JP2002226446A - Diazonium salt and heat sensitive recording material containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a diazonium salt important as a heat sensitive recording material and a heat sensitive recording material excellent in optical fixing and hardly having a color of texture. SOLUTION: This diazonium salt is expressed by general formula (1) [wherein R1, R2, R3, R4, R5, R6, R7 and R8 independently express each H, a halogen, an alkyl, an alkoxy, an alkylthio or an arylthio; R9 and R10 independently express each H, an alkyl or an aryl; R2 and R3, R1 and R4, R3 and R6, R4 and R5, R6 and R7, R5 and R8, R7 and R9, R8 and R10 and R9 and R10 may each form a ring by bonding to each other; X- expresses an anion]. This heat sensitive recording material contains the diazonium salt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a diazonium salt which is important as a synthetic intermediate or analytical reagent for azo dyes and a material for thermal recording materials. Further, the present invention relates to a heat-sensitive recording material using a diazonium salt and a coupler as a color-forming component, and more particularly to a heat-sensitive recording material which is excellent in fixability by light and has little background coloring.

[0002]

2. Description of the Related Art Diazonium salts are known as important synthetic intermediates for azo dyes. Various methods for synthesizing azo dyes have been conventionally known, and are described in “New Experimental Chemistry Course” (Maruzen Co., Ltd., Vol. 14-III, Volume 1516-15).
34), there are synthesis by oxidation, synthesis by reduction, synthesis by substitution, synthesis by addition, synthesis by condensation, and other synthesis methods. However, widely used as an industrial production method of azo dyes, in view of availability of raw materials, cost, yield, etc., synthesis is performed by azo coupling of a diazonium salt with a coupler such as aniline or phenol. How to In such a method, there is a danger that a diazonium salt explodes in the course of the synthesis. Therefore, the development of a stable diazonium salt with less fear of explosion has been demanded.

[0003] Also, diazonium salts are disclosed in
As described in No. 28517, it is used for quantitative analysis of bilirubin, which is a main component of bile pigment contained in body fluids, and is positioned as an important compound in the medical and pharmaceutical fields.

A diazonium salt is generally a compound having a very high chemical activity, and easily reacts with a compound having a phenol derivative or an active methylene group, a so-called coupler, to easily form an azo dye, and has a photosensitivity. Has its activity decomposed by light irradiation and loses its activity. Therefore,
A diazonium salt has been used for a long time as an optical recording material represented by diazo copy ("Photographic Engineering Fundamentals-Non-Silver Salt Photography-" edited by The Photographic Society of Japan, Corona Co., Ltd. (1982)).
p. 89-P117, p. 182 to P201).

[0005] Furthermore, recently, utilizing the property of decomposing by light and losing activity, it is applied to a recording material which requires fixing of an image, and a typical example is a recording material containing a diazonium salt and a coupler. A photo-fixing type heat-sensitive recording material has been proposed in which a recording material provided with a layer is heated and reacted in accordance with an image signal to form an image, and then irradiates light to fix the image (Koji Sato et al., The Institute of Image Electronics Engineers of Japan). Journal Vol. 11, No. 4, (1982) pp. 290-296).

In these recording materials using a diazonium salt as a color-forming component, the chemical activity of the diazonium salt is very high, and even in a dark place, the diazonium salt gradually decomposes thermally and loses its reactivity. There is a disadvantage that the shelf life as a recording material is short. In addition, there is a disadvantage that the residual diazonium salt compound is decomposed at the background portion, which is a non-image portion, at the time of light fixing, and the non-image portion is colored due to generation of a colored decomposition product (stain). Furthermore, even in the completed image after fixing, the non-image portion has a weak light resistance, and there is a drawback that coloring is increased when the image is left for a long time under sunlight or a fluorescent lamp.

Various methods have been proposed as means for improving the instability of such diazonium salts. One of the most effective means is to encapsulate a diazonium salt in microcapsules. Microencapsulation of the diazonium salt isolates the diazonium salt from substances that promote decomposition, such as water and bases, so that its decomposition is significantly suppressed and the shelf life of the recording material using it is dramatically improved. (Masamasa Usami et al., "Journal of the Electrographic Society of Japan," Vol. 26, No. 2, (1987) pp. 115-125).

As a general method for encapsulating a diazonium salt in microcapsules, a diazonium salt is dissolved in a hydrophobic solvent (oil phase), and this is added to an aqueous solution (water phase) in which a water-soluble polymer is dissolved. While emulsifying and dispersing with a homogenizer or the like, the monomer or prepolymer serving as the wall material of the microcapsules is added to either the oil phase side or the aqueous phase side, or both, so that the oil phase and the aqueous phase Is a method in which a polymerization reaction is caused at the interface of the polymer or a polymer is precipitated to form a wall made of a polymer compound to form microcapsules. Such a method
For example, it is described in detail in "Microcapsule" (by Asashi Kondo, published by Nikkan Kogyo Shimbunsha, 1970) and "Microcapsule" (by Tamotsu Kondo et al., Published by Sankyo Publishing, 1977).

As the capsule wall of the formed microcapsule, various materials such as cross-linked gelatin, alginate, celluloses, urea resin, urethane resin, melamine resin, nylon resin and the like can be used.

In particular, in the case of a microcapsule having a glass transition temperature such as a urea resin or a urethane resin and having a wall whose glass transition temperature is slightly higher than room temperature, the capsule wall exhibits material impermeability at room temperature. On the other hand, since it shows a substance permeability above its glass transition temperature, it is called a thermoresponsive microcapsule, and it can be said that it is very useful for a heat-sensitive recording material.

That is, in a thermosensitive recording material in which a thermoresponsive microcapsule containing a diazonium salt on a support and a thermosensitive recording layer containing a coupler as a main component for color development outside the capsule, the diazonium salt is long. At the same time, the color image can be easily formed by heating, and the formed image can be fixed by further light irradiation. The microencapsulation of the diazonium salt makes it possible to dramatically improve the stability as a recording material.

As described above, although the stability as a heat-sensitive recording material is remarkably improved, the instability caused by the diazonium salt itself is not completely suppressed, and the heat-sensitive recording material or the like is not sufficiently controlled. It has not yet achieved long-term storage stability. In addition, even after printing and fixing, if exposed to a light source for a long period of time, the photodegradation product of the diazonium salt causes a photodecomposition reaction, and the coloring stain increases with the reaction, resulting in a non-image after photofixation. There is also a problem that the whiteness of the portion (background portion) is reduced and the contrast with the colored portion is also reduced.

Further, it is known that the above photodecomposition reaction cannot occur uniformly, and various decomposition products are produced depending on the surrounding environment and the like. This results in a product called photolytic stain, which has absorption in the visible region in particular. Here, if the occurrence of this stain is remarkable, the whiteness of the non-image portion (background portion) after light fixing is reduced, and the contrast with the color-developed portion is also reduced. As a result, the commercial value of the recording material itself is significantly impaired. Become.

However, since the photolysis reaction of the diazonium salt is complicated and it is difficult to specify the product, it is difficult to suppress the photolysis stain. Accordingly, in recent years, studies on the improvement of long-term stabilization caused by photodegradation stain have been actively conducted. For example, in Japanese Patent Application Laid-Open No. 8-324129, a specific hydrophobic property of a microcapsule containing a photo-fixing type diazonium salt is disclosed. A light-fixing type heat-sensitive recording material that has excellent raw storability and excellent image storability without loss of whiteness even after being exposed to light for a long time after image formation has been proposed by using a hydrophobic oil in combination. I have. Japanese Unexamined Patent Application Publication No. 11-78232 proposes a non-fixing type heat-sensitive recording material using a novel diazonium salt for the purpose of improving the stability of the diazonium salt itself.
That is, a diazonium salt having a maximum light absorption wavelength in a shorter wavelength range than near 350 nm is encapsulated in a microcapsule,
The non-fixing type thermosensitive recording material using the microcapsules improves the whiteness and image storability of the background after image formation under a light source having a wavelength longer than about 350 nm, typically represented by a fluorescent lamp. Proposed.

However, depending on the preservation environment, raw preservability,
At present, image storability in a color-developed portion and a background portion (non-image portion) after image recording is not yet sufficient, and a further improvement in stability is currently required.

Further, in recent years, there has been a strong demand for shortening the recording time required for image recording, that is, for increasing the speed of image formation including printing and fixing. In particular, in a light-fixing type heat-sensitive recording material using a diazonium salt, there has been a demand. There is a high demand for a technique capable of achieving high speed while improving the stability as described above, and in order to meet the demand, an improvement in the photodecomposition rate of the diazonium salt itself is an essential condition.

These recording materials using a diazonium salt as a color-forming component are generally irradiated with ultraviolet light having a wavelength of about 360 nm in the fixing step in order to efficiently fix light. However, ultraviolet light requires a special light source, and furthermore, there is a problem that the influence on the eyes is concerned. Therefore, a recording material using a diazonium salt that can be efficiently fixed to a light source of visible light having a wavelength longer than 400 nm is used. Was required.

However, the conventional recording material using a diazonium salt has a problem in that when it is deactivated with a light source having a wavelength longer than 400 nm, the fixing is slow and takes a long time. Further, when light fixing is performed for a long time for the purpose of completely fixing, there is a problem that a product generated by the fixing is further reacted and a color image having a low background whiteness may be obtained.

[0019]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and achieve the following objects. SUMMARY OF THE INVENTION An object of the present invention is to provide a diazonium salt which has no concern about explosiveness and is important as an intermediate for azo dye synthesis or an analytical reagent or a material for a heat-sensitive recording material.
Another object of the present invention is to provide a heat-sensitive recording material using a diazonium salt and a coupler as a color-forming component, and in particular, to provide a heat-sensitive recording material that is excellent in fixability by light and has little background coloring.

[0020]

The object of the present invention can be achieved by the following means. <1> A diazonium salt represented by the following general formula (1).

