JP2013001080A - Resin for thermal transfer image receiving sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin for a thermal transfer image receiving sheet which makes it possible to manufacture a thermal transfer image receiving sheet having excellent dyeing property and excellent mold releasability in both high image concentration area and low image concentration area, and to provide the thermal transfer image receiving sheet and manufacturing methods for them.SOLUTION: The resin for the thermal transfer image forming sheet contains a graft polymer composed of a main chain segment (A1) made of a polyester resin having a carboxy group as an acid group and a carboxy group derived acid number of 5 to 40 mgKOH/g and a side chain segment (A2) made of an addition polymer-based resin. The main chain segment (A1) is a resin obtained by polycondensation of an alcohol component containing 60 mol% or more of an alkylene oxide adduct of a 2,2-bis (4-hydroxyphenyl) propane and a carboxylic acid component. The side chain segment (A2) is composed of component units derived from a styrene and a (meta) acrylic acid alkyl having an alkyl group carrying 12 to 22 carbon atoms. In the side chain segment (A2), a weight ratio between the component unit derived from the styrene and the component unit derived from the (meta) acrylic acid alkyl, i.e., styrene/(meta) acrylic acid alkyl having the alkyl group carrying 12 to 22 carbon atoms is 20/80 to 90/10.

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 resin for the thermal transfer image receiving sheet and a method for producing the 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 or the like 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, and a polyester resin is used as the dye receiving layer.

For example, Patent Document 1 discloses a dye 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. A dye-receiving material for thermal sublimation printing comprising a receiving layer and a support is disclosed.
Patent Document 2 discloses a polyester containing an alcohol component containing 80 mol% or more of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane for the purpose of improving dyeability and releasability of dyes. A thermal transfer image-receiving sheet resin obtained by addition polymerization and polycondensation of a raw material monomer, an addition polymerization resin raw material monomer containing styrene and the like, and a bi-reactive monomer such as acrylic acid is disclosed. .

JP-A-4-318989 JP 2010-131906 A

Since the printing is performed by coloring the dye from the ink sheet to the thermal transfer image receiving sheet by heating from the thermal head, a high dye dyeing property is required to express the target color. It is said.
Further, there has been a problem that during the coloring, fusion is likely to occur between the ink sheet and the thermal transfer image receiving sheet. In particular, in a high image density region, high energy is applied to the ink sheet and the image receiving sheet at the time of printing, so that fusion is likely to occur, and there is a problem in releasability.
On the other hand, even in the low image density region, all the ink portions are transferred to the image receiving sheet so that the ink portions are peeled off from the ink sheet, and there is a problem in releasability.
From the viewpoint of compatibility between dyeability and releasability in both the high image density region and the low image density region, there is still room for improvement in the thermal transfer image receiving sheets described in Patent Documents 1 and 2.
Therefore, thermal transfer image receiving having high releasability in both the high image density region and the low image density region by suppressing the dyeing property of the high dye, fusing with the ink sheet, and peeling of the ink part of the ink sheet. A sheet is desired.

  The present invention provides a thermal transfer image-receiving sheet resin that can produce a thermal transfer image-receiving sheet that has excellent dyeing properties and has excellent releasability in both high and low image density regions, and a dye-receiving layer containing the resin. It is an object of the present invention to provide a thermal transfer image receiving sheet, a resin for the thermal transfer image receiving sheet, and a method for producing the thermal transfer image receiving sheet.

  The present inventors consider that the factors affecting the dyeing property, the releasability in the high image density region and the releasability in the low image density region are the state of the dye receiving layer when heated by the thermal head. And examined. As a result, the above problem can be solved by using a resin containing a graft polymer composed of a main chain segment composed of a specific polyester resin and a side chain segment composed of a specific addition polymerization resin for the dye-receiving layer. I found it.

That is, the present invention provides the following [1] to [4].
[1] A main chain segment (A1) made of a polyester resin having a carboxy group as an acid group and having an acid value derived from the carboxy group of 5 to 40 mgKOH / g, and a side chain segment (A2) made of an addition polymerization resin A resin for a thermal transfer image-receiving sheet comprising a graft polymer, wherein the segment (A1) includes an alcohol component containing 60 mol% or more of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane; It is a polyester resin obtained by condensation polymerization with a carboxylic acid component, and the segment (A2) consists of a structural unit derived from styrene and an alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms, In the segment (A2), the structural unit derived from the styrene and the alkyl group having 12 to 22 carbon atoms Thermal transfer image receiving, wherein the weight ratio (styrene / alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms) to the structural unit derived from the alkyl (meth) acrylate is 20/80 to 90/10 Sheet resin.
[2] A thermal transfer image receiving sheet having a dye receiving layer containing the resin for thermal transfer image receiving sheet of [1].
[3] The method for producing a resin for a thermal transfer image receiving sheet according to the above [1], comprising the following steps (1) and (2).
Step (1): Non-aromatic carbon-obtained by condensation polymerization of an alcohol component containing 60 mol% or more of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and a carboxylic acid component A polyester resin (a1) having a carbon unsaturated bond, having a carboxy group as an acid group, and having an acid value of 5 to 40 mg KOH / g derived from the carboxy group is prepared. The polyester resin (a1) is prepared by dissolving an alkyl (meth) acrylate having 12 to 22 alkyl groups in an organic solvent, adding a neutralizing agent, and then mixing with an aqueous medium to invert the phase to an aqueous phase. Step (2) for obtaining an aqueous dispersion of (meth) acrylic acid having styrene and an alkyl group having 12 to 22 carbon atoms in the aqueous dispersion in the aqueous dispersion obtained in the step (1) Styrene is added so that the weight ratio to rualkyl (styrene / alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms) is 20/80 to 90/10, and polymerized to contain a graft polymer. Step 4 of obtaining an aqueous dispersion of a resin for thermal transfer image-receiving sheets [4] A dye-receiving layer coating solution containing an aqueous dispersion of a resin for thermal transfer image-receiving sheets obtained by the production method described in [3] above, A method for producing a thermal transfer image-receiving sheet, comprising a step of providing a dye-receiving layer using the dye-receiving layer coating solution.

