DE60210824T2 - Thermal recording material - Google Patents

Description

The The present invention relates to a heat-sensitive recording material. in which a color forming reaction between a leuco dye and a developer is used.

Recording devices, where a heat-sensitive Recording material is used as a recording medium, the a heat sensitive A recording layer comprising a leuco dye, a developer and a binder and on one side of a vehicle is formed of paper, synthetic paper, a plastic film or the like, are compact and cheap and can also easy to be serviced. Therefore, they become additional for use as recording media in facsimile systems, in ticket machines, in scientific measuring instruments, etc., also extensively as output media in printers or plotters for POS labels, CAD, medical CRT images and the like.

For printers for medical CRT instruments, which in the recorded images a uniformity and a high resolution require, and for CAD plotters that measure dimensional stability and fine line recording require, be heat sensitive Recording materials used in which synthetic papers with multilayer structures and a heat-sensitive recording material be used, in which a biaxially oriented thermoplastic Resin film is used, optionally inorganic pigments contains.

The Extension of the field of application of such heat-sensitive recording materials has an increasing demand for a thermosensitive recording material guided, wherein a recorded portion (i.e., a recorded portion Picture), which results from a color-forming reaction between a leuco dye and a developer has excellent stability against Chemicals such as e.g. Plasticizers, consumable oils, cosmetics and the like has, and for a heat-sensitive recording material, which gives a recorded portion whose density is in the Time changes less.

heat-sensitive Recording materials in which at least two types of hydroxydiphenylsulfone compounds, such as. 4-hydroxy-4'-isopropoxydiphenylsulfone, 4,4'-dihydroxydiphenyl sulfone and the like, as developers used to ensure the stability of a recorded section are in Japanese unaudited Patent Publications Nos. 1990-020385, 1990-249690, 1993-286255, 1995-172068, 2000-263944 and 2001-001647 described. However, there is another need for a smaller change the density of a recorded section over time, which is caused by the humidity and the temperature, and for one improved gradation of the recorded section.

at some applications it is regarding the heat sensitive Recording materials required that they be recorded Section with an achromatic black color (or a pale Charcoal color, gray). Japanese Unexamined Patent Publications Nos. 1993-254254 and 1996-324130 describe thermosensitive recording materials, in which a combination of a leuco dye, which is a black Color and a leuco dye that forms a red color is such a achromatic to a recorded portion of it to give black color. JP-A-2001-088450 describes a heat-sensitive one Recording material containing at least one leuco dye, the forms a black color, and a leuco dye that has a red color Color forms, contains, wherein at least 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran in it as the black coloring Leuco dye is included. JP-A-05-278328 describes a heat-sensitive one Recording material containing a support and a heat-sensitive Coloring layer, which on at least one surface of the carrier is trained. In such heat-sensitive However, recording materials are concerned with the recording sensitivity and the hue or gradation of a recorded section which requires further improvements.

The term "gradation" as used herein means that the recording energy used and the density (optical density) of the recorded portion (recorded image) are substantially directly proportional (linearly proportional). Specifically, a recorded image having a density is formed , which is proportional to the intensity of the applied energy, and the density of the recorded portion (recorded image) and the applied recording energy are in a nearly linear relationship to each other. As a result, when a plurality of recorded portions (recorded images) by stepwise changing (increasing or decreasing) the intensity of the applied recording energy, the formed recorded portions (recorded images) become a clear grada over its entire density range (from the lowest density to the highest density). An excellent gradation leads to an excellent picture quality.

A The object of the invention is to provide a heat-sensitive Recording material in which the hue of the recorded Section (recorded image) a nearly achromatic black Color is, the recorded section (recorded image) one has excellent gradation and recorded density Section over time under the influence of moisture or the Temperature shows essentially no change.

When Means of solution The above object is achieved according to the invention in a thermosensitive Recording material comprising a heat-sensitive recording layer, which contains a leuco dye, a developer and a binder a carrier has at least two kinds of hydroxydiphenylsulfone compounds as a developer and also as a leuco dye a leuco dye, the forms a black color, and 0.5 to 3.5 wt .-%, based on the leuco dye, which forms a black color, a leuco dye, which forms a red color, used.

