JP3156401B2 - Thermal recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosensitive recording medium which forms a color image by heating, and is particularly suitable for use in an optical character (or mark) reading device having a reading wavelength range in the near infrared region. Also, the present invention relates to a heat-sensitive recording medium which is excellent in oil resistance, plasticizer resistance, light resistance, etc. and forms a color image having excellent long-term storage properties.

[0002]

2. Description of the Related Art In general, a heat-sensitive recording material is formed on a support such as paper, synthetic paper, plastic film or the like, and a color-forming substance such as an electron-donating leuco dye and an electron-accepting phenolic compound or an organic acid compound. A heat-sensitive color-developing layer containing a color-developing substance as a main component is provided, and the color-developing substance and the color-developing substance are reacted by heat energy to obtain a recorded color-developed image. Such a thermosensitive recording medium is disclosed, for example, in JP-B-43-4160 and JP-B-45-14.
No. 039 and JP-A-48-27736, etc., and are widely used.

[0003] The thermal recording medium has a compact recording device,
Since it is inexpensive and easy to maintain, it is used in a wide range of applications such as computer output, facsimile, automatic ticket vending machines, printers for scientific measuring instruments, and printers for CRT medical measurement.

In recent years, optical character (or mark) reading devices (OCR) have been frequently used for input to computers. In particular, POS systems that collect and process product information and sales management information required for business management at supermarkets, department stores, and other large-volume retailers and restaurants are remarkably widespread. It employs a system that performs it. One of these systems is to display barcodes and OCR characters on products,
A method of optically reading these is in practical use, and is currently growing rapidly.

For reading a bar code or the like based on a color image, a He-Ne gas laser beam (wavelength 633n) has been conventionally used.
m), but semiconductor lasers (near-infrared light) have recently become widespread. This is because the semiconductor laser is small, lightweight, easy to handle, inexpensive, and has an oscillation wavelength in the infrared region (700 to 1600 nm), so that there is little erroneous operation and reading error due to soiling of the article. Things.

A color image formed on a general thermosensitive recording paper can be read by a He-Ne gas laser beam because its absorption wavelength is in a visible region (400 to 700 nm), but cannot be read by a semiconductor laser. Can not. Therefore, it is desired to provide a thermosensitive recording medium having a near-infrared absorption image readable by a semiconductor laser.

In producing a thermosensitive recording medium for forming a near-infrared absorption image, a basic compound having a lactone ring in a molecule as a dye (precursor) and a developer for coloring the dye (precursor) The technique of using a phenolic organic compound or an organic compound having a carboxyl group as the
5-115448 and JP-A-59-199757.
No., etc. However, the near-infrared absorption image formed by the combination of the dye and the developer described above is
It is known that the color is faded or erased with time, or the color is erased in a short time by contact with an oil or a plasticizer. This decoloring phenomenon is caused by the fact that the heat-sensitive recording medium that forms a conventional near-infrared absorption image
When used as an OCR medium in an OS system, it is a major drawback in terms of its reliability.

Further, in many of the above-mentioned conventional thermosensitive recording media for forming a near-infrared absorbing image, a near-infrared absorbing dye (particularly, a fluoran leuco dye disclosed in JP-A-59-199757) is used. ) Are easily decomposed when exposed to ultraviolet light for a long period of time, so that there is a problem in light resistance such as discoloration of the background, discoloration or fading of the color image.

Many techniques have been disclosed for suppressing the fading and decoloring of a color image on a heat-sensitive recording medium over time and the decoloring when contacting with an oil or a plasticizer. Many of them include a phenolic antioxidant incorporated in a thermosensitive coloring layer as disclosed in JP-A-60-78782 and JP-A-59-167292, or
A hydrophobic polymer emulsion or the like as disclosed in JP-A-56-146796 can be classified as a protective layer formed on a thermosensitive coloring layer.

In the print pattern formed on the heat-sensitive coloring layer containing the above-mentioned phenolic antioxidant, the fading with the passage of time is somewhat suppressed, but the fading also occurs rapidly due to the contact with the oil and the plasticizer. There is a disadvantage that it will.

On the other hand, in a thermosensitive recording medium having a protective layer formed thereon,
Decoloring immediately after contact with oil is greatly suppressed in the formed print pattern, but the color image disappears with time due to oil penetration and penetration, eliminating the disadvantage in terms of recording reliability. Have not succeeded.

