JP5298739B2 - Dye for thermal transfer recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an azomethine-based dye for heat sensitive transfer recording, which is excellent in light resistance and hue, and of which the production cost is drastically reduced. <P>SOLUTION: The azomethine-based dye is obtained by bonding a pyridine ring with 1H-pyrazolo[1,5-b][1,2,4]triazole ring expressed by formula (I), via a nitrogen atom. Wherein, R<SB>1</SB>is phenyl or naphthyl, and the phenyl or naphthyl may be replaced with alkyl or halogen, and R<SB>2</SB>and R<SB>3</SB>are each independently C2-4 alkyl. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a dye for thermal transfer recording comprising a novel azomethine compound, and more specifically, it can be produced at low cost with excellent light resistance, and has excellent color tone when used as a magenta dye. It relates to pigments.

  The heat-sensitive sublimation transfer method uses a thermal transfer film that carries a dye layer in which a sublimable dye is dissolved or dispersed in a binder resin. The thermal transfer film is layered on the image-receiving film and is transferred to a heating device such as a thermal head. By applying energy according to the above, the sublimation dye contained in the dye layer on the thermal transfer film is transferred to the image receiving film to form an image.

This heat-sensitive sublimation transfer method can control the amount of dye transfer in dot units according to the amount of energy applied to the thermal transfer film, so that it is excellent in forming a gradation image and has advantages such as easy formation of characters, symbols, etc. have.
The image obtained by such a thermal transfer method can form a high-quality image similar to a silver salt photograph, and accordingly, there is an extremely high demand for prevention of image quality degradation due to factors such as light, heat, and humidity of the image. Development of various sublimation dyes for improving image storage stability has been made.

  For example, as a thermal transfer dye having excellent transferability and storage stability, Patent No. 3013137 (Patent Document 1) and Patent No. 3078308 (Patent Document 2) include 1H-pyrazolo [5,1-C] [1 , 2,4] An azomethine compound having a structure in which a triazole ring is a coupler and a pyridine ring group is bonded to the coupler via a nitrogen atom is disclosed. Japanese Patent No. 2840901 (Patent Document 3) uses a 1H-pyrazolo [1,5-b] [1,2,4] triazole ring as a coupler, and a phenylamino group is bonded to the coupler via a nitrogen atom. An azomethine compound of structure is disclosed. Further, JP-A-5-239367 (Patent Document 4) describes a 1H-pyrazolo [1,5-b] [1,2,4] triazole ring coupler, which is a combination of both, to a pyridine ring group. An azomethine compound having a structure in which is bonded to a coupler via a nitrogen atom is disclosed.

  Although the azomethine dyes disclosed in the above patents 3013137 and 3078308 are excellent in light resistance, the 1H-pyrazolo [1,5-b] [1,2,4] triazole ring is used as a coupler. There is a cost problem. The azomethine dye described in Japanese Patent No. 2840901 using a 1H-pyrazolo [1,5-b] [1,2,4] triazole ring compound as a raw material coupler has a merit that it can be produced at a relatively low cost. May be insufficient.

On the other hand, the dye described in JP-A-5-239367, which is a combination of 1H-pyrazolo [1,5-b] [1,2,4] triazole ring coupler and pyridine ring group, can be produced at low cost and is light resistant There is an advantage that it is excellent in performance. In particular, a phenyl group introduced as a substituent R ₆ of the 1H-pyrazolo [1,5-b] [1,2,4] triazole ring proposed in JP-A-5-239367 (9, (10, 11, 22, 112) is excellent in that the color tone of the pigment is close to the required color gamut. The required hue is the OD value in the region of b ^* <− 0.34a ^* and b ^* > − 0.63a ^{* on} the ab-plane of the L ^* a ^* b ^* color system. Is 1.0.