Especially The present invention provides the following heat-sensitive recording materials ready.

object 1. Heat-sensitive A recording material comprising (a) a support and (b) a heat-sensitive one Recording layer, which is formed on the support and a Leuco dye, a developer and a binder, wherein the heat sensitive Recording layer at least two hydroxydiphenylsulfone compounds as the developer and a leuco dye which is a black color forms and a leuco dye which forms a red color, contains as the leuco dye, wherein the leuco dye, which forms a red color, in one Amount of 0.5 to 3.5 wt .-%, based on the leuco dye, which forms a black color, wherein the hydroxydiphenylsulfone compounds a mixture of 4-hydroxy-4'-isopropoxydiphenylsulfone and at least one member selected from the group consisting from 2,4'-dihydroxydiphenyl sulfone and 4,4'-dihydroxydiphenyl sulfone, wherein the leuco dye which forms a black color, at least one representative selected from the group consisting of 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 3-di (n-pentyl) amino-6-methyl-7-anilinofluoran and 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran, and wherein the Leuco dye which forms a red color, 3-diethylamino-7-chlorofluoran is.

object 2. Heat sensitive Recording material according to item 1, wherein the at least one Representatives, selected from the group consisting of 2,4'-dihydroxydiphenylsulfone and 4,4'-dihydroxydiphenyl sulfone, in an amount of about 0.5 to about 2.0 parts by weight per part by weight to 4-hydroxy-4'-isopropoxydiphenylsulfone is used.

object 3. Heat sensitive A recording material according to item 1, wherein the leuco dye, which forms a black color, a mixture of 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran and at least one representative, selected from the group consisting from 3-di (n-butyl) amino-6-methyl-7-anilinofluoran and 3-di (n-pentyl) amino-6-methyl-7-anilinofluoran.

object 4. Heat sensitive The recording material of item 3, wherein 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran in an amount of 30 to 300 wt .-%, based on at least one Representatives, selected from the group consisting of 3-di (n-butyl) amino-6-methyl-7-anilinofluoran and 3-di (n-pentyl) amino-6-methyl-7-anilinofluoran.

object 5. Heat sensitive Recording material according to item 1, which contains the leuco dye, which forms a red color, in an amount of about 0.8 to about 3.0% by weight, based on the leuco dye, which is a black Color forms, contains.

object 6. Heat sensitive Recording material according to item 1, wherein the heat-sensitive The recording layer further comprises a leuco dye which has a blue color Color forms, in an amount of about 0.5 to 5 wt .-%, based to the leuco dye which forms a black color.

object 7. Heat sensitive Recording material according to item 1, wherein a water-dispersible Resin in the heat-sensitive Recording layer is included as the binder.

Item 8. Heat-sensitive recording material according to item 1, wherein the heat sensitive recording layer further comprises a sensitizer, a printing stability improving agent or a mixture thereof.

object 9. Heat sensitive A recording material according to item 1, which further comprises a protective layer includes that on the heat-sensitive Recording layer is formed.

object 10. Heat sensitive Recording material according to item 1, which contains the leuco dye, which forms a red color in an amount of 0.5 to 3.0% by weight, based on the leuco dye, which forms a black color, contains.

The 1 Fig. 15 is a graph illustrating the relationship between the intensity of the applied recording energy and the density of the recorded portion with respect to the heat-sensitive recording materials of Example 1 and Comparative Example 3.

As As stated above, the present invention is characterized in that the heat-sensitive recording layer at least two hydroxydiphenylsulfone compounds as a developer contains and at least one leuco dye that forms a black color, and 0.5 to 3.5% by weight, based on the leuco dye, of a forms black color, a leuco dye that is a red color forms, contains.

developer

In The invention provides excellent gradation and excellent performance Long-term stability a recorded section through the combined use of at least two hydroxydiphenylsulfone compounds as a developer receive.

hydroxy-diphenylsulfone

Specific examples for the hydroxydiphenylsulfone compounds include 4-hydroxy-4'-methoxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-4'-n-propoxydiphenylsulfone, 4-hydroxy-4'-benzyloxydiphenylsulfone, 2,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl sulfone, 3,3'-diallyl-4,4'-dihydroxydiphenyl sulfone, 3,4-dihydroxy-4'methyldiphenylsulfone, 2,2 '- [4- (4-hydroxyphenylsulfonyl) phenoxyjdiethylether and the same.

In The present invention provides a mixture of 4-hydroxy-4'-isopropoxydiphenylsulfone and at least one member selected from the group from 2,4'-dihydroxydiphenyl sulfone and 4,4'-dihydroxydiphenyl sulfone, used.

Especially results in the use of about 0.2 to about 5.0 parts by weight, in particular from about 0.5 to about 2.0 parts by weight of at least a representative from the group consisting of 2,4'-dihydroxydiphenylsulfone and 4,4'-dihydroxydiphenylsulfone per Part by weight of 4-hydroxy-4'-isopropoxydiphenylsulfone even in recorded low density sections with a optical density of 0.4 to 0.8 a nearly achromatic black Colour.

From 2,4'-dihydroxydiphenyl and 4,4'-dihydroxydiphenylsulfone 2,4'-dihydroxydiphenylsulfone is preferred, because it is better resistance against a background fog.