As a method for suppressing the fading of the image and the discoloration of the background due to the exposure of the heat-sensitive recording medium which forms the near-infrared absorbing image, for example, a film containing a specific ultraviolet absorbent or a fluorescent dye is coated with phenol. Japanese Patent Application Laid-Open No. 48-5 / 48 discloses a technique for forming a thermosensitive coloring layer containing a thermosensitive compound as a color developer.
No. 1644. Japanese Patent Application Laid-Open No. 62-184880 discloses a technique for forming a protective layer containing a fluorescent whitening agent on a thermosensitive coloring layer containing a near infrared absorbing dye having a specific structure and a phenolic developer bisphenol A. Issue. JP-A-63-203379 discloses a technique for forming a protective layer containing a fluorescent dye on a thermosensitive coloring layer containing a substantially phenolic developer and a near infrared absorbing dye.

These prior arts all deal with fading of a printed portion or discoloration of a heat-sensitive recording layer due to light irradiation when a phenolic compound or an aromatic carboxyl compound is used as a developer. When the coloring agent is composed of other compounds, it is completely unknown whether or not it has the same effect as described above. In addition, when the above-described conventional type color developer is used, a heat-sensitive recording material is obtained in which the color image, which is the object of the present invention, has oil resistance, plasticizer resistance, and discoloration due to light exposure, and little discoloration. It is extremely difficult.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical character (or mark) reading device having a reading wavelength range in the near-infrared region, which is sufficiently readable, and which is resistant to oil, plasticizer, and light. It is an object of the present invention to provide a thermosensitive recording medium which forms a color image having excellent storage stability.

[0015]

Means for Solving the Problems In order to form a color image having high storage stability, the present inventors have studied a color developer of a thermosensitive recording paper, and as a result, have found a group of color developing agents having a specific chemical structure. Arylsulfonyl (thio) urea derivatives have excellent color-developing ability, and the color images formed thereby exhibit significantly higher storage stability than when conventional color developers are used. Then, by using this compound group as a developer of a dye precursor for forming a near-infrared absorbing dye, the object of the present invention was successfully achieved, and the present invention was completed.

Further, in the present invention, at least one protective layer is provided on the heat-sensitive recording layer, and at least one of the protective layers contains a fluorescent dye or an ultraviolet absorber to further improve the light fastness of the color image. I found that it can be improved.

The heat-sensitive recording material of the present invention comprises a sheet-like substrate,
Formed on at least one surface of the sheet-like substrate, and
A colorless or light-colored dye precursor, and a heat-sensitive coloring layer containing a coloring agent that reacts with the dye precursor under heating to form a color, and the coloring agent has one or more in the molecule. An arylsulfonylamino (thio) carbonylamino group of the formula (I):

Embedded image (Where X represents an oxygen or sulfur atom, and R ¹ ,
R ² , R ³ , R ⁴ , and R ⁵ each independently represent a member selected from a hydrogen atom, an alkoxyl group, an acetyl group, a nitro group, a lower alkyl group, and a halogen atom. ) Comprising one or more aromatic compounds having
Further, the present invention is characterized in that the dye precursor forms a color-developed image having absorption in the near infrared region of 700 to 1000 nm.

Further, the heat-sensitive recording material of the present invention has at least one protective layer containing a fluorescent dye or an ultraviolet absorber formed on the heat-sensitive coloring layer, if necessary.

[0019]

The arylsulfonyl (thio) urea compound used in the present invention acts as a color developer. That is, this compound has a phenolic hydroxyl group,
Alternatively, it does not have an acidic functional group such as a carboxyl group, but has a strong color developing ability with respect to a basic leuco dye. This is presumably because the (thio) urea group in the arylsulfonylamino (thio) carbonylamino group of the formula (I) is activated by a sulfonyl group adjacent thereto.

