JP2013001081A - Thermal transfer image receiving sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal transfer image receiving sheet that has superior releasability and obtains a printed matter without bleeding, and to provide a method of manufacturing the thermal transfer image receiving sheet.SOLUTION: The thermal transfer image receiving sheet includes a dye receiving layer which contains: polyether denatured silicone having HLB of 4-9 and viscosity of 1,000-5,000 mPa at 25°C; and polyester resin having acid value of 10-40 mgKOH/g.

Description

  The present invention relates to a 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. For this reason, thermal transfer image-receiving sheets have been developed to exhibit these performances, and resin is used for the dye-receiving layer, requiring releasability due to thermal fusion with the transfer sheet (ink ribbon). Therefore, polyether-modified silicone is used as a release agent.

For example, Patent Document 1 discloses an alcohol component containing 50 mol% or more of an alkylene oxide adduct of bisphenol A and an alicyclic carboxylic acid for the purpose of improving dyeing property, release property, and the like. A composition for a receiving layer for a thermal transfer image-receiving sheet, comprising: a resin containing a polyester obtained by condensation polymerization with a carboxylic acid component containing more than 50 mol%; and a polyether-modified silicone having an oxyethylene group and / or an oxypropylene group. Things are disclosed.
Patent Document 2 discloses a heat-sensitive transfer image-receiving sheet that has at least two heat-insulating layers and at least one receiving layer in order on a support for the purpose of improving transfer density and the like. And a heat-sensitive transfer image-receiving sheet containing a water-soluble polymer, wherein the mass ratio of the hollow particles and the water-soluble polymer in the heat insulating layer closest to the support satisfies a specific relationship, and the receiving layer contains a polymer latex and a polyether-modified silicone Is disclosed.
Patent Document 3 discloses a thermal transfer image-receiving sheet in which a dye-receiving layer is formed on at least one surface of a substrate sheet for the purpose of improving releasability and the like, on at least the outermost surface portion of the dye-receiving layer. There is disclosed a thermal transfer image-receiving sheet comprising a specific polyether-modified silicone, wherein the polyether-modified silicone has a siloxane content of 25 to 65% by weight.

JP 2009-262337 A JP 2010-149464 A JP 2003-11528 A

  In the printing, since the dye is dyed from the ink ribbon to the thermal transfer image receiving sheet by heating from the thermal head and coloring is performed by this, fusion is likely to occur between the ink ribbon and the thermal transfer image receiving sheet at the time of coloring. There was a problem in the releasability. In particular, in a high image density region, high energy is applied to the ink ribbon and the image receiving sheet during printing, and fusion is likely to occur. On the other hand, even in the low image density region, there is a problem that the ink part is peeled off from the ink ribbon and all the ink part is transferred to the image receiving sheet.

Further, the printed matter stored under high temperature and high humidity has a problem that “bleeding” due to diffusion of the dye is observed.
From the viewpoint of achieving both the above-described improvement in releasability and suppression of bleeding, the thermal transfer image receiving sheets described in Patent Documents 1 to 3 still have room for improvement.
Therefore, there is a demand for a thermal transfer image-receiving sheet that is excellent in releasability for suppressing fusing with an ink ribbon and peeling of an ink portion of the ink ribbon, and that can provide a print without bleeding.

  It is an object of the present invention to provide a thermal transfer image-receiving sheet that is excellent in releasability in both a high image density region and a low image density region and that can obtain a print product without blur, and a method for producing the thermal transfer image-receiving sheet. .

The present inventors have considered that the factors affecting the releasability and bleeding are the surface state of the dye-receiving layer during heating by the thermal head and the state of the resin during storage. As a result, it has been found that the above-described problems can be solved by using a specific polyether-modified silicone and a specific polyester resin in the dye-receiving layer.
That is, the present invention provides the following [1] and [2].
[1] A dye-receiving layer containing a polyether-modified silicone having an HLB of 4 to 9 and a viscosity of 1000 to 5000 mPa · s at 25 ° C., and a polyester resin having an acid value of 10 to 40 mgKOH / g Thermal transfer image receiving sheet.
[2] A method for producing a thermal transfer image-receiving sheet comprising the following steps (3) to (5).
Step (3): Polyether-modified silicone having an HLB of 4 to 9 and a viscosity at 25 ° C. of 1000 to 5000 mPa · s is added to an aqueous dispersion of a polyester resin having an acid value of 10 to 40 mgKOH / g. Step of preparing a dye-receiving layer coating solution Step (4): Step of providing a dye-receiving layer using the dye-receiving layer coating solution obtained in Step (3) Step (5): Dye-receiving layer Drying at 40 to 110 ° C. for 1 to 10 minutes

  The thermal transfer image-receiving sheet of the present invention is excellent in releasability in both the high image density region and the low image density region, and a print product without blur can be obtained.

  The thermal transfer image-receiving sheet of the present invention (hereinafter also simply referred to as “image-receiving sheet”) has a polyether-modified silicone having an HLB of 4 to 9, a viscosity at 25 ° C. of 1000 to 5000 mPa · s, and an acid value of 10 to 10. It has a dye-receiving layer containing a polyester resin that is 40 mg KOH / g.