  The resin for thermal transfer image-receiving sheets of the present invention can provide a thermal transfer image-receiving sheet having excellent dyeing properties and excellent releasability in both high and low image density regions. Therefore, the thermal transfer image-receiving sheet having the dye-receiving layer containing the resin is less likely to cause fusion with the ink sheet due to heat or peeling of the ink portion of the ink sheet during printing.

[Resin for thermal transfer image-receiving sheet]
The thermal transfer image-receiving sheet resin of the present invention has a main chain segment (A1) (hereinafter referred to as “segment”) comprising a polyester resin having a carboxy group as an acid group and an acid value derived from the carboxy group of 5 to 40 mgKOH / g (Also referred to as (A1) ") and a side chain segment (A2) made of an addition polymerization resin (hereinafter also referred to as" segment (A2) ").
Here, the segment (A1) is a main chain in the graft polymer, and is a polycondensation of an alcohol component containing 60 mol% or more of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and a carboxylic acid component. It is a polyester resin obtained.
The segment (A2) is a side chain in the graft polymer, and includes a structural unit derived from styrene and an alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms. In the segment (A2), Weight ratio of structural unit derived from styrene and structural unit derived from alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms (styrene / having alkyl group having 12 to 22 carbon atoms (meta ) Alkyl acrylate) is 20/80 to 90/10.

Although the thermal transfer image-receiving sheet having the resin for a thermal transfer image-receiving sheet of the present invention in the dye-receiving layer is excellent in dyeability, it is not clear why it has excellent releasability in both the high image density region and the low image density region. It is considered as follows.
The raw material monomer of the segment (A1) in the graft polymer contained in the thermal transfer image-receiving sheet resin of the present invention contains an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane as an alcohol component. Since this compound has two aromatic rings derived from 2,2-bis (4-hydroxyphenyl) propane in the molecule, that is, a structure similar to a dye, it has a high affinity with the dye and dyes the thermal transfer image-receiving sheet. Contributes to improvement of wearability, and because it has a rigid and low moisture affinity structure, the resin becomes hard and contributes to improvement of releasability in the high image density region of the thermal transfer image-receiving sheet. it is conceivable that.

In addition, the segment (A2) in the graft polymer, particularly the portion derived from styrene, has a structure different from that of the main chain segment (A1) made of the polyester resin having the structure described above, and is difficult to be compatible. As a result, the permeability of the dye from the interface is increased, and a portion having poor affinity with the ink sheet is oriented on the surface of the dye receiving layer. Thereby, it is considered that the dyeing property and release property of the thermal transfer image receiving sheet are greatly improved.
Furthermore, the segment (A2) contains a structural unit derived from an alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms in a specific weight ratio. Therefore, hydrophobicity can be imparted to the side chain of the graft polymer, the affinity with the ink sheet is lowered, and flexibility can be imparted. It is possible to leave. This is considered to improve the releasability in the low image density region.

  Moreover, in this invention, a segment (A1) has a carboxy group as an acid group, and an acid value is 5-40 mgKOH / g. The carboxy group uniformly disperses the rigid polyester resin segment (A1) and addition polymerization resin segment (A2) having poor dispersibility in the liquid, and as a result, the surface of the dye receiving layer becomes smooth. Therefore, it is considered that the dyeing property and the release property can be improved.

  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%, still more preferably substantially, from the viewpoints of dyeability and releasability. Is 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 is the main chain in the graft polymer.
Since the segment (A1) is a segment composed of a polyester resin, the segment (A1) is composed of a structural unit derived from an alcohol component and a structural unit derived from a carboxylic acid component. Hereinafter, an alcohol component and a carboxylic acid component used as a raw material monomer from which the structural unit of the segment (A1) is derived (hereinafter also simply referred to as a raw material monomer of the segment (A1)) will be described.

In this invention, 60 mol% or more of alkylene oxide adducts of 2,2-bis (4-hydroxyphenyl) propane are contained as an alcohol component which is a raw material monomer of the segment (A1).
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 alkyleneoxy groups, preferably each independently an alkyleneoxy group having 1 to 4 carbon atoms, more preferably an ethyleneoxy group or a propyleneoxy group. It is.
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 a propyleneoxy 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 releasability of the thermal transfer image-receiving sheet, particularly releasability in a high image density region, and dyeing property, the content of the propyleneoxy group is preferably 50 to 100 mol% in the alkyleneoxy group. Preferably it is 60-100 mol%, More preferably, it is 70-100 mol%, More preferably, it is 85-100 mol%, More preferably, it is substantially 100 mol%.
The other alkyleneoxy group is preferably an ethyleneoxy group or a trimethyleneoxy group, and more preferably an ethyleneoxy group, from the viewpoint of dyeability of the thermal transfer image-receiving sheet.

The content of the alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane is 60 mol% or more in the alcohol component from the viewpoint of releasability and dyeing property of the thermal transfer image-receiving sheet, preferably Is 70 mol% or more, more preferably 80 mol% or more, still more preferably 90 mol% or more, and still more preferably substantially 100 mol%. When the content is less than 60 mol%, the affinity with the dye is lowered, the dyeing property of the thermal transfer image-receiving sheet is inferior, the resin becomes soft, and the releasability in the high image density region of the thermal transfer image-receiving sheet. Is unfavorable because of lowering.
In the present invention, the alkylene oxide adduct means the entire structure in which an alkyleneoxy 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 an alcohol component other than this, together with an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane.
Specifically, as the raw material monomer for the segment (A1), an alcohol having a non-aromatic carbon-carbon unsaturated bond is preferable. As the alcohol having a non-aromatic carbon-carbon unsaturated bond, an unsaturated aliphatic alcohol is preferable from the viewpoint of improving the dyeability and releasability of the thermal transfer image-receiving sheet. 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 unsaturated aliphatic alcohol include unsaturated aliphatic alcohols such as allyl alcohol.
Other alcohol components include, for example, ethylene glycol, propylene glycol (1,2-propanediol), glycerin, pentaerythritol, trimethylolpropane, hydrogenated bisphenol A, sorbitol, or alkylene thereof (2 to 4 carbon atoms). Examples include oxide adducts (average number of added moles of 1 to 16).
These alcohol components may be used alone or in combination of two or more.

