JPH05338366A - Resin for forming dye receiving layer of image receiving sheet - Google Patents

Abstract

PURPOSE:To enhance storage stability and recording density by forming the title resin for sublimation type thermal transfer printing by acetilating a partially saponified polyvinyl alcohol resin and setting the content of the vinyl acetate unit in the resin to a predetermined value. CONSTITUTION:A resin for forming the dye receiving layer of an image receiving sheet is formed by acetylating one or more kinds of a partially saponified polyvinyl alcohol resin (including a resin with vinyl alcohol unit content of 50mol% or less) (hereinbelow referred to as partially saponified PVA) with one or more kinds of aldehyde in the presence of an acid catalyst. This partially saponified PVA is formed by saponifying a vinyl acetate resin obtained by polymerizing vinyl acetate and/or a copolymer resin of vinyl acetate and other monomers and the content of a vinyl acetate unit at this time is set to 30-70mol%. The glass transition temp. of this polyvinyl acetal resin is set to 60-100 deg.C and the average polymerization degree thereof is set to 200-3500.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyvinyl acetal resin for forming a dye receiving layer of an image receiving sheet used for 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 and a dye receiving layer surface of an image receiving sheet having a dye receiving layer on the surface are in contact with each other. After superimposing on each other, the sublimable dye in the color material layer is transferred to the dye receiving layer of the image receiving sheet by heating with a thermal head or laser light according to the image information, and after thermal diffusion, the thermal transfer sheet is placed. A sublimation type thermal transfer technique has been developed in which an image corresponding to image information is recorded on an image receiving sheet by peeling.

The dye receiving layer of the image receiving sheet used in this technique is required to have the following performances, for example. (I) Good dyeability, high density, glossy and clear image can be obtained. (II) Good image storage stability, for example, (a) When an image comes in contact with a part of the human body (hands, fingers, etc.), a plastic eraser containing a plasticizer, or its eraser, an image is formed. Dye does not cause aggregation, fading, etc., fingerprint resistance,
Good plasticizer resistance. (b) The image shall not fade or discolor when exposed to light, and shall have good light resistance. (c) The image should not fade or discolor when it is heated by blocking light, and it should have good heat resistance (dark fading). (III) When the thermal transfer sheet and the image receiving sheet are separated after thermal transfer, they are easy to separate without fusing.

Various image receiving sheets for use in sublimation 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. 3-65391 and Japanese Patent Laid-Open No. 3-
Japanese Patent No. 162989 discloses an image-receiving sheet having a receiving layer containing, as a main component, a polyvinyl acetal resin obtained by acetalizing polyvinyl alcohol with an aldehyde having a specific group such as an aryl group.

However, the image recorded on the image receiving sheet of the former (Japanese Patent Laid-Open No. 61-11293) has low storage stability such as light resistance, fingerprint resistance and plasticizer resistance, and is suitable for long-term image storage. It has the drawback of not being suitable. The image recorded on the image receiving sheet of the latter (Japanese Patent Laid-Open No. 3-65391 and Japanese Patent Laid-Open No. 3-162989) has poor gloss and sharpness, light resistance, fingerprint resistance, plasticizer resistance, etc. However, it has the drawback that its storage stability is still insufficient.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks of the prior art, and is excellent in storage stability such as light resistance, fingerprint resistance, plasticizer resistance, and sufficient recording. An object of the present invention is to provide a polyvinyl acetal resin for forming a dye receiving layer of an image receiving sheet for sublimation type thermal transfer printing, which can obtain a clear image having a density.

[0007]

As a result of various investigations, the present inventor has found that a polyvinyl acetal resin having a specific proportion of vinyl acetate units as a constitutional unit achieves the object, The present invention has been completed.

That is, the present invention is a polyvinyl acetal resin obtained by acetalizing a partially saponified polyvinyl acetal resin, wherein the content of vinyl acetate units in the resin is 30 to 70 mol%. A gist is a polyvinyl acetal resin for forming a dye receiving layer of an image receiving sheet for printing.

The present invention will be described in more detail below. The polyvinyl acetal-based resin for forming the dye receiving layer of the image-receiving sheet for sublimation type thermal transfer printing of the present invention is one or more partially saponified polyvinyl alcohol-based resins (resin having a vinyl alcohol unit content of 50 mol% or less. Inclusive) is acetalized with one or more aldehydes in the presence of an acid catalyst.

The partially saponified polyvinyl alcohol resin (hereinafter referred to as partially saponified PVA) used in the above is saponified by an acid catalyst during the acetalization reaction and a part of the vinyl acetate unit is decreased, so that the decrease In consideration of the amount, a polyvinyl acetal-based resin having a residual acetic acid group content such that the average content of vinyl acetate units is 30 to 70 mol% is selected and used.