The reason why the thermal transfer image-receiving sheet of the present invention is excellent in releasability and produces a print without bleeding is not clear, but is considered as follows.
The dye-receiving layer of the thermal transfer image-receiving sheet of the present invention contains a polyester resin having a specific acid value and a polyether-modified silicone having a relatively low HLB and a high viscosity.
Polyester resins have a high hydrophilicity because they have a large number of ester bonds, which are polar groups, and also have an acid value attributable to the raw carboxylic acid. On the other hand, since the polyether-modified silicone used in the present invention has a relatively low HLB, the hydrophobicity is high and the viscosity is relatively high. Therefore, it is considered that the polyether-modified silicone is hardly compatible with a polyester resin. Therefore, the polyether-modified silicone is dispersed in the polyester resin dispersion at the time of coating, but after the dye-receiving layer is formed as a film, it exudes to the film surface, thereby releasing the release agent. It is thought that the effect as can be fully exhibited. In addition, since the polyether-modified silicone does not dissolve in the polyester-based resin, the hardness of the resin is maintained, the dye after printing is difficult to diffuse in the resin, and the printed matter can be stored for a long time. It is thought that there is no blur.

[Dye-receiving layer]
The dye-receiving layer in the thermal transfer image-receiving sheet of the present invention has a polyether-modified silicone having an HLB of 4 to 9, a viscosity of 1000 to 5000 mPa · s at 25 ° C., and a polyester resin having an acid value of 10 to 40 mgKOH / g Containing.

[Polyether-modified silicone]
The polyether-modified silicone used in the present invention has an HLB of 4 to 9, and a viscosity at 25 ° C. of 1000 to 5000 mPa · s.
The HLB of the polyether-modified silicone is 4 to 9 from the viewpoint of improving the releasability of the image receiving sheet, suppressing bleeding, and improving dyeability, but preferably 4.5 to 8.5. Preferably it is 4.8-8.2, More preferably, it is 6-7.8. When the HLB is less than 4, the polyether-modified silicone is not dispersed in the resin dispersion. When the HLB exceeds 9, the efficiency of the polyether-modified silicone exuding on the surface of the receiving layer is inferior, and the image receiving sheet is released. This is not preferable because the properties are lowered.

In addition, in this invention, HLB value is the following from cloud number A measured by the following method described in 324 page of surfactant manual (edited by Nishiichiro et al., Sangyo Tosho Co., Ltd., 1960 issue). It calculates from Formula (1).
HLB value = 0.89 × A + 1.11 Formula (1)
<Measuring method of cloud number A>
0.5 g of an evaluation sample (polyether-modified silicone) is dissolved in 5 ml of 98% ethyl alcohol and titrated with a 2% aqueous phenol solution while stirring at 25 ° C., and the end point is when the liquid becomes turbid. The number of ml of 2% phenol aqueous solution required for this titration is defined as the cloud number A.

The viscosity of the polyether-modified silicone at 25 ° C. is 1000 to 5000 mPa · s from the viewpoint of improving the releasability of the image-receiving sheet, suppressing bleeding and improving dyeability, but preferably 1200 to 4600 mPa · s. s, more preferably 1400 to 4200 mPa · s, still more preferably 1800 to 3600 mPa · s, still more preferably 2000 to 3300 mPa · s. This is presumably because adhesion with the ink ribbon resin is efficiently suppressed. When the viscosity is less than 1000 mPa · s, the efficiency of the polyether-modified silicone oozing out to the surface of the receiving layer is increased, but the amount of adhesion to the ink ribbon during printing increases, and the printing is accepted before printing with yellow, magenta, and cyan. The amount of the polyether-modified silicone present on the surface of the layer is not preferable because it decreases, and if it exceeds 5000 mPa · s, the efficiency of the polyether-modified silicone exuding on the surface of the receiving layer is extremely decreased.
In the present invention, the viscosity at 25 ° C. is a value measured based on JIS K6503-2001.

The polyether-modified silicone used in the present invention has a polyether group at the side chain with respect to the main chain of the polydimethylsiloxane structure, or has a polyether group at both ends of the main chain, and has a poly group at the side chain. Those having an ether group are preferred.
Examples of the polyether group include a polyethylene oxide group, a polypropylene oxide group, and a group made of a copolymer of ethylene oxide and propylene oxide. Among these, from the viewpoint of improving releasability of the image-receiving sheet and suppressing bleeding, a group consisting of a polyethylene oxide group and a copolymer of ethylene oxide and propylene oxide is preferable, and a group consisting of a copolymer of ethylene oxide and propylene oxide Is more preferable.
As a commercially available product suitable as the polyether-modified silicone used in the present invention, KF-6012 manufactured by Shin-Etsu Chemical Co., Ltd. (HLB: 7, viscosity at 25 ° C .: 1500 mPa · s (hereinafter the same)), X-22-4515 (5, 4000), SF8410 (7, 2900), L-7002 (7, 1300), FZ2164 (8, 3500) manufactured by Toray Dow Corning Co., Ltd., and the like.
These polyether-modified silicones may be used alone or in combination of two or more.

  The content of the polyether-modified silicone in the dye-receiving layer is preferably based on 100 parts by weight of the polyester resin contained in the dye-receiving layer, from the viewpoint of improving the releasability of the image-receiving sheet and suppressing bleeding. 1-10 weight part, More preferably, it is 2.5-9.5 weight part, More preferably, it is 5.0-9.0 weight part.

