JP2010253892A - Thermal transfer receiving sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal transfer receiving sheet which is excellent in mold releasability from a dye thermal transfer sheet, and is excellent in laminate protective layer transferability, and which can obtain high density print image which excels in light resistance and is usable for photograph application. <P>SOLUTION: In the thermal transfer receiving sheet having a sheet-like support and an image receiving layer on at least one surface of this sheet-like support, the image receiving layer includes polyurethane resin composed from polymerization component including following (A) to (C) and furthermore includes a release layer which includes release agent as a principal component on the image receiving layer. (A) Polyisocyanate of which more than 90 mass% comprises cyclo-aliphatically bound polyisocyanate and/or aliphatic polyisocyanate. (B) Polyol of which more than 50 mass% comprises aromatic diol. (C) Low molecular weight polyamine compound. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a thermal transfer receiving sheet having an image receiving layer containing a dye dyeable thermoplastic resin as a main component. More specifically, the present invention relates to a thermal transfer receiving sheet having good printing runnability, excellent image sharpness, good image light resistance, and excellent transferability of a laminate protective layer.

  The dye thermal transfer method uses a dye thermal transfer sheet having a dye layer and a thermal transfer receptor sheet having an image receiving layer for receiving the dye. The dye layer and the image receiving layer are superimposed, and the dye is transferred onto the image receiving layer by heating. To form an image. Heating is performed with a thermal head, and a full-color image is formed with multicolored dots. Since the dye is used, the image is clear and highly transparent, and a high-quality image usable for photographic use is obtained.

  As the resin forming the image receiving layer, dyeable thermoplastic resins such as vinyl chloride resins, polyester resins, polyvinyl acetal resins, acrylic resins, and cellulose resins have been proposed. In general, the dyeable thermoplastic resin is dissolved or dispersed in water or an organic solvent to prepare an image-receiving layer coating solution, which is applied to a sheet-like support and dried to form a thermal transfer receiving sheet. Commercialization is carried out by the method.

  Conventionally, in order to obtain a high printing density, when a resin having a high dyeing property is selected from the dye dyeing thermoplastic resins, a resin having a high dyeing property generally has a low softening point. Due to the heat of the head, a part of the image receiving layer peels off and sticks to the dye thermal transfer sheet, or the dye thermal transfer sheet does not peel off while sticking to the image receiving layer. In other words, there are problems such as a defect in the sheet and a sheet not being discharged.

In Patent Documents 1 and 2, a urethane resin is proposed as a resin for an image receiving layer that achieves both high printing density and peelability of the thermal transfer sheet. However, the thermal transfer receiving sheet using the urethane resin shown in Patent Documents 1 and 2 as the image receiving layer does not provide sufficient light resistance of the printed image, and can provide a printed image with more excellent light resistance. There is a need for a thermal transfer receiving sheet.
In recent years, as the speed of printers has increased, the image receiving layer during printing is given a higher applied energy in a shorter time so that the dye thermal transfer sheet can be peeled off from the image receiving layer in a high temperature state at a high speed. It has become to. Therefore, there is a need for a thermal transfer receiving sheet that is likely to cause fusing in a high-speed printer and has better releasability.
In general, a thermal transfer printer is a method in which a laminate protective layer is transferred onto an image receiving layer after image formation in order to improve image storage stability. If a release agent is added to the image receiving layer in order to avoid the fusion of the dye thermal transfer sheet and the image receiving layer, transfer failure of the laminate protective layer will occur, resulting in decreased storability of the printed image and gloss spots. There are problems such as.

JP-A-10-337968 (pages 1 to 3) JP-A-10-337969 (pages 1 and 2)

  The present invention eliminates the above-mentioned disadvantages of the prior art, has good releasability from the dye thermal transfer sheet, is excellent in laminate protective layer transferability, and can obtain a printed image having high density and excellent light resistance. It is an object of the present invention to provide a thermal transfer receiving sheet that can be used for, for example.

The present invention includes the following inventions.
(1) In a thermal transfer receiving sheet having a sheet-like support and an image receiving layer on at least one surface of the sheet-like support, the image receiving layer is synthesized from polymerization components including the following (A) to (C) And a release layer containing a release agent as a main component on the image receiving layer.
(A) Polyisocyanate comprising 90% by mass or more of alicyclic polyisocyanate and / or aliphatic polyisocyanate.
(B) A polyol comprising 50% by mass or more of an aromatic diol.
(C) Low molecular weight polyamine compound.
(2) The blending ratio of the (A) and the (B) at the time of synthesizing the polyurethane resin is 100: 40 in terms of a molar ratio of the isocyanate group that the (A) has and the hydroxyl group that the (B) has. The thermal transfer receiving sheet according to (1), which is in a range of ˜100: 90.
(3) The polyurethane resin is further synthesized from a polymerization component containing the following (D), and the content ratio of the carboxyl group is 0.3 to 6% by mass with respect to 100% by mass of the polyurethane resin. The thermal transfer receiving sheet according to (1) or (2).
(D) A diol having a carboxyalkyl group as a side chain.
(4) The thermal transfer receiving sheet according to (1) to (3), wherein the release agent is a resin having polysiloxane in the molecule.
(5) The thermal transfer receiving sheet according to (1) to (4), wherein the coating amount of the release layer is 0.01 to ² g / m ² .
(6) The thermal transfer receiving sheet according to (1) to (5), wherein the image receiving layer contains a carbodiimide compound.
(7) The thermal transfer receiving sheet according to (1) to (6), wherein an undercoat layer containing hollow particles is provided between the sheet-like support and the image receiving layer.
(8) The thermal transfer receiving sheet according to (1) to (7), wherein two or more layers including the image receiving layer and the release layer are layers formed by simultaneous multilayer coating.

