JPH0698834B2 - Thermal recording material - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a diazo coloring type heat-sensitive recording material using a novel diazo compound.

[Prior Art] As a recording material used in a thermal recording method, a leuco color-developing thermal recording material is usually used. In this heat-sensitive recording material, an image is formed on the recording material by utilizing the fact that one of the leuco dye and the acidic substance dispersed in the heat-sensitive recording layer is melted by thermal energy to cause a color reaction. It is a thing.

Since this recording material has low fixability of a recorded image, it has a drawback that the recorded image is contaminated by color development at an unexpected place due to severe handling after recording or heating.

As a heat-sensitive recording material without such a defect, diazo color-developing heat-sensitive recording material has been actively researched in recent years. For example, JP-A-57-123086, Journal of the Institute of Image Electronics Engineers of Japan, 11 ,
290 (1982), etc., describes a recording material having a recording layer containing a coloring component composed of a diazo compound, a coupling component and a basic component (including a substance which becomes basic by heat). According to the material, after an image is formed on the recording material by heating, the recording material can be irradiated with light to decompose the unreacted diazo compound and stop (fix) the color development.

However, even in recording materials that use diazo compounds,
Precoupling (coloring reaction) gradually progressed in the storage stage before thermal recording, and undesired coloring (fogging) was likely to occur.

Various improvements have been made in order to eliminate this coloring (fog). For example, one of the components involved in color development should be present in the form of discontinuous particles (solid dispersion), or one of the components involved in color development should be separated as a separate layer (JP-A-57-123086). Are provided. This prevents contact between the components and prevents the progress of pre-coupling. However, in either case, the storability (so-called raw storability) is satisfactorily improved, but the thermal responsiveness (meltability to heat), which is one of the important performances, tends to decrease.

Further, as a technique for simultaneously improving both the raw preservation property and the thermal response property, a non-polar wax-like substance (JP-A-57-44141).
JP-A-57-142636) or a hydrophobic polymer substance (JP-A-57-192944) is used to encapsulate one of the color-forming components and separate it from the other components. Has been.

In these encapsulation methods, a wax-like substance or a polymer substance is dissolved in an appropriate solvent, and a coloring component or the like is dissolved or dispersed in the solution to form a capsule. It is different from the concept of a normal capsule covered with. Therefore, when the color-forming component is dissolved to form a capsule, the color-forming component is not necessarily the core substance of the capsule but is uniformly mixed with the encapsulating substance, and pre-coupling gradually proceeds at the capsule wall interface. When the raw storability is not maintained, and when the color-forming component is dispersed to form a capsule, the color-forming reaction does not occur unless the wall of the capsule is melted by heat, which causes a problem that the thermal response is deteriorated. Further, there is a manufacturing problem that the solvent used for dissolving the wax-like substance or the polymer substance must be removed after the formation of the capsule, which is not satisfactory.

Therefore, as a method for solving these problems, a method in which at least one of the components involved in the color development reaction is contained in the core substance, and a wall is formed around the core substance by polymerization to form microcapsules (special feature JP-A-59-190886 and JP-A-60-6493) are also proposed.

By the way, the diazo compound which has been conventionally used as a color-forming component needs to use a large amount of solvent when the diazo compound is to be contained as a core substance in the microcapsules as described above. In addition, this compound generally does not have sufficient dispersibility in a solvent. Therefore, when a recording material is produced using these compounds, there is a problem in that not only manufacturing problems such as removal of a solvent but also the obtained recording material cannot be expected to improve recorded image characteristics. . Further, conventional diazo compounds have not been sufficiently satisfactory in stability to heat or light (melting property to heat, decomposition reactivity to light, etc.). Therefore, these also reduce various properties of the heat-sensitive recording material. It was a cause.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-sensitive recording material excellent in recorded image characteristics such as color density.

Another object of the present invention is to provide a heat-sensitive recording material having improved storability (raw storability).

That is, the present invention provides a thermosensitive recording material having a thermosensitive recording layer comprising a diazo compound and a binder containing a supporting component on a support, wherein the thermosensitive recording layer is at least a diazo compound represented by the following general formula (I). The present invention provides a heat-sensitive recording material characterized by being a layer containing

(However, R ¹ represents a substituted or unsubstituted acyl group having 1 to 30 carbon atoms, R ² represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and X ⁻ represents an acid anion).

The present inventor has studied the diazo color-developing heat-sensitive recording material, and as a result, by using a novel compound represented by the above general formula (I) as a diazo compound which is a color forming component,
They have found that a heat-sensitive recording material having excellent properties can be obtained, and have reached the present invention.

