JP5607521B2 - Process for producing resin composition for thermal transfer image-receiving sheet - Google Patents

Description

  The present invention relates to a method for producing a resin composition for a thermal transfer image-receiving sheet, a resin composition obtained by the production method, and a thermal transfer image-receiving sheet having a dye-receiving layer containing the resin composition.

  There has been proposed a method of forming a color image on a thermal transfer image-receiving sheet that can be dyed with a sublimation dye, using a sublimation dye as a recording agent and a thermal transfer sheet carried on a substrate. In this method, a thermal head of a printer is used as a heating means, and a dye is transferred to an image receiving sheet by heating to obtain a color image. The image formed in this way is very clear because it uses a dye, and is excellent in transparency. Therefore, it is excellent in reproducibility of intermediate colors and gradation, and a high-quality image can be expected. Therefore, a thermal transfer image receiving sheet for exhibiting these performances has been developed.

In Patent Document 1, for the purpose of improving density and image defects, the support has at least one receiving layer containing a polymer latex and at least one heat insulating layer containing a hollow polymer on the support. A thermal transfer image-receiving sheet is disclosed in which the polymer latex contained in the layer is composed of two or more dyeable polymers having different glass transition temperatures.
In Patent Document 2, for the purpose of improving film physical properties and transfer density, an image receiving layer for forming an image by receiving a dye transferred from a thermal transfer dye donating material when heated on a support is provided. In the thermal transfer image-receiving material provided at least in one layer, the image-receiving layer is made of a composition in which a dye-accepting substance is dispersed in a water-soluble binder, and the uppermost layer of the image-receiving surface constituting layer of the image-receiving material has a silicone compound and [organic / [Inorganic] A thermal transfer image-receiving material containing a co-dispersion of a plasticizer having a value of 1.5 or more is disclosed.
Further, Patent Document 3 includes an alcohol component containing 50 mol% or more of an alkylene oxide adduct of bisphenol A and an alicyclic carboxylic acid of more than 50 mol% for the purpose of improving dyeability and releasability. Disclosed is a composition for a receiving layer of a thermal transfer image-receiving sheet, which comprises a resin containing a polyester obtained by condensation polymerization of a carboxylic acid component and a polyether-modified silicone having an oxyethylene group and / or an oxypropylene group. Yes.

JP 2007-229987 A Japanese Patent Laid-Open No. 3-101993 JP 2009-262337 A

Printing is performed by coloring the ink sheet to the thermal transfer image-receiving sheet by heating from the thermal head, so that high dye dyeability is required to express the target color. Is done. For this reason, there is a problem that fusion occurs between the ink sheet and the thermal transfer image receiving sheet during coloring. In addition, there has been a problem that the printed material is faded due to a change with time. Therefore, there is a demand for a thermal transfer image-receiving sheet excellent in dyeing property of high dyes, releasability that suppresses fusion with an ink sheet, and light resistance that suppresses fading of printed matter. From the viewpoint of achieving both the dyeing property, the release property and the light resistance, there is still room for improvement in the thermal transfer image receiving sheets described in Patent Documents 1 to 3.
The present invention relates to a method for producing a resin composition for a thermal transfer image-receiving sheet that can provide a thermal transfer image-receiving sheet excellent in dyeing property, releasability and light resistance, a resin composition obtained by the production method, and the resin composition It is an object of the present invention to provide a thermal transfer image-receiving sheet having a dye-receiving layer containing a product.

The present inventors have considered that the factors affecting the dyeing property, the release property and the light resistance are in the state of the dye-receiving layer when heated by a thermal head. As a result, a resin composition containing a resin having a specific polyester resin portion, and a resin composition containing a resin and a plasticizer and having a glass transition temperature lower than that of the resin composition within a certain range. It has been found that by using it in the dye-receiving layer, the dyeing property, releasability and light resistance are improved.
That is, the present invention provides the following [1] to [3].
[1] Contains a resin (A0) containing a polyester part obtained by condensation polymerization of an alcohol component containing 50 mol% or more of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and a carboxylic acid component An aqueous dispersion of the resin composition (A) and a resin composition (B) in which the plasticizer (C) is encapsulated in the resin (B0) and the glass transition temperature is 10 to 80 ° C. lower than that of the resin composition (A) And an aqueous dispersion of the resin composition for thermal transfer image-receiving sheet, and a method for producing an aqueous dispersion of the resin composition for thermal transfer image-receiving sheet.
[2] A resin composition for a thermal transfer image-receiving sheet obtained by the production method according to [1] above.
[3] A thermal transfer image-receiving sheet having a dye-receiving layer containing the resin composition for a thermal transfer image-receiving sheet described in [2].

  According to the present invention, a method for producing a resin composition for a thermal transfer image-receiving sheet capable of providing a thermal transfer image-receiving sheet excellent in dyeing property, releasability and light resistance, a resin composition obtained by the production method, and the A thermal transfer image-receiving sheet having a dye-receiving layer containing a resin composition can be provided.

[Method for producing resin composition for thermal transfer image-receiving sheet]
The method for producing a resin composition for a thermal transfer image-receiving sheet according to the present invention comprises a condensation polymerization of an alcohol component containing 50 mol% or more of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and a carboxylic acid component. Aqueous dispersion of a resin composition (A) (hereinafter also simply referred to as “resin composition (A)”) containing a resin (A0) (hereinafter also simply referred to as “resin (A0)”) containing the resulting polyester portion The resin composition (B) (hereinafter simply referred to as “resin composition (B)), the plasticizer (C) is encapsulated in the liquid and the resin (B0), and the glass transition temperature is 10 to 80 ° C. lower than that of the resin composition (A). B) ”) is mixed with the aqueous dispersion to obtain an aqueous dispersion of the thermal transfer image-receiving sheet resin composition. In the present specification, when the resin composition (A) contains the resin (A0) in an amount of 100 mol% in the resin composition (A), that is, when the resin composition (A) is composed only of the resin (A0), This is expressed as “resin composition (A)”.

The reason why the thermal transfer image-receiving sheet having the resin composition for the thermal transfer image-receiving sheet obtained by the production method of the present invention in the dye-receiving layer is excellent in dyeing property, releasability and light resistance is not clear, but is considered as follows. It is done.
First, since the resin composition (B) in the present invention has a low glass transition temperature and contains a plasticizer, the dye easily penetrates into the resin composition (B) having a high molecular mobility, whereby the thermal transfer image-receiving sheet. It is considered that the dyeing property and light resistance of the ink are improved. Furthermore, an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane, which is an alcohol component of the resin (A0) in the resin composition (A) in the resin composition for a thermal transfer image receiving sheet, is contained in the molecule. Since it has a structure similar to two aromatic rings, that is, a dye, it has high affinity with the dye, the dye penetrates into the receiving layer, improves the dyeing property and light resistance of the thermal transfer image-receiving sheet, and has a rigid structure Therefore, it is considered that the resin becomes hard and contributes to the improvement of the releasability of the thermal transfer image receiving sheet.
Further, it is considered that the plastic composition is contained in the resin composition (B), whereby the surface of the image receiving sheet is smoothed and the releasability of the thermal transfer image receiving sheet is greatly improved.

<Resin composition (A)>
The resin composition (A) used in the method for producing a resin composition for a thermal transfer image-receiving sheet of the present invention comprises an alcohol component containing 50 mol% or more of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane. A resin (A0) containing a polyester resin portion (hereinafter also referred to as “polyester resin segment (A1)” or simply “segment (A1)”) obtained by condensation polymerization with a carboxylic acid component is contained.
Resin composition (A) may consist only of resin (A0), and may contain a plasticizer. When a plasticizer is included, the plasticizer is preferably encapsulated in the resin (A0).
Moreover, the below-mentioned plasticizer (C) can be used as a plasticizer.

≪Resin (A0) ≫
The resin (A0) may be a polyester resin composed only of the polyester resin segment (A1), but from the viewpoint of releasability of the thermal transfer image-receiving sheet, the polyester resin segment (A1) and the addition polymerization resin segment (A2). ) (Hereinafter also simply referred to as “segment (A2)”), preferably a graft polymer having the segment (A1) as the main chain and the segment (A2) as the side chain. .
When the resin (A0) is a graft polymer having the segment (A1) as the main chain and the segment (A2) as the side chain, the weight ratio of the segment (A1) and the segment (A2) constituting the graft polymer [segment (A1) / segment (A2)] is preferably 55/45 to 95/5, more preferably 65/35 to 95/5, and more preferably 75/25 from the viewpoint of improving the dyeing property of the thermal transfer image-receiving sheet. To 95/5, more preferably 85/15 to 95/5. With more segments (A1) than segments (A2), the dyeing property derived from the molecular structure of segments (A1) can be sufficiently exhibited while forming a fine phase separation structure. Conceivable.

