JP2007112079A - Thermal-transfer receiving sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal-transfer receiving sheet which is manufactured by a melt-extrusion method advantageous to environmental suitability during manufacture, which has high-density printing characteristics even in high-speed printing conditions, which is excellent in the property of adhesion to a thermally-transferrable protective layer, and which improves image stability in a high-temperature storage state. <P>SOLUTION: In this thermal-transfer receiving sheet, at least one thermally-diffusible dye receiving layer, which is formed by the melt-extrusion method, is provided on a base material. The thermal-transfer receiving sheet is characterized in that the receiving layer contains a compound, the melting point or softening point of which is in the range of 80-140°C, in the quantity equivalent to 10 mass% or more of the total mass of the receiving layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thermal transfer receiving sheet that is used while being superposed on a thermal transfer ink sheet.

  Conventionally, as a color or monochrome image forming technology, an ink sheet containing a heat diffusible dye having a property of diffusing and transferring by heating is opposed to a receiving layer of a receiving sheet, and thermal printing such as a thermal head or a laser is performed. A technique is known in which the thermal diffusible dye is transferred in an image-like manner to the receiving layer using a means, and an image is formed by a dye thermal transfer method. Such a thermal transfer method is capable of forming an image using digital data, and is well-known as a method that does not use a processing solution such as a developing solution and can obtain a high-quality image comparable to a silver salt photograph.

  However, recently, the quality required for image printing based on digital data has become increasingly severe, and it has become an important issue to provide customers with higher-speed, higher-density prints with higher image quality. Yes. On the other hand, improvement in environmental suitability and cost reduction in the manufacturing process of these thermal transfer recording materials are also very important issues. In particular, de-VOC (reduction of volatile organic compounds) is urgent from the viewpoint of social responsibility.

  For such a situation, a technique for forming each layer (heat insulating / cushion functional layer, receiving layer, etc.) of the thermal transfer receiving sheet by an aqueous coating method is conventionally known. For example, a thermal transfer receiving sheet produced by simultaneously layering an aqueous intermediate layer mainly composed of an aqueous binder and hollow particles, and an aqueous image receiving layer mainly composed of an aqueous binder and a release agent (hereinafter also referred to as receiving layer). Is disclosed (for example, see Patent Document 1). However, with this technology, the transfer speed required under high-speed printing conditions has not been reached, and since the heat resistance of the receiving layer is low, the surface unevenness of the high-energy printing area (high density area) is noticeable and large. There was a problem of damaging. Further, only by the technique of adjusting the liquid viscosity by adding a thickener to the water-dispersed type or water-soluble resin, the drying load does not decrease, and the coating speed is naturally limited in order to avoid inter-layer mass transfer.

  As another method of removing VOC, a technique for forming each layer of a thermal transfer receiving sheet by a melt extrusion method is known. For example, a method of producing a multilayer film comprising at least a surface layer and a tie layer adjacent to the surface layer by a melt extrusion method is disclosed (for example, see Patent Document 2). In general, the resin used for melt extrusion has good heat resistance, and on the contrary, it tends to be low in dye receptivity. Therefore, in Patent Document 2, a method of adding an aliphatic ester plasticizer as a technology to compensate for this tends to be low. Are listed. However, since the addition amount described remains relatively small, the effect of improving the transfer efficiency from the non-addition state is small, and there is no clear description regarding the melting point of the plasticizer, and therefore a preferred plasticizer If the amount is simply increased for the purpose of improving the transfer efficiency, image bleeding may occur at room temperature or high temperature after printing. In addition, the use of a plasticizer can generally improve the peelability from the thermal transfer ink sheet by increasing the amount, but the adhesiveness with the protective layer transferred from the hot melt transferable protective sheet deteriorates. In addition, there arises a problem that unevenness occurs in glossiness and subsequent light resistance. This phenomenon tends to be particularly noticeable under high-speed transfer conditions.

Therefore, although the production of a thermal transfer receiving sheet by melt extrusion may be more advantageous than the solvent system in terms of environmental suitability and production cost during production, the conventional technology has a very high density printing property even under high speed conditions. Thus, it was impossible to obtain a thermal transfer receiving sheet that was excellent in adhesion to the thermal transferable protective layer and excellent in image storage stability under high temperature storage in a range that can occur every day.
JP-A-6-171240 JP 2004-255878 A

  The present invention has been made in view of the above problems, and its object is to produce a heat transferable protective layer which is produced by a melt extrusion method advantageous for environmental suitability during production, has high density printing characteristics even under high speed printing conditions, and It is an object of the present invention to provide a thermal transfer receiving sheet that is excellent in adhesiveness and has improved image storage stability under high temperature storage.

  The above object of the present invention is achieved by the following configurations.

