JPH0825811A - Heat transfer image receiving sheet - Google Patents

Abstract

PURPOSE:To provide a heat transfer image receiving sheet which has a feel equivalent to that of paper, and in which curling is suppressed and an image of high quality of printing density and resolution is imparted. CONSTITUTION:A heat transfer image receiving sheet 1 uses pulp paper as a base material 2 and has at least a receiving layer 3 in such a manner that, as the entire sheet 1, the water content after it is left to stand for 24 hours in an atmosphere at 25 deg.C and 60%RH is set to a specific range of 3.0-6.0%. When the sheet 1 having such specific water content characteristic has a curl preventive layer 7 at the rear side of the material 2, the curl preventing effect becomes remarkable. Further, a foaming layer 4 is provided between the material 2 and the layer 3 to provide high quality, a waterproof layer 5 is provided between the layer 4 and the material 2 or an intermediate layer 6 is provided between the layer 4 and the layer 3 to improve performance. Even in such structures, the water content of the specific range is set thereby to effectively prevent the curling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer image-receiving sheet used for image formation by a thermal transfer sheet for sublimation transfer. In particular, the present invention relates to a thermal transfer image-receiving sheet that has the same texture as plain paper and has little curl.

[0002]

2. Description of the Related Art In recent years, the image recording method by sublimation thermal transfer is capable of easily obtaining a high-quality image having high resolution, high gradation and high transparency, and a relatively inexpensive printer.
It has become popular in computer image output, presentation image output (OHP, etc.), print proofing application, and design field. In this image recording method, a dye having a heat sublimation property or a heat diffusion property is used as a color material, and as a heat transfer sheet, a transfer layer obtained by dispersing and mixing the color material in a thermoplastic resin such as polyester resin is formed on a base film. On the other hand, as the thermal transfer image receiving sheet, as the thermal transfer image receiving sheet, a receiving layer which mainly receives a thermoplastic resin for receiving a color material which migrates from the thermal transfer sheet, is used which is provided on a sheet-shaped substrate, An image is formed by superposing these and transferring the color material from the thermal transfer sheet to the thermal transfer image receiving sheet by heating from the thermal head. Then, by transferring and superimposing images of yellow, magenta, cyan, and, if necessary, black, a high-quality full-color image can be formed by subtractive color mixing.

However, in order to further improve the characteristics by making use of the feature of this image recording method that high-quality images can be formed, the thermal transfer sheet and the thermal transfer image-receiving sheet are not in close contact with each other. It is essential to prevent the transfer omission due to. Further, in order to obtain a high density image, it is also necessary to effectively utilize the thermal energy given by the thermal head. Furthermore, the thermal transfer sheet and the thermal transfer image receiving sheet should not be vulnerable to heat. For this reason, the thermal transfer image-receiving sheet is required to have appropriate flexibility, cushioning properties, heat insulation properties, and heat resistance and fastness. Due to these requirements, the main thermal transfer image-receiving sheets currently on the market are based on a structure in which a synthetic paper having hollow cells is used as a base material, and a receiving layer mainly made of polyester resin or vinyl resin is provided on the base material. There is.

[0004]

However, the thermal transfer image-receiving sheet as described above is laminated with plain paper or a resin sheet in order to prevent the synthetic paper used as the base material from being expensive and to prevent curling. In some cases, it was necessary to have a multi-layer structure, and this would lead to further cost improvement, so many parts were not desirable. Also, because it is made of synthetic paper and has a texture like a plastic sheet, it feels strange compared to plain paper such as copy paper and heat transfer paper that are usually used in the office, and it can be folded, folded, or stacked. There is also a drawback that it is difficult to handle like paper when binding or filing. Further, when used for printing proofreading, there is a problem that the glossy surface texture is far from the actual plain paper print.

However, using plain paper as the base material,
Even if a receiving layer is provided directly or via an intermediate layer,
There are problems that the recording density is low and transfer omission occurs due to the influence of the surface property and heat insulating property of the paper. As a means for solving this problem, it is possible to improve recording density and transfer loss by providing a foam layer using a foaming agent such as microspheres as an intermediate layer having a cushioning property. JP-A-5-147364 discloses the method. Has been proposed by. However, if pulp paper is used as a base material and a receiving layer or the like is provided on one side thereof, the expansion and contraction of the paper base material occurs due to humidity, whereas the layer made of resin such as the receiving layer hardly changes, There is a problem in that environmental curling occurs, which is not desirable in appearance, and the curling makes it difficult to feed and eject paper in a printer.

Therefore, an object of the present invention is to solve the above-mentioned drawbacks by using pulp paper as a base material so that the gloss and handleability are similar to those of paper, and there is no environmental curl. Another object of the present invention is to provide a thermal transfer image-receiving sheet capable of providing a high quality image similar to that of the conventional synthetic paper base material.

[0007]

In order to achieve the above object, the image receiving sheet of the present invention is a thermal transfer image receiving sheet having at least an receiving layer on one surface of a base material made of pulp paper, and the thermal transfer image receiving sheet. 6 at 25 ° C as a whole
The water content after leaving for 24 hours in an atmosphere of 0% RH is 3.0
The composition is defined within the range of 6.0%.

The thermal transfer image-receiving sheet may have a foamed layer between the base material and the receiving layer. Further, the thermal transfer image-receiving sheet may have a waterproof layer between the base material and the foam layer. Further, in the above-mentioned thermal transfer image-receiving sheet, a curl-preventing layer made of a hydrophilic resin is provided on the opposite side of the surface of the substrate having the receiving layer.

