JPH0428585A - Multicolor thermal recording method - Google Patents

Abstract

PURPOSE:To record a full color image by using two thermal recording layers wherein two kinds of diazonium salts are combined with a coupler which makes color with different hue thermally reacting to each diazonium salt, and a thermal recording material on which a thermal recording layer made by combining a base dyestuff precursor with an electron accepting compound is laid. CONSTITUTION:At least three thermal coloring layers are to be laid on a support in regular order. A first thermal coloring layer contains an electron donative dyestuff precursor and an electron accepting compound as main components. A second thermal coloring layer contains a coupler which makes a color reacting thermally to a diazonium salt compound of which maximum absorbing wavelength is 36O+ or -20nm. A third thermal coloring layer contains a coupler which makes a color reacting thermally to the diazonium salt compound of which maximum absorbing wavelength is 400+ or -2Onm. The third thermal coloring layer is colored with heat by a thermal head, a light of 420+ or -40nm is irradiated on a recording material, and unreacted diazonium salt is resolved. The second thermal coloring layer is colored with heat, a light of 34O+ or -40nm is irradiated, unreacted diazonium salt is resolved, and the first thermal coloring layer is colored with heat by the thermal head so as to perform a multicolor thermal recording.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a multicolor thermal recording method, and more particularly to a multicolor thermal recording method capable of reproducing full-color images.

(Prior Art) Thermal recording has continued to develop in recent years because recording devices are simple, highly reliable, and require no maintenance. Taking advantage of this advantage, it has been applied to a variety of applications, but it has been said that it is difficult to reproduce multicolor images compared to electrophotography, inkjet, etc.

Examples of multicolor images using thermal recording include the so-called melt transfer method, which uses a film coated with dye, overlaps it with a transfer sheet, heats the film, transfers the dye to the transfer sheet, and performs recording. The sublimation transfer method is well known. However, although these methods are thermal recording, they use transfer sheets and involve the movement of dye, making the recording device complicated, and at least three transfer sheets are required to obtain one full-color image. Not only does it not take advantage of the features of thermosensitive recording, but it is also disadvantageous in terms of cost. Attempts have been made for a long time to reproduce multiple colors through so-called direct thermal recording, in which heat is directly applied to recording materials to develop colors.

In Japanese Patent Publication No. 49-69, a heat-sensitive recording material was prepared in which a plurality of electron-donating dye precursors and an electron-accepting compound coexisted. Attempts to obtain images of different hues by applying different temperatures have been proposed.

Furthermore, Special Publication No. 49-27708, Special Publication No. 51-579
No. 2 proposed an attempt to obtain a two-color heat-sensitive recording material by laminating two heat-sensitive recording layers that develop colors in different hues, with the upper layer developing colors at low temperatures and both the upper and lower layers developing colors at high temperatures. There is.

In Japanese Patent Publication No. 51-5791, a first heat-sensitive coloring layer consisting of a diazonium salt compound and a coupler, an intermediate layer containing a polyether compound, and a second layer consisting of a basic dye precursor and an electron-accepting compound are arranged on a support. A multicolor thermosensitive recording material having a laminated thermosensitive coloring layer has been proposed. The second heat-sensitive coloring layer develops color at a low temperature, and then, at a high temperature, the polyether compound erases the second heat-sensitive coloring layer, and at the same time, the first heat-sensitive coloring layer develops color, resulting in a two-color image. The feature is that when the first heat-sensitive coloring layer is coloring, the second heat-sensitive coloring layer is decolored, so it is said that color separation without color mixing is possible.
No. 24 discloses a two-color thermosensitive recording material in which two heat-sensitive coloring layers made of a basic dye precursor and an electron-accepting compound are laminated, and guanidines, which are organic basic compounds, are added to the low-temperature coloring layer. A method has been proposed in which the coloring of the low-temperature coloring layer is erased when the coloring layer is coloring.

Furthermore, in Japanese Patent Publication No. 51-37542, a high-temperature heat-sensitive coloring layer made of an acidic dye precursor and an organic basic compound and a low-temperature coloring layer made of a basic dye precursor and an electron-accepting compound are laminated on a support. A multicolor thermosensitive recording material has been proposed in which an organic basic compound in the lower layer diffuses into the upper layer to erase the color of the color former.

