JP2571684B2 - Heat transfer sheet - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat transfer sheet, and more particularly, to a heat transfer sheet used in combination with a heat transfer sheet on which heat printing according to image information is performed by a thermal head or the like.

[Conventional technology]

In recent years, as a thermal transfer sheet used in the thermal transfer recording method adopted to directly record an image such as a photograph directly from the image on a CRT display, it has been conventionally used as a base material for synthetic paper, art paper, coated paper, etc. One provided with a receiving layer is known. The thermal transfer recording method is a thermal transfer sheet comprising a base material such as a polyester film provided with a color material layer comprising a sublimable dye and a binder (if necessary, heat-protecting the opposite surface of the base material provided with the color material layer). The color material layer is also superimposed on a receiving layer of the heat transfer sheet, and the heat transfer sheet is heated by a thermal head or the like, which suppresses heat generation by an electric signal. In this method, the sublimable dye in the material layer is transferred onto a sheet to be thermally transferred, and printing is performed by heating.

This type of heat transfer sheet has a drawback that, particularly when the base material is synthetic paper, the synthetic paper partially shrinks due to heating and tends to curl during heating printing for transfer. In general, high-quality paper other than synthetic paper is often used as the material.

[Problems to be solved by the invention]

However, a heat transfer sheet using a high-quality paper other than synthetic paper as a base material has a problem that the density of an image printed by heating is difficult to increase. Generally, when heat printing is performed using art paper or coated paper having a higher degree of smoothness as compared to high-quality paper as the base material of the heat-transferred sheet, an image that is uniform and has less white spots is obtained as compared with high-quality paper. The image density cannot be increased simply by increasing the smoothness of the substrate of the thermal transfer sheet.

[Means for solving the problem]

As a result of intensive studies in view of the above points, the present invention shows that the image density is easily increased by heating printing by providing a porous layer between the substrate and the receiving layer in the heat transfer sheet, that is, the sensitivity of sublimation transfer is increased. And completed the present invention.

That is, the present invention provides a heat-transferable sheet comprising a substrate, on which a receptor layer for receiving a dye transferred from the thermal transfer sheet when heated to form an image is provided. A porous layer formed using a W / O emulsion in which water is dispersed in a solution obtained by dissolving a thermoplastic resin in an organic solvent in which water is not completely dissolved is provided between the layers. The heat transfer sheet is a feature of the invention.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. The thermal transfer sheet 1 of the present invention basically includes a porous layer 3 provided on a base material 2 and a receiving layer provided on the porous layer 3. And a layer 4. The substrate 2 is made of art paper, coated paper, cast coated paper, high quality paper coated with a barrier coating, cellulose fiber paper such as synthetic resin rubber impregnated paper, synthetic paper, polyethylene terephthalate, vinyl chloride, polyolefin, or the like. Examples thereof include plastic films and sheets, and plastic sheets mixed with an extender pigment.

The porous layer 3 in the present invention is a W / O emulsion in which water is dispersed in a solution in which a thermoplastic resin is dissolved in an organic solvent that is not completely soluble in water (water is dispersed in an organic solvent solution of a resin). (Emulsion).
That is, the thermoplastic resin is dissolved in an organic solvent that is not completely soluble in water, and then water is added to the solution to obtain a W / O emulsion.
By coating on top and drying, first the organic solvent volatilizes and the resin solidifies, then the water evaporates to form voids, thereby forming a porous layer.

Examples of the thermoplastic resin include resins such as polyurethane, polyester, and vinyl chloride-vinyl acetate copolymer. Organic solvents that do not completely dissolve in water include
Methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, and the like.In the present invention, the solvent is a mixture of a water-immiscible solvent such as toluene and xylene and a water-miscible solvent such as methanol and isopropylene alcohol. A solvent can be used, and an organic solvent that does not completely dissolve in water and a solvent that is hardly miscible with water or a solvent that is miscible with water can be used in combination.

The desired pore size and the like in the porous layer 3 can be obtained by adjusting the ratio of the organic solvent to water, the mixing conditions of the components, the drying conditions, and the like.

As the material of the receiving layer 4, a thermoplastic resin such as a saturated polyester, an acrylate, a polyurethane, or a nylon is used. If necessary, a pigment such as calcium carbonate, titanium oxide, or zinc oxide can be contained in the resin. . The receiving layer 4 can be formed by applying a liquid in which the pigment is dispersed in an organic solvent solution of the thermoplastic resin, if necessary, onto the porous layer 3 and drying the liquid. The thickness of the receiving layer 4 is generally 5 to 10
μm is preferred.

