JP2022102084A - Thermal transfer image-receiving sheet - Google Patents

Abstract

To provide a thermal transfer image-receiving sheet which can suitably suppress recessed curling generated after printing, and has good printing density.SOLUTION: A thermal transfer image-receiving sheet 1 includes a sheet-like base material 10, a first polyolefin resin layer 21 formed on a first surface 10a of the base material, a second polyolefin resin layer 22 formed on a second surface 10b on a side opposite to the first surface in the base material, a microvoid layer 30 formed on the first polyolefin resin layer, a substrate layer 40 formed on the microvoid layer, and an image-receiving layer 50 formed on the substrate layer. The microvoid layer has a thickness of 27 μm or more and 33 μm or less, thermal conductivity of 0.1 W/m K or less and a thermal shrinkage (heating at 120°C for 15 minutes) measured based on ASTM D1204 of 3.0% or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a thermal transfer image receiving sheet used in a thermal transfer printer.

As a printing method for forming characters or images on a transfer target, a sublimation type thermal transfer method, a melt type thermal transfer method, and the like are known. In the sublimation type thermal transfer method, the dye layer of the thermal transfer ribbon and the image receiving layer of the thermal transfer image receiving sheet are superposed on each other, and then the thermal transfer ribbon is heated by a thermal head whose heat generation is controlled by an electric signal. This is a method in which a dye is sublimated and transferred to an image receiving layer to form desired characters, images, etc. on the image receiving layer.

In the sublimation type thermal transfer method, since the density gradation can be freely adjusted by using the sublimation type dye, the natural image can be reproduced relatively faithfully. For this reason, thermal transfer image receiving sheets for sublimation thermal transfer are also used as photographic printing paper for various purposes such as for general printers, amusement, and vending machines for ID photos.
In many cases, the thermal transfer image receiving sheet is distributed as a single-wafer type cut out in units of use.

The thermal transfer image receiving sheet has various required characteristics. One of the important characteristics is curl suppression after printing. When printing is performed using a single-wafer type thermal transfer image receiving sheet, the heat of the thermal head is applied to the thermal transfer image receiving sheet. When a part of the thermal transfer image receiving sheet is thermally shrunk due to the heat, the thermal transfer image receiving sheet after printing may have a concave curl in which the printing screen is concave and rounded. If the concave curl becomes large, clogging (jam) may occur in the transport or ejection of the thermal transfer image receiving sheet in the printer, or the thermal transfer image receiving sheets after printing may not be stacked well.

In Patent Document 1, the stiffness S1 in the length direction and the stiffness S2 in the width direction of the thermal transfer image receiving sheet measured according to the method for measuring the stiffness of paper described in TAPPI T543pm 84 are set in a predetermined numerical range. A technique for reducing the later curl is disclosed.

Japanese Unexamined Patent Publication No. 2007-1072

The technique described in Patent Document 1 aims to suppress a convex curl in which the stamp screen side is convex. Since the thermal transfer image receiving sheet has a structure asymmetrical in the thickness direction, concave curl cannot be sufficiently suppressed even by using the technique of Patent Document 1.
Further, although the details will be described later, there are cases where the printing density is not good with the conventional measures against concave curl.

Based on the above circumstances, it is an object of the present invention to provide a thermal transfer image receiving sheet which can suitably suppress concave curl generated after printing and has a good printing density.

The present invention has a sheet-like substrate, a first polyolefin resin layer formed on the first surface of the substrate, and a second surface of the substrate opposite to the first surface. (Ii) A thermal transfer image receiving sheet including a polyolefin resin layer, a microvoid layer formed on the first polyolefin resin layer, an underlayer formed on the microvoid layer, and an image receiving layer formed on the underlayer. ..
The microvoid layer has a thickness of 27 μm or more and 33 μm or less, a thermal conductivity of 0.1 W / m · K or less, and a thermal shrinkage (120 ° C., 15 minutes heating) measured based on ASMD 1204 of 3.0% or less. Is.

