Thermal transfer imaging sheet

Abstract

To provide a thermal transfer image receiving sheet that has a high biomass content while also having good printability. [Solution] A thermal transfer image receiving sheet comprising a paper substrate, an insulating layer, and a receiving layer in this order in the thickness direction, wherein the biomass content of the thermal transfer image receiving sheet is 75% or more, the thickness of the paper substrate is 60 μm or more and 300 μm or less, and the insulating layer contains at least one resin of vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, chlorinated polypropylene, and polypropylene.

Description

[Technical Field]

[0001] This disclosure relates to a thermal transfer image receiving sheet. [Background technology]

[0002] Various image formation methods have been known conventionally. Among them, the dye-sublimation thermal transfer method allows for free adjustment of density gradation, making it possible to form high-quality images comparable to those produced by silver halide photography.

[0003] The dye-sublimation thermal transfer method involves overlapping a thermal transfer sheet having a colorant layer containing a sublimable dye with a thermal transfer image receiving sheet having a receiving layer. Then, the thermal transfer sheet is heated by a thermal head on a thermal transfer printer, causing the sublimable dye in the colorant layer to transfer to the receiving layer on the thermal transfer image receiving sheet, thereby forming an image and obtaining a printed product.

[0004] Patent Document 1 discloses a thermal transfer image receiving sheet comprising a substrate, a first resin layer, and a receiving layer, wherein the first resin layer contains inorganic hollow particles and a resin material. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-123075 [Overview of the project] [Problems that the invention aims to solve]

[0006] In recent years, with the growing demand for a circular economy, there is a desire to move away from fossil fuels in the materials sector, just as there is a desire for energy, and the use of biomass is attracting attention. Biomass is an organic compound produced through photosynthesis from carbon dioxide and water, and by utilizing it, it can be converted back into carbon dioxide and water, making it a so-called carbon-neutral renewable energy source. Recently, the practical application of biomass plastics made from these biomass materials has been progressing rapidly, and attempts are also being made to manufacture various resins from biomass raw materials.

[0007] Conventional thermal transfer imaging sheets often contain layers made from fossil fuel-derived resin materials, resulting in a low biomass content. Therefore, there is a need to improve the biomass content of thermal transfer imaging sheets.

[0008] To improve the biomass content, one possible method is to use a paper substrate instead of a resin substrate as the base material for the thermal transfer image receiving sheet. Furthermore, to further improve the biomass content, it is possible to increase the thickness of the paper substrate. However, increasing the thickness of the paper substrate may reduce the transportability of the thermal transfer image receiving sheet.

[0009] Furthermore, to improve the biomass content, one possible method is to reduce the thickness of layers containing resin materials derived from fossil fuels. For example, in conventional thermal transfer image receiving sheets, the insulating layer placed between the receiving layer and the paper substrate, and the resin coating layer placed on the surface of the paper substrate, contain resin materials derived from fossil fuels. Therefore, one possible method is to reduce the thickness of these layers containing fossil fuel-derived resin materials. However, reducing the thickness of the insulating layer or resin coating layer may result in a decrease in image density or image unevenness in the printed image. A decrease in image density or image unevenness leads to a decrease in image quality.

[0010] Thus, with thermal transfer imaging sheets, it is difficult to achieve both a high biomass content and printability in terms of image density, image uniformity, and transportability.

[0011] The present disclosure has been made in view of the above problems, and the main object thereof is to provide a thermal transfer image receiving sheet having a high biomass content and good printing suitability.

Means for Solving the Problems

[0012] In the present disclosure, there is provided a thermal transfer image receiving sheet including a paper base material, a heat insulating layer, and a receiving layer in this order in the thickness direction, wherein the biomass content of the thermal transfer image receiving sheet is 75% or more, the thickness of the paper base material is 60 μm or more and less than or equal to 300 μm, and the heat insulating layer contains at least one resin selected from vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, chlorinated polypropylene, and polypropylene.

Advantages of the Invention

[0013] According to the present disclosure, there is an effect that a thermal transfer image receiving sheet having a high biomass content and good printing suitability can be provided.

Brief Description of the Drawings

[0014] [Figure 1] It is a schematic cross-sectional view illustrating the thermal transfer image receiving sheet in the present disclosure. [Figure 2] It is a schematic cross-sectional view illustrating the thermal transfer image receiving sheet in the present disclosure. [Figure 3] It is a schematic cross-sectional view illustrating the thermal transfer image receiving sheet in the present disclosure. [Figure 4] It is a schematic cross-sectional view illustrating the thermal transfer image receiving sheet in the present disclosure. [Figure 5] It is a schematic cross-sectional view illustrating the thermal transfer image receiving sheet in the present disclosure. [Figure 6] It is a schematic cross-sectional view illustrating the thermal transfer image receiving sheet in the present disclosure.

Modes for Carrying Out the Invention

[0015] The embodiments will be described below with reference to the drawings and other figures. However, this disclosure can be implemented in many different ways and should not be limited to the embodiments described below. In addition, the drawings may schematically represent the width, thickness, and shape of each part compared to the actual form in order to make the explanation clearer, but this is merely an example and should not be interpreted as limiting.

[0016] In this specification, when describing a manner in which one member is placed on another member, the term "above" or "below" includes, unless otherwise specified, both cases: when the other member is placed directly above or directly below the member so as to be in contact with it, and when the other member is placed above or below the member via yet another member. Similarly, in this specification, when describing a manner in which one member is placed on the surface of a member, the term "on the surface" includes, unless otherwise specified, both cases: when the other member is placed directly above or directly below the member so as to be in contact with it, and when the other member is placed above or below the member via yet another member.

[0017] The inventors of this application conducted diligent research to obtain a thermal transfer image receiving sheet that has a high biomass content while also having good printability. As a result, they found that by using a paper substrate, keeping the thickness of the paper substrate within a predetermined range, and using a specific resin with excellent heat insulation properties as the material for the heat insulation layer, it is possible to improve the biomass content while obtaining good printability (image density, image uniformity, and transportability).

[0018] The thermal transfer imaging sheet described in this disclosure will be explained in detail below.

[0019] Figure 1 is a schematic cross-sectional view illustrating a thermal transfer image receiving sheet in this disclosure. As shown in Figure 1, the thermal transfer image receiving sheet 1 in this disclosure comprises a paper substrate 2, an insulating layer 3, and a receiving layer 4, with a thickness direction D TThe following components are provided in this order: The biomass content of the thermal transfer image receiving sheet 1 is 75% or more; the thickness of the paper substrate 2 is 60 μm or more and 300 μm or less; and the heat insulating layer 3 contains at least one of the following resins: vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, chlorinated polypropylene, and polypropylene.

[0020] As shown in Figure 2, the thermal transfer image receiving sheet 1 in this disclosure may have a resin layer 7 on at least one side of the paper substrate 2. The resin layer is a layer called a resin coating layer that is placed on the surface of the paper substrate. The resin layer placed on the side of the paper substrate 2 that faces the heat insulating layer 3 may be referred to as the first resin layer 71. The resin layer placed on the side of the paper substrate 2 opposite to the heat insulating layer 3 may be referred to as the second resin layer 72.