Patent No. 3013137 Japanese Patent No. 3078308 Japanese Patent No. 2840901 JP-A-5-239367

However, the compounds described in JP-A-5-239367, in particular, compounds having a phenyl group introduced as the substituent R ₆ of the triazole ring are excellent in terms of production cost and light resistance, but have a low coupling reaction rate. As described in JP-A-5-239367, the yield is about 20%.

  The present inventors now perform a coupling reaction well in an azomethine compound in which a pyridine ring is bonded to a 1H-pyrazolo [1,5-b] [1,2,4] triazole ring through a nitrogen atom. And the production cost of the obtained azomethine compound can be greatly reduced. The present invention is based on this finding.

  Accordingly, the object of the present invention is to make 1H-pyrazolo [1,5-b] [1,5-b] [1], which can satisfactorily carry out the coupling reaction of the azomethine compound and can greatly reduce the production cost of the resulting thermal transfer recording dye. An object of the present invention is to provide a thermal transfer recording dye comprising an azomethine compound in which a pyridine ring is bonded to a 1,2,4] triazole ring through a nitrogen atom.

  Another object of the present invention is to provide a method for producing the above thermal transfer recording dye.

（式中、
Ｒ_１は、フェニル基またはナフチル基であるが、該フェニル基またはナフチル基は、アルキル基もしくはハロゲンにより置換されていてもよく、
Ｒ_２およびＲ_３は、それぞれ独立して、炭素数Ｃ２〜４のアルキル基を示す。）。 The thermal transfer recording dye according to the present invention comprises an azomethine compound represented by the following formula (I).

(Where
R ₁ is a phenyl group or a naphthyl group, and the phenyl group or naphthyl group may be substituted with an alkyl group or a halogen,
R ₂ and R ₃ each independently represents an alkyl group having 2 to 4 carbon atoms. ).

Also, a method for producing a thermal transfer recording dye according to another aspect of the present invention comprises reacting a compound represented by the following formula II with a compound represented by the following formula III with an oxidizing agent in the presence of a base. Obtaining an azomethine compound of formula I above.

  According to the present invention, in an azomethine compound in which a pyridine ring is bonded to a 1H-pyrazolo [1,5-b] [1,2,4] triazole ring represented by the formula I through a nitrogen atom, the above formula II Can be satisfactorily carried out and the production cost of the resulting thermal transfer recording dye can be greatly reduced. Therefore, it is possible to realize an inexpensive azomethine-based magenta dye that is excellent in sensitivity and light resistance.

  In addition, the thermal transfer recording dyes described above are excellent in human skin color reproducibility compared to conventional azomethine-based magenta dyes. In particular, the reproducibility of fine hues such as a human face is excellent.

  The thermal transfer recording dye according to the present invention comprises an azomethine compound represented by the following formula I.

式中、Ｒ_１は、フェニル基またはナフチル基であるが、該フェニル基またはナフチル基は、アルキル基もしくはハロゲンにより置換されていてもよく、Ｒ_２およびＲ_３は、それぞれ独立して、炭素数Ｃ２〜４のアルキル基を示す。

In the formula, R ₁ is a phenyl group or a naphthyl group, and the phenyl group or naphthyl group may be substituted with an alkyl group or a halogen, and R ₂ and R ₃ each independently represent a carbon number A C2-4 alkyl group is shown.

  Like the compound represented by the formula I, an azomethine compound in which a 1H-pyrazolo [1,5-b] [1,2,4] triazole ring coupler and a pyridine ring group are bonded via a nitrogen atom has a light resistance. It has the advantage that it can be manufactured at low cost. However, a compound in which a pyridine ring group having no substituent is bonded to a coupler, such as the azomethine compound described in JP-A-5-239367, has a reaction yield of 1 between the coupler and the pyridine ring in the production process. It is as low as ˜20%. In the present invention, focusing on the pyridine ring and introducing a methyl group at the ortho position of the pyridine ring, the coupling reaction rate is remarkably improved, and the reaction yield is 40% or more.

