JPH11158407A - Evaporable colorant and method for recording therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an evaporable colorant having excellent heat stability and being desirable for use in a colorant evaporation type thermal recording system by purifying an evaporable colorant to a specified or lower total iron and copper content. SOLUTION: This colorant has a total iron and copper content of 10 ppm or below. The colorant is exemplified by a methine colorant, an azomethine colorant, an azo colorant, a quinophthalone colorant, a coumarin colorant, an anthraquinone colorant or a fused polycyclic colorant. The colorant having a total iron and copper content of 10 ppm or below is produced by subjecting a colorant synthesized by a usual method to an advanced purification process such as recrystallization utilizing a solvent, a reprecipitation utilizing a solvent, column chromatography or evaporation purification and suitably selecting purification conditions, for example, temperatures, pressure, atmospheres, solvents, and so on. Among the purification processes, column chromatography, evaporation purification, etc., are particularly effective.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vaporizable dye and a dye vaporization type thermal recording method using the vaporizable dye (the dye is vaporized from a thermal recording head by selective heating according to image information, and (An image recording method for recording on photographic paper).

[0002]

2. Description of the Related Art In recent years, the demand for hard copy colorization has been rapidly increasing, and recording techniques such as electrophotography, ink jet, fusion type thermal transfer, and dye thermal transfer (sublimation type thermal transfer) have been studied. Among these recording technologies, the dye thermal transfer recording method accepts an ink ribbon or ink sheet, in which an ink layer in which a heat transferable dye is dispersed at a high concentration in a suitable binder resin, and a dye to be thermally transferred. The printing paper coated with the dye-dyeing resin is superimposed, and from the back surface of the ink sheet where the dye is applied, heat is applied by a thermal head according to the image information, and the transfer amount of the dye is determined according to the amount of heat. Is controlled to record a gradation image. By repeating the above operation for the image signals decomposed into the three primary colors of subtractive color mixing, that is, yellow, magenta, and cyan, a full-color image having continuous gradation can be obtained. This method is characterized in that high-quality images equivalent to silver halide color photographs can be obtained, and that the apparatus can be reduced in size and maintenance is easy. However, this method is a major drawback in that a large amount of waste is generated due to disposable use of the ink sheet and high running costs are hampered. The fusion type thermal transfer recording method also has the same drawbacks because it uses an ink ribbon or an ink sheet.

On the other hand, in the ink jet recording method, small droplets of a recording liquid are provided on a recording head by a method such as an electrostatic suction method, a vibration generation method (piezo method), or a thermal method (bubble jet method) in accordance with image information. The recording medium is made to fly from a given nozzle and adhere to photographic paper for recording.
Therefore, unlike the case where an ink sheet is used, there is almost no generation of waste, and the running cost is low. Therefore, the technology for easily outputting a color image has been widely used.
However, in the ink-jet method, the density gradation in the pixel is basically difficult, and it is difficult to reproduce a high-quality color image in a short time as obtained by the dye thermal transfer recording method. That is, in the conventional ink jet system, since one droplet of ink forms one pixel having a constant density, in-pixel gradation is difficult in principle. Attempts have been made to represent pseudo gradation by the dither method, but the image quality is inferior to that of the dye thermal transfer recording method, and the recording time is significantly reduced.

[0004] The electrophotographic method has a low running cost,
Although the recording speed is fast, it is difficult to reduce the size of the apparatus and the cost of the apparatus is high. As described above, there is no recording technology that satisfies all requirements such as image quality, running cost, apparatus cost, and recording speed. A new thermal recording method (dye vaporization type thermal recording method) that solves these problems has been proposed (JP-A-52-36033, JP-A-54-7).
1636, JP-A-54-71637, JP-A-59-22
759, JP-A-62-162593 and JP-A-62-18
3392, JP-A-62-220388, etc.).
In other words, in these methods, a recording liquid (ink composition) containing a vaporizable (sublimable) dye or a vaporizable dye is directly heated to vaporize (sublimate) the dye and fly the vaporized dye to print. This is a method of recording on paper. In this thermal recording method, according to the recording energy to the heating means,
Since the amount of dye vaporization can be controlled, density gradation can be achieved, and high-quality color recording similar to the conventional dye thermal transfer recording method using an ink sheet becomes possible, and since no ink sheet is used, Low running costs similar to those of the ink jet system can be realized.

