JP2006007431A - Thermosensitive recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermosensitive recording material, which develops no printing obstacle, is highly sensible and can realize a beautiful monochrome high color density. <P>SOLUTION: In the thermosensitive recording material having at least one thermosensitive recording layer on a support, at least one layer among the thermosensitive recording layer emits light by lower heat energy than that emitting before irradiation with light by irradiating light before thermal recording. Further, a thermosensitive recording method performed by employing the thermosensitive recording material with the light emitted through the irradiation with light before thermal recording and a thermosensitive recording device with the irradiation wavelength of a light irradiating means before thermal recording of 330-390 nm are dealt. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material that achieves both storage stability and high sensitivity.

Thermal recording has been developed recently because the recording apparatus is simple, reliable and does not require maintenance. Recently, multicolor thermal recording has been performed using thermal recording.
The thermosensitive recording material using microcapsules has good storage stability with little change in the density of the background even when stored for a long time in the state before recording, but does not use microcapsules. There was a problem that the thermal color development sensitivity was lower than that of a heat-sensitive recording material and a large amount of energy was required.
Conventionally, various microcapsule wall plasticizing materials have been studied in order to solve this problem. However, all have taken a method in which the microcapsule wall plasticizing material exists inside and outside the capsule wall.
Multi-color heat-sensitive layers comprising yellow (hereinafter also referred to as “Y”), magenta (hereinafter also referred to as “M”), and cyan (hereinafter also referred to as “C”) color developing layers using microcapsules. In the recording material, in order to sufficiently develop each single color, it is necessary to widen the color development energy region of each single color, and in order to sufficiently develop the lowermost color development layer, a large amount of energy is required. There was a problem that the image surface was disturbed by heat, and the gloss of the image was deteriorated.
On the other hand, in order to avoid this, the energy for starting the color development is packed with YMC as in the conventional case, because the Y color development does not occur sufficiently, the M color development starts before reaching Dmax, or the M color development does not occur sufficiently, C color development started before it reached, and there was a problem that it was difficult to produce a beautiful single color high color density.

  In order to solve the above-described conventional problems, an object of the present invention is to provide a heat-sensitive recording material that is free of printing problems, has high sensitivity, and is capable of realizing a high color density of a beautiful single color. The challenge is to achieve.

  Means for solving the above problems are as follows. That is, the present invention

<1> In a heat-sensitive recording material having one or more heat-sensitive recording layers on a support, at least one layer of the heat-sensitive recording layer is irradiated with light before heat recording, so that color develops with lower thermal energy than before light irradiation. A heat-sensitive recording material.

<2> It has two or more heat-sensitive recording layers that develop colors of different hues on the support, and at least one of the heat-sensitive recording layers is irradiated with light before heat recording, so that the heat energy is lower than before light irradiation. The heat-sensitive recording material as described in <1> above, which is a heat-sensitive recording layer that develops color.

<3> Two or more heat-sensitive recording layers that develop colors having different hues are provided on a support, and at least one of the heat-sensitive recording layers is a light-fixing type heat-sensitive recording layer, and is irradiated with light before the heat recording. The thermal recording layer that develops color with low thermal energy is on the support side of the photo-fixing type thermal recording layer, and it absorbs the fixing light of the upper photo-fixing type thermal recording layer and develops color with lower thermal energy than before light irradiation. The heat-sensitive recording material as described in <1> or <2> above.

<4> At least one heat-sensitive recording layer that develops color with lower thermal energy than before light irradiation by irradiation with light before thermal recording contains microcapsules having a color former, and the microcapsules are irradiated with light. The heat-sensitive recording material according to any one of <1> to <3>, wherein the color is developed with lower thermal energy than before light irradiation.

<5> The above-mentioned <4>, wherein the wall material forming the microcapsule absorbs light in the wavelength region of the fixing light of the upper layer, and develops color with lower thermal energy than before light irradiation. Thermal recording material.

<6> The thermosensitive recording material according to <4>, wherein the wall material forming the microcapsule has absorption in a region of 330 nm to 390 nm.

<7> The wall material forming the microcapsule partially includes a structure of a compound represented by the following general formula (P), wherein any one of the above <4> to <6> Thermal recording material.

[In General Formula (P), R ¹ represents L ¹ -X ¹ or X ¹ , and R ² represents a hydrogen atom or L ² -X ² . L ¹ and L ² represent a divalent linking group, and X ¹ and X ² represent a group selected from a hydroxyl group, an amino group, and a mercapto group. n represents an integer of 1 to 4. ]

<8> A thermal recording method using the thermal recording material according to any one of the above items <1> to <7>, wherein light is irradiated before thermal recording, and then thermal energy is applied. Thermal recording method.

<9> A thermal recording apparatus for recording an image by thermally recording and fixing the thermal recording material according to any one of the above items <1> to <7>, and means for irradiating light before the thermal recording The thermal recording apparatus is characterized in that the irradiation wavelength of the light irradiation means is 330 nm to 390 nm.

According to the present invention, since the maximum color development energy can be lowered, it is possible to provide a heat-sensitive recording material which is free from printing problems, has high sensitivity, and has a clean single color high color density.
In addition, according to the present invention, it is possible to provide a thermal recording method that uses the thermal recording material to irradiate light before thermal recording and subsequently apply thermal energy.
Furthermore, according to the present invention, there is provided a thermal recording apparatus which records an image using the thermal recording material by irradiation, thermal recording and fixing by means of irradiating light having an irradiation wavelength of 330 nm to 390 nm before thermal recording. can do.

The heat-sensitive recording material of the present invention has one or more heat-sensitive recording layers on a support, and at least one of the heat-sensitive recording layers is irradiated with light before heat recording, thereby developing color with lower thermal energy than before light irradiation. It is characterized by doing.
By adopting such a configuration, the maximum color development energy can be lowered, and a heat sensitive recording material having a high sensitivity and a beautiful monochromatic color density can be obtained.
The one or more heat-sensitive recording layers in the heat-sensitive recording material of the present invention are a single-layer structure in which only one heat-sensitive recording layer is formed, and a multi-color multilayer heat-sensitive recording material having a plurality of heat-sensitive recording layers. Either may be sufficient.
The heat-sensitive recording material of the present invention can further be provided with an intermediate layer and a protective layer.

  In the single-layer structure, since the heat-sensitive recording material is stored before light irradiation, its thermochromic sensitivity is low and the raw storage property can be improved. On the other hand, at the time of thermal recording, by irradiating with light before thermal recording, the color can be sufficiently developed after the light irradiation by heating with lower thermal energy than before the light irradiation. That is, since the maximum color development energy can be lowered, it is possible to reduce the printing trouble that has occurred in the maximum color development energy portion while maintaining the conventional single color development density.

  In the case of multiple layers (multicolor), as in the case of the single layer, at least one of the two or more thermosensitive recording layers that develop colors having different hues is irradiated with light before thermal recording, so that the thermal energy is lower than before the light irradiation. Therefore, it is preferable in that the color can be easily fractionated by heat and a high color density of a single color can be improved.

  As a method for causing the heat-sensitive recording layer to develop color with lower thermal energy than before light irradiation by irradiating with light before the thermal recording, 1) a substance-degradable portion is provided in the structure of the microcapsule wall material. 2) A method of increasing the material permeability by separating and generating the plasticizer of the microcapsule wall material from the wall material. 3) Decomposing and generating the material to be transmitted through the microcapsule wall material by light. 4) A method of increasing the permeability by reducing the size of the substance itself to be permeated, 4) A method of increasing the substance permeability by generating a substance that decomposes the microcapsule wall material, and 5) of the microcapsule wall material. There is a method of increasing the material permeability by providing a phase transition site by light in the structure, and it is not particularly limited. From the viewpoint of ease of material design, the 1), 2), preferably the method of 3), among others, the 1) method of 2) it is particularly preferred.

  Hereinafter, each layer such as a heat-sensitive recording layer, an intermediate layer, and a protective layer in the heat-sensitive recording material of the present invention and its constituent components will be described in detail.

[Thermosensitive recording layer]
The heat-sensitive recording layer contains a color forming component as a color former and, if necessary, other components such as a binder and a base. As the coloring component, a diazonium salt compound and a combination of a coupler that reacts with the diazonium salt compound to form a dye, an electron-donating dye precursor, and an electron-accepting compound that reacts with the electron-donating dye precursor to cause color development In addition to the combination, conventionally known coloring components can be used.
Color formers such as diazonium salt compounds and electron donating dye precursors are preferably encapsulated in microcapsules.
Next, the coloring components used in the heat-sensitive recording layer of the present invention 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 a thermal recording layer (C layer) different from the diazo thermosensitive recording 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 the general formulas (1) to (5).

In general formulas (1) to (5), R ¹ , R ² , R ^{4 to} R ¹¹ , and R ^{13 to} R ¹⁵ may be the same or different and each represents a hydrogen atom, an alkyl group, or an aryl group, R ³ , R ¹² , and R ¹⁶ represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a sulfonyl group, an acyl group, or an alkoxycarbonyl group, and D ¹ is an electron donor having a Hammett σp value of −0.05 or less. In particular, a substituted amino group, an alkylthio group, an arylthio group, an alkoxy group, or an aryloxy group is preferable. X ⁻ represents a counter anion. A represents an electron-withdrawing group having a Hammett σp value of 0.3 or more. Y ¹ and Y ² represent an oxygen atom or a sulfur atom. Each benzene ring in the general formulas (1) to (5) may further have a substituent.

R ¹ , R ² , R ^{4 to} R ¹¹ , and R ^{13 to} R ¹⁵ 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 , R ² , R ^{4 to} R ¹¹ , and R ^{13 to} R ¹⁵ include the following.

R ³ , R ¹² and R ¹⁶ 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 a carbon number. A 6-18 arylsulfonyl group, a C1-C18 acyl group, or a C1-C18 alkoxycarbonyl group is preferable. 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 ³ , R ¹² , and R ¹⁶ include those shown below.

As A, a sulfonyl group, an acyl group, an alkoxycarbonyl group, or a cyano group is preferable. The sulfonyl group, acyl group and alkoxycarbonyl group have the same meanings as the sulfonyl group, acyl group and alkoxycarbonyl group represented by R ³ .
R ⁸ and R ⁹ , R ¹³ and R ¹⁴ may be bonded to each other to form a ring.

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.