In the heat transfer sheet 1 of the present invention, as shown in FIG. 2, a resin layer 5 is provided on the surface of the substrate 2 opposite to the surface on which the receiving layer 4 is provided. It has the effect of playing a reinforcing role and imparting smoothness for obtaining smooth running in the thermal transfer device. As a material of the resin layer 5, a vinyl chloride-vinyl acetate copolymer, a polymethacrylic acid ester and its copolymer, a polystyrene resin, or the like can be used. Is formed by a coating method such as a coating method.

Further, the heat transfer sheet 1 is provided with a release agent layer for improving the releasability from the transfer sheet on the receiving layer 4 (not particularly shown). The release agent layer may be formed directly on the receiving layer 4 or may contain a release agent in the receiving layer 4 to cause the release agent to bleed on the surface of the receiving layer. A release agent layer may be formed on the substrate. As the material of the layer, solid waxes such as polyethylene wax, amide wax, and Teflon powder, fluorine-based and phosphate-based surfactants, and release agents such as silicone oil are used.

Further, the heat transfer sheet 1 is provided with an antistatic layer on the surface side of one or both of the receiving layer 4 and the resin layer 5, and the antistatic layer is a cationic or anionic surfactant. And the like.

In the case where irregularities occur due to bubbles of the porous layer 3 on the surface of the receiving layer 4 and become uneven, a smoothness adjusting layer 6 is provided between the porous layer 3 and the receiving layer 4 as shown in FIG. be able to.

As a material of the smoothness adjusting layer 6, a thermoplastic resin such as a saturated polyester or polyolefin is used. If necessary, a pigment such as titanium oxide or calcium carbonate can be contained in the resin. The smoothness adjusting layer 6 is formed as a porous layer 3
As the method of providing the above, 1) a method of laminating a thermoplastic resin film, 2) a method of applying the thermoplastic resin by hot melt coating or the like, and 3) an application of a high viscosity solution of the thermoplastic resin by reverse roll coating or the like. And the like. As the lamination method in the above 1), an extraction method, a dry lamination method, a wet lamination method, or the like can be used. The smoothness adjusting layer 6
The surface of the receiving layer 4 can be formed with good smoothness without being affected by the unevenness due to the bubbles of the porous layer 3 by the provision of the resin layer. There is an advantage that the image becomes uniform.

In using the heat transfer sheet 1 of the present invention having the above-described structure, the transfer sheet 7 is used as shown in FIG.
After the heat transfer sheet 7 is overlapped with the heat transfer sheet 7 so that the color material layer 8 and the receiving layer 4 of the heat transfer sheet 1 are in contact with each other, and the heat transfer sheet 7 is heated by a thermal head or the like according to image information, By removing the thermal transfer sheet 7, the sublimable dye in the color material layer 8 is transferred to the receiving layer 4 of the heat transfer sheet 1, and an image is transferred and recorded on the heat transfer sheet 1.

Hereinafter, the present invention will be described in more detail with reference to specific examples.

Example 1 A composition for forming a porous layer having the following composition was applied to the glossy surface of a commercially available cast-coated paper (130 g / m ² ) using a miller bar (coating amount 4 g / m ² at the time of drying) and dried to form a porous sheet. A layer was formed.

Composition for forming porous layer Polyurethane W / O emulsion (Sanyo Chemical Co., Ltd .: Samprene UE-1000N) 100 parts by weight Methyl ethyl ketone 35 parts by weight Polyisocyanate (Nippon Polyurethanes Inc .: Coronate L) 3 parts by weight Water 50 parts by weight A composition for forming a receiving layer having the following composition was applied to the porous layer using a miller bar (coating amount: 7 g / m ² ), and dried to form a receiving layer.

Receptive layer forming composition Saturated polyester (Toyobo: Byron 200) 10 parts by weight Saturated polyester (Toyobo: Byron 290) 10 parts by weight Silicone oil (Shin-Etsu Chemical: KF-393) 1.5 parts by weight Silicone oil (Shin-Etsu Chemical) : X-22-343) 1.5 parts by weight Toluene / methyl ethyl ketone (weight ratio = 1: 1) 120 parts by weight On the other hand, heat resistance of a 6 μm thick polyethylene terephthalate film provided with a heat-resistant layer made of a thermosetting acrylic resin on one side The following composition was applied to the side opposite to the side on which the functional layer was provided using a wire bar (coating amount 1 g / m ² ), and dried to form a thermal transfer layer to obtain a thermal transfer sheet.

