JP2000033779A - Thermal transfer sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high quality image capable of coping with the improvement of image forming speed by incorporating sulfonic acid salt-containing polyvinylacetal resin and inorganic pigment in a heat resistance glide layer. SOLUTION: The thermal transfer sheet is formed by dispersing about 5.0 pts.wt. of sulfonic acid salt-containing polyvinyl acetal resin as binder resin in a heat resistance glide layer 3, about 1.0 pts.wt. of polyisocyanate compound as an additive, about 1.0 pts.wt. of silicone oil as a lubricant, and about 0.5 pts.wt. of calcium carbonate of an average grain diameter of 0.04 μm as an inorganic pigment in a solvent consisting of about 41.5 pts.wt. of methylethyl ketone and toluene respectively, and thereby preparing a heat resistance layer forming composition. In this manner, a superior photographic image can be obtained having no sticking caused by head melting or drop of a photographic image due to dropping of adhered matter on the head.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat transfer sheet having a heat-resistant lubricating layer formed on a surface of a substrate opposite to a surface on which a heat transfer dye layer is formed. In particular, it relates to a thermal transfer sheet that can be suitably used for sublimation thermal transfer recording.

[0002]

2. Description of the Related Art In recent years, a sublimation thermal transfer recording method capable of continuous full-color gradation expression has attracted attention as a technique for hard-copying video image signals and digital images.

In this sublimation thermal transfer recording method, for example, a thermal transfer sheet in which a thermal transfer dye layer formed by dispersing a sublimable or thermally diffusible dye in a binder resin on a plastic substrate such as polyester is usually used. 2. Description of the Related Art An image is formed by using a photographic paper formed by forming a dye receiving layer made of a dye-receptive resin on a substrate.
Then, in the image formation, the thermal transfer dye layer of the thermal transfer sheet is superimposed on the dye receiving layer of the photographic paper, and the thermal transfer sheet is heated by a thermal head from the side opposite to the thermal transfer dye layer of the thermal transfer sheet. This is done by transferring the dye to the dye receiving layer of the photographic paper.

[0004] In recent years, in order to improve the image forming speed, the heating energy for the thermal transfer sheet at the time of image formation tends to increase more and more. For this reason, in the thermal transfer sheet, in order to prevent fusion between the thermal transfer sheet and the thermal head at the time of image formation, a heat-resistant resin is mainly used on the back surface of the substrate opposite to the surface on which the thermal transfer dye layer is formed. A heat-resistant lubricating layer is formed.

The heat-resistant lubricating layer contains various crosslinking agents for improving the heat resistance of the resin, a lubricant for reducing the coefficient of friction against the thermal head, and the like. Antistatic treatment is often performed to prevent sticking to the traveling system.

[0006] In addition, an inorganic pigment has been widely added to the heat-resistant lubricating layer as a filler to prevent fusion with a thermal head and to improve the storage stability of the thermal transfer sheet. As inorganic pigments used, silica,
Examples include talc, calcium carbonate, clay, zeolite, titanium oxide, zinc oxide, and carbon.

[0007]

However, in the conventional thermal transfer sheet described above, the inorganic pigment contained in the heat-resistant lubricating layer and the binder resin do not have a sufficient interaction. Therefore, when the thermal transfer sheet is run while being in contact with the thermal head, the inorganic pigment in the heat-resistant lubricating layer falls off the thermal transfer sheet, adheres to the thermal head and becomes soiled, and further, the pigment is deposited on the surface of the thermal transfer dye layer. Color transfer may occur during transfer printing.

Further, in the conventional binder resin used for the heat-resistant lubricating layer, the inorganic pigment cannot be sufficiently dispersed, and the inorganic pigment tends to be aggregated. For this reason, in this thermal transfer sheet, there is a problem that the amount of abrasion with the thermal head becomes large, and the dispersion stability of the inorganic pigment in the binder resin is poor, so that the inorganic pigment sediments and the quality varies.