  The carboxylic acid component that is a raw material monomer of the segment (A1) contains a carboxylic acid having a non-aromatic carbon-carbon unsaturated bond from the viewpoint of improving the dyeability and releasability of the thermal transfer image-receiving sheet. Is preferable, and it is more preferable that an unsaturated aliphatic carboxylic acid and / or an unsaturated alicyclic carboxylic acid is included. The carbon-carbon unsaturated bond portion is preferably a bond portion with the segment (A2) in the graft polymer. 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. Examples thereof include unsaturated alicyclic carboxylic acids such as tetrahydrophthalic acid, and anhydrides of these acids. Among these, fumaric acid, maleic acid, and tetrahydrophthalic acid are preferable from the viewpoint of reactivity, and fumaric acid is more preferable.

  The content of the unsaturated aliphatic carboxylic acid and / or the unsaturated alicyclic carboxylic acid as the raw material monomer from which the structural unit of the segment (A1) is derived is a viewpoint of improving the dyeability and releasability of the thermal transfer image-receiving sheet. Therefore, in the carboxylic acid component, it is preferably 5 to 30 mol%, more preferably 7 to 25 mol%, still more preferably 10 to 20 mol%.

Examples of other carboxylic acids include 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; cyclohexanedicarboxylic acid Alicyclic dicarboxylic acids such as acids and decalin dicarboxylic acids; Trivalent or higher polyvalent carboxylic acids such as trimellitic acid and pyromellitic acid, and anhydrides of these acids and their alkyl (1 to 3 carbon atoms) esters Etc. Among these, aromatic dicarboxylic acid and alicyclic dicarboxylic acid are preferable, and cyclohexanedicarboxylic acid and isophthalic acid are more preferable from the viewpoint of dyeability of the thermal transfer image-receiving sheet.
These carboxylic acid components may be used alone or in combination of two or more.

  As a raw material monomer having a non-aromatic carbon-carbon unsaturated bond in the raw material monomer derived from the structural unit of the main chain segment (A1), from the viewpoint of improving the dyeability and releasability of the thermal transfer image-receiving sheet It is preferable that 1 or more types chosen from unsaturated aliphatic carboxylic acid, unsaturated alicyclic carboxylic acid, and unsaturated aliphatic alcohol are included. Among these, from the viewpoint of reactivity, it is preferable to include an unsaturated aliphatic carboxylic acid and / or an unsaturated alicyclic carboxylic acid, and only an unsaturated aliphatic carboxylic acid and / or an unsaturated alicyclic carboxylic acid is contained. More preferably.

  In the present invention, the acid group contained in the segment (A1) has a carboxy group. The content of the carboxy group is preferably 90 mol% or more, more preferably 95 mol%, still more preferably substantially 100 mol% of the acid groups in the segment (A1). A sulfonic acid group is mentioned as an acid group contained in segment (A1) other than a carboxy group. The content of the sulfonic acid group is preferably 10 mol% or less, more preferably 5 mol% or less, and still more preferably substantially free (0 mol%) of the acid groups in the segment (A1). When many sulfonic acid groups are contained, the water solubility becomes too high, and the reactivity with the monomer of the side chain segment (A2) becomes poor. Further, the interaction with the dye is weakened, and the dyeing property and releasability which are the effects of the present invention are inferior.

The acid value of the segment (A1) is 5 to 40 mgKOH / g, preferably 7 to 35 mgKOH / g, more preferably 10 to 30 mgKOH / g, from the viewpoint of releasability and storage stability of the thermal transfer image-receiving sheet. Yes, more preferably 15-25 mg KOH / g, still more preferably 18-23 mg KOH / g.
If it is less than 5 mgKOH / g, it becomes difficult to uniformly disperse the segment (A1) and segment (A2) having poor dispersibility in the liquid, and the surface of the dye receiving layer to be formed is not smooth, and thermal transfer image receiving The dyeability and releasability of the sheet are poor. If it exceeds 40 mgKOH / g, the hydrophilicity of the dye-receiving layer is increased, so the affinity with the ink sheet is increased and the releasability of the thermal transfer image-receiving sheet is inferior.

Further, the number average molecular weight of the segment (A1) is preferably 1,000 to 10,000, more preferably 2,500 to 6,000, and still more preferably, from the viewpoint of film forming properties when used in the dye-receiving layer. Is 3,000 to 5,000.
In addition, in this invention, an acid value and a number average molecular weight show the value measured by the method as described in an Example (hereinafter the same).

  The segment (A1) may be modified to such an extent that the characteristics are not substantially impaired within the above range. In the present invention, the content of the polyester portion in the segment (A1) is preferably 50 to 100% by weight, more preferably 70 to 100% by weight, and more preferably 70 to 100% by weight, from the viewpoint of releasability and dyeing property of the thermal transfer image-receiving sheet. Preferably it is 85-100 weight%, More preferably, it is substantially 100 weight%.

(Side chain segment (A2) made of addition polymerization resin)
The segment (A2) is a side chain in the graft polymer and is composed of structural units derived from styrene and an alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms.
In the present invention, (meth) acrylic acid refers to both methacrylic acid and acrylic acid.

The number of carbon atoms of the alkyl group of the alkyl (meth) acrylate used in the present invention is 12 to 22 from the viewpoint of dyeability of the thermal transfer sheet and releasability in both the high image density region and the low image density region. However, Preferably it is 12-20, More preferably, it is 12-18, More preferably, it is 16-18.
Examples of the alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms include alkyl methacrylate having an alkyl group having 12 to 22 carbon atoms and alkyl acrylate having an alkyl group having 12 to 22 carbon atoms. From the viewpoint of dyeability of the thermal transfer sheet and releasability in both the high image density region and the low image density region, alkyl methacrylate having an alkyl group having 12 to 22 carbon atoms is preferable.
Examples of the alkyl methacrylate having an alkyl group having 12 to 22 carbon atoms include lauryl methacrylate, stearyl methacrylate, behenyl methacrylate, and the like, but the dyeing property of the thermal transfer sheet and the high image density region and the low image density region. From the viewpoint of releasability in both, lauryl methacrylate and stearyl methacrylate are preferred, and stearyl methacrylate is more preferred.

