JP3339041B2 - 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 having excellent ground color stability.

[0002]

2. Description of the Related Art In general, a thermosensitive recording medium is prepared by grinding and dispersing a colorless or light-colored electron-donating colorless dye and a developer such as a phenol compound into fine particles, and then mixing the two. , A binder, a filler, a sensitivity improver, a lubricant, and a coating solution obtained by adding other auxiliaries are applied to a support such as paper, synthetic paper, film, plastic,
The color is developed by an instantaneous chemical reaction due to the heating of a thermal head, a hot stamp, a laser beam, or the like to obtain a visible record.

[0003] Thermal recording media have been applied to a wide range of fields, such as measurement recorders, computer terminal printers, facsimile machines, automatic ticket vending machines, and bar code labels. However, recently, diversification of recording devices for thermal recording media,
As the performance has been improved, the quality required for the thermosensitive recording medium has become higher. For example, from the viewpoint of high-speed recording, it is possible to obtain a high-density and clear color image even with a smaller amount of thermal energy. On the other hand, from the viewpoint of storage stability of the recording medium, light resistance, oil resistance, and water resistance are obtained. Also, it is required to have excellent solvent resistance and the like.

[0004] On the other hand, as systems for recording on plain paper such as the electrophotographic system and the ink jet system have become widespread, there are increasing opportunities for comparing thermal recording with plain paper recording. For example, it is required that the stability of a recording portion (image) and the stability of a non-recording portion (ground color portion) before and after recording (hereinafter referred to as ground color stability) approach the quality of plain paper recording. ing. In particular, the thermal recording has been required to have a ground color stability against heat and a solvent. It is desired that the recording be thermosensitive only at the time of recording and insensitive to other times.

Regarding the ground color stability of a thermal recording medium, for example,
Japanese Patent Application Laid-Open No. 4-353490 discloses a thermosensitive recording medium in which the whiteness of the ground color and the recording density do not decrease even under a high temperature condition of about 90 ° C.

[0006]

The ground color stability of the heat-sensitive recording medium disclosed in Japanese Patent Application Laid-Open No. 4-353490 is 95%
When treated at 5 ° C. for 5 hours, the Macbeth density of the ground color was about 0.11, which showed considerable stability but was still insufficient. Therefore, an object of the present invention is to provide a thermosensitive recording medium having excellent ground color stability.

[0007]

The above object is achieved by an asymmetric type.
The problem was solved by a thermal recording medium using a 1,3-diphenylurea derivative as a color developer. That is, the present invention relates to a thermosensitive recording medium having a thermosensitive coloring layer containing a colorless or pale-colored dye precursor and a developer that reacts upon heating to form the dye precursor, wherein the developer is represented by the following general formula: A heat-sensitive recording material, which is a urea compound represented by the formula (1), wherein the heat-sensitive coloring layer contains at least one kind of the urea compound.

Embedded image (Where X is an alkyl group having 1 to 4 carbon atoms, 1 carbon atom
Represents an alkoxy group, a trihalogenated methyl group, a nitro group, a halogen atom, or a hydrogen atom. Y represents an alkyl group having 2 to 18 carbon atoms. n represents an integer of 1 to 3. However, when n = 1, X and Y are different. )

The urea compound represented by the general formula (1)
This is an asymmetric 1,3-diphenylurea compound having an alkyl group on at least one side of 1,3-diphenylurea.
The urea compound represented by the general formula (1) can be easily synthesized, for example, by reacting an amine with an isocyanate compound.

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For example, as amines, o-ethylaniline, m-ethylaniline, p-ethylaniline, on-propylaniline, o-iso-propylaniline, pn-propylaniline, p-iso-propylaniline, pn- Butylaniline, p-sec-butylaniline, p-tert-butylaniline,
pn-amylaniline, pn-hexylaniline, pn-heptylaniline, pn-octylaniline, pn-noylaniline, pn-decylaniline, pn-undecylaniline,
pn-dodecylaniline, pn-tridecylaniline, pn-
Alkyl anilines such as tetradecyl aniline, pn-pentadecyl, pn-hexadecyl aniline, pn-heptadecyl aniline, and pn-octadecyl aniline;
Further, as monoisocyanate compounds, phenyl isocyanate, o-tolyl isocyanate, m-tolyl isocyanate, p-tolyl isocyanate, 3,4-dimethylphenyl isocyanate, 2,6-dimethylphenyl isocyanate, 3 isocyanate , 4,5-Trimethylphenyl, o-trifluoromethylphenyl isocyanate, m-trifluoromethylphenyl isocyanate, p-trifluoromethylphenyl isocyanate, 2-methoxyphenyl isocyanate, 3-methoxyphenyl isocyanate, isocyanate 4-methoxyphenyl acid, p-bromophenyl isocyanate, o-fluorophenyl isocyanate, m-fluorophenyl isocyanate, p-fluorophenyl isocyanate, o-chlorophenyl isocyanate, m-chlorophenyl isocyanate, p-isocyanate Chlorophenyl, isocyanic acid 2,5 -Dichlorophenyl, 3,4-dichlorophenyl isocyanate, isocyanic acid
Aromatic isocyanate compounds such as 2,6-dichlorophenyl, o-nitrophenyl isocyanate, m-nitrophenyl isocyanate, p-nitrophenyl isocyanate, p-dimethylaminophenyl isocyanate, and p-diethylaminophenyl isocyanate And any combination can be selected from both.