When D ¹ represents a substituted amino group as an electron donating group having a Hammett's σp value of −0.05 or less, the substituted amino group includes an alkylamino group having 1 to 20 carbon atoms, and 2 to 20 carbon atoms. Dialkylamino groups, C6-C10 arylamino groups, C7-C20 N-alkyl-N-arylamino groups, and C2-C20 acylamino groups are preferred. You may have the above substituent. Moreover, substituents, such as the said alkyl group, may couple | bond together and a cyclic amino group may be formed.
When D ¹ represents an alkylthio group as an electron donating group having a Hammett's σp value of −0.05 or less, an alkylthio group having 1 to 18 carbon atoms is preferable, and when an arylthio group is represented, an arylthio group having 6 to 10 carbon atoms is preferable. Group is preferable, when an alkoxy group is represented, an alkoxy group having 1 to 18 carbon atoms is preferable, and when an aryloxy group is represented, an aryloxy group having 6 to 10 carbon atoms is preferable, and these groups further include 1 or 2 or more. It may have a substituent.
From the viewpoint of the stability of the diazonium salt compound, D ¹ is preferably a dialkylamino group, an N-alkyl-N-arylamino group, an acylamino group, an alkylthio group, an arylthio group, an alkoxy group, or an aryloxy group.

The alkyl group or aryl group in the substituted amino group, alkylthio group, arylthio group, alkoxy group, or aryloxy group, which is an electron donating group having a Hammett σp value of −0.05 or less represented by D ^1, is as follows: Such a thing is mentioned.

When D ¹ in the general formula (1) represents a substituted amino group, a cyclic amino group formed by bonding of substituents, and —N (R ⁸ ) R ⁹ in the general formula (2), and Examples of the cyclic group represented by —N (R ¹³ ) R ^{14 in} the general formula (5) include the following.

The benzene ring on the indolyl group of the general formula (3) may have a nuclear substituent, and an electron-withdrawing group is particularly preferable from the viewpoint of ring stability. The Hammett σp value of the electron withdrawing group is preferably 0.1 or more. Among these, an acyl group, a sulfonyl group, an alkoxycarbonyl group, a sulfonamide group, or a carbonamido group is preferable. An acyl group, a sulfonyl group, and an alkoxycarbonyl group have the same meanings as R ³ , and preferred embodiments are also the same. The sulfonamide group preferably has 1 to 12 carbon atoms, and specific examples thereof include the following.

  The carbonamido group preferably has 2 to 13 carbon atoms, and specific examples thereof include the following.

  Specific examples (exemplary compounds (DA1) to (DA16)) of the diazonium salt compounds (DA compounds) represented by the general formulas (1) to (5) are shown below, but the present invention is not limited to the following. Absent.

-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 (6).

In General Formula (6), R ¹⁷ and R ¹⁸ have the same meaning as R ¹ , and preferred examples are also the same.

D ² represents an alkoxy group or an aryloxy group. The alkyl part of the alkoxy group and the aryl part 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.

  Although the specific example (exemplary compound (DB-1)-(DB-6)) of the diazonium salt compound represented by General formula (6) 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.
As the diazonium salt compound having the maximum absorption wavelength of 305 ± 30 nm, diazonium salt compounds represented by the following general formulas (7) and (8) are preferable.

In the general formulas (7) and (8), D ³ and D ⁴ each represent a group having a Hammett σp value of −0.45 or more. R ¹⁹ represents a perfluoroalkyl group, an acyl group, or a sulfonyl group, and the acyl group and the sulfonyl group have the same meanings as R ³ described above.
As the perfluoroalkyl group, those having 1 to 8 carbon atoms are preferable, and —CF ₃ , —C ₃ F ₇ or —C ₈ F ₁₇ is particularly preferable.
X ⁻ in the general formula (7) represents a counter anion. Z in the general formula (8) represents —SO ₂ — or —CO—.

D ³ and D ⁴ representing 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. More preferably, it is a group having a Hammett σp value of −0.30 or more.
The alkoxy group is preferably a substitutable alkoxy group having 1 to 20 carbon atoms such as methoxy (σp = −0.27), ethoxy, butyloxy (σp = −0.32), hexyloxy, octyloxy, 2 -Ethylhexyloxy, 3-methyl-5,5-dimethylhexyloxy, 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 (σp = −0.03), methylphenoxy, isopropylphenoxy, 2,4-di-t-pentylphenoxy, Examples include chlorophenoxy and methoxyphenoxy.
As an alkyl group, a C1-C8 alkyl group is preferable, for example, methyl ((sigma) p = -0.17), 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 (σp = 0.03), 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 (σp = 0.18), methylphenylthio, chlorophenylthio, methoxyphenylthio and the like.
As the halogen atom, a chlorine atom (σp = 0.23), a fluorine atom (σp = 0.06) and the like are preferable.
The alkylsulfonyl group is preferably an alkylsulfonyl group having 1 to 8 carbon atoms, and examples thereof include methylsulfonyl (σp = 0.72), ethylsulfonyl, butylsulfonyl, octylsulfonyl, benzylsulfonyl and the like.
The alkoxycarbonyl group is preferably an alkoxycarbonyl group having 2 to 10 carbon atoms, and examples thereof include methoxycarbonyl, ethoxycarbonyl (σp = 0.45), butyloxycarbonyl, octyloxycarbonyl and the like.

X ⁻ in the general formula (7) has the same meaning as in the general formula (1).
The benzene ring in the general formulas (7) and (8) 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 General formula (7), it is preferable that it is substituted by the ortho position (o-position) of the diaionio group on the said benzene ring.
Specific examples (exemplary compounds (DC-1) to (DC-6)) of the diazonium salt compounds represented by the general formulas (7) and (8) are shown below, but the present invention is not limited to the following. Absent.

  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.

(Coupler compound)
In the present invention, together with the above-described diazonium salt compound, a coupler compound that reacts with the diazonium salt compound to develop a color (hereinafter sometimes simply referred to as “coupler”) is contained in the heat-sensitive recording layer.

  Examples of the coupler include JP-B-4-75147, JP-B-6-55546, JP-B-6-79867, JP-A-4-201483, JP-A-60-49991, JP-A-60. No. 242094, No. 61-5983, No. 63-87125, No. 4-59287, No. 5-185717, No. 7-88356, No. 7 -96671, JP-A-8-324129, JP-A-9-38389, JP-A-5-185736, JP-A-5-8544, JP-A-59-190866, JP-A-62. -55190, JP-A-60-6493, JP-A-60-259492, JP-A-63-3318546, JP-A-4-65291, For example, see Japanese Laid-Open Patent Application No. 5-1855736, Japanese Laid-Open Patent Application No. Hei 5-204089, Japanese Laid-Open Patent Application No. 8-310133, Japanese Laid-Open Patent Application No. 8-324129, Japanese Laid-Open Patent Application No. 9-156229, Japanese Laid-Open Patent Application No. 9-175017. As specific compound examples, the following exemplary compounds (B-1 to B-24, (1) to (28), II-1 to II-11, and VI-1 to VI-6) are shown below as specific compound examples. Shown in However, the present invention is not limited to these.

  The content of the coupler compound in the heat-sensitive recording layer is preferably 0.5 to 20 parts by mass and more preferably 1 to 10 parts by mass with respect to 1 part by mass of the diazonium salt compound. If the content is less than 0.5 parts by mass, sufficient color developability may not be obtained, and if it exceeds 20 parts by mass, the coating suitability may be deteriorated.

  The coupler compound (along with other components added as desired) can be used by adding a water-soluble polymer and solid-dispersing it with a sand mill or the like. It can also be used. Here, the method for solid dispersion or emulsification is not particularly limited, and a conventionally known method can be used. Details of these methods are described in JP-A-59-190886, JP-A-2-141279, and JP-A-7-17145.

(Other ingredients)
The heat-sensitive recording layer according to the present invention may contain a basic substance, a coloring aid, a binder, an antioxidant, and the like as the other components.
The basic substance is contained for the purpose of promoting the coupling reaction between the diazonium salt compound and the coupler compound. Specifically, one kind or two or more kinds of conventionally known substances can be used, and they can be appropriately selected from the basic substances described in the publications listed in the section of the coupler compound.
Examples of the basic substance include nitrogen-containing compounds such as tertiary amines, piperidines, piperazines, amidines, formamidines, pyridines, guanidines and morpholines.

  Among them, in particular, 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-hydroxy) propyloxy) Piperazines such as benzene, N- (3- (β-naphthoxy) -2-hydroxy) propylmorpholine, 1,4-bis ((3-morpholino- Morpholines such as -hydroxy) propyloxy) benzene and 1,3-bis ((3-morpholino-2-hydroxy) propyloxy) benzene, N- (3-phenoxy-2-hydroxypropyl) piperidine, N-dodecylpiperidine And guanidines such as triphenylguanidine, tricyclohexylguanidine and dicyclohexylphenylguanidine are preferred.

The coloring aid is contained for the purpose of rapid and complete thermal printing with low energy. That is, the color assistant is a substance that increases the color density at the time of heat recording or controls the color development temperature, lowers the melting point of coupler compounds, basic substances, diazonium salt compounds, etc., and reduces the softening point of the capsule wall. Due to the lowering action, the diazonium salt compound, the basic substance, the coupler compound, etc. are made to react easily.
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 binder can be selected from conventionally known binders, and examples thereof include water-soluble polymers such as polyvinyl alcohol and gelatin, and polymer latex.

  The antioxidant is contained for the purpose of improving fastness to light and heat of a thermochromic image or reducing yellowing due to light of an unprinted portion (non-image portion) after fixing. Examples of the antioxidant include European Patent No. 223739, Patent No. 309401, Patent No. 309402, Patent No. 310551, Patent No. 310552, Patent No. 457416, Patent Published German 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. And 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.

(Electron-donating dye precursor)
Details of the electron donating dye precursor are described in JP-A-6-328860, JP-A-7-290826, JP-A-7-314904, JP-A-8-324116, and JP-A-3-37727. 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 used in the present invention are described in detail in JP-A-2003-21184 [0120] to [0123], JP-A 2003-211843 [0036] to [0038], and the like. Although described, the present invention is not limited to this.
The content of the heat-sensitive recording layer of the electron-donating dye precursor, is not particularly limited, 0.1 g / m ² is preferably to 0.5 g / m ^2, 0.2 g in terms of color density / M ^{2 to} 0.4 g / m ² is more preferable.