[Polyester resin]
The acid value of the polyester-based resin used in the present invention is 10 to 40 mgKOH / g, preferably 11 to 30 mgKOH / g, more preferably 12 to 25 mgKOH / g, from the viewpoint of emulsifying properties and dispersion stability of the emulsified particles. g, more preferably 13 to 21 mg KOH / g, still more preferably 15 to 18 mg KOH / g. When it is less than 10 mgKOH / g, it becomes difficult to disperse uniformly, the surface of the dye receiving layer to be formed is not smooth, and the dyeability and releasability of the thermal transfer image receiving sheet are inferior. On the other hand, if it exceeds 40 mgKOH / g, the hydrophilicity increases and the moisture resistance decreases, which is not preferable.
In addition, the value of the acid value in the present invention is a value measured by the method shown in the examples (hereinafter the same).

The glass transition point of the polyester-based resin is preferably 45 to 100 ° C, more preferably 50 to 90 ° C, still more preferably 55 to 80 ° C, and still more preferably, from the viewpoint of improving the releasability and dyeing property of the image receiving sheet. Preferably it is 60-75 degreeC.
In addition, the value of the glass transition point in the present invention is a value measured by the method shown in the examples (the same applies hereinafter).

  In the present invention, the dye-receptive layer may contain other resins such as vinyl chloride polymers other than the above-mentioned polyester resins, as long as the effects of the present invention are not impaired. It is preferable to contain only a resin. The content of the polyester resin in the dye-receiving layer is preferably 90% by weight or more, more preferably 95% by weight or more, and still more preferably 100% by weight with respect to the total resin components.

  The polyester resin used in the present invention may be a resin having only a polyester structure, but from the viewpoint of releasability, it is composed of a segment (A1) made of polyester and a segment (A2) made of an addition polymerization resin. A graft polymer is preferred. In addition, the graft polymer may be either a segment (A1) or a segment (A2) as a main chain, but the segment (A1) is a main chain and the segment (A2) is a side chain. It is preferable that

The weight ratio [segment (A1) / segment (A2)] of the segment (A1) and the segment (A2) constituting the graft polymer is preferably 60/40 to 90 / from the viewpoint of improving the dyeing property of the image receiving sheet. 10, more preferably 70/30 to 87/13, still more preferably 75/25 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 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 components having an unsaturated group of A1) is preferably from 1/1 to 15/1, more preferably from 2/1 to 12/1, from the viewpoint of dyeability and releasability of the image receiving sheet. More preferably, it is 5/1 to 10/1.

The content of the graft polymer in the polyester resin used in the present invention is preferably 80 to 100% by weight, more preferably 90 to 100% by weight or more, and still more preferably substantially, from the viewpoint of improving the dyeability of the image receiving sheet. 100% by weight.
Hereinafter, the graft polymer composed of the segment (A1) made of polyester and the segment (A2) made of addition polymerization resin will be described in detail.

(Segment made of polyester (A1))
The segment (A1) constituting the graft polymer is preferably made of polyester and is the main chain in the graft polymer. Since the segment (A1) is made of polyester, it can be obtained by condensation polymerization of an alcohol component and a carboxylic acid component. Hereinafter, the alcohol component and the 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 “the raw material monomer of the segment (A1)”) will be described in detail.

In the present invention, an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane is used as the alcohol component which is a raw material monomer of the segment (A1) from the viewpoint of releasability and dyeing property of the image receiving sheet. It is preferable.
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 from each other, but the dyeing property of the thermal transfer image-receiving sheet and the heat-insulating 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 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, more preferably an ethyleneoxy group, from the viewpoint of dyeability of the image receiving sheet.

The content of the alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane is preferably 60 mol% or more, more preferably in the alcohol component, from the viewpoint of releasability and dyeing property of the image receiving sheet. 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%. If the content is 60 mol% or more, the affinity with the dye is excellent, the dyeing property of the image receiving sheet is improved, the resin has an appropriate hardness, and in the high image density region of the image receiving sheet. Release property is improved.
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.
As a specific 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 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 which is a raw material monomer of the segment (A1) includes a carboxylic acid having a non-aromatic carbon-carbon unsaturated bond from the viewpoint of improving the dyeability and releasability of the image receiving sheet. Preferably, it contains an unsaturated aliphatic carboxylic acid and / or an unsaturated alicyclic carboxylic acid. The carbon-carbon unsaturated bond portion is preferably a bond portion with the segment (A2) in the 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 unsaturated aliphatic carboxylic acid and / or unsaturated alicyclic carboxylic acid as a raw material monomer from which the structural unit of segment (A1) is derived is from the viewpoint of improving dyeability and releasability of the image receiving sheet. 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. From the viewpoint of dyeability of the thermal transfer image-receiving sheet, aromatic dicarboxylic acids and alicyclic dicarboxylic acids are preferable, and cyclohexanedicarboxylic acid and isophthalic acid are more preferable. Among these, aromatic dicarboxylic acids are preferable, and isophthalic acid is more preferable. The said carboxylic acid component may be individual or 2 or more types may be contained.

  From the viewpoint of improving dyeability and releasability of the image receiving sheet, unsaturated aliphatic carboxylic acid as a raw material monomer having a non-aromatic carbon-carbon unsaturated bond among the raw material monomers of segment (A1). It is preferable that 1 or more types chosen from an 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) preferably contains a carboxy group. The content of the carboxy group is preferably 90 mol% or more, more preferably 95 mol% or more, and further preferably substantially 100 mol% of the acid groups in the segment (A1).
When the sulfonic acid is included as the acid group contained in the segment (A1), 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%). 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 from 10 to 40 mgKOH / g, preferably from 12 to 30 mgKOH / g, more preferably from 15 to 25 mgKOH / g, even more preferably, from the viewpoint of releasability and storage stability of the image receiving sheet. Is 18-21 mg KOH / g.
The number average molecular weight of the segment (A1) is preferably 1,000 to 10,000, more preferably 2,000 to 8,000, and still more preferably, from the viewpoint of film forming properties when used in the dye-receiving layer. Is 2,500 to 6,000, more preferably 3,000 to 4,000. In addition, the number average molecular weight in this invention is a value measured by the method as described in an Example (hereinafter the same).

