JPH11100523A - Volatile dye and recording method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dye for a thermal recording system of direct dye volatiliza tion type by preparing a volatile dye which has no exothermal peak at temperatures not higher than a specific temperature, shows a weight reduction of not higher than a specific value at a specific temperature measured by means of a TG-DTA and has a purity of not less than a specific value. SOLUTION: A prepared volatile dye has a purity of not less than 97%, shows no exothermal peak at 300 deg.C or below and shows a weight reduction of not less than 1% at 300 deg.C measured at a rate of temperature increase of 10 deg.C/min and at a flow rate of air as a carrier gas of 200 ml/min by means of a Thermogravimetry-Differential Thermal Analysis using 5 mg of the sample. Such a dye can be obtained by purifying various dyes by means of a column chromatography, sublimation purification, etc. The dye has sufficient volatility and shows excellent thermal stability for a long period and excellent color purity as yellow, Magenta and cyanide dyes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-purity vaporizable dye having good heat resistance and color purity, and a dye direct vaporization type thermal recording method using such a dye. In addition, the dye direct vaporization type thermal recording method is a vaporizable (sublimable) dye or
In this method, a recording liquid containing a vaporizable dye is directly heated to vaporize (sublimate) the dye, cause the vaporized dye to fly, and guide the recording to photographic paper for recording.

[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 techniques, the dye thermal transfer recording method receives an ink ribbon or an ink sheet coated with an ink layer in which a heat transferable dye is dispersed at a high concentration in an appropriate binder resin, and receives the dye to be thermally transferred. Overlay the photographic paper coated with the dye-dyeing resin, from the back of the ink sheet coated with the dye,
By applying heat according to the image information with the thermal head and controlling the transfer amount of the dye in accordance with the amount of heat, a gradation image can be recorded. The above operation is performed for the three primary colors of subtractive color mixing,
That is, by repeating each of the image signals separated into 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. But,
This method has large drawbacks such as generation of a large amount of waste due to disposable ink sheets and high running cost, which hinders its spread. 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 speed 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. As a new recording method for solving these problems, a dye direct vaporization type thermal recording method has been proposed (JP-A-52-36033, JP-A-54-71636, JP-A-54-71637, and JP-A-54-71637). (JP-A-59-22759, JP-A-62-162593, JP-A-62-183392, JP-A-62-220388, JP-A-8-169171, JP-A-7-89107). In other words, these methods vaporize (sublimate) the dye by directly heating a vaporizable (sublimable) dye or a recording liquid containing the vaporizable dye, fly the vaporized dye, and guide the recording paper to print. How to do it. In this thermal recording method, the amount of dye vaporization can be controlled according to the recording energy to the heating means, so that density gradation can be achieved, and high image quality similar to the conventional dye thermal transfer recording method using an ink sheet can be obtained. Color printing is possible, and since no ink sheet is used, low running costs similar to those of the ink jet system can be realized.

[0005]

However, in these dye direct vaporization type thermal recording methods, since the dye is directly heated and vaporized, the thermal stress on the dye is extremely large.
Conventional dyes used in the dye thermal transfer recording method undergo thermal decomposition during recording, and it is difficult to perform stable recording. Therefore, development of a vaporizable dye having excellent heat resistance (thermal decomposition resistance) is an important issue. In addition, for full color recording, yellow with excellent color purity as well as heat resistance,
Magenta and cyan three primary color pigments are required. An object of the present invention is to provide a dye for the above-described new dye direct vaporization type thermal recording system, which has sufficient vaporizability, excellent heat resistance over a long period of time, and excellent color purity as yellow, magenta, and cyan dyes. The present invention is to provide a dye having the same.

[0006]

As a result of various studies, the present inventors have found that a dye having specific thermal properties and purity can achieve the object of the present invention. That is, the gist of the present invention is that TG-DTA (Thermogravimetry) is used.
-Differential ThermalAnaly
sis), the exothermic peak measured under the following conditions was 3
It is a vaporizable dye having a weight loss rate at 300 ° C. of not less than 00 ° C. of 1% or more and a purity of 97% or more.