[0021] In this disclosure, since a paper substrate is used, the biomass content of the thermal transfer image receiving sheet can be improved.

[0022] Furthermore, in this disclosure, the heat insulating layer contains at least one resin of vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, chlorinated polypropylene, and polypropylene. The above resins have high heat insulating properties. Therefore, the thickness of the heat insulating layer can be reduced. When the thickness of the heat insulating layer is reduced, the ratio of the thickness of the paper substrate to the overall thickness of the thermal transfer image receiving sheet can be increased relatively, thereby further improving the biomass content of the thermal transfer image receiving sheet. Also, the heat insulating layer is a layer containing resin, similar to the resin coating layer. Therefore, even without placing a resin coating layer on the surface of the paper substrate, the surface of the paper substrate can be made smooth by the presence of the heat insulating layer. Without a resin coating layer, the ratio of the thickness of the paper substrate to the overall thickness of the thermal transfer image receiving sheet can be increased relatively, thereby further improving the biomass content of the thermal transfer image receiving sheet.

[0023] Furthermore, the biomass content of the thermal transfer image receiving sheet can be further improved by, for example, replacing some or all of the specific resins contained in the insulation layer with biomass-derived resins, adding biomass-derived resins to the insulation layer, or replacing some or all of the resins contained in the resin layer with biomass-derived resins.

[0024] Therefore, in this disclosure, it is possible to increase the biomass content of the thermal transfer image receiving sheet to a predetermined value or higher.

[0025] Furthermore, in this disclosure, the heat insulating layer comprises at least one resin of vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, chlorinated polypropylene, and polypropylene. The above resins have high heat insulating properties and are also flexible. Therefore, they can increase the image density of the printed material and suppress image unevenness. Even if the thickness of the heat insulating layer is reduced or the resin coating layer is eliminated, sufficient image density can be obtained and image unevenness can be suppressed.

[0026] Furthermore, in this disclosure, the transportability of the thermal transfer image receiving sheet is improved because the thickness of the paper substrate is within a predetermined range.

[0027] Therefore, this disclosure makes it possible to achieve both improved biomass content and good printability (image density, image uniformity, and transportability).

[0028] In this disclosure, it is preferable that the resin layer 7 is not disposed on the surface of the paper substrate 2 in order to improve the biomass content.

[0029] Furthermore, as shown in Figure 2, if the thermal transfer image receiving sheet 1 has a resin layer 7 on at least one surface of the paper substrate 2, it is preferable that at least one of the resin layer 7 and the heat insulating layer 3 contains a biomass-derived resin.

[0030] As shown in Figure 3, in the thermal transfer image receiving sheet 1 of this disclosure, a primer layer 5 may be placed between the paper substrate 2 and the heat insulating layer 3, and between the heat insulating layer 3 and the receiving layer 4. The primer layer placed between the paper substrate 2 and the heat insulating layer 3 may be referred to as the second primer layer 52. The primer layer placed between the heat insulating layer 3 and the receiving layer 4 may be referred to as the first primer layer 51. Furthermore, as shown in Figure 4, in the thermal transfer image receiving sheet 1 of this disclosure, a back surface layer 6 may be placed on the side of the paper substrate 2 opposite to the heat insulating layer 3.

[0031] The following describes the various components of the thermal transfer image receiving sheet in this disclosure.

[0032] 1. Biomass In this disclosure, the biomass content of the thermal transfer image receiving sheet is 75% or more, may be 77% or more, may be 80% or more, or may be 83% or more. The upper limit of the biomass content is preferably higher, but may be, for example, 95% or less, or 90% or less. Specifically, the biomass content of the thermal transfer image receiving sheet may be 75% or more and 95% or less, may be 77% or more and 95% or less, may be 80% or more and 90% or less, or may be 83% or more and 90% or less.

[0033] The biomass content is determined in accordance with ASTM-D6866-22, by the ratio of radioactive carbon C14 to the total carbon atoms in the thermal transfer imaging sheet (P C14 (pMC) is measured, and the proportion of carbon derived from biomass P is calculated using the following formula. bioThe percentage of carbon derived from biomass can be calculated by measuring the proportion of C14 contained in the total carbon atoms in the thermal transfer imaging sheet (content: pMC). P bio (%)=P C14 / REF(pMC)×100

[0034] The biomass content of a thermal transfer imaging sheet can be adjusted by the layer structure, the material of each layer, and the thickness of each layer.

[0035] In this disclosure, the biomass content of the thermal transfer image receiving sheet is high, above a predetermined value. As a means of making the biomass content of the thermal transfer image receiving sheet above a predetermined value, for example, as shown in Figures 1, 3, and 4, one method is to make the thickness of the paper substrate above a predetermined thickness while not placing a resin coating layer on the surface of the paper substrate. However, if a resin coating layer is not placed on the surface of the paper substrate, the smoothness of the paper substrate may decrease, which may reduce printability. In contrast, in this disclosure, the heat insulating layer contains at least one of the following resins: vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, chlorinated polypropylene, and polypropylene. These resins have high heat insulating properties and flexibility, so even without placing a resin coating layer on the surface of the paper substrate, the image density of the printed material is high and image unevenness is suppressed.

[0036] Furthermore, other means of increasing the biomass content of the thermal transfer image receiving sheet to a predetermined value or higher include, for example, a method in which the thickness of the paper substrate is set to a predetermined thickness or higher and a specific resin contained in the heat insulating layer is replaced with a biomass-derived resin; a method in which the thickness of the paper substrate is set to a predetermined thickness or higher and a biomass-derived resin is added to the heat insulating layer; and a method in which the thickness of the paper substrate is set to a predetermined thickness or higher and a biomass-derived resin is used as the resin material for the resin layer instead of a fossil fuel-derived resin.

[0037] 2.Paper base material The thermal transfer imaging sheet in this disclosure has a paper substrate as a base material from the viewpoint of improving biomass content. The paper substrate can be used without particular limitations as long as it has heat resistance that can withstand the heat applied during transfer, for example, the heat from the thermal head, and mechanical strength that can support the layer provided on the paper substrate.

[0038] In this disclosure, "paper substrate" refers to a substrate mainly composed of cellulose. Examples of paper substrates include coated paper, art paper, fine paper, medium-grade paper, and glassine paper. Among these, coated paper is preferred from the viewpoint of smoothness. Coated paper refers to a paper in which a coating layer is arranged on at least one side of a base paper such as medium-grade paper or fine paper. The thickness of the coating layer is, for example, 10 μm or more and 30 μm or less. Since the coating layer in coated paper mainly contains inorganic materials, it is a layer that does not affect the biomass content of the thermal transfer image receiving sheet.

[0039] The thickness of the paper substrate is 60 μm or more, may be 100 μm or more, or 150 μm or more. If the thickness of the paper substrate is within the above range, a high biomass content is easily obtained. On the other hand, the thickness of the paper substrate is 300 μm or less, may be 250 μm or less, or 200 μm or less. If the thickness of the paper substrate is within the above range, good transportability can be obtained. Specifically, the thickness of the paper substrate is 60 μm or more and 300 μm or less, may be 100 μm or more and 250 μm or less, or 150 μm or more and 200 μm or less.

