JP2011255524A - Resin for thermal transfer image-receiving sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin for thermal transfer image-receiving sheets which can provide the thermal transfer image-receiving sheets excellent in dyeing capacity, mold releasability and light resistance, and to provide a thermal transfer image-receiving sheet which has a dye receiving layer that includes the resin.SOLUTION: The resin for thermal transfer image-receiving sheets contains a graft polymer composed of a main chain segment (A1) formed of a polyester resin and a side chain segment (A2) formed of an addition polymer-based resin. The segment (A1) is obtained by polycondensing an alcohol component which includes a propylene oxide adduct of 2,2-bis(4-hydroxyphenyl) propane in an amount of 50 mol% or more with a carboxylic acid component which includes an alicyclic carboxylic acid in an amount of 50 mol% or more. The segment (A2) contains a constitutional unit derived from an addition polymerizable monomer with an aromatic group in an amount of 70 wt.% or more.

Description

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

  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, in order to exhibit these performances, a thermal transfer image receiving sheet using a polyester resin has been developed.

Patent Document 1 discloses a dye receiving layer containing a graft polymer comprising an unsaturated copolyester as a trunk and a vinyl copolymer as a branch for the purpose of improving color density, sharpness, image stability, and adhesion to a dye supply material. And a dye-receiving material for thermal sublimation printing comprising a substrate and a support.
Patent Document 2 discloses an alcohol component containing 50 mol% or more of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane for the purpose of improving dyeability, light resistance and releasability, 80. Polyester A obtained from an acid component containing at least 80 mol% of aliphatic carboxylic acid and / or alicyclic carboxylic acid, and alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane A thermal transfer image-receiving sheet using a polyester for a thermal transfer image-receiving sheet containing polyester B obtained from an alcohol component containing at least mol% and an acid component containing 10 to 35 mol% of a trivalent or higher aromatic polyvalent carboxylic acid is disclosed. Has been.

JP-A-4-318989 JP 2010-36409 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. In addition, 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 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 and 2.
The present invention relates to a thermal transfer image receiving sheet resin capable of providing a thermal transfer image receiving sheet excellent in dyeing property, releasability and light resistance, a thermal transfer image receiving sheet having a dye receiving layer containing the resin, and the thermal transfer image receiving sheet. It is an object to provide a method for producing a resin.

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, by using a resin containing a main chain segment made of a specific polyester resin and a side chain segment made of an addition polymerization resin for the dye-receiving layer, it is possible to improve dyeability, mold release and light resistance. I found it.
That is, the present invention provides the following [1] to [3].
[1] A thermal transfer image-receiving sheet resin comprising a graft polymer composed of a main chain segment (A1) made of a polyester resin and a side chain segment (A2) made of an addition polymerization resin, wherein the segment (A1) is Obtained by polycondensation of an alcohol component containing 50 mol% or more of a propylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and a carboxylic acid component containing 50 mol% or more of an alicyclic carboxylic acid, The resin for thermal transfer image receiving sheets, wherein the segment (A2) contains 70% by weight or more of a structural unit derived from an addition polymerizable monomer having an aromatic group.
[2] A thermal transfer image receiving sheet having a dye receiving layer containing the resin for thermal transfer image receiving sheet of [1].
[3] Step (1): an alcohol component containing 50 mol% or more of a propylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and 50 mol% or more of an alicyclic carboxylic acid and an unsaturated aliphatic A polyester resin (a1) having a non-aromatic carbon-carbon unsaturated bond is prepared by condensation polymerization with a carboxylic acid component containing a carboxylic acid and / or an unsaturated alicyclic carboxylic acid, and the polyester resin ( a step of mixing a1) with an aqueous medium to obtain an aqueous dispersion of the polyester resin (a1); and step (2): addition polymerization having an aromatic group in the aqueous dispersion obtained in step (1). A method for producing a resin for a thermal transfer image-receiving sheet, comprising a step of adding an addition-polymerizable monomer (a2) containing at least 70% by weight of a polymerizable monomer and polymerizing to obtain an aqueous dispersion of a graft polymer.

  The resin for a thermal transfer image receiving sheet of the present invention can provide a thermal transfer image receiving sheet excellent in dyeing property, releasability and light resistance. In addition, the thermal transfer image-receiving sheet having a dye-receiving layer containing the resin has excellent dyeability, releasability and light resistance, and can form an image with a high color density. Hateful.

