JP2010253704A - Thermal transfer receptive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellent thermal transfer receptive sheet which provides a clear printed image having high printing density and high light resistance, cause no damage to an image receptive layer due to blocking even when the receptive sheets are stored in a superposed manner and cause no printer running obstacle due to the occurrence of curling. <P>SOLUTION: The thermal transfer receptive sheet comprises: a sheet-like support; and the image receptive layers laminated on at least one surface of the sheet-like support, wherein the image receptive layer contains a polyurethane resin synthesized from polymerizable components including the following (A) to (C) and a rear surface layer contains a polyvinyl alcohol derivative. (A) is polyisocyanate the 90 mass% or more of which is an alicyclic polyisocyanate and/or aliphatic polyisocyanate, (B) is polyol the 50% or more of which is aromatic diol. (C) is low-molecular-weight polyamine compound. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a thermal transfer receiving sheet (hereinafter also simply referred to as a receiving sheet) having an image receiving layer (hereinafter also simply referred to as a receiving layer) containing a dye dyeable thermoplastic resin as a main component. More specifically, the present invention provides a print image having a high print density, a clear and high light resistance, no damage to the image receiving layer due to blocking even when the thermal transfer receiving sheet is stored in an overlapping manner, and curling The present invention relates to an excellent thermal transfer receiving sheet that does not cause printer running trouble due to occurrence.

  The dye thermal transfer system is a thermal transfer receiving sheet (hereinafter also referred to as “receiving layer”) having a dye thermal transfer sheet (hereinafter also referred to as “ink ribbon”) and an image receiving layer (hereinafter also referred to as “receiving layer”) that receives the dye. The dye layer and the receiving layer are superposed, and the dye is transferred onto the 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 for forming the receptor layer, dyeable thermoplastic resins such as vinyl chloride resins, polyester resins, polyvinyl acetal resins, acrylic resins, cellulose resins, and polyurethane resins have been proposed. In general, the dyeable thermoplastic resin is dissolved or dispersed in water or an organic solvent to prepare a receiving layer coating solution, which is applied to a sheet-like support and dried to form a receiving sheet. The product has been commercialized.

Conventionally, in order to obtain a high printing density, when a resin having a high dyeing property is selected from the above-mentioned dye-dyeing thermoplastic resins, a resin having a high dyeing property has a low softening point. Due to this heat, the dye receiving layer and the dye thermal transfer sheet are fused, causing problems such as defects in the image and the 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 ink ribbon peelability. However, the thermal transfer receiving sheet using the urethane resin disclosed in Patent Documents 1 and 2 as an image receiving layer does not provide sufficient light resistance of a printed image, and a thermal transfer receiving sheet from which an excellent light resistant image can be obtained. Is required.

Also, in the manufacturing process, the receiving sheet is coated with the receiving layer coating on the sheet-like substrate, dried, wound up in a roll, and stored in a state where the receiving layer surface is in contact with the back side of the sheet-like substrate. It is normal to receive a load. Since the urethane resin has good adhesiveness with the sheet-like base material, a problem (blocking) occurs in which the receiving layer surface and the back surface of the sheet-like base material adhere to each other. When blocking occurs, the glossiness of the surface of the receiving layer is lowered, so that the appearance as a receiving sheet is impaired and the product value is lowered, or the smoothness of the surface of the receiving layer is lowered. There were problems such as worsening.
In addition, when paper is used for the sheet-like substrate, placing the receiving sheet in a high humidity environment will cause the receiving sheet to absorb moisture, causing curling of the receiving sheet and causing problems with feeding and discharging in the printer. there were.

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

  The problem of the present invention is to solve the above-mentioned problems of the prior art, high printing density, excellent image sharpness and light resistance, and the back surface layer of the receiving sheet prevents blocking between the back surface of the receiving sheet and the receiving layer surface. By doing so, an object of the present invention is to provide a receiving sheet that is free from image defects due to blocking and has less curling even when the receiving sheet is placed in a high humidity environment.

