JPH08310136A - Binder for thermal transfer layer and thermal transfer ink ribbon - Google Patents

Abstract

PURPOSE: To provide a binder resin for a thermal transfer layer excellent in the releasability thermal transfer with recording paper having a receiving layer containing no release agent and the preservability of an ink ribbon and a sublimable thermal transfer ink ribbon. CONSTITUTION: A binder for a thermal transfer layer contains a polyvinyl acetal resin and a silicone resin having a three-dimensional reticulated structure containing a siloxane bond as a main skeleton and solid at the normal temp. and soluble in an org. solvent. A thermal transfer ink ribbon is obtained by providing a thermal transfer layer containing a sublimable dye and the binder for the thermal transfer layer on a base material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binder for a thermal transfer layer and a thermal transfer ink ribbon having the thermal transfer layer containing the binder.

[0002]

2. Description of the Related Art Conventionally, image recording by a sublimation thermal transfer system has been carried out using an ink ribbon and recording paper. More specifically, a thermal transfer layer containing a sublimable dye, a binder and the like is provided on a substrate. Head in which the temperature and the like are controlled based on image signals when the thermal transfer layer surface of the ink ribbon and the receiving layer surface of the recording sheet having the dye receiving layer on the base sheet are in contact with each other. Or laser to apply heat energy to the ink ribbon to sublimate the dye in the thermal transfer layer, and the dye sublimated from the thermal transfer layer is transferred to the receiving layer of the recording paper.

In this sublimation thermal transfer system, a television, a CRT color display, a color facsimile,
The amount of thermal energy applied to the thermal transfer layer of the ink ribbon is changed in response to changes in the image signal obtained by a magnetic camera, etc., and the amount of dye sublimated and transferred from the thermal transfer layer is changed, thereby receiving recording paper. Image recording having good gradation on the layer can be obtained. Further, at the time of thermal transfer, by using three kinds of ink ribbons each containing a dye of one of the three primary colors of yellow, magenta and cyan in the thermal transfer layer, each color is superposed and transferred to the same receiving layer surface of the recording paper,
Full-color image recording can also be performed.

A polyvinyl butyl acetal resin, a polyvinyl acetoacetal resin, etc. are used as the binder for the dye of the thermal transfer layer, and the polyvinyl acetoacetal resin is particularly excellent in the compatibility with the dye and the recording density.

On the other hand, the receptive layer used in the conventional sublimation thermal transfer method is usually a vinyl chloride-based copolymer such as a vinyl chloride-vinyl acetate copolymer, a polyester resin or a polycarbonate resin as described above. , It is used together with a release agent such as silicone oil to prevent fusion with the ink ribbon during thermal transfer and to achieve high recording density. Especially, those using vinyl chloride-vinyl acetate copolymer are Excellent weather resistance and dark fading resistance.

[0006]

However, since the conventional receiving layer contains a release agent such as silicone oil,
In addition to the problem of fusing, there was a problem that the writability of the recording paper surface was poor and the oil-based magic ink or the like was repelled.

Therefore, when a liquid release agent such as silicone oil is simply blended in the thermal transfer layer, not on the receiving layer side, at room temperature, the release agent is not stored together with the sublimable dye during storage of the ink ribbon. However, there is a problem in that the initial releasability and the recording density cannot be maintained by transferring to the back coat surface of the ink ribbon that is in contact with the thermal transfer layer.

Further, the silicon compound or the fluorine compound is added in an amount of 0.0 to 1 part by weight of the polyvinyl acetal resin.
When a resin copolymerized in the range of 5 to 1 parts by weight is used as the binder for the thermal transfer layer, it is excellent in releasing property from the receiving paper, but a releasing agent such as a silicon compound which is reacted with the polyvinyl acetal resin. However, there is a problem that the storability is deteriorated due to the crystallization of the dye and the like because the reaction amount is too large (JP-A-2-141289).

Further, in order to achieve a higher recording density, a method is generally known in which the compounding ratio (P / B) of the dye (P) to the binder resin (B) is made as high as possible. However, for example, when the P / B ratio is set to 1.5 or more, the compounding amount and the reaction amount of the silicon compound contained in the binder resin are too large as described above, and thus the compatibility with the silicon compound is basically poor. The dye tends to bleed, which eventually reduces the storage stability.