However, the multicolor heat-sensitive recording materials as described above,
Despite various efforts, the aim is to reproduce two or a few colors, which is far short of the full-color image reproduction required by the recent market.

As a result of intensive research into a method for reproducing full-color images using direct thermal recording, the present inventors discovered two types of diazonium salts with different photosensitive wavelengths and a coupler that reacts with each diazonium salt to produce different hues when heated. By laminating two combined heat-sensitive recording layers and a heat-sensitive recording layer made of a combination of a basic dye precursor and an electron-accepting compound, a heat-sensitive recording material capable of reproducing good multicolor images has been realized.

More specifically, a first thermosensitive coloring layer containing an electron-donating dye precursor and an electron-accepting compound as main components on a support, a diazonium salt compound having a maximum absorption wavelength of 360±20 nm, and the diazonium salt compound. A second thermosensitive coloring layer containing a coupler that develops a color by reacting with the diazonium salt compound when heated, a diazonium salt compound having a maximum absorption wavelength of 400±20 nm, and a coupler that develops a color by reacting with the diazonium salt compound when heated. A multicolor image,
Furthermore, it became possible to record full-color images.

That is, an example of the structure of the heat-sensitive recording material is shown in FIG.
1. is a support; 2. a first thermosensitive coloring layer containing an electron-donating dye precursor and an electron-accepting compound as main components; 3. a second thermosensitive coloring layer containing a diazonium salt compound having a maximum absorption wavelength of 360±20 nm and a coupler that develops a color by reacting with the diazonium salt compound when heated;
is a third thermosensitive coloring layer containing a diazonium salt compound having a maximum absorption wavelength of 400±20 nm and a coupler that develops a color by reacting with the diazonium salt compound when heated. Further, 21 is an electron-donating dye precursor, 22 is an electron-accepting compound, and 31. is a diazonium salt compound having a maximum absorption wavelength of 360±20 nm, 32. is a coupler that develops a color by reacting with the diazonium salt compound when heated 41. 42 represents a diazonium salt compound having a maximum absorption wavelength of 400±20 nm, and 42 represents a coupler that develops a color by reacting with the diazonium salt compound under heat.

(Objective of the present invention) The object of the present invention is to provide two heat-sensitive recording layers in which the two types of diazonium salts having different photosensitive wavelengths as described above and couplers that react with each diazonium salt and develop different hues when heated are combined. The purpose of the present invention is to propose a method for recording full-color images using a heat-sensitive recording material in which a heat-sensitive recording layer is laminated with a combination of a basic dye precursor and an electron-accepting compound.

(Structure of the present invention) The object of the present invention is to provide a first thermosensitive coloring layer containing at least an electron-donating dye precursor and an electron-accepting compound as main components on a support, and having a maximum absorption wavelength of 360±20 nm. a second thermosensitive color forming layer containing a diazonium salt compound and a coupler that reacts with the diazonium salt compound to form a color when heated; A step of thermally coloring the third thermosensitive coloring layer with a thermal head using a multicolor thermosensitive recording material characterized by sequentially laminating a third thermosensitive coloring layer containing a coupler that develops color in the process, a recording material. A step of irradiating light with main energy at 420±40 nm to decompose unreacted diazonium salt in the first thermosensitive coloring layer, a step of thermally coloring the second thermosensitive coloring layer with a thermal head, and a recording material. 340±4
A step of decomposing unreacted diazonium salt in the second thermosensitive coloring layer by irradiating light with 0n≧required energy;
This is achieved by a multicolor thermal recording method characterized by performing multicolor thermal recording by a step of thermally coloring the first thermosensitive coloring layer using a thermal head. To explain in more detail, first, heat capable of coloring only the third heat-sensitive recording layer indicated by 4 in Figure 1 is applied to cause the diazonium salt and coupler contained in the layer to develop color.
The recording material is irradiated with light whose main energy is to decompose the diazonium salt contained in the third heat-sensitive recording layer and fix the third recording layer. Next, 3 in Figure 1. Heat is applied by a thermal head such that the second heat-sensitive recording layer can develop color and the first heat-sensitive recording layer does not develop color, thereby causing the diazonium salt and coupler contained in the layer to develop color. At this time, sufficiently strong thermal energy is applied to the third heat-sensitive recording layer, but no color develops because the diazonium salt has already decomposed and the color-developing ability has been lost. Then 340±40
The recording material is irradiated with light having a main energy key in nm to decompose and fix the diazonium salt contained in the second heat-sensitive recording layer. Finally, enough heat is applied to enable recording on the first heat-sensitive recording layer, indicated by 2 in Figure 1, to develop color. At this time, sufficiently strong thermal energy is applied to the third and second heat-sensitive recording layers, but in this example, the first and second layers do not develop color because the diazonium salt has already decomposed and lost its color-forming ability. If the coloring hues of the second and third heat-sensitive recording layers are selected to be the three primary colors of subtractive color mixture, yellow, magenta, and cyan, full-color image recording becomes possible.