Specific examples of the color developer used in the present invention are as follows. Examples of the aromatic compound having one group of the formula (I) in the molecule include N- (p-toluenesulfonyl) -N'-phenylurea (melting point: 165)
C), N- (p-toluenesulfonyl) -N '-(p-
Methoxyphenyl) urea (melting point 155 ° C), N- (p-
Toluenesulfonyl) -N ′-(o-tolyl) urea (melting point 148 ° C.), N- (p-toluenesulfonyl) -N ′
-(M-tolyl) urea (melting point 184 ° C), N- (p-toluenesulfonyl) -N '-(p-tolyl) urea (melting point 149 ° C), N- (p-toluenesulfonyl) -N'-
(Pn-butylphenyl) urea, N- (p-toluenesulfonyl) -N ′-(o-chlorophenyl) urea (melting point 180 ° C.), N- (p-toluenesulfonyl) -N ′
-(M-chlorophenyl) urea (melting point 193 ° C), N-
(P-toluenesulfonyl) -N '-(2,4-dichlorophenyl) urea, N- (p-toluenesulfonyl)-
N′-benzylurea (melting point 177 ° C.), N- (p-toluenesulfonyl ) -N ′-(1-naphthyl) urea (melting point 124 ° C.), N- (p-toluenesulfonyl) -N′-
(1- (2-methylnaphthyl)) urea, N- (benzenesulfonyl) -N′-phenylurea (melting point: 153 ° C.),
N- (p-chlorobenzenesulfonyl) -N′-phenylurea, N- (o-toluenesulfonyl) -N′-phenylurea, N- (p-toluenesulfonyl) -N′-methylurea (melting point 172 ° C.), N- (p-toluenesulfonyl) -N′-ethylurea (melting point 141 ° C.), N- (p
-Toluenesulfonyl) -N '-(2-phenoxyethyl) urea (melting point 191 ° C), N, N'-bis (p-toluenesulfonyl) urea (melting point 155 ° C), N- (p-toluenesulfonyl) -N '-(O-diphenyl) urea (melting point 148 ° C), N- (p-toluenesulfonyl)-
N '-(p-ethoxycarbonylphenyl) urea, N-
(P-toluenesulfonyl) -N′-butylurea (melting point 126 ° C.), N- (p-chlorobenzenesulfonyl)-
N'-propylurea (melting point 127 ° C), N- (p-methoxybenzenesulfonyl) -N'-phenylurea (melting point 149 ° C), N- (p-methoxybenzenesulfonyl)
-N'-p-biphenylurea, N- (p-acetylbenzenesulfonyl) -N'-phenylurea (mp 164
C), N- (3-nitrobenzenesulfonyl) -N'-
Phenylurea (melting point 159 ° C.), N- (4-nitrobenzenesulfonyl) -N′-phenylurea (melting point 159)
C), N- (3-nitro-4-methoxybenzenesulfonyl) -N'-phenylurea (melting point 182C), N-
(Benzenesulfonyl) -N ′-(p-methoxyphenyl) urea (melting point 138 ° C.), N- (toluenesulfonyl) -N ′-(p-methoxyphenyl) urea, N- (toluenesulfonyl) -N ′-( 4-nitro-1-naphthyl) urea, N- (benzenesulfonyl) -N′-p-acetylphenylurea (melting point 177 ° C.), N- (benzenesulfonyl) -N ′-(p-nitrophenyl) urea (melting point) 234 ° C.), N- (4-methoxy-1-naphthalenesulfonyl) -N ′-(p-tolyl) urea, N- (p-acetylbenzenesulfonyl) -N ′-(m-tolyl) urea (mp 158 ° C.) ), N- (3-nitro-4-methylbenzenesulfonyl) -N ′-(p-tolyl) urea (melting point 188 ° C.), N- (3-nitro-4-methylbenzenesulfonyl) -N ′-(p -Chloro Eniru) urea (melting point 200 ° C.), N-(p-methoxybenzenesulfonyl)
-N'-phenylthiourea, N- (p-methoxybenzenesulfonyl) -N'-benzylurea (mp 166
C), N- (p-acetylbenzenesulfonyl) -N '
-Benzylurea (melting point 178 ° C.), N- (p-nitrobenzenesulfonyl) -N′-benzylurea (melting point 226)
C), N- (p-methoxybenzenesulfonyl) -N '
-(P-chlorobenzyl) urea (melting point 201 ° C.), N-
(P-methoxybenzenesulfonyl) -N '-(p-chlorobenzyl) thiourea.

Examples of the aromatic compound having two or more groups of the formula (I) in the molecule include bis (p-toluenesulfonylaminocarbonylamino) ketone,
2-bis (p-toluenesulfonylaminocarbonylamino) ethane, 1,1,6,6-tetra (p-toluenesulfonylaminocarbonylamino) hexane, 1,5
-Bis (p-toluenesulfonylaminocarbonylamino) -3-oxapentane, 1,5-bis (p-toluenesulfonylaminocarbonylamino) -3-thiopentane, 1,5-bis (p-toluenesulfonylaminocarbonylamino) -3- (2 '-(p-toluenesulfonylaminocarbonylamino) ethyl) -3-azapentane, 1,3-bis (p-toluenesulfonylaminocarbonylaminomethyl) -benzene, 4,4'-bis (p- Toluenesulfonylaminocarbonylamino)-
Diphenylmethane, 4,4′-bis (o-toluenesulfonylaminocarbonylamino) -diphenylmethane,
4,4'-bis (benzenesulfonylaminocarbonylamino) -diphenylmethane, 4,4'-bis (1-naphthalenesulfonylaminocarbonylamino) -diphenylmethane, 4,4'-bis (p-toluenesulfonylaminothiocarbonylamino) -Diphenylmethane,
2,2-bis (4 ′-(p-toluenesulfonylaminocarbonylamino) phenyl) propane, 1,2-bis (4- (p-toluenesulfonylaminocarbonylamino) phenyl) ethane, 1,2-bis (4 '-(P-toluenesulfonylaminocarbonylamino) phenyloxy) ethane, 3,3'-bis (p-toluenesulfonylaminocarbonylamino) diphenylsulfone, 3,
3′-bis (p-chlorobenzenesulfonylaminocarbonylamino) diphenyl sulfone, 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenyl ether, 2,5-bis (p-toluenesulfonylaminocarbonylaminomethyl) furan, 1,3-
Bis (p-toluenesulfonylaminocarbonylamino) benzene, 1,4-bis (p-toluenesulfonylaminocarbonylamino) benzene, 1,5-bis (p
-Toluenesulfonylaminocarbonylamino) naphthalene, 1,8-bis (p-toluenesulfonylaminocarbonylamino) naphthalene, 1,4-bis (3′-
(P-toluenesulfonylaminocarbonylamino) phenyloxy) benzene, 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenylsulfide, 2,8-dimethyl-3,7- (p-toluenesulfonylaminocarbonylamino) ) Dibenzothiophene 5,5-dioxide and the like. These developer compounds may be used alone or in combination of two or more.

