JP3339043B2 - 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 also become higher. For example, from the viewpoint of high-speed recording, a heat-sensitive recording medium capable of obtaining a high-density and clear color image even with a smaller amount of heat energy is desired. On the other hand, from the viewpoint of storage stability of the recording medium, a heat-sensitive recording medium having excellent light resistance, oil resistance, water resistance, solvent resistance, and the like has been required.

On the other hand, as plain paper recording systems such as an electrophotographic system and an ink jet system have become widespread, the thermal recording system has been frequently compared with these plain paper recording systems. For example, the stability of the recording portion (image) of the thermal recording medium or the stability of the non-recording portion (ground color portion) before and after recording on the thermal recording material (hereinafter referred to as ground color stability) is recorded on plain paper. It is required that the quality approach that of the system. In particular, the thermal recording medium is required to have a ground color stability to heat (hereinafter, ground color heat resistance) and a ground color stability to a solvent. In other words, in other words, it is desired that the recording medium has "thermosensitivity" only during recording, and "non-thermosensitive" other than during recording.

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 is stable even under a high temperature condition of about 90 ° C. This heat-sensitive recording material is a heat-sensitive recording material containing a 4-hydroxydiphenylsulfone compound and a metal salt of phosphate.

[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 is about 0.11, indicating considerable stability. However, the ground color stability at a higher temperature, for example, 120 ° C, is still insufficient. Was.

Accordingly, an object of the present invention is to provide a thermosensitive recording medium having excellent ground color stability.

[0008]

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.

JP-A-53-140043, JP-A-57-87993
JP-A-57-82787, JP-A-59-67083, and the like disclose a thermosensitive recording medium using a urea compound and a phenol compound in combination. In these publications,
The urea compound is limited only in the number of carbon atoms, and is basically used only as a melting point modifier of the phenol compound. As described above, as long as it is used as an aid for the phenol compound, sufficient ground color heat resistance was not obtained. Also, for example, in JP-A-57-87993, as an exemplary compound, 1- (4-octadecyloxyphenyl)
Although -3-phenylurea is mentioned, sufficient ground color heat resistance could not be obtained by using this compound alone.

Patents using a specific monourea compound as a heat-sensitive recording material are disclosed in Japanese Patent Application Laid-Open Nos. 58-211496, 59-184694, and 61-211085. I have. The monourea compounds used in these publications are urea compounds obtained by substituting only one amino group of urea, and sufficient ground color heat resistance cannot be obtained even with this. Also in these publications, a phenol compound is used in combination, and with this combination, satisfactory ground color heat resistance was not obtained. Thermal recording medium using a bisurea type compound is disclosed in JP-A-5-131715.
No. 2, JP-A-5-147357 and the like. The bis-urea type compound, a structure is sulfonyl group adjacent to the urea group _{(Ar-SO 2 -NH- (C} =
O) -NH-). However, even these urea compounds have insufficient heat resistance under high temperature conditions of 120 ° C. or higher.

The present inventors have found that by using a specific urea compound as a color developer, it is possible to obtain a heat-sensitive recording material having excellent ground color heat resistance, and have completed the present invention. .

That is, the present invention relates to a thermosensitive recording medium having a thermosensitive coloring layer containing a colorless or pale color dye precursor and a developer which reacts upon heating to form the dye precursor. Is a urea compound represented by the following general formula (1), wherein the thermosensitive coloring layer contains at least one kind of the urea compound.

[0013]

Embedded image (Here, X represents an alkoxy group having 1 to 12 carbon atoms, a methyl trihalide group, a nitro group, or a hydrogen atom. Y represents an alkoxy group having 1 to 12 carbon atoms. And Y are different.)

The urea compound represented by the general formula (1)
It is an asymmetric 1,3-diphenylurea compound having an alkoxy group on at least one side of 1,3-diphenylurea. The urea compound represented by the general formula (1) is, for example,
As shown in the formulas (2) and (3), it can be easily synthesized by the reaction of an amine with an isocyanate compound. That is, the former reaction is a reaction between a substituted or unsubstituted aniline derivative and an aromatic isocyanate compound having an alkoxy group (Y), and the latter reaction is a reaction between an alkoxylated aniline and a substituted or unsubstituted aromatic isocyanate. Reaction with a compound.