[0040] From the viewpoint of improving the biomass content of the thermal transfer image receiving sheet, the ratio of the thickness of the paper substrate to the thickness of the thermal transfer image receiving sheet is preferably 80% or more, may be 84% or more, or may be 88% or more. On the other hand, a higher ratio of the thickness of the paper substrate to the thickness of the thermal transfer image receiving sheet is preferable, but may be, for example, 96% or less, or 93% or less. Specifically, the ratio of the thickness of the paper substrate to the thickness of the thermal transfer image receiving sheet is preferably 80% or more and 96% or less, may be 84% or more and 93% or less, or may be 88% or more and 93% or less.

[0041] 3. Insulation layer The thermal insulation layer in this disclosure is placed between the paper substrate and the receiving layer. The thermal insulation layer has thermal insulation properties that suppress the loss of heat applied during image formation by thermal transfer to the paper substrate and the like.

[0042] (1) Form The heat insulating layer may be formed by coating one side of a paper substrate with a resin composition, or it may be a resin film.

[0043] The insulating layer may or may not have internal voids. If the insulating layer has internal voids, it may be, for example, a porous film with internal voids, or a hollow particle-containing layer containing hollow particles.

[0044] (2) Material (a) resin The thermal insulation layer contains at least one of the following resins: vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, chlorinated polypropylene, and polypropylene. The thermal insulation layer may contain only one of the above resins, or two or more. Since the above resins tend to have low thermal conductivity, a thermal insulation layer containing these resins has high thermal insulation performance. High thermal insulation performance allows heat to be stored near the receiving layer, thereby increasing the image density of the printed material. Furthermore, since the above resins are flexible, a thermal insulation layer containing these resins tends to have good cushioning properties. Therefore, image unevenness in the printed material can be suppressed.

[0045] In particular, the heat insulating layer preferably contains at least one of the following resins: vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, and chlorinated polypropylene. These resins contain chlorine and are therefore polar. The inclusion of a polar resin in the heat insulating layer facilitates the penetration of dyes into the receiving layer placed on the heat insulating layer during thermal transfer. As a result, the image density of the printed material is further improved.

[0046] Furthermore, it is preferable to use modified polypropylene in which polar groups have been introduced as the polypropylene. As mentioned above, the image density of the printed material is further improved by including modified polypropylene in the heat insulating layer.

[0047] The degree of chlorination of chlorinated polypropylene is preferably 20% or more, and more preferably 30% or more. A degree of chlorination within this range further improves the image density of the printed material. On the other hand, the degree of chlorination of chlorinated polypropylene may be 35% or less, and may be less than 32%. If the degree of chlorination of chlorinated polypropylene is too high, the insulation layer may become hard, reducing its cushioning properties. A degree of chlorination within this range results in good cushioning properties for the insulation layer, further reducing image unevenness in the printed material. Specifically, the degree of chlorination of chlorinated polypropylene is preferably 20% to 35%, and more preferably 30% to less than 32%. The degree of chlorination of chlorinated polypropylene is measured in accordance with JIS K7229-1995.

[0048] When the insulation layer contains polyvinyl chloride, it is preferable that the insulation layer further contains a plasticizer from the viewpoint of improving cushioning properties. The plasticizer is not particularly limited as long as it is compatible with polyvinyl chloride, and examples include phthalate-based plasticizers such as dibutyl phthalate (DBP), dioctyl phthalate (DOP), diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), and diundecyl phthalate (DUP); adipic acid-based plasticizers such as dibutyl adipate; phosphate-based plasticizers such as tributyl phosphate, tricresyl phosphate, and triphenyl phosphate; trimellitic acid-based plasticizers such as tributyl trimellitic acid and trimellitic trioctyl trimellitic acid; various known polyester-based plasticizers; and citrate esters such as acetyl tributyl citrate and acetyl trioctyl citrate. These plasticizers may be used individually or in combination of two or more.

[0049] The plasticizer content in the heat insulating layer is, for example, 10 to 50 parts by mass per 100 parts by mass of polyvinyl chloride, and may be 20 to 40 parts by mass.

[0050] When vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, chlorinated polypropylene, and polypropylene are designated as the specified resin, the proportion of the specified resin to the total resin components in the heat insulating layer may be, for example, 90% by mass or more, or 95% by mass or more. On the other hand, the proportion of the specified resin to the total resin components in the heat insulating layer may be, for example, 100% by mass or less than 100% by mass.

[0051] The heat insulating layer may contain a biomass-derived resin. This can increase the biomass content of the thermal transfer image receiving sheet. The biomass-derived resin may be at least one of the following resins: vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, chlorinated polypropylene, and polypropylene, and may also be a resin other than vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, chlorinated polypropylene, and polypropylene. That is, the vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, chlorinated polypropylene, and polypropylene mentioned above may each be partially or entirely biomass-derived resins. Furthermore, the heat insulating layer may contain a biomass-derived resin other than vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, chlorinated polypropylene, and polypropylene, to the extent that it does not impair the heat insulating properties and cushioning properties.

[0052] When the biomass-derived resin is at least one of the following resins: vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, chlorinated polypropylene, and polypropylene, the proportion of the biomass-derived resin to the total resin components in the heat insulating layer is preferably 55% by mass or more, and more preferably 70% by mass or more.

[0053] For example, if the insulation layer contains polypropylene, biomass-derived polypropylene, i.e., biomass polypropylene, may be used as part or all of the above polypropylene. Biomass polypropylene is a polymer containing biomass-derived propylene. When the insulation layer contains only polypropylene as a resin component and biomass polypropylene is used as part or all of the above polypropylene, the proportion of biomass polypropylene in the total polypropylene is preferably 55% by mass or more, and more preferably 70% by mass or more.

[0054] If the insulating layer contains a biomass-derived resin, the biomass content of the insulating layer may be, for example, 50% or more, 55% or more, 65% or more, or 70% or more. A higher biomass content is preferable for the insulating layer, but may be, for example, 95% or less, or 90% or less. Specifically, the biomass content of the insulating layer may be 50% to 95%, 55% to 95%, 65% to 95%, or 70% to 90%. The insulating layer can be obtained by impregnating a thermal transfer image receiving sheet in a sodium hydroxide solution and peeling off each layer. The method for measuring the biomass content of the insulating layer is the same as the method for measuring the biomass content of the thermal transfer image receiving sheet described above.

[0055] (b) Hollow particles The insulating layer may or may not contain hollow particles. The hollow particles may be organic hollow particles, inorganic hollow particles, or organic-inorganic composite hollow particles. The insulating layer may contain only one type of hollow particle, or two or more types.