The above partially saponified PVA is obtained by partially saponifying a vinyl acetate resin obtained by polymerizing vinyl acetate and / or a copolymer resin of vinyl acetate and another monomer with an alkali or an acid. can get.

Other monomers that can be used for the copolymerization with vinyl acetate include, for example, (meth) acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid and their alkyl esters and salts, maleic anhydride. Acid, (meth) acrylic acid, (meth) acrylonitrile, (meth) acrylic acid alkyl ester, glycidyl (meth) acrylate,
Examples include allyl glycidyl ether, ethylene, propylene, vinyl chloride, vinyl fluoride, vinylidene chloride, vinylidene fluoride, alkyl vinyl ether, vinyl pyridine, vinyl pyrrolidone, vinyl versatate, vinyl propionate, etc. It is also possible to use a combination of two or more species.

There are no particular restrictions on the method and conditions for acetalizing the partially saponified PVA, and known methods and conditions can be used. For example, an organic solvent such as methanol,
A method of suspending or dissolving the partially saponified PVA in an aldehyde and a system containing an acid as a catalyst to carry out the acetalization reaction, or adding an aldehyde and an acid catalyst to an aqueous solution of the partially saponified PVA or an alcohol-containing aqueous solution to perform the acetalization. Examples include a method of causing the reaction. Moreover,
In these methods, instead of partially saponified PVA, the
A method may also be used in which the saponification reaction and the acetalization reaction with an acid catalyst are performed in parallel for the vinyl acetate resin before saponification and / or the copolymer resin of vinyl acetate and another monomer used for obtaining PVA.

The aldehyde used for the above acetalization is not particularly limited, and for example, a linear or branched alkyl aldehyde such as formaldehyde, acetaldehyde, butyraldehyde, valeraldehyde, isovaleraldehyde, benzaldehyde, phenylacetaldehyde. And aromatic aldehydes. Two or more aldehydes can be used in combination.

As the acid catalyst used in the acetalization reaction, a strong inorganic acid is usually used, and hydrochloric acid is preferable.
To neutralize the acid catalyst for the purpose of stopping the acetalization reaction, for example, ethylene oxide, alkylene oxide such as propylene oxide, caustic soda, sodium carbonate, ammonia and the like can be added to the acetal reaction system, It is preferable to use alkylene oxide from the viewpoint that inorganic salts do not remain in the obtained resin.

The polyvinyl acetal resin of the present invention is
It is usually composed of vinyl acetal units, unreacted vinyl alcohol units and vinyl acetate units. Furthermore, when the partially saponified PVA used as a raw material has another monomer unit that is copolymerizable with vinyl acetate, it also has the monomer unit or a unit derived from the monomer. In this case, the proportion of the total of the units of other monomers and the units derived from the units of the monomers in the polyvinyl acetal resin is preferably 15 mol% or less.

The content of vinyl acetate unit in the polyvinyl acetal resin of the present invention is 30 to 70 mol% in the resin. If this content is less than 30 mol%, sufficient effects of improving the storage stability of the dye receiving layer such as fingerprint resistance and plasticizer resistance cannot be obtained. On the other hand, if it exceeds 70 mol%, the image-receiving sheet and the thermal transfer sheet are easily fused by thermal transfer, or the glass transition temperature is low and the obtained image is blurred over time, which is not preferable.

The content of vinyl acetate units is determined by adding an aqueous solution of caustic soda to a polyvinyl acetal resin dissolved in ethyl alcohol and heating it to hydrolyze the acetic acid ester portion to produce sodium acetate (the remaining caustic soda is Neutralize with sulfuric acid), then add the internal standard substances propionic acid and phosphoric acid, and quantify the acetic acid produced by the decomposition of sodium acetate by gas chromatography, and calculate the amount of this acetic acid in vinyl acetate units. You can

The glass transition temperature of the resin of the present invention is 60 to 10
The range of 0 ° C is preferred. If the glass transition temperature is too low,
The peelability between the thermal transfer sheet and the image receiving sheet during thermal transfer may be low, the obtained image may be blurred over time, or the fingerprint resistance and the plasticizer resistance may be insufficient. on the other hand,
If the glass transition temperature is too high, the dyeing property is likely to decrease. The glass transition temperature of the resin can be variously changed by appropriately selecting and combining the amount of vinyl acetate units, the type of aldehyde used for acetalization, and the amount of vinyl acetal units.