[Resin for thermal transfer image-receiving sheet]
The thermal transfer image-receiving sheet resin of the present invention comprises a main chain segment (A1) made of a polyester resin (hereinafter also simply referred to as “segment (A1)”) and a side chain segment (A2) made of an addition polymerization resin (hereinafter simply referred to as “segment”). A resin for thermal transfer image-receiving sheet comprising a graft polymer composed of “segment (A2)”, wherein the segment (A1) is a propylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane Obtained by condensation polymerization of an alcohol component containing 50 mol% or more and a carboxylic acid component containing 50 mol% or more of an alicyclic carboxylic acid, and the segment (A2) is derived from an addition polymerizable monomer having an aromatic group Is contained in an amount of 70% by weight or more.

The reason why the thermal transfer image-receiving sheet having the resin for thermal transfer image-receiving sheet 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.
The raw material monomer of the polyester resin segment (A1) of the resin for thermal transfer image receiving sheets of the present invention contains a propylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane as an alcohol component. Since this compound has two aromatic rings in the molecule, that is, a structure similar to a dye, it has a high affinity with the dye and excellent dye permeability, so that the dyeing property and light resistance of the thermal transfer image-receiving sheet are improved. In addition, since it has a rigid structure, the resin is hardened, which is considered to contribute to the improvement of the releasability of the thermal transfer image receiving sheet.
Furthermore, it is considered that by using alicyclic carboxylic acid as a raw material monomer for the polyester resin segment (A1), structural decomposition of the resin and the dye is less likely to occur, so that the light resistance can be greatly improved. Moreover, since it has an annular structure, the hardness of the resin can be maintained and the mold release property is excellent.
Further, the addition polymerization resin segment (A2) containing 70% by weight or more of a structural unit derived from an addition polymerizable monomer having an aromatic group is not compatible with the polyester resin segment (A1) having the above structure. , Forming a fine phase separation structure, increasing the permeability of the dye from the interface, contributing to the improvement of the dyeing property and light resistance of the thermal transfer image-receiving sheet, and the addition polymerization resin segment has an affinity for the ink sheet Since it is scarce, it is considered that the resin is excellent in releasability.

  The weight ratio [segment (A1) / segment (A2)] of the segment (A1) and the segment (A2) constituting the graft polymer contained in the resin for the thermal transfer image-receiving sheet of the present invention is the dyeing property of the thermal transfer image-receiving sheet. From a viewpoint of improvement, Preferably it is 55 / 45-95 / 5, More preferably, it is 65 / 35-95 / 5, More preferably, it is 75 / 25-95 / 5, More preferably, it is 85 / 15-95 / 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.

  Further, from the viewpoint of releasability and storage stability of the thermal transfer image receiving sheet, the softening point of the resin for thermal transfer image receiving sheet of the present invention is preferably 80 to 165 ° C. From the same viewpoint, the acid value of the resin is preferably 5 to 40 mgKOH / g, more preferably 5 to 35 mgKOH / g, and still more preferably 10 to 35 mgKOH / g.

  The resin for a thermal transfer image receiving sheet of the present invention contains a graft polymer composed of a main chain segment (A1) made of a polyester resin and a side chain segment (A2) made of an addition polymerization resin. The content of the graft polymer in the resin for thermal transfer image-receiving sheets of the present invention is preferably 80 to 100 mol%, more preferably 90 to 100 mol% or more, and still more preferably substantially 100 mol%.

(Main chain segment (A1) made of polyester resin)
The segment (A1) constituting the graft polymer contained in the thermal transfer image-receiving sheet resin of the present invention comprises an alcohol component containing 50 mol% or more of a propylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane, This is a segment made of a polyester resin obtained by condensation polymerization with a carboxylic acid component containing 50 mol% or more of an alicyclic carboxylic acid. The segment (A1) is a main chain in the graft polymer contained in the thermal transfer image-receiving sheet resin of the present invention.

Specifically, the propylene 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 oxypropylene groups.
x and y correspond to the added mole number of propylene 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.

