JP3140145B2 - Resin for forming dye receiving layer of image receiving sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyvinyl acetal resin, and more particularly to a carboxy-modified polyvinyl acetal resin suitable for forming a dye receiving layer of an image receiving sheet used in sublimation type thermal transfer printing.

[0002]

2. Description of the Related Art In recent years, as one method of thermal transfer, a color material layer surface of a thermal transfer sheet having a color material layer containing a sublimable dye on one surface thereof and a receptor layer surface of an image receiving sheet having a dye receiving layer on the surface thereof come into contact with each other. The sublimation dye in the color material layer is transferred to the receiving layer of the image receiving sheet by heating with a thermal head or laser light corresponding to the image information, and the heat transfer sheet is heated. A sublimation thermal transfer technique for recording an image corresponding to image information on an image receiving sheet by peeling has been developed.

The dye receiving layer of the image receiving sheet used in such a sublimation thermal transfer technique usually requires the following performance. (A) Good dyeing properties, high density, glossy and clear images can be obtained. (B) Good storage stability of images, for example,
(A) When the image comes into contact with a part of the human body (such as a hand or a finger), a plastic eraser containing a plasticizer or its eraser, the dye forming the image does not cause aggregation, fading, etc.
Good oil resistance. (B) The image does not fade or discolor when exposed to light, and has good light resistance. (C) The image does not fade or discolor when heated while blocking light, and has good heat resistance (dark discoloration). (C) When the thermal transfer sheet and the image receiving sheet are separated from each other after the thermal transfer, the thermal transfer sheet and the image receiving sheet are easily fused without fusing.

Various image receiving sheets for use in sublimation type thermal transfer printing have been proposed. For example, Japanese Patent Application Laid-Open No. 61-11293 discloses an image receiving sheet in which the dye receiving layer of the image receiving sheet contains a butyral resin. JP-A-3-65391 and JP-A-3-1621989 disclose an image-receiving sheet having a receiving layer mainly composed of a polyvinyl acetal resin obtained by acetalizing polyvinyl alcohol using an aldehyde having a specific group such as an aryl group. Each is disclosed.

However, the former (JP-A-61-112)
The image recorded on the image receiving sheet of JP-A-93-93 has low storage stability such as light resistance and oil resistance, and is not suitable for long-term storage of the image.

[0006] Further, images recorded on the image receiving sheet of the latter (JP-A-3-65391 and JP-A-3-162289) are poor in gloss and sharpness, and have good storage stability such as light resistance and oil resistance. It has the disadvantage that the properties are still insufficient. Furthermore, these documents describe that a dye-accepting layer is formed using a polyvinyl acetal-based resin acetalized with an aldehyde having a carboxyl-substituted phenyl group. However, in the image receiving sheet obtained by applying this resin, the dye receiving layer (coating) is whitened,
In addition, the resulting printed matter has the disadvantage of low gloss and low recording density, and its oil resistance and light resistance are not sufficient.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks of the prior art, and has been made in consideration of the above-mentioned drawbacks, and is an image-receiving sheet used in sublimation thermal transfer printing which has an image having high gloss and excellent storage stability. It is an object of the present invention to provide a carboxy-modified polyvinyl acetal-based resin for forming a dye receiving layer.

[0008]

The present inventors have conducted various studies to solve the drawbacks of the prior art. As a result, a polyvinyl acetal resin having a structural unit having a specific functional group forms a receiving layer of an image receiving sheet. It has been found that the present invention exerts an excellent effect as a resin to be used, and has completed the present invention.

That is, the gist of the present invention is a carboxy-modified polyvinyl acetal resin for forming a dye-receiving layer of an image-receiving sheet for sublimation-type thermal transfer printing obtained by acetalizing a carboxy-modified polyvinyl alcohol-based resin.

Hereinafter, the present invention will be described in more detail.

A carboxy-modified polyvinyl acetal-based resin for forming a dye-receiving layer of an image-receiving sheet for sublimation-type thermal transfer printing according to the present invention (hereinafter sometimes referred to as the resin of the present invention)
Is obtained by acetalizing a carboxy-modified polyvinyl alcohol-based resin with one or more aldehydes in the presence of an acid catalyst.