The inventors of the present invention have conducted various studies to solve the above problems, and as a result, by incorporating a specific amount of a specific silicone-based resin into a polyvinyl acetal-based resin as a binder for a thermal transfer layer, a release agent-free receiving agent was obtained. It has been found that a sublimation thermal transfer ink ribbon having excellent releasability at the time of thermal transfer from a recording paper having a layer and storability of the ink ribbon can be obtained, and the present invention has been completed.

[0011]

[Means for Solving the Problems] That is, the present invention relates to a polyvinyl acetal resin and a three-dimensional network structure having a siloxane bond as a main skeleton, which is solid at room temperature and soluble in an organic solvent. A binder for a thermal transfer layer comprising a resin.

The present invention also provides a recording paper having a receptive layer containing no release agent, which has a thermal transfer layer containing a sublimable dye and the above-mentioned binder for thermal transfer layer on a substrate. Is a thermal transfer ink ribbon used in combination.

Furthermore, the present invention is a thermal transfer method characterized by carrying out recording by bringing the above-mentioned thermal transfer ink ribbon into contact with a recording paper having a receiving layer containing no release agent.

The present invention will be described in detail below. First, the binder for the thermal transfer layer of the present invention will be described. The binder resin used in the binder for the thermal transfer layer of the present invention is a polyvinyl acetal resin, which has a three-dimensional network structure having a siloxane bond as a main skeleton as exemplified in the following formula 1, and is solid at room temperature. The composition contains a silicone resin soluble in an organic solvent.

[0015]

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The content of the silicon-based resin contained in the binder for the thermal transfer layer of the present invention is 0.5 to 4.5 parts by weight based on 100 parts by weight of the polyvinyl acetal resin.
Preferably 0.5 to 3.0 parts by weight is desirable. If the content of the silicon-based resin exceeds 4.5 parts by weight, a dye that is basically incompatible with the silicon-based resin is likely to bleed and storage stability is deteriorated. On the other hand, if the content of the silicon-based resin is less than 0.5 parts by weight, the releasability from the recording paper which does not contain a releasing agent in the receiving layer at the time of thermal transfer is insufficient.

Examples of the organic solvent which dissolves the silicone resin include alcohols such as ethanol and isopropanol, esters such as methyl acetate and ethyl acetate, aromatics such as toluene and xylene, and methyl ethyl ketone.
Examples thereof include ketones such as methyl isobutyl ketone, aliphatic hydrocarbons such as N-hexane, and ethers such as petroleum ether.

Further, in place of the above-mentioned silicone resin as the binder for the thermal transfer layer, a conventionally known silicone oil having a two-dimensional structure having a siloxane bond as a main skeleton as shown in the following formula 2 is used as a releasing agent. In this case, since the silicone oil has a linear molecular structure and is a liquid at room temperature, the silicone oil of the release agent remains in contact with the thermal transfer layer with the sublimable dye over time during storage of the ink ribbon. Transfer to the back coat surface, and initial release properties and recording density cannot be maintained.

[0019]

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On the other hand, in the case of a silicon-based resin which has a three-dimensional network structure and is insoluble in an organic solvent even if it is a solid at room temperature, it is dissolved and dispersed in an organic solvent together with a sublimable dye to form a dye composition. When the silicon-based resin settles down with time during the production, and the thermal transfer layer is formed as it is, there is a problem that the releasability from the recording paper which does not contain a releasing agent in the receiving layer during the thermal transfer is deteriorated. is there.

The silicon resin used in the present invention is SiO 2.
₂ , RSiO _3/2 , R ₂ SiO, R ₃ SiO _1/2 (R represents a hydrocarbon group having 1 to 6 carbon atoms or a phenyl group) and a three-dimensional structure composed of a combination of structural units. It is a polymer. The ratio is based on the average formula R _n SiO
It is desirable that it is selected so as to satisfy _{(4-n) / 2} (n represents a value of 1.0 to 1.8) and has an average molecular weight of about 1500 to 10000.

