JP2022071574A - Heat-sensitive recording medium - Google Patents

Abstract

To provide a heat-sensitive recording medium that has excellent white paper storage properties even when neutral paper is used as a support and a sulfonyl urea compound is used as a developer.SOLUTION: A heat-sensitive recording medium has a heat-sensitive recording layer containing a leuco dye and a coloring agent on one side of a support. As the coloring agent, 4,4'-bis(3-tosylureido) diphenyl methane is contained. Furthermore, a layer containing a condensed phosphate compound of 0.3 g/m2 or more is included between the support and heat-sensitive recording layer and/or on the other side of the support.SELECTED DRAWING: None

Description

The present invention relates to a heat-sensitive recorder using a color reaction between a leuco dye and a color developer.

A heat-sensitive recorder that utilizes the color reaction between a leuco dye and a color developer is relatively inexpensive, and because the recording equipment is compact and its maintenance is relatively easy, it can be used as a recording medium for facsimiles, various printers, and the like. Not only is it used in a wide range of fields.

With the expansion of the fields of use and the diversification and higher performance of recording equipment, the usage environment of recording media is becoming harsher, and not only the image quality and sensitivity of recorded images and image storage stability, but also blank paper storage stability are satisfied at the same time. That is, it is required that the recording medium exhibits the initial performance without deterioration even after being stored in a blank sheet state before recording.

Conventionally, high-quality paper has been generally used as a support for a thermal recording body. For acidic papermaking, rosin-based sizing agents and fillers such as clay and talc are added internally for papermaking. Generally, a sulfuric acid band is used as a fixing agent for this rosin-based sizing agent, but the pH of the paper becomes acidic due to the sulfuric acid roots remaining in the paper, and the color-developing substance constituting the thermal recording body is the paper. There is a problem that it reacts with acidic ions on the surface of the rosin and easily causes skin fog during a long-term storage period. Therefore, acid-free paper containing an alkaline filler such as calcium carbonate may be used as a support for the thermal recording body for the purpose of preventing skin fog and reducing the papermaking cost.

On the other hand, a heat-sensitive recorder containing a sulfonylurea compound as a color developer is known to be excellent in storage stability of recorded images (Patent Documents 1 and 2). Specifically, the recording unit has good long-term storage stability, and at the same time, it has excellent environmental resistance such as moisture resistance and heat resistance of the recorded image, as well as oil resistance and plasticizing agent resistance, and is excellent in image recording paper, facsimile paper, cash dispenser. It is a heat-sensitive recorder useful for paper, tickets, commuter tickets, labels such as POS labels, cards such as prepaid cards, and toll tickets.

However, when the sulfonylurea compound is used as a color developer, if acid-free paper is used as a support for the thermal recorder, the thermal recorder is stored, for example, less than a year later, before recording. If there is, the color development ability will be reduced, and if it is after recording, the color will fade and the print will be faint, unclear, or in some cases almost invisible. In particular, if the color-developing ability is reduced before recording, the print density of the heat-sensitive recording body is reduced and it becomes difficult to read, and the original function of the heat-sensitive recording body is lost. The reason why the color-developing ability is lowered is not clear, but it is presumed that the sulfonylurea compound forms a salt with the alkaline filler contained in the acid-free paper and causes a morphological change, so that the performance as a color developer is lowered.

In order to solve the above problems, acid-free paper using an alkyl ketene polymer as a synthetic sizing agent and having a zeta potential of a solution having a solid content concentration of 0.02% under pH 8.0 of the synthetic sizing agent is +20 mV or less. It is used as a support (Patent Document 3), and a heat-sensitive recording layer containing an alkali salt of a diisobutylene-maleic anhydride copolymer is provided on a neutral paper using an alkyl ketene dimer as a sizing agent (Patent Document 4). ) Etc. have been proposed, but the current situation is that satisfactory results have not always been obtained.

It has also been reported that an undercoat layer containing a polycarboxylic acid and a thermal recording layer containing a sulfonylurea compound as a color developer are provided on a neutral paper (Patent Document 5).

Japanese Unexamined Patent Publication No. 5-147357 Japanese Unexamined Patent Publication No. 5-221144 Japanese Unexamined Patent Publication No. 7-205545 Japanese Unexamined Patent Publication No. 8-197846 Japanese Unexamined Patent Publication No. 2014-172284

An object of the present invention is to provide a thermal recording body having excellent storage stability on blank paper even when a neutral paper is used as a support and a sulfonylurea compound is used as a color developer.

As a result of diligent studies to solve the above object, the present inventors have placed a layer containing 0.3 g / m ² or more of the condensed phosphoric acid compound between the support and the heat-sensitive recording layer, and / or the support. It has been found that the above-mentioned problems can be solved by providing the same on the other side of the above, and the present invention has been solved. That is, the present invention relates to the following thermal recording body.