[0056] Organic hollow particles have a shell made of a resin material. Examples of resin materials include (meth)acrylonitrile resins such as (meth)acrylonitrile copolymers, styrene resins such as polystyrene and crosslinked styrene-(meth)acrylic resins, vinyl resins such as polyvinylidene chloride, (meth)acrylic resins such as polymethyl (meth)acrylate, phenolic resins, fluororesins, imide resins, and polycarbonates.

[0057] Examples of organic-inorganic composite hollow particles include hollow particles in which the shell surface of an organic hollow particle is modified with an inorganic material such as an inorganic powder. Examples of organic hollow particles include the organic hollow particles mentioned above. Examples of inorganic materials include talc, calcium carbonate, silica, titania, and alumina.

[0058] Examples of inorganic hollow particles include hollow silica particles, hollow glass particles, and hollow ceramic particles.

[0059] The average particle diameter of the hollow particles is preferably 0.1 μm to 30 μm, more preferably 0.5 μm to 30 μm, and even more preferably 1 μm to 25 μm. The average particle diameter of the hollow particles is measured using an electron microscope. Specifically, a cross-sectional image of the insulating layer is obtained using a scanning electron microscope, and the particle diameter is obtained as the average value of the major axis diameter and minor axis diameter for each particle in the cross-sectional image. The arithmetic mean of the particle diameters of 100 particles is taken as the average particle diameter.

[0060] If the insulating layer contains hollow particles, the content of hollow particles in the insulating layer may be, for example, 5% by mass or more and 70% by mass or less, or 15% by mass or more and 60% by mass or less.

[0061] (3) Thickness The thickness of the insulating layer is preferably 3 μm or more, may be 6 μm or more, or may be 10 μm or more. A thickness within this range improves both thermal insulation and cushioning, resulting in higher image density and reduced image unevenness in the printed material. On the other hand, the thickness of the insulating layer is preferably 40 μm or less, but may be 30 μm or less. A thickness within this range makes it easier to obtain the desired biomass density. Specifically, the thickness of the insulating layer is preferably 3 μm to 40 μm, may be 6 μm to 30 μm, or may be 10 μm to 30 μm.

[0062] (4) Thermal conductivity The thermal insulation layer in this disclosure has low thermal conductivity because it contains the resin described above. The thermal conductivity of the thermal insulation layer is preferably 0.25 W / m·K or less, and more preferably 0.20 W / m·K or less. Because the thermal insulation layer has the above thermal conductivity, the thermal insulation layer is less likely to conduct heat to the paper substrate, and the image density of the printed material is improved.

[0063] The thermal conductivity of the insulation layer shall be measured using a thermal conductivity meter at room temperature (24°C) in accordance with JIS R 2616:2001 (transient hot-wire method). A thermal conductivity meter such as the QTM-500 manufactured by Kyoto Electronics Manufacturing Co., Ltd. may be used.

[0064] (5) Formation method The method for forming the heat insulating layer is not particularly limited, but for example, one method involves dispersing or dissolving the above-mentioned material in a solvent to prepare a resin composition, and then applying the resin composition to one side of a paper substrate and drying it. When the heat insulating layer is formed by application, the thickness of the heat insulating layer can be made relatively thin. Known methods such as the roll coating method, reverse roll coating method, gravure coating method, reverse gravure coating method, bar coating method, and rod coating method can be used as methods for applying the resin composition.

[0065] Furthermore, as mentioned above, if the insulating layer has internal voids, a porous film can be used as the insulating layer. A porous film can be made, for example, by adding a polyester or (meth)acrylic resin having a higher melting point than polypropylene to a mixture, forming a film, and stretching it as needed. The polyester or (meth)acrylic resin acts as a nucleating agent that forms fine voids. The porous film is not limited to the porous film made by the above method, and commercially available porous films may also be used.

[0066] 4. Receptive layer The receiving layer is a layer that receives the sublimable dye transferred from the colorant layer of the heat transfer sheet and maintains the formed image. The receiving layer is located on the side opposite the paper substrate side of the insulating layer. The receiving layer and the insulating layer may or may not be in direct contact.

[0067] The receiving layer may contain resins such as polyolefin, vinyl resin, (meth)acrylic resin, cellulose resin, polyester, polyamide, polycarbonate, polystyrene, polyurethane, and ionomer resin. The receiving layer may contain only one of the above resins or two or more.

[0068] The resin content in the receiving layer may be 80% by mass or more and 98% by mass or less, or 90% by mass or more and 95% by mass or less.

[0069] The receiving layer may contain a release agent. This improves the release properties from the heat transfer sheet. Examples of release agents include solid waxes such as polyethylene wax, amide wax, and Teflon® powder, fluorine-based or phosphate ester-based surfactants, various modified silicone oils such as silicone oil, reactive silicone oil, and curable silicone oil, and various silicone resins. Modified silicone oil is preferred as the silicone oil. Preferred modified silicone oils include amino-modified silicone, epoxy-modified silicone, aralkyl-modified silicone, epoxy-aralkyl-modified silicone, alcohol-modified silicone, vinyl-modified silicone, and urethane-modified silicone. Among these, epoxy-modified silicone, aralkyl-modified silicone, and epoxy-aralkyl-modified silicone are particularly preferred. The receiving layer may contain only one type of release agent, or two or more types.

[0070] The content of the release agent in the receiving layer may be, for example, 0.5% by mass or more and 20% by mass or less, or 1.0% by mass or more and 10% by mass or less.

[0071] The thickness of the receiving layer is preferably 0.5 μm or more, and more preferably 1.0 μm or more. A thickness of the receiving layer within this range improves release properties from the thermal transfer sheet during printing and further improves image density. On the other hand, the thickness of the receiving layer is preferably 10 μm or less, and more preferably 5 μm or less. A thickness of the receiving layer within this range tends to increase the biomass content of the thermal transfer image receiving sheet. Specifically, the thickness of the receiving layer is preferably 0.5 μm or more and 10 μm or less, and more preferably 1.0 μm or more and 5 μm or less.

[0072] One method for forming the receiving layer is to prepare a resin composition by dispersing or dissolving the above-mentioned material in a solvent, and then to apply the resin composition to one side of the heat insulating layer and dry it. An example of a method for applying the resin composition is the method exemplified in the method for forming the heat insulating layer described above.

[0073] 5. Primer layer The thermal transfer image receiving sheet in this disclosure may have a primer layer 5, as shown in Figures 3 to 6. This can improve adhesion. The primer layer 5 may be placed between the paper substrate 2 and the heat insulating layer 3, or between the heat insulating layer 3 and the receiving layer 4. When the resin layer described later is not placed between the paper substrate and the heat insulating layer, and the heat insulating layer is formed by coating, it is preferable to place the primer layer between the paper substrate and the heat insulating layer. When the heat insulating layer is formed by coating, the thickness of the heat insulating layer can be made relatively thin. In this case, the presence of the primer layer between the paper substrate and the heat insulating layer can improve the adhesion between the paper substrate and the heat insulating layer.

[0074] The primer layer typically contains a resin. Examples of resins include polyester, polyamide, polyolefin, vinyl resin, (meth)acrylic resin, imide resin, cellulose resin, styrene resin, polycarbonate, and ionomer resin. The primer layer may contain only one of the above resins or two or more.

