Thermosensitive recording layer forming liquid, thermosensitive recording medium and its manufacturing method, and image recording method

Abstract

To provide a thermosensitive recording medium which has all of hot water resistance, water resistance, ethanol resistance, resistance to temperature and humidity, water scrubbing resistance and heat resistance, and can give an image having high density.SOLUTION: A thermosensitive recording layer contains a compound represented by the following general formula (1), and a styrene-acrylic resin. In the general formula (1), R2 is a linear, branched or alicyclic 1-12C alkyl group, an unsubstituted or 1-12C alkyl group, a 1-12C alkoxy group, a 6-12C aryl group or a 7-12C aralkyl group substituted with a halogen atom, or an unsubstituted or 1-12C alkyl group, a 1-12C alkoxy group, a 6-12C aryl group or a 6-12C aryl group substituted with a halogen atom, and the plurality of R2 may be the same or different. A1 represents a hydrogen atom, or a 1-4C alkyl group. The plurality of A1 may be the same or different.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a thermosensitive recording layer forming liquid, a thermosensitive recording medium and a method for producing the same, and an image recording method. [Background technology]

[0002] Compared with other recording methods, thermal recording methods using thermal recording media have the advantages of not requiring processes such as development and fixing, being able to record in a short time using relatively simple equipment, and being inexpensive. For these reasons, they are rapidly becoming more widely used in the food industry, where image reliability is important for boxed lunches, prepared foods, and the like.

[0003] In the food industry, thermosensitive recording media are increasingly being used for labels on PET bottles and labels on fresh food, and are expected to be used in conditions where they are exposed to water or hot water, and there is a risk that the image area of ​​the thermosensitive recording media will fade if it comes into contact with water or hot water. In particular, there is a risk that fading will occur due to the temperature of hot drinks in vending machines (e.g., several hours at 60°C), the temperature of hot water coming from a faucet (e.g., several minutes at 60°C), the temperature of the hot water course of a washing machine (40°C to 60°C for several hours), etc. Furthermore, packaging films for various containers such as PET bottles for soft drinks, metal cans for canned coffee, bottles for energy drinks, medicines, and beer, and packaging labels in the POS field for fresh foods, boxed lunches, prepared dishes, and the like, are required to have not only the above-mentioned warm water resistance and water resistance, but also ethanol resistance, temperature and humidity resistance, water abrasion resistance, and heat resistance.

[0004] Therefore, for example, in order to improve the water resistance of the image area, it has been proposed to incorporate polyvinyl alcohol and polyamide epichlorohydrin resin into the thermosensitive recording layer, to use hydrophobic resin emulsions such as vinyl acetate emulsion, acrylic emulsion, and SBR latex as binders for the thermosensitive recording layer, and to use non-phenolic color developers that do not contain phenolic compounds as color developers for the thermosensitive recording layer (see, for example, Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a thermosensitive recording medium which has all of warm water resistance, water resistance, ethanol resistance, temperature and humidity resistance, water abrasion resistance and heat resistance and which is capable of providing high density images. [Means for solving the problem]

[0006] The thermosensitive recording medium of the present invention as a means for solving the above-mentioned problems is a thermosensitive recording medium having a support and a thermosensitive recording layer on the support, wherein the thermosensitive recording layer contains a compound represented by the following general formula (1) and a styrene-acrylic resin. [ka] In the above general formula (1), R 2 is a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms, an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 12 carbon atoms substituted with a halogen atom, or an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms substituted with a halogen atom; 2 may be the same or different. A 1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 1 may be the same or different. Effect of the Invention

[0007] According to the present invention, it is possible to provide a thermal recording medium which has all of the following properties: warm water resistance, water resistance, ethanol resistance, temperature and humidity resistance, water abrasion resistance and heat resistance, and which is capable of producing high density images. [Brief description of the drawings]

[0008] [Figure 1]FIG. 1 is a schematic cross-sectional view showing an example of a thermosensitive recording medium according to the first embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing an example of a thermosensitive recording medium according to the second embodiment. [Diagram 3] FIG. 3 is a schematic cross-sectional view showing an example of a thermosensitive recording medium according to the third embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view showing an example of a thermosensitive recording medium according to the fourth embodiment. [Diagram 5] FIG. 5 is a schematic cross-sectional view showing an example of a thermosensitive recording medium according to the fifth embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional view showing an example of a thermosensitive recording medium according to the sixth embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view showing an example of a thermosensitive recording medium according to the seventh embodiment. [Figure 8] FIG. 8 is a schematic cross-sectional view showing an example of a thermosensitive recording medium according to the eighth embodiment. [Figure 9] FIG. 9 is a schematic diagram showing an example of an image recording apparatus used in the image recording method of the present invention. [Figure 10] FIG. 10 is a schematic diagram showing another example of an image recording apparatus used in the image recording method of the present invention. [Figure 11] FIG. 11 is a diagram for explaining the arrangement of a laser array in an image recording device used in the image recording method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (Thermal recording media) The thermosensitive recording medium of the present invention is a thermosensitive recording medium having a support and a thermosensitive recording layer on the support, the thermosensitive recording layer containing a compound represented by the following general formula (1) and a styrene-acrylic resin, and further having other layers as necessary.

[0010] [ka] In the above general formula (1), R2 is a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms, an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 12 carbon atoms substituted with a halogen atom, or an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms substituted with a halogen atom; 2 may be the same or different. A 1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 1 may be the same or different.

[0011] In conventional technology, the use of a specific non-phenolic developer allows the image to retain water resistance at room temperature (25°C), but there is a problem in that the image fades when exposed to hot water (60°C or higher).

[0012] In the present invention, a thermosensitive recording medium has a support and a thermosensitive recording layer on the support, and the thermosensitive recording layer contains a compound represented by the above general formula (1) and a styrene-acrylic resin, thereby providing hot water resistance, water resistance, ethanol resistance, hot and humid resistance, water abrasion resistance and heat resistance, and also providing a high density image.

[0013] <Thermal recording layer> The heat-sensitive recording layer contains the compound represented by the above general formula (1) and a styrene-acrylic resin, and preferably contains a leuco dye and a light-to-heat conversion material, and further contains other components as necessary.

[0014] <<Compound represented by general formula (1)>> The compound represented by the above general formula (1) is a non-phenolic color developer, and non-phenolic means that it does not have a phenol skeleton. By containing a non-phenolic color developer, it is not necessary to contain a phenolic color developer, which may be an endocrine disrupting substance, and therefore it is superior in terms of impact on the environment.

[0015] In the above general formula (1) and the above general formula (2), R 2 is a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms, an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms substituted with a halogen atom, or an aryl group having 6 to 12 carbon atoms; 2 may be the same or different. A 1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 1 may be the same or different.

[0016] In the above general formula (3), R represents an alkyl group, and n represents an integer of 0 to 3. The alkyl group of R may have 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms.

[0017] In the above general formula (1), multiple R 2 -SO 3 The substitution positions of - may be the same or different, and are preferably the 3-position, 4-position or 5-position, more preferably the 3-position.

[0018] R 2 Examples of the linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms include a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a t-butyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, a 2-ethylhexyl group, and a lauryl group.

[0019] Examples of the aralkyl group include benzyl group, 1-phenylethyl group, 2-phenylethyl group, 3-phenylpropyl group, p-methylbenzyl group, m-methylbenzyl group, m-ethylbenzyl group, p-ethylbenzyl group, pi-propylbenzyl group, pt-butylbenzyl group, p-methoxybenzyl group, m-methoxybenzyl group, o-methoxybenzyl group, m,p-di-methoxybenzyl group, p-ethoxy-m-methoxybenzyl group, p-phenylmethylbenzyl group, p-cumylbenzyl group, p-phenylbenzyl group, o-phenylbenzyl group, m-phenylbenzyl group, p-tolylbenzyl group, m-tolylbenzyl group, o-tolylbenzyl group, and p-chlorobenzyl group, and other unsubstituted or aralkyl groups substituted with an alkyl group, an alkoxy group, an aralkyl group, an aryl group, or a halogen atom.

[0020] Examples of the aryl group include unsubstituted aryl groups or aryl groups substituted with an alkyl group, an alkoxy group, an aralkyl group, an aryl group, or a halogen atom, such as a phenyl group, a p-tolyl group, an m-tolyl group, an o-tolyl group, a 2,5-dimethylphenyl group, a 2,4-dimethylphenyl group, a 3,5-dimethylphenyl group, a 2,3-dimethylphenyl group, a 3,4-dimethylphenyl group, a mesitylene group, a p-ethylphenyl group, a p-propylphenyl group, a p-butylphenyl group, a p-methoxyphenyl group, a 3,4-dimethoxyphenyl group, a p-ethoxyphenyl group, a p-chlorophenyl group, a 1-naphthyl group, a 2-naphthyl group, or a t-butylated naphthyl group.

[0021] Multiple A's 1 The substitution positions of may be the same or different, and are preferably the 3-, 4- and 5-positions. A 1 is a hydrogen atom or an alkyl group such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, or t-butyl.

[0022] Specific examples of the compounds represented by the above general formulas (1) to (3) include the following compounds, but are not limited to these compounds. In addition, two or more compounds may be used in combination as a color developer.

[0023] Furthermore, by using the present invention in combination with existing color developers, for example, known non-phenolic color developers such as N-3-[(p-toluenesulfonyl)oxy]phenyl-N'-(p-toluenesulfonyl)-urea and N-[2-(3-phenylureido)phenyl]-benzenesulfonamide, and known color developers such as 4,4'-isopropylidenediphenol (BPA), 4,4'-dihydroxydiphenyl sulfone (BPS), 4-allyloxy-4'-hydroxydiphenyl sulfone, 4-allyloxy-4'-hydroxy-diphenyl sulfone, 4-hydroxy-4'-isopropoxysulfone, N-(m-tolylaminocarbonyl)-methionine, N-(m-tolylaminocarbonyl)-phenylalanine, and N-(phenylaminocarbonyl)-phenylalanine, it is possible to further improve the storage stability, which is an issue with these known color developers.

[0024] Examples of the compounds represented by the above general formulas (1) to (3) include N,N'-di-[3-(benzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-4-methyl-phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-4-ethyl-phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-5-methyl-phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-4-propyl-phenyl]urea,

[0025] N,N'-di-[3-(o-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(m-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-toluenesulfonyloxy)-4-methyl-phenyl]urea, N,N'-di-[3-(p-xylenesulfonyloxy)phenyl]urea, N,N'-di-[3-(m-xylenesulfonyloxy)phenyl]urea, N,N'-di-[3-(mesitylenesulfonyloxy)phenyl]urea, N,N'-di-[3-(1-naphthalenesulfonyloxy)phenyl]urea, N,N'-di-[3-(2-naphthalenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-ethylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-propylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-isopropylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(pt-butylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(m-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(o-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(m,p-dimethoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-ethoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-propoxybenzenesulfonyloxy)phenyl]urea, nyl]urea, N,N'-di-[3-(p-butoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-cumylbenzylsulfonyloxy)phenyl]urea, N,N'-di-[3-(p-cumylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(o-phenylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-phenylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-chlorobenzenesulfonyloxy)phenyl]urea,

[0026] N-[3-(benzenesulfonyloxy)phenyl]-N'-[3-(p-toluenesulfonyloxy)phenyl]urea, N-[3-(benzenesulfonyloxy)phenyl]-N'-[3-(m-toluenesulfonyloxy)phenyl]urea, N-[3-(benzenesulfonyloxy)phenyl]-N'-[3-(o-toluenesulfonyloxy)phenyl] N-[3-(benzenesulfonyloxy)phenyl]-N'-[3-(p-xylenesulfonyloxy)phenyl]urea, N-[3-(benzenesulfonyloxy)phenyl]-N'-[3-(mesitylenesulfonyloxy)phenyl]urea, N-[3-(benzenesulfonyloxy)phenyl]-N'-[3-(1-naphthalenesulfonyloxy)phenyl]urea, N-[3-(benzenesulfonyloxy)phenyl]-N'-[3-(2-naphthalenesulfonyloxy)phenyl]urea N-[3-(benzenesulfonyloxy)phenyl]-N'-[3-(p-ethylbenzenesulfonyloxy)phenyl]urea, N-[3-(benzenesulfonyloxy)phenyl]-N'-[3-(p-methoxybenzenesulfonyloxy)phenyl]urea, N-[3-(benzenesulfonyloxy)phenyl]-N'-[3-(benzylsulfonyloxy)phenyl]urea, N-[3-(benzenesulfonyloxy)phenyl]-N'-[3-(ethane sulfonyloxy)phenyl]urea, N-[3-(benzenesulfonyloxy)phenyl]-N'-[3-(benzenesulfonyloxy)-4-methylphenyl]urea, N-[3-(p-toluenesulfonyloxy)phenyl]-N'-[3-(m-toluenesulfonyloxy)phenyl]urea, N-[3-(p-toluenesulfonyloxy)phenyl]-N'-[3-(o-toluenesulfonyloxy)phenyl]urea, N-[3-(p-toluenesulfonyloxy)phenyl] -N'-[3-(p-toluenesulfonyloxy)-4-methylphenyl]urea, N-[3-(p-toluenesulfonyloxy)phenyl]-N'-[3-(p-ethylbenzenesulfonyloxy)phenyl]urea, N-[3-(p-toluenesulfonyloxy)phenyl]-N'-[3-(p-methoxybenzenesulfonyloxy)phenyl]urea, N-[3-(p-toluenesulfonyloxy)phenyl]-N'-[3-(2-naphthalenesulfonyloxy)phenyl]urea,

[0027] N-[3-(p-toluenesulfonyloxy)phenyl]-N'-[3-(benzylsulfonyloxy)phenyl]urea, N-[3-(p-toluenesulfonyloxy)phenyl]-N'-[3-(p-methylbenzylsulfonyloxy)phenyl]urea, N-[3-(p-toluenesulfonyloxy)phenyl]-N'-[3-(p-methoxybenzylsulfonyloxy)phenyl]urea, N-[3-(p-toluenesulfonyloxy)phenyl]-N'-[3-(methanesulfonyloxy)phenyl]urea, N-[3-(p-toluenesulfonyloxy)phenyl]-N'-[3-(propanesulfonyloxy)phenyl]urea, N-[3-(p-toluenesulfonyloxy)phenyl]-N'-[3-(butanesulfonyloxy)phenyl]urea,

[0028] N,N'-di-[3-(benzylsulfonyloxy)phenyl]urea, N,N'-di-[3-(benzylsulfonyloxy)-4-methyl-phenyl]urea, N,N'-di-[3-(phenylethanesulfonyloxy)phenyl]urea, N,N'-di-[3-(phenylpropanesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-methoxybenzylsulfonyloxy)phenyl]urea,

[0029] N-[3-(benzylsulfonyloxy)phenyl]-N'-[3-(p-methoxybenzylsulfonyloxy)phenyl]urea, N-[3-(benzylsulfonyloxy)phenyl]-N'-[3-(ethanesulfonyloxy)phenyl]urea, N-[3-(benzylsulfonyloxy)phenyl]-N'-[3-(butanesulfonyloxy)phenyl]urea,

[0030] N,N'-di-[3-(methanesulfonyloxy)phenyl]urea, N,N'-di-[3-(methanesulfonyloxy)-4-methyl-phenyl]urea, N,N'-di-[3-(methanesulfonyloxy)-4-ethyl-phenyl]urea, N,N'-di-[3-(methanesulfonyloxy)-5-methyl-phenyl]urea, N,N'-di-[3-(methanesulfonyloxy)-4,5-dimethyl-phenyl]urea, N,N'-di-[3-(ethanesulfonyloxy) ... -methyl-phenyl]urea, N,N'-di-[3-(1-propanesulfonyloxy)phenyl]urea, N,N'-di-[3-(2-propanesulfonyloxy)phenyl]urea, N,N'-di-[3-(butanesulfonyloxy)phenyl]urea, N,N'-di-[3-(pentanesulfonyloxy)phenyl]urea, N,N'-di-[3-(hexanesulfonyloxy)phenyl]urea, N,N'-di-[3-(cyclohexanesulfonyloxy)phenyl]urea, N,N'-di-[3-(dodecanesulfonyloxy)phenyl]urea,

[0031] N-[3-(methanesulfonyloxy)phenyl]-N'-[3-(ethanesulfonyloxy)phenyl]urea, N-[3-(ethanesulfonyloxy)phenyl]-N'-[3-(propanesulfonyloxy)phenyl]urea, N-[3-(methanesulfonyloxy)phenyl]-N'-[3-(butanesulfonyloxy)phenyl]urea, N-[3-(ethanesulfonyloxy)phenyl]-N'-[3-(cyclohexanesulfonyloxy)phenyl]urea,

[0032] N,N'-di-[4-(benzenesulfonyloxy)phenyl]urea, N,N'-di-[4-(benzenesulfonyloxy)-3-methyl-phenyl]urea, N,N'-di-[4-(benzenesulfonyloxy)-3-ethyl-phenyl]urea, N,N'-di-[4-(benzenesulfonyloxy)-3-propyl-phenyl]urea, N,N'-di-[4-(benzenesulfonyloxy)-3-t-butyl-phenyl]urea,