The carboxy-modified polyvinyl alcohol-based resin (hereinafter referred to as carboxy-modified PVA) used as a raw material for obtaining the resin of the present invention can be obtained by a known method, for example, Japanese Patent Publication No. 46-7605, Japanese Patent Application Laid-Open No. 940
It can be obtained by the method described in Japanese Patent Publication No. Specifically, one or more fatty acid vinyl esters (vinyl acetate, vinyl propionate, vinyl formate, etc.)
And unsaturated monocarboxylic acids (acrylic acid, methacrylic acid, crotonic acid, etc.), ethylenically unsaturated dicarboxylic acids (maleic acid, fumaric acid, itaconic acid, etc.), ethylenically unsaturated dicarboxylic anhydrides (maleic anhydride, (Eg, itaconic anhydride) can be obtained by a method of completely or partially saponifying a copolymer with one or more kinds thereof.

Further, a monomer having a side chain which is converted into a carboxyl group by reacting with a fatty acid vinyl ester and an acid used as a catalyst in performing an acetalization reaction [for example, acrylamide (described in JP-B-46-7605) , Methacrylamide, etc.] can be obtained by completely or partially saponifying or alcoholyzing a copolymer with carboxy-modified PVA.

Further, a polyvinyl alcohol resin (hereinafter referred to as PVA) obtained by completely or partially saponifying a polymer of a fatty acid vinyl ester or a copolymer of a fatty acid vinyl ester and another monomer. Post-modified PVA, such as a carboxymethylation of a part of the hydroxyl groups of) by the action of monochloroacetic acid or the like in the presence of an alkali catalyst,
Included in carboxy-modified PVA.

The carboxyl group in the carboxy-modified PVA may be in the form of an acid, a salt (a salt of sodium, potassium, lithium, ammonia, amines, etc.), an acid amide, or an alkyl ester, or a combination thereof. .

The carboxy-modified PVA described above is
As a part of the structural unit, a monomer unit other than the above which can be copolymerized with the fatty acid vinyl ester may be provided as long as the invention is not hindered.

The carboxy-modified polyvinyl acetal resin of the present invention can be obtained by acetalizing one or more of the carboxy-modified PVAs thus obtained. There are no particular restrictions on the conditions at that time, and the reaction can be performed by known methods and conditions. For example, in a system containing an organic solvent such as methanol, an aldehyde and an acid as a catalyst, the powdery and granular carboxy-modified PVA is added.
Is suspended and allowed to undergo an acetalization reaction, a method of adding water or the like to the generated polyvinyl acetal solution to precipitate a carboxy-modified polyvinyl acetal resin, or adding the aldehyde and the acid catalyst to an aqueous solution of carboxy-modified PVA. To carry out an acetalization reaction to precipitate a carboxy-modified polyvinyl acetal in an aqueous reaction system as the reaction proceeds. Furthermore, in these methods, the carboxy-modified PVA
Instead of using the carboxy-modified fatty acid vinyl ester copolymer resin before saponification or alcoholysis used to obtain the PVA, an acid-catalyzed saponification reaction and an acetalization reaction are performed in parallel. Good.

The aldehyde used in the acetalization reaction is not particularly limited. For example, linear or branched alkyl aldehydes such as formaldehyde, acetaldehyde and butyl aldehyde, aromatic aldehydes such as benzaldehyde and phenylacetaldehyde can be used. And the like.

Further, a carboxy-modified polyvinyl acetal resin obtained by allowing two or more aldehydes to coexist in an acetalization reaction system is also included in the resin of the present invention.

As the acid catalyst used in the acetalization reaction, a strong inorganic acid is usually used, and among them, hydrochloric acid is preferable.

Further, in the acetalization reaction system, carboxy-modified PVA and non-carboxy-modified PVA are allowed to coexist within a range that does not interfere with the present invention, and the average degree of polymerization of the resulting carboxy-modified polyvinyl acetal resin is determined. The content of the group and the like can be adjusted.

The carboxy-modified polyvinyl acetal resin of the present invention has a vinyl acetal unit and a monomer unit having a carboxyl group, and usually comprises a unit obtained by adding a vinyl alcohol unit and a fatty acid vinyl ester unit to these units. Is done. Further, when the carboxy-modified PVA or PVA used as a raw material has another monomer unit copolymerizable with the above-mentioned fatty acid vinyl ester, it also has that monomer unit.