The Total amount of hydroxydiphenylsulfone compounds used is about 15 to about 60% by weight, preferably about 20 to about 50% by weight, based on the total solids of the heat-sensitive recording layer.

Other developers

The thermosensitive Recording layer contains the above-described hydroxydiphenylsulfone compounds as Developers and if necessary can additional various other known developers are used, provided that the desired Effects of the invention are not affected.

Examples of other developers include phenolic compounds such as 1,3,3-trimethyl-1- (p-hydroxyphenyl) -6-hydroxyindane, 4,4'-isopropylidenediphenol, 4,4'-cyclohexylidenediphenol, 2,2-bis ( 4-hydroxyphenyl) -4-methylpentane, benzyl 4-hydroxybenzoate, 1,1-bis (4-hydroxyphenyl) -1-phenylethane and the like; those having one or more -SO ₂ NH bond (s) within the molecule, such as p-cumylphenyl-N- (p-tolylsulfonyl) carbamate, N- (o-tolyl) -p-tolylsulfoamide, 4,4 Bis (Np-tolylsulfonylaminocarbonylamino) diphenylmethane and the like; Zinc salts of aromatic carboxylic acids such as zinc 4- [2- (p-methoxyphenoxy) ethyloxy] salicylate, zinc 4- [3- (p-tolylsulfonyl) propyloxy] salicylate, zinc 5- [p- (2-p methoxyphenoxyethoxy) cumyl] salicylate and the like.

The The amount of these other developers is selected appropriately, but is usually in the range of about 3 to about 15 wt .-%, in particular of about 5 to about 10 wt .-%, based on the total amount of the above Hydroxydiphenylsulfonverbindungen mentioned used.

leuco

The thermosensitive Recording layer of the heat-sensitive recording material of the invention contains at least one leuco dye that forms a black color, and a specific amount of a leuco dye that has a red color Color forms. In the invention, recorded portions with an excellent color, an excellent gradation and excellent background fogging resistance and also with excellent heat resistance and moisture resistance additionally for use of at least two hydroxydiphenylsulfone compounds, which have been described above, by the combined use a leuco dye that forms a black color, and a specific amount of a leuco dye that forms a red color, receive.

Leuco dyes containing a form black color

Specific examples for Leuco dyes that form a black color include many various known leuco dyes which form a black color, which are used in the art, e.g. 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluoran, 3-Diethylamino-6-methyl-7-anilinofluoran, 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 3-di (n-pentyl) amino-6-methyl-7-anilinofluoran, 3 ' di (n-butyl) amino-7- (o-chloroanilino) fluoran, 3-di (n-butyl) amino-7- (o-fluoroanilino) fluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-N-tetrahydrofurfuryl) amino-6-methyl-7-anilinofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-anilinofluoran and the like.

In The present invention provides at least one member selected from the group consisting of 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 3-di (n-pentyl) amino-6-methyl-7-anilinofluoran and 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran used to obtain the recorded sections an excellent gradation and a to provide excellent background fogging resistance.

Especially preferred is the use of 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran in combination with at least one representative selected from the group consisting of 3-di (n-butyl) amino-6-methyl-7-anilinofluoran and 3-di (n-pentyl) amino-6-methyl-7-anilinofluoran.

In In this case, it is preferable to use 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran in an amount of from about 30 to about 300% by weight, more preferably from from about 50 to about 150% by weight, based on at least one member, selected from the group consisting of 3-di (n-butyl) amino-6-methyl-7-anilinofluoran and 3-di (n-pentyl) amino-6-methyl-7-anilinofluoran.

Leuco dyes containing a form red color

Specific examples for Leuco dyes that form a red color are in the art known, e.g. 3,3'-bis (p-dimethylaminophenyl) phthalide, 3- (N-ethyl-N-isoamyl) amino-7-phenoxyfluoran, 3-cyclohexylamino-6-chlorofluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-7,8-benzofluoran, 3-diethylamino-7-chlorofluoran, Rhodamine (o-chloroanilino) lactam, 3-diethylamino-6,8-dimethylfluoran, 3,3'-bis (7-n-butyl-2-methylindol-3-yl) phthalide and the same. In the present invention, 3-diethylamino-7-chlorofluoran used.

The Leuco dyes are not limited to the leuco dyes listed above limited and two or more leuco dyes that form a black color, and two or more leuco dyes that form a red color, can also be used in a combination.

In of the invention, the leuco dye, which forms a red color, in an amount of 0.5 to 3.5% by weight, based on the leuco dye, which forms a black color used. With low density recorded sections that have an optical density of 0.2 to 0.6, tend to be a blackish color with a greenish one To exhibit hue when the leuco dye is a red color forms, in an amount of less than 0.5 wt .-% is formed, and tend to have a black color with a reddish hue, when the leuco dye that forms a red color is in an amount of more than 3.5 wt .-% is used. Therefore, the amount is of the leuco dye which forms a red color, preferably about 0.8 up to about 3.0% by weight, more preferably about 1.0 to about 2.0% by weight, based on the leuco dye, which forms a black color.