The thermal transfer image-receiving sheet of the present invention will be described in detail below. The thermal transfer image-receiving sheet of the present invention is characterized in that it effectively prevents environmental curl by keeping the water content of the entire thermal transfer image-receiving sheet within a specific range. Its layer structure and materials of each layer, and manufacturing conditions. By appropriately selecting the above, a thermal transfer image-receiving sheet that meets various required performances can be obtained. The most basic layer structure is that the thermal transfer image-receiving sheet is composed of a base material and a receiving layer. However, unless a rough texture is expressed, sublimation thermal transfer that usually gives high image quality is obtained. In order to take advantage of the image recording method according to (1), it is common to have a structure in which a foaming layer is provided between the base material and the receiving layer. FIG.
Shows an example of such a thermal transfer image-receiving sheet 1 of the present invention, in which a foam layer 4 and a receiving layer 3 are sequentially formed on a base material 2.

FIG. 2 shows another embodiment of the thermal transfer image-receiving sheet of the present invention. A waterproof layer 5 is provided between the foam layer 4 and the base material 2, and a foam layer 4 and a receiving layer 3 are provided. Middle layer 6 between
Is formed. 3 shows another embodiment of the thermal transfer image-receiving sheet of the present invention, in which a waterproof layer 5 is provided between the foam layer 4 and the base material 2, and a curl prevention layer 7 is provided on the back surface side of the base material 2. Is formed. Further, FIG. 4 shows another embodiment of the thermal transfer image-receiving sheet of the present invention.
In the above configuration, the curl prevention layer 7 is further formed on the back surface side of the base material 2.

Next, the layers constituting the thermal transfer image-receiving sheet of the present invention will be described in order. The thermal transfer image-receiving sheet of the present invention may have various layer configurations as described above, and these layer configurations are appropriately selected depending on various performances such as required image quality, texture and cost. In addition, in the various layer configurations, the specific water content characteristic described above is extremely effective in preventing environmental curl.

[0012] as the substrate base material, pulp paper, i.e., paper is used that is normally used. The material of such a base material is not particularly limited,
For example, fine paper, art paper, lightweight coated paper, lightly coated paper,
Coated paper, cast coated paper, synthetic resin or emulsion-impregnated paper, synthetic rubber latex-impregnated paper, synthetic resin internal-added paper, resin mixed paper, thermal transfer paper, etc., among which preferred materials are high-quality paper and lightweight coated paper. , Lightly coated paper, coated paper, thermal transfer paper, etc. Alternatively, it may be a laminate of these pulp papers and a plastic film.

The coated paper or the like can be obtained by coating a base paper with a resin such as SBR latex mixed with calcium carbonate, talc, or the like. Since the liquid penetrates, it is advisable to provide a waterproof layer on the base material. When providing a foam layer with such a permeable coating liquid, since offset printing paper and the like are designed assuming a drying temperature of about 200 ° C., they are relatively heat-resistant, and will be described later. Curling due to heat wrinkles and heat shrinkage during the layer heating process is unlikely to occur, and since heat transfer paper is also premised on being heated by the thermal head, curl due to heat wrinkles and heat shrinkage during the heating process of the foam layer It is suitable because it is hard to cause.

Further, when the same paper as that used for proofreading of various prints such as gravure printing, offset printing and screen printing is used as the base material, the thermal transfer image-receiving sheet of the present application is not subjected to proofing printing. It is possible to perform a trial print using. On the other hand, although resin impregnated paper and cast coated paper have water resistance, the texture of the paper is different from that of paper and the cost is high.

These substrates have a thickness of 40 to 300 μm, preferably 60 to 200 μm. In order to give the obtained thermal transfer image-receiving sheet the texture of plain paper, the total thickness of the thermal transfer image-receiving sheet should be 80 to 20.
It is desirable to make the thickness of the substrate such that it is about 0 μm. Therefore, the thickness of the receptive layer formed on the base material, as well as the total thickness of the waterproof layer, the foam layer, the intermediate layer, and the curl prevention layer formed on the back surface of the base material (about 30 to 80 μm).
The value obtained by subtracting (degree) is the thickness of the substrate. 100μ
When a thin base material having a thickness of m or less is used, wrinkles are apt to occur due to water absorption when a water-based coating solution used for forming a foamed layer is applied, which is remarkable when a waterproof layer is provided. Has a waterproof effect.

Receiving Layer The receiving layer is composed of a vehicle containing a resin that easily dyes a coloring material as a main component, and if necessary, various additives such as a release agent. Resins that are easily dyed include polyolefin resins such as polypropylene, halogenated resins such as polyvinyl chloride and polyvinylidene chloride, vinyl resins such as polyvinyl acetate and polyacrylate, and copolymers thereof, polyethylene terephthalate. Polyester resins such as polybutylene terephthalate, polystyrene resins, polyamide resins, copolymers of olefins such as ethylene and propylene with other vinyl monomers, ionomers and cellulose derivatives. A single substance or a mixture can be used, and among these, a polyester resin and a vinyl resin are preferable. Further, it may be a composite of the above various resins.

The receptive layer may contain a releasing agent in order to prevent heat fusion with the thermal transfer sheet during image formation.
As the release agent, silicone oil, phosphoric acid ester plasticizer, fluorine compound and the like can be used, and silicone oil is particularly preferably used. As silicone oil, epoxy modified, alkyl modified, amino modified, carboxyl modified, alcohol modified, fluorine modified,
A modified silicone oil such as alkylaralkylpolyether-modified, epoxy-polyether-modified, or polyether-modified is preferably used, and among them, a reaction product of a vinyl-modified silicone oil and hydrogenorganopolysiloxane is preferable. The amount of the release agent added is 10
0.2 to 30 parts by weight is preferable with respect to 0 parts by weight.