  1. In a thermal transfer receiving sheet having a heat diffusible dye receiving layer formed on a substrate by at least one melt extrusion method, the receiving layer has a melting point or softening point in the range of 80 ° C. or higher and 140 ° C. or lower. A thermal transfer receiving sheet comprising a certain compound in an amount of 10% by mass or more of the total mass of the receiving layer.

  2. 2. The thermal transfer receiving sheet as described in 1 above, wherein the compound having a melting point or softening point in the range of 80 ° C. or more and 140 ° C. or less is a wax mainly composed of a fatty acid ester or a fatty acid amide.

  3. 3. The thermal transfer receptor according to 1 or 2, wherein the content of the compound having the melting point or softening point in the range of 80 ° C. or more and 140 ° C. or less with respect to the total mass of the receptor layer is 25% by mass or more. Sheet.

  4). 4. The thermal transfer receiving sheet according to 3 above, wherein the content of the compound having the melting point or softening point in the range of 80 ° C. or more and 140 ° C. or less with respect to the total mass of the receiving layer is 50% by mass or more.

  5. 5. The thermal transfer receiving sheet according to any one of 1 to 4, wherein the receiving layer contains a siloxane-containing polymer having a mass average molecular weight of 100,000 or more as a release agent.

  According to the present invention, it is produced by a melt extrusion method advantageous for environmental suitability at the time of production, has high density printing characteristics even under high speed printing conditions, has excellent adhesion to a heat transferable protective layer, and has an image under high temperature storage. A thermal transfer receiving sheet having improved storage stability could be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the present inventor, as a result, in a thermal transfer receiving sheet having a heat diffusible dye receiving layer formed on a substrate by at least one layer of melt extrusion method, And a thermal transfer receiving sheet characterized by containing a compound having a melting point or softening point in the range of 80 ° C. or higher and 140 ° C. or lower in an amount of 10% by mass or more of the total mass of the receiving layer. Thermal transfer that can be produced by a melt extrusion method that is advantageous for printing, has high density printing characteristics even under high-speed printing conditions, has excellent adhesion to the heat transferable protective layer, and has improved image storability under high temperature storage As soon as it has been found that a receiving sheet can be realized, the present invention has been achieved.

  Details of the present invention will be described below.

[Receptive layer]
The thermal transfer receiving sheet of the present invention has a heat diffusible dye receiving layer formed on a substrate by a melt extrusion method, and this receiving layer has a melting point or softening point in the range of 80 ° C. or higher and 140 ° C. or lower. It contains 10% by mass or more of the compound.

(binder)
The binder used in the receiving layer according to the thermal transfer receiving sheet of the present invention is not particularly limited, but is preferably a polyester material, and among the polyester materials, those having the following structures are more preferable.

  (A) Dicarboxylic acid repeating unit and polyol-derived unit, wherein at least 50 mol% of the dibasic acid-derived unit contains an alicyclic ring containing 4 to 10 ring carbon atoms An aromatic or alicyclic ring comprising between the two carbon atoms of each carboxyl group of the corresponding dicarboxylic acid comprising an acid-derived unit, and (b) not immediately adjacent to each hydroxyl group of the corresponding diol 25 to 75 mol% of the polyol-derived unit containing a ring, and (c) 25 to 75 mol% of the polyol-derived unit of the polyester includes an alicyclic ring containing 4 to 10 ring carbon atoms. Including.

  Such polyester polymers are condensation-type polyesters based on repeating units derived from alicyclic dicarboxylic acids (Q) and aromatic diols (L) and alicyclic diols (P), wherein (Q) is Each carboxyl group represents one or more cycloaliphatic ring-containing dicarboxylic acid units between (preferably directly adjacent) two carbon atoms of the cycloaliphatic ring, wherein (L) represents each hydroxyl group One or more diol units each comprising at least one aromatic ring which is not directly adjacent to the group (preferably 1 to about 4 carbon atoms apart) or an alicyclic ring which may be adjacent to a hydroxyl group To express.

  In the case of an extrudable polyester, a monomer having three or more functional groups, preferably a polyfunctional polyol (N) or a polyacid and its derivative (O) capable of giving a branch (either a diacid or a diol) It is advantageous to use one or more). Multifunctional polyols include, for example, glycerin, 1,1,1-trimethylolethane and 1,1,1-trimethylolpropane or combinations thereof. Examples of polyacids having three or more carboxylic acid groups (including esters or anhydride derivatives) include trimellitic acid, trimesic acid, 1,2,5-, 2,3,6- or 1,8,4 -Naphthalene tricarboxylic acid anhydride, 3,4,4'-diphenyltricarboxylic acid anhydride, 3,4,4'-diphenylmethane tricarboxylic acid anhydride, 3,4,4'-diphenyl ether tricarboxylic acid anhydride, 3,4, There are 4'-benzophenone tricarboxylic anhydrides and their derivatives.

  A small amount of the aromatic compound (S) mixed due to the inclusion of the aromatic diacid or anhydride is not preferable because it tends to reduce the imaged dye density.