[0005] In the present specification, "vaporization" in the case of a vaporizable dye or dye vaporization type thermal recording means that at least a part of a solid or liquid state dye is vaporized, specifically, at least a part of the dye. Some include pseudosublimation in which a solid state is directly sublimated or liquefied and then vaporized. However, in these methods, since the dye is directly heated and vaporized, heat stress on the dye is extremely large, and thermal decomposition occurs during recording with the conventional dye, making it difficult to perform stable recording. Was. Therefore, improvement of the heat resistance of the dye is an important issue.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a highly purified dye having excellent thermal stability suitable as a dye for the above-mentioned new thermal recording method, and a novel heat-resistant dye using the dye. It is to provide a recording method.

[0007]

SUMMARY OF THE INVENTION The present invention provides a vaporizable dye characterized in that the total content of iron and copper is 10 ppm or less, and a dye vaporization type thermal recording method using the dye. I do.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a conventional dye thermal transfer recording system using an ink ribbon or an ink sheet, since the dye is thermally transferred to photographic paper by both mechanisms of vaporization and thermal diffusion, the thermal stress on the dye is not so large. Also, the required level of thermal stability for the dye is not so high. For this reason, the dye to be used has been used as it is, a dye synthesized by an ordinary method, or after purification by a hot suspension purification method using a general-purpose purification solvent.

However, in the dye vaporization type thermal recording method, since the dye is directly heated and vaporized, the thermal stress on the dye is extremely large, and if the conventional dye is used, thermal decomposition occurs during recording. It is difficult to perform stable recording, and improving the heat resistance of the dye is an important issue. From dye synthesis to thermal transfer recording, the handling process (synthesis, transportation, storage, recording environment)
Therefore, even a very small amount of an element having a great effect on the recording characteristics is mixed. The present inventors have noted that it is necessary to strictly control the elements mixed in the dye with respect to the performance of the vaporizable dye.

The present inventors have found that when the total content of iron and copper in the dye is 10 ppm or less, especially 1 ppm or less, excellent heat stability is exhibited. Iron and copper are used in the dye synthesis process such as raw materials for dye synthesis, solvents used in the synthesis, auxiliaries, catalysts, and materials for reactors such as stainless steel reactors and mild steel reactors, as well as various utilities such as water and nitrogen. In addition, it is mixed into the coloring matter from building materials and paints in the storage environment, pipes and storage containers involved in transportation, and is mixed in an amount of 15 ppm or more, for example, as shown in a comparative example described later.

Dyes having a total content of iron and copper of 10 ppm or less can be prepared by a method such as recrystallization, reprecipitation, column chromatography, and vaporization purification using a solvent with respect to dyes synthesized by a general method. Apply advanced purification methods and purify conditions such as temperature conditions, pressure conditions, atmosphere,
It can be manufactured only by carefully examining and selecting the type and composition of the solvent, the dye concentration, the heating and cooling rates, the stirring conditions, the type of column packing material, and the flow-through conditions.

Therefore, in the purification, when a purified solvent is used, the total content of iron and copper contained in the solvent is as follows:
It is preferably 1 ppm or less, more preferably 0.1 ppm or less.
ppm or less. Further, it is preferable that the apparatus to be used is sufficiently washed with the high-purity purified solvent before use. The vaporization purification method is a method of purifying by solidifying or liquefying a solid or liquid state dye after evaporating it.Specifically, the dye is directly vaporized from a solid state and then directly solidified from a gas state. Sublimation purification method, including pseudo-sublimation purification method in which the dye is vaporized after being liquefied and then directly solidified from the vaporized state, but after the dye is vaporized after being liquefied and then once liquefied from the gaseous state It may be solidified. The solvent may be removed after the dye solution in which the dye is dissolved in the solvent is vaporized and then liquefied. Hereinafter, these are collectively referred to as vaporization purification. Among the above advanced purification methods, column chromatography, vaporization purification method and the like are particularly effective. In particular, the vaporization purification method is advantageous because it can be carried out without using a solvent.

