JP2005271301A - Recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording medium excellent in light fastness in an imaging section. <P>SOLUTION: In the recording material having at least one layer of recording layer on a support, at least one of the recording layers is a diazo thermal recording layer which contains a diazonium salt compound and a coupler reacting with the diazonium salt compound to form a developing pigment and the developing pigment exists in a protonated state. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a recording material containing a diazonium salt compound and a coupler as color forming components, and particularly to a heat-sensitive recording material having excellent image fastness.

  The diazonium salt compound is a compound having a very high chemical activity, reacts with a compound called a coupler having a phenol derivative or an active methylene group, easily forms an azo dye, and also has photosensitivity, Decomposes by light irradiation and loses its activity. Therefore, diazonium salt compounds have been used for a long time as optical recording materials represented by diazocopy (see, for example, Non-Patent Document 1).

  Furthermore, utilizing the property of decomposing by light and losing activity, it has recently been applied to recording materials that require image fixing, and as a typical example, a diazonium salt compound and a coupler are heated in accordance with an image signal, There has been proposed a photo-fixing type heat-sensitive recording material in which an image is formed by reacting with heat and then irradiated with light to fix the image (see, for example, Non-Patent Document 2).

  However, these recording materials containing a diazonium salt compound as a color-developing element have a very high activity of the diazonium salt compound, and the diazonium salt compound loses its reactivity due to gradual thermal decomposition even in the dark. There was the fault that the shelf life as a material was short. Various methods have been proposed as means for improving the instability of such a diazonium salt compound, and one of the most effective means is a method of encapsulating a diazonium salt compound in a microcapsule.

  By microencapsulating the diazonium salt compound, the diazonium salt compound is isolated from those that promote decomposition such as water and base, so that the decomposition is remarkably suppressed and the shelf life of the recording material can be drastically improved. (For example, see Non-Patent Document 3.)

  As a general method of encapsulating a diazonium salt compound in a microcapsule, a diazonium salt compound is dissolved in a hydrophobic solvent to form an oil phase, and this is added to an aqueous solution (water phase) in which a water-soluble polymer is dissolved. By emulsifying and dispersing with a homogenizer or the like, and adding a monomer or prepolymer that becomes a wall material of the microcapsule to either the oil phase side or the water phase side or both in advance, at the interface between the oil phase and the water phase. There is a method in which a polymer reaction is caused or a polymer wall is formed by depositing a polymer to form a microcapsule (see, for example, Non-Patent Document 4 or 5).

  As the microcapsule wall formed by the above method, various materials such as cross-linked gelatin, alginate, celluloses, polyurea, polyurethane, melamine resin, and nylon resin can be used.

In particular, in the case of a microcapsule having a glass transition temperature and a glass transition temperature slightly higher than room temperature, such as a urea resin or a urethane resin, the capsule wall at room temperature exhibits a substance impermeableness, Since it exhibits material permeability above the glass transition temperature, it is called a thermoresponsive microcapsule and is applied to a heat-sensitive recording material. That is, the thermosensitive recording layer formed on the support is formed by coating using a coating solution containing a thermoresponsive microcapsule encapsulating a diazonium salt compound, a coupler and a base, whereby the diazonium salt in the layer is formed. The compound can be stably held for a long period of time, and a color image can be easily formed by heating, and image fixing by light irradiation is also possible. By microencapsulating in this manner, the stability of the diazonium salt compound can be dramatically improved.
Edited by the Japan Photography Society, “Basics of Photographic Engineering-Non-Silver Salt Photo Edition”, Corona (1982) p. 89-117, p. Koji Sato et al., Journal of the Institute of Image Electronics Engineers of Japan, Vol. 11 No. 4 (1982), p. 290-296. Tomomasa Usami et al., Journal of Electrophotographic Society, Vol. 26, No. 2 (1987), p. "Microcapsule", published by Nikkan Kogyo Shimbun, Asa Kondo, 1970. "Microcapsule", published by Sankyo Publishing, Tamotsu Kondo et al., 1977.

It is desired to improve the storability of the image area in the heat-sensitive recording material. In particular, although it is desired to improve light fastness, it is caused by photooxidation of an azo dye formed in an image area because a photosensitive diazonium salt, that is, a benzenediazonium salt having an electron donating group introduced therein is used. A fading reaction tends to occur, and a solution has been desired.
The present invention has been made to solve the above problems, and an object of the present invention is to provide a recording material having excellent light fastness in an image area.

  As a method for improving the color fading of the image portion, conventionally, (1) a method for improving a dye-forming material, that is, a benzenediazonium salt or a coupler for enhancing the light fastness of an azo dye, (2) a method using an antioxidant, (3) A method of blocking UV light, (4) a method of blocking oxygen, (5) a method of forming a metal chelate, and the like have been performed.

  Known examples of (1) include JP-A-10-337961, JP-A-11-78233, JP-A-11-116553, JP-A-4-201483, JP-A-9-156229, and JP-A-9-216468. Gazette, 9-216469, 9-203472, 9-319025, 10-35113, 10-193801, 10-264532, and JP-A-2001-162946. Japanese Patent Publication No. 2002-326981, Japanese Patent Publication No. 3-213120, No. 3-394613, No. 8-310133, No. 2002-241646, No. 2002-261318, etc. are known. Yes.

Known examples of (2) include JP-A-6-135153, JP-A-6-135154, JP-A-7-17138, JP-A-7-17145, and JP-A-9-301969. .
Known examples of (3) include JP-A-9-95487, JP-A-9-1928, JP-A-9-39395, JP-A-9-39396, JP-A-9-301959, and JP-A-2002-264500. No. publication etc. are known.
As known examples of (4), JP-A 2000-177244, 2003-118236, 2003-127548 and the like are known.
Known examples of (5) include Japanese Patent Application Laid-Open No. 7-290825, Japanese Patent Application No. 2002-187723, and the like.

  The present inventor searched for a method different from the above (1) to (5) as a means for suppressing the photooxidation reaction of the azo dye, and the specific azo dye into which the electron donating group is introduced is easily protonated. We focused on the phenomenon and examined it eagerly. As a result, it was found that the light fastness of the image area was improved by protonating the azo dye during or after color development.

That is, the present invention
<1> A recording material having at least one recording layer on a support, wherein at least one of the recording layers reacts with a diazonium salt compound and the diazonium salt compound to form a coloring dye. The recording material is characterized in that the coloring dye is present in a protonated state.

  <2> Two diazo thermosensitive recording layers comprising a combination of two diazonium salt compounds having different maximum absorption wavelengths and a coupler that reacts with each diazonium salt compound to form a coloring dye having a different hue. The coloring material formed at least one of the diazo thermosensitive recording layers is protonated and is present in the recording material according to <1>.

  <3> The recording material according to <1> or <2>, wherein the diazonium salt compound is a compound represented by at least one of the following general formula (1) and the following general formula (2). .

(In the general formulas (1) and (2), R ^{1 to} R ⁴ each independently represents a hydrogen atom, an alkyl group, or an aryl group, and R ⁵ and R ⁶ each independently represent a hydrogen atom, an alkyl group, or an alkoxy group. , A halogen atom, a sulfonyl group, an acyl group, or an alkoxycarbonyl group, Y ¹ and Y ² each independently represent an oxygen atom or a sulfur atom, and X ⁻ represents a counter anion.)

  <4> The recording material according to any one of <1> to <3>, wherein the diazonium salt compound is encapsulated in a microcapsule.

  The recording material of the present invention is excellent in light fastness of the image area.

Hereinafter, the recording material of the present invention will be described in detail.
The recording material of the present invention is a recording material having at least one recording layer on a support, and at least one of the recording layers reacts with a diazonium salt compound and the diazonium salt compound to form a coloring dye. A diazo heat-sensitive recording layer containing a coupler that forms a dye, wherein the coloring dye is protonated and exists. Since the chromogenic dye according to the present invention exists in a protonated state, it hardly causes a photo-oxidation reaction. Therefore, the recording material of the present invention is excellent in light fastness.

<Protonation of coloring dye>
The protonation of the coloring dye according to the present invention means that the basic site of the coloring dye is protonated by acidic protons that coexist in the presence of the dye. Hereinafter, the protonated coloring dye may be referred to as a protonated coloring dye, and the non-protonated coloring dye may be referred to as an unprotonated coloring dye.
Generally, the protonated coloring dye changes its absorption spectrum and oxidation-reduction potential as compared with the non-protonating coloring dye. Many coloring dyes having a basic site such as a dialkylamino group have a low oxidation potential and are likely to fade due to a photo-oxidation reaction. For such a coloring dye, when the amino group is protonated, the oxidation potential increases, and the photooxidation reaction can be suppressed. However, it is difficult to stabilize the coloring dye in a protonated state. This is because there exists an equilibrium with the non-protonated coloring dye as shown in Scheme 1 below.

Therefore, as shown in Scheme 1, when the non-protonated coloring dye is photobleached, a part of the protonated coloring dye is changed to the non-protonated coloring dye by the equilibrium reaction, resulting in a photobleaching cycle. As a result, photobleaching is not improved.
Similarly, in a coloring dye having a large change in absorption spectrum before and after protonation, if equilibrium is mixed, it causes color turbidity.

  For example, the following coloring dyes have a large color change due to protonation.

  In such a coloring dye, as long as an equilibrium exists between the protonated coloring dye and the non-protonated coloring dye, a dull magenta or cyan color is exhibited, and a desired color cannot be obtained.

The present inventors have discovered a dye skeleton exhibiting a stable protonated state by chance while searching for a new azo dye. Specifically, the dye skeleton showing a stable protonated state is an azo dye skeleton using a diazonium salt compound corresponding to the general formula (1) or (2) described later as a raw material.
Further, when this coloring dye is used for a recording material utilizing a coloring reaction in the system, as shown in the following scheme 2, the yellow coloring system has little color change, so it is not noticeable even if it is not completely protonated. I found that there is a feature.

The protonated coloring dye [A] and the non-protonizing coloring dye [B] in Scheme 2 have the following characteristics.
The color difference between the protonated coloring dye [A] and the non-protonizing coloring dye [B] is small and the color difference is constant (not noticeable).
There is no equilibrium between the protonated coloring dye [A] and the non-protonizing coloring dye [B].
-Photobleaching of a non-protonated coloring dye [B] is likely to occur.

  In the conventional dye skeleton, the following scheme 3 is established. Here, the conventional dye skeleton is specifically an azo dye skeleton using a diazonium salt compound corresponding to the following general formulas (4) to (6) as a raw material.

The protonated coloring dye [C] and the non-protonized coloring dye [D] in Scheme 3 have the following characteristics.
-Although the difference in color (absorption spectrum) between the protonated coloring dye [C] and the non-protonizing coloring dye [D] is small, the hue tends to change because it becomes an equilibrium mixture.
-There is an equilibrium between the protonated coloring dye [C] and the non-protonating coloring dye [D].
The photobleaching of the non-protonated coloring dye [D] is likely to occur, and the change from the protonated coloring dye [C] to the non-protonated coloring dye [D] occurs at equilibrium. As a result, the protonated coloring dye [C] also Light fading.

  The protonated coloring dye according to the present invention is achieved by a diazonium salt compound having a special structure.

The amount of the protonated coloring dye in the recording layer is preferably 90% or more, and particularly preferably 95% or more of the total coloring dye (protonated coloring dye + unprotonated coloring dye).
The abundance of the protonated coloring dye can be confirmed by extracting the colored portion of the recording material and measuring the absorption spectrum to obtain the abundance ratio (protonated coloring dye / non-protonated coloring dye).