The present invention has been made in view of the above circumstances, and prevents fusion with a thermal head and effectively prevents powder from dropping on the thermal head and abrasion with the thermal head. It is an object of the present invention to provide a high-quality thermal transfer sheet which is prevented, can sufficiently cope with further improvement in image forming speed, and can obtain a high-quality image.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have used a polyvinyl acetal resin having a specific side chain for a heat-resistant lubricating layer of a thermal transfer sheet. As a result, it has been found that fusion with a thermal head and powder dropping of the inorganic pigment in the heat-resistant lubricating layer are effectively prevented, and the present invention has been completed.

That is, the thermal transfer sheet according to the present invention comprises a sheet-like substrate having a thermal transfer dye layer formed on one surface and a heat-resistant lubricating layer formed on the other surface. The lubricating layer is characterized by containing a polyvinyl acetal resin containing a sulfonate and an inorganic pigment. Here, the concentration of the sulfonic acid salt contained in the polyvinyl acetal resin is preferably 0.1 mol% to 2.0 mol%.

As described above, in the thermal transfer sheet according to the present invention, a material having good compatibility with the inorganic pigment in the heat-resistant lubricating layer is specified as the binder resin in the heat-resistant lubricating layer.
The interaction between the binder resin and the inorganic pigment in the heat-resistant lubricating layer is improved, and the heat-resistant lubricating layer is formed stably on the base material. Is prevented.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view of an example of a thermal transfer sheet to which the present invention is applied. FIG. 2 is a plan view of the thermal transfer ink sheet shown in FIG.

The thermal transfer ink sheet to which the present invention is applied is
As shown in FIG. 1, a heat transfer dye layer 2 is formed on one surface 1a of a sheet-like substrate 1, and a heat-resistant lubricating layer 3 is formed on the other surface 1b of the substrate 1. .

As shown in FIG. 2, the thermal transfer dye layer 2 comprises, for example, a yellow dye layer 2a, a magenta dye layer 2b, and a cyan dye layer 2c. These series of dye layers 2a, 2b, 2c are provided on one surface 1a of the sheet-like substrate 1 along the longitudinal direction. The thermal transfer dye layer 2 is formed by dispersing a sublimable dye in a binder resin.

As the binder resin contained in the thermal transfer dye layer 2, conventionally known binder resins can be used. For example, cellulose resins such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and cellulose acetate, polyvinyl resins such as polyvinyl alcohol, polyvinyl butyral, polyvinyl acetoacetal, polyvinyl acetate, and polystyrene, and various urethane resins. .

The dyes contained in the thermal transfer dye layer 2 include various conventionally known dyes, for example, azo dyes, disazo dyes, methine dyes, styryl dyes, pyridone azo dyes, and mixtures thereof as yellow dyes, and magenta dyes. As an azo type,
Anthraquinone-based, styryl-based, heterocyclic-based azo dyes and the like and a mixture thereof, and as a cyan dye, anthraquinone-based,
Examples include naphthoquinone-based, heterocyclic-based azo dyes, indoaniline-based dyes and the like, and mixtures thereof.

As shown in FIG. 2, a series of dye layers 2a, 2b, 2c are formed on the surface 1a of the substrate 1 of the thermal transfer sheet.
Sensor marks 4 for detecting the position of the thermal transfer sheet may be provided on both sides of the thermal transfer dye layer 2 made of.

As shown in FIG. 3, as the thermal transfer dye layer 2, a black dye layer 2d is provided in addition to the yellow dye layer 2a, the magenta dye layer 2b, and the cyan dye layer 2c. It may be something.

As another embodiment of the thermal transfer sheet, as shown in FIG. 4, a transparent transfer protection layer for protecting the printing screen so that other ink is not transferred onto the printing screen of the printing paper after printing. 5 may be formed on the surface 1 a of the substrate 1.