The novel diazo compound represented by the above general formula (I) of the present invention has extremely good solubility in a solvent, as compared with diazo compounds conventionally used in diazo color-forming type heat-sensitive recording materials, and It is sparingly soluble in water. Therefore, for example, when it is intended to be contained as a core substance in the microcapsules, the solvent can be minimized and high dispersibility can be obtained, so that the diazo compound is in a concentrated (dense) state. The contained microcapsules can be formed.

Further, this diazo compound also has excellent properties in stability to heat or light. That is, in terms of heat characteristics, it is possible to extremely sensitively respond (melt) in a specific temperature range (a temperature range of heat applied from, for example, a thermal head at the time of image recording). It can respond (decompose) quickly to light. Therefore, this means that the reactivity with the coupling component in the recording layer can be remarkably enhanced, and at the same time, a reliable fixed state can be formed in the developing step (light irradiation after image recording). To do.

From the above, the thermosensitive recording material using the diazo compound according to the present invention can form a high density image on the recording layer. Further, since the light fixing property can be improved, it becomes possible to remarkably reduce coloring (fog) during storage (during raw storage).

[Structure of the Invention] The heat-sensitive recording material of the present invention basically has a structure of a support and a heat-sensitive recording layer provided thereon.

The heat-sensitive recording layer can be formed on the support by, for example, the method described below.

The heat-sensitive recording layer is a layer containing a diazo compound and a coupling component in a dispersed state by a binder.

The diazo compound, which is a characteristic requirement of the present invention, is a diazonium salt represented by the following general formula (I), and is a compound that causes a coupling reaction with a coupling component to develop a color.

(However, R ¹ represents a substituted or unsubstituted acyl group having 1 to 30 carbon atoms, R ² represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and X ⁻ represents an acid anion).

In the above general formula (I), the diazo compound used in the present invention preferably has a total number of carbon atoms of R ¹ and R ² in the range of 5 to 30.

Further, in the general formula (I), examples of the acid anion representing X ⁻ include (a) CjF ₂ j ₊₁ CO ₂ ⁻ (j is an integer of 3 to 9) (b) CkF ₂ k _{+ 1} SO ₃ ^- (k is an integer of 2 to _{8) (c) (ClF 2} l +1 SO 2) 2 CH - (l is an integer of 1 to 18) ^{_{(I) BF 4 - (j}} ) PF 6 - (k) ZnCl 3 - and the like. Of these, those containing a perfluoroalkyl group, a perfluoroalkenyl group, or the acid anion of PF ₆ ⁻ are particularly preferable because the increase in fog during raw storage is small.

Specific examples of the diazo compound (diazonium salt) according to the present invention include (A) 4-N- (β- (2,4-di-tert-amylphenoxy) butyroyl) amino-benzenediazonium hexafluorophosphate, [melting point : 132 degrees] (B) 4-N-methyl-N- (β- (2,4-di-tert-
Amylphenoxy) butyroyl) amino-benzenediazonium hexafluorophosphate, [melting point: 132 degrees] (C) 4-N- (2-ethylhexanoyl) amino-benzenediazonium hexafluorophosphate, [melting point: 117 degrees] (D) 4-N- (2-ethylhexyl) -N-aminocetylamino-benzeneazonium hexafluorophosphate, [melting point: 118 degrees] (E) 2-N-methyl-N- (β- (2,4-di- tert−
Amylphenoxy) butyroyl) amino-benzenediazonium hexafluorophosphate, [melting point: 123 degrees] (F) 4-N-methyl-N- (2-ethylhexanoyl) amino-benzenediazonium hexafluorophosphate, [melting point: 93 degrees ] Etc. can be mentioned.

The diazo compound according to the present invention may be used alone or in combination with a known diazo compound depending on the purpose.

