dimethylaminophthalide, 3,6-bis(dimethylamino)fluorene spiro(9,3’)-6’-pyrrolidinophthalide, 3-dimethylamino-6-diethylamino fluorene spiro(9,3’)-6’-pyrrolidinophthalide, and the like.

[0021] The vinyl phthalide compound as a color former is not particularly limited as long as it is a compound having a vinyl phthalide skeleton generally used as a color former for thermal recording paper. Specific examples of the vinyl phthalide compound include 3-[2,2-bis(4-diethylaminophenyl)vinyl]-6-dimethylaminophthalide (H-3035) and 3,3-bis[2-(4-dimethylaminophenyl)-2-(4-methoxyphenyl)vinyl]-4,5,6,7-tetrachlorophthalide (NIR Black78), and the like.

[0022] The thermosensitive recording composition of the present invention contains a color former containing, as essential components, [3-(3-phenylureido)phenyl]=4-methylbenzenesulfonate (hereinafter referred to as "first color-forming compound A") or N-[2-(3-phenylureido)phenyl]benzenesulfonamide (hereinafter referred to as "first color-forming compound B"), which is a first color-forming compound, and 4,4'-bis(3-tosylureido)diphenylmethane (hereinafter referred to as "second color-forming compound"), which is a second color-forming compound.

[0023] The content ratio of the first color-forming compound and the second color-forming compound in the thermosensitive recording composition of the present invention is usually 95:5 to 60:40, preferably 90:10 to 70:30, more preferably 90:10 to 75:25. When the content ratio of the first color-forming compound and the second color-forming compound is outside the above range, problems such as a decrease in printing density and discoloration of the printed portion in the presence of a plasticizer, oil, or moisture may occur, making it impossible to visually recognize and distinguish.

[0024] As long as it does not impair the effects of the present invention, a color former other than the first color-forming compound and the second color-forming compound may be used in combination with the color former contained in the thermosensitive recording composition of the present invention. The color-forming compounds that can be used in combination are not particularly limited, and examples thereof include benzotriazole derivatives (compounds having a benzotriazole skeleton, hereinafter "derivative" has the same meaning), saccharin derivatives, sulfonamide derivatives, malonamide derivatives, thiourea derivatives, sulfonylurea derivatives, and aromatic carboxylic acid derivatives.

[0025] Specific examples of the benzotriazole derivative include benzotriazole, 5-methyl-1H-benzotriazole, 4-methyl-1H-benzotriazole, phenyl-6-benzotriazole, phenyl-5-benzotriazole, chloro-5-benzotriazole, chloro-5-methylbenzotriazole, chloro-5-isopropyl-7-methyl-4-benzotriazole, and bromo-5-benzotriazole.

[0026] Specific examples of the saccharin derivative include saccharin, 1-bromosaccharin, 1-nitrosaccharin, and 1-aminosaccharin.

[0027] Specific examples of the sulfonamide derivatives include methanilyl anilide, N-phenyl-4-aminobenzenesulfonamide, neourylone, N-phenyl-3-nitrobenzenesulfonamide, N-(4-methyl-2-nitrophenyl)benzenesulfonamide, N-(2-methoxyphenyl)-p-toluenesulfonamide, N-(4-toloxyphenyl)-p-toluenesulfonamide, N-(2-chlorophenyl)-p-toluenesulfonamide, N-(4-methylphenyl)-4-methylbenzenesulfonamide, N-(2-methylphenyl)-p-toluenesulfonamide, N-phenylbenzenesulfonamide, 4-bromo-4'-methylbenzenesulfonanilide, N-(4-bromophenyl)benzenesulfonamide, N-(3-nitrophenyl)benzenesulfonamide, N-(4-nitrophenyl)-4-methylbenzenesulfonamide, N-(4-methylphenyl)benzenesulfonamide, N-phenyl-p-toluenesulfonamide, N-phenylbenzenesulfonamide, and the like.

[0028] Specific examples of the malonamide derivatives include N,N'-bis(2-hydroxy-5-phenyl)phenyl-malonamide, N,N'-diphenylmalonamide, N,N'-bis(2,4,6-tribromophenyl)malonamide, N,N'-bis(2-aminophenyl)malonamide, N,N'-bis(m-trifluoromethylphenyl)malonamide, N,N'-bis(m-trifluoromethylphenyl)α,α-dichloromalonamide, diethyl malondianilide, and the like.

[0029] Specific examples of the thiourea derivatives include 1,3-bis(4-methylphenyl)thiourea, 1,3-bisphenylthiourea, 1,3-bis(4-chlorophenyl)thiourea, 1,3-bis(4-methoxyphenyl)thiourea, N,N'-bis(3-chlorophenyl)thiourea, 1,3-bis(3-methoxyphenyl)thiourea, 1,3-bis(3-methylphenyl)thiourea, 1,3-bis(4-benzylphenyl)thiourea, 1,3-bis(4-bromophenyl)thiourea, 1-phenyl-3-butylthiourea, 1-phenyl-3-ethylthiourea, and the like.