<Diazonium salt compound>
In the present invention, the diazonium salt compound capable of forming a coloring dye that can be protonated is not particularly limited, but at least one of the following general formula (1) and the following general formula (2): The compounds shown are preferred.

In general formulas (1) and (2), R ^{1 to} R ⁴ each independently represent a hydrogen atom, an alkyl group, or an aryl group, and R ⁵ and R ⁶ each independently represent a hydrogen atom, an alkyl group, an alkoxy group, Represents a halogen atom, a sulfonyl group, an acyl group, or an alkoxycarbonyl group. Y ¹ and Y ² each independently represents an oxygen atom or a sulfur atom. X ⁻ represents a counter anion.

R ^{1 to} R ⁴ are preferably a hydrogen atom, an alkyl group having 1 to 15 carbon atoms, or an aryl group having 6 to 10 carbon atoms. In particular, a hydrogen atom, a C1-C10 alkyl group, and a phenyl group are preferable. The alkyl group may be branched and may be substituted with a halogen atom, an alkoxy group, an aryloxy group, a phenyl group, an alkoxycarbonyl group, an acyloxy group, or a carbamoyl group. The phenyl group may be substituted with a halogen atom, an alkyl group, an aryl group, an acyloxy group, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, or an acyl group.
Specific examples of R ^{1 to} R ⁴ include the following.

R ⁵ and R ⁶ are each a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a chlorine atom, a fluorine atom, an alkoxy group having 1 to 15 carbon atoms, an alkylsulfonyl group having 1 to 12 carbon atoms, or 6 to 18 carbon atoms. Are preferably an arylsulfonyl group, an acyl group having 1 to 18 carbon atoms, or an alkoxycarbonyl group having 1 to 18 carbon atoms. The alkyl group and alkylsulfonyl group may be branched and may be substituted with a halogen atom, an alkoxy group, an aryloxy group, a phenyl group, an alkoxycarbonyl group, an acyloxy group, or a carbamoyl group.
The arylsulfonyl group may be substituted with a halogen atom, an alkyl group, or an alkoxy group.
Specific examples of R ⁵ and R ⁶ include those shown below.

Examples of the counter anion X ⁻ include perfluoroalkyl carboxylic acids having 1 to 20 carbon atoms (for example, perfluorooctanoic acid, perfluorodecanoic acid, perfluorododecanoic acid), and perfluoroalkyl sulfonic acids having 1 to 20 carbon atoms. (For example, perfluorooctanesulfonic acid, perfluorodecanesulfonic acid, perfluorohexadecanesulfonic acid), aromatic carboxylic acid having 7 to 50 carbon atoms (for example, 4,4-di-t-butylsalicylic acid, 4-t- Octyloxybenzoic acid, 2-n-octyloxybenzoic acid, 4-t-hexadecylbenzoic acid, 2,4-bis-n-octadecyloxybenzoic acid, 4-n-decylnaphthoic acid), fragrance having 6 to 50 carbon atoms Group sulfonic acids (for example, 1,5-naphthalene disulfonic acid, 4-t-octyloxybenzene sulfone) Acid, 4-n-dodecylbenzenesulfonic acid), 4,5-di-t-butyl-2-naphthoic acid, tetrafluoroboric acid, tetraphenylboric acid, hexafluorophosphoric acid, bis (2-20 carbon atoms) Alkylsulfonyl) imine, bis (perfluoromethanesulfonyl) imine having 2 to 20 carbon atoms, and the like. Among them, perfluoroalkylcarboxylic acids having 6 to 16 carbon atoms, aromatic carboxylic acids having 10 to 40 carbon atoms, aromatic sulfonic acids having 10 to 40 carbon atoms, tetrafluoroboric acid, tetraphenylboric acid, hexafluorophosphoric acid Bis (perfluoromethanesulfonyl) imine having 2 to 20 carbon atoms is preferable.

  Specific examples of the diazonium salt compounds represented by the general formulas (1) and (2) are shown below, but the present invention is not limited to the following.

<Coupler>
Next, couplers (coupling components) that can be used in the recording material of the present invention will be described.
As the coupler, any compound can be used as long as it forms a dye by coupling with a diazonium salt compound in a basic atmosphere and / or a neutral atmosphere. All so-called 4-equivalent coupler compounds for silver halide photographic light-sensitive materials can be used as couplers. A part of a 2-equivalent coupler can also be used. These can be selected according to the target hue.

  The details of the coupler are described in JP-A-4-201483, JP-A-7-223367, JP-A-7-223368, JP-A-7-323660, JP-A-7-125446, JP-A-7-96671, JP-A-7-167671. JP-A-7-223367, JP-A-7-223368, JP-A-9-156229, JP-A-9-216468, JP-A-9-216469, JP-A-9-203472, JP-A-9-319025, JP-A-10 -35113, JP-A-10-193801, JP-A-10-264532, and the like.

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

In the general formula (3), E ¹ and E ² each independently represent an electron-withdrawing group, and L represents a group that can be separated when azo coupling to form an azo dye. E ¹ and E ² may be bonded to form a ring.

The electron-withdrawing group represented by E ¹ and E ² means a substituent having a positive Hammett σp value, which may be the same or different. For example, acetyl group, propionyl Group, pivaloyl group, chloroacetyl group, trichloroacetyl group, trifluoroacetyl group, 1-methylcyclopropylcarbonyl group, 1-ethylcyclopropylcarbonyl group, 1-benzylcyclopropylcarbonyl group, benzoyl group, 4-methoxybenzoyl group An acyl group such as a thenoyl group; an oxycarbonyl group such as a methoxycarbonyl group, an ethoxycarbonyl group, a 2-methoxyethoxycarbonyl group, or a 4-methoxyphenoxycarbonyl group; a carbamoyl group, an N, N-dimethylcarbamoyl group, an N, N- Diethylcarbamoyl group, N-phenylcarbamoyl Carbamoyl groups such as N- [2,4-bis (pentyloxy) phenyl] carbamoyl group, N- [2,4-bis (octyloxy) phenyl] carbamoyl group, morpholinocarbonyl group; methanesulfonyl group, benzenesulfonyl group Alkylsulfonyl group such as toluenesulfonyl group or arylsulfonyl group; phosphono group such as diethylphosphono group; benzoxazol-2-yl group, benzothiazol-2-yl group, 3,4-dihydroquinazolin-4-one- Preferred examples include a heterocyclic group such as a 2-yl group and a 3,4-dihydroquinazolin-4-sulfon-2-yl group; a heterocyclic group; a nitro group; an imino group; and a cyano group.

Further, the electron-withdrawing groups represented by E ¹ and E ² may be bonded to form a ring. The ring formed by E ¹ and E ² is preferably a 5- to 6-membered carbocyclic or heterocyclic ring.

  L represents a group capable of leaving during azo coupling, and examples of the leaving group L include a halogen atom (fluorine, bromine, chlorine, iodine), a substituted alkyl group (hydroxymethyl group, dimethylaminomethyl group), an alkylthio group (for example, , Ethylthio group, 2-carboxyethylthio group, dodecylthio group, 1-carboxydodecylthio group), arylthio group (for example, phenylthio group, 2-butoxy-t-octylphenylthio group), alkoxyl group (for example, ethoxy group, Dodecyloxy group, methoxyethylcarbamoylmethoxy group, carboxypropyloxy group, methylsulfonylethoxy group, ethoxycarbonylmethoxy group), aryloxy group (for example, 4-methylphenoxy group, 4-chlorophenoxy group, 4-methoxyphenoxy group, 4-carboxyphenoxy Group, 3-ethoxycarboxyphenoxy group, 3-acetylaminophenoxy group, 2-carboxyphenoxy group), acyloxy group (for example, acetoxy group, tetradecanoyloxy group, benzoyloxy group), arylsulfonyloxy group (for example, toluene) Sulfonyloxy group), dialkylaminocarbonyloxy group (for example, dimethylaminocarbonyloxy group, diethylaminocarbonyloxy group), diarylaminocarbonyloxy group (for example, diphenylaminocarbonyloxy group), alkoxycarbonyloxy group (for example, ethoxycarbonyloxy group) Group, benzyloxycarbonyloxy group), aryloxycarbonyloxy group (for example, phenoxycarbonyloxy group), or heterocyclic group (for example, imidazolyl group, Razoriru group, triazolyl group, tetrazolyl group).

  Specific examples of the coupler represented by the general formula (3) are shown below, but the present invention is not limited thereto. The following tautomers of couplers can also be mentioned as suitable.

  Further, couplers (C-1), (C-2), (C-) are particularly preferred as couplers that form yellow dyes with little apparent color change between protonated coloring dyes and non-protonated coloring dyes. In addition to 3), (C-4), (C-5), (C-13) and (C-30), the following are preferable.

  The tautomers of the couplers exist as isomers of the couplers typified above, and have a relationship in which the structure easily changes between the two. As the coupler to be used, the tautomer is also preferable.

The recording material of the present invention has at least one recording layer on a support, and at least one of the recording layers reacts with a diazonium salt compound and the diazonium salt compound to form a coloring dye. And a diazo thermosensitive recording layer.
For the recording layers other than the diazo thermosensitive recording layer, known ones such as leuco coloring components can be used without limitation.
The diazo thermosensitive recording layer is preferably fixed after thermal recording.

<Multicolor thermal recording material>
When the recording material of the present invention is used as a multicolor thermosensitive recording material, the recording layer reacts with two diazonium salt compounds having different maximum absorption wavelengths and forms a coloring dye having a different hue by reacting with each diazonium salt compound. Two diazo thermosensitive recording layers containing a coupler in combination and one thermosensitive recording layer (hereinafter also referred to as another thermosensitive recording layer), and formed at least one of the diazo thermosensitive recording layers. It is preferable that the chromogenic dye to be present is protonated. More preferably, the other heat-sensitive recording layer and the two diazo heat-sensitive recording layers are laminated in order from the closest to the support.
The other thermosensitive recording layer may be a diazo thermosensitive recording layer containing a diazo coloring component, a thermosensitive recording layer containing a leuco coloring component, or a base coloring system or chelate coloring system that develops color upon contact with a basic compound. Further, it may be a heat-sensitive recording layer containing any color developing component such as a color forming system that reacts with a nucleophile to generate an elimination reaction to develop a color.

The two diazo thermosensitive recording layers are a diazo thermosensitive recording layer (A layer) containing a diazonium salt compound (DA compound) having a maximum absorption wavelength of 445 ± 50 nm, and a maximum absorption wavelength of 365 in order to fractionate the fixing wavelength at the time of photofixing. It is preferably composed of a diazo thermosensitive recording layer (B layer) containing a ± 30 nm diazonium salt compound (DB compound).
As the other thermosensitive recording layer (C layer), either a leuco dye (LC compound) or a diazonium salt compound (DC compound) having a maximum absorption wavelength of 305 ± 30 nm may be used. Of the three thermosensitive recording layers, the C layer is preferably closest to the support, but the A layer and the B layer may be provided in any order from the support. That is, the heat-sensitive recording layer may be laminated in the order of C layer / A layer / B layer from the support or may be laminated in the order of C layer / B layer / A layer.

In order to prevent color mixing between the heat-sensitive recording layers, an intermediate layer may be provided between the heat-sensitive recording layers.
The intermediate layer is made of a water-soluble polymer compound such as gelatin, phthalated gelatin, polyvinyl alcohol, or polyvinylpyrrolidone, and may contain various additives as appropriate.

If necessary, the multicolor thermosensitive recording material may further include a light transmittance adjusting layer or protective layer, or a light transmittance adjusting layer and a protective layer as an upper layer.
The light transmittance adjusting layer is described in JP-A Nos. 9-39395, 9-39396, and Japanese Patent Application No. 7-208386.

