JP7091645B2 - Thermal transfer image receiving sheet - Google Patents

Description

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

Conventionally, a sublimation type thermal transfer method, a melt type thermal transfer method, or the like has been adopted as a method for forming characters, images, or the like on a transfer target. For example, in the case of the sublimation type thermal transfer method, a thermal transfer layer surface of a thermal transfer recording medium having a thermal transfer layer containing a dye, a binder, etc. on the support and a dye receiving layer for receiving the dye are provided on another support. The surface of the dye receiving layer of the heat transfer body is overlapped with each other, and the surface of the heat transfer recording medium not provided with the heat transfer layer is heated by a thermal head or the like whose temperature is controlled by text or image information to obtain the dye in the heat transfer layer. Is sublimated and transferred to the dye receiving layer to form a desired character or image.

On the other hand, in the case of the melt-type thermal transfer method, the surface of the thermal transfer recording medium having a heat-meltable thermal transfer layer containing a pigment, wax, etc. on the support and the heat transfer having a receiving layer on another support are provided. By superimposing the surface of the receiving layer on the body and heating it with a thermal head or the like, the thermal transfer layer is fused and transferred to the receiving layer to form a desired character or image. Of the above methods, the sublimation thermal transfer method is widely used for monochrome printing of characters and charts, and color printing of digital camera images or computer graphics images.

By the way, there is a problem that white spots occur in forming a printed matter on a thermal transfer image receiving sheet by a sublimation type thermal transfer method using a thermal transfer sheet. White spots mean that when a printed matter is created using a thermal transfer image receiving sheet, a partially unprinted area is generated in the area to be printed on the thermal transfer image receiving sheet. The main cause of whiteout is the formation of uneven shapes on the surface of the thermal transfer image receiving sheet.

That is, when printing on a thermal transfer image receiving sheet by a sublimation type thermal transfer method, when the dye of the thermal transfer sheet is transferred to a predetermined area of the thermal transfer image receiving sheet by heating by a heating means such as a thermal head, it is applied to the surface of the thermal transfer image receiving sheet. When the uneven shape exists, the adhesion (following property) between the thermal transfer sheet and the thermal head is hindered by the uneven shape, and the region where heat is not sufficiently transferred from the thermal head is partially transferred to the thermal transfer sheet or the thermal transfer image receiving sheet. Occurs in. As a result, white spots occur in the areas where the heat generated by the thermal head is not sufficiently transferred.

It should be noted that there is unevenness in shading as a phenomenon similar to white spots. White spots are a phenomenon in which areas that are not completely imprinted occur, whereas shading unevenness is a phenomenon in which areas with a lighter color density than the surroundings occur. Similar to white spots, it is affected by the uneven shape of the thermal transfer image receiving sheet, but white spots are affected by so-called swells with a large cycle, while shading unevenness is affected by unevenness with a small cycle.

Various improved techniques have been proposed for the above-mentioned white spots.
For example, Patent Document 1 below discloses an invention of a thermal transfer image receiving sheet that controls the content of hollow particles in a porous layer to have high-concentration printing characteristics and maintains printing uniformity.

Further, Patent Document 2 discloses an invention of a thermal transfer image receiving sheet that controls the particle system of hollow particles in a porous layer to prevent roughness.

Further, Patent Document 3 discloses an invention of a thermal transfer image receiving sheet that prevents uneven transfer of ink by imparting unevenness suppressing and cushioning properties to the inner paper in the two coat layers of the paper substrate.

Japanese Unexamined Patent Publication No. 2006-88691 Japanese Unexamined Patent Publication No. 2007-98693 Japanese Unexamined Patent Publication No. 2010-234762

However, when printing was performed using the thermal transfer image receiving sheets of Patent Documents 1 to 3, white spots could not be sufficiently suppressed, and bleeding and uneven shading occurred.
Therefore, an object of the present invention is to provide a thermal transfer image receiving sheet in which white spots do not occur, bleeding does not occur, and shading unevenness does not occur.