  The propylene 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 propylene oxide adduct means the whole structure in which an oxypropylene 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 together with the propylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane.
Specifically, as a raw material monomer derived from the structural unit of segment (A1) (hereinafter, also simply referred to as “raw material monomer of segment (A1)”), an alcohol having a non-aromatic carbon-carbon unsaturated bond For example, unsaturated fatty alcohols can also be used. In the graft polymer contained in the resin for thermal transfer sheets, the carbon-carbon unsaturated bond portion can be a bond portion with the segment (A2). In this case, the unsaturated bond is a saturated bond and Become. Examples of the alcohol having a non-aromatic carbon-carbon unsaturated bond (unsaturated aliphatic alcohol) include allyl alcohol.
Other alcohol components include polyhydric alcohols having two or more hydroxyl groups, such as ethylene glycol, propylene glycol (1,2-propanediol), glycerin, pentaerythritol, trimethylolpropane, 2,2-bis. (4-Hydroxyphenyl) propane, hydrogenated bisphenol A, sorbitol, or their alkylene (2 to 4 carbon) oxide adduct (average number of added moles 1 to 16). An alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane other than the propylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane can also be preferably used, and an ethylene oxide adduct is more preferred. . Among these alcohol components, it is preferable from the viewpoint of dyeing property that 1,2-propanediol is contained in the alcohol component of the segment (A1). In addition, you may use these alcohol components individually or in combination of 2 or more types.

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. In the present invention, the alicyclic carboxylic acid is contained in an amount of 50 mol% or more.
The alicyclic carboxylic acid is preferably an alicyclic dicarboxylic acid or an acid anhydride or alkyl ester of these acids, and more preferably cyclohexane dicarboxylic acid from the viewpoint of reactivity with alcohol during polyester synthesis and heat resistance of the polyester. Acids, decalin dicarboxylic acids, or anhydrides of these acids.

  Specific examples of the alicyclic carboxylic acid include 1,4-cyclohexanedicarboxylic acid, 2-methyl-1,4-cyclohexanedicarboxylic acid, 2-ethyl-1,4-cyclohexanedicarboxylic acid, 2-propyl-1,4. -Cyclohexanedicarboxylic acid, 2-butyl-1,4-cyclohexanedicarboxylic acid, 2-t-butyl-1,4-cyclohexanedicarboxylic acid, 2,3-dimethyl-1,4-cyclohexanedicarboxylic acid, 2,3-diethyl -1,4-cyclohexanedicarboxylic acid, 2,3-dipropyl-1,4-cyclohexanedicarboxylic acid, 2,3-dibutyl-1,4-cyclohexanedicarboxylic acid, 2-methyl-3-ethyl-1,4-cyclohexane Dicarboxylic acid, 2-methyl-3-propyl-1,4-cyclohexanedicarboxylic acid, 2-methyl 3-butyl-1,4-cyclohexanedicarboxylic acid, 2-ethyl-3-propyl-1,4-cyclohexanedicarboxylic acid, 2-ethyl-3-butyl-1,4-cyclohexanedicarboxylic acid, 2-methyl-3- t-butyl-1,4-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 2,6-decalindicarboxylic acid, 3-methyl-2,6-decalindicarboxylic acid, 3-ethyl-2,6-decalindicarboxylic acid Acid, 3-propyl-2,6-decalin dicarboxylic acid, 3-butyl-2,6-decalin dicarboxylic acid, 3,4-dimethyl-2,6-decalin dicarboxylic acid, 3,4-diethyl-2,6- Decalin dicarboxylic acid, 3,4-dipropyl-2,6-decalin dicarboxylic acid, 3,4-dibutyl-2,6-decalin dicarboxylic acid, , 8-dimethyl-2,6-decalin dicarboxylic acid, 3,8-diethyl-2,6-decalin dicarboxylic acid, 3,8-dipropyl-2,6-decalin dicarboxylic acid, 3,8-dibutyl-2,6 -Decalin dicarboxylic acid, 3-methyl-4-ethyl-2,6-decalin dicarboxylic acid, 3-methyl-4-propyl-2,6-decalin dicarboxylic acid, 3-methyl-4-butyl-2,6-decalin Examples thereof include dicarboxylic acid, 3-ethyl-4-butyl-2,6-decalin dicarboxylic acid, and acid anhydrides of these acids. Among these, 1,2-cyclohexanedicarboxylic acid and its acid anhydride, hexahydrophthalic anhydride and 1,4-cyclohexanedicarboxylic acid are preferable, and 1,4-cyclohexanedicarboxylic acid is preferable from the viewpoint of light resistance of the thermal transfer image-receiving sheet. More preferred.

  The alicyclic carboxylic acid is contained in the carboxylic acid component in an amount of 50 mol% or more, preferably 70 mol% or more, more preferably 80 mol% or more, and still more preferably, from the viewpoint of dyeability and light resistance of the thermal transfer image-receiving sheet. Is substantially 100 mol%.

  The carboxylic acid component that is a raw material monomer of the segment (A1) includes a carboxylic acid having a non-aromatic carbon-carbon unsaturated bond, such as an unsaturated aliphatic carboxylic acid and / or an unsaturated alicyclic carboxylic acid. It is preferable. 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.