[0030] Specific examples of the sulfonylurea derivatives include N-(p-toluenesulfonyl)-N'-(3-n-butylaminosulfonylphenyl)urea, N-(p-toluenesulfonyl)-N'-(4-trimethylacetophenyl)urea, N-(benzenesulfonyl)-N'-(3-p-toluenesulfonyloxyphenyl)urea, N-(p-toluenesulfonyl)-N'-(3-p-toluenesulfonylphenyl)urea, N-(p-toluenesulfonyl)-N'-(3-phenylsulfonyloxyphenyl)urea, tolbutamide, chlorpropamide, and the like.

[0031] Specific examples of the aromatic carboxylic acid derivatives include benzyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, dibenzyl 4-hydroxyphthalate, dimethyl 4-hydroxyphthalate, ethyl 5-hydroxyisophthalate, 3,5-di-t-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, and aromatic carboxylic acids or their polyvalent metal salts, and the like.

[0032] In the thermosensitive recording composition of the present invention, if necessary, optional components such as a sensitizer, a preservability improver, a binder, a filler, and other additives may be used in combination. These optional components may be contained in the thermosensitive recording layer composed of the thermosensitive recording composition of the present invention, but in the case of a multilayer structure, or when an undercoat layer (undercoat layer) or a protective layer (overcoat layer) is provided above and / or below the thermosensitive recording layer, they can also be contained in each of these layers.

[0033] Specific examples of the sensitizer (thermofusible compound) that can be used in combination with the thermosensitive recording composition of the present invention include waxes such as animal and vegetable waxes and synthetic waxes, higher fatty acids, higher fatty acid amides, higher fatty acid anilides, naphthalene derivatives, aromatic ethers, aromatic carboxylic acid derivatives, aromatic sulfonic acid ester derivatives, carbonic acid or oxalic acid diester derivatives, biphenyl derivatives, terphenyl derivatives, sulfone derivatives, aromatic ketone derivatives, and aromatic hydrocarbon compounds, and the like.

[0034] Specific examples of waxes include wood wax, carnauba wax, shellac, paraffin, montan wax, oxidized paraffin, polyethylene wax, and oxidized polyethylene. Specific examples of higher fatty acids include stearic acid and behenic acid. Specific examples of higher fatty acid amides include stearic acid amide, oleic acid amide, N-methyl stearic acid amide, erucic acid amide, methylol behenic acid amide, methylene bis stearic acid amide, and ethylene bis stearic acid amide. Specific examples of higher fatty acid anilides include stearic acid anilide and linoleic acid anilide. Specific examples of naphthalene derivatives include 1-benzyloxynaphthalene, 2-benzyloxynaphthalene, 1-hydroxynaphthoic acid phenyl ester, and 2,6-diisopropylnaphthalene. Specific examples of aromatic ethers include 1,2-diphenoxyethane, 1,4-diphenoxybutane, 1,2-bis(3-methylphenoxy)ethane, 1,2-bis(4-methylphenoxy)ethane, 1,2-bis(4-methoxyphenoxy)ethane, 1,2-bis(3,4-dimethylphenyl)ethane, 1-phenoxy-2-(4-chlorophenoxy)ethane, 1-phenoxy-2-(4-methoxyphenoxy)ethane, 1,2-diphenoxymethylbenzene, and diphenyl glycol. Specific examples of aromatic carboxylic acid derivatives include benzyl p-hydroxybenzoate, benzyl p-benzyloxybenzoate, and dibenzyl terephthalate. Specific examples of aromatic sulfonic acid ester derivatives include phenyl p-toluenesulfonate, phenyl mesitylenesulfonate, 4-methylphenyl mesitylenesulfonate, and 4-tolyl mesitylenesulfonate. Specific examples of carbonic acid or oxalic acid diester derivatives include diphenyl carbonate, dibenzyl oxalate, di(4-chlorobenzyl) oxalate, and di(4-methylbenzyl) oxalates. Specific examples of biphenyl derivatives include p-benzylbiphenyl and p-allyloxybiphenyl.Specific examples of terphenyl derivatives include m-terphenyl and the like. Specific examples of sulfone derivatives include p-toluenesulfonamide, benzenesulfonanilide, p-toluenesulfonanilide, diphenyl sulfone and the like. Specific examples of aromatic ketone derivatives include 4,4'-dimethylbenzophenone, dibenzoylmethane and the like. Specific examples of aromatic hydrocarbon compounds include p-acetotoluidine and the like, respectively.