According to the present invention, it is possible to suitably suppress the concave curl generated after printing, and to provide a thermal transfer image receiving sheet having a good printing density.

It is sectional drawing which shows typically the thermal transfer image receiving sheet which concerns on one Embodiment of this invention.

An embodiment of the present invention will be described with reference to FIG.
FIG. 1 is a diagram showing a thermal transfer image receiving sheet 1 of the present embodiment. The heat transfer image receiving sheet 1 includes a sheet-shaped base material 10, a first polyolefin resin layer 21 provided on the first surface 10a of the base material 10, and a second surface of the base material 10 opposite to the first surface 10a. The second polyolefin resin layer 22 provided on the 10b, the microvoid layer 30 provided on the first polyolefin resin layer 21, the base layer 40 provided on the microvoid layer 30, and the base layer 40 provided on the base layer 40. The image receiving layer 50 is provided.

As the base material 10, known materials can be used. For example, condenser paper, glassin paper, sulfate paper, synthetic paper (polyolefin-based, polystyrene-based), high-quality paper, medium-quality paper, art paper, coated paper, resin-coated paper, cast-coated paper, wallpaper, backing paper, synthetic resin or Emulsion impregnated paper, synthetic rubber latex impregnated paper, synthetic resin inner sheet paper, resin laminated paper, paper, papers such as cellulose fiber paper, polyester such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyacrylate , Polycarbonate, Polyurethane, Polyimide, Polyetherimide, Cellulous derivative, Polyethylene, Ethylene-vinyl acetate copolymer, Polypropylene and other polyolefins, Polystyrene, Acrylic, Polyvinyl chloride, Polyvinylidene chloride, Polyvinyl alcohol, Polyvinylbutyral, Nylon, Poly Etherketone, polysulfone, polyether sulfone, tetrafluoroethylene, perfluoroalkyl vinyl ether, polyvinylfluoride, tetrafluoroethylene / ethylene, tetrafluoroethylene / hexafluoropropylene, polychlorotrifluoroethylene, polyvinylidenefluoride, polycarbonate, Examples thereof include films such as synthetic resin films such as polyvinyl alcohol, polystyrene, and polyamide. The resin film and papers may be used alone, or a composite of both may be used as the base material 10.

As for the thickness of the base material 10, considering the stiffness (rigidity), strength, heat resistance, etc. of the printed matter, those in the range of 25 micrometers (μm) or more and 250 μm or less can be used. More preferably, the thickness is about 50 μm or more and 200 μm or less.

The resin used as the material of the first polyolefin resin layer 21 and the second polyolefin resin layer 22 preferably contains low-density polyethylene (LDPE) as a main component from the viewpoint of moldability.
The second polyolefin resin layer 22 may contain high density polyethylene (HDPE). The mixing ratio of LDPE and HDPE can be set as appropriate.

The microvoid layer 30 has a large number of fine voids, and imparts heat insulating properties, cushioning properties, and the like when heat is applied from the thermal head to the thermal transfer image receiving sheet 1. The resin forming the microvoid layer 30 is not particularly limited, and a known resin material can be appropriately selected. For example, a plastic sheet that has been foamed to form microvoids can be used. It is also possible to use a sheet in which a thermoplastic resin containing an inorganic powder is melt-extruded into a sheet and then stretched to form a microvoid around the inorganic powder as a core. Further, it is also possible to use a sheet in which microvoids are formed by melt-extruding a thermoplastic resin containing a water-soluble inorganic powder and then dissolving and removing the water-soluble inorganic powder. From the viewpoint of heat insulation and cushioning properties, a foamed polypropylene resin sheet is preferable, and from the viewpoint of productivity and cost, organic fine particles or inorganic fine particles incompatible with an olefin resin such as polypropylene resin or polyethylene terephthalate resin are blended, and after molding. Stretched sheets are preferred.
The method of joining the microvoid layer 30 and the first polyolefin resin layer 21 is not particularly limited, but dry lamination using an adhesive is preferable. In this case, an adhesive layer exists between the microvoid layer 30 and the first polyolefin resin layer 21.