The carboxy-modified polyvinyl acetal resin of the present invention is a monomer unit having a carboxyl group (including a structural unit having a carboxyl group added by post-modification).
Contains a carboxyl group bonded as a side chain. The content of the carboxyl group (in terms of COOH) is preferably 0.5 to 10% by weight relative to the resin, and more preferably 1 to 8%.
A range of weight percent is desirable. This content is 0.5% by weight
If the amount is less than 10%, the effect of improving the storage stability of the dye-receiving layer such as light resistance and oil resistance may not be obtained.

The content of the carboxyl group is expressed as a percentage of the weight of the resin in which the value obtained by converting the carboxyl group into a sodium salt and quantifying the sodium using an atomic absorption spectrometer is converted into the carboxyl group.

The carboxyl group in the resin of the present invention may be partially or wholly in the form of an acid (—COOH), in the form of a salt (salts such as sodium, potassium, lithium, ammonia and amines), and in lower alkyl (methyl). , Ethyl, propyl,
Butyl, etc.), an ester form, or a combination of these forms. Among them, at least a part of the carboxyl group is in an acid form. It is preferable in improving the value.

The content of the monomer unit having a carboxyl group in the resin of the present invention can be arbitrarily selected according to the desired content of the carboxyl group.

The content of the vinyl acetal unit in the resin of the present invention depends on the solubility of the resin in an organic solvent,
From the viewpoint that the gloss and clarity of the image printed on the dye-receiving layer obtained using the resin are good, 50 to 9
It is preferably 5% by weight, more preferably 60-95% by weight. When the resin contains two or more vinyl acetal units, the weight ratio between each vinyl acetal is measured using an infrared spectrophotometer.

Further, the resin of the present invention usually contains a vinyl alcohol unit and a fatty acid vinyl ester unit based on the raw material resin.

The vinyl alcohol unit is left unacetalized in the acetalization reaction, and the content of this unit is 25% by weight or less from the viewpoint of solubility of the obtained resin in an organic solvent. Preferably, there is.

The content of the fatty acid vinyl ester unit is usually 10% by weight or less.

The content of the fatty acid vinyl ester unit is determined by adding an aqueous solution of caustic soda to a resin dissolved in ethyl alcohol and heating it to hydrolyze the ester portion to produce fatty acid soda. Sum), then add an internal standard substance (in the case of vinyl acetate, use propionic acid) and phosphoric acid, determine the amount of fatty acid produced by the decomposition of fatty acid soda by gas chromatography, and convert the amount of this fatty acid. Can be.

The average degree of polymerization of the resin of the present invention is not particularly limited, but is preferably from 200 to 3,500, more preferably from 300 to 3,000, from the viewpoint of storage stability of an image and solubility in an organic solvent.

In the present invention, the content of the carboxyl group, the constitutional unit and its content, and the average degree of polymerization are different.
More than one resin of the present invention can be used in combination.
In addition, the resin of the present invention can be used in combination with a polyvinyl acetal-based resin which is not carboxy-modified and has the same weight or less.

The image-receiving sheet using the resin of the present invention is generally prepared by adding a solution obtained by dissolving the resin in an organic solvent or a solution obtained by adding various additives to an emulsion containing the resin as required, for example, synthetic paper, paper, plastic It can be obtained by coating and drying a substrate surface such as a film or sheet to form a coating film. The coating is then a dye-receiving layer.

Any one of the above organic solvents may be used alone or
It can be used in combination of more than one kind, for example, alcohol solvents, cellosolve solvents, aromatic solvents, ketone solvents, ester solvents, halogen-containing solvents, ether solvents, amide solvents, tetrahydrofuran solvents, And the like.

Examples of the above additives include a release agent such as a hardening type silicone oil for preventing the thermal transfer sheet and the image receiving sheet from being fused by heat at the time of thermal transfer and for easily separating these sheets after the transfer. Agents, UV absorbers and light stabilizers to further enhance the light fastness of images, and white pigments to further enhance the sharpness of images by improving the whiteness of the image receiving sheet and to provide writability to the surface of the image receiving sheet , Antistatic agents, defoamers and the like.