In the present invention, in the segment (A2), the weight ratio of the structural unit derived from styrene to the structural unit derived from alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms (styrene / carbon). The alkyl (meth) acrylate having an alkyl group of several 12 to 22 is 20/80 to 90/10 from the viewpoint of dyeability and releasability in both the high image density region and the low image density region. However, it is preferably 25/75 to 87/13, more preferably 35/65 to 85/15, still more preferably 40/60 to 80/20, and still more preferably 45/55 to 75/25.
When the weight ratio is less than 20/80, the content of the structural unit derived from styrene is insufficient, so that the dyeing property and the release property are inferior. On the other hand, when it exceeds 90/10, the content of the structural unit derived from the alkyl (meth) acrylate is insufficient, so that the releasability is particularly poor in a low image density region.

  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 5/1 to 14/1, from the viewpoint of dyeability and releasability of the thermal transfer image-receiving sheet. Is more preferably 10/1 to 13/1.

The weight ratio [segment (A1) / segment (A2)] of the segment (A1) and the segment (A2) constituting the graft polymer is preferably 55 from the viewpoint of dyeing property and releasability of the thermal transfer image-receiving sheet. / 45 to 95/5, more preferably 60/40 to 93/7, still more preferably 65/35 to 90/10, still more preferably 67/13 to 85/15.
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 acid value of the thermal transfer image-receiving sheet resin is preferably 5 to 40 mgKOH / g, more preferably 5 to 35 mgKOH / g, from the viewpoint of the releasability of the thermal transfer image-receiving sheet and the stability of the aqueous dispersion of the thermal transfer image-receiving sheet resin. More preferably, it is 10-35 mgKOH / g.

[Method for producing resin for thermal transfer image-receiving sheet]
The method for producing a resin for a thermal transfer image-receiving sheet of the present invention is obtained by condensation polymerization of an alcohol component containing 60 mol% or more of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and a carboxylic acid component. A polyester resin (a1) (hereinafter, also referred to as “resin (a1)”) was prepared, and an alkyl (meth) acrylate and styrene having an alkyl group having 12 to 22 carbon atoms in the presence of the polyester resin (a1). A polymerization method is preferred.

(Polyester resin (a1))
The resin (a1) is a polyester resin obtained by condensation polymerization of an alcohol component containing 60 mol% or more of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and a carboxylic acid component.
The resin (a1) has a non-aromatic carbon-carbon unsaturated bond, has a carboxy group as an acid group, and an acid value derived from the carboxy group is 5 to 40 mgKOH / g, It is preferable for constituting the main chain segment (A1) made of a polyester resin.
In addition, said "non-aromatic carbon-carbon unsaturated bond" is 1 selected from the above-mentioned unsaturated aliphatic carboxylic acid, unsaturated alicyclic carboxylic acid and unsaturated aliphatic alcohol used as a raw material monomer. It comes from more than a seed.

Resin (a1) is obtained using an alcohol component containing 60 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 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). These alcohols may be used alone or in combination of two or more.

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 10 to 20 mol%. It is.
Other carboxylic acids are the same as those in the segment (A1), and cyclohexanedicarboxylic acid and isophthalic acid are preferable, and isophthalic acid is more preferable. 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 and di (2-ethylhexanoic acid) tin 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.

The softening point of the resin (a1) is preferably 80 to 165 ° C., more preferably 85 to 130 ° C., from the viewpoint of releasability and storage stability of the thermal transfer image receiving sheet.
From the same viewpoint, the glass transition temperature of the resin (a1) is preferably 50 to 85 ° C, more preferably 52 to 70 ° C.
In addition, in this invention, a softening point and a glass transition temperature show the value measured by the method as described in an Example (hereinafter the same).
The acid value of the resin (a1) is 5 to 40 mgKOH / g, preferably 7 to 35 mgKOH / g, more preferably 10 to 30 mgKOH / g, from the viewpoint of releasability and storage stability of the thermal transfer image-receiving sheet. More preferably, it is 15-25 mgKOH / g, More preferably, it is 18-23 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.
The number average molecular weight of the resin (a1) is preferably 1,000 to 10,000, more preferably 2,500 to 6,000, and still more preferably, from the viewpoint of film forming properties when used in the dye-receiving layer. Is 3,000 to 5,000.

In the present invention, the resin (a1) may be modified within the above range so as not to substantially impair the characteristics.
In the present invention, the content of the polyester portion in the resin (a1) is preferably 50 to 100% by weight, more preferably 70 to 100% by weight, and still more preferably, from the viewpoint of dyeability and releasability of the thermal transfer image receiving sheet. Is 85 to 100% by weight, more preferably substantially 100% by weight.

(Alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms)
The alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms used in the present invention is the same as that described as the raw material monomer for the segment (A2) comprising the above addition polymerization resin, and lauryl methacrylate. , Stearyl methacrylate, behenyl methacrylate and the like, lauryl methacrylate and stearyl methacrylate are preferable, and stearyl methacrylate is more preferable.

(Method for producing resin for thermal transfer image receiving sheet)
The resin for a thermal transfer image receiving sheet of the present invention can be obtained by a method of polymerizing the alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms and styrene in the presence of the resin (a1). There is no restriction | limiting in the polymerization method, Resin (a1) and the method of superposing | polymerizing by directly mixing (meth) acrylic-acid alkyl and styrene which have a C12-C22 alkyl group, Resin (a1) and C12-C12 Examples thereof include a method of polymerizing by dissolving an alkyl (meth) acrylate having 22 alkyl groups and styrene in an organic solvent.
Among these, it is preferable to obtain the resin for a thermal transfer image receiving sheet of the present invention by a method having the following steps (1) and (2).
Step (1): Non-aromatic carbon-obtained by condensation polymerization of an alcohol component containing 60 mol% or more of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and a carboxylic acid component A polyester resin (a1) having a carbon unsaturated bond, having a carboxy group as an acid group, and having an acid value of 5 to 40 mg KOH / g derived from the carboxy group is prepared. The polyester resin (a1) is prepared by dissolving an alkyl (meth) acrylate having 12 to 22 alkyl groups in an organic solvent, adding a neutralizing agent, and then mixing with an aqueous medium to invert the phase to an aqueous phase. Step (2) for obtaining an aqueous dispersion of (meth) acrylic acid having styrene and an alkyl group having 12 to 22 carbon atoms in the aqueous dispersion in the aqueous dispersion obtained in the step (1) Styrene is added so that the weight ratio to rualkyl (styrene / alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms) is 20/80 to 90/10, and polymerized to contain a graft polymer. A step of obtaining an aqueous dispersion of resin for thermal transfer image-receiving sheet.