Item 1. A heat-sensitive recording body having a heat-sensitive recording layer containing a leuco dye and a color-developing agent on one surface of the support.
It contains 4,4'-bis (3-tosylureido) diphenylmethane as the color-developing agent.
A heat-sensitive recorder having a layer containing 0.3 g / m ² or more of a condensed phosphoric acid compound between the support and the heat-sensitive recording layer and / or on the other surface of the support.
Item 2. Item 2. The heat-sensitive recorder according to Item 1, wherein the condensed phosphoric acid compound is an acid, a sodium salt, a potassium salt, or an ammonium salt having an average degree of polymerization in the range of 3 to 30.
Item 3. Item 2. The heat-sensitive recording material according to Item 1 or 2, wherein the layer containing the condensed phosphoric acid compound further contains a polyvalent carboxylic acid compound.
Item 4. Item 3. The heat-sensitive recorder according to Item 3, wherein the polyvalent carboxylic acid compound is at least one compound selected from a divalent carboxylic acid, a trivalent carboxylic acid, and a salt thereof.
Item 5. Item 3. The heat-sensitive recorder according to Item 3 or 4, wherein the total content of the condensed phosphoric acid compound and the polyvalent carboxylic acid compound is 3 g / m ² or less.
Item 6. Item 2. The heat-sensitive recording body according to any one of Items 1 to 5, wherein the support is acid-free paper.

In the thermal recording body of the present invention, even when a neutral paper is used as a support and a sulfonylurea compound is used as a color developer, the color development ability of the blank paper (unprinted) before recording is reduced. It is small and has excellent storage stability.

In the present specification, the expression "contains, contains" includes the concepts of "contains", "consists of substance only", and "consists of only".

Further, in the present invention, the "average particle diameter" refers to a volume-based median diameter measured by a laser diffraction method. More simply, the particle size may be measured from the particle image (SEM image) using an electron microscope and shown as an average value of 10 particles.

The present invention is a heat-sensitive recording body having a heat-sensitive recording layer containing a leuco dye and a color-developing agent on one surface of the support.
It contains 4,4'-bis (3-tosylureido) diphenylmethane as the color-developing agent.
Further, it is characterized by having a layer containing 0.3 g / m ² or more of the condensed phosphoric acid compound between the support and the heat-sensitive recording layer and / or on the other surface of the support.

[Support]
The support in the present invention is not particularly limited in type, shape, size, etc., for example, high-quality paper (acidic paper, neutral paper), medium-quality paper, coated paper, art paper, cast-coated paper, glassin paper, etc. In addition to resin laminated paper, polyolefin synthetic paper, synthetic fiber paper, non-woven fabric, synthetic resin film and the like, various transparent supports and the like can be appropriately selected and used. In the present invention, it is desirable to use acid-free paper as a support from the viewpoint of preventing deterioration due to acid paper generally used as a support and suppressing background fog. The type of acid-free paper and the manufacturing method are not particularly limited, but pulp fibers, generally calcium carbonate as a filler, alkylketene dimer (AKD) as a sizing agent, alkenylsuccinic anhydride (ASA), etc., and polyamide as a fixing agent, It can be obtained by papermaking a pulp slurry containing acrylic amide, cationic starch and the like. As such a neutral paper, the hot water extraction pH (based on JIS P 8133) is preferably in the range of about 6.0 to 11, more preferably in the range of 6.5 to 10, and further in the range of 7.5 to 10. preferable. By setting the pH of the acid-free paper to 6.0 or more, it is possible to effectively suppress the background fog in the storage of blank paper. On the other hand, by setting the pH to 11 or less, it is possible to effectively suppress a decrease in color development ability after storage of blank paper. In addition, aggregation of the pulp slurry itself can be suppressed. Further, the pH can be adjusted by using an aluminum sulfate band as needed within a range where the pH does not become smaller than 6.0, and the papermaking property can be improved. Here, the acid paper in the present invention has a pH range of 2 or more and does not exceed pH 6, preferably in the range of pH 2 to 5.7.

The type of pulp fiber used in the present invention, the manufacturing method, etc. are not particularly limited, and for example, various high yield pulps in addition to chemical pulps such as softwood pulps and hardwood pulps obtained by KP, SP, AP methods, etc. Alternatively, used paper pulp and the like can be mentioned.

An internal aid for papermaking such as a dye, a fluorescent whitening agent, a pH adjuster, a defoaming agent, a pitch control agent, and a slime control agent can be appropriately added to the pulp slurry depending on the intended use of the paper. .. It is also possible to attach starch or the like in a size press. As the paper machine, a long net paper machine, a twin wire paper machine, a circular net paper machine, a Yankee dryer paper machine and the like can be appropriately used.

The thickness of the support is not particularly limited, and is usually about 20 to 200 μm. The density of the support is not particularly limited, and is preferably about 0.60 to 0.95 g / cm ³ .

[Layer containing condensed phosphoric acid compound]
In the present invention, a layer containing 0.3 g / m ² or more of the condensed phosphoric acid compound is provided between the support and the heat-sensitive recording layer and / or on the other surface of the support. As a result, even when neutral paper is used as the support and a sulfonylurea compound is used as the color developer, excellent blank paper storage stability is exhibited, and the color density is developed even when printing is performed after long-term storage in the blank paper state. Can be kept at a sufficiently legible level. The layer containing the condensed phosphoric acid compound is formed, for example, on the support surface where the heat-sensitive recording layer is present, the support surface opposite to the surface where the heat-sensitive recording layer is present, and between the undercoat layer and the heat-sensitive recording layer. Furthermore, by incorporating the condensed phosphoric acid compound in the undercoat layer, the undercoat layer can be made into a layer containing the condensed phosphoric acid compound.