The thermal energy applied from the third to the first thermosensitive coloring layer can be easily controlled by changing the electrical energy applied to the thermal head. Specifically, this is done by changing the voltage applied to the thermal head or by changing the time for which the voltage is applied, but the latter is more common.

The raw materials used in the present invention will be briefly described below.

First, the raw materials used for the first thermosensitive coloring layer containing an electron-donating dye precursor and an electron-accepting compound as main components include an electron-donating dye precursor, an electron-accepting compound, and a compound that reacts with the electron-donating dye precursor and an electron-accepting compound when heated. There are organic compounds with low melting points that help. Many of these are already known and have been used in known pressure-sensitive recording papers and heat-sensitive recording papers.

Examples of electron-donating dye precursors include triarylmethane compounds, diphenylmethane compounds, thiazine compounds,
Examples include xanthine compounds and spiropyran compounds, and triarylmethane compounds and xanthine compounds are particularly useful because of their high color density. Some examples of these include 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (i.e. crystal violet lactone), 3.3-bis(p-dimethylamino)phthalide, 3- (p-dimethylaminophenyl)
-3-(1,3-dimethylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2
-methylindol-3-yl)phthalide, 3-(o-
Methyl-p-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide, 4,4'-bis(dimethylamino)benzhydrin benzyl ether, N-halophenylleukoolamine, N2.4 .5-
t-dichlorophenylleucoauramine, rhodamine-
B-anilinolactam, rhodamine (p-nitroanilino)lactam, rhodamine-B-(p-chloroanilino)lactam, 2-benzylamino-6-diethylaminofluoran 2-anilino-6-diethylaminofluoran 2-anilino-3-methyl -6-diethylaminofluorane, 2-anilino-3-methyl-6-chlorohexylmethylaminofluorane, 2-anilino-3-methyl-6
-Itsamylethylaminofluorane, 2-(0-chloroanilino)-6-diethylaminofluorane, 2-year-old cutylamino-6-diethylaminofluorane, 2-ethoxyethylamino-3-chloro-2-diethylaminofluorane, 2 -anilino-3-chloro-6 diethylaminofluorane, benzoylleucomethylene blue p
-Nitrobenzylleucomethylene blue 3-methyl-
spiro-dinaphthopyran 3-ethyl-spiro-dinaphthopyran, 3,3 cyclospirodinaphthopyran, 3
-benzylspirodinaphthopyran, 3-propyl-spiro-dibenzopyran and the like.

Examples of electron-accepting compounds include phenol derivatives, salicylic acid derivatives, and hydroxybenzoic acid esters. Particularly preferred are bisphenols and hydroxybenzoic acid esters.