The present invention is for solving the above-mentioned problems, and in the invention according to claim 1, at least the base sheet, the intermediate layer composed of one layer or a plurality of layers, and the receiving layer are in this order. In the laminated thermal transfer image receiving sheet, the maximum valley depth of the swell curve in the surface texture measured from the receiving layer side of the thermal transfer receiving sheet according to JIS0601: 2013 is defined as Wv, and the receiving of the thermal transfer receiving sheet. Let d be the thickness at which the thermal transfer image receiving sheet shrinks when a pressure of 0.5 MPa is applied to the layer side using a planar indenter in a room temperature environment.
Assuming that d ≧ Wv and the thickness of the thermal transfer image receiving sheet is t, d / t ≦ 1.48%
The thermal transfer image receiving sheet is characterized in that the maltens hardness measured from the receiving layer side of the thermal transfer receiving sheet according to ISO14577 is 30 to 120 N / mm ² .

In the thermal transfer image receiving sheet according to claim 1, if the maximum valley depth of the swell curve is Wv and the thickness at which the thermal transfer image receiving sheet shrinks is d, then d ≧ Wv, so that the unevenness of the thermal transfer image receiving sheet 1 becomes uneven. It is absorbed by shrinkage due to pressurization during printing, and the contact surface of the thermal head becomes uniform, so that white spots do not occur.

Further, in the thermal transfer image receiving sheet according to claim 1, since d / t ≦ 1.48%, the shrinkage of the thermal transfer image receiving sheet 1 due to pressurization does not become excessive, so that the demand layer 30 and the thermal transfer recording medium are used. Bleeding does not occur because the releasability does not decrease and the contact time is appropriate.

Further, in the thermal transfer image receiving sheet according to claim 1, the maltens hardness (ISO14577) measured according to ISO14577 from the receiving layer side of the thermal transfer image receiving sheet is 30 to 120 N / mm ² , and thus the cushion of the thermal transfer image receiving sheet 1. The sexual effect is fully exhibited, and white spots and uneven shading do not occur.
As described above, the thermal transfer image receiving sheet according to the present invention can provide a thermal transfer image receiving sheet that does not cause white spots, bleeding, and uneven shading.

It is a schematic sectional drawing which shows the structure of the thermal transfer image receiving sheet which concerns on embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Also, the following detailed description describes many specific details to provide a complete understanding of the embodiments of the present invention. However, it will be clear that one or more embodiments can be implemented without such specific details. In addition, for the sake of brevity, the description of well-known structures and devices is omitted.

<Thermal transfer image receiving sheet>
As shown in FIG. 1, the thermal transfer image receiving sheet 1 of the present invention is formed by laminating an intermediate layer 20 composed of one layer or a plurality of layers and a receiving layer 30 in order on one surface of the base material 10. Hereinafter, the configuration of the thermal transfer image receiving sheet 1 of the present invention will be described with reference to FIG.

(Base material 10)
The base material 10 in the present invention has a role of holding the intermediate layer 20 and the receiving layer 30, and since heat is applied during thermal transfer, it has a mechanical strength to the extent that it does not hinder handling even in a heated state. It is preferable that the material has.

Examples of the material of the base material 10 include condenser paper, glassin paper, sulfate paper, high-sized paper, synthetic paper (polyolefin-based, polystyrene-based), high-quality paper, art paper, coated paper, and resin coat. Paper, cast coated paper, wallpaper, backing paper, synthetic resin or emulsion impregnated paper, synthetic rubber latex impregnated paper, synthetic resin inner sheet paper, paperboard, etc., cellulose fiber paper, or polyester, polyacrylate, polycarbonate, polyurethane, polyimide, poly Etherimide, cellulose derivatives, polyethylene, ethylene-vinyl acetate copolymer, polypropylene, polystyrene, acrylic, polyvinyl chloride, vinylidene chloride, polyvinyl alcohol, polyvinyl butyral, nylon, polyether ether ketone, polysulfone, polyether sulfone, Examples thereof include films such as tetrafluoroethylene, perfluoroalkyl vinyl ether, polyvinylfluoride, tetrafluoroethylene / ethylene, tetrafluoroethylene / hexafluoropropylene, polychlorotrifluoroethylene, and polyvinylidenefluoride, and synthetic resins thereof. A white opaque film formed by adding a white pigment or a filler to the paper can also be used, and is not particularly limited.

