JP2002331753A - Heat-sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-sensitive recording material which can be observed by high quality of image on an X-ray film viewer. SOLUTION: In the heat-sensitive recording material with a heat-sensitive recording layer on a transparent substrate, the heat-sensitive material is characterized by chromaticity coordinates by JIS Z 8729 when energy is loaded just before color development is started being in a range of L: 73-85, a*: -4.0-0 and b*: 8-16 and the chromaticity coordinates at a transmission density of 3.0 measured by means of a Macbeth transmission density meter TD904 (a visual filter) being in a range of L: 0.5-1.0, a*: 0-2.0 and b*: -1.0-+1.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly, to a heat-sensitive recording material capable of obtaining high image quality when observed on a Schaukasten.

[0002]

2. Description of the Related Art The thermal recording method is characterized in that (1) development is unnecessary, and (2) when the support is paper, the paper quality is close to that of ordinary paper.
(3)) easy handling, (4) high color density,
(5) The recording device is simple and inexpensive, and (6) there are no recording noises. Therefore, the use of the recording device is expanding in the fields of facsimile and printers, and labels such as POS. For this reason, the demand for heat-sensitive recording materials has been diversified, and materials capable of multicolor recording and transparent heat-sensitive recording materials for overhead projectors have been developed (for example, JP-A-63-46084).

In recent years, ultrasonic scanners, CT
With the digitization of medical devices such as scanners and X-rays, transparent thermosensitive recording materials capable of directly recording digital images of these have been developed. In this case, generally, in a diagnosis by a doctor or the like, light such as a fluorescent lamp is applied to the image recorded on the heat-sensitive recording material from behind (a device for applying such light is referred to as a shakasten). Observe from.

[0004]

However, when an image recorded on a conventional heat-sensitive recording material having a heat-sensitive recording layer provided on a transparent support is observed from the support side on a shakasten, it is low in medical use such as radiography. There is a problem that the image diagnostic ability in the density portion is poor and it is difficult to observe.
An object of the present invention is to solve the conventional problems and achieve the following objects. That is, an object of the present invention is to provide a heat-sensitive recording material that can be observed with high image quality on a shakasten.

[0005]

Means for solving the above problems are as follows. <1> In a heat-sensitive recording material having a heat-sensitive recording layer on a transparent support, the chromaticity coordinates according to JIS Z 8729 when applying energy immediately before starting color development are as follows:
L: 73-85, a ^* : -4.0-0, b ^* : 8-16, and the chromaticity coordinates at a transmission density of 3.0 measured with a Macbeth transmission density meter TD904 (visual filter). , L: 0.5 to 1.0, a ^* : 0
2.0, b ^* : a heat-sensitive recording material characterized by being in the range of -1.0 to 1.0. <2> Further, the transparent support has a back layer and a back protective layer on the side not having the heat-sensitive recording layer, and the absorption maximum wavelength is 550 to 68 in the back layer and / or the back protective layer.
<1.
> The thermosensitive recording material described in (1).

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the heat-sensitive recording material of the present invention will be described in detail. The heat-sensitive recording material of the present invention has a heat-sensitive recording layer on a support, a transparent support, and, if necessary, other layers. JIS Z 87 when the energy immediately before the start of color development is applied
29, L: 73 to 85, a ^* : -4.
0 to 0, b ^* : 8 to 16 and the chromaticity coordinates at a transmission density of 3.0 measured by a Macbeth transmission densitometer TD904 (visual filter) are L: 0.
5 to 1.0, a ^* : 0 to 2.0, b ^* : -1.0 to 1.0
Range. As a result, in medical applications such as X-rays, image diagnostic performance in low density areas is improved.

Further, the chromaticity coordinates according to JIS Z 8729 are L: 75 to 83, a ^* : -3.0 to 0, b ^* :
More preferably, it is in the range of 8 to 12.

The above range of chromaticity coordinates is obtained by including a dye in any of the layers, and the dye preferably has a maximum absorption wavelength of 550 to 680 nm. More specifically, the range of the chromaticity coordinates can be obtained by appropriately adjusting the amount of the dye to be contained in any one of the layers. Such dyes include, for example,
The following are mentioned.

[0009]

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The above dye may be contained in any layer of the heat-sensitive recording material, but is preferably contained in the back layer on the side of the transparent support not having the heat-sensitive recording layer.

Hereinafter, each layer of the heat-sensitive recording material of the present invention will be described in detail.

[Protective Layer] The protective layer is formed on the heat-sensitive recording layer, or when an intermediate layer is provided as the other layer on the heat-sensitive recording layer. The protective layer is formed by applying a protective layer coating solution, and the protective layer coating solution is used to improve head-twitching properties.
Aliphatic compound derivative having at least a -CONH- structure in the molecule (hereinafter sometimes referred to as an amide compound)
It is preferable to have Further, other components can be contained.

(Amide compound) The amide compound is represented, for example, by the following structural formulas (1) to (3).

[0014]

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In the structural formulas (1), (2) and (3), X represents H or CH ₂ OH, and R ¹ , R ² , R ³ and R ⁴ are each a saturated or unsaturated compound having 8 to 24 carbon atoms. It may be branched by a saturated alkyl group or hydroxylated. R ³ and R ⁴ may be the same or different. L is represented by the following structural formula (4).

[0016]

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In the structural formula (4), n + m = 0 to 8.
Among these, the compounds represented by the structural formulas (1) and (3) are particularly preferable, and R ¹ , R ³ and R ⁴ have 12 carbon atoms.
Preferred are -20 saturated or unsaturated alkyl groups. The alkyl group may be branched, and may have a hydroxy group in the structure. n + m is preferably 0 to 4, particularly 2 when h = 0, and preferably 0 to 2 when h = 1.

When the amide compound is a solid, 1) in the presence of a water-soluble polymer such as polyvinyl alcohol and a dispersing agent such as various surfactants, a known dispersing machine such as a homogenizer, a dissolver, or a sand mill is used to remove the acid hydrate. 2) After being dissolved in a solvent, used in the form of an emulsion with a known emulsifying device such as a homogenizer, a dissolver, or a colloid mill in the presence of a dispersant such as a water-soluble polymer or various surfactants. Can be When the amide compound is a liquid, the dispersion and the emulsion used in the form of an emulsion as described above preferably have an average particle size of 0.1 to 5.0 μm, more preferably 0.1 to 2 μm. The average particle diameter here is measured by a Horiba Seisakusho laser diffraction particle size distribution analyzer LA700 with a transmittance of 75.
% Refers to a 50% average particle size measured at ± 1%.

The ratio of the amide compound to the total dry coating amount of the protective layer is in the range of 0.5 to 10% by mass. No problem such as stickiness occurs. A more preferred range is 1 to 5% by mass. A known lubricant (paraffin wax, paraffin wax,
Higher fatty acids, higher fatty acid salts, higher fatty acid amides, silicone compounds, fluorine-containing compounds, etc.).

The protective layer of the heat-sensitive recording material of the present invention may contain a pigment in addition to the amide compound. The pigment is usually used for the purpose of making recording by a thermal head suitable, that is, for the purpose of suppressing the occurrence of sticking and abnormal noise, but it is preferable to use an organic and / or inorganic pigment.

The pigment that can be used in the protective layer has an average particle size, more specifically, a 50% volume average particle size measured by a laser diffraction method (Laser diffraction particle size distribution analyzer LA700 (manufactured by Horiba, Ltd.) ),
Average particle size of pigment particles corresponding to 50% volume in pigment. Hereinafter, it may be simply referred to as “average particle size”. ) Is 0.
The thickness is preferably from 10 to 5.00 μm. In particular, from the viewpoint of preventing the occurrence of sticking and abnormal noise between the head and the thermosensitive recording material when recording with a thermal head, the 50% volume average particle diameter is preferably 50%. 0.20-0.5
More preferably, it is in the range of 0 μm. When the 50% volume average particle size is in the range of 0.10 to 5.00 μm,
The effect of reducing abrasion on the thermal head is great, and the effect of preventing welding between the thermal head and the binder in the protective layer is great. As a result, the so-called thermal head and the protective layer of the thermal recording material adhere to each other during printing. Sticking can be effectively prevented.