Some examples of these include 2,2-bis(p-hydroxyphenyl)propane (i.e., bisphenol A);
2.2-bis(p-hydroxyphenyl)pentane, 2
, 2-bis(p-hydroxyphenyl)ethane, 2,2
-bis(p-hydroxyphenyl)butane, 2,2-bis(4"-hydroxy-3',5°-dichlorophenyl)propane, 1.l -(p-hydroxyphenyl)
Cyclohexane, 1.1-(p-hydroxyphenyl)
Propane, 1.1-(p-hydroxyphenyl)pentane, +, 1-(p-hydroxyphenyl)-2-ethylhexane, 3,5-di(α-methylbenzyl)salicylic acid and its polyvalent metal salt, 3 .5-di(tert-butyl)salicylic acid and its polyvalent metal salts, 3-α, α-
Dimethylbenzylsalicylic acid and its polyvalent metal salts, p
Examples include butyl -hydroxybenzoate, benzyl p-hydroxybenzoate, 2-ethylhexyl p-hydroxybenzoate, p-phenylphenol, p-cumylphenol, and the like.

The sensitizer is preferably a low melting point organic compound having an appropriate amount of aromatic groups and polar groups in the molecule, such as benzyl p-benzyloxybenzoate, α-naphthylbenzyl ether, β-naphthylbenzyl ether, β- Naphthoic acid phenyl ester, α-hydroxy-β-naphthoic acid phenyl ester, β-naphthol-(p-chlorobenzyl)
Etenope 1,4-butanediol phenyl ether 1,4-butanediol-p-methylphenyl ether, 1,4-butanediol-p-ethylphenyl ether, 1,4-butanediol-mmethylphenyl ether, l-phenoxy -2(p-tolyloxy)ethane,
Examples include 1-phenoxy-2-(p-ethylphenoxy)ethane, 1-phenoxy-2-(p-chlorophenoxy)ethane, and p-benzylbiphenyl.

The compound used in the second and third thermosensitive coloring layers containing a diazonium salt compound and a coupler that develops color by reacting with the diazonium salt compound when heated is a diazonium salt compound,
Examples include couplers that can react with the diazonium salt compound to form a dye, and basic substances that promote the reaction between the diazonium salt compound and the coupler. Many of them are well-known and are used in thermosensitive recording paper.

Diazonium salt compounds are compounds represented by the general formula % (in the formula, Ar represents an aromatic moiety, N2 nium salt, and X- represents an acid anion) and are represented by diazo, and these are the substituents of the Ar moiety. They have various maximum absorption wavelengths depending on their location and type.

Specific examples of the diazonium salt compound used in the present invention having a maximum absorption wavelength of 360±2 Onm include 4
- (N-(2-(2,4-di-tert-amylphenoxy)butyryl)piperazino)penzenediazonium, 4-dioctylaminobenzenediazonium, 4-
(N-(2-ethylhexanoyl)piperazino)penzendiazonium, 4-dimoxylamino-2-hexyloxybenzenediazonium, 4-N-ethyl-N-hexadecylamino-2-ethoxybenzodiazonium,
Examples include 3-chloro-4-dioctylamino-2-octylokidiobenzenediazonium, and these fexafluorophosphate salts, tetrafluoroborate salts, and 1,5-naphthalenesulfonate salts have low water solubility. Useful for the purposes of the invention.

Specific examples of the diazonium salt compound used in the present invention having a maximum absorption wavelength of 400±20 nm include 2
, 5-dibutoxy-4-morpholinobenzenediazonium, 2,5-octoxy-4-morpholinobenzenediazonium, 2,5 dibutoxy-4-(N-(2-ethylhexanoyl)piperazino)benzenediazonium, 2
5-jethoxy-1-(N-(2-(2,4-di-te)
rt-amylphenoquine)butyryl)piperazino)penzenediazonium, 2,5-dibutoxy-4-tolylthiobenzenediazonium, 3(2-octyloxyethoxy)-4-morpholinobenzenediazonium, etc. Exafluorophosphate salts, tetrafluoroborate salts, and 1,5-naphthalene sulfonate salts are useful for purposes of this invention because of their low water solubility.