As still another embodiment of the thermal transfer sheet, as shown in FIG. 5, a dye-receiving layer 6 having thermal transferability is provided on a base material 1 so that sublimation heat transfer can be performed on plain paper.
May be formed on the surface 1a.

On the other hand, the heat-resistant lubricating layer 3 is for preventing the fusion between the thermal transfer sheet and the thermal head in response to an increase in the heating energy for the thermal transfer sheet as the image forming speed is further improved. The substrate 1 is formed on a surface 1b opposite to the surface 1a on which the thermal transfer dye layer 2 is formed.

In particular, in the present invention, the heat-resistant lubricating layer 3 is
It contains a polyvinyl acetal resin having a sulfonate as a binder resin and an inorganic pigment. As the binder resin used for the heat-resistant lubricating layer 3, a polyvinyl acetal resin having a sulfonic acid salt as shown in the following Chemical Formula 2 can be used.

[0025]

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As described above, in the thermal transfer sheet to which the present invention is applied, a material compatible with the inorganic pigment in the heat-resistant lubricating layer 3 is specified as the binder resin in the heat-resistant lubricating layer 3. The interaction between the binder resin in the conductive layer 3 and the inorganic pigment is improved, and the heat-resistant lubricating layer 3 is stably formed on the base material 1. Can be effectively prevented.

Specifically, a polyvinyl acetal resin having a sulfonate represented by the following chemical formulas 3 and 4 is preferable.

[0028]

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[0029]

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Here, the higher the content of the sulfonate, the more advantageous the dispersion of the inorganic pigment. However, if the content is too high, the viscosity of the resin solution increases and stirring becomes difficult. The salt content is
0.1-2.0 mol% is preferable.

In order to improve the heat stability of the heat-resistant lubricating layer 3, a resin may be crosslinked by adding a polyisocyanate compound. The polyisocyanate compound to be used is not particularly limited as long as it is an isocyanate compound having at least two or more isocyanate groups in a molecule. For example, tolylene diisocyanate, 4,4′-
Diphenylmethane diisocyanate, 4,4'-xylene diisocyanate, hexamethylene diisocyanate, 4,4'-methylene bis (cyclohexyl isocyanate), methylcyclohexane-2,4 (or 2,
6) -Diisocyanate, 1,3-di (isocyanatomethyl) cyclohexane, isophorone diisocyanate, trimethyl hexamethylene diisocyanate, or an adduct of polyisocyanate obtained by partially reacting diisocyanate with polyol (polyisocyanate prepolymer) For example, an adduct obtained by reacting tolylene diisocyanate with trimethylolpropane can be used.

The inorganic pigment used for the heat-resistant lubricating layer 3 includes
Conventionally known ones can be used. Specifically, nip seals E-75, E-170, E-200,
E-220, E-220 (Nippon Silica Industry Co., Ltd.
Silica), calcium carbonate such as white gloss DD, white gloss PZ, homocal D, and Tunex E (all, manufactured by Shiraishi Kogyo Co., Ltd.), microace P-3, L-1 (all,
Talc such as Nippon Talc Co., Ltd.), MT-500B,
Titanium oxide such as MT-600B (both manufactured by Teikoku Chemical Co., Ltd.) and the like can be mentioned.

If the amount of the inorganic pigment in the heat-resistant lubricating layer 3 is too small, the effect of preventing fusion between the thermal transfer sheet and the thermal head is insufficient. Since the adhesiveness of the base material 2 to the base material 2 is unfavorably reduced, the content is preferably 0.1 to 30% by weight, more preferably 5 to 20% by weight.

The average particle size of the inorganic pigment is from 0.01 to 5.0 in consideration of the balance between heat resistance and head wear.
0 μm is preferable, and more preferably 0.02 to 1.0 μm
m is good.