The content of the vinyl acetal unit in the resin of the present invention is preferably 15 to 60 mol%, and more preferably 20 to 60 mol% from the viewpoints of light resistance of the obtained image and fixing property of the dye.
Is more preferable. Further, by selecting the content of vinyl acetal units in the polyvinyl acetal resin,
The glass transition temperature of the resin can be changed.

The vinyl alcohol unit in the resin of the present invention is the one left unacetalized in the acetalization reaction, and the content of this unit depends on the solubility of the resin, the solution viscosity and its stability, From the viewpoint of image recording density, moisture resistance, etc., 5 to 30 mol% in the resin is preferable,
20 mol% is more preferable.

The average degree of polymerization of the resin of the present invention is not particularly limited, but storage stability of images, solubility in organic solvents,
From the viewpoint of solution viscosity, etc., 200 to 3500 is preferable, and further 30
The range of 0 to 3000 is desirable.

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

Any of the above organic solvents may be used alone or in combination of two or more. For example, alcohol solvents, cellosolve solvents, aromatic solvents, ketone solvents, ester solvents, halogen-containing solvents. Examples thereof include solvents, ether solvents, amide solvents, and tetrahydrofuran solvents.

As an example of the above-mentioned additive, a releasing agent such as a curable silicone oil for preventing fusion of the thermal transfer sheet and the image receiving sheet due to heat during thermal transfer and easily separating the sheets after transfer from each other. Agent, an ultraviolet absorber or a light stabilizer for further enhancing the light resistance of the image, a white pigment for improving the whiteness of the image receiving sheet to further enhance the sharpness of the image and imparting writability to the surface of the image receiving sheet. , Antistatic agents, defoamers, etc.

[0026]

EXAMPLES The present invention will be described below based on Examples and Comparative Examples. In the following, “parts” means parts by weight unless otherwise specified.

Example 1 (Production of polyvinyl acetal resin) 400 parts of methanol were placed in a reactor equipped with a stirrer, a reflux condenser and a thermometer.
5 parts of 35% hydrochloric acid was charged, and then 80 parts of partially saponified PVA (average degree of polymerization: 1000, residual acetic acid group: 30 mol%, vinyl alcohol unit: 70 mol%) was added thereto with stirring. Next, 80 parts of acetaldehyde was added thereto, and acetalization reaction was carried out at a temperature of 60 ° C. for 6 hours under stirring to obtain a methanol solution of polyvinyl acetal resin. This solution was cooled, and ethylene oxide was added thereto for neutralization to obtain a polyvinyl acetal resin (a). The obtained resin (a) had an average composition of 50 mol% vinyl acetoacetal units, 15 mol% vinyl alcohol units and 35 mol% vinyl acetate units, and a glass transition temperature of 85 ° C.

(Preparation of Image-Receiving Sheet) Using the obtained polyvinyl acetal resin (a), the following composition for forming a dye-receptive layer was prepared, and the composition was used as a base sheet for polypropylene synthetic paper (manufactured by Oji Yuka Co., Ltd., YUPO FPG 150) was coated on one side by 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-receptive layer Polyvinyl acetal resin (b) 3 parts Amino-modified silicone oil 0.1 part (Shin-Etsu Silicone Co., Ltd., KF-393) Epoxy-modified silicone oil 0.1 part (Shin-Etsu Silicone Co., Ltd., X- 22-343) Isopropyl alcohol 20 parts Methyl ethyl ketone 30 parts Toluene 50 parts

(Preparation of thermal transfer sheet) Corona discharge treatment was applied to one surface and heat-resistant lubricity was applied to the other surface to a thickness of 6 μm.
m of polyethylene terephthalate film on the surface subjected to corona discharge treatment, the thickness of the coating film after drying the ink composition of the following composition by wire bar coating is about 1 μm.
It was applied so as to have a thickness of m and dried to prepare a thermal transfer sheet having a color material layer on one surface.

Ink composition Sublimation dye (Kayaset Blue 714 manufactured by Nippon Kayaku Co., Ltd.) 4 parts Ethylhydroxyethyl 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 in contact with each other. As described above, thermal transfer printing was performed under the following conditions using a thermal transfer printer equipped with a thermal head (KMT-85-6MPD2 manufactured by Kyocera Corp., a thin film head of partial grace) to obtain a printed matter.

Thermal transfer conditions: Head applied voltage: 11.2 V Pulse width: 1.0-16.0 msec Printing speed: 33.3 msec / line Density: 6 lines / mm Platen hardness: 70 ° Platen diameter: 25 mm Line pressure: 4 kg / 10 cm Feed rate: 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 (5) were evaluated, and the evaluation results are shown in Table 3.