[0015]

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In the case of synthesis by the synthesis method of the formula (2), for example, amines such as aniline, o-anisidine, m-anisidine, p-anisidine, o-phenetidine, p-phenetidine, p-isopropoxyaniline, pn- Butoxyaniline, p-tert-butoxyaniline, o-aminobenzotrifluoride, m-aminobenzotrifluoride, p-aminobenzotrifluoride, o-nitroaniline, m-nitroaniline, p-nitroaniline, and the like, In addition, examples of the monoisocyanate compound include aromatic isocyanates such as 4-methoxyphenyl isocyanate, and any combination thereof can be selected.

In the case of synthesis by the synthesis method of the formula (3), for example, amines include p-anisidine, p-phenetidine, p-isopropoxyaniline, pn-butoxyaniline, p-tert-butoxyaniline and the like. And monoisocyanate compounds such as phenyl isocyanate, 2-methoxyphenyl isocyanate, and 3-isocyanate.
Methoxyphenyl, 4-methoxyphenyl isocyanate,
O-trifluoromethylphenyl isocyanate, m-trifluoromethylphenyl isocyanate, p-trifluoromethylphenyl isocyanate, o-nitrophenyl isocyanate, m-nitrophenyl isocyanate, p-isocyanate
Aromatic isocyanate compounds such as nitrophenyl can be mentioned, and any combination can be selected from both.

Specific examples of the urea compound represented by the general formula (1) include the following compounds.

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[0019]

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Regarding the substituent (X) of the urea compound represented by the general formula (1), the melting point of the urea compound, the decomposition temperature, the solubility in a solvent, and the like, or the performance (recording) Density, the stability of the recording portion, the ground color stability, etc.), and should not be particularly limited. However, from the viewpoint of recording density, higher recording density is obtained when the substituent of the urea compound is a hydrogen atom (that is, when it is unsubstituted) or when the substituent is an electron-withdrawing group (trihalogen). Methyl group, nitro group). On the other hand, from the viewpoint of the heat resistance of the ground color, the higher heat resistance of the ground color is obtained because (a) the substituent is an alkoxy group, a methyl trihalide group, or a nitro group, and the substituent Is present only in the para position to the urea bond, or (b)
This is the case where the substituent is a hydrogen atom. When the recording density, the heat resistance of the ground color, the cost, and the like are comprehensively considered, the case where the substituent is a hydrogen atom (that is, the case where the substituent is not substituted) is most preferable.

The alkoxy group (Y) of the urea compound
Is an alkoxy group having 1 to 12 carbon atoms, but preferably has 1 to 6 carbon atoms in consideration of heat resistance. Regarding the position of Y with respect to the urea bond, in any of the ortho position, meta position, and para position, when the high energy of the thermal head is instantaneously applied, a deep color is formed. Is obtained. However, considering the ground color stability, compounds having an alkoxy group at the ortho position (for example,
Compound B-7) shown later in Comparative Examples or a compound having an alkoxy group at the meta position (eg, compound B-8) has insufficient heat resistance. On the other hand, only a compound having an alkoxy group only at the para position (for example, compound A-1) shows sufficient heat resistance. Further, even a compound having an alkoxy group at the para-position and further having an alkoxy group introduced at a position other than the para-position (for example, compound B-9) cannot provide satisfactory heat resistance.

The thermal recording medium using the urea compound represented by the general formula (1) of the present invention has excellent ground color stability against heat and solvents. That is, the recording medium is heated to 120 ° C.
Even under the above high temperature environment, the ground color of the recording surface of the thermal recording medium does not substantially change (color does not develop). But,
When the high energy of the thermal head, which is usually 200 ° C. to 300 ° C., is instantaneously applied to this recording medium, the recording medium develops a dark color. With respect to the heat resistance of the background color, the thermal recording medium known so far does not develop color even when a heat block of 120 ° C or higher is applied to the surface of the thermal recording layer. Thus, it was impossible to imagine that recording of a density sufficient for practical use could be performed. Also, no material capable of such a thing was known at all.

Since the heat-sensitive recording material of the present invention has high heat resistance, for example, (a) heat laminating the recording surface after heat-sensitive recording with a plastic film or the like;
(b) using as a transfer sheet for electrophotography, adhering toner to the surface of the heat-sensitive recording layer and thermally fixing it, or
(c) It is also possible to fix toner by attaching toner to the heat-sensitive recording surface of the heat-sensitive-recorded sheet.

