JPH0768949A - Image receiving sheet for heat transfer - Google Patents

Abstract

PURPOSE:To obtain an image receiving sheet for heat transfer with good sensitivity and generating no curl after printing by providing respectively a specified biaxially oriented polyolefin film and a specified polyolefin film on both faces of a base as a substrate on the upper face of which an image receiving layer is provided. CONSTITUTION:An image, receiving layer receiving a heat transfer dye from a heat transfer medium is provided on the upper face of a substrate in an image receiving sheet for heat transfer. In this case, the substrate is constituted by providing film layers on both faces of a base material. The film layer on the side where an image receiving layer is provided is formed of a biaxially oriented polyethylene film with a density of 0.4-0.8g/cm<3> and a thickness of 20-60mum. On the other hand, the film layer on the side where the image receiving layer is not provided is formed of a polyolefin film formed by means of a melt extrusion process and with a solid content wt. ratio of a low density polyethylene resin of at least 60%. It is possible thereby to obtain the image receiving sheet for heat transfer with good sensitivity and generating no curl after printing.

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 recording by transferring a heat transferable dye in thermal transfer recording of a thermal printer or the like. The present invention relates to a thermal transfer image-receiving sheet that is good and has no curl after printing.

[0002]

2. Description of the Related Art In recent years, as a means for color hard copy, an apparatus using a thermal transfer recording system has been widely spread because of its advantages such as light weight, compactness, no noise, excellent operability and maintainability. There is. In this thermal transfer recording system,
There are two types of methods, which are roughly classified into a heat melting type and a heat transfer type or a sublimation type. In particular, the latter is excellent in reproducibility of multi-color gradation images and is printed by using a sublimation type thermal transfer type printer. The principle of such a sublimation type thermal transfer printer is to convert an image into an electric signal, and
This electric signal is converted into a heat signal by a thermal head to heat a heat transfer medium coated with a heat transferable dye (hereinafter referred to as an ink donor sheet), and then sublimated or diffused in the medium for thermal transfer from the ink donor sheet. Information is recorded by transferring the dye to the image receiving layer of the image receiving sheet.

In addition, the demand for color hard copy has increased,
Since it has become necessary to increase the printing speed, it is required to improve the sensitivity, that is, the transfer density, so that a clear image can be obtained even when the applied energy is low. For high-sensitivity recording, the film support of the ink donor sheet is made thinner, the platen pressure is increased, the adhesion between the ink donor sheet and the image receiving sheet is improved, the heat insulation of the image receiving sheet is improved, and the heat transfer of the dye of the ink donor sheet It is known that this can be achieved by improving the image quality and the dyeing property of the image receiving layer. Among them, the adhesion between the ink donor sheet and the image receiving sheet and the heat insulating property of the image receiving sheet have a great influence on the sensitivity. Therefore, it has become common to use a low density polyolefin film having high heat insulating property and cushioning property as a support. There is.

However, when such a low-density polyolefin film is used as a support, the low-density polyolefin film on the image-receiving layer side is softened by the extremely high heating during printing, and a negative curl occurs. Therefore, even if the image receiving paper has a good curl before printing, the curl deteriorates after printing and the handling property deteriorates.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to solve various problems relating to such a thermal transfer image-receiving sheet and to provide a thermal transfer image-receiving sheet having good sensitivity and no curl after printing.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have made a substrate having a film layer provided on both sides of the substrate as a support, A low-density polyolefin film is used as the film layer on the side where the layer is provided, and a polyolefin film having a solid content weight ratio of 60% or more of the low-density polyethylene resin is prepared by the melt extrusion method as the film layer on the side where the image receiving layer is not provided. Since the elastic modulus decreases when it is provided on the substrate, even if the low-density polyolefin film on the side where the image-receiving layer is provided is softened by the heat during printing, negative curl does not easily occur, the sensitivity is good and the curl after printing is high. It was discovered that an image receiving sheet for thermal transfer which does not exist can be obtained, and the present invention has been completed.

That is, the thermal transfer image-receiving sheet of the present invention is a thermal transfer image-receiving sheet in which an image-receiving layer for receiving a heat transferable dye from a thermal transfer medium is provided on a support, the support being provided on both sides of a substrate. A film layer is provided, and the film layer on the side where the image receiving layer is provided has a density of 0.4 to 0.8 g / cm.
³ , a biaxially stretched polyolefin film having a thickness of 20 to 60 μm, wherein the film layer on the side not provided with the image receiving layer is provided on the substrate by a melt extrusion method, and the solid content weight ratio of the low density polyethylene resin is It is characterized by comprising 60% or more of a polyolefin film.