In the present invention, the segment (A1) may be modified within the range so as not to substantially impair the characteristics.
In the present invention, the content of the polyester portion in the segment (A1) is preferably 50 to 100% by weight, more preferably from the viewpoints of releasability of the image receiving sheet, releasability at high temperature and high humidity, and dyeability. Is 70 to 100% by weight, more preferably 85 to 100% by weight, and still more preferably substantially 100% by weight.

(Segment made of addition polymerization resin (A2))
The segment (A2) constituting the graft polymer is a segment made of an addition polymerization resin composed of a structural unit derived from the addition polymerizable monomer (a2) (hereinafter also referred to as “monomer (a2)”). A side chain in the polymer is preferred.
Examples of the addition polymerizable monomer (a2) include styrenes such as styrene, methylstyrene, α-methylstyrene, β-methylstyrene, t-butylstyrene, chlorostyrene, chloromethylstyrene, methoxystyrene, styrenesulfonic acid, or a salt thereof. ; (Meth) acrylic acid esters such as alkyl (meth) acrylate (C1-18), benzyl (meth) acrylate, dimethylaminoethyl (meth) acrylate; olefins such as ethylene, propylene, butadiene; Halovinyls such as vinyl; 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; Among these, styrenes and (meth) acrylic acid esters are preferable, and addition polymerizable monomers having an aromatic group are more preferable. As the addition polymerizable monomer having an aromatic group, styrene, methylstyrene, benzyl methacrylate and benzyl acrylate are preferable, and styrene is more preferable from the viewpoint of the raw material price of the monomer, the releasability of the image receiving sheet and storage stability. In the present invention, (meth) acrylic acid refers to both methacrylic acid and acrylic acid.

  The content of the structural unit derived from the addition-polymerizable monomer having an aromatic group is determined in the segment (A2) from the viewpoint of releasability of the thermal transfer image-receiving sheet, particularly releasability at high image density and dyeing property. It is preferably 85% by weight or more, more preferably 90% by weight or more, still more preferably 95% by weight or more, and still more preferably substantially 100% by weight.

[Method for producing graft polymer]
As a method for producing the graft polymer of the present invention, a polyester resin (a1) having a non-aromatic carbon-carbon unsaturated bond (hereinafter referred to as resin (a1)) is obtained by condensation polymerization of the alcohol component and the carboxylic acid component. (Also referred to as the above) and the addition polymerization of the addition polymerizable monomer (a2) in the presence of the polyester resin (a1) is preferred.

(Polyester resin (a1))
The resin (a1) is a polyester resin having a non-aromatic carbon-carbon unsaturated bond obtained by condensation polymerization of the alcohol component and the carboxylic acid component, and the segment (A1) made of the polyester resin. Preferred for construction.
The “non-aromatic carbon-carbon unsaturated bond” is one or more selected from the aforementioned unsaturated aliphatic carboxylic acid, unsaturated alicyclic carboxylic acid and unsaturated aliphatic alcohol used as a raw material monomer. It is derived from.

  As the alcohol component which is a raw material component of the resin (a1), the alcohol component can be used, and an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane is preferably used. 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. In addition, the suitable structure of these alcohol components and content are the same as that of the above-mentioned segment (A1).

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 is preferable to use it.
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.
In addition, the suitable structure of these carboxylic acid components and content are the same as that of the above-mentioned segment (A1).

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, di (2-ethylhexanoic acid) tin or the like is 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, and still more preferably 95 to 120 ° C, from the viewpoints of releasability and storage stability of the image receiving sheet. In addition, the softening point in this invention is the value measured by the method as described in an Example (hereinafter the same).
The glass transition point of the resin (a1) is preferably 45 to 100 ° C., more preferably 50 to 90 ° C., still more preferably 52 to 80 ° C., from the viewpoint of improving the releasability and dyeing property of the image receiving sheet. More preferably, it is 54-70 degreeC.
The acid value of the resin (a1) is 10 to 40 mgKOH / g, preferably 12 to 30 mgKOH / g, more preferably 15 to 25 mgKOH / g, more preferably from the viewpoint of releasability and storage stability of the image receiving sheet. Is 18-21 mg KOH / g.
The glass transition point, 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 2,000 to 8,000, and still more preferably, from the viewpoint of film forming properties when used in the dye-receiving layer. Is 2,500 to 6,000, more preferably 3,000 to 4,000.

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.

(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) comprising the above addition polymerization resin, and an addition polymerizable monomer having an aromatic group is used. Is preferred. The content of the addition polymerizable monomer having an aromatic group is preferably 85% by weight or more, more preferably 90% by weight or more, still more preferably 95% by weight or more, and still more preferably, among the addition polymerizable monomer (a2). Preferably, it is substantially 100% by weight.
As the addition polymerizable monomer having an aromatic group, styrene, benzyl methacrylate, and benzyl acrylate are preferable, and styrene is more preferable from the viewpoint of the raw material price of the monomer, the releasability of the image receiving sheet, and storage stability.