Other carboxylic acids include, for example, aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid; aliphatic dicarboxylic acids such as adipic acid, succinic acid, succinic acid having an alkyl group and / or alkenyl group; Examples thereof include trivalent or higher polyvalent carboxylic acids such as acid and pyromellitic acid, anhydrides of these acids, and alkyl (C1 to C3) esters thereof. From the viewpoint of dyeability of the thermal transfer image-receiving sheet, aromatic dicarboxylic acid is preferable, and isophthalic acid is more preferable. The said carboxylic acid component may be individual or 2 or more types may be contained.
Of the raw material monomers derived from the structural unit of the main chain segment (A1) made of polyester resin, as the raw material monomer having a non-aromatic carbon-carbon unsaturated bond, unsaturated aliphatic carboxylic acid, unsaturated fat One or more selected from cyclic carboxylic acids and unsaturated aliphatic alcohols may be included, but from the viewpoint of reactivity, it is preferable to include an unsaturated aliphatic carboxylic acid and / or an unsaturated alicyclic carboxylic acid, More preferably, it is only an unsaturated aliphatic carboxylic acid and / or an unsaturated alicyclic carboxylic acid.

From the viewpoint of releasability and storage stability of the thermal transfer image-receiving sheet, the acid value of the segment (A1) is 5 to 40 mgKOH / g, preferably 5 to 35 mgKOH / g, more preferably 5 to 30 mgKOH / g. More preferably, it is 10-20 mgKOH / 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)
The segment (A2) constituting the graft polymer contained in the thermal transfer image-receiving sheet resin of the present invention is an addition polymerization system composed of structural units derived from the addition polymerizable monomer (a2) (hereinafter also referred to as monomer (a2)). It is a segment made of a resin and contains 70% by weight or more of a structural unit derived from an addition polymerizable monomer having an aromatic group. The segment (A2) is a side chain in the graft polymer contained in the thermal transfer image-receiving sheet resin of the present invention.

Examples of the addition polymerizable monomer having an aromatic group include styrene, methylstyrene, α-methylstyrene, β-methylstyrene, t-butylstyrene, chlorostyrene, chloromethylstyrene, methoxystyrene, styrenesulfonic acid or a salt thereof. Styrenes; (meth) acrylic acid esters such as benzyl (meth) acrylate and the like. Of these, styrene, methylstyrene, benzyl methacrylate and benzyl acrylate are preferable. Among these, styrene is particularly 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.
In the segment (A2), the content of the structural unit derived from the addition polymerizable monomer having an aromatic group is from the viewpoint of releasability of the thermal transfer image-receiving sheet, releasability at high temperature and high humidity, and dyeing property. 70% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, and further preferably substantially 100% by weight.
Other addition polymerizable monomers (a2) include (meth) acrylic acid esters (carbon number 1-18), (meth) acrylic acid esters such as dimethylaminoethyl (meth) acrylate; polyethylene, propylene, butadiene, etc. Olefins; Halovinyls 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-vinylpyrrolidone Can be mentioned.

  The weight ratio of the segment (A2) and the total amount of unsaturated aliphatic carboxylic acid, unsaturated alicyclic carboxylic acid and unsaturated aliphatic alcohol among the raw material monomers of segment (A1) [segment (A2) / segment ( The total of the above-mentioned components having an unsaturated group of A1) 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. Is more preferably 2/1 to 5/1.

[Method for producing resin for thermal transfer image-receiving sheet]
As a method for producing the resin for thermal transfer image-receiving sheets of the present invention, an alcohol component containing 50 mol% or more of a propylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and 50 mol% of an alicyclic carboxylic acid are used. Polyester resin (a1) (hereinafter also referred to as resin (a1)) having a non-aromatic carbon-carbon unsaturated bond is prepared by condensation polymerization with the carboxylic acid component contained above, and the polyester resin (a1) The addition polymerization of the addition polymerizable monomer (a2) in the presence of is preferable.

(Polyester resin (a1))
The resin (a1) is obtained by condensing an alcohol component containing 50 mol% or more of a propylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and a carboxylic acid component containing 50 mol% or more of an alicyclic carboxylic acid. It is a polyester resin having a non-aromatic carbon-carbon unsaturated bond obtained by polymerization, and is preferable for constituting the polyester resin segment (A1). The “non-aromatic carbon-carbon unsaturated bond” is derived from the unsaturated aliphatic carboxylic acid, unsaturated alicyclic carboxylic acid and unsaturated aliphatic alcohol described above.