Embedded image

[In the general formula (1), R ¹ , R ² , R ³ , R ⁴ ,
R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an alkylthio group or an arylthio group, and R ⁹ and R ¹⁰ each independently represent a hydrogen atom, an alkyl group or Represents an aryl group. R ² and R ^3, R ¹ and R ^4, R ³ and R ^6, R ⁴ and R ^5, R ⁶ and R ^7, R ⁵ and R ^8, R ⁷ and R ^9, R ⁸ and R ¹⁰ and R ⁹ And R ¹⁰
May combine to form a ring. X ^- represents an anion. ]

<2> The diazonium salt according to <1>, wherein the diazonium salt is represented by the following general formula (2).

Embedded image

[In the general formula (2), R ² and R ⁴ each independently represent a hydrogen atom, a halogen atom, an alkyl group or an alkoxy group, and R ⁹ and R ¹⁰ each independently represent a hydrogen atom, an alkyl group or an aryl group. Represents a group. R ⁹ and R ¹⁰ may combine to form a ring. X ^- represents an anion. ]

<3> A heat-sensitive recording material provided with a heat-sensitive recording layer containing a diazonium salt and a coupler on the surface of a support, wherein the diazonium salt is the diazonium salt described in <1>. It is a thermosensitive recording material.

<4> The thermosensitive recording material according to <3>, wherein the diazonium salt is the diazonium salt according to <2>.

<5> The coupler is a compound represented by the following general formula (3): <3>
Or the heat-sensitive recording material according to any one of <4>.

Embedded image

[In the general formula (3), E ¹ and E ² each independently represent an electron-withdrawing group. E ¹ and E ² may combine to form a ring. ]

<6> The diazonium salt is encapsulated in a microcapsule, <3> to <5>.
The thermal recording material according to any one of the above.

<7> The thermosensitive recording material according to <6>, wherein the capsule wall of the microcapsule contains polyurethane and / or polyurea.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the diazonium salt of the present invention and a heat-sensitive recording material containing the same will be described in detail.

<Diazonium Salt> The diazonium salt of the present invention is characterized by being represented by the following general formula (1).

Embedded image

[In the general formula (1), R ¹ , R ² , R ³ , R ⁴ ,
R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an alkylthio group or an arylthio group, and R ⁹ and R ¹⁰ each independently represent a hydrogen atom, an alkyl group or Represents an aryl group. R ² and R ^3, R ¹ and R ^4, R ³ and R ^6, R ⁴ and R ^5, R ⁶ and R ^7, R ⁵ and R ^8, R ⁷ and R ^9, R ⁸ and R ¹⁰ and R ⁹ And R ¹⁰
May combine to form a ring. X ^- represents an anion. ]

The diazonium salt of the present invention has the general formula (1)
As represented by the above formula, it is constituted by a 4'-aminobiphenyl skeleton having an amino group at the 4'-position. This allows
The maximum light absorption wavelength of the diazonium salt is longer than 450 nm. In addition, the diazonium salt has relatively good thermal stability, and it can be said that there is no concern about explosiveness.

In the general formula (1), R ¹ , R ² , R ³ ,
R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an alkylthio group or an arylthio group. R ⁹ and R ¹⁰ each independently represent a hydrogen atom, an alkyl group or an aryl group.

The above R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷
And a halogen atom represented by R ⁸ is preferably a fluorine atom, a chlorine atom, a bromine atom or an iodine atom,
Particularly, a chlorine atom and a bromine atom are preferable.

The above R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ ,
The alkyl group represented by R ⁷ , R ⁸ , R ⁹ and R ¹⁰ is preferably an alkyl group having a total of 1 to 30 carbon atoms,
Twelve alkyl groups are more preferred. The alkyl group may be unsubstituted or may have a substituent, and the substituent may be a phenyl group, a halogen atom, an alkoxy group, an aryloxy group, an alkoxycarbonyl group,
Acyloxy group, acylamino group, carbamoyl group, cyano group, alkylsulfonyl group, allylsulfonyl group, sulfonamide group, sulfamoyl group, acyl group,
Heterocyclic groups are preferred.

The above R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ ,
Examples of the alkyl group represented by R ⁷ , R ⁸ , R ⁹ and R ¹⁰ include a methyl group, an ethyl group, a normal propyl group, an isopropyl group, a normal butyl group, a tertiary butyl group, a normal hexyl group, a normal octyl Group,
2-ethylhexyl group, 3,5,5-trimethylhexyl group, normal dodecyl group, cyclohexyl group, benzyl group, α-methylbenzyl group, allyl group, 2-chloroethyl group, 2-methoxyethyl group, 2-ethoxyethyl Group, 2-phenoxyethyl group, 2- (2,5-di-tert-amylphenoxy) ethyl group, 2-benzoyloxyethyl group, methoxycarbonylmethyl group, methoxycarbonylethyl group, butoxycarbonylethyl group,
2-isopropyloxyethyl group, 2-methanesulfonylethyl group, 2-ethoxycarbonylmethyl group, 1-
(4-Methoxyphenoxy) -2-propyl group, trichloromethyl group, and trifluoromethyl group are preferable, and among them, methyl group, ethyl group, normal butyl group, normal hexyl group, normal octyl group, and 2-methoxyethyl group are preferable. More preferred are a methyl group, an ethyl group, a normal butyl group, a normal hexyl group, and a normal octyl group.

The above R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷
And the alkoxy group represented by R ⁸ has a total carbon number of 1 to 2
An alkoxy group having 0 is preferable, and an alkoxy group having 1 to 12 carbon atoms is more preferable. Further, the alkoxy group is
It may have a substituent, and as the substituent, a phenyl group, a halogen atom, an alkoxy group, an aryloxy group,
Preferred are an alkoxycarbonyl group, an acyloxy group, an acylamino group, a carbamoyl group, a cyano group, an alkylsulfonyl group, an allylsulfonyl group, a sulfonamide group, a sulfamoyl group, an acyl group, and a heterocyclic group.

The above R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷
And the alkoxy group represented by R ⁸ include, for example,
Methoxy group, ethoxy group, normal propyloxy group,
Isopropyloxy group, normal butyloxy group, tertiary butyloxy group, normal hexyloxy group,
Normal heptyloxy group, normal octyloxy group, 2-ethylhexyloxy group, 3,5,5, -trimethylhexyloxy group, normal decyloxy group, normal dodecyloxy group, cyclohexyloxy group, benzyloxy group, allyloxy group, 2 -Methoxyethoxy group, 2-ethoxyethoxy group, 2-phenoxyethoxy group, 2- (2,5-di-tert-amylphenoxy) ethoxy group, 2-benzoyloxyethoxy group, methoxycarbonylmethyloxy group, methoxycarbonylethyl An oxy group, a butoxycarbonylethyloxy group,
A 2-isopropyloxyethyloxy group is preferable, and among them, a methoxy group, an ethoxy group, a normal butyloxy group, a tertiary butyloxy group, a normal hexyloxy group, a normal heptyloxy group, a normal octyloxy group, and a 2-methoxyethoxy group Are more preferable, and a methoxy group, an ethoxy group, a normal butyloxy group, a normal hexyloxy group, a normal heptyloxy group, and a normal octyloxy group are particularly preferable.

The above R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷
And the alkylthio group represented by R ⁸ has a total carbon number of 1 to
20 alkylthio groups are preferred, and alkylthio groups having a total of 1 to 12 carbon atoms are more preferred. Further, the alkylthio group may be unsubstituted or may have a substituent,
Examples of the substituent include a phenyl group, a halogen atom, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an acyloxy group, an acylamino group, a carbamoyl group, a cyano group, an alkylsulfonyl group, an arylsulfonyl group, a sulfonamide group, a sulfamoyl group, Acyl groups and heterocyclic groups are preferred.

The above R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷
And alkylthio groups represented by R ⁸ include, for example, methylthio, ethylthio, normal butylthio, tertiary butylthio, normal hexylthio, normal octylthio, 2-ethylhexylthio, normal dodecylthio Group, cyclohexylthio group,
A benzylthio group and an ethoxycarbonylmethylthio group are preferable, and among them, a normal octylthio group, a normal dodecylthio group, and a cyclohexylthio group are more preferable, and a normal octylthio group and a normal dodecylthio group are particularly preferable.

The above R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷
And the arylthio group represented by R ⁸ has a total carbon number of 6 to
30 arylthio groups are preferred, and arylthio groups having a total of 6 to 12 carbon atoms are more preferred. Further, the arylthio group may be unsubstituted or may have a substituent,
Examples of the substituent include a phenyl group, a halogen atom, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an acyloxy group, an acylamino group, a carbamoyl group, a cyano group, an alkylsulfonyl group, an arylsulfonyl group, a sulfonamide group, a sulfamoyl group, Acyl groups and heterocyclic groups are preferred.

The above R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷
And the arylthio group represented by R ⁸ include, for example, a phenylthio group, a 4-methylphenylthio group,
Methylphenylthio group, 2-methylphenylthio group, 4
-Chlorophenylthio group, 2-chlorophenylthio group,
A 1-naphthylthio group is preferred, and among these, a phenylthio group, a 4-methylphenylthio group, and a 2-chlorophenylthio group are more preferred, and a phenylthio group and a 4-methylphenylthio group are particularly preferred.

The aryl group represented by R ⁹ and R ¹⁰ is preferably an aryl group having 6 to 30 carbon atoms, and more preferably an aryl group having 6 to 12 carbon atoms. Further, the aryl group may be unsubstituted or may have a substituent, and the substituent includes a phenyl group, a halogen atom,
Preferable are an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an acyloxy group, an acylamino group, a carbamoyl group, a cyano group, an alkylsulfonyl group, an arylsulfonyl group, a sulfonamide group, a sulfamoyl group, an acyl group, and a heterocyclic group.