  According to the present invention, there can be obtained a thermal transfer receiving sheet that is excellent in releasability from a dye thermal transfer sheet and excellent in transferability of a laminate protective layer, and can obtain a printed image having high density and excellent light resistance.

Hereinafter, the present invention will be described in more detail.
(Sheet support)
As the sheet-like support used for the thermal transfer receiving sheet of the present invention, papers and synthetic resin sheets mainly composed of cellulose pulp are used. Examples of paper include high-quality paper (acidic paper, neutral paper), medium-quality paper, coated paper, art paper, glassine paper, and resin-laminated paper.
Examples of the sheet mainly composed of a synthetic resin include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, polyamide, polyvinyl chloride, polystyrene, polycarbonate, and polyvinyl chloride.
Examples of the porous stretched sheets include, for example, synthetic paper, porous polyester sheet and the like mainly composed of a thermoplastic resin such as polyolefin and polyester. These materials may be used alone, or may be a laminate sheet obtained by laminating and adhering porous stretched sheets, porous stretched sheets, and other sheets and / or papers.
The sheet-like support may have a structure in which a first base material layer on which an image receiving layer is formed, an adhesive layer, a release agent layer, and a second base material layer are sequentially laminated. Of course, a sheet-like support having a structure of a sticker or a seal type can also be used.
Among the sheet-like supports, papers mainly composed of cellulose pulp are preferable. The texture of the resulting thermal transfer receiving sheet is close to that of photographic paper, is low in cost, and has little environmental impact.

(Image receiving layer)
The present invention relates to a thermal transfer receiving sheet in which an image receiving layer is formed on at least one surface of a sheet-like support, wherein the image receiving layer contains a polyurethane resin having a specific composition in the molecule. Is.

(Polyurethane resin)
In the present invention, the method for synthesizing the polyurethane resin to be used is not particularly limited. Generally, after synthesizing a urethane prepolymer obtained from polyisocyanate and polyol as raw materials, a low molecular weight polyamine compound is used, Obtained by chain extension of urethane prepolymer.

(Urethane prepolymer)
The urethane prepolymer used as an intermediate raw material for the polyurethane resin is synthesized by polycondensation of polyisocyanate and polyol. In this invention, it is preferable to synthesize | combine in ratio of polyisocyanate and polyol in the range of 100: 40-100: 90 in the molar ratio of the isocyanate group: hydroxyl group of a raw material, More preferably, it is 100: 55-100: 85 It is preferable to synthesize in the range, even more preferably in the range of 100: 60 to 100: 70. When the ratio of the polyol to the polyisocyanate is less than 40, the synthesized polyurethane resin has an excessive crystal region, the dyeability is lowered, and the color density of the printed matter printed by thermal transfer is lowered. On the other hand, if it exceeds 90, the amorphous region of the synthesized polyurethane resin becomes excessive, the heat resistance of the obtained image receiving layer is lowered, and there are problems such as fusion with the dye thermal transfer sheet and peeling of the image receiving layer during printing. It tends to occur. In addition, the prints that have been heat-transfer printed have bleeding over time, which impairs the storage stability of the prints.

(Polyisocyanate)
The polyisocyanate combines with a low molecular weight polyamine compound to form a hard block in the polyurethane resin. The hard block forms a crystalline region by electrical or chemical bonding with the hard block of another molecular chain. This crystal region imparts heat resistance to the polyurethane resin.
Polyisocyanates are mainly classified into alicyclic, aliphatic, and aromatic types. Among these, when aromatic polyisocyanates are used as raw materials for polyurethane resins, the light resistance of images is significantly reduced. The reason why the aromatic polyisocyanate reduces the light resistance of the image is not clear, but the hard block in which the aromatic rings of the polyisocyanate are regularly arranged prevents the dye molecules from penetrating into the image receiving layer, This is presumably because the dye tends to be unevenly distributed in the surface layer portion of the image receiving layer which is easily affected by ultraviolet rays.

  The present invention is characterized by containing 90% by mass or more of alicyclic polyisocyanate and / or aliphatic polyisocyanate in 100% by mass of polyisocyanate used for the synthesis of urethane prepolymer, more preferably 95% by mass. As described above, it is more preferably 98% by mass or more. When the content of the alicyclic polyisocyanate and / or the aliphatic polyisocyanate is less than 90% by mass, the light resistance of the printed matter thermally transferred to the obtained thermal transfer receiving sheet is remarkably lowered. Moreover, it is preferable to adjust content of aliphatic polyisocyanate to the range of 20 mass% or less of the polyisocyanate used for the synthesis | combination of a urethane prepolymer. When the content of the aliphatic polyisocyanate exceeds 20% by mass, the heat resistance of the obtained polyurethane resin is lowered, and the peelability between the dye thermal transfer sheet and the thermal transfer receiving sheet is lowered, or the bleeding of the printed matter is deteriorated. It tends to occur.