The pigments contained in the protective layer include:
There is no particular limitation, and known organic and inorganic pigments can be mentioned. In particular, inorganic pigments such as calcium carbonate, titanium oxide, kaolin, aluminum hydroxide, amorphous silica and zinc oxide, and urea formalin Organic pigments such as resins and epoxy resins are preferred. Among them, kaolin,
Aluminum hydroxide and amorphous silica are more preferred. These pigments may be used alone or in combination of two or more. Among them, the surface may be coated with at least one selected from the group consisting of higher fatty acids, metal salts of higher fatty acids, and higher alcohols. As the higher fatty acid, stearic acid,
Palmitic acid, myristic acid, lauric acid and the like.

These pigments include, for example, dispersing aids such as sodium hexametaphosphate, partially saponified or completely saponified modified polyvinyl alcohol, polyacrylic acid copolymers and various surfactants, preferably partially saponified or completely saponified. In the presence of saponified modified polyvinyl alcohol and a polyacrylic acid copolymer ammonium salt, it is preferable to use the dispersion with a known disperser such as a dissolver, a sand mill, a ball mill or the like to the above-mentioned average particle size. That is, 50 of the pigment
It is preferred that the dispersion be used after being dispersed until the% volume average particle diameter becomes a particle diameter in the range of 0.10 to 5.00 μm.

(Binder) From the viewpoint of improving the transparency of the protective layer, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silica-modified polyvinyl alcohol, and the like are preferable as the binder.

(Other Components) The protective layer may contain a known hardener or the like. In order to uniformly form the protective layer on the heat-sensitive recording layer or the intermediate layer, it is preferable to add a surfactant to the coating liquid for forming the protective layer. Examples of the surfactant include sulfosuccinic acid-based alkali metal salts, fluorine-containing surfactants, and the like. Specific examples thereof include di- (2-ethylhexyl) sulfosuccinic acid and di- (n-hexyl) sulfosuccinic acid. Examples thereof include a sodium salt or an ammonium salt of an acid or the like.

Further, a surfactant, metal oxide fine particles, an inorganic electrolyte, a polymer electrolyte and the like may be added to the protective layer for the purpose of preventing the heat-sensitive recording material from being charged.

The protective layer may have a single-layer structure or a laminated structure of two or more layers. The dry coating amount of the protective layer is preferably 0.2 to 7 g / m ² , and 1 to 4 g.
/ M ² is more preferred.

[Thermal Recording Layer] The thermal recording layer contains at least a color-forming component and, if necessary, other components.

(Coloring component) The heat-sensitive recording layer may be of any composition as long as it has excellent transparency when not processed and has a property of being colored by heating. As such a heat-sensitive recording layer, a so-called two-component type heat-sensitive recording layer containing a substantially colorless color-forming component A and a substantially colorless color-forming component B that forms a color by reacting with the color-forming component A is used. However, the coloring component A or the coloring component B is preferably encapsulated in a microcapsule. Examples of the combination of the two components constituting the two-component type thermosensitive recording layer include the following (a) to (m).

(A) A combination of an electron-donating dye precursor and an electron-accepting compound. (B) Combination of a photodegradable diazo compound and a coupler. (C) an organic metal salt such as silver behenate or silver stearate;
Combination with reducing agents such as protocatechinic acid, spiroindane and hydroquinone. (D) A combination of a long-chain aliphatic salt such as ferric stearate or ferric myristate, and a phenol such as gallic acid or ammonium salicylate. (E) organic acid heavy metal salts such as salts with nickel, cobalt, lead, copper, iron, mercury, silver and the like such as acetic acid, stearic acid and palmitic acid; calcium sulfide and strontium sulfide;
Combination with alkaline earth metal sulfides such as potassium sulfide,
Alternatively, a combination of the organic acid heavy metal salt and an organic chelating agent such as s-diphenylcarbazide and diphenylcarbazone. (F) Combination of (heavy) metal sulfates such as silver sulfide, lead sulfide, mercury sulfide, and sodium sulfide with sulfur compounds such as Na-tetrathionate, sodium thiosulfate, and thiourea. (G) an aliphatic ferric salt such as ferric stearate;
Combination with an aromatic polyhydroxy compound such as 4-dihydroxytetraphenylmethane. (H) organic noble metal salts such as silver oxalate and mercury oxalate;
Combination with organic polyhydroxy compounds such as polyhydroxy alcohol, glycerin and glycol. (I) A combination of an aliphatic ferric salt such as ferric pelargonate and ferric laurate with a thiocetyl carbamide or isothiocesyl carbamide derivative. (J) A combination of a lead salt of an organic acid such as lead caproate, lead pelargonate or lead behenate with a thiourea derivative such as ethylenethiourea or N-dodecylthiourea. (K) A combination of a heavy metal salt of a higher fatty acid such as ferric stearate and copper stearate with zinc dialkyldithiocarbamate. (L) A substance that forms an oxazine dye such as a combination of resorcinol and a nitroso compound. (M) A combination of a formazan compound and a reducing agent and / or a metal salt.

Among them, in the heat-sensitive recording material of the present invention, (a) a combination of an electron-donating dye precursor and an electron-accepting compound, (b) a combination of a photodegradable diazo compound and a coupler, or ( c) It is preferable to use a combination of an organometallic salt and a reducing agent, and in particular, the above (a) or (b)
Is more preferable.

Further, the heat-sensitive recording material of the present invention comprises a heat-sensitive recording layer having a haze value calculated from (diffuse transmittance / total light transmittance) × 100 (%), and
An image having excellent transparency can be obtained. The haze value is an index indicating the transparency of the material, and is generally calculated from the total light transmission amount, the diffuse transmission light amount, and the parallel transmission light amount using a haze meter. In the present invention, as a method of lowering the haze value, for example, the 50% volume average particle diameter of both the color forming components A and B contained in the heat-sensitive recording layer is set to 1.0 μm.
m or less, preferably 0.6 μm or less, and a method in which a binder is contained in a range of 30 to 60% by mass of the total solid content of the heat-sensitive recording layer. One of the color-forming components A and B is microencapsulated, For example, there is a method in which the other layer substantially forms a continuous layer after coating and drying, for example, a method of using an emulsion or the like. It is also effective to make the refractive index of the component used in the heat-sensitive recording layer as close to a certain value as possible.

Next, the combinations (a, b, c) of the above-mentioned compositions which are preferably used in the above-mentioned heat-sensitive recording layer will be described in detail. First, (a) the combination of the electron-donating dye precursor and the electron-accepting compound will be described. The electron donor dye precursor preferably used in the present invention,
It is not particularly limited as long as it is substantially colorless, but has a property of donating electrons, or having a property of receiving a proton such as an acid to develop color,
It is preferably a colorless compound having a partial skeleton such as lactone, lactam, sultone, spiropyran, ester, amide and the like, and when these partial skeletons are contacted with an electron-accepting compound, these partial skeletons are opened or cleaved.

Examples of the electron-donating dye precursor include a triphenylmethanephthalide compound, a fluoran compound, a phenothiazine compound, an indolylphthalide compound, a leuco auramine compound, a rhodamine lactam compound, and a triamine compound. Examples include phenylmethane-based compounds, triazene-based compounds, spiropyran-based compounds, fluorene-based compounds, pyridine-based compounds, and pyrazine-based compounds.