[0037]

The present invention will be described below with reference to examples and comparative examples. In the following, “parts” means “parts by weight” unless otherwise specified. Example 1 (Production of carboxy-modified polyvinyl acetal resin) 400 parts of methanol and 5 parts of 35% hydrochloric acid were charged into a reactor equipped with a stirrer, a reflux condenser and a thermometer, and then acrylamide copolymer-modified PVA (average polymerization degree). 1730, residual acetic acid group 8.1% by weight, acrylamide content 11.1
85% by weight) were added with stirring. Next, 60 parts of acetaldehyde was added thereto, and the mixture was stirred at a temperature of 60 parts.
The reaction was performed at 6 ° C. for 6 hours to obtain a methanol solution of a carboxy-modified polyvinyl acetal resin. After the solution was cooled and neutralized with ethylene oxide, water was added with stirring to carry out a precipitation operation, followed by washing with water, filtration and drying to obtain a white powdery carboxy-modified polyvinyl acetal resin (a).

The average composition of the obtained resin was 77.9% by weight of vinyl acetal unit and 12.5% of vinyl alcohol unit.
% By weight, 3.9% by weight of a vinyl acetate unit, and 5.7% by weight of a monomer unit having a carboxyl group. The carboxyl group content of this resin was 3.6% by weight. (Preparation of Image Receiving Sheet) Using the obtained carboxy-modified polyvinyl acetal resin, the following composition for forming a dye receiving layer was blended, and the resulting composition was mixed with a base sheet of polypropylene synthetic paper (Yupo FPG150, manufactured by Oji Oil Chemical Co., Ltd.). One side was coated by a wire bar coating so that the thickness of the coating layer after drying was about 5 μm, and dried to prepare an image receiving sheet.

Composition for forming dye-receiving layer Above carboxy-modified polyvinyl acetal resin (A) 3 parts Amino-modified silicone oil 0.1 part (KF-393, manufactured by Shin-Etsu Silicone Co., Ltd.) Epoxy-modified silicone oil 0.1 part (Shin-Etsu Silicone Co., Ltd., X-22-343) Isopropyl alcohol 20 parts Methyl ethyl mutone 30 parts Toluene 50 parts (Preparation of thermal transfer sheet) Corona discharge treatment was applied to one surface, and the other surface was heat-resistant and lubricated to a thickness of 6 μm. An ink composition having the following composition is applied to the surface of the polyethylene terephthalate film which has been subjected to the corona discharge treatment by wire bar coating so that the thickness of the coating film after drying becomes about 1 μm, and dried, and the coloring material is applied to one side. A thermal transfer sheet having a layer was produced.

Ink composition Dye (Kayaset Blue 714, manufactured by Nippon Kayaku Co., Ltd.) 4 parts Ethyl hydroxyethyl cellulose (manufactured by Hercules) 5 parts Toluene 45 parts Methyl ethyl ketone 45 parts Dioxane 10 parts (thermal transfer printing test and evaluation of printed matter) 1 Thermal transfer printing test Using the image receiving sheet and the thermal transfer sheet obtained as described above, the color material layer of the thermal transfer sheet and the dye receiving layer of the image receiving sheet are overlapped so as to be in contact with each other, and a thermal head (manufactured by Kyocera Corp., KMT) Thermal transfer printing was performed using a thermal transfer printer equipped with -85-6MPD2 (partial grace thin film type head) under the following conditions to obtain a printed material.

Thermal transfer conditions: Head application voltage: 11.2 V Pulse width: 1.0 to 16.0 msec Printing speed: 33.3 msec / line Density: 6 / mm Platen hardness: 70 ° Platen diameter: 25 mm Linear pressure: 4 kg / 10 cm Feeding speed: 5.0 mm / sec 2 Evaluation of printed matter Using the printed matter obtained in 1 above as a sample, the following items (1) to (4) were evaluated, and the evaluation results are shown in Table 1.

(1) Recording Density The energizing pulse width of the image transferred and formed on the image receiving sheet is 14
The reflection density at a location corresponding to msec was measured using a Macbeth reflection densitometer (RD-918), and the value was used as the recording density.