Resin (a1) includes, as a raw material component, an alcohol component containing 50 mol% or more of a propylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and a carboxylic acid component containing 50 mol% of an alicyclic carboxylic acid. Is obtained.
Here, the propylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and the alicyclic carboxylic acid are the same as the polyester resin segment (A1), and the preferred structure and the preferred content are also the same. It is.

As an alcohol component which is a raw material component of the resin (a1), other alcohol components can be used together with a propylene 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 in the case of the polyester resin segment (A1). You may use alcohol individually or in combination of 2 or more types.

The resin (a1) preferably has a non-aromatic carbon-carbon unsaturated bond, and a carboxylic acid component 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 preferred structure and the preferred content are the same. Cyclohexanedicarboxylic acid and isophthalic acid are preferred, and isophthalic acid is more preferred. Carboxylic acids may be used alone or in combination of two or more.

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, still more preferably 5 to 30 mgKOH / g, More preferably, it is 10-20 mgKOH / 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 the same as that described as the raw material monomer of the segment (A2) made of the above addition polymerization resin, and is an addition polymerizable monomer having an aromatic group (meta ) Acrylic acid alkyl ester and the like are mentioned, and an addition polymerizable monomer having an aromatic group is preferable. Among them, styrene, methylstyrene, benzyl methacrylate and benzyl acrylate are more preferable, and styrene is still more preferable.
The addition-polymerizable monomer having an aromatic group is 70% by weight or more in the addition-polymerizable monomer (a2) from the viewpoint of releasability of the thermal transfer image-receiving sheet, releasability at high temperature and high humidity, and dyeing property. It is preferably 80% by weight or more, more preferably 90% by weight or more, and still more preferably 100% by weight.

[Method for producing resin for thermal transfer image-receiving sheet]
The resin for thermal transfer image receiving sheets of the present invention can be obtained by a method of polymerizing the addition polymerizable monomer (a2) in the presence of the resin (a1). The polymerization method is not limited, and examples thereof include a method in which the resin (a1) and the monomer (a2) are directly mixed and polymerized, a method in which the resin (a1) and the monomer (a2) are dissolved in an organic solvent, and the like. It is done. The thermal transfer image-receiving sheet resin of the present invention is preferably obtained by a method having the following steps (1) and (2).
Step (1): A step of mixing the polyester resin (a1) with an aqueous medium to obtain an aqueous dispersion of the polyester resin (a1).
Step (2): A step of adding the addition polymerizable monomer (a2) to the aqueous dispersion obtained in the step (1) and polymerizing it to obtain an aqueous dispersion of a resin for a thermal transfer image-receiving sheet.

<Step (1)>
Step (1) is a step of mixing the polyester resin (a1) with an aqueous medium to obtain an aqueous dispersion of the polyester resin (a1).
The aqueous medium in which the polyester resin (a1) is dispersed is a water-based medium, 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 100% by weight. Components other than water include alcohol solvents such as methanol, ethanol, isopropanol and butanol; ketone solvents such as acetone, methyl ethyl ketone, diethyl ketone, dipropyl ketone, methyl isobutyl ketone and methyl isopropyl ketone; ether solvents such as tetrahydrofuran And an organic solvent that dissolves in water.

As a method of dispersing the polyester resin (a1) in the aqueous medium, the polyester resin (a1) is dissolved in a ketone solvent, a neutralizing agent described later is added to ionize the carboxyl group of the polyester resin (a1), Next, a method of adding water to invert the phase to the aqueous phase, preferably a method of adding water and then distilling off the ketone solvent to invert to the aqueous phase.
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 the neutralizing agent is added to the polyester resin (a1) dissolved in the ketone solvent. Etc., ionize the carboxyl group (not necessary if already ionized), then add water and invert to the aqueous phase, preferably after adding the water, the ketone solvent is distilled off to the aqueous phase Phase inversion.
The dissolving operation of the polyester resin (a1) in the ketone solvent and the subsequent addition of the neutralizing agent are usually performed at a temperature not higher than the boiling point of the ketone solvent. Examples of the water used include deionized water.

  As the ketone solvent, those mentioned above can be used, and methyl ethyl ketone is preferable from the viewpoint of the solubility of the polyester resin (a1) and the ease of distilling off the solvent.

  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 amount of the neutralizing agent used may be an amount that can neutralize at least the acid value of the polyester resin (a1).