The near-infrared absorbing dye-forming compound used as a dye precursor in the present invention develops a color by the reaction with the above-mentioned developer, and is in the near-infrared region, that is, 700 to 100.
Those which form a dye having an absorption at 0 nm are used.
Such a dye precursor can be selected from, for example, conventionally known dyes such as a fluoran leuco dye, a fluorene leuco dye, a divinylphthalide compound, and a styryl compound. Specifically, Japanese Patent Application Laid-Open No. 62-106964
JP-A-62-196177, JP-A-62-243
No. 653, JP-A-59-199757, JP-A-55-1997.
And compounds described in JP-A-115448 and JP-A-60-230890. They are, for example, 2-chloro-3-methyl-6- (N, N-dibutylaminoanilino) fluoran, 3- (p-anilinoanilino) -6-methyl-7-anilinofluoran, 3,6
-Bis (dimethylamino) fluorene-9-spiro-
3 ′-(6′-dimethylaminophthalide), 3,3-bis (2- (p-dimethylaminophenyl) -2- (p-
Methoxyphenyl) ethenyl) -4,5,6,7-tetrachlorophthalide, bis- (p-dimethylaminostyryl) -p-toluenesulfonylmethane and the like.

For the purpose of increasing the color density in the visible region, a conventionally known leuco dye having absorption in the visible region may be used in combination. Examples of these dyes include triphenylmethane-based, fluoran-based and diphenylmethane-based compounds. And the like. For example, 3- (4-diethylamino-2)
-Ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, crystal violet lactone, 3- (N-ethyl-N-isopentylamino) -6-methyl-7- Anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-
(O, p-dimethylanilino) fluoran, 3- (N-
Ethyl-Np-toluidino) -6-methyl-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-
7-anilinofluoran, 3- (N-cyclohexyl-
N-methylamino) -6-methyl-7-anilinofluoran, 3-diethylamino-7- (o-chloroanilino) fluoran, 3-dibutylamino-7- (o-chloroanilino) fluoran, 3-diethylamino-7-
(M-trifluoromethylanilino) fluoran, 3-
Diethylamino-6-methyl-7-chlorofluoran,
3-diethylamino-6-methylfluoran, and 3
-Cyclohexylamino-6-chlorofluoran, 3-
(N-ethyl-N-hexylamino) -6-methyl-7
-Selected from (p-chloroanilino) fluoran and the like
More than one species can be used.

In order to further improve the storability of a color image, the heat-sensitive coloring layer is formed of an aromatic compound having at least one aziridinyl group and / or an aromatic compound having at least one epoxy group. An image stabilizer can be further included.

Examples of the aromatic compound having at least one aziridinyl group and the aromatic compound having at least one epoxy group are described in JP-A-62-164579.
JP-A-2-220885, JP-A-2-25537
No. 6, JP-A-4-113888 and the like, and specific examples include the following compounds.

