JP3326771B2 - Thermal transfer recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer recording medium suitable for a video printer and the like. More specifically,
The present invention relates to a heat-sensitive transfer recording medium capable of forming a black image with high quality without substantially causing hue shift when density gradation is expressed.

[0002]

2. Description of the Related Art When a hard copy is obtained from video information or the like, a layer in which a sublimable or thermally diffusible dye is dispersed in a binder such as a cellulose ester resin is used as an ink layer.
A thermal transfer recording medium in which the ink layer is laminated on a polyethylene terephthalate film is used. When a full-color image is to be obtained using such a thermal transfer recording medium, it can be realized in principle by using a thermal transfer recording medium having ink layers of three colors of yellow, cyan and magenta. However, when black is to be expressed using yellow, magenta, and cyan, the respective colors of yellow, cyan, and magenta such as those used for a thermal transfer recording medium have the same saturation as the absorption spectrum shown in FIG. Is not flat absorption over the entire visible light range, and a low light absorption portion (arrow A in FIG. 4) appears between the maximum absorption wavelengths of yellow, magenta, and cyan. Therefore, even if these three colors are mixed, there is a problem that it is difficult to express pure black. Therefore, it is common to use a black ink layer in addition to the three color ink layers of yellow, cyan and magenta.

When such a black ink layer is formed on a thermal transfer recording medium, a dye having a flat absorption spectrum in the visible light region of 380 to 780 nm as shown in FIG. May be contained in the ink layer at a high concentration. However, at present, a single dye exhibiting such properties has not been practically obtained.
Therefore, conventionally, in order to produce black, the ink layer of the thermal transfer recording medium contains several kinds of dyes having different maximum absorption wavelengths so that light is absorbed flatly in the entire visible light region.

[0004]

However [0007] If you were use a thermal transfer recording medium of black using a conventional several dyes like, even if the printing energy is changed to a gray scale representation, printing Since the degree of sublimation or thermal diffusion of each dye does not change in the same manner according to the change in energy, there has been a problem that a monotone black image that is constant over the entire density range cannot be obtained. For example, there is a problem in that the hue varies depending on the image density, such as obtaining a reddish black image at a low density and obtaining a bluish image at a high density. In other words, when the a ^* value and the b ^* value of images of different densities are measured in the (CIE 1976) L ^* a ^* b ^* color system, the measured values are considered to have little change in hue in practice. a ^* value and b
^* Range of values ^{(-10 ≦ a * ≦ 10,} -5 ≦ b * ≦ 5) there is a problem that the exceeds at least one.

Further, even in a black ink layer using several types of dyes, the light absorption does not become flat in the entire visible light range, and a low light absorption portion is generated between the maximum absorption wavelengths of the respective dyes.
In order to cope with this, it is conceivable that the dye is contained in the ink layer at a high concentration. However, when the dye is contained in the ink layer at such a very high concentration, the heat transfer recording medium is stored or transported. There is a problem in that the dye crystallizes or blocking occurs, which causes the storage stability of the thermal transfer recording medium to deteriorate.

SUMMARY OF THE INVENTION The present invention is to solve such a problem of the prior art, and is intended to prevent the hue of the black image from being substantially shifted in the entire density range when the density gradation expression is performed. It is an object of the present invention to provide a heat-sensitive transfer recording medium which can be produced and has excellent storage stability by using as few kinds of dyes as possible.

[0007]

The present inventor has found that there is no dye having a flat and strong light absorption in the entire visible light region, but the maximum light absorption wavelength is in the visible light region, and the half width of the light absorption peak is small. Broad, i.e., the presence of a dye having a half-width of at least 100 nm, and at least two such non-overlapping wavelengths of maximum absorption so as to achieve uniform and strong light absorption throughout the visible light range. The present inventors have found that the above object can be achieved by incorporating a dye in the ink layer of the thermal transfer recording medium, and have completed the present invention.