Examples of the condensed phosphoric acid compound include pyrophosphoric acid, tripolyphosphoric acid, tetrapolyphosphoric acid, polyphosphoric acid, metaphosphoric acid, hexametaphosphoric acid, adenosine triphosphate, and alkali metal salts and ammonium salts thereof. Among these, those having an average degree of polymerization of 3 to 30, such as tripolyphosphoric acid, tetrapolyphosphoric acid, and metaphosphoric acid, are particularly preferable, and commercially available metaphosphoric acid compounds having a degree of polymerization generally said to be about 10 to 23 are the most excellent. These condensed phosphoric acid compounds are preferably in the form of any of an acid, a sodium salt, a potassium salt or an ammonium salt. The condensed phosphoric acid compound can also be used in combination of two or more kinds.

The content of the condensed phosphoric acid compound in the layer containing the condensed phosphoric acid compound is 0.3 g / m ² or more, preferably 0.7 g / m ² or more, and more preferably 1.0 g / m ² or more. .. By setting the coating amount to 0.3 g / m ² or more, the storage stability of blank paper can be improved. The content of the condensed phosphoric acid compound is preferably 2.0 g / m ² or less.

The content of the condensed phosphoric acid compound in the layer containing the condensed phosphoric acid compound is from the viewpoint of improving the storage stability of blank paper with respect to 100 parts by mass of 4,4'-bis (3-tosyl ureido) diphenylmethane in the heat-sensitive recording layer. 30 parts by mass or more is preferable, and 100 parts by mass or more is more preferable. On the other hand, from the viewpoint of improving the skin fog resistance, 450 parts by mass or less is preferable, and 320 parts by mass or less is more preferable.

Condensed phosphoric acid compounds are generally deliquescent, and surface stickiness may be a problem. For example, while the thermal recorder having a layer containing the condensed phosphoric acid compound on the other surface of the support is wound and stored in a roll shape, the sticky condensed phosphoric acid compound is transferred to the surface of the thermal recorder. , It is possible that printing problems may occur when printing with a thermal printer. In order to prevent such a problem, the layer containing the condensed phosphoric acid compound may further contain a polyvalent carboxylic acid compound. By using the condensed phosphoric acid compound and the polyvalent carboxylic acid compound in combination, it is possible to improve the storage stability of blank paper and further suppress the stickiness.

Examples of the polyvalent carboxylic acid compound include malic acid, citric acid, succinic acid, dodecenyl succinic acid, itaconic acid, citraconic acid, adipic acid, hexahydrophthalic acid, methylhexahydrophthalic acid, tetrahydrophthalic acid, and methylhexahydrophthalic acid. Acid, phthalic acid, tetrachlorophthalic acid, nadic acid, methylnadic acid, polyacrylic acid, glutamic acid, aspartic acid, ethylenediamine tetraacetic acid, hydroxyethylimino diacetic acid, nitrilotriacetic acid, hydroxyethylethylenediamine triacetic acid, diethylenetriaminepentaacetic acid, Examples thereof include triethylenetetraamine hexaacetic acid, ethylenediamine-N, N'-disuccinic acid, ethylenediaminehydroxyethyl triacetic acid, glycol ether diamine tetraacetic acid and the like. These polyvalent carboxylic acid compounds may be in the form of salts such as alkali metal salts and ammonium salts. Among these, divalent carboxylic acids and trivalent carboxylic acids typified by malic acid, citric acid, succinic acid and the like, and sodium salts, potassium salts or ammonium salts thereof are particularly preferably used. Two or more kinds of polyvalent carboxylic acid compounds can be used in combination.

When the condensed phosphoric acid compound and the polyvalent carboxylic acid compound are used in combination in the layer containing the condensed phosphoric acid compound, the ratio is not particularly limited, and the content of the condensed phosphoric acid compound is within the above range. Just do it. Further, in the layer containing the condensed phosphoric acid compound, the total content of the condensed phosphoric acid compound and the polyvalent carboxylic acid compound is preferably 3 g / m ² or less, more preferably 2 g / m ² or less. By setting the total content to 3 g / m ² or less, it is possible to suppress skin fog. The total content of the condensed phosphoric acid compound and the polyvalent carboxylic acid compound is preferably 0.5 g / m ² or more.

When applying a condensed phosphoric acid compound or a polyvalent carboxylic acid compound to a support or an undercoat layer, various known dyes and pigments, binders, surfactants such as defoaming agents and coating agents, lubricants, and additions are required. Auxiliary agents such as a thickener and a pH adjuster may be added, but the addition ratio is preferably less than 70% by mass in terms of solid content so as not to impair the desired effect of the present invention. As described above, the layer containing the condensed phosphoric acid compound may contain at least the condensed phosphoric acid compound together with the polyvalent carboxylic acid compound as a composition so that the total amount thereof is 30% by mass or more. preferable. As a method of applying the condensed phosphoric acid compound or the polyvalent carboxylic acid compound, various coating devices such as brush coating, spray coating, roll coater, bar coater, gravure roll coater, blade coater, air knife coater, and curtain coater are used. The drying is performed by a conventional method combined with the above-mentioned coating device.

[Undercoat layer]
In the present invention, if necessary, an undercoat layer may be provided between the support and the heat-sensitive recording layer. This can also increase the recording sensitivity. When the undercoat layer is a layer containing a condensed phosphoric acid compound, the undercoat layer contains a condensed phosphoric acid compound and, if necessary, a polyvalent carboxylic acid compound. The contents of the condensed phosphoric acid compound and the polyvalent carboxylic acid compound may be in the above range.