The coupling component used in the present invention causes a coupling reaction with the above-mentioned diazo compound in a basic atmosphere to develop a color, and can be selected according to the desired hue. Specific examples thereof include resorcin, phloroglucin, and 2,3-hydroxynaphthalene 6
-Sodium sulfonate, sodium 2-hydroxy-3-naphthalene sulfonate, 2-hydroxy-3-naphthalene sulfonic acid anilide, 2-hydroxy-3-naphthalene sulfonic acid morpholinoamide, 2-hydroxy-
3-naphthalenesulfonic acid morpholinopropylamide,
2-Hydroxy-3-naphthalenesulfonic acid 2-ethylhexyloxypropylamide, 2-hydroxy-3-
Naphthalenesulfonic acid 2-ethylhexylamide, 1-
Hydroxy-8-acetylaminonaphthalene-3,6-disulfonic acid sodium salt, 1-hydroxy-8-acetylaminonaphthalene-3,6-disulfonic acid dianilide, 1
-Hydroxy-2-naphthoic acid morpholinopropylamide, 1,5-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,3-dihydroxy-6-sulfanylnaphthalene, 2-hydroxy-3-naphthoic acid morpholinopropylamide, 2- Hydroxy-3-naphthoic acid anilide, 2-hydroxy-3-naphthoic acid-2'-methylanilide, 2-hydroxy-3-naphthoic acid ethanolamide, 2-hydroxy-3-naphthoic acid octylamide, 2-hydroxynaphthoic acid Morpholinoethylamide, 2-hydroxynaphthoic acid piperidinopropylamide, 2-hydroxynaphthoic acid piperidinoethylamide, 2-hydroxy-3-naphthoic acid-N-dodecyl-
Oxy-propylamide, 2-hydroxy-3-naphthoic acid tetradecylamide, acetanilide, acetoacetanilide, benzoylacetanilide, 1-phenyl-3-methyl-5-pyrazolone, 1- (2 ', 4', 6'-
Trichlorophenyl) -3-benzamido-5-pyrazolone, 1- (2 ', 4', 6'-trichlorophenyl) -3
-Anilino-5-pyrazolone, 1-phenyl-3-phenylacetamido-5-pyrazolone and the like can be mentioned.

These coupling components may be used alone,
It is also possible to use two or more types in combination.

The diazo compound represented by the above general formula (I) is usually contained in the heat-sensitive recording layer in the range of 0.02 to ² gm ² , and preferably 0.
It is included in the range of 1 to 1.

The basic substance for forming the basic atmosphere used in the present invention can be arbitrarily selected from organic basic substances or substances which generate alkali upon heating. Specific examples of these include, for example, ammonium acetate, tricyclohexylamine, tribenzylamine, octadecylbenzylamine, stearylamine,
2-benzylimidazole, 4-phenylimidazole, 2-phenyl-4-methyl-imidazole, 2-undecyl-imidazoline, 2,4,5-trifuryl-2-imidazoline, 1,2-diphenyl-4,4-dimethyl- 2-imidazoline, 2-phenyl-2-imidazoline, 1,2,3
-Triphenylguanidine, 1,2-ditolylguanidine, 1,2-dicyclohexylguanidine, 1,2,3-tricyclohexylguanidine, guanidine trichloroacetate, N, N'-dibenzylpiperazine, 4,4'-dithio Examples thereof include morpholine, morpholinium trichloroacetate, 2-amino-benzothiazole and 2-benzoylhydrazino-benzothiazole. These compounds may be used alone or in combination of two or more depending on the purpose.

Examples of the binder used in the heat-sensitive recording layer are polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, arabic rubber, gelatin, polyvinyl pyrrolidone, casein, styrene / butadiene latex, acrylonitrile / butadiene latex, polyvinyl acetate, polyacrylic. Mention may be made of acid esters and ethylene / vinyl acetate copolymers, and these compounds are used in the form of various emulsions.

The amount of binder used is in the range of 0.5 to 5 g / m ² of solid content.

The heat-sensitive recording layer is prepared by mixing and dispersing the above diazo compound, the coupling component, the basic substance and the binder with an appropriate solvent using an attritor, a sand mill or the like to prepare a coating liquid, and then applying this coating liquid to a support. It can be formed by coating and drying by a coating method such as bar coating, blade coating, air knife coating, gravure coating, roll coating coating, spray coating and dip coating.

The recording layer can also be formed by encapsulating a diazo compound.

As a method for forming the microcapsules, a known method can be used. Below is a brief description.

First, the above diazo compound is dissolved or dispersed in a suitable organic solvent, and then this solution or dispersion (oil liquid) is emulsified and dispersed in an aqueous medium.

The organic solvent preferably has a boiling point of 180 ° C. or higher because evaporation loss occurs during storage when an organic solvent having a low boiling point is used. As the organic solvent, phosphoric acid ester, phthalic acid ester, other carboxylic acid ester, fatty acid amide, alkylated biphenyl, alkylated terphenyl,
Chlorinated paraffin, alkylated naphthalene, diarylethane and the like are used.