[0033] N,N'-di-[4-(o-toluenesulfonyloxy)phenyl]urea, N,N'-di-[4-(m-toluenesulfonyloxy)phenyl]urea, N,N'-di-[4-(p-toluenesulfonyloxy)phenyl]urea, N,N'-di-[4-(p-toluenesulfonyloxy)-3-methyl-phenyl]urea,

[0034] N,N'-di-[4-(p-xylylenesulfonyloxy)phenyl]urea, N,N'-di-[4-(m-xylylenesulfonyloxy)phenyl]urea, N,N'-di-[4-(mesitylenesulfonyloxy)phenyl]urea,

[0035] N,N'-di-[4-(1-naphthalenesulfonyloxy)phenyl]urea, N,N'-di-[4-(2-naphthalenesulfonyloxy)phenyl]urea,

[0036] N,N'-di-[4-(p-ethylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[4-(p-propylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[4-(p-isopropylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[4-(pt-butylbenzenesulfonyloxy)phenyl]urea,

[0037] N,N'-di-[4-(p-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[4-(m-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[4-(o-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[4-(m,p-dimethoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[4-(p-ethoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[4-(p-propoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[4-(p-butoxybenzenesulfonyloxy)phenyl]urea,

[0038] N,N'-di-[4-(p-cumylbenzylsulfonyloxy)phenyl]urea, N,N'-di-[4-(p-cumylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[4-(o-phenylbenzenesulfonyloxy)phenyl]urea, N,N'-di- [4-(p-phenylbenzenesulfonyloxy)phenyl]urea,

[0039] N,N'-di-[4-(p-chlorobenzenesulfonyloxy)phenyl]urea,

[0040] N-[4-(benzenesulfonyloxy)phenyl]-N'-[4-(p-toluenesulfonyloxy)phenyl]urea, N-[4-(benzenesulfonyloxy)phenyl]-N'-[4-(m-toluenesulfonyloxy)phenyl]urea, N-[4-(benzenesulfonyloxy)phenyl]-N'-[4-(o-toluenesulfonyloxy)phenyl]urea, N-[4-(benzenesulfonyloxy)phenyl]-N'-[4-(p-xylenesulfonyloxy)phenyl]urea, N-[4- (benzenesulfonyloxy)phenyl]-N'-[4-(mesitylenesulfonyloxy)phenyl]urea, N-[4-(benzenesulfonyloxy)phenyl]-N'-[4-(1-naphthalenesulfonyloxy)phenyl]urea, N-[4-(benzenesulfonyloxy)phenyl]-N'-[4-(2-naphthalenesulfonyloxy)phenyl]urea, N-[4-(benzenesulfonyloxy)phenyl]-N'-[4-(p-ethylbenzenesulfonyloxy)phenyl]urea, N-[4-( N-[4-(benzenesulfonyloxy)phenyl]-N'-[4-(p-methoxybenzenesulfonyloxy)phenyl]urea, N-[4-(benzenesulfonyloxy)phenyl]-N'-[4-(benzylsulfonyloxy)phenyl]urea, N-[4-(benzenesulfonyloxy)phenyl]-N'-[4-(ethanesulfonyloxy)phenyl]urea, N-[4-(p-toluenesulfonyloxy)phenyl]-N'-[4-(m-toluenesulfonyloxy)phenyl]urea, N-[4-(p-toluenesulfonyloxy)phenyl]-N'-[4-(m-toluenesulfonyloxy)phenyl]urea, N-[4-(p-toluenesulfonyloxy)phenyl]-N'-[4-(p-ethylbenzenesulfonyloxy)phenyl]urea, N-[4-(p-toluenesulfonyloxy)phenyl]-N'-[4-(p-methoxybenzenesulfonyloxy)phenyl]urea, N-[4-(p-toluenesulfonyloxy)phenyl]-N'-[4-(2-naphthalenesulfonyloxy)phenyl]urea,

[0041] N-[4-(p-toluenesulfonyloxy)phenyl]-N'-[4-(benzylsulfonyloxy)phenyl]urea, N-[4-(p-toluenesulfonyloxy)phenyl]-N'-[4-(p-methylbenzylsulfonyloxy)phenyl]urea, N-[4-(p-toluenesulfonyloxy)phenyl]-N'-[4-(p-methoxybenzylsulfonyloxy)phenyl]urea, N-[4-(p-toluenesulfonyloxy)phenyl]-N'-[4-(methanesulfonyloxy)phenyl]urea, N-[4-(p-toluenesulfonyloxy)phenyl]-N'-[4-(propanesulfonyloxy)phenyl]urea, N-[4-(p-toluenesulfonyloxy)phenyl]-N'-[4-(butanesulfonyloxy)phenyl]urea,

[0042] N,N'-di-[4-(benzylsulfonyloxy)phenyl]urea, N,N'-di-[4-(benzylsulfonyloxy)-3-methyl-phenyl]urea, N,N'-di-[4-(phenylethanesulfonyloxy)phenyl]urea, N,N'-di-[4-(phenylpropanesulfonyloxy)phenyl]urea, N,N'-di-[4-(p-methoxybenzylsulfonyloxy)phenyl]urea,

[0043] N-[4-(benzylsulfonyloxy)phenyl]-N'-[4-(methanesulfonyloxy)phenyl]urea, N-[4-(benzylsulfonyloxy)phenyl]-N'-[4-(ethanesulfonyloxy)phenyl]urea,

[0044] N,N'-di-[4-(methanesulfonyloxy)phenyl]urea, N,N'-di-[4-(methanesulfonyloxy)-3-methyl-phenyl]urea, N,N'-di-[4-(methanesulfonyloxy)-4-ethyl-phenyl]urea, N,N'-di-[4-(methanesulfonyloxy)-4-ethyl-phenyl]urea, N,N'-di-[4-(methanesulfonyloxy)-3,5-dimethyl-phenyl]urea, N,N'-di-[4-(ethanesulfonyloxy)phenyl]urea, N,N'-di-[4-(ethanesulfonyloxy)-3-methyl-phenyl]urea, N,N'-di-[4-(1-propanesulfonyloxy)phenyl]urea, N,N'-di-[4-(2- propanesulfonyloxy)phenyl]urea, N,N'-di-[4-(butanesulfonyloxy)phenyl]urea, N,N'-di-[4-(pentanesulfonyloxy)phenyl]urea, N,N'-di-[4-(hexanesulfonyloxy)phenyl]urea, N,N'-di-[4-(cyclohexanesulfonyloxy)phenyl]urea, N,N'-di-[4-(dodecanesulfonyloxy)phenyl]urea,

[0045] N-[4-(methanesulfonyloxy)phenyl]-N'-[4-(ethanesulfonyloxy)phenyl]urea, N-[4-(methanesulfonyloxy)phenyl]-N'-[4-(propanesulfonyloxy)phenyl]urea,

[0046] N,N'-di-[2-(benzenesulfonyloxy)phenyl]urea, N,N'-di-[2-(benzenesulfonyloxy)-4-methyl-phenyl]urea, N,N'-di-[2-(benzenesulfonyloxy)-4-ethyl-phenyl]urea, N,N'-di-[2-(benzenesulfonyloxy)-5-methyl-phenyl]urea, N,N'-di-[2-(benzenesulfonyloxy)-4-propyl-phenyl]urea,

[0047] N,N'-di-[2-(o-toluenesulfonyloxy)phenyl]urea, N,N'-di-[2-(m-toluenesulfonyloxy)phenyl]urea, N,N'-di-[2-(p-toluenesulfonyloxy)phenyl]urea, N,N'-di-[2-(p-toluenesulfonyloxy)-4-methyl-phenyl]urea,

[0048] N,N'-di-[2-(p-xylylenesulfonyloxy)phenyl]urea, N,N'-di-[2-(m-xylylenesulfonyloxy)phenyl]urea, N,N'-di-[2-(mesitylenesulfonyloxy)phenyl]urea,

[0049] N,N'-di-[2-(1-naphthalenesulfonyloxy)phenyl]urea, N,N'-di-[2-(2-naphthalenesulfonyloxy)phenyl]urea,

[0050] N,N'-di-[2-(p-ethylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[2-(p-propylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[2-(p-isopropylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[2-(pt-butylbenzenesulfonyloxy)phenyl]urea,

[0051] N,N'-di-[2-(p-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[2-(m-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[2-(o-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[2-(m,p-dimethoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[2-(p-ethoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[2-(p-propoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[2-(p-butoxybenzenesulfonyloxy)phenyl]urea,

[0052] N,N'-di-[2-(p-cumylbenzylsulfonyloxy)phenyl]urea, N,N'-di-[2-(p-cumylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[2-(o-phenylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[2-(p-phenylbenzenesulfonyloxy)phenyl]urea,

[0053] N,N'-di-[2-(p-chlorobenzenesulfonyloxy)phenyl]urea,

[0054] N-[2-(benzenesulfonyloxy)phenyl]-N'-[2-(p-toluenesulfonyloxy)phenyl]urea, N-[2-(benzenesulfonyloxy)phenyl]-N'-[2-(m-toluenesulfonyloxy)phenyl]urea, N-[2-(benzenesulfonyloxy)phenyl]-N'-[2-(o-toluenesulfonyloxy)phenyl]urea, N-[2-(benzenesulfonyloxy)phenyl]-N'-[2-(p-xylenesulfonyloxy)phenyl]urea, N-[2- (benzenesulfonyloxy)phenyl]-N'-[2-(mesitylenesulfonyloxy)phenyl]urea, N-[2-(benzenesulfonyloxy)phenyl]-N'-[2-(1-naphthalenesulfonyloxy)phenyl]urea, N-[2-(benzenesulfonyloxy)phenyl]-N'-[2-(2-naphthalenesulfonyloxy)phenyl]urea, N-[2-(benzenesulfonyloxy)phenyl]-N'-[2-(p-ethylbenzenesulfonyloxy)phenyl]urea, N-[2-( N-[2-(benzenesulfonyloxy)phenyl]-N'-[2-(p-methoxybenzenesulfonyloxy)phenyl]urea, N-[2-(benzenesulfonyloxy)phenyl]-N'-[2-(benzylsulfonyloxy)phenyl]urea, N-[2-(benzenesulfonyloxy)phenyl]-N'-[2-(ethanesulfonyloxy)phenyl]urea, N-[2-(p-toluenesulfonyloxy)phenyl]-N'-[2-(m-toluenesulfonyloxy)phenyl]urea, N-[2-(p-toluenesulfonyloxy)phenyl]-N'-[2-(m-toluenesulfonyloxy)phenyl]urea, N-[2-(o-toluenesulfonyloxy)phenyl]-N'-[2-(p-ethylbenzenesulfonyloxy)phenyl]urea, N-[2-(p-toluenesulfonyloxy)phenyl]-N'-[2-(p-methoxybenzenesulfonyloxy)phenyl]urea, N-[2-(p-toluenesulfonyloxy)phenyl]-N'-[2-(2-naphthalenesulfonyloxy)phenyl]urea,

[0055] N-[2-(p-toluenesulfonyloxy)phenyl]-N'-[2-(benzylsulfonyloxy)phenyl]urea, N-[2-(p-toluenesulfonyloxy)phenyl]-N'-[2-(p-methylbenzylsulfonyloxy)phenyl]urea, N-[2-(p-toluenesulfonyloxy)phenyl]-N'-[2-(p-methoxybenzylsulfonyloxy)phenyl]urea, N-[2-(p-toluenesulfonyloxy)phenyl]-N'-[2-(methanesulfonyloxy)phenyl]urea, N-[2-(p-toluenesulfonyloxy)phenyl]-N'-[2-(propanesulfonyloxy)phenyl]urea, N-[2-(p-toluenesulfonyloxy)phenyl]-N'-[2-(butanesulfonyloxy)phenyl]urea,

[0056] N,N'-di-[2-(benzylsulfonyloxy)phenyl]urea, N,N'-di-[2-(benzylsulfonyloxy)-4-methyl-phenyl]urea, N,N'-di-[2-(phenylethanesulfonyloxy)phenyl]urea, N,N'-di-[2-(phenylpropanesulfonyloxy)phenyl]urea, N,N'-di-[2-(p-methoxybenzylsulfonyloxy)phenyl]urea,

[0057] N-[2-(benzylsulfonyloxy)phenyl]-N'-[2-(propanesulfonyloxy)phenyl]urea, N-[2-(benzylsulfonyloxy)phenyl]-N'-[2-(p-methoxybenzylsulfonyloxy)phenyl]urea,

[0058] N,N'-di-[2-(methanesulfonyloxy)phenyl]urea, N,N'-di-[2-(methanesulfonyloxy)-4-methyl-phenyl]urea, N,N'-di-[2-(methanesulfonyloxy)-4-ethyl-phenyl]urea, N,N'-di-[2-(methanesulfonyloxy)-5-methyl-phenyl]urea, N,N'-di-[2-(methanesulfonyloxy)-4,5-dimethyl-phenyl]urea, N,N'-di-[2-(ethanesulfonyloxy) ... -methyl-phenyl]urea, N,N'-di-[2-(1-propanesulfonyloxy)phenyl]urea, N,N'-di-[2-(2-propanesulfonyloxy)phenyl]urea, N,N'-di-[2-(butanesulfonyloxy)phenyl]urea, N,N'-di-[2-(pentanesulfonyloxy)phenyl]urea, N,N'-di-[2-(hexanesulfonyloxy)phenyl]urea, N,N'-di-[2-(cyclohexanesulfonyloxy)phenyl]urea, N,N'-di-[2-(dodecanesulfonyloxy)phenyl]urea,

[0059] N-[2-(ethanesulfonyloxy)phenyl]-N'-[2-(propanesulfonyloxy)phenyl]urea, N-[2-(ethanesulfonyloxy)phenyl]-N'-[2-(hexanesulfonyloxy)phenyl]urea,

[0060] N-[3-(benzenesulfonyloxy)phenyl]-N'-[4-(benzenesulfonyloxy)phenyl]urea, N-[3-(p-toluenesulfonyloxy)phenyl]-N'-[4'-(p-toluenesulfonyloxy)phenyl]urea, N-[3-(m-toluenesulfonyloxy)phenyl]-N'-[4-(m-toluenesulfonyloxy)phenyl]urea, N-[3-(o-toluenesulfonyloxy)phenyl]-N'-[3-(o-toluenesulfonyloxy)phenyl]urea,

[0061] N-[3-(p-xylylenesulfonyloxy)phenyl]-N'-[4-(p-xylylenesulfonyloxy)phenyl]urea, N-[3-(m-xylylenesulfonyloxy)phenyl]-N'-[4-(m-xylylenesulfonyloxy)phenyl]urea, N-[3-(mesitylenesulfonyloxy)phenyl]-N'-[4-(mesitylenesulfonyloxy)phenyl]urea,

[0062] N-[3-(1-naphthalenesulfonyloxy)phenyl]-N'-[4-(1-naphthalenesulfonyloxy)phenyl]urea, N-[3-(2-naphthalenesulfonyloxy)phenyl]-N'-[3-(2-naphthalenesulfonyloxy)phenyl]urea,

[0063] N-[3-(p-ethylbenzenesulfonyloxy)phenyl]-N'-[4-(p-ethylbenzenesulfonyloxy)phenyl]urea, N-[3-(p-propylbenzenesulfonyloxy)phenyl]-N'-[4-(p-propylbenzenesulfonyloxy)phenyl]urea, N-[3-(p-isopropylbenzenesulfonyloxy)phenyl]-N'-[4-(p-isopropylbenzenesulfonyloxy)phenyl]urea, N-[3-(pt-butylbenzenesulfonyloxy)phenyl]-N'-[4-(pt-butylbenzenesulfonyloxy)phenyl]urea,

[0064] N-[3-(p-methoxybenzenesulfonyloxy)phenyl]-N'-[4-(p-methoxybenzenesulfonyloxy)phenyl]urea, N-[3-(m-methoxybenzenesulfonyloxy)phenyl]-N'-[4-(m-methoxybenzenesulfonyloxy)phenyl]urea, N-[3-(o-methoxybenzenesulfonyloxy)phenyl]-N'-[4-(o-methoxybenzenesulfonyloxy)phenyl]urea, N-[3-(m,p-dimethoxybenzenesulfonyloxy)phenyl]-N' -[4-(m,p-dimethoxybenzenesulfonyloxy)phenyl]urea, N-[3-(p-ethoxybenzenesulfonyloxy)phenyl]-N'-[4-(p-ethoxybenzenesulfonyloxy)phenyl]urea, N-[3-(p-propoxybenzenesulfonyloxy)phenyl]-N'-[4-(p-propoxybenzenesulfonyloxy)phenyl]urea, N-[3-(p-butoxybenzenesulfonyloxy)phenyl]-N'-[4-(p-butoxybenzenesulfonyloxy)phenyl]urea,

[0065] N-[3-(p-cumylbenzylsulfonyloxy)phenyl]-N'-[4-(p-cumylbenzylsulfonyloxy)phenyl]urea, N-[3-(p-cumylbenzenesulfonyloxy)phenyl]-N'-[4-(p-cumylbenzenesulfonyloxy)phenyl]urea, N-[3-(o-phenylbenzenesulfonyloxy)phenyl]-N'-[4-(o-phenylbenzenesulfonyloxy)phenyl]urea, N-[3-(p-phenylbenzenesulfonyloxy)phenyl]-N'-[4-(p-phenylbenzenesulfonyloxy)phenyl]urea,