The aryl groups represented by R ⁹ and R ¹⁰ include, for example, phenyl, 4-methylphenyl, 3-methylphenyl, 2-methylphenyl,
-Chlorophenyl group, 2-chlorophenyl group, 4-nitrophenyl group, 4-acetamidophenyl group, 4-octanoylaminophenyl group, 4- (4-methylphenylsulfonylamino) phenyl group, and naphthyl group are preferred. Phenyl group, 4-methylphenyl group,
4-chlorophenyl group is more preferred, phenyl group, 4
-A methylphenyl group is particularly preferred.

In the general formula (1), X ⁻ represents an anion. The anion may be either an inorganic anion or an organic anion. Preferable examples of the inorganic anion include hexafluorophosphate ion, borofluoride ion, chloride ion, and sulfate ion, and among them, hexafluorophosphate ion and borofluoride ion are particularly preferable. Further, as the organic anion, for example, polyfluoroalkyl carboxylate ion,
Preferable examples include polyfluoroalkyl sulfonate ion, tetraphenyl borate ion, aromatic carboxylate ion, and aromatic sulfonate ion. Among them, polyfluoroalkyl sulfonate ion, tetraphenyl borate ion, and aromatic sulfonate ion are exemplified. Is particularly preferred.

R ¹ , R ³ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are preferably hydrogen atoms. In addition, R ² and / or
Alternatively, an alkoxy group is preferable as R ⁴ , and an alkyl group is preferable as R ⁹ and / or R ^10. The maximum light absorption wavelength of the diazonium salt having such a structure is 52.
The wavelength is increased to about 0 nm, and photodegradability is improved. Further, R ³ and R ⁶ may have a fluorene skeleton bonded by a methylene group, and a diazonium salt having such a structure has improved photodegradability.

Further, among the diazonium salts represented by the general formula (1), a diazonium salt represented by the following general formula (2) is more preferable.

Embedded image

[In the general formula (2), R ² and R ⁴ each independently represent a hydrogen atom, a halogen atom, an alkyl group or an alkoxy group, and R ⁹ and R ¹⁰ each independently represent a hydrogen atom, an alkyl group or an aryl group. Represents a group. R ⁹ and R ¹⁰ may combine to form a ring. X ^- represents an anion. ]

In the general formula (2), R ² and R ⁴ are
Each independently represents a hydrogen atom, a halogen atom, an alkyl group or an alkoxy group, and the hydrogen atom, the halogen atom,
The alkyl group or the alkoxy group has the same meaning as that of R ² and R ⁴ in the general formula (1), and preferred examples are also the same. R ⁹ and R ¹⁰ each independently represent a hydrogen atom, an alkyl group, or an aryl group, and the hydrogen atom, the alkyl group, or the aryl group have the same meanings as R ⁹ and R ¹⁰ in Formula (1). The same applies to preferred examples. Further, X ^- represents an anion,
It has the same meaning as that of X ⁻ in the general formula (1), and preferred examples are also the same.

Further, the diazonium salts represented by the general formulas (1) and (2) include R ¹ , R ² , R ³ , R ⁴ , R ⁵ ,
R ⁶ , R ⁷ , R ⁹ and R ¹⁰ may have a diazoniophenyl group as a substituent to form a bis-form or a multimer thereof.

The general formula (1) or (2) of the present invention is described below.
Illustrative compounds (A-1) to (A-24) are shown as specific examples of the diazonium salt represented by the formula, but the present invention is not limited thereto.

[0053]

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[0054]

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[0055]

Embedded image

The diazonium salt represented by the general formula (1) or (2) can be produced by a known method. That is, it can be obtained by diazotizing the corresponding aniline using sodium nitrite, nitrosylsulfuric acid, isoamyl nitrite or the like in an acidic solvent.

The diazonium salt represented by the general formula (1) or (2) may be oily or crystalline, but is preferably in a crystalline state at room temperature in terms of handleability. These diazonium salts may be used alone,
Two or more kinds may be used in combination, or may be used in combination with an existing diazonium salt.

When the diazonium salt is used in a heat-sensitive recording layer of a heat-sensitive recording material, the content of the diazonium salt is 0.1 to 0.1.
02 to 5 g / m ² , preferably 0.1 to 5 g / m ² in terms of color density.
４4 g / m ² is more preferred.

In order to stabilize the diazonium salt of the present invention, a complex compound may be formed using zinc chloride, cadmium chloride, tin chloride or the like to stabilize the diazonium salt.

The diazonium salt represented by the general formula (1) or (2) develops a color by a reaction with a coupler described later to obtain a high color density, while the 380 to 380 of a fluorescent lamp or the like is obtained.
It is excellent in photodecomposability in the wavelength range of 460 nm and has a high-speed decomposability that can sufficiently complete fixation even with short-time light irradiation. Therefore, it is very useful as a color-forming component used in a photo-fixing type thermosensitive recording material. .

<Coupler> Next, a coupler (coupling component) usable in the heat-sensitive recording material of the present invention will be described. The coupler has a basic atmosphere and / or
Alternatively, any compound that can form a dye by coupling with a diazonium salt in a neutral atmosphere can be used. All so-called 4-equivalent couplers for silver halide photographic materials can be used as couplers. These can be selected according to the desired hue. For example, there are a so-called active methylene compound having a methylene group next to a carbonyl group, a phenol derivative, a naphthol derivative, and the like. Specific examples include the following, which are used within a range that meets the purpose of the present invention.

Specific examples of the coupler include, for example,
Resorcin, phloroglucin, 2,3-dihydroxynaphthalene, sodium 2,3-dihydroxynaphthalene-6-sulfonate, morpholinopropylamide 1-hydroxy-2-naphthoate, sodium 2-hydroxy-3-naphthalenesulfonate, 2-hydroxy -3-naphthalenesulfonic acid anilide, 2-hydroxy-3-naphthalenesulfonic acid morpholinopropylamide, 2-hydroxy-3-naphthalenesulfonic acid-2-ethylhexyloxypropylamide, 2-hydroxy-3-naphthalenesulfonic acid-2- Ethylhexylamide, 5-acetamido-1-naphthol, 1-hydroxy-8-acetamidonaphthalene-3,6-disulfonate sodium, 1-hydroxy-8-acetamidonaphthalene-
3,6-disulfonic acid dianilide, 1,5-dihydroxynaphthalene, 2-hydroxy-3-naphthoic acid morpholinopropylamide, 2-hydroxy-3-naphthoic acid octylamide, 2-hydroxy-3-naphthoic acid anilide, 5, 5-dimethyl-1,3-cyclohexanedione, 1,3-cyclopentanedione, 5- (2-n-tetradecyloxyphenyl) -1,3-cyclohexanedione, 5-phenyl-4-methoxycarbonyl-1 ,
3-cyclohexanedione, 5- (2,5-di-n-octyloxyphenyl) -1,3-cyclohexanedione,

N, N'-dicyclohexyl barbituric acid, N, N'-di-n-dodecyl barbituric acid, N-
n-octyl-N'-n-otatadecyl barbituric acid, N-phenyl-N '-(2,5-di-n-octyl oxdiphenyl) barbituric acid, N, N'-bis (octadecyloxycarbonyl) Methyl) barbituric acid,
1-phenyl-3-methyl-5-pyrazolone, 1-
(2,4,6-trichlorophenyl) -3-anilino-
5-pyrazolone, 1- (2,4,6-trichlorophenyl) -3-benzamido-5-pyrazolone, 6-hydroxy-4-methyl-3-cyano-1- (2-ethylhexyl) -2-pyridone, 2 , 4-bis- (benzoylacetamido) toluene, 1,3-bis- (pivaloylacetamidomethyl) benzene, benzoylacetonitrile, thenoylacetonitrile, acetoacetanilide,
Benzoylacetanilide, pivaloylacetanilide, 2-chloro-5- (Nn-butylsulfamoyl) -1-bivaloylacetamidobenzene, 1- (2
-Ethylhexyloxypropyl) -3-cyano-4-
Methyl-6-hydroxy-1,2-dihydropyridine-
2-one, 1- (dodecyloxypropyl) -3-acetyl-4-methyl-6-hydroxy-1,2-dihydropyridin-2-one, 1- (4-n-octyloxyphenyl) -3-tert- Butyl-5-aminopyrazole and the like.

For details of the coupler, see JP-A-4-4-2.
01483, JP-A-7-223267, JP-A-7-223
223368, JP-A-7-323660, Japanese Patent Application No. 5
-278608, Japanese Patent Application No. 5-297024, Japanese Patent Application No. 6-18669, Japanese Patent Application No. 6-18670, Japanese Patent Application No. 7
No. 316280, Japanese Patent Application No. 8-027095, Japanese Patent Application No. 8-027096, Japanese Patent Application No. 8-030799, Japanese Patent Application No. 8-12610, Japanese Patent Application No. 8-132394, Japanese Patent Application No. 8-358755. And Japanese Patent Application Nos. 8-358756 and 9-0699990.

Among the above, in the present invention, a compound represented by the following general formula (3) or a tautomer thereof is particularly preferred. Hereinafter, the coupler represented by Formula (3) will be described in detail.

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[In the general formula (3), E ¹ and E ² each independently represent an electron-withdrawing group. E ¹ and E ² may combine to form a ring. ]

The electron-withdrawing group represented by E ¹ and E ² means a substituent having a positive Hammett's σ _p value, which may be the same or different. Acetyl, propionyl, pivaloyl, chloroacetyl, trichloroacetyl, trifluoroacetyl, 1-methylcyclopropylcarbonyl, 1
Acyl groups such as -ethylcyclopropylcarbonyl group, 1-benzylcyclopropylcarbonyl group, benzoyl group, 4-methoxybenzoyl group, and thenoyl group; methoxycarbonyl group, ethoxycarbonyl group, 2-methoxyethoxycarbonyl group, 4-methoxyphenoxy An oxycarbonyl group such as a carbonyl group; a carbamoyl group, N, N-
Dimethylcarbamoyl group, N, N-diethylcarbamoyl group, N-phenylcarbamoyl group, N- [2,4-bis (pentyloxy) phenyl] carbamoyl group, N-
Carbamoyl groups such as [2,4-bis (octyloxy) phenyl] carbamoyl group and morpholinocarbonyl group;
Alkylsulfonyl or arylsulfonyl such as methanesulfonyl, benzenesulfonyl and toluenesulfonyl; phosphono such as diethylphosphono; benzoxazol-2-yl, benzothiazole-2
-Yl group, 3,4-dihydroquinazolin-4-one-2
A heterocyclic group such as -yl group, 3,4-dihydroquinazoline-4-sulfon-2-yl group; a heterocyclic group; a nitro group; an imino group; and a cyano group.