The coating of the receiving layer and other layers described later is carried out by a general method such as roll coat, bar coat, gravure coat, gravure river coat and the like. The coating amount of the receptor layer is preferably from 0.5 to 10 g / m ² (solid content conversion, hereinafter, the “coating amount” of the present invention is a numerical value in terms of solid content, unless otherwise specified).

[0019] Between the foam layer above, a substrate-receiving layer, by providing a foam layer or the like, a superior thermal transfer image-receiving sheet. The foam layer is
The bubbles have heat insulating properties and cushioning properties, and a thermal transfer image-receiving sheet having high printing sensitivity can be obtained even when paper is used as the substrate. The foam layer is
For example, a resin solution in which a foaming agent is dispersed is applied and then foamed. The resin forming the foamed layer is not particularly limited, but for example, polyvinyl alcohol resin, styrene-acrylic resin, urethane resin, vinyl chloride resin,
Vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, vinyl acetate resin, polyethylene resin, acrylic resin modified with a simple substance such as acrylic acid or methacrylic acid or other monomers, modified olefin resin, etc. Known resins described above, or a mixture thereof can be used.

The resin and the foaming agent are dissolved and / or dispersed in an organic solvent or water to form a foamed layer. The coating solution for the foamed layer does not affect the foaming agent. It is preferably an aqueous coating liquid which does not give, for example, water-soluble, water-dispersible or SBR latex, urethane emulsion, polyester emulsion, emulsion of vinyl acetate and its copolymer, acrylic and acrylic such as acrylic styrene. Emulsion of copolymer, emulsion such as vinyl chloride emulsion,
Alternatively, these dispersions or the like can be used, but when the microspheres described later are used as the foaming agent, in the above-mentioned resin, emulsion of vinyl acetate and its copolymer, acrylic and acrylic-styrene, etc. Preference is given to using emulsions of acrylic copolymers.

In these resins, the glass transition point, flexibility and film-forming property can be easily controlled by changing the type of the monomer to be copolymerized and the compounding ratio thereof, so that the plasticizer and the film-forming aid can be easily controlled. It is suitable in that desired physical properties can be obtained without adding an agent, that there is little change in color during storage in various environments after film formation, and that there is little change with time in physical properties. However, among the above-mentioned resins, SBR latex is generally not preferable because it has a low glass transition point, is likely to cause blocking, and tends to cause yellowing after film formation or during storage. Urethane emulsion is NMP, DMF
Since many of them contain a solvent such as, and are likely to adversely affect the foaming agent, it is not preferable. Polyester emulsions, dispersions, and vinyl chloride emulsions are generally not used because they have a high glass transition point and deteriorate the foamability of microspheres. There are also soft ones, but these are preferably not used because they impart flexibility by adding a plasticizer.

The foaming performance of the foaming agent is greatly affected by the hardness of the resin forming the foamed layer. In order for the foaming agent to expand to a desired expansion ratio, the glass transition point is -30 to 20.
C. or the minimum film forming temperature of 20.degree. C. or less is desirable. When the glass transition point exceeds 20 ° C., the flexibility is insufficient and the foaming performance of the foaming agent is deteriorated. When the glass transition point is lower than -30 ° C, blocking (occurs on the foam layer and the back surface of the base material when the base material after forming the foam layer is wound) due to the adhesiveness occurs, or the thermal transfer image-receiving sheet. When cutting the sheet, a defect (when cutting the image-receiving sheet, the resin of the foam layer sticks to the blade of the cutter, resulting in a poor appearance, and a cut dimension may occur) is there. Further, when the minimum film forming temperature exceeds 20 ° C., a film forming defect occurs during coating / drying, and defects such as surface cracking occur.

As the foaming agent, decomposition of dinitropentamethylenetetramene, diazoaminobenzene, azobisisobutyronitrile, azodicarbamide, etc., which decomposes upon heating to generate gases such as oxygen, carbon dioxide, nitrogen, etc. Known foaming agents such as microspheres such as microspheres obtained by covering a low boiling point liquid such as a mold foaming agent or butane or pentane with a resin such as polyvinylidene chloride or polyacrylonitrile to form microcapsules. Among these, microspheres in which a low boiling point liquid such as butane or pentane is covered with a resin such as polyvinylidene chloride or polyacrylonitrile to form microcapsules are preferably used. These foaming agents are foamed by heating after the foamed layer is formed, so that the foamed layer exhibits high cushioning properties and heat insulating properties.

The amount of these foaming agents used is preferably in the range of 0.5 to 100 parts by weight per 100 parts by weight of the resin forming the foamed layer. If it is less than 0.5 part by weight, the cushioning property of the foam layer is low and the effect of the foam layer cannot be obtained. If it exceeds 100 parts by weight, the hollow ratio after foaming becomes too large, and the mechanical strength of the foam layer decreases, and it becomes impossible to withstand normal handling. In addition, the surface of the foam layer loses smoothness, which adversely affects the appearance and print quality. The thickness of the foam layer is 30 to 100 μm
Is good. When it is less than 30 μm, the cushioning property and heat insulating property are insufficient, and when it exceeds 100 μm, the effect of the foam layer is not improved and the strength is lowered.