Further, a laminated body made of any combination of the above-mentioned base materials can also be used. As an example of a typical laminate, a synthetic paper of a cellulose fiber paper and a synthetic paper or a synthetic paper of a cellulose synthetic paper and a plastic film can be mentioned. In the present invention, a commercially available base material can also be used, and for example, RC paper (manufactured by Mitsubishi Paper Mills Limited, trade name) or the like is preferable.

The thickness of the base material can be appropriately changed depending on the strength and heat resistance required for the thermal transfer image receiving sheet and the material of the material used as the base material. Specifically, the thickness of the base material is 50 μm. It is preferably in the range of about 1000 μm, and more preferably in the range of 100 μm to 300 μm.

(Middle layer 20)
According to one embodiment of the present invention, an intermediate layer 20 of one layer or a plurality of layers including at least a heat insulating layer 22 is provided between the base material 10 and the receiving layer 30.

(Insulation layer 22)
The heat insulating layer 22 in the present invention has a heat insulating property capable of preventing heat applied during image formation by thermal transfer from being lost due to heat transfer to the base material 10 or the like.
The heat insulating layer 22 provided on one surface of the base material 10 can be a conventionally known one, and one composed of hollow particles and a binder resin, a foamed film such as a foamed polypropylene film or a foamed polyethylene terephthalate, or the like is used. Further, a heat insulating layer using a composite film having a skin layer on one side or both sides of the foamed film can be mentioned. However, as the heat insulating layer using a foamed film or the like, it is preferable to use a heat insulating layer using hollow particles in consideration of cost and curl generated in the bonding process with the base material.

(Cushion layer 21)
According to the embodiment of the present invention, at least one cushion layer 21 may be provided between the base material 10 and the heat insulating layer 22 as the layer included in the intermediate layer 20.
The cushion layer 21 is a layer having a function of uniformly heating from the thermal head by absorbing the unevenness of the thermal transfer image receiving sheet 1 by shrinkage due to pressure between the platen roller and the thermal head at the time of printing. The base material 10 and the heat insulating layer 22 have the same function, but the cushion layer 21 can be provided when it is not enough.
The cushion layer 21 includes a styrene-butadiene copolymer (styrene-butadiene rubber (SBR)), an acrylonitrile-butadiene copolymer (NBR latex), a methyl methacrylate-butadiene copolymer (MBR latex), and a styrene-butadiene acrylic type. Resins such as polymers can be used alone or in admixture of two or more.

(Cushioning property of thermal transfer image receiving sheet)
If the surface of the thermal transfer image receiving sheet 1 is uneven, the contact surface of the thermal head at the time of printing becomes non-uniform, and white spots occur due to uneven heating. In order to prevent this, it is necessary to give the thermal transfer image receiving sheet 1 a cushioning property that absorbs unevenness. The characteristics of the thermal transfer image receiving sheet for satisfying the required cushioning property are as follows.
(1) The maximum valley depth (JIS0601: 2013) of the waviness curve measured from the receiving layer 30 side of the thermal transfer image receiving sheet 1 is set to Wv, and 0.5 MPa is applied to the receiving layer 30 side of the thermal transfer image receiving sheet 1 with a flat indenter. Let d be the thickness at which the thermal transfer image receiving sheet shrinks when pressure is applied.
d ≧ Wv
To be.
(2) Assuming that the thickness of the thermal transfer image receiving sheet 1 is t,
d / t ≦ 1.48%
To be.

In the above-mentioned (1), if d ≧ Wv, the unevenness of the thermal transfer image receiving sheet 1 is absorbed by the shrinkage due to the pressurization at the time of printing, and the contact surface of the thermal head becomes uniform, so that white spots do not occur.
On the other hand, when d <Wv, the unevenness of the thermal transfer image receiving sheet 1 is not sufficiently absorbed by the shrinkage due to the pressurization at the time of printing, and the contact surface of the thermal head becomes non-uniform, so that white spots occur.

In the above-mentioned (2), if d ≧ Wv of (1) is satisfied and d / t ≦ 1.48%, white spots are suppressed and bleeding does not occur.
On the other hand, when d / t> 1.48%, the shrinkage of the thermal transfer image receiving sheet 1 due to pressurization becomes excessive, the releasability between the receiving layer 30 and the thermal transfer recording medium decreases, and the contact time becomes long. , There is a risk of bleeding.