The present invention includes the following inventions.
(1) In a thermal transfer receiving sheet in which an image receiving layer is formed on one surface of the sheet-like support and a back surface layer is formed on the other surface, the image receiving layer is: A thermal transfer receiving sheet comprising a polyurethane resin synthesized from polymerization components including A) to (C), wherein the back layer contains a polyvinyl alcohol derivative.
(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 synthesized by further containing the following (D) as a raw material, 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 item (1) or (2).
(D) The diol having a carboxyl alkyl group as a side chain (4) The thermal transfer receiving sheet according to (1) to (3), wherein the back layer contains at least one pigment selected from organic and inorganic pigments.
(5) The thermal transfer receiving sheet according to (4), wherein the pigment is a nylon filler having a number average particle diameter of 0.5 to 20 μm.
(6) The thermal transfer receiving sheet according to any one of (1) to (5), wherein the back layer contains an acrylic resin.
(7) The thermal transfer receiving sheet according to any one of (1) to (6), wherein an undercoat layer containing hollow particles is further provided between the sheet-like support and the image receiving layer.

  According to the present invention, the printing density is high, the image sharpness and the light resistance of the image are excellent, the back layer has sufficient strength, and even if the back layer and the receiving layer are left in contact with each other, sufficient blocking is achieved. It is possible to obtain a thermal transfer receiving sheet which has a preventive property, does not cause image defects such as white spots due to blocking, and has little curling even when placed in a high humidity environment.

Hereinafter, the present invention will be described in more detail.
(Sheet support)
As the support for the receiving sheet in 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 paper.
The support may have a structure in which a first base layer on which a receiving layer is formed, an adhesive layer, a release agent layer, and a second base layer are sequentially laminated. Of course, a support having a structure (also referred to as a type) can be used.
Among the above supports, papers mainly composed of cellulose pulp are preferable. The texture of the obtained receiving sheet is close to that of photographic paper, and the cost is low and the environmental load is small.

(Receptive 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 resulting receiving layer is lowered, and troubles such as fusion with the dye ribbon and peeling of the receiving layer are likely to occur during printing. . 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 urethane 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 weight. 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 ink ribbon and the receiving sheet is lowered, or the bleeding of the printed matter is deteriorated. It becomes easy.

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 ribbon Problems such as fusing and peeling of the 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, it is preferable that the low molecular weight polyamine compound is non-aromatic because the light resistance of the dye thermally transferred to the receiving layer is reduced 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 urethane 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 receiving layer is inferior, and when the printed matter is stored in a high-temperature and high-humidity environment, bleeding of the printed matter occurs or the storage stability is lowered. There is.

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 urethane resin is less than −30 ° C., fusion between the image receiving layer and the ink ribbon 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 urethane resin exceeds 60 ° C., the dyeing property of the image receiving layer is inferior and a sufficient print density may not 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.

(Release agent)
The image receiving layer of the present invention preferably contains a release agent. Various known materials can be used as the release agent used in the image receiving layer of the present invention, and examples thereof include hydrophilic group-containing silicone oil, silicone oil emulsion, polysiloxane segment-containing aqueous resin, and waxes.

(Crosslinking agent)
The dyeable resin used in the receiving layer of the present invention is preferably crosslinked with a crosslinking agent after coating. Examples of the crosslinking agent used in the 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.
A carbodiimide-based crosslinking agent is particularly preferable because it has good reactivity with the carboxyl group of the polyurethane resin. 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 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.

(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, when the thickness exceeds 10 μm, surface irregularities of the obtained receiving sheet are increased and image uniformity may be deteriorated.
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)
When an undercoat layer is provided on a sheet-like support, the dye is stained between the undercoat layer and the receiving layer so that the dye dyed on the receiving layer does not move to the undercoat layer or the sheet-like support, thereby blurring the image. An intermediate layer may be further provided for the purpose of preventing or for obtaining a smooth surface by filling the unevenness of the undercoat layer.

(Back layer)
The back layer of the thermal transfer receiving sheet of the present invention contains a polyvinyl alcohol derivative.
Examples of the polyvinyl alcohol derivative include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, silanol-modified polyvinyl alcohol, and ethylene vinyl alcohol copolymer. The polyvinyl alcohol derivative is excellent in heat resistance and hardly sticks even if it contacts the receiving layer surface containing a urethane resin at a high temperature, and is highly effective in preventing blocking. Furthermore, silanol-modified polyvinyl alcohol has good adhesion to organic and inorganic pigments when adding organic and inorganic pigments for the purpose of further enhancing the blocking effect on the back layer, and the organic and inorganic pigments from the back layer. Highly effective in preventing powder falling off. This is because the silanol group of the silanol-modified polyvinyl alcohol is obtained by hydrogen bonding or dehydration condensation with a hydroxyl group present on the surface of the organic or inorganic pigment contained in the receiving sheet support or the back surface layer, thereby obtaining high adhesiveness. Conceivable.