The base layer 40 is a layer for the purpose of improving the adhesion between the microvoid layer 30 and the image receiving layer 50, improving the storage stability of the thermal transfer image receiving sheet after printing, and the like.
As the material of the base layer 40, various known materials can be selected and used while considering the purpose. For example, polyolefin resins, polyester resins, polyvinyl resins, polyurethane resins, polyacrylic acid resins, and copolymers of these resins can be mentioned. The above-mentioned materials may be used alone or in combination of two or more.
The thickness of the base layer 40 may be 0.1 μm or more and 3 μm or less, and preferably 0.2 μm or more and 1.0 μm or less.

As the image receiving layer 50, various known binder resins can be used. As an example of the binder resin, vinyl chloride-acrylic copolymer, vinyl chloride-vinyl acetate copolymer, vinyl acetate-acrylic copolymer, styrene-acrylic copolymer, vinyl chloride-acrylic-ethylene copolymer, vinyl chloride -Acrylic-styrene copolymer, polycarbonate resin, polyester resin, polyamide resin, acrylic resin, cellulose resin, polysulphon resin, polyvinyl chloride resin, vinyl acetate resin, polyvinyl acetal resin, polyvinyl butyral resin , Polyurethane resin, polystyrene resin, polypropylene resin, polyethylene resin, ethylene-vinyl acetate copolymer resin, epoxy resin and the like can be mentioned. These may be used alone or in combination of two or more.
The thickness of the image receiving layer 50 may be 0.1 μm or more and 10 μm or less, but more preferably 0.2 μm or more and 8 μm or less. Further, the image receiving layer 50 improves the whiteness of the film-forming auxiliary, the mold-removing agent, the ultraviolet absorber, the antistatic agent, the cross-linking agent, the fluorescent dye, the plasticizer, and the receiving layer, if necessary, to improve the whiteness of the transferred image. For the purpose of further enhancing the sharpness, various known additives such as pigments such as titanium oxide, zinc oxide, kaolin, clay, calcium carbonate and fine powder silica and fillers may be contained.

The inventor focused on and examined the microvoid layer as a factor causing concave curl. Stress relaxation when heat is applied to the microvoid layer affects the generation of concave curls. Conventionally, a biaxially stretched polyester film having high heat resistance has often been used as the microvoid layer of the image receiving paper used for the sheet-fed printer.
However, although polyester is effective in suppressing concave curl after printing, the heat insulating performance of the resin itself is not sufficient, and it may not be possible to obtain a sufficient printing density. On the other hand, although the polypropylene porous film has high heat insulating properties, it has lower heat resistance than polyester, so that the printing density is kept high, but the concave curl after printing cannot be sufficiently controlled.
As a result of the study by the inventor, by satisfying the following three points, even if polypropylene was used for the microvoid layer 30, sufficient printing density and suppression of concave curl after printing could be achieved at the same time.
-The thickness of the microvoid layer shall be 27 μm or more and 33 μm or less.
-The thermal conductivity shall be 0.1 W / m · K or less.
The heat shrinkage rate (heated at 120 ° C. for 15 minutes) measured based on ASTMD1204 is set to 3.0% or less.
The thermal conductivity varies depending on the mode of the fine voids in the microvoid layer. The mode of the fine voids and the heat shrinkage rate vary depending on the amount of stretching of the polypropylene film to be the microvoid layer. By appropriately changing these, the microvoid layer 30 satisfying the above three points can be formed.

The thermal transfer image receiving sheet 1 of the present embodiment provided with the microvoid layer 30 can suitably suppress concave curl generated after printing, and the printing density is also good.