4,4'-bis (2 ", 3" -epoxypropyloxy) diphenylsulfone, 2,2-bis (4 '-(2 ", 3" -epoxypropyloxy) phenyl) propane, 1,4 -Bis (2 ', 3'-epoxypropyloxy) benzene, 4- (2'-methyl-
2 ', 3'-epoxypropyloxy) -4'-benzyloxy-diphenylsulfone, 4- (2 ", 3" -epoxypropyloxy) -4'-(p-methylbenzyloxy) -diphenylsulfone, epoxidation Ortho novolac cresol resin, 4,4'-bis (2 ", 3"
-Epoxypropyloxy) diphenylmethane, 4,
4'-bis (2 ", 3" -epoxypropylamino) diphenylmethane, bis (2 ", 3" -epoxypropyl) -4,4'-methylenedibenzoate, 4,4'-
Bis (2 ″, 3 ″ -epoxypropyloxy) biphenyl, 4,4′-bis (2 ″, 3 ″ -epoxypropyloxy) 3,3 ′, 5,5′-tetramethylbiphenyl,
2,6-bis (2 ', 3'-epoxypropyloxy)
Naphthalene, bis (2,3-epoxypropyl) terephthalate, 2,4-bis (1-aziridinylcarbonylamino) toluene, bis (4- (1-aziridinylcarbonylamino) phenyl) methane, bis (3- Chloro-
4- (1-aziridinylcarbonylamino) phenyl)
Methane, 2,2-bis (4- (1-aziridinylcarbonyloxy) phenyl) propane, 1,4-bis (1-
Aziridinylcarbonyloxy) benzene, 1,4-bis (1-aziridinylcarbonyl) benzene.

Further, in the present invention, it is preferable that the heat-sensitive coloring layer contains a heat-fusible substance (a so-called sensitizer). As such a sensitizer, a heat-fusible organic compound having a melting point of 50 to 150 ° C. is used, and examples thereof include 1-hydroxy-2-naphthoic acid phenyl ester (Japanese Patent Application Laid-Open No. Sho.
7-19089), p-benzylbiphenyl (JP-A-60-82382), benzylnaphthyl ether (JP-A-58-87094), dibenzyl terephthalate (JP-A-58-98285), p-benzyloxy Benzyl benzoate (JP-A-57-201691),
Diphenyl carbonate, ditolyl carbonate (JP-A-58-1364)
No. 89), m-terphenyl (JP-A-57-89994).
No.), 1,2-bis (m-tolyloxy) ethane (JP-A-60-56588), 1,5-bis (p-methoxyphenoxy) 3-oxapentane (JP-A-62-181)
183), oxalic acid diesters (JP-A-64-15)
No. 83), 1,4-bis (p-tolyloxy) benzene (Japanese Patent Application Laid-Open No. 2-153787), diphenyl sulfone (Japanese Patent Publication No. 59-25673), and phenyl p-toluenesulfonic acid (Japanese Patent Application Laid-Open No. 59-73990). ), Mesitylenesulfonic acid p-tolyl ester (JP-A-2-8)
0285), 4,4'-diallyloxydiphenylsulfone, 4,4'-diisopentyloxydiphenylsulfone, 4,4'-dimethoxydiphenylsulfone (JP-B 2-9951), 4,4'-di- n-pentyloxydiphenyl sulfone (JP-A-60-47070)
You can choose from.

In the present invention, the heat-sensitive coloring layer may further contain a hindered phenol compound or an ultraviolet absorber. They are described, for example, in JP-A-57-15139.
4, JP-A-58-160191, JP-A-58-69
No. 096, JP-A-59-2884, JP-A-59-95
No. 190, JP-A-60-22288, JP-A-60-2
55485, JP-A-61-44686, JP-A-62
169683, JP-A-63-17081, JP-A-1-249385, JP-A-4-144786, and the like.
1,3-tris (3′-cyclohexyl-4′-hydroxyphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl)
Butane, 4,4′-thiobis (3-methyl-6-ter
t-butylphenol), 1,3,5-trimethyl-
2,4,6-tris (3,5-di-tert-butyl-
4-hydroxybenzyl) benzene, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, p-octylphenyl salicylate, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, ethyl-2 -Cyano-3,3'-diphenylacrylate, tetra (2,2,6,6-tetramethyl-4-piperidyl) 1,2,3,4-butanetetracarboate.

The thermosensitive coloring layer of the thermosensitive recording medium of the present invention mainly contains a dye precursor, a color developer and, if necessary, a sensitizer. The heat-sensitive coloring layer may further contain an aromatic compound having at least one aziridinyl group and / or an aromatic compound having at least one epoxy group, if necessary, as described above. Further, the thermosensitive coloring layer may contain an antioxidant, an ultraviolet absorber, or waxes. Further, it preferably contains an organic or inorganic pigment. Further, it contains a binder for fixing these components to the support.

The content of the dye precursor in the heat-sensitive coloring layer is generally preferably 5 to 20% by weight of the dry weight of the heat-sensitive coloring layer, and the content of the developer compound of the present invention is generally 10 to 50% by weight. %. When the content of the color developing compound of the present invention is less than 10% by weight, the color developing ability becomes insufficient, and even when the content exceeds 50% by weight, the color developing ability is saturated, and no particular improvement is seen. May not be economically disadvantageous. When the thermosensitive coloring layer contains a coloring image stabilizer comprising an epoxy compound and / or an aziridine compound, its content is preferably 1 to 30% by weight based on the weight of the thermosensitive coloring layer. If the content is less than 1%, the effect of preserving the image is small, and even if the content exceeds 30% by weight, the effect of further improving the preservability is saturated and no further improvement is observed.