The electron-withdrawing groups represented by E ¹ and E ² may be combined with each other to form a ring. E ¹ and E ²
Is preferably a 5- or 6-membered carbocyclic or heterocyclic ring.

The following are illustrative compounds (B-1) to (B-38) as specific examples of the coupler represented by the general formula (3), but the present invention is not limited thereto.
In addition, the tautomers of the couplers shown below can also be mentioned as preferable ones.

[0070]

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[0071]

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[0072]

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[0073]

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[0074]

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[0075]

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The tautomers of the above-mentioned couplers are those which exist as isomers of the above-mentioned couplers, and which have a relationship in which the structure easily changes between the two. The tautomers are also preferable as the coupler used in the above.

<Microencapsulation> In the heat-sensitive recording material of the present invention, a diazonium salt is preferably encapsulated in microcapsules for the purpose of improving the raw preservability before use. The method for forming the microcapsules can be appropriately selected from known methods.

The polymer substance forming the capsule wall of the microcapsule is required to have a property of being impermeable at normal temperature and permeable at the time of heating.
In particular, those having a glass transition temperature of 60 to 200 ° C. are preferable, for example, polyurethane, polyurea, polyamide,
Examples include polyester, urea / formaldehyde resin, melamine resin, polystyrene, styrene / methacrylate copolymer, styrene / acrylate copolymer, and a mixture thereof.

As a method for forming microcapsules, specifically, an interfacial polymerization method or an internal polymerization method is suitable. For details of the capsule forming method and specific examples of the reactants, see US Pat.
796,669 and the like. For example, when polyurea or polyurethane is used as the capsule wall material, a polyisocyanate and a second substance (for example, polyol or polyamine) which reacts with the polyisocyanate to form a capsule wall are mixed in an aqueous medium or an oil medium to be encapsulated. Then, these are emulsified and dispersed in water and then heated to cause a polymer forming reaction at the oil droplet interface to form a microcapsule wall. Note that polyurea can be generated even when the addition of the second substance is omitted.

In the present invention, the polymer substance forming the capsule wall of the microcapsule preferably contains at least one of polyurethane and polyurea as a component.

Next, a method for producing a diazonium salt-containing microcapsule (polyurea / polyurethane wall) will be described. First, a diazonium salt is dissolved or dispersed in a hydrophobic organic solvent serving as a core of a capsule to prepare an oil phase serving as a core of a microcapsule. At this time, a polyvalent isocyanate is further added as a wall material.

In preparing the oil phase, the hydrophobic organic solvent used for forming the core of the microcapsules by dissolving and dispersing the diazonium salt is preferably an organic solvent having a boiling point of 100 to 300 ° C., for example, alkylnaphthalene, Alkyl diphenyl ethane, alkyl diphenyl methane, alkyl biphenyl, alkyl terphenyl, chlorinated paraffin, phosphates, maleates, adipic esters, phthalates, benzoates, carbonates, ethers, Sulfuric esters, sulfonic esters and the like can be mentioned. These are 2
You may mix and use more than one kind.

When the solubility of the diazonium salt to be encapsulated in the organic solvent is poor, a low-boiling solvent having high solubility for the diazonium salt to be used may be used in combination. For example, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, methylene chloride, tetrahydrofuran, acetonitrile, acetone and the like can be mentioned.

For this reason, the diazonium salt preferably has an appropriate solubility in a high-boiling hydrophobic organic solvent and a low-boiling solvent. Specifically, the diazonium salt has a solubility of 5% or more in the solvent. Is preferred. The solubility in water is preferably 1% or less.

On the other hand, an aqueous solution in which a water-soluble polymer is dissolved is used for the aqueous phase, and after the oil phase is added thereto, emulsification and dispersion are carried out by means of a homogenizer or the like. And acts as a dispersion medium for stabilizing the emulsified aqueous solution. Here, in order to more uniformly emulsify and disperse and stabilize, a surfactant may be added to at least one of the oil phase and the aqueous phase. As the surfactant, a known surfactant for emulsification can be used. When the surfactant is added, the addition amount is preferably 0.1 to 5% by mass relative to the mass of the oil phase,
0.5 to 2% by mass is more preferable.

The water-soluble polymer used for the aqueous solution of the prepared water-soluble polymer in which the oil phase is dispersed is preferably a water-soluble polymer having a water solubility of 5% or more at the temperature at which the emulsion is to be emulsified. And modified products thereof, polyacrylamide and derivatives thereof, ethylene-vinyl acetate copolymer, styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyvinylpyrrolidone , Ethylene-acrylic acid copolymer, vinyl acetate-acrylic acid copolymer, carboxymethylcellulose, methylcellulose, casein, gelatin, starch derivatives, gum arabic, sodium alginate and the like.

The water-soluble polymer preferably has no or low reactivity with the isocyanate compound.
For example, those having a reactive amino group in the molecular chain, such as gelatin, are preferably modified beforehand to eliminate the reactivity.

As the polyvalent isocyanate compound,
A compound having a trifunctional or higher isocyanate group is preferable, but a bifunctional isocyanate compound may be used.
Specifically, diisocyanates such as xylene diisocyanate and its hydrogenated product, hexamethylene diisocyanate, tolylene diisocyanate and its hydrogenated product, and isophorone diisocyanate are used as main raw materials, and a dimer or trimer thereof (buret or isocyanate) is used. Nurate), as well as polyfunctional adducts of polyols such as trimethylolpropane and bifunctional isocyanates such as xylylene diisocyanate, and adducts of polyols such as trimethylolpropane and bifunctional isocyanates such as xylylene diisocyanate And a compound in which a high molecular weight compound such as polyether having active hydrogen such as polyethylene oxide is introduced, and a formalin condensate of benzene isocyanate.

The compounds described in JP-A-62-212190, JP-A-4-26189, JP-A-5-317694, JP-A-8-268721 and the like are preferred.

The amount of the polyvalent isocyanate used is determined so that the average particle size of the microcapsules is 0.3 to 12 μm and the wall thickness is 0.01 to 0.3 μm. The diameter of the dispersed particles is generally about 0.2 to 10 μm.

In an emulsified dispersion obtained by adding an oil phase to an aqueous phase,
At the interface between the oil phase and the aqueous phase, a polymerization reaction of the polyvalent isocyanate occurs to form a polyurea wall.

If a polyol and / or a polyamine are further added to the hydrophobic solvent in the aqueous phase or the oil phase, the polyol and / or polyamine can react with the polyvalent isocyanate and be used as one of the components of the microcapsule wall. . In the above reaction, it is preferable to keep the reaction temperature high or to add an appropriate polymerization catalyst from the viewpoint of increasing the reaction rate.

Specific examples of these polyols or polyamines include propylene glycol, glycerin, trimethylolpropane, triethanolamine, sorbitol, hexamethylenediamine and the like. When a polyol is added, a polyurethane wall is formed.

The details of polyvalent isocyanates, polyols, reaction catalysts, and polyamines for forming a part of the wall material are described in detail in the book (Polyurethane Handbook, edited by Keiji Iwata, Nikkan Kogyo Shimbun (1987)).

The emulsification can be carried out by appropriately selecting from known emulsifying apparatuses such as a homogenizer, a Manton-Gawley, an ultrasonic disperser, a dissolver and a Keddy mill.
After the emulsification, the emulsion is heated to 30 to 70 ° C. in order to promote the capsule wall forming reaction. During the reaction, in order to prevent aggregation of the capsules, it is necessary to lower the probability of collision between the capsules by adding water or to perform sufficient stirring.

During the reaction, a dispersion for preventing aggregation may be added again. Generation of carbon dioxide gas is observed with the progress of the polymerization reaction, and the end thereof can be regarded as an approximate end point of the capsule wall forming reaction. Usually, by reacting for several hours, a desired diazonium salt-encapsulated microcapsule can be obtained.

Next, the coupler used in the present invention can be used as a solid dispersion with a water-soluble polymer, an organic base, other color-forming auxiliaries and the like by a sand mill or the like. After dissolving in a high-boiling organic solvent that is hardly soluble or insoluble in water, this is mixed with a polymer aqueous solution (aqueous phase) containing a surfactant and / or a water-soluble polymer as a protective colloid, and emulsified with a homogenizer or the like. It is preferably used as a dispersion. In this case, if necessary, a low boiling point solvent can be used as a dissolution aid. Further, the coupler and the organic base can be separately emulsified and dispersed, or can be mixed and then dissolved in a high boiling organic solvent to be emulsified and dispersed. The preferred emulsified dispersion particle size is 1 μm or less. The amount of the coupler used is 0.1 to 30 parts by mass based on 1 part by mass of the diazonium salt.
Parts by weight are preferred.

The high boiling organic solvent used in this case is
For example, it can be appropriately selected from high boiling oils described in JP-A-2-141279. Among them, esters are preferable and tricresyl phosphate is particularly preferable from the viewpoint of the emulsion stability of the emulsified dispersion. It is also possible to use the above oils together or with other oils.

A low-boiling auxiliary solvent may be further added to the organic solvent as a solubilizing agent. Examples of the auxiliary solvent include ethyl acetate, isopropyl acetate, butyl acetate, and methylene chloride. Can be. Depending on the case, it is also possible to use only low-boiling auxiliary solvents without high-boiling oils.