(Electron-accepting compound)
Details of the electron-accepting compound are described in JP-A-6-328860, JP-A-7-290826, JP-A-7-314904, JP-A-8-324116, JP-A-3-37727, This is described in detail in Kaihei 9-31345, JP-A-9-111136, JP-A-9-118073, JP-A-11-157221, and the like.

In addition, specific examples of the electron-accepting compound used in the present invention are described in detail in [0039] of Japanese Patent Application Laid-Open No. 2003-211843, [0124] of Japanese Patent Application Laid-Open No. 2003-21844, and the like. It is not limited to.
The content of the electron-accepting compound in the heat-sensitive recording layer is preferably 0.1 to 40 parts by mass with respect to 1 part by mass of the electron-donating dye precursor.

(Method of microencapsulation)
In the heat-sensitive recording material of the present invention, at least one heat-sensitive recording layer on the support contains a microcapsule having the color former, and the microcapsule is irradiated with light before heat recording, so that it is more than before light irradiation. It is preferable to develop color with low heat energy.
By irradiating the microcapsules with light, the thermosensitive recording layer is colored with lower thermal energy than before the light irradiation, which is a change that enhances the material permeability of the wall material of the microcapsules irradiated with light. As a result of the enhancement of the material permeability of the wall material, the component encapsulated in the microcapsule and the color developing component existing outside the microcapsule can be colored by applying lower thermal energy.

  The color hue when one or more heat-sensitive recording layers on the support is colored is not particularly limited and can be appropriately selected according to the purpose, but is preferably yellow, magenta, cyan, or black, and more preferably yellow. Cyan is preferable, and cyan is particularly preferable.

Any method can be used without particular limitation as long as the material permeability of the microcapsule wall material is enhanced, and A) a method by cleavage of a compound constituting the microcapsule wall material, and B) a microcapsule wall material. Examples thereof include a method for increasing the mobility of a compound.
Among these, A) a method by cleavage of the compound constituting the microcapsule wall material is preferable, and the compound constituting the wall material is more preferably a compound represented by the following general formula (P).
By including in part the structure of the compound represented by the general formula (P) in the wall material, the structure of the microcapsule wall material irradiated with light is partially cleaved, and the free volume of the wall material Increases and substance permeability is enhanced. As a result, the maximum coloring energy can be lowered. As a result, it is possible to reduce the printing trouble that occurs in the highest color development energy portion while maintaining the conventional monochromatic color density.
Including part of the structure of the compound represented by the general formula (P) means that the compound of the general formula (P) is added to the structural formula of the polymer by being added as a raw material when forming the wall material (polymer). It means that part of the structure forms part of the structural formula of the polymer. For example, when the polyurea / polyurethane wall is formed, the general formula (P) is added together with the polyisocyanate, polyamine, polyol and the like to be described later and reacted, and a part of the structural formula of the general formula (P) Is incorporated as a component of the capsule wall. The addition of the general formula (P) is not particularly limited as long as it is added to the polyvalent isocyanate, polyamine, polyol and the like before the encapsulation reaction and is involved in the reaction, but the polyvalent isocyanate before the encapsulation reaction is not limited. It is preferable that a part of the structural formula of the general formula (P) is incorporated by adding it to the reaction.

  When the at least one thermosensitive recording layer that amplifies the thermochromic sensitivity contains a microcapsule, and the thermosensitive recording layer is a single layer, the inside and outside of the microcapsule having a color former are irradiated by light irradiation before thermal recording. The substance permeability is improved, and the thermochromic sensitivity of the thermosensitive recording layer is improved.

When the thermosensitive recording layer containing the microcapsules in the present invention forms a multilayer structure, it is preferable that the wall material forming the microcapsules absorbs light in the wavelength region of the upper fixing light to amplify the thermochromic sensitivity. . Furthermore, it is preferable that the thermosensitive recording layer containing the microcapsules is the lowermost thermosensitive recording layer.
By adopting such an embodiment, the thermal coloring sensitivity of the lowermost layer is simultaneously increased at the time of fixing light irradiation of the upper layer. This not only improves the thermochromic sensitivity, but can also reduce the thermal energy of the lowermost layer.

It is preferable that the wall material forming the microcapsule has absorption in a region of 330 to 390 nm.
When the wall material has absorption in the wavelength region, ultraviolet rays can be used as a light source, and the coloring hue is not affected. In the case where the upper layer has a color developing layer using a diazonium compound, fixing light of the diazonium compound can be used.

As the light source for light irradiation used in the present invention, a semiconductor laser, LED, xenon light, fluorescent lamp, mercury lamp or the like can be used, and is not particularly limited.
The wavelength of the light source can be appropriately selected from a wide range from ultraviolet to near infrared depending on the absorption wavelength of each layer. It is also possible to use light sources having two or more wavelengths according to the absorption wavelength. Among them, it is preferable to have a light emission wavelength region that overlaps with an absorption wavelength region of the wall material of the microcapsule, so that light irradiation energy is effectively used.

  Hereinafter, the compound represented by the general formula (P) will be described in detail.

Next, in the present invention, the compound represented by formula (P) will be described in detail.
In the formula, R ¹ represents L ¹ -X ¹ or X ¹ , and R ² represents a hydrogen atom or L ² -X ² . L ¹ and L ² represent a divalent linking group, and X ¹ and X ² represent a nucleophilic substituent selected from a hydroxyl group, an amino group, and a mercapto group. n represents an integer of 1 to 4, and R ¹ and R ² may be the same or different. When n is plural, R ¹ may be the same as or different from each other.

Next, L ¹ and L ² will be described in detail. L ¹ and L ² each represent a divalent linking group that connects X ¹ and X ² to the pyrithione ring. Specifically, an alkylene group, an alkenylene group, an alkynylene group, an arylene group, —O—, —S—, —NR—, —CO—, —COO—, —NRCO—, —SO ₂ — or the like alone or these It consists of a combination. Here, R represents a hydrogen atom or a substituent. In the case of a combination of an alkylene group and —NR—, R may be bonded to the alkylene group to form a ring.

  Examples of the substituent in the previous item include an alkyl group (for example, methyl group, ethyl group), an aralkyl group (for example, phenylmethyl group), an alkenyl group (for example, allyl group), an alkynyl group, a hydroxyalkyl group (for example, hydroxyethyl group), and an aryl group. (For example, phenyl group, p-methoxyphenyl group) Carbonyl group, acyl group (for example, acetyl group, benzoyl group), alkoxycarbonyl group (for example, methoxycarbonyl group), acyloxy group (for example, acetoxy group) and the like can be mentioned. An alkyl group and a hydroxyalkyl group are preferable. When the substituent has a carbon atom, it preferably has 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms.

Describing in more detail about L ¹ and L ² , the alkylene group may be linear, branched or cyclic, preferably an alkylene group having 1 to 20 carbon atoms, such as a methylene group, an ethylene group, a trimethylene group, A propylene group, a butylene group, a hexylene group, a cyclohexylene group, and the like. The alkylene group may further have a substituent, and examples of the substituent include an alkyl group (for example, a methyl group and an ethyl group), an aralkyl group (for example, a phenylmethyl group), an alkenyl group (for example, an allyl group), and an alkynyl group. , An alkoxy group (for example, methoxy group, ethoxy group), a hydroxyalkyl group (for example, hydroxyethyl group), an aryl group (for example, phenyl group, p-methoxyphenyl group), an amino group (for example, dimethylamino group or —NH ₂ ). Group), acylamino group (eg acetylamino group), sulfonylamino group (eg methanesulfonylamino group), ureido group, urethane group, aryloxy group (eg phenyloxy group), sulfamoyl group (eg methylsulfamoyl group) Carbamoyl group (for example, carbamoyl group, methyl Bamoyl group), alkylthio group (eg methylthio group), arylthio group (eg phenylthio group), sulfonyl group (eg methanesulfonyl group), sulfinyl group (eg methanesulfinyl group), hydroxy group, halogen atom (eg chlorine atom, bromine atom) Fluorine atom), cyano group, sulfo group, carbonyl group, phosphono group, aryloxycarbonyl group (for example, phenyloxycarbonyl group), acyl group (for example, acetyl group, benzoyl group), alkoxycarbonyl group (for example, methoxycarbonyl group), Examples include acyloxy groups (for example, acetoxy group), carbonamido groups, sulfonamido groups, nitro groups, hydroxamic acid groups, and heterocyclic groups. An alkyl group, a hydroxyl group, and a hydroxyalkyl group are preferable. When the substituent has a carbon atom, it preferably has 1 to 30 carbon atoms, more preferably 1 to 10 carbon atoms.

  The alkenylene group and alkynylene group may be linear, branched or cyclic, and preferably have 2 to 10 carbon atoms. The alkenylene group and the alkynylene group may further have a substituent, and the substituent is the same as described in the alkylene group in the previous section.

  As the arylene group, a coal industry number of 6-10 is preferable. The arylene group may further have a substituent, and the substituent is the same as described in the alkylene group in the previous section. The arylene group is preferably a phenylene group.

L ¹ and L ² are more preferably an alkylene group, an arylene group, —O—, —S—, —NR—, —COO—, —NRCO— alone or a combination thereof, or an alkylene group and —NR In combination with-(R is a substituent), R is bonded to an alkylene group to form a ring. More preferably, it consists of a combination of an alkylene group and —O—, —NRCO—, —COO—, and particularly preferably an —O-alkylene group in order from the pyrithione ring.

  Specific examples of the compound represented by the general formula (P) are shown below, but are not limited thereto.

  The content of the general formula (P) in the microcapsule wall material is preferably 1 to 70% by mass with respect to the total capsule wall material amount from the viewpoint of increasing the color development energy difference before and after the light irradiation. 3 to 50% by mass is more preferable, and 5 to 40% by mass is particularly preferable.

Moreover, you may use the compound of general formula (P) individually or in combination of two or more.
By including the compound of the general formula (P) in a part of the structure of the wall material, the bond of the general formula (P) contained in the wall material is cleaved by light irradiation, thereby increasing the free volume of the microcapsule wall. Thus, the permeability of the substance is improved, and as a result, the permeability of the coloring components inside and outside the microcapsule is improved, and coloring can be performed with less heat energy.