Further, the thermosensitive recording medium of the present invention has an advantage that the management of the manufacturing process is very easy. In other words, conventionally, in the production of a thermosensitive recording medium, the drying process after the application of the thermosensitive coloring layer requires extremely strict temperature control so as not to cause color development on the coated surface, and is therefore limited to high-speed coating. was there. However, the thermosensitive recording medium of the present invention has a temperature of 120 ° C.
It does not cause ground color development even when exposed to hot air, so high-temperature drying in the drying process is possible, and the management range of drying temperature can be greatly expanded, so it can be expected to dramatically improve productivity. it can.

The heat-sensitive recording medium of the present invention does not cause discoloration due to oil-based ink, probably because the urea compound used has low solubility in organic solvents. Therefore, it is also possible to write on the surface of the heat-sensitive recording layer of the heat-sensitive recording medium with oil-based ink.

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.).

The 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. Also, for example, Japanese Patent Application No. 5-231105,
Japanese Patent Application No. 5-250328, Japanese Patent Application No. 5-250329, Japanese Patent Application No. 5-311502, Japanese Patent Application No. 5-315023, Japanese Patent Application No. 5-317211, It can be used in combination with a urea compound described in Japanese Patent Application No. 5-321506.

Further, in the heat-sensitive recording medium of the present invention, in principle, it is better not to use together with a phenol compound conventionally known as a color developer. When a phenol compound is used, the performance (recording suitability, heat resistance, solvent resistance, etc.) of the thermosensitive recording medium mainly depends on the phenol compound. Therefore, the thermosensitive recording medium used in combination with the phenol compound cannot obtain sufficient heat resistance of the ground color. However, 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 within a range not hindered, a conventionally known color developer for forming a dye precursor (for example, bispheno) -A, bisphenol S, benzyl 4-hydroxybenzoate, 4-hydroxy-4'-isopropoxydiphenylsulfone) in small amounts.

As the dye precursor 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-7- (o-chloroanilino) fluoran 3-dibutylamino-6-methylfluoran 3-dibutylamino-6- Methyl-7-chlorofluoran 3-dibutylamino-6-methyl-7-anilinofluoran 3-dibutylamino-6-methyl-7-p-methylanilinofluoran 3-dibutylamino-6-methyl-7 -(o, p-dimethylanilino) fluoran 3-dibutylamino-6-methyl-7- (m-trifluoromethylanilino) fluoran 3-dibutylamino-6-methyl-7- (o-chloroanilino) fluoran 3 -Dibutylamino-6-methyl-7- (p-chloroanilino) fluoran 3-dibutylamino-6-methyl-7- (o-fluoroanilino) fluoran 3-dibutylamino-6-methyl-7- ( pn-butylanilino) fluoran 3-dibutylamino-6-methyl-7-n-octylaminofluoran 3-dibutylamino-6-chloro-7-anilinofluoran 3-dibutylamino-6-ethoxyethyl-7-ani Linofluoran 3-di-n-pentylamino-6-methyl-7-anilino Luoran 3-di-n-pentylamino-6-methyl-7- (o, p-dimethylanilino) 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-propyl Amino) -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.

In the heat-sensitive recording medium of the present invention, particularly when heat resistance of the ground color is required, it is generally better 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 alone or in combination depending on the required performance of the manufactured thermal recording medium. Examples of the sensitizer used include 2-di (3-methylphenoxy) ethane, p-benzylbiphenyl, β-benzyloxynaphthalene, 1-hydroxy-2-naphthoic acid phenyl ester, dibenzyl terephthalate, and p-benzyl-2-naphthoic acid. -Benzylbenzyloxybenzoate,
Diphenyl carbonate, ditolyl carbonate, 4-biphenyl-p-tolyl ether, m-terphenyl, 1,2-diphenoxyethane, 1,2-bis (m-tolyloxy) ethane, 1,5-bis (p-
Examples thereof include (methoxyphenoxy) -3-oxapentane, dibenzyl oxalate, di (p-methylbenzyl) oxalate, and di (p-chlorobenzyl) oxalate.