[0035] Specific examples of the preservative improver that can be used in combination with the heat-sensitive recording composition of the present invention include 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 2,2'-ethylidenebis(4,6-di-t-butylphenol), 4,4'-thiobis(2-methyl-6-t-butylphenol), 4,4'-butylidenebis(6-t-butyl-m-cresol), 1-[α-methyl-α-(4'-hydroxyphenyl)ethyl]-4-[α',α'-bis(4'-hydroxyphenyl)ethyl]benzene, 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, tris(2,6-dimethyl-4-tert-butyl-3-hydroxybenzyl)isocyanurate, 4,4'-thiobis(3-methylphenol), 4,4'-dihydroxy-3,3',5,5'-tetrabromodiphenyl sulfone, 4,4'-dihydroxy-3,3',5,5'-tetramethyldiphenyl sulfone, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane and other hindered phenol compounds, 1,4-diglycidyloxybenzene, 4,4'-diglycidyloxydiphenyl sulfone, 4-benzyloxy-4'-(2-methylglycidyloxy)diphenyl sulfone, terephthalic acid diglycidyl, cresol novolak type epoxy resin, phenol novolak type epoxy resin, bisphenol A type epoxy resin and other epoxy compounds, N,N'-di-2-naphthyl-p-phenylenediamine, sodium or polyvalent metal salts of 2,2'-methylenebis(4,6-di-t-butylphenyl) phosphate, bis(4-ethyleneiminocarbonylaminophenyl)methane, ureaurethane compounds (such as the color-developing compound UU manufactured by Chemipro Kasei Co., Ltd.), and diphenyl sulfone crosslinked type compounds represented by the following formula (1) or mixtures thereof. In the formula (1), a is an integer from 0 to 6.

[0036] [Chemistry]

[0037] Specific examples of the binder that can be used in combination with the heat-sensitive recording composition of the present invention include cellulose derivatives such as methyl cellulose, methoxy cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, and cellulose; polyvinyl alcohol (PVA), carboxy-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, silyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, acetacetyl-modified polyvinyl alcohol, etc., with various degrees of saponification and polymerization degrees of polyvinyl alcohol; polyvinyl pyrrolidone, polyacrylamide, sodium polyacrylate, starch and its derivatives, sulfosuccinic acid esters such as sodium dioctyl sulfosuccinate; sodium dodecyl benzene sulfonate, sodium salt of lauryl alcohol sulfate ester, fatty acid salts, casein, gelatin, water-soluble isoprene rubber, alkali salts of styrene / maleic anhydride copolymer, alkali salts of iso (or diiso) butylene / maleic anhydride copolymer, etc., water-soluble ones or (meth) acrylic acid ester copolymers, styrene / (meth) acrylic acid ester copolymers, polyurethanes, polyester-based polyurethanes, polyether-based polyurethanes, polyvinyl acetate, ethylene / vinyl acetate copolymer, polyvinyl chloride, vinyl chloride / vinyl acetate copolymer, polyvinylidene chloride, polystyrene, styrene / butadiene (SB) copolymer, carboxylated styrene / butadiene (SB) copolymer, styrene / butadiene / acrylic acid copolymer, acrylonitrile / butadiene (NB) copolymer, carboxylated acrylonitrile / butadiene (NB) copolymer, composite particles of colloidal silica and (meth) acrylic resin, etc., hydrophobic polymer emulsions, and the like.

[0038] Specific examples of the filler that can be used in combination with the thermosensitive recording composition of the present invention include calcium carbonate, magnesium carbonate, magnesium oxide, silica, white carbon, kaolin, calcined kaolin, lithopone, talc, clay, magnesium hydroxide, aluminum hydroxide, titanium oxide, zinc oxide, aluminum oxide, barium sulfate, diatomaceous earth, acid-treated clay, bentonite, synthetic aluminum silicate, and inorganic pigments such as surface-treated calcium carbonate and silica; and organic pigments such as urea-formalin resin, styrene-methacrylic acid copolymer resin, polystyrene resin, and raw starch particles.

[0039] Other additives that can be used in combination with the thermosensitive recording composition of the present invention include, for example, higher fatty acid metal salts such as zinc stearate and calcium stearate used for the purpose of preventing wear of the thermal head and preventing sticking, and ultraviolet absorbers such as phenolic derivatives, benzophenone-based compounds, and benzotriazole-based compounds used for the purpose of imparting an antioxidant or anti-aging effect, various crosslinking agents, surfactants, defoaming agents, and the like. These antioxidants or ultraviolet absorbers may be microencapsulated as necessary.