[0075] The primer layer may contain additives such as plasticizers, UV stabilizers, color inhibitors, surfactants, fluorescent whitening agents, matting agents, deodorants, flame retardants, weathering agents, antistatic agents, thread friction reducers, slip agents, antioxidants, ion exchange agents, dispersants, UV absorbers, and colorants such as pigments and dyes.

[0076] The thickness of the first primer layer, which is placed between the insulating layer and the receiving layer, is preferably 3.0 μm or less, and more preferably 2.0 μm or less. Setting the thickness of the first primer layer within this range tends to increase the biomass content of the thermal transfer image receiving sheet. On the other hand, the thickness of the first primer layer is preferably 0.1 μm or more, and more preferably 1.0 μm or more. Setting the thickness of the first primer layer within this range ensures good adhesion between the receiving layer and the insulating layer. Specifically, the thickness of the first primer layer is preferably 0.1 μm or more and 3.0 μm or less, and more preferably 1.0 μm or more and 2.0 μm or less.

[0077] The thickness of the second primer layer, which is placed between the paper substrate and the heat insulating layer, is preferably 2.0 μm or less, and more preferably 1.5 μm or less. Setting the thickness of the second primer layer within this range tends to increase the biomass content of the thermal transfer image receiving sheet. On the other hand, the thickness of the second primer layer is preferably 0.1 μm or more, and more preferably 1.0 μm or more. Setting the thickness of the second primer layer within this range ensures adhesion between the heat insulating layer and the paper substrate or resin layer. Specifically, the thickness of the second primer layer is preferably 0.1 μm or more and 2.0 μm or less, and more preferably 1.0 μm or more and 1.5 μm or less.

[0078] The method for forming the primer layer is not particularly limited, but for example, one method is to prepare a resin composition by dispersing or dissolving the above material in a solvent, and then apply the resin composition to one side of the heat insulating layer and dry it. The method for applying the resin composition is the method exemplified as the application method in the method for forming the heat insulating layer described above.

[0079] 6. Resin layer In the thermal transfer image receiving sheet described herein, a resin layer may or may not be disposed on at least one surface of the paper substrate. Generally, when a paper substrate is used in a thermal transfer image receiving sheet, a resin layer, referred to as a resin coating layer, is often disposed on at least one surface of the paper substrate. Such a resin layer is provided to smooth the surface of the paper substrate and is therefore generally formed to be thick. For this reason, in this disclosure, it is preferable that no resin layer is disposed on the surface of the paper substrate in order to improve the biomass content of the thermal transfer image receiving sheet.

[0080] On the other hand, if a resin layer is placed on the surface of the paper substrate, as shown in Figures 5 and 6, the resin layer 7 may be placed on the side of the paper substrate 2 that is on the side of the heat insulating layer 3, or on the side of the paper substrate 2 that is on the opposite side of the heat insulating layer 3.

[0081] The resin layer contains a resin. Examples of the resin include polyethylene. Preferably, part or all of the resin contained in the resin layer is a biomass-derived resin. The biomass-derived resin may be biomass-derived polyethylene, i.e., biomass polyethylene.

[0082] Biomass polyethylene is a polymer containing biomass-derived ethylene. Because biomass-derived ethylene is used as the monomer raw material, the polymerized polyethylene is biomass-derived. However, the monomer raw material for polyethylene does not have to contain 100% by mass of biomass-derived ethylene. The monomer raw material for biomass polyethylene may further contain ethylene monomer derived from fossil fuels and / or α-olefin monomer derived from fossil fuels, or α-olefin monomer derived from biomass. Biomass polyethylene includes biomass LDPE, biomass LLDPE, biomass MDPE, and biomass HDPE. These may be used individually or in mixtures of two or more.

[0083] For example, biomass-derived ethylene can be produced using biomass-derived ethanol as a raw material. In particular, it is preferable to use biomass-derived fermented ethanol obtained from plant materials. The plant materials are not particularly limited, and conventionally known plants can be used. Conventionally known plants include, for example, corn, sugarcane, beet, and manioc.

[0084] In the resin layer, the proportion of biomass-derived resin to the total resin components is preferably 55% by mass or more, and more preferably 70% by mass or more.

[0085] For example, if the resin layer contains polyethylene, the proportion of biomass-derived polyethylene in the total polyethylene is preferably 55% by mass or more, and more preferably 70% by mass or more.

[0086] If the resin layer contains biomass-derived resin, the biomass content of the resin layer may be, for example, 50% or more, 55% or more, 65% or more, or 70% or more. A higher biomass content of the resin layer is preferable, but may be, for example, 95% or less, or 90% or less. Specifically, the biomass content of the resin layer may be, for example, 50% to 95%, 55% to 95%, 65% to 95%, or 70% to 90%. The method for measuring the biomass content of the resin layer is the same as the method for measuring the biomass content of the thermal transfer image receiving sheet described above.

[0087] The thickness of the first resin layer, which is placed on the heat insulating layer side of the paper substrate, is, for example, 5 μm or more, may be 7 μm or more, or 9 μm or more. The thickness of the first resin layer being within the above range smooths out the surface irregularities of the paper substrate. On the other hand, the thickness of the first resin layer is, for example, 30 μm or less, may be 15 μm or less, or 10 μm or less. Specifically, the thickness of the first resin layer is, for example, 5 μm or more and 30 μm or less, may be 7 μm or more and 15 μm or less, or 9 μm or more and 10 μm or less.

[0088] The thickness of the second resin layer, which is positioned on the side of the paper substrate opposite to the heat insulating layer, is, for example, 5 μm or more, may be 7 μm or more, or 9 μm or more. The thickness of the second resin layer being within the above range smooths out the irregularities of the paper substrate. On the other hand, the thickness of the second resin layer is, for example, 50 μm or less, may be 40 μm or less, or 30 μm or less. Specifically, the thickness of the second resin layer is, for example, 5 μm or more and 50 μm or less, may be 7 μm or more and 40 μm or less, or 9 μm or more and 30 μm or less.

[0089] The resin layer can be formed on a paper substrate by melt-extruding a resin composition containing the above-mentioned materials.

[0090] 7. Back layer In this disclosure, the thermal transfer image receiving sheet preferably has a back layer on the side opposite to the heat insulating layer of the paper substrate. The presence of a back layer in the thermal transfer image receiving sheet suppresses curling of the printed image.

[0091] The back layer contains, for example, a resin. Examples of resins include polyester, polyolefin, (meth)acrylic resin, polyamide, vinyl resin, cellulose resin, imide resin, and ionomer resin. Among these, vinyl resin and polyolefin are preferred from the viewpoint of curl suppression.

[0092] The back layer may contain additives such as release agents, plasticizers, UV stabilizers, color inhibitors, surfactants, fluorescent whitening agents, matting agents, deodorants, flame retardants, weather-resistant agents, antistatic agents, thread friction reducers, slip agents, antioxidants, ion exchange agents, dispersants, UV absorbers, and colorants such as pigments and dyes.