As the particle size of the granular foaming agent such as microspheres, the volume average particle size before foaming is 5 to 15 μm.
It is preferable that the particle size is about m and the particle size after foaming is 20 to 50 μm. The volume average particle size before foaming is less than 5 μm,
If the particle size after foaming is less than 20 μm, the cushioning effect is low, while if the volume average particle size before foaming exceeds 15 μm, or if the particle size after foaming exceeds 50 μm, the surface of the foam layer becomes uneven. Further, it is not preferable because it adversely affects the image quality of the formed image.

Among the foaming agents, it is particularly preferable that the partition walls have a softening temperature and a foaming initiation temperature of 100 ° C. or less, and an optimum foaming temperature (the temperature at which the expansion ratio becomes highest in 1 minute of heating time).
It is preferable to use low-temperature foaming type microspheres having a temperature of 140 ° C. or lower, and to make the heating conditions during foaming as low as possible. By using microspheres having a low foaming temperature, it is possible to prevent heat wrinkles and curling of the substrate during foaming. This microsphere having a low foaming temperature can be obtained by adjusting the blending amount of a thermoplastic resin such as polyvinylidene chloride or polyacrylonitrile that forms the partition wall. In the foam layer using this microsphere, the bubbles obtained by foaming are closed cells, foaming is performed in a simple process only by heating, and the thickness of the foam layer can be easily controlled by the amount of microspheres mixed. There are advantages.

However, the microspheres are vulnerable to an organic solvent, and when a coating solution using an organic solvent as a foam layer is used, the partition walls of the microspheres are eroded,
The foamability will be reduced. Therefore, when the microspheres as described above are used, organic solvents that attack the partition walls, for example, ketones such as acetone and methyl ethyl ketone, ester solvents such as ethyl acetate, lower alcohols such as methanol and ethanol, and the like. It is better to use a water-based coating liquid that does not contain. Therefore, it is preferable to use an aqueous coating solution, specifically, one using a water-soluble or water-dispersible resin, or a resin emulsion, preferably an acrylic-styrene emulsion or a modified vinyl acetate emulsion. Even when the foamed layer is formed with an aqueous coating liquid, NMP, DMF,
Addition of a high-boiling point highly polar solvent such as ethylene glycol monoether will affect the microspheres, so check the composition of the aqueous resin to be used and the amount of the high-boiling point solvent added, and check if there is any adverse effect on the microcapsules. It is necessary to be careful.

Waterproof layer When the above-mentioned foam layer is provided between the substrate and the receiving layer, when an aqueous solution or dispersion or an aqueous emulsion coating solution is used in consideration of the foaming agent used, It is effective to provide a waterproof layer in order to prevent water from entering the base material made of pulp paper and to easily control the water content, which is the point of the present invention. In addition, when a thin base material having a thickness of 100 μm or less is used, wrinkles are likely to occur due to water absorption when a water-based coating liquid used for forming a foamed layer is applied, and this waterproof layer is provided. And there is a remarkable waterproof effect. Further, even if the coating solution for the foam layer is applied onto the base material after the waterproof layer is provided, the foam layer should be formed to the desired thickness because the coating solution does not penetrate into the base material. You can Further, when such a foam layer is foamed by heating, the expansion ratio can be increased, and the cushioning property of the entire image receiving sheet is improved,
Further, it is economical because the amount of coating liquid for the foam layer can be reduced with respect to the desired thickness of the foam layer after formation. Furthermore, without a waterproof layer, the water of the coating liquid for the foam layer penetrates into the base paper, and in order to dry this, it is necessary to lengthen the drying time as a drying condition and tighten it. ,
The processing speed is slowed down, the drying furnace is lengthened, and the like, which is an obstacle to production, and such a problem can be solved by the waterproof layer.

The resin that can be used for the waterproof layer is not particularly limited as long as it is a water-insoluble resin, and examples thereof include urethane resin, acrylic resin, polyester resin, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, Examples thereof include vinyl acetate resin, polyvinyl acetal resin, polycarbonate resin, polyolefin resin, and modified resins thereof.

Since the waterproof layer coating liquid comprising the above resin is intended to prevent the water-based foaming layer coating liquid from adversely affecting the substrate due to water, the waterproof layer is dissolved in an organic solvent rather than an aqueous system. Alternatively, it is preferably dispersed. If the coating is performed with a water-based material, unevenness of water absorption on the surface of the base material may cause wrinkles and undulations on the base material, which may adversely affect texture and print quality. This tendency is particularly remarkable when a thin substrate having a thickness of 100 μm or less is used. From this point of view, as the organic solvent that can be used, for example, toluene,
Methyl ethyl ketone, isopropanol, ethyl acetate,
Examples thereof include butanol and other general industrial organic solvents.

Further, talc, silica, calcium carbonate,
Improving the coating suitability of the waterproof layer itself by adding an inorganic filler such as an extender pigment such as titanium oxide, barium sulfate or zinc oxide,
Improves adhesion to the substrate and foam layer (especially when an aqueous coating liquid is used to form the foam layer), improves wettability when coating the foam layer, and also imparts whiteness it can. Also,
As the filler, an organic filler of fine resin particles such as an acrylic resin, a melamine resin, and a polyamide resin can also be used. The coating amount of this waterproof layer is preferably in the range of 1 to ²⁰ g / m ² . If it is less than 1 g / m ² , the effect as a waterproof layer cannot be obtained, and if it exceeds 20 g / m ² , the expected effect is not improved.
This adversely affects the texture of the base material, resulting in a synthetic resin sheet-like texture. It is also uneconomical.