[0040] The composition ratio of each component in the thermosensitive recording composition of the present invention is not particularly limited as long as the effects of the present invention are not impaired. However, the content of the developer is usually 10 to 1000% by mass, preferably 50 to 700% by mass, more preferably 100 to 500% by mass of the content of the color former. Further, the content of the optional component is such that in the thermosensitive recording composition, the sensitizer is 80% by mass or less, the preservability improver is 30% by mass or less, the binder is 90% by mass or less, the filler is 80% by mass or less, and other additives such as lubricants, surfactants, defoaming agents, and ultraviolet absorbers are, for example, 30% by mass or less (% by mass is based on the solid content of each component).

[0041] The thermosensitive recording material of the present invention essentially comprises a support and a thermosensitive recording layer provided on the support and composed of the thermosensitive recording composition of the present invention. The material and shape of the support are not particularly limited. For example, paper (ordinary paper, high-quality paper, coated paper, etc. can be used), synthetic paper, laminated paper, recycled paper such as waste paper pulp, film, film made of synthetic resin such as plastic and foamed plastic, and non-woven fabric, etc. can be mentioned. The method of providing the heat-sensitive recording layer on the support is not particularly limited either. For example, using water as a dispersion medium, the dispersion liquid of the composition for heat-sensitive recording of the present invention obtained by grinding and dispersing with a disperser such as a ball mill, attritor, sand mill or high-pressure jet mill is applied on the support and dried, and the dry mass is preferably 1 to 20 g / m 2 of the heat-sensitive recording layer can be produced.

[0042] An undercoat layer (undercoat layer) may be provided between the support and the heat-sensitive recording layer as needed, and a protective layer (overcoat layer) may also be provided on the heat-sensitive recording layer. The undercoat layer and the protective layer can be prepared, for example, in the same manner as the above-described method for preparing the heat-sensitive recording layer, using a dispersion liquid of a binder and other additives. The dry mass of the undercoat layer and the protective layer is preferably 0.1 to 10 g / m 2 is.

[0043] The undercoat layer preferably contains at least one selected from either organic pigments or inorganic pigments in order to further enhance the recording sensitivity and recording running property.

[0044] As the inorganic pigment used in the undercoat layer, from the viewpoint of suppressing caking and sticking to the thermal head, an oil-absorbing inorganic pigment having an oil absorption of preferably 70 ml / 100 g or more, more preferably 80 to 150 ml / 100 g is used. The oil absorption referred to here can be determined according to the method of JIS K 5101. As the oil-absorbing inorganic pigment, various types can be used. For example, calcined kaolin, aluminum oxide, magnesium carbonate, amorphous silica, light calcium carbonate, talc, etc. can be mentioned. The average particle diameter of the primary particles of these oil-absorbing inorganic pigments is preferably 0.01 to 5 μm, more preferably 0.02 to 3 μm. The usage ratio of the oil-absorbing inorganic pigment can be selected from a wide range, but generally 2 to 95% by mass in the total solid content of the undercoat layer is preferred, and 5 to 90% by mass is more preferred.

[0045] As the organic pigment used for the undercoat layer, for example, non-foaming organic hollow particles (plastic hollow particles) having a thermoplastic resin as a shell and containing gas inside and already in a hollow shape, or thermally expandable particles containing a foaming agent of a low-boiling solvent inside and becoming in a foamed state by heating are preferably used. Thereby, the recording sensitivity can be improved. In addition, since the organic hollow particles (plastic hollow particles) stay on the support and form a uniform undercoat layer, the barrier property is improved, so that the color former is prevented from contacting with the plasticizer or the alkaline filler contained in the neutral paper, and a decrease in color forming ability can be suppressed. As the organic hollow particles, conventionally known ones, for example, particles having a hollow ratio of 50 to 99% and a film material made of an acrylic resin, a styrene resin, a vinylidene chloride resin, etc. can be exemplified. Here, the hollow ratio is a value obtained by (d / D)×100. In this formula, d represents the inner diameter of the organic hollow particles, and D represents the outer diameter of the organic hollow particles. The average particle diameter of the organic hollow particles is preferably 0.5 to 10 μm, more preferably 1 to 4 μm, and even more preferably 1 to 3 μm. By setting the average particle diameter to 10 μm or less, when the coating liquid for the undercoat layer is applied by the blade coating method, it does not cause troubles such as streaks and scratches, and good coating suitability can be obtained. The usage ratio of the organic hollow particles can be selected from a wide range, but generally 2 to 90% by mass in the total solid content of the undercoat layer is preferred, and 5 to 70% by mass is more preferred.

[0046] When using the oil-absorbing inorganic pigment in combination with the organic hollow particles, the oil-absorbing inorganic pigment and the organic hollow particles are used within the range of the above-mentioned usage ratio, and the total amount of the oil-absorbing inorganic pigment and the organic hollow particles is preferably 5 to 90% by mass, more preferably 10 to 90% by mass, and still more preferably 10 to 80% by mass in the total solid content of the undercoat layer.