[0093] The thickness of the back layer is preferably 5 μm or less, more preferably 3 μm or less, and particularly preferably 1 μm or less. When the thickness of the back layer is within the above range, the biomass content of the thermal transfer image receiving sheet tends to be high. On the other hand, the thickness of the back layer is, for example, 0.2 μm or more. When the thickness of the back layer is within the above range, curling of the printed material is suppressed. Specifically, the thickness of the back layer is preferably 0.2 μm or more and 5 μm or less, more preferably 0.2 μm or more and 3 μm or less, and particularly preferably 0.2 μm or more and 1 μm or less.

[0094] 8. Prints The prints of this disclosure are made using the thermal transfer image receiving sheet described above, and comprise a paper substrate, an insulating layer, and an image receiving layer on which an image is formed. Details of each layer are as described above.

[0095] Methods for forming images include, for example, using conventionally known dye-sublimation thermal transfer recording methods and fused thermal transfer recording methods with thermal transfer sheets. In the dye-sublimation thermal transfer recording method, an image is formed by transferring a sublimable dye to a receiving layer using a thermal transfer sheet equipped with a dye-sublimation colorant layer containing a dye-sublimation dye. In the fused thermal transfer recording method, an image is formed by transferring a fused-transfer colorant layer onto a receiving layer using a thermal transfer sheet equipped with a fused-transfer colorant layer. Alternatively, images may be formed by combining these methods.

[0096] Specifically, the above image is formed by superimposing the above-mentioned thermal transfer sheet and the thermal transfer image receiving sheet of this disclosure, applying heat from the back side of the thermal transfer sheet using a heating element such as a thermal head, thereby transferring the sublimable dye contained in the sublimation transfer type colorant layer to the receiving layer, or by transferring the molten transfer type colorant layer onto the receiving layer.

[0097] This disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of this disclosure and achieves similar effects is included within the technical scope of this disclosure. [Examples]

[0098] The paper substrates used in the examples and comparative examples are described below. (Paper base material) • Paper substrate 1: Coated paper (manufactured by Daio Paper Corporation, iCOAT SAU 186.1, thickness 165 μm) • Paper substrate 2: Coated paper (manufactured by Moorem P&P Co., Ltd., NeoStar Gloss 300gsm, thickness 290μm) • Paper substrate 3: Coated paper (manufactured by Daio Paper Corporation, S Utrillo Coat 79.1, thickness 64 μm) • Paper substrate 4: Coated paper (manufactured by Moorem P&P Co., Ltd., NeoStarGloss 180gsm, thickness 149μm) ·Paper base material 5: Coated paper (manufactured by Moorim P&P Co., Ltd., NeoStarGloss150gsm, thickness 125μm) • Paper substrate 6: Coated paper (manufactured by Moorem P&P Co., Ltd., NeoStarGloss 350gsm, thickness 342μm)

[0099] [Example 1] As a paper substrate, the above-mentioned paper substrate 1 was prepared. A second primer layer with a thickness of 1.2 μm was formed by applying the following coating liquid for the second primer layer to one side of the paper substrate 1 and drying it. Next, a heat insulating layer with a thickness of 6 μm was formed by applying the following coating liquid for the heat insulating layer to the second primer layer and drying it.

[0100] (Coating liquid for the second primer layer) • Polyester 15 parts by mass (Byron® 200, Toyobo MC Co., Ltd.) • Fluorescent whitening agent 0.23 parts by mass (Doubletex® OB, Double Bond Chemical) Methyl ethyl ketone 73.8 parts by mass

[0101] (Insulation coating liquid 1) • Chlorinated polypropylene 1 (manufactured by Toyobo Co., Ltd., Hardlen® 15-LLP, degree of chlorination 30%) 75 parts by mass • Toluene 12.5 parts by mass Methyl ethyl ketone 12.5 parts by mass

[0102] Next, a coating liquid for the first primer layer was applied to the insulation layer and dried to form a first primer layer with a thickness of 1.7 μm. Then, the following coating liquid for the receiving layer was applied to the first primer layer and dried to form a receiving layer with a thickness of 3 μm. (Coating liquid for the first primer layer) • Polyester 4.2 parts by mass (Nichigo Polyester (registered trademark) WR-905, Mitsubishi Chemical Corporation) Titanium dioxide 8.4 parts by mass (TCA-888, Tochem Products Co., Ltd.) • Fluorescent whitening agent 0.07 parts by mass (Ubitex® BAC, BASF Japan) • Isopropyl alcohol 7.2 parts by mass ·Water 21 parts by mass

[0103] (Coating liquid for the receiving layer) • Vinyl chloride-vinyl acetate copolymer 36 parts by mass (Manufactured by Nisshin Chemical Industry Co., Ltd., Solvine® CNL) Epoxy-modified silicone 1.9 parts by mass (Manufactured by Shin-Etsu Chemical Co., Ltd., X-22-3000T) • Amino-modified silicone 0.18 parts by mass (Manufactured by Shin-Etsu Chemical Co., Ltd., X-22-1660B-3) • Toluene 20 parts by mass • Methyl ethyl ketone (MEK) 80 parts by mass

[0104] Next, the following coating solution for the back layer was applied to the other side of the paper substrate and dried to form a back layer with a thickness of 0.5 μm.

[0105] (Coating liquid for the back surface layer) • Polyvinyl butyral resin (PVB) 10 parts by mass (Esrec® BL-7, Sekisui Chemical Co., Ltd.) • Silicon dioxide 0.75 parts by mass (Silysia 380, Fuji Silysia Chemical Co., Ltd.) • Titanium chelate compound 0.117 parts by mass (AT chelating agent, Denka Polymer Co., Ltd.) • Toluene 40 parts by mass • Methyl ethyl ketone 40 parts by mass

[0106] Based on the above, a thermal transfer image receiving sheet was obtained comprising a back layer, a paper substrate, a second primer layer, a heat insulating layer, a first primer layer, and a receiving layer in this order.

[0107] [Example 2] A thermal transfer image receiving sheet was obtained in the same manner as in Example 1, except that paper substrate 2 was used as the paper substrate.

[0108] [Example 3] A thermal transfer image receiving sheet was obtained in the same manner as in Example 1, except that paper substrate 3 was used as the paper substrate.

[0109] [Example 4] A thermal transfer image receiving sheet was obtained in the same manner as in Example 1, except that a paper substrate 2 was used as the paper substrate and a 40 μm thick heat insulating layer was formed using a heat insulating layer coating liquid 1.

[0110] [Example 5] A thermal transfer image receiving sheet was obtained in the same manner as in Example 1, except that a thermal insulation layer with a thickness of 3 μm was formed using the thermal insulation coating liquid 1.