Specific examples of the phthalides include US Pat. No. Re. 23,024, US Pat. Nos. 3,491,111, 3,491,112, and 3,491. , 116, and 3,509,174. Specific examples of the fluorans are described in US Pat. No. 3,624,107.
No. 3,627,787, No. 3,641,01
No. 1, No. 3,462,828, No. 3,681,3
No. 90, No. 3,920,510, No. 3,959,
No. 571 and the like. Specific examples of the spiropyrans include US Pat.
71,808 and the like. Examples of the pyridine-based and pyrazine-based compounds include U.S. Patent Nos. 3,775,424 and 3,853,8.
No. 69, No. 4,246,318 and the like. Specific examples of the fluorene-based compound include compounds described in Japanese Patent Application No. 61-240989. Among these, black-colored 2-arylamino-3- [H, halogen, alkyl or alkoxy-6-substituted aminofluoran] is particularly preferable.

Specifically, for example, 2-anilino-3-
Methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-N-cyclohexyl-N-methylaminofluoran, 2-p-chloroanilino-3-methyl-6-dibutylaminofluoran, 2-anilino- 3-
Methyl-6-dioctylaminofluoran, 2-anilino-3-chloro-6-diethylaminofluoran, 2-
Anilino-3-methyl-6-N-ethyl-N-isoamylaminofluoran, 2-anilino-3-methyl-6
N-ethyl-N-dodecylaminofluoran, 2-anilino-3-methoxy-6-dibutylaminofluoran,
2-o-chloroanilino-6-dibutylaminofluoran, 2-p-chloroanilino-3-ethyl-6-N-ethyl-N-isoamylaminofluoran, 2-o-chloroanilino-6-p-butylanilinofur Oran, 2-
Anilino-3-pentadecyl-6-diethylaminofluoran, 2-anilino-3-ethyl-6-dibutylaminofluoran, 2-o-toluidino-3-methyl-6
Diisopropylaminofluoran, 2-anilino-3-
Methyl-6-N-isobutyl-N-ethylaminofluoran, 2-anilino-3-methyl-6-N-ethyl-N
-Tetrahydrofurfurylaminofluoran, 2-anilino-3-chloro-6-N-ethyl-N-isoamylaminofluoran, 2-anilino-3-methyl-6-N-
Methyl-N-γ-ethoxypropylaminofluoran,
2-anilino-3-methyl-6-N-ethyl-N-γ-
Ethoxypropylaminofluoran, 2-anilino-3
-Methyl-6-N-ethyl-N- [gamma] -propoxypropylaminofluoran and the like.

Examples of the electron-accepting compound acting on the electron-donating dye precursor include acidic substances such as phenol compounds, organic acids or metal salts thereof, and oxybenzoic acid esters. And the compounds described in Japanese Patent Application Publication No. In particular,
2,2-bis (4'-hydroxyphenyl) propane (generic name: bisphenol A), 2,2-bis (4'-
Hydroxyphenyl) pentane, 2,2-bis (4′-
Hydroxy-3 ′, 5′-dichlorophenyl) propane, 1,1-bis (4′-hydroxyphenyl) cyclohexane, 2,2-bis (4′-hydroxyphenyl)
Hexane, 1,1-bis (4'-hydroxyphenyl)
Propane, 1,1-bis (4'-hydroxyphenyl)
Butane, 1,1-bis (4′-hydroxyphenyl) pentane, 1,1-bis (4′-hydroxyphenyl) hexane, 1,1-bis (4′-hydroxyphenyl) heptane, 1,1-bis ( 4'-hydroxyphenyl) octane, 1,1-bis (4'-hydroxyphenyl)-
2-methyl-pentane, 1,1-bis (4′-hydroxyphenyl) -2-ethyl-hexane, 1,1-bis (4′-hydroxyphenyl) dodecane, 1,4-bis (p-hydroxyphenylc) Mille) benzene, 1,3-
Bis (p-hydroxyphenylcumyl) benzene, bis (p-hydroxyphenyl) sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, bis (p
Bisphenols such as -hydroxyphenyl) acetic acid benzyl ester;

3,5-di-α-methylbenzylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3-
α-α-dimethylbenzylsalicylic acid, 4- (β-p-
Salicylic acid derivatives such as methoxyphenoxyethoxy) salicylic acid;

Or polyvalent metal salts thereof (particularly zinc and aluminum are preferred); benzyl ester of p-hydroxybenzoate, 2-ethylhexyl p-hydroxybenzoate, and 2- (2-phenoxyethyl) -β-resorcinate Oxybenzoic acid esters such as esters; p-phenylphenol, 3,5-diphenylphenol, cumylphenol, 4-hydroxy-4′-isopropoxy-diphenylsulfone, 4-hydroxy-4′-phenoxy-diphenylsulfone, etc. Phenols. Among them, bisphenols are particularly preferable from the viewpoint of obtaining good color-forming properties. The above-mentioned electron accepting compounds may be used alone or in combination of two or more.

Next, the combination (b) of the photodegradable diazo compound and the coupler will be described. The photodegradable diazo compound is a compound that undergoes a coupling reaction with a coupler, which is a coupling component described below, to produce a desired hue, and is decomposed when receiving light in a specific wavelength range before the reaction, and is no longer coupled. It is a photo-degradable diazo compound that does not have a coloring ability even if a component is present. The hue in this color forming system is determined by the diazo dye formed by the reaction between the diazo compound and the coupler. Therefore, the color hue can be easily changed by changing the chemical structure of the diazo compound or the coupler, and depending on the combination,
Any color hue can be obtained.

The photo-decomposable diazo compound preferably used in the present invention includes an aromatic diazo compound, and specifically, an aromatic diazonium salt, a diazosulfonate compound, a diazoamino compound and the like. Examples of the aromatic diazonium salt include compounds represented by the following general formula, but are not limited thereto. The aromatic diazonium salt is preferably one having excellent light fixing property, little generation of colored stain after fixing, and a stable coloring part. Ar-N ₂ ⁺ X ^{-In the} above formula, Ar represents a substituted or unsubstituted aromatic hydrocarbon ring group, N ₂ ⁺ represents a diazonium group, X
^- represents an acid anion.

Many diazosulfonate compounds are known in recent years, and are obtained by treating each diazonium salt with a sulfite, and can be suitably used in the heat-sensitive recording material of the present invention. .

The diazoamino compound can be obtained by coupling a diazo group with dicyandiamide, sarcosine, methyltaurine, N-ethylanthranic acid-5-sulfonic acid, monoethanolamine, diethanolamine, guanidine or the like. It can be suitably used for the heat-sensitive recording material of the present invention. Details of these diazo compounds are described in detail, for example, in JP-A-2-136286.

On the other hand, examples of the coupler capable of performing a coupling reaction with the above-mentioned diazo compound include, for example, 2-hydroxy-
In addition to 3-naphthoic anilide, resorcinol, and those described in JP-A-62-146678 and the like can be mentioned.

In the case where a combination of a diazo compound and a coupler is used in the heat-sensitive recording layer, the sensitization is carried out from the viewpoint that the coupling reaction is carried out in a basic atmosphere so that the reaction can be further accelerated. A basic substance may be added as an agent. Examples of the basic substance include a water-insoluble or hardly soluble basic substance and a substance that generates an alkali by heating, for example, an inorganic or organic ammonium salt, an organic amine, an amide, urea or thiourea or a derivative thereof, Thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indoles, imidazoles, imidazolines, triazoles, morpholines, piperidines, amidines,
Nitrogen-containing compounds such as forimazines or pyridines are exemplified. Specific examples of these are described in, for example,
No. 1,291,183, and the like.

Next, (c) a combination of an organic metal salt and a reducing agent will be described. Specific examples of the organic metal salt include silver salts of long-chain aliphatic carboxylic acids such as silver laurate, silver myristate, silver palmitate, silver stearate, silver arachiate or silver behenate; silver benzotriazole Silver salt of an organic compound having an imino group such as salt, silver benzimidazole, silver carbazole or silver phthalazinone; silver salt of a sulfur-containing compound such as s-alkylthioglycolate; fragrance such as silver benzoate and silver phthalate Silver salt of aromatic carboxylic acid; silver salt of sulfonic acid such as silver ethanesulfonate; o
Silver salts of sulfinic acids such as silver toluenesulfinate; silver salts of phosphoric acid such as silver phenylphosphate; silver barbiturates;
Examples include silver saccharinate, silver salt of salicyl asdoxime, or any mixture thereof. Of these, silver salts of long-chain aliphatic carboxylic acids are preferred, and silver behenate is more preferred. Also, behenic acid may be used together with silver behenate.