Next, a wall made of a polymer material is formed around the emulsified and dispersed oil droplets. Reactants for forming polymeric substances are added to oily liquids and / or aqueous media.

The polymer substance forming the capsule wall is impermeable at room temperature and needs to become permeable at the time of heating, and a glass transition temperature of 60 to 200 ° C. is particularly preferable. Examples of these are polyurethane, polyurea, polyamide,
Examples thereof include polyester, urea / formaldehyde resin, melamine resin, polystyrene, styrene / methacrylate copolymer, styrene / acrylate copolymer, and mixed systems thereof.

The interfacial polymerization method and the internal polymerization method are suitable as the microcapsule formation method.

Details of the capsule forming method and specific examples of actants are described in US Pat. Nos. 3,726,804 and 3,796,669. For example, when polyurea polyurethane is used as a capsule wall material, polyisocyanate and a second substance (for example, polyol, polyamine) which reacts therewith to form a capsule wall are mixed in an aqueous medium or an oily liquid to be encapsulated, By emulsifying and dispersing these in water and then heating, a polymer forming reaction occurs at the oil droplet interface to form a microcapsule wall. An auxiliary solvent having a low boiling point and a strong dissolving power may be added to the oily liquid. Polyurea is produced even when the addition of the second substance is omitted.

Further, when forming microcapsules, a water-soluble polymer compound can be used as a protective colloid. Examples of the water-soluble polymer compound include water-soluble anionic polymer compounds, nonionic polymer compounds and amphoteric polymer compounds.

These water-soluble polymer compounds are used as 0.01 to 10% by weight aqueous solution.

A substance for further improving the thermal recording density can be added to the binder solution for forming the thermal recording layer. Specifically, the melting point is in the range of 50 to 150 ° C, preferably 9
It is in the temperature range of 0 ° C to 130 ° C, and is selected from compounds having good compatibility with diazo compounds, coupling components or basic substances. Examples thereof include fatty acid amides, ketone compounds, ether compounds, urea compounds and esters.
These compounds are usually dispersed in particles of 1 to 10 μm and used in an amount of solid content of 0.2 to 7 g / m ² .

Further, pigments such as kaolin, talc, silica, barium sulfate, titanium dioxide, aluminum hydroxide, zinc oxide, and calcium carbonate; and styrene beads, for the purpose of preventing sticking to the thermal head and improving the writability.
A beauty powder such as urea / melamine resin can be added. Similarly, metal soaps can be used to prevent sticking. The amount of these additives added is usually in the range of 0.2 to 7 g / m ² .

In addition to the above additives, citric acid, tartaric acid, oxalic acid, boric acid, phosphoric acid and the like can be added as stabilizers.

The recording layer is usually provided in a solid content range of 2.5 to 25 g / m ² .

The support used in the present invention can be arbitrarily selected from materials known as supports for heat-sensitive recording materials such as high-quality paper, synthetic paper, and synthetic resin film, depending on the purpose. For example, as the paper support, heat-extracted pH 6 to 9 neutral paper sized with a neutral sizing agent such as an alkyl ketene dimer (described in JP-A-55-14281) is preferable in terms of storage stability over time. Others include JP-A-57-116687, JP-A-58-136492, JP-A-58-69091, JP-A-58-65695 and JP-A-59-35985. It is possible to use the paper and the like described in, for example.

Examples and comparative examples of the present invention will be described below. However, each of these examples does not limit the present invention. In the following examples, "parts" means "parts by weight" unless otherwise specified. [Example 1] (i) 20.7 parts of p-nitroaniline and 15.2 parts of triethylamine were dissolved in 120 parts of acetonitrile. Under ice cooling, 50.8 parts of β-2,4-di-tert-amylphenoxybutyric acid chloride was added dropwise and reacted. After completion of the reaction, the product was poured into water, extracted with ethyl acetate, and washed with water. Then, ethyl acetate was distilled off to obtain 62.5 parts of β-2,4-di-tert-amylphenoxy-butyric acid p-nitroanilide.

(Ii) 52.8 parts of the compound obtained in (i) above was reduced in methanol using hydrazine hydrate to give β-2,4-di-tert.
48.2 parts of amylphenoxy-butyric acid p-aminoanilide are obtained.