  The glass transition temperature of the resin (A0) is preferably 50 ° C. or higher, more preferably 50 to 100 ° C., still more preferably 50 to 80 ° C., and still more preferably 60 to 60 ° C. from the viewpoint of releasability of the thermal transfer image receiving sheet. 80 ° C. From the same viewpoint, the acid value of the resin (A0) is preferably 1 to 35 mgKOH / g, more preferably 5 to 35 mgKOH / g, and still more preferably 10 to 35 mgKOH / g.

(Polyester resin segment (A1))
The polyester resin segment (A1) constituting the resin (A0) contained in the resin composition (A) is an alcohol component containing 50 mol% or more of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane. And a carboxylic acid component.

  Specifically, the alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane is preferably a compound represented by the following general formula (I).

In the general formula (I), R ¹ O and R ² O are both oxyalkylene groups, preferably each independently an oxyalkylene group having 1 to 4 carbon atoms, and more preferably an oxyethylene group or an oxyethylene group. Propylene group.
x and y correspond to the added mole number of alkylene oxide, and are positive numbers. Furthermore, from the viewpoint of reactivity with the carboxylic acid component, the average value of the sum of x and y is preferably 2 to 7, more preferably 2 to 5, and still more preferably 2 to 3.
Further, x R ¹ O or y R ² O may be the same or different, but the dyeing property of the thermal transfer image-receiving sheet and the intermediate layer and the dye-receiving layer in the thermal transfer image-receiving sheet From the viewpoint of adhesion, it is preferably the same and more preferably an oxypropylene group. The alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane may be used alone or in combination of two or more.

  From the viewpoint of dyeability and releasability of the thermal transfer image-receiving sheet, the content of the oxypropylene group is preferably 50 to 100 mol%, more preferably 60 to 100 mol%, still more preferably in the oxyalkylene group. It is 70-100 mol%, More preferably, it is substantially 100 mol%. The other oxyalkylene group is preferably an oxyethylene group or an oxytrimethylene group from the viewpoint of dyeing property of the dye on the thermal transfer image-receiving sheet, and more preferably an oxyethylene group from the viewpoint of dyeing property of the thermal transfer image-receiving sheet.

  The alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane is contained in the alcohol component in an amount of 50 mol% or more, preferably 70 mol%, from the viewpoint of releasability and dyeing property of the thermal transfer image-receiving sheet. More preferably, it is 80 mol% or more, and still more preferably 100 mol%. In the present invention, the alkylene oxide adduct means the whole structure in which an oxyalkylene group is added to 2,2-bis (4-hydroxyphenyl) propane.

The alcohol component which is a raw material monomer of the segment (A1) can contain other alcohol components in addition to the alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane.
Specifically, examples of the alcohol component of the raw material monomer derived from the structural unit of the segment (A1) (hereinafter also simply referred to as “raw material monomer of the segment (A1)”) include ethylene glycol, propylene glycol (1,2 -Propanediol), glycerin, pentaerythritol, trimethylolpropane, hydrogenated bisphenol A, sorbitol, or their alkylene (2 to 4 carbon) oxide adduct (average number of added moles 1 to 16). You may use the said alcohol component individually or in combination of 2 or more types.

  When the resin (A0) is a graft polymer having the segment (A1) as the main chain and the segment (A2) as the side chain, an alcohol having a non-aromatic carbon-carbon unsaturated bond, for example, unsaturated Alcohol components including aliphatic alcohols can be used. The portion of the carbon-carbon unsaturated bond in the unsaturated aliphatic alcohol can be a bonding portion with the segment (A2) in the graft polymer, in which case the unsaturated bond becomes a saturated bond. Examples of the alcohol having a non-aromatic carbon-carbon unsaturated bond include unsaturated aliphatic alcohols such as allyl alcohol.

Since the segment (A1) is a polyester resin, a carboxylic acid component is used as a raw material monomer in addition to the alcohol component.
Examples of the carboxylic acid component that is a raw material monomer of the segment (A1) include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid; succinic acid having adipic acid, succinic acid, an alkyl group, and / or an alkenyl group. Aliphatic dicarboxylic acids; cycloaliphatic dicarboxylic acids, alicyclic dicarboxylic acids such as decalin dicarboxylic acids; trivalent or higher polyvalent carboxylic acids such as trimellitic acid and pyromellitic acid, and anhydrides of these acids and their alkyls (C1-C3) ester etc. are mentioned. From the viewpoint of dyeability of the thermal transfer image-receiving sheet, aromatic dicarboxylic acids and alicyclic dicarboxylic acids are preferable, and cyclohexanedicarboxylic acid and isophthalic acid are more preferable. Among these, aromatic dicarboxylic acids are preferable, and isophthalic acid is more preferable. The said carboxylic acid component may be individual or 2 or more types may be contained.
When the resin (A0) is a graft polymer having the segment (A1) as the main chain and the segment (A2) as the side chain, a carboxylic acid having a non-aromatic carbon-carbon unsaturated bond, for example, It is preferable to contain a saturated aliphatic carboxylic acid and / or an unsaturated alicyclic carboxylic acid. The carbon-carbon unsaturated bond portion is preferably a bond portion with the segment (A2) in the resin for thermal transfer sheets of the present invention. In this case, the unsaturated bond is a saturated bond.

  Examples of carboxylic acids having non-aromatic carbon-carbon unsaturated bonds (unsaturated aliphatic carboxylic acids and unsaturated alicyclic carboxylic acids) include unsaturated fats such as fumaric acid, maleic acid, acrylic acid, and methacrylic acid. Group carboxylic acids; unsaturated alicyclic carboxylic acids such as tetrahydrophthalic acid. From the viewpoint of reactivity, fumaric acid, maleic acid and tetrahydrophthalic acid are preferable, and fumaric acid is more preferable.

  In the carboxylic acid component, the content of the carboxylic acid having a non-aromatic carbon-carbon unsaturated bond is preferably 5 to 30 mol%, more preferably 7 to 25 mol%, still more preferably 8 to 15 mol%. It is.

  In the case where the resin (A0) is a graft polymer having the segment (A1) as the main chain and the segment (A2) as the side chain, among the raw material monomers from which the structural unit of the segment (A1) is derived, non-aromatic As a raw material monomer having a functional carbon-carbon unsaturated bond, one or more selected from unsaturated aliphatic carboxylic acids, unsaturated alicyclic carboxylic acids, and unsaturated aliphatic alcohols may be included. From the above, it is preferable that an unsaturated aliphatic carboxylic acid and / or an unsaturated alicyclic carboxylic acid is contained, and it is more preferable that substantially only an unsaturated aliphatic carboxylic acid and / or an unsaturated alicyclic carboxylic acid is contained. .

  The segment (A1) has a molar ratio (hydroxyl group / carboxy group) between the hydroxyl group of the alcohol component and the carboxy group of the carboxylic acid component from the viewpoint of dyeability and releasability of the thermal transfer image-receiving sheet. 100/120, more preferably 100/100 to 100/110, still more preferably 100/102 to 100/107, still more preferably 100/102 to 100/104.

From the viewpoint of releasability and storage stability of the thermal transfer image-receiving sheet, the acid value of the segment (A1) is preferably 5 to 40 mgKOH / g, more preferably 5 to 35 mgKOH / g, still more preferably 5 to 30 mgKOH / g. Yes, more preferably 10 to 20 mg KOH / g.
Moreover, from the viewpoint of film forming properties when used in the dye-receiving layer, the number average molecular weight of the segment (A1) is preferably 1,000 to 10,000, more preferably 2,000 to 8,000.

(Side chain segment (A2) made of addition polymerization resin)
When the resin (A0) contained in the resin composition (A) is a graft polymer, the segment (A2) constituting the graft polymer is an addition polymerizable monomer (a2) (hereinafter also referred to as “monomer (a2)”). ) Is a segment composed of an addition polymerization resin composed of structural units derived from. The segment (A2) is a side chain in the graft polymer when the resin (A0) is a graft polymer.
Examples of the addition polymerizable monomer (a2) used in the present invention include styrene, methylstyrene, α-methylstyrene, β-methylstyrene, t-butylstyrene, chlorostyrene, chloromethylstyrene, methoxystyrene, styrenesulfonic acid or the like. Styrenes such as salts; (meth) acrylic acid esters such as alkyl (meth) acrylate (1 to 18 carbon atoms), benzyl (meth) acrylate, dimethylaminoethyl (meth) acrylate; ethylene, propylene, butadiene, etc. Olefins such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as vinyl methyl ether; vinylidene halides such as vinylidene chloride; N-vinyl compounds such as N-vinyl pyrrolidone; Is mentioned.
Among these, styrenes and (meth) acrylic acid esters are preferable, addition polymerizable monomers having an aromatic group are more preferable, and styrene, methylstyrene, benzyl methacrylate, and benzyl acrylate are still more preferable. Among these, styrene is preferable from the viewpoint of the raw material price of the monomer, the releasability of the thermal transfer image-receiving sheet, and the storage stability.
The content of the structural unit derived from the addition-polymerizable monomer having an aromatic group is preferably 55% by weight or more in the segment (A2) from the viewpoint of releasability of the thermal transfer image-receiving sheet and storage stability of the resin. Preferably it is 70 weight% or more, More preferably, it is 85 weight% or more, More preferably, it is 90 weight% or more, More preferably, it is substantially 100 weight%.