The silanol-modified polyvinyl alcohol resin used in the present invention can be produced by a conventionally known synthesis method, and is obtained by copolymerization of vinyltrimethoxysilane and vinyl acetate in a solvent such as methanol, and then methanolysis using sodium hydroxide as a catalyst. The desired polymer can be obtained by saponifying vinyl acetate. Examples of commercially available products include R-1130, R-2105, R-2130 (manufactured by Kuraray). The silanol-modified polyvinyl alcohol resin of the present invention preferably has a saponification degree of 85% or more and a silanol group content in the molecule of 0.05 to 3 mol% as a monomer unit.

  In order to prevent curling that occurs when the receiving sheet is placed in a high-humidity environment, an acrylic resin is preferably contained in the back layer of the present invention. Of these, polyacrylate resin is more preferable. Polyacrylate resin has good stability when preparing the coating liquid, uniformity of the formed coating film and water resistance, and prevents curling that occurs when the receiving sheet is placed in a high humidity environment. High effect. Commercially available products include, for example, Jurimer FC80 (manufactured by Nippon Pure Chemicals), Polyzol AM2250 (manufactured by Showa High Polymer), Rikabond SAR615A (manufactured by Chuo Rika), Barrier Star B1000 (manufactured by Mitsui Chemicals), Jurimer AT510, 515, 613 (Nippon Pure) And the like).

  As for the solid content ratio of a polyvinyl alcohol derivative and acrylic resin, 10-200 mass parts is preferable with respect to 100 mass parts of solid content of a polyville alcohol derivative. When the solid content of the acrylic resin exceeds 200 parts by mass, the adhesion to the substrate is insufficient, peeling of the back layer, powdering off of organic and inorganic pigments, and blocking between the back layer and the receiving layer. May occur. When the solid content of the acrylic resin is less than 10 parts by mass, when the receiving sheet is placed in a high humidity environment, the back surface layer of the receiving sheet absorbs moisture, and the receiving sheet may curl.

  In addition to the polyvinyl alcohol derivative and the acrylic resin, the back layer of the present invention can be used in combination with an adhesive resin that is generally used within a range not impairing the effects of the present invention. For example, a polyethylene oxide resin, a polyethylene glycol resin, Examples include starch, styrene-butadiene copolymer resin, urethane resin, polyvinyl acetal resin, polyvinyl butyral resin, polyester resin, epoxy resin, melamine resin, phenol resin, phenoxy resin, cellulose derivative resin, and polyvinyl acetal resin. Two or more resins may be used in combination. Also, reaction cured products of these resins can be used.

  The back layer of the present invention can contain known inorganic and organic pigments for the purpose of enhancing the antiblocking effect. Examples of inorganic pigments include metals such as aluminum, iron and copper, metal oxides such as silica, titanium oxide, zinc oxide and alumina, inorganic salts such as calcium carbonate, barium sulfate and calcium sulfate, kaolin, calcined kaolin, clay, Examples include minerals such as talc and diatomaceous earth. Examples of the organic pigment include nylon resin, styrene resin, acrylic resin, urea resin, melamine resin, benzoguanamine resin, phenol resin, silicone resin, and fluorine resin.

  In the present invention, among these inorganic and organic pigments, a nylon filler is preferably used, and examples thereof include a filler made of nylon 12, nylon 6, nylon 6, 6 or the like. As the type of nylon filler, nylon 12 filler is more preferable because it is superior in water resistance and less in characteristic change due to water absorption than nylon 6, nylon 6/6 filler. Nylon filler has a moderately low hardness and will not damage the receiving layer surface even if it comes in contact with the receiving layer surface. Even if the receiving sheet is stacked or wound, it will not impair the print quality. .

In the present invention, the number average particle diameter of the nylon filler is preferably 0.5 to 20 μm or less, and more preferably 1 to 10 μm. When the number average particle size of the nylon filler is less than 0.5 μm, the blocking prevention effect may not be enhanced. When the average particle size of the nylon filler exceeds 20 μm, the protrusion of the nylon filler from the surface of the back surface layer becomes large, and when the back surface layer and the receiving layer are in strong contact, In some cases, dents occur or white spots occur in the printed image. In addition, it becomes difficult to adhere to the sheet base material, and the nylon filler may fall off when the receiving sheet is rubbed. The number average particle diameter of the nylon filler can be measured using a general particle size measuring device. Yes, it can be measured using, for example, a laser diffraction particle size distribution analyzer (trade name: SALD2000, manufactured by Shimadzu Corporation).