The binder which can be used in the heat-sensitive recording material of the present invention includes completely saponified polyvinyl alcohol having a degree of polymerization of 200 to 1900, partially saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, and sulfonic acid. Polyvinyl alcohols such as modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, and other modified polyvinyl alcohol; cellulose derivatives such as hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, ethyl cellulose, and acetyl cellulose; styrene-maleic anhydride copolymer, styrene -Butadiene copolymer, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylate, polyacrylate, polyvinylate Butyral, polystyrene,
And synthetic polymers such as copolymers of these combinations; polyamide resins, silicone resins, petroleum resins,
Resins such as terpene resin, ketone resin, and coumarone resin can be exemplified. Among these examples, the polyvinyl alcohol-based binder has dispersibility, binder properties,
This is desirable from the viewpoint of thermal stability of the ground color. These binders are used in a state of being dissolved in a solvent such as water, alcohol, ketone, ester, or hydrocarbon, or emulsified in water or another medium, or used in a state of being dispersed in a paste form, and used together according to required quality. It is also possible.

The filler used in the thermal recording medium of the present invention includes inorganic fillers such as silica, calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, talc, zinc oxide, titanium oxide, zinc hydroxide, and aluminum hydroxide. Or a polystyrene organic filler, a styrene / butadiene organic filler, a styrene / acrylic organic filler, a hollow organic filler, and the like.

In the heat-sensitive recording medium of the present invention, in addition to the above, release agents such as fatty acid metal salts, lubricants such as waxes, ultraviolet absorbers such as benzophenone and benzotriazole, water resistance agents such as glyoxal, dispersants, etc. An antifoaming agent or the like can also be used.

In the heat-sensitive recording material of the present invention, (a) the amount of the dye precursor and (b) the amount of the urea compound represented by the general formula (1), and (c) the types and amounts of other various components Is determined according to the required performance and recordability,
Although not particularly limited, usually, 1 to 8 parts of a urea compound and 1 to 20 parts of a filler are used with respect to 1 part of a dye precursor, and the binder is 10 to 25% by weight based on the total solid content. . 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.

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

Further, the thermosensitive recording medium of the present invention may be provided with an overcoat layer made of a polymer substance on the thermosensitive coloring layer for the purpose of enhancing the storage stability of the recording medium, or with a filler for enhancing the coloring sensitivity of the recording medium. An undercoat layer such as a polymer substance containing the same may be provided below the thermosensitive coloring layer.

Further, the thermal recording medium of the present invention can be provided with a transparent and strong protective coating by thermally laminating a plastic film utilizing high ground color stability. For example, even after thermal recording on the thermal recording medium of the present invention, a card excellent in various stability such as heat resistance can be easily prepared using a commercially available simple laminating machine. Examples of the plastic film used in the thermal recording medium of the present invention include low-density polyethylene, ethylene / vinyl acetate copolymer, ethylene / ethyl acrylate copolymer,
Ethylene / methyl methacrylate copolymer, ethylene /
A thermoplastic resin such as a methacrylic acid copolymer can be used.

In the heat-sensitive recording medium of the present invention, the heat-sensitive recording layer may contain a light absorber 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 light source for recording, the light absorber described in JP-A No. 2-206583, Japanese Patent Application No. 5-30954, etc. Examples of the heated reaction product of a thiourea derivative / copper compound include graphite, copper sulfide, lead sulfide, molybdenum trisulfide, black titanium and the like 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 as disclosed in JP-A-54-4142.
JP, JP-A-58-94494, JP-A-58-209594, JP-A-2-217287, JP-A-3-73814, etc., polymethine dyes (cyanine dyes),
Azolenium-based dye, pyrylium-based dye, thiopyrylium-based dye, squarylium-based dye, croconium-based dye, dithiol complex, mercaptophenol-based metal complex, mercapton-naphthol-based metal complex, phthalocyanine-based dye, naphthalocyanine-based dye, triarylmethane-based Dyes, immonium-based dyes, diimmonium-based dyes, naphthoquinone-based dyes, anthraquinone-based dyes, metal complex salt-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.

More specifically, for example, Color Chemical Dictionary (edited by the Society of Organic Synthesis, CMC Publishing (1988), p196-2)
00), Table 3 of the chemical industry (vol. 5, 1986, p379-389).
Described near infrared absorbing dyes, JP-A-61-69991, JP-A
No. 61-246391, US-PATENT: 35570122, US-PATENT: 35
75871, near-infrared absorbing dyes described in US-PATENT: 3637769, etc., 1,1,5,5-tetrakis (p-dimethylaminophenyl)
-3-methoxy-1,4-pentadiene (or its cation), 1,1,5,5-tetrakis (p-diethylaminophenyl) -3-methoxy-1,4-pentadiene (or its cation), toluene Dithio-nickel complex, 4-tert
-Butyl-1,2-benzenedithiol nickel complex, bisdithiobenzylnickel complex, bis (4-ethyldithiobenzyl) nickel complex, bis (4-n-propyldithiobenzyl) nickel complex and the like. These light absorbers may be used alone or in combination of two or more.