  In such a polyester polymer, for example, Tg, solubility, adhesiveness and the like of the polymer can be precisely adjusted by appropriately adjusting the addition amount of the diacid (R) and the diol (M). The diacid comonomer may have a cyclic structure (Q), but may be a linear aliphatic unit or a certain degree of aromaticity. The additional diol monomer may be aliphatic or aromatic, but is preferably not phenolic.

  The above-described alicyclic dicarboxylic acid (Q), aromatic diol (L), alicyclic diol (P), polyfunctional polyol (N), polyacid and its derivative (O), aromatic compound (S) As for the specific structures of diacid (R) and diol (M), the compounds described in JP-A No. 2004-255878 can be referred to.

  Although the specific example of polyester obtained by copolymerizing said each monomer is shown, in this invention, it is not limited only to these illustrated polyester.

  In the above formula, P is an alicyclic diol, O is a polyacid and derivatives thereof, L is an aromatic diol, Q is an alicyclic dicarboxylic acid, M is a diol, R is a diacid, N is a polyfunctional polyol, S Represents an aromatic compound, and o + q + r + s = 100 mol% and p + m + n + l = 100 mol% (based on the polyol component). For diacids, q is preferably at least 50 mol%, r is less than 40 mol%, and s is preferably less than 10 mol%. With respect to the polyol, it is preferable that p is 25 to 75 mol%, l is 25 to 50 mol%, and m is 0 to 50 mol%. With respect to the polyfunctional monomer (having three or more functional groups), the total amount of n or o is preferably 0.1 to 10 mol%, preferably 1 to 5 mol%.

  The polyester according to the present invention preferably does not contain an aromatic diacid such as terephthalate or isophthalate.

  The polyester according to the present invention preferably has a Tg of 40 to 100 ° C. and a molecular weight of 5,000 to 250,000, more preferably 10,000 to 100,000.

  In the receiving layer according to the present invention, in addition to the polyester binder, other polymers such as polycarbonate, polyurethane, polyester, polyvinyl chloride, poly (styrene-coacrylonitrile), and polycaprolactone may be included. When two polyester-polycarbonate binders are used, unmodified bisphenol-A polycarbonate having a molecular weight of at least 25,000 can be used, and specific examples of these compounds are described in, for example, US Pat. The compound currently disclosed by 695,286 specification can be mentioned. Specific examples include polycarbonates such as MAKROLON 5700 (Bayer AG) and LEXAN 141 (General Electric Co.).

  When polycarbonate is used as the binder together with polyester, the polycarbonate preferably has a Tg of 100 to 200 ° C., in which case the polyester has a lower Tg than the polycarbonate and preferably acts as a polymeric plasticizer for the polycarbonate. The final polyester / polycarbonate blend preferably has a Tg of 40-100 ° C. Higher Tg polyester and polycarbonate polymers can also be used if a plasticizer is added.

  In the receiving layer according to the present invention, the polyester polymer can be blended with the unmodified bisphenol-A polycarbonate at a certain mass ratio, and the final blend can achieve a desired Tg, thereby reducing the cost. The mixing ratio of the polycarbonate and the polyester polymer is 90:10 to 10:90, preferably 80:20 to 20:80, and more preferably 75:25 to 25:75.

  Specific examples of the polyester polymer applicable to the receiving layer according to the present invention include the following exemplified compounds E1 to E-3.

  Exemplary compounds E-1 to E-3 shown below are 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexanedimethanol, 4,4′-bis (2-hydroxyethyl) bisphenol-A and 2-ethyl- It is a polyester polymer derived from 2- (hydroxymethyl) -1,3-propanediol.

(Compound with melting point or softening point of 80-140 ° C)
The receiving layer according to the present invention is characterized by containing 10% by mass or more of a compound having a melting point or softening point in the range of 80 ° C. or higher and 140 ° C. or lower.

  The melting point and softening point in the present invention refer to temperatures obtained by measurement based on JIS K0064 and JIS K7196, respectively.

  The compound having a melting point or softening point in the range of 80 to 140 ° C. according to the present invention has a value in the range of 80 to 140 ° C. when the melting point or softening point of all components constituting the compound is mass averaged. This includes the case of a single compound or a mixture. There is no particular limitation as long as it is a compound that satisfies this condition and is compatible with other binders, additives, and heat-diffusible dyes constituting the receiving layer, and does not significantly reduce other properties such as melt extrusion suitability. .

  If the melting point is less than 80 ° C, when the pre-printing receiving sheet is stored in a relatively high temperature environment, the surface may become sticky, and when printing with it, it may cause problems such as density unevenness. Deterioration of background stains and bleeding deterioration during image storage after printing become problems, which is not preferable. Further, when the melting point is higher than 140 ° C., sufficient transfer efficiency cannot be obtained.

  Specific examples of the compound having a melting point or softening point of 80 to 140 ° C. according to the present invention include, for example, the following antioxidants, ultraviolet absorbers, compounds known as waxes, or mixtures containing these as main components. Can do.