(1) Recording density Energization pulse width 14 ms of the image transferred and formed on the image receiving sheet
The reflection density of the part corresponding to ec is calculated by the Macbeth reflection densitometer (RD
-918) was used as the recording density.

(2) Light resistance The printed surface should be printed with a xenon fade meter (Atlas Co., Ci
-35A), irradiate 200 KJ / m ² (integrated light amount of 420 nm),
The recording density before and after irradiation was measured, and the residual ratio of the recording density was calculated by the following formula. Light resistance is shown by the following criteria corresponding to this residual rate (%). Remaining rate (%) = (recording density after irradiation / recording density before irradiation) x 100 A: Remaining rate is 90% or more B: Remaining rate is 80% or more and less than 90% C: Remaining rate is 70% or more and 80% Less than D: Residual rate less than 70%

(3) Fingerprint resistance After imprinting a fingerprint on the printed surface and leaving it at room temperature for 5 days, the degree of discoloration and density change of the fingerprint imprinted portion was visually evaluated. A: Almost no difference between the fingerprint imprinted part and the non-imprinted part was recognized. B: Discoloration or change in density was observed. C: The imprinted part of the fingerprint was blank, and the fingerprint shape was clearly recognized. D: White spots occurred around the fingerprint imprinted portion, and at the same time, dye aggregation was observed.

(4) Plasticizer resistance The same portion of the printed surface where the change was observed was lightly rubbed with a commercially available plastic eraser three times, and the degree of change in density was visually judged. A: Almost no change in concentration was observed. B: A change in concentration was observed. C: The density changed significantly.

(5) Bleeding After the printed matter was left in an oven at 60 ° C. for 120 hours, the diffusion of printed dots was observed with a loupe. ◯: Diffusion of dots was not recognized. X: Diffusion of dots was recognized.

Examples 2 to 9 Evaluation of printed matters obtained in the same manner as in Example 1 except that a polyvinyl acetal resin having the properties shown in Table 2 was used in place of the polyvinyl acetal resin (a) was evaluated as Example 1. It carried out similarly. The evaluation results are shown in Table 3.

Example 10 As a partially saponified PVA, a partially saponified product of vinyl acetate and isobutyl vinyl ether copolymer resin (average degree of polymerization 2400, residual acetic acid group 30 mol%, isobutyl vinyl ether unit 8 mol%, vinyl alcohol unit 62 mol%) Polyvinyl acetal resin (average composition: 37 mol% vinyl acetoacetal units, 38 mol% vinyl acetate units, 14 mol% vinyl alcohol units) in the same manner as in Example 1 except that
And an isobutyl vinyl ether unit (11 mol%, glass transition temperature 65 ° C.) were obtained. The thermal transfer printing test and the evaluation of the printed matter of the image-receiving sheet obtained in the same manner as in Example 1 were carried out except that the polyvinyl acetal resin obtained above was used in place of the polyvinyl acetal resin (a). The results are shown in Table 3.
Shown in.

Comparative Examples 1 to 9 Printed matter obtained in the same manner as in Example 1 except that the polyvinyl acetal resin (a) used in Example 1 was replaced by a polyvinyl acetal resin having the properties shown in Table 2. Was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 3.

When separating the image-receiving sheet and the thermal transfer sheet after printing in the thermal transfer printing test, no fusion was observed between the surfaces of the sheets in Examples 1 to 10, and the sheets could be easily separated. In No. 8, fusion was recognized in part.

[0044]

[Table 1]

[0045]

[Table 2]

[0046]

[Table 3]

[0047]

The dye-receiving layer-forming polyvinyl acetal-based resin of the image-receiving sheet for sublimation-type thermal transfer printing of the present invention has a light-resisting image obtained by sublimation-type thermal transfer printing on an image-receiving sheet having a dye-receiving layer using the same. It is excellent in storage stability such as fingerprint resistance and plasticizer resistance, and has an effect that it is clear with sufficient recording density.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Akio Nishijima 1,135 Nakamura, Shibukawa, Gunma Denki Kagaku Kogyo Co., Ltd. Shibukawa factory

Claims (3)

[Claims] 1. A polyvinyl acetal resin obtained by acetalizing a partially saponified polyvinyl alcohol resin, wherein the content of vinyl acetate units in the resin is 30 to 70.
A polyvinyl acetal resin for forming a dye receiving layer of an image receiving sheet for sublimation type thermal transfer printing having a mol%. 2. The polyvinyl acetal resin according to claim 1, which has a glass transition concentration of 60 to 100 ° C. 3. The average degree of polymerization is 200 to 3500.
The polyvinyl acetal resin described.