These light absorbers are 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 is a developer, a dye precursor,
It may be co-dispersed (simultaneous mixing and dispersion) with a sensitizer, a mixture of a developer and a sensitizer, or a mixture of a dye precursor and a sensitizer.

The heat-sensitive recording material of the present invention does not change its performance such as ground color stability (heat resistance, solvent resistance, etc.) even if it contains a light absorbing agent. Therefore, even in the case of a thermosensitive recording medium containing a light absorbing agent, toner recording,
Alternatively, heat lamination or the like can be performed.

A heat-sensitive card prepared by subjecting a heat-sensitive recording medium containing a light absorber to heat lamination with a plastic film before or after the heat-sensitive recording is used. Can also be recorded.

[0048]

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 clear reason why the urea compound represented by the general formula (1) of the present invention provides high ground color stability has not been elucidated yet. However, it is estimated as follows.

The structure of the urea compound of the present invention changes as follows according to the 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 developer. The enolization requires high temperature conditions. Since the thermal head instantaneously rises to a high temperature of 200 to 300 ° C, the urea compound that comes into contact with the thermal head undergoes enolization, develops a color developing function, and cleaves the lactone ring of the dye precursor to develop color. I think that the. Therefore, the urea compound does not change and does not react with the dye precursor until the temperature at which enolization occurs, so that the ground color is stable, which is considered to be the reason for the high heat resistance.

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 a low solubility in the solvents used in the oil-based inks. This is considered to be because mixing with the color developer does not substantially occur.

[0052]

【Example】

<Synthesis of urea compound> As a synthesis example of a urea compound,
Examples of the compounds A-1 and A-2 are shown below. Other synthesis was performed in accordance with Synthesis Examples 1 and 2.

[Synthesis Example 1] p-anisidine (12.3 g, 100 mM)
Was dissolved in ethyl acetate (200 ml). To this solution was added dropwise a solution of phenyl isocyanate (11.9 g, 100 mM) dissolved in ethyl acetate (50 ml). After stirring at room temperature for 1 hour, the mixture was concentrated to about 100 ml of ethyl acetate using an evaporator, and poured into n-hexane (500 ml) to produce a precipitate. This was filtered and washed with n-hexane to give Compound A-
1 was obtained.

Synthesis Example 2 p-phenetidine (13.7 g, 100 m
M) was dissolved in ethyl acetate (200 ml). To this solution, phenyl isocyanate (11.9 g, 100 mM) was added to ethyl acetate (50 ml).
Was added dropwise. After stirring for 1 hour at room temperature, a precipitate formed. This was filtered and washed with ethyl acetate and n-hexane to obtain compound A-2.

<Production of Thermosensitive Recording Material> In the following description, parts and% indicate parts by weight and% by weight, respectively.

[Examples 1 to 10] As described below, a heat-sensitive recording material was prepared by using the urea compound of the present invention as a color developer and any of the following six dye precursors as a dye precursor. Was manufactured. (See Table 1) ODB: 3-diethylamino-6-methyl-7-anilinofluoran ODB-2: 3-dibutylamino-6-methyl-7-anilinofluoran TH-107: 3-dibutylamino-7 -(o-chloroanilino) fluoran CVL: 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide New Blue: 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl -2-Methylindole-3-yl) -4-
Azaphthalide Indolyl Red: 3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide That is, first, a developer dispersion liquid (solution A) having the following composition and a dispersion liquid of a dye precursor (B) Liquid) was ground with a sand grinder to an average particle size 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) 2.0 parts of each dye precursor 10 parts of aqueous 10% polyvinyl alcohol 4.6 parts 2.6 parts of water Next, a coating liquid was prepared by mixing a liquid A (a developer dispersion), a liquid B (a dye precursor dispersion), and a kaolin clay dispersion at the following ratios. 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 10] In the following manner, heat-sensitive recording media for Comparative Examples were prepared in the same manner as in Examples 1 to 10, except that the following compounds were used as color developers. (See Table 1) (Developer compound) Bisphenol A (B-1) Bisphenol S (B-2) 4-hydroxy-4'-iso-propoxydiphenylsulfone (B-3) 4-hydroxy-4'-n -Butyroxydiphenyl sulfone (B
-4) Phenylurea (B-5) Bisurea compound (B-6) described in JP-A-58-211496 2-methoxydiphenylurea (B-7) 3-methoxydiphenyl described in JP-A-5-147357 Urea (B-8) 2,4-dimethoxydiphenylurea (B-9) 1- (4-octadecyloxyphenyl) -3-phenylurea (B-10) JP-A-57-87993