Other leuco dyes

Furthermore can be the heat sensitive Recording layer have other leuco dyes, if the desired Effects of the invention are not affected. Special examples Such leuco dyes include leuco dyes that have a blue color Color, e.g. 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3-diethylamino-7-dibenzylaminobenzo [a] fluoran and the like; leuco dyes, the one green color form such. 3- (N-ethyl-N-p-tolyl) amino-7-N-methylanilinofluoran, 3-diethylamino-7-anilinofluoran, 3-diethylamino-7-dibenzylaminofluoran and the same; and leuco dyes having absorption wavelengths in the near infrared region, such as. 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-chlorofluoran, 3-p- (p-chloroanilino) anilino-6-methyl-7-chlorofluoran, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '- (6'-dimethylamino) phthalide and the same.

These other leuco dyes are preferably present in an amount of about From 0.3 to about 15% by weight, in particular from about 0.5 to about 10% by weight, based on the leuco dye which forms a black color, used. In particular, in the invention, the leuco dye, which forms a blue color, preferably in an amount of about 0.5 to about 5% by weight, in particular from about 1.0 to about 3.0% by weight, based on the leuco dye which forms a black color, used.

In of the invention the total amount of leuco dye that forms a black color, and the leuco dye which forms a red color, about 5 to about 35 wt .-%, in particular about 10 to about 25 wt .-%, based on the entire solid content of the heat-sensitive recording layer.

heat-sensitive recording layer

The thermosensitive Recording layer is e.g. formed as follows. A leuco dye, which forms a black color, a leuco dye that has a red color Color forms, a developer containing at least two hydroxydiphenylsulfone compounds and, optionally, a sensitizer, a pressure stability improving Means and the like usually become in water, which serves as a dispersion medium, either together or separated by means of a ball mill, an attrition mill, a sand mill or a corresponding mixing and Pulverizer to an average particle diameter of about 2 μm or less pulverized. Then, the resulting dispersion becomes Binder added, creating a coating composition for the thermosensitive Recording layer is obtained. The coating composition gets on a carrier applied and the coating is dried.

Examples for such Binders include water-soluble Resins, e.g. Graft copolymers of starch and polyvinyl acetate, polyvinyl alcohol, Carboxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, Silicon-modified polyvinyl alcohol, oxidized starch, casein, Styrene-maleic anhydride copolymer, Methyl vinyl ether-maleic anhydride copolymer, Isobutylene-maleic anhydride copolymer and the same; and water-dispersible resins, e.g. one Styrene-butadiene-based latex, an acrylic latex, a latex Urethane base and the like. Of these, water dispersible Resins preferred. The amount of binder to be used is not specifically limited, is however, preferably about 5 to about 40% by weight, especially about 20 to about 35% by weight, based on the heat-sensitive recording layer.

Further can be the heat sensitive Recording layer containing a sensitizer to the recording sensitivity as well as a pressure stability enhancing agent the long-term stability recorded sections.

Examples for sensitizers include stearic acid amide, Methylenebisstearamide, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, 2-naphthylbenzyl ether, m-terphenyl, p-benzylbiphenyl, p-tolylbiphenyl ether, di (4-methoxyphenoxyethyl) ether, 1,2-di (3-methylphenoxy) ethane, 1,2-di (4-methylphenoxy) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-di (4-chlorophenoxy) ethane, 1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (3-methylphenoxy) ethane, p-methylthiophenyl benzyl ether, di (β-biphenylethoxy) benzene, di (p-chlorobenzyl) oxalate, Dibenzyl oxalate and the like.

Examples for the the pressure stability Improving agents include hindered phenolic compounds, such as e.g. 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4'-thiobis (2-methyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-m-cresol); 1,3,5-tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 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-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane and the like; and Epoxy compounds, e.g. 4,4'-Diglycidyloxydiphenylsulfon, 4-benzyloxy-4 '- (2-methylglycidyloxy) diphenyl sulfone, Diglycidyl terephthalate, cresol novolac epoxy resin, phenol novolak epoxy resin, epoxy resin Ice phenol A-base and the like.

The Quantities of the sensitizer and the pressure stability improving Means used are not particularly limited, however is their amount each usually from about 0.1 to about 4 parts by weight, preferably from about 0.5 to about 3 parts by weight, per part by weight of the total amount of leuco dyes, which in the heat-sensitive Recording layer are included.