[0047] The content ratio of the organic hollow particles can be selected from a wide range, but generally 2 to 90% by mass of the total solid content of the undercoat layer is preferable. From the viewpoints of improving the color development effect and enhancing the barrier property, the lower limit is more preferably 5% by mass or more, and still more preferably 10% by mass or more. On the other hand, from the viewpoint of suppressing the adhesion of scum to the thermal head, the upper limit is more preferably 80% by mass or less, still more preferably 70% by mass or less, particularly preferably 60% by mass or less, and most preferably 50% by mass or less.

[0048] The undercoat layer is generally formed by applying and drying an undercoat layer coating solution prepared by mixing organic hollow particles, pigments such as oil-absorbing pigments, adhesives, auxiliaries, etc. using water as a medium onto a support. The coating amount of the undercoat layer coating solution is not particularly limited, but is preferably 3 to 20 g / m 2 in terms of dry weight, and more preferably 5 to 12 g / m 2 in terms of dry weight.

[0049] The adhesive used for the undercoat layer can be appropriately selected from those that can be used for the heat-sensitive recording layer and the protective layer. In particular, from the viewpoint of improving the coating film strength, oxidized starch, starch-vinyl acetate graft copolymer, polyvinyl alcohol, styrene-butadiene latex, etc. are preferable. The content ratio of the adhesive can be selected within a wide range, but generally 5 to 30% by mass of the total solid content of the undercoat layer is preferable, and 10 to 20% by mass is more preferable.

[0050] In the heat-sensitive recording material of the present invention, a back layer mainly composed of a pigment and an adhesive can be provided on the surface of the support opposite to the heat-sensitive recording layer, if necessary. Thereby, the storage stability can be further enhanced, and the curl suitability and printer running performance can be improved. Further, various known techniques in the field of manufacturing heat-sensitive recording bodies, such as applying an adhesive treatment to the back surface to process it into an adhesive label, providing a magnetic recording layer, a coating layer for printing, a thermal transfer recording layer, or an inkjet recording layer, can be added as necessary.

[0051] The method of applying various dispersion liquids and various coating liquids on the support is not particularly limited. For example, known coating methods such as bar coating, air knife coating, bar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating, etc. can be mentioned. Further, each coating liquid may be applied and dried layer by layer to form each layer, or the same coating liquid may be applied in two or more layers. Furthermore, simultaneous multilayer coating in which two or more layers are applied simultaneously may be performed.

[0052] From the viewpoint of improving the surface properties of the undercoat layer, the blade coating method is preferable for the method of applying the undercoat layer coating liquid. Thereby, the unevenness of the support can be eliminated to form a heat-sensitive recording layer with a uniform thickness, and the recording sensitivity can be increased. Also, in terms of quality, since the surface smoothness of the undercoat layer is further enhanced, the coating uniformity of the heat-sensitive recording layer coating liquid can be increased for curtain coating, and the barrier property of the protective layer provided if necessary can be improved. The blade coating method is not limited to the coating method using a blade typified by a bevel type or a vent type, and also includes pure blade coating, rod blade method, or bill blade method.

[0053] The heat-sensitive recording layer and the protective layer are preferably formed by simultaneous multilayer coating such as curtain coating. This can form a uniform coating layer, improve the barrier property of the protective layer, and enhance productivity. Curtain coating is a method of flowing and freely dropping a coating liquid to coat a support without contact, and known methods such as the slide curtain method, the couple curtain method, and the twin curtain method can be adopted, and there is no particular limitation. Also, as described in Japanese Patent Application Laid-Open No. 2006-247611 (Patent Document 7), a coating liquid can be ejected downward from a curtain head to form a coating liquid layer on an inclined surface, and a curtain of the coating liquid can be formed from a downward curtain guide portion at the end of the inclined surface and transferred to a web surface to form a coating liquid layer. In simultaneous multilayer coating, after laminating each coating liquid, it may be applied and then dried to form each layer, or after applying the coating liquid for forming the lower layer and without drying, while the lower layer coating surface is in a wet state, the coating liquid for forming the upper layer may be applied on the lower layer coating surface, and then dried to form each layer.

[0054] From the viewpoint of enhancing recording sensitivity and improving image uniformity, after forming each layer or at an arbitrary process after forming all the layers, a smoothing process may be performed using a known method such as a supercalender or a soft calender.

[0055] The method of recording information on the heat-sensitive recording material of the present invention may be appropriately selected according to the purpose. For example, a thermal head printer, CO 2 laser, semiconductor laser, etc. may be mentioned.