The following compounds can be exemplified as specific examples of the urea compound represented by the general formula (1).

[0011]

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Further, the substituent (X) of the urea compound represented by the general formula (1) may be a melting point, a decomposition temperature, a solubility in a solvent, or the like of the urea compound, or a performance of a heat-sensitive recording medium to be produced. (The recording density, the stability of the recording portion, the ground color stability, etc.) should be appropriately selected, and is not particularly limited. However, from the viewpoint of recording density, it seems more preferable that the substituent is a hydrogen atom (that is, unsubstituted) or that the substituent is an electron-withdrawing group.

Regarding the other substituent (Y), the melting point of the urea compound, the decomposition temperature, the solubility in a solvent, and the like, or the performance (recording density,
Stability of the recording portion, ground color stability, etc.) should be appropriately selected, and there is no particular limitation. However, from the viewpoint of recording density, it is better that the number of carbon atoms is short, and an alkyl group having 2 to 8 carbon atoms is desirable. Further, with respect to the stability of the recorded image against heat, an alkyl group having 3 to 6 carbon atoms is more preferable. Further, in an alkyl group having 7 or more carbon atoms, as the number of carbon atoms increases, the stability of a recorded image at the time of heat rolling tends to decrease. In other words, the greater the number of carbon atoms, the higher the decolorability of the recorded image due to the heat roll.

Patents using a monourea compound as a heat-sensitive recording material are disclosed in JP-A-58-211496 and JP-A-59-184694.
And Japanese Patent Application Laid-Open No. 61-211085. These monourea compounds are urea compounds in which only the amino group on one side of urea is substituted, and have a fundamentally different structure from the phenylurea compound of the present invention.
Further, heat-sensitive recording materials using a dimerized urea-type compound are disclosed in JP-A-5-317152, JP-A-5-147357 and the like. This dimerized urea-type compound has a structure having a sulfonyl group adjacent to a urea group (Ar-SO ₂ -N
H- (C = O) -NH-). However, these urea compounds have insufficient heat resistance at a high temperature of 120 ° C. or higher.

However, the thermosensitive recording medium using the urea compound represented by the general formula (1) of the present invention has excellent basic color stability against heat and solvents as basic performance. That is, even if this recording medium is placed in a high temperature environment of 120 ° C. or higher, the ground color of the recording surface does not substantially develop color. However, when the high energy of the thermal head, which is usually 200 ° C. to 300 ° C., is instantaneously applied, a deep color develops.
Regarding the heat resistance of the ground color, the common sense of thermal recording media up to now has shown that a thermal block of 120 ° C or higher does not produce any color when exposed to a heat block of 120 ° C or more, but the density is sufficient for a thermal head. It is inconceivable that such a record could be recorded, and no material capable of such a record was known.

Since the heat-sensitive recording material of the present invention has such a high heat resistance, it is possible to perform heat lamination by thermally bonding the recording surface after heat-sensitive recording with a plastic film or the like, which has been impossible in the prior art, It can be used as a transfer sheet for use to adhere toner to the surface of a heat-sensitive layer and heat-fix it, or it can be toner-adhered to the recording surface of a heat-sensitive recording sheet and heat-fixed.

Further, the production process of the thermal recording medium of the present invention is extremely easy. In other words, conventionally, in the production of a thermosensitive recording medium, the drying step after the application of the thermosensitive coloring layer requires extremely strict temperature control so as to prevent the occurrence of ground coloration on the coated surface. there were. However, the heat-sensitive recording medium of the present invention does not develop a ground color even when exposed to hot air of 100 ° C. in a dry state, so that drying at a high temperature is possible and the control range of the drying temperature can be greatly expanded. Therefore, a dramatic improvement in productivity can be expected.

Further, in the heat-sensitive recording medium of the present invention, discoloration due to oil-based ink does not occur, probably because the urea compound used has low solubility in an organic solvent.

As described above, the urea compound represented by the general formula (1) is a material excellent in ground color stability (heat resistance, solvent resistance, etc.).

A general method for producing the thermosensitive recording medium of the present invention comprises: (a) a dye precursor; and (b) a urea compound represented by the general formula (1) as a color developer. This is a method in which each is dispersed together with a binder, and if necessary, auxiliaries such as fillers and lubricants are added to prepare a coating liquid, which is then coated and dried on a support by an ordinary method.