(Underlay layer 23)
According to one embodiment of the present invention, as a layer included in the intermediate layer 20, at least one undercoat layer 23 may be provided between the heat insulating layer 22 and the receiving layer 30.
By providing the undercoat layer 23, functions such as solvent resistance, dye diffusion barrier when storing images under high temperature / high humidity, interlayer adhesion, whitening, concealing glare and unevenness of the base material, and antistatic function are provided. Can be added. As a means for forming the intermediate layer, a known means can be used. For example, a fluorescent whitening agent, inorganic fine particles, hollow fine particles, and an organic conductive material such as a conductive filler or polyaniline sulfonic acid can be used in the undercoat layer 23. Can be mentioned as a method of adding.

(Receptive layer 30)
The receiving layer 30 of the present invention receives the sublimation dye transferred from the thermal transfer recording medium at the time of image formation by thermal transfer, and holds the received sublimation dye in the receiving layer 30 so that the surface of the receiving layer 30 is covered. Images can be formed and maintained. The receiving layer 30 may contain a binder resin, a mold release agent, and a curing agent. According to a preferred embodiment, the receiving layer 30 may further contain a surfactant and a film-forming auxiliary depending on various purposes.

Examples of the binder resin include acrylic resins, vinyl chloride resins, polyolefin resins such as polyethylene and polypropylene, polyvinyl chloride, vinyl chloride / vinyl acetate copolymers (vinyl chloride resin), and halogenation of polyvinylidene chloride and the like. Polymers, polyvinyl acetate / acrylic copolymers, vinyl polymers such as polyvinyl acid esters, polystyrene resins, polyamide resins, copolymer resins of olefins such as ethylene and propylene with other vinyl monomers, ionomers, cellulose di Examples thereof include a cellulose-based resin such as acetate, polycarbonate and the like, and a mixed system of these resins, and a vinyl chloride-based resin is preferable. It is more preferable that the vinyl chloride-based resin is at least one selected from a vinyl chloride / vinyl acetate copolymer and a vinyl chloride / acrylic copolymer.

As the release agent contained in the receiving layer 30, for example, various oils such as silicone-based, fluorine-based, and phosphoric acid ester-based, surfactants, various fillers such as metal oxides and silica, waxes, and the like can be used. .. These may be used alone or in combination of two or more. Above all, it is preferable to use silicone oil.

As the curing agent contained in the receiving layer 30, for example, an isocyanate-based curing agent or the like can be used. A polyisocyanate resin can be preferably used as the isocyanate-based curing agent. Various types of polyisocyanate resins are conventionally known, and it is desirable to use an aromatic isocyanate adduct. Examples of the aromatic polyisocyanate include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, or a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate, 1,5-naphthalene diisocyanate, and trizine diisocyanate. Examples include p-phenylene diisocyanate, trans-cyclohexane, 1,4-diisocyanate, xylylene diisocyanate, triphenylmethane triisocyanate, and tris (isocyanisocyanene phenyl) thiophosphate, especially 2,4-toluene diisocyanate and 2,6-toluene diisocyanate. Or, a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate is preferable.

The blending ratio of the binder resin and the curing agent of the receiving layer 30 is not particularly limited, but the Martens hardness (ISO14577) measured from the receiving layer 30 side of the thermal transfer image receiving sheet 1 is 30 to 120 N / mm ² . It is necessary to adjust the mixing ratio. When the Martens hardness is 30 to 120 N / mm ² , white spots are suppressed and image quality defects other than white spots do not occur because the above-mentioned cushioning effect is sufficiently exhibited.
On the other hand, if the Martens hardness exceeds 120 N / mm ² , the surface of the thermal transfer image receiving sheet 1 is too hard, and even if the cushioning property is sufficient at the time of printing, the unevenness cannot be offset and white spots occur. Further, when the Martens hardness is less than 30 N / mm ² , fine unevenness that cannot be offset by the cushioning effect is affected, and unevenness in shading occurs during printing, so that good printing quality cannot be obtained. It ends up.

The thickness of the receiving layer 30 can be in the range of 0.1 μm or more and 10 μm or less, but more preferably 0.2 μm or more and 8 μm or less. Further, if necessary, an antioxidant, a fluorescent dye, or a known additive may be contained.