Furthermore For example, the coating composition for the heat-sensitive recording layer optionally contain various excipients. Examples of such auxiliaries include pigments, e.g. Kaolin, precipitated calcium carbonate, ground Calcium carbonate, calcined kaolin, titanium oxide, magnesium carbonate, Aluminum hydroxide, amorphous silica, urea-formaldehyde resin filler and the same; surfactants Means, e.g. Sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium laurylsulfate, Fatty acid metal salts and the same; Waxes, e.g. Zinc stearate, calcium stearate, polyethylene wax, Carnauba wax, paraffin wax, ester wax and the like; insoluble Means, e.g. Glyoxal, urea-formaldehyde resin, polyamide-epoxy resin, polyamidoamine-epichlorohydrin resin, adipic, boric acid, Borax, ammonium zirconium carbonate and the like; and ultraviolet absorbent, Foam suppressants, Fluorescent dyes, coloring dyes and the like.

The coating composition for the heat-sensitive recording layer is applied in an amount of about 2 to about 12 g / m ² , preferably about 3 to about 7 g / m ² , on a dry weight basis.

The Coating composition for the heat sensitive Recording layer is according to a Coating method conventionally used in the art is such. Air knife coating, pure knife coating, bar doctor coating, Bar coating, curtain coating, melt coating, gravure coating or the like on a support applied, and then the resulting coating layer dried.

carrier

When the aforementioned carrier can any known carrier, used in the art. Especially include examples of ink-freed pulp-containing Recycled paper, neutralized or acid woodfree paper, coated paper, synthetic paper, a transparent one Plastic film, a colored transparent plastic film, a white plastic film and the like. The thickness of these carriers is suitably selected from a wide range. The preferred thickness is generally about 40 to about 250 microns.

protective layer

Possibly Can be on the heat sensitive Recording layer, a protective layer can be provided to the chemical resistance or the water resistance of the recorded portion, or the slipperiness during the To improve on drawing. Such a protective layer is e.g. by applying a coating composition for the protective layer, which contains a binder with film-forming ability on the heat-sensitive Recording layer, and drying the resulting layer formed.

When Binder used in the coating composition for the protective layer can be included those binders are used which are described in the above Coating composition for the heat sensitive Recording layer can be included. Such a binder is preferably in an amount of about 20 to about 100 wt .-%, in particular from about 30 to about 95% by weight, based on the total solids content the protective layer used.

Further For example, the protective layer coating composition may optionally be contain the above-mentioned various excipients which in the coating composition for the heat-sensitive recording layer can be included.

The coating composition for the protective layer is applied in an amount of about 0.5 to about 10 g / m ² , preferably about 1 to about 5 g / m ² , on a dry weight basis.

The Coating composition for the protective layer can be on the heat-sensitive Recording layer according to a Coating method known in the art, such as e.g. Air knife coating, pure knife coating, bar doctor coating, Bar coating, curtain coating, melt coating, gravure coating or the like, and then the resulting Coating layer dried.

Around about that addition, to improve the recording sensitivity and image quality, can between the carrier and the heat sensitive Recording layer applied a base coat layer Be the oil-absorbing Contains pigments or hollow particles as main components, a glossy layer can be achieved by applying a coating composition containing a Electron beam or UV curable Compound as the main component, on the protective layer and hardening the coating by an electron beam or by UV rays or a smoothing treatment may be provided the formation of each layer provided by a supercalender become. Further, the heat-sensitive recording material of the present invention optionally by the use of various other known Techniques are modified, which are more sensitive to heat during production Recording materials are used.

Examples

The The present invention will be described with reference to the following Examples illustrated in more detail. It should be noted the scope of the invention is not limited by the examples. Here are "parts" and "%" for "parts by weight" and "% by weight", if nothing else is specified.

example 1

Preparation of a developer dispersion (Dispersion A)

A Composition consisting of 10 parts of 4-hydroxy-4'-isopropoxydiphenylsulfone, 4 parts a 10% aqueous solution a sulfone-modified polyvinyl alcohol and 8 parts of a 5% aqueous solution of Hydroxypropylmethylcellulose was composed by a Ultra Visco mill (manufactured by Aymex Co., Ltd.) to an average particle diameter of 1.5 μm pulverized, so that the dispersion A was obtained.

Preparation of a developer dispersion (Dispersion B)

A A composition consisting of 10 parts of 2,4'-dihydroxydiphenylsulfone, 4 parts of a 10% aqueous solution a sulfone-modified polyvinyl alcohol and 8 parts of a 5% aqueous Solution of Hydroxypropylmethylcellulose was composed by a Ultra Visco mill (manufactured by Aymex Co., Ltd.) to an average particle diameter of 1.5 μm pulverized so that the dispersion B was obtained.