<Compounds known as antioxidants>
1) Bisphenols such as 2,2'-methylenebis (4-methyl-6-t-butylphenol), 2,2'-methylenebis (4-ethyl-6-t-butylphenol),
2) Polymer type phenolic systems such as tetrakis- [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane,
3) Phosphoric acid series such as 9,10-dihydro-9-oxa-10-phosphaphenanthrene = 10-oxide.

<Compounds known as UV absorbers>
1) benzophenone series such as 2,2'-dihydroxy-4,4'-methoxybenzophenone,
2) 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2-hydroxy-3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2 (2 ' Benzotriazoles such as -hydroxy-5'-methacryloxyphenyl) -2H-benzotriazole,
3) Hindered amine light stabilizers such as trade name Sanol LS-770 (manufactured by Sankyo Lifetech Co., Ltd.), trade names ADK STAB LA-63, ADK STAB LA-68 (above, manufactured by Asahi Denka Kogyo Co., Ltd.), and the like.

<Compound known as wax>
1) Paraffin such as tetracontane, dodetracontane, pentacontane, hexacontane, heptacontane,
2) Product names Cardis TM10, Petronauba TMC, Petrolite TME-1040 (above, Baker Petrolite Company) and other oxidized hydrocarbons,
3) Long chain aliphatic alcohols having 28 or more carbon atoms such as Unilin TM425, Unilin TM550, Unilin TM700 (above, manufactured by Baker Petrolite),
4) Brand name Long chain saturated fatty acid type having 22 or more carbon atoms such as Unicid TM350, Unicid TM425, Unicid TM550, Unicid TM700 (above, manufactured by Baker Petrolite),
5) Lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxy stearic acid amide, erucic acid amide, N-palmityl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl 12 hydroxystearic acid amide Fatty acid amides such as methylol stearic acid amide, methylene bis lauric acid amide, ethylene bis isostearic acid amide, hexamethylene bis stearic acid amide, methylene bis oleic acid amide, N, N′-dioleyl adipic acid amide,
6) Zinc stearate, magnesium stearate, aluminum stearate, zinc laurate, magnesium 12-hydroxystearate, calcium montanate, zinc montanate, magnesium montanate, zinc behenate, magnesium behenate, barium ricinoleate, myristic Metal soaps such as zinc oxide and zinc palmitate,
7) Fatty acid esters such as esters of higher fatty acids such as myricyl serotiate and monohydric higher alcohols, esters of higher polybasic acids and monohydric higher alcohols, esters of higher fatty acids and higher polyhydric alcohols, and derivatives thereof, Furthermore, natural waxes represented by carnauba wax mainly composed of these.

  As other compounds, some sulfonic acid amide-based, carboxylic acid-based, alcohol-based, phenol-based and other thermal solvents as shown in the following structural formulas (1) to (4) can also be used.

  When a compound having a melting point in the range of 80 to 140 ° C. according to the present invention is selected, the index LogP indicating the degree of hydrophobicity of the compound is a measure to some extent. The log P value of a compound is determined by dissolving the compound in an organic solvent that does not mix with water and mixing it with water, and the concentration ratio when both are reached (concentration in organic solvent / concentration in water, ie, partition coefficient) This is the value displayed in. The LogP value of the compound having a melting point of 80 to 140 ° C. according to the present invention is preferably 0.0 or more, more preferably 1.0 or more. Moreover, the compound which contains the location which has moderate polarity in a compound is preferable from a viewpoint which can give a favorable result.

  Among the above compound examples, particularly preferred compounds from the viewpoint of transfer efficiency and image storage stability are fatty acid amide waxes, fatty acid ester waxes, and carnauba wax containing fatty acid esters as main components.

  In the present invention, a thermoplastic resin having a softening point in the range of 80 to 140 ° C. is also preferably used. Here, the softening point refers to the secondary transition point in the case of an amorphous resin and has the same meaning as the glass transition point, and in the case of a resin having high crystallinity, it refers to the primary transition point. Specifically, a polymethyl methacrylate resin such as trade name Roplex B-85 (manufactured by Rohm & Haas) or a polyester resin such as trade name Byron 300, Byron GM900180 (above, manufactured by Toyobo Co., Ltd.) Etc. can be used.

  The resin having a softening point in the range of 80 to 140 ° C. according to the present invention preferably has a molecular weight of 8000 or more and 50000 or less, and more preferably has high crystallinity in order to increase transfer efficiency. In addition, the highly crystalline resin having a softening point in the range of 80 to 140 ° C. according to the present invention preferably has a primary transition point (glass transition point) of 20 ° C. or higher, and 50 ° C. or higher from the viewpoint of image storage stability. It is more preferable that

  The receiving layer according to the present invention contains the compound having the melting point or softening point in the range of 80 to 140 ° C. in an amount of 10% by mass or more based on the total solid content of the components constituting the receiving layer. From the viewpoint of increasing the content, it is preferably 25% by mass or more, more preferably 50% by mass or more, particularly preferably 50% by mass or more, and preferably 90% by mass or less, more preferably 80% by mass. It is below mass%.