The silicon resin used in the present invention may be either a commercially available resin or a resin produced by a known method. Specific examples of commercially available products include X-40-2134, X-40-2135 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.), Trefil R-91.
0 (trade name, Toray Dow Corning Silicone Co., Ltd.)
And the like).

An example of the method for producing the silicone resin used in the present invention is given by the general formulas R ₂ SiX ₂ , RSiX ₃ ,
A compound represented by SiX ₄ (X is a hydrolyzable group such as a chlorine atom, a bromine atom, a fluorine atom or an alkoxy group, and R is a hydrocarbon group having 1 to 6 carbon atoms or a phenyl group),
Add to a suitable solvent such as toluene, benzene, xylene, etc. depending on the desired resin composition, then add this solvent to a sufficient amount of water to obtain the desired hydrolysis and cocondensation in a suitable acidic solvent. . Hydrolyzed siloxane has a terminal substituted with a hydroxyl group, and the condensation of the hydroxyl group causes polymerization to give a three-dimensional structure. For example, in the case of a methylsilicone resin, SiO ₂ or CH is generally used.
₃ SiO _3/2 , (CH ₃ ) ₂ SiO, (CH ₃ ) ₃ Si
It becomes a copolymer composed of structural units represented by O _1/2 . The aqueous phase is removed from the thus obtained two-phase system, the residual resinous substance is neutralized with a sufficient amount of sodium bicarbonate or another alkaline substance, and the solvent is removed to obtain the desired silicone resin. To be

The silicone resin used in the present invention can be adjusted to have a desired hydroxyl group content depending on the reaction conditions. Therefore, a crosslinking agent such as isocyanate is used to add it to the vinyl alcohol moiety of the polyvinyl acetal resin. It may be used after reacting, or a silicone resin modified with fluorine, a carboxyl group, an amino group, an epoxy group, a long chain alkyl group, a higher alcohol group, a fatty acid, a polyether or the like may be used.

Examples of the polyvinyl acetal-based resin which is the main component of the binder for the thermal transfer layer of the present invention include single acetal resins such as polyvinyl form acetal, polyvinyl acetoacetal and polyvinyl butyl acetal resins, and acetoacetal / butyl acetal mixed polyvinyl. Examples thereof include acetal, formacetal / acetoacetal / butylacetal-mixed polyvinyl acetal and the like, or a combination thereof. These may be used alone or as a mixture, but the compatibility with sublimable dyes and recording A polyvinyl acetoacetal resin is preferable in terms of concentration.

The degree of acetalization of the polyvinyl acetal resin is not particularly limited, but in general, it is preferably 60% by weight or more from the viewpoint of compatibility with sublimable dyes and image recording density, and preferably 75% by weight or more,
More preferably, those highly acetalized with 85% by weight or more are used.

The portion other than the acetalized portion of the polyvinyl acetal resin is a portion of a vinyl alcohol unit derived from a raw material polyvinyl alcohol resin (hereinafter abbreviated as PVA), a portion of a fatty acid vinyl ester unit, and the like, Furthermore, when the raw material PVA is a saponified product of a copolymer of a fatty acid vinyl ester and another monomer copolymerizable with a fatty acid vinyl ester, or PVA
In the case of the post-modification product, in addition to the above-mentioned two kinds of units, the other monomer copolymerized, or the part of the unit based on the post-modification is also included.

The average degree of polymerization of the polyvinyl acetal resin used in the present invention is not particularly limited, but is usually 200 to 4
000, particularly preferably in the range of 300 to 3000. If the average degree of polymerization is less than 200, the heat transfer layer is retained in its shape and the force for fixing the heat transfer layer to the substrate of the ink ribbon is weak.
If it exceeds 00, the solubility in organic solvents decreases,
Since the viscosity of the reaction liquid during the acetalization reaction becomes high, it is necessary to take measures such as lowering the concentration of the reaction system, which may reduce the productivity of the resin.