As the water-soluble polymer to be contained as a protective colloid in the aqueous phase, a known anionic polymer,
It can be appropriately selected from nonionic polymers and amphoteric polymers, and among them, for example, polyvinyl alcohol, gelatin, cellulose derivatives and the like are preferable.

As the surfactant to be contained in the aqueous phase, an anionic or nonionic surfactant which does not cause precipitation or aggregation by acting with the above protective colloid is appropriately selected and used. can do. Examples of the surfactant include sodium alkylbenzene sulfonate, sodium alkyl sulfate, dioctyl sodium sulfosuccinate, polyalkylene glycol (for example, polyoxyethylene nonylphenyl ether) and the like.

In the present invention, in a preferred embodiment, an organic base is added as a basic substance in order to promote the coupling reaction between the diazonium salt and the coupler.
Examples of the organic base include nitrogen-containing compounds such as tertiary amines, piperidines, piperazines, amidines, formamidines, pyridines, guanidines, morpholines, and the like. -46806, JP-A-62-70082, JP-A-57-16
9745, JP-A-60-94381, JP-A-57-123086, JP-A-60-49991
JP-B, JP-B-2-24916, JP-B-2-28
479, JP-A-60-165288, and JP-A-57-185430 can be suitably mentioned. These may be used alone or in combination of two or more.

Of the above, specifically, N, N'-bis (3-phenoxy-2-hydroxypropyl) piperazine, N, N'-bis [3- (p-methylphenoxy)-
2-hydroxypropyl] piperazine, N, N′-bis [3- (p-methoxyphenoxy) -2-hydroxypropyl] piperazine, N, N′-bis (3-phenylthio-2-hydroxypropyl) piperazine, N, N N'-
Bis [3- (β-naphthoxy) -2-hydroxypropyl] piperazine, N-3- (β-naphthoxy) -2-hydroxypropyl-N′-methylpiperazine, 1,4-
Piperazines such as bis {[3- (N-methylpiperazino) -2-hydroxy] propyloxy) benzene;
[3- (β-naphthoxy) -2-hydroxy] propylmorpholine, 1,4-bis (3-morpholino-2-hydroxy-propyloxy) benzene, 1,8-bis (3
Morpholinos such as -morpholino-2-hydroxy-propyloxy) benzene, piperidines such as N- (3-phenoxy-2-hydroxypropyl) piperidine, N-dodecylpiperidine, triphenylguanidine, tricyclohexylguanidine, dicyclohexylphenylguanidine And the like are preferred.

The amount of the organic base to be used is preferably 0.1 to 30 parts by mass relative to 1 part by mass of the diazonium salt. If the amount is less than 0.1 part by mass, a sufficient color density may not be obtained. If the amount exceeds 30 parts by mass, decomposition of the diazonium salt may be promoted.

Further, in addition to the above-mentioned organic base, a coloring aid may be added to the heat-sensitive recording layer for the purpose of accelerating the coloring reaction, that is, rapidly and completely performing thermal printing with low energy. Here, the coloring aid is a substance that increases the coloring density during heating recording or controls the coloring temperature, such as lowering the melting point of a coupler, a basic substance or a diazonium salt, or the softening point of the capsule wall. The condition is such that a diazonium salt, a basic substance, a coupler, and the like are easily reacted by an action capable of lowering the concentration.

Examples of the coloring aid include phenol derivatives, naphthol derivatives, alkoxy-substituted benzenes, alkoxy-substituted naphthalenes, aromatic ethers, thioethers, esters, amides, ureides, urethanes, and the like.
Examples thereof include a sulfonamide compound and a hydroxy compound.

The coloring aid also includes a heat-meltable substance. The heat-meltable substance is a substance that is solid at room temperature and melts by heating and has a melting point of 50 ° C. to 150 ° C., and is a substance that can dissolve a diazonium salt, a coupler, an organic base, or the like. Specific examples include carboxylic amides, N-substituted carboxylic amides, ketone compounds, urea compounds, esters and the like.

In the heat-sensitive recording material of the present invention, the fastness of a thermochromic image to light and heat is improved, or
For the purpose of reducing the yellowing of the unprinted portion (non-image portion) after fixing by light, it is also preferable to use the following known antioxidants and the like.

The antioxidants are described, for example, in European Patent Publication Nos. 223739 and 30940.
Nos. 1, 309, 402, and 310,551
JP-A-310552, JP-A-59416, JP-A-3435443, JP-A-54-48535, JP-A-62-262047, JP-A-63-113536 and JP-A-63-16335.
No. 1, JP-A-2-262654, JP-A-2-262654
No. 71262, JP-A-3-121449, JP-A-5-61166, JP-A-5-119449, U.S. Pat. No. 4,814,262, U.S. Pat. No. 4,980,275, and the like. It is also effective to use various known additives already used in heat-sensitive or pressure-sensitive recording materials.

Examples of the various additives include, for example, JP-A-60-107384, JP-A-60-107383, JP-A-60-125470 and JP-A-60-12547.
No. 1, No. 60-125472, No. 60-28
7485, 60-287486, 60
-287487, 60-287488,
No. 61-160287, No. 61-185483, No. 61-211079, No. 62-1466
No. 78, No. 62-146680, No. 62-1
Nos. 46679 and 62-282885 and 6
JP-A-3-051174, JP-A-63-89877,
JP-A-63-88380, JP-A-63-088381, JP-A-63-203372, and JP-A-63-22498.
Nos. 9 and 63-251282, 63-26
No. 7594, No. 63-182484, Japanese Patent Application Laid-Open No. 1-239282, No. 4-291885,
JP-A-4-291684, JP-A-5-188687, JP-A-5-188686, JP-A-5-110490, JP-A-5-170361, JP-B-48-043
No. 294, No. 48-033212 and the like.

Specifically, 6-ethoxy-1-phenyl-2,2,4-trimethyl-1,2-dihydroquinoline, 6-ethoxy-1-octyl-2,2,4-trimethyl-1,2 -Dihydroquinoline, 6-ethoxy-1-
Phenyl-2,2.4-trimethyl-1,2,3,4-
Tetrahydroquinoline, 6-ethoxy-1-octyl-
2,2,4-trimethyl-1,2,3,4-tetrahydroquinoline, nickel cyclohexanoate, 2,2-bis (4-hydroxyphenyl) propane, 1,1-bis (4-hydroxyphenyl) -2- Ethyl hexane, 2
-Methyl-4-methoxy-diphenylamine, 1-methyl-2-phenylindole and the like.

The amount of the above-mentioned antioxidant or various additives to be added is 0.0 to 1 part by mass of the diazonium salt.
It is preferably from 5 to 100 parts by mass, more preferably from 0.2 to 30 parts by mass. The antioxidant and various additives may be contained in a microcapsule together with a diazonium salt, or may be contained as a solid dispersion together with a coupler, a basic substance and other color forming aids, or may be emulsified. May be contained together with a suitable emulsifying aid, or may be contained in both forms. Also,
The antioxidant or various additives may be used alone or in combination of two or more. Further, it can be contained in a protective layer.

The antioxidant and various additives need not always be added to the same layer. When a plurality of the antioxidants and / or various additives are used in combination, they are structurally classified as anilines, alkoxybenzenes, binderd phenols, hindered amines, hydroquinone derivatives, phosphorus compounds, and sulfur compounds. And
Different structures may be combined, or a plurality of same structures may be combined.

For the purpose of reducing the yellowing of the background after image recording, a free radical generator (a compound that generates free radicals upon irradiation with light) used in a photopolymerizable composition or the like can be added. Examples of the free radical generator include aromatic ketones, quinones, benzoin, benzoin ethers, azo compounds, organic disulfides, acyl oxime esters, and the like. The amount of the free radical generator to be added is 0.01 to 1 part by mass of the diazonium salt.
5 parts by weight are preferred.

Similarly, for the purpose of reducing yellow coloration, a polymerizable compound having an ethylenically unsaturated bond (hereinafter, referred to as a polymerizable compound)
It is called "vinyl monomer". ) Can also be used. The vinyl monomer is a compound having at least one ethylenically unsaturated bond (vinyl group, vinylidene group, etc.) in its chemical structure, and has a chemical form of a monomer or prepolymer.

Examples of the vinyl monomer include unsaturated carboxylic acids and salts thereof, esters of unsaturated carboxylic acids with aliphatic polyhydric alcohols, and amides of unsaturated carboxylic acids with aliphatic polyamine compounds. Can be The vinyl monomer is based on 1 part by mass of a diazonium salt.
Used in a ratio of 0.2 to 20 parts by mass. The free radical generator and the vinyl monomer can be used in a microcapsule together with a diazonium salt. Further, citric acid, tartaric acid, oxalic acid, boric acid, phosphoric acid, pyrophosphoric acid and the like can be added as an acid stabilizer.

<Thermal Recording Material> The thermosensitive recording material of the present invention has at least a thermosensitive recording layer on a support, and the thermosensitive recording layer has at least one of the general formulas (1) and (2). It comprises the diazonium salt represented and a coupler, and if necessary, an organic base and other additives. The diazonium salt represented by the general formula (1) or (2) may be used in combination of two or more.

The heat-sensitive recording layer contains a microcapsule containing a diazonium salt represented by formula (1) or (2), a coupler, and if necessary, an organic base and other additives. A coating solution can be prepared by preparing a coating solution, coating the coating solution on a support such as paper or a synthetic resin film, and drying.

In the present invention, the heat-sensitive recording layer is an organic
An embodiment containing a base is preferred. The coating is performed using a known coating.
It can be appropriately selected from cloth methods, for example, a bar
Coating, blade coating, air knife coating, gravure coating,
Roll coating, spray coating, dip coating
Cloth coating, curtain coating and the like can be mentioned. Also, after coating and drying
The dry coated amount of the heat-sensitive recording layer of 2.5 to 30 g /
m ^TwoIs preferred.