When the heat-sensitive coloring layer contains an antioxidant or an ultraviolet absorber, the content is preferably 1 to 10% by weight. When a sensitizer is contained, its content is preferably from 10 to 40% by weight. When waxes and white pigments are contained in the heat-sensitive coloring layer, the content is preferably 5 to 20% by weight and 10 to 50% by weight, respectively, and the content of the binder is generally 5 to 2% by weight.
0% by weight.

Examples of the organic or inorganic pigments include calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, calcined clay, talc, and surface-treated calcium carbonate. And inorganic fine powders such as silica and urea-formalin resin, styrene / methacrylic acid copolymer,
And organic fine powder such as polystyrene resin.

As the waxes, for example, known waxes such as paraffin, amide wax, bisimide wax, and metal salts of higher fatty acids can be used.

Examples of the binder include polyvinyl alcohol having various molecular weights, starch and derivatives thereof, cellulose derivatives such as methoxycellulose, carboxymethylcellulose, methylcellulose and ethylcellulose;
Sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylate copolymer, acrylamide / acrylate / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, polyacrylamide, alginic acid Water-soluble polymer materials such as soda, gelatin, and casein, and polyvinyl acetate, polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylate, vinyl chloride / vinyl acetate copolymer, and polybutyl methacrylate , Ethylene / vinyl acetate copolymer, and styrene /
Each latex such as a butadiene / acrylic copolymer can be used.

The sheet-like substrate used in the heat-sensitive recording medium of the present invention is selected from paper, coated paper having a surface coated with pigment, latex, etc., laminated paper, synthetic paper made from polyolefin resin, plastic film, and the like. be able to.

In order to prepare the thermosensitive recording medium of the present invention, a coating solution containing a mixture of the above-mentioned required components is applied on at least one surface of the above-mentioned sheet-like substrate, and dried to form a thermosensitive coloring layer. The coating amount of the thermosensitive coloring layer is preferably from 1 to 15 g / m ² , more preferably from ² to 10 g / m ² , in a state where the coating liquid layer is dried.

In the heat-sensitive recording medium of the present invention, in order to further improve the environmental resistance of a color image and a white background depending on the use, to improve the head matching with a thermal head used for a color-forming operation, and to improve the writing property. At least one coating layer such as a protective layer and a printing layer may be further formed on the thermosensitive coloring layer in order to achieve a purpose such as improving the color.

In particular, for the purpose of improving the light fastness of the obtained heat-sensitive recording material, a protective layer containing one or more fluorescent dyes or ultraviolet absorbers may be formed. In that case, the content of the fluorescent dye or the ultraviolet absorber to be added is preferably 1 to 40% by weight of the dry weight of the formed protective layer.
If the content is less than 1% by weight, a sufficient effect of improving light resistance cannot be obtained. If the content exceeds 40% by weight, problems may occur in the coating properties and writing properties of the protective layer. is there.

Further, it is more preferable that the fluorescent dye or the ultraviolet absorber is present in a continuous state on the thermosensitive coloring layer instead of as solid particles separated from each other. This is because, when applied in the form of a solution dissolved in water or an organic solvent, the light stabilizing effect of the fluorescent dye or ultraviolet absorber is sufficiently exhibited. Therefore, when forming the protective layer with an aqueous paint, the fluorescent dye or the ultraviolet absorber is preferably water-soluble, and when forming the protective layer with an organic solvent-based paint, the fluorescent dye or the ultraviolet absorber is Preferably, it is soluble in a solvent.

Examples of the UV absorber used in the present invention may be the same as the UV absorber which can be contained in the above-mentioned thermosensitive coloring layer, and specifically, 2,2'-dihydroxy-4 , 4'-Dimethoxybenzophenone, p-octylphenyl salicylate, 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2,4-di-t -Butylphenyl-3 ', 5'-di-t-butyl-4'-hydroxybenzoate, ethyl-2-cyano-3,3'-diphenylacrylate, tetra (2,2,6,6-tetramethyl- 4-piperidyl) -1,2,3,4-butanetetracarboate and the like.