That is, in a thermal transfer recording medium having an ink layer laminated on a substrate, the ink layer has a maximum absorption wavelength λm
ax = 420 to 500 nm and a half width of at least 100
a first dye having a light absorption peak of nm and a second dye having a light absorption peak having a maximum absorption wavelength λmax = 570 to 650 nm and a half width of at least 100 nm , wherein the second dye is described below. Specific isothiazole
Provided is a thermal transfer recording medium characterized by using an azo dye .

Further, according to the present invention, the ink layer is formed of the first layer.
In addition to the dye and the second dye, the maximum absorption wavelength λmax
= A third dye having a light absorption peak at 500 to 550 nm and / or a fourth dye having a light absorption peak at λmax = 620 to 680 nm, or a thermal transfer recording medium further containing either one I will provide a.

Hereinafter, the present invention will be described in detail.

In the thermal transfer recording medium of the present invention,
At least the maximum absorption wavelength λmax = 420 to 500 nm
A first dye having a light absorption peak having a half width of at least 100 nm, and a maximum absorption wavelength λmax = 570 to 65
A second dye having a light absorption peak at 0 nm and a half bandwidth of at least 100 nm is contained in the ink layer. FIG. 1 schematically shows light absorption curves of at least two kinds of dyes having such characteristics in the visible light region. As can be seen from this figure, by combining at least two types of dyes having such characteristics, large light absorption can be achieved in the entire visible light range, and a black image can be formed. Moreover, since the half width of the light absorption peaks is at least 100 nm, even if the peaks overlap in a wide range, and even if the two have different sublimability or thermal diffusivity, a black image with a constant tone in density gradation display is realized. it can. In other words, (CIE 1976) L ^* a
^* B ^* in the color system, when measuring a ^* values and b ^* values of the thermal transfer recording medium images of different concentrations obtained by the present invention, the a ^* value they are changed in hue is small b
^* It is possible to fall within the value range (−10 ≦ a ^* ≦ 10, −5 ≦ b ^* ≦ 5).

The first dye and the second dye are as follows:
By combining dyes having the same sublimability and thermal diffusivity, a black image with a constant tone can be formed with a higher density gradation display.

The mixing ratio of the first dye and the second dye varies depending on the light absorption intensity of the dye and the like. Generally, the mixing ratio of the first dye to the second dye is based on the total weight of the first dye and the second dye. 1
Is 35 to 65% by weight, preferably 40 to 60% by weight, and the second dye is 35 to 65% by weight, preferably 40 to 60% by weight.

As the first dye, disazo dyes such as those represented by formulas (1) to (5)

[0015]

Embedded image At least one selected from the dyes represented by As the second dye , formulas ( 7 ) to (8)

[0016]

Embedded image To use at least one a use selected in the isothiazole azo dye represented.

In the ink layer of the thermal transfer recording medium of the present invention, in addition to the above-described first dye and second dye, a third dye having a light absorption peak at a maximum absorption wavelength λmax = 500 to 550 nm is further added. Can be added. this is,
Depending on the type of the first dye and the second dye, it may be better to further increase the light absorption in the region of 500 to 550 nm, for example, as shown in FIG. In such a case, it is possible to realize a flatter light absorption in the visible light region as shown in FIG. 3 by adding a third dye (so-called red dye) having absorption to that portion. Become. As a result, an image closer to perfect black can be obtained. For the same reason, instead of the third dye, the maximum absorption wavelength λmax = 620 to 680 nm.
A fourth dye having a light absorption peak of (a so-called blue dye) can also be added. Or the first dye and the second
In addition to the above dye, a third dye and a fourth dye can be simultaneously added to the ink layer.

The mixing ratio of the third dye and the fourth dye is preferably 10 parts by weight or less, more preferably 4 to 4 parts by weight, based on 100 parts by weight of the first dye and the second dye. It can be added in a proportion of 8 parts by weight.

As the third dye, azo dyes, tricyanomethine dyes, benzothiazole dyes and anthraquinone dyes, for example, formulas (9) to (12)

[0020]

Embedded image At least one selected from the dyes represented by As the fourth dye, an indoaniline dye, for example, of the formulas (13) to (14)

[0021]

Embedded image At least one selected from the dyes represented by

In the present invention, since the types of dyes to be added to the ink layer of the thermal transfer recording medium can be reduced as compared with the prior art, the dye is added to the ink layer in a P / B ratio (P is the weight of the dye, B is the weight of the dye). (Weight of the binder) in a wide range of about 0.5 to 3.0, and an image having a desired density can be formed according to the purpose. The storage stability of the thermal transfer recording medium can be improved.