As a method for acetalizing PVA,
After dispersing PVA in an organic solvent such as alcohol,
Addition of an aldehyde to an acetalization reaction by adding an aldehyde to an acid catalyst such as hydrochloric acid or sulfuric acid to obtain a polyvinyl acetal solution, and then adding water to precipitate the resin, or a solvent method of precipitating the resin, or adding an aldehyde and an acid catalyst to an aqueous PVA solution. Then, an acetalization reaction is carried out, and an aqueous medium method in which the resin is precipitated in an aqueous reaction system according to the progress of the reaction, and further an aldehyde and an acid catalyst are added to the PVA aqueous solution to carry out the acetalization reaction, It is possible to use a uniform method in which an organic solvent is added according to the progress to keep the inside of the reaction system uniform.

Next, the sublimation heat transfer ink ribbon of the present invention is prepared by forming a heat transfer layer on a substrate using the above-mentioned binder for the heat transfer layer containing the polyvinyl acetal resin and the silicon resin and the sublimable dye. It will be.

The thermal transfer layer containing the above binder is
It can be formed by coating and drying a dye composition in which a sublimable dye, a binder and various additives are dissolved and dispersed in an organic solvent, and dried.

As the sublimable dye, a wide range is used without particular limitation, and examples thereof include anthraquinone dyes, azo dyes and methine dyes. In addition, various additives that are used as needed include dispersants such as various surfactants, drying accelerators such as cellulose derivatives, and various defoaming agents.

As the base material, a wide range is used without particular limitation. For example, a film of polyester, polyamide, polyimide, triacetate or the like having a thickness of about 3 to 20 μm is preferably used.

A sublimation heat transfer ink ribbon can be obtained by applying the above-mentioned dye composition onto a substrate by using a known method and apparatus such as printing and coating and drying to form a heat transfer layer. .

The resulting thermal transfer layer has a thickness of about 0.5-5 μm.
The degree is preferred. Further, the proportion of the binder contained in the thermal transfer layer is about 3 to 80% by weight, preferably about 20 to 50% by weight, based on the thermal transfer layer, and about 3 to 200% by weight, preferably about 3 to 200% by weight, based on the dye. Is 50 to 150% by weight
Is.

Since the thermal transfer ink ribbon of the present invention is excellent in releasability, it can be used in combination with a recording paper having a receptive layer containing no release agent. The receiving layer and the recording paper may be ordinary ones,
For example, paper coated with a resin having good dyeability of a sublimable dye such as polyester or vinyl chloride resin is preferably used.

The method of thermal transfer recording using the thermal transfer ink ribbon of the present invention is carried out by a conventional recording method.
A thermal head or laser whose temperature and the like are controlled based on image signals in a state where the thermal transfer layer surface of the thermal transfer ink ribbon and the receiving layer surface of the recording paper having a receiving layer containing no release agent are brought into contact with each other. By applying thermal energy to the ink ribbon to sublimate the dye in the thermal transfer layer, the dye sublimated from the thermal transfer layer is transferred to the receiving layer of the recording paper.

[0038]

EXAMPLES The present invention will be described below based on examples.
Unless otherwise specified, "parts" and "%" represent parts by weight and% by weight, respectively.

Example 1 (Production of Silicon Resin) 100 parts of pure water, 0.3 part of dibutyltin laurate, 8.7 parts of 35% concentrated hydrochloric acid aqueous solution were placed in a reactor equipped with a stirrer, a reflux condenser and a thermometer. Charge
While maintaining the reaction temperature at 20 ° C., from the upper part of the reactor, 230 parts of xylene, 40 parts of SiCl ₄ and (CH ₃ ) ₃ Si
A solution obtained by uniformly mixing 60 parts of Cl with 3 parts of the above aqueous solution was added.
After dropping over a period of time, a polymerization reaction was further performed for 3 hours to obtain a resin solution. Next, the stirring was stopped, the aqueous phase was separated and removed, and sodium bicarbonate was added to the remaining resin solution for neutralization.

Further, the resin solution was heated again to 140 ° C. to remove xylene out of the reactor, and as a result, an average molecular weight of about 5000, SiO ₂ : (CH ₃ ) ₃ SiO _1/2 =
A silicon-based resin powder represented by an average formula (CH ₃ ) _1.8 SiO _1.1 of 1.5: 1 was obtained.