  As for the compounding quantity of a nylon filler, 1-25 mass% is preferable with respect to the total solid of a back surface layer. If the blending amount is less than 1% by mass, the anti-blocking effect may not be enhanced. On the other hand, when the blending amount exceeds 25% by mass, when coating the back surface layer coating material with a coater, streaks due to settling of the nylon filler are likely to occur, and problems such as deterioration of the coated surface may occur. is there.

In the present invention, the solid coating amount of the back layer is preferably in the range of 0.5 to 10 g / ^{m 2,} more preferably from 1 to 7 g / ^{m 2.} Incidentally, when the solid content coating amount is less than 0.5 g / m ² , the back surface layer cannot completely cover the surface of the sheet-like support, and the blocking prevention effect and the curl prevention effect may not be obtained. On the other hand, if the solid content coating amount exceeds 10 g / m ² , the anti-blocking effect and the anti-curl effect are saturated, and the cost tends to increase, which is disadvantageous economically.

The back surface layer of the present invention may contain an antistatic agent in order to prevent troubles in feeding and discharging due to electrostatic charging and troubles in running. Antistatic agents include anionic, cationic, nonionic and amphoteric surfactants, polymeric resin-type conductive agents such as anionic, cationic and nonionic conductive resins, as well as electronically conductive inorganic fine particles. Examples thereof include powders and fine carbon powders, but a polymer resin type conductive agent is preferably used from the standpoint of maintaining the antistatic effect for a long period of time and the hue of the antistatic agent.
Furthermore, in the coating liquid for forming the back layer, various additives such as an antistatic agent, a lubricant, a release agent, an antifoaming agent, a dispersant, a resin crosslinking agent, a colored dye, and a fluorescent dye are used as necessary. Fluorescent pigments, ultraviolet absorbers and the like may be appropriately selected and used.

(Calendar processing)
The receiving sheet may be calendered. By the calendering process, the unevenness of the surface of the obtained receiving sheet can be reduced and a uniform image can be obtained. 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>
(Sheet support)
As the support, art paper (trade name: OK Kanto N, manufactured by Oji Paper Co., Ltd., basis weight 174.4 g / m ² ) having a thickness of 150 μm was used. An undercoat layer coating solution A-1 having the following composition is coated on one side of the support so that the solid content coating amount is 15 g / m ² and dried to form an undercoat layer. The following receiving layer coating solution B-1 is coated and dried so as to have a solid coating amount of 3 g / m ² to form a receiving layer, and on the surface of the sheet-like support on which the receiving layer is not formed. The following back surface layer coating liquid C-1 was applied and dried so as to have a solid content coating amount of 3 g / m ² to form a back surface layer to obtain a thermal transfer receiving sheet.

[Preparation of receiving sheet]
[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 receiving layer coating liquid B-1]
Urethane resin UP1 of the above synthesis example 88 parts carbodiimide-based crosslinking agent 10 parts (trade name: Carbodilite E-02, manufactured by Nisshinbo Co., Ltd.)
2 parts polysiloxane graft acrylic resin (trade name: US450, manufactured by Toagosei)
300 parts of water [Preparation of backside layer coating liquid C-1]
Silanol-modified polyvinyl alcohol resin (trade name: R2105, saponification degree 98%,
Degree of polymerization: 700, manufactured by Kuraray) 70 parts polyacrylic ester resin (trade name: Polysol AM2250, manufactured by Showa High Polymer Co., Ltd.) 10 parts zinc stearate (trade name: KW509, manufactured by Kyosei Chemical) 10 parts nylon filler (trade name: 2001EXDNAT1, manufactured by Erphalchem,
Average particle diameter 10μ, coefficient of variation 4.5%) 3 parts anionic conductive resin (trade name: Chemistat SA-9,
Main component: Sodium polystyrene sulfonate, manufactured by Sanyo Chemical) 10 parts Water 500 parts

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

<Example 4>
A receiving sheet was obtained in the same manner as in Example 1 except that the following back surface layer coating liquid C-2 was used instead of the back surface layer coating liquid C-1.
[Preparation of Back Layer Coating Liquid C-2]
80 parts of silanol-modified polyvinyl alcohol resin (trade name: R2105, saponification degree 98%, polymerization degree: 700, manufactured by Kuraray)
Zinc stearate (trade name: KW509, manufactured by Kyoyo Chemical Co., Ltd.) 10 parts nylon filler 3 parts (trade name: 2001 EXDNAT1, manufactured by Erphalt Chem,
(Average particle size 10μ, coefficient of variation 4.5%)
Anion-type conductive resin (trade name: Chemistat SA-9, 10 parts main component: sodium polystyrene sulfonate, manufactured by Sanyo Chemical)
500 parts of water