Examples of the aliphatic polyisocyanate that can be used in the present invention include hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate, and hexamethylene triisocyanate. Among these, hexamethylene diisocyanate is preferably used.
Examples of the alicyclic polyisocyanate that can be used in the present invention include isophorone diisocyanate, dicyclohexylmethane diisocyanate, cyclohexane diisocyanate, and triisocyanate cyclohexane. Among these, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and cyclohexane diisocyanate are preferably used. The aliphatic polyisocyanate and alicyclic polyisocyanate that can be used in the present invention are not limited to the above examples, and can be used alone or in combination of two or more.

  In addition to the aliphatic polyisocyanate and the alicyclic polyisocyanate, an aromatic polyisocyanate can be used within a range that does not impair the effects of the present invention. Examples of aromatic polyisocyanates include aromatics such as phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and polyisocyanates such as xylylene diisocyanate, tetramethylxylylene diisocyanate, and triisocyanate methylbenzene. Group polyisocyanate etc. are mentioned, These can be used independently and can also use 2 or more types together.

(Polyol)
The polyol that forms a urethane prepolymer together with the polyisocyanate forms a soft block in the polyurethane resin. The soft block contributes to the dyeing property of the image receiving layer. The polyurethane resin used in the present invention is characterized by containing 50% by mass or more of an aromatic polyol with respect to 100% by mass of all polyol components as a polyol component, preferably 60% by mass or more, more preferably 70% by mass or more. Further, it is preferable to contain 80% by mass or more. When the aromatic polyol is less than 50% by mass, the dyeing property of the obtained image receiving layer is lowered, and a highly sensitive thermal transfer receiving sheet cannot be obtained, or the heat resistance of the image receiving layer is lowered, and the dye thermal transfer sheet Troubles such as fusion of the toner and peeling of the image receiving layer occur.

  Examples of aromatic polyols that can be used in the present invention include aromatic polyester polyols such as polyethylene terephthalate diol, polyethylene isophthalate diol, polyhexamethylene isophthalate adipate diol, polyethylene oxide adducts and ethylene oxide adducts of aromatic polyesters. These may be used alone or in combination of two or more.

  Also, it is possible to use a polyol other than the aromatic polyol in combination as long as the effects of the present invention are not hindered. Examples of polyols other than aromatic polyols include polyethylene adipate diol, polybutylene adipate diol, polyethylene butylene adipate diol, polyethylene succinate diol, polybutylene succinate diol, polyethylene sebacate diol, polybutylene sebacate diol, and poly-ε. -Polyester polyols such as caprolactone diol, poly (3-methyl-1,5-pentylene adipate) diol, polytetramethylene carbonate diol, polyhexamethylene carbonate diol, poly (1,4-cyclohexanedimethylene carbonate) diol, poly (Hexamethylene-1,4-cyclohexanedimethylene) polycarbonate polyol such as carbonate diol, polyethylene glycol , Polypropylene glycol, polyether polyol such as polytetramethylene glycol, and acrylic polyols and the like, which can be used alone or may be used in combination of two or more.

  Examples of the low molecular weight polyol include ethylene glycol, propylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, pentaerythritol, sorbitol, and the like. It can be used or two or more types can be used in combination.

(Polyamine compound)
The polyurethane resin used in the present invention is obtained by synthesizing the urethane prepolymer and then chain-extending the urethane prepolymer with a low molecular weight polyamine compound. The low molecular weight polyamine compound forms a hard block in the polyurethane resin together with the polyisocyanate. As described above, the low molecular weight polyamine compound is preferably non-aromatic because the light resistance of the dye thermally transferred to the image receiving layer is lowered when a large amount of aromatic component is contained in the crystalline region.

  Examples of the low molecular weight polyamine compound that can be used in the present invention include hydrazine, ethylenediamine, propylenediamine, hexamethylenediamine, bisaminomethylcyclohexane, di (aminocyclohexyl) methane, piperazine, 2-methylpiperazine, isophoronediamine, diethylenetriamine, and imino. Examples thereof include low molecular weight polyamines such as bispropylamine and triethylenetetramine, and these can be used alone or in combination of two or more.

The method for synthesizing the polyurethane resin of the present invention is not particularly limited, and is synthesized using various known methods, reaction catalysts, and reaction inhibitors.
The polyurethane resin of the present invention may be a solvent-soluble type or a water-dispersed type such as a self-emulsifying type or a forced emulsifying type using a dispersing agent. In recent years, it is preferable to use a water-dispersed type in consideration of the environment, and among the water-dispersed types, a self-emulsifying type is preferable because a film-forming property during coating can be obtained and a uniform image-receiving layer can be obtained.