The undercoat layer preferably contains as a pigment an oil-absorbing pigment having an oil absorption amount of 70 ml / 100 g or more, particularly about 80 to 150 ml / 100 g, and / or organic hollow particles and / or thermally expandable particles. Here, the oil absorption amount is a value obtained according to the method of JIS K 5101.

As the oil-absorbing pigment, various pigments can be used, and specific examples thereof include inorganic pigments such as calcined kaolin, amorphous silica, light calcium carbonate, and talc. The average particle size of the primary particles of these oil-absorbing pigments is preferably about 0.01 to 5 μm, particularly preferably about 0.02 to 3 μm. The content ratio of the oil-absorbent pigment can be selected from a wide range, but is generally preferably about 2 to 95% by mass, more preferably about 5 to 90% by mass, based on the total solid content of the undercoat layer.

Examples of the organic hollow particles include conventionally known particles, for example, particles having a film material of an acrylic resin, a styrene resin, a vinylidene chloride resin, or the like and having a hollow ratio of about 50 to 99%. Here, the hollow ratio is a value obtained by (d / D) × 100. In the formula, d indicates the inner diameter of the organic hollow particles, and D indicates the outer diameter of the organic hollow particles. The average particle size of the organic hollow particles is preferably about 0.5 to 10 μm, more preferably about 1 to 3 μm. The content ratio of the organic hollow particles can be selected from a wide range, but is generally preferably about 2 to 90% by mass, more preferably about 5 to 70% by mass, based on the total solid content of the undercoat layer.

When the oil-absorbing inorganic pigment is used in combination with the organic hollow particles, the oil-absorbing inorganic pigment and the organic hollow particles are used within the above-mentioned content ratio, and the total amount of the oil-absorbing inorganic pigment and the organic hollow particles is primed. It may be adjusted so as to be preferably about 5 to 90% by mass, more preferably about 10 to 80% by mass, based on the total solid content of the layer.

The undercoat layer generally uses water as a dispersion medium, and a coating liquid for the undercoat layer prepared by mixing a pigment, a binder, a condensed phosphoric acid compound, a polyvalent carboxylic acid compound, various auxiliaries, etc. as necessary is placed on the support. It is formed by coating and drying so that the dry mass is preferably about 3 to 20 g / m ² , more preferably about 5 to 12 g / m ² .

Examples of the binder in the undercoat layer include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, Arabic gum, partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and acetacetyl-modified. Polyvinyl alcohol, silicon-modified polyvinyl alcohol, sulfone-modified polyvinyl alcohol, diisobutylene-maleic anhydride copolymer salt, styrene-maleic anhydride copolymer salt, ethylene-acrylic acid copolymer salt, styrene-acrylic acid copolymer Examples thereof include salt, urea resin, melamine resin, amide resin, urethane resin-based latex, acrylic resin-based latex, and styrene-butadiene resin-based latex. Among these, starch-vinyl acetate graft copolymer, polyvinyl alcohol, styrene-butadiene resin-based latex and the like are preferable from the viewpoint of improving the strength of the coating film. The content ratio of the binder can be selected from a wide range, but generally, it is preferably about 5 to 30% by mass, more preferably about 10 to 20% by mass, based on the total solid content of the undercoat layer.

Examples of the auxiliary agent contained in the undercoat layer coating liquid include dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzene sulfonate, sodium lauryl alcohol sulfate, fatty acid metal salt, zinc stearate, calcium stearate, and polyethylene. Waxes such as waxes, carnauba wax, paraffin waxes, ester waxes, hydrazide compounds, glioxal, boric acid, dialdehyde starch, glyoxyphosphates, methylolurea, water resistant agents such as epoxy compounds, defoaming agents, coloring dyes, fluorescent dyes, etc. Can be mentioned.

[Thermal recording layer]
The heat-sensitive recording layer in the present invention contains a leuco dye and a color-developing agent. Various known leuco dyes can be used, and specific examples thereof include 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide and 3- (4-diethylamino-2-methylphenyl). ) -3- (4-Dimethylaminophenyl) -6-dimethylaminophthalide, 3- (N-ethyl-N-p-tolyl) amino-7-N-methylanilinofluorane, 3-cyclohexylamino-6 -Chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorine, 3-diethylamino-7-chlorofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilino Fluolane, 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 3-di (n-pentyl) amino-6-methyl-7-anilinofluoran, 3- (N-) Ethyl-p-toluidino) -6-methyl-7-anilinofluorane, 3-di (n-butyl) amino-6-chloro-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-ani Renofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3,3-bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl]- 4,5,6,7-Tetrachlorophthalide, 3-p- (p-dimethylaminoanilino) anilino-6-methyl-7-chlorofluorane, 3-p- (p-chloroanilino) anilino-6- Examples thereof include methyl-7-chlorofluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3'-(6'-dimethylamino) phthalide and the like. Of course, the present invention is not limited to these, and two or more types can be used in combination.

The content ratio of the leuco dye is not particularly limited, and is preferably about 3 to 50% by mass, more preferably about 5 to 40% by mass, based on the total solid content of the heat-sensitive recording layer.