[0013] The vaporization purification is carried out under heating at a high temperature, but it is necessary to carry out the heating at a temperature higher than the vaporization temperature of the dye and lower than the decomposition temperature. The heating temperature is usually 5 to 100 ° C. higher than the vaporization temperature of the dye, preferably 10 to
The temperature is raised by 70 ° C. and usually lower by 5 to 200 ° C., preferably by 20 to 200 ° C. than the decomposition temperature. Further, in order to prevent the decomposition of the dye and to lower the heating temperature and to accelerate the vaporization rate of the dye, it is effective to carry out the treatment under reduced pressure.
Usually, the pressure condition is 0.0001 to 500 torr.
r, preferably 0.001 to 50 torr, particularly preferably 0.01 to 20 torr. If necessary, a carrier gas may be used. As this gas, nitrogen, argon, helium, or the like, which has no reactivity with the dye, can be passed.

In the case of sublimation purification and pseudo-sublimation purification in the vaporization purification method, a solidified purified dye is directly obtained, so that the process is not complicated and is industrially advantageous. FIG. 1 is a cross-sectional view showing a main structure of an automatic heating apparatus having a gold furnace electric furnace used as an example in sublimation purification and pseudo sublimation purification of a dye. 1 is a gold furnace electric furnace, 2 is an alumina fiber, 3 is a test tube containing a raw material dye, 4 is a goochroth, 5 is a quartz tube, 6 is a raw material dye,
7 represents a purified sublimation dye, and 8 and 8 'represent thermocouple positions.

In an industrial vaporization purification process, a container containing a vaporizable dye to be purified is heated by a heater or the like, and is heated at a temperature higher than the vaporization temperature of the dye, preferably higher than 10 ° C., and The dye is vaporized at a temperature below the thermal decomposition temperature. The vaporized dye gas is cooled by, for example, being guided to a cooling surface such as a cooling drum and adhered as a purified dye (solid), and then the purified dye is recovered by scraping off with a scraper or the like.

Examples of the material for the vaporizable dye of the present invention include methine dyes, azomethine dyes, azo dyes, quinophthalone dyes, coumarin dyes, anthraquinone dyes, and condensed polycyclic dyes. It is desirable that these dyes have a nonionic structure in order to have good vaporizability. Examples of the methine dye include a dye represented by the following general structural formula (I).

[0017]

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Here, X ¹ and Y ¹ are X ¹ (Y ¹ ) CH
Represents the residue of an active methylene compound represented by _2, X ¹ and Y ^1, respectively, a cyano group, -COZ ² or -S
O ₂ Z ³ (As Z ² and Z ³ , respectively, -R ¹ ,
—OR ² , —NR ³ R ⁴ , or a 5- to 6-membered heterocyclic group, wherein R ^{1 to} R ⁴ are each a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group , A 5- or 6-membered heterocyclic group, or a 5- or 6-membered cycloalkyl group. ) Or X ¹ and Y
^{And 1} may be combined with each other to form a 5- to 6-membered carbocyclic or heterocyclic ring, and these rings may be condensed with another ring. Specific examples include those of the following general formulas (II) to (VII).