  When a component that functions as a precursor of an ultraviolet absorber is used in the light transmittance adjustment layer, it does not function as an ultraviolet absorber before irradiating light in a wavelength region necessary for fixing, so that a high light transmittance is obtained. Therefore, when fixing the light-fixing type thermosensitive recording layer, the wavelength of the region necessary for fixing can be sufficiently transmitted, and the visible light transmittance is also high, which may hinder the fixing of the thermosensitive recording layer. Absent.

On the other hand, the precursor of the ultraviolet absorber is irradiated with light in a wavelength region necessary for photofixation (photodecomposition of a diazonium salt compound by light irradiation) of the photofixing type thermosensitive recording layer, and then reacts with the light to cause ultraviolet light. It will function as an absorbent. This ultraviolet absorber absorbs most of the light having a wavelength in the ultraviolet region and lowers its transmittance, thereby making it possible to improve the light resistance of the heat-sensitive recording material. However, since there is no visible light absorptivity, the visible light transmittance is not substantially changed.
The light transmittance adjusting layer can be provided in at least one layer in the heat-sensitive recording material, and in particular, it is preferably formed between the heat-sensitive recording layer and the protective layer. Further, the protective layer may have the function of the light transmittance adjusting layer and may be used in combination.

Next, the coloring components used in the multicolor thermosensitive recording material will be described.
(Diazonium salt compound)
For details of the diazonium salt compound, JP-A-4-59287, JP-A-4-59288, JP-A-10-337961, JP-A-11-78233, JP-A-11-116553, JP-A-7-223368, JP-A-7-323660, JP-A-7-125446, JP-A-7-96671, JP-A-2001-162946, JP-A-2002-326981, JP-B-3-213120, JP-B-3-394613, JP-A-3-394613 No. 8-310133, Japanese Patent Application No. 2002-241646, and Japanese Patent Application No. 2002-261318.
In the multicolor thermosensitive recording material, as described above, one of the two diazo thermosensitive recording layers is a diazonium salt compound having a maximum absorption wavelength of 445 ± 50 nm, and the other is a diazonium salt compound having a maximum absorption wavelength of 365 ± 30 nm. It is desirable to contain. When a diazonium salt compound is used in the other heat-sensitive recording layer (C layer), it is desirable to contain a 305 ± 30 nm diazonium salt compound.

-Diazonium salt compound (DA compound) having a maximum absorption wavelength of 445 ± 50 nm-
When the maximum absorption wavelength exceeds the upper limit, the stability of the diazonium salt compound is deteriorated and the practicality is insufficient, and when the lower limit is exceeded, the maximum absorption wavelength range of the diazonium salt compound having a maximum absorption wavelength of 365 ± 30 nm is not preferable. The range of the maximum absorption wavelength of the diazonium salt compound (DA compound) is more preferably 395 to 475 nm.
The diazonium salt compound having a maximum absorption wavelength of 445 ± 50 nm is preferably a diazonium salt compound represented by at least one of the general formulas (1) and (2) as described above.
Thereby, the coloring dye can exist in a protonated state.

-Diazonium salt compound (DB compound) having a maximum absorption wavelength of 365 ± 30 nm-
When the maximum absorption wavelength exceeds the upper limit, the maximum absorption wavelength range of 445 ± 50 nm of the diazonium salt compound is not preferable. If the lower limit is exceeded, the stability and photodegradability of the diazonium salt compound are deteriorated. The range of the maximum absorption wavelength of the diazonium salt compound (DB compound) is more preferably 350 to 375 nm.
The diazonium salt compound having a maximum absorption wavelength of 365 ± 30 nm is preferably a diazonium salt compound represented by the following general formula (4).

In General Formula (4), R ⁷ and R ⁸ have the same meaning as R ¹ , and preferred examples are also the same. X ⁻ represents a counter anion.

D ¹ represents an alkoxy group or an aryloxy group. The alkyl group of the alkoxy group and the aryl group of the aryloxy group have the same meanings as the alkyl group and aryl group represented by R ¹ , and preferred examples are also the same.
X ⁻ in the general formula (4) has the same meaning as in the general formula (1), and specific examples and preferred examples thereof are also the same.

  Although the specific example (exemplary compound (DB-1)-(DB-6)) of the diazonium salt compound represented by General formula (4) below is given, this invention is not limited to the following.

-Diazonium salt compound (DC compound) having a maximum absorption wavelength of 305 ± 30 nm-
When the maximum absorption wavelength exceeds the upper limit, the maximum absorption wavelength 365 ± 30 nm of the maximum absorption wavelength range of the diazonium salt compound is not preferable. When the lower limit is exceeded, the stability of the diazonium salt compound is deteriorated. The range of the maximum absorption wavelength of the diazonium salt compound (DC compound) is more preferably 280 to 325 nm.
The diazonium salt compound having the maximum absorption wavelength of 305 ± 30 nm is preferably a diazonium salt compound represented by the following general formulas (5) and (6).

In the general formulas (5) and (6), D ² and D ³ each represent a group having a Hammett σp value of −0.45 or more.
X ⁻ in the general formula (5) represents a counter anion. R ^{9 in the} general formula (6) represents a sulfonyl group, an acyl group or an alkoxycarbonyl group, and Z represents —SO ₂ — or —CO—.

The sulfonyl group of R ^9, replaceable arylsulfonyl group having 6 to 20 carbon atoms, an alkylsulfonyl group having 1 to 18 carbon atoms preferably. The acyl group for R ⁹ is preferably an acyl group having 2 to 20 carbon atoms. The alkoxycarbonyl group for R ⁹ is preferably an alkoxycarbonyl group having 2 to 20 carbon atoms.
Specific examples include the following.

D ² and D ³ representing a group having a Hammett σp value of −0.45 or more include an alkoxy group, an aryloxy group, an alkyl group, an alkylthio group, an arylthio group, a halogen atom, a hydrogen atom, a nitro group, a cyano group, An alkylsulfonyl group and an alkoxycarbonyl group are preferred.
The alkoxy group is preferably a substitutable alkoxy group having 1 to 20 carbon atoms, such as methoxy, ethoxy, butyloxy, hexyloxy, octyloxy, 2-ethylhexyloxy, 3-methyl-5,5-dimethylhexyloxy, Examples include decyloxy, phenoxyethoxy, 2- (2,4-di-t-pentylphenyl) oxyethyloxy and the like.
The aryloxy group is preferably a substitutable aryloxy group having 6 to 20 carbon atoms such as phenoxy, methylphenoxy, isopropylphenoxy, 2,4-di-t-pentylphenoxy, chlorophenoxy, methoxyphenoxy and the like. It is done.
As an alkyl group, a C1-C8 alkyl group is preferable, for example, methyl, ethyl, isopropyl, t-butyl, hexyl, octyl etc. are mentioned.
The alkylthio group is preferably a substitutable alkylthio group having 1 to 8 carbon atoms, and examples thereof include methylthio, ethylthio, butylthio, octylthio, benzylthio and the like.

The arylthio group is preferably a substitutable arylthio group having 6 to 10 carbon atoms, and examples thereof include phenylthio, methylphenylthio, chlorophenylthio, methoxyphenylthio and the like.
As a halogen atom, a chlorine atom, a fluorine atom, etc. are preferable.
As an alkylsulfonyl group, a C1-C8 alkylsulfonyl group is preferable, for example, methylsulfonyl, ethylsulfonyl, butylsulfonyl, octylsulfonyl, benzylsulfonyl, etc. are mentioned.
The alkoxycarbonyl group is preferably an alkoxycarbonyl group having 2 to 10 carbon atoms, and examples thereof include methoxycarbonyl, ethoxycarbonyl, butyloxycarbonyl, octyloxycarbonyl and the like.

X ⁻ in the general formula (5) has the same meaning as in the general formula (1), and specific examples and preferred examples thereof are also the same.
The benzene ring in the general formulas (5) and (6) may further have a substituent.
The substituent can be any substituent, but is preferably an alkyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, a halogen atom, a nitro group, a cyano group, an alkylsulfonyl group, an alkoxycarbonyl group, or the like. . The alkyl group, alkoxy group, alkylthio group, arylthio group, halogen atom, alkylsulfonyl group and alkoxycarbonyl group have the same meanings as the substituents corresponding to each of D ³ .
In the general formula (5), the benzene ring is preferably substituted at the ortho position (o-position) of the diaionio group.
Specific examples of the diazonium salt compounds represented by the general formulas (5) and (6) (Exemplary compounds (DC-1) to (DC-6)) are shown below, but the present invention is not limited thereto. .

  The diazonium salt compound may be either oily or crystalline, but is preferably in a crystalline state at room temperature from the viewpoint of handleability. This diazonium salt compound may be used alone or in combination of two or more, or may be used in combination with an existing diazonium salt compound.

The content of the diazo heat-sensitive recording layer of the diazonium salt compound is preferably 0.02 to 5 g / m ^2, more preferably 0.1-4 g / m ² from the viewpoint of color density.

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

(Microencapsulation)
In the recording material of the present invention, the diazonium salt compound is preferably encapsulated in a microcapsule for the purpose of improving the raw storage stability 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 has a glass transition temperature of 60 to 200 ° C. in particular because it is necessary to have a property of being impermeable at normal temperature and permeable when heated. Preferred examples include polyurethane, polyurea, polyamide, polyester, urea / formaldehyde resin, melamine resin, polystyrene, styrene / methacrylate copolymer, styrene / acrylate copolymer, and mixed systems thereof.

  Specifically, an interfacial polymerization method or an internal polymerization method is suitable as the microcapsule formation method. Details of the capsule forming method and specific examples of the reactant are described in the specifications of US Pat. Nos. 3,726,804 and 3,796,669. For example, when polyurea or polyurethane is used as the capsule wall material, polyisocyanate and a second substance that reacts therewith to form a capsule wall (for example, polyol or polyamine) are mixed in an aqueous medium or an oily medium to be encapsulated. Then, these are emulsified and dispersed in water and then heated to cause a polymer formation reaction at the oil droplet interface to form a microcapsule wall. Polyurea can also be produced when the addition of the second substance is omitted.

  In the present invention, it is preferable that the polymer material forming the capsule wall of the microcapsule contains polyurethane and / or polyurea as components because of excellent manufacturing suitability and thermal response sensitivity.

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

  In the preparation of the oil phase, the hydrophobic organic solvent used for forming the core of the microcapsule by dissolving and dispersing the diazonium salt compound is preferably an organic solvent having a boiling point of 100 to 300 ° C., for example, alkylnaphthalene, alkyldiphenyl. Ethane, alkyldiphenylmethane, alkylbiphenyl, alkylterphenyl, chlorinated paraffin, phosphate ester, maleate ester, adipate ester, phthalate ester, benzoate ester, carbonate ester, ether, sulfate ester And sulfonic acid esters. You may use these in mixture of 2 or more types.

When the solubility of the diazonium salt compound to be encapsulated in the organic solvent is inferior, a low-boiling solvent having a high solubility of the diazonium salt compound to be used can be supplementarily used together. For example, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, methylene chloride, tetrahydrofuran, acetonitrile, acetone and the like can be mentioned.
Therefore, the diazonium salt compound preferably has an appropriate solubility in a high boiling hydrophobic organic solvent and a low boiling solvent, and specifically has a solubility of 5% by mass or more in the solvent. It is preferable. The solubility in water is preferably 1% by mass or less.