<Example 5>
A receiving sheet was obtained in the same manner as in Example 7 except that the following back surface layer coating liquid C-3 was used instead of the back surface layer coating liquid C-1 (prepared in Example 7).
[Preparation of Back Layer Coating Liquid C-3]
73 parts of silanol-modified polyvinyl alcohol resin (trade name: R2105, degree of saponification 98%, degree of polymerization: 700, manufactured by Kuraray)
Polyacrylic acid ester resin (trade name: Polysol AM2250, manufactured by Showa High Polymer Co., Ltd.) 10 parts Zinc stearate (trade name: KW509, manufactured by Kyoyo Chemical Co., Ltd.) 10 parts Anionic conductive resin 10 parts (trade name: Chemistat SA-9, Sanyo Chemical,
Main component: Sodium polystyrene sulfonate,)
500 parts of water

<Comparative Example 1>
A receiving sheet was obtained in the same manner as in Example 1 except that no back layer was formed in the preparation of the receiving sheet.
<Comparative example 2>
A receiving sheet was obtained in the same manner as in Example 1 except that in the production of the receiving sheet, the back layer coating solution C-4 obtained by the following method was used instead of the back layer coating solution C-1.
[Preparation of Back Layer Coating Liquid C-4]
70 parts of polyvinyl acetal resin (trade name: ESREC KX-1, Sekisui Chemical Co., Ltd.)
Polyacrylic acid ester resin (trade name: Polysol AM2250, manufactured by Showa High Polymer Co., Ltd.) 10 parts Zinc stearate (trade name: KW509, manufactured by Kyoyo Chemical Co., Ltd.) 10 parts Nylon filler 3 parts (trade name: 2001 EXDNAT1, manufactured by Elfalt Chem,
(Average particle size 10μ, coefficient of variation 4.5%)
Anion-type conductive resin 10 parts (trade name: Chemistat SA-9, manufactured by Sanyo Kasei,
Main component: Sodium polystyrene sulfonate,)
500 parts of water

<Comparative Example 3>
A receiving sheet was obtained in the same manner as in Example 1 except that the urethane resin UP4 of the above synthesis example was used instead of the urethane resin UP1 in the preparation of the receiving layer coating solution B-1 of Example 1.
<Comparative example 4>
A receiving sheet was obtained in the same manner as in Example 1 except that in the preparation of the receiving layer coating liquid B-1 of Example 1, the urethane resin UP5 of the above synthesis example was used instead of the urethane resin UP1.

〔quality evaluation〕
The receiving sheets obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were evaluated for the quality of the following items, and the results are shown in Table 3.
[Blocking properties]
The receiving sheet is stacked on the receiving layer so that the back surface layer is in contact, and a weight is placed so that the load is 800 g / cm ^2, and the receiving sheet is treated in a dryer at 50 ° C. for 3 days. The receiving layer and the back surface layer were peeled off slowly, and the appearance of the superimposed surface and the resistance when peeling off were evaluated according to the following criteria.
○: No resistance at all, no appearance abnormality on the peeled surface, and no problem in practical use.
Δ: There is a slight resistance, but there is no appearance abnormality on the peeled surface and it is practical.
X: There is resistance, appearance abnormality is seen on the peeled surface, and it is not suitable for practical use.

[High humidity environment curl]
The receiving sheet is cut into a sheet having a width of 126 mm and a length of 177 mm as a sample for evaluating moisture absorption curl, and placed flat on a flat table so that the receiving layer surface is the upper surface and the receiving layer surface is the lower surface. Treat in a high humidity environment of 20 ° C. and 90% RH for 12 hours. Measure the height of the four corners of the receiving sheet from the table in two ways when the receiving sheet surface is placed on the upper and lower surfaces of the receiving layer, and calculate the average of 4 points x 2 different heights. Evaluation was made according to the following criteria.
A: The average value is less than 5 mm, and it can be used practically without any problem.
Δ: The average value is not less than 5 mm and less than 20 mm, and is practical.
X: An average value is 20 mm or more, and is not suitable for practical use.