The constitution of the heat-sensitive recording layer in the heat-sensitive recording material of the present invention is not particularly limited. For example, the heat-sensitive recording layer is composed of a single layer in which microcapsules, couplers, organic bases and the like are all contained in the same layer. It may be an embodiment, or may be an embodiment of a multi-layer laminate type included in another layer. Further, on a support, Japanese Patent Application No. 59-177669 was used.
After providing the intermediate layer described in the specification, a thermosensitive recording layer may be applied and formed.

Further, as will be described later, a full-color color developing mode in which a plurality of single-color and single heat-sensitive recording layers having different hues are laminated.

In the heat-sensitive recording material of the present invention, a binder may be contained in each layer such as a heat-sensitive recording layer, an intermediate layer, and a protective layer described below. As the binder, a known water-soluble polymer compound or latex may be used. Etc. can be selected as appropriate.

Examples of the water-soluble polymer compound include methyl cellulose, carboxymethyl cellulose,
Hydroxyethyl cellulose, hydroxypropyl cellulose, starch derivatives, casein, gum arabic, gelatin, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, polyvinyl alcohol, silanol-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, epichlorohydrin-modified Polyamide, isobutylene-maleic salicylic anhydride copolymer,
Examples thereof include polyacrylic acid, polyacrylamide and the like, and modified products thereof.

Examples of the latex include styrene-butadiene rubber latex and methyl acrylate-
Butadiene rubber latex, vinyl acetate emulsion and the like. Among them, hydroxyethyl cellulose,
Preferred are starch derivatives, gelatin, polyvinyl alcohol derivatives, polyacrylamide derivatives and the like.

The heat-sensitive recording material of the present invention may contain a pigment. The pigment may be any known organic or inorganic pigment, for example, kaolin, calcined kaolin, talc, wax , Diatomaceous earth, calcium carbonate, aluminum hydroxide, magnesium hydroxide, zinc oxide, lithopone, amorphous silica, colloidal silica, calcined stone, silica, magnesium carbonate, titanium oxide, alumina, barium carbonate, barium sulfate, mica, Examples include microballoons, urea-formalin fillers, polyester particles, cellulose fillers, and the like.

If necessary, various additives such as known waxes, antistatic agents, defoaming agents, conductive agents, fluorescent dyes, surfactants, ultraviolet absorbers and precursors thereof can also be used. .

In the heat-sensitive recording material of the present invention, a protective layer may be provided on the heat-sensitive recording layer, if necessary. Two or more protective layers may be laminated as necessary. Materials used for the protective layer include polyvinyl alcohol, carboxy-modified polyvinyl alcohol, vinyl acetate-acrylamide copolymer, silicon-modified polyvinyl alcohol, starch, modified starch, methyl cellulose, carboxymethyl cellulose, hydroxymethyl cellulose, gelatins,
Arabic gum, casein, styrene-maleic acid copolymer hydrolyzate, styrene-maleic acid copolymer half ester hydrolyzate, isobutylene-maleic anhydride copolymer hydrolyzate, polyacrylamide derivative, polyvinylpyrrolidone, polystyrene sulfone Acid-soluble compounds, water-soluble polymer compounds such as sodium alginate, and styrene-
Latexes such as butadiene rubber latex, acrylonitrile-butadiene rubber latex, methyl acrylate-butadiene rubber latex, and vinyl acetate emulsion are exemplified.

The storage stability can be further enhanced by crosslinking the water-soluble polymer compound.
The crosslinking agent can be appropriately selected from known crosslinking agents, for example, a water-soluble initial condensate such as N-methylol urea, N-methylol melamine, urea-formalin; Aldehyde compounds; inorganic crosslinking agents such as boric acid and borax; and polyamide epichlorohydrin.

For the protective layer, known pigments, metal soaps, waxes, surfactants and the like can be further used.
The coating amount of the protective layer is 0.2 to 5 g / dry coating amount.
m ² is preferred, and 0.5 to ² g / m ² is more preferred. The film thickness is preferably from 0.2 to 5 μm, and from 0.5 to 5 μm.
2 μm is more preferred.

When a protective layer is provided, a known ultraviolet absorber or a precursor thereof may be contained in the protective layer. The protective layer can be provided by the above-mentioned known coating method as in the case of forming the heat-sensitive recording layer on the support.

As the support usable in the heat-sensitive recording material of the present invention, any paper support used for ordinary pressure-sensitive paper, heat-sensitive paper, dry or wet diazo copy paper and the like can be used. Acid paper, neutral paper, coated paper, plastic film laminated paper, synthetic paper, plastic films such as polyethylene terephthalate and polyethylene naphthalate can be used.

On the support, a back coat layer may be provided for the purpose of correcting the curl balance or for improving the chemical resistance from the back surface. The back coat layer can be provided in the same manner as the protective layer.

Further, if necessary, an antihalation layer may be provided between the support and the heat-sensitive recording layer or on the surface of the support on which the heat-sensitive recording layer is provided, and a slip layer or an anti-halation layer may be provided on the back surface. A static layer, a pressure-sensitive adhesive layer and the like can be provided. A label may be formed by combining a release paper on the back surface of the support (the surface on the side where the heat-sensitive recording layer is not provided) with an adhesive layer interposed therebetween.

As described above, by using the diazonium salt of the present invention for the heat-sensitive recording layer, a high color density can be obtained, and high-speed light fixing can be performed. This increase in the optical fixing speed shortens the recording time,
Further, since the diazonium salt itself is excellent in its decomposability, a sufficient fixing effect can be expected. Therefore, it is possible to prevent a decrease in whiteness due to coloring of a non-image portion (background portion), and it is possible to obtain a high-contrast image with little density fluctuation. That is, it is possible to realize both improvement in stability as a recording material and high speed. Further, by enclosing the diazonium salt in the microcapsules, the long-term stability as a recording material can be further improved.

<Image Forming Method> Image formation using the heat-sensitive recording material of the present invention may be performed by the following method.
That is, for example, by heating and printing the surface of the heat-sensitive recording material on the side where the heat-sensitive recording layer is provided by a heating device such as a thermal head, the polyurea and / or Alternatively, the capsule wall containing the polyurethane is softened to become material-permeable, and when a coupler or a basic substance (organic base) outside the capsule enters the microcapsule, an image-like color is formed to form an image. Is also good. In this case, after the color is formed, by further irradiating light corresponding to the absorption wavelength of the diazonium salt (light fixing), the diazonium salt causes a decomposition reaction and loses reactivity with the coupler, thereby fixing the image. . By applying light fixing as described above, unreacted diazonium salt causes a decomposition reaction and loses its activity. Therefore, the density of the formed image fluctuates, and coloring occurs due to generation of stain in the non-image area (background area). That is, a decrease in whiteness and a decrease in image contrast due to the decrease can be suppressed.

Examples of the light source used for the light fixing include various fluorescent lamps, xenon lamps, mercury lamps and the like. The light emission spectrum of these light sources is almost identical to the absorption spectrum of the diazonium salt in the thermosensitive recording material. It is preferable in that it can be fixed with high efficiency. In particular, in the present invention,
It is particularly preferable to use a light source having a light emission center wavelength of 380 to 460 nm of the irradiated light.

In addition, writing is performed imagewise by light,
It can also be used as a photo-writing heat-developing type thermosensitive recording material which forms an image by heat development. In this case, the printing process
A light source such as a laser is used instead of the above-described heating device.

In the heat-sensitive recording material of the present invention, a multi-color heat-sensitive recording material can be formed by laminating a plurality of heat-sensitive recording layers having different coloring hues. Examples of the heat-sensitive recording layer to be laminated include a heat-sensitive recording layer containing a photodegradable diazonium salt. The multi-color heat-sensitive recording materials are described in JP-A-3-288688 and JP-A-3-1688.
Nos. 35787, 4-144784, 4-
Nos. 144785, 4-194842 and 4
JP-A-247747, JP-A-4-247448, JP-A-4-340540, JP-A-4-340541,
JP-A-5-34860, JP-A-5-194842,
It is described in Japanese Patent Application No. 7-316280.

For example, the layer constitution of the full-color thermosensitive recording material may be constituted in the following manner.
However, the present invention is not limited to this. That is, two kinds of diazonium salts having different photosensitive wavelengths,
Two heat-sensitive recording layers having different coloring hues (layer B, layer B) which are contained in separate layers in combination with couplers capable of reacting with the respective diazonium salts upon heating to form different hues.
C), and a full-color heat-sensitive recording material in which a heat-sensitive recording layer (layer A) in which an electron-donating colorless dye and an electron-accepting compound are combined may be used. Full-color thermosensitive recording in which a (B layer, C layer) and a thermosensitive recording layer (A layer) in which a diazonium salt having a different photosensitive wavelength and a coupler which reacts with the diazonium salt to generate a color when heated are combined. It may be a material.

Specifically, an electron-donating colorless dye and an electron-accepting compound or a compound having a maximum absorption wavelength of 3
A first heat-sensitive recording layer (A layer) containing a diazonium salt shorter than 50 nm and a coupler which reacts with the diazonium salt when heated to form a color, and has a maximum absorption wavelength of 360 nm ± 20 nm.
A second heat-sensitive recording layer (B) containing a diazonium salt which is
Layer), a third thermal recording layer (C layer) containing a diazonium salt having a maximum absorption wavelength of 400 ± 20 nm and a coupler which reacts with the diazonium salt when heated to form a color. Is also good.

In this case, a full-color image can be recorded by selecting the coloring hues of the respective heat-sensitive recording layers so as to be three primary colors, yellow, magenta, and cyan in the subtractive color mixing. As the layer structure of the full-color recording material, any of the yellow, magenta, and cyan coloring layers may be laminated in any manner, but in terms of color reproducibility, from the support side,
It is preferable to stack yellow, cyan, magenta, or yellow, magenta, and cyan in this order.