The reducing agent is disclosed in JP-A-53-102.
No. 0, page 227, lower left column, line 14 to page 229, upper right column, line 11 can be used as appropriate. Among them, mono, bis, tris or tetrakisphenols, mono or bisnaphthols, di or polyhydroxynaphthalenes, di or polyhydroxybenzenes,
Hydroxy monoethers, ascorbic acids, 3-pyrazolidones, pyrazolines, pyrazolones, reducing sugars, phenylenediamines, hydroxylamines, reductones, hydroxamic acids, hydrazides, amide oximes, N-hydroxyurea It is preferable to use a class or the like. Among the above, aromatic organic reducing agents such as polyphenols, sulfonamidophenols and naphthols are particularly preferred.

In order to ensure sufficient transparency of the heat-sensitive recording material, the heat-sensitive recording layer may contain (a) a combination of an electron-donating dye precursor and an electron-accepting compound, or (b) a photo-decomposable diazo compound. It is preferable to use a combination of and a coupler. In the present invention, it is preferable to use one of the color-forming component A and the color-forming component B after microencapsulation, and use the electron-donating dye precursor or the photodecomposable diazo compound after microencapsulation. Is more preferable.

(Microcapsules) The method for producing microcapsules will be described below in detail. The production of microcapsules includes an interfacial polymerization method, an internal polymerization method, an external polymerization method and the like, and any method can be adopted. As described above, the heat-sensitive recording material of the present invention is an electron-donating dye precursor,
Alternatively, it is preferable to microencapsulate the photodegradable diazo compound, particularly, an oil phase prepared by dissolving or dispersing the electron-donating dye precursor serving as the core of the capsule, or the photodegradable diazo compound in a hydrophobic organic solvent. Is mixed in an aqueous phase in which a water-soluble polymer is dissolved, and emulsified and dispersed by means of a homogenizer or the like, and then heated to cause a polymer formation reaction at the oil droplet interface, thereby forming a microcapsule wall of the polymer substance. Is preferably employed.

The reactant forming the polymer substance is added to the inside and / or outside of the oil droplet. Specific examples of the polymer substance include polyurethane, polyurea, polyamide, polyester, polycarbonate, urea-formaldehyde resin, melamine resin, polystyrene, styrene methacrylate copolymer, styrene-acrylate copolymer and the like. Among these, polyurethane, polyurea, polyamide, polyester,
Polycarbonates are preferred, and polyurethanes and polyureas are particularly preferred.

For example, when polyurea is used as a capsule wall material, a polyisocyanate such as diisocyanate, triisocyanate, tetraisocyanate and polyisocyanate prepolymer, and a polyamine such as diamine, triamine and tetraamine are used. The microcapsule wall can be easily formed by reacting the above prepolymer having an amino group, piperazine or a derivative thereof, or a polyol with the above-mentioned aqueous phase by an interfacial polymerization method.

Further, for example, a composite wall composed of polyurea and polyamide or a composite wall composed of polyurethane and polyamide is, for example, a polyisocyanate and a second substance which reacts therewith to form a capsule wall (for example, acid chloride or polyamine, Polyol) can be prepared by mixing a water-soluble polymer aqueous solution (aqueous phase) or an oil medium (oil phase) to be encapsulated, emulsifying and dispersing these, and then heating. Details of the method for producing the composite wall composed of polyurea and polyamide are described in JP-A-58-66948.

As the polyisocyanate compound,
A compound having a trifunctional or higher isocyanate group is preferred, but a bifunctional isocyanate compound may be used in combination. Specifically, diisocyanates such as xylene diisocyanate and its hydrogenated product, hexamethylene diisocyanate, tolylene diisocyanate and its hydrogenated product, and isophorone diisocyanate are used as main raw materials, and dimers of these dimers are used. Alternatively, in addition to a trimer (buret or isocyanurate), a polyfunctional adduct of a polyol such as trimethylolpropane and a bifunctional isocyanate such as xylylene diisocyanate, or a polyol such as trimethylolpropane and xylylene Examples thereof include a compound obtained by introducing a high molecular weight compound such as polyether having active hydrogen such as polyethylene oxide into an adduct with a bifunctional isocyanate such as range isocyanate, and a formalin condensate of benzene isocyanate. JP-A-62-2
Compounds described in JP-A-12190, JP-A-4-26189, JP-A-5-317694, and Japanese Patent Application No. 8-268721 are preferred.

The polyisocyanate is preferably added so that the microcapsules have an average particle size of 0.3 to 12 μm and the thickness of the capsule wall is 0.01 to 0.3 μm. The dispersed particle diameter is generally about 0.2 to 10 μm.

Specific examples of polyols and / or polyamines added to the aqueous phase and / or the oil phase as one of the constituents of the microcapsule wall by reacting with the polyisocyanate include propylene glycol, glycerin, trimethylol Examples include propane, triethanolamine, sorbitol, hexamethylenediamine and the like. When a polyol is added, a polyurethane wall is formed.
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. The details of polyisocyanates, polyols, reaction catalysts, and polyamines for forming a part of the wall material are described in detail in Polygraphs (Polyurethane Handbook, edited by Keiji Iwata, Nikkan Kogyo Shimbun (1987)).

Further, a metal-containing dye, a charge control agent such as nigrosine, or any other additive substance can be added to the microcapsule wall as required. These additives can be included in the capsule wall at the time of wall formation or at any time. In addition, a monomer such as a vinyl monomer may be graft-polymerized in order to adjust the chargeability of the capsule wall surface as needed.

Further, in order to make the microcapsule wall excellent in material permeability even under a lower temperature condition and rich in color developability, it is preferable to use a plasticizer suitable for the polymer used as the wall material. The plasticizer preferably has a melting point of 50 ° C. or higher, and more preferably has a melting point of 120 ° C. or lower. Among them, those solid at room temperature can be suitably selected and used. For example, when the wall material is made of polyurea or polyurethane, a hydroxy compound,
Carbamate compounds, aromatic alkoxy compounds, organic sulfonamide compounds, aliphatic amide compounds,
Arylamide compounds and the like are preferably used.

In the preparation of the oil phase, the hydrophobic organic solvent used for dissolving the electron-donating dye precursor or the photo-decomposable diazo compound to form the core of the microcapsule has a boiling point of 100 to 300. Organic solvents at 0 ° C are preferred. Specifically, in addition to esters, dimethylnaphthalene, diethylnaphthalene, diisopropylnaphthalene,
Dimethylbiphenyl, diisopropylbiphenyl, diisobutylbiphenyl, 1-methyl-1-dimethylphenyl-2-phenylmethane, 1-ethyl-1-dimethylphenyl-1-phenylmethane, 1-propyl-1-dimethylphenyl-1-phenylmethane , Triallylmethane (eg, tritolylmethane, toluyldiphenylmethane), terphenyl compound (eg, terphenyl), alkyl compound, alkylated diphenylether (eg, propyldiphenylether), hydrogenated terphenyl (eg, hexahydroterphenyl) , Diphenyl ether and the like. Among these, the use of esters is particularly preferred from the viewpoint of the emulsion stability of the emulsified dispersion.