<Step (2)>
In the step (2), the addition-polymerizable monomer (a2) is added to the aqueous dispersion obtained in the step (1) and polymerized to form an aqueous dispersion of a thermal transfer image-receiving sheet resin (hereinafter referred to as an aqueous dispersion (A). It is a process of obtaining also.
First, the addition polymerizable monomer (a2) is added to the aqueous dispersion of the polyester resin (a1). The addition amount is a weight ratio of the polyester resin (a1) and the addition polymerizable monomer (a2) [polyester resin (a1) / addition polymerizable monomer (a2)], preferably 55/45 to 95/5, more preferably 65/35 to 95/5, more preferably 75/25 to 95/5, still more preferably 85/15 to 95/5.
Moreover, you may add water etc. further from the point of the efficiency of stirring.

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.

The glass transition temperature of the graft polymer (A) in the aqueous dispersion (A) obtained as described above is preferably from the viewpoint of storage stability, storage stability of the thermal transfer image-receiving sheet, and dyeability. 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, “volume median particle size (D50)” means a particle size at which the cumulative volume frequency calculated by the volume fraction is 50% when calculated from the smaller particle size. The measuring method is as described in the examples.

[Thermal transfer image-receiving sheet]
The thermal transfer image receiving sheet of the present invention has a dye receiving layer containing the resin for 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.
The thickness of these base materials can be about 10 to 300 μm, 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 in the thermal transfer image receiving sheet of the present invention contains the resin for 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. From the viewpoint of environmental safety and the like, the latter is preferable, and it is more preferable to manufacture by the method including the following steps (3) and (4).
Step (3): A step of preparing a dye-receiving layer coating solution containing an aqueous dispersion of the thermal transfer image-receiving sheet resin obtained in the step (2).
Step (4): A step of providing a dye receiving layer using the dye receiving layer coating solution obtained in the step (3).

<Step (3)>
Step (3) is a step of preparing a dye-receiving layer coating solution containing an aqueous dispersion of the thermal transfer image-receiving sheet resin obtained in step (2).
The dye-receiving layer coating solution preferably 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 thermal transfer image-receiving sheet resin and the aqueous solution of the film-forming agent are mixed and stirred. It is preferable to obtain a coating solution. 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 preferably contains a release agent from the viewpoint of further improving the releasability 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.
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 sharpness of the transferred image. can do. From the viewpoint of the whiteness of the thermal transfer image-receiving sheet of the present invention, these pigments and fillers can be contained in an amount of 0.1 to 20 parts by weight with respect to 100 parts by weight of the resin in the dye-receiving layer coating solution. The dye-receiving layer coating solution may further contain other additives such as a catalyst and a curing agent, if necessary.
The dye-receiving layer coating solution may contain other resins than the thermal transfer image-receiving sheet resin of the present invention as long as the effects of the present invention are not impaired. Specific examples of the other resin include a vinyl chloride polymer, a vinyl chloride vinyl acetate copolymer, a vinyl chloride acrylic copolymer, and a polyurethane. The dyeing property and light resistance of the thermal transfer image-receiving sheet, and the resin dispersion From the viewpoint of dispersibility, a vinyl chloride acrylic copolymer is preferred.
These other resins can also be contained in the dye-receiving layer coating solution by dissolving them in an organic solvent together with the thermal transfer image-receiving sheet resin of the present invention during the resin production process. In addition, the resin dispersion can be added to the aqueous dispersion of the resin for thermal transfer image-receiving sheet and mixed to be contained in the dye-receiving layer coating liquid.

<Process (4)>
Step (4) is a step of providing a dye receiving layer using the dye receiving layer coating solution obtained in step (3).
The dye-receiving layer in the thermal transfer image-receiving sheet of the present invention is obtained by applying and drying a coating solution on one surface of a substrate, and for example, using a gravure printing method, a screen printing method, or a gravure plate It is preferable to apply 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 to be formed 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.