<Step (1)>
In step (1), an alcohol component containing 60 mol% or more of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and a carboxylic acid component are first subjected to polycondensation to produce a non-aromatic A polyester resin (a1) having a carbon-carbon unsaturated bond, having a carboxy group as an acid group, and an acid value derived from the carboxy group of 5 to 40 mgKOH / g is prepared. And after dissolving the obtained polyester resin (a1) and the alkyl (meth) acrylate which has a C12-C22 alkyl group in an organic solvent, and adding a neutralizer, it mixes with an aqueous medium, water The phase is phase-inverted to obtain an aqueous dispersion of the polyester resin (a1).

The method for preparing the polyester resin (a1) is as described above. That is, it can be produced by polycondensing an alcohol component containing an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and a carboxylic acid component.
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. 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 from the viewpoint of environmental safety.
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 for dispersing the polyester resin (a1) in an aqueous medium, the polyester resin (a1) and an alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms are dissolved in an organic solvent, and neutralization described later. A method in which a carboxyl group of the polyester resin (a1) is ionized by adding an agent, and then water is added to invert the phase to an aqueous phase, preferably, after adding water, the organic solvent is distilled off to invert the phase to the aqueous phase. Are preferred.
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 neutralizer or the like is added to the polyester resin (a1) dissolved in an organic solvent. , Ionize the carboxyl group (unnecessary if already ionized), then add water and invert to the aqueous phase. After adding water, the organic solvent is distilled off to the aqueous phase. Phase inversion is preferred.
The operation of dissolving the polyester resin (a1) in the organic solvent and the subsequent addition of the neutralizing agent are preferably performed at a temperature not higher than the boiling point of the organic solvent to be used. Moreover, as water to be used, deionized water etc. are mentioned, for example.

  Thus, in this step, the (alkyl) (meth) acrylate having a hydrophobic alkyl group having 12 to 22 carbon atoms is mixed with the polyester resin (a1) to be added in the subsequent step (2). It is considered that the copolymerization with styrene and the bonding with the polyester resin (a1) can be promoted with high reaction efficiency, and consequently, both the dyeing property and the high image density region and the low image density region, which are the effects of the present invention. A thermal transfer image-receiving sheet having excellent releasability can be obtained.

  As the organic solvent, those described above can be used. From the viewpoint of the solubility of the polyester resin (a1) and the ease of distilling off the solvent, a ketone solvent is preferable, and methyl ethyl ketone is more preferable.

  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.

The solid content concentration of the aqueous dispersion of the polyester resin (a1) obtained as described above is preferably 20 to 50% by weight, more preferably 25 to 45% by weight from the viewpoint of the dispersibility and productivity of the resin particles. %, More preferably 30 to 45% by weight, and the pH at 25 ° C. is preferably 5 to 9, more preferably 5.5 to 8, and further preferably 6 to 6 from the viewpoint of the storage stability of the aqueous dispersion. 7.
The volume median particle size (D ₅₀ ) of the resin particles in the aqueous dispersion is preferably 50 to 500 nm, more preferably 75 to 200 nm, and still more preferably 100 to 140 nm, from the viewpoint of the dispersibility of the resin particles. Here, “volume median particle size (D ₅₀ )” 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.

<Step (2)>
In step (2), in the aqueous dispersion obtained in step (1), the weight ratio of styrene and alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms in the aqueous dispersion (styrene / Aqueous dispersion of resin for thermal transfer image-receiving sheet containing graft polymer by adding styrene and polymerizing (alkyl (meth) acrylate having alkyl group having 12 to 22 carbon atoms) to 20/80 to 90/10 This is a step of obtaining a liquid (hereinafter also referred to as “aqueous dispersion (A)”).

First, styrene is added to the aqueous dispersion of the polyester resin (a1) obtained in the step (1). In addition, water or the like may be further added from the viewpoint of stirring efficiency.
In this step, from the viewpoint of dyeability and releasability in both the high image density region and the low image density region, styrene and (meth) acrylic having an alkyl group having 12 to 22 carbon atoms in the aqueous dispersion Styrene is added so that the weight ratio with the acid alkyl (styrene / alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms) is 20/80 to 90/10. The weight ratio is 20/80 to 90/10, preferably 25/75 to 87/13, more preferably 35/65 to 85/15, still more preferably 40/60 to 80/20, and more. More preferably, it is 45 / 55-75 / 25.

  Further, the weight ratio of the polyester resin (a1) and the total amount of styrene and alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms [polyester resin (a1) / styrene and alkyl having 12 to 22 carbon atoms]. The total amount of alkyl (meth) acrylate having a group] is preferably 55/45 to 95/5, more preferably 60/40 to 93/7, from the viewpoint of dyeability and releasability of the thermal transfer image-receiving sheet. Furthermore, it is preferable to add styrene so that it becomes 65/35 to 90/10, more preferably 67/13 to 85/15. That is, it is preferable to add so that the weight ratio of the segment (A1) and the segment (A2) constituting the graft polymer obtained may be the same.