  Moreover, the pigment | dye which consists of said azomethine compound has the effect that it is excellent in the reproducibility of the color of human skin. A conventional azomethine-based magenta dye, for example, a magenta dye described in Japanese Patent No. 3013137 is excellent in color reproducibility in a wide range, but has a 1H-pyrazolo [1,5-C] [1,2,4] triazole ring. Since the coupler is used, there is a problem that the production cost of the dye increases. On the other hand, the azomethine dye used for the thermal transfer recording dye according to the present invention has a 1H-pyrazolo [1,5-b] [1,2,4] triazole ring coupler and a pyridine ring group via a nitrogen atom. Therefore, both color reproducibility and low cost can be achieved.

からなる群から選択されるものであることが好ましい。このような置換基を有していてもよいフェニル基またはナフチル基等のアリール基を導入することにより、所望の色相に近似させることができるとともに、吸収スペクトルがシャープ化する。また、耐光性や溶解性も向上する。 Dye for thermal transfer recording according to the present invention, wherein R ₁ is the following substituents (i) to (v):

It is preferably selected from the group consisting of By introducing an aryl group such as a phenyl group or a naphthyl group which may have such a substituent, it is possible to approximate a desired hue and sharpen an absorption spectrum. Moreover, light resistance and solubility are also improved.

Among these, R ₁ is more preferably substituents (ii) and (iv) from the viewpoint of sharpening the absorption spectrum and improving light resistance.

  The above azomethine compound is represented by a 1H-pyrazolo [1,5-b] [1,2,4] triazole coupler represented by the following formula II and a formula III as shown in the following synthesis scheme. It can be obtained by reacting a pyridyldiamino derivative with an oxidizing agent in the presence of a base.

  The 1H-pyrazolo [1,5-b] [1,2,4] triazole derivative represented by the formula II, which is a coupler, is synthesized using a method similar to the method described in JP-A-5-239367. be able to. For example, the compounds of formula II and formula III can be obtained as follows.

First, as shown in the following synthesis scheme, a benzoic acid ester compound as a starting material is reacted with acetonitrile in the presence of potassium t-butoxide to obtain compound a, and then compound a is reacted with hydrazine to obtain compound b. Prepare. Subsequently, imidate hydrochloride is allowed to act on compound b to obtain an amidine compound, and then hydroxylamine is allowed to act on compound b to obtain compound c.

Then, compound p is reacted with p-tolylsulfonic acid chloride as described below. The compound of formula II can be obtained by heating to reflux in the presence of pyridine.

  Moreover, the pyridyldiamine derivative which is a compound of Formula III can be obtained according to the method described in Japanese Patent No. 3078308, for example.

  The azomethine compound of the present invention can be obtained by reacting the compound of formula II obtained above and the compound of formula III with an oxidizing agent in the presence of a base.

  The heat-sensitive thermal transfer material according to the present invention can be used as a magenta dye for sublimation thermal transfer, and can be suitably used in combination with other known yellow dyes, cyan dyes, other dyes and the like. For example, it can be set as the thermal transfer sheet which provided the dye layer which contains said pigment | dye and binder resin, and the other dye layer as needed on one surface of the base material.

  The base material can be the same base material as that used in conventional thermal transfer sheets, and is not particularly limited. Specific examples of preferable base materials include glass paper, condenser paper, thin paper such as paraffin paper, polyethylene terephthalate, polyphenylene sulfide, polyether ketone, polyether sulfone and other high heat resistant polyester, polypropylene, polycarbonate, cellulose acetate, Examples thereof include stretched or unstretched films of plastics such as polyethylene derivatives, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide, polyimide, polymethylpentene, and ionomer, and laminates of these materials.

Although the thickness of a base material can be suitably selected according to material so that intensity | strength, thermal conductivity, heat resistance, etc. may become appropriate, the thing about 1-100 micrometers is normally used normally. When the substrate is poorly adhered to the heat transferable color material layer formed on this surface, it is preferable to subject the surface to primer treatment (formation of a primer layer) or corona treatment.
In the present invention, the above-described dye is used as the thermal transfer recording dye contained in the heat transferable color material layer provided on one surface of the substrate, but may contain other known dyes. As the other dyes, any conventionally known dyes that are sublimable or heat diffusible can be appropriately used.