Examples of the fluorescent dye used in the present invention include a stilbene-based fluorescent dye, that is, a bis (triazinylamino) stilbene disulfonic acid-based compound. Specific examples thereof include Kayahole 3BS, Kayahole S, Kayahole FOL, Kayahole SAH, and Kayahole PAS (trademarks, manufactured by Nippon Kayaku), Whitetex PRBLiq (trademark, Sumitomo Chemical), Mikehoa B
E (trademark, Mitsui Toatsu Chemicals), and Keikoru BUL,
And Keikoru CPNL (both trademarks, Nippon Soda)
And the like, but are not limited thereto.

The protective layer of the present invention comprises the above-mentioned ultraviolet absorber and / or fluorescent dye and an adhesive as main components, and if necessary, the above-mentioned pigment, and further contains a lubricant such as zinc stearate, a dispersant, An auxiliary agent such as an antifoaming agent can be added.
The coating amount of the protective layer is not particularly limited.
It is preferably in the range of ２０20 g / m ² .

[0043]

The present invention will be described in detail with reference to the following examples. In the following examples, “parts” and “%” represent “parts by weight” and “% by weight”, respectively, unless otherwise specified.

Example 1 A thermosensitive recording paper was prepared by the following operation. 1. Dispersion A prepared INGREDIENT AMOUNT (parts) 3,3-bis (2-(p-dimethylaminophenyl) -2 20 - (p-methoxyphenyl) ethenyl) -4,5,6,7-tetrachloro phthalide Polyvinyl alcohol 10% aqueous solution 10 water 70 The above composition has a mean particle size of 1 using a sand glider.
It was pulverized until it became not more than μm.

[0045] 2. Dispersion B prepared INGREDIENT AMOUNT (parts) of 4,4'-bis (p- toluenesulfonyl-amino carbonylation 10 arylamino) - using a sand grinder diphenylmethane sulfone 10 Polyvinyl 10% alcohol aqueous solution 10 Water 70 The composition, average Particle size is 1
It was pulverized until it became not more than μm.

[0046] 3. Preparation of Pigment- Primed Paper 85 parts of calcined clay (trade name: Ansilex) was mixed with 320 parts of water.
The resulting dispersion was mixed with 40 parts of a styrene / butadiene copolymer emulsion (solid content 50%) and 50 parts of a 10% aqueous starch oxide solution to prepare a coating solution. on both sides of the basis weight of 48 g / m ² base paper, the coating amount after drying was coated so as to 7.0 g / m ^2,
A pigment-coated paper was prepared.

[0047] 4. Formation of heat-sensitive coloring layer 50 parts of the above-mentioned liquid A and 200 parts of liquid B were mixed with 30 parts of calcium carbonate pigment, 20 parts of a 25% zinc stearate dispersion liquid,
15 parts of a 30% paraffin dispersion and 100 parts of a 10% aqueous solution of polyvinyl alcohol were mixed and stirred to prepare a coating solution. This coating solution is applied on one side of the pigment-coated paper,
The coating was applied so that the coating amount after drying was 5.0 g / m ^2, and dried to form a thermosensitive coloring layer, thereby producing a thermosensitive recording paper.

[0048] 5. A heat-sensitive recording paper obtained in the manner of the calendar processing the processed by a super calender, the smoothness of the surface 800-120
0 seconds.

6 Coloring test The sample thus obtained was colored using a commercially available thermal label printing machine (PortablePrinter B411) manufactured by TEC. This color image is read by a near-infrared absorption reading device (INSPECTOR III, manufactured by RJS. Inc., USA).
80 nm)) to perform a reading test. The test results are read by the reading level (C, D:
Pass, x: mark cannot be sensed, fail). Table 1 shows the test results.

[0050] 7. Oil resistance and plasticizer resistance test Further, the color-developed sample was immersed in salad oil, or sandwiched between two pieces of vinyl chloride wrap (Asahi Kasei Saran wrap) and placed in a weather resistance tester adjusted to 40 ° C.
After 4 hours, it was taken out, and the plasticizer transferred from the salad oil or vinyl chloride wrap was removed by immersing and washing in a hexane solution, and left to dry at room temperature. The residual image on the sample was subjected to a reading test using the above-mentioned near-infrared absorption reader, and the read level was used as an index indicating the oil resistance and the plasticizer resistance of the image. Table 1 shows the test results.

Example 2 A thermosensitive recording paper was prepared and tested in the same manner as in Example 1. However, in preparing dispersion A, 3,3-bis (2
Instead of-(p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl) -4,5,6,7-tetrachlorophthalide, 2-chloro-3-methyl-6-
(N, N-dibutylaminoanilino) fluorane was used. Table 1 shows the test results.