  The weight ratio of the total amount of unsaturated aliphatic carboxylic acid, unsaturated alicyclic carboxylic acid and unsaturated aliphatic alcohol among the raw material monomers of segment (A2) and segment (A1) [segment (A2) / segment (A1 The total of the above-mentioned components having unsaturated groups] is preferably from 1/1 to 15/1, more preferably from 1/1 to 10/1, from the viewpoint of dyeability and releasability of the thermal transfer image-receiving sheet. More preferably, it is 2/1 to 5/1.

(Production of graft polymer)
When the resin (A0) contained in the resin composition (A) is a graft polymer, the graft polymer is produced by using 50 mol% of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane. A polyester resin (a1) (hereinafter also referred to as “resin (a1)”) having a non-aromatic carbon-carbon unsaturated bond is prepared by polycondensing the alcohol component and the carboxylic acid component contained above, and the polyester A method of addition polymerization of the addition polymerizable monomer (a2) in the presence of the resin (a1) is preferred.

-Polyester resin (a1)-
Resin (a1) is a non-aromatic carbon obtained by condensation polymerization of an alcohol component containing 50 mol% or more of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and a carboxylic acid component. -A polyester resin having a carbon unsaturated bond, which is preferable for constituting the main chain segment (A1) made of the polyester resin. The “non-aromatic carbon-carbon unsaturated bond” is derived from one or more selected from the above-mentioned unsaturated aliphatic carboxylic acid, unsaturated alicyclic carboxylic acid and unsaturated aliphatic alcohol. It is.

The resin (a1) is obtained using an alcohol component containing 50 mol% or more of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane as a raw material component.
Here, the alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane is the same as in the case of the segment (A1), and the preferred structure and the preferred content are also the same.

As an alcohol component which is a raw material component of the resin (a1), an alcohol component other than this can be used together with an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane. The resin (a1) has a non-aromatic carbon-carbon unsaturated bond, and an alcohol having a non-aromatic carbon-carbon unsaturated bond can be used. Examples of the alcohol having a non-aromatic carbon-carbon unsaturated bond include unsaturated aliphatic alcohols such as allyl alcohol.
Other alcohols are the same as those in the segment (A1). You may use alcohol individually by 1 type or in combination of 2 or more types.

The resin (a1) has a non-aromatic carbon-carbon unsaturated bond, and a carboxylic acid having a non-aromatic carbon-carbon unsaturated bond is used as a carboxylic acid component as a raw material component of the polyester. It can be preferably used.
The carboxylic acid having a non-aromatic carbon-carbon unsaturated bond is the same as in the case of the segment (A1), the preferred structure and the preferred content are the same, and fumaric acid is more preferred.
In the carboxylic acid component, the content of the carboxylic acid having a non-aromatic carbon-carbon unsaturated bond is preferably 5 to 30 mol%, more preferably 7 to 25 mol%, still more preferably 8 to 15 mol%. It is.
The other carboxylic acid is the same as in the case of the segment (A1), and the same structure and preferable content are the same. Cyclohexanedicarboxylic acid and isophthalic acid are preferable, and isophthalic acid is more preferable. You may use these individually by 1 type or in combination of 2 or more types.

The polyester resin (a1) is produced, for example, by subjecting the alcohol component and the carboxylic acid component to condensation polymerization at a temperature of 180 to 250 ° C. in an inert gas atmosphere, if necessary, using an esterification catalyst. be able to.
From the viewpoint of releasability of the thermal transfer image-receiving sheet, the polyester preferably has a sharp molecular weight distribution, and is preferably subjected to condensation polymerization using an esterification catalyst. Examples of the esterification catalyst include metal compounds such as tin catalyst, titanium catalyst, antimony trioxide, zinc acetate, and germanium dioxide. From the viewpoint of the reaction efficiency of the esterification reaction in the synthesis of the polyester, a tin catalyst is preferable. As the tin catalyst, dibutyltin oxide, tin dioctylate, salts thereof and the like are preferably used.
In the present invention, since a carboxylic acid having a non-aromatic carbon-carbon unsaturated bond is used, it is preferable to use a radical polymerization inhibitor. As the radical polymerization inhibitor, 4-t-butylcatechol and the like are preferable.

From the viewpoint of releasability and storage stability of the thermal transfer image-receiving sheet, the softening point of the resin (a1) is preferably 80 to 165 ° C, and the glass transition temperature is preferably 50 to 85 ° C. From the viewpoint of releasability and storage stability of the thermal transfer image-receiving sheet, the acid value of the resin (a1) is preferably 5 to 40 mgKOH / g, more preferably 5 to 35 mgKOH / g, more preferably 5 to 30 mgKOH / g. g, more preferably 10 to 20 mg KOH / g.
The glass transition temperature, softening point, and acid value can all be obtained by appropriately adjusting the type of monomer used, the blending ratio, the temperature of condensation polymerization, and the reaction time.
Moreover, from the viewpoint of film forming properties when used in the dye-receiving layer, the number average molecular weight of the resin (a1) is preferably 1,000 to 10,000, more preferably 2,000 to 8,000.

-Addition polymerizable monomer (a2)-
The addition polymerizable monomer (a2) used in the present invention is as described above, and the addition polymerizable monomer having an aromatic group is preferably 55% by weight or more, more preferably 70% by weight or more, more preferably 85% by weight. %, More preferably 90% by weight or more, and still more preferably substantially 100% by weight. The addition polymerizable monomer having an aromatic group is preferably styrene, benzyl methacrylate or benzyl acrylate. Among these, styrene is preferable from the viewpoint of the raw material price of the monomer, the releasability of the thermal transfer image-receiving sheet, and the storage stability.

<< Production of Resin Composition (A) >>
When resin composition (A) consists only of polyester resin (A0) which consists only of polyester resin segments (A1), resin composition (A) is obtained by the manufacturing method of the above-mentioned polyester resin (a1).
When the resin composition (A) is composed only of the resin (A0) which is a graft polymer containing the segments (A1) and (A2), there is no limitation on the polymerization method of the resin (A0), and the resin (a1) and the monomer Examples thereof include a method in which (a2) is directly mixed and polymerized, and a method in which the resin (a1) and the monomer (a2) are dissolved in an organic solvent for polymerization, and the following steps (1) and (2) are included. Preferably obtained by a method.
Step (1): Step of mixing the polyester resin (a1) with an aqueous medium to obtain an aqueous dispersion of the polyester resin (a1) Step (2): Adding to the aqueous dispersion obtained in Step (1) Step of obtaining an aqueous dispersion containing a graft polymer (A) by adding a polymerizable monomer (a2) to obtain a graft polymer (hereinafter also referred to as “graft polymer (A)”) Resin composition (A) However, when a plasticizer is included, resin (A0) or a resin (A0) precursor (for example, polyester resin (a1)) and a plasticizer are mixed, water is added, and resin (A0) It is preferably obtained by a production method including a step of obtaining an aqueous dispersion in which a plasticizer is encapsulated. Especially, it is preferable that the said process (1) consists of the following process (1A) and process (1B).
Step (1A): Step of obtaining a resin mixture by mixing the polyester resin (a1) and a plasticizer Step (1B): Mixing the resin mixture obtained in Step (1A) with an aqueous medium to obtain a resin mixture Of obtaining an aqueous dispersion of

(Process (1))
In the step (1), a polyester resin (a1) or a resin mixture obtained by mixing a polyester resin (a1) and a plasticizer (hereinafter also referred to as “resin mixture (a1)”) is mixed with an aqueous medium, In this step, an aqueous dispersion of the polyester resin (a1) is obtained.
The aqueous medium is a medium containing water as a main component, that is, a medium having a water content of 50% by weight or more. From the viewpoint of environmental safety, the content of water in the aqueous medium is preferably 80% by weight or more, more preferably 90% by weight or more, and still more preferably substantially 100% by weight. Examples of components other than water include organic solvents that dissolve in water, such as alcohol solvents such as methanol, ethanol, isopropanol, and butanol; ketone solvents such as acetone and methyl ethyl ketone; and ether solvents such as tetrahydrofuran.