Next, the thermal transfer image receiving sheet of the present invention will be further described with reference to Examples. The present invention is not limited to the description of the examples.

(Example 1)
As the microvoid layer 30, a biaxially stretched polypropylene film having a thickness of 30 μm was used. A urethane-based paint (Superflex 120 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was applied to one surface of the microvoid layer 30 so that the film thickness would be 1 μm after drying to form the base layer 40. Further, an ink mainly composed of vinyl chloride-vinyl acetate resin was applied onto the base layer 40 so that the film thickness would be 3 μm after drying to form the image receiving layer 50.
In Example 1, the heat shrinkage rate (heating condition 120 ° C. for 15 minutes) measured according to ASTMD-1204 was 3.0% in the transport direction (MD) and 1.0% in the width direction (TD). rice field.

Paper (basis weight 150 g / m ² ) was prepared as the base material 10. LDPE was laminated with a thickness of 20 μm on one surface of the base material 10 to form the first polyolefin resin layer 21. A resin containing LDPE and HDPE in a ratio of 2: 8 was extruded on the other surface of the base material 10 to form a second polyolefin resin layer 22 having a thickness of 20 μm.
The microvoid layer 30 and the first polyolefin resin layer 21 were bonded by a dry laminate using an adhesive (Takenate A525 / A56) to obtain a thermal transfer image receiving sheet of Example 1.

(Example 2)
As the microvoid layer 30, a biaxially stretched polypropylene film having a thickness of 30 μm was used. The heat shrinkage of this film (according to ASTMD-1204) was MD 2.8% and TD 0.8%.
The other points were the same as in Example 1, and the thermal transfer image receiving sheet of Example 2 was obtained.

(Example 3)
As the microvoid layer 30, a biaxially stretched polypropylene film having a thickness of 27 μm was used.
The other points were the same as in Example 1, and the thermal transfer image receiving sheet of Example 3 was obtained.

(Example 4)
As the microvoid layer 30, a biaxially stretched polypropylene film having a thickness of 33 μm was used.
The other points were the same as in Example 1, and the thermal transfer image receiving sheet of Example 4 was obtained.

(Example 5)
As the microvoid layer 30, a biaxially stretched polypropylene film having a thickness of 33 μm was used.
The heat shrinkage of this film (according to ASTMD-1204) was MD 1.5% and TD 0.5%.
The other points were the same as in Example 1, and the thermal transfer image receiving sheet of Example 5 was obtained.

(Comparative Example 1)
A biaxially stretched polypropylene film having a thickness of 40 μm was used as the microvoid layer.
The heat shrinkage of this film (according to ASTMD-1204) was MD 3.6% and TD 2.0%.
In other respects, the thermal transfer image receiving sheet of Comparative Example 1 was obtained in the same manner as in Example 1.

(Comparative Example 2)
As the microvoid layer, a biaxially stretched polypropylene film having a thickness of 33 μm was used.
The heat shrinkage of this film (according to ASTMD-1204) was MD 16.8% and TD 10.4%.
In other respects, the thermal transfer image receiving sheet of Comparative Example 2 was obtained in the same manner as in Example 1.

(Comparative Example 3)
As the microvoid layer, a biaxially stretched polypropylene film having a thickness of 30 μm was used.
The heat shrinkage of this film (according to ASTMD-1204) was MD5.7% and TD5.1%.
In other respects, the thermal transfer image receiving sheet of Comparative Example 3 was obtained in the same manner as in Example 1.

(Comparative Example 4)
A biaxially stretched polypropylene film having a thickness of 20 μm was used as the microvoid layer.
The heat shrinkage of this film (according to ASTMD-1204) was MD3.0% and TD1.0%.
In other respects, the thermal transfer image receiving sheet of Comparative Example 4 was obtained in the same manner as in Example 1.