Examples

[0056] Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited by the following examples. In the examples, "parts" means parts by mass and "%" means mass %. The median particle diameter of the dispersion in the examples was measured by a laser diffraction / scattering particle size distribution measuring device Microtrac MT3300EXII (manufactured by Microtrac Bell Co., Ltd.). Also, in the following text and Tables 1 and 2, Examples 6, 7, 8, 9, 10, 12, and 14 shall be read as Reference Examples 1, 2, 3, 4, 5, 6, and 7, respectively.

[0057] Example 1 (Preparation of the heat-sensitive recording composition and heat-sensitive recording material of the present invention) (Step 1) Preparation of the dispersion liquid [A] of the first color-developing compound A A mixture having the following composition was pulverized and dispersed using a bead mill (Laboster Mini LMZ015) manufactured by Asazawa Fine Tech Co., Ltd. to prepare a dispersion liquid [A] of the first color-developing compound A having a median particle diameter of 0.7 μm. Note that [3-(3-phenylureido)phenyl]=4-methylbenzenesulfonate, which is the first color-developing compound A, was synthesized with reference to the description in Patent Document 3. [A] liquid [3-(3-phenylureido)phenyl]=4-methylbenzenesulfonate 30.0 parts Sulfonic acid-modified polyvinyl alcohol (Kuraray Poval 3-86SD, Kuraray Co., Ltd.) 20% aqueous solution of 15.0 parts Water 55.0 parts

[0058] (Step 2) Preparation of the dispersion liquid [B] of the first color-developing compound B A mixture having the following composition was pulverized and dispersed using a bead mill (Laboster Mini LMZ015) manufactured by Asazawa Fine Tech Co., Ltd. to prepare a dispersion liquid [B] of the first color-developing compound B having a median particle diameter of 0.7 μm. Note that N-[2-(3-phenylureido)phenyl]benzenesulfonamide, which is the first color-developing compound B, was synthesized with reference to the description in Patent Document 4. [B] liquid N-[2-(3-phenylureido)phenyl]benzenesulfonamide 30.0 parts Sulfonic acid-modified polyvinyl alcohol (Kuraray Poval 3-86SD, Kuraray Co., Ltd.) 20% aqueous solution of 15.0 parts Water 55.0 parts

[0059] (Step 3) Preparation of the dispersion liquid [C] of the second color-developing compound The mixture with the following composition was pulverized and dispersed using a bead mill (Laboster Mini LMZ015) manufactured by Asazawa Fine Tech Co., Ltd. to prepare a dispersion [C] of a second color-forming compound having a median particle diameter of 0.7 μm. Incidentally, 4,4'-bis(3-tosylureido)diphenylmethane, which is the second color-forming compound, was synthesized with reference to the description in Patent Document 6. [C] solution 4,4'-bis(3-tosylureido)diphenylmethane 30.0 parts 20% aqueous solution of sulfonic acid-modified polyvinyl alcohol (Kuraray Poval 3-86SD, Kuraray Co., Ltd.) 15.0 parts Water 55.0 parts

[0060] (Step 4) Preparation of the dispersion [D] of the color former The mixture with the following composition was pulverized and dispersed using a bead mill (Laboster Mini LMZ015) manufactured by Asazawa Fine Tech Co., Ltd. to prepare a dispersion [D] of a color-forming compound having a median particle diameter of 1.0 μm. [D] solution 3-dibutylamino-6-methyl-7-anilinofluoran (BLACK400, Fukui Yamada Chemical Industry Co., Ltd.) 30.0 parts Sulfonic acid-modified polyvinyl alcohol (Kuraray Poval 3-86SD, Kuraray Co., Ltd.) 20% aqueous solution 15.0 parts Water 55.0 parts

[0061] (Step 5) Preparation of the heat-sensitive recording composition of the present invention Each liquid obtained above and the following chemicals were mixed in the following composition to prepare a heat-sensitive recording composition. [A] solution 22.2 parts [C] solution 1.2 parts [D] solution 8.3 parts 67% calcium carbonate aqueous dispersion 6.6 parts 12% polyvinyl alcohol aqueous solution 27.3 parts 37% zinc stearate aqueous dispersion 2.7 parts Water 28.5 parts

[0062] (Step 6) Production of the heat-sensitive recording material of the present invention Grammage: 50 g / m² 2 A thermosensitive recording composition obtained in Step 5 in an amount such that the mass of the color-forming compound upon drying is 0.5 g / m² was applied onto a high-quality paper, dried, and then calendered to produce the thermosensitive recording material of the present invention. 2

[0063] Example 2 (Production of the thermosensitive recording composition and thermosensitive recording material of the present invention) In Step 5, a thermosensitive recording composition and a thermosensitive recording material of the present invention were obtained in the same manner as in Example 1, except that the amount of Dispersion [A] used was changed to 21.0 parts and the amount of Dispersion [C] used was changed to 2.3 parts.