Couplers that react with the above-mentioned diazonium salt and develop a color when heated include resorcinol, flurglucin, sodium 2,3-dihydroxynaphthalene-6-sulfonate, 1-hydroxy-2-naphthoic acid morpholinopropylamide, 15- Dihydroxynaphthalene, 2.3
-dihydroxynaphthalene, 2,3-dihydroxy-6
-Sulfanylnaphthalene, 2-hydroxy-3-naphthoic acid anilide, 2-hydroxy-3-naphthoic acid ethanolamide, 2-hydroxy-3-naphthoic acid octylamide, 2-hydroxy-3-naphthoic acid-N-dodecyloxypur Pyramide, 2-hydroxy-3-naphthoic acid tetradecylamide, acetanilide, acetoacetanilide, benzoylacetanilide, 2-chloro-5-octylacetoacetanilide, 1-phenyl-
3-Methyl-5-pyrazolone, ■-(2°-octylphenyl)-3-methyl-5-pyrazolone 1-(2'
4',6°-trichlorophenyl)-3-benzamido-5-pyrazolone, 1-(2'4'
6°-trichlorophenyl)-3-anilitu-5-pyraone, 1-phenyl-3-phenylacetamide-5
- Examples include pyrazolone. Two or more of these couplers can be used in combination to obtain the desired color hue.

In addition to inorganic or organic basic compounds, the basic substances include compounds that decompose upon heating and release alkaline substances. Typical examples include organic ammonium salts, organic amines, amides, urea and thiourea, and their derivatives, thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indoles, imidazoles, imidacillins, and triazoles. Examples include nitrogen-containing compounds such as morpholines, piperidines, amidines, formazines, and pyridines. Specific examples of these include tricyclohexylamine, tribenzylamine, octadecylbenzylamine, stearylamine, allyl urea, thiourea, methylthiourea, allylthiourea, ethylenethiourea, 2-benzylimidazole, 4-phenylimidazole, 2-phenyl- 4-
Methylimidazole, 2-undecylimidacillin2.
4.5-) Riphcleu 2-imidacillin, 1.2-diphenyl-4,4-dimethyl-2-imidacillin, 2-phenyl-2-imidacillin, 1.2.3-) Riphenylguanidine, l,2-dicyclo hexylguanidine, 1
, 2.3-) lycyclohexylguanidine, guanine trichloroacetate, N,N'-dibenzylpiperazine,
These include 44''-dithiomorpholine, morpholinium trichloroacetate, 2-aminobenzothiazole, 2-benzoylhydrazinobenzothiazole, etc.
As the material for the intermediate layer used in the present invention, which can be used in combination with more than one kind, water-soluble polymer or hydrophobic polymer emulsion or latex can be used.

Examples of water-soluble polymers include polyvinyl alcohol silanol-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, styrene-maleic anhydride copolymer and its ester, butiene-maleic anhydride copolymer,
Ethylene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyacrylamide, polystyrene sulfonic acid, polyvinylpyrroline, ethylene-acrylic acid copolymer, vinyl acetate-acrylic acid copolymer, oxidized starch, phosphorylation Examples include starch, ceratin, carboxymethylcellulose, methylcellulose, sodium alginate, sulfated cellulose, and hydroxyethylcellulose.

Examples of the hydrophobic polymer emulsion or latex include styrene-butadiene copolymer, carboxy-modified styrene-butadiene copolymer, and acrylonitrile-butadiene copolymer.

As the support, known materials such as paper, laminated paper obtained by laminating polyethylene or the like on paper, synthetic paper, and plastic bases such as polyethylene terephthalate, polyimide, and triacetylcellulose are used.

In the present invention, as a light source for decomposing the diazonium salt compound included in the third thermosensitive coloring layer and having a maximum absorption wavelength of 400±20 nm, the main emission energy is 42 nm.
Method using fluorescent lamp existing at 0±40 nm, 42
There is a method of using a light source having optical energy in the wavelength range of 0±40 nm and cutting off unnecessary wavelengths of light using an optical filter.

However, in any case, it is necessary that at least 60% or more of the light energy irradiated onto the recording material exists in the wavelength range of 420±40 nm, and more preferably 80% or more.

If the fixing light source contains many light components of 380 nm or less, the maximum absorption wavelength contained in the second thermosensitive coloring layer will be 360±.
The diazonium salt compound having a diameter of 20 nm is undesirably decomposed. On the other hand, light of 460 nm or more often hardly contributes to decomposing a diazonium salt compound whose maximum absorption wavelength is 420±20 nm, and the decomposition efficiency is significantly reduced.