[0111] [Example 6] A thermal transfer image receiving sheet was obtained in the same manner as in Example 1, except that a thermal insulation layer with a thickness of 6 μm was formed using the thermal insulation coating liquid 2 described below. (Insulation coating liquid 2) • Chlorinated polypropylene 275 parts by mass (Manufactured by Toyobo Co., Ltd., Hardlen® 16-LP, chlorination degree 32%) • Toluene 12.5 parts by mass Methyl ethyl ketone 12.5 parts by mass

[0112] [Example 7] A thermal transfer image receiving sheet was obtained in the same manner as in Example 1, except that a thermal insulation layer with a thickness of 6 μm was formed using the thermal insulation coating liquid 3 described below. (Insulation coating liquid 3) • Polypropylene 20 parts by mass (Manufactured by Mitsui Chemicals, Inc., Unistol XP13B, 0% chlorination) • Isopropyl alcohol 16 parts by mass ·Water 64 parts by mass

[0113] [Example 8] A thermal transfer image receiving sheet was obtained in the same manner as in Example 1, except that a thermal insulation layer with a thickness of 6 μm was formed using the thermal insulation coating liquid 4 described below. (Insulation coating liquid 4) • Vinyl chloride-vinyl acetate copolymer 36 parts by mass (Manufactured by Nisshin Chemical Industry Co., Ltd., Solvine® CNL) • Toluene 20 parts by mass • Methyl ethyl ketone (MEK) 80 parts by mass

[0114] [Example 9] As a paper substrate, the above-mentioned paper substrate 1 was prepared. On one side of the paper substrate 1, the resin layer composition 1 described below was melt-extruded to form a first resin layer with a thickness of 9 μm. Subsequently, on the other side of the paper substrate, the resin layer composition 2 described below was melt-extruded to form a second resin layer with a thickness of 29 μm.

[0115] (Composition 1 for resin layer) Low-density polyethylene (LDPE) containing 70% by mass of biomass polyethylene. 100 parts by mass (Manufactured by Nippon Polyethylene Co., Ltd., Novatec® LC600A, density 0.918 g / cm³) 3 )

[0116] (Composition 2 for resin layer) • High-density polyethylene (HDPE) containing 70% by mass of biomass polyethylene. 80 parts by mass (Manufactured by Nippon Polyethylene Co., Ltd., Novatec® HS471, density 0.956 g / cm³) 3 ) Low-density polyethylene (LDPE) containing 70% by mass of biomass polyethylene. 20 parts by mass (Manufactured by Nippon Polyethylene Co., Ltd., Novatec® LC600A, density 0.918 g / cm³) 3 )

[0117] Next, the coating liquid for the second primer layer was applied to the first resin layer and dried to form a second primer layer with a thickness of 1.2 μm. Then, the coating liquid for the heat insulating layer 1 was applied to the second primer layer and dried to form a heat insulating layer with a thickness of 6 μm.

[0118] Next, the coating liquid for the first primer layer was applied to the insulation layer and dried to form a first primer layer with a thickness of 1.7 μm. Then, the coating liquid for the receiving layer was applied to the first primer layer and dried to form a receiving layer with a thickness of 3 μm.

[0119] Next, the coating liquid for the back layer was applied to the side of the second resin layer opposite to the paper substrate 1 side, and dried to form a back layer with a thickness of 0.5 μm.

[0120] Based on the above, a thermal transfer image receiving sheet was obtained comprising a back layer, a second resin layer, a paper substrate, a first resin layer, a second primer layer, a heat insulating layer, a first primer layer, and a receiving layer in this order.

[0121] [Example 10] As the heat insulation layer, an OPP film 1 (Mitsui Chemicals Toagosei Co., Ltd. SP-U#35) with a thickness of 35 μm, which has voids (microvoids) inside and contains 70% by mass of biomass polypropylene, was used. A heat transfer image receiving sheet was obtained in the same manner as in Example 9, except that it was laminated on the first resin layer to form a heat insulation layer. Thus, a heat transfer image receiving sheet including a back layer, a second resin layer, a paper substrate, a first resin layer, a heat insulation layer, a first primer layer, and a receiving layer in this order was obtained.

[0122] [Example 11] A heat transfer image receiving sheet was obtained in the same manner as in Example 1, except that a heat insulation layer with a thickness of 6 μm was formed using the following coating liquid 5 for the heat insulation layer. (Coating Liquid 5 for Heat Insulation Layer) · 25 parts by mass of polyvinyl chloride emulsion (manufactured by Nisshin Chemical Industry Co., Ltd., Vinibran (registered trademark) 985) · 15 parts by mass of isopropyl alcohol · 60 parts by mass of water

[0123] [Comparative Example 1] As the paper substrate, the above paper substrate 4 was prepared. On one surface of the paper substrate 4, the following resin layer composition 3 was melt-extruded to form a first resin layer with a thickness of 9 μm. Subsequently, on the other surface of the paper substrate, the following resin layer composition 4 was melt-extruded to form a second resin layer with a thickness of 29 μm.

[0124] (Resin Layer Composition 3)<00​​​​​​​​​​​​​​​​​ (Manufactured by Nippon Polyethylene Co., Ltd., Novatec® LC600A, density 0.918 g / cm³) 3 )

[0126] Next, a 35 μm thick OPP film (Mitsui Chemicals Tohcello Co., Ltd. SP-U#35) with internal voids (microvoids) was laminated to the side of the first resin layer opposite to the paper substrate side to form an insulating layer.

[0127] Next, the coating liquid for the first primer layer was applied to the insulation layer and dried to form a first primer layer with a thickness of 1.7 μm. Then, the coating liquid for the receiving layer was applied to the first primer layer and dried to form a receiving layer with a thickness of 3 μm.

[0128] Next, the coating liquid for the back layer was applied to the side of the second resin layer opposite to the paper substrate 4 side, and dried to form a back layer with a thickness of 0.5 μm.

[0129] Based on the above, a thermal transfer image receiving sheet was obtained comprising a back layer, a second resin layer, a paper substrate, a first resin layer, a heat insulating layer, a first primer layer, and a receiving layer in this order.

[0130] [Comparative Example 2] As a paper substrate, the above-mentioned paper substrate 5 was prepared. The following resin layer composition 5 was melt-extruded onto one side of the paper substrate to form a second resin layer with a thickness of 29 μm. (Composition for resin layer 5) • 100 parts by mass of polypropylene derived from fossil fuels (Manufactured by Nippon Polypropylene Co., Ltd., Novatec® FL02A, density 0.90 g / cm³) 3 )

[0131] Next, the following heat insulating layer composition 6 was melt-extruded onto the other side of the paper substrate to form a heat insulating layer with a thickness of 46 μm. (Composition for thermal insulation layer 6) • 100 parts by mass of ethylene-vinyl acetate copolymer (EVA) derived from fossil fuels (Manufactured by Mitsui Dow Polychemical Co., Ltd., Evaflex® EV550, density 0.93 g / cm³) 3 )

[0132] Next, the coating liquid for the first primer layer was applied to the insulation layer and dried to form a first primer layer with a thickness of 1.7 μm. Then, the coating liquid for the receiving layer was applied to the first primer layer and dried to form a receiving layer with a thickness of 30 μm.

[0133] The coating liquid for the back layer was applied to the side of the second resin layer opposite to the paper substrate side, and dried to form a back layer with a thickness of 0.5 μm.