As a method for dispersing the polyester resin (a1) or the resin mixture (a1) in the aqueous medium, the polyester resin (a1) or the resin mixture (a1) is dissolved in a ketone solvent, and a neutralizer described later is added to the polyester. A method of ionizing the carboxyl group of the resin (a1) and then adding water to invert the phase to an aqueous system, preferably a method of adding water and then distilling off the ketone solvent to invert to an aqueous system.
More specifically, for example, a reactor equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel and a nitrogen gas introduction pipe is prepared, and a polyester resin (a1) or a resin mixture (a1) dissolved in a ketone solvent is prepared. ) To add a neutralizer, etc., ionize the carboxyl group (not necessary if already ionized), and then add water to phase-shift to an aqueous system. Preferably, after adding water, a ketone solvent is added. Distill off to phase in water.
The dissolving operation of the polyester resin (a1) or the resin mixture (a1) in the ketone solvent and the subsequent addition of the neutralizing agent are usually performed at a temperature equal to or lower than the boiling point of the ketone solvent. Examples of the water used include deionized water.
Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, dipropyl ketone, methyl isobutyl ketone, and methyl isopropyl ketone. From the viewpoint of the solubility of the polyester resin (a1) or the resin mixture (a1) and the ease of distilling off the solvent, methyl ethyl ketone is preferred.

  Examples of the neutralizing agent include aqueous alkaline solutions such as aqueous ammonia and sodium hydroxide, allylamine, isopropylamine, diisopropylamine, ethylamine, diethylamine, triethylamine, 2-ethylhexylamine, tri-n-octylamine, t-butylamine, sec-butylamine, propylamine, methylaminopropylamine, dimethylaminopropylamine, n-propanolamine, butanolamine, 5-amino-4-octanol, monoethanolamine, N, N-dimethylethanolamine, isopropanolamine, neopen Examples include amines such as tanolamine, diglycolamine, ethylenediamine, and piperazine. The usage-amount of a neutralizing agent should just be the quantity which can neutralize the acid value of a polyester resin (a1) at least.

(Process (2))
In step (2), the addition-polymerizable monomer (a2) is added to the aqueous dispersion obtained in step (1) and polymerized to obtain a graft polymer (A), and the aqueous dispersion containing the graft polymer (A) This is a step of obtaining a liquid (hereinafter also referred to as “aqueous dispersion (A)”).
First, the addition polymerizable monomer (a2) is added to the aqueous dispersion of the polyester resin (a1) or the resin mixture (a1). The addition amount is a weight ratio [polyester resin (a1) / addition polymerizable monomer (a2)] of the polyester resin (a1) and the addition polymerizable monomer (a2), preferably 55/45 to 95/5, more preferably Is 65/35 to 95/5, more preferably 75/25 to 95/5, still more preferably 85/15 to 95/5.
Further, from the viewpoint of stirring efficiency, water or the like may be further added.

Next, the addition polymerizable monomer (a2) is polymerized in the presence of the polyester resin (a1).
In the polymerization, a known radical polymerization initiator, a crosslinking agent and the like are added as necessary. As the radical polymerization initiator, a water-soluble radical polymerization initiator is preferably used, and a persulfate is more preferably used.
The polymerization reaction is advanced by heating a mixed solution containing the polyester resin (a1) and the addition polymerizable monomer (a2). The polymerization temperature depends on the type of polymerization initiator used, but for example, when sodium persulfate is used, it is preferably 60 to 100 ° C., more preferably 70 to 90, from the viewpoint of efficiently performing the polymerization reaction. ° C.

From the viewpoints of the glass transition temperature of the graft polymer (A) in the aqueous dispersion (A) obtained as described above, the storage stability of the dispersion, and the dyeing property and light resistance of the thermal transfer image-receiving sheet. Preferably it is 40-80 degreeC, More preferably, it is 50-80 degreeC, More preferably, it is 60-80 degreeC. The softening point of the graft polymer (A) is preferably 80 to 250 ° C, more preferably 120 to 220 ° C.
The solid content concentration of the aqueous dispersion (A) is preferably 20 to 40% by weight, more preferably 25 to 40% by weight, and still more preferably 30 to 40% by weight, from the viewpoint of the dispersibility and productivity of the resin particles. It is. The pH of the aqueous dispersion (A) at 25 ° C. is preferably 5 to 10, more preferably 6 to 9, and still more preferably 7 to 9 from the viewpoint of storage stability of the aqueous dispersion (A). is there.

  The volume median particle size (D50) of the resin particles in the aqueous dispersion (A) is preferably 20 to 1000 nm, more preferably 50 to 800 nm, and still more preferably, from the viewpoint of film forming properties when obtaining a thermal transfer image-receiving sheet. Is 80-500 nm. Here, the “volume median particle size (D50)” means a particle size at which the cumulative volume frequency calculated by the volume fraction is 50% calculated from the smaller particle size. The measuring method is as described in the examples.

<Resin composition (B)>
The resin composition (B) contained in the resin composition for a thermal transfer image receiving sheet of the present invention contains a resin (B0) and a plasticizer from the viewpoint of dyeability and releasability of the thermal transfer image receiving sheet. It is a resin composition whose glass transition temperature is 10-80 degreeC lower than (A).

  In the resin composition (B), the weight ratio of the resin (B0) to the plasticizer (C) [resin (B0) / plasticizer (C)] is the dyeing property, light resistance and release property of the thermal transfer image-receiving sheet. From this viewpoint, the ratio is preferably 100/5 to 100/60, more preferably 100/5 to 100/40, still more preferably 100/10 to 100/30, and still more preferably 100/10 to 100/20.

The difference in glass transition temperature between the resin composition (B) and the resin composition (A) [(glass transition temperature of the resin composition (A)) − (glass transition temperature of the resin composition (B))] is the same. From this viewpoint, it is 10 to 80 ° C, preferably 20 to 55 ° C, more preferably 30 to 45 ° C, and further preferably 30 to 40 ° C. The glass transition temperature of the resin composition (B) is preferably 60 ° C. or less, more preferably 45 ° C. or less, and more preferably −20 to 45 from the viewpoints of dyeability, releasability and light resistance of the thermal transfer image receiving sheet. ° C, more preferably 0 to 45 ° C, still more preferably 25 to 45 ° C.
The glass transition temperatures of the resin composition (B) and the resin composition (A) can be obtained as desired by appropriately adjusting the type and blending ratio of the monomers used. It is preferable to obtain a desired one by adjusting the kind and amount of the agent (C).

≪Resin (B0) ≫
Although there is no restriction | limiting in the kind of resin (B0) contained in a resin composition (B), For example, polyester, a vinyl chloride polymer, a vinyl chloride vinyl acetate copolymer, a vinyl chloride acrylic copolymer, and a polyurethane are mentioned.
From the viewpoint of dyeability, releasability and light resistance of the thermal transfer image-receiving sheet, a resin having the same structure as that of the resin (A0), that is, an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane is 50 A resin having a polyester resin portion containing an alcohol component containing at least mol% is preferred, and a graft polymer containing a segment comprising the polyester resin and a segment comprising an addition polymerization resin is more preferred.

When the resin (B0) is a graft polymer, the polymerization method of the resin (B0) is not limited, but it is preferably obtained by the same method as the resin (A0).
The resin composition (B) is a resin (B0) in which a plasticizer (C) is encapsulated, and is a resin (B0) or a resin (B0) precursor, preferably a polyester resin (b1). ) And the plasticizer (C), water is added, and it is preferably obtained by a production method including a step of obtaining an aqueous dispersion in which the plasticizer (C) is encapsulated in the resin (B0).
Especially, it is preferable to obtain by the method which has the following process (3)-(5).
Step (3): A step of mixing the polyester resin (b1) and the plasticizer (C) to obtain a resin mixture Step (4): The resin mixture obtained in the step (3) is mixed with an aqueous medium, Step of obtaining aqueous dispersion of resin mixture Step (5): Addition-polymerizable monomer (b2) is added to the aqueous dispersion obtained in step (4) for polymerization, and plasticizer (C) is a graft polymer. Step of obtaining an aqueous dispersion of resin composition (B) encapsulated in resin (B0) Steps (4) and (5) are steps (1) and (2) for producing resin composition (A). Perform the same operation as.

  The polyester resin (b1) is the same as the polyester resin (a1), and is formed by condensing an alcohol component containing 50 mol% or more of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and a carboxylic acid component. A polyester resin having a non-aromatic carbon-carbon unsaturated bond obtained by polymerization is preferred. The addition polymerizable monomer (b2) is the same as the addition polymerizable monomer (a2), and the addition polymerizable monomer having an aromatic group is preferably 55% by weight or more, more preferably 70% by weight or more. More preferably 85% by weight or more, more preferably 90% by weight or more, and still more preferably substantially 100% by weight. Examples of the addition polymerizable monomer having an aromatic group include styrene, benzyl methacrylate, benzyl Acrylate is preferred. Among these, styrene is preferable from the viewpoint of the raw material price of the monomer, the releasability of the thermal transfer image-receiving sheet, and the storage stability.