In the present invention, the urea compounds represented by the general formula (1) may be used alone or in combination. In addition, as long as the performance such as the ground color stability (heat resistance, solvent resistance, etc.) of the heat-sensitive recording material to be produced is not impaired, the heat-sensitive recording material may be used in combination with a conventionally known color developer for coloring a dye precursor.

As the dye precursor to be used in the heat-sensitive recording material of the present invention, those which are conventionally known in the field of heat-sensitive recording can be used, and are not particularly limited. Preferred are fluoran leuco dyes, fluorene leuco dyes and the like. Hereinafter, typical dye precursors will be exemplified.

3,3-bis (4'-dimethylaminophenyl)
-6-Dimethylaminophthalide (also known as crystal violet lactone (CVL)) 3,3-bis (4'-dimethylaminophenyl) -6-pyrrolidylphthalide 3,3-bis (4'-dimethylamino Phenyl) phthalide (alias: malachite green lactone (MGL)) tris [4- (dimethylamino) phenyl] methane (alias: leuco crystal violet (LCV)) 3-dimethylamino-6-methyl-7- (m -Trifluoromethylanilino) fluoran 3-diethylamino-6-methyl-fluoran 3-diethylamino-7-methyl-fluorane 3-diethylamino-7-chloro-fluoran 3-diethylamino-6-methyl-7-chlorofluoran 3- Diethylamino-6-methyl-7-anilinofluoran 3-diethylamino-6-methyl-7-p-methylanilinofluoran 3-diethylamino-6-methyl-7- ( o, p-Dimethylanilino) fluoran 3-diethylamino-6-methyl-7- (m-trifluoromethylanilino) fluoran 3-diethylamino-6-methyl-7- (o-chloroanilino) fluoran 3-diethylamino-6 -Methyl-7- (p-chloroanilino) fluoran 3-diethylamino-6-methyl-7- (o-fluoroanilino) fluoran 3-diethylamino-6-methyl-7- (pn-butylanilino)
Fluoran 3-diethylamino-6-methyl-7-n-octylaminofluoran 3-diethylamino-6-chloro-7-anilinofluoran 3-diethylamino-6-ethoxyethyl-7-anilinofluoran 3-diethylamino- Benzo [a] fluoran 3-diethylamino-benzo [c] fluoran 3-diethylamino-6-methyl-7-benzylaminofluoran 3-diethylamino-6-methyl-7-dibenzylaminofluoran 3-diethylamino-7-di (P-methylbenzyl) aminofluorane 3-diethylamino-6-methyl-7-diphenylmethylaminofluoran 3-diethylamino-7-dinaphthylmethylaminofluoran 10-diethylamino-4-dimethylaminobenzo [a] fluoran 3 -Dibutylamino-6-methyl-fluoran 3-dibutylamino-6-methyl-7-chlorofluorane 3-dibutylamino-6- Methyl-7-anilinofluoran 3-dibutylamino-6-methyl-7-p-methylanilinofluoran 3-dibutylamino-6-methyl-7- (o, p-dimethylanilino) fluoran 3-dibutyl Amino-6-methyl-7- (m-trifluoromethylanilino) fluoran 3-dibutylamino-6-methyl-7- (o-chloroanilino) fluoran 3-dibutylamino-6-methyl-7- (p-chloroanilino ) Fluoran 3-dibuethylamino-6-methyl-7- (o-fluoroanilino) fluoran 3-dibuethylamino-6-methyl-7- (pn-butylanilino) fluoran 3-dibutylamino-6-methyl- 7-n-octylaminofluoran 3-dibutylamino-6-chloro-7-anilinofluoran 3-dibutylamino-6-ethoxyethyl-7-anilinofluoran 3-di-n-pentylamino-6-methyl -7-anilinofluoran 3-di-n-pentylamino-6-methyl-7- (o, p-di Methylanilino) fluoran 3-di-n-pentylamino-6-methyl-7- (m-trifluoromethylanilino) fluoran 3-di-n-pentylamino-6-methyl-7- (o-chloroanilino) fluoran 3-di n-pentylamino-6-methyl-7- (p-chloroanilino) fluoran 3-di-n-pentylamino-6-methyl-7- (o-fluoroanilino) fluoran 3-pyrrolidino-6-methyl-7- Anilinofluoran 3-piperidino-6-methyl-7-anilinofluoran 3- (N-methyl-Nn-propylamino) -6-methyl-7-anilinofluoran 3- (N-ethyl-Nn- Propylamino) -6-methyl-7-anilinofluoran 3- (N-ethyl-N-iso-propylamino) -6-methyl-7-
Anilinofluoran 3- (N-ethyl-Nn-butylamino) -6-methyl-7-anilinofluoran 3- (N-ethyl-N-iso-butylamino) -6-methyl-7-anilino Fluoran 3- (N-ethyl-Nn-hexylamino) -6-methyl-7-p-
Methylanilinofluoran 3- (N-ethyl-Nn-hexylamino) -6-methyl-7- (o,
p-Dimethylanilino) fluoran 3- (N-ethyl-Nn-hexylamino) -6-methyl-7- (m-
Trifluoromethylanilino) fluoran 3- (N-ethyl-Nn-hexylamino) -6-methyl-7- (o-
Chloroanilino) fluoran 3- (N-ethyl-N-iso-amylamino) -6-methyl-7-anilinofluoran 3- (N-ethyl-N-iso-amylamino) -6-chloro-7-anilinofur Oran 3- (N-ethyl-N-3-methylbutylamino) -6-methyl-7
-Anilinofluoran 3- (N-ethyl-Np-toluidino) -6-methyl-7-anilinofluoran 3- (N-ethyl-Np-toluidino) -6-methyl-7- (p-methylanilino) Fluoran 3- (N-ethyl-Np-toluidino) -6-methyl-7- (o, p-dimethylanilino) fluoran 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-
Methyl-7-anilinofluoran 3- (N-cyclohexyl-N-methylamino) -6-methyl-7
-Anilinofluoran 3- (N-cyclohexyl-N-methylamino) -7-anilinofluoran 3- (N-ethyl-N-3-methoxypropylamino) -6-methyl-7-anilinofluoran 3- (N-ethyl-N-3-ethoxypropylamino) -6-methyl-7-anilinofluoran 2- (4-oxahexyl) -3-dimethylamino-6-methyl
-7-anilinofluoran 2- (4-oxahexyl) -3-diethylamino-6-methyl
-7-anilinofluoran 2- (4-oxahexyl) -3-dipropylamino-6-methyl-7-anilinofluoran 3- (4 ''-aminostilbuldyl-4'-amino)- 7,8-benzofuran 3,6,6'-tris (dimethylamino) spiro [fluorene
-9,3'-phthalide] 3,6,6'-tris (diethylamino) spiro [fluorene
-9,3'-phthalide] 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide 3- (4-diethylamino- 2-ethoxyphenyl) -3- (1-octyl-2-methylindol-3-yl) -4-azaphthalide 3- (4-diethylamino-2-n-hexylphenyl) -3- (1-
Ethyl-2-methylindol-3-yl) -4-azaphthalide 3- (4-cyclohexylmethylamino-2-methoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -Four-
Azaphthalide 3- (4-cyclohexylethylamino-2-methoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-
Azaphthalide 3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide 3,3-bis (2-methyl-1-octylindol-3-yl)
Phthalide 3- (1-ethyl-2-methylindol-3-yl) -3- (1-
n-butyl-2-methylindol-3-yl) phthalide 3,7-bis (dimethylamino) -10-benzoylphenothiazine 3,7-bis (dimethylamino) -N- [pN-bis (4,4 '-Dimethylaminophenyl) methylamino] benzoylphenothiazine 3,7-bis (dimethylamino) -N- [pN-bis (4,4'-diethylaminophenyl) methyl] benzoylphenothiazine 3,6-bis (diethylamino) fluoran- γ- (2′-nitro) anilinolactam 3,6-bis (diethylamino) fluoran-γ- (3′-nitro) anilinolactam 3,6-bis (diethylamino) fluoran-γ- (4′-nitro) Anilinolactam 3,6-bis (diethylamino) fluoran-γ-anilinolactam