[0066] N-[3-(p-chlorobenzenesulfonyloxy)phenyl]-N'-[4-(p-chlorobenzenesulfonyloxy)phenyl]urea,

[0067] N-[3-(benzenesulfonyloxy)phenyl]-N'-[4-(p-toluenesulfonyloxy)phenyl]urea, N-[3-(p-toluenesulfonyloxy)phenyl]-N'-[4-(o-toluenesulfonyloxy)phenyl]urea, N-[3-(p-toluenesulfonyloxy)phenyl]-N'-[4-(benzenesulfonyloxy)phenyl]urea, N-[3-(benzenesulfonyloxy)phenyl]-N'-[4-(ethanesulfonyloxy)phenyl]urea, N-[3-(p-toluenesulfonyloxy)phenyl]-N'-[4-(benzylsulfonyloxy)phenyl]urea,

[0068] N-[3-(benzylsulfonyloxy)phenyl]-N'-[4-(benzylsulfonyloxy)phenyl]urea, N-[3-(phenylethanesulfonyloxy)phenyl]-N'-[4-(phenylethanesulfonyloxy)phenyl]urea, N-[3-(phenylpropanesulfonyloxy)phenyl]-N'-[4-(phenylpropanesulfonyloxy)phenyl]urea, N-[3-(p-methoxybenzylsulfonyloxy)phenyl]-N'-[4-(p-methoxybenzylsulfonyloxy)phenyl]urea,

[0069] N-[3-(benzylsulfonyloxy)phenyl]-N'-[4-(butanesulfonyloxy)phenyl]urea, N-[3-(benzylsulfonyloxy)phenyl]-N'-[4-(p-methylbenzylsulfonyloxy)phenyl]urea,

[0070] N-[3-(methanesulfonyloxy)phenyl]-N'-[4-(methanesulfonyloxy)phenyl]urea, N-[3-(ethanesulfonyloxy)phenyl]-N'-[4-(ethanesulfonyloxy)phenyl]urea, N-[3-(1-propanesulfonyloxy)phenyl]-N'-[4-(1-propanesulfonyloxy)phenyl]urea, N-[3-(2-propanesulfonyloxy)phenyl]-N'-[4-(2-propanesulfonyloxy)phenyl]urea, N-[3-(butanesulfonyloxy)phenyl]-N' -[4-(butanesulfonyloxy)phenyl]urea, N-[3-(pentanesulfonyloxy)phenyl]-N'-[4-(pentanesulfonyloxy)phenyl]urea, N-[3-(hexanesulfonyloxy)phenyl]-N'-[4-(hexanesulfonyloxy)phenyl]urea, N-[3-(cyclohexanesulfonyloxy)phenyl]-N'-[4-(cyclohexanesulfonyloxy)phenyl]urea, N-[3-(dodecanesulfonyloxy)phenyl]-N'-[4-(dodecanesulfonyloxy)phenyl]urea,

[0071] N-[3-(methanesulfonyloxy)phenyl]-N'-[4-(ethanesulfonyloxy)phenyl]urea, N-[3-(methanesulfonyloxy)phenyl]-N'-[ 4-(butanesulfonyloxy)phenyl]urea,

[0072] N-[2-(benzenesulfonyloxy)phenyl]-N'-[4-(benzenesulfonyloxy)phenyl]urea, N-[2-(p-toluenesulfonyloxy)phenyl]-N'-[4-(p-toluenesulfonyloxy)phenyl]urea, N-[2-(m-toluenesulfonyloxy)phenyl]-N'-[4-(m-toluenesulfonyloxy)phenyl]urea, N-[2-(o-toluenesulfonyloxy)phenyl]-N'-[4-(o-toluenesulfonyloxy)phenyl]urea,

[0073] N-[2-(p-xylylenesulfonyloxy)phenyl]-N'-[4-(p-xylylenesulfonyloxy)phenyl]urea, N-[2-(m-xylylenesulfonyloxy)phenyl]-N'-[4-(m-xylylenesulfonyloxy)phenyl]urea, N-[2-(mesitylenesulfonyloxy)phenyl]-N'-[4-(mesitylenesulfonyloxy)phenyl]urea,

[0074] N-[2-(1-naphthalenesulfonyloxy)phenyl]-N'-[4-(1-naphthalenesulfonyloxy)phenyl]urea, N-[2-(2-naphthalenesulfonyloxy)phenyl]-N'-[4-(2-naphthalenesulfonyloxy)phenyl]urea,

[0075] N-[2-(p-ethylbenzenesulfonyloxy)phenyl]-N'-[4-(p-ethylbenzenesulfonyloxy)phenyl]urea, N-[2-(p-propylbenzenesulfonyloxy)phenyl]-N'-[4-(p-propylbenzenesulfonyloxy)phenyl]urea, N-[2-(p-isopropylbenzenesulfonyloxy)phenyl]-N'-[4-(p-isopropylbenzenesulfonyloxy)phenyl]urea, N-[2-(pt-butylbenzenesulfonyloxy)phenyl]-N'-[4-(pt-butylbenzenesulfonyloxy)phenyl]urea,

[0076] N-[2-(p-methoxybenzenesulfonyloxy)phenyl]-N'-[4-(p-methoxybenzenesulfonyloxy)phenyl]urea, N-[2-(m-methoxybenzenesulfonyloxy)phenyl]-N'-[4-(m-methoxybenzenesulfonyloxy)phenyl]urea, N-[2-(o-methoxybenzenesulfonyloxy)phenyl]-N'-[4-(o-methoxybenzenesulfonyloxy)phenyl]urea, N-[2-(m,p-dimethoxybenzenesulfonyloxy)phenyl]-N' -[4-(m,p-dimethoxybenzenesulfonyloxy)phenyl]urea, N-[2-(p-ethoxybenzenesulfonyloxy)phenyl]-N'-[4-(p-ethoxybenzenesulfonyloxy)phenyl]urea, N-[2-(p-propoxybenzenesulfonyloxy)phenyl]-N'-[4-(p-propoxybenzenesulfonyloxy)phenyl]urea, N-[2-(p-butoxybenzenesulfonyloxy)phenyl]-N'-[4-(p-butoxybenzenesulfonyloxy)phenyl]urea,

[0077] N-[2-(p-cumylbenzylsulfonyloxy)phenyl]-N'-[4-(p-cumylbenzylsulfonyloxy)phenyl]urea, N-[2-(p-cumylbenzenesulfonyloxy)phenyl]-N'-[4-(p-cumylbenzenesulfonyloxy)phenyl]urea, N-[2-(o-phenylbenzenesulfonyloxy)phenyl]-N'-[4-(o-phenyl)benzenesulfonyloxyphenyl]urea, N-[2-(p-phenylbenzenesulfonyloxy)phenyl]-N'-[4-(p-phenylbenzenesulfonyloxy)phenyl]urea,

[0078] N-[2-(p-chlorobenzenesulfonyloxy)phenyl]-N'-[4-(p-chlorobenzenesulfonyloxy)phenyl]urea,

[0079] N-[2-(ethanesulfonyloxy)phenyl]-N'-[4-(benzenesulfonyloxy)phenyl]urea, N-[2-(ethanesulfonyloxy)phenyl]-N'-[4-(p-toluenesulfonyloxy)phenyl]urea, N-[2-(benzenesulfonyloxy)phenyl]-N'-[4-(ethanesulfonyloxy)phenyl]urea, N-[2-(benzenesulfonyloxy)phenyl]-N'-[4-(benzylsulfonyloxy)phenyl]urea, N-[2-(benzenesulfonyloxy)phenyl]-N'-[4-(p-toluenesulfonyloxy)phenyl]urea, N-[2-(benzenesulfonyloxy)phenyl]-N'-[4-(o-toluenesulfonyloxy)phenyl]urea N-[2-(benzenesulfonyloxy)phenyl]-N'-[4-(p-ethylbenzenesulfonyloxy)phenyl]urea, N-[2-(benzenesulfonyloxy)phenyl]-N'-[4-(p-methoxybenzenesulfonyloxy)phenyl]urea, N-[2-(p-toluenesulfonyloxy)phenyl]-N'-[4-[benzenesulfonyloxy]phenyl]urea, N-[2-(p-toluenesulfonyloxy)phenyl]-N'-[4-(mesitylenesulfonyloxy)phenyl]urea, N-[2-(p-toluenesulfonyloxy)phenyl]-N'-[4-(1-naphthalenesulfonyloxy)phenyl]urea,

[0080] N-[2-(benzylsulfonyloxy)phenyl]-N'-[4-(benzylsulfonyloxy)phenyl]urea, N-[2-(phenylethanesulfonyloxy)phenyl]-N'-[4-(phenylethanesulfonyloxy)phenyl]urea, N-[2-(phenylpropanesulfonyloxy)phenyl]-N'-[4-(phenylpropanesulfonyloxy)phenyl]urea, N-[2-(p-methoxybenzylsulfonyloxy)phenyl]-N'-[4-(p-methoxybenzylsulfonyloxy)phenyl]urea,

[0081] N-[2-(ethanesulfonyloxy)phenyl]-N'-[4-(benzylsulfonyloxy)phenyl]urea, N-[2-(benzylsulfonyloxy)phenyl]-N'-[4-(methanesulfonyloxy)phenyl]urea, N-[2-(benzylsulfonyloxy)phenyl]-N'-[4-(butanesulfonyloxy)phenyl]urea,

[0082] N-[2-(methanesulfonyloxy)phenyl]-N'-[4-(methanesulfonyloxy)phenyl]urea, N-[2-(ethanesulfonyloxy)phenyl]-N'-[4-(ethanesulfonyloxy)phenyl]urea, N-[2-(1-propanesulfonyloxy)phenyl]-N'-[4-(1-propanesulfonyloxy)phenyl]urea, N-[2-(2-propanesulfonyloxy)phenyl]-N'-[4-(2-propanesulfonyloxy)phenyl]urea, N-[2-(butanesulfonyloxy)phenyl]-N' -[4-(butanesulfonyloxy)phenyl]urea, N-[2-(pentanesulfonyloxy)phenyl]-N'-[4-(pentanesulfonyloxy)phenyl]urea, N-[2-(hexanesulfonyloxy)phenyl]-N'-[4-(hexanesulfonyloxy)phenyl]urea, N-[2-(cyclohexanesulfonyloxy)phenyl]-N'-[4-(cyclohexanesulfonyloxy)phenyl]urea, N-[2-(dodecanesulfonyloxy)phenyl]-N'-[4-(dodecanesulfonyloxy)phenyl]urea,

[0083] N-[2-(methanesulfonyloxy)phenyl]-N'-[4-(propanesulfonyloxy)phenyl]urea, N-[2-(ethanesulfonyloxy)phenyl]-N'-[4-(propanesulfonyloxy)phenyl]urea, N-[2-(ethanesulfonyloxy)phenyl]-N'-[4-(butanesulfonyloxy)phenyl]urea,

[0084] N-[2-(benzenesulfonyloxy)phenyl]-N'-[3-(benzenesulfonyloxy)phenyl]urea, N-[2-(p-toluenesulfonyloxy)phenyl]-N'-[3-(p-toluenesulfonyloxy)phenyl]urea, N-[2-(m-toluenesulfonyloxy)phenyl]-N'-[3-(m-toluenesulfonyloxy)phenyl]urea, N-[2-(o-toluenesulfonyloxy)phenyl]-N'-[3-(o-toluenesulfonyloxy)phenyl]urea,

[0085] N-[2-(p-xylylenesulfonyloxy)phenyl]-N'-[3-(p-xylylenesulfonyloxy)phenyl]urea, N-[2-(m-xylylenesulfonyloxy)phenyl]-N'-[3-(m-xylylenesulfonyloxy)phenyl]urea, N-[2-(mesitylenesulfonyloxy)phenyl]-N'-[3-(sitylenesulfonyloxy)phenyl]urea,

[0086] N-[2-(1-naphthalenesulfonyloxy)phenyl]-N'-[3-(1-naphthalenesulfonyloxy)phenyl]urea, N-[2-(2-naphthalenesulfonyloxy)phenyl]-N'-[3-(2-naphthalenesulfonyloxy)phenyl]urea,

[0087] N-[2-(p-ethylbenzenesulfonyloxy)phenyl]-N'-[3-(p-ethylbenzenesulfonyloxy)phenyl]urea, N-[2-(p-propylbenzenesulfonyloxy)phenyl]-N'-[3-(p-propylbenzenesulfonyloxy)phenyl]urea, N-[2-(p-isopropylbenzenesulfonyloxy)phenyl]-N'-[3-(p-isopropylbenzenesulfonyloxy)phenyl]urea, N-[2-(pt-butylbenzenesulfonyloxy)phenyl]-N'-[3-(pt-butylbenzenesulfonyloxy)phenyl]urea,

[0088] N-[2-(p-methoxybenzenesulfonyloxy)phenyl]-N'-[3-(p-methoxybenzenesulfonyloxy)phenyl]urea, N-[2-(m-methoxybenzenesulfonyloxy)phenyl]-N'-[3-(m-methoxybenzenesulfonyloxy)phenyl]urea, N-[2-(o-methoxybenzenesulfonyloxy)phenyl]-N'-[3-(o-methoxybenzenesulfonyloxy)phenyl]urea, N-[2-(m,p-dimethoxybenzenesulfonyloxy)phenyl]-N' -[3-(m,p-dimethoxybenzenesulfonyloxy)phenyl]urea, N-[2-(p-ethoxybenzenesulfonyloxy)phenyl]-N'-[3-(p-ethoxybenzenesulfonyloxy)phenyl]urea, N-[2-(p-propoxybenzenesulfonyloxy)phenyl]-N'-[3-(p-propoxybenzenesulfonyloxy)phenyl]urea, N-[2-(p-butoxybenzenesulfonyloxy)phenyl]-N'-[3-(p-butoxybenzenesulfonyloxy)phenyl]urea,

[0089] N-[2-(p-cumylbenzylsulfonyloxy)phenyl]-N'-[3-(p-cumylbenzylsulfonyloxy)phenyl]urea, N-[2-(p-cumylbenzenesulfonyloxy)phenyl]-N'-[3-(p-cumylbenzenesulfonyloxy)phenyl]urea, N-[2-(o-phenylbenzenesulfonyloxy)phenyl]-N'-[3-(o-phenylbenzenesulfonyloxy)phenyl]urea, N-[2-(p-phenylbenzenesulfonyloxy)phenyl]-N'-[3-(p-phenylbenzenesulfonyloxy)phenyl]urea,

[0090] N-[2-(p-chlorobenzenesulfonyloxy)phenyl]-N'-[3-(p-chlorobenzenesulfonyloxy)phenyl]urea,

[0091] N-[2-(ethanesulfonyloxy)phenyl]-N'-[3-(benzenesulfonyloxy)phenyl]urea, N-[2-(ethanesulfonyloxy)phenyl]-N'- [3-(p-toluenesulfonyloxy)phenyl]urea, N-[2-(benzenesulfonyloxy)phenyl]-N'-[3-(ethanesulfonyloxy)phenyl]urea, N-[2-(benzenesulfonyloxy)phenyl]-N'-[3-(benzylsulfonyloxy)phenyl]urea, N-[2-(benzenesulfonyloxy)phenyl]-N'-[3-(p-toluenesulfonyloxy)phenyl]urea, N-[2-(benzenesulfonyloxy)phenyl]-N'-[3-(o-toluenesulfonyloxy)phenyl]urea, N-[2-(benzenesulfonyloxy)phenyl]-N'-[3-(o-toluenesulfonyloxy)phenyl]urea, N-[2-(benzenesulfonyloxy)phenyl N-[2-(benzenesulfonyloxy)phenyl]-N'-[3-(p-methoxybenzenesulfonyloxy)phenyl]urea, N-[2-(p-toluenesulfonyloxy)phenyl]-N'-[3-(benzenesulfonyloxy)phenyl]urea, N-[2-(p-toluenesulfonyloxy)phenyl]-N'-[3-(mesitylenesulfonyloxy)phenyl]urea, N-[2-(p-toluenesulfonyloxy)phenyl]-N'-[3-(1-naphthalenesulfonyloxy)phenyl]urea,

[0092] N-[2-(benzylsulfonyloxy)phenyl]-N'-[3-(benzylsulfonyloxy)phenyl]urea, N-[2-(phenylethanesulfonyloxy)phenyl]-N'-[3-(phenylethanesulfonyloxy)phenyl]urea, N-[2-(phenylpropanesulfonyloxy)phenyl]-N'-[3-(phenylpropanesulfonyloxy)phenyl]urea, N-[2-(p-methoxybenzylsulfonyloxy)phenyl]-N'-[3-(p-methoxybenzylsulfonyloxy)phenyl]urea,

[0093] N-[2-(ethanesulfonyloxy)phenyl]-N'-[3-(benzylsulfonyloxy)phenyl]urea, N-[2-(benzylsulfonyloxy)phenyl]-N'-[3-(methanesulfonyloxy)phenyl]urea, N-[2-(benzylsulfonyloxy)phenyl]-N'-[3-(butanesulfonyloxy)phenyl]urea,

[0094] N-[2-(methanesulfonyloxy)phenyl]-N'-[3-(methanesulfonyloxy)phenyl]urea, N-[2-(ethanesulfonyloxy)phenyl]-N'-[3-(ethanesulfonyloxy)phenyl]urea, N-[2-(1-propanesulfonyloxy)phenyl]-N'-[3-(1-propanesulfonyloxy)phenyl]urea, N-[2-(2-propanesulfonyloxy)phenyl]-N'-[3-(2-propanesulfonyloxy)phenyl]urea, N-[2-(butanesulfonyloxy)phenyl]-N' -[3-(butanesulfonyloxy)phenyl]urea, N-[2-(pentanesulfonyloxy)phenyl]-N'-[3-(pentanesulfonyloxy)phenyl]urea, N-[2-(hexanesulfonyloxy)phenyl]-N'-[3-(hexanesulfonyloxy)phenyl]urea, N-[2-(cyclohexanesulfonyloxy)phenyl]-N'-[3-(cyclohexanesulfonyloxy)phenyl]urea, N-[2-(dodecanesulfonyloxy)phenyl]-N'-[3-(dodecanesulfonyloxy)phenyl]urea,

[0095] N-[2-(methanesulfonyloxy)phenyl]-N'-[3-(propanesulfonyloxy)phenyl]urea, N-[2-(ethanesulfonyloxy)phenyl]-N'-[3-(propanesulfonyloxy)phenyl]urea, N-[2-(ethanesulfonyloxy)phenyl]-N'-[3-(butanesulfonyloxy)phenyl]urea, and the like.