The heat-resistant lubricating layer 3 may contain various known lubricants, antistatic agents and the like, if necessary. Lubricants that can be blended in the heat-resistant lubricating layer 3 include liquid paraffin, fatty acids, fatty acid esters, phosphate esters,
Known lubricants such as silicone oil and perfluoropolyether can be used. As antistatic agents,
Known ionic and nonionic antistatic agents such as quaternary ammonium salts, alkyl sulfonates, alkyl polyoxyethylene phosphates and alkyl polyoxyethylene ethers can be mentioned.

As the substrate 1, various conventionally known substrates can be used. For example, a polyester film, an polystyrene film, a polypropylene film, a polysulfone film, a polycarbonate film, a polyimide film, an aramid film, and the like. The thickness of the substrate 1 is 1 to 30 μm, preferably 2 to 10 μm.

The thermal transfer sheet of the present invention configured as described above can be manufactured by a conventional method.

Specifically, first, the composition for forming a thermal transfer dye layer is prepared by uniformly dispersing the above-mentioned dye, binder resin and the like in a solvent. Then, the composition for forming a thermal transfer dye layer is applied on one surface 1a of the prepared substrate 1 and dried to form a thermal transfer dye layer 2.

Next, a composition for forming a heat-resistant lubricating layer is prepared by uniformly dissolving or dispersing a polyvinyl acetal resin containing a sulfonic acid salt, an inorganic pigment and various additives as necessary in a solvent. . Then, the composition for forming a heat-resistant lubricating layer is applied on the other surface 1b of the substrate 1 and dried to form the heat-resistant lubricating layer 3, whereby the thermal transfer sheet of the present invention is obtained.

[0040]

Embodiments of the present invention will be described below based on experimental results. Hereinafter, the binder resin and the inorganic pigment constituting the heat-resistant lubricating layer were examined by preparing the following thermal transfer sheet.

Example 1 First, a 6 μm-thick polyester film (trade name: Lumirror, manufactured by Toray Industries, Inc.) was prepared as a substrate.

Next, Disperse Vi is used as a dye.
5.0 parts by weight of olet 26 and polyvinyl butyral resin (trade name, manufactured by Sekisui Chemical Co., Ltd.) as a binder resin
BX-1) 5.0 parts by weight with methyl ethyl ketone 4
The composition for thermal transfer dye layer formation was prepared by dispersing in a solvent consisting of 5.0 parts by weight and 45.0 parts by weight of toluene.

Then, the composition for forming a thermal transfer dye layer was applied on one surface of the substrate by a wire bar method so as to have a dry thickness of 1 μm and dried to form a thermal transfer dye layer.

Next, 5.0 parts by weight of a polyvinyl acetal resin containing a sulfonate shown in Chemical Formula 1 as a binder resin and a polyisocyanate compound (trade name, manufactured by Nippon Polyurethane Industry Co., Ltd.) as an additive 1.0 part by weight of Coronate L), 1.0 part by weight of silicone oil (trade name: KF6003, manufactured by Shin-Etsu Chemical Co., Ltd.) as a lubricant, and calcium carbonate having an average particle size of 0.04 μm as an inorganic pigment (Shiraishi Kogyo) (Trade name: white gloss flower DD)
0.5 part by weight was dispersed in a solvent composed of 41.5 parts by weight of methyl ethyl ketone and 41.5 parts by weight of toluene to prepare a composition for forming a heat-resistant lubricating layer.

Then, the composition for forming a heat-resistant lubricating layer was applied on the other surface of the substrate by a wire bar method and dried to form a heat-resistant lubricating layer, thereby obtaining a thermal transfer sheet.

Examples 2 and 3 Thermal transfer sheets were prepared in the same manner as in Example 1 except that the inorganic pigments used in the heat-resistant lubricating layer were as shown in Table 1.

Comparative Examples 1 to 3 Thermal transfer sheets were prepared in the same manner as in Example 1 except that the inorganic pigments used in the heat-resistant lubricating layer were as shown in Table 1.