  When the content is 10% by mass or more, sufficient transfer efficiency can be obtained, and when the content is 90% by mass or less, transfer from a receiving layer film strength, peelability from an ink sheet, or a heat-melt transferable protective sheet. As adhesiveness with the protective layer to be applied, preferable characteristics can be maintained.

  In the receiving layer according to the present invention, two or more compounds having a melting point or softening point of 80 to 140 ° C. according to the present invention may be used in combination.

The coating amount of the receptor layer according to the present invention is not particularly limited as long as the objective effect of the present invention can be exhibited, but is generally 0.5 to 20 g / m ² , preferably 1 to 15 g / m ² , and more. preferably from 2 to 8 g / m ^2.

〔paint remover〕
In the thermal transfer receiving sheet of the present invention, the receiving layer according to the present invention preferably contains a siloxane-containing polymer having a mass average molecular weight of 100,000 or more as a release agent.

  The receiving layer according to the present invention may contain a release agent such as a silicone-based or fluorine-based compound known in the art. By adding such a release agent to the receiving layer or the protective layer, it is possible to improve the adhesion resistance during thermal printing. Examples of the release agent are disclosed in US Pat. No. 4,820,687 and US Pat. No. 4,695,286.

  The release agent applied in the present invention, particularly the release agent preferably applied to the receiving layer formed by the melt extrusion method, is an ultrahigh molecular weight silicone compound. Preferably, the compound or polymer has a mass average molecular weight of at least 100,000, more preferably at least 500,000, most preferably 5,000,000 or more and 1,000,000 or less. Silicone release agents must be as compatible as possible with the polymer used in the receiving layer. When the receiving layer includes polycarbonate, it is preferred that the release agent has hydroxy end groups to improve the compatibility of the silicone compound in the polycarbonate-containing blend.

  Examples of the high molecular weight or ultra high molecular weight silicone release agent according to the present invention include those commercially available from Dow Corning, such as MB50-315 and MB-010. MB50-315 is a hydroxy-terminated dimethylsiloxane polymer. However, depending on the composition of the receiving layer, organic end groups such as methyl and phenyl can be used. MB50-315 silicone release agent is commercially available as a 50 wt% mixture of pelletized solid polydimethylsiloxane dispersed in a polycarbonate polymer. Depending on the composition of the receiving layer, other dispersions may be preferred, such as MB50-010 commercially available from Dow Corning, which is a dispersion in polyester. The release agent is suitably used in an amount of 0.5 to 10%, preferably 2 to 10%, most preferably 3 to 8%, by solids mass of the receiving layer.

(Formation of receiving layer)
One feature of the receptor layer according to the present invention is that it is formed by a melt extrusion method.

  The method for forming the receiving layer by the melt extrusion method according to the present invention is a method in which each constituent material used for forming the receiving layer is first sufficiently dried and then melted and mixed by a blending operation. The polycarbonate and polyester are preferably added separately to prevent or minimize the formation of a network structure that can make extrusion difficult and to minimize the tendency to stick between the thermal transfer ink sheet and the thermal transfer receiving sheet. At this time, a phosphorous-containing stabilizer such as phosphorous acid or organic phosphorous acid such as bis (2-ethylhexyl) phosphite is added to these materials together with about 0.01 to 1% by mass with respect to the total solid content of the receiving layer. It is preferable to do. Also, a plasticizer having a liquid at room temperature, specifically, a plasticizer having a melting point of 79 ° C. or less (for example, an aliphatic ester plasticizer such as dioctyl sebacate) can be added. It is preferable to suppress the content to 2.5% by mass or less from the viewpoint of reverse transfer resistance to the thermal transfer ink sheet, adhesion to the thermal transfer protective layer, and image storage stability. A compound having a melting point or softening point in the range of 80 to 140 ° C. according to the present invention can also be added during this blending operation.

  Regarding the method for forming the receiving layer using the melt extrusion method according to the present invention, for example, the methods described in paragraphs [0099] to [0116] of JP-A No. 2004-255878 can be referred to.

[Middle layer]
When the receptor layer according to the present invention is formed by directly extruding onto a substrate, it is generally preferable to provide an intermediate layer between the substrate and the receptor layer because adhesion to the substrate is generally lowered.

  As the binder constituting the intermediate layer, resins containing various polyolefins, LD polyethylene, ethylene methacrylic acid and the like can be used, but by adding various antistatic agents or antistatic polymers to these, not only the adhesion function, An antistatic function can also be imparted.