[0064] Example 3 (Production of the thermosensitive recording composition and thermosensitive recording material of the present invention) In Step 5, a thermosensitive recording composition and a thermosensitive recording material of the present invention were obtained in the same manner as in Example 1, except that the amount of Dispersion [A] used was changed to 17.5 parts and the amount of Dispersion [C] used was changed to 5.8 parts.

[0065] Example 4 (Production of the thermosensitive recording composition and thermosensitive recording material of the present invention) In Step 5, a thermosensitive recording composition and a thermosensitive recording material of the present invention were obtained in the same manner as in Example 1, except that the amount of Dispersion [A] used was changed to 16.3 parts and the amount of Dispersion [C] used was changed to 7.0 parts.

[0066] Example 5 (Production of the thermosensitive recording composition and thermosensitive recording material of the present invention) In Step 5, a thermosensitive recording composition and a thermosensitive recording material of the present invention were obtained in the same manner as in Example 1, except that the amount of Dispersion [A] used was changed to 14.0 parts and the amount of Dispersion [C] used was changed to 9.3 parts.

[0067] Examples 6 to 10 (Production of the thermosensitive recording composition and thermosensitive recording material of the present invention) In the same manner as in Examples 1 to 5, except that the [A] liquid in Step 5 of each of Examples 1 to 5 was changed to the [B] liquid, thermosensitive recording compositions and thermosensitive recording materials of Examples 6 to 10 were obtained, respectively.

[0068] ​Example 11 (Preparation of the thermosensitive recording composition and thermosensitive recording material of the present invention) A thermosensitive recording composition and a thermosensitive recording material of Example 11 were obtained in the same manner as in Example 1, except that the amount of Dispersion [A] used was changed to 22.6 parts and the amount of Dispersion [C] used was changed to 0.7 part.

[0069] Example 12 (Preparation of the thermosensitive recording composition and thermosensitive recording material of the present invention) A thermosensitive recording composition and a thermosensitive recording material of Example 12 were obtained in the same manner as in Example 11, except that Dispersion [A] was changed to Dispersion [B].

[0070] Example 13 (Preparation of the thermosensitive recording composition and thermosensitive recording material of the present invention) A thermosensitive recording composition and a thermosensitive recording material of Example 13 were obtained in the same manner as in Example 11, except that the amount of Dispersion [A] used was changed to 11.7 parts and the amount of Dispersion [C] used was changed to 11.7 parts.

[0071] Example 14 (Preparation of the thermosensitive recording composition and thermosensitive recording material of the present invention) A thermosensitive recording composition and a thermosensitive recording material of Example 14 were obtained in the same manner as in Example 13, except that Dispersion [A] was changed to Dispersion [B].

[0072] Comparative Example 1 (Preparation of a comparative thermosensitive recording composition and thermosensitive recording material) A comparative thermosensitive recording composition and a thermosensitive recording material were obtained in the same manner as in Example 1, except that in Step 5, the amount of Dispersion [A] used was changed to 23.4 parts and Dispersion [C] was not used.

[0073] Comparative Example 2 (Preparation of a comparative thermosensitive recording composition and thermosensitive recording material) A comparative thermosensitive recording composition and a thermosensitive recording material were obtained in the same manner as in Comparative Example 1, except that Dispersion [A] was changed to Dispersion [B].

[0074] Comparative Example 3 (Preparation of a comparative thermosensitive recording composition and thermosensitive recording material) A comparative heat-sensitive recording composition and a heat-sensitive recording material were obtained in the same manner as in Comparative Example 1, except that the dispersion liquid [A] was changed to the dispersion liquid [C].

[0075] [Printing and color development by a dynamic color development sensitivity tester] For each of the heat-sensitive recording materials prepared in Examples 1 to 14 and Comparative Examples 1 to 3, printing was performed at an applied energy of 0.39 mJ / dot using a thermal printer (TH-M2 / PP) manufactured by Okura Engineering Co., Ltd., and the optical density (OD value) of the printed portion was measured under the following conditions using a reflection densitometer (product name: FD-7, manufactured by Konica Minolta, Inc.). The larger the numerical value of the printing density, the higher the density of the printing, which means excellent heat responsiveness. The results are shown in Tables 1 and 2. ·Measurement conditions Measurement method: Reflection measurement Illumination condition: C Observation field of view: 2° Density white reference: Absolute value