  As a microcapsule formation method, a conventionally known microcapsule formation method (specifications such as US Pat. Nos. 3,726,804 and 3,796,669) can be used. Interfacial polymerization and internal polymerization are suitable. Specifically, a diazonium salt compound is dissolved in a water-insoluble or insoluble organic solvent together with a microcapsule wall precursor (wall material) to form an oil phase, and this is dissolved in an aqueous solution (water phase) of a water-soluble polymer. And then emulsified and dispersed with a homogenizer or the like, and heated to form a polymer film (wall film) that becomes a microcapsule wall at the oil / water interface.

Examples of the polymer material (wall material) used as the wall film include polyurethane resin, polyurea resin, polyamide resin, polyester resin, polycarbonate resin, aminoaldehyde resin, melamine resin, polystyrene resin, styrene-acrylate copolymer resin, and styrene. -Methacrylate copolymer resin, gelatin, polyvinyl alcohol and the like. Among these, microcapsules having a wall film made of polyurethane / polyurea resin are preferable.
The amount of the wall material of the capsule is appropriately determined depending on the amount of the polymer substance (wall material) to be used as the wall film, but the wall material and the volatile component are excluded in terms of the balance between fog and sensitivity and stain. It is preferably 5 to 150% by mass, more preferably 10 to 120% by mass, and particularly preferably 15 to 100% by mass with respect to the weight of the core material.

A method for producing a diazonium salt compound-encapsulating microcapsule (polyurea / polyurethane wall) will be described below as an example.
First, the diazonium salt compound is dissolved or dispersed in a hydrophobic organic solvent (including a low-boiling point solvent as necessary) serving as a capsule core to prepare an oil phase (organic solvent solution) serving as a microcapsule core. At this time, a polyvalent isocyanate as a wall material or a surfactant may be further added to the oil phase side for the purpose of uniformly emulsifying and dispersing. Further, additives such as an anti-fading agent and an anti-stain agent may be added.

The polyvalent isocyanate compound is preferably a compound having a trifunctional or higher functional isocyanate group, and may be a bifunctional isocyanate compound. Specifically, xylene diisocyanate and hydrogenated products thereof, hexamethylene diisocyanate, tolylene diisocyanate and hydrogenated products thereof, and diisocyanates such as isophorone diisocyanate are used as main raw materials, and these dimers or trimers (burette or isocyanate). Nurate), other polyfunctional adducts such as trimethylolpropane polyols and bifunctional isocyanates such as xylylene diisocyanate, adducts of trimethylolpropane polyols and xylylene diisocyanate and other bifunctional isocyanates 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 also preferable.

  The amount of polyisocyanate used is determined so that the average particle diameter 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 0.2 About 10 μm is common.

  As the surfactant, a known surfactant for emulsification can be used, and the addition amount in the case of adding the surfactant is preferably 0.1 to 5% by mass relative to the mass of the oil phase, -2 mass% is more preferable.

In the preparation of the oil phase, the hydrophobic organic solvent that dissolves and disperses the diazonium salt compound is preferably an organic solvent having a boiling point of 100 to 300 ° C., for example, alkylnaphthalene, alkyldiphenylethane, alkyldiphenylmethane, alkylbiphenyl, Alkyl terphenyl, chlorinated paraffin, phosphate ester, maleate ester, adipate ester, phthalate ester, benzoate ester, carbonate ester, ether, sulfate ester, sulfonate ester, etc. Can be mentioned. You may use these in mixture of 2 or more types.
Further, when the solubility of the diazonium salt compound in the organic solvent is inferior, a low-boiling solvent having high solubility of the diazonium salt compound may be supplementarily used, and examples of the low-boiling solvent include ethyl acetate, Examples include propyl acetate, isopropyl acetate, butyl acetate, methylene chloride, tetrahydrofuran, acetonitrile, acetone and the like.

  That is, the diazonium salt compound preferably has an appropriate solubility in a hydrophobic organic solvent and a low-boiling solvent, and specifically, the solubility in a solvent in that the concentration of the following diazonium salt compound can be easily adjusted. Is preferably 5% or more. The solubility in water is preferably 1% or less.

  Subsequently, the prepared oil phase is emulsified and dispersed in the aqueous phase. At this time, an aqueous solution in which a water-soluble polymer is dissolved is used for the aqueous phase, and after the oil phase is added thereto, emulsification and dispersion are performed by means such as a homogenizer. The water-soluble polymer acts as a dispersion medium that makes the dispersion uniform and easy and stabilizes the emulsified and dispersed aqueous solution. Here again, the same surfactant as described above may be added for the purpose of further uniformly emulsifying and dispersing.

The water-soluble polymer used in the aqueous phase is preferably a water-soluble polymer having a water solubility of 5% or more at the temperature to be emulsified, such as polyvinyl alcohol and its modified products, polyacrylic acid amide and its derivatives. , 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 copolymers, carboxymethylcellulose, methylcellulose, casein, gelatin, starch derivatives, arabic gum, sodium alginate and the like can be mentioned.
The water-soluble polymer preferably 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 may be modified beforehand. It is desirable to eliminate the reactivity.

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 oil phase, it can react with the polyvalent isocyanate and can 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 the polyol or polyamine include propylene glycol, glycerin, trimethylolpropane, triethanolamine, sorbitol, hexamethylenediamine and the like. When a polyol is added, a polyurethane wall is formed.
The polyvalent isocyanate, polyol, reaction catalyst, or polyamine for forming a part of the walling agent is described in detail in Seisho (Polyurethane Handbook edited by Keiji Iwata, Nikkan Kogyo Shimbun (1987)). is there.

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 teddy mill.
After emulsification, the emulsion is heated to 30 to 70 ° C. for the purpose of promoting 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 during the reaction.
During the polymerization reaction, generation of carbon dioxide gas is observed as the polymerization progresses, and the end thereof can be regarded as an 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.

  On the other hand, in the preparation of a coating solution for forming a heat-sensitive recording layer (coating solution for a heat-sensitive recording layer), a coupler that develops color of the diazonium salt compound includes, for example, a sand mill and the like together with a water-soluble polymer, an organic base, and other color forming aids. However, it is particularly preferable to dissolve this in a high-boiling organic solvent that is hardly soluble or insoluble in water, and then contain a surfactant and / or a water-soluble polymer as a protective colloid. It is preferably used as an emulsified dispersion obtained by mixing with an aqueous polymer solution (aqueous phase) and emulsifying with a homogenizer or the like. If necessary, a low boiling point solvent may be used as a dissolution aid.

Furthermore, couplers, organic bases, and the like 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 high-boiling organic solvent can be appropriately selected from, for example, high-boiling oils described in JP-A-2-141279, and esters are preferable and tricresyl phosphate is particularly preferable from the viewpoint of emulsion stability.
Examples of the low-boiling solvent include those similar to the low-boiling solvent in the oil phase.

  Further, as the surfactant contained in the aqueous phase, an anionic or nonionic surfactant that does not cause precipitation or aggregation with a water-soluble polymer can be appropriately selected. For example, sodium alkylbenzene sulfonate, Examples include sodium alkyl sulfate, dioctyl sulfosuccinate sodium salt, polyalkylene glycol (for example, polyoxyethylene nonyl phenyl ether), and the like.

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.
In the present invention, it is preferable that the thermosensitive recording layer contains a basic substance.

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.

(Protective layer)
The protective layer usually contains a binder, a pigment, a lubricant, a dispersant, a fluorescent brightening agent, a metal soap, a surfactant, a hardener, an ultraviolet absorber, a crosslinking agent and the like.
Examples of the binder include vinyl acetate-acrylamide copolymer, polyvinyl alcohol, modified polyvinyl alcohol (for example, carboxy modified polyvinyl alcohol, alkyl modified polyvinyl alcohol, silicon modified polyvinyl alcohol, acetoacetyl modified polyvinyl alcohol, etc.), starch, modified Starch, methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, gelatin, gum arabic, casein, styrene-maleic acid copolymer hydrolyzate, styrene-maleic acid copolymer half ester hydrolysate, isobutylene-maleic anhydride copolymer Hydrolysates, polyacrylamide derivatives, polyvinyl pyrrolidone, polystyrene sulfonate soda, sodium alginate and other water-soluble polymers and styrene-butane Ene rubber latex, an acrylonitrile - butadiene rubber latex, methyl acrylate - butadiene rubber latex, synthetic rubber latex and vinyl acetate emulsion, synthetic resin emulsion and the like.
Among the binders, polyvinyl alcohols, modified polyvinyl alcohols, and gelatins are preferable. Examples of the gelatin include alkali-treated gelatin having a low isoelectric point, derivative gelatin reacted with an amino group (for example, phthalated gelatin). Etc. are preferred. The polyvinyl alcohols and modified polyvinyl alcohols are particularly preferably those having a polymerization degree of 300 or more and a saponification degree of 80% or more.

The pigment is not particularly limited. For example, kaolin, calcined kaolin, talc, wax, diatomaceous earth, calcium carbonate, aluminum hydroxide, magnesium hydroxide, zinc oxide, lithopone, amorphous silica, colloidal silica, Examples thereof include calcined stone, silica, magnesium carbonate, titanium oxide, alumina, barium carbonate, barium sulfate, mica, microballoon, urea-formalin filler, polyester particles, and cellulose filler.
As content of the said binder, 10-500 mass% is preferable with respect to the pigment in a protective layer, and 50-400 mass% is more preferable.

For the purpose of further improving the water resistance, it is effective to use a crosslinking agent and a catalyst for promoting the reaction in combination. Examples of the crosslinking agent include epoxy compounds, blocked isocyanates, vinyl sulfone compounds, and aldehyde compounds. , Methylol compounds, boric acid, carboxylic acid anhydrides, silane compounds, chelate compounds, halides, and the like, and those capable of adjusting the pH of the coating solution for forming the protective layer to 6.0 to 7.5 are preferable. Examples of the catalyst include known acids, metal salts, and the like, and those that can adjust the pH of the coating solution to 6.0 to 7.5 as described above are preferable.
Preferable examples of the lubricant include zinc stearate, calcium stearate, paraffin wax, polyethylene wax, and the like.

  Further, the protective layer may contain a surfactant, and as the surfactant, in addition to the acetylene glycol surfactant and silicone surfactant described above, sulfosuccinic acid alkali metal salt, fluorine-containing Surfactant etc. are mentioned suitably, Specifically, sodium salts, such as di- (2-ethylhexyl) sulfosuccinic acid and di- (n-hexyl) sulfosuccinic acid, ammonium salt, etc. are mentioned.