In the present invention, 4,4'-bis (3-tosylureido) diphenylmethane is used as a color developer. Further, other color-developing agents can be used as long as the desired effects of the present invention are not impaired, and specific examples thereof include, for example, 4,4'-isopropyridendiphenol, 4,4'-cyclohexylidenediphenyl, 1. , 1-bis (4-hydroxyphenyl) -ethane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4- Hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-n-propoxydiphenyl sulfone, 4-hydroxy-4'-allyloxydiphenyl sulfone, 3,3'-diallyl-4,4'-dihydroxydiphenyl sulfone , 4,4'-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenyl sulfone, 2,2'-bis [4- (4-hydroxyphenyl) phenoxy] diethyl ether, 4-hydroxybenzoic acid Benzyl ester, N, N'-di-m-chlorophenylthiourea, 4- [2- (p-methoxyphenoxy) ethyloxy] zinc salicylate, 4- {3- (p-tolylsulfonyl) propyloxy] zinc salicylate, 5 -[P- (2-p-methoxyphenoxyethoxy) cumyl] zinc salicylate, 1,5- (3-oxapentylene) -bis (3- (3'-(p-toluenesulfonyl) ureido) benzoate, 1- (4-Butoxycarbonylphenyl) -3-tosylurea, N-p-toluenesulfonyl-N'-3- (p-toluenesulfonyloxy) phenylurea, N- (p-toluenesulfonyl) -N'-phenylurea, etc. Can be mentioned.

The content ratio of the color-developing agent may be appropriately selected depending on the type of leuco dye and color-developing agent to be used, but is preferably about 10 to 70% by mass, preferably 12 to 50% by mass, based on the total solid content of the heat-sensitive recording layer. The degree is more preferable.

The heat-sensitive recording layer may contain a storage stability improving agent. This makes it possible to improve the storage stability of the recording unit. Specific examples of such a preservative improving agent include, for example, 2,2'-ethylidenebis (4,6-di-tert-butylphenol), 4,4'-thiobis (2-methyl-6-tert-butylphenol), 1 , 1,3-Tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-Tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 2,2 -Hindered phenolic compounds such as bis (4-hydroxy-3,5-dimethylphenyl) propane, 4,4'-diglycidyloxydiphenylsulfone, 4-benzyloxy-4'-(2-methylglycidyloxy) diphenylsulfone , Epoxy compounds such as diglycidyl terephthalate, cresol novolac type epoxy resin, phenol novolac type epoxy resin, bisphenol A type epoxy resin, N, N'-di-2-naphthyl-p-phenylenediamine, bis (4-ethyleneiminocarbonyl) Aminophenyl) methane and the like can be mentioned.

The content ratio of the storage stability improving agent may be an amount effective for improving the storage stability, and is not particularly limited, but is usually preferably about 1 to 30% by mass in the total solid content of the heat-sensitive recording layer, and 5 to 5 to. About 20% by mass is more preferable.

Further, the heat-sensitive recording layer may contain a sensitizer. This makes it possible to increase the recording sensitivity. Specific examples of the sensitizer include stearate amide, methylenebis stearate amide, diphenyl sulfone, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, 2-naphthylbenzyl ether, m-terphenyl, and p-benzylbiphenyl. , P-tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ether, 1,2-di (3-methylphenoxy) ethane, 1,2-di (4-methylphenoxy) ethane, 1,2-di (4) -Methylphenoxy) Ester, 1,2-di (4-chlorophenoxy) Ester, 1,2-Diphenoxyetane, 1- (4-Methylphenoxy) -2- (3-Methylphenoxy) Ethan, p-Methylthiophenyl Benzyl ether, 1,4-di (phenylthio) butane, p-acetotoluidide, p-acetophenetidine, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, di-p-chlorobenzyl oxalate Examples thereof include esters, oxalic acid di-p-methylbenzyl esters, and oxalic acid dibenzyl esters.

The content ratio of the sensitizer may be an amount effective for sensitization and is not particularly limited, but is usually preferably about 2 to 50% by mass in the total solid content of the heat-sensitive recording layer, and 5 to 40% by mass. % Is more preferable.

The heat-sensitive recording layer may also contain a binder. The binder is not particularly limited and may be appropriately selected from those that can be used for the undercoat layer. For example, partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, sulfone-modified polyvinyl alcohol, styrene-butadiene resin-based latex and the like. Can be mentioned. The content ratio of the binder is preferably about 2 to 30% by mass in the total solid content of the heat-sensitive recording layer.

The heat-sensitive recording layer is generally made of water as a dispersion medium, and average particles are used with a leuco dye, a color developer, a sensitizer if necessary, a storage improver, or separately by a stirrer / crusher such as a ball mill, an Atlanta, or a sand mill. A coating liquid for a heat-sensitive recording layer prepared by mixing a binder, a pigment, an auxiliary agent, etc. as necessary using a dispersion liquid finely dispersed so as to have a diameter of 2 μm or less is preferably applied on a support in terms of dry mass. Is formed by coating and drying so as to be about 2 to 12 g / m ² , more preferably about 2 to 10 g / m ² . The heat-sensitive recording layer can be formed by dividing it into two or more layers as needed, and the composition and the coating amount of each layer may be the same or different.

The pigment and auxiliary agent that can be contained in the coating liquid for the heat-sensitive recording layer can be appropriately selected from those that can be used in the coating liquid for the undercoat layer. For example, light (heavy) calcium carbonate and firing. Examples thereof include pigments such as kaolin, dispersants such as sodium dioctyl sulfosuccinate, waxes such as zinc stearate, hydrazide compounds, water resistant agents such as glyoxyphosphate, antifoaming agents, coloring dyes, and fluorescent dyes.