[0007]

[Table 2] TG-DTA measurement conditions Heating rate: 10 ° C / min Carrier gas and flow rate: air, 200 ml / min Sample amount: 5 mg

The present invention also relates to a dye direct vaporization type thermal recording method using such a dye. Hereinafter, the present invention will be described in detail. In the dye direct vaporization thermal recording method of the present invention, a laser beam, a thermal head, or the like is used as a heating means. In order to achieve a sufficient recording speed and recording density, the heating temperature of the dye is about 300 ° C. Expected to reach. Therefore, the dye applied to the thermal recording of the present method is required to have no thermal decomposition point at 300 ° C. or lower and to have sufficient vaporization required at 300 ° C. for recording.

The thermal decomposability and vaporization properties of the dye are determined by TG-DTA.
(Thermogravimetry-Differe
Tial Thermal Analysis). That is, when a certain amount of a dye sample is heated at a certain rate and heated, and the dye has thermal decomposition property, the thermal decomposition temperature is detected as a temperature at which an exothermic peak is exhibited. Therefore, the dye of the present invention suitable for the recording method needs to have no exothermic peak at 300 ° C. or lower in TG-DTA measurement.

The degree of vaporization of the dye is determined by TG-DT
In A measurement, it appears as a weight loss rate of the dye at a predetermined temperature. The dye applied to the thermal recording method according to the present invention is more advantageous as the vaporization property is larger, that is, the weight loss rate is higher. However, if the weight loss rate is at least 1%, the dye is applied to the recording method according to the present invention. be able to. The weight loss rate is preferably 3% or more.

Usually, dyes used in various recording methods are not necessarily required to have high purity. Also in the dye of the thermal recording method according to the present invention, the presence of impurities has not been particularly problematic so far. Thus, the present inventors consider that there is a possibility that the heat resistance of the dye may be reduced due to the influence of impurities in the dye, and as a result of examining the relationship between the purity and the heat resistance of the dye, the following Examples As shown, it has been found that the unpurified dye after synthesis has a lower heat resistance when heated at a higher temperature for a longer time than the purified dye. In the thermal recording method of the present invention, the heat resistance of the dye is very important. In particular, in this thermal recording method, since the dye is repeatedly heated, it is necessary that the dye does not decompose even when heated at a high temperature for a long time. The higher the purity of the dye, the better the heat resistance of the dye. However, as long as the purity is at least 97%, the dye can be applied to the thermal recording method of the present invention.
Preferably, the purity of the dye is at least 98%.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The specific chemical structures of the dyes suitable for the present invention are shown in Table 1, but the dyes suitable for the present invention are not limited to these. Various dyes selected from methine dyes, azomethine dyes, azo dyes, quinophthalone dyes, coumarin dyes, anthraquinone dyes, and condensed polycyclic dyes can be used as long as they have vaporization and purity. May be.

The vaporizable dye of the present invention can be obtained, for example, by purifying the dye of Table 1 synthesized according to a known method so as to have the purity and thermal properties specified in the present invention. As a method for purifying the dye, known purification methods such as a recrystallization method using a solvent, a reprecipitation method, a column chromatography and a sublimation purification method using no solvent can be applied.
Column chromatography, sublimation purification, and the like are particularly effective. In particular, sublimation purification is particularly advantageous because it can be performed without using a solvent.

When a full-color image is recorded by the recording method of the present invention, three primary color dyes of yellow, magenta and cyan are required. As a yellow dye, the absorption maximum wavelength of the visible absorption spectrum in acetone is 410 to 460 nm.
The magenta dye has a maximum absorption wavelength of 510 to 510 in a visible absorption spectrum in acetone.
It must be at 560 nm, and as the cyan dye, the absorption maximum wavelength of the visible absorption spectrum in acetone must be at 610 to 670 nm. Therefore,
The vaporizable dye of the present invention preferably has an absorption maximum wavelength in the visible absorption spectrum within the above range.