Examples of the esters include phosphoric esters such as triphenyl phosphate, tricresyl phosphate, butyl phosphate, octyl phosphate and cresyl phenyl phosphate;
Phthalates such as dibutyl phthalate, 2-ethylhexyl phthalate, ethyl phthalate, octyl phthalate, and butyl benzyl phthalate; dioctyl tetrahydrophthalate; ethyl benzoate, propyl benzoate, butyl benzoate, isopentyl benzoate; Benzoic acid esters such as benzyl benzoate; abietic acid esters such as ethyl abietic acid and benzyl abietic acid; dioctyl adipate; isodecyl succinate; dioctyl azelate;
Oxalic esters such as dibutyl oxalate and dipentyl oxalate; diethyl malonate; maleic esters such as dimethyl maleate, diethyl maleate and dibutyl maleate; tributyl citrate; methyl sorbate, ethyl sorbate, butyl sorbate and the like Sorbic acid esters; sebutylic acid esters such as dibutyl sebacate and dioctyl sebacate; monoesters and diesters of formic acid;
Butyric acid monoesters and diesters, lauric acid monoesters and diesters, palmitic acid monoesters and diesters, stearic acid monoesters and diesters,
Ethylene glycol esters such as oleic acid monoesters and diesters; triacetin; diethyl carbonate; diphenyl carbonate; ethylene carbonate; propylene carbonate; and boric esters such as tributyl borate and tripentyl borate.

Of these, the use of tricresyl phosphate alone or as a mixture is particularly preferred because the emulsion has the best stability. It is also possible to use the above oils together or in combination with other oils.

When the solubility of the electron-donating dye precursor or the photo-decomposable diazo compound to be encapsulated in the hydrophobic organic solvent is poor, a low-boiling solvent having high solubility is used in combination. Can also. Preferred examples of such a low-boiling solvent include ethyl acetate, isopropyl acetate, butyl acetate, and methylene chloride.

When the electron-donating dye precursor or the photo-decomposable diazo compound is used in the heat-sensitive recording layer of the heat-sensitive recording material, the content of the electron-donating dye precursor is 0.1 to 5.
Preferably ^{0g / m 2, 1.0~4.0g / m} 2 is more preferable. Further, the content of the photodegradable diazo compound,
0.02 to 5.0 g / m ² is preferable, and 0.10 to 4.0 g / m ² is more preferable from the viewpoint of color density.

When the content of the electron-donating dye precursor is 0.1%,
To be in the range of 1~5.0g / m ^2, sufficient color density can be obtained and a sufficient color density ,, the content of both is within 5.0 g / m ² is held, and The transparency of the heat-sensitive recording layer can be maintained.

On the other hand, an aqueous solution in which a water-soluble polymer is dissolved as a protective colloid is used for the aqueous phase to be used. After the oil phase is added to the aqueous phase, emulsification and dispersion are performed by means of a homogenizer or the like. Serves as a dispersion medium for making the dispersion uniform and easy and for stabilizing the emulsified aqueous solution. Here, in order to more uniformly emulsify and disperse and stabilize, a surfactant may be added to at least one of the oil phase and the aqueous phase. As the surfactant, a well-known surfactant for emulsification can be used. The amount of the surfactant added was 0.1 to the mass of the oil phase.
-5% is preferable, and 0.5-2% is more preferable.

As the surfactant to be contained in the aqueous phase, a surfactant which does not cause precipitation or aggregation by acting on the protective colloid is preferably selected from anionic or nonionic surfactants. it can. Preferred surfactants include, for example, sodium alkylbenzenesulfonate, sodium alkylsulfate, dioctyl sodium sulfosuccinate, polyalkylene glycol (eg, polyoxyethylene nonyl phenyl ether) and the like.

In the emulsification, the oil phase containing the above components and the aqueous phase containing the protective colloid and the surfactant are stirred at a high speed.
The emulsification can be easily carried out by using a means commonly used for emulsification of fine particles such as ultrasonic dispersion, for example, a known emulsifying apparatus such as a homogenizer, a Manton-Gawley, an ultrasonic disperser, a dissolver, and a Keddy mill. After the emulsification, the emulsion is preferably heated to 30 to 70 ° C. in order to promote the capsule wall forming reaction. During the reaction, in order to prevent aggregation of the capsules, it is preferable to reduce the probability of collision between the capsules by adding water or to perform sufficient stirring.

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

(Emulsified Dispersion) When an electron-donating dye precursor or a photo-decomposable diazo compound is encapsulated as a core substance, the electron-accepting compound or coupler to be used is:
For example, together with a water-soluble polymer and an organic base, other color-forming auxiliaries, etc., it can be used as a solid dispersion by means of a sand mill or the like, but after previously dissolved in a hardly water-soluble or insoluble high-boiling organic solvent, This is more preferably mixed with a polymer aqueous solution (aqueous phase) containing a surfactant and / or a water-soluble polymer as a protective colloid and emulsified with a homogenizer or the like and used as an emulsified dispersion. In this case, if necessary, a low boiling point solvent can be used as a dissolution aid. Further, the coupler and the organic base can be separately emulsified and dispersed, or can be mixed and then dissolved in a high boiling organic solvent to be emulsified and dispersed. Preferred emulsified dispersion particle size is 1 μm
It is as follows.

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

The water-soluble polymer contained as the above protective colloid can be appropriately selected from among known anionic polymers, nonionic polymers, and amphoteric polymers. A water-soluble polymer having a solubility in water of 5% or more is preferable. Specific examples thereof include polyvinyl alcohol or a modified product thereof, polyacrylamide or a derivative thereof, an ethylene-vinyl acetate copolymer, and a styrene-maleic anhydride copolymer. Coalesce, ethylene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyvinylpyrrolidone, ethylene-acrylic acid copolymer, vinyl acetate-acrylic acid copolymer,
Examples include cellulose derivatives such as carboxymethylcellulose and methylcellulose, casein, gelatin, starch derivatives, gum arabic, sodium alginate and the like. Among these, polyvinyl alcohol, gelatin and cellulose derivatives are particularly preferred.

The mixing ratio of the oil phase to the aqueous phase (mass of the oil phase / mass of the aqueous phase) is preferably 0.02 to 0.6.
1 to 0.4 is more preferable. When the mixing ratio is 0.02-0.
When it is in the range of 6, the viscosity can be maintained at an appropriate level, the production suitability is excellent, and the coating liquid stability is excellent.

When an electron-accepting compound is used in the heat-sensitive recording material of the present invention, the amount of the electron-accepting compound is preferably 0.5 to 30 parts by mass, and more preferably 1 to 30 parts by mass, based on 1 part by mass of the electron-donating dye precursor. 0.0 to 10 parts by mass is more preferable. When a coupler is used in the heat-sensitive recording material of the present invention, the amount of the coupler is preferably 0.1 to 30 parts by mass with respect to 1 part by mass of the diazo compound.

(Coating solution for heat-sensitive recording layer) The coating solution for heat-sensitive recording layer can be prepared, for example, by mixing the microcapsule solution prepared as described above with an emulsified dispersion. Here, the water-soluble polymer used as a protective colloid in the preparation of the microcapsule liquid, and the water-soluble polymer used as a protective colloid in the preparation of the emulsified dispersion, as a binder in the thermosensitive recording layer Function. Further, a coating solution for a heat-sensitive recording layer may be prepared by adding and mixing a binder separately from these protective colloids. As the binder to be added, a water-soluble binder is generally used, and polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, epichlorohydrin-modified polyamide, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer Coalescing,
Isobutylene-maleic salicylic anhydride copolymer, polyacrylic acid, polyacrylamide, methylol-modified polyacrylamide, starch derivatives, casein, gelatin and the like. Further, a water-proofing agent may be added to these binders for the purpose of imparting water resistance, or an emulsion of a hydrophobic polymer, specifically, a styrene-butadiene rubber latex, an acrylic resin emulsion, or the like may be added.

When applying the coating solution for a heat-sensitive recording layer onto a support, a known coating means used for an aqueous or organic solvent-based coating solution is used. In this case, the coating solution for a heat-sensitive recording layer can be used safely and safely. In order to uniformly coat and maintain the strength of the coating film, in the heat-sensitive recording material of the present invention, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, starch, gelatin, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, polyacrylamide, polystyrene or The copolymer, polyester or its copolymer, polyethylene or its copolymer, epoxy resin, acrylate resin or its copolymer, methacrylate resin or its copolymer, polyurethane resin, polyamide resin, polyvinyl butyral resin Using etc. It can be.