The coating solution for forming the protective layer (protective layer coating solution) is obtained by mixing the above-described components. Furthermore, you may add a mold release agent, a wax, a water repellent, etc. as needed.
The protective layer coating liquid containing these components has a dynamic surface tension of 35 mN / m or less when one bubble is generated in 200 ms by the bubble pressure differential pressure method, and one bubble in 1000 ms. When the dynamic surface tension when generated is 30 mN / m or less, it is applied as it is. When exceeding that, it is preferable to adjust the value of the dynamic surface tension of the coating liquid in the above range by adjusting the kind and amount of the surfactant to be added, from the viewpoint of ease of control.
The protective layer can be provided by the above-described known coating method as in the case of forming the heat-sensitive recording layer.

The dry coating amount of the protective layer is preferably ^{0.2~7g / m 2, 1~4g / m} 2 is more preferable. If the dry coating amount is less than 0.2 g / m ² , the water resistance may not be maintained, and if it exceeds 7 g / m ² , the thermochromic sensitivity may be significantly lowered. You may perform a calendar process after application | coating formation of a protective layer as needed.

(Middle layer)
When a plurality of heat-sensitive recording layers are laminated, it is preferable to provide an intermediate layer between each heat-sensitive recording layer. In the intermediate layer, as in the protective layer, pigments, lubricants, surfactants, dispersants, fluorescent brighteners, metal soaps, ultraviolet absorbers and the like can be further added to various binders. As the binder, the same binder as the protective layer can be used. The intermediate layer can be applied by the same coating method as that for the protective layer.

(Support)
As the support, for example, plastic film, paper, plastic resin laminated paper, synthetic paper, and the like can be used.
On the support, a backcoat layer can 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.

[Thermal recording material, thermal recording method]
Examples of the heat-sensitive recording material of the present invention include a multicolor heat-sensitive recording material in which two or more heat-sensitive recording layers that develop colors having different hues are provided on a support.
As the multicolor thermosensitive recording material, at least one of the two or more thermosensitive recording layers that develop colors with different hues is a photo-fixing type thermosensitive recording layer, and the thermosensitive color that develops with low thermal energy when irradiated with light before thermal recording. It is preferable that the recording layer is closer to the support than the photo-fixing type thermosensitive recording layer and absorbs the fixing light of the photo-fixing type thermosensitive recording layer and develops color with lower thermal energy than before photo-fixing. This is preferable in that a high color density of a single color can be improved.
Here, “coloring in different hues” refers to color development in two or more hues selected from yellow (Y), magenta (M), and cyan (C), and the coloring hues are not particularly limited. Absent.
The photofixable thermosensitive recording layer refers to a thermosensitive recording layer having a color former that can be fixed by light irradiation in the thermosensitive recording layer. The color former is not particularly limited, but a diazonium salt compound is particularly preferable.

Hereinafter, the thermal recording material and thermal recording method of the present invention will be described.
Here, as the heat-sensitive recording material, each heat-sensitive recording layer (C layer, M layer, and Y layer) that develops colors in the order of C, M, and Y from the support side is layered, and the C layer is formed by fixing light of the M layer. A full-color photo-fixing type multicolor thermosensitive recording material in the case where color is developed with lower thermal energy than before photo-fixing will be described as an example. Note that the present invention is not limited to this.
The C, M, and Y color formers include C color development by an electron donating colorless dye and an electron accepting compound, and M color development and Y color development by a diazo color development system using a combination of a diazonium salt compound and a coupler compound. The present invention will be described with reference to FIG.

  FIG. 1 shows an image diagram of sensitivity curves (C, M, Y) of the thermosensitive recording material of the present invention. It is the figure which expressed the color density when the thermal energy was applied to the horizontal axis and the thermal energy was applied to the vertical axis. Here, Y, M, C, and C1 indicate sensitivity curves in each hue. C1 is a sensitivity curve of the cyan layer before light irradiation, and C indicates a sensitivity curve in which the thermal color development sensitivity is lower than that of light irradiation by light irradiation.

The heat-sensitive recording method of the present invention is a heat-sensitive recording method using the heat-sensitive recording material, and is characterized by irradiating with light before heat recording and subsequently applying heat energy.
In thermal recording using a thermal recording material, first, the least heat energy is applied so as to color the thermal recording layer (Y layer) farthest from the support, and the color former (diazonium salt compound and The coupler compound) is colored yellow (see the Y sensitivity curve in FIG. 1). Next, the unreacted diazonium salt compound is decomposed by irradiating the fixing light of the Y layer.

Next, sufficient thermal energy is applied to the M layer to develop color, and the color formers (diazonium salt compound and coupler compound) contained in the layer are developed (see the M sensitivity curve in FIG. 1). At this time, the Y layer is also strongly heated at the same time, but the diazonium salt compound has already decomposed, and the color development ability is lost, so no color is produced. Thereafter, the M layer fixing light is irradiated to decompose the diazonium salt compound contained in the M layer.
At this time, the light irradiation to the M layer decomposes the diazonium salt compound of the M layer and at the same time lowers the thermal coloring sensitivity of the lowermost C layer. Lowering the thermal coloring sensitivity of the C layer means that the sensitivity curve “C1” before light irradiation shifts to the low energy side from the sensitivity curve “C” after light irradiation. Means that the color former (electron-donating colorless dye and electron-accepting compound) of the C layer can be colored.
For example, in order to obtain the conventional color density b, it was necessary to apply a1 energy. However, it is possible to reduce the thermal energy by irradiating light before thermal recording, and to apply a energy having lower energy. Thus, the conventional color density can be maintained.

Finally, color is developed by applying sufficient heat to the C layer to develop color.
At this time, both the Y layer and the M layer are strongly heated at the same time, but since the diazonium salt compound has already decomposed and the coloring ability is lost, no color is developed.
Further, as shown in FIG. 1, since the light has already been irradiated with the M fixing light, the C layer has already been irradiated with light before thermal recording from the conventional C1 sensitivity curve to the C sensitivity curve. Even if the thermal energy sufficient to develop the color is low, it is possible to reduce the conventional printing trouble occurring at the highest color development energy portion while maintaining the conventional monochromatic color density.

Here, the lowermost layer (C layer) has been described as an example of a layer that develops color with low thermal energy by irradiating light before thermal recording, but at least one of the thermal recording layers that develop colors in two or more different hues has been described. In the above example, the heat-sensitive recording layer that is a light-fixing type heat-sensitive recording layer and develops color with low heat energy when irradiated with light before heat recording may be an M layer or a Y layer. The heat-sensitive recording layer is preferably a heat-sensitive recording layer that is closer to the support than the light-fixing type heat-sensitive recording layer and absorbs the fixing light of the upper light-fixing type heat-sensitive recording layer and develops color with lower thermal energy than before light irradiation. .
By using at least one layer as a heat-sensitive recording layer in which the thermal energy is reduced by light irradiation, the amount of energy for obtaining the highest color density in the lowermost layer can be reduced.
Among the heat-sensitive recording layers, it is preferable that the lowermost heat-sensitive recording layer absorbs light in the wavelength region of the fixing light above the heat-sensitive recording layer and develops color with lower thermal energy than before light irradiation. By using the light of the fixing light of the upper layer, it is possible to reduce the thermal energy without providing a new light irradiation device or light irradiation operation.

The above example is a full-color image recording in which the heat-sensitive recording layer is composed of three layers, and each color hue is selected to be the three primary colors in the subtractive color mixing, yellow, magenta, and cyan.
In this case, the color development mechanism of the heat-sensitive recording layer (lowermost layer) directly laminated on the support surface is not limited to a diazo color development system using a combination of a diazonium salt compound and a coupler compound. For example, an electron donating dye and the electron Coloring system combining electron-accepting dyes that react with donor dyes, color developing systems that come into contact with basic compounds, color forming systems that chelate, chelate coloring systems, and reaction with nucleophiles to cause elimination reactions Any of coloring systems that develop color may be used.
The diazo color-forming heat-sensitive recording layer may be a diazo color-generating heat-sensitive recording layer having different maximum absorption wavelengths and different color hues.
In addition, the hue that develops color in the multicolor thermosensitive recording material may be provided on the support in any order, but from the viewpoint of ease of production, Y / M / C, M from the farthest side of the support. The order of / Y / C and M / C / Y is preferred, Y / M / C and M / Y / C are more preferred, and Y / M / C is particularly preferred.

  Specifically, from the support side, it contains an electron-donating colorless dye and an electron-accepting compound, or a diazonium salt compound having a maximum absorption wavelength shorter than 350 nm and a coupler compound that reacts with the diazonium salt compound when heated to develop a color. A first thermosensitive recording layer (first layer), a second thermosensitive recording layer (first layer) containing a diazonium salt compound having a maximum absorption wavelength of 365 nm ± 25 nm and a coupler compound that reacts with the diazonium salt compound when heated 2 layers), a third thermosensitive recording layer (third layer) containing a diazonium salt compound having a maximum absorption wavelength of 425 ± 30 nm and a coupler compound that reacts with the diazonium salt compound when heated to form a color. Things.

The recording of the multicolor thermosensitive recording material will be described with reference to the above specific example, but the present invention is not limited to this.
First, the third thermosensitive recording layer (third layer) farthest from the support is heated to develop color, and the diazonium salt compound and coupler compound contained in the layer are developed. Next, irradiation with light of 425 ± 30 nm is performed to decompose the unreacted diazonium salt compound contained in the third layer.
Next, the second heat-sensitive recording layer (second layer) is heated enough to develop color, and the diazonium salt compound and coupler compound contained in the layer are colored. At this time, the third layer is also strongly heated at the same time, but the diazonium salt compound has already decomposed and the color development ability is lost, so no color is produced. Thereafter, the diazonium salt compound contained in the second layer is decomposed by irradiation with light of 365 ± 25 nm. At this time, the thermochromic sensitivity of the first layer is amplified by the fixing light of the second layer.
Finally, the first heat-sensitive recording layer (first layer) is colored by applying sufficient heat. At this time, the third layer and the second layer are also strongly heated at the same time, but since the diazonium salt compound has already decomposed and the coloring ability is lost, no color is developed.