Similarly, the maximum absorption wavelength contained in the second thermosensitive coloring layer is 3.
As a light source for decomposing diazonium salt compounds whose wavelength is 60±20 nm, the main emission energy is 340±4.
Method using fluorescent lamp light existing at 0 nm, 340
There is a method using a light source having optical energy within ±40 nm. In this case, as long as there is sufficient light intensity at 340±40 nm, it may have energy distribution at other wavelengths.

In the above recording method, the fluorescent lamp used for photolyzing the diazonium compound is a fluorescent tube filled with mercury vapor, and fluorescent tubes having various emission wavelengths can be obtained depending on the type of phosphor coated on the inner wall of the tube. Ultraviolet lamps with sharp emission wavelengths that meet the purpose of the present invention are very limited, and in order to have the main energy at 420±40 nm, Sr2PzO7:Eu", Srt
(PO4)*:Eu'+ or (S rMg)
2 P20: Phosphors such as Eu'+ are preferred.
Similarly, in order to have the main energy present at 340±40 nm, phosphors such as 5rB40tF:Eu2+ or Sr(B20x):Pb'' are preferable.

In a method in which a light source having light energy in the ultraviolet region is used as the diazo decomposition light source and unnecessary light is cut off with an optical filter, a mercury lamp, an AFL lamp, or the like can be used as the light source.

Furthermore, as optical filters to be combined, there are commercially available ones in which an ultraviolet absorber is kneaded into a support, those in which an ultraviolet absorber is dissolved or dispersed in a binder and coated on a transparent support, and interference filters. These are easily available.

Examples are shown below, but the present invention is not limited thereto. Note that all "parts" in the examples indicate parts by weight.

"Example" Example 1 A multicolor heat-sensitive recording material was prepared by the following method.

(1) Preparation of first thermosensitive recording layer liquid [Preparation of electron-donating dye precursor capsule liquid] 3-(o-methyl-p-dimethylaminophenyl)-3-(1' 3.0 parts of ethyl-2'-methylindol-3-yl)phthalide was dissolved in 20 parts of ethyl acetate, and 20 parts of alkylnaphthalene, which is a high boiling point solvent, was added and mixed uniformly by heating.

As a capsule wall agent, 20 parts of xylylene diisocyanate/trimethylolpropane adduct was further added to this solution and stirred uniformly.

Separately, 54 parts of a 6% by weight aqueous solution of polyvinyl alcohol (degree of polymerization 1700, degree of saponification 88%) was prepared, the above electron-donating dye precursor solution was added, and the mixture was emulsified and dispersed using a homogenizer.

After 68 parts of water was added to the obtained emulsion to make it homogeneous, the temperature was raised to 60°C while stirring, and the encapsulation reaction was carried out for 3 hours to obtain the desired capsule liquid. The average particle size of the capsule is 1
．． It was 6μ.

[Preparation of electron-accepting compound dispersion]

30 parts of bisphenol A as an electron-accepting compound was added to 150 parts of a 4% by weight aqueous solution of polyvinyl alcohol and dispersed for 24 hours in a ball mill to prepare a dispersion.

The average particle size of the electron-accepting compound in the dispersion is 1.2 μm
Met.

[Preparation of coating liquid]

Next, the above electron-donating dye precursor capsule liquid and electron-accepting compound dispersion are mixed so that the ratio of electron-donating dye precursor/electron-accepting compound is 1/2 to prepare the desired coating liquid. did.

(2) Preparation of second thermosensitive recording layer liquid [Preparation of diazonium salt compound capsule liquid] As a diazonium salt compound, 4-(N-(2(2,4-di-te)
Dissolve 2.0 parts of rt-amylphenoxy)butyryl)piperazinobenzenediazonium hexafluorophosphate in 20 parts of ethyl acetate, add 20 parts of alkylnaphthalene, a high boiling point solvent, and mix uniformly by heating. did.