(Production of Ink Ribbon) Methyl ethyl ketone 5 was placed in a reactor equipped with a stirrer, a reflux condenser and a thermometer.
50 parts of toluene and 550 parts of toluene were charged, 100 parts of polyvinyl acetoacetal resin (polymerization degree 2430, acetoacetal part 90.0%, vinyl alcohol part 8.5%, vinyl acetate part 1.5%), and the above-mentioned average formula. (CH
₃ ) Silicon-based resin powder represented by _1.8 SiO _1.1 2.
0 part was added with stirring and dissolved at a temperature of 50 ° C. for 4 hours.

The obtained resin solution was used as a binder resin in the following dye composition to obtain a dye composition having the following composition.

Compounding Composition of Dye Composition Binder Resin Solution 35 parts (resin solid content = 8.5%) Sublimable dye (SUMIPLA Red FB) 5 parts Methyl ethyl ketone 46 parts Toluene 14 parts

This dye composition was applied onto one side of a 6 μm thick polyester film by wire bar coating so that the film thickness after drying was 1 μm, and dried to produce an ink ribbon.

(Preparation of Recording Paper) In order to evaluate the performance of the ink ribbon obtained as described above by performing thermal transfer on the recording paper, a recording paper having a dye receiving layer on the surface was obtained as follows. It was That is, the composition for forming a dye-receptive layer having the following composition was coated on one side of a base sheet polypropylene synthetic paper (Yupo FPG150 manufactured by Oji Yuka Synthetic Paper Co., Ltd.) so that the coating layer thickness after drying was 5 μm. A receptive layer was formed by applying and drying by bar coating to prepare a recording paper.

Compounding composition of the composition for forming the dye receiving layer Saturated polyester resin 10 parts (Vylon # 200, manufactured by Toyobo Co., Ltd.) Toluene 70 parts Methyl ethyl ketone 10 parts Cyclohexanone 20 parts

(Evaluation of Ink Ribbon) (1) Releasing Property Using the ink ribbon and recording paper obtained as described above,
1 on a video printer CVP-G7 (manufactured by Sony Corporation)
It was confirmed whether or not the printing operation could be completed without fusing the ink ribbon and the recording paper by carrying out a 2-step steer step printing.

The evaluation of the code in the table represents the following. Good: No trace of fusion is observed on the surface of the recording paper after printing. Δ: A slight fusion trace is recognized on the surface of the recording paper after printing. X: Many fusion marks are recognized on the surface of the recording paper after printing.

(2) Storability After the ink ribbon obtained as described above was subjected to roll aging (temperature 50 ° C., humidity 80%, 120 Hr), the same operation as in (1) was carried out to measure the recording density and the ink. The state of the ribbon surface was observed. The evaluation results are shown in Tables 1 to 3.

Examples 2-5 and Comparative Examples 1, 2 As shown in Tables 1 to 3, Example 1 was repeated except that the type of the silicone resin, the blending amount with respect to the polyvinyl acetal resin and the type of the polyvinyl acetal resin were changed. A binder resin solution for a thermal transfer layer was prepared in the same manner as above, an ink ribbon was produced using these resin solutions, and the ink ribbon was evaluated. The evaluation results are shown in Tables 1 to 3.

Example 6 (Production of Ink Ribbon) A reactor equipped with a stirrer, a reflux condenser and a thermometer was charged with 550 parts of methyl ethyl ketone and 550 parts of toluene, and a polyvinyl acetoacetal resin (polymerization degree 2430, acetoacetal part 90) was prepared. .0
%, Vinyl alcohol portion 8.5%, vinyl acetate portion 1.5%) 100 parts, and silicone resin powder (Trefil R-910, manufactured by Toray Dow Corning Silicone Co., Ltd.) 2.0 parts. While adding, temperature 50
It dissolved at 4 ° C. for 4 hours.

An ink ribbon was produced and evaluated in the same manner as in Example 1 except that the obtained resin solution was used as the binder resin. The evaluation results are shown in Tables 1 to 3.

Example 7 (Production of Ink Ribbon) 550 parts of methyl ethyl ketone and 550 parts of toluene were charged into a reactor equipped with a stirrer, a reflux condenser and a thermometer, and a polyvinyl acetoacetal resin (polymerization degree 2470, acetoacetal part 36) was added. .2
%, Butyl acetal portion 36.2%, vinyl alcohol portion 15.6%, vinyl acetate portion 10.5%, acrylic acid portion 1.5%) 100 parts, and silicon resin powder (X-40-2134, Shin-Etsu Chemical) Industrial Co., Ltd.) 2.
0 part was added with stirring and dissolved at a temperature of 50 ° C. for 4 hours.