[Thermal recording device]
The thermal recording apparatus of the present invention is a thermal recording apparatus for recording an image by thermally recording and fixing the thermal recording material, and has means for irradiating light before the thermal recording, and the irradiation wavelength of the light irradiation means Is 330 nm to 390 nm.
The light irradiation means is a light source that emits and emits light for fixing the heat-sensitive recording material, and the irradiation wavelength of the light source needs to be 330 nm to 390 nm. By irradiating light before the thermal recording with the irradiation wavelength of the light source within the range, the maximum color development energy of the heat-sensitive recording material can be reduced, and the printing trouble generated in the conventional maximum color development energy part can be reduced. it can.
The light source has the same meaning as the light source described in the section of the microencapsulation method.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples. Hereinafter, “parts” and “%” in the examples represent “parts by mass” and “% by mass”, respectively.

Example 1
<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 solution>
25.5 parts of alkali-treated low-ion gelatin (trade name: # 750 gelatin, manufactured by Nitta Gelatin Co., Ltd.), 1,2-benzthiazolin-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 aqueous gelatin solution for preparing an emulsion.

<Preparation of coating solution (a) for yellow thermosensitive recording layer>
-Preparation of diazonium salt compound-encapsulating microcapsule solution (a ')-
16.1 parts of ethyl acetate, 3.0 parts of the following compound A (diazonium salt compound, maximum absorption wavelength 420 nm), 1.4 parts of the following compound B (diazonium salt compound, maximum absorption wavelength 420 nm), monoisopropylbiphenyl 4.0 Part, 5.6 parts diphenyl phthalate, and 0.44 parts diphenyl- (2,4,6-trimethylbenzoyl) phosphine oxide (trade name: Lucillin TPO, manufactured by BASF Japan Ltd.), 40 ° C. And uniformly dissolved.
The resulting mixture was mixed with xylylene diisocyanate / trimethylolpropane adduct and xylylene diisocyanate / bisphenol A adduct (trade name: Takenate D119N (50 mass% ethyl acetate solution), Takeda Pharmaceutical Co., Ltd.) 8.6 parts) and mixed uniformly to obtain a mixed liquid (I; oil phase).

  Separately, 16.3 parts of ion-exchanged water and 0.34 part of Scratch AG-8 (50% by mass; manufactured by Nippon Seika Co., Ltd.) were added to 58.6 parts of the phthalated gelatin aqueous solution, and the mixture (II An aqueous phase) was obtained.

The mixed liquid (I) was added to the mixed liquid (II) obtained above, and the mixture was emulsified and dispersed at 40 ° C. using a homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.). 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.
Subsequently, the ion exchange resin was removed by filtration, and the concentration was adjusted so that the solid content concentration of the microcapsule solution was 20.0% to obtain a diazonium salt compound-encapsulated microcapsule solution (a ′). As a result of measuring the particle size of the obtained microcapsule using LA-700 (manufactured by Horiba, Ltd.), the median diameter was 0.38 μm.

-Preparation of coupler emulsion (a '')-
To 33.0 parts of ethyl acetate, 9.9 parts of the following coupler compound (C), 9.9 parts of triphenylguanidine (manufactured by Hodogaya Chemical Co., Ltd.), and 4,4 ′-(m-phenylenediisopropylidene) di 20.8 parts of phenol (trade name: bisphenol M, manufactured by Mitsui Petrochemical Co., Ltd.) and 3,3,3 ′, 3′-tetramethyl-5,5 ′, 6,6′-tetra (1-propyloxy) ) -1,1'-spirobisindane, 3.3 parts, 4- (2-ethylhexyloxy) benzesisulfonic acid amide (manac) 13.6 parts, 4-n-pentyloxybenzenesulfone 6.8 parts of acid amide (manac Co., Ltd.) and 4.2 parts of calcium dodecylbenzenesulfonate (trade name: Pionein A-41-C (70% methanol solution), Takemoto Yushi Co., Ltd.) Dissolve the mixture (III) It was.

Separately, 107.3 parts of ion-exchanged water was mixed with 206.3 parts of the alkali-treated gelatin aqueous solution obtained above to obtain a mixed liquid (IV).
Subsequently, 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 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% by mass. As a result of measuring the particle diameter of the obtained coupler emulsion (a ′ ″) with LA-700 (manufactured by Horiba, Ltd.), the median diameter was 0.23 μm.
Further, 9 parts of SBR latex (trade name: SN-307 (48%), manufactured by Nippon A & L Co., Ltd.) adjusted to 26.5% is added to 100 parts of the coupler emulsion after concentration adjustment. The resulting mixture was stirred uniformly to obtain a coupler emulsion (a ″).

-Preparation of coating solution (a) for yellow thermosensitive recording layer-
The diazonium salt compound-encapsulating microcapsule liquid (a ′) and the coupler emulsion (a ″) obtained above were mixed so that the mass ratio of the coupler compound / diazonium salt compound was 2.2 / 1. A yellow thermosensitive recording layer coating solution (a) was obtained.

<Preparation of coating solution (b) for magenta thermosensitive recording layer>
-Preparation of diazonium salt compound-encapsulated microcapsule solution (b ')-
12.8 parts of ethyl acetate, 3.8 parts of the following compound D (diazonium salt compound, maximum absorption wavelength 365 nm), 3.2 parts of isopropyl biphenyl, 3.2 parts of tricresyl phosphate, 3.2 parts of diphenyl phthalate, sulfuric acid 1.1 parts of dibutyl, 0.38 parts of 2,4,6-trimethylbenzoylphenylphosphinic acid ethyl ester, and calcium dodecylbenzenesulfonate (surfactant; trade name: Pionine A-41-C (70% methanol solution) ); 0.15 part of Takemoto Yushi Co., Ltd.) was added and heated to dissolve uniformly.

10.9 parts of xylylene diisocyanate / trimethylolpropane adduct (trade name: Takenate D110N (75% ethyl acetate solution), manufactured by Takeda Pharmaceutical Co., Ltd.) as a capsule wall material is added to the resulting mixture. It stirred uniformly and the liquid mixture (V; oil phase) was obtained.
Separately, 59.8 parts of the phthalated gelatin aqueous solution was mixed with 22.8 parts of ion-exchanged water to obtain a mixed liquid (VI; aqueous phase).

The mixed solution (V) was added to the mixed solution (VI) obtained above, and the mixture was emulsified and dispersed at 40 ° C. using a homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.). To the obtained emulsion, 27.3 parts of water was added for homogenization, and the mixture was stirred at 40 ° C. for 3 hours while removing ethyl acetate. Thereafter, 1.16 parts of ion exchange resin Amberlite IRA67 (manufactured by Organo Corporation) and 2.33 parts of SWA100-HG (manufactured by Organo Corporation) were added, and the mixture was further stirred for 0.5 hours.
Subsequently, the ion exchange resin was removed by filtration, and the concentration was adjusted so that the solid content of the microcapsule solution was 18.5%, thereby obtaining a diazonium salt compound-encapsulating microcapsule solution (b ′). As a result of measuring the particle size of the obtained microcapsule using LA-700 (manufactured by Horiba, Ltd.), the median diameter was 0.57 μm.

-Preparation of coupler emulsion (b '')-
33.0 parts of ethyl acetate, 6.3 parts of the following coupler compound (E), 14.0 parts of triphenylguanidine (manufactured by Hodogaya Chemical Co., Ltd.), and 4,4 ′-(m-phenylenediisopropylidene) 14.0 parts of diphenol (trade name: bisphenol M (manufactured by Mitsui Petrochemical Co., Ltd.)), 14 parts of 1,1 ′-(-p-hydroxyphenyl) -2-ethylhexane, 3,3,3 ', 3'-tetramethyl-5,5', 6,6'-tetra (1-propyloxy) -1,1'-spirobisindane, 3.5 parts of the following compound (G), 2.5 parts of tricresyl phosphate and 4.5 parts of calcium dodecylbenzenesulfonate (trade name: Pionein A-41-C (70% methanol solution), Takemoto Yushi Co., Ltd.) are dissolved and mixed ( VII) was obtained.

Separately, 106.3 parts of ion-exchanged water was mixed with 206.3 parts of the alkali-treated gelatin aqueous solution obtained above 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). The resulting coupler 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% by mass to obtain a coupler emulsion (b ″). As a result of measuring the particle diameter of the obtained coupler emulsion (b ″) using LA-700 (manufactured by Horiba, Ltd.), the median diameter was 0.24 μm.

-Preparation of coating solution (b) for magenta thermosensitive recording layer-
The diazonium salt compound-encapsulating microcapsule liquid (b ′) and coupler emulsion liquid (b ″) obtained above were mixed so that the mass ratio of coupler compound / diazonium salt compound was 1.9 / 1. Further, an aqueous solution (5% by mass) of polystyrene sulfonic acid (partially potassium hydroxide neutralized) was mixed in an amount of 0.015 part with respect to 10 parts of the mixed diazonium salt compound-encapsulated microcapsule liquid (b ′). As a result, a magenta thermosensitive recording layer coating solution (b) was obtained.

<Preparation of Cyan Thermal Recording Layer Coating Liquids (c1 to c5)>
-Preparation of electron donating dye precursor encapsulated microcapsule liquid (c1 ')-
18.1 parts of ethyl acetate, 7.6 parts of the following electron donating dye precursor (H), and 4.0 parts of trimethylolpropane trimethacrylate (trade name: Light Ester TMP, manufactured by Kyoeisha Yushi Chemical Co., Ltd.) , Diisopropylnaphthalene (trade name: KMC113, manufactured by Kureha Chemical Industry Co., Ltd.) 8.0 parts, 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane (trade name: 4.0 parts of Adeka Cruz DH-37 (manufactured by Asahi Denka Kogyo Co., Ltd.) were added and heated to dissolve uniformly to prepare an oil phase solution (Y).
Compound 2: 1.00 part of acetonitrile was added to 0.214 parts (1.7% by mass with respect to the total amount of the wall material), dissolved, and 1.626 parts of xylylene diisocyanate were added, In the presence, a pre-reaction was performed at 40 ° C. for about 5 minutes to prepare a wall material compound solution (Z).
6.84 parts of xylylene diisocyanate / trimethylolpropane adduct (trade name: Takenate D110N (75% by mass ethyl acetate solution), manufactured by Mitsui Takeda Chemical Co., Ltd.) as a capsule wall material in the oil phase solution (Y), phenyl Formalin condensate of isocyanate (trade name: Millionate MR-200, manufactured by Nippon Polyurethane Industry Co., Ltd.) 3.86 parts, xylylene diisocyanate / the following compound (I) adduct (50 mass% ethyl acetate solution) 3.56 parts Further, 2.84 parts of the above wall material compound solution (Z) was added and stirred uniformly to obtain a mixed liquid (IX).