On the other hand, an aqueous solution in which a water-soluble polymer is dissolved is used for the aqueous phase to be used, and after the oil phase is added thereto, emulsification and dispersion are performed by means of a homogenizer or the like. It facilitates and acts as a dispersion medium for stabilizing the emulsified and dispersed 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 emulsifying surfactant can be used.
As addition amount in the case of adding surfactant, 0.1-5 mass% is preferable with respect to the oil phase mass, and 0.5-2 mass% is more preferable.

  The water-soluble polymer used in the water-soluble polymer aqueous solution for dispersing the prepared oil phase is preferably a water-soluble polymer having a solubility in water of 5% by mass or more at the temperature to be emulsified, such as polyvinyl alcohol and its Modified products, polyacrylic acid amide 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 derivative, arabic gum, sodium alginate and the like.

  It is preferable that the water-soluble polymer has no or low reactivity with an isocyanate compound. For example, a polymer having a reactive amino group in a molecular chain such as gelatin reacts by being modified in advance. It is preferable to eliminate the property.

The polyvalent isocyanate compound is preferably a compound having a trifunctional or higher functional isocyanate group, but may be a bifunctional isocyanate compound. Specifically, xylene diisocyanate and hydrogenated products thereof, hexamethylene diisocyanate, tolylene diisocyanate and hydrogenated products thereof, diisocyanates such as isophorone diisocyanate, and the like, and these dimers or trimers (burette or isocyanate). Nurate), other polyfunctional adducts of polyols such as trimethylolpropane and bifunctional isocyanates such as xylylene diisocyanate, adducts of polyols such as trimethylolpropane and bifunctional isocyanates such as xylylene diisocyanate Examples thereof include 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, and Japanese Patent Application No. 8-268721 are preferable.

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 dispersed particle diameter is generally about 0.2 to 10 μm.
In an emulsified dispersion in which an oil phase is added to an aqueous phase, a polyisocyanate polymerization reaction occurs at the interface between the oil phase and the aqueous phase to form a polyurea wall.

If a polyol and / or polyamine is further added to the hydrophobic solvent in the aqueous phase or the oil phase, it 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 polyisocyanate, polyol, reaction catalyst, polyamine for forming a part of the wall agent, etc. are well-known in the book (Keiji Iwata, Polyurethane Handbook, Nikkan Kogyo Shimbun (1987)).

  The emulsification can be carried out by appropriately selecting from known emulsifiers such as a homogenizer, a manton gorey, an ultrasonic disperser, a dissolver, and a kedy mill. After emulsification, the emulsion is heated to 30 to 70 ° C. in order to promote the capsule wall formation reaction. Further, during the reaction, in order to prevent aggregation between the capsules, it is necessary to add water to reduce the collision probability between the capsules or to perform sufficient stirring.

  Further, a dispersion for preventing aggregation may be added again during the reaction. As the polymerization reaction proceeds, the generation of carbon dioxide gas is observed, and its end can be regarded as the approximate end point of the capsule wall formation reaction. Usually, the target diazonium salt compound-containing microcapsules can be obtained by reacting for several hours.

  Next, the coupler used in the present invention can be used in the form of a solid dispersion by a sand mill or the like together with, for example, a water-soluble polymer, an organic base, and other color forming aids. Alternatively, after being dissolved in an insoluble high-boiling organic solvent, 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 as an emulsified dispersion. It is preferable to use it. In this case, a low boiling point solvent can be used as a dissolution aid, if necessary. Further, the coupler and the organic base can be emulsified and dispersed separately, or mixed and then dissolved in a high boiling point organic solvent to be emulsified and dispersed. A preferable emulsified and dispersed particle size is 1 μm or less.

  The amount of the coupler used is preferably 0.1 to 30 parts by mass with respect to 1 part by mass of the diazonium salt compound.

  The high boiling point organic solvent used in this case can be appropriately selected from, for example, high boiling point oils described in JP-A-2-141279. Among these, from the viewpoint of emulsion stability of the emulsified dispersion, esters are preferable, and tricresyl phosphate is particularly preferable. The above oils can be used together with other oils.

  A low-boiling auxiliary solvent can also be added to the organic solvent as a dissolution aid. Examples of the auxiliary solvent include ethyl acetate, isopropyl acetate, butyl acetate, and methylene chloride. Depending on the case, it is possible to use only a low-boiling point auxiliary solvent without containing a high-boiling point oil.

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

  Further, as the surfactant to be contained in the aqueous phase, an anionic or nonionic surfactant that does not cause precipitation or aggregation by acting on the protective colloid may be appropriately selected and used. it can. Examples of the surfactant include sodium alkylbenzene sulfonate, sodium alkyl sulfate, dioctyl sulfosuccinate sodium salt, polyalkylene glycol (for example, polyoxyethylene nonylphenyl ether), and the like.

(Requirements for causing protonation)
In order to efficiently produce the protonated coloring dye in the present invention in the recording material, it is preferable to make the coloring dye production field acidic. When color is developed using a microcapsule encapsulating a diazonium salt compound and an oil droplet (outside the microcapsule) in which a coupler compound is dissolved, a dye is produced in the microcapsule. The atmosphere in the microcapsule after color development needs to be acidic.
In order to make the atmosphere in the microcapsule after color development acidic, (1) oil droplets in which the coupler compound is dissolved are kept acidic, and (2) oil droplets in which the coupler compound is dissolved are weakly basic to neutral. (In this case, HX produced from the diazonium salt compound by the azo coupling reaction becomes an acidic source.) (3) The microcapsules are kept acidic to cause color development. (4) Light or heat in the microcapsules. It is effective to introduce an acid generator and generate an acid by light or heat stimulation during or after color development.
Among these, in the present invention, the method of coloring under the condition (2) is preferable from the practical point of view.
In order to cause color development under the condition (2), it is preferable to use a coupler that develops color rapidly from weakly basic to neutral conditions.
Among the couplers that form yellow dyes, the structures of couplers that develop colors quickly from weakly basic to neutral conditions are particularly described above as (C-4), (C-5), (C-13), (C- 31) to (C-40) are preferable.

  In addition to the above, in order to maximize the protonation efficiency of the coloring dye, it is preferable to use the condition (4) in combination. Specific examples of the light or thermal acid generator in (4) include benzophenone, 4,4-bis (dimethylamino) benzophenone, 4-methoxy-4′-dimethylaminobenzophenone, 4,4′-dimethoxybenzophenone, 4- Dimethylaminobenzophenone, 4-dimethylaminoacetophenone, benzylanthraquinone, 2-tert-butylanthraquinone, 2-methylanthraquinone, xanthone, thioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, fluorenone, acridone, bis (2,4 , 6-Trimethylbenzoyl) -bisphosphine oxides such as phenylphosphine oxide, acylphosphine oxides such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide Aromatic ketones such as side like;

  Benzoin and benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether and benzoin phenyl ether; 2- (o-chlorophenyl) -4,5-diphenylimidazole duplex, 2- (o-chlorophenyl) -4, 5-di (m-methoxyphenyl) imidazole duplex, 2- (o-fluorophenyl) -4,5-diphenylimidazole duplex, 2- (o-methoxyphenyl) -4,5-diphenylimidazole dimer, 2,4,6-triarylimidazole duplexes such as 2- (p-methoxyphenyl) -4,5-diphenylimidazole duplexes; polyhalogens such as carbon tetrabromide, phenyltribromomethylsulfone, phenyltrichloromethylketone Compound; JP 59-133 No. 28, JP-B-57-1819, JP-B-57-6096, compounds described in U.S. Patent No. 3,615,455;

  2,4,6-tris (trichloromethyl) -S-triazine, 2-methoxy-4,6-bis (trichloromethyl) -S-triazine, 2-amino-4,6-bis (trichloromethyl) -S- S-triazine derivatives having a trihalogen-substituted methyl group described in JP-A No. 58-29803, such as triazine and 2- (P-methoxystyryl) -4,6-bis (trichloromethyl) -S-triazine;

  Methyl ethyl ketone peroxide, cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, benzoyl peroxide, ditertiary-butyldiperoxyisophthalate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, Tertiary butyl peroxybenzoate, α, α′-bis (tertiary butyl peroxy isopropyl) benzene, dicumyl peroxide, 3,3 ′, 4,4′-tetra- (tertiary butyl peroxycarbonyl) benzophenone, etc. An organic peroxide described in JP-A-59-189340;

  Azinium salt compounds described in US Pat. No. 4,743,530; tetraphenylammonium salt of triphenylbutyrate borate, tetrabutylammonium salt of triphenylbutyrate borate, tetramethylammonium salt of tri (p-methoxyphenyl) butyrate borate, etc. And organic boron compounds described in European Patent No. 023587; other diaryliodonium salts and iron allene complexes.

Moreover, what combined 2 or more types of compounds is also known, and these can also be used.
Examples of combinations of two or more compounds include a combination of 2,4,5-triarylimidazole dimer and mercaptobenzoxazole, etc., 4,4′- described in US Pat. No. 3,427,161. A combination of bis (dimethylamino) benzophenone and benzophenone or benzoin methyl ether, benzoyl-N-methylnaphthothiazoline and 2,4-bis (trichloromethyl) -6- (4′-) described in US Pat. No. 4,239,850 Combination of methoxyphenyl) -triazole, combination of dialkylaminobenzoate and dimethylthioxanthone described in JP-A-57-23602, 4,4′-bis (dimethylamino) of JP-A-59-78339 ) Of benzophenone, benzophenone and polyhalogenated methyl compounds It includes the kind of combinations and the like.

  Other photoactivators include organic borate compounds or cationic dyes described in JP-A-62-143044, JP-A-9-188865, JP-A-9-188686, JP-A-9-188710, and the like. Spectral sensitizing dye-based borate compounds obtained from the above.

  Among the above, at least one of the compounds listed in the following (AG-1) to (AG-9) is more preferable in the present invention.

Therefore, as a requirement for making the present invention more efficient and practical, it is preferable to use the above (2) and (4) in combination.
In this case, the use ratio of the diazonium salt compound and the coupler is preferably 1: 0.5 to 1: 5 (molar ratio), and particularly preferably 1: 1 to 1: 3 (molar ratio).
Further, assuming that an acidic substance generated from one molecule of the light or thermal acid generator is n moles, the amount of the light or thermal acid generator used is 0.01 × 1 / n to 2 to 1 mole of the diazonium salt compound. × 1 / n mol is preferable, and 0.1 × 1 / n to 1 × 1 / n mol is particularly preferable. For example, since a maximum of 6 molecules of HCl are generated from one molecule of AG-1, n = 6 in this case.

  In summary, the use ratio of the diazonium salt compound, the coupler, and the light or thermal acid generator in the present invention is as follows: diazonium salt compound: coupler: light or thermal acid generator: 1: 0.5: 0.01 / n-1: 5: 2 / n is preferable, and 1: 1: 0.1 / n-1: 3: 1 / n is particularly preferable.

In the heat-sensitive recording layer, a coloring aid can be added for the purpose of accelerating the coloring reaction under weak basic to neutral conditions, that is, for rapid and complete thermal printing with low energy. Here, the coloring aid is a substance that increases the coloring density during heat recording or controls the coloring temperature, lowers the melting point of couplers, basic substances or diazonium salt compounds, and softens the capsule wall. This is for the purpose of making the diazonium salt compound, the basic substance, the coupler, etc. easy to react by the action that can lower the point.
Examples of the coloring aid include phenol derivatives, naphthol derivatives, alkoxy-substituted benzenes, alkoxy-substituted naphthalenes, aromatic ethers, thioethers, esters, amides, ureidos, urethanes, sulfonamide compounds, hydroxy compounds, and the like.