(Middle 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 the intermediate layer more preferably contains 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 degreeC) measured by JISK6503-2001 from the viewpoint of the mold release property and film forming property of a thermal transfer image receiving sheet, Preferably it is 2.5-6.0 mPa * s, More preferably, it is 3. 0 to 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 viewpoint of the dyeing property of the thermal transfer image-receiving sheet and the 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, Acrylic resins such as a mixture thereof, polystyrene, polyvinylidene chloride, polyacrylonitrile, vinylidene chloride-acrylonitrile copolymer, and the like can be used. In the present invention, a styrene-acrylic copolymer, a vinylidene chloride-acrylonitrile copolymer, and the like are preferable from the viewpoint of the dyeing property of the thermal transfer image-receiving sheet and the adhesion between the intermediate layer and the dye-receiving layer in the thermal transfer image-receiving sheet. 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.
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 having a solid concentration of preferably 10 to 40% by weight, more preferably 15 to 35% by weight are used.
The hollow particles have a methyl ethyl ketone (MEK) insoluble content, preferably 70% by weight or less, from the viewpoint of dyeing property 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. Examples of commercially available hollow particles that can be preferably used include “Nipol MH8101” manufactured by Nippon Zeon Co., Ltd. and “SX8782” manufactured by JSR Corporation. (D) "etc. (all are trade names).
The intermediate layer has a weight ratio (hollow particles / water-soluble polymer) of the hollow particles to the water-soluble polymer 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 formed on at least one surface of the base material of the thermal transfer image-receiving sheet by dispersing or dissolving a water-soluble polymer and various additives used as necessary in an organic solvent or water, and applying and drying. be able to.
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 thermal transfer using the thermal transfer image receiving sheet of the present invention is usually obtained by receiving 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 to be transferred onto the image is provided, and any 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 pyridoneazo series, dicyanostyryl series, quinophthalone series, merocyanine series for yellow dyes; benzeneazo series, pyrazolone azomethine series, isothiazole series for magenta dyes, Pyrazolotriazole series: As cyan dyes, anthraquinone series, cyanomethylene series, indophenol series, and indonaphthol series are listed.

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

Production Examples 1-6
(Production of polyester resins (a1) a to f)
The raw material monomer of polyester resin (a1) excluding fumaric acid shown in Table 1 and tin (II) dioctylate salt were mixed with a thermometer, a stainless stir bar, a flow-down condenser, and a nitrogen introduction pipe with an inner volume of 5 liters. The mixture was placed in a one-necked flask, reacted in a mantle heater at 235 ° C. for 5 hours in a nitrogen atmosphere, and further reacted 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. It was made to react and polyester resin (a1) af was obtained.

  About each physical property of obtained polyester resin (a1) af, it measured with the following method. The results are shown in Table 1.

[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 baseline extension line below the maximum peak temperature of endotherm and the tangent showing the maximum slope from the peak rising portion to the peak apex was defined as the glass transition temperature.

[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)).

[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 chloroform 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. Of monodisperse polystyrene; 2.10 × 10 ³ , 7.00 × 10 ³ , 5.04 × 10 ⁴ (weight average molecular weight)) were used as standard samples.
Measuring device: CO-8010 (trade name, manufactured by Tosoh Corporation)
Analytical column: GMHXL + G3000HXL (both trade names, manufactured by Tosoh Corporation)

Production Examples 7-12
(Production of aqueous dispersions (i) to (vi) of polyester resin (a1): Step (1))
Polyester resins (a1) a to f were added to a four-necked flask equipped with a nitrogen inlet tube, a reflux condenser, a stirrer, and a thermocouple in the types and formulations shown in Table 2 and dissolved in methyl ethyl ketone at 25 ° C. 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 (vi) of the polyester resin (a1).
The physical properties of the obtained aqueous dispersions (i) to (vi) were measured by the following methods. The results are shown in Table 2.

[Volume Median Particle Size (D50) of Resin Particles in 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 13-18
(Production of aqueous dispersions (I) to (VI) of resin for thermal transfer image-receiving sheet: Step (2))
A four-necked flask with an internal volume of 2 liters equipped with a nitrogen inlet tube, a reflux condenser, a dropping funnel, a stirrer, and a thermocouple. Styrene (a2) was charged 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 (VI) of resins for thermal transfer image-receiving sheets. In addition, as for the compounding amount of each material, the weight ratio between the polyester resin segment (A1) and the addition polymerization resin segment (A2) in the resin for thermal transfer image-receiving sheet in the obtained aqueous dispersion is as shown in Table 3. Was decided.
The physical properties of the obtained aqueous dispersions (I) to (VI) of the obtained resin for thermal transfer image-receiving sheets were measured by the above-described methods. The results are shown in Table 3.

Examples 1-4 and Comparative Examples 1 and 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, it mixed at 25 degreeC by the composition and compounding quantity shown in Table 4, and produced dye receiving layer coating liquid A1-F1. The aqueous dispersion of the resin for thermal transfer image-receiving sheet used for the preparation of the dye-receiving layer coating solution was adjusted to a solid content concentration of 30% by weight and pH of 9.0 with a 25% aqueous ammonia solution. 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 dye-receiving layer coating solutions is applied to the intermediate layer-coated sheet by a wire bar so as to be 5.0 g / m ² and dried at 50 ° C. for 2 minutes to obtain a thermal transfer image-receiving sheet. It was.