≪Plasticizer (C) ≫
There is no restriction | limiting in particular in the plasticizer (C) used by this invention, The organic compound which plasticizes resin can be selected suitably.
The plasticizer (C) preferably has a melting point of less than 30 ° C. from the viewpoint of plasticizing the resin and improving the dyeability, releasability and light resistance of the thermal transfer image-receiving sheet. The melting point is obtained by measuring under the following conditions using a differential scanning calorimeter (trade name: DSC210, manufactured by Seiko Denshi Kogyo Co., Ltd. (measuring condition: heated up to 150 ° C., and 10 ° C./min from that temperature). The temperature of the endothermic peak observed by lowering the temperature at -100 ° C. and raising the temperature at 10 ° C./min is taken as the melting point).
Further, the viscosity of the plasticizer at 30 ° C. is preferably 1 to 500 mPa · s, more preferably 20 to 500 mPa · s, still more preferably 30 to 400 mPa · s, and still more preferably, from the viewpoint of obtaining a homogeneous resin composition. 200 to 400 mPa · s, more preferably 300 to 400 mPa · s. The viscosity can be measured with a B-type viscometer.
Specific examples of the plasticizer (C) include esters of polyhydric alcohols, polybasic acid esters, polyester plasticizers, phosphoric esters, chlorinated paraffins, alkylphenols, and the like. Acid esters, polyester plasticizers, and alkylphenols are preferred, polyhydric alcohol esters, polybasic acid esters, and alkylphenols are more preferred. Above all, from the viewpoint of obtaining a homogeneous resin composition, polyhydric alcohol esters having a phenol structure, Alkylphenols are more preferred, and polyhydric alcohol esters are even more preferred.
Examples of the polyhydric alcohol ester include polyoxyalkylene bisphenol A aliphatic carboxylic acid diester, and polyoxyethylene bisphenol A lauric acid diester is preferable.
Examples of the polybasic acid ester include dibasic acid esters and tribasic acid esters, and tribasic acid esters are particularly preferable.
Examples of the dibasic acid ester include aromatic dibasic acid esters such as phthalic acid esters and aliphatic dibasic acid esters.
Examples of the tribasic acid ester include aromatic tribasic acid esters and aliphatic tribasic acid esters, such as trimellitic acid ester and acetyl citrate ester, and trimellitic acid ester is preferable. Mellitic acid tri-2-ethylhexyl (melting point: −46 ° C., viscosity at 30 ° C .: 25 mPa · s) is preferable.
Examples of the polyester plasticizer include aliphatic polyester, and a preferable example is D620N (polyester composed of adipic acid / 1,2-butanediol / hydroformylated octene diester) (viscosity at 30 ° C.). : 40 mPa · s).
Examples of the alkylphenol include alkylphenols having 4 to 12 carbon atoms, and 4-nonylphenol (melting point: −8 ° C., viscosity at 30 ° C .: 240 mPa · s) is preferable.
Among these, the plasticizer (C) plasticizes the resin, and the 2,2-bis (4-hydroxyphenyl) propane moiety is used from the viewpoint of improving the dyeing property, releasability and light resistance of the thermal transfer image receiving sheet. Among them, an aliphatic carboxylic acid diester of polyoxyalkylene bisphenol A is preferable, and a lauric acid diester of polyoxyethylene bisphenol A (melting point: −2 ° C., viscosity at 30 ° C .: 350 mPa · s) is preferable.

[Method for producing resin composition for thermal transfer image-receiving sheet]
The resin composition for a thermal transfer image-receiving sheet of the present invention comprises an aqueous dispersion of a resin composition (A) and an aqueous dispersion of a resin composition (B) in which a plasticizer (C) is encapsulated in a resin (B0). It can be obtained by a method including a step of mixing and obtaining as an aqueous dispersion.

From the viewpoint of dyeing property, light resistance and releasability of the thermal transfer image-receiving sheet, the resin composition (A) and the resin composition (B) are contained in a total of 80% by weight or more in the resin composition for the thermal transfer image-receiving sheet. Preferably, it is contained in an amount of 90% by weight or more, and more preferably occupies substantially 100% by weight.
The weight ratio [resin composition (A) / resin composition (B)] of the resin composition (A) and the resin composition (B) in the resin composition for a thermal transfer image receiving sheet is the dyeing property of the thermal transfer image receiving sheet. From the viewpoint of light resistance and releasability, it is preferably 50/50 to 95/5, more preferably 65/35 to 95/5, still more preferably 67/33 to 90/10, still more preferably 67/33 to 85/15, more preferably 67/33 to 75/25.
It is preferable that the amount and weight ratio of the resin composition when the aqueous dispersion of the resin composition (A) and the aqueous dispersion of the resin composition (B) are mixed are also the above amounts and weight ratios.

(Process (6))
Step (6) includes an aqueous dispersion (A) obtained in step (2) and an aqueous dispersion of resin composition (B) obtained by the method such as step (5) (hereinafter referred to as “aqueous dispersion ( B) ”) is mixed to obtain an aqueous dispersion of the resin composition for a thermal transfer image-receiving sheet.
The aqueous dispersion (A) obtained in the step (2) contains the graft polymer (A). It is preferable to obtain an aqueous dispersion of the resin composition for a thermal transfer image receiving sheet of the present invention by mixing the aqueous dispersion (B) containing the resin composition (B) with the aqueous dispersion (A). From the viewpoint of obtaining a uniform aqueous dispersion of the resin composition, the solid content concentration when mixing both is preferably 10 to 50% by weight, more preferably 20 to 40 for the aqueous dispersion (A). The aqueous dispersion (B) is preferably 10 to 50% by weight, more preferably 20 to 40% by weight, still more preferably 25 to 35% by weight. . The solid content concentration is preferably adjusted by diluting with deionized water or the like.
The pH of the aqueous dispersion of the resin composition for a thermal transfer image receiving sheet obtained in step (6) is preferably adjusted to 7 to 10, more preferably 8 to 9. The pH is preferably adjusted with an aqueous ammonia solution or the like.
The mixing method of the aqueous dispersions (A) and (B) in the step (6) is not particularly limited as long as the aqueous dispersions are sufficiently mixed with each other. If the amount of each aqueous dispersion is small, they can be sufficiently mixed by putting both in a glass container and shaking.

[Thermal transfer image-receiving sheet]
The thermal transfer image receiving sheet of the present invention has a dye receiving layer containing the resin composition for a thermal transfer image receiving sheet on a substrate.
<Base material>
Examples of the base material include synthetic paper (polyolefin, polystyrene, etc.), fine paper, art paper, coated paper, cast coated paper, wallpaper, backing paper, synthetic resin or emulsion-impregnated paper, synthetic rubber latex-impregnated paper, synthetic resin Various resin films or sheets such as internal paper, paperboard, cellulose fiber paper, polyolefin, polyvinyl chloride, polyethylene terephthalate, polystyrene, polymethacrylate, polycarbonate, etc. can be used. A white opaque film formed by adding an agent or a foamed foam sheet can also be used. Moreover, the laminated body which combined the said base material can also be used.
As for the thickness of these base materials, about 10-300 micrometers is common, for example. From the viewpoint of improving the adhesion to the dye-receiving layer, it is preferable that the surface of the substrate is subjected to primer treatment or corona discharge treatment.

<Dye-receiving layer>
The dye receiving layer contains the resin composition for a thermal transfer image receiving sheet of the present invention.
The dye-receiving layer is manufactured using a coating liquid form obtained by dissolving a resin in an organic solvent, or a coating liquid form containing a resin dispersion liquid obtained by dispersing each resin in an organic solvent or water. The latter is preferable from the viewpoint of environmental safety and the like, and it is more preferable to manufacture by performing the following steps (7) to (8).
Step (7): Step of preparing a dye-receiving layer coating solution containing an aqueous dispersion of the resin composition for a thermal transfer image-receiving sheet obtained in Step (6) Step (8): Obtained in Step (7) A step of providing a dye-receiving layer using the dye-receiving layer coating solution

(Process (7))
Step (7) is a step of preparing a dye-receiving layer coating solution containing an aqueous dispersion of the thermal transfer image-receiving sheet resin composition obtained in step (6).
The dye-receiving layer coating solution preferably contains a release agent from the viewpoint of further improving the release property of the thermal transfer image-receiving sheet during thermal transfer. As the release agent, for example, a dispersible or water-soluble modified silicone oil can be appropriately used. These release agents can be contained in the dye-receiving layer coating solution in an amount of 0.1 to 20 parts by weight, preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the resin. As a commercially available release agent, “KF-615A” (trade name) manufactured by Shin-Etsu Chemical Co., Ltd. can be preferably used.
In order to uniformly disperse or dissolve the release agent, it is preferable to use a stirrer such as a ball mill, and the dispersion or dissolution temperature is preferably 20 to 40 ° C.