  The method of self-emulsification or forced emulsification of the polyurethane resin is not particularly limited, and various known methods can be used. By adding a diol having a carboxyl alkyl as a side chain as a raw material to the polyurethane resin. A method of introducing a carboxyl group to make it hydrophilic is preferable. The content ratio of the carboxyl group derived from the diol having the carboxyl alkyl as a side chain is preferably 0.3 to 6% by mass, more preferably 0.5 to 5% by mass, more preferably 100% by mass of the polyurethane resin. Preferably it is 2.5-4 mass%. When the content ratio of the carboxyl group is less than 0.3% by mass, the polyurethane resin becomes unstable in the coating liquid, smears occur in the coating drying process, and the print image quality may deteriorate. Further, when the content ratio of the carboxyl group exceeds 6% by mass, the water resistance of the obtained image receiving layer is inferior, and when the printed material is stored in a high temperature and high humidity environment, the printed material is smeared or the storage stability is lowered. There is danger.

The lower limit value of the glass transition temperature of the polyurethane resin used in the present invention is preferably −30 ° C., more preferably −10 ° C., and still more preferably 0 ° C. When the glass transition temperature of the polyurethane resin is less than −30 ° C., fusion between the image receiving layer and the dye thermal transfer sheet is likely to occur. The upper limit of the glass transition temperature of the polyurethane resin used in the present invention is preferably 60 ° C, more preferably 50 ° C, and even more preferably 40 ° C. When the glass transition temperature of the polyurethane resin exceeds 60 ° C., the dyeing property of the image receiving layer is inferior, and a sufficient print density cannot be obtained, which is not preferable.
In the present invention, the glass transition temperature is measured according to ISO-11359-2.
(Measurement example of glass transition temperature of resin)
Measuring instrument: Dynamic viscoelasticity measuring device DMS6100 type (manufactured by Seiko Instruments Inc.)
Drive frequency: 10Hz
Measurement mode: Tensile mode Distance between chucks: 20 mm
Temperature increase rate: 5 ° C / min
From the measurement results of the viscoelasticity / temperature characteristics of the resin, a viscoelasticity / temperature graph was created, and the glass transition temperature was determined as the peak value of tan δ.

(Crosslinking agent)
The polyurethane resin used in the image receiving layer of the present invention is preferably crosslinked with a crosslinking agent after coating. Examples of the crosslinking agent used in the image receiving layer of the present invention include an isocyanate crosslinking agent, a titanium chelate crosslinking agent, a carbodiimide crosslinking agent, and an oxazoline crosslinking agent.
When a polyurethane resin having a carboxyl group is used in the image receiving layer, the addition of a carbodiimide-based crosslinking agent to the image receiving layer causes the carboxyl group and the carbodiimide-based crosslinking agent to crosslink, thereby improving the heat resistance of the image receiving layer. And the effect of preventing fusion with the dye thermal transfer sheet is particularly high and preferable.
The content ratio of the carbodiimide-based crosslinking agent is preferably 0.5 to 40% by mass and more preferably 1 to 30% by mass with respect to 100% by mass of the resin used in the image receiving layer.
The coating amount of the image-receiving layer, 0.5 to 10 g / ^{m 2} is preferred. When the coating amount of the image receiving layer is less than 0.5 g / m ² , there may be cases where sufficient print image quality and image light resistance cannot be obtained.
If it exceeds m ² , the heat insulating effect of the sheet-like support cannot be exhibited, and a sufficient print density may not be obtained.

(Release layer)
The release layer of the present invention is formed on the image receiving layer and on the outermost layer of the thermal transfer receiving sheet, and contains a release agent as a main component.
Since the release layer of the present invention provides the release property of the dye thermal transfer sheet without impairing the heat resistance strength of the image receiving layer as compared with the case where a release agent is contained in the image receiving layer, the dye thermal transfer sheet High anti-fusing effect. In addition, when a release agent-containing image receiving layer is used without providing a release layer, the amount of the release agent that bleeds out on the surface of the image receiving layer varies depending on the coating concentration and drying conditions during coating. The mold releasability of the dye thermal transfer sheet and the transferability of the laminate protective layer vary. Therefore, an apparatus and labor for precisely controlling manufacturing conditions are required. On the other hand, the thermal transfer receiving sheet of the present invention is not easily affected by the manufacturing conditions, and can be easily manufactured while maintaining the releasability of the dye thermal transfer sheet and the transferability of the laminate protective layer within a certain range.
Examples of the release agent contained in the release layer of the present invention include waxes, fluorine compounds, silicone oils, silicone resins, higher fatty acids, higher fatty acid metal salts, higher fatty acid esters, higher fatty acid amides, pigments, fine particles, and the like. Various known release agents can be used, but a resin having a polysiloxane segment in the molecule is preferably used.