In the present invention, the structure of the invention other than the feature relating to the dye contained in the ink layer of the thermal transfer recording medium can be the same as that of the conventional thermal transfer recording medium. For example, as the substrate, a polyester film such as polyethylene terephthalate, a polyimide film, a polyamide film such as nylon, an aramid film, or the like can be used. Also, as the binder resin used for the ink layer, butyral,
Polyvinyl alkyl acetal, cellulose ester,
Cellulose ether, urethane and the like can be used.

The thicknesses of the substrate and the ink layer are not particularly limited, and can be appropriately determined according to the purpose of use.
Further, a heat-resistant lubricating layer may be provided outside the substrate.

The thermal transfer recording medium of the present invention can be manufactured by a conventional method, for example, by using a coil bar or the like.
The ink composition can be produced by laminating an ink composition in which a dye is uniformly dispersed in a binder on a substrate, and drying to form an ink layer.

The thermal transfer recording medium of the present invention can be used by a general method. For example, the ink layer is superimposed on a normal photographic paper having a dye receiving layer made of a polyester resin, a cellulose ester resin, a urethane resin, an epoxy resin, a vinyl chloride resin, or the like, and according to an image such as a video signal. By selectively heating the medium with a heating means such as a thermal head, the dye is transferred to the photographic paper by sublimation or thermal diffusion, and fixed to the dye receiving layer of the photographic paper to form an image. .

[0027]

The thermal transfer recording medium of the present invention uses at least two types of dyes having a maximum absorption wavelength that does not overlap and a light absorption peak having a half width of at least 100 nm. In addition, it is possible to form a black image such that a hue shift does not substantially occur in the entire density range.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments.

Examples 1 to 9 and Comparative Examples 1 to 11 Ink compositions were prepared by uniformly mixing the components of the formulations shown in Table 1. This ink composition is applied to a polyethylene terephthalate film (thickness: 6 μm, 6CF53, manufactured by Toray Industries, Inc.) having a dry thickness of 1 μm using a coil bar to produce a thermal transfer ink ribbon. did. The dyes used in each of the Examples and Comparative Examples were dye mixtures having the formulations shown in Tables 2 and 3.
In Comparative Example 1, SUMIPL manufactured by Sumitomo Chemical Co., Ltd. was used.
AST BLACK 2BA was used. In Comparative Example 2, Sumiplast BRAC manufactured by Sumitomo Chemical Co., Ltd. was used.
KG was used.

[0030]

Table 1 Ingredients of ink : parts by weight Dye 6.54 Butyral (6000EP, manufactured by Denka Butyral Co., Ltd.) 3.27 Methyl ethyl ketone 47.75 Toluene 42.43

[0031]

[Table 2] Example Dye Formula No. Weight% Example Dye Formula No. Weight% 1 (1) 452 (1) 45 (6) 55 (6) 55 (9) 7 (9) 6.5 (13) 6.5 3 ( 1) 554 (1) 45 (6) 45 (6) 56 (9) 7 (10) 75 (1) 456 (1) 35 (6) 55 (6) 65 (11) 7 (9) 10 7 (1) 65 8 (1) 35 (6) 35 (6) 65 (9) 10 (9) 10 (13) 10 (13) 10 9 (1) 45 (6) 55 (9) 7

[0032]

[Table 3] Comparative Example Dye Formula No. wt% Comparative Example Dye Formula No. wt% 3 (1) 744 (1) 26 (6) 26 (6) 74 (9) 5 (9) 55 (1) 536 (1) 32 (6) 47 (6) 68 (9) 18 (9) 57 (1) 688 (1) 35 (6) 32 (6) 65 (9) 5 (9) 11 9 (1) 35 10 (1) ) 65 (6) 65 (6) 35 (9) 10 (9) 10 (13) 11 (13) 11 11 (1) 47 (6) 53 (9) 15