[0096] <Method for producing the compound represented by formula (1)> The compound represented by the above general formula (1) can be synthesized by reacting a compound represented by the following general formula (4) with an aromatic amine compound represented by the following general formula (5). In addition, the compound represented by the above general formula (1) can be synthesized by reacting a compound represented by the following general formula (6) with an aromatic amine compound represented by the following general formula (7).

[0097] [ka]

[0098] [ka]

[0099] In the general formulas (4) and (5), R 1 represents an alkyl group or an aryl group. 1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 1 may be the same or different. 2 is a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms, an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms substituted with a halogen atom, or an aryl group having 6 to 12 carbon atoms.

[0100] [ka]

[0101] [ka] In the general formulas (6) and (7), R 1 represents an alkyl group or an aryl group, R represents an alkyl group, and n represents an integer of 0 to 3.

[0102] For example, it can be synthesized by the following method. [Process 1] 3-[(R) n -PhSO 3 ]-Ph-NH 2 / Deoxidizer + XCOOR 1 → 3-[(R) n -PhSO 3 ]-Ph-NHCOOR 1 +HX Deoxidizer [Process 2] 3-[(R) n -PhSO 3 ]-Ph-NHCOOR 1 +3-[(R) n -PhSO 3 ]-Ph-NH 2 / base →3-{[(R) n -PhSO 3 ]-Ph-NH} 2 =CO+R1OH In the above formula, R 1 represents an alkyl group or an aryl group, R represents an alkyl group, Ph represents a phenyl group, and n represents an integer of 0 to 3.

[0103] XCOOR used in step 1 of the above synthesis method 1 is a halogenated carbonate or diester carbonate, X is chlorine, bromine, OMe, OEt, OPro or OPh, R 1 is a Me group, an Et group, a Pro group, a Ph group, etc. Me group represents a methyl group, Et group represents an ethyl group, Pro group represents a propyl group, and pH represents a phenyl group. Particularly preferred are methyl monochlorocarbonate, ethyl monochlorocarbonate, phenyl monochlorocarbonate, diethyl carbonate, and diphenyl carbonate.

[0104] R 1 The alkyl group of R is the same as the alkyl group of R.

[0105] In the reaction, an organic base or an inorganic base is used as an acid scavenger and a base. Inorganic bases include, for example, LiOH, NaOH, KOH, NaHCO 3 , K.H.C.O. 3 , Na 2 CO 3 , K 2 CO 3 , MeONa, EtONa, etc. The organic base is, for example, trimethylamine, triethylamine, tributylamine, pyridine, N,N-dimethylpyridine, 1,8-diazabicyclo[5,4,0]undecane-7-ene (DBU), or the like. 2 CO 3 , triethylamine, pyridine, N,N-dimethylpyridine, and 1,8-diazabicyclo[5,4,0]undecane-7-ene (DBU).

[0106] 3-[(R) n -PhSO 3 ]-Ph-NH 2 can be synthesized by direct O-sulfonylation of 3-hydroxyaniline, or can be readily obtained by O-sulfonylation of a nitrophenol compound followed by reduction of the nitro group.

[0107] 3-[(R) n -PhSO 3 ]-Ph-NH 2 Examples of the sulfonyloxyaniline include 3-benzenesulfonyloxyaniline, 3-(p-toluene)sulfonyloxyaniline, 3-(m-toluene)sulfonyloxyaniline, 3-(o-toluene)sulfonyloxyaniline, 3-(p-xylene)sulfonyloxyaniline, and 3-mesitylenesulfonyloxyaniline. Preferred are 3-benzenesulfonyloxyaniline and 3-(p-toluene)sulfonyloxyaniline.

[0108] In general, an aprotic solvent can be used as the reaction solvent, and the reaction is carried out at a temperature of 0° C. to 180° C. In the present invention, the reaction is carried out at a temperature in the range of, for example, 0° C. to 180° C., preferably 10° C. to 100° C., and the solvent and reaction temperature are suitably selected in accordance with the boiling point of the solvent and the stability of the reaction product.

[0109] Examples of aprotic solvents include aromatic hydrocarbons such as benzene, toluene, xylene, and mesitylene; halogenated hydrocarbons such as dichloromethane, chloroform, dichloroethane, and chlorobenzene; acetates such as ethyl acetate, propyl acetate, butyl acetate, phenyl acetate, and benzyl acetate; ether compounds such as diethyl ether, dimethoxyethane, diethoxyethane, diethylene glycol dimethyl ether, dioxane, tetrahydrofuran, and anisole; ketone compounds such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; acetonitrile, dimethylsulfamide, dimethylsulfoxide, and dimethylimidazolidine.

[0110] In step 2, 3-[(R) n -PhSO 3 ]-Ph-NHCOOR and 3-[(R) n -PhSO 3 ]-Ph-NH 2 The reaction is carried out by reacting in the presence of a base. The base, reaction solvent, and reaction temperature used in step 2 may be the same as those used in step 1.

[0111] In order to simplify the reaction procedure, 2 or more equivalents of 3-[(R) n -PhSO 3 ]-Ph-NH 2 It is also possible to carry out steps 1 and 2 simultaneously by using the above.

[0112] Various methods for introducing urea groups have been proposed, such as the use of metal catalysts such as palladium or molybdenum, or the introduction of carbon monoxide using carbonylbisimidazole to form urea groups, but these methods are not necessarily industrially feasible because the catalysts and reagents are expensive and the operations are complicated.

[0113] The N,N'-diphenylurea derivatives represented by the above general formulas (1) to (3) can also be synthesized by reacting dihydroxydiphenylurea represented by the following general formula (8) with a sulfonating agent represented by the following general formula (9) in the presence of an aprotic solvent. In particular, when synthesizing a symmetric compound, the above production method in which dihydroxydiphenylurea is synthesized and then O-sulfonylated is the most versatile and economical.

[0114] [ka] In the above general formula (8), A 1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 1 may be the same or different.

[0115] [ka] In the above general formula (9), R 2 is a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms, an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms substituted with a halogen atom, or an aryl group having 6 to 12 carbon atoms. X is a halogen atom.

[0116] In addition, the above-mentioned production method has industrial advantages in that the reaction can be carried out smoothly in a slurry state in the dihydroxydiphenylurea production process by selecting a reaction solvent, and further, the next reaction step can be carried out continuously without isolating dihydroxydiphenylurea.

[0117] The N,N'-diphenylurea derivatives represented by the above general formulas (1) to (3) can also be synthesized by reacting an aminophenol compound represented by the following general formula (8-1) with urea in the presence of an aprotic solvent, and then reacting with a sulfonating agent represented by the above general formula (9). The process of reacting an aminophenol compound represented by the general formula (8-1) with urea in the presence of an aprotic solvent allows the production process of dihydroxydiphenylurea to proceed smoothly, and makes it possible to carry out the reaction in a slurry state. Furthermore, it becomes possible to carry out the process of reacting a sulfonating agent represented by the general formula (9) continuously without isolating dihydroxydiphenylurea.

[0118] [ka] In the above general formula (8-1), A1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

[0119] The reaction for synthesizing dihydroxydiphenylurea from aminophenol and urea is carried out in an aprotic solvent at a reaction temperature of 80°C to 200°C, preferably 125°C to 180°C.

[0120] Aminophenols are 2-aminophenol, 3-aminophenol, 4-aminophenol, 2-amino-5-methylphenol, 2-amino-4-methylphenol, 2-amino-6-methylphenol, 2-amino-4,5-dimethylphenol, 2-methyl-5-aminophenol, 3-methyl-5-aminophenol, 2,3-dimethyl-5-aminophenol, 2,4-dimethyl-5-aminophenol, 2,6-dimethyl-5-aminophenol, 3,4-dimethyl-5-aminophenol, 2-methyl-4-aminophenol, Examples include phenol, 3-methyl-4-aminophenol, and 2,6-dimethyl-4-aminophenol.

[0121] Examples of aprotic solvents include hydrocarbons such as tetralin, benzene, toluene, xylene, and mesitylene; halogenated hydrocarbons such as trichloroethylene, chlorobenzene, and dichlorobenzene; acetates such as ethyl acetate, propyl acetate, isobutyl acetate, butyl acetate, isoamyl acetate, amyl acetate, hexyl acetate, phenyl acetate, and benzyl acetate; ether compounds such as diethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, dioxane, tetrahydrofuran, and anisole; ketone compounds such as methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, acetophenone, and benzophenone; tertiary amines such as tributylamine, pyridine, dimethylpyridine, and diazabicycloundecene; and aprotic polar solvents such as acetonitrile, benzonitrile, dimethylformamide, dimethylsulfoxide, dimethylimidazolidine, and dimethylacetamide. Two or more of these solvents may be used in combination.

[0122] Preferred solvents are aprotic water-insoluble solvents having a boiling point of 110° C. or higher, and particularly preferred are acetates having a boiling point of butyl acetate or higher, and aromatic hydrocarbons such as toluene and xylene. Methods for treating after completion of the reaction include (1) cooling the reaction mixture and filtering to isolate dihydroxydiphenylurea and subjecting it to the next reaction, and (2) cooling to the next reaction temperature and subjecting the reaction mixture to the next reaction as it is without isolating dihydroxydiphenylurea.

[0123] Next, the O-sulfonation reaction of dihydroxydiphenylurea can be carried out by adding a sulfonating agent dropwise to a reaction solution consisting of dihydroxydiphenylurea, a scavenger, and an aprotic solvent, or alternatively, it may be carried out by adding a scavenger dropwise to a reaction solution consisting of dihydroxydiphenylurea, a sulfonating agent, and an aprotic solvent. The O-sulfonation reaction is carried out in the presence of a deoxidizing agent at a reaction temperature in the range of 0°C to 200°C, preferably 10°C to 150°C.

[0124] O-sulfonation is carried out using a sulfonyl halide, etc., and as the sulfonyl halide, a sulfonyl chloride is preferred. Examples of the sulfonyl halide include ethanesulfonyl chloride, ethanesulfonyl chloride, n-propanesulfonyl chloride, i-propanesulfonyl chloride, butanesulfonyl chloride, benzylsulfonyl chloride, benzenesulfonyl chloride, p-toluenesulfonyl chloride, o-toluenesulfonyl chloride, p-xylenesulfonyl chloride, mesitylenesulfonyl chloride, p-ethylbenzenesulfonyl chloride, p-methoxybenzenesulfonyl chloride, p-chlorobenzenesulfonyl chloride, 1-naphthalenesulfonyl chloride, and 2-naphthalenesulfonyl chloride.

[0125] Examples of the acid scavenger include organic bases such as trimethylamine, triethylamine, tributylamine, pyridine, and dimethylaminopyridine; inorganic bases such as lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, potassium hydrogen carbonate, sodium hydrogen carbonate, sodium carbonate, potassium carbonate, and calcium carbonate; and bases such as sodium hydride, sodium methoxide, and sodium ethoxide.

[0126] The solvent used in the O-sulfonation step of dihydroxydiphenylurea is an aprotic solvent, and particularly preferred are acetates such as butyl acetate, isoamyl acetate, amyl acetate, and hexyl acetate used in the previous step, and aromatic hydrocarbons such as toluene, xylene, and mesitylene. As the reaction solvent, the solvent used in the previous step may be used alone, or a mixed solvent of two or more kinds, or a two-phase solvent system of water and a water-insoluble aprotic solvent may be used.

[0127] In carrying out the reaction, the solvent and the reaction temperature are suitably selected depending on the reaction method, taking into consideration the boiling point of the solvent, the physical properties of the sulfonating agent, and the stability of the reaction product. After the reaction is completed, water is added to the reaction solution to wash away the deoxidizing agent and the like. Furthermore, when high purity is required, washing or recrystallization of the crystals may be carried out using aromatic hydrocarbons such as benzene and toluene, acetates such as ethyl acetate and isoamyl acetate, and alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol.

[0128] The content of the developer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 1 part by weight to 20 parts by weight, more preferably 2 parts by weight to 10 parts by weight, relative to 1 part by weight of the leuco dye.

[0129] <<Leuco dye>> The leuco dye is not particularly limited and can be appropriately selected according to the purpose from those used in thermal recording media. Suitable examples include leuco compounds of dyes such as triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, spiropyran-based, and indolinophthalide-based dyes.

[0130] The leuco dye is not particularly limited and can be appropriately selected depending on the purpose. For example, 3,3-bis(p-dimethylaminophenyl)-phthalide, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis(p-dimethylaminophenyl)-6-diethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)-6-chlorophthalide, 3,3-bis(p-dibutylaminophenyl)phthalide, 3-cyclohexylamino-6-chlorofluoran, 3-dimethylamino-5,7-dimethylfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-7-methylfluoran, 3-diethylamino-7,8-benzfluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-(Np-tolyl-N-ethyl)phenyl ... 2-{N-(3'-trifluoromethylphenyl)amino}-6-diethylaminofluoran, 2-{3,6-bis(diethylamino)-9-(o-chloroanilino)xanthylenhylbenzoic acid lactam}, 3-diethylamino-6-methyl-7-(m-trichloromethylanilino)fluoran, 3-diethylamino-7-(o-chloroanilino)fluoran, 3- Pyrrolidino-6-methyl-7-anilinofluoran, 3-di-n-butylamino-7-o-chloroanilino)fluoran, 3-N-methyl-N,n-amylamino-6-methyl-7-anilinofluoran, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-(N,N-diethylamino)-5-methyl-7-(N,N-Dibenzylamino)fluoran, Benzoyl leuco methylene blue, 6'-chloro-8'-methoxy-benzoindolino-spiropyran, 6'-bromo-3'-methoxy-benzoindolino-spiropyran, 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-chlorophenyl)phthalide, 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-nitrophenyl)phthalide, 3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2'-methoxy-5'-methyl phenyl)phthalide, 3-(2'-methoxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-5'-methylphenyl)phthalide, 3-(N-ethyl-N-tetrahydrofurfuryl)amino-6-methyl-7-anilinofluoran, 3-N-ethyl-N-(2-ethoxypropyl)amino-6-methyl-7-anilinofluoran, 3-N-methyl-N-isobutyl-6-methyl-7-anilinofluoran, 3-morpholino-7-(N-propyl-trifluoromethylanilino)fluoran, 3-pyrrolidino-7-trifluoro Methylanilinofluoran, 3-diethylamino-5-chloro-7-(N-benzyl-trifluoromethylanilino)fluoran, 3-pyrrolidino-7-(di-p-chlorophenyl)methylaminofluoran, 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluoran, 3-(N-ethyl-p-toluidino)-7-(α-phenylethylamino)fluoran, 3-diethylamino-7-(o-methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7-(α-phenylethylamino)fluoran, 3 -Diethylamino-7-piperidinofluoran, 2-chloro-3-(N-methyltoluidino)-7-(pn-butylanilino)fluoran, 3-di-n-butylamino-6-methyl-7-anilinofluoran, 3,6-bis(dimethylamino)fluorenespiro(9,3')-6'-dimethylaminophthalide, 3-(N-benzyl-N-cyclohexylamino)-5,6-benzo-7-α-naphthylamino-4'-bromofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-diethylamino-6-methyl-7-mesitidino-4',5'-Benzofluoran, 3-N-methyl-N-isopropyl-6-methyl-7-anilinofluoran, 3-N-ethyl-N-isoamyl-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-(2',4'-dimethylanilino)fluoran, 3-morpholino-7-(N-propyl-trifluoromethylanilino)fluoran, 3-pyrrolidino-7-trifluoromethylanilinofluoran, 3-diethylamino-5-chloro-7 -(N-benzyl-trifluoromethylanilino)fluoran, 3-pyrrolidino-7-(di-p-chlorophenyl)methylaminofluoran, 3-diethylamino-5-chloro-(α-phenylethylamino)fluoran, 3-(N-ethyl-p-toluidino)-7-(α-phenylethylamino)fluoran, 3-diethylamino-7-(o-methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7-(α-phenylethylamino)fluoran 3-(N-phenylamino)fluoran, 3-diethylamino-7-piperidinofluoran, 2-chloro-3-(N-methyltoluidino)-7-(pN-butylanilino)fluoran, 3,6-bis(dimethylamino)fluorenespiro(9,3')-6'-dimethylaminophthalide, 3-(N-benzyl-N-cyclohexylamino)-5,6-benzo-7-α-naphthylamino-4'-bromofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3 -N-ethyl-N-(-2-ethoxypropyl)amino-6-methyl-7-anilinofluoran, 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-mesitidino-4',5'-benzofluoran, 3-p-dimethylaminophenyl)-3-{1,1-bis(p-dimethylaminophenyl)ethylene-2-yl}phthalide, 3-(p-dimethylaminophenyl)-3-{1,1-bis(p-dimethylaminophenyl)ethylene-2-yl}-6-dimethylaminophthalide, 3-(p-dimethylaminophenyl)-3-(1-p-dimethylaminophenyl-1-phenylethylene-2-yl)phthalide, 2-ortho-chloroanilino-6-diethylaminofluoran, 2-anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-(N-ethyl-Np-tolyl)aminofluoran, 3-N-cyclohexyl-N-methylamino-6-methyl-7-anilinofluoran, 3-(p-dimethylaminophenyl)-3-(1-p-dimethylaminophenyl-1-p-chlorophenylethylene-2-yl)-6-dimethylaminophthalide, 3-(4'-dimethylamino-2'-methoxy)-3-(1”-p-dimethylaminophenyl-1”-p-chlorophenyl-1”,3”-butadiene-4”-yl)betaine benzophthalide, 3-(4'-dimethylamino-2'-benzyloxy)-3-(1"-p-dimethylaminophenyl-1"-phenyl-1",3"-butadien-4"-yl)benzophthalide, 3-dimethylamino-6-dimethylamino-fluorene-9-spiro-3'-(6'-dimethylamino)phthalide, 3,3-bis(2-(p-dimethylaminophenyl)-2-p-methoxyphenyl)ethenyl)-4,5,6,7-tetramethylphenyl Examples of the phthalic acid include trachlorophthalide, 3-bis{1,1-bis(4-pyrrolidinophenyl)ethylene-2-yl}-5,6-dichloro-4,7-dibromophthalide, bis(p-dimethylaminostyryl)-1-naphthalenesulfonylmethane, bis(p-dimethylaminostyryl)-1-p-tolylsulfonylmethane, and 6'-(diethylamino)-2'-(2-fluoroanilino)spiro[phthalide-3,9'-xanthene]. These may be used alone or in combination of two or more.