When a release agent having a low affinity with the image receiving layer resin, such as waxes, fluorine compounds, and silicone oil, is used in the release layer, yellow, magenta, and cyan are printed for each color print. The release agent on the surface of the image receiving layer is reduced by the dye thermal transfer sheet, and it may not be possible to maintain a good release property at the time of cyan printing of the third color, which may cause fusion.
The resin having a polysiloxane segment in the molecule contributes to the adhesiveness of the copolymerized resin to the adjacent image receiving layer, so that the release agent is fixed on the surface of the image receiving layer, and such a problem does not occur. .
Further, it is preferable to use a release layer containing a polysiloxane segment and a resin having a functional group in the molecule in order to improve adhesion to the image receiving layer, and the polysiloxane segment has a carboxyl group in the molecule. When a release layer containing a resin and an image receiving layer containing a carbodiimide crosslinking agent are used in combination, the carboxyl group of the release agent undergoes a crosslinking reaction with the carbodiimide crosslinking agent on the surface of the image receiving layer. Is particularly preferred since it can be strongly fixed to the surface of the image receiving layer.

Moreover, in order to suppress the release | release to the air | atmosphere of the harmful organic solvent at the time of coating drying as much as possible, it is preferable that a mold release agent is aqueous solvent dispersibility. Water-based solvent dispersibility means water-soluble and water-dispersible properties, as well as those that dissolve only in a specific organic solvent at a high concentration, and can disperse a resin organic solvent solution in water at a low concentration. Including things.
For resins with polysiloxane segments in the molecule, when the polysiloxane monomer material and copolymer resin monomer material are copolymerized, a monomer material that adds a carbonyl group, sulfonyl group, or hydroxyl group to the resin after polymerization is added. It can be made water-soluble or water-dispersible by various known production methods such as the method of Examples of monomer materials that impart a carbonyl group, a sulfonyl group, or a hydroxyl group to the polymer include dimethylolpropionic acid and 5-sulfoisophthalic acid. Alternatively, a resin having a polysiloxane segment in the molecule is obtained by emulsifying a mixture of a polysiloxane monomer material, a copolymer resin monomer material, and a polymerization initiator in water using a surfactant, and a temperature required for the polymerization reaction. Can be made water-dispersible by, for example, a method of preparing a copolymer emulsion.

Examples of commercially available resins having a polysiloxane segment in the molecule include Cymac US450 (manufactured by Toagosei Co., Ltd., water dispersibility), US480 (manufactured by Toagosei Co., Ltd., water dispersibility), and the like.
As commercial products, X-22-8053 (manufactured by Shin-Etsu Chemical Co., Ltd., isopropyl alcohol dissolved product, aqueous solvent dispersibility), X-24-798A (manufactured by Shin-Etsu Chemical Co., Ltd., isopropyl alcohol dissolved product, aqueous solvent dispersed) Sex).
The solid content coating amount of the release layer used in the present invention is preferably 0.01 to ² g / m ² , more preferably 0.03 to 1 g / m ² . If it is less than 0.01 g / m ² , the releasability from the dye thermal transfer sheet becomes insufficient at the time of printing and may be fused. If it exceeds ² g / m ² , the dye dyed on the release layer may diffuse into the release layer, and image bleeding may be significant.

(Undercoat layer)
Since the undercoat layer containing hollow particles can impart heat insulation and cushioning properties, it can improve image clarity and image uniformity.
Examples of the material for forming the walls of the hollow particles used in the undercoat layer include polymers of acrylonitrile, vinylidene chloride, and styrene acrylate. As a method for producing these hollow particles, a method of heating and foaming microcapsules in which butane gas is sealed in resin particles, an emulsion polymerization method, and the like can be mentioned.
The particle size of the hollow particles is preferably 0.1 to 10 μm. When the particle size of the hollow particles is less than 0.1 μm, the walls of the hollow particles become thin and the heat resistance is insufficient, and is easily broken in the coating and drying process. On the other hand, if it exceeds 10 μm, the surface irregularity of the obtained thermal transfer receiving sheet becomes large and the image uniformity may be inferior.
The volume hollow ratio of the hollow particles is preferably 50 to 90%. When the volumetric hollow ratio of the hollow particles is less than 50%, the effect of imparting heat insulating properties and cushioning properties may be insufficient. If it exceeds 90%, the walls of the hollow particles become thin and the durability may be lowered.
The coating amount of the undercoat layer is, 1 to 30 g / ^{m 2} is preferred. If the coating amount of the undercoat layer is less than 1 g / m ² , sufficient heat insulating properties and cushioning properties cannot be expected, and if it exceeds 30 g / m ² , the effect obtained for an increase in cost is small.

(Middle layer)
For the purpose of preventing bleeding of the image by blocking the dye dyed on the image receiving layer from moving to the undercoat layer or the sheet-like support, and for obtaining a smooth surface by filling the unevenness of the undercoat layer Further, an intermediate layer may be provided between the undercoat layer and the image receiving layer.

(Back layer)
In the thermal transfer receiving sheet of the present invention, a back layer can be appropriately provided on the surface (back surface) of the sheet-like support on which the image receiving layer is not provided.
The purpose of the back layer is to improve running performance, to prevent static electricity, to prevent the surface of the thermal transfer receiving sheet from being scratched by rubbing between the thermal transfer receiving sheets, and to prevent dye transfer to the back side when the thermal transfer receiving sheets are stacked. The back layer contains a resin as an adhesive component and, if necessary, a pigment and an additive.