  Specific examples of sublimable or heat diffusible dyes include various kinds of non-azo compounds such as azo, anthraquinone, nitro, styryl, naphthoquinone, quinophthalone, azomethine, coumarin, and condensed polycyclic compounds. Examples include ionic dyes.

The binder resin used for the heat transferable colorant layer is a water-soluble polymer such as cellulose, polyacrylic acid, polyvinyl alcohol, or polyvinylpyrrolidone, acrylic resin, methacrylic resin, polystyrene, polycarbonate, polysulfone, polyethersulfone, polyvinyl. Examples thereof include polymers soluble in organic solvents such as butyral, polyvinyl acetal, ethyl cellulose, and nitrocellulose. Among these resins, polyvinyl butyral, polyvinyl acetal or cellulose resin having excellent storage stability is preferable. When using a polymer that is soluble in an organic solvent, one or more polymers may be used in the form of a latex dispersion in addition to being used by dissolving them in an organic solvent. The amount of the binder resin used is preferably 0.1 g to 50 g per 1 m ² of the base material.

  In order to improve the releasability from the image receiving layer, a release agent may be added or a release layer may be provided. As the release agent, reactive curable silicones, phosphate ester surfactants, fluorine compounds, and the like can be used. As for the usage-amount of a mold release agent, 0.5-40 mass% is preferable with respect to solid content of the layer to contain. When providing a release layer, the same binder as that used for the dye-donating layer can be used.

  The heat transferable color material layer is obtained by, for example, preparing a heat transferable color material layer forming ink by dissolving and mixing or dispersing a dye and a binder resin in a solvent, and applying and drying the ink on a base film.

  Solvents used in this ink include aromatic solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ester solvents such as ethyl acetate and butyl acetate; isopropanol, butanol and methyl cellosolve And alcohol solvents such as dioxane and tetrahydrofuran; amide solvents such as dimethylformamide and N-methylpyrrolidone. The ink may contain various conventionally known additives as required.

  The thickness of the heat transferable color material layer formed on the substrate is usually 0.1 μm or more, preferably 0.3 μm or more and 10 μm or less, preferably 5 μm or less after drying. The dye content in the heat transferable color material layer is 5% by weight or more, preferably 20% by weight, based on the total solid content of the heat transferable color material layer (component excluding the solvent from the heat transferable color material layer ink). As mentioned above, it is 70 weight% or less, Preferably it is 60 weight% or less.

  Further, a heat-resistant slipping phase may be provided on the other surface of the substrate (the surface opposite to the surface provided with the heat transferable color material layer). The thickness of the heat resistant slipping layer is usually 0.1 μm or more, preferably 0.3 μm or more and 10 μm or less, preferably 5 μm or less.

  The heat resistant slipping layer usually contains additives such as a binder resin, fine particles and a lubricant. As the binder resin, a binder resin made of a thermosetting resin, a photocurable resin, a thermoplastic resin, or the like is used.

Examples of the thermosetting resin include an active hydrogen-containing resin such as ethyl cellulose resin, cellulose acetate resin, polyvinyl alcohol resin, polyvinyl acetoacetal resin, and polyvinyl butyral resin, and a crosslinked product such as isocyanate. Examples of the photocurable resin include polyester acrylate resin, epoxy acrylate resin, polyol acrylate resin, and the like. Examples of the thermoplastic resin include thermoplastic resins having a glass transition temperature of 50 ° C. or more. Specifically, acrylic resins, vinyl chloride copolymers, acrylonitrile-styrene copolymers, polycarbonate resins, polyester resins, polyvinyl butyral resins, A polyacetal resin etc. are mentioned.
Examples of the fine particles include inorganic particles such as silica, alumina, and titanium oxide, and organic fine particles such as silicone resin, urea resin, and benzoguanamine resin.