In the present invention, as the substrate, high-quality paper,
Uncoated paper such as medium quality paper, super calendered paper, single-gloss base paper, tracing paper, art paper, coated paper, lightweight coated paper, slightly coated paper, coated paper such as cast coated paper,
A plastic film such as a polyester film or a cellulose acetate film can be used.

In the present invention, the thickness of the substrate is 50 to 20.
It is preferably 0 μm. When the thickness of the base material is less than 50 μm, the rigidity of the thermal transfer image-receiving sheet decreases,
Bending is likely to occur in the transport guide of the printer, and when it exceeds 200 μm, the rigidity is too high and biting failure in the transport roll of the printer is likely to occur.

In the present invention, printing may be performed on the side of the base material on which the image receiving layer is not provided for displaying the coated surface of the image receiving layer or displaying the manufacturer's logo. As a printing method, a general printing method such as offset printing, gravure printing, flexo printing, screen printing can be used, and either single-color or multi-color printing may be used.

[0011] In the present invention, the film layer on the side of providing the image-receiving layer of the support 2 of Density 0.4 to 0.8 g / cm ³
It is preferably an axially stretched polyolefin film.
If the density of the film is less than 0.4 g / cm ³ , the cushioning property will be too high and the surface of the image-receiving sheet will be easily scratched. If it exceeds 0.8 g / cm ³ , the cushioning property will be lowered and the image White spots and uneven halftone image density are likely to occur.

The biaxially stretched polyolefin film preferably has a thickness of 20 to 60 μm. here,
When the thickness of the film is less than 20 μm, the heat insulating property is lowered and thus the sensitivity is lowered, and when it exceeds 60 μm,
The rigidity is lowered due to the limitation of the thickness of the support, and bending in the transport guide of the printer is likely to occur.

As such a biaxially oriented polyolefin film, a film made of a homopolymer of α-olefin such as ethylene or propylene or a copolymer of two or more types of α-olefin can be used. From the viewpoint of smoothness and heat insulation, it is particularly preferable to use, for example, a foamable polypropylene film, a foamable polyethylene film, or the like. Further, in these films, a white pigment, a coloring pigment, a stabilizer, an antioxidant, a plasticizer,
A lubricant or the like can be added.

In the present invention, the biaxially stretched polyolefin film is required to be firmly bonded to the substrate in order to suppress the occurrence of blisters during printing. As a method for laminating films, a dry lamination method using an organic solvent solution of vinyl acetate, polyurethane, acrylic resin or the like as an adhesive, an aqueous solution of starch, polyvinyl alcohol, casein or the like, vinyl acetate, polyurethane, acrylic is used. There are a wet laminating method using an emulsion such as a system resin as an adhesive, a hot-melt method using a wax-based resin as an adhesive and a polylamination method using a molten polyolefin-based resin extruded from a T-die as an adhesive. Among them, the dry laminating method is preferable because it provides high adhesive strength, heat resistance and water resistance.

As the dry laminating adhesive, a room temperature curable polyurethane resin is particularly preferable from the viewpoint of adhesive strength. The room-temperature-curable polyurethane-based resin mentioned here has a polyurethane structure containing one or more urethane groups in one molecule of the final cured coating film, and does not require heating for curing. These adhesives are used in combination with a one-pack type adhesive that uses a resin having an isocyanate group at the end, a base compound made of a resin having a hydroxyl group at the end, and a curing agent made of a compound having an isocyanate group at the end. It is classified as a two-component adhesive. Two-component adhesives are used because they have better water resistance and heat resistance than single-component adhesives, the curing reaction is less affected by humidity, and there is less foaming due to carbon dioxide. Is preferred.

As a method of applying the adhesive, a general application method such as a gravure method, a wire bar method, a rod method, a reverse roll method, an extrusion die method, a blade method, or the like is used.

The amount of the adhesive applied is preferably in the range of 1 to 10 g / m ² in terms of dry solid content, because the adhesive strength decreases when the amount is too small and the cost increases when the amount is too large.