(Production of graft polymer)
The graft polymer 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.
Among these, it is preferable to obtain the polyester resin having an acid value of 10 to 40 mgKOH / g, which is a graft polymer used in the thermal transfer image-receiving sheet of the present invention, by a method having the following steps (1) and (2).
Step (1): Step of obtaining an aqueous dispersion of the polyester resin (a1) by mixing the polyester resin (a1) having a non-aromatic carbon-carbon unsaturated bond with an aqueous medium Step (2): The addition polymerizable monomer (a2) is added to the aqueous dispersion obtained in the step (1) and polymerized to obtain an aqueous dispersion of a polyester resin having an acid value of 10 to 40 mgKOH / g as a graft polymer. Obtaining process

<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 medium mainly containing water, 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 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 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.

  As the organic solvent, those described above can be used, and 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.

<Step (2)>
In step (2), the addition-polymerizable monomer (a2) is added to the aqueous dispersion obtained in step (1) and polymerized to produce a polyester polymer having an acid value of 10 to 40 mgKOH / g as a graft polymer. This is a step of obtaining an aqueous dispersion of resin (hereinafter also referred to as “aqueous dispersion (A)”).
First, the addition polymerizable monomer (a2) is added to the aqueous dispersion of the polyester resin (a1). 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 60/40 to 90/10, more preferably 70/30 to 87/13, more preferably 75/25 to 85/15.
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, 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 can be advanced by heating the 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 point of the graft polymer in the aqueous dispersion (A) obtained as described above is preferably 45 to 100 ° C. from the viewpoints of storage stability and releasability and dyeing property of the image receiving sheet. More preferably, it is 50-90 degreeC, More preferably, it is 55-80 degreeC, More preferably, it is 60-75 degreeC.
Further, as described above, the acid value of the graft polymer is 10 to 40 mgKOH / g, preferably 11 to 30 mgKOH / g, more preferably 12 to 25 mgKOH, from the viewpoints of emulsifying properties and dispersion stability of the emulsified particles. / G, more preferably 13 to 21 mg KOH / g, still more preferably 15 to 18 mg KOH / g.

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.
Further, the pH of the aqueous dispersion (A) at 25 ° C. is preferably 5 to 10, more preferably 5.3 to 9, and still more preferably 5.5 from the viewpoint of storage stability of the aqueous dispersion (A). ~ 8.

The volume median particle size (D ₅₀ ) of the resin particles in the aqueous dispersion (A) is preferably 20 to 1000 nm, more preferably 50 to 800 nm, more preferably 50 to 800 nm, from the viewpoint of film forming properties when obtaining a thermal transfer image-receiving sheet. Preferably it is 80-500 nm, More preferably, it is 90-150 nm. In the present invention, “volume median particle size (D ₅₀ )” means a particle size at which the cumulative volume frequency calculated by the volume fraction is 50% calculated from the smaller particle size. The measuring method is as described in the examples.

(Method for forming dye receiving layer)
The dye-receiving layer is formed using a coating liquid form obtained by dissolving a resin in an organic solvent, or a coating liquid form including 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 form by performing the following steps (3) to (5).
Step (3): Polyether-modified silicone having an HLB of 4 to 9 and a viscosity at 25 ° C. of 1000 to 5000 mPa · s is added to an aqueous dispersion of a polyester resin having an acid value of 10 to 40 mgKOH / g. Step of preparing a dye-receiving layer coating solution Step (4): Step of providing a dye-receiving layer using the dye-receiving layer coating solution obtained in Step (3) Step (5): Dye-receiving layer Drying at 40 to 110 ° C. for 1 to 10 minutes

<Step (3)>
In the step (3), an aqueous dispersion of a polyester resin having an acid value of 10 to 40 mgKOH / g, a polyether-modified silicone having an HLB of 4 to 9 and a viscosity at 25 ° C. of 1000 to 5000 mPa · s. Is a step of preparing a dye-receiving layer coating solution by adding. As the aqueous dispersion of the polyester resin, it is preferable to use the aqueous dispersion of the graft polymer obtained in the step (2).
In the dye receiving layer coating solution, it is considered that the efficiency of the polyether-modified silicone exuding on the surface of the receiving layer is increased, but from the viewpoint of improving the releasability of the image receiving sheet, It contains a polyether-modified silicone having an HLB of 4 to 9 and a viscosity at 25 ° C. of 1000 to 5000 mPa · s.

The content of the polyether-modified silicone in the dye-receiving layer is preferably based on 100 parts by weight of the polyester resin contained in the dye-receiving layer, from the viewpoint of improving releasability of the image-receiving sheet and suppressing bleeding. 1-10 weight part, More preferably, it is 2.5-9.5 weight part, More preferably, it is 5.0-9.0 weight part.
In order to uniformly disperse or dissolve the polyether-modified silicone, stirring is preferably performed. The stirring is preferably performed by rotating a container, and a stirrer such as a ball mill is preferably used. The dispersion or dissolution temperature is preferably 10 to 50 ° C., but more preferably held at 35 to 50 ° C. after stirring at 20 to 30 ° C.
The glass transition point of the dried product obtained by mixing the aqueous dispersion (A) and the polyether-modified silicone as a release agent at a ratio used for the dye-receiving layer and freeze-drying the water to 1% or less is as follows: From the viewpoint of suppressing bleeding of the thermal transfer image-receiving sheet, the temperature is preferably 50 to 70 ° C, more preferably 52 to 68 ° C, and still more preferably 55 to 65 ° C. If the glass transition point of the dried product is within this range, it is considered that the dye after printing is difficult to diffuse in the resin while maintaining high dyeability, so that bleeding can be suppressed.