Intermediate layer Further , when the above-mentioned foaming layer is provided between the substrate and the receiving layer, the use of microspheres as a foaming agent weakens the organic solvent. The agent is damaged and the foamability is likely to decrease. To prevent this phenomenon,
In addition, unevenness that may appear on the surface of the foam layer reaches the surface of the receiving layer and is caused by poor adhesion between the thermal transfer sheet and the thermal transfer image receiving sheet, resulting in a decrease in resolution due to defective transfer such as white spots or voids in the image. If an intermediate layer is provided in order to prevent this, a more excellent thermal transfer image-receiving sheet can be obtained.

From this point of view, the intermediate layer is assumed to have flexibility and elasticity that can be transmitted to the receiving layer without reducing the cushioning effect of the foam layer, and the intermediate layer coating liquid is water-based. It is preferable. The resin forming the intermediate layer is not particularly limited as long as it is a water-based coating liquid and has the above-mentioned physical properties, for example, acryl-styrene copolymer, acryl-based copolymer such as acrylic resin, polyurethane. Examples thereof include resins, polyester resins, vinyl chloride resins, vinyl chloride-vinyl acetate copolymers, vinyl acetate resins, and the like, alone or in a mixture. Above all, a resin having a glass transition point in the range of −30 to 10 ° C. is preferable. If the glass transition point is less than -30 ° C, the tackiness is large and blocking (occurs on the intermediate layer and the back surface of the substrate) may occur, or a defect may occur when the thermal transfer image-receiving sheet is cut. . If the glass transition point is higher than 10 ° C., the flexibility is insufficient and the above object cannot be achieved.

If the intermediate layer coating liquid composed of the above resin is an organic solvent system, it will attack the foamed layer when it is coated on the foamed layer, and the effect of cushioning property and the like due to the foamed layer cannot be obtained. There is. Therefore, this problem can be solved by using an aqueous coating solution for the intermediate layer between the foam layer and the receiving layer. This water-based coating liquid is a water-based coating liquid that does not include organic solvents such as ketones such as acetone and methyl ethyl ketone, ester-based solvents such as ethyl acetate, and lower alcohols such as lower alcohols such as methanol and ethanol. It is preferably formed. Specifically, it is preferable to use a water-soluble or water-dispersible resin, or a resin emulsion, preferably an acrylic-styrene copolymer emulsion.

Calcium carbonate, talc, silica as an inorganic filler is added to the above-mentioned intermediate layer and the above-mentioned foamed layer as inorganic fillers in order to impart the hiding property and whiteness of the thermal transfer image-receiving sheet and to adjust the texture. Kaolin, calcium carbonate,
Known inorganic fillers such as titanium oxide, barium sulfate and zinc oxide, organic fillers of fine resin particles such as acrylic resin, melamine resin and polyamide resin, and optical brighteners may be contained. The compounding ratio is preferably 10 to 200 parts by weight with respect to 100 parts by weight of the resin solid content. If it is less than 10 parts by weight, the effect is poor, and if it exceeds 200 parts by weight, dispersion stability may be poor and the performance of the resin may not be obtained.
The coating amount of the intermediate layer is preferably in the range of from 1 to 20 g / m ^2, is less than 1 g / m ^2, it is not sufficiently exhibited function of protecting the bubbles. On the other hand, if it exceeds 20 g / m ² , the original effects of the foamed layer, such as heat insulating property and cushioning property, cannot be exhibited, which is not preferable.

Curling Prevention Layer Furthermore, if the substrate paper is exposed on the back side, the thermal transfer image-receiving sheet may curl due to the humidity and temperature in the environment. Therefore, one method is to form a resin layer having a barrier property against water on the back surface of the substrate,
If the quality of the paper is more emphasized, it is preferable to form a curl prevention layer made of a hydrophilic resin on the side of the substrate opposite to the surface having the receiving layer.

To form such an anti-curl layer,
A hydrophilic resin having hydrophilicity and a water retention effect is preferable, and therefore, for example, polyvinyl alcohol, polyethylene glycol, polypropylene glycol, polyvinyl acetal resin having a hydroxyl group or an ether bond is preferable. The resin is impregnated into the base material or the resin layer is formed on the back surface of the base material by coating the back surface of the base material with a coating solution obtained by dissolving, dispersing or emulsifying these resins alone or in water. Or as both impregnated and formed on the backside, an anti-curl layer can be provided. Therefore, having an anti-curl layer made of a hydrophilic resin on the opposite side of the surface of the base material having the receiving layer means that the anti-curl layer may be formed in the base material by impregnation,
Further, it may be formed as an independent layer on the back surface of the base material, or may be formed of both of them, and includes all of these forms.

By providing the anti-curl layer, the expansion and contraction of the pulp fibers in the paper of the base material due to the moisture are suppressed,
The curl prevention ability can be further improved. It is also possible to adjust the water content of the base material by adjusting the solid content of the coating liquid. Further, a lubricant such as an inorganic or organic filler, a lubricant such as silicone, or a release agent may be added to the anti-curl layer. The anti-curl layer is
A coating amount of 0.05 to 3 g / m ² is preferable. Is less than the coating amount is 0.05 g / m ^2, less the effect of preventing curling, exceeds 3 g / m ^2, impaired the texture of the paper.