[0019]

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[0020]

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[0021]

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[0022]

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[0023]

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[0024]

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Where R^Five~ R^{twenty one}Are the hydrogen sources, respectively.
, Substituted or unsubstituted alkyl group, substituted or unsubstituted
Substituted aryl group, cyano group, -COZ^Four, -SO_TwoZ
^Five, -NR^{twenty two}R^{twenty three}, -OR^{twenty four}, -NR^{twenty five}COZ⁶, -N
R²⁶SO_TwoZ⁷, Nitro group or halogen atom
Then Z^Four~ Z⁷Is -R²⁷, -OR²⁸, -N
R ²⁹R³⁰Or a 5- to 6-membered heterocyclic group,^{twenty two}
~ R³⁰Is a hydrogen atom, a substituted or unsubstituted
Alkyl group, substituted or unsubstituted aryl group, 5 to 6
Membered heterocyclic group or 5- or 6-membered cycloalkyl
Represents a group. )

Z represents a hydrogen atom or a cyano group;
¹ is a benzene ring or a thiazole ring, a quinoline ring,
Represents a heterocyclic ring such as a pyridine ring, a thiophene ring or an imidazole ring, and these are represented by —NR ³¹ R ³² (R ³¹ and R ³² are
Each represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, -COZ ¹² or -SO ₂ Z ¹³ (Z ¹² and Z ¹³ are each -R ^42,, -
OR ⁴³ , —NR ⁴⁴ R ⁴⁵ or a 5- to 6-membered heterocyclic group (R ^{42 to} R ⁴⁵ are a hydrogen atom, a substituted or unsubstituted aryl group, a 5- to 6-membered heterocyclic group, or a 5- to 6-membered ring; Represents a cycloalkyl group of a ring). ). ), A substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group or a halogen atom. Specific examples of methine dyes are shown in Tables 1a to 1j. Examples of the azomethine dye include a dye represented by the following general structural formula (VIII).

[0027]

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Here, X ² and Y ² are X ² (Y ² ) CH
A residue of an active methylene compound represented by ₂ are defined as for each of the X ¹ and Y ^1, A ² is the A
¹ and are similarly defined. Specific examples of the azomethine dyes are shown in Tables 2a to 2j. Examples of the azo dye include a dye represented by the following general structural formula (IX).

[0029]

Embedded image A ³ -N = NB (IX)

Here, A ³ represents a residue of a diazo component represented by A ³ —NH ₂ and is a benzene ring or a hetero ring which may have an arbitrary substituent. Examples of the heterocyclic ring represented by A ³ include thiazole, isothiazole, imidazole, pyrazole, triazole, 1,
Rings such as 2,4-thiadiazole, 1,3,4-thiadiazole, benzothiazole, benzoisothiazole and thiophene are exemplified. Examples of the substituent on the benzene ring or hetero ring represented by A ³ include a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group, a cyano group, a nitro group, a halogen atom, _{^{-COZ 8, -SO 2 Z 9,}} -NR
^{33 R 34, -NR 35 COZ 10} , can be mentioned -NR ³⁶ SO ₂ Z ¹¹ or -SR ^41, Z ⁸ ~Z ^11, respectively, -
R ³⁷ , —OR ³⁸ , —NR ³⁹ R ⁴⁰ or a 5- to 6-membered heterocyclic ring, wherein R ^{33 to} R ⁴¹ are each a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl Group, a 5- to 6-membered heterocyclic group, or a 5- to 6-membered cycloalkyl group.

B represents a residue of a coupling component represented by BH, and is a residue of a benzene ring, a hetero ring, or an active methylene compound which may have an arbitrary substituent. Examples of the hetero ring represented by B include rings such as thiazole, quinoline, pyridine, thiophene, and imidazole. Examples of the substituent of the benzene ring or heterocyclic ring represented by B, those similar to the substituent of the A ¹ and the like. Specific examples of the azo dyes are shown in Tables 3a to 3j. Quinophthalone dyes (4a to 4
b), coumarin dyes (5a-5b), anthraquinone dyes (6a-6k) and other condensed polycyclic dyes (7
Specific examples of a to 7j) are shown in Table 1. Of these dyes, methine dyes and anthraquinone dyes are particularly suitable for the purpose of the present invention because of their excellent heat resistance and good vaporization.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

[0035]

[Table 4]

[0036]

[Table 5]

The dye purified as described above is used as it is or as an ink composition (recording liquid) mixed with a high boiling point organic solvent in a dye vaporization type thermal recording system. The pigment concentration of the ink composition is 5
% To 90%, preferably 10% to 70%. Further, it may contain a surfactant or the like. Mixing can be at room temperature, but can also be heated or sonicated to enhance the mixing effect. The heating temperature is
Preferably 30 to 130 ° C, particularly preferably 50 to 90 ° C
It is.