  As the lubricant, various modified silicone oils, phosphate ester-based, fatty acid metal salt-based surfactants and the like are used. In addition, additives such as organic or inorganic non-sublimable particles, a dispersant, an antistatic agent, an antiblocking agent, an antifoaming agent, an antioxidant and a viscosity modifier are added to the heat resistant slipping layer as necessary. be able to.

  Furthermore, when energy rays such as laser beams are used for thermal transfer recording, a photothermal conversion material is contained in the thermal transferable color material layer, or a photothermal conversion material-containing layer is provided between the thermal transferable color material layer and the base film. Just do it. Examples of the photothermal conversion material include an infrared absorber and carbon black.

  The formation method of each layer, such as a heat transferable color material layer and a heat-resistant slip layer provided on these substrates, is arbitrary, and the formation thereof may be performed sequentially or simultaneously. Generally, it is formed by applying and drying a composition of a heat transferable color material layer or a heat resistant slipping layer. As this coating method, for example, any conventionally known method such as a gravure coater, a reverse coater, an air doctor coater or the like can be used.

  The above-described thermal transfer sheet can be subjected to a conventionally known thermal transfer recording method to perform thermal transfer recording. As a heat source for transferring the dye in the heat transferable color material layer onto the recording material, a line type thermal head or a laser beam can be used.

  The recording material is usually provided with an image receiving layer on at least one surface of the substrate. As the base material, a synthetic paper, cellulose paper, cast coated paper, film, or cellulose paper bonded with synthetic paper is usually used. The higher the adhesion to the color material layer, the more uniformly the dye is transferred during recording. Therefore, it is preferable that the surface be smooth, and if possible, use a substrate having a Beck smoothness of 10,000 seconds or more. preferable. In this respect, a base material using synthetic paper or a film is preferable.

  The image receiving layer is a layer mainly composed of a resin, and has a function of accepting a dye to form an image. As the resin, a resin that is easily dyed is preferable. For example, vinyl acetate resin, vinyl chloride resin, polyester resin, acrylonitrile-styrene resin, polyvinyl acetal resin and the like can be mentioned. These can be used in combination. If a resin having a glass transition point that is too low is used, an image may bleed during storage, and therefore it is preferable to use a resin having a glass transition point of 35 ° C. or higher.

  In addition to the resin, an additive can be added to the image receiving layer as necessary. As additives, curing agents such as isocyanate to cure the resin, release agents such as silicone added to prevent fusion with the color material layer during thermal transfer, ultraviolet absorbers to increase light resistance, Examples thereof include an antioxidant for improving weather resistance.

  The present invention will be described in more detail with reference to examples, but the present invention is not limited to the examples.

Example 1
(1) Synthesis of azomethine dyes
To 442 ml of ethyl 2-chlorobenzoate, 1500 ml of tetrahydrofuran was added, 142 ml of acetonitrile was added at 0 ° C., and 304 g of potassium-t-butoxide was added over 30 minutes. After stirring for about 1 hour, 900 ml of water was added and the mixture was separated with hexane, and the aqueous layer was neutralized to about pH 2 with concentrated hydrochloric acid. After neutralization, the mixture was separated with toluene, and the oil layer was distilled off under reduced pressure to obtain 407 g of Compound A as an acetonitrile derivative (yield 84%). Compound A was identified by HPLC and ESIMS. A synthesis scheme is shown below.

Next, 400 ml of 3-propanol was added to 405 g of Compound A and stirred at 40 ° C. To this, 136 g of hydrazine monohydrate was added dropwise and reacted at reflux temperature for 3 hours. Thereafter, about 300 ml of the reaction system was distilled off under reduced pressure, and 100 ml of saturated brine and 500 ml of toluene were added to separate the layers. After removing the aqueous layer, the oil layer was dried over magnesium sulfate. This toluene solution was distilled off under reduced pressure, and 450 ml of methanol was added to the residue. The methanol solution was added dropwise to 8000 ml of a saturated aqueous NaHCO ₃ solution to precipitate crystals. The crystals were collected by filtration and dried to obtain 368 g of Compound B, which is an aminopyrazole derivative (yield 84%). Compound B was identified by HPLC and ESIMS. A synthesis scheme is shown below.