As a capsule wall agent, 15 parts of xylylene diisocyanate/trimethylolpropane adduct was further added to this solution and stirred uniformly.

Separately, 54 parts of a 6% by weight aqueous solution of polyvinyl alcohol (degree of polymerization 1700, degree of saponification 88%) was prepared, the above diazonium salt compound solution was added, and the mixture was emulsified and dispersed using a homogenizer.

After 68 parts of water was added to the obtained emulsion to make it homogeneous, the temperature was raised to 40° C. while stirring, and the encapsulation reaction was carried out for 3 hours to obtain the desired capsule liquid. The average particle size of the capsules is 1.1
It was μ.

[Preparation of coupler emulsion dispersion]

1-(2'-octylphenyl) as a coupler
-3-Methyl-5-pyrazolone 2 parts, 1°2.3-1
- Dissolve 2 parts of liphenylguanisine, 0.3 parts of tricresyl phosphate, 0.1 part of diethyl maleate in 10 parts of ethyl acetate, add 50 g of 6% aqueous polyvinyl alcohol solution and 2 g of 2% sodium dodecylbenzenesulfonate solution. The mixture was poured into the mixed aqueous solution and emulsified using a homogenizer for 10 minutes.

[Preparation of coating liquid]

Next, the above-mentioned diazonium salt compound capsule liquid and coupler emulsion dispersion were mixed so that the ratio of the diazonium salt compound to the coupler was 2/3 to prepare a desired coating liquid.

(3) Preparation of third heat-sensitive recording layer liquid [Preparation of diazonium salt compound capsule liquid] As a diazonium salt compound, 3.0 parts of 2,5-sibutquine-4-tolylthiobenzenediazonium hexafluorophosphate was added to 20 parts of ethyl acetate. After dissolving, 20 parts of alkylnaphthalene, which is a high boiling point solvent, was added, and the mixture was heated and mixed uniformly.

As a capsule wall agent, 10 parts of xylylene diisocyanate/trimethylolpropane adduct was further added to this solution and stirred uniformly.

Separately, 54 parts of a 6% by weight aqueous solution of polyvinyl alcohol (degree of polymerization 1700, degree of saponification 88%) was prepared, the above diazonium salt compound solution was added, and the mixture was emulsified and dispersed using a homogenizer.

After adding 68 parts of water to the obtained emulsion to make it homogeneous, the temperature was raised to 40°C with stirring, and the encapsulation reaction was carried out for 3 hours to obtain the desired capsule liquid. The average particle size of the capsules is J,
It was 0μ.

[Preparation of coupler emulsion dispersion]

2-chloro as a coupler 4-tert-pentyl) pyramino) acetoacetanili 2.3-triphenylguanidine Resyl phosphate 0. 3 parts, 5- (:3- (2 phenoxypro 2 parts, l.

2 parts and 0.1 part of diethyl tricumarate were dissolved in 10 parts of ethyl acetate;
% polyvinyl alcohol aqueous solution and 2 g of 2% sodium dodecylbenzenesulfonate solution were poured into an aqueous solution and emulsified for 10 minutes using a homogenizer.

[Preparation of coating liquid]

Next, the above-mentioned diazonium salt compound capsule liquid and coupler emulsion dispersion liquid were mixed so that the ratio of diazonium salt compound/coupler was 415 to prepare a desired coating liquid.

(5) The first heat-sensitive recording layer, the second heat-sensitive recording layer, and the third heat-sensitive recording layer are sequentially coated and dried on a photographic paper support made of coated high-quality paper laminated with polyethylene using a Meyer bar. A color thermosensitive recording material was obtained.

The coating amounts as solid content were 5.2g, 63g, and 6.
It was 8g.

Using the multicolor heat-sensitive recording material prepared as described above, Kyocera's Su-Mulhead KST type (print density in the main scanning direction 8d) was used.
ot/mm) using a thermal printer equipped with a printing energy of 0.5 W/dat and a printing density of 81 in the sub-scanning direction.
in/mm, and the applied pulse width was changed from 0.4 ms to 2
．． Printing was performed by changing the time every 02 m5 up to 0 ms. As a result, a yellow printed image with gradation from light to dark was obtained. Figure 2 shows the results of measuring the concentration using a Macbeth RD-918 densitometer equipped with a blue filter.