[0131] The content of the electron donating compound is not particularly limited and can be appropriately selected depending on the purpose, but is preferably from 5% by mass to 40% by mass, and more preferably from 10% by mass to 30% by mass, based on the total amount of the thermosensitive recording layer.

[0132] <<Styrene-acrylic resin>> The styrene-acrylic resin may be a synthetic product or a commercially available product. The synthetic method may be, for example, emulsion polymerization, dispersion polymerization, suspension polymerization, pulverization or solution / bulk polymerization, followed by post-emulsification. Examples of the commercially available products include trade names: PDX-7357, PDX-7616A, PDX-7732, PDX-7741, PDX-7787, PDX-7734, PDX-7777, PDX-7615, HPD-71, and HPD-196 (all manufactured by BASF), trade names: EK-15 and EK-61 (all manufactured by Saiden Chemical Industries, Ltd.), and trade names: A-2092 and XK-110 (all manufactured by DSM Coating Resins).

[0133] The styrene-acrylic resin is preferably a resin emulsion. The resin emulsion refers to a state in which resin particles are dispersed in an aqueous medium, regardless of whether the resin particles are solid or liquid. The aqueous medium refers to a medium containing water or a hydrophilic solvent as a component.

[0134] Methods for dispersing the resin particles in an aqueous medium include a forced emulsification method using a dispersant, a self-emulsification method using a resin having an anionic group, etc. In the case of the forced emulsification method, the dispersant may remain in the image formed by the ink, which may reduce the strength of the image, so it is preferable to use the self-emulsification method.

[0135] The content of the styrene-acrylic resin is not particularly limited and can be appropriately selected depending on the purpose, but is preferably from 1.0% by mass to 50.0% by mass, more preferably from 10.0% by mass to 50.0% by mass, and even more preferably from 20.0% by mass to 40.0% by mass, based on the entire thermosensitive recording layer.

[0136] Other resins other than the styrene-acrylic resin may be added as necessary. Examples of the other resins include polyvinyl alcohol resin, starch or its derivatives; cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, and ethyl cellulose; water-soluble polymers such as sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acrylic acid ester copolymer, acrylamide-acrylic acid ester-methacrylic acid terpolymer, styrene-maleic anhydride copolymer alkali salt, isobutylene-maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and casein; emulsions such as polyvinyl acetate resin, polyurethane resin, polyacrylic acid, polyacrylic acid ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, and ethylene-vinyl acetate copolymer; latexes such as styrene-butadiene copolymer and styrene-butadiene-acrylic copolymer. These may be used alone or in combination of two or more. When the other resin is contained, the content of the other resin is preferably 100 parts by mass or less, and more preferably 50 parts by mass or less, per 100 parts by mass of the styrene-acrylic resin from the viewpoint of warm water resistance.

[0137] <<Photothermal conversion materials>> The photothermal conversion material is a material that absorbs laser light and converts it into heat, and can be roughly divided into inorganic materials and organic materials. Examples of the inorganic material include carbon black, metal borides, and particles of at least one of metal oxides such as Ge, Bi, In, Te, Se, and Cr. Among these, materials that absorb light in the near-infrared wavelength region and absorb light in the visible wavelength region are preferred, and the metal borides and metal oxides are more preferred. As the metal borides and metal oxides, at least one selected from, for example, hexaborides, tungsten oxide compounds, antimony tin oxide (ATO), indium tin oxide (ITO), and zinc antimonate is preferred. The hexaboride is, for example, LaB 6 , CeB 6 , PrB 6 , NdB 6 , GdB 6 , TbB 6 , DyB 6 , HoB 6 , Y.B. 6 , SmB 6 ,EuB 6 , ErB 6 , TmB 6 , YbB 6 , LuB 6 , SrB 6 , CaB 6 , (La,Ce)B 6 etc. The tungsten oxide compound may be, for example, fine particles of tungsten oxide represented by the general formula: WyOz (wherein W is tungsten, O is oxygen, and 2.2≦z / y≦2.999), as described in WO 2005 / 037932 and JP 2005-187323 A, or fine particles of tungsten oxide represented by the general formula: MxWyOz (wherein M is H, He, an alkali metal, an alkaline earth metal, a rare earth element, Mg, Zr, Cr, Mn, Fe, and fine particles of composite tungsten oxide represented by the formula (I) (wherein W is tungsten, O is oxygen, and 0.001≦x / y≦1, 2.2≦z / y≦3.0) and the like. Among these, cesium-containing tungsten oxide is particularly preferred because it has a high absorption in the near infrared region and a low absorption in the visible region. Among antimony tin oxide (ATO), indium tin oxide (ITO), and zinc antimonate, ITO is particularly preferable because it has high absorption in the near infrared region and low absorption in the visible region. These are formed in layers by vacuum deposition or by bonding particulate materials with resin or the like. As the organic material, various dyes can be appropriately used depending on the light wavelength to be absorbed, but when a semiconductor laser is used as the light source, a near-infrared absorbing dye having an absorption peak in the vicinity of 600 nm to 1,200 nm is used.Specific examples include cyanine dyes, quinone dyes, quinoline derivatives of indonaphthol, phenylenediamine nickel complexes, and phthalocyanine dyes. The photothermal conversion materials may be used alone or in combination of two or more kinds. The light-heat conversion material may be contained in the heat-sensitive recording layer or in a layer other than the heat-sensitive recording layer. When the light-heat conversion material is contained in a layer other than the heat-sensitive recording layer, it is preferable to provide a light-heat conversion layer adjacent to the heat-sensitive recording layer. The content of the photothermal conversion material is preferably from 0.1% by mass to 10% by mass, and more preferably from 0.3% by mass to 5% by mass, based on the heat-sensitive recording layer.

[0138] <<Other ingredients>> Examples of the other components include auxiliary additives, heat-fusible substances, lubricants, fillers, ultraviolet absorbers, antioxidants, sensitizers, light stabilizers, and crosslinking agents.

[0139] As the auxiliary additive, for example, various hindered phenol compounds or hindered amine compounds which have electron accepting properties but relatively little color-developing ability may be added. Examples of the auxiliary additives include 2,2'-methylenebis(4-ethyl-6-tertiary butylphenol), 4,4'-butylidenebis(6-tertiary butyl-2-methylphenol), 1,1,3-tris(2-methyl-4-hydroxy-5-tertiary butylphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, 4,4'-thiobis(6-tertiary butyl-2-methylphenol), Examples of suitable bisphenols include tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate, tetrakis(1,2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate, and the like. These may be used alone or in combination of two or more.

[0140] -Thermofusible substance- Examples of the heat-fusible substance include fatty acids such as stearic acid and behenic acid; fatty acid amides such as stearic acid amide and palmitic acid amide; fatty acid metal salts such as zinc stearate, aluminum stearate, calcium stearate, zinc palmitate and zinc behenate; p-benzylbiphenyl, terphenyl, triphenylmethane, benzyl p-benzyloxybenzoate, β-benzyloxynaphthalene, β-phenyl naphthoate, 1-hydroxy-2-naphthoate, and the like. Phenyl terephthalate, methyl 1-hydroxy-2-naphthoate, diphenyl carbonate, glycol carbonate, dibenzyl terephthalate, dimethyl terephthalate, 1,4-dimethoxynaphthalene, 1,4-diethoxynaphthalene, 1,4-dibenzyloxynaphthalene, 1,2-diphenoxyethane, 1,2-bis(3-methylphenoxy)ethane, 1,2-bis(4-methylphenoxy)ethane, 1,4-diphenoxy-2-butene, 1,2-bis(4-methoxyphenyl) ruthio)ethane, dibenzoylmethane, 1,4-diphenylthiobutane, 1,4-diphenylthio-2-butene, 1,3-bis(2-vinyloxyethoxy)benzene, 1,4-bis(2-vinyloxyethoxy)benzene, p-(2-vinyloxyethoxy)biphenyl, p-aryloxybiphenyl, p-propargyloxybiphenyl, dibenzoyloxymethane, dibenzoyloxypropane, dibenzyl disulfide, 1,1-diphenylethanol, 1, Examples of such compounds include 1-diphenylpropanol, p-benzyloxybenzyl alcohol, 1,3-phenoxy-2-propanol, N-octadecylcarbamoyl-p-methoxycarbonylbenzene, N-octadecylcarbamoylbenzene, 1,2-bis(4-methoxyphenoxy)propane, 1,5-bis(4-methoxyphenoxy)-3-oxapentane, dibenzyl oxalate, bis(4-methylbenzyl) oxalate, and bis(4-chlorobenzyl) oxalate. These compounds may be used alone or in combination of two or more.

[0141] - Lubricant - Examples of the lubricant include higher fatty acids or metal salts thereof, higher fatty acid amides, higher fatty acid esters, animal waxes, vegetable waxes, mineral waxes, petroleum waxes, synthetic waxes, etc. These may be used alone or in combination of two or more.

[0142] -Filler- Examples of the filler include inorganic fine powders such as calcium carbonate, silica, zinc oxide, titanium oxide, zirconium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, kaolin, talc, surface-treated calcium, and surface-treated silica; and organic fine powders such as urea-formaldehyde resin, styrene-methacrylic acid copolymer, polystyrene resin, and vinylidene chloride resin. These may be used alone or in combination of two or more. The content of the filler is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.4 parts by mass or less, and more preferably 0.2 parts by mass or less, per 1 part by mass of the binder resin.

[0143] -Crosslinking agent- The crosslinking agent is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include glyoxal derivatives, methylol derivatives, epichlorohydrin, polyamide epichlorohydrin, epoxy compounds, aziridine compounds, hydrazine, hydrazide derivatives, oxazoline derivatives, carbodiimide derivatives, etc. These may be used alone or in combination of two or more.

[0144] -Ultraviolet absorber- The ultraviolet absorbing agent is not particularly limited and may be appropriately selected depending on the purpose. Examples of the ultraviolet absorbing agent include salicylic acid-based ultraviolet absorbing agents, benzophenone-based ultraviolet absorbing agents, and benzotriazole-based ultraviolet absorbing agents. Examples of the ultraviolet absorber include phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis(2-methoxy-4-hydroxy-5-benzoylphenyl)methane, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di ... di-tert-butylphenyl)chlorobenzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 2-{2'-hydroxy-3'-(3",4",5",6"-tetrahydrophthalimidomethyl)-5'-methylphenyl}benzotriazole, 2,2'-methylenebis{4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol}, 2-(2'-hydroxy-5'-methacryloxyphenyl)-2H-benzotriazole, 2-(3,5-di-t-amyl-2-hydroxyphenyl)benzotriazole, 2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole, 2-(5-methyl-2-hydroxyphenyl)benzotriazole, and the like. These may be used alone or in combination of two or more.

[0145] <Support> The shape, structure, size, material, etc. of the support are not particularly limited and can be appropriately selected depending on the purpose. The shape can be, for example, a flat plate or a sheet, the structure can be a single-layer structure or a laminated structure, and the size can be appropriately selected depending on the size of the thermal recording medium, etc.

[0146] As the support, for example, in addition to ordinary paper, synthetic paper, or plastic films such as polyethylene, transparent polyethylene terephthalate, polypropylene, and vinyl chloride can be used. When using these plastic films, the surface of the support may be subjected to surface treatment such as matte treatment and corona treatment in order to improve the fixation of the coating liquid. Among these, biaxially oriented polyethylene terephthalate sheets are preferable because they are excellent in strength, heat resistance, dimensional stability, and the like. Furthermore, white opaque films formed by adding white raw materials or fillers to these or foamed foam sheets can also be used. Laminates of the above materials can also be used, and representative examples include laminates of cellulose fibers and synthetic paper, cellulose fibers and plastic films, or plastic films and synthetic paper. The support is preferably a transparent film from the viewpoint of enabling visual confirmation of the contents in applications in the POS field for fresh foods, boxed lunches, prepared foods, etc. Here, transparency means that there is no particular problem if the haze (turbidity), which is an index of the transparency of the film, is about 10% or less, but in order to achieve the object of the present invention, 5% or less is more preferable. The average thickness of the support can be arbitrarily selected as necessary, and is preferably 3 μm to 500 μm, more preferably 10 μm to 100 μm, from the viewpoint of transparency and ease of processing. If the average thickness of the support is less than 3 μm, the strength is insufficient, and if it exceeds 500 μm, the transparency is reduced and the stiffness is too high, resulting in poor processability.

[0147] <Protective layer> The protective layer contains a binder resin and a crosslinking agent, and may further contain other components as required. The protective layer is preferably provided on the heat-sensitive recording layer.

[0148] The binder resin is not particularly limited and can be appropriately selected according to the purpose, and examples thereof include acrylic resin, polyvinyl alcohol resin, starch or derivatives thereof; cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, and ethyl cellulose; water-soluble polymers such as sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acrylic acid ester copolymer, styrene-acrylic copolymer, acrylamide-acrylic acid ester-methacrylic acid ternary copolymer, styrene-maleic anhydride copolymer alkali salt, isobutylene-maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and casein; emulsions such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, and ethylene-vinyl acetate copolymer; and latexes such as styrene-butadiene copolymer and styrene-butadiene-acrylic copolymer. These may be used alone or in combination of two or more.

[0149] The crosslinking agent is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include glyoxal derivatives, methylol derivatives, epichlorohydrin, polyamide epichlorohydrin, epoxy compounds, aziridine compounds, hydrazine, hydrazide derivatives, oxazoline derivatives, carbodiimide derivatives, etc. These may be used alone or in combination of two or more.

[0150] In addition, it is preferable to incorporate a pigment (filler) in the protective layer as necessary. Examples of the pigment used in the protective layer include inorganic pigments such as zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, rosewood, kaolin, aluminum hydroxide, and calcined kaolin, and organic pigments such as crosslinked polystyrene resin, urea resin, silicone resin, crosslinked polymethyl methacrylate resin, and melamine-formaldehyde resin. In addition to the above-mentioned resin, waterproofing agent and pigment, the protective layer may contain conventionally used auxiliary additives such as surfactants, heat-fusible substances, lubricants and pressure color-developing inhibitors.

[0151] The protective layer is not particularly limited and can be formed by a commonly known method. The average thickness of the protective layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably from 0.5 μm to 5 μm, and more preferably from 1 μm to 3 μm.