Comparative Example 4 Example 1 except that no inorganic pigment was used in the heat-resistant lubricating layer.
In the same manner as in the above, a thermal transfer sheet was produced.

[0049]

[Table 1]

<Characteristic evaluation>
Inorganic pigment powder drop and linear printing unevenness (sticking)
Was examined.

(1) Evaluation of powder removal of inorganic pigment in heat-resistant lubricating layer For each sample, the surface of the heat-resistant lubricating layer was rubbed with black high-quality paper, and the presence or absence of powder removal of inorganic pigment was visually examined. Table 2 shows the results. Regarding powder dropping, the mark ○ indicates no powder dropping, and the mark × indicates that there is powder dropping.

(2) Evaluation of sticking Each sample was mounted on a full-color printer (trade name: UP-D7000) manufactured by Sony Corporation, gradation printed on photographic paper (trade name: UPC7010, manufactured by Sony Corporation), and sticking was visually performed. Was examined. Table 2 shows the results. Regarding sticking, those that did not occur were marked with a circle, and those that did occur were marked with a cross.

[0053]

[Table 2]

As is clear from the results in Table 2, each of the samples of Examples 1 to 3 in which the heat-resistant lubricating layer contains a polyvinyl acetal resin having a sulfonic acid salt and an inorganic pigment, shows that all of the samples have a powdery property. It can be seen that sticking did not occur, indicating good running stability.

On the other hand, in Comparative Examples 1 to 3 in which the polyvinyl acetal resin having a sulfonic acid salt was not contained in the heat-resistant lubricating layer, no sticking was observed, but powder fell off, and the heat-resistant lubricating layer was not. It turns out that there is a problem in the inorganic pigment holding power. In Comparative Example 4 in which no inorganic pigment was contained in the heat-resistant lubricating layer, no powder dropping was observed, but sticking was observed, and the effect of preventing fusion between the thermal transfer sheet and the thermal head was insufficient. You can see that there is.

As can be seen from the above results, the inclusion of the polyvinyl acetal resin having a sulfonic acid salt and the inorganic pigment in the heat-resistant lubricating layer ensures that the heat-resistant lubricating layer retains the inorganic pigment and that the inorganic pigment falls off. And the effect of preventing fusing between the thermal transfer sheet and the thermal head.

[0057]

As is clear from the above description, the thermal transfer sheet of the present invention has a good interaction between the binder resin and the inorganic pigment in the heat-resistant lubricating layer. At this time, no fusion occurs with the thermal head and no powder of the inorganic pigment falls onto the thermal head. Therefore, according to the thermal transfer sheet of the present invention, it is possible to obtain a good printed image without sticking due to head fusion or missing of print due to dropping off of the head attached matter.

[Brief description of the drawings]

FIG. 1 is a sectional view of an example of a thermal transfer sheet to which the present invention is applied.

FIG. 2 is a plan view of an example of a thermal transfer sheet to which the present invention is applied.

FIG. 3 is a plan view of another example of the thermal transfer sheet to which the present invention is applied.

FIG. 4 is a plan view of another example of the thermal transfer sheet to which the present invention is applied.

FIG. 5 is a plan view of another example of the thermal transfer sheet to which the present invention is applied.

[Explanation of symbols]

 1 base material, 2 heat transfer dye layer, 3 heat resistant slip layer

Claims (3)

[Claims] 1. A heat transfer dye layer is formed on one surface of a sheet-like base material, and a heat-resistant lubricating layer is formed on the other surface, wherein the heat-resistant lubricating layer contains a sulfonic acid salt. A thermal transfer sheet comprising a polyvinyl acetal resin and an inorganic pigment. 2. The thermal transfer sheet according to claim 1, wherein the concentration of the sulfonic acid salt contained in the polyvinyl acetal resin is 0.1 mol% to 2.0 mol%. 3. The thermal transfer sheet according to claim 1, wherein the polyvinyl acetal resin containing the sulfonate is represented by the following chemical formula 1. Embedded image