(Iii) 41 parts of β-2,4-di-tert-amylphenoxy-butyric acid p-aminoanilide obtained in (ii) above was added to 20 parts of methanol.
It was dissolved in 0 part, 18 parts of hydrochloric acid was added, and the mixture was cooled to -5 to 0 ° C. Add an aqueous solution of 6.9 parts of sodium nitrite to the solution at 0
Diazonium hydrochloride was added so as not to exceed ℃.
To this, 18.4 parts of potassium hexafluorophosphate was added and stirred at 0 ° C. for 2 hours, and the precipitated crystals were collected by filtration and dried to give 4-N- (β- (2,4-di-tert-aminophenoxy). Butyroyl) amino-benzenediazonium hexafluorophosphate (50 parts) was obtained (yield 88%).

Thus, the diazonium compound (A) was synthesized.

Example 2 (i) 44 parts of the compound obtained in (i) of Example 1 was reacted with dimethylsulfate in acetone in the presence of potassium carbonate to give 4-N-methyl-N- (β- ( 2,4-di-tert-aminophenoxy) butyroyl) aminonitrobenzene 37
Parts were obtained (yield 82%).

(Ii) 35 parts of the compound obtained in (i) above was treated in the same manner as in (ii) of Example [I] to give 4-N-methyl-N- (β- (2,4- J-ter
t-amylphenoxy) butyroyl) aminoaniline 29
Parts were obtained (yield 89%).

(Iii) The compound obtained in (ii) above is treated in the same manner as in the method in (iii) of Example [I] to give 4-N-methyl-N- (β- (2,4-di- −t
30 parts of ert-amylphenoxy) butyroyl) amino-benzenediazonium hexafluorophosphate was obtained (yield 76%).

Thus, the diazonium compound (B) was synthesized.

[Example 3] (i) In (i) of Example 1, p-nitroaniline was used.
27.6 parts, triethylamine 21 parts and acetonitrile 10
0 part was used, and 2-ethylhexanoic acid chloride was used instead of β-2,4-di-tert-amylphenoxybutyric acid chloride 50.8 parts.
By performing the same operation as in the method (i) of Example 1 except that 32.5 parts is used, p-ethyl 2-ethylhexanoate is obtained.
48.6 parts of nitroanilide was obtained (yield 92%).

(Ii) 45 parts of the compound obtained in (i) above was treated in the same manner as in the method of (ii) of Example [I] to give 2-ethylhexanoic acid p-aminoanilide 36.7.
Parts were obtained (yield 92%).

(Iii) 30 parts of the compound obtained in (ii) above was treated in the same manner as in (iii) of Example [I] to give 4-N- (2-ethylhexanoyl) amino-benzenediazonium hexa. Fluorophosphate
32.6 parts were obtained (yield 65%).

Thus, the diazonium compound (C) was synthesized.

The physical properties (melting point, solubility) of each of the diazonium compounds (A), (B) and (C) obtained above were evaluated by a usual test method.

The above evaluation results are summarized in Table 1.

However, the solubility in tricresyl phosphate (TCP) means the value measured at a liquid temperature of 50 ° C.

As is clear from the results shown in Table 1, all of the diazo compounds according to the present invention have a melting point within a preferable temperature range (60 to 15) as heat imparted to the heat-sensitive recording material.
At 0 ° C), these compounds showed high solubility in the solvent (TCP), but showed poor solubility in water.

Example 4 (i) Diazonium compound (A) obtained in Example 1
20 parts of [4-N- (β- (2,4-di-tert-amylphenoxy) butyroyl) amino-benzenediazonium hexafluorophosphate] was added to 100 parts of an aqueous solution of polyvinyl alcohol (5% by weight solution) to give Dynomil (Brelia -Bacophage AG product) was used for dispersion to prepare a diazo compound dispersion liquid having an average particle diameter of 2 μm.

(Ii) 20 parts of triphenylguanidine was added to 100 parts of a polyvinyl alcohol aqueous solution (5% by weight solution) and dispersed using Dynomill (manufactured by Brielia Bacofenage) to obtain a basic substance dispersion liquid having an average particle diameter of 3 μm. Prepared.

(Iii) 20 parts of 2-hydroxy-3-naphthoic acid anilide was added to 100 parts of an aqueous solution of polyvinyl alcohol (5% by weight solution) and dispersed using Dynomill (manufactured by Billier Bacofen AG) to obtain an average particle size of 3 μm. A coupling component dispersion was prepared.

(Iv) 40 parts of calcium carbonate was added to 60 parts of water prepared by dissolving 0.4 part of sodium hexametaphosphate and dispersed with Dynomill to prepare a calcium carbonate dispersion liquid.