〔Base material〕
In the thermal transfer receiving sheet of the present invention, as a substrate for holding the receiving layer according to the present invention, for example, a microporous composite film commercially available from Mobil Corporation can be used. Or a cellulose fiber paper base material or those laminated bodies may be sufficient.

When using a cellulose fiber paper base material, it is preferable to extrusion laminate the fine pore composite film using a polyolefin resin. In the process of laminating them, it is desirable to maintain the minimum tension of the microporous film. The back side of the paper substrate (i.e., the side opposite the microporous composite film and receiving layer) may also be extrusion coated with a polyolefin resin layer (e.g., applied 10-75 g / m < ² >). , 011,814 and 5,096,875 may also include a back layer. The high humidity applications (greater than 50% relative humidity), preferably to the back surface resin coating rate of 30 to 75 g / m ^2, it is preferred even at 35~50g / m ^2.

  In addition, when obtaining a thermal transfer receiving sheet having a tactile sensation similar to a silver salt photograph, a relatively thick paper base (for example, a thickness of 120 μm or more, preferably 120 to 250 μm) and a relatively thin fine sheet The use of a pore composite film (for example, a thickness of less than 50 μm, preferably a thickness of 20 to 50 μm, more preferably a thickness of 30 to 50 μm) is preferred.

  The thermal transfer receiving sheet of the present invention is brought into close contact with the thermal transfer ink sheet, and receives an image of the sublimable dye from the thermal transfer ink sheet by imagewise heating to form an image. Hereinafter, the thermal transfer ink sheet applicable to the present invention will be described.

<Thermal transfer ink sheet>
The thermal transfer ink sheet that can be used in the present invention has a configuration in which each ink layer is provided in the surface order on a substrate. In the case of forming a three-color image, for example, a yellow image, a magenta image, or a cyan image, the thermal transfer ink sheet having each color ink layer described above is scanned three times while heat is applied by the thermal print head.

  In the present invention, any dye that can be applied to the thermal transfer ink sheet can be used as long as it can be transferred to the receiving layer of the thermal transfer receiving sheet by the action of heat. Particularly good results have been obtained with sublimable dyes. For details of the thermal transfer ink sheet, for example, the methods described in US Pat. Nos. 4,916,112, 4,927,803, and 5,023,228 are used. You can refer to it.

  As the thermal transfer ink sheet applicable to the present invention, a thermal transfer ink sheet comprising a polyethylene terephthalate support in which cyan, magenta and yellow dyes are coated in a sequential order on continuous repeating regions can be used. The process is carried out continuously for each color to obtain a dye image consisting of three colors.

As a dye applicable to the thermal transfer ink sheet, a particularly good result is obtained when a sublimable dye is used. Examples of sublimable dyes include anthraquinone dyes such as Sumikaron Violet RS (trade name, manufactured by Sumitomo Chemical Co., Ltd.), Dianix Fast Violet 3R FS (trade name, manufactured by Mitsubishi Chemical Co., Ltd.), Kayalon Polyol Brilliant Blue BM BM Black 146 (trade name, above, manufactured by Nippon Kayaku Co., Ltd.); azo dyes such as Kayalon Polyol Brilliant Blue BM, Kayalon Polyol Dark Blue 2BM, and KST Black KR (trade names, above, manufactured by Nippon Kayaku Co., Ltd.), Sumikar Black 5G (trade name, manufactured by Sumitomo Chemical Co., Ltd.) and Mikazol Black 5GH (trade name, manufactured by Mitsui Toatsu); Direct Dark Green B Direct trade dyes such as (trade name, manufactured by Mitsubishi Chemical Corporation) and Direct Brown M and Direct Fast Black D (trade name, manufactured by Nippon Kayaku Co., Ltd.); Kayanol Milling Cyanine 5R (trade name, manufactured by Nippon Kayaku Co., Ltd.), etc. Acidic dyes; basic dyes such as Sumicryl Blue 6G (trade name, manufactured by Sumitomo Chemical Co., Ltd.) and Aizen Malachite Green (trade name, manufactured by Hodogaya Chemical Co., Ltd.); or disclosed in US Pat. No. 4,541,830 Can be mentioned. When the above dyes are used alone or in combination, a single color is obtained. The dye can be used in an adhesion amount of 0.05 to 1 g / m ² and is preferably hydrophobic.

  The ink layer and the protective layer of the thermal transfer ink sheet can be printed on a support by a printing technique such as coating or gravure.

  A slip layer can be provided on the back surface of the thermal transfer ink sheet to prevent the print head from sticking to the thermal transfer ink sheet. Such a slip layer will contain a solid or liquid lubricant or mixture thereof, but may or may not have a polymer binder or surfactant. Preferred lubricants are oils or semi-crystalline organic solids that melt below 100 ° C. and are polyvinyl stearate, beeswax, perfluoroalkyl ester polyether, polycaprolactone, silicone oil, polytetrafluoroethylene, carbowax, polyethylene glycol or the United States There are substances disclosed in patents 4,717,711; 4,717,712; 4,737,485 and 4,738,950. Suitable polymer binders for the slip layer include poly (vinyl alcohol-co-butyral), poly (vinyl alcohol-co-acetal), polystyrene, polyvinyl acetate, cellulose acetate butyrate, cellulose acetate propionate, cellulose acetate or ethyl cellulose. There is.