(Back layer)
Further, the thermal transfer image receiving sheet 1 of the embodiment of the present invention may be provided with a back surface layer on the side opposite to the side on which the intermediate layer 20 of the base material 10 is provided. The back surface layer is provided to improve the transportability of the printer, prevent blocking with the receiving layer 30, and prevent curling of the thermal transfer image receiving sheet before and after printing.
Conventionally known materials can be used for the back surface layer, for example, polyolefin resins such as polyethylene resin and polypropylene resin, acrylic resins, polycarbonate resins, polyvinyl alcohol resins, polyvinyl acetal resins, polyester resins, and polystyrene resins. , Binder resin such as polyamide can be used. Further, if necessary, known additives such as fillers and antistatic agents may be contained.

The materials used in each Example and Comparative Examples of the present invention are shown below. In addition, "part" or% in the text is based on weight unless otherwise specified. Further, the present invention is not limited to the examples.

(Example 1)
<< Thermal transfer image receiving sheet >>
<Base material>
A high-quality paper having a thickness of 140 μm was used, and a polyethylene resin layer A (not shown) having a thickness of 30 μm was formed on one surface by a melt extrusion method.

Next, a polyethylene resin layer B (not shown) having a thickness of 40 μm was formed on the surface of the high-quality paper opposite to the polyethylene resin layer A side to prepare a base material 10 composed of three layers.

<Cushion layer>
Next, the cushion layer 21 was formed by applying a coating liquid for a cushion layer having the following composition on the polyethylene resin layer A of the base material 10 so that the film thickness after drying was 10 μm.
"Cushion layer coating liquid"
-Styrene-butadiene rubber solution (trade name Nipol LX110, Zeon Corporation) (solid content 40.5%)
74.07 parts, pure water 25.93 parts

<Insulation layer>
The heat insulating layer 22 was formed by applying a coating liquid for a heat insulating layer having the following composition on the cushion layer 21 of the base material 10 so that the film thickness after drying was 20 μm.
"Coating liquid for heat insulating layer"
・ Gelatin (trade name: SN, Nitta Gelatin Co., Ltd.) 55 parts ・ Hollow particles (trade name: AF-1055, Dow Chemical Japan Co., Ltd.) 30 parts ・ Pure water 11 parts ・ Epoxy cross-linking agent (trade name: Carbodilite E-02, manufactured by Nagase ChemteX Corporation)
Part 4

<Underground layer>
The undercoat layer 23 was formed by applying a coating liquid for an undercoat layer having the following composition on the heat insulating layer 22 of the base material 10 so that the film thickness after drying was 1 μm.
"Coating liquid for undercoat layer"
-Polyester (Byronal MD-1480, solid content concentration 25%, manufactured by Toyobo Co., Ltd.)
100 copies, pure water 25 copies

<Receptive layer>
A coating liquid for a receiving layer having the following composition was applied onto the undercoat layer 23 of the base material 10 so that the film thickness after drying was 3 μm to form the receiving layer 30, and a thermal transfer image receiving sheet was obtained.
"Coating liquid for receiving layer"
-Vinyl chloride emulsion (Viniblanc 900, Nissin Chemical Industry Co., Ltd., Tg = 70 ° C, solid content = 40%)
100.00 parts ・ Ethylene glycol diethyl ether 0.25 parts ・ Silicone mold release agent
(Dimethyl Silicon NP2406, Asahi Kasei Wacker Silicon Co., Ltd., solid content = 60%)
0.17 parts ・ Isocyanate-based curing agent (model number: DNW-6000, DIC Corporation) 1.29 parts

(Example 2)
A thermal transfer image receiving sheet was produced in the same manner as in Example 1 except that the film thickness of the cushion layer after drying was set to 15 μm.

(Example 3)
A thermal transfer image receiving sheet was produced in the same manner as in Example 1 except that the film thickness of the cushion layer after drying was set to 20 μm.

(Example 4)
A thermal transfer image receiving sheet was produced in the same manner as in Example 1 except that the film thickness of the cushion layer after drying was set to 30 μm.

(Example 5)
A thermal transfer image receiving sheet was produced in the same manner as in Example 3 except that the compounding ratio of the isocyanate-based curing agent was 0.65 parts.

(Example 6)
A thermal transfer image receiving sheet was produced in the same manner as in Example 3 except that the compounding ratio of the isocyanate-based curing agent was 1.03 parts.