<Evaluation>
(Dyeing property)
A black (K) gradation pattern (L value was changed from 0 to 255 in increments of 15 using a commercially available sublimation printer (trade name, MEGAPICEL III, manufactured by Altec Co., Ltd.) on the produced thermal transfer image-receiving sheet. .6 cm square image), and the transfer color density at the high density print (18th gradation (L = 0: highest density)) is measured with a Gretag densitometer (manufactured by GRETAG-MACBETH). Sex was evaluated. The greater the concentration value, the better the dyeing property. The results are shown in Table 4.

(Releasability)
A black solid of 5 × 5 cm was printed on the produced 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. The results are shown in Table 4.
A: There is no noise and can be peeled off.
B: Although there is abnormal noise, it can be peeled off.
C: It is heat-sealed, peeling is difficult, and chipping is observed in the image.

(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) Measure the optical reflection density of R) and Blue (B), and use the color difference meter (manufactured by Gretag Macbeth) to measure L ^* a ^* b ^* before and after irradiation for steps where the optical reflection density before irradiation is around 1.0. The hue change amount was calculated by the following formula, and the light resistance of each black (K) + chromatic print was evaluated. 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 )

  As is clear from Table 4, compared with the thermal transfer image receiving sheets of Comparative Examples 1 and 2, each of the thermal transfer image receiving sheets of Examples 1 to 4 has a high maximum density at the time of high density printing and excellent dyeing property. In solid continuous printing, the ink ribbon and the image receiving sheet are excellent in releasability without thermal fusion, and the printed material is less likely to fade and has excellent light resistance. .

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

Claims (8)

  A thermal transfer image-receiving sheet resin comprising a graft polymer composed of a main chain segment (A1) made of a polyester resin and a side chain segment (A2) made of an addition polymerization resin, wherein the segment (A1) is 2, 2 A segment (A2) obtained by polycondensation of an alcohol component containing 50 mol% or more of a propylene oxide adduct of bis (4-hydroxyphenyl) propane and a carboxylic acid component containing 50 mol% or more of an alicyclic carboxylic acid. ) Contains 70% by weight or more of a structural unit derived from an addition polymerizable monomer having an aromatic group.   The resin for a thermal transfer image receiving sheet according to claim 1, wherein the weight ratio of the segment (A1) to the segment (A2) [segment (A1) / segment (A2)] is 55/45 to 95/5.   Resin for thermal transfer image receiving sheets of Claim 1 or 2 in which the carboxylic acid component of a segment (A1) contains 5-30 mol% in total of unsaturated aliphatic carboxylic acid and unsaturated alicyclic carboxylic acid.   Weight ratio of segment (A2) to the total amount of unsaturated aliphatic carboxylic acid, unsaturated alicyclic carboxylic acid and unsaturated aliphatic alcohol which are raw material monomers of segment (A1) [segment (A2) / segment The resin for a thermal transfer image receiving sheet according to claim 3, wherein (total of the components having an unsaturated group of (A1)] is 1/1 to 15/1.   The resin for thermal transfer image receiving sheets according to any one of claims 1 to 4, wherein the alicyclic carboxylic acid is 1,4-cyclohexanedicarboxylic acid.   Resin for thermal transfer image receiving sheets in any one of Claims 1-5 in which the alcohol component of a segment (A1) contains 1, 2- propanediol.   The thermal transfer image receiving sheet which has a dye receiving layer containing the resin for thermal transfer image receiving sheets in any one of Claims 1-6. Step (1): an alcohol component containing 50 mol% or more of a propylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane, 50 mol% or more of an alicyclic carboxylic acid, an unsaturated aliphatic carboxylic acid, and A polyester resin (a1) having a non-aromatic carbon-carbon unsaturated bond is prepared by condensation polymerization with a carboxylic acid component containing an unsaturated alicyclic carboxylic acid, and the polyester resin (a1) Step of obtaining an aqueous dispersion of the polyester resin (a1) by mixing with an aqueous medium, and Step (2): An addition polymerizable monomer having an aromatic group is added to the aqueous dispersion obtained in Step (1). A method for producing a resin for thermal transfer image-receiving sheets, comprising a step of adding and polymerizing an addition polymerizable monomer (a2) containing 70% by weight or more to obtain an aqueous dispersion of a graft polymer.