When the vaporizable dye of the present invention is used for dye vaporization type thermal recording, the total content of iron and copper is 10 p.
Needless to say, it should be kept below pm. That is, the vaporization recording is performed by maintaining the organic solvent used in the above-described ink composition and the dye within the above-mentioned specific range without being stained before being provided for the vaporization recording in the apparatus. It can be carried out industrially advantageously. The dye of the present invention is suitably used as a dye in the above-described new thermal recording system for performing dye vaporization type thermal recording. That is, the recording method is excellent in thermal stability, which is an extremely important physical property, and has a feature that good recording can be performed.

[0039]

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

COMPARATIVE EXAMPLE 1 (Synthesis of Dye) 192 g of 1,4-dihydroxyanthrahydroquinone, 258 g of 2-ethylhexylamine and 1572 g of isopropyl alcohol were charged.
After stirring for 8 hours, 8 g of copper sulfate was added, and the mixture was further reacted at 80 ° C. for 4 hours while blowing air. After cooling to room temperature, the precipitated crystals were filtered, and the obtained crystals were suspended in 1876 g of 7% aqueous hydrochloric acid and stirred at 70 ° C. for 1 hour.
Thereafter, the crystals were filtered, washed with water and dried, and
o. 309 g of a synthetic dye A represented by a structural formula of 6k was obtained. The purity of this synthetic dye was 99.7% as a result of analysis by high performance liquid chromatography. Further, after the synthetic pigment was wet-decomposed, the content of iron was 8 ppm and the content of copper was 10 ppm as a result of measurement by ICP-AES (high frequency inductively coupled plasma atomic emission spectrometer).

(Thermal Stability Test of Dye) 0.5 g of the synthetic dye A obtained by the above method was placed in the bottom of a glass test tube having an inner diameter of 2 cm and a length of 20 cm, and a thin film of alumina fiber was packed on the upper part of the sample. . The test tube is put into a quartz tube 5 of an automatic heating device (manufactured by Thermo Riko Co., Ltd.) having the gold furnace electric furnace 1 of FIG. 1 used for vaporization and purification of the vaporizable dye, and the gooch funnel 4 is placed at the outlet of the test tube. Overlay synthetic dye A (raw material dye) 6 was set. However, in the thermal stability test, as a heating condition, a quartz tube was connected to an oil rotary vacuum pump, exhausted, reduced to 0.1 torr, and exceeded a vaporization temperature of 200 ° C. employed in Example 2 described later by 40 ° C. After heating at 240 ° C. for 3 hours, a thermal stability test was conducted to examine the thermal decomposition behavior of the dye. As a result, as shown in FIG. 1, the dye 7 vaporized (pseudo-sublimation) and cooled was deposited as blue crystals on the vessel wall at the outlet of the test tube 3. The temperature near the outlet of the test tube 3 was 30 ° C. A black, non-vaporizable residue remained at the bottom of the test tube. The purity of the dye precipitated at the outlet of the test tube was 97.9% as a result of analysis by high performance liquid chromatography, and the purity was reduced by 2.7%.
No dye remained in the residue remaining at the bottom of the test tube, the amount was 0.0024 g, corresponding to 0.48% of the treated dye.

Example 1 Purification of Dye 50 g of the synthetic dye A obtained in Comparative Example 1 was
The solution was dissolved in 500 ml of N, N-dimethylformamide (manufactured by Kanto Chemical Co., Ltd.) at 500C and dropped into 2500 ml of demineralized water, which was vigorously stirred at room temperature, over 2 hours to precipitate a dye. The precipitated dye is filtered, washed with demineralized water, dried,
Purified dye B was obtained by the reprecipitation method. The purity of the purified dye B obtained by the reprecipitation method was 99.7%. Also,
Since iron was detected by ICP-AES, but copper was below the detection limit and was not detected, the purified dye was dry-ashed in an infrared heating furnace placed in a class 1000 clean room, and then purified for semiconductors. After heating and dissolving in an acid and quantifying the volume with ultrapure water, the content of iron was 3 ppm and the content of copper was 5 ppm as measured by ICP-MS (high frequency inductively coupled plasma mass spectrometer).