[0015]

[Table 3]

[0016]

[Table 4]

[0017]

[Table 5]

[0018]

[Table 6]

[0019]

[Table 7]

[0020]

[Table 8]

[0021]

[Table 9]

[0022]

[Table 10]

[0023]

[Table 11]

[0024]

[Table 12]

[0025]

[Table 13]

The method for using the vaporizable dye of the present invention in a dye direct vaporization type thermal recording method is not particularly limited.
The same applies to the dyes used in this type of recording method.
That is, the dye may be used as it is, but is usually used as a dye composition (ink) containing a solvent, a surfactant, various stabilizers, and the like. The solvent has a boiling point of 15
It is preferable that the dye has excellent thermal stability at about 0 ° C. to 400 ° C. and sufficiently dissolves or disperses the dye of the present invention. Specific examples include phthalates, alkylbenzenes, and alkylnaphthalenes. Examples of the stabilizer include phenols and amines known as antioxidants, light stabilizers, rubber aging inhibitors, and the like. Further, the dye of the present invention may be used as a mixture of two or more kinds.

[0027]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which, however, are not intended to limit the scope of the present invention. The dye Nos. Is the dye No. in Table 1. Corresponding to The “exothermic peak” and “weight loss rate” are TG-DTA measurement values performed under the above-described conditions.

[Recording Apparatus] The recording apparatus used in the thermal recording test of the embodiment will be schematically described with reference to FIG. Glass beads (particle size: 5 to 7 μm) are ultrasonically dispersed in ethanol to form a 25% by weight liquid, and coated on the quartz glass substrate 1 of FIG.
After drying, sinter for 5 minutes in a furnace at 655 ° C.
Thus, a bead layer 2 having a porous structure of m was formed. A chromium metal film was deposited on the surface layer of the beads on the glass substrate, and an ITO film 3 was deposited on the back surface of the glass substrate, thereby producing a recording head. 50 μm above the bead layer 2 by the spacer 4
, A receiving paper SCT-CK150S (5) manufactured by Mitsubishi Electric Co., Ltd. is attached, and the structure is such that irradiation can be performed with a laser diode 6 movable from the back surface of the glass substrate.

[Recording conditions] Bead layer 2 on glass substrate surface
The recording head is heated to 100 ° C., and a laser diode is driven from the back surface at a frequency of 1 kHz (duty: 5).
(0%). The power of the laser diode on the back surface of the glass substrate is 33 mW, and the beam diameter is 10 μm.

Example 1 It has a structure of 38 and a purity of 97.5%.
A dye having no exothermic peak below 00 ° C., a weight loss at 300 ° C. of 3.8%, and a maximum absorption wavelength of 639 nm was added to dioctyl phthalate at 5% by weight, and ultrasonically dispersed for 15 minutes to prepare an ink. Using this ink, recording was performed under the above recording conditions by changing the number of laser pulses by the above recording apparatus. As a result, clear cyan high-density recording dots were obtained. FIG. 2 shows the relationship between the number of laser pulses and the optical density of the obtained recording dots, and FIG. 3 shows the relationship between the number of laser pulses and the recording dot diameter. Optical density is Konica Micro Densitometer PDM-5A / AR
Was measured. The dye used here is a dye having a relatively low weight loss rate, but even with such a dye, it exhibits a sufficiently practical optical density (FIG. 2), and can be stably recorded with good reproducibility. It is clear that there is (Figure 3). FIGS. 2 and 3 show that the optical density and the dot diameter change according to the number of pulses, and it is clear that gradation recording is possible.

Example 2 No. 2 in Table 1 Having a structure of 57 and a purity of 98.2%, 3
A recording test was carried out in the same manner as in Example 1 using a dye having no exothermic peak below 00 ° C., a weight loss at 300 ° C. of 4.0%, and a maximum absorption wavelength of 645 nm. As a result, clear cyan high-density recording dots were obtained. FIG. 4 shows the relationship between the number of laser pulses and the optical density of the obtained recording dots, and FIG. 5 shows the relationship between the number of laser pulses and the recording dot diameter. The dye used here is a dye having a relatively low weight loss rate. However, from FIGS. 4 and 5, even such a dye shows a sufficiently practical optical density and is stably recorded with good reproducibility. It is clear that the gradation recording is possible.