Then, as a phosphor, S rt P207: Eu
The sample was irradiated for 10 seconds using a 15W fluorescent lamp with an emission center wavelength of 419 nm and a half-width of emission energy of 35 nm. Furthermore, using the above thermal printer, the pulse width was changed from 2.4 ms to 4.0 ms under the same conditions except for the pulse width.
Printing was performed by changing the time every 0.2 ms up to 0 ms. As a result, a magenta printed image with gradation from light to dark was obtained.

The concentration was measured using a McHess RD918 densitometer equipped with a green filter, and the results are shown in Figure 2.

Then, irradiation was performed for 20 seconds with a 15W fluorescent lamp using 5rB407F:ELI2+ as a phosphor, having an emission center wavelength of 367 nm and a half-width of emission energy of 18 nm.

Further, using the above-mentioned thermal printer, printing was carried out under the same conditions except for the pulse width, changing the pulse width from 4.4 ms to 6.0 ms every 0.2 ms. As a result, a cyan printed image with gradation from light color to dark color was obtained.

The concentration was measured using a Macbeth RD-918 densitometer equipped with a red filter, and the results are shown in Figure 2. As is clear from FIG. 2, by the recording method of the present invention, it was possible to independently obtain images with yellow, macenta, and cyan gradation. Further, a red image was obtained from the overlapped portion of the yellow image and the magenta image, a blue image was obtained from the overlapped portion of the magenta image and the cyan image, and a green image was obtained from the overlapped portion of the cyan image and the yellow image.

As described above, it has been proven that the present invention enables the recording of multicolor, even full-color images.

[Brief explanation of drawings]

FIG. 1 shows an example of a cross-sectional view of a multicolor thermosensitive recording material according to the present invention. In FIG. 1, 16 support 2, first thermosensitive coloring layer 3, second thermosensitive coloring layer 4, third thermosensitive coloring layer 21, electron-donating dye precursor 22, electron-accepting compound 31, diazonium salt compound 32, coupler. 33, diazonium salt compound 34, and coupler. FIG. 2 shows the recording density characteristics of images recorded according to the example, and shows the voltage pulse width applied to the therma head, yellow (Y), macenter (M), and cyan (C).
) shows the relationship between each color density.

Claims (2)

[Claims] (1) A first thermosensitive coloring layer containing at least an electron-donating dye precursor and an electron-accepting compound as main components on a support, a diazonium salt compound having a maximum absorption wavelength of 360±20 nm, and the diazonium salt compound; a second thermosensitive coloring layer containing a coupler that develops color when heated; a second thermosensitive coloring layer containing a diazonium salt compound having a maximum absorption wavelength of 400±20 nm; and a coupler that develops color when reacted with the diazonium salt compound; A step of thermally coloring the third thermosensitive coloring layer using a thermal head using a multicolor thermosensitive recording material characterized by sequentially laminating three thermosensitive coloring layers, where main energy exists in the recording material at 420±40 nm. irradiation with light to decompose unreacted diazonium salt in the third thermosensitive coloring layer; process of thermally coloring the second thermosensitive coloring layer with a thermal head; main energy exists in the recording material at 340±40 nm; The method is characterized by performing multicolor thermal recording by irradiating light to decompose unreacted diazonium salt in the second thermosensitive coloring layer, and thermally coloring the first thermosensitive coloring layer with a thermal head. A multicolor thermosensitive recording method. (2) Sr_2P_2O_7:Eu^2^+, Sr_2(PO_4)_2:Eu^2^+, or (SrMg)_2P_2O_7:Eu^2^+ as a light source with main energy at 420±40 nm. Using a fluorescent lamp that uses phosphor as the main component, 340±4
As a light source with main energy at 0 nm, S
rB_4O_7F: EU^2^+ or Sr(B_2
O_3)_n: A multicolor thermosensitive recording method according to claim 1, characterized in that a fluorescent lamp using a phosphor containing Pb^2^+ as a main component is used.