An ink ribbon was manufactured and evaluated in the same manner as in Example 1 except that the obtained resin solution was used as the binder resin. The evaluation results are shown in Tables 1 to 3.

Comparative Example 3 Dimethyl silicone oil KF was used instead of silicone resin powder.
-96-3000 (viscosity 3000 mm ² / S (25
C.), a specific gravity of 0.97, manufactured by Shin-Etsu Chemical Co., Ltd.), a binder resin solution for a thermal transfer layer was prepared in the same manner as in Example 1, and an ink ribbon was manufactured using these resin solutions. Then, the ink ribbon was evaluated. The evaluation results are shown in Tables 1 to 3.

Comparative Example 4 Instead of the silicon resin powder, a highly three-dimensionally crosslinked organic solvent-insoluble silicone resin: Trefil R-930 (average particle diameter 1 μm, true sphere, true specific gravity 1.3, Toray Dow Corning A binder resin solution for a thermal transfer layer was prepared in the same manner as in Example 1 except that Silicone Co., Ltd.) was used, and an ink ribbon was manufactured using these resin solutions.
The ink ribbon was evaluated. The evaluation results are shown in Tables 1 to 3.

[0057]

[Table 1]

(Note) The vinyl alcohol portion, vinyl acetate portion and acetal portion of the polyvinyl acetal resin were measured according to JIS K-6728.

[0059]

[Table 2]

[0060]

[Table 3]

(Note) 1) Trade name: Trefil R-910, R-930 (manufactured by Toray Dow Corning Silicone Co., Ltd.) X-40-2134, KF-96-3000 (Shin-Etsu Chemical Co., Ltd.) 2) Methyl ethyl ketone / toluene = 1/1 3) Amount to be mixed with 100 parts of polyvinyl acetal resin 4) Immediately after preparation of the dye composition (initial stage) and after standing for 7 days at room temperature (after lapse of time), an ink ribbon was formed. Manufacturing and evaluation 5) Evaluation of initial product

As is clear from the results shown in Table 3 above, the ink ribbons of the respective examples obtained by using the binder for thermal transfer layer of the present invention have excellent releasability as compared with the comparative examples, and It is recognized that the shelf life is excellent.

In each of the examples, the dispersibility of the dye was good when the dye composition was obtained, and the thermal transfer layer formed on the substrate was excellent in both the shape retention property and the fixing property.

[0064]

As described above, the sublimation thermal transfer ink ribbon using the binder for the thermal transfer layer, which is the polyvinyl acetal resin of the present invention blended with the specific silicone resin, contains the release agent in the receiving layer. Not only it has excellent releasability when printing with recording paper, but the dye in the thermal transfer layer does not leach to the surface during storage and does not crystallize, and it has excellent storability and is heated by a thermal head etc. It is possible to realize image recording with excellent recording density without inhibiting the sublimation and divergence of the dye at the time of exposure.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshio Fujiwara, 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation (72) Inventor, Satoru Shinohara 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation

Claims (5)

[Claims] 1. A polyvinyl acetal resin and a three-dimensional network structure having a siloxane bond as a main skeleton, which is solid at room temperature and contains a silicon resin soluble in an organic solvent. Binder for thermal transfer layer. 2. The binder for a thermal transfer layer according to claim 1, wherein the content of the silicon-based resin is 0.5 to 4.5 parts by weight with respect to 100 parts by weight of the polyvinyl acetal-based resin. 3. A thermal transfer ink ribbon comprising a thermal transfer layer containing a sublimable dye and the thermal transfer layer binder according to claim 1 on a substrate. 4. The thermal transfer ink ribbon according to claim 3, which is used in combination with a recording paper having a receiving layer containing no release agent. 5. A thermal transfer ink ribbon according to claim 3,
A thermal transfer method characterized by carrying out recording by contacting with a recording paper having a receiving layer containing no release agent.