The thermal transfer ink ribbon thus produced and a commercially available printing paper (VP) having a polyester-based image receiving layer
M-30ST, manufactured by Sony Corporation) was set in a thermal transfer printer (CVP-G500, manufactured by Sony Corporation), and steer step printing of 12 gradations was performed. However, in Example 10, photographic paper manufactured as follows was used. That is, synthetic paper (FPG-15) having a thickness of 150 μm.
0) was coated with the image receiving layer composition having the composition shown in Table 4 so as to have a dry thickness of 10 μm, and cured at 50 ° C. for 48 hours to produce a printing paper having a cellulose ester-based receiving layer.

[0034]

TABLE 4 Component name of image receiving layer composition Component parts by weight Cellulose ester resin 20 (CAB500-5, manufactured by E. Kodak Company) Dicyclohexyl phthalate 4 (manufactured by Osaka Organic Chemical Co., Ltd.) Modified silicone oil 0.6 (SF8427, Toray) -Dow Corning Co., Ltd.) Fluorescent brightener 0.4 (Iupitex OB, Ciba-Geigy) Isocyanate-based cross-linking agent 1.0 (Takenate D-110N, Takeda Pharmaceutical Co., Ltd.) Methyl ethyl ketone 50 Toluene 50

The printed images thus obtained were evaluated as follows.

1. (CIE1976) L ^* a ^* b ^* Color System Display Printed images were observed with a spectrophotometer (MCPD-1000, manufactured by Otsuka Electronics Co., Ltd.), and the a ^* value and b ^* value of an image displayed in 12-step gradation were observed. Are shown in Table 5. In this case, the a ^* value and the b ^* value are simultaneously −10 ≦ a ^* ≦ 10 and −5 ≦ b ^* ≦
If it is within the range of 5, it can be evaluated that there is no problem in practically the hue shift.

2. Print Density (Max Density) The Max density of the obtained image is measured using a Macbeth densitometer TR-92.
4 (Status A filter). Table 5 shows the results. In this case, if the Max concentration is 1.8 or more, it can be evaluated that there is no practical problem.

3. Transferability A synthetic paper (FPG-60, manufactured by Oji Paper Co., Ltd.) was overlaid on the Max density image, a pressure of 40 g / cm ² was applied, and aging was performed at 60 ° C. for 48 hours in that state to transfer to the synthetic paper. The dye concentration was measured with a Macbeth densitometer. Table 5 shows the results. In this case, it is considered that the smaller the numerical value is, the lower the migration property is, and it is practically necessary to be 0.02 or less.

[0039]

[Table 5] MAX concentration migration a ^* range b ^* range Example 1 2.3 0.01 0 to +9.0 0 to +2.0 2 2.5 0.02 -1.5 to +0.5 -2.5 to 0 3 2.4 0.01 0 to +8.0 0 to +4.0 4 2.3 0.01 -0.5 to +7.5 0 to +4.05 2.3 0.01 -0.5 to +8 0.0 to -2.0 6 2.3 0.01 0 to +9.0 -4.0 to +1.0 7 2.5 0.02 0 to +7.5 0 to +4.5 8 2.50 0.02 -1.0 to +5.0 -4.0 to +0.5 9 2.4 0.01 0 to +8.5 0 to +2.0 Comparative Example 1 1.6 0.05 0 to +5.0 0 -12.0 21.5 0.04 0 to +10.0 0 to +10.0 32.0 0.010 to +7.50 to +7.542.00.01 -2.5 ~ + 2.5 -12.0 ~ 0 5 2.2 0.02 0 to +20.0 0 to +2.0 6 2.2 0.01 0 to +5.0 -10.0 to 0 7 2.3 0.01 0 to +10.5 0 to +6.0 8 2 .3 0.01 0 + 10.5 -3.5～0 9 2.4 0.02 -1.0 + 7.5 -6.0～0 10 2.4 0.02 -0.5 + 6 0.0 -0.5 to +6.0 11 2.2 0.01 0 to +20.0 0 to +2.0