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

In the present invention, for the purpose of adjusting acid-basic conditions at the time of color development, it is also a preferred aspect to use a basic substance such as an organic base or an acidic substance such as an organic acid in combination.
Examples of the organic base include tertiary amines, piperidines, piperazines, amidines, formamidines, pyridines, guanidines, morpholines, nitrogen-containing compounds, and the like. JP-A-46806, JP-A-62-20082, JP-A-57-169745, JP-A-60-94381, JP-A-57-123086, JP-A-60-49991, Preferred examples include those described in JP-B-2-24916, JP-B-2-28479, JP-A-60-165288, and JP-A-57-185430. These may be used alone or in combination of two or more.

  Among 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′-bis [3- (Β-naphthoxy) -2-hydroxypropyl] piperazine, N-3- (β-naphthoxy) -2-hydroxypropyl-N′-methylpiperazine, 1,4-bis {[3- (N-methylpiperazino) -2 Piperazines such as -hydroxy] propyloxy) benzene, N- [3- (β-naphthoxy) -2-hydroxy] propylmorpholine, 1,4-bis (3-morpholine Morpholines such as 2-hydroxy-propyloxy) benzene and 1,8-bis (3-morpholino-2-hydroxy-propyloxy) benzene, N- (3-phenoxy-2-hydroxypropyl) piperidine, N-dodecyl Piperidines such as piperidine and guanidines such as triphenylguanidine, tricyclohexylguanidine and dicyclohexylphenylguanidine are preferred.

As the usage-amount of the said basic substance, 0-0.5 mass part is preferable with respect to 1 mass part of diazonium salt compounds, and 0-0.3 mass part is especially preferable.
When the amount used exceeds 0.5 mass, the proportion of the non-protonated coloring dye increases, and the protonated coloring dye cannot be obtained with high selectivity.

  Examples of the organic acid include compounds such as carboxylic acids, disulfonimides, dicarbonimides, and sulfoncarbonimides. These may be used alone or in combination of two or more.

  Of the above, specifically, 2-ethylhexylcarboxylic acid, stearic acid, benzoic acid, salicylic acid, 3,5-di-tert-butylsalicylic acid, anthranilic acid, bismethanesulfonimide, bistrifluoromethanesulfonimide, and the like are preferable. .

  In the recording material of the present invention, when a compound having a group L that is eliminated during azo coupling is used as a coupler, an aminophenol type, phenol type, catechol type, Hydroquinone, amine, hydroxyamine, alcohol, thiol, sulfide, alkali metal, alkaline earth metal, metal hydride, hydrazine, phenidone, aniline, phenyl ether, L-ascorbic acid, etc. It is preferable to add a reducing agent, and among these, hydroquinone-based, catechol-based, and aminophenol-based reducing agents are preferable. Of these, hydroquinone, catechol, and aminophenol are preferable.

  These reducing agents may be solid-dispersed in a fine particle state in the recording layer. When the diazonium salt compound is microencapsulated, it can be added inside the microcapsule or both inside and outside.

  Moreover, it is preferable that it is 1-10 times mole with respect to a diazonium salt compound, and, as for content of the said reducing agent, it is more preferable that it is 1-4 times mole. If the addition amount is less than 1 mol of the diazonium salt compound content, the effect of improving the color developability and the effect of improving the image preservability may not be sufficiently obtained. The effect of improving color developability may be reduced, and the raw storage stability may be deteriorated.

In the recording material of the present invention, for the purpose of improving fastness to light and heat of a thermochromic image or reducing yellowing due to light in an unprinted portion (non-image portion) after fixing, the following publicly known It is also preferable to use an antioxidant or the like.
Examples of the antioxidant include, for example, European Patent Publication No. 223739, Publication No. 309401, Publication No. 309402, Publication No. 310551, Publication No. 310552, Publication No. 457416, and German Patent No. 3435443, JP-A-54-48535, JP-A-62-262047, JP-A-63-113536, JP-A-63-163351, JP-A-2-262654, JP-A-2-71262. JP-A-3-121449, JP-A-5-61166, JP-A-5-119449, US Pat. No. 4,814,262, US Pat. No. 4,980,275, and the like.

It is also effective to use known various 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, JP-A-60-125471, JP-A-60-125472, and JP-A-60-287485. No. 60-287486, No. 60-287487, No. 60-287488, No. 61-160287, No. 61-185483, No. 61-2111079, No. 62-146678. Gazette, 62-146680 gazette, 62-146679 gazette, 62-282858 gazette, 63-051174 gazette, 63-898877 gazette, 63-88380 gazette, 63-088381 gazette. 63-203372, 63-224989, 63-25128 No. 63-267594, No. 63-182484, JP-A-1-239282, No. 4-29185, No. 4-291684, No. 5-188687, No. 5-188686. And JP-A-5-110490, JP-A-5-170361, JP-B-48-043294, JP-A-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 cyclohexaneate, 2,2-bis (4-hydroxyphenyl) propane, 1,1-bis (4-hydroxyphenyl) -2-ethylhexane, 2-methyl-4-methoxy-diphenylamine, 1 -Methyl-2-phenylindole and the like.

  As addition amount of the said antioxidant or various additives, 0.05-100 mass parts is preferable with respect to 1 mass part of diazonium salt compounds, and 0.2-30 mass parts is more preferable.

  The antioxidant and various additives may be contained in a microcapsule together with a diazonium salt compound, or may be contained as a solid dispersion together with a coupler, a basic substance and other color forming aids, An emulsion may be contained together with a suitable emulsification aid, or may be contained in both forms. Moreover, antioxidant or various additives may be used independently and can also be used together. Furthermore, it can also be contained in the protective layer.

The antioxidant and various additives are not necessarily 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, sulfur compounds. In addition, different structures may be combined with each other, or a plurality of the same structures may be combined.

For the purpose of reducing yellowing of the background after image recording, a free radical generator (compound that generates free radicals upon light irradiation) 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 addition amount of the free radical generator is preferably 0.01 to 5 parts by mass with respect to 1 part by mass of the diazonium salt compound.

Similarly, for the purpose of reducing yellow coloring, a polymerizable compound having an ethylenically unsaturated bond (hereinafter referred to as “vinyl monomer”) can also be used. A 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 monomer or prepolymer.
Examples of the vinyl monomer include unsaturated carboxylic acids and salts thereof, esters of unsaturated carboxylic acids and aliphatic polyhydric alcohols, amides of unsaturated carboxylic acids and aliphatic polyvalent amine compounds, and the like. The vinyl monomer is used in a proportion of 0.2 to 20 parts by mass with respect to 1 part by mass of the diazonium salt compound.
The free radical generator and the vinyl monomer can be used in a microcapsule together with a diazonium salt compound.

  Furthermore, citric acid, tartaric acid, oxalic acid, boric acid, phosphoric acid, pyrophosphoric acid and the like can be added as an acid stabilizer.

  The heat-sensitive recording layer is prepared, for example, by preparing a coating solution containing a microcapsule containing a diazonium salt compound, a coupler, and a basic substance and other components as necessary, and applying the coating solution to paper, a synthetic resin film, etc. It can be coated by applying and drying on the support.

The coating can be appropriately selected from known coating methods, and examples thereof include bar coating, blade coating, air knife coating, gravure coating, roll coating coating, spray coating, dip coating, and curtain coating.
The coating, as a dry coating amount of the heat-sensitive recording layer after drying, 2.5~30g / m ² is preferred.

  The configuration of the heat-sensitive recording layer in the recording material of the present invention is not particularly limited. For example, it is an embodiment composed of a single layer in which microcapsules, couplers, basic substances, etc. are all contained in the same layer. Alternatively, it may be a multi-layer stacked type that is included in a separate layer. Alternatively, an intermediate layer described in JP-A-61-54980 or the like may be provided on a support, and then a heat-sensitive recording layer may be applied and formed. Each of these embodiments is a full color color development type in which a plurality of monochromatic and single thermosensitive recording layers having different hues are laminated.

In the recording material of the present invention, each layer such as a heat-sensitive recording layer, an intermediate layer or a protective layer described later can contain a binder, and examples of the binder include known water-soluble polymer compounds and latexes. It can be selected appropriately.
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, polyacrylic acid, polyacrylic acid amide and the like, and modified products thereof.

Examples of the latex include styrene-butadiene rubber latex, methyl acrylate-butadiene rubber latex, and vinyl acetate emulsion.
Of these, hydroxyethyl cellulose, starch derivatives, gelatin, polyvinyl alcohol derivatives, polyacrylic acid amide derivatives and the like are preferable.

  In addition, the recording material of the present invention may contain a pigment, and examples of the pigment include organic and inorganic materials such as 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, microballoon, urea -Formalin filler, polyester particle, cellulose filler and the like.

  In addition, various additives such as known waxes, antistatic agents, antifoaming agents, conductive agents, fluorescent dyes, surfactants, ultraviolet absorbers and their precursors can be used as necessary.

In the recording material of the present invention, a protective layer may be provided on the thermosensitive recording layer as 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, methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, gelatins, gum arabic, and casein , Styrene-maleic acid copolymer hydrolyzate, styrene-maleic acid copolymer half ester hydrolyzate, isobutylene-maleic anhydride copolymer hydrolyzate, polyacrylamide derivative, polyvinylpyrrolidone, polystyrene sulfonate soda, alginic acid Water-soluble polymer compounds such as soda, styrene-butadiene rubber latex, acrylonitrile-butadiene rubber latex, methyl acrylate-butadiene rubber latex , Latexes such as vinyl acetate emulsion.

  The water-soluble polymer compound can be further improved in storage stability by crosslinking. The crosslinking agent can be appropriately selected from known crosslinking agents, and examples thereof include water-soluble initial condensates such as N-methylol urea, N-methylol melamine, urea-formalin; dioxal, glutaraldehyde and the like. Aldehyde compounds; inorganic crosslinking agents such as boric acid and borax; polyamide epichlorohydrin and the like.

For the protective layer, known pigments, metal soaps, waxes, surfactants and the like can also be used. The fluorescent brightener precursor may be contained in a protective layer.
The coating amount of the protective layer is preferably 0.2 to 5 g / m ^{2 and} more preferably 0.5 to ² g / m ^{2 in} terms of dry coating amount. The film thickness is preferably 0.2-5 μm, more preferably 0.5-2 μm.
Moreover, when providing a protective layer, you may contain a well-known ultraviolet absorber and its precursor in this protective layer.
The protective layer can be provided by the above-described known coating method as in the case of forming the heat-sensitive recording layer on the support.

  As the support that can be used for the recording material of the present invention, any of the paper supports used for ordinary pressure-sensitive paper, heat-sensitive paper, dry or wet diazo copy paper, etc. can be used. Paper, coated paper, plastic film laminated paper, synthetic paper, and 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 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 is provided between the support and the heat-sensitive recording layer or on the surface of the support on the side where the heat-sensitive recording layer is provided, and a slip layer or an antistatic layer is provided on the back surface. An adhesive layer or the like can also be provided.
Also, a label may be formed by combining release paper with an adhesive layer on the back surface of the support (the surface on which the thermosensitive recording layer is not provided).

  By encapsulating the diazonium salt compound in microcapsules, the long-term stability as a recording material can be further enhanced.

The recording layer of the recording material of the present invention may contain an electron donating dye precursor and an electron accepting compound. Further, the electron donating dye precursor is preferably encapsulated in a microcapsule like the diazonium salt compound.
The electron donating dye precursor and the electron accepting compound are disclosed in JP-A-6-328860, JP-A-7-290826, JP-A-7-314904, JP-A-8-324116, and JP-A-3-3. JP-A-37727, JP-A-9-31345, JP-A-9-111136, JP-A-9-118073, JP-A-11-157221, and the like.
Specific examples of the electron donating dye precursor are shown below, but the present invention is not limited thereto.