(Comparative Example 1)
A thermal transfer image receiving sheet was produced in the same manner as in Example 1 except that the cushion layer was not provided and the heat insulating layer was directly provided on the polyethylene resin layer A of the base material.

(Comparative Example 2)
A thermal transfer image receiving sheet was produced in the same manner as in Example 1 except that the film thickness of the cushion layer after drying was set to 5 μm.

(Comparative Example 3)
A thermal transfer image receiving sheet was produced in the same manner as in Example 1 except that the film thickness of the cushion layer after drying was set to 40 μm.

(Comparative Example 4)
A thermal transfer image receiving sheet was produced in the same manner as in Example 3 except that the compounding ratio of the isocyanate-based curing agent was 0.39 parts.

(Comparative Example 5)
A thermal transfer image receiving sheet was produced in the same manner as in Example 3 except that the compounding ratio of the isocyanate-based curing agent was 1.94 parts.

<< Thermal transfer recording medium >>
As a base material, a 4.5 μm polyethylene terephthalate film with easy-adhesion treatment on one side is used, and a coating liquid for a heat-resistant slipping layer having the following composition is applied to the non-easy-adhesion-treated surface, and the coating amount after drying is 1.0 g / m. It was applied and dried so as to be No. ² , and a substrate with a heat-resistant slipping layer was obtained. Next, a coating liquid for a thermal transfer layer having the following composition is applied to the easily adhesive-treated surface of the base material with a heat-resistant slipping layer so that the coating amount after drying is 1.0 g / m ² , and the thermal transfer layer is dried. Was formed, and a thermal transfer recording medium was obtained.

<Coating liquid for heat-resistant slip layer>
-Silicone acrylic graft polymer (Toagosei Co., Ltd. US-350)
50.00 parts, methyl ethyl ketone 50.00 parts

<Coating liquid for thermal transfer layer>
・ C. I. Solvent Blue 36 2.50 copies · C.I. I. Solvent Blue 63 2.50 parts ・ Polyvinyl acetal resin 5.0 parts ・ Toluene 45.0 parts ・ Methyl ethyl ketone 45.0 parts

<< Image quality evaluation >>
Using the thermal transfer image receiving sheets of Examples 1 to 6 and Comparative Examples 1 to 5 and the thermal transfer recording medium, printing was performed with a thermal simulator, and white spots, bleeding, and uneven shading were evaluated. All printing is done under the following conditions.
-Printing environment: 23 ° C 50% RH
・ Applied voltage: 24V
-Printing speed: 10 inch / sec
-Print density: main scan 300 dpi, sub scan 300 dpi

(Evaluation of white spots)
Using the thermal transfer image receiving sheets of Examples 1 to 6 and Comparative Examples 1 to 5 and the thermal transfer recording medium, printing was performed with a thermal simulator, and white spots on the printed matter were evaluated. As the evaluation image, a solid image having a gradation between white and black was used. The evaluation results are shown in Table 1.
The evaluation criteria are as follows, and a level above Δ is a level at which there is no practical problem.
◯: White spots are not observed △: White spots are slightly observed ×: White spots are observed on the entire surface

(Blur evaluation)
Using the thermal transfer image receiving sheets of Examples 1 to 6 and Comparative Examples 1 to 5 and the thermal transfer recording medium, printing was performed with a thermal simulator, and bleeding of the printed matter was evaluated. As the evaluation image, a natural image (human image) was used. The evaluation results are shown in Table 1.
The evaluation criteria are as follows, and a level above Δ is a level at which there is no practical problem.
○: No bleeding is observed △: Slight bleeding is observed ×: Bleeding is observed on the entire surface

(Evaluation of uneven shading)
Using the thermal transfer image receiving sheets of Examples 1 to 6 and Comparative Examples 1 to 5 and the thermal transfer recording medium, printing was performed with a thermal simulator to evaluate the unevenness of shading of the printed matter. As the evaluation image, a solid image having a gradation between white and black was used. The evaluation results are shown in Table 1.
The evaluation criteria are as follows, and a level above Δ is a level at which there is no practical problem.
◯: Light and shade unevenness is not observed Δ: Light and shade unevenness is observed very slightly ×: Light and shade unevenness is observed on the entire surface