[Protective layer]
In the present invention, a protective layer may be provided on the heat-sensitive recording layer as needed. This makes it possible to improve the barrier property against chemicals such as plasticizers and oils. The protective layer can be formed, for example, by applying and drying a coating liquid for a protective layer composed mainly of a pigment and a binder on a heat-sensitive recording layer. In particular, it is preferable to add a lubricant such as polyolefin wax or zinc stearate to the protective layer for the purpose of preventing sticking to the thermal head, and an ultraviolet absorber may also be contained. Further, by providing a glossy protective layer, it is possible to increase the added value of the product. The binder contained in the protective layer is not particularly limited, and can be appropriately selected from those that can be used for the undercoat layer. The protective layer can be divided into two or more layers as needed, and the composition and the amount of coating of each layer may be the same or different.

[Other layers]
Further, in the present invention, in order to increase the added value of the heat-sensitive recording body, the heat-sensitive recording body can be processed to have higher functions. For example, by applying an adhesive, a re-wet adhesive, a delayed tack type adhesive, etc. to the back surface opposite to the heat-sensitive recording layer and applying adhesive processing, adhesive paper, re-wet adhesive paper, delayed tack paper, etc. Can be used as. Further, by applying magnetic processing, a heat-sensitive recording body having a magnetically recordable layer on the back surface can be obtained. In particular, those subjected to adhesive processing or magnetic processing are useful for applications such as thermal labels and thermal magnetic tickets. Further, the back surface can be used to provide functions as thermal transfer paper, inkjet paper, carbonless copy paper, electrostatic recording paper, xerographic paper, etc., to make a recording body capable of double-sided recording. Of course, it can also be a double-sided thermal recorder. Further, it is also possible to suppress the permeation of oil and the plasticizer from the back surface of the heat-sensitive recording body, and to provide a back layer for curl control and electric resistance prevention.

It is also possible to obtain a linerless label that does not require a release paper by applying a release layer containing silicon on the protective layer and applying an adhesive on the back surface.

[Thermal recording body]
The method of forming each layer on the support is not particularly limited, and for example, an appropriate coating method such as air knife coating, variver blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating, etc. can be used. It is formed by a method such as applying and drying each coating liquid. Further, each coating liquid may be applied and dried one layer at a time to form each layer, or the same coating liquid may be applied in two or more layers. Further, simultaneous multi-layer coating may be performed in which two or more layers are simultaneously coated. Further, a smoothing process using a super calendar or the like can be performed in an arbitrary process after the formation of each layer is completed.

For the formation of the undercoat layer provided if necessary, pure blade coating or rod blade coating is preferable from the viewpoint of improving the surface property of the undercoat layer and obtaining a uniform heat-sensitive recording layer. Further, regarding the formation of the heat-sensitive recording layer and the protective layer provided if necessary, the uniformity can be improved by the successive coating or the simultaneous multi-layer coating by the curtain coating, and it is also preferable in terms of productivity.

In the present invention, in order to further increase the added value of the product, a multicolor heat-sensitive recorder can be used. Generally, a multicolor thermal recorder is an attempt to utilize a difference in heating temperature or a difference in thermal energy, and is generally configured by laminating a high-temperature color-developing layer and a low-temperature color-developing layer that develop colors in different tones on a support. These are roughly classified into two types, a decolorizing type and an additive type, and a multicolor thermal recording body is made by using a method using microcapsules and a composite particle composed of an organic polymer and a leuco dye. There is a method of manufacturing.

The present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. Unless otherwise specified, "parts" and "%" indicate "parts by mass" and "% by mass", respectively.

Example 1
-Preparation of coating liquid for undercoat layer Plastic hollow particle dispersion (trade name: Low Pake SN-1055, hollow ratio: 55%, average particle size: 1.0 μm, manufactured by Dow Chemical Co., Ltd., solid content concentration 26.5% by mass) 75.5 parts, 50% aqueous dispersion of calcined kaolin (trade name: Ansilex, manufactured by BASF) (average particle size: 0.6 μm) 147.2 parts, styrene-butadiene latex (trade name: L-1571) , Asahi Kasei Chemicals Co., Ltd., solid content concentration 48% by mass) 18.4 parts, 30 parts of 10% aqueous solution of oxidized starch, 5.3 parts of sodium hexametaphosphate, 5.3 parts of ammonium citrate, and 100 parts of water. The materials were mixed to obtain a coating liquid for an undercoat layer.

-Preparation of solution A (leuco dye dispersion) 3-di (n-butyl) amino-6-methyl-7-anilinofluorane 100 parts, sulfone-modified polyvinyl alcohol (trade name: Goceran L-3266, Nippon Synthetic Chemistry) A composition consisting of 50 parts of a 20% aqueous solution (manufactured by Sannopco), 10 parts of a 5% emulsion of a natural oil-based defoamer (trade name: Nopco 1407H, manufactured by Sannopco), and 90 parts of water was prepared by a sand mill using a laser diffraction type particle size. Liquid A was obtained by grinding with a distribution measuring device SALD2200 (manufactured by Shimadzu Corporation) until the medium diameter became 0.5 μm.

-Preparation of liquid B (coloring agent dispersion) 4,4'-bis (3-tosyl ureido) 100 parts of diphenylmethane, 20% aqueous solution of sulfone-modified polyvinyl alcohol (trade name: Goceran L-3266, manufactured by Nippon Synthetic Chemical Co., Ltd.) A composition consisting of 50 parts, 10 parts of a 5% emulsion of a natural oil-based defoamer (trade name: Nopco 1407H, manufactured by Sannopco), and 90 parts of water was prepared by a sand mill with a laser diffraction type particle size distribution measuring device SALD2200 (Shimadzu Seisakusho). The solution B was obtained by pulverizing until the median diameter was 1.0 μm.