Various auxiliary agents such as wetting agents, dispersants, thickeners, antifoaming agents, colorants, antistatic agents, preservatives and the like used in general coated paper production can be appropriately added to each of the coating layers. .
The image receiving layer, release layer, intermediate layer and other coating layers of the thermal transfer receiving sheet of the present invention are bar coater, gravure coater, comma coater, blade coater, air knife coater, gate roll coater, die coater, curtain coater. And using a known coater such as a slide bead coater, a predetermined coating solution can be applied and dried.
The release layer of the present invention, the optimum coat weight is optimum coating weight of 0.01 to 2 g / ^{m 2.} In the case of coating such a low coating amount layer on the image receiving layer, in the sequential coating method in which coating and drying are performed for each single layer, the release layer is not uniformly formed, and coating spots In some cases, the desired releasability and transferability of the laminate protective layer cannot be obtained, and print spots and a decrease in print density may occur. The release layer and the image receiving layer of the present invention are preferably formed using a simultaneous multilayer coating method. A uniform release layer can be formed even with a low coating amount by the simultaneous multilayer coating method. It is also preferable to form the intermediate layer and the undercoat layer together with the release layer and the image receiving layer by the simultaneous multilayer coating method from the viewpoint of uniform coating formation and efficiency.

(Calendar processing)
In the present invention, the thermal transfer receiving sheet may be calendered. Since the unevenness of the surface of the obtained thermal transfer receiving sheet can be reduced by the calendar process and a uniform image can be obtained, it is preferably used. The calendar process may be performed at any stage. As the calendar apparatus used for the calendar process, a calendar apparatus generally used in the paper industry such as a super calendar, a soft calendar, a gloss calendar, and a clearance calendar can be appropriately used.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Further, “parts” and “%” in the examples represent “parts by mass” and “% by mass”, respectively, unless otherwise specified, and are solid contents.

Examples [Polyurethane resin synthesis examples UP1 to UP5]
After the urethane prepolymer obtained from polyisocyanate and polyol was synthesized by the following method, the urethane prepolymer was chain-extended using low molecular weight polyamine compounds to synthesize polyurethane resins UP1 to UP5.
To a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen blowing tube, the polyol components shown in Table 1 and 2,2-dimethylolbutanoic acid were added in the amounts shown in Table 1, and further dibutyl 0.001 g of tin dilaurate and 120 g of methyl ethyl ketone were added and mixed uniformly. Next, the amount of the isocyanate component shown in Table 1 was added to this and the amount shown in Table 1 was added, and the mixture was reacted at 80 ° C. for 5 hours to obtain a methyl ethyl ketone solution of a prepolymer.
The resulting prepolymer solution of methyl ethyl ketone was cooled to 30 ° C., neutralized by adding triethylamine in the amount shown in Table 1, and then 403 g of water was gradually added to emulsify and disperse. To this emulsified dispersion, a 20% by mass aqueous solution of ethylenediamine was added in the amount shown in Table 1 (in terms of solid content) and stirred for 2 hours. The solvent was removed while the temperature was raised to 50 ° C. over 2 hours under reduced pressure to obtain a polyurethane resin emulsion having a nonvolatile content of about 39% by mass. In the present invention, the nonvolatile content of the polyurethane resin emulsion means the residual weight ratio after the aqueous dispersion is dried at 105 ° C. for 3 hours.

  Polyisocyanate, polyol, low molecular weight polyamine compound used for the synthesis of polyurethane resins UP1 to UP5, and types of diols having carboxylalkyl as a side chain, alicyclic polyisocyanate, aliphatic polyisocyanate and aromatic polyisocyanate in polyisocyanate component Table 2 shows the content ratio (mass ratio) of the isocyanate, the ratio of polyisocyanate and polyol in the prepolymer (isocyanate group: molar ratio of hydroxyl groups), and the content ratio of carboxyl groups to the polyurethane resin obtained by synthesis. there were.

<Example 1>
[Preparation of thermal transfer receiving sheet]
As the sheet-like support, art paper having a thickness of 150 μm (trade name: OK Kanto N, manufactured by Oji Paper Co., Ltd., basis weight 174.4 g / m ² ) was used. On one side of the sheet-like support, an undercoat layer coating solution A-1 having the following composition, an image receiving layer coating solution B-1 having the following composition, and a release layer coating solution C-1 having the following composition are as follows. Three layers were simultaneously coated and dried using a slide bead coater so as to obtain a solid content coating amount, to prepare a thermal transfer receiving sheet.
Undercoat layer solid content coating amount: 15 g / m ²
Image receiving layer solid content coating amount: 3 g / m ²
Release layer solid content coating amount: 0.1 g / m ²