In the present invention, the film layer on the side of the support on which the image receiving layer is not provided has a solid content weight ratio of the low density polyethylene resin of 60% provided on the substrate by the melt extrusion method.
The above polyolefin film is preferable.
Here, the solid content weight ratio of the low-density polyolefin resin is 6
In the case of the polyolefin film of less than 0%, the elastic modulus becomes too high, and it is difficult to suppress the negative curl after printing.

The thickness of the film layer on the side of the support on which the image receiving layer is not provided is preferably 20 to 60 μm. Here, the thickness of the polyolefin film is 20 μm
If it is less than 60 μm, it is difficult to suppress the positive curl of the support before printing, and if it exceeds 60 μm, it is difficult to suppress the negative curl of the support before printing.

In the present invention, as the resin for the polyolefin film, a homopolymer of α-olefin such as ethylene or propylene, a copolymer of two or more kinds of α-olefins, and a copolymer of α-olefin as a main component with it. Copolymers with other possible monomers or mixtures thereof can be used. Further, a colorant, a stabilizer, an antioxidant, an ultraviolet absorber, a plasticizer and the like can be added to the polyolefin film, if necessary.

In the present invention, the polyolefin film on the side not provided with the image receiving layer is produced by a so-called melt extrusion method in which a resin which is heated and melted is cast on a running substrate.

In the present invention, an image receiving layer containing a resin having a dyeing property to a dye which is melted or sublimated by heat and migrates is provided on a support directly or via an intermediate layer to form an image receiving sheet for thermal transfer. Create. As the resin having such dye-dyeability, any resin having a strong interaction with the dye and capable of stably diffusing the dye into the resin can be preferably used. For example, polyester resin, polyacrylic ester resin, polycarbonate resin, polyvinyl acetate resin, styrene acrylate resin, polyurethane resin, polyamide resin, urea resin, polycaprolactone resin, polystyrene resin, polyvinyl chloride, polyacrylonitrile resin, etc. can be used. Is. In addition, vinyl chloride / containing one or more of the constitutional units of these resins as a main component
Copolymers such as vinyl acetate copolymer and styrene / butadiene copolymer can also be used. Further, these resins can be used alone or in combination of two or more.

A releasing agent may be added to such an image receiving layer in order to prevent blocking with the ink donor sheet. Examples of the release agent include higher fatty acids or esters thereof, amides or metal salts thereof, waxes such as shellac wax, montan wax, carnauba wax, polyethylene wax, Teflon powder, fluorine-based or phosphate ester-based surfactants, and silicone oil. It is possible to use modified silicone oil such as amino-modified silicone, epoxy-modified silicone, alkyd-modified silicone, polyester-modified silicone and the like. Further, as the silicone compound, a reaction-curable type, an ionizing radiation-curable type, a catalyst-curable type, or the like can be used if necessary.

If necessary, additives such as dyes, pigments, wetting agents, defoaming agents, dispersants, antistatic agents, fluorescent whitening agents, ultraviolet absorbers and light stabilizers are added to the image receiving layer. can do.

The coating amount of the image receiving layer is preferably 0.5 to 30 g / m ² in terms of dry solid content. As a method for applying the image receiving layer, a general application method such as an air knife method, a gravure method, a wire bar method, a rod method, a reverse roll method, an extrusion die method, a blade method, and a slide hopper method is used.

In the present invention, an intermediate layer may be provided in order to improve the adhesion between the support and the image receiving layer. For the intermediate layer, it is preferable to use a resin having good adhesiveness to both the support and the image receiving layer, for example, acrylic resin, vinyl chloride resin, vinyl acetate resin, urethane resin,
A styrene / butadiene copolymer or the like can be used. As a method for applying such an intermediate layer, a general application method such as an air knife method, a gravure method, a wire bar method, a rod method, a reverse roll method, an extrusion die method, a blade method, a slide hopper method, or the like is used. .

In the present invention, in order to improve the adhesiveness between the support and the image receiving layer, it is possible to modify the surface of the support by corona discharge treatment, plasma treatment, flame treatment or the like, instead of providing an intermediate layer. is there.

In the present invention, for the purpose of improving the transportability of the thermal transfer image-receiving sheet during printing and imparting writability and conductivity to the back surface, an inorganic pigment, an organic pigment or a charge is provided on the opposite side of the support from the image-receiving layer. A backing layer containing an inhibitor or the like can be provided. As such an inorganic pigment added to the back coating layer,
Silica, alumina, titanium oxide, calcium carbonate, kaolin, clay, zinc oxide, barium sulfate, etc. Antistatic agents such as quaternary ammonium salts, cationic surfactants such as polyamine derivatives, and anionic interfaces such as alkyl phosphates. Examples include activators, amphoteric surfactants such as sulfobetaine, and nonionic surfactants such as polyethylene glycol. Further, as the coating method of the back coating layer, a general coating method such as an air knife method, a gravure method, a wire bar method, a rod method, a reverse roll method, an extrusion die method, a blade method, and a slide hopper method is used. .