Preparation of liquid C (sensitizer dispersion) 100 parts of diphenyl sulfone, 50 parts of 20% aqueous solution of sulfone-modified polyvinyl alcohol (trade name: Goceran L-3266, above), natural oil-based defoaming agent (trade name:) A composition consisting of 10 parts of 5% emulsion of Nopco 1407H (manufactured by San Nopco) and 90 parts of water was prepared by a sand mill with a laser diffraction type particle size distribution measuring device SALD2200 (manufactured by Shimadzu Corporation) until the median diameter became 1.0 μm. The mixture was pulverized to obtain a liquid D.

-Preparation of coating liquid for heat-sensitive recording layer 20 parts of A liquid, 32.5 parts of B liquid, 25 parts of C liquid, aluminum hydroxide (trade name: Heidilite H-42, average particle diameter 1.0 μm, manufactured by Showa Denko Co., Ltd.) ) 35 parts, 150 parts of 10% solution of oxidized starch, 30 parts of 10% aqueous solution of completely saponified polyvinyl alcohol (trade name: PVA110, manufactured by Claret), zinc stearate dispersion (trade name: Hydrin Z-8-36). , Solid content concentration 36%, manufactured by Chukyo Oil & Fat Co., Ltd.) 22.2 parts, paraffin wax (trade name: Hydrin P7, solid content concentration 30%, manufactured by Chukyo Oil & Fat Co., Ltd.) 6.7 parts, and 100 parts of water. Was mixed to obtain a coating liquid for a heat-sensitive recording layer.

-Preparation of thermal recording body As a support, the mass of the undercoat layer coating liquid after drying is 6.6 g on one side of high-quality paper (neutral paper with hot water extraction pH 8.0) with a basis weight of 58 g / m ² . An undercoat layer is formed by applying and drying by a blade coating method using a blade coater so as to be / m ² , and the weight of the coating liquid for a heat-sensitive recording layer on the undercoat layer after drying is 3.5 g / m ² . After coating and drying by a curtain coating method using a slide hopper type curtain coating device, a super calendar treatment was performed to obtain a heat-sensitive recorder.

Example 2
In the preparation of the coating liquid for the undercoat layer of Example 1, 5.3 parts of sodium hexametaphosphate was changed to 13.2 parts and 5.3 parts of ammonium citrate was changed to 13.2 parts, and the undercoat in the preparation of the heat-sensitive recording body was changed. A heat-sensitive recorder was obtained in the same manner as in Example 1 except that the coating amount of the layer coating liquid after drying was 7.5 g / m ² .

Example 3
In the preparation of the coating liquid for the undercoat layer of Example 1, 5.3 parts of sodium hexametaphosphate was changed to 24.6 parts, and 5.3 parts of ammonium citrate was changed to 24.6 parts, and the undercoat in the preparation of the heat-sensitive recording body was changed. A heat-sensitive recorder was obtained in the same manner as in Example 1 except that the coating amount of the layer coating liquid after drying was set to 8.8 g / m ² .

Example 4
In the preparation of the coating liquid for the undercoat layer of Example 1, 5.3 parts of sodium hexametaphosphate was changed to 35.1 parts and 5.3 parts of ammonium citrate was changed to 35.1 parts, and the undercoat in the preparation of the heat-sensitive recording body was changed. A heat-sensitive recorder was obtained in the same manner as in Example 1 except that the coating amount of the layer coating liquid after drying was set to 10.0 g / m ² .

Example 5
In the preparation of the coating liquid for the undercoat layer of Example 1, 5.3 parts of sodium hexametaphosphate was changed to 26.4 parts and 5.3 parts of ammonium citrate was changed to 0 parts for the undercoat layer in the production of the thermal recording body. A heat-sensitive recorder was obtained in the same manner as in Example 1 except that the coating amount after drying of the coating liquid was 7.5 g / m ² .

Example 6
-Preparation of an organic acid aqueous solution 13.2 parts of sodium hexametaphosphate, 13.2 parts of ammonium citrate, and 100 parts of water were mixed to obtain a 20.9% organic acid aqueous solution.

-Preparation of the undercoat layer coating solution The undercoat layer coating solution was obtained in the same manner as in Example 1 except that sodium hexametaphosphate and ammonium citrate were not added in the preparation of the undercoating solution of Example 1. ..

-Preparation of heat-sensitive recording body As a support, the mass of the undercoat layer coating liquid after drying is 6.0 g on one side of high-quality paper (neutral paper with hot water extraction pH 8.0) having a basis weight of 58 g / m ² . An undercoat layer is formed by applying and drying by a blade coating method using a blade coater so as to have a mass of / m ² , and the mass of the heat-sensitive recording layer coating liquid according to Example 1 after drying is 3 on the undercoat layer. After coating and drying by a curtain coating method using a slide hopper type curtain coating device so as to be .5 g / m ² , the mass of the organic acid aqueous solution after drying is applied to the support surface opposite to the surface where the undercoat layer is present. After applying and drying with a bar coater so as to have a mass of 1.5 g / m ² to form a back surface layer, a super calendar treatment was performed to obtain a heat-sensitive recorder.