As a recording method in the case of a multicolor heat-sensitive recording material, for example, it can be carried out as follows. That is, first, the third heat-sensitive recording layer (C layer) is heated so that the diazonium salt and the coupler contained in the layer are colored. Next, light of 400 ± 20 nm is irradiated to decompose unreacted diazonium salts contained in the C layer. Next, sufficient heat is applied to the second thermosensitive recording layer (B layer) to develop color,
The diazonium salt and the coupler contained in the layer are colored. At this time, the C layer is also heated strongly, but the diazonium salt has already been decomposed and the color forming ability has been lost, so that no color is formed. Thereafter, light of 360 ± 20 nm is irradiated to decompose the diazonium salt contained in the B layer. Finally, heat is applied to the first heat-sensitive recording layer (A layer) to develop a color, and the color is developed. At this time, the C layer and the B layer are also strongly heated at the same time, but the diazonium salt has already been decomposed and the color forming ability has been lost, so that no color is formed.

The heat-sensitive recording material of the present invention is preferably a multicolor heat-sensitive recording material as described above. As described above, the heat-sensitive recording layer (A
The coloring mechanism of the layer is not limited to a combination of an electron-donating dye and an electron-accepting dye, or a combination of a diazonium salt and a coupler that reacts with the diazonium salt when heated to form a color. Any of a base color system, a chelate color system, and a color system that reacts with a nucleophile to form a color by causing an elimination reaction may be used. By providing a heat-sensitive recording layer containing a diazonium salt and a coupler which reacts with the diazonium salt to form a color on the heat-sensitive recording layer, a multicolor heat-sensitive recording material can be formed. When a multicolor heat-sensitive recording material is used, an intermediate layer may be provided between the heat-sensitive recording layers in order to prevent color mixing between the heat-sensitive recording layers.

The intermediate layer is made of a water-soluble polymer compound such as gelatin, phthalated gelatin, polyvinyl alcohol and polyvinyl pyrrolidone, and may optionally contain various additives.

In the case where the heat-sensitive recording material of the present invention is a multicolor heat-sensitive recording material having a light-fixing type heat-sensitive recording layer on a support, if necessary, a light transmittance adjusting layer or a protective layer may be further provided thereon. It is desirable to provide a layer, or a light transmittance adjusting layer and a protective layer. The light transmittance adjusting layer is described in JP-A-9-39395, JP-A-9-39396, Japanese Patent Application No. 7-208386, and the like.

When a component that functions as a precursor of an ultraviolet absorber is used in the light transmittance adjusting layer, a high light is not emitted before irradiation with light in a wavelength range necessary for fixing because the component does not function as an ultraviolet absorber. Due to the transmittance, when fixing the light-fixing type thermosensitive recording layer, it is possible to sufficiently transmit wavelengths in the region required for fixing, and the transmittance of visible light is high, which hinders fixing of the thermosensitive recording layer. Will not come.

On the other hand, the precursor of the ultraviolet absorbent is irradiated with light in a wavelength region necessary for light fixing (photodecomposition of a diazonium salt by light irradiation) of the light fixing type thermosensitive recording layer, and then the reaction is performed by the light. It will work as a wake-up UV absorber. This ultraviolet absorber absorbs most of the light having a wavelength in the ultraviolet region, lowers its transmittance, and makes it possible to improve the light resistance of the heat-sensitive recording material. However, since there is no absorption of visible light, the transmittance of visible light is not substantially changed.

At least one light transmittance adjusting layer can be provided in the heat-sensitive recording material, and it is particularly preferable to form it between the heat-sensitive recording layer and the protective layer. Further, the function of the light transmittance adjusting layer may be imparted to the protective layer, and may be shared.

[0149]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 Synthesis Example of Exemplified Compound A-1 4.0 g of 2,5-di-n-heptyloxy-4- (4-dimethylaminophenyl) acetanilide was dissolved in 20 ml of methanol. 3.2 ml of concentrated hydrochloric acid was added to prepare a reaction solution, which was heated under reflux for 3 hours. Thereafter, the reaction solution was cooled to 0 ° C., and an aqueous solution in which 0.64 g of sodium nitrite was dissolved in 2 ml of water was dropped into the reaction solution. After stirring at 10 ° C. for 1 hour, 1.9 g of potassium hexafluorophosphate was added, and the mixture was stirred at room temperature for 30 minutes. Then, 10 ml of water was added for crystallization. The precipitated crystals were collected by filtration, washed sequentially with water and isopropanol, and then recrystallized from isopropanol.
After filtration and drying, 2.4 g of Exemplified Compound A-1 was obtained.

The obtained diazonium salt A-1 was obtained by adding ¹ H-
It was identified by NMR (solvent: CDCl ₃ , 300 MHz). The data is shown below. ^{1 H-NMR (δ, ppm} ): 7.88 (s, 1H),
7.65 (d, 2H), 7.12 (s, 1H), 6.7
7 (d, 2H), 4.36 (t, 2H), 4.08
(T, 2H), 3.08 (s, 6H), 1.86-1.
92 (m, 2H), 1.75-1.82 (m, 2H),
1.24 to 1.52 (m, 16H), 0.81 to 0.9
4 (m, 6H) The maximum absorption wavelength λmax in methanol is 519
nm, and the extinction coefficient ε was 1.8 × 10 ⁴ .

Example 2 (Synthesis Example of Exemplified Compound A-2) 3.5 g of 4- (4-dimethylaminophenyl) -2-n-hexyloxyacetanilide was dissolved in 20 ml of methanol, and concentrated hydrochloric acid was added.
0 ml was added to prepare a reaction solution, which was heated under reflux for 3 hours. Thereafter, the reaction solution was cooled to 0 ° C., and an aqueous solution of 0.83 g of sodium nitrite dissolved in 2 ml of water was added dropwise to the reaction solution. After stirring at 10 ° C. for 1 hour, 2.4 g of potassium hexafluorophosphate was added, and the mixture was stirred at room temperature for 60 minutes. Then, 10 ml of water was added for crystallization. The precipitated crystals were collected by filtration, washed sequentially with water and isopropanol, and then recrystallized from a mixed solvent of ethyl acetate and isopropanol. After filtration and drying, Exemplified Compound A-2
3.5 g was obtained.

The obtained diazonium salt A-2 was obtained by adding ¹ H-
It was identified by NMR (solvent: CDCl ₃ , 300 MHz). The data is shown below. ¹ H-NMR (δ, ppm): 8.23 (d, 1H),
7.66 (d, 2H), 7.47 (d, 1H), 7.2
5 (s, 1H), 6.79 (d, 2H), 4.40
(T, 2H), 3.10 (s, 6H), 1.87-1.
96 (m, 2H), 1.45-1.58 (m, 2H),
1.31-1.44 (m, 4H), 0.88-0.98
(M, 3H) The maximum absorption wavelength λmax in methanol is 510
nm, and the extinction coefficient ε was 3.2 × 10 ⁴ .

Example 3 (Synthesis Example of Exemplified Compound A-21) 4-Amino-4'-n
9.4 g of dioctylaminobiphenyl was dissolved in 50 ml of methanol, and 6.0 ml of concentrated hydrochloric acid was added to prepare a reaction solution, which was cooled to 0 ° C. An aqueous solution in which 2.0 g of sodium nitrite was dissolved in 5 ml of water was dropped into the reaction solution. After stirring at 10 ° C. for 1 hour, 5.5 g of potassium hexafluorophosphate was added, and the mixture was stirred at room temperature for 60 minutes. Then, 20 ml of water was added for crystallization. The precipitated crystals were collected by filtration, washed sequentially with water and isopropanol, and then recrystallized from a mixed solvent of ethyl acetate and isopropanol.
After filtration and drying, 6.6 g of Exemplified Compound A-21 was obtained.

The obtained diazonium salt A-21 was prepared from ¹ H
-NMR: was identified by (solvent CDCl _3, 300MHz). The data is shown below. ¹ H-NMR (δ, ppm): 8.38 (d, 2H),
7.95 (d, 2H), 7.67 (d, 2H), 6.7
8 (d, 2H), 3.38 (t, 4H), 1.58-
1.68 (m, 4H), 1.21-1.40 (m, 20
H), 0.84-0.94 (m, 6H). The maximum absorption wavelength λmax in methanol is 532.
nm and the extinction coefficient ε was 3.0 × 10 ⁴ .

Example 4 Synthesis Example of Exemplified Compound A-22 2-Acetamino-7
6.0 g of dioctylaminofluorene was dissolved in 30 ml of methanol, and 5.0 ml of concentrated hydrochloric acid was added to prepare a reaction solution, which was heated under reflux for 4 hours. Thereafter, the reaction solution was cooled to 0 ° C., and sodium nitrite 1.
An aqueous solution in which 1 g was dissolved in 3 ml of water was added dropwise. After stirring at 10 ° C. for 1.5 hours, 3.1 g of potassium hexafluorophosphate was added, and the mixture was stirred at room temperature for 60 minutes. Then, 10 ml of water was added for crystallization. The precipitated crystals were collected by filtration, washed sequentially with water and isopropanol, and then recrystallized from isopropanol. After filtration and drying, Exemplified Compound A
4.8 g of -22 was obtained.

The obtained diazonium salt A-22 was a ¹ H
-NMR: was identified by (solvent CDCl _3, 300MHz). The data is shown below. ^{1 H-NMR (δ, ppm} ): 8.30 (s, 1H),
8.22 (d, 1H), 7.77 (m, 2H), 6.8
1 (m, 2H), 3.96 (s, 2H), 3.40
(T, 4H), 1.58-1.69 (m, 4H), 1.
11-1.40 (m, 20H), 0.79-0.94
(M, 6H) The maximum absorption wavelength λmax in methanol is 536.
nm, and the extinction coefficient ε was 3.4 × 10 ⁴ .

[0158] [Example 5] Hereinafter, in Example 5, to prepare a heat-sensitive recording material M ₁ containing a diazonium salt of the present invention.