These dye precursors may be used alone or in combination of two or more. In the present invention, among these dye precursors, a fluoran dye precursor can be preferably used. In particular, when importance is placed on thermal stability, naturally, a dye precursor having a high melting point and a high decomposition temperature is preferable.

As the binder which can be used in the present invention, fully silicified polyvinyl alcohol having a polymerization degree of 200 to 1900, partially saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol,
Butyral modified polyvinyl alcohol, other modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer, styrene-butadiene copolymer and ethyl cellulose, cellulose derivatives such as acetyl cellulose, polyvinyl chloride, poly Vinyl acetate, polyacrylamide, polyacrylate,
Polyacrylamide, polyacrylate, polyvinyl butyral, polystyrene and copolymers thereof, polyamide resin, silicone resin, petroleum resin, terpene resin, ketone resin, cumarone resin can be exemplified, among these polyvinyl Alcohol-based binders are desirable in terms of dispersibility, binder properties, and thermal stability of the ground color. These binders are water,
It can be dissolved in a solvent such as alcohol, ketone, ester, or hydrocarbon, or emulsified in water or another medium, or used in a state of being dispersed in the form of a paste.

In the present invention, particularly when heat resistance of the ground color is required, it is generally preferable not to use a sensitizer. If a sensitizer is used, the color development temperature depends on the melting point of the sensitizer. However, these may be used depending on the required performance of the manufactured thermal recording medium. Sensitizers used for that purpose include 2-di (3-methylphenoxy) ethane, p-benzylbiphenyl, β-benzyloxynaphthalene, 1-hydroxy-2-naphthoic acid phenyl ester, dibenzyl terephthalate Benzyl, p-benzyloxybenzoate, diphenyl carbonate, ditolyl carbonate, 4-biphenyl-p-tolyl ether, m-terphenyl, 1,2-diphenoxyethane, 1,2-bis (m-tolyloxy) ethane, 1 , 5-bis (p-methoxyphenoxy) -3-
Oxapentane, dibenzyl oxalate, dioxalate (p-
Methylbenzyl), di (oxa-oxalate) (p-chlorobenzyl) and the like.