Preparation of a dispersion a leuco dye that forms a black color (dispersion C)

A A composition consisting of 10 parts of 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 10 parts of a 10% aqueous solution a sulfone-modified polyvinyl alcohol and 10 parts of water was composed by an Ultra Visco mill (from Aymex Co., Ltd. prepared) to an average particle diameter of 1.0 μm pulverized so that the dispersion C was obtained.

Preparation of a dispersion a leuco dye that forms a black color (dispersion D)

A A composition consisting of 10 parts of 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran, 10 parts of a 10% aqueous solution a sulfone-modified polyvinyl alcohol and 10 parts of water was composed by an Ultra Visco mill (from Aymex Co., Ltd. prepared) to an average particle diameter of 1.0 μm pulverized so that the dispersion D was obtained.

Preparation of a dispersion a leuco dye that forms a red color (dispersion E)

A A composition consisting of 10 parts of 3-diethylamino-7-chlorofluoran, 10 parts of a 10% aqueous solution a sulfone-modified polyvinyl alcohol and 10 parts of water was composed by an Ultra Visco mill (from Aymex Co., Ltd. prepared) to an average particle diameter of 1.0 μm pulverized so that the dispersion E was obtained.

Preparation of a dispersion a leuco dye that forms a red color (dispersion F)

A A composition consisting of 10 parts of 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 10 Divide a 10% aqueous solution composed of a sulfone-modified polyvinyl alcohol and 10 parts of water was through an Ultra Visco mill (manufactured by Aymex Co., Ltd.) pulverized to an average particle diameter of 1.0 μm, so that the dispersion F was obtained.

Preparation of a sensitizer dispersion (Dispersion G)

A A composition consisting of 10 parts of 1,2-di (3-methylphenoxy) ethane, 10 parts of a 10% aqueous solution a sulfone-modified polyvinyl alcohol and 10 parts of water was composed by an Ultra Visco mill (from Aymex Co., Ltd. prepared) to an average particle diameter of 1.5 μm pulverized so that the dispersion G was obtained.

Preparation of a coating composition for the thermosensitive recording layer

A coating composition for the heat-sensitive recording layer was prepared by stirring a composition consisting of 30 parts of Dispersion A, 30 parts of Dispersion B, 30 parts of Dispersion C, 30 parts of Dispersion D, 0.6 part of Dispersion E, 1.0 part of dispersion F, 18 parts of dispersion G, 45 parts of styrene-butadiene latex (glass transition temperature: -5 ° C, solid content: 48%), 95 parts of a 13% aqueous solution of polyvinyl alcohol (trade name: PVA105 ^{®, manufactured} by Kuraray Co ., Ltd.), 12 parts of amorphous silica (trade name: Mizukasil ^® P-527, manufactured by Mizusawa Industrial Chemicals Ltd.) and 60 parts of water was composed prepared.

manufacturing a coating composition for the protective layer

A coating composition for protective layer was prepared by stirring a composition composed of 70 parts of a 60% aqueous slurry of kaolin (average particle diameter: 0.8 micron), 15 parts of an aqueous dispersion of zinc stearate (trade name: Hidorin Z-7-30 ^® , solid content: 31.5%), 2.00 parts of a 10% aqueous solution of Acetoacety modified polyvinyl alcohol (trade name: Gohsefimer Z-200 ^®, Ltd.) manufactured by The Nippon Synthetic Chemical Industry Co., 3 parts of a 10% aqueous solution of glyoxal and 120 parts of water was prepared.

manufacturing a heat sensitive recording material

A thermosensitive recording material was prepared by applying the coating composition for the heat sensitive recording layer and the coating composition for the protective layer to one side of a synthetic paper (trade name: manufactured Yupo ^® FPG-80, from Yupo Corporation) in amounts were such that the respective amounts after 5 g / m ² and 3 g / m ² , and drying the resulting coating layers. After the formation of the protective layer, the thermosensitive recording material was subjected to a smoothing treatment by a supercalender.

Examples 2 to 11 and Comparative Examples 1 to 4

Preparation of a developer dispersion (Dispersion H)

A A composition consisting of 10 parts of 4,4'-dihydroxydiphenylsulfone, 4 parts of a 10% aqueous solution a sulfone-modified polyvinyl alcohol and 8 parts of a 5% aqueous Solution of Hydroxypropylmethylcellulose was composed by a Ultra Visco mill (manufactured by Aymex Co., Ltd.) to an average particle diameter of 1.5 μm pulverized so that the dispersion H was obtained.

sensitizer (Dispersion I)

A commercial Stearinsäureamiddispersion (trade name: Himicron ^® G-270, solid content: 21%, manufactured by Chukyo Yushi Co., Ltd.) was used as Dispersion I.

heat-sensitive Recording materials were prepared in the same manner as in Example 1, but the components and their proportions were so selected, as shown in Table 1, rather than 30 parts of the dispersion A, 30 parts of the dispersion B, 30 parts of the dispersion C, 30 parts of dispersion D, 0.6 part of dispersion E, 1.0 part of the dispersion F and 18 parts of the dispersion G to use.