[0058]

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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-10) 6.0 parts 10% aqueous solution of polyvinyl alcohol 18.8 parts Water 11.2 parts Then, at the following ratio, solution C (developer dispersion liquid) ), A dispersion of the dye precursor (solution B) used in Examples 1 to 4 and a dispersion of kaolin clay were mixed to form a coating liquid. Liquid C: developer dispersion 36.0 parts Liquid B: dye precursor dispersion 9.2 parts Kaolin clay (50% dispersion) 12.0 parts This coating liquid was applied to one side of a 50 g / m ² base paper at 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.

<Evaluation of Thermosensitive Recording Material> The obtained thermosensitive recording material was subjected to a recording test, a heat resistance test, and an oil-based ink suitability test using a word processor.

[Recording test]: In order to check the recording suitability, using a word processor (RUPO-90F / manufactured by Toshiba Corporation), recording was performed on the produced thermosensitive recording medium with the maximum applied energy, and the recording section was used. Was measured using a Macbeth densitometer (RD-914, using an amber filter; hereinafter, the concentration was measured under these conditions). In this case, the larger the Macbeth value, the higher the recording density and the better the recording suitability.

[Heat resistance test]: A thermal recording made at a pressure of 10 g / cm ² on a hot plate heated to 90 ° C., 120 ° C., and 135 ° C. in order to check the thermal stability of the ground color of the recording sheet. The body was pressed for 5 seconds and the recorded body was measured with a Macbeth densitometer. In this case, the smaller the Macbeth value, the lower the degree of coloring of the ground color portion (in other words, the ground color portion is white), indicating that the thermal stability of the ground color portion is higher.

[Oil-based ink suitability test (discoloration test of ground color with oil-based ink)]: Oil-based red magic ink No. 500
(Manufactured by Teranishi Chemical Co., Ltd.), and the degree of discoloration with respect to the original red color was visually observed by writing on the produced thermal recording medium. ◎: No discoloration ○: Almost no discoloration △: Slight discoloration ×: Significant discoloration

The evaluation results of Examples 1 to 10 and Comparative Examples 1 to 10 using the urea compound of the present invention as a developer are shown in Table 1.

[0065]

[Table 1]

[Example 11] A simple laminating apparatus (MS pouch) with the thermal recording medium of Example 1 sandwiched 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 1.31 and the ground color area was 0.13.

[Example 12] A simple laminating apparatus (MS pouch) with the thermal recording medium of Example 2 sandwiched 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 13 In the thermal recording medium of Example 1, when toner recording was performed with a copying machine (NP6060 / manufactured by Canon Inc.), no change was observed in the ground color, and printing was performed. I was able to.

Example 14 The thermal recording medium of Example 2 was subjected to toner recording with a copying machine (NP6060 / manufactured by Canon Inc.). As a result, no change was observed in the ground color, and printing was performed. I was able to.

Example 15 The thermal recording medium of Example 3 was subjected to toner recording with a copying machine (NP6060 / manufactured by Canon Inc.). As a result, no change was observed in the ground color, and printing was performed. I was able to.

Example 16 The thermal recording medium of Example 4 was subjected to toner recording with a copying machine (NP6060 / manufactured by Canon Inc.). As a result, no change was observed in the ground color, and printing was performed. I was able to.

<Production of a heat-sensitive recording medium containing a light absorbing agent> [Examples 17 to 21] As a dye precursor,
Using N, N-diethylamino-6-methyl-7-anilinofluoran (alias: ODB) as a developer, compound A-1
Then, a heat-sensitive recording material was manufactured by using a hot melt of the following absorbing dye and sensitizer as a light absorber. Cyanine dye (trade name: NK-2015 / Japan Photographic Dye Laboratories) Naphthalocyanine dye (trade name: NIR-14 / Yamamoto Kasei Co., Ltd.) Immonium dye (trade name: IRG- 002 / Nippon Kayaku Co., Ltd.) Anthraquinone dye (trade name: IR-750 / Nippon Kayaku Co., Ltd.) Bisdithiobenzylnickel complex (BDBNi) That is, first, 94 parts of 4-biphenyl-p-tolyl ether , 6 parts of bidithiobenzylnickel complex,
The mixture was heated to 150 ° C., 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 solution of polyvinyl alcohol 10.0 parts Water 6.0 parts Then, compound A- used in Example 1 at the following ratio:
The dispersion liquid (liquid A), the dispersion liquid (liquid B) of the dye precursor (ODB) used in Examples 1 to 4, the liquid liquid (light absorber dispersion liquid), and the dispersion liquid 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,
A thermosensitive recording medium was produced.