[Preparation of undercoat layer coating solution A-1]
50 parts of previously expanded hollow particles mainly composed of acrylonitrile and methacrylonitrile (average particle diameter 3.2 μm, volume hollow ratio 76%)
10 parts of polyvinyl alcohol (trade name: PVA205, manufactured by Kuraray)
30 parts of vinyl chloride vinyl acetate copolymer emulsion (trade name: Viniblanc 603, manufactured by Nissin Chemical, Tg: 60 ° C)
10 parts of carbodiimide crosslinking agent (trade name: Carbodilite E-02, manufactured by Nisshinbo Co., Ltd.)
200 parts of water [Preparation of image-receiving layer coating solution B-1]
90 parts of polyurethane resin UP1 of the above synthesis example 10 parts of carbodiimide-based crosslinking agent (trade name: Carbodilite E-02, manufactured by Nisshinbo Co., Ltd.)
300 parts of water [Releasing layer coating liquid C-1]
99 parts of an aqueous solvent dispersible polysiloxane graft acrylic resin (trade name: X-22-8053, manufactured by Shin-Etsu Chemical Co., Ltd.,
Carboxyl group-containing, isopropyl alcohol dissolved product)
Wetting agent (trade name: Nopco Wet 50, manufactured by San Nopco Company) Adjusted water was added so that the solid content concentration of 1 part was 1% to prepare a release layer coating solution C1.

<Example 2>
A thermal transfer receiving sheet was obtained in the same manner as in Example 1 except that the polyurethane resin UP2 of the above synthesis example was used in place of the polyurethane resin UP1 in the preparation of the image receiving layer coating liquid B-1 of Example 1.
<Example 3>
A thermal transfer receiving sheet was obtained in the same manner as in Example 1 except that the polyurethane resin UP3 of the synthesis example was used instead of the polyurethane resin UP1 in the preparation of the image receiving layer coating liquid B-1 of Example 1.

<Example 4>
A thermal transfer receiving sheet was obtained in the same manner as in Example 1 except that the release layer coating solution C-2 having the following composition was used instead of the release layer coating solution C-1.
[Coating liquid C-1 for release layer]
99 parts of aqueous solvent dispersible polysiloxane graft acrylic resin (trade name X-24-798A, manufactured by Shin-Etsu Chemical Co., Ltd.,
Carboxyl group free, isopropyl alcohol dissolved product)
Wetting agent (trade name: Nopco Wet 50, manufactured by San Nopco Company) Adjusted water was added so that the solid content concentration of 1 part was 0.5% to prepare a release layer coating solution C1.

<Example 5>
[Preparation of thermal transfer receiving sheet]
As the sheet-like support, art paper having a thickness of 150 μm (trade name: OK Kanto N, manufactured by Oji Paper Co., Ltd., basis weight 174.4 g / m ² ) was used. The undercoat layer coating liquid A-1 is applied to one side of the sheet-like support so that the solid content coating amount is 15 g / m ² and dried to form an undercoat layer, and the undercoat layer is formed on the undercoat layer. The image-receiving layer coating solution B-1 is applied and dried so as to have a solid content coating amount of 3 g / m ² to form an image-receiving layer. Further, the mold release layer is formed on the image-receiving layer. The layer coating liquid C-1 was coated and dried so that the solid content coating amount was 0.1 g / m ² to prepare a thermal transfer receiving sheet.

<Comparative Example 1>
Example 1 In place of the image receiving layer coating solution B-1, the image receiving layer coating solution B-2 having the following composition was used, and the thermal transfer receiving was performed in the same manner as in Example 1 except that no release layer was provided. A sheet was obtained.
[Preparation of Image Receiving Layer Coating Liquid B-2]
Polyurethane resin UP1 of the above synthesis example 88 parts Carbodiimide type cross-linking agent 10 parts (trade name: Carbodilite E-02, Nisshinbo Co., Ltd.)
Aqueous solvent dispersible polysiloxane graft acrylic resin 2 parts (trade name: X-22-8053, manufactured by Shin-Etsu Chemical Co., Ltd.,
Carboxyl group-containing, isopropyl alcohol dissolved product)
300 parts of water

<Comparative example 2>
A thermal transfer receiving sheet was obtained in the same manner as in Example 1 except that the polyurethane resin UP4 of the above synthesis example was used instead of the polyurethane resin UP1 in the preparation of the image receiving layer coating liquid B-1 of Example 1.
<Comparative Example 3>
A thermal transfer receiving sheet was obtained in the same manner as in Example 1 except that the polyurethane resin UP5 of the above synthesis example was used instead of the polyurethane resin UP1 in the preparation of the image receiving layer coating liquid B-1 of Example 1.

(Evaluation)
The following tests were conducted on the coating solutions prepared in the above Examples and Comparative Examples and the obtained thermal transfer receiving sheet. The obtained results are shown in Table 3.

[Releasability from dye thermal transfer sheet]
A commercially available thermal transfer video printer (trade name: UP-50, manufactured by Sony Corporation) equipped with a sublimation dye thermal transfer sheet (trade name: UP-540, manufactured by Sony Corporation) was used. Under a 45 ° C. environment, 10 black solid images were continuously printed on the thermal transfer receiving sheet. The releasability from the dye thermal transfer sheet was evaluated according to the following criteria.
A: There is no fusion between the surface of the thermal transfer receiving sheet and the dye thermal transfer sheet, and 10 sheets are normally discharged continuously, and there is no problem in practical use.
○: Some noise is caused by light fusion between the surface of the thermal transfer receiving sheet and the dye thermal transfer sheet, but all 10 sheets are discharged and practical.
X: The surface of the thermal transfer receiving sheet and the dye thermal transfer sheet cause fusing, and some sheets are not normally discharged, and are not suitable for practical use.