-Specific examples of electron accepting compounds-
Examples of the electron-accepting compound include phenol derivatives, salicylic acid derivatives, and hydroxybenzoic acid esters. In particular, bisphenols and hydroxybenzoic acid esters are preferable. Some examples of these are 2,2-bis (p-hydroxyphenyl) propane (ie, bisphenol A), 4,4 ′-(p-phenylenediisopropylidene) diphenol (ie, bisphenol P), 2,2-bis (p-hydroxyphenyl) pentane, 2,2-bis (p-hydroxyphenyl) ethane, 2,2-bis (p-hydroxyphenyl) butane, 2,2-bis (4′-hydroxy-) 3 ', 5'-dichlorophenyl) propane, 1,1- (p-hydroxyphenyl) cyclohexane, 1,1- (p-hydroxyphenyl) propane, 1,1- (p-hydroxyphenyl) pentane, 1,1- (P-hydroxyphenyl) -2-ethylhexane, 3,5-di (α-methylbenzyl) salicylic acid and its polyvalent metal salt, 3,5-di (te t-butyl) salicylic acid and its polyvalent metal salt, 3-α, α-dimethylbenzylsalicylic acid and its polyvalent metal salt, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, p-hydroxybenzoic acid-2- Examples include ethylhexyl, p-phenylphenol, and p-cumylphenol.

(Recording method)
The recording method using the recording material of the present invention is as follows.
The image recording process will be described by taking, as an example, a thermal recording material provided with a diazo thermal recording layer containing a diazonium salt compound as a recording layer. The surface of the thermal recording material on the side where the diazo thermal recording layer is provided is a thermal head or the like. By image-wise heating printing with a heating device, the capsule wall containing polyurea and / or polyurethane in the layer becomes soft and becomes material permeable in the heating part of the diazo thermosensitive recording layer, and couplers and basic substances outside the capsule When the (organic base) enters the microcapsule, the image may be colored to form an image. In this case, after color development, by further irradiating light corresponding to the absorption wavelength of the diazonium salt compound (photofixing), the diazonium salt compound undergoes a decomposition reaction and loses reactivity with the coupler, thereby fixing the image. Can do. By carrying out photofixing as described above, the unreacted diazonium salt compound loses its activity by causing a decomposition reaction, and therefore, due to density fluctuations in the formed image and the occurrence of stain in the non-image area (background area) Coloring, that is, a decrease in whiteness and a decrease in image contrast accompanying the decrease can be suppressed.

  Examples of the light source used for the light fixing include various light-emitting diodes, fluorescent lamps, xenon lamps, mercury lamps, and the like, and the emission spectrum of these light sources substantially matches the absorption spectrum of the diazonium salt compound in the heat-sensitive recording material. Is preferable in that it can be fixed with high efficiency. In addition, a light emitting diode is preferable from the viewpoint of the temporal stability of light fixing. Heating may be performed by a thermal head or using a heat roller.

  Further, it can also be used as a light-writing heat-developable heat-sensitive recording material in which image-like writing is performed with light and heat development is performed to form an image. In this case, the printing process is performed by a light source such as a laser instead of the heating device as described above.

In the recording material of the present invention, a recording process in a multicolor thermosensitive recording material provided with a plurality of thermosensitive recording layers that develop colors having different hues will be described.
When the heat-sensitive recording layer is laminated in the order of the support, C layer / B layer / A layer, for example, it can be carried out as follows. The following is a second thermosensitive recording layer comprising a third thermosensitive recording layer (C layer) containing an electron donating dye precursor and an electron accepting compound on a support, and a diazonium salt compound having a maximum absorption wavelength of 365 ± 30 nm. This is a multicolor thermosensitive recording material having a recording layer (B layer) and a first thermosensitive recording layer (A layer) containing a diazonium salt compound having a maximum absorption wavelength of 445 ± 50 nm.
First, the first thermosensitive recording layer (A layer) is heated, and the diazonium salt compound (DA compound) contained in the layer is reacted with a coupler to develop a color. Next, 445 ± 50 nm light is irradiated to decompose the unreacted diazonium salt compound (DA compound) contained in the first thermosensitive recording layer (A layer). Next, sufficient heat is applied to the second heat-sensitive recording layer (B layer) to develop color, and the diazonium salt compound (DB compound) contained in the layer reacts with the coupler compound to develop color. At this time, the first thermosensitive recording layer (A layer) is also strongly heated at the same time. However, since the diazonium salt compound (DA compound) has already been decomposed and the coloring ability is lost, no color is developed. Thereafter, irradiation with 365 ± 30 nm light is performed to decompose the diazonium salt compound (DB compound) contained in the second thermosensitive recording layer (B layer). Finally, the third heat-sensitive recording layer (C layer) is colored by applying sufficient heat. At this time, the first and second heat-sensitive recording layers are also strongly heated at the same time, but the diazonium salt compound has already been decomposed and does not develop color because the coloring ability is lost.

  When the heat-sensitive recording layer is laminated in the order of C layer / B layer / A layer from the support, the coloring hues of the support are cyan / magenta / yellow, magenta / cyan / yellow, yellow / cyan / magenta. A combination is preferred. When the heat-sensitive recording layer is laminated in the order of C layer / A layer / B layer from the support, the coloring hues of the support are cyan / yellow / magenta, magenta / yellow / cyan, yellow / magenta / cyan. A combination is preferred.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to this. In the following description, “part” means “part by mass” and “%” means “% by mass” unless otherwise specified.

(Example 1)
Synthesis of Protonated Coloring Dye 5.5 g of the diazonium salt compound (DA-2) of the present invention and 4.2 g of coupler compound (C-31) were mixed in methanol at 25 ° C. and stirred for 1 hour. The precipitated crystals were filtered and dried to obtain 9.2 g of yellow dye A (protonated coloring dye).
Separately, 1.2 g of triethylamine was mixed at 25 ° C. in a methanol solution of 5.5 g of diazonium salt compound (DA-2) and 4.2 g of coupler compound (C-31), and stirred for 1 hour. The precipitated crystals were filtered and dried to obtain 8.6 g of yellow dye B (unprotonated coloring dye).
The structure of the dye was confirmed by NMR.
Table 1 shows the absorption characteristics and oxidation potentials of yellow dye A (protonated coloring dye) and yellow dye B (unprotonated coloring dye).

The absorption spectrum and molar absorption coefficient (ε / M ⁻¹ cm ⁻¹ ) of the coloring dye were measured in a chloroform / methanol (1: 1 volume ratio) solution. The oxidation potential was measured with an acetonitrile solution. A rotating platinum electrode and a hydrogen electrode as a reference electrode were used, and tetraethylammonium perchlorate was used as an electrolyte.
It was also confirmed that when yellow dye A and yellow dye B were irradiated with a xenon lamp in an ethyl acetate solution, yellow dye A was less likely to fade against yellow dye B.

(Example 2)
When the heat-sensitive recording layer is laminated in the order of C layer / B layer / A layer from the support.
<Preparation of aqueous solution of phthalated gelatin>
Phthalated gelatin (trade name: MGP gelatin, manufactured by Nippi Collagen Co., Ltd.) 32 parts, 1,2-benzothiazolin-3-one (3.5% methanol solution, manufactured by Daito Chemical Industry Co., Ltd.) 0.9143 Part and 367.1 parts of ion-exchanged water were mixed and dissolved at 40 ° C. to obtain a phthalated gelatin aqueous solution.

<Preparation of alkali-treated gelatin aqueous solution>
25.5 parts of alkali-treated low ion gelatin (trade name; # 750 gelatin, manufactured by Nitta Gelatin Co., Ltd.), 1,2-benzothiazolin-3-one (3.5% methanol solution, Daito Chemical Industry Co., Ltd.) ) 0.7286 parts, calcium hydroxide 0.153 parts, and ion-exchanged water 143.6 parts were mixed and dissolved at 50 ° C. to obtain an alkali-treated gelatin aqueous solution.

(1) Preparation of first thermosensitive recording layer (A layer) solution <Preparation of diazonium salt compound-encapsulated microcapsule solution (a)>
To 16.1 parts of ethyl acetate, 4.4 parts of diazonium salt compound (DA-2), 4.8 parts of isopropyl biphenyl, 4.8 parts of diphenyl phthalate, and 0.1 part of photoacid generator (AG-4) Added and heated to 40 ° C. to dissolve uniformly. Mixture of xylylene diisocyanate / trimethylolpropane adduct and xylylene diisocyanate / bisphenol A adduct as a capsule wall material in the above mixture (trade name: Takenate D119N (50% ethyl acetate solution), manufactured by Takeda Pharmaceutical Co., Ltd.) 8.6 parts was added and stirred uniformly to obtain a mixture (I).
Separately, 16.3 parts of ion-exchanged water and 0.34 part of Scratch AG-8 (50%) manufactured by Nippon Seika Co., Ltd.) were added to 58.6 parts of the phthalated gelatin aqueous solution to obtain a mixed liquid (II). It was.
The mixed solution (I) was added to the mixed solution (II), and the mixture was emulsified and dispersed at 40 ° C. using a homogenizer (manufactured by Nippon Seiki Seisakusho). After adding 20 parts of water to the obtained emulsion and homogenizing it, the mixture was stirred at 40 ° C. to carry out an encapsulation reaction for 3 hours while removing ethyl acetate. Thereafter, 4.1 parts of ion exchange resin Amberlite IRA68 (manufactured by Organo Corp.) and 8.2 parts of Amberlite IRC50 (manufactured by Organo Corp.) were added and further stirred for 1 hour. Thereafter, the ion exchange resin was removed by filtration, and the concentration was adjusted so that the solid content concentration of the capsule liquid was 20.0% to obtain a diazonium salt compound-encapsulating microcapsule liquid (a). The obtained microcapsules had a median diameter of 0.36 μm as a result of particle size measurement (LA-700, manufactured by Horiba, Ltd.).

<Preparation of coupler compound emulsion (a)>
33.0 parts of ethyl acetate and 9.9 parts of coupler compound (C-31) and 4,4 ′-(m-phenylenediisopropylidene) diphenol (trade name: Bisphenol M (manufactured by Mitsui Petrochemical Co., Ltd.)) 20.8 parts, 4- (2-ethylhexyloxy) benzenesulfonic acid amide (manac) 13.6 parts, 4-n-pentyloxybenzenesulfonic acid amide (manac) 6.8 parts Then, 4.2 parts of calcium dodecylbenzenesulfonate (trade name: Pionein A-41-C 70% methanol solution, manufactured by Takemoto Yushi Co., Ltd.) was dissolved to obtain a mixed solution (III).
Separately, 107.3 parts of ion-exchanged water was mixed with 206.3 parts of the alkali-treated gelatin aqueous solution to obtain a mixed liquid (IV).
The mixed solution (III) was added to the mixed solution (IV), and the mixture was emulsified and dispersed at 40 ° C. using a homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.). The obtained coupler compound emulsion was heated under reduced pressure to remove ethyl acetate, and then the concentration was adjusted so that the solid content concentration was 26.5%. The resulting coupler compound emulsion had a median diameter of 0.21 μm as a result of particle size measurement (LA-700, manufactured by Horiba, Ltd.).
Further, 9 parts of SBR latex (trade name: SN-307, 48% solution, manufactured by Sumika Aves Latex Co., Ltd.) adjusted to 26.5% are added to 100 parts of the above coupler compound emulsion. The mixture was stirred uniformly to obtain a coupler compound emulsion (a).