The cushion layer thickness of the thermal transfer image receiving sheets of Examples 1 to 6 and Comparative Examples 1 to 5, the total film thickness t of the thermal transfer image receiving sheets (hereinafter referred to as the total film thickness t), and the receiving layer side are flat under a normal temperature environment. The thickness d at which the thermal transfer image receiving sheet shrinks when a pressure of 0.5 MPa is applied using an indenter (the shrinking thickness is the depth of the dent formed by the pressure; hereinafter referred to as the shrinking thickness d), d. / t, maximum valley depth Wv (hereinafter, maximum valley depth Wv) of the surface texture undulation curve measured from the receiving layer side of the thermal transfer image receiving sheet, blending ratio of isocyanate-based curing agent in the receiving layer of the thermal transfer image receiving sheet, thermal transfer Table 1 shows the Martens hardness (hereinafter referred to as Martens hardness) measured from the receiving layer side of the image receiving sheet and the above-mentioned image quality evaluation results.

From Table 1, comparing Examples 1 to 4 having the same Martens hardness but different thicknesses d, and Comparative Examples 1 to 3, Examples 1 to 4 having a shrinkage thickness d of a maximum valley depth Wv or more. No white spots have occurred in Comparative Example 3. On the other hand, in Comparative Examples 1 and 2 in which the shrinking thickness d is less than the maximum valley depth Wv, white spots occur. From this, it was found that it is necessary to make the shrinking thickness d equal to or more than the maximum valley depth Wv in order to prevent white spots from occurring.

From Table 1, when Examples 1 to 4 and Comparative Examples 1 to 3 having the same Martens hardness and shrinking thickness d divided by the total film thickness t and having different d / t are compared, d / t is 1.48%. No bleeding occurred in Examples 1 to 4 and Comparative Examples 1 and 2 described below, but bleeding occurred in Comparative Example 3 in which the d / t exceeded 1.48%. From this, it was found that it is necessary to set the d / t to 1.48% or less in order to prevent bleeding.

From Table 1, when the shrinking thickness d, the total film thickness t, and the maximum valley depth Wv are the same, but the Martens hardness is different, Examples 3, 5 and 6, and Comparative Examples 4 and 5 have a Martens hardness of 30 N. At 120 N / mm ² of / mm ² or more, no white spots or uneven shading occur. On the other hand, in Comparative Example 4 having a Martens hardness of less than 30 N / mm ² , shading unevenness occurred, and in Comparative Example 5 having a Martens hardness of more than 120 N / mm ² , white spots occurred. From this, it was found that it is necessary to set the Martens hardness to 30 N / mm ² or more and 120 N / mm ² or more in order to prevent white spots and uneven shading.

Although the description has been made here with reference to a limited number of embodiments, the scope of rights is not limited thereto, and modifications of each embodiment based on the above disclosure are obvious to those skilled in the art. ..

The thermal transfer image receiving sheet obtained by the present invention can be used in a sublimation transfer type printer, and various images can be easily formed in full color in addition to increasing the speed and functionality of the printer. Therefore, it can be widely used for self-printing of digital cameras, cards such as identification cards, and output materials for amusement.

1: Thermal transfer image receiving sheet 10: Base material 20: Intermediate layer 21: Cushion layer 22: Insulation layer 23: Undercoat layer 30: Receiving layer 40: Back surface layer

Claims (1)

A thermal transfer image sheet in which at least a base sheet, an intermediate layer composed of one layer or a plurality of layers, and a receiving layer are laminated in this order, and JIS0601: 2013 from the receiving layer side of the thermal transfer image receiving sheet. The maximum valley depth of the swell curve in the surface texture measured according to the above is defined as Wv, and the thermal transfer is performed when a pressure of 0.5 MPa is applied to the receiving layer side of the thermal transfer image receiving sheet in a normal temperature environment using a planar indenter. Assuming that the thickness at which the image receiving sheet shrinks is d,
d ≧ Wv
And
Assuming that the thickness of the thermal transfer image receiving sheet is t,
d / t ≦ 1.48%
The thermal transfer image receiving sheet is characterized in that the maltens hardness measured from the receiving layer side of the thermal transfer receiving sheet according to ISO14577 is 30 to 120 N / mm ² .

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