[0076] [Resistance test of printed portion and background] The resistance of the printed portion and the background (unprinted portion) under the following various environmental conditions was evaluated. For each of the heat-sensitive recording materials obtained in Examples 1 to 14 and Comparative Examples 1 to 3, printing was performed at an applied energy of 0.39 mJ / dot using a thermal printer (TH-M2 / PP) manufactured by Okura Engineering Co., Ltd., and the optical density (OD value) of the printed portion and the background before and after treatment under various environmental conditions was measured using a reflection densitometer (product name: FD-7, manufactured by Konica Minolta, Inc.) (the measurement conditions for the optical density are the same as those in the above-mentioned "[Printing and color development by a dynamic color development sensitivity tester]"), and the residual ratio of the printed portion after the test was calculated by the following formula. The results are shown in Tables 1 and 2. Residual ratio (%) = (Optical density of the printed portion after the test) / (Optical density of the printed portion before the test) × 100 Generally, if the optical density of the printed portion after treatment is less than 0.70 OD value, it is difficult to visually distinguish, and it is required that the optical density of the background portion after treatment is 0.20 OD value or less.

[0077] [Treatment conditions for water resistance test] Immerse the printed sample in water at 25°C for 24 hours. [Treatment conditions for heat resistance to water test] Immerse the printed sample in warm water at 40°C for 24 hours. [Treatment conditions for heat resistance test] Keep the printed sample at 100°C for 1 hour using a forced-air constant temperature incubator (product name: DKM-600) manufactured by Yamato Scientific Co., Ltd. [Method and treatment conditions for plasticizer resistance test] Wrap a vinyl chloride wrap film (containing a plasticizer) once around a glass plate, place the printed sample on it, and then wrap another vinyl chloride wrap film once on top, and keep it at 40°C for 24 hours. [Oil resistance test] Drop 3 drops of cottonseed oil onto the color development recording part of the printed sample and leave it at 40°C for 24 hours. [Alcohol resistance test] Immerse the printed sample in a 20% ethanol aqueous solution at 25°C for 2 hours.

[0078]

Table 1

[0079]

Table 2

[0080] From the results of Table 1 and Table 2, it can be seen that the thermal recording materials having a thermal recording layer composed of the thermosensitive composition of the present invention all have excellent thermal responsiveness, and also have excellent heat resistance, water resistance, plasticizer resistance, oil resistance of the printed part, and heat resistance of the background.

Industrial applicability

[0081] According to the present invention, it is possible to provide a thermal recording material excellent in thermal responsiveness and storage stability of the printed part and the background.

Claims

1. A heat-sensitive recording composition containing a color former and a developer, wherein the developer contains [3-(3-phenylureido)phenyl]=4-methylbenzenesulfonate which is a first color-developing compound and 4,4'-bis(3-tosylureido)diphenylmethane which is a second color-developing compound.

2. The heat-sensitive recording composition according to claim 1, wherein the color former contains a compound selected from the group consisting of a triarylmethane compound, a fluoran compound, an azaphthalide compound and a fluorene compound.

3. The color former contains a fluoran compound selected from the group consisting of 3-diethylamino-6-methyl-7-anilinofluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-(o,p-dimethylanilino)fluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-(cyclohexyl-N-methylamino)-6-methyl-7-anilinofluorane, 3-diethylamino-7-(m-trifluoromethylanilino)fluorane, 3-N-n-dibutylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-(m-methylanilino)fluorane, 3-N-n-dibutylamino-7-(o-chloroanilino)fluorane, 3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-ethoxypropylamino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-isobutylamino)-6-methyl-7-anilinofluorane and 3-dipentylamino-6-methyl-7-anilinofluorane. The heat-sensitive recording composition according to claim 6.

4. The heat-sensitive recording composition according to any one of claims 1 to 3, wherein the content of the developer is 100 to 500% by mass of the content of the color former.

5. The heat-sensitive recording composition according to any one of claims 1 to 4, wherein the content ratio of the first color-developing compound to the second color-developing compound is 95:5 to 60:

40.

6. A heat-sensitive recording material having a heat-sensitive recording layer composed of the heat-sensitive recording composition according to any one of claims 1 to 5 on a support.

7. The heat-sensitive recording material according to claim 6, wherein the support is a high-quality paper, synthetic paper or plastic film.

8. The heat-sensitive recording material according to claim 6 or 7, wherein the heat-sensitive recording layer is 1 to 20 g / m2.

9. The heat-sensitive recording material according to any one of claims 6 to 8, further comprising an undercoat layer containing an organic pigment and / or an inorganic pigment between the support and the heat-sensitive recording layer.

10. The heat-sensitive recording material according to claim 9, wherein the inorganic pigment is an oil-absorbing inorganic pigment having an oil absorption of 70 to 150 ml / 100 g.

11. The heat-sensitive recording material according to claim 10, wherein the inorganic pigment is calcined kaolin.

12. The heat-sensitive recording material according to claim 9, wherein the organic pigment is plastic hollow particles having a value of average inner diameter of the pigment / average outer diameter of the pigment of 0.5 to 0.99.

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