<Preparation of thermosensitive recording layer coating solution (a)>
The diazonium salt compound-encapsulated microcapsule liquid (a) and the coupler compound-emulsified liquid (a) are mixed so that the mass ratio of the encapsulated coupler compound / diazo compound is 2.1 / 1, and thermal recording is performed. A layer coating solution (a) was obtained.

(2) Preparation of second thermosensitive recording layer (B layer) solution <Preparation of diazonium salt compound-encapsulated microcapsule solution (b)>
15.1 parts of ethyl acetate, 2.8 parts of diazonium compound (DB-4) (maximum absorption wavelength 365 nm), 3.5 parts of diphenyl phthalate, 3.5 parts of phenyl 2-benzoyloxybenzoate and trimethylolpropane tri Methacrylate (trade name; Light Ester TMP, manufactured by Kyoei Yushi Chemical Co., Ltd.) 4.2 parts and calcium dodecylbenzenesulfonate (trade name: Pionein A-41-C 70% methanol solution, manufactured by Takemoto Yushi Co., Ltd.) 1 part was added and heated to dissolve uniformly. Mixture of xylylene diisocyanate / trimethylolpropane adduct and xylylene diisocyanate / bisphenol A adduct as a capsule wall material in the above mixture (trade name: Takenate D119N (50% ethyl acetate solution), manufactured by Takeda Pharmaceutical Co., Ltd.) 2.5 parts and 6.8 parts of xylylene diisocyanate / trimethylolpropane adduct (trade name: Takenate D110N (75% ethyl acetate solution), Takeda Pharmaceutical Co., Ltd.) are added, and the mixture is stirred uniformly. (V) was obtained.
Separately, 21.0 parts of ion-exchanged water was added to and mixed with 55.3 parts of the phthalated gelatin aqueous solution to obtain a mixed liquid (VI).
The mixed solution (V) was added to the mixed solution (VI), and the mixture was emulsified and dispersed at 40 ° C. using a homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.). After 24 parts of water was added to the obtained emulsion and homogenized, the mixture was stirred at 40 ° C. to carry out an encapsulation reaction for 3 hours while removing ethyl acetate. Thereafter, 4.1 parts of ion exchange resin Amberlite IRA68 (manufactured by Organo Corp.) and 8.2 parts of Amberlite IRC50 (manufactured by Organo Corp.) were added and further stirred for 1 hour. Thereafter, the ion exchange resin was removed by filtration, and the concentration was adjusted so that the solid content of the capsule liquid was 20.0%, whereby a diazonium salt compound-encapsulating microcapsule liquid (b) was obtained. The obtained microcapsules had a median diameter of 0.43 μm as a result of particle size measurement (LA-700, carried out by Horiba, Ltd.).

<Preparation of coupler compound emulsion (b)>
36.9 parts of ethyl acetate, 11.9 parts of coupler compound (C-9), 14.0 parts of triphenylguanidine (Hodogaya Chemical Co., Ltd.), 4,4 '-(m-phenylenediisopropylidene) diphenol (Product name: Bisphenol M (Mitsui Petrochemical Co., Ltd.)) 14.0 parts, 1,1- (p-hydroxyphenyl) -2-ethylhexane 14 parts, tricresyl phosphate 1.7 parts, diethyl maleate 0.8 part and 4.5 parts of calcium dodecylbenzenesulfonate (trade name: Piionin A-41-C 70% methanol solution, manufactured by Takemoto Yushi Co., Ltd.) were dissolved to obtain a mixed liquid (VII).
Separately, 107.3 parts of ion-exchanged water was mixed with 206.3 parts of an alkali-treated gelatin aqueous solution to obtain a mixed liquid (VIII).
The mixed solution (VII) was added to the mixed solution (VIII), and the mixture was emulsified and dispersed at 40 ° C. using a homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.). The obtained coupler compound emulsion was heated under reduced pressure to remove ethyl acetate, and then the concentration was adjusted so that the solid content concentration was 24.5% to obtain a coupler compound emulsion (b). The resulting coupler compound emulsion had a median diameter of 0.22 μm as a result of particle size measurement (LA-700, manufactured by Horiba, Ltd.).

<Preparation of thermal recording layer coating liquid (b)>
The diazonium salt compound-encapsulated microcapsule liquid (b) and the coupler compound emulsion liquid (b) were mixed so that the mass ratio of the encapsulated coupler compound / diazo compound was 3.5 / 1. Further, an aqueous solution (5%) of polystyrene sulfonic acid (partially potassium hydroxide neutralized) was mixed so as to be 0.2 parts with respect to 10 parts of the capsule liquid, and the coating liquid for thermal recording layer (b) was prepared. Obtained.

(3) Preparation of third thermosensitive recording layer (C layer) liquid <Preparation of electron donating dye precursor-encapsulated microcapsule liquid (c)>
A mixture of 7.6 parts of an electron donating dye (LC-4), 1-methylpropylphenyl-phenylmethane and 1- (1-methylpropylphenyl) -2-phenylethane (commercial product) Name: Hysol SAS-310, manufactured by Nippon Oil Co., Ltd. (8.0 parts) and the following compound (I) (trade name; Irgaperm 2140, Ciba Geigy Co., Ltd. trade name) are added and heated to dissolve uniformly. did. 7.2 parts of xylylene diisocyanate / trimethylolpropane adduct (trade name; Takenate D110N (75% ethyl acetate solution), Takeda Pharmaceutical Co., Ltd.) and polymethylene polyphenyl polyisocyanate as capsule wall material in the above mixture (Product name: Millionate MR-200, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added in an amount of 5.3 parts, and stirred uniformly to obtain a mixed solution (IX).
Separately, 28.8 parts of the aqueous phthalated gelatin solution, 9.5 parts of ion-exchanged water, 0.17 part of Scraph AG-8 (50%) manufactured by Nippon Seika Co., Ltd., and sodium dodecylbenzenesulfonate (10% aqueous solution) ) 4.3 parts were added and mixed to obtain a mixed solution (X).
The mixed solution (IX) was added to the mixed solution (X), and the mixture was emulsified and dispersed at 40 ° C. using a homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.). 50 parts of water and 0.12 part of ethyltriamine were added to the resulting emulsion to homogenize, and the mixture was stirred at 65 ° C. for 3 hours while removing ethyl acetate, so that the solid concentration of the capsule liquid was 33%. The concentration was adjusted to obtain a microcapsule solution. The obtained microcapsules had a median diameter of 1.00 μm as a result of particle size measurement (LA-700, manufactured by Horiba, Ltd.).
Furthermore, to 100 parts of the above microcapsule solution, 3.7 parts of a 25% aqueous solution of sodium dodecylbenzenesulfonate (trade name; Neoperex F-25, manufactured by Kao Corporation) was added and stirred uniformly to make microcapsules A dispersion (c) was obtained.

<Preparation of electron-accepting compound dispersion (c)>
11.3 parts of the phthalated gelatin aqueous solution, 30.1 parts of ion-exchanged water, 15 parts of 4,4 ′-(p-phenylenediisopropylidene) diphenol (trade name; bisphenol P, manufactured by Mitsui Petrochemical Co., Ltd.) 3.8 parts of 2% -2-ethylhexyl sodium succinate aqueous solution was added and dispersed overnight with a ball mill to obtain a dispersion. The solid content concentration of this dispersion was 26.6%.
After adding 45.2 parts of the alkali-treated gelatin aqueous solution to 100 parts of the above dispersion and stirring for 30 minutes, ion-exchanged water was added so that the solid content concentration of the dispersion was 23.5% to obtain an electron-accepting compound. A dispersion (c) was obtained.

<Preparation of thermal recording layer coating solution (c)>
The electron donating dye precursor-encapsulated microcapsule liquid (c) and the electron accepting compound dispersion liquid (c) were mixed to obtain a thermal recording layer coating liquid (c). The compounding ratio (mass) of the microcapsule liquid (c) and the dispersion liquid (c) was such that the electron-accepting compound / electron-donating dye precursor was 10/1 (mass).

<Preparation of coating solution for intermediate layer>
100.0 parts of alkali-treated low ion gelatin (trade name; # 750 gelatin, manufactured by Nitta Gelatin Co., Ltd.), 1,2-benzothiazolin-3-one (3.5% methanol solution, Daito Chemical Industries, Ltd.) )) 2.857 parts, 0.5 parts of calcium hydroxide and 521.643 parts of ion-exchanged water were mixed and dissolved at 50 ° C. to obtain an aqueous gelatin solution for forming an intermediate layer.
10.0 parts gelatin aqueous solution for intermediate layer preparation, 0.05 parts sodium (4-nonylphenoxytrioxyethylene) butyl sulfonate (2.0% aqueous solution manufactured by Sankyo Chemical Co., Ltd.), boric acid (4.0%) 1.5 part aqueous solution, 0.19 part polystyrene sulfonic acid (partially potassium hydroxide neutralized) aqueous solution (5%), 4% aqueous solution of the following compound (J) (manufactured by Wako Pure Chemical Industries, Ltd.) 42 parts, 1.13 parts of a 4% aqueous solution of the following compound (J ′) and 0.67 parts of ion-exchanged water were mixed to obtain a coating solution for an intermediate layer.

<Preparation of coating solution for light transmittance adjusting layer>
(Iii-1) Preparation of Ultraviolet Absorber Precursor Microcapsule Solution [2-Allyl-6- (2H-benzotriazol-2-yl) -4-t-octylphenyl] as an ultraviolet absorber precursor in 71 parts of ethyl acetate ] 4.5 parts of benzenesulfonate, 1.0 part of 2,2′-t-octylhydroquinone, 3.8 parts of tricresyl phosphate, α-methylstyrene dimer (trade name: MSD-100, manufactured by Mitsui Chemicals, Inc.) 5.7 parts, calcium dodecylbenzenesulfonate (trade name: Piionin A-41-C (70% methanol solution), manufactured by Takemoto Yushi Co., Ltd.) 0.45 parts were dissolved and dissolved uniformly. Add 54.7 parts of xylylene diisocyanate / trimethylolpropane adduct (trade name; Takenate D110N (75% ethyl acetate solution), Takeda Pharmaceutical Co., Ltd.) as capsule wall material to the above mixture, and stir uniformly An ultraviolet absorber precursor mixed solution (VII) was obtained.
Separately, 8.9 parts of 30% phosphoric acid aqueous solution and 532.6 parts of ion-exchanged water were mixed with 52 parts of itaconic acid-modified polyvinyl alcohol (trade name: KL-318, manufactured by Kuraray Co., Ltd.), and ultraviolet absorber precursor micro A PVA aqueous solution for capsule liquid was prepared.
The UV absorber precursor mixed solution (VII) is added to 516.06 parts of the PVA aqueous solution for the UV absorber precursor microcapsule solution, and the mixture is used at 20 ° C. using a homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.). Emulsified and dispersed. After adding 254.1 parts of ion-exchanged water to the obtained emulsion and homogenizing it, an encapsulation reaction was carried out for 3 hours with stirring at 40 ° C. Thereafter, 94.3 parts of ion exchange resin Amberlite MB-3 (manufactured by Organo Corporation) was added, and the mixture was further stirred for 1 hour. Thereafter, the ion exchange resin was removed by filtration, and the concentration was adjusted so that the solid concentration of the capsule liquid was 13.5%. The obtained microcapsules had a median diameter of 0.23 ± 0.05 μm as a result of particle size measurement (LA-700, manufactured by Horiba, Ltd.). To this capsule solution 859.1 parts, carboxy-modified styrene butadiene latex (trade name: SN-307, (48% aqueous solution), manufactured by Sumitomo Nougatac Co., Ltd.) 2.416 parts and ion-exchanged water 39.5 parts were mixed. An ultraviolet absorber precursor microcapsule solution was obtained.
(Iii-2) Preparation of coating solution for light transmittance adjusting layer 1000 parts of the above-mentioned UV absorber precursor microcapsule liquid, fluorine-based surfactant (trade name: Megafac F-120, 5% aqueous solution, Dainippon Ink and Chemicals, Inc. Industrial Co., Ltd.) 5.2 parts, 4.75 parts of 4% aqueous sodium hydroxide, sodium (4-nonylphenoxytrioxyethylene) butyl sulfonate (2.0% aqueous solution manufactured by Sankyo Chemical Co., Ltd.) 39 parts were mixed to obtain a coating solution for light transmittance adjusting layer.