(Preparation of diazonium salt) In the same manner as in Example 1, diazonium salt A-1 (exemplified compound A-1) was synthesized.

[0160] (Preparation of a diazonium salt-encapsulating microcapsule solution L _a) in ethyl acetate 19 g, uniformly mixed by adding the diazonium salt (A-1) and 3.4g obtained from the above, and tricresyl phosphate 10g did. Then
To this mixed solution, Takenate D110 was used as a capsule wall material.
7.6 g of N (manufactured by Takeda Pharmaceutical Co., Ltd.) was added and mixed to obtain Liquid I. Then, 8% aqueous solution of phthalated gelatin 4
Solution I obtained above was added to a mixed solution of 6 g, 17.5 g of water and 2 g of a 10% aqueous solution of sodium dodecylbenzenesulfonate.
The mixture was milk-dispersed at 10,000 rpm for 10 minutes. After adding 20 g of water to the obtained emulsified dispersion and mixing uniformly, a microencapsulation reaction is carried out at 40 ° C. for 3 hours with stirring to obtain a diazonium salt-encapsulated microcapsule liquid L.
It was obtained _a. The average particle size of the microcapsules is 0.8 to
It was 1.0 μm.

[0161] (the coupler emulsion L _b Preparation of) ethyl acetate 10.5 g, Coupler (Compound B-1) 3.4
g, 3 g of triphenylguanidine, 0.5 g of tricresyl phosphate and 0.24 g of diethyl maleate were dissolved to obtain a liquid II. Next, 15% of lime-processed gelatin
49 g of aqueous solution, 1 of sodium dodecylbenzenesulfonate
Solution II obtained above was added to a mixed solution obtained by uniformly mixing 9.5 g of a 0% aqueous solution and 35 g of water at 40 ° C., and the mixture was used at 40 ° C. and 1000 rpm using a homogenizer.
The mixture was emulsified and dispersed at 0 rpm for 10 minutes. After the obtained emulsified dispersion to remove the 2 hours with stirring to ethyl acetate at 40 ° C., the amount of evaporation of ethyl acetate and water compensated by the addition of water to obtain a coupler emulsion L _b.

[0162] (Preparation of heat-sensitive recording layer coating solution L _c) a diazonium salt-encapsulating microcapsule solution L _a 3.6 g, water 3.3
mixed g and coupler emulsion L _b 9.5 g, to obtain a heat-sensitive recording layer coating solution L _c.

[0163] (protective layer coating solution L _d Preparation of) itaconic acid-modified polyvinyl alcohol (KL-318; manufactured by Kuraray Co., Ltd.) 6% aqueous solution of 100g and epoxy-modified polyamide (FL-71; manufactured by Toho Chemical Co., Ltd.) 30% Dispersion 1
A mixture obtained by mixing 0 g, zinc stearate 40% dispersion (Hydrin Z; Chukyo Yushi Co., Ltd.) 15 g were homogeneously mixed to give a coating solution L _d for protective layer.

(Coating) As a support, a photographic paper support obtained by laminating polyethylene on a high-quality paper was prepared, and the heat-sensitive recording layer coating solution L _{c was} coated on the photographic paper support with a wire bar.
In the order of protective layer coating liquid L _d, successively and dried in the coating and 50 ° C., to obtain a heat-sensitive recording material M ₁ of Example 5. The coating amounts of the heat-sensitive recording layer and the protective layer as solids were 5.9 g / m ² and 1.2 g / m ² , respectively.

(Coloring test) Using a thermal head (KST type) manufactured by Kyocera Corporation, the power and pulse width applied to the thermal head were determined so that the recording energy per unit area was 50 mJ / mm ^2. It was to obtain a thermal printing image on the thermosensitive recording material M _1. Thereafter, the obtained image was irradiated with ultraviolet rays for 15 seconds using an ultraviolet lamp having an emission center wavelength of 450 nm and an output of 40 W, and the color density and the background density (density of the non-image portion) were measured. The results are shown in Table 1 below.

(Light fastness test) The colored portion developed using a thermal head (KST type) manufactured by Kyocera Corporation was irradiated with a fluorescent lamp tester at 30,000 lux for 24 hours, and then the density of the colored portion was measured. . The results are shown in Table 1 below.

(Light fixability test) Emission center wavelength 450n
m, after irradiating for 10 seconds in the heat-sensitive recording material M ₁ in the non-printing a UV using a UV lamp output 40W, was carried out similar coloring tests described above. The results are shown in Table 1 below.

(Measurement of Density) In the above-described color development test and light fastness test, the image density and the background density of the color-developed portion were measured at the Y position using Macbeth RD918.

Example 6 The heat sensitivity was the same as in Example 5, except that 2.7 g of the above-mentioned compound (A-2) was used as the diazonium salt instead of 3.4 g of the compound (A-1). to prepare a recording material M _2. For the manufactured heat-sensitive recording material M _2, the color development test was conducted light resistance test and light fixability test. The results are shown in Table 1 below.

[Example 7] Illustrative examples of diazonium salts
The above-exemplified compound instead of 3.4 g of compound (A-1)
(A-21) Except that 3.2 g was used, as in Example 5.
Heat-sensitive recording material M _ThreeWas prepared. The heat record created
Recording material M_ThreeAbout the above color development test, light fastness test and
A light fixability test was performed. The results are shown in Table 1 below.

Example 8 Illustrated as a diazonium salt
The above-exemplified compound instead of 3.4 g of compound (A-1)
(A-22) Same as Example 5 except that 3.3 g was used.
Heat-sensitive recording material M _FourWas prepared. The heat record created
Recording material M_FourAbout the above color development test, light fastness test and
A light fixability test was performed. The results are shown in Table 1 below.

[Comparative Example 1] As a diazonium salt, 2.7 g of 2,5-dibutyl-4-morpholinobenzenediazonium hexafluorophosphate was used in place of 3.4 g of the exemplary compound (A-1). In the same manner as in Example ₅ , a thermosensitive recording material M5 of Comparative Example 1 was produced. For heat-sensitive recording material M ₅ that fabricated, the color development test was conducted light resistance test and light fixability test. The results are shown in Table 1 below.

Comparative Example 2 As a diazonium salt, 2.9 g of 2,5-dibutyl-4- (4-methylthiophenyl) benzenediazonium hexafluorophosphate was used instead of 3.4 g of the exemplary compound (A-1). Others
To prepare a heat-sensitive recording material M ₆ of Comparative Example 2 in the same manner as in Example 5. For heat-sensitive recording material M ₆ that fabricated, the color development test was conducted light resistance test and light fixability test. The results are shown in Table 1 below.

[0174]

[Table 1]

From the results shown in Table 1, the heat-sensitive recording materials M _{1 to} M _{4 of the} present invention containing the diazonium salt of the present invention as a color-forming component.
Shows that compared to the heat-sensitive recording materials M ₅ and M ₆ of the comparative example, the color density after light fixation is excellent in low light fixability. As a result, a diazonium salt having excellent photodegradability and a high decomposition rate was obtained.

Further, the thermosensitive recording materials M _{1 to} M ₄ were able to obtain a sufficient coloring density and the background density could be suppressed lower than the thermosensitive recording materials M ₅ and M ₆ of the comparative examples.
Furthermore, the heat-sensitive recording material M ₁ ~M ₄ had a high light resistance as compared with the heat-sensitive recording materials M ₅ and M ₆ of the comparative examples. Therefore, the heat-sensitive recording material of the present invention was able to form a robust and high-contrast image having excellent whiteness in the non-image area (background area) and little fluctuation in density in the image area.

[0177]

According to the present invention, there is no fear of explosion,
A diazonium salt having excellent photodegradability with respect to light in a wavelength region of nm or more can be provided. Also, the present invention
It is possible to provide a heat-sensitive recording material which is excellent in light fixing property and light resistance and has little background coloring. Further, according to the heat-sensitive recording material of the present invention, shortening of the printing time can be expected due to improvement of the light fixing property.

Claims (7)

[Claims] 1. A diazonium salt represented by the following general formula (1). Embedded image [In the general formula (1), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R
⁷ and R ⁸ are each independently a hydrogen atom, a halogen atom,
It represents an alkyl group, an alkoxy group, an alkylthio group or an arylthio group, and R ⁹ and R ¹⁰ each independently represent a hydrogen atom, an alkyl group or an aryl group. R ² and R ^3, R ¹ and R ^4, R ³ and R ^6, R ⁴ and R ^5, R ⁶ and R ^7, R ⁵ and R ^8, R ⁷ and R ^9, R ⁸ and R ¹⁰ and R ⁹ And R ¹⁰ may combine to form a ring. X ^- represents an anion. ] 2. The diazonium salt according to claim 1, wherein the diazonium salt is represented by the following general formula (2). Embedded image [In the general formula (2), R ² and R ⁴ each independently represent a hydrogen atom, a halogen atom, an alkyl group or an alkoxy group, and R ⁹ and R ¹⁰ each independently represent a hydrogen atom, an alkyl group or an aryl group. . R ⁹ and R ¹⁰ may combine to form a ring. X ^- represents an anion. ] 3. A heat-sensitive recording material having a heat-sensitive recording layer containing a diazonium salt and a coupler on the surface of a support, wherein the diazonium salt is the diazonium salt according to claim 1. Recording material. 4. The heat-sensitive recording material according to claim 3, wherein the diazonium salt is the diazonium salt according to claim 2. 5. The compound according to claim 3, wherein the coupler is a compound represented by the following general formula (3).
A heat-sensitive recording material according to any one of the above. Embedded image [In the general formula (3), E ¹ and E ² each independently represent an electron-withdrawing group. E ¹ and E ² may combine to form a ring. ] 6. The heat-sensitive recording material according to claim 3, wherein the diazonium salt is encapsulated in a microcapsule. 7. The capsule wall of the microcapsule,
7. The heat-sensitive recording material according to claim 6, comprising a polyurethane and / or a polyurea.