Next, styrene and alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms are polymerized in the presence of the polyester resin (a1).
In the polymerization, it is preferable to add an arbitrary radical polymerization initiator, a crosslinking agent and the like 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), styrene, and an alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms. 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 in the aqueous dispersion (A) obtained as described above is preferably 40 to 80 from the viewpoints of storage stability and storage stability and dyeing property of the thermal transfer image-receiving sheet. ° C, more preferably 50 to 75 ° C, still more preferably 60 to 70 ° C.
The solid content concentration of the aqueous dispersion (A) is preferably 20 to 50% by weight, more preferably 25 to 45% by weight, and still more preferably 30 to 40% by weight from the viewpoint of the dispersibility and productivity of the resin particles. is there.
The pH of the aqueous dispersion (A) at 25 ° C. is preferably 5 to 10, more preferably 5.5 to 9, still more preferably 6 to 8 from the viewpoint of storage stability of the aqueous dispersion (A). It is.
The volume median particle size (D ₅₀ ) of the resin particles in the aqueous dispersion (A) is preferably 30 to 500 nm, more preferably 90 to 150 nm, more preferably 90 to 150 nm, from the viewpoint of film forming properties when obtaining a thermal transfer image-receiving sheet. Preferably it is 95-120 nm.

[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 substrates is not particularly limited, but is preferably 10 to 300 μm, for example. From the viewpoint of improving the adhesion to the dye receiving layer, it is preferable to subject the surface of the substrate 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. However, from the viewpoint of environmental safety and the like, the latter is preferable, and it is more preferable to manufacture by performing the following steps (3) to (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 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 used as appropriate, and a polyether-modified silicone is preferable.

  The compounding amount of these release agents is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the resin for thermal transfer image receiving sheet obtained in the step (2) in the dye receiving layer coating solution. More preferably, it is 0.5 to 10 parts by weight. As commercially available products of these release agents, “KF-615A” (trade name) manufactured by Shin-Etsu Chemical Co., Ltd. can be preferably used.

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, and gelatin is preferable from the viewpoint of the strength and releasability of the dye receiving layer.
As the viscosity of the film-forming agent, the viscosity (60 ° C.) measured according to 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. Preferably, it is 3.0 to 5.5 mPa · s.
The amount of the film-forming agent is preferably 0.1 to 20 parts by weight, based on 100 parts by weight of the thermal transfer image-receiving sheet resin obtained in step (2), in the dye-receiving layer coating solution. More preferably, it is 0.5 to 10 parts by weight.

  Further, from the viewpoint of uniformly dissolving the film-forming agent, it is preferable to previously dissolve the film-forming agent in water, and an aqueous dispersion of the resin composition for a thermal transfer image-receiving sheet and an aqueous solution of the film-forming agent are mixed. It is more preferable to obtain a coating solution by stirring. A ball mill etc. are mentioned as an agitator used suitably. The stirring temperature at this time is preferably 30 to 60 ° C, more preferably 40 to 50 ° C, from the viewpoint of uniformly mixing the film-forming agent in a dissolved state.

  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, the blending amount of these pigments and fillers is 100 parts by weight of the resin for the thermal transfer image-receiving sheet obtained in step (2) in the dye-receiving layer coating solution. On the other hand, it is preferably 0.1 to 20 parts by weight, more preferably 0.5 to 10 parts by weight. 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. Alternatively, the resin dispersion may be added to the aqueous dispersion of the resin composition for a thermal transfer image-receiving sheet and mixed to be contained in the dye-receiving layer coating liquid.
The preparation of the dye-receiving layer coating solution may be performed by mixing the above-mentioned components. In particular, in order to uniformly disperse or dissolve the release agent, it is preferable to use a stirrer such as a ball mill. The melting temperature is preferably 20 to 40 ° C.

<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 not particularly limited, but is preferably 1 to 50 μm, more preferably 3 to 15 μm from the viewpoint of image quality and productivity. The solid content after drying is preferably 3 to 15 g, more preferably 4 to 10 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 from the viewpoint of dyeability. The intermediate layer 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, and polyvinyl pyrrolidone. Among these, gelatin is preferable from the viewpoint of thermal characteristics of having a gelation temperature of an aqueous solution near room temperature of 10 to 30 ° C.
As the viscosity of the water-soluble polymer, the viscosity (60 ° C.) measured according to 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 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, based on the entire intermediate layer.

<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 made 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 obtained by heating and foaming the above-mentioned 2) by heating the particles coated with a resin to heat the particles so that the low-boiling liquid in the particles expands to become hollow. 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 method 1) or 3) are preferred from the viewpoints 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.

  The material constituting the hollow particles is not particularly limited, and various known materials used in the methods 1) to 3) can be mentioned. For example, polyacrylic acid, polyacrylic acid ester, styrene-acrylic copolymer Acrylic resins such as polymers and mixtures thereof, polystyrene, polyvinylidene chloride, polyacrylonitrile, vinylidene chloride-acrylonitrile copolymers, and the like can be used. Among these, a styrene-acrylic copolymer, a vinylidene chloride-acrylonitrile copolymer, and the like are preferable from the viewpoints of dyeability 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 shape of the hollow particles is not particularly limited, and may be any shape other than spherical as well as spherical, but from the viewpoint of the adhesion between the intermediate layer and the dye-receiving layer in the thermal transfer image-receiving sheet, it is substantially spherical. Those are preferred.
The volume-median particle size (D ₅₀ ) 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).

The solid content concentration of the hollow particles is preferably 10 to 40% by weight, more preferably 15 to 35% by weight.
The hollow particles have a methyl ethyl ketone insoluble content of preferably 70% by weight or less, more preferably 10% 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. It is -70 weight%, More preferably, it is 30-70 weight%. “Methyl ethyl ketone insoluble matter of hollow particles” in the present invention means the weight of insoluble hollow particle components of hollow particles when 2.0 parts by weight of hollow particles are dissolved in 95 parts by weight of methyl ethyl ketone at 25 ° C. It is defined as a percentage. The methyl ethyl ketone insoluble matter of the hollow particles can be adjusted by controlling the degree of crosslinking of the resin constituting the hollow particles, for example.
The hollow ratio of the hollow particles is preferably 40 to 60%, more preferably 45 to 55%.

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 weight ratio of the hollow particles to the water-soluble polymer in the intermediate layer (hollow particles / water-soluble polymer) is preferably from the viewpoint of dyeing property and adhesion between the intermediate layer and the dye-receiving layer in the thermal transfer image-receiving sheet. Is 30/70 to 90/10, more preferably 40/60 to 80/20, still more preferably 50/50 to 75/25.

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. The blending amount of these pigments and fillers is preferably 0.1 to 20 parts by weight, more preferably 0 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. .1 to 10 parts by weight.
Further, 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, if necessary.