Moreover, it is preferable that the coating liquid for dye receiving layers contains a film forming agent. Examples of the film forming agent include butyl carbitol acetate, diethyl carbitol, gelatin and the like. From the viewpoint of the strength and releasability of the dye receiving layer, gelatin is preferred.
From the viewpoint of uniformly dissolving the film-forming agent, it is preferable to previously dissolve the film-forming agent in water. The aqueous dispersion of the resin composition for a thermal transfer image-receiving sheet and the aqueous solution of the film-forming agent are mixed and stirred. It is preferable to do. A ball mill etc. are mentioned as an agitator used suitably. In order to uniformly mix the film-forming agent in a dissolved state, the stirring temperature is preferably 30 to 60 ° C, more preferably 40 to 50 ° C.
The dye receiving layer coating solution further contains pigments and fillers such as titanium oxide, zinc oxide, kaolin clay, and calcium carbonate from the viewpoint of improving the whiteness of the dye receiving layer and increasing the clarity of the transferred image. Can be contained. From the viewpoint of whiteness of the thermal transfer image-receiving sheet of the present invention, these pigments and fillers may be contained in an amount of 0.1 to 20 parts by weight with respect to 100 parts by weight of the resin composition in the dye-receiving layer coating solution. it can. The dye-receiving layer coating solution of the present invention may further contain other additives such as a catalyst and a curing agent, if necessary.
Further, the dye-receiving layer coating solution may contain a resin other than the resin composition for a thermal transfer image-receiving sheet of the present invention as long as the effects of the present invention are not impaired. Specific examples of the other resin include vinyl chloride polymer, vinyl chloride vinyl acetate copolymer, vinyl chloride acrylic copolymer, polyurethane, etc., from the viewpoint of dyeing property and light resistance of the thermal transfer image-receiving sheet, A vinyl chloride acrylic copolymer is preferred.
These other resins can be contained in the dye-receiving layer coating solution by being dissolved in an organic solvent together with the resin composition for a thermal transfer image-receiving sheet of the present invention in the process of producing the resin, or as a resin dispersion. The dye-receiving layer coating solution may be added to and mixed with the aqueous dispersion of the resin composition for a thermal transfer image-receiving sheet.

(Process (8))
Step (8) is a step of providing a dye-receiving layer using the dye-receiving layer coating solution obtained in step (7).
The dye-receiving layer of the thermal transfer image-receiving sheet of the present invention is obtained by forming a coating liquid on one surface of a substrate and drying it. For example, a gravure printing method, a screen printing method, or a gravure plate is used. It is preferably applied by a reverse roll coating method or the like. In addition, when an intermediate layer is provided between the substrate and the dye-receiving layer as described later, the intermediate layer coating solution and the dye-receiving layer coating solution are applied in layers and dried on one surface of the substrate. An intermediate layer and a dye-receiving layer can also be provided.
The thickness of the dye-receiving layer formed as described above is generally 1 to 50 μm, and preferably 3 to 15 μm from the viewpoint of image quality and productivity. The solid content after drying is preferably 3 to 15 g per 1 m ^{2 of} the dye receiving layer.

<Intermediate layer>
The thermal transfer image-receiving sheet of the present invention preferably has an intermediate layer between the substrate and the dye-receiving layer, and more preferably has an intermediate layer containing a water-soluble polymer and hollow particles.
(Water-soluble polymer)
The water-soluble polymer is used as a binder for fixing the hollow particles, and examples thereof include gelatin, polyvinyl alcohol, polyvinyl pyrrolidone and the like. Among these, the gelation temperature of the aqueous solution near room temperature of 10 to 30 ° C. From the viewpoint of thermal properties of having gelatin, gelatin is preferable. The viscosity (60 ° C.) measured by JIS K6503-2001 is preferably 2.5 to 6.0 mPa · s from the viewpoint of releasability and film-forming property of the thermal transfer image-receiving sheet. More preferably, it is -5.5 mPa * s.
The content of the water-soluble polymer in the intermediate layer is preferably 1 to 75% by weight, more preferably 1 to 50% by weight of the entire intermediate layer.
The water-soluble polymer contained in the intermediate layer is preferably crosslinked with a crosslinking agent such as aldehydes, epoxies, vinyl sulfones, triazines, and carbodiimides.

(Hollow particles)
The hollow particles contained in the intermediate layer are not particularly limited as long as they are polymer particles having pores at least partially. For example, 1) Non-foamed hollow particles in which the water present inside the particle partition walls formed of resin evaporates outside the particles after coating and drying, and the inside of the particles becomes hollow. 2) Low boiling point such as butane and pentane 3) Hollow polymer particles in which the low-boiling liquid inside the particles expands to become hollow by heating the particles coated with the resin, 3) Hollow polymer particles obtained by heating and foaming the above 2) in advance, 4) Resin particles And hollow particles formed by neutralizing at least a part of the acidic groups contained in the polymer forming the. In the present invention, those obtained by the above method 1) or 3) can be preferably used from the viewpoints of dyeability and light resistance of the thermal transfer image-receiving sheet and adhesion between the intermediate layer and the dye-receiving layer in the thermal transfer image-receiving sheet. .

  The material constituting the hollow particles is not particularly limited, and various known materials used in the methods 1) to 3) such as polyacrylic acid, polyacrylic acid ester, styrene-acrylic copolymer, and the like. Acrylic resins such as a mixture of these, polystyrene, polyvinylidene chloride, polyacrylonitrile, vinylidene chloride-acrylonitrile copolymer, etc. can be used, but in the present invention, the dyeing property and light resistance of the thermal transfer image-receiving sheet, and From the viewpoint of adhesion between the intermediate layer and the dye-receiving layer in the thermal transfer image-receiving sheet, a styrene-acrylic copolymer, a vinylidene chloride-acrylonitrile copolymer, or the like is preferably used.

The shape of the hollow particles is not particularly limited and may be any shape other than spherical as well as spherical, but in the present invention, from the viewpoint of adhesion between the intermediate layer and the dye-receiving layer in the thermal transfer image-receiving sheet, It is preferably substantially spherical.
Further, the volume median particle size (D50) of the hollow particles is preferably 0.1 to 5 μm, more preferably 0.3 to 3 μm, from the viewpoint of adhesion between the intermediate layer and the dye receiving layer in the thermal transfer image receiving sheet. More preferably, it is 0.3-1 micrometer. This value can be measured with a field emission scanning electron microscope (manufactured by Hitachi, Ltd., trade name: S-4800 type).

In the present invention, the hollow particles are preferably in the form of an aqueous dispersion and preferably have a solid concentration of 10 to 40% by weight, more preferably 15 to 35% by weight.
In addition, the hollow particles preferably have an insoluble content of methyl ethyl ketone (MEK) of 70% by weight or less from the viewpoint of dyeability and light resistance of the thermal transfer image-receiving sheet and adhesion between the intermediate layer and the dye-receiving layer in the thermal transfer image-receiving sheet. More preferably, it is 10-70 weight%, More preferably, it is 30-70 weight%. In the present invention, “MEK insoluble matter” is defined as the weight ratio of the insoluble hollow particle component of the hollow particles when 2.0 parts by weight of the hollow particles are dissolved in 95 parts by weight of MEK at 25 ° C. It is what is done.
The MEK insoluble content of the hollow particles can be adjusted, for example, by controlling the degree of crosslinking of the resin constituting the hollow particles.

In the present invention, the hollow particles are preferably used as a dispersion in an aqueous medium, and as commercially available hollow particles that can be preferably used, for example, “Ropeke HP-1055” manufactured by Rohm and Haas Japan Co., Ltd. Examples thereof include “Nipol MH8101” manufactured by Nippon Zeon Co., Ltd., “SX8782 (D)” manufactured by JSR Co., Ltd. (all are trade names).
In the intermediate layer, the weight ratio of the hollow particles to the water-soluble polymer (hollow particles / water-soluble polymer) is determined from the viewpoint of dyeing property and adhesion between the intermediate layer and the dye-receiving layer in the thermal transfer image-receiving sheet. The ratio is preferably 30/70 to 90/10, more preferably 40/60 to 80/20, and still more preferably 50/50 to 80/20.

The intermediate layer may contain pigments and fillers such as titanium oxide, zinc oxide, kaolin clay, calcium carbonate, fine powder silica from the viewpoint of improving the whiteness of the intermediate layer and increasing the clarity of the transferred image. it can. These pigments and fillers are preferably 0.1 to 20 parts by weight, more preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the water-soluble polymer in the intermediate layer from the viewpoint of the whiteness of the thermal transfer image-receiving sheet. 10 parts by weight can be contained.
If necessary, the intermediate layer may further contain additives such as a film-forming aid such as glycol ethers, a mold release agent, a curing agent, and a catalyst.

The intermediate layer is coated and dried on at least one surface of the base material of the thermal transfer image-receiving sheet by dispersing or dissolving a water-soluble polymer, hollow particles, and various additives used as necessary in an organic solvent or water. Can be formed.
The thickness of the intermediate layer is preferably 10 to 100 μm, more preferably 20 to 50 μm, from the viewpoint of cushioning properties and heat insulating properties. In addition, the solid content after drying is preferably 7 to 70 g / m ² per 1 m ² of the intermediate layer.
The intermediate layer is prepared by, for example, dissolving water-soluble polymer containing gelatin, hollow particles, and additives used as necessary in water on at least one surface of the base material of the thermal transfer image-receiving sheet or dispersing in water. The coating liquid obtained in this manner can be applied and dried by, for example, a gravure printing method, a screen printing method, a reverse roll coating method using a gravure plate, or the like.