  The substrate applicable to the thermal transfer ink sheet is not particularly limited as long as it has dimensional stability and can withstand the heat of the thermal print head. For example, polyester such as polyethylene terephthalate; polyamide; polycarbonate; glassine paper Condenser paper; cellulose esters such as cellulose acetate; fluoropolymers such as polyvinylidene fluoride or poly (tetrafluoroethylene-co-hexafluoropropylene); polyethers such as polyoxymethylene; polyacetals; polystyrene, polyethylene, polypropylene or methyl Mention may be made of polyolefins such as pentene polymers; polyimides such as polyimide amides and polyether imides, etc., with a thickness of 2 to 30 μm.

<Thermal transfer protection sheet>
Moreover, it is preferable to provide a protective layer using a thermal transfer protective sheet on the image formed on the thermal transfer receiving sheet by the thermal transfer ink sheet for the purpose of preventing the influence from light, heat, chemical substances and the like.

  As a protective layer capable of thermal transfer constituting the thermal transfer protective sheet, for example, a protective layer described in JP-A No. 2003-266960 can be applied.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

<Production of thermal transfer receiving sheet>
[Preparation of thermal transfer receiving sheet 1]
A receiving layer having the following constitution is laminated by a microporous composite film (OPPalite 350TW, Mobile Chemical Co.) having a thickness of 38 μm described in US Pat. No. 5,244,861 by a melt extrusion method. A thermal transfer receiving sheet 1 was prepared by forming on a paper base. The melt extrusion method used was in Example 1 of Example of JP-A No. 2004-255878 (the method described in paragraphs [0152] to [0162] and the intermediate layer (tie layer) was formed at the same time). It carried out according to the method of description.

<Receptor layer configuration>
70.07% polyester with 2% branching agent
Bisphenol A polycarbonate (LEXAN 151, manufactured by GE) 12.78%
Dioctyl sebacate 5.13%
Silicone release agent (MB50-315, manufactured by Dow Corning) 12.0%
Phosphorous acid 0.02%
[Preparation of thermal transfer receiving sheet 2]
The production of the thermal transfer receiving sheet 1 is the same except that the addition amount of the polyester containing 2% branching agent which is the additive of the receiving layer is changed to 45.2% and the addition amount of dioctyl sebacate is changed to 30.0%. Thus, a thermal transfer receiving sheet 2 was produced.

[Preparation of thermal transfer receiving sheet 3]
In the production of the thermal transfer receiving sheet 1, the amount of polyester containing 2% branching agent, which is an additive for the receiving layer, was changed to 37.2%, and dicyclohexyl phthalate (melting point: 60 ° C.) was used instead of dioctyl sebacate. A thermal transfer receiving sheet 3 was prepared in the same manner except that 50.0% was used and the silicone release agent (MB50-315, manufactured by Dow Corning) was removed.

[Preparation of thermal transfer receiving sheets 4 to 14]
Thermal transfer receiving sheets 4 to 14 were prepared in the same manner as in the preparation of the thermal transfer receiving sheet 3 except that dicyclohexyl phthalate was changed to the compounds shown in Table 1 and the blending ratios thereof. In addition, MB50-315 made by Dow Corning was added to the thermal transfer receiving sheets 8 and 14 as a release agent.

  Table 1 shows the configuration of each thermal transfer receiving sheet. The details of the items and compounds described in abbreviations in Table 1 are as follows.

* A: Content (% by mass) of polyester (PE) and polycarbonate (PC) in the receiving layer
<High melting point compound>
* 1: Dioctyl sebacate * 2: Dicyclohexyl phthalate * 3: Calcium stearate * 4: Zinc montanate * 5: Carnauba wax * 6: Hexamethylenebisstearic acid amide * 7: N-stearyl 12 hydroxystearic acid amide * 8 : 2,2'-methylenebis (4-ethyl-6-t-butylphenol)
* 9: 2- (2'-hydroxy-5'-methylphenyl) benzotriazole * 10: Polybutylene adipate-butylene terephthalate copolymer << Preparation of thermal transfer ink sheet >>
A thermal transfer ink sheet was prepared according to the method described in Examples of JP-A-2004-255878 (methods described in paragraphs [0168] to [0172]).

<Production of thermal transfer protection sheet>
A thermal transfer protective sheet was produced according to the production method of protective layer donor element I-9 described in Examples (paragraph number [0062]) of JP-A No. 2003-266960.