Table 1

Example 12

A heat-sensitive recording material was prepared in the same manner as in Example 1 However, in the preparation of Dispersion C, instead of 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 3-di (n-pentyl) amino-6-methyl-7-anilinofluoran was used.

Example 13 (reference)

One thermosensitive Recording material was in the same manner as in Example 1, but in the preparation of the dispersion C instead of 3-di (n-butyl) amino-6-methyl-7-anilinofluoran 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluoran used.

Example 14 (reference)

One thermosensitive Recording material was in the same manner as in Example 1, but in the preparation of dispersion B instead of 2,4'-dihydroxydiphenyl sulfone 3,3'-diallyl-4,4'-dihydroxydiphenylsulfone used.

Example 15

One thermosensitive Recording material was in the same manner as in Example 1, but were used in the preparation of the coating composition for the thermosensitive Recording layer 1.0 part of dispersion F not used.

The thus obtained heat-sensitive Recording materials were subjected to the evaluation tests described below and Table 2 shows the results.

Density of recorded section and gradation index

The thermosensitive recording materials were subjected to a 17-step gradation recording with a video printer (trade name: UP- ^880® manufactured by Sony Corporation), and the density of each recorded section was measured with a Macbeth densitometer (trade name: RD914, manufactured by Macbeth) in the visual mode measured. In Table 2, the difference in density between the recorded portion at the step 6 and the non-recorded portion is referred to as "gradation index." According to research conducted by the inventors, when the gradation index (difference in density between the recorded portion at the stage 6 and the unrecorded portion) is about 0.3 ± 0.1, achieving excellent gradation.

hue

at the above-described evaluation of the densities of the recorded Sections became the hue in the recorded sections visually rated at a density of about 0.4 to about 0.8.

Moisture resistance stability

• (1) From the recorded sections the heat sensitive Recording materials after recording as described above (i.e., the recording materials recording the 17-step gradation in the test described above, the "density of the recorded Section and gradation index " were the recorded sections that were obtained in the stages which gave a density of 0.70 to 0.90 (e.g. Step 9 in Examples and Comparative Examples 1 and 2), a density measurement using a Macbeth densitometer in the subjected to visual mode.
• (2) Thereafter, the heat-sensitive Recording materials under the conditions of 40 ° C and 90% relative humidity was allowed to stand for 24 hours, and then the densities of the recorded sections, which has a density of 0.70 to 0.90 (i.e., the recorded portions, in the above item (1) has been subjected to density measurement are measured again with the Macbeth densitometer in visual mode.

The residual ratios of the densities of the recorded portions were calculated using the following equation. Residual ratio (%) = (D 1 / D 0 ) × 100 wherein D _{1 represents} the density of the recorded portion after being subjected to the above conditions, and D _{0 represents} the density of the recorded portion before being subjected to the above conditions.

Heat resistance stability

• (a) From the recorded sections the heat sensitive Recording materials after recording as described above (i.e., the recording materials recording the 17-step gradation in the test described above, the "density of the recorded Section and gradation index " were the recorded sections that were obtained in the stages which gave a density of 0.70 to 0.90 (e.g. Step 9 in Examples and Comparative Examples 1 and 2), a density measurement using a Macbeth densitometer in the subjected to visual mode.
• (b) Thereafter, the heat-sensitive ones became Recording materials under the conditions of 50 ° C and 30% relative humidity was allowed to stand for 24 hours, and then the densities of the recorded sections, which has a density of 0.70 to 0.90 (i.e., the recorded portions, in the above item (a) has been subjected to density measurement are measured again with the Macbeth densitometer in visual mode.

The residual ratios of the densities of the recorded portions were calculated using the following equation. Residual ratio (%) = (D 2 / D 0 ) × 100 wherein D _{2 represents} the density of the recorded portion after being subjected to the above conditions, and D _{0 represents} the density of the recorded portion before being subjected to the above conditions.

Background fogging resistance

The thermosensitive Recording materials were under the conditions of 50 ° C and 30% relative humidity left for 24 hours. Then the Background fogging resistance the heat sensitive Recording layer with a Macbeth densitometer in the visual Mode measured.

Table 2

The 1 Fig. 15 is a graph showing the relationship between the intensity of applied recording energy (energy used with a video printer in the 17-step gradation recording described above) and the density of the recorded portion with respect to the heat-sensitive recording materials of Example 1 and Comparative Example 3 shows.