Example 3 A thermosensitive recording paper was prepared and tested in the same manner as in Example 1. However, in preparing dispersion A, 3,3-bis (2
Instead of 20 parts of-(p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl) -4,5,6,7-tetrachlorophthalide, 3,3-bis (2- (p
-Dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl) -10,5,6,7-tetrachlorophthalide and 3-dibutylamino-6-methyl-7-
A mixture with 10 parts of anilinofluorane was used. Table 1 shows the test results.

Example 4 A thermosensitive recording paper was prepared and tested in the same manner as in Example 1. However, when preparing the dispersion B, 4,4′-bis (p-toluenesulfonylaminocarbonylamino)-
Instead of 10 parts of diphenylmethane, a mixture of 5 parts of 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane and 5 parts of N- (p-toluenesulfonyl) -N'-phenylurea was used. Table 1 shows the test results.

Example 5 A thermosensitive recording paper was prepared and tested in the same manner as in Example 1. However, in preparing dispersion B, 4,4′-bis (p-toluenesulfonylaminocarbonylamino)-
Instead of diphenylmethane, 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenyl ether was used. Table 1 shows the test results.

Comparative Example 1 A thermosensitive recording paper was prepared and tested in the same manner as in Example 1. However, when preparing the dispersion B, 4,4′-bis (p-toluenesulfonylaminocarbonylamino)-
Instead of diphenylmethane, 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) was used. Table 1 shows the test results.

[0056]

[Table 1]

Example 6 A protective layer was formed on the thermosensitive coloring layer formed in Example 1 as follows. 8. Formation of protective layer 200 parts of a 10% aqueous solution of polyvinyl alcohol and 50 parts of calcium carbonate were mixed and stirred. This dispersion 100
To each part, 40 parts of an aqueous solution of a 50% fluorescent dye (Kayahole 3BS, manufactured by Nippon Kayaku) was added and stirred to prepare a protective layer dispersion. This dispersion was applied onto the heat-sensitive recording layer so that the coating amount after drying was 1.5 g / m ^2, and dried to form a protective layer. The obtained heat-sensitive recording paper was subjected to the calendering and color-forming tests described in Examples 5 and 6.

9. Samples were light resistance test color, temperature 63 ° C., 50% relative humidity adjusted light resistance tester (Toyo Seiki, trade: ATRAS-C
i35), and after 3 hours, the image was taken out. The residual image was measured by the above-mentioned near-infrared absorption reader, and this value was used as an index indicating the light fastness of the image. Table 2 shows the test results.

Example 7 A thermosensitive recording paper was prepared and tested in the same manner as in Example 6. However, the thermosensitive coloring layer of Example 3 was used instead of the thermosensitive coloring layer of Example 1. Table 2 shows the test results.

Comparative Example 2 On the thermosensitive coloring layer formed in Comparative Example 1, a protective layer similar to the protective layer of Example 6 but containing no fluorescent dye was formed. A color development test was performed, and a light resistance test similar to the above was performed. Table 2 shows the test results.

[0061]

[Table 2]

As is clear from Tables 1 and 2,
The near-infrared absorption image formed on the heat-sensitive recording medium of the present invention,
It can be clearly read by an optical character (or mark) reading device having a reading wavelength range in the near infrared region. Further, as is clear from Table 1, the color image formed on the thermosensitive recording medium of the present invention is superior in oil resistance and plasticizer resistance as compared with the near infrared absorption image of the conventional thermosensitive recording medium. . Further, as can be seen from Table 2, the color image formed on the thermosensitive recording medium having the protective layer of the present invention is excellent in light fastness.

[0063]

The heat-sensitive recording material of the present invention contains an N-arylsulfonyl (thio) urea compound having a specific chemical structure as a color developer in its heat-sensitive coloring layer. The images show better oil and plasticizer resistance than before. In addition, by providing a protective layer containing a fluorescent dye or an ultraviolet absorber, a color image has a light resistance superior to that of the conventional image, and has a reading wavelength in the near infrared region. It is suitable for reading by a device.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B41M 5/28-5/34 CA (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] 1. A sheet-like substrate, a colorless or light-colored dye precursor formed on at least one surface of the sheet-like substrate, and a developer which reacts with the dye precursor under heating to develop a color. Wherein the developer comprises one or more arylsulfonylamino (thio) carbonylamino groups (I) of the formula (I) in the molecule: (Where X represents an oxygen or sulfur atom, and R ¹ ,
R ² , R ³ , R ⁴ , and R ⁵ each independently represent a member selected from a hydrogen atom, an alkoxyl group, an acetyl group, a nitro group, a lower alkyl group, and a halogen atom. Wherein the dye precursor forms a color image having absorption in the near infrared region of 700 to 1000 nm. body. 2. The thermosensitive recording medium according to claim 1, wherein at least one protective layer containing a fluorescent dye or an ultraviolet absorber is formed on the thermosensitive coloring layer.