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 in accordance with JIS K6503-2001 is preferably 2.5 to 6.0 mPa · s, more preferably, from the viewpoint of mold releasability and film-forming property of the image receiving sheet. Is 3.0 to 5.5 mPa · s.
The content of the film-forming agent is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 8 parts by weight, still more preferably 1 with respect to 100 parts by weight of the polyester resin contained in the dye receiving layer. ~ 6 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 preferable to obtain a coating liquid by stirring. The stirring temperature at this time is preferably 30 to 60 ° C., more preferably 35 to 50 ° C., from the viewpoint of uniformly mixing the film forming agent in a dissolved state.

The dye-receiving layer coating solution can further contain a pigment such as titanium oxide or a filler from the viewpoint of improving the whiteness of the dye-receiving layer and increasing the sharpness of the transferred image. In addition, the dye-receptive compatibilizing public utility may further contain other additives such as a catalyst and a curing agent, if necessary.
Furthermore, the dye receiving layer coating solution may contain other resins such as vinyl chloride polymers other than polyester resins, as long as the effects of the present invention are not impaired. It is preferable to contain only. When other resins are included, they may be contained in the dye-receiving layer coating solution by dissolving them in an organic solvent together with the polyester-based resin during the resin production process.

<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 The method of apply | coating by a reverse roll coating method etc. is mentioned. In addition, as described later, when a heat insulating layer is provided between the base material and the dye receiving layer, the heat insulating layer coating liquid and the dye receiving layer coating liquid are applied on one surface of the base material to provide heat insulation. It is preferable to provide a layer and a dye receiving layer, respectively.

<Step (5)>
Step (5) is a step of drying the dye-receiving layer obtained in step (4) at 40 to 110 ° C. for 1 to 10 minutes.
The drying temperature is preferably 40 to 110 ° C., more preferably 42 to 80 ° C., and still more preferably 45 to 60 ° C. from the viewpoint of improving the film forming property and obtaining a crack-free surface.
The drying time is preferably 1 to 10 minutes, more preferably 1.5 to 7.5 minutes, and still more preferably 1.8 to 5 from the viewpoint of improving the film forming property and obtaining a crack-free surface. For minutes.

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 / m ² , more preferably 4 to 10 g / m ² per 1 m ^{2 of} the dye receiving layer.

[Base material]
The thermal transfer image receiving sheet of the present invention has the dye receiving layer on a substrate.
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.

[Insulation layer]
The thermal transfer image-receiving sheet of the present invention has the dye-receiving layer on a substrate, but from the viewpoint of dyeability, an image-receiving layer in which a heat insulating layer and a dye-receiving layer are formed in this order on the substrate. A sheet is preferred.
The heat insulating 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 that it has a gelation temperature of an aqueous solution near room temperature of 10 to 40 ° 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 image receiving sheet. Preferably, it is 3.0 to 5.5 mPa · s.
The content of the water-soluble polymer in the heat insulating layer is preferably 1 to 75% by weight, more preferably 1 to 50% by weight with respect to the entire heat insulating layer.

<Hollow particles>
The hollow particles contained in the heat insulating layer are not particularly limited as long as they are polymer particles having pores at least partially.
The material constituting the hollow particles is not particularly limited, but from the viewpoint of dyeing property of the image receiving sheet and adhesion between the heat insulating layer and the dye receiving layer in the image receiving sheet, styrene-acrylic copolymer, vinylidene chloride- An acrylonitrile copolymer is preferred.
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 heat insulating layer and the dye receiving layer in the image receiving sheet, a substantially spherical one may be used. preferable.
The volume median particle size (D50) of the hollow particles is preferably 0.1 to 5 μm from the viewpoint of the adhesion between the heat insulating layer and the dye receiving layer in the thermal transfer image receiving sheet. 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 to 70%, from the viewpoint of dyeability of the image receiving sheet and adhesion between the intermediate layer and the dye receiving layer in the image receiving sheet. % By weight, more preferably 30 to 70% by 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 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, and as commercially available hollow particles that can be preferably used, for example, “Nipol MH8101” manufactured by Nippon Zeon Co., Ltd., manufactured by Rohm and Haas Japan Co., Ltd. “HP-1055”, “SX8782 (D)” manufactured by JSR Corporation, etc. (all are trade names).
The weight ratio of the hollow particles to the water-soluble polymer in the heat-insulating layer (hollow particles / water-soluble polymer) is determined from the viewpoint of the dyeing property of the image-receiving sheet and the adhesion between the heat-insulating layer and the dye-receiving layer in the image-receiving sheet. Preferably they are 30 / 70-90 / 10, More preferably, they are 40 / 60-80 / 20, More preferably, they are 50 / 50-75 / 25.