[Back side adhesion]
As a sample for evaluating the adhesiveness between the substrate and the back surface layer in the receiving sheet, a strip-shaped receiving sheet having a width of 18 mm and a length of 170 mm is cut and prepared, and a receiving sheet sample is prepared using a double-sided adhesive tape. The receiving layer side of was fixed on a glass plate. Next, a commercially available adhesive tape (trade name: Cellotape (registered trademark), manufactured by Nichiban Co., Ltd., tape width: 18 mm) is adhered on the back surface layer of the fixed strip-shaped receiving sheet sample, and the adhesive tape is peeled at 180 degrees. It peeled and regarding the adhesiveness between a base material and a back surface layer, the generation | occurrence | production situation of peeling of a back surface layer or the powder fall of the filler component contained in a back surface layer was evaluated on the following references | standards.
○: There is no peeling or powder fall off of the base material and the back surface layer, and it can be used without any practical problem.
X: Peeling between the base material and the back surface layer or occurrence of powder falling off of the filler is conspicuous and is not suitable for practical use.

[Image density]
Using a commercially available thermal transfer video printer (trade name: UP-50, manufactured by Sony Corporation) equipped with a sublimation type thermal transfer ink ribbon (trade name: UP-540, manufactured by Sony Corporation), the blocking property test was performed in a room temperature environment. A black solid image was printed on the received receiving sheet. Using a Macbeth reflection densitometer RD914, the print density of the black solid image was measured. The image clarity of the receiving sheet was evaluated according to the following criteria.
A: Black solid print density is 2.2 or more, and can be used as a high-sensitivity receiving sheet without problems.
○: The black solid print density is 1.7 or more and less than 2.2, and can be used without any problem in practice.
X: The black solid print density is less than 1.7, which is not suitable for practical use.

[Image clarity]
Using a commercially available thermal transfer video printer (trade name: UP-50, manufactured by Sony Corporation) equipped with a sublimation type thermal transfer ink ribbon (trade name: UP-540, manufactured by Sony Corporation), the blocking property test was performed in a room temperature environment. An image was printed on the receiving sheet so that the image density when measured with a Macbeth reflection densitometer RD914 was 0.6 to 0.7, and the dot reproducibility of the image was visually evaluated according to the following criteria.
(Double-circle): There is no white spot and it is excellent in clearness.
○: Slight white spots are observed, but it can be used practically without any problem.
Δ: White spots are observed, but practical use is possible.
X: White spots are conspicuous and not suitable for practical use.

(Image light resistance)
Using a commercially available thermal transfer video printer (trade name: UP-50, manufactured by Sony Corporation) equipped with a sublimation type thermal transfer ink ribbon (trade name: UP-540, manufactured by Sony Corporation), solid black printing was performed at room temperature. The obtained black solid image print was processed with an Xe fade meter until the accumulated illuminance reached 10,000 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 10 and is practical.
Δ: ΔE ^* is 10 or more and less than 13 and is practical.
×: ΔE ^* is not less than 13, not suitable for practical use.

  As is apparent from Table 3, the thermal transfer receiving sheets of Examples 1 to 5 have high printing density, excellent image sharpness and image light resistance, the back layer has sufficient strength, and the back layer and the receiving layer. Even if left in contact with the layer, it has sufficient anti-blocking properties, does not cause image defects such as white spots due to blocking, and curls even when placed in a high humidity environment It is a receiving sheet with less occurrence of

  The thermal transfer receiving sheet of the present invention has a high printing density, excellent image sharpness, and light fastness of the image, the back layer has sufficient strength, and the back layer and the receiving layer are in contact with each other. Even if left untreated, it has sufficient anti-blocking properties, does not cause image defects such as white spots due to blocking, and is less likely to curl even when placed in a high humidity environment. It can be used as an excellent thermal transfer receiving sheet.

Claims (7)

In a sheet-like support and a thermal transfer receiving sheet in which an image receiving layer is formed on one side of the sheet-like support and a back layer is formed on the other side, the image receiving layer includes the following (A) to A thermal transfer receiving sheet comprising a polyurethane resin synthesized from a polymerization component containing (C), wherein the back layer contains a polyvinyl alcohol derivative.
(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 (D) below, and the carboxyl group content 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 back layer contains at least one pigment selected from organic and inorganic pigments.   The thermal transfer receiving sheet according to claim 4, wherein the pigment is a nylon filler having a number average particle diameter of 0.5 to 20 μm.   The thermal transfer receiving sheet according to claim 1, wherein the back layer contains an acrylic resin. The thermal transfer receiving sheet according to any one of claims 1 to 6, wherein an undercoat layer containing hollow particles is further provided between the sheet-like support and the image receiving layer.