(2) Gloss (%) At the same measurement point as the recording density, a 60 ° reflectance was measured using a gloss meter (GM-26D manufactured by Murakami Color Research Laboratory), and this value was defined as the gloss (%). did.

(3) Light fastness (%) The printed surface was measured at 200 KJ using a xenon fade meter.
/ M ² , and the reflection density (B) of the printed surface after the exposure was measured. The light fastness was calculated by the following equation using the reflection density (A) measured before exposure and the above (B).

Light resistance (%) = (B / A) × 100 (4) Oil resistance (%) 100 parts of petrolatum and plasticizer (dioctyl phthalate) 1
0 parts of the mixture was applied to the printing surface, which was left at 40 ° C. for 24 hours, and the petrolatum mixture was wiped off. Next, the reflection density (D) of the printed surface was measured.

The oil resistance was calculated by the following equation using the reflection density (C) measured before application of the petrolatum mixture and the above (D).

Oil resistance (%) = (D / C) × 100 Examples 2 to 10 In the same manner as in Example 1 except that a polyvinyl acetal resin having the properties shown in Table 1 was used instead of the resin (A). Evaluation of the obtained printed matter was performed in the same manner as in Example 1. Table 1 shows the results. Example 11 In the same manner as in Example 1, a methanol solution of a carboxy-modified polyvinyl acetal resin was obtained. Then, after cooling the solution, an aqueous solution of caustic soda was added to adjust the solution temperature to 20 to 30.
Stirring was continued for 5 hours while maintaining the temperature at ° C. Then, Example 1
By the same operation, precipitation, washing, filtration and drying were performed to obtain a carboxy-modified polyvinyl acetal resin having a carboxyl group in the form of a sodium salt. Table 1 shows the properties of the resin and the evaluation results of the printed matter of the image receiving sheet obtained in the same manner as in Example 1 except that the resin was used in place of the resin (a). Examples 12 to 16 Evaluation of the printed matter obtained in the same manner as in Example 1 except that the polyvinyl acetal resin having the properties shown in Table 1 was used instead of the resin (A), was evaluated in the same manner as in Example 1. . Table 1 shows the results. Comparative Examples 1 to 4 Evaluation of the printed matter of the image receiving sheet in the same manner as in Example 1 except that the polyvinyl acetal resin having the properties shown in Table 1 was used instead of the polyvinyl acetal resin (A) used in Example 1. Was performed. Table 1 shows the evaluation results.

In the image receiving sheet obtained in Comparative Example 4, the coating film (dye receiving layer) formed on the substrate was whitened, and the gloss and recording density of the printed matter were lower than those of the other examples.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

[Table 3]

[0052]

The image receiving sheet obtained by using the carboxy-modified polyvinyl acetal resin for forming the dye receiving layer of the image receiving sheet for sublimation type thermal transfer printing of the present invention has a clear and glossy image after transfer, and Excellent storage stability such as light resistance and oil resistance.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akio Nishijima 1135 Nakamura, Shibukawa-shi, Gunma Electrochemical Industry Co., Ltd. Inside the Shibukawa Plant (56) References JP-A-3-65391 (JP, A) JP-A-3-162689 (JP, A) JP-A-4-52193 (JP, A) JP-A-57-94002 (JP, A) JP-A-5-246151 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) B41M 5/38-5/40 C08F 8/28 C08F 16/38 C08L 29/14

Claims (4)

(57) [Claims] 1. A carboxy-modified polyvinyl alcohol-based resin obtained by acetalization.
A carboxy-modified polyvinyl acetal-based resin for forming a dye-receiving layer used in an image receiving sheet for sublimation-type thermal transfer printing. 2. A carboxy-modified polyvinyl acetal resin having a carboxyl group content of 0.5 to 0.5 wt.
The carboxy-modified polyvinyl acetal-based resin according to claim 1, which is in a range of from 10 to 10% by weight. 3. The carboxy-modified polyvinyl acetal resin according to claim 1, wherein the proportion of the vinyl acetal unit in the resin is in the range of 50 to 95% by weight. 4. The carboxy-modified polyvinyl acetal resin according to claim 1, wherein the average degree of polymerization is from 200 to 3,500.