[Examples 22 to 23] Thermosensitive recording media were produced by using an absorbing dye alone as a light absorbing agent instead of a hot melt of each absorbing dye and a sensitizer. Toluene dithiol nickel complex (TDNi) 1,1,5,5-tetrakis (p-diethylaminophenyl) -3-
Methoxy-1,4-pentadiene (TDEPMP) The following light-absorbing developer dispersion (solution H) was ground by a sand grinder to an average particle size of 1 micron. (H liquid: light-absorbing developer dispersion) Compound A-1 of Example 1 6.0 parts TDNi or TDEPMP 1.0 part 10% aqueous polyvinyl alcohol solution 18.8 parts Water 10.2 parts Colorant dispersion (H
Liquid), a dispersion of the dye precursor (ODB) used in Example 1 (Liquid B), and a dispersion of kaolin clay were mixed to form a coating liquid. Liquid H (light absorbing developer dispersion) 36.0 parts Liquid B (dye precursor dispersion) 9.2 parts Kaolin clay (50% dispersion) 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 prepared.

<Evaluation of heat-sensitive recording medium containing light absorber>
A recording test was performed on the obtained thermosensitive recording medium. Table 2 shows the evaluation results. [Optical recording test]: An optical recording medium was irradiated with a laser beam using a laser plotter described in JP-A-3-239598, and the recorded portion was measured with a Macbeth densitometer. The light irradiation conditions are as follows:
Recording using a semiconductor laser LT015MD (manufactured by Sharp Corporation) with an output of 830 nm and 30 mW, using an aspheric plastic lens AP4545 (manufactured by Konica Corporation) with a numerical aperture of 0.45 and a focal length of 4.5 mm as a light collection lens. Speed 50mm / sec, recording interval
The measurement was performed at 50 microns, and a solid recording of 1 cm in length and width was obtained.

[0075]

[Table 2]

[0076]

As described above, as described above, the urea compound of the present invention can be obtained under the environmental temperature conditions of 120 to 135 ° C.
It is an epoch-making developer that can record a sufficient image density with a thermal head or the like, even though the ground color portion is stable.

The effects of the present invention include the following. (1) The heat-sensitive recording medium of the present invention is a heat-sensitive recording medium that is excellent in ground color stability such as heat resistance and solvent resistance as compared with a conventional heat-sensitive recording medium. (2) The heat-sensitive recording medium of the present invention can be used under severe conditions that could not be used until now (for example, temperature conditions in the range of 90 ° C to 135 ° C). (3) The recording surface of the thermosensitive recording medium of the present invention can be freely written by using oil-based ink. (4) The thermosensitive recording medium of the present invention can be easily heat-laminated with a simple laminating device or the like. For example, a card or the like can be easily made. (5) The thermal recording medium of the present invention can perform toner recording.

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

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tosumi Satake 5-2-1-1, Oji, Kita-ku, Tokyo Nippon Paper Industries 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-63-239083 (JP, A) JP-A-63-81082 (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-A-63-68856 (JP, A) JP-A-57-185567 (JP, U) (58) Int.Cl. ⁷ , DB name) B41M 5/30 G03G 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 (Here, X represents an alkoxy group having 1 to 12 carbon atoms, a methyl trihalide group, a nitro group, or a hydrogen atom. Y represents an alkoxy group having 1 to 12 carbon atoms. And Y are different.) 2. A thermosensitive recording medium according to claim 1, wherein the thermosensitive coloring layer of the thermosensitive recording medium contains a light absorbing agent that absorbs light and converts it into heat. 3. A thermosensitive recording card comprising the thermosensitive recording medium according to claim 1 laminated with a plastic film. 4. An electrophotographic transfer sheet using the heat-sensitive recording material according to claim 1.