Example 3 20 g of N, N-di (n) butylaniline was charged into 50 ml of N, N-dimethylformamide, 11.5 g of tetracyanoethylene was added with stirring, and the mixture was stirred at room temperature for 3 hours. Reacted. The precipitated crystals were filtered, washed with methanol, and dried. 25 g of the dye represented by 33 was obtained. The purity of this synthetic dye was 96%.

1 g of the above synthetic dye was added to 7 × 10 ^-4 Torr
The mixture was heated at 170 ° C. for 3 hours under reduced pressure (0.0933 Pa) to carry out sublimation purification to obtain 0.95 g of a purified dye.
The purity of this purified dye was 99.9% or more. on the other hand,
1 g of the above synthetic dye was dissolved in chloroform and purified by column chromatography using silica gel as a carrier and chloroform as an eluent to obtain 0.93 g of a purified dye. The purity of the purified dye is 98.6%
And the TG-DTA measurement value is shown in Table 2 below. 3
As shown in FIG.

1 μg of each of the dye purified by the above method and the unpurified synthetic dye was sealed in an aluminum container (capacity: 40 μl), and the mixture was placed in a DSC apparatus (Seiko DSC).
20), the decomposition rate of the dye after heating at 200 ° C. for 2 hours was examined. As a result, the purified dye by sublimation purification did not decompose at all, but 0.5% of the purified dye by column chromatography and 6% of the unpurified synthetic dye were decomposed. The purity and decomposition rate of the dye were analyzed by high performance liquid chromatography. The measurement conditions of the high performance liquid chromatography are as follows.

Column: Unisil Pack 5C18-250B Moving bed: acetonitrile / water: 95/5 Flow rate: 1.0 ml / min Detector: UV (254 nm) From the above test results, if the purity of the dye is low, It is clear that the heat resistance of the sample is lower than the original heat resistance. From these results, it is considered that when a low-purity dye is applied to the thermal recording method of the present invention, stable recording for a long time becomes difficult due to thermal decomposition of the dye.

Example 4 3-Methyl-4-formyl-N, N-di (i) butylaniline (24.7 g) and malononitrile (6.9 g) were charged in methanol (100 ml), and a 1N aqueous sodium hydroxide solution (5 m) was charged.
1 was added and reacted under stirring at room temperature for 5 hours. The precipitated crystals were collected by filtration, washed with methanol, and dried.
No. 26 g of the dye represented by No. 4 was obtained. The purity of this synthetic dye was 95%.

1 g of the above synthetic dye was subjected to sublimation purification in the same manner as in Example 3. However, the heating temperature was 150 ° C. As a result, 0.93 g of the purified dye was obtained, and its purity was 99.9% or more. On the other hand, 1 g of the above synthetic dye was dissolved in chloroform, purified by column chromatography using silica gel as a carrier and chloroform as an eluent, and as a result, 0.91 g of the purified dye was recovered.
The purity of this purified dye was 99.5% and its TG-DTA
The measured values are shown in Table 2 As shown in FIG.

1 μg of each of the dye purified by the above-described method and the unpurified synthetic dye was sealed in an aluminum container (capacity: 40 μl), and the mixture was placed in a DSC apparatus (Seiko DSC).
20), the decomposition rate of the dye after heating at 200 ° C. for 2 hours was examined. As a result, the dye purified by sublimation purification and column chromatography did not decompose at all, but 5% of the unpurified dye was decomposed.

Example 5 1-isobutylamino-4-bromoanthraquinone
2 g, 56 g of aniline, 3.3 g of sodium acetate and 0.1 g of copper sulfate were charged and stirred at 155 to 160 ° C. for 1 hour.
Reacted. After cooling to room temperature, 100 ml of methanol and 50 ml of concentrated hydrochloric acid were added. After stirring for 30 minutes, the precipitated crystals were filtered, washed with methanol and water, and dried.
No. 1 5.5 g of the dye represented by No. 38 was obtained. The purity of this synthetic dye was 92%.