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. The solid content after drying is preferably 7 to 70 g / m ² , more preferably 10 to 50 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 sublimable dye on paper or a polyester film, and receiving the dye. A laminate layer made of a protective layer or the like transferred onto the image is provided, and any transfer sheet can be used.
Suitable sublimation dyes for the thermal transfer image-receiving sheet of the present invention include, for example, pyridoneazo, dicyanostyryl, quinophthalone, and merocyanine dyes for yellow dyes; Zorotriazole type; Examples of cyan dyes include anthraquinone type, cyanomethylene type, indophenol type, and indonaphthol type.

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.

The measuring method of each physical property of resin obtained by the manufacture example shown below and an aqueous dispersion is as follows.
[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 binder 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)

[Volume Median Particle Size (D ₅₀ ) of Resin Particles in Aqueous Dispersion]
Using a laser diffraction particle size measuring instrument (trade name: LA-920, manufactured by HORIBA, Ltd.), an aqueous dispersion and distilled water are added to the measurement cell, and the concentration is adjusted so that the absorbance is in the proper range. The particle size (D ₅₀ ) 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 water content (% 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: Water content 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 resin (a1) -a and b)
Polyester resin excluding fumaric acid shown in Table 1 (a1) raw material monomer and di (2-ethylhexanoic acid) tin, inner volume 5 liters equipped with thermometer, stainless steel stirring rod, flow-down condenser and nitrogen inlet tube The reaction was carried out in a mantle heater under a nitrogen atmosphere at 235 ° C. for 5 hours, further reduced in pressure, and reacted at a pressure of 8.3 kPa for 1 hour. Next, fumaric acid and 4-t-butylcatechol were added at 210 ° C. and reacted for 5 hours, then the pressure was reduced, and the softening point measured according to ASTM D36-86 under a pressure of 20 kPa reached the temperature shown in Table 1. It was made to react until it reached | attained, and polyester resin (a1) a and b was obtained.
Table 1 shows the measurement results of the physical properties of the obtained polyester resins (a1) -a and b.

Production Examples 3 to 11
(Production of aqueous dispersions (i) to (ix) of polyester resin (a1): Step (1))
Polyester resins (a1) -a, b, of the types and blending amounts shown in Table 2 in a four-necked flask with an internal volume of 10 liters or 2 liters equipped with a nitrogen inlet tube, a reflux condenser, a stirrer and a thermocouple An addition polymerizable monomer (a2) was added (however, (a2) was not added in Production Example 3) 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 (ix) of the polyester resin (a1).
Table 2 shows the measurement results of the physical properties of the obtained aqueous dispersions (i) to (ix).

Production Examples 12-24
(Production of aqueous dispersions (I) to (XIII) of resin for thermal transfer image-receiving sheet: Step (2))
An aqueous dispersion (i) of a polyester resin (a1) of the types and blending amounts shown in Table 3 was added to a 2-liter four-necked flask equipped with a nitrogen introduction tube, a reflux condenser, a dropping funnel, a stirrer and a thermocouple. ) To (ix), deionized water, and addition polymerizable monomer (a2) were charged and stirred for 30 minutes. Next, sodium persulfate was added under a nitrogen stream and reacted at 80 ° C. for 6 hours. Thereafter, the mixture was cooled to room temperature and filtered through a 200-mesh wire mesh to obtain aqueous dispersions (I) to (XIII) of resins for thermal transfer image-receiving sheets containing a graft polymer. 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.
Table 3 shows the measurement results of the physical properties of the aqueous dispersions (I) to (XIII) of the obtained resin for thermal transfer image-receiving sheets.

Examples 1-5 and Comparative Examples 1-8
(Manufacture of thermal transfer image receiving sheet)
First, hollow particles, a water-soluble polymer, and water were mixed at 45 ° C. with the compositions and blending amounts shown in Table 4 to prepare an intermediate layer coating solution. This intermediate layer coating solution is dried to 20.0 g / m2 after being dried on a synthetic paper (manufactured by YUPO Corporation, trade name: YUPO FGS-250, thickness 250 μm, basis weight 200 g / m2) with a wire bar. It apply | coated and was made to dry at 25 degreeC for 5 minute (s), and the intermediate | middle layer coating sheet was obtained.
In the preparation of the intermediate layer coating solution, the following styrene acrylic copolymer was used as the hollow particles, and the following gelatin was used as the water-soluble polymer.
Hollow particles: Styrene acrylic copolymer (manufactured by Nippon Zeon Co., Ltd., trade name: Nipol MH8101, hollow ratio = 50%, solid content concentration = 26% by weight, methyl ethyl ketone insoluble matter = 50%, volume-median particle size (D ₅₀ ) = 420nm)
Water-soluble polymer: gelatin (manufactured by Nitta Gelatin Co., Ltd., trade name: G0723K, viscosity 4.4 mPa · s (viscosity (60 ° C.) measured according to JIS K6503-2001))

Next, an aqueous dispersion of a thermal transfer image-receiving sheet resin, a film-forming agent, and a release agent are mixed at 25 ° C. with the compositions and blending amounts shown in Table 4 to prepare dye-receiving layer coating liquids A1 to M1. did. 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.
The following gelatin was used as a film-forming agent and the following polyether-modified silicone was used as a mold release agent for the preparation of a dye-receiving layer coating solution.
Film-forming agent: Gelatin (manufactured by Nitta Gelatin Co., Ltd., trade name: G0723K, viscosity 4.4 mPa · s (viscosity (60 ° C.) measured according to JIS K6503-2001))
Release agent: 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 above-mentioned intermediate layer coating sheet by a wire bar so as to be 5.0 g / m ² , dried at 50 ° C. for 2 minutes, and then the thermal transfer image-receiving sheet. Got.

<Evaluation of thermal transfer image receiving sheet>
The obtained thermal transfer image receiving sheet was evaluated by the following method. The results are shown in Table 4.
(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: MEGAPIXEL III, manufactured by Altec Co., Ltd.), and a high image density print (18th gradation (L = 0: highest density)), the transfer color density was measured with a Gretag densitometer (manufactured by GRETAG-MACBETH), and the dyeing property was evaluated. The higher the value, the better the dyeing property.