Even when the resin layer having a barrier property against water as described above is formed by melt extrusion coating of a resin such as polyethylene, polypropylene or polyester, a curl prevention layer is used, water flows in and out of the substrate. And a thermal transfer image-receiving sheet excellent in curl prevention can be obtained. However, the texture of the paper deteriorates.

In the thermal transfer image-receiving sheet of the present invention, each layer as described above is appropriately selected so that the water content falls within a specific range as a layer structure suitable for the required image quality, texture, texture, cost and the like. Good.

As a method of adjusting the water content within a specific range, first, there is a selection of the layer constitution and a selection of a material forming the layer. In selecting the layer forming material, there is a selection of paper, that is, a base material, which greatly affects the water content. For example, when resin is not coated on the surface of high quality paper,
If the water-based coating liquid is applied directly, the water permeates the paper violently. However, when it comes to coated paper such as coated paper and art paper, the penetration becomes mild. Furthermore, in the case of cast-coated paper or a composite of plastic film and paper, it becomes even milder. Therefore, when the water-based coating liquid is applied to these substrates, if the same drying conditions are used,
The water content can be reduced in the order of high-quality paper> coated paper> cast-coated paper, then composite. Specifically, as in Example 1 and Comparative Example 1, if only the base material is different, the water content changes.

However, even if the base materials are different, it is possible to adjust the water content by adjusting the drying conditions so that the water content falls within a desired specific water content range. Specifically, it can be seen in comparison between Example 6 and Comparative Example 1 and Example 5 and Comparative Example 4. The adjustment of the drying conditions is not to define the drying temperature and the drying time within specific ranges, but the drying conditions such that the water content of the thermal transfer image-receiving sheet obtained as a result of the drying is within the specific ranges. Therefore, as a method for producing the thermal transfer image-receiving sheet of the present invention, the drying condition is one important factor, but the condition is defined only by the resultant water content, and the characteristic value obtained by this result. The characteristic of the manufacturing method is that the manufacturing conditions are defined by.

Providing an anti-curl layer is a useful method for directly adjusting the water content of a paper substrate having a high water absorption. The anti-curl layer suppresses the expansion and contraction of the pulp fibers of the paper, and also acts as a barrier to the absorption of water into the base material to adjust the water content. Specifically, it is a comparison between Examples 3 and 4 and Comparative Example 3.

In addition, providing a waterproof layer in a structure having a foam layer is also a useful method for directly adjusting the water content. The waterproof layer can effectively prevent the water of the water-based foaming layer coating liquid from penetrating into the base material, and prevent the water content from increasing significantly. Specifically, it is a comparison between Example 2 and Comparative Example 2. The curl prevention layer and the waterproof layer, which have a direct action on the substrate, are easy and effective in adjusting the water content.

As described above, the thermal transfer image-receiving sheet of the present invention has a texture similar to that of paper by appropriately selecting and adjusting the layer structure, its constituent materials, and manufacturing conditions such as drying conditions, and High quality images can be obtained without any problems due to environmental curl.

The thermal transfer sheet used when performing thermal transfer using the thermal transfer image-receiving sheet of the present invention as described above is a known sublimation type thermal transfer sheet used in a sublimation transfer recording system, or a binder which is melted by heat. A hot-melt ink layer supporting a pigment or the like on the base material, formed by coating on a base material, and transferred to a transfer target together with the ink layer by heating,
A heat melting type heat transfer sheet can also be used. Further, as the means for applying the heat energy at the time of thermal transfer, any conventionally known applying means can be used, and for example, a thermal printer (for example, video printer VY-100 manufactured by Hitachi, Ltd.)
Adjust the recording time with a recording device such as
An image can be formed by applying a thermal energy of about 0 mJ / mm ² .

[0047]

According to the thermal transfer image-receiving sheet of the present invention, the entire thermal transfer image-receiving sheet is exposed to the atmosphere of 25% and 60% RH.
By setting the water content after standing for 4 hours to a specific range of 3.0 to 6.0%, it is possible to effectively prevent an environmental curl which is a hindrance even if various layer configurations are formed. Its mechanism of action is
Although it is not certain, in the environment where various temperature and humidity can be obtained, the above range has a neutral moisture content, and the absorption and release of water to and from the thermal transfer image receiving sheet, which corresponds to environmental changes, is relatively small, and the thermal transfer image receiving sheet. It is thought that this is because the shrinkage change of each layer can be softened.

[0048]

EXAMPLES Next, the present invention will be described more specifically by way of Examples and Comparative Examples. In the text, "part" means
Unless otherwise specified, it is based on weight. Further, the “application amount” corresponding to the thickness of each layer is a dry weight basis unless otherwise specified.

Method of measuring water content The water content after leaving at 25 ° C. in an atmosphere of 60% RH for 24 hours means that the thermal transfer image-receiving sheet is left in an oven at 25 ° C. and 60% RH for 24 hours, and is measured by the following method. It is calculated from the measurement results. That is, the weight of the test piece after being left for 24 hours is measured by an electronic balance to obtain a measured value A. Next, after measuring the measured value A, place it in an oven at 120 ° C.
The weight after standing for a time is measured in the same manner, and the measured value is B. Then, the water content is calculated by the following formula. Moisture content [%] = {(A−B) / A} × 100 Hereinafter, in the examples and comparative examples, all that is simply referred to as “moisture content” means the moisture content under the above conditions.