10 parts of the obtained diazo compound dispersion, 10 dispersions of a basic substance
15 parts of the coupling component dispersion liquid and 15 parts of the calcium carbonate dispersion liquid were mixed to prepare a coating liquid.

This coating solution was applied to the surface of a smooth wood free paper (50 parts / m ² ) and dried at a temperature of 40 ° C. for 30 minutes to provide a thermosensitive recording layer having a dry weight of 5 g / m ² .

Thus, a thermosensitive recording sheet having the diazonium compound (A) dispersed therein was produced.

[Example 5] In Example 4, as a diazonium compound, (B) [4-N-methyl-N- (β- (2,4-di-tert-amylphenoxy) butyroyl) amino- was used instead of (A). A thermosensitive recording sheet having the diazonium compound (B) dispersed therein was produced by the same operation as in Example 4 except that benzenediazonium hexafluorophosphate] was used.

[Example 6] In Example 4, as the diazo compound, (C) [4-N- (2-ethylhexanoyl) amino- was used instead of (A).
A thermosensitive recording sheet having the diazonium compound (C) dispersed therein was produced by the same operation as in Example 4 except that benzenediazonium hexafluorophosphate was used.

[Example 7] In Example 4, as the diazo compound, (D) [4-N
A thermosensitive recording sheet in which the diazonium compound (D) is dispersed is obtained by performing the same operation as in the method of Example 4 except that-(2-ethylhexyl-N-acetylamino-benzenediazonium hexafluorophosphate) is used. Manufactured.

Comparative Example 1 The diazonium compound (a) was dispersed by performing the same operation as in Example 4 except that the diazonium compound (a) represented by the following formula was used as the diazo compound. A heat-sensitive recording sheet was produced as described above.

[Comparative Example 2] The diazonium compound (b) was dispersed in the same manner as in Example 4 except that the diazonium compound (b) represented by the following formula was used as the diazo compound. A heat-sensitive recording sheet was produced as described above.

Comparative Example 3 The diazonium compound (c) was dispersed by performing the same operation as in the method of Example 4 except that the diazonium compound (c) represented by the following formula was used as the diazo compound. A heat-sensitive recording sheet was produced as described above.

Next, thermal recording was performed using each of the obtained thermal recording sheets.

The thermal recording sheet was loaded into a facsimile (Melface 6200, manufactured by Mitsubishi Electric Corp.), and the thermal head was operated to perform thermal recording on the recording sheet. A clear red image was obtained on each of the heat-sensitive recording sheets.

Each thermosensitive recording sheet from which a recorded image was obtained was evaluated by the color density test described below.

Density test From the recording layer side of each thermal recording sheet, the coloring density (magenta density) of the sheet surface was measured by a Macbeth reflection densitometer (RD-918,
It was measured by Macbeth Co., Ltd.).

The above results are shown in Table 2.

From the results shown in Table 2, heat-sensitive recording sheets containing the diazo compound according to the present invention in a dispersed state (Examples 4 to 6).
It is clear that a printed image having a level substantially equal to the level of image density generally required as a thermal recording material can be obtained.

Further, each of the obtained heat-sensitive recording sheets was evaluated by conducting a raw storability test (moisture resistance, heat resistance, light resistance) described below.

Humidity resistance test Each thermosensitive recording sheet was left in an atmosphere of room temperature of 40 ° C. and relative humidity of 90% RH for 24 hours, and the coloring density on the surface of the sheet was measured in the same manner as above.

Heat resistance test Each thermosensitive recording sheet was allowed to stand in an atmosphere of room temperature of 60 ° C. and relative humidity of 30% RH for 24 hours, and the color density of the sheet surface was measured in the same manner as above.

Humidity resistance test The sheet surface side (recording layer side) of each thermal recording sheet was exposed for 16 hours under a fluorescent lamp (28000 lux), and the color density of the sheet surface was measured in the same manner as above.

The above results are summarized in Table 3. In addition, Table 3 also shows the coloring density before the test.

From the results shown in Table 3, thermosensitive recording sheets containing the diazo compound according to the present invention in a dispersed state (Examples 4 to 7).
It is clear that has excellent raw storage stability.
On the other hand, even if they have similar chemical structures, diazonium compounds with one or two methoxy, ethoxy, butoxy, or other substituents on the benzene ring that is bonded to the diazo group are more resistant to heat and light. It turns out that the sex is insufficient.