(Releasability-releasability in low image density area)
A solid image with a low image density of 5 × 5 cm (sixth gradation (L = 75) when the maximum density is the 18th gradation) is printed on the produced thermal transfer image-receiving sheet, and attached on the thermal transfer image-receiving sheet. The adhesion of the transferred transfer sheet (ink ribbon) component was evaluated for releasability (heat fusion property) based on the following criteria.
A: No ink ribbon component adheres on the image receiving sheet.
B: The ink ribbon component is slightly adhered on the image receiving sheet.
C: The ink ribbon component adheres to the entire surface of the image receiving sheet.
D: It is heat-sealed and cannot be peeled off.

(Releasability-releasability in high image density area)
A solid image with a high image density of 5 × 5 cm (18th gradation (L = 0: highest density)) was printed on the produced thermal transfer image receiving sheet, and the peeling sound between the ink ribbon and the thermal transfer image receiving sheet during black solid printing From the above, the releasability (heat fusion property) was evaluated according to the following criteria.
A: There is no abnormal noise, no fusion is observed, and peeling is possible.
B: Although there is a slight noise, no fusion is seen and peeling is possible.
C: There is a clear abnormal noise and a slight fusion is observed, but it can be peeled off.
D: It is heat-sealed and cannot be peeled off.

  As is clear from Table 4, compared with the thermal transfer image receiving sheets of Comparative Examples 1 to 8, all of the thermal transfer image receiving sheets of Examples 1 to 5 have excellent dyeing properties and are solid at a low image density, and It can be seen that the ink sheet and the image receiving sheet are not fused and excellent in releasability at any time of solid continuous printing at a high image density.

  The thermal transfer image-receiving sheet of the present invention is excellent in dyeability and can be suitably used as a thermal transfer image-receiving sheet having excellent releasability in both a high image density region and a low image density region.

Claims (13)

  As the acid group, it comprises a main chain segment (A1) made of a polyester resin having a carboxy group and an acid value derived from the carboxy group of 5 to 40 mgKOH / g, and a side chain segment (A2) made of an addition polymerization resin. A resin for a thermal transfer image-receiving sheet containing a graft polymer, wherein the segment (A1) contains 60 mol% or more of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and a carboxylic acid component And the segment (A2) is composed of structural units derived from styrene and an alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms, and the segment ( In A2), having a structural unit derived from the styrene and an alkyl group having 12 to 22 carbon atoms Thermal transfer image-receiving sheet having a weight ratio (styrene / alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms) to a structural unit derived from alkyl (meth) acrylate is 20/80 to 90/10 Resin.   2. The resin for a thermal transfer image receiving sheet according to claim 1, wherein a weight ratio of the segment (A1) to the segment (A2) [segment (A1) / segment (A2)] is 55/45 to 95/5.   In the segment (A2), the weight ratio of the structural unit derived from styrene to the structural unit derived from alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms (styrene / carbon number of 12 to 22 carbon atoms). The resin for thermal transfer image receiving sheets according to claim 1 or 2, wherein (alkyl (meth) acrylate having an alkyl group) is 35/65 to 85/15.   The resin for thermal transfer image receiving sheets according to any one of claims 1 to 3, wherein the alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms is stearyl methacrylate and / or lauryl methacrylate.   The raw material monomer from which the structural unit of the segment (A1) is derived includes one or more selected from unsaturated aliphatic carboxylic acids, unsaturated alicyclic carboxylic acids, and unsaturated aliphatic alcohols. Resin for thermal transfer image receiving sheets in any one.   The resin for thermal transfer image-receiving sheets according to claim 5, comprising an unsaturated aliphatic carboxylic acid and / or an unsaturated alicyclic carboxylic acid as a raw material monomer from which the constituent unit of the segment (A1) is derived.   As a raw material monomer from which the structural unit of the segment (A1) is derived, an unsaturated aliphatic carboxylic acid and / or an unsaturated alicyclic carboxylic acid is contained in an amount of 5 to 30 mol% in the carboxylic acid component of the segment (A1). The resin for thermal transfer image receiving sheets according to claim 6.   The resin for thermal transfer image-receiving sheets according to claim 6 or 7, wherein the unsaturated aliphatic carboxylic acid is at least one selected from the group consisting of fumaric acid, maleic acid and tetrahydrophthalic 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) The resin for a thermal transfer image receiving sheet according to any one of claims 5 to 8, wherein / total of the components having an unsaturated group of segment (A1)] is 1/1 to 15/1.   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 1-9.   The thermal transfer image-receiving sheet according to claim 10, comprising an intermediate layer containing a water-soluble polymer and hollow particles between the substrate and the dye-receiving layer. The manufacturing method of resin for thermal transfer image receiving sheets in any one of Claims 1-9 including following process (1) and (2).
Step (1): Non-aromatic carbon-obtained by condensation polymerization of an alcohol component containing 60 mol% or more of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and a carboxylic acid component A polyester resin (a1) having a carbon unsaturated bond, having a carboxy group as an acid group, and having an acid value of 5 to 40 mg KOH / g derived from the carboxy group is prepared. The polyester resin (a1) is prepared by dissolving an alkyl (meth) acrylate having 12 to 22 alkyl groups in an organic solvent, adding a neutralizing agent, and then mixing with an aqueous medium to invert the phase to an aqueous phase. Step (2) for obtaining an aqueous dispersion of (meth) acrylic acid having styrene and an alkyl group having 12 to 22 carbon atoms in the aqueous dispersion in the aqueous dispersion obtained in the step (1) Styrene is added so that the weight ratio to rualkyl (styrene / alkyl (meth) acrylate having an alkyl group having 12 to 22 carbon atoms) is 20/80 to 90/10, and polymerized to contain a graft polymer. Process for obtaining aqueous dispersion of resin for thermal transfer image-receiving sheet   A dye-receiving layer coating solution containing an aqueous dispersion of the resin for thermal transfer image-receiving sheets obtained by the production method according to claim 12 is prepared, and the dye-receiving layer is provided using the dye-receiving layer coating solution The manufacturing method of a thermal transfer image receiving sheet including a process.