The filler used in the present invention may be an inorganic filler such as silica, calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, talc, zinc oxide, titanium oxide, zinc hydroxide, aluminum hydroxide, or a polystyrene-based organic filler. Fillers, styrene / butadiene-based organic fillers, styrene / acrylic-based organic fillers, hollow organic fillers and the like.

In addition, a releasing agent such as a fatty acid metal salt, a lubricant such as a wax, a benzophenone-based or benzotriazole-based ultraviolet absorber, a water-proofing agent such as glyoxal, a dispersant, an antifoaming agent, etc. Can also.

The amount of the (a) dye precursor of the present invention and (b) the urea compound represented by the general formula (1), and the types and amounts of various other components are determined according to the required performance and recording. It is determined according to suitability and is not particularly limited, but is usually 1 to 8 parts of a urea compound and 1 to 20 parts of a filler with respect to 1 part of a dye precursor, and a binder is 10 to 25% by weight. These materials are pulverized to a particle size of several microns or less by a pulverizer such as a ball mill, attritor, sand grinder, or an appropriate emulsifying device, and a binder and various additive materials are added according to the purpose to form a coating liquid. And By applying a coating solution having the above composition to a support, an intended thermosensitive recording medium can be obtained.

The support used in the present invention may be paper,
Synthetic paper, non-woven fabric, metal foil, plastic film, plastic sheet, or composite sheet obtained by combining these are exemplified.

Further, an overcoat layer made of a polymer substance may be provided on the thermosensitive coloring layer for the purpose of enhancing the storage stability.
An undercoat layer of a filler-containing polymer substance or the like can be provided below the heat-sensitive layer for the purpose of enhancing color sensitivity.

Further, the heat-sensitive recording medium of the present invention may be provided with a transparent and strong protective coating by thermally laminating a plastic film, taking advantage of high ground color stability. For example,
Even after thermal recording, a heat-resistant card can be easily prepared using a commercially available simple laminating machine.

In the heat-sensitive recording medium of the present invention, the heat-sensitive recording layer may contain a light absorbing agent which absorbs light and converts it into heat. The light absorber is not particularly limited as long as it is a substance that absorbs the emission wavelength of various light sources.

For example, when a light source having a continuous wavelength, a strobe flash, or the like is used as a recording light source, the light absorbing agent described in JP-A No. 2-206583, Japanese Patent Application No. 5-30954, and the like can be used. Examples of the heated reaction product of a thiourea derivative / copper compound include graphite, copper sulfide, lead sulfide, molybdenum trisulfide, black titanium, etc. described in JP-A-3-86580, and carbon black.

On the other hand, when a semiconductor laser is used as a recording light source, a light absorbing agent may be used.
JP, JP-A-58-94494, JP-A-58-209594, JP-A-2-217287, JP-A-3-73814, etc., polymethine dyes (cyanine dyes),
Azorhenium dye, pyrylium dye, thiopyrylium dye, squarylium dye, croconium dye, dithiol complex, mercaptophenol metal complex dye, mercaptonaphthol metal complex dye, phthalocyanine dye, naphthalocyanine dye Dyes, triarylmethane-based dyes, immonium-based dyes, diimmonium-based dyes, naphthoquinone-based dyes, anthraquinone-based dyes, metal complex-based dyes, and the like can be given. Further, the light absorbing agents listed in the case of a light source having a continuous wavelength can be used in the same manner.

Specifically, examples of polymethine dyes (cyanine dyes) include, for example, indocyanine line (manufactured by Daiichi Pharmaceutical Co., Ltd.), NK-2014 (manufactured by Japan Photographic Dye Laboratories), and NK -2612 (manufactured by Japan Photographic Dye Laboratories), 1,1,1
5,5-tetrakis (p-dimethylaminophenyl) -3-methoxy-1,4-pentadiene, 1,1,5,5-tetrakis (p-diethylaminophenyl) -3-methoxy-1,4-pentadiene, etc. NK-277 as a squarylium dye
2 (manufactured by Japan Photographic Dye Laboratories, Inc.). Examples of the dithiol complex include a toluene dithiol nickel complex, a 4-tert-butyl-1,2-benzenedithiol nickel complex, and a bisdithiobenzyl nickel complex. , Bis (4-ethyldithiobenzyl) nickel complex, bis (4-n-propyldithiobenzyl) nickel complex and the like. Examples of the immonium dye or diimmonium dye include:
IRG002 (Nippon Kayaku Co., Ltd.), IRG022 (Nippon Kayaku Co., Ltd.)
NIR-14 (manufactured by Yamamoto Kasei Co., Ltd.) as an example of a naphthalocyanine dye, and IR-750 (Nippon Kayaku Co., Ltd.) as an anthraquinone dye.
Manufactured). These light absorbers may be used alone or in combination of two or more.