1 g of the above synthetic dye was subjected to sublimation purification in the same manner as in Example 3. However, the heating temperature was 180 ° C. As a result, 0.90 g of a dye purified by sublimation was obtained, and its purity was 99.9% or more. On the other hand, 1 g of the above synthetic dye was dissolved in chloroform, purified by column chromatography using silica gel as a carrier and chloroform as an eluent, and as a result, 0.89 g of the purified dye was recovered. The purity of this purified dye is 97.5% and its T
G-DTA measurement values are shown in Table 2 38.

1 μg of each of the dye purified by the above-described method and the unpurified synthetic dye was sealed in an aluminum container (capacity: 40 μl), and the mixture was placed in a DSC apparatus (Seiko DSC).
After heating at 200 ° C. for 2 hours in 20), the decomposition rate of the dye was examined. As a result, the purified dye by sublimation purification did not decompose at all, but 1.0% of the purified dye by column chromatography and 10% of the unpurified dye were decomposed. Purity and TG of the vaporizable dye of the present invention obtained by purifying the dye having the structure shown in Table 1 according to the description in Examples.
Table 2 shows the measured values of DTA and the maximum absorption wavelength.

[0042]

[Table 14]

[0043]

[Table 15]

[0044]

[Table 16]

[0045]

[Table 17]

[0046]

The dye of the present invention has the necessary vaporization properties at the heating temperature, has essentially no thermal decomposition at the heating temperature, and is subject to thermal decomposition due to the influence of impurities. And is stable for a long period of time, and has absorption in a specific region as a yellow, magenta or cyan dye. By applying the dye of the present invention to a dye direct vaporization type thermal recording system, full-color image recording can be advantageously performed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a recording apparatus used in an embodiment.

FIG. 2 is a diagram showing the relationship between the number of laser pulses and the optical density in a recording test of Example 1.

FIG. 3 is a diagram showing the relationship between the number of laser pulses and the dot diameter in a recording test of Example 1.

FIG. 4 is a diagram showing the relationship between the number of laser pulses and the optical density in a recording test of Example 2.

FIG. 5 is a diagram showing the relationship between the number of laser pulses and the dot diameter in a recording test of Example 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Quartz glass substrate 2 Bead layer (Chromium vapor deposition on the bead layer) 3 ITO vapor deposition film 4 Spacer 5 Image receiving paper 6 Laser diode

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09B 29/09 B41M 5/26 S 57/00 101K 101Z (72) Inventor Takashi Fukada 1000 Kamoshita-cho, Aoba-ku, Yokohama-shi, Kanagawa Prefecture Mitsubishi Chemical Research Institute Yokohama Research Laboratory

Claims (6)

[Claims] 1. TG-DTA (Thermogravi)
metry-Differential Thermal
(Analysis), the exothermic peak does not fall below 300 ° C., the weight loss rate at 300 ° C. is 1% or more, and the purity is 97% or more. [Table 1] TG-DTA measurement conditions Heating rate: 10 ° C / min Carrier gas and flow rate: air, 200 ml / min Sample amount: 5 mg 2. TG-DTA (Thermogravi)
metry-Differential Thermal
An exothermic peak as measured by Analysis (Analysis) is 30.
2. The vaporizable dye according to claim 1, which is not at 0 ° C. or lower, has a weight loss at 300 ° C. of 3% or more, and has a purity of 98% or more. 3. The vaporizable dye according to claim 1, wherein an absorption maximum wavelength of a visible absorption spectrum in acetone is in a range of 410 to 460 nm. 4. The vaporizable dye according to claim 1, wherein a maximum absorption wavelength of a visible absorption spectrum in acetone is in a range from 510 to 560 nm. 5. The vaporizable dye according to claim 1, wherein the absorption maximum wavelength of a visible absorption spectrum in acetone is in the range of 610 to 670 nm. 6. A dye direct vaporization type thermal recording method, comprising using the vaporizable dye according to claim 1.