[0029]

According to the present invention, an image-receiving sheet for thermal transfer having an image-receiving layer for receiving a heat transferable dye from a thermal transfer medium on the surface of a support, wherein the support has film layers on both sides of a substrate. The film layer on the side where the image receiving layer is provided has a density of 0.4 to 0.8 g / cm ³ , 20 to 60 μm.
A polyolefin film having a solid content weight ratio of 60% or more of a low density polyethylene resin, which is provided on the substrate by a melt extrusion method as a film layer on the side not provided with an image receiving layer By using, a thermal transfer image-receiving sheet having good sensitivity and no curl after printing can be obtained.

[0030]

EXAMPLES Next, the present invention will be described in more detail by way of examples, but the contents of the present invention are not limited to these. Further, "parts" and "%" shown in Examples and Comparative Examples are parts by weight and% by weight, respectively. The ink donor sheet for evaluation was prepared as follows.

[Ink Donor Sheet] A biaxially stretched polyester film having a film thickness of 5 μm and subjected to a heat treatment, was coated with a heat resistant slipping layer coating solution having the following composition by a wire bar to give a dry coating amount of 0.5 g / m ^2. Coated and dried to achieve 140W / c
It was cured by irradiating it with ultraviolet rays with a high-pressure mercury lamp of m ² . (Heat resistant slipping layer coating liquid formulation) TMPTA (Daiichi Kogyo Seiyaku Co., Ltd.) 10 parts Lipoxy SP1509 (Showa High Polymer) 20 parts Trefil E500 (Toray, silicone fine particles) 9 parts KF-393 (Shin-Etsu silicone, amino-modified silicone oil) 0 .3 parts Coronate L (Japan polyurethane, isocyanate) 0.3 parts Darocur1173 (Merck, initiator) 0.4 parts Ethyl acetate 40 parts Isopropyl alcohol 20 parts

Further, a sublimable dye coating solution having the following composition was ground on a surface opposite to the heat resistant slipping layer for 2 days by a ball mill, and then coated and dried by a wire bar so that a dry coating amount was 1.5 g / m ^2. Then, an ink donor sheet was prepared. (Sublimation dye coating liquid blend) Kayaset Blue 906 (Nippon Kayaku, sublimation dye) 10 parts Ethyl semellose 10 parts Syloid 244 (Fuji Davison silica gel) 10 parts Isopropyl alcohol 30 parts

Example 1 One side of a coated paper having a basis weight of 135 g / m ² was subjected to corona treatment, and then a polyolefin resin having the following composition was formed to a thickness of 35 μm.
It was applied by the melt extrusion method so as to be m. (Resin resin film layer combination) High density polyethylene 30% Low density polyethylene 70%

On the other side of the coated paper, an adhesive coating solution having the following composition was applied by a gravure coater so that the dry coating amount was 5.0 g / m ^2, and the density was 0.42 g / c.
A foamed polypropylene film having a thickness of m ³ and a thickness of 35 μm was laminated by a dry lamination method to prepare a support. (Adhesive coating liquid formulation) Polyester polyol (Takelac A-606: Takeda Yakuhin) 90 parts Polyurethane polyisocyanate (Takenate A-12: Takeda Yakuhin) 10 parts Ethyl acetate 90 parts

Further, the surface of the foamed polypropylene film of this support was subjected to corona discharge treatment, and then an image receiving layer coating solution having the following composition was dried to a coating amount of 5. with an air knife coater.
The coating was dried so as to be 0 g / m ^2, and the thermal transfer image-receiving sheet of Example 1 was produced. (Combined with the image-receiving layer coating liquid) Polyester emulsion (Vylonal MD-1220: Toyobo) 60 parts Polyerylene emulsion (Hydrin G-314: Chukyo Yushi) 15 parts Colloidal silica (Snowtex O: Nissan Chemical) 25 parts Amino-modified silicone emulsion 5 parts Surfactant 4 parts Crosslinking agent 1 part

Examples 2 to 7 and Comparative Examples 1 to 7 Except that the density and thickness of the expanded polypropylene film and the low-density polyethylene solid content weight ratio of the back resin film layer were changed as shown in Table 1 below. Examples 2 to 2 as in Example 1
7 and the image receiving sheets for thermal transfer of Comparative Examples 1 to 7 were produced.