[Transfer sheet]
The transfer sheet (ink ribbon) used when performing the thermal transfer using the thermal transfer image receiving sheet of the present invention as described above is usually a dye layer containing a sublimation dye on paper or a polyester film, and receiving the dye. A laminate layer composed of a protective layer or the like transferred onto the obtained image is provided, and any conventionally known transfer sheet can be used.
Examples of sublimable dyes that can be suitably used for the thermal transfer image-receiving sheet of the present invention include pyridone azo series, dicyanostyryl series, quinophthalone series, merocyanine series for yellow dyes; benzeneazo series, pyrazolone azomethine series, isothiazole for magenta dyes. Examples of cyan dyes include anthraquinone, cyanomethylene, indophenol, and indonaphthol.

As the means for applying thermal energy at the time of thermal transfer, any conventionally known means for applying can be used. For example, by controlling the recording time with a recording apparatus such as a thermal printer, thermal energy of about 5 to 100 mJ / mm ^{2 is obtained.} It can be done by giving.

  Hereinafter, the present invention will be described more specifically with reference to examples and the like. In the following examples and the like, each physical property was measured by the following method.

[Acid value of resin]
The measurement solvent was measured according to JIS K0070, except that the mixed solvent of ethanol and ether was changed to a mixed solvent of acetone and toluene (acetone: toluene = 1: 1 (volume ratio)).

[Softening point of resin]
Using a flow tester (manufactured by Shimadzu Corporation, trade name: CFT-500D), a 1 g sample was heated at a heating rate of 6 ° C./min. Extruded from a 1 mm nozzle. The amount of flow tester drop by the flow tester was plotted against the temperature, and the temperature at which half the sample flowed out was taken as the softening point.

[Glass transition temperature of resin]
Using a differential scanning calorimeter (manufactured by Perkin Elmer, trade name: Pyris 6 DSC), the temperature was raised to 200 ° C., and the sample cooled to 0 ° C. at a temperature lowering rate of 10 ° C./min was heated at a rate of 10 ° C. / The temperature was raised in minutes, and the temperature at the intersection of the extended line of the baseline and the tangent indicating the maximum slope from the peak rising portion to the peak apex was defined as the glass transition temperature.

[Number average molecular weight of resin]
The molecular weight distribution was measured by gel permeation chromatography and the number average molecular weight was calculated by the following method.
(1) Preparation of sample solution The resin was dissolved in tetrahydrofuran so that the concentration was 0.5 g / 100 ml. Subsequently, this solution was filtered using a fluororesin filter having a pore size of 2 μm (manufactured by Sumitomo Electric Industries, Ltd., trade name: FP-200) to remove insoluble components to obtain a sample solution.
(2) Molecular weight measurement Tetrahydrofuran was flowed as a dissolution liquid at a flow rate of 1 ml / min, and the column was stabilized in a constant temperature bath at 40 ° C. Measurement was performed by injecting 100 μl of the sample solution. The number average molecular weight of the sample was calculated based on a calibration curve prepared in advance. The calibration curves are several types of monodisperse polystyrene (monodisperse polystyrene manufactured by Tosoh Corporation; 2.63 × 10 ³ , 2.06 × 10 ⁴ , 1.02 × 10 ⁵ (weight average molecular weight), manufactured by GL Sciences Inc. Monodisperse polystyrene; 2.10 × 10 ³ , 7.00 × 10 ³ , 5.04 × 10 ⁴ (weight average molecular weight)) were prepared as standard samples.
Measuring device: CO-8010 (trade name, manufactured by Tosoh Corporation)
Analytical column: GMHXL + G3000HXL (both trade names, manufactured by Tosoh Corporation)

[Volume Median Particle Size (D50) of Resin Particles of Aqueous Dispersion]
Using a laser diffraction particle size measuring machine (Horiba, Ltd., trade name: LA-920), add an aqueous dispersion of each resin and distilled water to the measurement cell, and at a concentration where the absorbance is in an appropriate range, Volume median particle size (D50) was measured.

[Solid content concentration of aqueous dispersion]
Using an infrared moisture meter (trade name: FD-230, manufactured by Kett Scientific Laboratory Co., Ltd.), 5 g of an aqueous dispersion was measured at a drying temperature of 150 ° C. and a measurement mode 96 (monitoring time 2.5 minutes / variation width 0.05%). ) And the wet base moisture (% by weight) of the aqueous dispersion was measured. The solid content concentration was calculated according to the following formula.
Solid content concentration (% by weight) = 100-M
M: wet base moisture of aqueous dispersion (% by weight) = [(W−W ₀ ) / W] × 100
W: Sample weight before measurement (initial sample weight)
W ₀ : Sample weight after measurement (absolute dry weight)

[PH of aqueous dispersion]
It measured at 25 degreeC with the pH meter (The product name: HM-20P by Toa DKK Corporation).

Production Examples 1 and 2
(Production of polyester resins a and b)
The raw material monomer and dioctylic acid tin (II) salt of the polyester resin excluding fumaric acid shown in Table 1 were put into a 5 L four-necked flask equipped with a thermometer, a stirrer, a flow-down condenser and a nitrogen inlet tube, The reaction was carried out in a mantle heater under a nitrogen atmosphere at 235 ° C. for 5 hours, and further under reduced pressure (8.3 kPa) for 1 hour. Next, after adding fumaric acid and 4-t-butylcatechol at 210 ° C. and reacting for 5 hours, the softening point measured according to ASTM D36-86 under reduced pressure (20 kPa) reaches the temperature shown in Table 1. By reacting, polyesters a and b were obtained.
Table 1 shows the physical properties and the like of the obtained polyesters a and b.

Production Examples 3-12
(Production of aqueous dispersions (i) to (x) containing polyester resin)
A polyester resin and a plasticizer of the type and amount shown in Table 2 are placed in a 10 L four-necked flask equipped with a nitrogen inlet tube, a reflux condenser, a stirrer, and a thermocouple, and dissolved in methyl ethyl ketone at 25 ° C. It was. Next, 25% aqueous ammonia was added, deionized water was added with stirring, and methyl ethyl ketone was distilled off at 60 ° C. under reduced pressure. After cooling to room temperature, the mixture was filtered through a 200-mesh wire mesh to obtain aqueous dispersions (i) to (x) containing a polyester resin. The polyoxyethylene bisphenol A laurate used as a plasticizer (EXEPARL BP-DL (trade name, manufactured by Kao Corporation)) has a 2,2-bis (4-hydroxyphenyl) propane moiety in its structure. The melting point is −2 ° C., the viscosity at 30 ° C. is 350 mPa · s, 4-nonylphenol has a melting point of −8 ° C., the viscosity at 30 ° C. is 240 mPa · s, and D620N is manufactured by J Plus Polyester plasticizer (polyester consisting of adipic acid / 1,2-butanediol / hydroformylated octene diester), the viscosity at 30 ° C. is 40 mPa · s, and the trimellitate tri-2-ethylhexyl has a melting point of − The viscosity at 46 ° C. and 30 ° C. is 25 mPa · s.
Table 2 shows the physical properties and the like of the obtained aqueous dispersions (i) to (x).

Production Examples 13-22
(Production of aqueous dispersions (I) to (X) of resin composition for thermal transfer image-receiving sheet)
Polyester dispersion, deionized water, and addition polymerizable monomer shown in Table 3 in a four-neck flask with an internal volume of 2 L equipped with a nitrogen inlet tube, a reflux condenser, a dropping funnel, a stirrer, and a thermocouple Was charged with styrene and stirred for 30 minutes. Under a nitrogen stream, sodium persulfate was added and reacted at 80 ° C. for 6 hours. After cooling to room temperature, the mixture was filtered through a 200-mesh wire mesh to obtain aqueous dispersions (I) to (X) of the resin composition for a thermal transfer image-receiving sheet.
Table 3 shows the physical properties and the like of the obtained aqueous dispersions (I) to (X).
In addition, as shown in Table 4 to be described later, the aqueous dispersions (I) and (VI) are mainly used as the aqueous dispersion (A) of the resin composition (A), and the aqueous dispersions (I) to (I) to (V), (VII), (IX) and (X) were used as an aqueous dispersion (B) of the resin composition (B). However, only in Comparative Example 2, the aqueous dispersion (VIII) was used as the aqueous dispersion (A) of the resin composition (A), and the aqueous dispersion (VI) was used as the aqueous dispersion (B) of the resin composition (B). ).