[Laminate protective layer transferability]
On the image-receiving layer of the obtained thermal transfer receiving sheet, a thermal transfer tester (trade name: TH-PMI2, manufactured by Okura Electric Co., Ltd.) was used to vary the applied energy, and a sublimation dye thermal transfer sheet (trade name: UP-540 (manufactured by Sony Corporation) was transferred, and the minimum energy that the laminate protective layer could transfer was determined.
A: Laminate protective layer transfer minimum energy is less than 0.6 mJ / dot, and there is no problem even if it is used in a high-speed printer.
○: The minimum transfer energy of the laminate protective layer is 0.6 to 1.1 mJ / dot and can be used in a high-speed printer.
X: The laminate protective layer transfer minimum energy exceeds 1.1 mJ / dot and is not suitable for a high-speed printer.

(Image light resistance)
Using a commercially available thermal transfer video printer (trade name: UP-50, manufactured by Sony Corporation) equipped with a sublimation dye thermal transfer sheet (trade name: UP-540, manufactured by Sony Corporation), a black solid on the thermal transfer receiving sheet at room temperature. Printed. The obtained black solid image print was processed with an Xe fade meter until the integrated illuminance reached 13,000 kJ / m ² .
The color tone before and after the light resistance test of the image was measured using a color difference meter (Gretag) in accordance with JIS Z 8721. The measured values were recorded in the L ^* a ^* b ^* color system based on JIS Z 8729, and the color difference (ΔE ^* ) before and after treatment was calculated by the method based on JIS Z 8730 to evaluate the light resistance.
A: ΔE ^* is less than 7, and there is no problem in practical use.
○: ΔE ^* is 7 or more and less than 13 and is practical.
×: ΔE ^* is not less than 13, not suitable for practical use.

[Image density]
By using a commercially available thermal transfer video printer (trade name: DPP-SV55, manufactured by Sony Corporation), heating controlled by a thermal head was performed to form a solid black image on the thermal transfer receiving sheet. About the obtained black solid image, the reflection density was measured using the Macbeth reflection densitometer (brand name: RD-914, Kollmorgen), and the printing density was evaluated.
A: The print density is 1.9 or more, and there is no problem in practical use.
○: The print density is 1.7 or more and less than 1.9, and is practical.
X: The print density is less than 1.7 and is not suitable for practical use.

表３から明らかなように、実施例１〜５の熱転写受容シートは、染料熱転写シートとの離型性が良好で、かつラミネート保護層の転写性に優れ、高濃度で耐光性に優れた印画画像が得られる熱転写受容シートである。

As is apparent from Table 3, the thermal transfer receiving sheets of Examples 1 to 5 have good releasability from the dye thermal transfer sheet, excellent transferability of the laminate protective layer, and high density and excellent light resistance. It is a thermal transfer receiving sheet from which an image can be obtained.

  According to the present invention, a releasability with a dye thermal transfer sheet is excellent, and the transfer property of the laminate protective layer is excellent, and a receiving sheet for a thermal transfer printer is obtained from which a printed image with high density and excellent light resistance can be obtained. There is a great contribution to the industry.

Claims (8)

In a thermal transfer receiving sheet having a sheet-like support and an image receiving layer on at least one surface of the sheet-like support, the image receiving layer is synthesized from a polymerization component containing the following (A) to (C) A thermal transfer receiving sheet comprising a resin and a release layer containing a release agent as a main component on the image receiving layer.
(A) Polyisocyanate comprising 90% by mass or more of alicyclic polyisocyanate and / or aliphatic polyisocyanate.
(B) A polyol comprising 50% by mass or more of an aromatic diol.
(C) Low molecular weight polyamine compound. The blending ratio of the (A) and the (B) at the time of synthesizing the polyurethane resin is a molar ratio of the isocyanate group possessed by the (A) and the hydroxyl group possessed by the (B), from 100: 40 to 100: The thermal transfer receiving sheet according to claim 1, which is in the range of 90. The polyurethane resin is further synthesized from a polymerization component containing the following (D), and the content ratio of the carboxyl group is 0.3 to 6% by mass with respect to 100% by mass of the polyurethane resin. Item 3. The thermal transfer receiving sheet according to Item 1 or 2.
(D) A diol having a carboxyalkyl group as a side chain.   The thermal transfer receiving sheet according to any one of claims 1 to 3, wherein the release agent is a resin having polysiloxane in a molecule. The thermal transfer receiving sheet according to any one of claims 1 to 4, wherein a coating amount of the release layer is 0.01 to ² g / m2.   The thermal transfer receiving sheet according to claim 1, wherein the image receiving layer contains a carbodiimide compound. The thermal transfer receiving sheet according to any one of claims 1 to 6, wherein an undercoat layer containing hollow particles is provided between the sheet-like support and the image receiving layer. The thermal transfer receiving sheet according to claim 1, wherein the two or more layers including the image receiving layer and the release layer are layers formed by simultaneous multilayer coating.