(Comparative Example 5)
As the microvoid layer, a biaxially stretched polyester film having a thickness of 30 μm was used.
The heat shrinkage of this film (according to ASTMD-1204) was MD 0.6% and TD 0.1%.
In other respects, the thermal transfer image receiving sheet of Comparative Example 5 was obtained in the same manner as in Example 1.

Next, the following two items were evaluated for the thermal transfer image receiving sheets of each example.

<Evaluation of print density>
An 11-step image was printed on the thermal transfer image receiving sheet of each example using the attached ribbon with a printer (DS40 manufactured by Dai Nippon Printing Co., Ltd.). When the maximum gradation density of the gray scale was 2.00 or more, it was evaluated as 〇 (good), and when it was less than 2.00, it was evaluated as × (bad).
<Curl evaluation after printing>
The thermal transfer image receiving sheet of each example was cut into a size of 177 mm × 100 mm, printed entirely in black using a sheet-fed printer (“SELPHY” CP1200 manufactured by Canon Inc.), and then placed with the printing screen facing up. The maximum distance between the peripheral edge and the center in the thickness direction of the thermal transfer image receiving sheet was measured as the curl amount. When the peripheral edge is higher than the center, it is represented by "-" as a concave curl, and when the peripheral edge is lower than the center, it is represented by "+" as a convex curl. The curl amount was evaluated on the following two stages.
◯ (good): Of the 100 printed matter, none has a curl amount exceeding ± 2 mm.
× (bad): Of the 100 prints, one or more has a curl amount of more than ± 2 mm.
<Comprehensive evaluation>
When both of the above two items were 〇, it was evaluated as ◯ (good), and in other cases, it was evaluated as × (bad).

The results are shown in Table 1.

As shown in Table 1, in each of the examples having the microvoid layer satisfying the above-mentioned three points, both suppression of concave curl and sufficient printing density were achieved.
In Comparative Examples 1 to 3 having a polypropylene microvoid layer that does not satisfy the above three points, strong concave curl was generated after printing, and the concave curl could not be suppressed.
In Comparative Example 5 having a polyethylene microvoid layer satisfying the above-mentioned three points, concave curl could be suppressed, but the printing density was not sufficient.

Although one embodiment of the present invention has been described above, the technical scope of the present invention is not limited to the above-described embodiment, and the combination of components may be changed or each component may be changed without departing from the spirit of the present invention. It is possible to make various changes to, add other configurations to, and delete.

The thermal transfer image receiving sheet of the present invention can be suitably used for a sublimation transfer type printer.

1 Thermal transfer image receiving sheet 10 Base material 10a First surface 10b Second surface 21 First polyolefin resin layer 22 Second polyolefin resin layer 30 Microvoid layer 40 Underlayer 50 Image receiving layer

Claims (5)

Sheet-shaped base material and
The first polyolefin resin layer formed on the first surface of the base material and
In the base material, the second polyolefin resin layer formed on the second surface opposite to the first surface, and
The microvoid layer formed on the first polyolefin resin layer and
The underlying layer formed on the microvoid layer and
The image receiving layer formed on the base layer and
Equipped with
The microvoid layer is
The thickness is 27 μm or more and 33 μm or less.
Thermal conductivity is 0.1 W / m · K or less,
The heat shrinkage rate (heated at 120 ° C. for 15 minutes) measured based on ASTMD1204 is 3.0% or less.
Thermal transfer image receiving sheet. The thermal transfer image receiving sheet according to claim 1, wherein the microvoid layer is made of polypropylene. The thermal transfer image receiving sheet according to claim 1, wherein the microvoid layer is made of a biaxially stretched film. The thermal transfer image receiving sheet according to claim 1, wherein the image receiving layer contains any one of vinyl chloride, vinyl chloride-acrylic copolymer, vinyl chloride-vinyl acetate copolymer, and polyester. The microvoid layer and the first polyolefin resin layer are joined by dry lamination.
The thermal transfer image receiving sheet according to claim 1.

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