[0037]

[Table 1]

[Evaluation Method] Each thermal transfer image-receiving sheet obtained as described above was evaluated by the following method. (1) Sensitivity An ink donor sheet was superposed on an image-receiving sheet for thermal transfer, and after printing with a sublimation type thermal transfer printer S3600-30 manufactured by Mitsubishi Electric Corporation, the maximum print density of the printing section was changed to Macbeth RD-9.
19 Measured with an optical densitometer. (2) Scratch on image receiving layer surface After overlaying an ink donor sheet on an image receiving sheet for thermal transfer and printing with a sublimation type thermal transfer printer S3600-30 manufactured by Mitsubishi Electric Corporation, the degree of scratching on the image receiving layer surface was visually evaluated, and A sample without scratches was marked with ◯ and a sample with existing scratches was marked with x. (3) Density unevenness in the halftone part After overlaying the ink donor sheet on the thermal transfer image-receiving sheet and printing with a sublimation type thermal transfer printer S3600-30 manufactured by Mitsubishi Electric Corporation, the density unevenness in the halftone part is visually evaluated to determine the density unevenness. There is no mark ○, there is uneven density ×
And (4) Bending of the image receiving sheet in the printer When 10 sheets of the image receiving sheet for thermal transfer are printed by the sublimation type thermal transfer printer S3600-30, those with no bending in 10 sheets are ○, and 2 to 3 sheets are the conveyance guides of the printer. Bent ones were evaluated as Δ, and five or more bent ones were evaluated by the conveyance guide of the printer as x. (5) Curl property after printing An ink donor sheet is superposed on the thermal transfer image-receiving sheet, and a sublimation type thermal transfer printer S3600-30 manufactured by Mitsubishi Electric Corp.
When a black solid image of 4 color inks is printed, the height of the four corners of the thermal transfer image-receiving sheet is measured when the image-receiving layer surface is left stationary, and the average value is calculated to obtain the curl after printing. evaluated. The above evaluation results are summarized in Table 2.

[0039]

[Table 2]

[Evaluation Results] As is clear from the results in Table 1, the thermal transfer image-receiving sheets of Examples 1 to 7 according to the present invention had good sensitivity and no curl after printing. In particular, as seen in Examples 5 to 7, the higher the solid content weight ratio of the low-density polyethylene, the less the curl after printing. On the other hand, in the thermal transfer image-receiving sheet of Comparative Example 1, since the density of the film layer on the side where the image-receiving layer was provided was too low, the cushioning property became too high and the surface of the image-receiving layer was damaged. Comparative example 2
In the thermal transfer image-receiving sheet, since the density of the film layer on the side where the image-receiving layer is provided was too high, the cushioning property was deteriorated and the density unevenness occurred in the halftone portion. In the image-receiving sheet for thermal transfer of Comparative Example 3, the thickness of the film layer on the side where the image-receiving layer was provided was too small, so the heat insulating property was lowered and the sensitivity was lowered.
In the thermal transfer image-receiving sheet of Comparative Example 4, the rigidity of the film layer on the side where the image-receiving layer is provided was too large, resulting in a decrease in rigidity.
Bending occurred in the transport guide of the printer. In the thermal transfer image-receiving sheets of Comparative Examples 5 to 7, the solid content weight ratio of the low-density polyethylene was too low, so the curl after printing was large and the handleability was poor.

[0041]

According to the present invention, it is possible to obtain an image-receiving sheet for thermal transfer which has good sensitivity and does not curl after printing.

Claims (1)

[Claims] 1. An image-receiving sheet for thermal transfer, comprising an image-receiving layer for receiving a heat transferable dye from a thermal transfer medium on a support, wherein the support has film layers on both sides of a substrate, The film layer on the side where the image receiving layer is provided has a density of 0.4.
0.8 g / cm ^3, a biaxially oriented polyolefin film having a thickness of 20 to 60 [mu] m, the side of the film layer without the image receiving layer, provided on the substrate by a melt extrusion method,
An image-receiving sheet for thermal transfer, comprising a polyolefin film having a low-density polyethylene resin solid content weight ratio of 60% or more.