(Other Components) Hereinafter, other components that can be used in the heat-sensitive recording layer will be described. The other components are not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include known heat-fusible substances, ultraviolet absorbers, and antioxidants.

The heat-fusible substance can be contained in the heat-sensitive recording layer for the purpose of improving the thermal response. As the heat-fusible substance, aromatic ether, thioether,
Esters, aliphatic amides, ureides and the like. These examples are described in JP-A-58-57989 and JP-A-58-87.
Nos. 094, 61-58789, 62-10968
No. 1, 62-132677, 63-151478
No. 63-235961, JP-A-2-184489.
And JP-A-2-215585.

Examples of the ultraviolet absorber preferably include a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, a salicylic acid ultraviolet absorber, a cyanoacrylate ultraviolet absorber, and an oxalic acid anilide ultraviolet absorber. Can be These examples are disclosed in
Nos. 7-10537, 58-111942, 58-
No. 212844, No. 59-19945, No. 59-46
No. 646, No. 59-109055, No. 63-5354
No. 4, JP-B-36-10466, 42-26187
No. 48-30492, No. 48-31255, No. 48-41572, No. 48-54965, No. 50-
10726, U.S. Pat. No. 2,719,086
No. 3,707,375, No. 3,754,919
No. 4,220,711.

The antioxidants include hindered amine antioxidants, hindered phenol antioxidants,
An aniline-based antioxidant and a quinoline-based antioxidant are preferably exemplified. These examples are disclosed in JP-A-59-15509.
No. 0, No. 60-107383, No. 60-107384
Nos. 61-137770 and 61-139481
And JP-A-61-160287.

The amount of the other components to be applied is set to 0.1.
About 0.5 to 1.0 g / m ² , preferably 0.1 to 0.4 g / m ^2.
g / m ² is more preferred. The other components are
It may be added inside the microcapsule or outside the microcapsule.

The heat-sensitive recording layer has an energy necessary for obtaining a saturated transmission density (D _T-max ) in order to suppress a density unevenness or the like caused by a slight difference in thermal conduction of a thermal head and to obtain a high-quality image. It is preferable that the thermosensitive recording layer has a wide range, that is, a wide dynamic range. The heat-sensitive recording material of the invention has a heat-sensitive recording layer as described above, and has a thickness of 90 to 150 m.
J / mm ² range of thermal energy, transmission density D
It is preferably a heat-sensitive recording layer having a characteristic which can be obtained _T 3.0.

The heat-sensitive recording layer is coated so that the dry coating amount after coating and drying is 1 to 25 g / m ² .
It is preferable that the coating be performed so that the thickness of the layer is 1 to 25 μm. The heat-sensitive recording layer can be used by laminating two or more layers. In this case, application of the entire thermosensitive recording layer,
The dry coating amount after drying is preferably 1 to 25 g / m ² .

[Support] In the heat-sensitive recording material of the present invention, a transparent support is used to obtain a transparent heat-sensitive recording material.
As a transparent support, polyester films such as polyethylene terephthalate and polybutylene terephthalate,
Synthetic polymer films such as cellulose triacetate film and polyolefin films such as polypropylene and polyethylene can be used, and these can be used alone or in combination. The thickness of the synthetic polymer film is preferably from 25 to 250 μm, more preferably from 50 to 200 μm.

The above-mentioned synthetic polymer film may be colored in an arbitrary hue. As a method of coloring a polymer film, a method of kneading a resin with a dye before forming a resin film to form a film, a coating solution in which the dye is dissolved in an appropriate solvent is prepared, and this is a colorless transparent resin A known coating method such as a gravure coating method, a roller coating method, a wire coating method, or the like, may be used on the film. Among them, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate in which a blue dye is kneaded is formed into a film, which is subjected to a heat treatment, a stretching treatment, and an antistatic treatment.

[Back Layer] A back layer (ultraviolet filter layer) may be provided on the back side of the support opposite to the coated surface of the heat-sensitive recording layer for the purpose of preventing image fading. The back layer contains a benzotriazole-based, benzophenone-based, hindered amine-based ultraviolet absorber or the like.

[Back Protective Layer] A back protective layer containing fine particles having an average particle size of 1 to 20 μm, preferably 1 to 10 μm, is formed on the back surface of the support opposite to the coated surface of the heat-sensitive recording layer (light reflection preventing layer). ) May be provided. By applying this back protective layer, the glossiness measured at an incident light angle of 20 ° is 50%.
It is preferably at most 30%, more preferably at most 30%. Examples of the fine particles contained in the back protective layer include fine particles such as starch obtained from barley, wheat, corn, rice, and beans, cellulose fiber, polystyrene resin, epoxy resin, polyurethane resin, urea formalin resin, poly (meta). A) acrylate resin, polymethyl (meth) acrylate resin, copolymer resin such as vinyl chloride or vinyl acetate, fine particles of synthetic polymer such as polyolefin, calcium carbonate, titanium oxide, kaolin, smectite clay, aluminum hydroxide, silica, oxidation Examples include fine particles of inorganic substances such as zinc. These may be used alone or in combination of two or more. Also,
From the viewpoint of improving the transparency of the heat-sensitive recording material, it is preferable that the heat-sensitive recording material is a particulate material having a refractive index of 1.45 to 1.75.

[Other Layers] The heat-sensitive recording material of the present invention comprises:
On the support, an intermediate layer, an undercoat layer and the like can be provided as other layers.

(Intermediate Layer) The intermediate layer is preferably formed on the thermosensitive recording layer. The intermediate layer is provided to prevent mixing of the layers and to block gases (such as oxygen) that are harmful to image storability. The binder used is not particularly limited, and polyvinyl alcohol, gelatin, polyvinylpyrrolidone, a cellulose derivative, or the like can be used depending on the system. In addition, various surfactants may be added to impart coating suitability. Further, in order to further enhance gas barrier properties, inorganic fine particles such as mica are used in an amount of 2 to 20% by mass, more preferably 5 to 10% by mass, based on the binder.
It may be added.

(Undercoat layer) In the heat-sensitive recording material of the present invention, before the heat-sensitive recording layer containing microcapsules or the like, the anti-reflection layer, etc. In addition, an undercoat layer can be provided on the support. As the undercoat layer, an acrylate copolymer, polyvinylidene chloride, SBR, aqueous polyester, or the like can be used.
5 to 0.5 μm is preferred.

When the heat-sensitive recording layer is coated on the undercoat layer, the undercoat layer may swell due to moisture contained in the heat-sensitive recording layer coating solution, and the image recorded on the heat-sensitive recording layer may be deteriorated. Glutaraldehyde, 2,
It is preferable to harden using a dialdehyde such as 3-dihydroxy-1,4-dioxane and a hardening agent such as boric acid. The addition amount of these hardeners can be appropriately added in the range of 0.2 to 3.0% by mass according to the mass of the undercoat material in accordance with the desired degree of curing.

(Thermal head) The thermal head used in the thermal recording system of the present invention is formed on the glaze layer by using a known film forming apparatus so that the carbon ratio of the uppermost layer in contact with the thermal recording material is 90% or more. In addition, a protective layer is provided on a heating element having a heating resistor and an electrode. The head protective layer may be two or more layers, but at least the uppermost layer must have a carbon ratio of 90% or more.

The heat-sensitive recording material of the present invention can be suitably produced by the method for producing a heat-sensitive recording material of the present invention described below, but is not limited thereto, and is produced by another production method. You can also. Since the heat-sensitive recording material of the present invention contains a specific amide compound in the protective layer, it does not easily generate sticking or noise at the time of application, has excellent abrasion resistance, and has a carbon ratio of 90% or more. Since it has a sufficient head matching property even with a thermal head having an upper layer, it is suitably used particularly in a field requiring high image quality such as a medical recording medium.