<Preparation of coating solution for protective layer>
(Iv-1) Preparation of polyvinyl alcohol solution for protective layer 160 parts of vinyl alcohol-alkyl vinyl ether copolymer (trade name: EP-130, manufactured by Denki Kagaku Kogyo Co., Ltd.), sodium alkyl sulfonate and polyoxyethylene alkyl ether A mixture of phosphate ester (trade name: Neoscore CM-57, (54% aqueous solution), manufactured by Toho Chemical Industry Co., Ltd.) 8.74 parts and ion-exchanged water 3832 parts are mixed and heated at 90 ° C. for 1 hour. A uniform polyvinyl alcohol solution for protective layer was obtained by dissolution.
(Iv-2) Preparation of pigment dispersion for protective layer Barium sulfate (trade name: BF-21F, barium sulfate content 93% or more, manufactured by Sakai Chemical Industry Co., Ltd.) 8 parts anionic special polycarboxylic acid type Polymer protective agent (trade name: Poise 532A (40% aqueous solution), manufactured by Kao Corporation) 0.2 part, 11.8 parts of ion-exchanged water are mixed and dispersed in a dynomill to produce a pigment dispersion for protective layer It was created. As a result of particle size measurement (LA-910, manufactured by HORIBA, Ltd.), this dispersion was found to have a median diameter of 0.15 μm or less.
To 45.6 parts of the above barium sulfate dispersion, 8.1 parts of colloidal silica (trade name: Snowtex O (20% aqueous dispersion), manufactured by Nissan Chemical Co., Ltd.) is added to obtain the desired dispersion. It was.

(Iv-3) Preparation of Matting Agent Dispersion for Protective Layer An aqueous dispersion of 1,2-benzisothiazolin-3-one in 180 parts of wheat starch (trade name: Wheat Starch S, manufactured by Shinshin Food Industry Co., Ltd.) (Trade name: PROXEL BD, manufactured by IC Corporation) 3.81 parts and 1976.19 parts of ion-exchanged water were mixed and dispersed uniformly to obtain a matting agent dispersion for protective layer.
(Iv-4) Preparation of Coating Solution for Protective Layer Fluorosurfactant (trade name: Megafac F-120, 5% aqueous solution, Dainippon Ink & Chemicals, Inc.) was added to 1000 parts of the polyvinyl alcohol solution for protective layer. 40 parts, sodium (4-nonylphenoxytrioxyethylene) butyl sulfonate (manufactured by Sankyo Chemical Co., Ltd., 2.0% aqueous solution) 50 parts, 49.87 parts of the pigment dispersion for the protective layer, for the protective layer 16.65 parts of matting agent dispersion, 48.7 parts of zinc stearate dispersion (trade name: Hydrin F115, 20.5% aqueous solution, manufactured by Chukyo Yushi Co., Ltd.) and 280 parts of ion-exchanged water are uniformly mixed for protection. A layer coating solution was obtained.

<Application of coating solution for each thermosensitive recording layer>
From above, the thermal recording layer coating solution (c), the intermediate layer coating solution, the thermal recording layer coating solution (b), and the intermediate layer are formed on a photographic paper support laminated with polyethylene on fine paper. 7 layers of coating liquid, heat-sensitive recording layer coating liquid (a), light transmittance adjusting layer coating liquid, and protective layer coating liquid were successively applied in the order of 30 ° C. humidity 30% and 40 ° C. humidity. Each was dried under the condition of 30% to obtain a multicolor thermosensitive recording material.
At this time, the coating amount of the thermal recording layer coating solution (a) is similarly set so that the coating amount of the diazo compound (DA-2) contained in the solution is 0.150 g / m ^{2 in} terms of solid content coating amount. The heat sensitive recording layer coating solution (b) is applied in the same manner so that the coating amount of the diazo compound (DB-4) contained in the solution is 0.206 g / m ^{2 in} terms of solid content. The coating amount of the recording layer coating liquid (c) was applied such that the coating amount of the electron donating dye (LC-4) contained in the liquid was 0.355 g / m ^{2 in} terms of the solid content coating amount.
The intermediate layer coating solution has a solid coating amount of 2.39 g / m ² between (a) and (b), and a solid coating amount of 3.b between (b) and (c). The light transmittance adjusting layer coating solution was 34 g / m ² , and the solid content was 2.20 g / m ² , and the protective layer was applied so that the solid content was 1.39 g / m ² .

(Example 3)
In the preparation of the coupler compound emulsion (a) of Example 2, 8.7 parts of the coupler compound (C-39) was used instead of 9.9 parts of the coupler compound (C-31), and the coating was applied. Produced a thermosensitive recording material in the same manner as in Example 2.

Example 4
In the preparation of the coupler compound emulsion (a) of Example 2, 4- (2-ethylhexyloxy) instead of 13.6 parts of 4- (2-ethylhexyloxy) benzenesulfonic acid amide (manac Co., Ltd.) A thermosensitive recording material was prepared in the same manner as in Example 2 except that 10.6 parts of benzenesulfonic acid amide (manac Co., Ltd.) and 3 parts of 2-ethylhexanoic acid were applied and applied.

(Example 5)
In the preparation of the coupler compound emulsion (a) of Example 2, 4- (2-ethylhexyloxy) instead of 13.6 parts of 4- (2-ethylhexyloxy) benzenesulfonic acid amide (manac Co., Ltd.) A thermosensitive recording material was produced in the same manner as in Example 2 except that 10.6 parts of benzenesulfonic acid amide (manac Co., Ltd.) and 3 parts of bistrifluoromethanesulfonimide were applied and coated.

(Comparative Example 1)
In the preparation of the diazonium salt compound-encapsulating microcapsule liquid (a) of Example 2, the photoacid generator (AG-4) was not used, and in the preparation of the coupler compound emulsion (a), triphenylguanidine (Hodogaya Chemical ( A heat-sensitive recording material was produced in the same manner as in Example 2 except that 9.9 parts of the product) were added and prepared.

(Comparative Example 2)
In the preparation of the diazonium salt compound-encapsulating microcapsule liquid (a) of Example 3, the photoacid generator (AG-4) was not used, and in the preparation of the coupler compound emulsion (a), triphenylguanidine (Hodogaya Chemical ( A heat-sensitive recording material was produced in the same manner as in Example 3 except that 9.9 parts of the product were added and prepared.

[Image recording, whiteness test and fixability test]
<Image recording>
Image recording was performed by the following method using a thermal head KST (manufactured by Kyocera Corporation) and a light emitting diode.
First, the first thermosensitive recording layer (A layer) was recorded. Printing is performed in the range of 25 to 75 mJ / mm ² as recording energy per unit area while leaving an unprinted portion, and then exposed to a light emitting diode having an emission center wavelength of 450 nm for 20 seconds to form a first thermosensitive recording layer (A layer). The diazonium salt compound (DA compound) was completely photodegraded to fix the image. As the output of the light emitting diode, the input power was set so that the first thermosensitive recording layer (A layer) in Comparative Example 1 was completely photodegraded in 20 seconds.
Next, the second heat-sensitive recording layer (B layer) was recorded. Printing is performed in the range of 80 to 120 mJ / mm ² as the recording energy per unit area while leaving the unprinted area, and then exposed to a light emitting diode having an emission center wavelength of 380 nm for 20 seconds, and the second thermosensitive recording layer (B layer) The diazonium salt compound (DB compound) was completely photodegraded to fix the image. The output of the light emitting diode was set such that the second thermosensitive recording layer (B layer) in Comparative Example 1 was completely photodegraded with the diazonium salt compound in 20 seconds.
Finally, printing was performed in the range of 135 to 170 mJ / mm ² as recording energy per unit area while leaving an unprinted portion, and recording was performed on the third thermosensitive recording layer (C layer).

<Abundance of protonated coloring dye>
The abundance of the protonated coloring dye in the heat-sensitive recording layer (A layer) of the heat-sensitive recording material was determined by the following method.
The color-developed portion (image portion) of the obtained heat-sensitive recording material was cut out from the portion where only the A layer was colored, soaked in methanol for 30 minutes, and tetrahydrofuran (THF) was added to extract the coloring dye. The absorption spectrum of the extract was measured and subjected to multi-component analysis (in this case, two components) to determine the abundance of protonated coloring dye in all coloring dyes (protonated coloring dye + non-protonated coloring dye).
The obtained results are shown in Table 2.

<Light resistance test>
Yellow image DY ₀ and white background of the obtained image samples yellow density Dy ₀ (non-image portion) X-rite model 310 (X -rite, Incorporated -made) measured at.
The image sample was irradiated with light for 24 hours using a xenon fade meter (FAL-25AX-HC type, Suga Test Instruments Co., Ltd.). The yellow image DY ₁ after light irradiation and the yellow density Dy ₁ of the white background portion (non-image portion) are measured. Similarly to measure the yellow density Dy ₂ of 72 hours light irradiated yellow image DY ₂ and a blank portion after (non-image portion).
The light resistance of the image sample is evaluated by comparing these densities.
As an evaluation index, the density residual ratio of the image area and the density change of the white background (non-image area) were used. Each was calculated by the following formula.

24 hour compulsory test:
Yellow image portion Density remaining rate (%) = (DY ₁ / DY ₀ ) × 100
White background portion (non-image portion) Yellow density change (ΔDy) = Dy ₁ −Dy ₀

72 hours compulsory test:
Yellow image portion Density remaining rate (%) = (DY ₂ / DY ₀ ) × 100
White background portion (non-image portion) Yellow density change (ΔDy) = Dy ₂ −Dy ₀

  It shows that light resistance is excellent, so that a density residual rate is large and yellow density change is small.

  Table 3 shows the results of the light resistance test.

  From Table 3, it can be seen that the recording material of the present invention is excellent in light fastness.

Claims (4)

  A recording material having at least one recording layer on a support, wherein at least one of the recording layers contains a diazonium salt compound and a coupler that reacts with the diazonium salt compound to form a coloring dye. A recording material, wherein the coloring dye is protonated and present.   The recording layer comprises two diazo thermosensitive recording layers containing a combination of two diazonium salt compounds having different maximum absorption wavelengths and a coupler that forms a coloring dye having a different hue by reacting with each diazonium salt compound; The recording material according to claim 1, wherein the coloring dye formed in at least one of the diazo heat-sensitive recording layers is protonated and exists. The recording material according to claim 1, wherein the diazonium salt compound is a compound represented by at least one of the following general formula (1) and the following general formula (2).

(In the general formulas (1) and (2), R ^{1 to} R ⁴ each independently represents a hydrogen atom, an alkyl group, or an aryl group, and R ⁵ and R ⁶ each independently represent a hydrogen atom, an alkyl group, or an alkoxy group. , A halogen atom, a sulfonyl group, an acyl group, or an alkoxycarbonyl group, Y ¹ and Y ² each independently represent an oxygen atom or a sulfur atom, and X ⁻ represents a counter anion.)   The recording material according to claim 1, wherein the diazonium salt compound is encapsulated in a microcapsule.