<Image formation>
A thermal transfer recording apparatus equipped with a thermal head of a line head having a resistor shape of square (main scanning direction length 80 μm × sub-scanning direction length 120 μm) and resolution of 300 dpi (dpi represents the number of dots per 2.54 cm). The receiving layer portion of each of the prepared thermal transfer receiving sheets and the ink layer of the prepared thermal transfer ink sheet were set to overlap each other, and the applied energy was sequentially increased while being in pressure contact with the thermal head and the platen roll. (Y), magenta (M), and cyan (C) step pattern patches are heated from the back side of the ink layer at a feed rate of 1.5 msec / line and a feed length per line of 85 μm for thermal transfer. Each dye was transferred onto the receiving layer of the receiving sheet to form an image. Thereafter, the thermal transfer protective sheet produced as described above is superposed on the receiving layer portion of the thermal transfer receiving sheet on which the image is formed, and heated with uniform applied energy in the same manner, and the protective layer is formed on the thermal transfer receiving sheet on which the image is formed. Was transcribed.

<Evaluation of formed image>
Each image printed as described above was evaluated according to the following method.

(Evaluation of sensitivity)
In the above image forming method, each thermal transfer receiving sheet is used to form an image while changing the applied energy, and the applied energy required to obtain a reflection density of 1.0 for each of Y, M, and C is measured. The average applied energy value was obtained. The sensitivity of each thermal transfer receiving sheet was evaluated based on the relative energy value when the average applied energy value of the thermal transfer receiving sheet 1 was 100. The lower this value, the higher the sensitivity.

(Evaluation of adhesion of protective sheet)
The state in the transfer process of the protective sheet after printing each color image was visually observed, and the adhesion of the protective sheet to each thermal transfer receiving sheet was evaluated according to the following criteria.

◎: Adhesiveness with the protective sheet is uniform, and no abnormalities such as reverse dye transfer are observed. ○: There are a few areas where adhesion to the protective sheet is weak, but there is no problem in practical use. : Adhesion with the protective sheet is slightly weak, and the reverse transfer phenomenon of the dye is slightly observed on the protective sheet after peeling. ×: The adhesive with the protective sheet is weak and hardly transferred, and after peeling. Dye reverse transfer phenomenon is noticeable on protective sheet (Evaluation of image preservation)
Each thermal transfer receiving sheet on which an image before transfer of the protective sheet was formed was stored for 2 weeks in an environment of 65 ° C. and 50% RH, and then the image storage stability of each thermal transfer receiving sheet was evaluated according to the following criteria.

A: The contours of the image forming portion and the white background portion after storage are as clear as the quality before storage, and no blur is observed. ○: The contours of the image forming portion and the white background portion after storage are preserved. Almost as clear as the previous quality and almost no blurring is observed. △: The outlines of the image forming part and the white background part after storage are slightly unclear compared to before storage and the occurrence of weak bleeding is recognized. Yes: The contours of the image forming portion and the white background portion after storage are considerably unclear compared to those before storage, and the occurrence of bleeding is noticeable. Table 1 shows the results obtained as described above.

  As is apparent from the results shown in Table 1, the thermal transfer receiving sheet of the present invention has high sensitivity under high-speed printing conditions, is excellent in adhesiveness with the heat-melt transferable protective layer, and has good image storage stability. I understand that. In addition, when the compound having a melting point or softening point in the range of 80 to 140 ° C. is a fatty acid ester type or a fatty acid amide type, the effect is great, and the content ratio with respect to the entire solid content of the receiving layer is 25% by mass or more. It can be seen that the sensitivity is higher without affecting other performance, and that the sensitivity is significantly higher at 50% by mass or more. It can also be seen that, under the same conditions, the addition of a siloxane-containing polymer release agent is more advantageous in terms of adhesion to the protective layer and image storage stability.

Claims (5)

In a thermal transfer receiving sheet having a heat diffusible dye receiving layer formed on a substrate by at least one melt extrusion method, the receiving layer has a melting point or softening point in the range of 80 ° C. or higher and 140 ° C. or lower. A thermal transfer receiving sheet comprising a certain compound in an amount of 10% by mass or more of the total mass of the receiving layer. 2. The thermal transfer receiving sheet according to claim 1, wherein the compound having a melting point or a softening point in the range of 80 ° C. or more and 140 ° C. or less is a wax mainly composed of a fatty acid ester or a fatty acid amide. 3. The thermal transfer according to claim 1, wherein the content of the compound having the melting point or softening point in the range of 80 ° C. or more and 140 ° C. or less with respect to the total mass of the receiving layer is 25% by mass or more. Receptor sheet. 4. The thermal transfer receiving sheet according to claim 3, wherein the content of the compound having the melting point or softening point in the range of 80 ° C. or more and 140 ° C. or less with respect to the total mass of the receiving layer is 50% by mass or more. . The thermal transfer receiving sheet according to any one of claims 1 to 4, wherein the receiving layer contains a siloxane-containing polymer having a mass average molecular weight of 100,000 or more as a release agent.