Further, 367 g of Compound B was stirred in 1800 ml of methanol, and 208.2 g of imidate hydrochloride obtained from acetonitrile and methanol was added. After stirring at room temperature for 3 hours, 132.1 g of hydroxylamine hydrochloride and 36 g of caustic soda were added, and the mixture was stirred at 40 ° C. with heating. After reacting for 3 hours, the reaction system was transferred to 9000 ml to precipitate crystals. The crystals were collected by filtration and dried to obtain 378 g of compound C which is an amide oxime derivative (yield 79%). Compound C was identified by HPLC and ESIMS. A synthesis scheme is shown below.

Subsequently, 85 g of Compound C was stirred in 85 ml of DMAC and 85 ml of acetonitrile, 65 g of P-toluenesulfonic acid chloride was added under water cooling, and 27.4 ml of pyridine was added. After stirring for 30 minutes, 27.4 ml of pyridine and 280 ml of methanol were added and stirred while heating under reflux. After stirring for 5 hours, it was transferred to 1600 ml of water, and the crystals were collected by filtration. The crystals were recrystallized in 80 ml of methanol to obtain 52.2 g of Compound D (yield 66%). Compound D was identified by HPLC and ESIMS. A synthesis scheme is shown below.

Next, 1.4 g of Compound D was stirred in 9.8 ml of methanol, and 1.67 g of sodium hydroxide and 1.82 g of Compound E were added. Thereafter, an aqueous solution obtained by dissolving 3.57 g of sodium persulfate in 5.0 ml of water was added dropwise to the reaction solution. After stirring for 1 hour, the reaction solution was filtered, and the obtained residue was suspended in warm water at 40 ° C. for 1 hour. After filtering the suspension, the obtained solid was dissolved in toluene and purified by silica gel chromatography to obtain 1.17 g of azomethine compound 1 (yield 48%). A synthesis scheme is shown below. The compound was identified by HPLC and ESIMS. The analysis results were as follows.
¹ H NMR, δ (ppm) (multiplicity, integral) (CDCl ₃ ) 9.29 (d, 1H), 7.46 (m, 4H), 6.67 (d, 1H), 3.66 (q, 4H), 2,59 (s, 3H), 2.43 (s, 3H), 1.26 (t, 6H)

(2) Preparation of dye ribbon 2.5 parts by weight of the obtained azomethine compound, 70 parts by weight of polyvinyl acetal resin (KS-5, 5% varnish, manufactured by Sekisui Chemical), 13.75 parts by weight of toluene, 13.75 parts by weight of methyl ethyl ketone The ink obtained by mixing and stirring the parts was applied onto a 4 μm thick substrate (4WF597, manufactured by Toray Industries, Inc.) using a bar coater so that the application amount was 0.5 g / m ^2, and And dried for 2 minutes to prepare a dye ribbon.

  Next, 20 parts of vinyl chloride-vinyl acetate copolymer resin (Solvine C, manufactured by Nissin Chemical Industry), 2 parts of epoxy-modified silicone (X-22-3000T, manufactured by Shin-Etsu Chemical Co., Ltd.), toluene / methyl ethyl ketone (1 1 mixture) 78 parts of the composition obtained by mixing and stirring the film thickness after drying using a bar coater on a synthetic paper made of polypropylene (trade name: YUPO FPG150, manufactured by YUPO Corporation) having a thickness of 150 μm. Was coated and dried so as to be 5 μm, and further treated in an oven at 80 ° C. for 12 hours to obtain an image receiving paper.

  Using the produced dye ribbon, printing was performed on the image receiving paper by a thermal transfer printer (CP740, manufactured by Canon).