Thermal transfer layer composition Disperse dye 4 parts by weight (Nippon Kayaku: Kayaset Blue 136) Ethyl hydroxyethyl cellulose 6 parts by weight Methyl ethyl ketone / toluene (weight ratio = 1: 1) 90 parts by weight The above-mentioned heat transfer sheet and thermal transfer sheet The thermal transfer layer and the receiving layer were overlapped so that they were in contact with each other, heated with a thermal head from the heat-resistant layer side of the thermal transfer sheet, and the dye was transferred to the receiving layer of the heat-transferred sheet to form an image. Also, the roughness of the halftone solid image was small.

Comparative Example Using the same paper base material and composition for forming a receiving layer as in Example 1, a heat transfer sheet comprising a base material and a receiving layer provided on the base material without providing a porous layer was obtained.

The heat transfer sheet was combined with the same heat transfer sheet used in Example 1 and the same image as in Example 1 was transferred to the heat transfer sheet. As a result, the roughness of the halftone solid image was severe and the image density was low.

Example 2 A heat transfer sheet similar to that of Example 1 was formed, and a 12% by weight of polymethyl methacrylate (manufactured by Mitsubishi Rayon Co., Ltd .: Dianal BR-85) was formed on the surface of the sheet on which the receiving layer was not provided. The methyl ethyl ketone solution was applied using a miller bar (coating amount at drying: 2.5 g / m ² ), and dried to form a resin layer. Next, an antistatic agent (manufactured by Analytical Chemical Laboratories of Skokie: Statiside) is applied on the resin layer with isopropyl alcohol for 100 hours.
The liquid diluted twice was applied on a solid gravure plate and dried to obtain a heat transfer sheet.

The heat transfer sheets were stacked and automatically fed to a thermal transfer printer, and a solid image was transferred to the heat transfer sheet using the same heat transfer sheet as in Example 1. As a result, the image density was high. The running performance was smooth, and there was no problem such as double sheets generated by static electricity or the like.

Example 3 A composition for forming a porous layer having the following composition was applied to white polyethylene terephthalate (manufactured by Toray: white PET) having a thickness of 250 μm using a miller bar (coating amount at drying: 7 g / m ² ), and dried to form a porous layer. Was formed.

Composition for forming porous layer Polyurethane-based W / O emulsion (Dainichiseika: Heimlen) 100 parts by weight Methyl ethyl ketone / toluene (weight ratio = 1: 1) 40 parts by weight Water 30 parts by weight The composition for forming a receiving layer was applied using a Miyabar (a coating amount at the time of drying of 5 g / m ² ) and dried to form a receiving layer.

Receiving layer forming composition Saturated polyester (Arakawa Chemical: KA-1039, 30% solution) 50 parts by weight Silicone oil (Shin-Etsu Chemical: KF-393) 1 part by weight Silicone oil (Shin-Etsu Chemical: X-22-343) 1 part by weight Toluene / methyl ethyl ketone (weight ratio = 1: 1) 25 parts by weight The same antistatic agent as in Example 2 was applied on the receiving layer with a solid gravure plate and dried to obtain a heat transfer sheet.

When the above-mentioned heat transfer sheet was combined with the same heat transfer sheet used in Example 1 and the same image as in Example 1 was transferred to the heat transfer sheet, the halftone solid image was less rough and the image density was good. Was.

[Effects of the Invention] As described above, the thermal transfer sheet of the present invention has a porous layer provided between the substrate and the receiving layer. The heat of printing is fully utilized in the receiving layer, and the cushioning effect of the porous layer is generated, and the heating printing of the thermal head and the like is performed evenly, and the white spots on the image are eliminated,
There is an effect that the density of the transferred image is improved.

According to the present invention, the porous layer is formed using a W / O emulsion in which water is dispersed in a solution obtained by dissolving a thermoplastic resin in an organic solvent that is not completely soluble in water. Thus, an excellent porous layer having uniform pores can be obtained, and as a result, there is an advantage that the above-mentioned effects can be further exerted.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the heat transfer sheet of the present invention, FIG. 2 is a longitudinal sectional view showing another embodiment of the heat transfer sheet of the present invention, and FIG. FIG. 4 is a longitudinal sectional view showing a state in which transfer is performed. DESCRIPTION OF SYMBOLS 1 ... Heat transfer sheet 2 ... Base material 3 ... Porous layer 4 ... Reception layer

Claims (2)

(57) [Claims] 1. A heat transfer sheet comprising a substrate and a receptor layer for receiving a dye transferred from the thermal transfer sheet when heated to form an image. Between the layers, W / dispersed water in a solution of a thermoplastic resin dissolved in an organic solvent that is not completely soluble in water
A heat transfer sheet comprising a porous layer formed using an O-type emulsion. 2. The heat transfer sheet according to claim 1, wherein a resin layer is provided on the surface of the substrate opposite to the surface on which the receiving layer is provided.