[0092]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples.

(Example 1) [Preparation of coating liquid for protective layer] (Preparation of pigment dispersion for protective layer) Stearic acid-treated aluminum hydroxide (trade name: Hygilite H42S, Showa Denko 30 g) 3
After stirring for an hour, a dispersion aid (trade name: Poise 53)
2A, manufactured by Kao Corporation) 0.8 g, 10% by mass aqueous solution of polyvinyl alcohol (trade name: PVA105, manufactured by Kuraray Co., Ltd.) 30 g, adjusted to the following structural formula [10
0], and dispersed by a sand mill to obtain a pigment dispersion for protective layer having an average particle size of 0.30 µm. The “average particle size” is obtained by dispersing a pigment to be used in the presence of a dispersing agent, diluting the pigment dispersion immediately after the dispersion to 0.5% by mass with water, and adding a test solution at 40 ° C. And adjusted to have a light transmittance of 75 ± 1.0%, then subjected to ultrasonic treatment for 30 seconds, and measured with a laser diffraction particle size distribution analyzer (trade name: LA700, manufactured by Horiba, Ltd.). The average particle size of the pigment particles corresponding to 50% volume of the total pigment is used, and the “average particle size” described below all represents the average particle size measured by the same method.

[0094]

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(Preparation of Coating Solution for Protective Layer) In 65 g of water, 8 mass% aqueous polyvinyl alcohol solution (trade name: PVA124C, manufactured by Kuraray Co., Ltd.) 90 g 20.5 mass% zinc stearate dispersion (trade name: F155) 5.5 g 21.5 mass% stearic acid amide compound (trade name: G-270, manufactured by Chukyo Yushi Co., Ltd.) 3.8 g 18.0 mass% stearic acid (trade name: Cerosol 920, manufactured by Chukyo Yushi Co., Ltd.) 2.8 g 40% aqueous solution of boric acid 10 g Pigment dispersion for protective layer (18% by mass) 70 g 35% by mass aqueous silicone oil dispersion (polydimethylsiloxane, trade name: BY22-840) Toray Dow Corning Co., Ltd.) 4.7 g 10 mass% sodium dodecylbenzenesulfonate aqueous solution 6.5 g 6 mass% styrene-male Aqueous solution of acid copolymer ammonium salt (trade name: Polymeron 385, manufactured by Arakawa Chemical Co., Ltd.) 17.5 g 20% colloidal silica (trade name: Snowtex, manufactured by Nissan Chemical Co., Ltd.) 14 g 10% Surflon S131S (Seimi Chemical Co., Ltd.) 16 g Plysurf A217 (Daiichi Kogyo Seiyaku Co., Ltd.) 1.1 g 2% acetic acid 8 g was mixed to obtain a coating solution for a protective layer.

[Preparation of Coating Solution for Thermosensitive Recording Layer] Each of a microcapsule coating solution and a developer emulsified dispersion was prepared as follows. (Preparation of Microcapsule Coating Solution A) As a color former, a compound represented by the following structural formula [201] 11.7 g A compound represented by the following structural formula [202] 1.5 g represented by the following structural formula [203] Compound 2.2 g Compound represented by the following structural formula [204] 5.65 g Compound represented by the following structural formula [205] 1.2 g Compound represented by the following structural formula [206] 1.1 g 0.57 g of the compound represented by [207]

[0097]

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[0098]

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[0099]

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Was added to 24.3 g of ethyl acetate.
, And then cooled to 45 ° C. To this, 13.1 g of capsule wall material (trade name: Takenate D140N, manufactured by Takeda Pharmaceutical Co., Ltd.) and 2.3 g of Vernock D750 (manufactured by Dainippon Ink Industries, Ltd.) were added and mixed.

An aqueous solution of 8% by mass of polyvinyl alcohol (trade name: PVA217C,
(Kuraray Co., Ltd.) was added to the aqueous phase mixed with 48 g,
Emulsification was carried out at 15,000 rpm for 5 minutes using an ace homogenizer (manufactured by Nippon Seiki Co., Ltd.). After 110 g of water and 1.0 g of tetraethylenepentamine were further added to the obtained emulsion, an encapsulation reaction was carried out at 60 ° C. for 4 hours to prepare a microcapsule coating solution having an average particle diameter of 0.35 μm.

(Preparation of Microcapsule B) Compound represented by Structural Formula [201] 12.2 g Compound represented by Structural Formula [202] 1.6 g Compound represented by Structural Formula [203] 2.4 g Structure Compound represented by formula [204] 3.3 g Compound represented by structural formula [205] 1.5 g Compound represented by structural formula [206] 0.2 g Compound represented by structural formula [207] 5 g was added to 21 g of ethyl acetate, heated and dissolved at 70 ° C., and then cooled to 35 ° C. N-Butanol 0.5
g, Takenate D127N (manufactured by Takeda Pharmaceutical Co., Ltd.)
1 g, and Takenate D110N (manufactured by Takeda Pharmaceutical Co., Ltd.)
2.5 g was added, and the temperature was kept at 35 ° C. for 40 minutes.

This solution was dissolved in 16.6 g of water with 8% by weight of polyvinyl alcohol (PVA217C, manufactured by Kuraray Co., Ltd.).
48.1 g was added to the mixed aqueous phase, and emulsified at 15000 rpm for 5 minutes using an ace homogenizer (manufactured by Nippon Seiki Co., Ltd.). Water 112 is further added to the obtained emulsion.
g and 0.9 g of tetraethylenepentamine were added, followed by performing an encapsulation reaction at 60 ° C. for 4 hours to prepare a microcapsule solution having an average particle diameter of 0.35 μm.

(Preparation of Developer Microemulsified Dispersion) A compound represented by the following structural formula [301] 6.7 g as a developer 8.0 g of a compound represented by the following structural formula [302] 8.0 g Compound represented by the following structural formula [305] 5.8 g Compound represented by the following structural formula [304] 1.5 g Compound represented by the following structural formula [305] 2.2 g Compound represented by the following structural formula [306] 0 .8 g Compound represented by the following structural formula [307] 4.3 g

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[0106]

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1.0 g of tricresyl phosphate,
15. ethyl acetate together with 0.5 g of diethyl maleate.
5 g and heated to 70 ° C. to dissolve. This solution was treated with 70 g of water, 57 g of an 8% by mass aqueous polyvinyl alcohol solution (PVA217C, manufactured by Kuraray Co., Ltd.), and a 15% by mass aqueous solution of polyvinyl alcohol (trade name: PVA20).
5C, manufactured by Kuraray Co., Ltd.) 20 g, the following structural formula [401]
And 11.5 g of a 2% by mass aqueous solution of a compound represented by the following formula and a compound represented by the following structural formula [402] were added to an aqueous phase, and then added.

[0108]

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Ace homogenizer (Nippon Seiki Co., Ltd.)
At 10,000 rpm and an average particle size of 0.7
The emulsion was emulsified to a thickness of μm to obtain a developer emulsified dispersion.

(Preparation of Coating Solution A for Thermosensitive Recording Layer) Microcapsule Coating Solution A (solid content: 23% by mass) 12
g, 2.5 g of microcapsule B (24%), 50 g of the developer emulsified dispersion (solid content: 22% by mass), and 0.7 g of a 50% by mass aqueous solution of a compound represented by the following structural formula [403]. 1.8 g of colloidal silica (manufactured by Snowtex Nissan Chemical Industries, Ltd.) was mixed to prepare a coating solution A for a heat-sensitive recording layer.

[0111]

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[Preparation of Coating Solution C for Thermosensitive Recording Layer] Microcapsule A (23%) 2.3 g Microcapsule B (24%) 6.6 g Developer (22%) 33 g Colloidal silica (Snowtex, Nissan Scientific) 1.5 g of the compound represented by the structural formula [403] was mixed to prepare a coating solution B for a heat-sensitive recording layer.