The heat insulating 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 heat insulating layer and enhancing the sharpness of the transferred image. it can. The content of these pigments and fillers is preferably from 0.1 to 20% by weight, more preferably from 0.1 to 20% by weight, based on the water-soluble polymer in the heat insulating layer, from the viewpoint of the whiteness of the thermal transfer image-receiving sheet. 10% by weight.
Further, the heat insulating 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 heat-insulating layer is coated and dried on at least one surface of the substrate 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 heat insulating layer is preferably 10 to 100 μm, more preferably 20 to 50 μm, from the viewpoint of cushioning properties and heat insulating properties. Further, 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 heat insulating layer.
For example, the heat-insulating layer is prepared by dissolving a 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 shown below is as follows.
<Measurement of physical properties>
[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 point 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 glass transition point was defined as the temperature at the intersection of the base line extension below the maximum peak temperature of endotherm and the tangent line indicating the maximum slope from the peak rising portion to the peak apex.

[Glass transition point of dried product of aqueous dispersion and polyether-modified silicone]
The aqueous dispersion and the polyether-modified silicone are mixed in the ratio used for the dye-receiving layer, and freeze-dried at −10 ° C. for 9 hours using a freeze dryer (Tokyo Rika Kikai Co., Ltd., trade name: FDU-2100). The dried product was obtained (confirmed that the water content was 1% by weight or less). And about the said dried material, the value measured like the measuring method of the glass transition point of the above-mentioned resin was made into the glass transition point of the said dried material.

[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)

[Volume Median Particle Size (D ₅₀ ) 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, The volume median 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).

[Viscosity of polyether-modified silicone]
Based on JIS K6503-2001, the viscosity at 25 ° C. was measured.

Production Examples 1 and 2
(Manufacture of polyester resins a and b)
The polyester resin raw material monomer and di (2-ethylhexanoic acid) tin excluding fumaric acid shown in Table 1 are provided with a thermometer, a stainless steel stirring rod, a flow-down condenser, and a nitrogen introduction pipe having an internal volume of 10 liters. The flask was placed in a neck flask, reacted in a mantle heater at 235 ° C. for 5 hours in a nitrogen atmosphere, further depressurized, 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 a and b was obtained.
Table 1 shows the measurement results of the physical properties of the obtained polyester resins a and b.

Production Examples 3-5
(Production of aqueous dispersions (i) to (iii) of polyester resin: Step (1))
Polyester resins a and b of the types and blending amounts shown in Table 2 were placed in a four-necked flask equipped with a nitrogen inlet tube, a reflux condenser, a stirrer, and a thermocouple, and dissolved in methyl ethyl ketone at 25 ° C. 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 polyester resin dispersions (i) to (iii).
Table 2 shows the measurement results of the physical properties of the obtained aqueous dispersions (i) to (iii).

Production Examples 6-8
(Production of aqueous dispersions (I) to (III) of resin for thermal transfer image-receiving sheet: Step (2))
An aqueous dispersion (i) of polyester resin having the types and blending amounts shown in Table 3 was added to a 2-liter four-necked flask equipped with a nitrogen inlet tube, a reflux condenser, a dropping funnel, a stirrer and a thermocouple. Ion water and styrene which is an 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 (III) of a resin for a thermal transfer image-receiving sheet 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 (III) of the obtained resin for thermal transfer image-receiving sheets. Table 4 shows the physical property values of the graft polymers P, Q, and R having the polyester resins a and b contained in the aqueous dispersions (I) to (III) as main chains.

Examples 1-7 and Comparative Examples 1-6
(Manufacture of thermal transfer image receiving sheet)
First, a water-soluble polymer having the composition and blending amount shown in Table 5 and water (deionized water) were stirred at 25 ° C. for 30 minutes, and then heated and mixed at 50 ° C. to dissolve uniformly. Thereafter, hollow particles having the composition and blending amount shown in Table 5 were mixed at 50 ° C. to prepare a heat insulating layer coating solution.
This insulation layer coating solution is dried to 20.0 g / m ² after drying with a wire bar on synthetic paper (manufactured by YUPO Corporation, trade name: YUPO FGS-250, thickness 250 μm, basis weight 200 g / m ² ). It applied so that it might become, and it was made to dry at 25 degreeC for 5 minute (s), and the heat insulation layer coating sheet was obtained.
In the preparation of the coating solution for the heat insulating layer, 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 Zeon Corporation, trade name: Nipol MH8101, hollow rate = 50%, solid content concentration = 26% by weight, methyl ethyl ketone insoluble matter = 50%, volume-median particle size (D50 ) = 420nm)
Water-soluble polymer: Gelatin (manufactured by Nitta Gelatin Co., Ltd., trade name: G0886K, viscosity 4.4 mPa · s (viscosity (60 ° C.) measured according to JIS K6503-2001))

Next, the film forming agent having the composition and blending amount shown in Table 5 and ion-exchanged water were stirred at 25 ° C. for 30 minutes, then heated and mixed at 60 ° C. until uniformly dissolved, and then kept at 40 ° C. Then, an aqueous dispersion of the resin for thermal transfer image-receiving sheet having the composition and blending amount shown in Table 5 and polyether-modified silicone were stirred at 25 ° C. for 30 minutes using a desktop ball mill, and then kept at 40 ° C. Both were mixed at 40 ° C. to prepare dye receiving layer coating liquids A to M. Each coating solution was kept at 40 ° C. The aqueous dispersion of the polyester resin used for the preparation of the dye-receiving layer coating solution was adjusted to a solid content concentration of 30% by weight and adjusted to pH 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.
Film-forming agent: Gelatin (manufactured by Nitta Gelatin Co., Ltd., trade name: G0886K, viscosity 4.4 mPa · s (viscosity (60 ° C.) measured according to JIS K6503-2001))
Polyether-modified silicone: Trade names: KF-615A, KF-6012, X-22-4515, KF-355A, KF-354L (above, manufactured by Shin-Etsu Chemical Co., Ltd.), trade names: SF8410, SH8400, L- 7002, FZ2164 (above, manufactured by Toray Dow Corning Co., Ltd.)