These light absorbers can be used by simply mixing (a) various materials necessary for a heat-sensitive recording medium and (b)
As described in 2-217287 No., etc., in various materials required for the thermosensitive recording medium, a method in which a light absorber is previously melted and mixed to be dissolved or dispersed, or (c)
The light absorbing agent may be dissolved or dispersed in a solvent in advance in various materials required for the heat-sensitive recording medium, and the dissolved or dispersed mixture may be used after removing the solvent and using the mixture. The light absorber may be co-dispersed (simultaneously mixed and dispersed) with a developer and / or a sensitizer, or a dye precursor and / or a sensitizer.

The thermosensitive recording medium of the present invention does not change its performance such as ground color stability (heat resistance, solvent resistance, etc.) even when a light absorbing agent is contained.

[0039]

The urea compound represented by the general formula (1) of the present invention is a color developer having excellent color development and excellent ground color stability against heat and solvents. The exact reason for the high ground color stability has not yet been elucidated. However, it is estimated as follows.

The structure of the urea compound of the present invention changes as follows according to conditions. Since this change is a phenomenon similar to keto / enol tautomerism, it is referred to herein as keto-enolization for convenience.

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It is considered that enolization is necessary for the urea compound to function as a color developer. High temperature is required for enolization, and the thermal head
It is thought that since the temperature rises to about 300 ° C., the urea compound which comes into contact with the thermal head undergoes enolization and develops a color developing function to cleave the lactone ring of the dye precursor to form a color. Therefore, the urea compound does not change until the temperature at which enolization occurs and does not react with the dye precursor, so that the ground color remains white, which seems to be the reason for the high heat resistance.

Also, the fact that the ground color does not change by writing with an oil-based ink is that the urea compound of the present invention has low solubility in solvents used in oil-based inks and, even when it comes into contact with these solvents, does not react with the dye precursor. This is considered to be because mixing with the color developer does not substantially occur.

[0043]

【Example】

<Synthesis of urea compound> As a synthesis example of a urea compound,
Examples of compounds A-4, A-8, and A-10 are shown below. Other synthesis was performed in accordance with Synthesis Examples 1 to 3.

Synthesis Example 1 pn-butylaniline (11.2 g,
(75 mM) was dissolved in ethyl acetate (200 ml). In this solution,
Phenyl isocyanate (8.9 g, 75 mM) in ethyl acetate (50 ml)
Was added dropwise. After stirring at room temperature for 1 hour, a precipitate was formed. This was filtered, and ethyl acetate, n-
After washing with hexane, compound A-4 was obtained.

Synthesis Example 2 pn-hexylaniline (12.4
g, 70 mM) was dissolved in acetone (200 ml). To this solution, phenyl isocyanate (8.3 g, 70 mM) was added to acetone (50 mM).
The solution dissolved in l) was added dropwise. After stirring at room temperature for 30 minutes, a precipitate formed, which was filtered, and ethyl acetate, n-
After washing with hexane, compound A-8 was obtained.

[Synthesis Example 3] pn-octylaniline (12.3
g, 60 mM) was dissolved in acetone (200 ml). To this solution, phenyl isocyanate (7.2 g, 70 mM) was added with acetone (50 mM).
The solution dissolved in l) was added dropwise. After stirring at room temperature for 20 minutes, a precipitate formed, which was filtered, and ethyl acetate, n-
After washing with hexane, compound A-10 was obtained.

<Production of Thermosensitive Recording Material> In the following description, parts and% indicate parts by weight and% by weight, respectively. [Examples 1 to 5] As a dye precursor,
A heat-sensitive recording material was manufactured using N, N-diethylamino-6-methyl-7-anilinofluoran (alias: ODB) as a developer and the urea compound of the present invention. (See Table 1) That is, first, a developer dispersion (solution A) and a dispersion of a dye precursor (solution B) having the following composition were ground by a sand grinder to an average particle diameter of 1 micron. (Solution A: developer dispersion) 6.0 parts of urea compound of the present invention 10% aqueous solution of polyvinyl alcohol 18.8 parts Water 11.2 parts (Solution B: dye precursor dispersion) 3-N, N-diethylamino-6-methyl-7 -Anilinofluoran (ODB) 2.0 parts 10% aqueous polyvinyl alcohol solution 4.6 parts Water 2.6 parts Then, at the following ratios, solution A (developer dispersion), solution B (dye precursor dispersion), and kaolin cream Were mixed to form a coating solution. Liquid A: developer dispersion liquid 36.0 parts Liquid B: dye precursor dispersion liquid 9.2 parts Kaolin clay (50% dispersion liquid) 12.0 parts This coating liquid was applied on one side of a 50 g / m ² base paper 6.0 g /
coating and drying so as to m ^2, was treated as smoothness of the sheet supercalendered is 500-600 seconds,
A thermosensitive recording medium was produced.