(3) Sensitivity evaluation About the printed matter printed, the sensitivity of the printed matter was measured using the spectroscopic colorimeter (Spectrolino, GretagMacbeth). As for the evaluation results of sensitivity, those with OD = 1.80 or more were marked with ◯, and those with OD = 1.80 or less were marked with ×. The results were as shown in Table 1 below.

(4) Light resistance evaluation The printed matter was irradiated for 24 hours at 400 kJ (420 nm integrated value) using a xenon fade meter (CI4000, manufactured by Atlas). CIRA soda lime was used as a filter. For the printed matter before and after the light irradiation, the optical density was measured using a spectrocolorimeter (Spectrolino, manufactured by GretagMacbeth), and the density residual ratio was calculated by the following formula.

Concentration residual ratio = (optical density after irradiation) / (optical density before irradiation) × 100
A density residual ratio of 70% or more was rated as ◯, and a density remaining ratio of less than 70% was marked as x. The results were as shown in Table 1 below.

(5) Hue measurement About the printed matter printed, the hue was measured using the spectroscopic color meter (Spectrolino, GretagMacbeth). Regarding the measurement results, there is a hue of OD = 1.0 in the region of b ^* <− 0.34a ^* and b ^* > − 0.63a ^{* on} the ab-plane of the L ^* a ^* b ^* color system. Things were marked with ○ and those without were marked with ×. The results were as shown in Table 1 below.

Examples 2-5
In the synthesis of the azomethine dye of Example 2, the dye was synthesized in the same manner as in Example 1 except that the starting material was changed to ethyl 2-toluate, and the same evaluation as in Example 1 was performed.

  Further, in the synthesis of the azomethine dye of Example 3, the dye was synthesized in the same manner as in Example 1 except that the starting material was changed to ethyl benzoate, and the same evaluation as in Example 1 was performed. The results were as shown in Table 1 below.

  Further, in the synthesis of the azomethine dye of Example 4, the dye was synthesized in the same manner as in Example 1 except that the starting material was changed to ethyl 2-bromobenzoate, and the same evaluation as in Example 1 was performed. The results were as shown in Table 1 below.

  Further, in the synthesis of the azomethine dye of Example 5, the dye was synthesized in the same manner as in Example 1 except that the starting material was changed to ethyl naphthoate, and the same evaluation as in Example 1 was performed. The results were as shown in Table 1 below. The results were as shown in Table 1 below.

Comparative Examples 1-3
A dye was synthesized in the same manner as in Example 1 except that a magenta dye represented by the following formula (D-9 dye described in Examples of Japanese Patent No. 3013137) was used as the dye of Comparative Example 1. The same evaluation as in Example 1 was performed. The results were as shown in Table 1 below.

Further, a dye was synthesized in the same manner as in Example 1 except that a magenta dye (Disperseviolet 26) represented by the following formula was used as the dye of Comparative Example 2, and the same evaluation as in Example 1 was performed. The results were as shown in Table 1 below.

Furthermore, the same evaluation as in Example 1 was performed except that a magenta dye represented by the following formula (Comparative dye A described in Japanese Patent No. 3013137) was used as the dye of Comparative Example 3. The results were as shown in Table 1 below. The magenta dye was produced by the method described in Japanese Patent No. 3013137.

Claims (3)

A thermal transfer recording dye comprising an azomethine compound represented by the following formula (I).

(Where
R ₁ represents the following substituents (i) to (v):

Is selected from the group consisting of:
R ₂ and R ₃ each independently represents an alkyl group having 2 to 4 carbon atoms. ). The thermal transfer recording dye according to claim 1 , wherein R ₂ and R ₃ are ethyl groups. A method for producing a thermal transfer recording dye according to claim 1 or 2 , wherein a compound represented by the following formula II and a compound represented by the following formula III are reacted with an oxidizing agent in the presence of a base. Obtaining an azomethine compound of the formula I.