As is clear from Table 5, the Max density and the transferability were practically sufficient except for Comparative Examples 1 and 2, but only the Example showed good results with respect to the density gradation display. Was. That is , in Examples 1 to 9 , (C
IE1976) Both the a ^* value and the b ^* value in the L ^* a ^* b ^* color system fall within the ranges of −10 ≦ a ^* ≦ 10 and −5 ≦ b ^* ≦ 5, and the density gradation display is performed. It was found that the hue shift was small even when the test was performed. On the other hand, in Comparative Examples 1 to 11 , one of the a ^* value and the b ^* value is -10 ≦ a
^* ≦ 10 and −5 ≦ b ^*
It was found that the hue shift was large when the density gradation display was performed.

[0041]

According to the thermal transfer recording medium of the present invention,
When the density gradation expression is performed, the shift of the black hue can be substantially eliminated in the entire density range.

[Brief description of the drawings]

FIG. 1 is a light absorption characteristic diagram of a dye.

FIG. 2 is a light absorption characteristic diagram of a dye.

FIG. 3 is a graph showing light absorption characteristics of a dye.

FIG. 4 is a graph showing light absorption characteristics of a dye.

FIG. 5 is a graph showing light absorption characteristics of a dye.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-185752 (JP, A) JP-A-52-87420 (JP, A) JP-A-56-55455 (JP, A) JP-A-5-85455 147366 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/38-5/40 CA (STN) REGISTRY (STN)

Claims (8)

(57) [Claims] 1. A thermal transfer recording medium having an ink layer laminated on a substrate, wherein the ink layer has a maximum absorption wavelength λmax.
= 420-500 nm and half width at least 100 nm
Dye having a light absorption peak of λm
ax = 570-650 nm and half width at least 100
a second dye having a light absorption peak of nm .
The dye of formula (7) is represented by formulas (7) and (8) : Selected from isothiazole azo dyes represented by
A thermal transfer recording medium characterized by at least one kind . 2. The compounding ratio of the first dye is 35 to 65% by weight and the compounding ratio of the second dye is 35 to 65% by weight based on the total weight of the first dye and the second dye. The thermal transfer recording medium according to claim 1, wherein Wherein the first thermal transfer recording medium of the dye 請 Motomeko 1 wherein Ru disazo dye der. 4. The disazo dye of the formula (1) to (5): The thermal transfer recording medium according to claim 3, wherein the thermal transfer recording medium is at least one selected from dyes represented by the following formulae. 5. In a thermal transfer recording medium having an ink layer laminated on a substrate, the ink layer has a maximum absorption wavelength λmax.
= 420-500 nm and half width at least 100 nm
Dye having a light absorption peak of λm
ax = 570-650 nm and half width at least 100
a second dye having a light absorption peak of 500 nm and a third dye having a light absorption peak of 500 to 550 nm and / or a maximum absorption wavelength of λmax = 62.
A fourth dye fees and containing <br/> chromatic having a light absorption peak of 0～680Nm, dye wherein the second equation (7) and (8) ## STR3 ## Selected from isothiazole azo dyes represented by
A thermal transfer recording medium characterized by at least one kind . 6. The compounding ratio of the first dye is 35 to 65% by weight and the compounding ratio of the second dye is 65 to 35% by weight based on the total weight of the first dye and the second dye. And
6. The heat-sensitive transfer recording medium according to claim 5, wherein the third dye and the fourth dye are contained in an amount of up to 10 parts by weight based on 100 parts by weight of the total of the first dye and the second dye. 7. The first dye is a disazo dye, and the third dye is an azo dye, a tricyanomethine dye, a benzothiazole dye or an anthraquinone dye.
7. The thermal transfer recording medium according to claim 6, wherein the fourth dye is an indoaniline dye. 8. The disazo dye of the formula (1) to (5): In Ri least one Der selected from dyes represented, A <br/> zone dyes, Tricia drink Chin dyes, benzothiazole dyes and anthraquinone dyes are formula (9) to
(12) And an indoaniline-based dye represented by the formula (13) to (14): The thermal transfer recording medium according to claim 7, which is at least one selected from dyes represented by the following formulae.