Separately, 57.6 parts of the phthalated gelatin aqueous solution obtained above were added to 9.5 parts of ion-exchanged water, 0.17 parts of Scraph AG-8 (50% by mass, manufactured by Nippon Seika Co., Ltd.), and dodecylbenzenesulfone. 4.3 parts of sodium acid (10% aqueous solution) was added and mixed to obtain a mixed solution (X).
The mixed solution (IX) was added to the mixed solution (X) obtained above, and the mixture was emulsified and dispersed at 40 ° C. using a homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.). To the obtained emulsion, 50 parts of water and 0.12 part of tetraethylenepentamine were homogenized, and the mixture was stirred at 65 ° C. for 3 hours while removing ethyl acetate. A microcapsule liquid whose concentration was adjusted so that the solid content concentration was 33% was obtained. As a result of measuring the particle size of the microcapsule at this time using LA-700 (manufactured by Horiba, Ltd.), the median diameter was 1.00 μm.

  Furthermore, 3.7 parts of sodium dodecylbenzenesulfonate 25% aqueous solution (trade name: Neoperex F-25, manufactured by Kao Corporation) and 4,4′- An optical brightener (trade name: Kaycoll BXNL, manufactured by Nippon Soda Co., Ltd.) containing 4.3 parts of a bistriazinylaminostilbene-2,2′-disulfone derivative is added and stirred uniformly to provide an electron donating property. A dye precursor-encapsulated microcapsule solution (c1 ′) was obtained.

-Preparation of electron donating dye precursor encapsulated microcapsule solution (c2 ')-
In the preparation of the electron donating dye precursor-encapsulated microcapsule solution (c1 ′), instead of Compound 2: 0.214 parts and xylylene diisocyanate: 1.626 parts, Compound 2: 0.6 parts (total wall material) 5 mass% based on the amount), xylylene diisocyanate: The same procedure was performed except that 1.24 parts were used, and an electron donating dye precursor-encapsulated microcapsule solution was prepared.

-Preparation of electron-donating dye precursor-encapsulated microcapsule solution (c3 ')-
In the preparation of the electron donating dye precursor-encapsulated microcapsule liquid (c1 ′), instead of Compound 2: 0.214 parts and xylylene diisocyanate: 1.626 parts, Compound 1: 1.2 parts (total wall material) 10 mass% with respect to the amount) and xylylene diisocyanate: 1.24 parts were used in the same manner to prepare an electron donating dye precursor-encapsulated microcapsule solution.

-Preparation of electron-donating dye precursor-encapsulated microcapsule solution (c4 ')-
In the preparation of the electron donating dye precursor-encapsulated microcapsule solution (c1 ′), instead of Compound 2: 0.214 parts and xylylene diisocyanate: 1.626 parts, Compound 1: 2.4 parts (all wall materials) 20 mass% based on the amount), xylylene diisocyanate: Except that 1.24 parts were used, an electron donating dye precursor-encapsulated microcapsule solution was prepared.

-Preparation of electron-donating dye precursor-encapsulated microcapsule solution (c5 ')-
In the preparation of the electron-donating dye precursor-encapsulated microcapsule solution (c1 ′), the same procedure was performed except that 0.214 parts of Compound 2: Electron-donating dye precursor-encapsulated microcapsule solution was prepared.

—Preparation of Electron-Accepting Compound Dispersion (c ″) —
To 11.3 parts of the phthalated gelatin aqueous solution obtained above, 30.1 parts of ion-exchanged water and 4,4 ′-(p-phenylenediisopropylidene) diphenol (trade names: bisphenol P, Mitsui Petrochemical Co., Ltd.) 15 parts) and 2% 2% sodium 2-ethylhexyl succinate aqueous solution were added and dispersed overnight using a ball mill to obtain a dispersion having a solid content concentration of 26.6%.
To 100 parts of this dispersion, 45.2 parts of the alkali-treated gelatin aqueous solution obtained above was added and stirred for 30 minutes, and then ion-exchanged water was added so that the solid content concentration of the dispersion was 23.5%. A receptive compound dispersion (c ″) was obtained.

-Preparation of coating solutions (c1 to c5) for cyan thermosensitive recording layer-
Each of the electron donating dye precursor-encapsulated microcapsule liquids (c1 ′) to (c5 ′) obtained above and the electron accepting compound dispersion liquid (c ″) is combined with an electron accepting compound / electron donating property. Mixing was performed so that the mass ratio of the dye precursor was 10/1 to obtain coating liquids c1 to c5 for cyan thermosensitive recording layers.

<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 Industry Co., 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 preparing a coating solution for an intermediate layer.
10.0 parts of the obtained gelatin aqueous solution, 0.05 parts of sodium (4-nonylphenoxytrioxyethylene) butyl sulfonate (manufactured by Sankyo Chemical Co., Ltd .; 2.0 mass% aqueous solution), boric acid (4.0 mass) 1.5 part aqueous solution), 1.5 part polystyrene sulfonic acid (partially potassium hydroxide neutralized) aqueous solution (5 mass%) 0.19 part, 4% aqueous solution of the following compound (J) (manufactured by Wako Pure Chemical Industries, Ltd.) 1.32 parts, 0.44 part of a 4% aqueous solution of the following compound (J ′), and 0.67 part of ion-exchanged water were mixed to obtain an intermediate layer coating solution.

<Preparation of coating solution for light transmittance adjusting layer>
-Preparation of UV absorber precursor microcapsule solution-
In 71 parts of ethyl acetate, 14.5 parts of [2-allyl-6- (2H-benzotriazol-2-yl) -4-tert-octylphenyl] benzenesulfonate as a UV absorber precursor, 2,2′- 5.0 parts of t-octylhydroquinone, 1.8 parts of tricresyl phosphate, 5.8 parts of α-methylstyrene dimer (trade name: MSD-100, manufactured by Mitsui Chemicals), calcium dodecylbenzenesulfonate (trade name) : Pionein A-41-C (70% methanol solution), Takemoto Yushi Co., Ltd. 0.45 part was mixed and dissolved uniformly.

54.7 parts of xylylene diisocyanate / trimethylolpropane adduct (trade name: Takenate D110N (75% by mass ethyl acetate solution), manufactured by Takeda Pharmaceutical Co., Ltd.) is added as a capsule wall material to the resulting mixture. And stirred uniformly to obtain a UV absorber precursor mixed solution.
Separately, 8.9 parts of a 30% phosphoric acid aqueous solution and 532.6 parts of ion-exchanged water are mixed with 52 parts of itaconic acid-modified polyvinyl alcohol (trade name: KL-318, manufactured by Kuraray Co., Ltd.) to obtain an ultraviolet absorber precursor. A body PVA aqueous solution was obtained.
The above-mentioned ultraviolet absorbent precursor mixed solution was added to 516.06 parts of the obtained ultraviolet absorbent precursor PVA aqueous solution, and the mixture was emulsified and dispersed at 20 ° C. using a homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.). After adding 254.1 parts of ion-exchanged water to the obtained emulsion and homogenizing it, an encapsulation reaction was performed 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 thereto, and the mixture was further stirred for 1 hour.

Subsequently, the ion exchange resin was removed by filtration, and the concentration was adjusted so that the solid content concentration of the microcapsule solution was 13.5%. As a result of measuring the particle size of the obtained microcapsule using LA-700 (manufactured by Horiba, Ltd.), the median diameter was 0.23 ± 0.05 μm.
To the 859.1 parts of this microcapsule liquid, 2.416 parts of carboxy-modified styrene-butadiene latex (trade name: SN-307 (48% aqueous solution), manufactured by Nippon A & L Co., Ltd.) and 39.5 parts of ion-exchanged water were mixed. Thus, an ultraviolet absorber precursor microcapsule solution was obtained.

-Preparation of coating solution for light transmittance adjusting layer-
1000 parts of the ultraviolet absorber precursor microcapsule solution obtained from the above, fluorinated surfactant (trade name: Megafac F-120 (5% aqueous solution), manufactured by Dainippon Ink & Chemicals, Inc.), 5.2 parts, 7.75 parts of a 4% aqueous sodium hydroxide solution and 73.39 parts of sodium (4-nonylphenoxytrioxyethylene) butyl sulfonate (manufactured by Sankyo Chemical Co., Ltd .; 2.0% aqueous solution) are mixed to transmit light. A coating solution for rate adjusting layer was obtained.

<Preparation of coating solution for protective layer>
-Preparation of PVA solution for protective layer-
160 parts of vinyl alcohol (PVA) -alkyl vinyl ether copolymer (trade name: EP-130, manufactured by Denki Kagaku Kogyo Co., Ltd.), a mixed liquid of sodium alkyl sulfonate and polyoxyethylene alkyl ether phosphate (trade name: Neoscore CM-57 (54% aqueous solution), Toho Chemical Industry Co., Ltd. (7.74 parts) and ion-exchanged water (3833 parts) are mixed, dissolved at 90 ° C. for 1 hour to homogenize, and the protective layer PVA solution is prepared. Obtained.

-Preparation of pigment dispersion for protective layer-
In 8 parts of barium sulfate (trade name: BF-21F (barium sulfate content 93% or more), manufactured by Sakai Chemical Industry Co., Ltd.), an anionic special polycarboxylic acid type polymer activator (trade name: Poise 532A ( 40% aqueous solution), manufactured by Kao Co., Ltd.) 0.3 parts and ion-exchanged water 11.7 parts were mixed and dispersed with a dynomill to obtain a barium sulfate dispersion. The particle size at this time was measured using LA-700 (manufactured by Horiba, Ltd.), and as a result, the median diameter was 0.17 μm or less.
Then, 8.1 parts of colloidal silica (trade name: Snowtex O (20% aqueous dispersion), manufactured by Nissan Chemical Co., Ltd.) is added to 45.6 parts of the obtained barium sulfate dispersion, and a protective layer is added. A pigment dispersion was obtained.

-Preparation of matting agent dispersion for protective layer-
An aqueous dispersion of 1,2-benzisothiazolin-3-one (trade name: PROXEL BD, IC) was added to 220 parts of wheat starch (trade name: Wheat Starch S, manufactured by Shinshin Food Industry Co., Ltd.). 3.81 parts manufactured by Co., Ltd. and 1976.19 parts ion-exchanged water were mixed and dispersed uniformly to obtain a matting agent dispersion for protective layer.