[0152] <Print layer> The printing layer is made of various colors, materials and thicknesses by printing ink, etc., and forms the background of the image printed on the thermal recording layer. By providing a printing layer, it is possible to write the product name, manufacturer name, ingredient list, etc. before packaging the product, and it is also possible to impart excellent design to the product. The print layer is preferably provided on the thermosensitive recording layer, between the support and the thermosensitive recording layer, or on the surface of the support opposite to the thermosensitive recording layer.

[0153] The print layer contains a coloring material, a binder resin, and a solvent, and further contains other components as required. The coloring material is not particularly limited and can be appropriately selected depending on the purpose. Pigments or dyes can be used.

[0154] The binder resin and other components may be the same as those in the heat-sensitive recording layer.

[0155] The printing layer is formed by gravure printing, flexographic printing, offset printing, UV printing, inkjet printing, or the like.

[0156] The average thickness of the printed layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.05 μm or more and 4 μm or less, and more preferably 0.1 μm or more and 2 μm or less.

[0157] <Other layers> The other layers are not particularly limited and may be appropriately selected depending on the purpose, and examples of the other layers include a back layer, an under layer, and a heat seal layer.

[0158] -Back layer- The back layer may be provided, if necessary, on the surface of the support on which the heat-sensitive recording layer is not provided. The back layer contains a filler and a binder resin, and may further contain other components such as a lubricant and a color pigment, if necessary. As the filler, for example, an inorganic filler or an organic filler can be used. Examples of the inorganic filler include carbonates, silicates, metal oxides, and sulfate compounds. Examples of the organic filler include silicone resin, cellulose, epoxy resin, nylon resin, phenol resin, polyurethane resin, urea resin, melamine resin, polyester resin, polycarbonate resin, styrene resin, acrylic resin, polyethylene resin, formaldehyde resin, and polymethyl methacrylate resin. The binder resin is not particularly limited and can be appropriately selected depending on the purpose. For example, the same binder resin as that of the thermosensitive recording layer can be used. The average thickness of the back layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably from 0.1 μm to 20 μm, and more preferably from 0.3 μm to 10 μm.

[0159] -Underlayer- The under layer is not particularly limited and may be appropriately selected depending on the purpose, but preferably contains a binder resin and thermoplastic hollow resin particles, and further contains other components as required.

[0160] The thermoplastic hollow resin particles are minute hollow particles which have a thermoplastic resin shell and contain air or other gases inside, and are already in a foamed state.

[0161] The average particle size (particle outer diameter) of the thermoplastic hollow resin particles is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.2 μm or more and 20 μm or less, and more preferably 2 μm or more and 5 μm or less. If the average particle size is smaller than 0.2 μm, it is technically difficult to make it hollow, and the undercoat layer does not function adequately. On the other hand, if the average particle size is larger than 20 μm, the surface smoothness after coating and drying decreases, making the coating of the thermosensitive recording layer non-uniform, and it is necessary to coat more than the required amount of thermosensitive recording layer forming liquid to make it uniform.

[0162] The hollow ratio of the thermoplastic hollow resin particles is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 50% to 95%, and more preferably 80% to 95%. If the hollow ratio is less than 30%, the heat insulation is insufficient, so that the thermal energy from the thermal head is released to the outside of the thermal recording medium through the support, and the sensitivity improvement effect is insufficient. The hollow ratio referred to here is the ratio of the outer diameter to the inner diameter (diameter of the hollow part) of the hollow particle, and is expressed by the following formula. Hollow ratio (%) = (inner diameter of hollow particle / outer diameter of hollow particle) x 100

[0163] The thermoplastic hollow resin particles have a thermoplastic resin as the shell as described above. The thermoplastic resin is not particularly limited and can be appropriately selected according to the purpose. For example, styrene-acrylic resin, polystyrene resin, acrylic resin, polyethylene resin, polypropylene resin, polyacetal resin, chlorinated polyether resin, polyvinyl chloride resin, copolymer resin mainly composed of vinylidene chloride and acrylonitrile, etc. can be mentioned. Among these, styrene-acrylic resin and copolymer resin mainly composed of vinylidene chloride and acrylonitrile are preferable in that they have a high hollow ratio, small variation in particle diameter, and are suitable for blade coating.

[0164] The coating amount of the plastic hollow particles is not particularly limited and can be appropriately selected according to the purpose. However, in terms of maintaining sensitivity and coating uniformity, 1 g to 3 g per 1 m of the support is required. 2 If it is less than 1 g / m, sufficient sensitivity cannot be obtained. Also, if it exceeds 3 g / m, a decrease in layer binding property occurs. 2 If it is less than 1 g / m, sufficient sensitivity cannot be obtained. Also, if it exceeds 3 g / m, a decrease in layer binding property occurs. 2 If it exceeds 3 g / m, a decrease in layer binding property occurs.

[0165] -Heat-sealing layer- Since the heat-sealing layer is formed by laminating a film of LDPE (low-density polyethylene) used as a sealant, it can be welded by heating the heat-sealing layers in a state where they are in close contact with each other. Utilizing this property, a packaging sheet formed in a bag shape can be sealed, that is, heat-sealed, by heating it in a similar state. Therefore, as long as it has the property of being heat-sealable, that is, a substance having heat-sealing property, the heat-sealing layer can be formed without being limited to LDPE. As the material having heat sealability, for example, films such as HDPE (high density polyethylene), CPP (non-oriented polypropylene), OPP (biaxially oriented polypropylene), and EVA (ethylene-vinyl acetate copolymer) are preferably used, but polyolefin resins such as polyethylene and polypropylene; vinyl acetate resins such as ethylene-vinyl acetate copolymer (olefin-vinyl acetate copolymer, etc.); acrylic resins such as ethylene-(meth)acrylic acid copolymer and ionomer (olefin-(meth)acrylic acid copolymer, or metal crosslinked product thereof, etc.) may also be used. Also, it may be formed using a known heat sealable adhesive. Since the packaged item can be seen, it is preferable to use a member that becomes transparent after formation. The average thickness of the heat seal layer is preferably from 5 μm to 50 μm, more preferably from 10 μm to 30 μm, from the viewpoints of transparency and seal strength.

[0166] (Thermal recording layer forming liquid) The thermosensitive recording layer forming liquid of the present invention contains a compound represented by any one of the above general formulas (1) to (3), a styrene-acrylic resin, and a solvent, and preferably contains a leuco dye, and further contains other components as necessary. The leuco dye, the compound represented by any one of the general formulas (1) to (3), the styrene-acrylic resin, and other components may be the same as those in the heat-sensitive recording layer.

[0167] Examples of the solvent include water, aromatic solvents, ester solvents, ketone solvents, alcohol solvents, aliphatic hydrocarbons, glycol solvents, petroleum-based solvents containing 1% or less of aromatic components, mainly composed of paraffin or naphthene, etc. These may be used alone or in combination of two or more. Examples of the aromatic solvent include benzene, toluene, and xylene. Examples of the ester solvent include methyl acetate, ethyl acetate, and isopropyl acetate. Examples of the ketone solvent include acetone and methyl ethyl ketone. Examples of the alcohol solvent include methanol, ethanol, isopropyl alcohol, and n-propyl alcohol. Examples of the aliphatic hydrocarbon include n-hexane, n-heptane, and cyclohexane. Examples of the glycol solvent include ethylene glycol and diethylene glycol.

[0168] The thermosensitive recording layer forming liquid of the present invention can be prepared by pulverizing and dispersing the leuco dye, the compound represented by any one of the above general formulas (1) to (3), the styrene-acrylic resin, and the other components described above using a dispersing machine such as a ball mill, an attritor, or a sand mill until the dispersed particle size is 0.1 μm or more and 3 μm or less, and then mixing the resulting mixture with other components as necessary.

[0169] (Method of manufacturing a thermal recording medium) The method for producing a thermosensitive recording medium of the present invention includes a thermosensitive recording layer forming step of forming a thermosensitive recording layer by applying the thermosensitive recording layer forming liquid of the present invention onto a support, and further includes other steps as necessary.

[0170] The application method is not particularly limited and can be appropriately selected depending on the purpose. Examples of the application method include blade coating, gravure coating, gravure offset coating, bar coating, roll coating, knife coating, air knife coating, comma coating, U comma coating, AKKU coating, smoothing coating, microgravure coating, reverse roll coating, 4- to 5-roll coating, dip coating, curtain coating, slide coating, and die coating.

[0171] The amount of the thermosensitive recording layer forming solution applied after drying is not particularly limited and can be appropriately selected depending on the purpose. 2 More than 20g / m 2 Less than 2 g / m is preferred. 2 More than 10g / m 2 The following is more preferred:

[0172] The embodiment of the thermosensitive recording medium of the present invention is not particularly limited and can be appropriately selected according to the purpose. For example, it may be used as a label as it is, or a layer for printing information such as characters, marks, pictures, bar codes, or two-dimensional codes such as QR Code (registered trademark) may be provided on the protective layer or the support. In addition, an adhesive layer may be provided on the side opposite to the side on which the thermosensitive recording layer is provided on the support. The shape of the thermosensitive recording medium of the present invention is not particularly limited and may be appropriately selected depending on the purpose. For example, it may be in the form of a label, a sheet, a roll, or the like.

[0173] <Application> The thermal recording medium of the present invention can be used in a wide range of applications, such as packaging films for various containers, such as PET bottles for soft drinks, metal cans for canned coffee, bottles for drinks, medicines, beer, etc., and packaging labels in the POS field for fresh foods, boxed lunches, prepared dishes, etc.

[0174] Here, an embodiment of the thermosensitive recording medium of the present invention will be described with reference to the drawings. In each drawing, the same components are given the same reference numerals, and duplicated explanations may be omitted. In addition, the number, position, shape, etc. of the following components are not limited to this embodiment, and may be any number, position, shape, etc. that is preferable for implementing the present invention.

[0175] <First embodiment> 1 is a schematic cross-sectional view showing an example of a thermosensitive recording medium according to the first embodiment. The thermosensitive recording medium according to the first embodiment has a thermosensitive recording layer 2 on a support 1.

[0176] <Second embodiment> 2 is a schematic cross-sectional view showing an example of a thermosensitive recording medium according to a second embodiment. The thermosensitive recording medium of the second embodiment has a thermosensitive recording layer 2 and a protective layer 3 on a support 1 in this order.

[0177] <Third embodiment> 3 is a schematic cross-sectional view showing an example of a thermosensitive recording medium according to a third embodiment. The thermosensitive recording medium of the third embodiment has a print layer 4 and a thermosensitive recording layer 2 on a support 1 in this order.

[0178] <Fourth embodiment> 4 is a schematic cross-sectional view showing an example of a thermosensitive recording medium according to a fourth embodiment. The thermosensitive recording medium according to the third embodiment has a print layer 4, a thermosensitive recording layer 2, and a protective layer 3 on a support 1 in this order.

[0179] <Fifth embodiment> 5 is a schematic cross-sectional view showing an example of a thermosensitive recording medium according to a fifth embodiment. The thermosensitive recording medium of the fifth embodiment has a thermosensitive recording layer 2 on a support 1, and a printing layer 4 on the side of the support 1 that does not have the thermosensitive recording layer.

[0180] Sixth embodiment 6 is a schematic cross-sectional view showing an example of a thermosensitive recording medium according to a sixth embodiment. The thermosensitive recording medium of the sixth embodiment has a thermosensitive recording layer 2 and a protective layer 3 in this order on a support 1, and has a printing layer 4 on the side of the support 1 that does not have the thermosensitive recording layer.

[0181] <Seventh embodiment> 7 is a schematic cross-sectional view showing an example of a thermosensitive recording medium according to a seventh embodiment. The thermosensitive recording medium of the seventh embodiment has a thermosensitive recording layer 2 and a printing layer 4 on a support 1 in this order.

[0182] <Eighth embodiment> 8 is a schematic cross-sectional view showing an example of a thermosensitive recording medium according to an eighth embodiment. The thermosensitive recording medium of the eighth embodiment has a thermosensitive recording layer 2, a protective layer 3, and a printing layer 4 on a support 1, in this order.

[0183] (Image recording method) In the image recording method of the present invention, an image is recorded on the heat-sensitive recording medium of the present invention by using a thermal head. The thermal head is not particularly limited in shape, structure, size, etc., and may be appropriately selected depending on the purpose. In this case, taking into consideration the storage resistance of the heat-sensitive recording layer and matching with a thermal head, it is more preferable to provide a protective layer on the heat-sensitive recording layer. However, if a color-developing agent system with high image and background preservation properties is applied, or if the heat-sensitive recording layer itself is endowed with matching properties with a thermal head using a filler, a lubricant, or the like, it is not necessarily necessary to provide a protective layer. In addition, when a filler is added to the protective layer or the thermal recording layer for the purpose of matching with the thermal head, the 50% cumulative volume particle size (D 50 If the particle size is too small, it will not be possible to achieve matching with a thermal head, which is the original purpose, and if the particle size is too large, the head will be more susceptible to wear and it will be difficult to impart transparency, so it is preferable that the particle size is in the range of about 0.25 μm to 0.75 μm, but this is not limitative.

[0184] In the image recording method of the present invention, an image is recorded by irradiating the thermosensitive recording medium of the present invention with laser light. Although various means for heating using laser light are conceivable, it is preferable to use laser light which can heat without contact. The laser light is not particularly limited and can be appropriately selected depending on the purpose. For example, 2 Gas lasers using gases such as YAG and YVO 4 Various commonly known laser devices can be used, such as solid-state lasers using solids such as those mentioned above, and semiconductor lasers using III-V semiconductors or IV-VI semiconductors. The device can be selected according to the purpose and method of use. Among these, CO 2 In the case of lasers, since the laser wavelength is 10,000 nm, most materials absorb the light, so it is also used as a method of thermal recording without adding special absorbing materials. In addition, it is necessary to add a photothermal conversion material, which is a material that absorbs laser wavelengths of 800nm ​​to 1100nm and converts them into heat when using semiconductor lasers or solid-state lasers such as YAG or fiber lasers. However, since transparent plastic films such as PET and OPP do not absorb laser light, it is possible not only to irradiate the thermal recording layer directly with a laser, but also to irradiate the laser from the transparent film side and record on the thermal recording layer on the opposite side of the film, expanding the range of uses. The output of the laser light irradiated in the image forming process in the image forming apparatus is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 1 W or more, more preferably 3 W or more, and particularly preferably 5 W or more. If it is less than 1 W, it takes a long time to form an image, and if an attempt is made to shorten the image formation time, the output will be insufficient. The upper limit of the output of the laser light is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 200 W or less, more preferably 150 W or less, and particularly preferably 100 W or less. If it exceeds 200 W, the laser device may become large.

[0185] When recording an image on a thermal recording medium at high speed, it is preferable to use an image forming apparatus having a laser array in which a plurality of laser light emitting elements are arranged in an array.

[0186] Next, as an example, a laser recording device for recording an image on a long thermal recording medium will be described.

[0187] Here, FIG. 9 is a schematic perspective view of an image recording system 100 which is a laser recording device. In the following description, the transport direction (movement direction) of the thermosensitive recording medium is defined as the X-axis direction, the vertical direction as the Z-axis direction, and the direction perpendicular to both the movement direction and the vertical direction as the Y-axis direction. As described in detail below, the image recording system 100 irradiates a laser beam onto a thermal recording medium 101, which is an object to be recorded, to perform surface processing and image recording processing. As shown in FIG. 9, the image recording system 100 includes a conveying device 10, a recording device 20, a main body section 30, an optical fiber 42, an encoder section 60, and the like. The recording device 20 irradiates a laser beam onto the recording object to process the surface of the recording object or to record a visible image on the recording object, and corresponds to a laser irradiation device. The recording device 20 is disposed on the -Y side of the transport device 10, i.e., on the -Y side of the transport path. The conveying device 10 conveys a thermosensitive recording medium 101, which is an object to be recorded, by using, for example, a plurality of rotating rollers. The main body 30 is connected to the transport device 10, the recording device 20, etc., and controls the image recording system 100 as a whole. The encoder unit 60 acquires the moving speed of the thermal recording medium 101 .