Example 1 As a base material, the basis weight is 84.1 g.
/ M ² coated paper (New V Matt, manufactured by Mitsubishi Paper Mills Co., Ltd.), and coated on one side with a coating solution for the foam layer having the following composition with a miya bar so that the coating amount is 10 g / m ^2. rear,
It was dried in an oven at 100 ° C. for 1 minute and foamed to form a foamed layer. Foaming layer coating liquid ethylene-vinyl acetate copolymer emulsion 100 parts (manufactured by Tope Co., XB3647B) Microspheres (manufactured by Expancel, 551WU20) 20 parts water 20 parts Further on the foamed layer, the following composition After coating the receptor layer coating liquid of No. 1 with a bar to a coating amount of 3 g / m ² , 130
It was dried at ℃ 15 seconds to obtain a thermal transfer image-receiving sheet of the present invention. Receptor layer coating liquid polyester resin (Toyobo Co., Ltd., Byron 200) 20 parts Amino-modified silicone (Shin-Etsu Chemical Co., Ltd., X22-3050C) 1 part Epoxy-modified silicone (Shin-Etsu Chemical Co., Ltd.) , X22-3000E) 1 part Methylethylketone / toluene = 1/80 80 parts The water content of the thermal transfer image-receiving sheet thus obtained was 5.8%.

Example 2 As a base material, the basis weight is 127.9.
Use g / m ² coated paper (OK Royal Coat manufactured by Shin Oji Paper Co., Ltd.), and apply a waterproof layer coating solution of the following composition to one side of the Miya Bar with a coating amount of 3 g / m ^2. After coating, the coating was dried in an oven at 100 ° C. for 15 seconds to form a waterproof layer. Acrylic resin for waterproof layer (Mitsubishi Rayon Co., Ltd., Dianal BR-85) 25 parts Rutile titanium oxide (Ishihara Sangyo Co., Ltd., Taipek CR-50) 10 parts Methyl ethyl ketone / toluene = 1/150 Part Next, a foam layer was formed on the waterproof layer in the same manner as in Example 1. Further, an intermediate layer coating solution having the following composition was applied on the foamed layer with a miya bar so that the coating amount was 1 g / m ^2, and dried in an oven at 100 ° C. for 35 seconds to form an intermediate layer. . 80 parts of coating liquid acrylic ester emulsion for intermediate layer (RX669R manufactured by Nippon Carbide Industry Co., Ltd.) 20 parts of water Further, a receiving layer was formed on the intermediate layer in the same manner as in Example 1 to form the present invention. A thermal transfer image receiving sheet was obtained. The water content of the thermal transfer image-receiving sheet thus obtained was 5.2%.

Example 3 As a base material, a basis weight of 157 g /
m ² cast coated paper (Miracoat Platinum, manufactured by Shin Oji Paper Co., Ltd.) is used, and one side is coated with a waterproof layer coating solution of the following composition with a miya bar so that the coating amount becomes 5 g / m ^2. After coating, it was dried in an oven at 100 ° C. for 1 minute to form a waterproof layer. Waterproof layer coating liquid Urethane resin 40 parts (Nipporan N5199, manufactured by Nippon Polyurethane Industry Co., Ltd.) Toluene 40 parts Methyl ethyl ketone 40 parts Isopropyl alcohol 5 parts Next, on the waterproof layer, a foam layer coating liquid having the following composition Was coated with a bar to a coating amount of 10 g / m ² , dried in an oven at 100 ° C. for 30 seconds, and foamed to form a foamed layer. Foaming layer coating liquid Styrene-acrylic copolymer emulsion 100 parts (Nippon Carbide Industry Co., Ltd., RX941A) Microspheres (Matsumoto Yushi Kagaku Co., Ltd. F30VS) 10 parts Water 20 parts Further on the foaming layer , A receiving layer coating solution having the following composition,
After coating with a bar to a coating amount of 4 g / m ² , it was dried in an oven at 130 ° C. for 2 minutes to form a receiving layer. Receptor layer coating liquid Vinyl chloride-vinyl acetate copolymer 20 parts (Denka Vinyl 1000A manufactured by Denki Kagaku Kogyo Co., Ltd.) Amino modified silicone (X22-343 manufactured by Shin-Etsu Chemical Co., Ltd.) 5 parts Epoxy-modified silicone (Shin-Etsu) KF-393 manufactured by Kagaku Kogyo Co., Ltd. 5 parts Methyl ethyl ketone / toluene = 1/80 80 parts Furthermore, a coating liquid for curl prevention layer having the following composition is applied on the surface of the base material opposite to each of the above layers in an amount of 1 g. / m ² and made like after coating impregnated with wire bar, and dried 100 ° C. 15 seconds in an oven to obtain a thermal transfer image-receiving sheet of the present invention. Coating liquid for anti-curl layer Polyvinyl alcohol (Kuraray Co., Ltd., PVA124) 2 parts Water 100 parts The water content of the thermal transfer image-receiving sheet thus obtained was 4.5%.

Example 4 As a base material, a basis weight of 127.9
g / m ² coated paper (Satin Kinto, manufactured by Shin Oji Paper Co., Ltd.) is used, and polyethylene resin is applied to a thickness of 2 on one side.
A curl preventive layer is formed by extrusion coating from a T-die to a thickness of 0 μm, and a waterproof layer, a foam layer, and a receiving layer are formed in this order on the opposite surface of the substrate in the same manner as in Example 3. Then, a thermal transfer image-receiving sheet of the present invention was obtained. The water content of the thermal transfer image-receiving sheet thus obtained is 4.
7%.