Examples 1-11 and Comparative Examples 1-2
(Manufacture of thermal transfer image receiving sheet)
First, the composition and blending amount shown in Table 4 were mixed at 45 ° C. to prepare an intermediate layer coating solution. This coating solution was applied to synthetic paper (manufactured by YUPO Corporation, trade name: YUPO FGS-250, thickness 250 μm, basis weight 200 g / m ² ) with a wire bar so that it would be 20.0 g / m ² after drying. And it was made to dry at 25 degreeC for 5 minutes, and the intermediate | middle layer coating sheet was obtained.
In the preparation of the intermediate layer, the following styrene acrylic copolymer was used as the hollow particles, and the following gelatin was used as the binder.
Styrene acrylic copolymer (manufactured by Nippon Zeon Co., Ltd., trade name: Nipol MH8101, hollow rate = 50%, solid content = 26% by weight)
Gelatin (made by Nitta Gelatin Co., Ltd., trade name: G0723K, viscosity 4.4 mPa · s)

Next, the aqueous dispersion (A) and the aqueous dispersion (B) shown in Table 4 were each diluted with deionized water to a solid content concentration of 30% by weight, and then placed in a screw tube with the formulation shown in Table 4. The pH was adjusted to 9.0 with a 25% aqueous ammonium solution (Wako Pure Chemical Industries, Ltd.).
Subsequently, a release agent (polyether-modified silicone) was added and stirred at 25 ° C. for 1 hour with a ball mill. Thereafter, a film-forming agent (gelatin aqueous solution having a solid content concentration of 8% by weight (Table 4 shows the effective amount used)) was added at 45 ° C., and the mixture was stirred for 3 hours with a ball mill. A1 to M1 were prepared. For the preparation of the dye receiving layer, the following gelatin was used as a film-forming agent, and the following polyether-modified silicone was used as a mold release agent.
Gelatin (made by Nitta Gelatin Co., Ltd., trade name: G0723K, viscosity 4.4 mPa · s)
Polyether-modified silicone (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: KF-615A)
Each of the obtained dye-receiving layer coating solutions was applied to the above-mentioned intermediate layer coating sheet so as to be 5.0 g / m ² after drying with a wire bar, and dried at 50 ° C. for 2 minutes. A thermal transfer image-receiving sheet was obtained.
The obtained thermal transfer image-receiving sheet was measured and evaluated for glass transition temperature, dyeability, release property and light resistance by the following methods. The results are shown in Table 4.

[Glass transition temperature of resin composition in aqueous dispersion]
Each aqueous dispersion was freeze-dried at −10 ° C. for 9 hours using a freeze dryer (trade name: FDU-2100, manufactured by Tokyo Rika Kikai Co., Ltd.) to prepare a sample for measuring the glass transition temperature.
Using a differential scanning calorimeter (manufactured by Perkin Elmer, trade name: Pyris 6 DSC), the temperature was raised to 200 ° C., and the sample cooled to 0 ° C. at a temperature lowering rate of 10 ° C./min was heated at a rate of 10 ° C. / The temperature was raised in minutes, and the temperature at the intersection of the extended line of the baseline and the tangent indicating the maximum slope from the peak rising portion to the peak apex was defined as the glass transition temperature.

[Evaluation method]
(Dyeing property)
A black (K) gradation pattern was printed on the produced thermal transfer image-receiving sheet using a commercially available sublimation printer (trade name, MEGAPICEL III, manufactured by Altec Co., Ltd.), and high density printing (18th gradation (L = The transfer color density at 0: highest density)) was measured with a Gretag densitometer (manufactured by Gretag Macbeth Co., Ltd.) to evaluate the dyeing property. The greater the concentration value, the better the dyeing property.

(Releasability)
A 5 × 5 cm black solid was printed on the obtained thermal transfer image-receiving sheet, and the releasability (thermal fusing property) was evaluated based on the following criteria from the peeling sound between the ink ribbon and the thermal transfer image-receiving sheet during continuous black solid printing. .
A: There is no abnormal noise and can be peeled off.
B: Although there is some abnormal noise, it can be peeled off.
C: It is heat-sealed and peeling is difficult.

(Light resistance)
A light resistance test was performed using a xenon weather meter under the following conditions, and the light resistance was evaluated by the amount of hue change.
・ Irradiation tester: Suga Test Instruments Co., Ltd., trade name: SX75
Light source: Xenon lamp Filter: Inside = quartz filter, outside = # 320
・ Panel temperature: 50 ℃
-Humidity in the tank: 35-50% RH
・ Irradiation intensity: 50 W / m ² , measured value at 300 to 400 nm • Integrated illuminance: 10,000 kJ / m ² , integrated value at 300 to 400 nm

-Hue change amount: Using an optical densitometer (manufactured by Gretag Macbeth Co., Ltd.), black (K), yellow (Y), magenta (M), cyan (C), green (G), red (tone) R) and blue (B) are measured for optical reflection density, and L ^* a ^* b ^* (L ^* is lightness, a ^* , b ^*) before and after irradiation for steps where the optical reflection density before irradiation is around 1.0 ^. Is an index of chromaticity), measured with a color difference meter (manufactured by Gretag Macbeth Co., Ltd.), calculated the amount of hue change by the following formula, and evaluated the light resistance of each black (K) + chromatic color print did. The smaller the hue change amount, the better the light resistance.
The light resistance of black and chromatic colors (for each print) is black (K), yellow (Y), magenta (M), cyan (C), green (G), red (R), blue ( This is the sum of the hue changes of each color of B).
Hue variation _{^{= [(a * 1 -a *}} 2) 2 + (b * 1 -b * 2) 2] 1/2
(L ^* a ^* b ^* values before irradiation: L ^* ₁ , a ^* ₁ , b ^* ₁ )
(L ^* a ^* b ^* values after irradiation: L ^* ₂ , a ^* ₂ , b ^* ₂ )

  It can be seen that the thermal transfer image-receiving sheets obtained in the examples are excellent in all of dyeing property, releasability and light resistance as compared with the thermal transfer image-receiving sheet obtained in the comparative example.

  Since the thermal transfer image receiving sheet of the present invention is excellent in all of dyeing property, releasability and light resistance, it can be suitably used as a thermal transfer image receiving sheet.

Claims (11)

  Resin composition containing resin (A0) containing polyester part obtained by condensation polymerization of alcohol component and carboxylic acid component containing 50 mol% or more of alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane An aqueous dispersion of the product (A) and an aqueous resin composition (B) containing the plasticizer (C) in the resin (B0) and having a glass transition temperature of 10 to 80 ° C. lower than that of the resin composition (A). The manufacturing method of the resin composition for thermal transfer image receiving sheets including the process of mixing with a dispersion liquid and obtaining the aqueous dispersion liquid of the resin composition for thermal transfer image receiving sheets.   The resin (B0) or the polyester resin (b1) serving as a precursor of the resin (B0) and the plasticizer (C) are mixed, water is added, and the plasticizer (C) is included in the resin (B0). The manufacturing method of the resin composition for thermal transfer image receiving sheets of Claim 1 including the process of obtaining the aqueous dispersion liquid of the obtained resin composition (B).   The weight ratio [resin composition (A) / resin composition (B)] of the resin composition (A) and the resin composition (B) is 50/50 to 95/5. The manufacturing method of the resin composition for thermal transfer image receiving sheets.   In resin composition (B), weight ratio [resin (B0) / plasticizer (C)] of resin (B0) and a plasticizer (C) is 100 / 5-100 / 60. The manufacturing method of the resin composition for thermal transfer image receiving sheets in any one of these.   The manufacturing method of the resin composition for thermal transfer image receiving sheets in any one of Claims 1-4 whose resin (B0) is resin containing a polyester part.   Resin (A0) is a main chain segment comprising a polyester resin obtained by condensation polymerization of an alcohol component containing 50 mol% or more of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and a carboxylic acid component. The manufacturing method of the resin composition for thermal transfer image receiving sheets in any one of Claims 1-5 which is a graft polymer which consists of (A1) and the side chain segment (A2) which consists of addition polymerization type resin.   The alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane is a propylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane according to any one of claims 1 to 6. A method for producing a resin composition for a thermal transfer image-receiving sheet.   The plasticizer (C) has a viscosity at 30 ° C. of 1 to 500 mPa · s and is at least one selected from esters of polyhydric alcohols, polybasic acid esters, polyester plasticizers, phosphate esters, chlorinated paraffins, and alkylphenols. The manufacturing method of the resin composition for thermal transfer image receiving sheets in any one of Claims 1-7.   The thermal transfer image-receiving sheet according to any one of claims 1 to 8, wherein the plasticizer (C) contains a compound having a 2,2-bis (4-hydroxyphenyl) propane moiety and a melting point of less than 30 ° C. For producing a resin composition for use.   The resin composition for thermal transfer image receiving sheets obtained by the manufacturing method in any one of Claims 1-9.   The thermal transfer image receiving sheet which has a dye receiving layer containing the resin composition for thermal transfer image receiving sheets of Claim 10.