[0188] FIG. 10 is a schematic perspective view showing the configuration of an image recording system 100. As shown in FIG. The image recording system 100 includes a laser processing device 30 that is a laser light source. The laser processing device 30 includes a laser irradiation device 14 having a laser array section 14a and a fiber array section 14b, and an optical section 43. In this embodiment, a fiber array recording device is used as the laser irradiation device 14, which performs surface processing and image recording using a fiber array in which laser emission sections of multiple optical fibers are arranged in an array in a main scanning direction (Z-axis direction) perpendicular to a sub-scanning direction (X-axis direction) that is the moving direction of a thermal recording medium 101 that is a recording object. The laser processing device 30 irradiates the thermal recording medium with laser light emitted from a laser light emitting element 41 via the fiber array, and records an image (visible image) consisting of drawing units. The laser array section 14a includes a plurality of laser light-emitting elements 41 arranged in an array, a cooling unit 50 for cooling the laser light-emitting elements 41, a plurality of drivers 45 provided corresponding to the laser light-emitting elements 41 for driving the corresponding laser light-emitting elements 41, and a controller 46 for controlling the plurality of drivers 45. The controller 46 is connected to a power supply 48 for supplying power to the laser light-emitting elements 41 and an image information output section 47 such as a personal computer for outputting image information. Usually, in the laser light emitting element 41, energy that is not converted into laser light is converted into heat, generating heat. Therefore, the laser light emitting element 41 is cooled by the cooling unit 50, which is a cooling means. In addition, the laser irradiation device 14 here can arrange each laser light emitting element 41 apart by using the fiber array unit 14b. This makes it possible to reduce the influence of heat from the adjacent laser light emitting elements 41, and the laser light emitting elements 41 can be cooled efficiently, so that the temperature rise and variation of the laser light emitting elements 41 can be avoided, the output variation of the laser light can be reduced, and the density unevenness can be improved. Note that the output of the laser light is the average output measured by a power meter. There are two types of methods for controlling the output of the laser light: a method for controlling the peak power and a method for controlling the emission ratio of the pulse (duty: laser emission time / cycle time). The cooling unit 50 is a liquid-cooling type that cools the laser light-emitting elements 41 by circulating a coolant, and includes a heat receiving section 51 where the coolant receives heat from each laser light-emitting element 41, and a heat dissipating section 52 that dissipates the heat of the coolant. The heat receiving section 51 and the heat dissipating section 52 are connected by cooling pipes 53a and 53b. The heat receiving section 51 is provided with a cooling pipe made of a good thermal conductive material inside a case made of a good thermal conductive material through which the coolant flows. The multiple laser light-emitting elements 41 are arranged in an array on the heat receiving section 51. The heat dissipation unit 52 includes a radiator and a pump for circulating the coolant. The coolant sent out by the pump of the heat dissipation unit 52 flows into the heat receiving unit 51 through the cooling pipe 53a. The coolant then moves through the cooling tubes in the heat receiving unit 51, absorbing heat from the laser light emitting elements 41 arranged in the heat receiving unit 51 to cool the laser light emitting elements 41. The coolant that has risen in temperature after absorbing heat from the laser light emitting elements 41 and flowing out of the heat receiving unit 51 moves through the cooling pipe 53b and flows into the radiator of the heat dissipation unit 52, where it is cooled by the radiator. The coolant that has been cooled by the radiator is sent out again to the heat receiving unit 51 by the pump. The fiber array unit 14b includes a plurality of optical fibers 42 provided corresponding to the laser light-emitting elements 41, and an array head 44 that holds the vicinity of the laser emission portions 42a of these optical fibers 42 in an array in the vertical direction (Z-axis direction). The laser entrance portion of each optical fiber 42 is attached to the laser emission surface of the corresponding laser light-emitting element 41. If one array head 44 were to hold all the optical fibers 42, the array head 44 would become long and would be easily deformed. As a result, it would be difficult to maintain the linearity of the beam arrangement and the uniformity of the beam pitch with one array head 44. For this reason, the array head 44 is designed to hold 100 to 200 optical fibers 42. In addition, it is preferable that the laser irradiation device 14 has a plurality of array heads 44 each holding 100 to 200 optical fibers 42 arranged in the Z-axis direction, which is a direction perpendicular to the moving direction of the thermal recording medium 101.

[0189] Fig. 11 is a diagram for explaining the arrangement of the laser array. As shown in Fig. 11, the optical fibers 42 of the array head 44 in Fig. 10 are arranged so that the dots R1 formed by irradiating the thermal recording medium with a laser and developing color are continuous at the focal position where the optical unit 43 focuses the light. The scanning direction of the laser light is a main scanning direction and a sub-scanning direction, which are perpendicular to each other. The main scanning direction is the direction in which the optical fibers 42 are arranged. The sub-scanning direction is the direction in which the thermal recording medium moves. In addition, since the array head 44 and the thermal recording medium are moved relatively to each other to record an image on the thermal recording medium, the array head 44 may move relative to the thermal recording medium, or the thermal recording medium may move relative to the array head 44. Even when the array head 44 is moved relative to the thermal recording medium, the expression "moving speed of the thermal recording medium" can be used if the array head 44 is used as the observation point.

[0190] 10, an optical section 43, which is an example of an optical system, has a collimator lens 43a that converts the divergent laser light beams emitted from each optical fiber 42 into parallel light beams, and a focusing lens 43b that focuses the laser light on the surface of the thermal recording medium, which is the laser irradiation surface. Whether or not to provide the optical section 43 can be appropriately selected depending on the purpose.

[0191] An image information output unit 47 such as a personal computer inputs image information to the controller 46. The controller 46 generates a drive signal (control pulse) for driving each driver 45 based on the input image information. The controller 46 transmits the generated drive signal (control pulse) to each driver 45. Specifically, the controller 46 includes a clock generator. When the number of clocks oscillated by the clock generator reaches a specified number of clocks, the controller 46 transmits the drive signal (control pulse) for driving each driver 45 to each driver 45. When each driver 45 receives a drive signal (control pulse), it transmits a current pulse to drive the corresponding laser light emitting element 41. The laser light emitting element 41 outputs a light emitting pulse and irradiates a laser light according to the drive of the driver 45. The laser light irradiated from the laser light emitting element 41 enters the corresponding optical fiber 42 and is emitted from the laser emission section 42a of the optical fiber 42. The laser light emitted from the laser emission section 42a of the optical fiber 42 passes through the collimator lens 43a and the condenser lens 43b of the optical section 43, and is then irradiated onto a thermal recording medium, which is a recording target. An image is recorded on the thermal recording medium by heating it with the laser light irradiated onto it.

[0192] Incidentally, when a recording device that uses a galvanometer mirror to deflect a laser beam and record an image on a recording medium is used, images such as characters are recorded by irradiating the laser beam in a single stroke with the rotation of the galvanometer mirror. Therefore, when a certain amount of information is to be recorded on a recording medium, there is a restriction that the recording cannot be completed in time unless the transport of the recording medium is stopped. On the other hand, the laser irradiation device 14 uses a laser array in which a plurality of laser light-emitting elements 41 are arranged in an array, and can record an image on the thermosensitive recording medium by controlling ON / OFF of the laser light-emitting elements corresponding to each pixel. This makes it possible to record an image on the thermosensitive recording medium without stopping the transport of the thermosensitive recording medium, even if the amount of information is large. Therefore, the laser irradiation device 14 makes it possible to record an image without reducing productivity, even when a large amount of information is to be recorded on the recording object.

[0193] The laser irradiation device 14 records an image on the thermal recording medium by irradiating the thermal recording medium with a laser beam and heating the thermal recording medium, so it is necessary to use a laser light emitting element 41 with a certain degree of high output. Therefore, the amount of heat generated by the laser light emitting element 41 is large. In a conventional laser array recording device that does not have the fiber array unit 14b, it is necessary to arrange the laser light emitting elements 41 in an array at intervals according to the resolution. Therefore, in a conventional laser array recording device, in order to achieve a resolution of 200 dpi, the laser light emitting elements 41 are arranged at a very narrow pitch. As a result, in the conventional laser array recording device, the heat of the laser light emitting element 41 is difficult to escape, and the laser light emitting element 41 becomes hot. In the conventional laser array recording device, when the laser light emitting element 41 becomes hot, the wavelength and light output of the laser light emitting element 41 fluctuate, so that the recording object cannot be heated to a specified temperature, and a good image cannot be obtained. In addition, in the conventional laser array recording device, in order to suppress such a temperature rise of the laser light emitting element 41, it is necessary to slow down the conveying speed of the recording object and increase the emission interval of the laser light emitting element 41, and productivity cannot be sufficiently improved.

[0194] Usually, the cooling unit 50 uses a chiller system, which only cools and does not heat. Therefore, the temperature of the light source does not exceed the set temperature of the chiller, but the temperature of the cooling unit 50 and the laser light emitting element 41 in contact with it fluctuates from the environmental temperature. On the other hand, when a semiconductor laser is used as the laser light emitting element 41, a phenomenon occurs in which the laser output changes depending on the temperature of the laser light emitting element 41 (when the temperature of the laser light emitting element 41 becomes low, the laser output becomes high). Therefore, in order to control the laser output, it is preferable to measure the temperature of the laser light emitting element 41 or the temperature of the cooling unit 50, and control the input signal to the driver 45 that controls the laser output so that the laser output is constant according to the result, thereby forming a normal image. In contrast, the laser irradiation device 14 is a fiber array recording device using the fiber array unit 14b. By using the fiber array recording device, it is only necessary to arrange the laser emission units 42a of the fiber array unit 14b at a pitch according to the resolution, and it is not necessary to set the pitch between the laser light emitting elements 41 of the laser array unit 14a to a pitch according to the image resolution. As a result, the laser irradiation device 14 can make the pitch between the laser light emitting elements 41 sufficiently wide so that the heat of the laser light emitting elements 41 can be sufficiently dissipated. As a result, the laser irradiation device 14 can prevent the laser light emitting elements 41 from becoming too hot, and can prevent the wavelength and light output of the laser light emitting elements 41 from fluctuating. As a result, the laser irradiation device 14 can record a good image on the thermal recording medium. In addition, even if the emission interval of the laser light emitting elements 41 is shortened, the temperature rise of the laser light emitting elements 41 can be suppressed, the moving speed of the thermal recording medium can be increased, and productivity can be improved.

[0195] Furthermore, in the laser irradiation device 14, a cooling unit 50 is provided to liquid-cool the laser light-emitting element 41, thereby further suppressing the temperature rise of the laser light-emitting element 41. As a result, the laser irradiation device 14 can further shorten the emission interval of the laser light-emitting element 41, and can increase the moving speed of the thermal recording medium, thereby improving productivity. In the laser irradiation device 14, the laser light-emitting element 41 is liquid-cooled, but the laser light-emitting element 41 may also be air-cooled using a cooling fan or the like. Liquid cooling has the advantage of being more efficient at cooling the laser light-emitting element 41 than air cooling, and can effectively cool the laser light-emitting element 41. On the other hand, air cooling has the advantage of being less efficient at cooling the laser light-emitting element 41 than liquid cooling, but can inexpensively cool the laser light-emitting element 41. EXAMPLES

[0196] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0197] Compounds Nos. 1 to 5 used in the following examples were synthesized in the same manner as in the synthesis examples described in Japanese Patent No. 6751479.

[0198] Example 1 <Preparation of thermal recording medium> -Preparation of dye dispersion- 36 parts by mass of 3-di-n-butylamino-6-methyl-7-anilinofluoran, 10 parts by mass of an aqueous solution of a carboxyl group-containing acrylic resin (styrene-acrylic resin, product name: HPD-196, solid content 36% by mass, manufactured by BASF), 3.6 parts by mass of a surfactant (product name: PD-001, solid content 10% by mass, manufactured by Nissin Chemical Industry Co., Ltd.), and 50.4 parts by mass of ion-exchanged water were added, and the 50% cumulative volume particle size (D 50 The particles were dispersed in a sand mill so that the particle size was 0.2 μm or less to obtain a dye dispersion.

[0199] -Preparation of developer dispersion- 36 parts by mass of Compound No. 1 represented by the following structural formula, 10 parts by mass of a carboxyl group-containing acrylic resin aqueous solution (styrene-acrylic resin, product name: HPD-196, solid content 36% by mass, manufactured by BASF), 3.6 parts by mass of a surfactant (product name: PD-001, solid content 10% by mass, manufactured by Nissin Chemical Industry Co., Ltd.), and 50.4 parts by mass of ion-exchanged water were added, and the 50% cumulative volume particle size (D 50 ) was dispersed in a sand mill to a particle size of 0.2 μm to obtain a developer dispersion.

[0200] <Compound No. 1> [ka]

[0201] - Preparation of thermosensitive recording layer forming solution - Next, 12.4 parts by mass of the dye dispersion liquid obtained, 37.3 parts by mass of the developer dispersion liquid, 21.8 parts by mass of acrylic emulsion (styrene-acrylic resin, product name: EK-61, solid content 41% by mass, manufactured by Saiden Chemical Co., Ltd.), and 28.5 parts by mass of ion-exchanged water were mixed and stirred to obtain a thermosensitive recording layer forming liquid.

[0202] - Formation of thermal recording layer - Next, the heat-sensitive recording layer forming solution was applied to one side of a polyethylene terephthalate film (product name: E5100, average thickness: 50 μm, manufactured by Toyobo Co., Ltd., haze degree: 4.5) in an amount of 4.0 g / m2 after drying. 2 The mixture was applied using a bar coater so as to obtain a thermal recording medium 1, which was then dried. The haze of the polyethylene terephthalate film is a value measured using a haze meter (device name: HZ-V3, manufactured by Suga Test Co., Ltd.).

[0203] Example 2 A color developer dispersion liquid was prepared in the same manner as in Example 1, except that in preparing the color developer dispersion liquid of Example 1, compound number 1 was changed to compound number 2 represented by the following structural formula. Next, a thermosensitive recording medium 2 was prepared in the same manner as in Example 1, except that the developer dispersion liquid was used to form the thermosensitive recording layer.

[0204] <Compound No. 2> [ka]

[0205] Example 3 A developer dispersion liquid was prepared in the same manner as in Example 1, except that in preparing the developer dispersion liquid of Example 1, compound number 1 was changed to compound number 3 represented by the following structural formula. Next, a thermosensitive recording medium 3 was prepared in the same manner as in Example 1, except that the developer dispersion liquid was used to form the thermosensitive recording layer.

[0206] <Compound No. 3> [ka]

[0207] Example 4 A developer dispersion liquid was prepared in the same manner as in Example 1, except that in preparing the developer dispersion liquid of Example 1, compound number 1 was changed to compound number 4 represented by the following structural formula. Next, a thermosensitive recording medium 4 was prepared in the same manner as in Example 1, except that the developer dispersion liquid was used to form the thermosensitive recording layer.

[0208] <Compound No. 4> [ka]

[0209] Example 5 A developer dispersion liquid was prepared in the same manner as in Example 1, except that in preparing the developer dispersion liquid of Example 1, compound number 1 was changed to compound number 5 represented by the following structural formula. Next, a thermosensitive recording medium 5 was prepared in the same manner as in Example 1, except that the developer dispersion liquid was used to form the thermosensitive recording layer.

[0210] <Compound No. 5> [ka]

[0211] Example 6 In Example 1, the protective layer coating solution described below was applied to the thermal recording layer in an amount of 2.0 g / m2 after drying. 2 A thermosensitive recording medium 6 was produced in the same manner as in Example 1, except that a protective layer was formed by applying the coating solution using a bar coater so as to form a protective layer.

[0212] <Preparation of Coating Solution for Protective Layer> 40.7 parts by mass of calcium carbonate, 11.3 parts by mass of a carboxyl group-containing acrylic resin aqueous solution (styrene-acrylic resin, product name: HPD-196, solid content 36% by mass, manufactured by BASF), 2 parts by mass of a surfactant (product name: PD-001, solid content 10% by mass, manufactured by Nissin Chemical Industry Co., Ltd.), and 46 parts by mass of ion-exchanged water were added, and the 50% cumulative volume particle size (D 50 The particles were dispersed in a sand mill so that the particle size was 0.2 μm or less to obtain a dispersion liquid. Next, 19.9 parts by mass of the obtained dispersion, 21.9 parts by mass of an acrylic emulsion (styrene-acrylic resin, product name: EK-61, solids content 41% by mass, manufactured by Saiden Chemical Co., Ltd.), 9.2 parts by mass of an oxazoline group-containing polymer emulsion (product name: WS-500, solids content 39% by mass, manufactured by Nippon Shokubai Co., Ltd.), 4.5 parts by mass of an oxidized polyethylene wax dispersion (solids content 30% by mass), and 44.5 parts by mass of ion-exchanged water were mixed and stirred to obtain a coating liquid for the protective layer.

[0213] Example 7 A dye dispersion was prepared in the same manner as in Example 1, except that in the preparation of the dye dispersion in Example 1, 3-di-n-butylamino-6-methyl-7-anilinofluoran was changed to 6'-(diethylamino)-2'-(2-fluoroanilino)spiro[phthalido-3,9'-xanthene]. Next, a thermosensitive recording medium 7 was prepared in the same manner as in Example 1, except that the dye dispersion liquid was used to form the thermosensitive recording layer.

[0214] Example 8 Thermosensitive recording medium 8 was produced in the same manner as in Example 1, except that the thermosensitive recording layer was formed using the thermosensitive recording layer forming liquid described below.

[0215] <Thermal recording layer forming liquid> A thermosensitive recording layer forming liquid was prepared by mixing and stirring 6.7 parts by mass of the dye dispersion liquid prepared in Example 1, 20 parts by mass of the developer dispersion liquid prepared in Example 1, 5.9 parts by mass of an acrylic emulsion (styrene-acrylic resin, product name: EK-61, solids content 41% by mass, manufactured by Saiden Chemical Co., Ltd.), 24.1 parts by mass of an aqueous itaconic acid-modified polyvinyl alcohol solution (product name: Kuraray Poval 25-88KL, solids content 10% by mass, manufactured by Kuraray Co., Ltd.), and 43.4 parts by mass of ion-exchanged water.