Example 7
In the preparation of the heat-sensitive recorder of Example 6, a heat-sensitive recorder was obtained in the same manner as in Example 6 except that the amount of the organic acid aqueous solution applied after drying was 4.0 g / m ² .

Example 8
-Preparation of thermal recording body The mass of the organic acid aqueous solution according to Example 6 after drying on one surface of high-quality paper (neutral paper with hot water extraction pH 8.0) having a basis weight of 58 g / m ² as a support. After applying and drying with a bar coater to form an undercoat prelayer so that the mass is 1.5 g / m ² , the mass of the undercoat layer coating solution according to Example 6 after drying is applied on the undercoat prelayer. An undercoat layer is formed by applying and drying by a blade coating method using a blade coater so as to have a mass of 6.0 g / m ² , and the coating liquid for a heat-sensitive recording layer according to Example 1 is dried on the undercoat layer. After coating and drying by a curtain coating method using a slide hopper type curtain coating device so that the mass was 3.5 g / m ² , a super calendar treatment was performed to obtain a heat-sensitive recorder.

Example 9
-Preparation of thermal recording body After drying the undercoat layer coating solution according to Example 6 on one surface of high-quality paper (neutral paper with hot water extraction pH 8.0) having a basis weight of 58 g / m ² as a support. The undercoat layer is formed by applying and drying by a blade coating method using a blade coater so that the weight of the undercoat layer is 6.0 g / m ² , and after drying the organic acid aqueous solution according to Example 6 on the undercoat layer. After applying and drying with a bar coater so that the weight of the above-mentioned material becomes 1.5 g / m ² , the heat-sensitive recording front layer is formed, and then the coating liquid for the heat-sensitive recording layer according to Example 1 is dried on the heat-sensitive recording front layer. After coating and drying by a curtain coating method using a slide hopper type curtain coating device so that the subsequent weight was 3.5 g / m ² , a super calendar treatment was performed to obtain a heat-sensitive recorder.

Comparative Example 1
In the preparation of the coating liquid for the undercoat layer of Example 1, 5.3 parts of sodium hexametaphosphate was changed to 3.5 parts and 5.3 parts of ammonium citrate was changed to 3.5 parts, and the undercoat in the preparation of the thermal recording body was prepared. A heat-sensitive recorder was obtained in the same manner as in Example 1 except that the coating amount of the layer coating liquid after drying was 6.4 g / m ² .

Comparative Example 2
In the preparation of the heat-sensitive recording body of Example 6, a heat-sensitive recording body was obtained in the same manner as in Example 6 except that the coating amount of the organic acid aqueous solution after drying was 0.4 g / m ² .

Comparative Example 3
In the preparation of the coating liquid for the undercoat layer of Example 1, 5.3 parts of sodium hexametaphosphate was changed to 0 part and 5.3 parts of ammonium citrate was changed to 17.6 parts, and the part was changed to 17.6 parts for the undercoat layer in the production of the thermal recording body. A heat-sensitive recorder was obtained in the same manner as in Example 1 except that the coating amount after drying of the coating liquid was 7.0 g / m ² .

The heat-sensitive recorders produced in Examples 1 to 9 and Comparative Examples 1 to 3 above were subjected to the following evaluations, and the results are shown in Table 1.

[Recorded concentration]
Using a heat-sensitive recording evaluation machine (trade name: TH-PMD, manufactured by Okura Electric Co., Ltd.), each heat-sensitive recorder was recorded at an applied energy of 0.24 mJ / dot, and the obtained printed portion was printed with a Macbeth densitometer (RD-). It was measured in the visual mode of 914 (manufactured by Macbeth). The larger the value, the darker the print density, and the recording density should be 1.10 or more in practice.

[Blank paper storage]
Each heat-sensitive recorder was stored at 40 ° C. under the condition of 90% RH for 7 days, recorded under the same conditions as the recording density evaluation, and the obtained printed portion was measured with a Macbeth densitometer. Then, the preservation rate was calculated by the following formula. There is no problem in use when the storage rate is 80% or more.
Preservation rate (%) = (recorded concentration after processing / recorded concentration before processing) x 100

[Evaluation of skin cover]
Each heat-sensitive recorder was stored at 40 ° C. under the condition of 90% RH for 7 days, and the blank part was measured with a Macbeth densitometer.

Claims (6)

A heat-sensitive recording body having a heat-sensitive recording layer containing a leuco dye and a color-developing agent on one surface of the support.
It contains 4,4'-bis (3-tosylureido) diphenylmethane as the color-developing agent.
A heat-sensitive recorder having a layer containing 0.3 g / m ² or more of a condensed phosphoric acid compound between the support and the heat-sensitive recording layer and / or on the other surface of the support. The heat-sensitive recorder according to claim 1, wherein the condensed phosphoric acid compound is an acid, a sodium salt, a potassium salt, or an ammonium salt having an average degree of polymerization in the range of 3 to 30. The heat-sensitive recorder according to claim 1 or 2, wherein the layer containing the condensed phosphoric acid compound further contains a polyvalent carboxylic acid compound. The heat-sensitive recorder according to claim 3, wherein the polyvalent carboxylic acid compound is at least one compound selected from a divalent carboxylic acid, a trivalent carboxylic acid, and a salt thereof. The heat-sensitive recorder according to claim 3 or 4, wherein the total content of the condensed phosphoric acid compound and the polyvalent carboxylic acid compound is 3 g / m ² or less. The heat-sensitive recording body according to any one of claims 1 to 5, wherein the support is acid-free paper.