[Comparative Examples 1 to 7] Thermosensitive recording media for comparative examples were prepared in the same manner as in Examples 1 to 5, using the following compounds as a color developer. (See Table 1) (Known developer compound) Bisphenol A (B-1) Bisphenol S (B-2) 4-hydroxy-4'-iso-propoxydiphenyl sulfone (B-3) 4- Hydroxy-4'-n-butyroxydiphenyl sulfone (B
-4) Phenyl urea (B-5) described in JP-A-58-211496 Dimerized urea (B-6) described in JP-A-5-147357 1-p-toluyl, 3-phenylurea (B- 7)

[0049]

Embedded image

That is, a dispersion of each of the above developer compounds having the following composition was mixed with a sand grinder to obtain an average particle diameter of 1: 1.
Milled to a micron. (C solution: developer dispersion) Developer compound (B-1 to B-7) 6.0 parts 10% aqueous polyvinyl alcohol solution 18.8 parts Water 11.2 parts Then, at the following ratio, solution C (developer dispersion liquid) ), The dispersion (B) of the dye precursor (ODB) used in Examples 1 to 5
Liquid) and a dispersion liquid of kaolin clay to obtain a coating liquid. Liquid C: developer dispersion liquid 36.0 parts Liquid B: dye precursor dispersion liquid (ODB dispersion liquid) 9.2 parts Kaolin clay (50% dispersion liquid) 12.0 parts This coating liquid was applied to one side of a 50 g / m ² base paper. 6.0g /
coating and drying so as to m ^2, was treated as smoothness of the sheet supercalendered is 500-600 seconds,
A thermosensitive recording medium was produced.

<Evaluation of Thermosensitive Recording Material> The obtained thermosensitive recording material was subjected to a recording test, a thermal stability test of a ground color, and an oil-based ink suitability test using a word processor. [Recording test (dynamic color density)]: To check the recording suitability, use a word processor (RUPO-90F (manufactured by Toshiba)) and record on the thermal recording medium with the maximum applied energy. The recording portion was measured with a Macbeth densitometer (RD-914, using an amber filter. The density was measured under the following conditions). In this case, the larger the Macbeth value, the higher the recording density and the better the recording suitability. [Heat resistance test (static color density)]: A pressure of 10 g / cm ² was applied to a hot plate heated to 90 ° C., 120 ° C., and 135 ° C. to check the thermal stability of the ground color of the recording sheet. Was pressed for 5 seconds, and the recording was measured with a Macbeth densitometer. In this case, the smaller the Macbeth value, the lower the degree of coloring of the ground color and the higher the thermal stability of the ground color. [Oil-based ink suitability test (discoloration test of ground color by oil-based ink)]: Write on the thermosensitive recording medium produced with oil-based red magic ink No. 500 (manufactured by Teranishi Kagaku) and visually check the degree of discoloration with respect to the original red color. It was measured. ◎: No discoloration ○: Almost no discoloration △: Slight discoloration ×: Significant discoloration

The evaluation results of Examples 1 to 6 using the urea compound of the present invention as a developer and Comparative Examples 1 to 7 using a known developer compound as a developer are shown in Table 1.

[0053]

[Table 1]

Example 6 A simple laminating apparatus (MS pouch) was prepared by sandwiching the heat-sensitive recording medium of Example 1 between pouch films.
Thermal lamination was performed using H-140 (manufactured by Meiko Shokai). The recording portion and the ground color portion were measured with a Macbeth densitometer to find that the recording portion was 1.29 and the ground color portion was 0.13.

Example 7 A simple laminating apparatus (MS pouch) was prepared by sandwiching the heat-sensitive recording medium of Example 2 between pouch films.
Thermal lamination was performed using H-140 (manufactured by Meiko Shokai). The recording area and the ground color area were measured with a Macbeth densitometer to find that the recording area was 1.18 and the ground color area was 0.13.

Example 8 Toner recording was performed on the heat-sensitive recording medium of Example 1 with a copy machine (manufactured by NP6060 Cannon Co., Ltd.). We were able to.

Example 9 Toner recording was performed on the heat-sensitive recording medium of Example 2 with a copy machine (NP6060 Cannon Co., Ltd.). We were able to.

Example 10 The thermal recording medium of Example 3 was subjected to toner recording using a copying machine (manufactured by NP6060 Canon Inc.), and no change was observed in the ground color. We were able to.

[Example 11] When the thermal recording medium of Example 4 was subjected to toner recording with a copying machine (manufactured by NP6060 Canon Inc.), no change was observed in the ground color, and printing was performed. We were able to.