-Preparation of coating solution for protective layer-
To 1000 parts of the PVA solution for protective layer obtained above, 40 parts of the fluorosurfactant (trade name: Megafac F-120 (5% aqueous solution), manufactured by Dainippon Ink & Chemicals, Inc.), (4- Nonylphenoxytrioxyethylene) sodium butyl sulfonate (manufactured by Sankyo Chemical Co., Ltd .; 2.0% aqueous solution), 49.87 parts of pigment dispersion for protective layer obtained from above, for protective layer obtained from above 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. A protective layer coating solution was obtained.

<Preparation of support with undercoat layer>
-Preparation of coating solution for undercoat layer-
40 parts of enzyme-degraded gelatin (average molecular weight 10,000, PAGI viscosity = 15 mP, PAGI jelly strength = 20 g) is added to 60 parts of ion-exchanged water, and stirred and dissolved at 40 ° C. to prepare a coating solution for an undercoat layer. An aqueous gelatin solution was prepared.
Separately, 8 parts of water-swelling synthetic mica (aspect ratio 1000; trade name: Somasif ME100, manufactured by Coop Chemical Co., Ltd.) and 92 parts of water were mixed and then wet-dispersed with Viscomil, and the average particle size was 2.0 μm. A mica dispersion was obtained. Water was added to this mica dispersion so that the mica concentration was 5% and mixed uniformly to obtain a mica dispersion.

  120 parts of water and 556 parts of methanol were added to 100 parts of an aqueous gelatin solution for preparing a coating solution for an undercoat layer adjusted to 40% at 40 ° C. and sufficiently stirred and mixed, and then 208 parts of the mica dispersion adjusted to 5%. Then, the mixture was further sufficiently stirred and mixed, and 9.8 parts of a 1.66% polyethylene oxide surfactant was added. And the liquid temperature was hold | maintained at 35-40 degreeC, 7.3 parts of gelatin hardeners which are an epoxy compound were added, and the coating liquid (5.7%) for undercoat layers was obtained.

-Production of support with undercoat layer-
Next, the wood pulp comprising 50 parts of LBPS and 50 parts of LBPK was beaten to 300 cc Canadian freeness with a disc refiner, 0.5 parts of epoxidized behenamide, 1.0 part of anionic polyacrylamide, 1.0 part of aluminum sulfate, polyamide polyamine 0.1 parts of epichlorohydrin and 0.5 parts of cationic polyacrylamide were added in an absolutely dry mass ratio with respect to the pulp, and a base paper having a basis weight of 114 g / m ² was made with a long net paper machine, and then the thickness was determined by a calendering process. The thickness was adjusted to 100 μm.
Subsequently, after corona discharge treatment was performed on both surfaces of the obtained base paper, polyethylene was coated to a resin thickness of 36 μm using a melt extruder to form a resin layer consisting of a mat surface (this surface was designated as “ It's called the back side.) Next, on the surface opposite to the side on which the resin layer is formed, polyethylene containing 10% anatase-type titanium dioxide and a small amount of ultramarine blue is coated using a melt extruder so as to have a thickness of 50 μm. A resin layer composed of a surface was formed (this surface is referred to as “front side”).

After the corona discharge treatment is applied to the resin surface of the back surface, aluminum oxide (trade name: Alumina Sol 100, manufactured by Nissan Chemical Industries, Ltd.) and silicon dioxide (trade name: Snowtex O, Nissan Chemical Industries, Ltd.) are used as antistatic agents. (Made by Co., Ltd.) was dispersed in water at a ratio of 1/2 (= aluminum oxide / silicon dioxide; mass ratio), and this was applied so that the dry mass was 0.2 g / m ² .
Subsequently, after the corona discharge treatment was performed on the surface of the polyethylene resin layer on the front side, the coating solution for the undercoat layer obtained above was applied so that the mica coating amount was 0.26 g / m ² and dried. A support with an undercoat layer was obtained.

<Preparation of thermal recording material>
Cyan heat-sensitive recording layer coating solution (c1), intermediate layer coating solution, magenta thermosensitive recording layer coating solution (b), and intermediate layer-use cloth on the surface of the undercoat layer of the undercoat support. Liquid, yellow thermosensitive recording layer coating liquid (a), light transmittance adjusting layer coating liquid, and protective layer coating liquid are simultaneously and continuously applied (seven layers are simultaneously coated), and drying conditions of 30 ° C. and 30% RH, And the drying process was performed on 40 degreeC and 30% of drying conditions, respectively, and the multicolor thermosensitive recording material was produced.

At this time, in the yellow thermosensitive recording layer coating solution (a), the total coating amount of the diazonium salt compounds (A) and (B) is 0.156 g / m ^{2 in} terms of the solid coating amount. The coating solution for layer (b) is an amount such that the coating amount of the diazonium salt compound (D) is 0.225 g / m ^{2 in} terms of the solid coating amount, and the coating solution for the cyan thermosensitive recording layer (c1) is electron donating. The coating amount of the dye precursor (H) was applied in such an amount that the solid content coating amount would be 0.355 g / m ² .
In addition, the intermediate layer coating solution is used in an amount such that the solid coating amount of gelatin is 2.064 g / m ² between the coating solution (a) and the coating solution (b). ) And coating solution (c1), the amount of gelatin solid content coating amount is 2.885 g / m ^2, and the light transmittance adjusting layer coating solution has a solid content coating amount of 2.35 g / m ^2. The amount of m ² was applied to the protective layer coating solution in such an amount that the solid content was 1.39 g / m ² .

(Examples 2 to 4, Comparative Example 1)
In the production of the heat-sensitive recording material of Example 1, the same as Example 1 except that the cyan heat-sensitive recording layer coating liquids (c2) to (c5) were used instead of the cyan heat-sensitive recording layer coating liquid (c1). Thus, a multicolor thermosensitive recording material was produced.

(Evaluation of color density and gloss of cyan thermal recording layer)
For the multicolor thermosensitive recording materials obtained in Examples 1 to 4 and Comparative Example 1, first, the diazonium salt compound in the yellow thermosensitive recording layer was deactivated by an ultraviolet lamp having an emission center wavelength of 420 nm and an output of 40 W, and then emitting light. The diazonium salt compound in the magenta thermosensitive recording layer was deactivated by irradiation with a UV lamp with a central wavelength of 365 nm and an output of 40 W for 10 seconds.
Next, using a thermal head (KST type, manufactured by Kyocera Corporation), the applied voltage and pulse width to the thermal head are set so that the recording energy per unit area is 90 mJ / mm ^2, and the cyan thermosensitive recording layer. Was heat-printed.
The maximum color density (Dmax) was measured with a red filter using a Macbeth densitometer (reflection densitometer RD918, manufactured by Macbeth Co.). The measurement results are shown in Table 1 below.

As shown in Table 1, the color density of the high energy application part (cyan color development part) when the color was developed without light irradiation and when the light irradiation was performed was that of Examples 1 to 4 in which the wall material additive was added. In all cases, the color density after light irradiation showed a higher value.
On the other hand, in the comparative example, there was no change in the color development sensitivity before and after the light irradiation, and the color density was not changed.

(A) It is an image figure which shows the sensitivity curve (Y, M, C, and C1) in one Embodiment of the thermosensitive recording material of this invention.

Explanation of symbols

Y sensitivity curve for yellow hue M sensitivity curve for magenta hue C1 sensitivity curve for cyan hue (before light irradiation)
C Cyan sensitivity curve (after light irradiation)
a1 Conventional applied thermal energy necessary to obtain color density b (cyan hue) (before light irradiation)
a Thermal energy of application of the present invention necessary for obtaining a color density b (cyan hue) (after light irradiation)

Claims (9)

In a heat-sensitive recording material having one or more heat-sensitive recording layers on a support, at least one of the heat-sensitive recording layers is colored with a lower thermal energy than before light irradiation when irradiated with light before heat recording. Thermal recording material. A heat-sensitive recording layer having two or more heat-sensitive recording layers that develop colors with different hues on a support, and at least one of the heat-sensitive recording layers is irradiated with light before thermal recording, thereby generating heat with lower thermal energy than before light irradiation. The heat-sensitive recording material according to claim 1, which is a recording layer. There are two or more heat-sensitive recording layers that develop colors of different hues on the support, and at least one of the heat-sensitive recording layers is a light-fixing type heat-sensitive recording layer. The heat-sensitive recording layer that develops color is located on the support side of the photo-fixing type thermo-sensitive recording layer and absorbs the light of the fixing light of the upper photo-fixing type thermo-sensitive recording layer and develops color with lower thermal energy than before light irradiation. The heat-sensitive recording material according to claim 1 or 2. By irradiating with light before thermal recording, at least one thermosensitive recording layer that develops color with lower thermal energy than before irradiating contains a microcapsule having a color former, and the microcapsule irradiates with light. The heat-sensitive recording material according to any one of claims 1 to 3, wherein the color is developed with lower thermal energy than before irradiation. The heat-sensitive recording material according to claim 4, wherein the wall material forming the microcapsules absorbs light in the wavelength region of the fixing light of the upper layer so that the color is developed with lower thermal energy than before light irradiation. . The heat-sensitive recording material according to claim 4, wherein the wall material forming the microcapsule has absorption in a region of 330 nm to 390 nm. The heat-sensitive recording material according to any one of claims 4 to 6, wherein the wall material forming the microcapsule partially contains a structure of a compound represented by the following general formula (P).

[In General Formula (P), R ¹ represents L ¹ -X ¹ or X ¹ , and R ² represents a hydrogen atom or L ² -X ² . L ¹ and L ² represent a divalent linking group, and X ¹ and X ² represent a group selected from a hydroxyl group, an amino group, and a mercapto group. n represents an integer of 1 to 4. ] A heat-sensitive recording method using the heat-sensitive recording material according to any one of claims 1 to 7, wherein irradiation with light is performed before heat recording, followed by application of heat energy. A thermal recording apparatus for recording an image by thermally recording and fixing the thermosensitive recording material according to any one of claims 1 to 7, comprising a means for irradiating light before the thermal recording, wherein the light irradiation A thermal recording apparatus, wherein the irradiation wavelength of the means is 330 nm to 390 nm.

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