[Example 8] (i) Diazonium compound (A) obtained in Example 1
[4-N- (β- (2,4-di-tert-amylphenoxy) butyroyl) amino-benzenediazonium hexafluorophosphate] 5.1 parts, tricresyl phosphate 6 parts, methylene chloride 12 parts, trimethylolpropane trimeta 18 parts acrylate and Takenate D-110N
24 parts (manufactured by Takeda Pharmaceutical Co., Ltd.) were mixed to prepare a solution as a core substance.

This solution was added to an aqueous solution in which 63 parts of a polyvinyl alcohol aqueous solution (8% by weight solution) was dissolved in 100 parts of distilled water, and the mixture was emulsified and dispersed at a temperature of 20 ° C. to obtain an emulsion having an average particle diameter of 2 μm. 20 while stirring this emulsion at 40 ° C for 3 hours.
The mixture was cooled to ° C to obtain a microcapsule liquid containing a diazo compound as a core substance.

(Ii) Triphenylguanine chloride (42 parts) was added to a polyvinyl alcohol aqueous solution (6.7% by weight solution) (124 parts) and dispersed using Dynomill (manufactured by Brielia-Bakofenage) to obtain a basic substance dispersion liquid having an average particle diameter of 3 μm. Was prepared.

(Iii) 28 parts of 2-hydroxy-3-naphthoic acid anilide was added to 138 parts of an aqueous solution of polyvinyl alcohol (4% by weight solution) and dispersed using Dynomill (manufactured by Billier Bacofen AG) to obtain an average particle size of 3 μm. A coupling component dispersion was prepared.

10 parts of the obtained microcapsule liquid, 10 basic substance dispersion liquid
Parts, 10 parts of the coupling component dispersion liquid and 30 parts of the calcium carbonate dispersion liquid (40% by weight solution) were mixed to prepare a coating liquid.

This coating solution was applied to the surface of a smooth wood free paper (50 parts / m ² ) and dried at a temperature of 40 ° C. for 30 minutes to provide a thermosensitive recording layer having a dry weight of 15 g / m ² .

Thus, a thermosensitive recording sheet containing the diazonium compound (A) in the microcapsules was produced.

[Example 9] In Example 8, as a diazonium compound, (B) [4-N-methyl-N- (β- (2,4-di-tert-amylphenoxy) butyroyl) amino- was used instead of (A). A heat-sensitive recording sheet having microcapsules containing the diazonium compound (B) was produced by performing the same operation as in Example 7 except that benzenediazonium hexafluorophosphate was used.

[Example 10] In Example 8, as the diazo compound, (C) was replaced with (C) [4-N- (2-ethylhexanoyl) amino-] instead of (A).
A heat-sensitive recording sheet having microcapsules containing the diazonium compound (C) was produced by the same procedure as in Example 7, except that benzenediazonium hexafluorophosphate was used.

[Example 11] In Example 8, as the diazo compound, (D) [4-N
-(2-ethylhexyl) -N-acetylamino-benzenediazonium hexafluorophosphate] is used, and the diazonium compound (D) is contained in microcapsules by the same operation as in the method of Example 8. A thermal recording sheet was manufactured.

Comparative Example 4 The procedure of Example 8 was repeated except that the diazonium compound (a) used in Comparative Example 1 was used as the diazo compound. A thermosensitive recording sheet containing the capsule was produced.

Comparative Example 5 The procedure of Example 8 was repeated except that the diazonium compound (b) used in Comparative Example 2 was used as the diazo compound. A thermosensitive recording sheet containing the capsule was produced.

Comparative Example 6 The procedure of Example 8 was repeated except that the diazonium compound (c) used in Comparative Example 3 was used as the diazo compound. A thermosensitive recording sheet containing the capsule was produced.

Next, thermal recording was performed using each of the obtained thermal recording sheets by using the same apparatus as above, and a clear red image was obtained on each of the thermal recording sheets.

Subsequently, the same coloring density test as above was performed for evaluation. The obtained results were almost the same as the measurement results shown in Table 2 above. That is, even in the thermal recording sheets containing microcapsules containing the diazo compound according to the present invention as the core substance (Examples 8 to 10), the thermal recording sheets containing the diazo compound in the dispersed state (Examples 4 to 6) were used. A similar recorded image (coloring density) could be obtained.

Further, each thermal recording sheet was evaluated by conducting a raw storability test (moisture resistance, heat resistance, light resistance) under the same conditions as above.

The above results are summarized in Table 4. In addition, Table 4 also shows the coloring density before the test.