As it is from the 1 As is apparent, the heat-sensitive recording material of Comparative Example 3, which contains only one kind of developer other than the present invention, has an opening density of only about 0.19 at stage 6, and the gradation index (difference in density between the recorded portion at stage 6 and the unrecorded portion) is only 0.12. Further, the densities of the recorded portions substantially increase as compared to the low densities of the recorded portions up to stage 9 after stage 9. As a result, considering all 17 levels, the graph showing the relationship between the intensity of the applied recording energy and the density of the recorded portions is not a straight line but a curved line, showing a poor gradation property.

in the Contrary to that, the heat sensitive Recording material of Example 1 of the invention, a recording density from about 0.37 at level 6 and the gradation index (difference at the density between the recorded section at the step 6 and the unrecorded portion) is 0.29, which is within the Difference of the density range of 0.3 ± 0.1 is. When considering of all 17 levels is obtained as a result that the graph, the the relationship between the intensity of the applied recording energy and the density of the recorded sections, essentially a straight line is what shows an outstanding gradation characteristic.

As it from the column in the table 2, which the densities of the recorded Sections at stage 17 shows, it can be seen, the heat-sensitive ones Recording materials of Examples 1 to 15 saturation densities (maximum densities of the recorded sections) which are larger as those of heat-sensitive ones Recording Materials of Comparative Examples.

As it has been shown in Table 2, gives the heat-sensitive according to the invention Recording material recorded sections with a nearly achromatic black color, has excellent density recorded portions (recording sensitivity), excellent gradation and background fog resistance on, has a high saturation density of the recorded section (maximum density of recorded Section), and further excellent in heat resistance and moisture resistance on, resulting in less change the density over time leads.

Claims (10)

thermosensitive A recording material comprising (a) a support and (b) a heat-sensitive one Recording layer, which is formed on the support and a Leuco dye, a developer and a binder, wherein the heat sensitive Recording layer at least two hydroxydiphenylsulfone compounds as the developer and a leuco dye which is a black Color forms, and a leuco dye, which is a red color forms as containing the leuco dye, wherein the leuco dye, which forms a red color in an amount of 0.5 to 3.5% by weight, based on the leuco dye, which forms a black color, is available, wherein the hydroxydiphenylsulfone compounds a mixture of 4-hydroxy-4'-isopropoxydiphenylsulfone and at least one member selected from the group consisting from 2,4'-dihydroxydiphenyl sulfone and 4,4'-dihydroxydiphenyl sulfone, are, wherein the leuco dye which is a black color forms, at least one member selected from the group consisting from 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 3-di (n-pentyl) amino-6-methyl-7-anilinofluoran and 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran is and wherein the leuco dye which is a red color forms 3-diethylamino-7-chlorofluoran is. thermosensitive The recording material of claim 1, wherein the at least one Representatives, selected from the group consisting of 2,4'-dihydroxydiphenylsulfone and 4,4'-dihydroxydiphenyl sulfone, in an amount of about 0.5 to about 2.0 parts by weight per part by weight used on 4-hydroxy-4'-isopropoxydiphenylsulfone becomes. thermosensitive The recording material of claim 1, wherein the leuco dye, which forms a black color, a mixture of 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran and at least one member selected from the group consisting from 3-di (n-butyl) amino-6-methyl-7-anilinofluoran and 3-di (n-pentyl) amino-6-methyl-7-anilinofluoran, is. thermosensitive The recording material of claim 3, wherein 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran in an amount of 30 to 300 wt .-%, based on at least one Representatives, selected from the group consisting of 3-di (n-butyl) amino-6-methyl-7-anilinofluoran and 3-di (n-pentyl) amino-6-methyl-7-anilinofluoran, is used. thermosensitive A recording material according to claim 1, which contains the leuco dye, which forms a red color, in an amount of about 0.8 to about 3.0% by weight, based on the leuco dye, which is a black Color forms, contains. thermosensitive The recording material of claim 1, wherein the heat-sensitive The recording layer further comprises a leuco dye which has a blue color Color forms, in an amount of about 0.5 to about 5 wt .-%, based to the leuco dye which forms a black color. thermosensitive A recording material according to claim 1, wherein a water-dispersible Resin in the heat-sensitive Recording layer is included as the binder. thermosensitive The recording material of claim 1, wherein the heat-sensitive The recording layer further comprises a sensitizer, a printing stability-improving Means or a mixture thereof. thermosensitive A recording medium according to claim 1, which further comprises a protective layer on the heat-sensitive Recording layer comprises. thermosensitive A recording material according to claim 1, which contains the leuco dye, which forms a red color, in an amount of about 0.5 to about 3.0% by weight, based on the leuco dye, which is a black Color forms, contains.