<Manufacture of optical recording medium> [Example 12] As a dye precursor, 3-N, N-
Diethylamino-6-methyl-7-anilinofluoran (also known as ODB), compound A-4 as a developer, and a hot melt of a bisdithiobenzylnickel complex and a sensitizer as a light absorber. The optical recording medium was manufactured using the same. That is, first, 6 parts of a bidithiobenzylnickel complex were added to 94 parts of 4-biphenyl-p-tolyl ether, and 100 to 150 ° C.
And melted and mixed, and then pulverized to obtain a light absorber. Then, a light absorbent dispersion having the following composition was ground by a sand grinder to an average particle diameter of 1 micron. (D solution: Light absorber dispersion) Light absorber 4.0 parts 10% aqueous polyvinyl alcohol solution 10.0 parts Water 6.0 parts Then, the following compound A- used in Example 1 at the following ratio:
The dispersion (liquid A) of Example 4, the dispersion (liquid B) of the dye precursor (ODB) used in Examples 1 to 5, the liquid D (light absorber dispersion), and the dispersion of kaolin clay were mixed. To obtain a coating solution. Liquid A (developer dispersion liquid) 36.0 parts Liquid B (dye precursor dispersion liquid) 9.2 parts Liquid D (light absorber dispersion liquid) 20.0 parts Kaolin clay (50% dispersion liquid) 12.0 parts This coating liquid is 50 g / m2. the coating amount on one side of ² of the base paper 6.0g /
coating and drying so as to m ^2, was treated as smoothness of the sheet supercalendered is 500-600 seconds,
An optical recording medium was produced. With respect to this recording medium, JP-A-3-2395
No. 98, using a laser plotter,
When the laser irradiation was performed, clear printing could be obtained.

[0061]

As described above, the urea compound of the present invention can be practically used by a thermal head or the like, even though the ground color does not substantially change at an environmental temperature in the range of 120 to 135 ° C. It can be seen that this is an epoch-making developer capable of obtaining a sufficient image density record. Therefore, the following points can be mentioned as effects of the present invention.

(1) Heat resistance,
This is a heat-sensitive recording material that has excellent storage stability such as solvent resistance. (2) Severe conditions that could not be used until now (for example, 9
(Temperature conditions in the range of 0 ° C. to 135 ° C.), it is possible to use the thermosensitive recording medium. (3) Since discoloration does not occur when writing with an oil-based ink, it is possible to freely write on a thermosensitive recording medium using these writing instruments. (4) The heat-sensitive recording medium can be easily heat-laminated by a simple laminating device or the like. Cards and the like can be easily made. (5) Since the ground color is stable even after passing through a heat roll, toner recording can be performed on a thermosensitive recording medium.

The same effect can be expected even if the heat-sensitive recording material of the present invention contains a light absorbing agent.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukiko Uebori 5-2-1-1, Oji, Kita-ku, Tokyo Nippon Paper Industries Co., Ltd. Central Research Laboratory (72) Inventor Tosumi Satake 5--21, Oji, Kita-ku, Tokyo No. 1 Nippon Paper Industries Co., Ltd. Central Research Laboratory (56) References JP-A-5-119510 (JP, A) JP-A-59-169888 (JP, A) JP-A-61-287788 (JP, A) JP-A-58-82787 (JP, A) JP-A-3-207688 (JP, A) JP-A-2-217287 (JP, A) JP-A-62-239083 (JP, A) JP-A-63-81082 (JP, A) JP, A) JP-A-62-202785 (JP, A) JP-A-5-58056 (JP, A) JP-A-3-133626 (JP, A) JP-A-2-29393 (JP, A) JP Sho-63-68856 (JP, A) Full-fledged Sho-57-185567 (JP, U) (58) Field surveyed (Int .Cl. ⁷ , DB name) B41M 5/30 G03B 7/00 101 CA (STN) REGISTRY (STN)

Claims (4)

(57) [Claims] 1. A thermosensitive recording medium having a thermosensitive coloring layer containing a colorless or pale-colored dye precursor and a developer which reacts upon heating to form the dye precursor, wherein the developer is represented by the following general formula: A heat-sensitive recording material, which is a urea compound represented by (1), wherein the heat-sensitive coloring layer contains at least one kind of the urea compound. Embedded image (Where X is an alkyl group having 1 to 6 carbon atoms, 1 carbon atom
To 6, an alkoxy group, a methyl trihalide group, a nitro group, a halogen atom, or a hydrogen atom. Y represents an alkyl group having 2 to 18 carbon atoms. n represents an integer of 1 to 3. However, when n = 1, X and Y are different. ) 2. The recording layer of the thermosensitive recording medium according to claim 1,
A heat-sensitive recording material containing a light absorber that absorbs light and converts it into heat. 3. A heat-sensitive recording card wherein the heat-sensitive recording medium according to claim 1 or 2 is laminated with a plastic film. 4. An electrophotographic transfer sheet using the heat-sensitive recording material according to claim 1.