From the results shown in Table 4, it can be seen that the thermosensitive recording sheets (Examples 8 to 11) containing the microcapsules containing the diazo compound according to the present invention as the core substance also have excellent raw storability. it is obvious. On the other hand, even if they have similar chemical structures, diazonium compounds with one or two methoxy, ethoxy, butoxy, or other substituents on the benzene ring that is bonded to the diazo group are more resistant to heat and light. It turns out that the sex is insufficient.

[Example 12] (i) In Example 8 (i), the diazo compound (A) was used.
Except that the diazo compound 2,5-dibutoxy-4-morpholinobenzenediazonium hexafluorophosphate is used in place of the diazo compound, by performing the same operation as in the method of (i) of Example 8, A microcapsule solution containing the diazo compound of was prepared.

(Ii) In (ii) of Example 8, 2-hydroxy-3
-A coupling component dispersion liquid was prepared by performing the same operation as in the method of (ii) of Example 8 except that metaxylylenediamine bispivaloyl acetic acid amide was used instead of naphthoic acid anilide.

In Example 8, (i) above and (i) of Example 8
5 parts each of the microcapsule liquid obtained in step 5, 20 parts of the basic substance dispersion liquid, 10 parts of each coupling component dispersion liquid obtained in (ii) above and (ii) of Example 8 and 40 parts of calcium carbonate dispersion liquid. Was mixed to prepare a coating solution, and the same procedure as in Example 8 was carried out except that this coating solution was used to provide a thermosensitive recording layer having a dry weight of 20 g / m ² .

Thus, a thermosensitive recording sheet containing both the diazonium compound (A) and microcapsules each having a diazo compound other than the diazo compound according to the present invention as a core substance was produced.

Next, thermal recording was performed using the above-obtained thermosensitive recording sheet by using the same apparatus as above, and a black clear image was obtained on the thermosensitive recording sheet.

Further, after irradiating the heat-sensitive recording sheet with light (wavelength 400 nm) for 6 minutes, heat recording was carried out by using the same device as above, and a clear red image was obtained on the heat-sensitive recording sheet.
The density at that time was evaluated by the same coloring density test as above. The obtained results were almost the same as the measurement results shown in Table 2 above (magenta concentration: 0.98). That is, the thermosensitive recording sheet (Example 12) containing the microcapsules having the diazo compound according to the present invention as a core substance and the microcapsules having other diazo compounds as a core substance in combination (Example 12) also relates to the present invention. The same recorded image (color density) as that of the thermosensitive recording sheet containing the diazo compound in a dispersed state (Examples 4 to 6) could be obtained.

Further, the above thermal recording sheet was evaluated by conducting a raw storability test (moisture resistance, heat resistance, light resistance) under the same conditions as above.

The above results are summarized in Table 5. In addition, Table 5 also shows the coloring density before the test.

From the results shown in Table 5, a thermosensitive recording sheet containing microcapsules having the diazo compound according to the present invention as a core substance and microcapsules having other diazo compounds as a core substance in combination (implementation) It is clear that Example 12) also has excellent raw preservation properties.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shohei Yoshida 200 Onakazato, Fujinomiya-shi, Shizuoka Prefecture Fuji Photo Film Co., Ltd. (56) References JP-A-60-49991 (JP, A) JP-A-59-165689 (JP, A) JP 59-27957 (JP, A)

Claims (5)

[Claims] 1. A heat-sensitive recording material having a heat-sensitive recording layer comprising a diazo compound and a binder containing a coupling component on a support, wherein the heat-sensitive recording layer is at least a diazo compound represented by the following general formula (I). Thermosensitive recording material characterized by being a layer containing a compound: (However, R ¹ represents a substituted or unsubstituted acyl group having 1 to 30 carbon atoms, R ² represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and X ⁻ represents an acid anion). 2. The heat-sensitive recording material according to claim 1, wherein the total number of carbon atoms of R ¹ and R ^{2 in} the general formula (I) is in the range of 5 to 30. 3. The heat-sensitive recording according to claim 1, wherein the diazo compound represented by the general formula (I) is contained in the heat-sensitive recording layer in an amount in the range of 0.02 to ² g / m ^2. material. 4. The heat-sensitive recording material according to claim 1, wherein the diazo compound and the coupling component are solid-dispersed in the heat-sensitive recording layer. 5. The heat-sensitive recording material according to claim 1, wherein the diazo compound is dispersed in the heat-sensitive recording layer in a state of being encapsulated in microcapsules, and the coupling component is solidly dispersed around it.