Example 5 As a base material, a basis weight of 72.3 g
/ M ² coated paper (Shin Oji Paper Co., Ltd., New Top) was used, and the same amount of the coating liquid for the receptor layer as in Example 1 was applied to one side directly so that the coating amount was 5 g / m ^2. After coating with a bar, it was dried in an oven at 130 ° C. for 30 seconds to obtain a thermal transfer image-receiving sheet of the present invention. The water content of the thermal transfer image-receiving sheet thus obtained was 5.2%.

Example 6 As a base material, a basis weight of 81.4 g
/ M ² of high-quality paper (Kishu Paper Co., Ltd., gold sand) is used.
A thermal transfer image-receiving sheet of the present invention was obtained in the same manner as in Example 1 except that the receiving layer coating liquid was dried at 130 ° C for 2 minutes. The thermal transfer image-receiving sheet thus obtained had a water content of 4.5%.

Example 7 In Example 5, after forming the receiving layer, a curl preventing layer similar to that of Example 3 was provided on the surface of the substrate opposite to the surface on which the receiving layer was formed, and the drying condition was 100 ° C. for 30 seconds. A thermal transfer image-receiving sheet of the present invention was obtained. The thermal transfer image-receiving sheet thus obtained had a water content of 4.8%.

Comparative Example 1 A thermal transfer image-receiving sheet was obtained in the same manner as in Example 6 except that the drying conditions of the receiving layer coating solution were the same as in Example 1 at 130 ° C. for 15 seconds. The thermal transfer image-receiving sheet thus obtained has a water content of 6.2%.
Met.

Comparative Example 2 A thermal transfer image-receiving sheet was obtained in the same manner as in Example 2 except that the waterproof layer was not used. The water content of the thermal transfer image-receiving sheet thus obtained was 7.8%.

Comparative Example 3 A thermal transfer image-receiving sheet was obtained in the same manner as in Example 3 except that the curl prevention layer was not used. The water content of the thermal transfer image-receiving sheet thus obtained is 2.
7%.

Comparative Example 4 The drying conditions after coating the receiving layer were as follows:
A thermal transfer image-receiving sheet was obtained in the same manner as in Example 5 except that the temperature was 130 ° C. for 2 minutes. The water content of the thermal transfer image-receiving sheet thus obtained was 1.7%.

Performance evaluation ◎ Environmental curl A thermal transfer image-receiving sheet cut into a size of 148 mm × 210 mm was placed on a flat table, and the maximum value of the warp at the four corners was measured after leaving it in each of the following environments for 2 hours. did. When the thermal transfer image receiving sheet was placed, the measurement was performed both with the receiving layer forming surface facing up and with the receiving layer forming surface facing down. 1.30 ° C., 80% RH 2. 5 ° C., 10% RH 3.30 ° C., 10% RH 4.25 ° C., 60% RH Image quality (printing sensitivity, missing transfer, uneven transfer) Color video printer (VY-2 manufactured by Hitachi, Ltd.)
00), a solid image of one color of magenta in halftone was transferred, and the printing sensitivity was measured by measuring the optical density with a reflection densitometer (RD-918 manufactured by Macbeth Co.). The presence or absence of transfer omission and transfer unevenness was visually determined. ◎ Printer suitability The same printer as above was used to observe how the paper was fed and discharged during the print test under each of the above environments.

Evaluation results of environmental curl of Examples and Comparative Examples,
The water content is shown in Table 1.

[0063]

[Table 1]

Table 2 shows the evaluation results of the printer suitability and the image quality of Examples and Comparative Examples.

[0065]

[Table 2]

[0066]

As described above in detail, according to the thermal transfer image-receiving sheet of the present invention, despite the fact that pulp paper is used as the substrate,
By defining the water content after standing in an atmosphere of 5% and 60% RH for 24 hours within the range of 3.0 to 6.0%, it is possible to effectively prevent the occurrence of environmental curl due to changes in temperature and humidity of the environment. . Further, if a curl prevention layer is provided on the back surface side of the substrate, environmental curl can be further prevented. Further, when a foaming layer, a waterproof layer, an intermediate layer and the like are provided between the receiving layer and the base material, a high quality image can be formed. As a result, the gloss and handleability are similar to those of paper, there is no environmental curl, and a high-quality image similar to that of a conventional synthetic paper substrate can be obtained.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a thermal transfer image receiving sheet of the present invention.

FIG. 2 is a vertical sectional view showing another embodiment of the thermal transfer image receiving sheet of the present invention.

FIG. 3 is a vertical sectional view showing another embodiment of the thermal transfer image receiving sheet of the present invention.

FIG. 4 is a vertical sectional view showing another embodiment of the thermal transfer image receiving sheet of the present invention.

[Explanation of Codes] 1 Thermal Transfer Image Receiving Sheet 2 Base Material 3 Receiving Layer 4 Foaming Layer 5 Waterproof Layer 6 Intermediate Layer 7 Curling Prevention Layer

Claims (4)

[Claims] 1. A thermal transfer image-receiving sheet having at least a receiving layer on one surface of a base material made of pulp paper, the moisture content of the thermal transfer image-receiving sheet after being left at 25 ° C. in an atmosphere of 60% RH for 24 hours. , 3.0 to 6.0%. 2. The thermal transfer image-receiving sheet according to claim 1, further comprising a foam layer between the base material and the receiving layer. 3. The thermal transfer image-receiving sheet according to claim 2, further comprising a waterproof layer between the base material and the foam layer. 4. The thermal transfer image-receiving sheet according to claim 1, further comprising a curl prevention layer made of a hydrophilic resin on the side opposite to the surface having the receiving layer of the substrate.