[Preparation of Coating Solution C for Thermosensitive Recording Layer] 6% by mass
35 g of an aqueous PVA solution (trade name: PVA124C, manufactured by Kuraray Co., Ltd.), 2 g of a 2% aqueous solution of a compound represented by the following structural formula [404], and microcapsule A (23%) 0.5
g was dissolved in 5 g of water to prepare a coating solution C for a heat-sensitive recording layer.

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[Preparation of Coating Solution for BC Layer (Back Layer)] A gelatin dispersion containing 1 kg of lime-processed gelatin and 12% by mass of a spherical PMMA matting agent having an average particle size of 5.7 μm was prepared by adding 7%.
57 g of an emulsion of an ultraviolet absorber containing the compounds represented by the structural formulas [501] to [505] at the following content:
761 g (The content of the ultraviolet absorbent per kg of the emulsion is 9.8 g of the compound represented by the structural formula [501] 8.4 g The compound represented by the structural formula [503] 9.8 g Compound represented by Structural Formula [504] 13.9 g Compound represented by Structural Formula [505] 29.3 g 1,2-Benzisothiazolin-3-one 1.75 g Poly (p-vinylbenzenesulfonic acid) (Sodium) (Molecular weight: about 400,000) 64.2 g Compound represented by the structural formula [506] 5.0 g Polyethyl acrylate latex 20% solution 3,180 ml N, N-ethylene-bis (vinylsulfonylacetamide) 75.0 g 1 2,3-bis (vinylsulfonylacetamide) propane 25.0 g Add water to a total volume of 62.77 liters. Was prepared.

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[Preparation of Coating Solution for BPC Layer (Back Protective Layer)] 1 kg of lime-treated gelatin, average particle size 0.70 μm
2,000 g of a gelatin dispersion containing 15% by mass of a spherical PMMA matting agent of m.
1,75-benzisothiazolin-3-one
g, sodium polyacrylate (molecular weight about 100,000)
4.4 g, 54.0 g of poly (sodium p-vinylbenzenesulfonate) (molecular weight: about 400,000), 25.2 g of sodium pt-octylphenoxypolyoxyethylene-ethylsulfonate, N-propyl-N- 5.3 g of sodium polyoxyethylene-perfluorooctanesulfonamidobutylsulfonate, 7.1 g of potassium perfluorooctanesulfonate, p with caustic soda
After adjusting to H = 7.0, water was added to adjust the total amount to 66.79 liters.

On a transparent PET support (having a thickness of 180 μm), the coating amount for the BC layer and the coating solution for the BPC layer were 44.0 ml / m ² and 1 in that order from the side close to the support.
The coating was performed at 8.5 ml / m ² and dried.

[Preparation of thermosensitive recording material] On the surface of the support coated with the BC layer opposite to the BC layer, from the side close to the support, the thermosensitive coloring layers A, B, C and the protective layer In the order of the coating liquid, the coating amounts were 50 ml / m ² , 20 ml / m ² ,
The coating was dried at 25 ml / m ² and 25 ml / m ² to obtain a transparent heat-sensitive recording material of the present invention.

Comparative Example 1 The procedure of Example 1 was repeated except that the following solution was used as the BC layer (back layer) coating solution.
A heat-sensitive recording material was obtained in exactly the same manner as in Example 1.

[Preparation of Coating Solution for BC Layer (Back Layer)] A gelatin dispersion containing 1 kg of lime-processed gelatin and 12% by mass of a spherical PMMA matting agent having an average particle diameter of 5.7 μm was prepared.
57 g of an emulsion of an ultraviolet absorber containing the compounds represented by the structural formulas [501] to [505] at the following content:
761 g (The content of the ultraviolet absorbent per kg of the emulsion is 9.8 g of the compound represented by the structural formula [501] 8.4 g The compound represented by the structural formula [503] 9.8 g Compound represented by Structural Formula [504] 13.9 g Compound represented by Structural Formula [505] 29.3 g 1,2-Benzisothiazolin-3-one 1.75 g Poly (p-vinylbenzenesulfonic acid) Sodium) (Molecular weight: about 400,000) 64.2 g 20% solution of polyethyl acrylate latex 3,180 ml N, N-ethylene-bis (vinylsulfonylacetamide) 75.0 g 1,3-bis (vinylsulfonylacetamide) propane 25. Water was added to 0 g or more to prepare a total amount of 62.77 liters.

(Comparative Example 2) In Example 1, the following solution was used as a coating solution for the BC layer (back layer), and as a support, x = chromaticity coordinates defined by the method described in JIS Z8701. A heat-sensitive recording material was obtained in exactly the same manner as in Example 1 except that a transparent PET support (thickness: 180 μm) dyed blue at 0.2850 and y = 0.29995 was used.

[Preparation of Coating Solution for BC Layer (Back Layer)] A gelatin dispersion containing 1 kg of lime-treated gelatin and 12% by mass of a spherical PMMA matting agent having an average particle diameter of 5.7 μm was prepared by adding 7%.
57 g of an emulsion of an ultraviolet absorber containing the compounds represented by the structural formulas [501] to [505] at the following contents was 3,7.
61 g (ultraviolet absorption content per kg of emulsion is 9.8 g of compound represented by Structural Formula [501] 8.4 g of compound represented by Structural Formula [502] 8.4 g Compound 9 represented by Structural Formula [503] .8 g Compound represented by structural formula [504] 13.9 g Compound represented by structural formula [505] 29.3 g 1,2-benzisothiazolin-3-one 1.75 g Poly (sodium p-vinylbenzenesulfonate) (Molecular weight: about 400,000) 64.2 g Compound represented by structural formula [506] 2.0 g Latex 20% solution of polyethyl acrylate 3,180 ml N, N-ethylene-bis (vinylsulfonylacetamide) 75.0 g 1, 3-bis (vinylsulfonylacetamide) propane 25.0 g Water was added to the mixture to adjust the total volume to 62.77 liters. Made.

Table 1 shows the chromaticity coordinates L, a ^* and b ^* of the heat-sensitive recording materials obtained in Examples 1 and 2 and Comparative Examples 1 and 2.

[0125]

[Table 1]

The image of the heat-sensitive recording material obtained in Example 1 was clear and had good reproducibility of the low-density portion when observed with a Schaukasten. When observed as a medical image, an image with high diagnostic performance was obtained. Was done. On the other hand, the image of the heat-sensitive recording material obtained in Comparative Example 1 was clear and had good reproducibility in the low-density portion, but was glaring and tired of eyes when observed for a long time. Further, the image of the heat-sensitive recording material obtained in Comparative Example 2 was a calm image with little glare, but the reproducibility of low-density portions was slightly insufficient, and reproducibility of low-density portions such as RI was required. The image was not suitable for the image to be obtained.

[0127]

According to the present invention, it is possible to provide a heat-sensitive recording material which can be observed with high image quality on a shakasten.

Claims (2)

[Claims] 1. A heat-sensitive recording material having a heat-sensitive recording layer on a transparent support, wherein JI when energy immediately before starting color development is applied.
The chromaticity coordinates according to SZ8729 are L: 73 to 85,
a ^* : -4.0 to 0, b ^* : 8 to 16, and the chromaticity coordinates at a transmission density of 3.0 measured with a Macbeth transmission densitometer TD904 (visual filter) are L: 0. 5 to 1.0, a ^* : 0 to 2.0, b ^* :-
A heat-sensitive recording material characterized by being in the range of 1.0 to +1.0. 2. A backing layer and a backing protective layer on the side of the transparent support not having a heat-sensitive recording layer, wherein the backing layer and / or the backing protective layer has an absorption maximum wavelength of 550.
The heat-sensitive recording material according to claim 1, further comprising a dye having a wavelength of from 680 nm to 680 nm.