[0216] Example 9 Thermosensitive recording medium 9 was produced in the same manner as in Example 1, except that the thermosensitive recording layer was formed using the thermosensitive recording layer forming liquid described below. <Thermal recording layer forming liquid> A thermosensitive recording layer forming liquid was prepared by mixing and stirring 12 parts by mass of the dye dispersion liquid prepared in Example 1, 36.2 parts by mass of the developer dispersion liquid prepared in Example 1, 21.2 parts by mass of an acrylic emulsion (styrene-acrylic resin, product name: EK-61, solid content 41% by mass, manufactured by Saiden Chemical Co., Ltd.), 3 parts by mass of a cesium tungsten oxide dispersion (product name: YMW-D20, solid content 28.5% by mass, manufactured by Sumitomo Metal Mining Co., Ltd.) as a photothermal conversion material, and 27.6 parts by mass of ion exchanged water.

[0217] Example 10 In Example 1, a printing ink (product name: Finart R794 White G8, solid content 42 mass%, manufactured by DIC Graphics Corporation) was applied to the support surface in an amount of 1.0 g / m2 after drying. 2 A thermosensitive recording medium 10 was produced in the same manner as in Example 1, except that a print layer was formed by applying the coating liquid using a bar coater so as to form a print layer.

[0218] Comparative Example 1 In preparing the developer dispersion liquid of Example 1, except that compound number 1 was changed to N-[2-[[(phenylamino)carbonyl]amino]phenyl]benzenesulfonamide (product name: NKK-1304, manufactured by Nippon Soda Co., Ltd.), the developer dispersion liquid was prepared in the same manner as in Example 1. Next, a thermosensitive recording medium 11 was prepared in the same manner as in Example 1, except that the developer dispersion liquid was used to form the thermosensitive recording layer.

[0219] Comparative Example 2 In preparing the developer dispersion liquid of Example 1, except that compound number 1 was changed to 4-methyl-N-[[[3-[[(4-methylphenyl)sulfonyl]oxy]phenyl]amino]carbonyl]benzenesulfonamide (product name: P-201, manufactured by BASF), the developer dispersion liquid was prepared in the same manner as in Example 1. Next, a thermosensitive recording medium 12 was produced in the same manner as in Example 1, except that the developer dispersion liquid was used to form the thermosensitive recording layer.

[0220] Comparative Example 3 In preparing the developer dispersion liquid of Example 1, except that compound number 1 was changed to 4-hydroxy-4'-isopropoxydiphenyl sulfone (product name: D-8, manufactured by Nippon Soda Co., Ltd.), the developer dispersion liquid was prepared in the same manner as in Example 1. Next, a thermosensitive recording medium 13 was prepared in the same manner as in Example 1, except that the developer dispersion liquid was used to form the thermosensitive recording layer.

[0221] Comparative Example 4 In preparing the developer dispersion liquid of Example 1, except that the compound number 1 was changed to bis(4-hydroxyphenyl)sulfone monoallyl ether (product name: BPS-MAE, manufactured by Nicca Chemical Co., Ltd.), the developer dispersion liquid was prepared in the same manner as in Example 1. Next, a thermosensitive recording medium 14 was prepared in the same manner as in Example 1, except that the developer dispersion liquid was used to form the thermosensitive recording layer.

[0222] Comparative Example 5 In preparing the dye dispersion and the color developer dispersion of Example 1, except that 10 parts by mass of a carboxyl group-containing acrylic resin aqueous solution (styrene-acrylic resin, product name: HPD-196, solid content 36% by mass, manufactured by BASF) was replaced with 18 parts by mass of a polyvinyl alcohol aqueous solution (product name: Gohsenex L-3266, solid content 30% by mass, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), and 50.4 parts by mass of ion-exchanged water was changed to 42.3 parts by mass, the dye dispersion and the color developer dispersion were prepared in the same manner as in Example 1. Next, 8.7 parts by weight of the obtained dye dispersion, 25.9 parts by weight of the developer dispersion, 31.2 parts by weight of an aqueous solution of itaconic acid-modified polyvinyl alcohol (product name: Kuraray Poval 25-88KL, solids content 10% by weight, manufactured by Kuraray Co., Ltd.), 5 parts by weight of an aqueous solution of polyamide epochlorohydrin resin (product name: WS-525, solids content 25% by weight, manufactured by Seiko PMC Co., Ltd.), and 29.3 parts by weight of ion-exchanged water were mixed and stirred to prepare a thermal recording layer forming liquid. Next, a thermosensitive recording medium 15 was produced in the same manner as in Example 1, except that the thermosensitive recording layer was formed using the thermosensitive recording layer forming liquid in Example 1.

[0223] Comparative Example 6 In preparing the dye dispersion and developer dispersion of Example 1, except that 10 parts by mass of a carboxyl group-containing acrylic resin aqueous solution (styrene-acrylic resin, product name: HPD-196, solid content 36% by mass, manufactured by BASF) was replaced with 7.2 parts by mass of a polyurethane resin aqueous solution (product name: Gen 0851, solid content 50% by mass, manufactured by Borchers) and 50.4 parts by mass of ion-exchanged water was changed to 53.2 parts by mass, the dye dispersion and developer dispersion were prepared in the same manner as in Example 1. Next, 14.7 parts by weight of the obtained dye dispersion, 44.1 parts by weight of the developer dispersion, 15.1 parts by weight of a polyurethane resin dispersion (product name: WLS-201, solid content 35% by weight, manufactured by DIC Corporation), and 26 parts by weight of ion-exchanged water were mixed and stirred to prepare a thermosensitive recording layer forming liquid. Next, a thermosensitive recording medium 16 was produced in the same manner as in Example 1, except that the thermosensitive recording layer was formed using the thermosensitive recording layer forming liquid in Example 1.

[0224] Next, using the thermal recording media prepared in Examples 1 to 10 and Comparative Examples 1 to 6, the following properties were evaluated: "Hot water resistance (60°C)", "Hot water resistance (40°C)", "Water resistance", "Ethanol resistance", "Hot and moist resistance", "Water abrasion resistance", "Heat resistance (110°C)", "Heat resistance (90°C)", and "LD laser printability". The results for "Hot water resistance (60°C)", "Hot water resistance (40°C)", "Water resistance", "Ethanol resistance", "Hot and wet resistance", "Water abrasion resistance", "Heat resistance (110°C)", and "Heat resistance (90°C)" are shown in Tables 1 and 2.

[0225] <Hot water resistance (60℃)> For each thermal recording medium, CO 2 A pre-test image sample was prepared by printing under the following printing conditions using a laser marker (device name: LP-435TU, manufactured by SUNX Corporation). The prepared pre-test image samples were immersed in tap water at 60°C and stored in a thermostatic bath at a water temperature of 60°C for 96 hours. The image density before and after storage was measured using a reflection densitometer (X-Rite eXact, manufactured by X-Rite). The image retention rate was calculated using the following formula and evaluated according to the following criteria. Image retention rate (%) = [(image density after test) / (image density before test)] x 100 [Printing conditions] Distance between workpieces: 275mm Scanning speed: 900mm / s Laser light wavelength: 10.6μm Laser power: 10% [Evaluation Criteria] ◎: Image retention rate is 90% or more ○: Image retention rate is 80% to 89% ×: Image remaining rate is 79% or less

[0226] <Hot water resistance (40℃)> Each of the prepared image samples before testing was immersed in tap water at 40°C and stored for 96 hours in a thermostatic bath with the water temperature kept at 40°C. The image density before and after storage was measured using a reflection densitometer (X-Rite eXact, manufactured by X-Rite Corporation). The image retention rate was calculated using the following formula and evaluated according to the following criteria. Image retention rate (%) = [(image density after test) / (image density before test)] x 100 [Evaluation Criteria] ◎: Image retention rate is 90% or more ○: Image retention rate is 80% to 89% ×: Image remaining rate is 79% or less

[0227] <Water resistance> Each prepared image sample was immersed in tap water at 23°C for 96 hours, and the image density was measured before and after using a reflection densitometer (X-Rite eXact, manufactured by X-Rite). The image retention rate was calculated using the following formula and evaluated according to the following criteria. Image retention rate (%) = [(image density after test) / (image density before test)] x 100 [Evaluation Criteria] ◎: Image retention rate is 90% or more ○: Image retention rate is 80% to 89% ×: Image remaining rate is 79% or less

[0228] <Ethanol resistance> Each prepared image sample was immersed in an 80% by weight aqueous ethanol solution for 30 seconds, and the image density was measured before and after using a reflection densitometer (X-Rite eXact, manufactured by X-Rite). The image retention rate was calculated using the following formula and evaluated according to the following criteria. Image retention rate (%) = [(image density after test) / (image density before test)] x 100 [Evaluation Criteria] ◎: Image retention rate is 90% or more ○: Image retention rate is 80% to 89% ×: Image remaining rate is 79% or less

[0229] <Temperature and humidity resistance> The image density before and after storing each of the prepared image samples at 40°C in an environment of 90% RH for 72 hours was measured using a reflection densitometer (X-Rite eXact, manufactured by X-Rite Inc.). The image retention rate was determined from the following formula and evaluated according to the following criteria. Image retention rate (%) = [(image density after the test) / (image density before the test)] × 100 [Evaluation criteria] ◎: Image retention rate is 90% or more ○: Image retention rate is 80% or more and 89% or less ×: Image retention rate is 79% or less

[0230] <Water rub resistance> One drop of water was dropped onto each of the prepared image samples and strongly rubbed 100 times with a finger. Then, the presence or absence of peeling, dissolution, and bleeding of each layer was visually observed and evaluated according to the following criteria. [Evaluation criteria] ○: No peeling, elution, or bleeding ×: Peeling, elution, or bleeding is present

[0231] <Heat resistance> After storing each of the prepared image samples under environmental conditions of 110°C and 90°C for 1 hour, the density of the sample base part was measured using a reflection densitometer (X-Rite eXact, manufactured by X-Rite Inc.) and evaluated according to the following criteria. [Evaluation criteria] ○: Density of the base part is 0.29 or less ×: Density of the base part is 0.30 or more

[0232] <Feasibility of LD laser printing> Using an LD laser marker (device name: Ricoh Rewritable Laser Marker LDM200, manufactured by Ricoh Company, Ltd.), image samples were prepared by printing the thermal recording media prepared in Examples 1 to 10 and Comparative Examples 1 to 6 under the following printing conditions and evaluated based on the following evaluation criteria. [Printing conditions] Work distance: 150 mm Scanning speed: 3,000 mm / s Laser light wavelength: 980 nm Laser power: 70% [Evaluation criteria] ○: Printable ×: Unable to print

[0233] [Evaluation Results] Example 9, which contained a photothermal conversion material in the thermosensitive recording layer, was printable (◯), whereas Examples 1 to 8 and 10 and Comparative Examples 1 to 6, which did not contain a photothermal conversion material in the thermosensitive recording layer, were not printable (×).

[0234] [Table 1]

[0235] [Table 2]

[0236] For example, aspects of the present invention are as follows. <1> A thermosensitive recording medium having a support and a thermosensitive recording layer on the support, The thermosensitive recording medium is characterized in that the thermosensitive recording layer contains a compound represented by the following general formula (1) and a styrene-acrylic resin. [ka] In the above general formula (1), R 2 is a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms, an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 12 carbon atoms substituted with a halogen atom, or an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms substituted with a halogen atom; 2 may be the same or different. A 1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 1 may be the same or different. <2> The compound represented by the general formula (1) is a compound represented by the following general formula (2): <1> The thermal recording medium according to claim 1, [ka] In the general formula (2), R 2 is a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms, an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 12 carbon atoms substituted with a halogen atom, or an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms substituted with a halogen atom; 2 may be the same or different. <3> The compound represented by the general formula (2) is a compound represented by the following general formula (3): <2> The thermal recording medium according to claim 1, [ka] In the general formula (3), R represents an alkyl group, and n represents an integer of 0 to 3. <4> The thermosensitive recording layer contains a photothermal conversion material. <1> from <3> 10. The thermosensitive recording medium according to claim 9, <5> The support is a plastic film. <1> from <4> 10. The thermosensitive recording medium according to claim 9, <6> The support is a transparent film. <1> from <5> 10. The thermosensitive recording medium according to claim 9, <7> The thermosensitive recording layer has a protective layer thereon. <1> from <6> 10. The thermosensitive recording medium according to claim 9, <8> a printing layer is provided between the support and the thermosensitive recording layer, on the surface of the support opposite to the thermosensitive recording layer, or on the support or on the thermosensitive recording layer; <1> from <6> 10. The thermosensitive recording medium according to claim 9, <9> The thermosensitive recording layer forming liquid is characterized by containing a compound represented by the following general formula (1), a styrene-acrylic resin, and a solvent. [ka] In the above general formula (1), R 2 is a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms, an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 12 carbon atoms substituted with a halogen atom, or an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms substituted with a halogen atom; 2 may be the same or different. A 1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 1 may be the same or different. <10> The compound represented by the general formula (1) is a compound represented by the following general formula (2): <9> 2. The thermosensitive recording layer forming liquid according to claim 1. [ka] In the general formula (2), R 2 is a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms, an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 12 carbon atoms substituted with a halogen atom, or an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms substituted with a halogen atom; 2 may be the same or different. <11> The compound represented by the general formula (2) is a compound represented by the following general formula (3): <10> 2. The thermosensitive recording layer forming liquid according to claim 1. [ka] In the general formula (3), R represents an alkyl group, and n represents an integer of 0 to 3. <12> On the support <9> from <11> 2. A method for producing a thermosensitive recording medium, comprising the step of forming a thermosensitive recording layer by applying the thermosensitive recording layer forming liquid according to any one of the above items 1 to 5 to form a thermosensitive recording layer. <13> The above <1> from <8> 2. A method for recording an image, comprising irradiating a laser beam onto the thermal recording medium according to claim 1 to record an image thereon. <14> The above <1> from <8> 2. An image recording method comprising the steps of: recording an image on the thermal recording medium according to claim 1 using a thermal head.

[0237] The above <1> from <8> The thermal recording medium according to any one of the preceding claims. <9> from <11> The thermosensitive recording layer forming liquid according to any one of the preceding claims. <12> The method for producing the thermosensitive recording medium according to the present invention <13> from <14> According to the image recording method described in any one of the above, the conventional problems can be solved and the object of the present invention can be achieved. [Explanation of symbols]

[0238] 1 Support 2. Thermal recording layer 3 protective layer 4 printing layer [Prior art documents] [Patent documents]

[0239] [Patent Document 1] Patent No. 6751479

Claims

1. A thermosensitive recording medium having a support and a thermosensitive recording layer on the support, The thermosensitive recording medium according to the present invention is characterized in that the thermosensitive recording layer contains a compound represented by the following general formula (1) and a styrene-acrylic resin: 【Chemistry 1】 In the above general formula (1), R ２ is a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms, an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms substituted with a halogen atom, an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms substituted with a halogen atom; ２ may be the same or different. １ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. １ may be the same or different.

2. 2. The thermosensitive recording medium according to claim 1, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (2): 【Chemistry 2】 In the above general formula (2), R ２ is a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms, an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms substituted with a halogen atom, an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms substituted with a halogen atom; ２ may be the same or different.

3. 3. The thermosensitive recording medium according to claim 2, wherein the compound represented by the general formula (2) is a compound represented by the following general formula (3): 【Chemistry 3】 In the above general formula (3), R represents an alkyl group, and n represents an integer of 0 to 3.

4. 4. The thermosensitive recording medium according to claim 1, wherein the thermosensitive recording layer contains a light-to-heat conversion material.

5. 5. The thermosensitive recording medium according to claim 1, wherein the support is a plastic film.

6. 6. The thermosensitive recording medium according to claim 1, wherein the support is a transparent film.

7. 7. The thermosensitive recording medium according to claim 1, further comprising a protective layer on the thermosensitive recording layer.

8. 7. The thermosensitive recording medium according to claim 1, further comprising a printing layer either between the support and the thermosensitive recording layer, on the surface of the support opposite to the thermosensitive recording layer, or on the support or on the thermosensitive recording layer.

9. A thermosensitive recording layer forming liquid comprising a compound represented by the following general formula (1), a styrene-acrylic resin, and a solvent: 【Chemistry 4】 In the above general formula (1), R ２ is a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms, an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms substituted with a halogen atom, an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms substituted with a halogen atom; ２ may be the same or different. １ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. １ may be the same or different.

10. 10. The thermosensitive recording layer forming liquid according to claim 9, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (2): 【Chemistry 5】 In the above general formula (2), R ２ is a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms, an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms substituted with a halogen atom, an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms substituted with a halogen atom; ２ may be the same or different.

11. 11. The thermosensitive recording layer forming liquid according to claim 10, wherein the compound represented by the formula (2) is a compound represented by the following formula (3): 【Chemistry 6】 In the above general formula (3), R represents an alkyl group, and n represents an integer of 0 to 3.

12. 12. A method for producing a thermosensitive recording medium, comprising the step of applying the thermosensitive recording layer forming liquid according to claim 9 onto a support to form a thermosensitive recording layer.

13. 9. A method for recording an image, comprising irradiating a laser beam onto the thermal recording medium according to claim 1 to record an image thereon.

14. 9. An image recording method comprising recording an image on the heat-sensitive recording medium according to claim 1 using a thermal head.

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