(Dye Thermal Stability Test) A dye thermal stability test was conducted in the same manner as in Comparative Example 1 except that the obtained purified dye B was used. As a result, the dye 7 precipitated as blue crystals on the vessel wall at the outlet of the test tube 3, and a small amount of black non-vaporizable residue remained at the bottom of the test tube. The purity of the dye deposited at the outlet of the test tube was 97.9%, and the purity was reduced by 1.8%. No dye remained in the residue remaining at the bottom of the test tube, the amount was 0.0007 g, corresponding to 0.14% of the treated dye.

From the above test results, the total of the iron and copper contents in the dye purified by the reprecipitation method using a solvent was 1%.
0 ppm or less of the vaporizable dye, the residue after heating is small, and the decomposition of the dye at the time of heating recording is suppressed due to the improvement in thermal stability. It is clear that the recording medium has a characteristic capable of performing accurate recording.

Example 2 (Purification of Dye) 5 g of the purified dye B obtained in Example 1 was subjected to vaporization (pseudo-sublimation) purification using the apparatus shown in FIG. However, the conditions for the vaporization and purification treatment were 200 ° C. under a reduced pressure of 0.1 torr.
For 3 hours. 4.8 g of a vaporized purified dye was obtained as blue crystals on the vessel wall at the outlet of the test tube 3. The purity of the obtained vaporized and purified dye C is 99.7%,
As a result of the measurement by ICP-MS, the iron content was 0.1%.
1 ppm, and the content of copper was 0.05 ppm.

(Determination of Thermal Stability of Dye) A thermal stability test of the dye was carried out in the same manner as in Comparative Example 1 except that 0.5 g of the purified and vaporized dye C obtained by the above method was used. As a result, the vaporized (pseudo-sublimated) and cooled dye 7 precipitates as blue crystals on the vessel wall at the outlet of the test tube 3, and at the bottom of the test tube,
A very small amount of black non-vaporizable residue remained. The purity of the dye deposited at the outlet of the test tube was 99.5%, and the purity was reduced by 0.2%. No dye remained in the residue remaining at the bottom of the test tube, and the amount was 0.0001 g or less, corresponding to 0.02% or less of the treated dye.

According to the above test results, the vaporizable dye purified by vaporization purification and having a total iron and copper content of 1 ppm or less in the dye has an extremely small residue after heating;
Further, since the decomposition of the dye at the time of heating recording is suppressed by the improvement of the thermal stability, it is clear that the present invention has a characteristic that enables extremely good recording when applied to the above-mentioned new thermal recording method.

[0048]

When the dye of the present invention is applied to a recording method based on a dye vaporization type thermal recording system, good recording can be performed industrially advantageously.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a main part structure of an automatic heating apparatus having a gold furnace electric furnace used as an example in the case of using a vaporization purification method in producing a vaporizable dye of the present invention.

Claims (4)

[Claims] 1. A vaporizable dye, wherein the total content of iron and copper is 10 ppm or less. 2. The vaporizable dye according to claim 1, wherein the total content of iron and copper is 1 ppm or less. 3. The method according to claim 1, wherein the vaporizable dye is a methine dye, an anthraquinone dye, an azomethine dye, an azo dye, a quinophthalone dye, a coumarin dye, a perinone dye, a xanthene dye, a thioxanthene dye, or an azathioxanthene dye. The vaporizable dye according to claim 1 or 2, wherein the dye is selected from the group consisting of a system dye, an oxazine dye, and a thiazine dye. 4. A dye vaporization type thermal recording method using the dye according to claim 1.