Each of the coating liquids for the dye-receiving layer kept at 40 ° C. was applied to the above-mentioned heat-insulating layer coating sheet with a wire bar so that it would be 3.5 g / m ² after drying, and cooled at 5 ° C. for 1 minute. And dried at 50 ° C. for 2 minutes to obtain a thermal transfer image receiving sheet.

<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 5.
(Releasability-releasability in low concentration region)
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 concentration region)
A solid image (18th gradation (L = 0: highest density)) at a high image density of 5 × 5 cm is printed on the produced thermal transfer image-receiving sheet, and the ink ribbon and the thermal transfer image-receiving sheet are peeled off when printing a black solid image. From the sound, the releasability (heat fusibility) 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.

(Image preservation-blur)
A thin line with a width of 1 mm and a length of 5 cm is printed, left standing for 168 hours in a constant temperature and humidity chamber (trade name: PR-1KT, manufactured by ESPEC CORP.) Set to 60 ° C. and 85%, and then visually observed using a microscope. The thickness of the thin line was measured at 10 points to evaluate the bleeding of the image.
A: There is no blur.
B: There is slight blurring, and the thickness of the thin wire having a width of 1 mm is more than 1.0 times and less than 1.2 times.
C: There is a blur, and a thin wire having a width of 1 mm is 1.2 times or more and less than 1.5 times.
D: There is a blur, and a thin line having a width of 1 mm is 1.5 times or more.

(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 high density printing (18th gradation (L = The transfer color density at 0: the highest density was measured with a Gretag densitometer (manufactured by GRETAG-MACBETH), and the dyeing property was evaluated. The higher the image density value, the better the dyeing property.

  As is apparent from Table 5, the thermal transfer image receiving sheets of Examples 1 to 7 are both low image density solid images and high image density solid image prints compared to the thermal transfer image receiving sheets of Comparative Examples 1 to 6. In FIG. 4, it is found that a print product having excellent releasability and no bleeding can be obtained without thermal fusion between the ink ribbon and the image receiving sheet. Furthermore, it can be seen that the thermal transfer image-receiving sheet of the example has a high maximum density at the time of high-density printing and excellent dyeability.

  The thermal transfer image-receiving sheet of the present invention is excellent in releasability in both the high image density region and the low image density region, and a printed product without blur can be obtained and a clear image can be formed. Therefore, it can be suitably used as a thermal transfer image receiving sheet for thermal transfer printing using a sublimable dye.

Claims (10)

  Thermal transfer image receiving having a dye-receiving layer containing a polyether-modified silicone having an HLB of 4 to 9, a viscosity at 25 ° C. of 1000 to 5000 mPa · s, and a polyester resin having an acid value of 10 to 40 mg KOH / g Sheet.   2. The thermal transfer image-receiving sheet according to claim 1, wherein the content of the polyether-modified silicone in the dye-receiving layer is 1 to 10% by weight based on the polyester resin contained in the dye-receiving layer.   The thermal transfer image receiving sheet according to claim 1, wherein the heat insulating layer and the dye receiving layer are formed in this order on the substrate.   The thermal transfer image receiving sheet according to any one of claims 1 to 3, wherein a glass transition point of the polyester resin is 45 to 100 ° C.   The thermal transfer image-receiving sheet according to any one of claims 1 to 4, wherein the polyester resin is a graft polymer composed of a segment (A1) made of polyester and a segment (A2) made of an addition polymerization resin.   The weight ratio [segment (A1) / segment (A2)] of the segment (A1) and the segment (A2) constituting the graft polymer is 60/40 to 90/10. Thermal transfer image receiving sheet.   The thermal transfer image-receiving sheet according to claim 5 or 6, wherein the graft polymer is a graft polymer in which the segment (A1) is a main chain and the segment (A2) is a side chain.   The segment (A1) is a polyester obtained by condensation polymerization of an alcohol component containing 50 mol% or more of an alkylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane and a carboxylic acid component. The thermal transfer image receiving sheet according to any one of? The manufacturing method of the thermal transfer image receiving sheet which has following process (3)-(5).
Step (3): Polyether-modified silicone having an HLB of 4 to 9 and a viscosity at 25 ° C. of 1000 to 5000 mPa · s is added to an aqueous dispersion of a polyester resin having an acid value of 10 to 40 mgKOH / g. Step of preparing a dye-receiving layer coating solution Step (4): Step of providing a dye-receiving layer using the dye-receiving layer coating solution obtained in Step (3) Step (5): Dye-receiving layer Drying at 40 to 110 ° C. for 1 to 10 minutes The method for producing a thermal transfer image-receiving sheet according to claim 9, wherein the method for preparing the aqueous dispersion of the polyester-based resin includes the following steps (1) and (2).
Step (1): Step of obtaining an aqueous dispersion of the polyester resin (a1) by mixing the polyester resin (a1) having a non-aromatic carbon-carbon unsaturated bond with an aqueous medium Step (2): An aqueous dispersion of a polyester resin having an acid value of 10 to 40 mgKOH / g as a graft polymer by adding and polymerizing the addition polymerizable monomer (a2) to the aqueous dispersion obtained in the step (1). The process of obtaining