[0134] Based on the above, a thermal transfer image receiving sheet was obtained comprising a back layer, a second resin layer, a paper substrate, a heat insulating layer, a first primer layer, and a receiving layer in this order.

[0135] [Comparative Example 3] A thermal transfer image receiving sheet was obtained in the same manner as in Comparative Example 1, except that a paper substrate 6 was used as the paper substrate and the first and second resin layers were not formed.

[0136] [Comparative Example 4] A thermal transfer image receiving sheet was obtained in the same manner as in Example 1, except that a thermal insulation layer and a second primer layer were not formed.

[0137] [Comparative Example 5] A thermal transfer image receiving sheet was obtained in the same manner as in Example 1, except that a thermal insulation layer with a thickness of 6 μm was formed using the thermal insulation coating liquid 7 described below. (Insulation coating liquid 7) • Ethylene-vinyl acetate copolymer (EVA) 25 parts by mass (Manufactured by Japan Coating Resin Co., Ltd., Aquatex EC-1700) • Isopropyl alcohol 15 parts by mass ·Water 60 parts by mass

[0138] [Comparative Example 6] A thermal transfer image receiving sheet was obtained in the same manner as in Example 1, except that a thermal insulation layer with a thickness of 6 μm was formed using the thermal insulation coating liquid 8 described below. (Insulation coating liquid 8) • Ethylene-based polyolefin 25 parts by mass (Manufactured by Mitsui Chemicals, Inc., Chemipearl ET300H) • Isopropyl alcohol 15 parts by mass ·Water 60 parts by mass

[0139] [Comparative Example 7] A thermal transfer image receiving sheet was obtained in the same manner as in Example 9, except that a second resin layer with a thickness of 29 μm was formed using the resin layer composition 7 described below, and a first resin layer with a thickness of 9 μm was formed using the resin layer composition 6 described below.

[0140] (Composition for resin layer 6) Low-density polyethylene (LDPE) containing 50% by mass of biomass polyethylene. 100 parts by mass (Manufactured by Nippon Polyethylene Co., Ltd., Novatec® LC600A, density 0.918 g / cm³) 3 )

[0141] (Composition for resin layer 7) • High-density polyethylene (HDPE) containing 50% by mass of biomass polyethylene as appropriate. 80 parts by mass (Manufactured by Nippon Polyethylene Co., Ltd., Novatec® HS471, density 0.956 g / cm³) 3 ) Low-density polyethylene (LDPE) containing 50% by mass of biomass polyethylene. 20 parts by mass (Manufactured by Nippon Polyethylene Co., Ltd., Novatec® LC600A, density 0.918 g / cm³) 3 )

[0142] [Comparative Example 8] A thermal transfer image receiving sheet was obtained in the same manner as in Comparative Example 7, except that a 35 μm thick biomass OPP film (Mitsui Chemicals Tohcello Co., Ltd. SP-U#35) containing 50% by mass of biomass polypropylene with internal voids (microvoids) was used as the thermal insulation layer and laminated onto the first resin layer to form the thermal insulation layer. Thus, a thermal transfer image receiving sheet was obtained comprising a back layer, a second resin layer, a paper substrate, a first resin layer, a thermal insulation layer, a first primer layer, and a receiving layer in this order.

[0143] Tables 1 and 2 show the layer configurations of the thermal transfer image receiving sheets obtained in Examples 1 to 11 and Comparative Examples 1 to 8.

[0144] [Table 1]

[0145] [Table 2]

[0146] [evaluation] The thermal transfer imaging sheets obtained in Examples 1 to 11 and Comparative Examples 1 to 8 were evaluated as follows. The results are shown in Tables 3 and 4.

[0147] 1. Measurement of biomass content Samples were cut from the thermal transfer imaging sheets obtained in Examples 1 to 11 and Comparative Examples 1 to 8. The C14 content was measured by radiocarbon (C14) assay in accordance with ASTM-D6866-22, and the biomass content was measured by the method described above. The measuring instrument was a tandem accelerator-based instrument. 14 A dedicated C-AMS device (manufactured by NEC Corporation) was used.

[0148] 2. Image density In the examples and comparative examples, an 11-step image was formed on the receiving layer of the thermal transfer image receiving sheet manufactured using a dye-sublimation thermal transfer printer (Dai Nippon Printing Co., Ltd., product name: DS-RX1) and the printer's genuine thermal transfer sheet (Dai Nippon Printing Co., Ltd.), and printed materials were produced. An 11-step image is an image in which the density gradually increases from white in the first step to black in the 11th step. The OD value (optical density) x of the 11th step (255 image gradations) of the 11-step image was measured using an optical densitometer (X-rite, i1Pro2) and evaluated based on the evaluation criteria below. The results are shown in Tables 3 and 4. (Evaluation Criteria) A: x ≥ 1.7 B: 1.7 > x ≥ 1.6 B - :1.6>x≧1.5 C:1.5>x

[0149] 3. Image unevenness In the examples and comparative examples, a grayscale image (128 / 255 image gradation) was formed on the receiving layer of the thermal transfer image receiving sheet manufactured in the examples and comparative examples using a dye-sublimation thermal transfer printer (manufactured by Dai Nippon Printing Co., Ltd., product name: DS-RX1) and genuine thermal transfer sheet (manufactured by Dai Nippon Printing Co., Ltd.), and printed materials were produced. The obtained printed materials were observed visually and evaluated based on the evaluation criteria below. The evaluation results are shown in Tables 3 and 4. (Evaluation Criteria) A: No inconsistencies were found. B: Mild unevenness was observed. B - Some unevenness was observed, but it was not to the extent that it would cause problems in practical use. C: Unevenness was observed, causing problems in practical use.

[0150] 4. Transportability Using a dye-sublimation thermal transfer printer (manufactured by Dai Nippon Printing Co., Ltd., product name: DS-RX1) and genuine thermal transfer ink sheets (manufactured by Dai Nippon Printing Co., Ltd.), a grayscale image (128 / 255 image gradation) was formed, and 10 consecutive prints were made to obtain the printed material. (Evaluation Criteria) A: Continuous printing was possible. B: Continuous printing was generally possible. C: Continuous printing was not possible.

[0151] [Table 3]

[0152] [Table 4]

[0153] The thermal transfer image receiving sheets in this disclosure (Examples 1 to 11) had a high biomass content while exhibiting good printability (image density, image uniformity, and transportability). On the other hand, in Comparative Example 1, the resin layer was thick, and a high biomass content could not be obtained. In Comparative Example 2, the receiving layer, resin layer, and heat insulating layer were thick, and a high biomass content could not be obtained. In Comparative Example 3, the paper substrate was thick, resulting in poor transportability. In Comparative Example 4, there was no heat insulating layer, resulting in low image density and image uniformity. In Comparative Examples 5 and 6, the heat insulating layer did not contain a specific resin, resulting in low image density. In Comparative Examples 7 and 8, the amount of biomass-derived resin in the resin layer or heat insulating layer was small, resulting in a reduced biomass content.

[0154] Thus, the present disclosure provides, for example, the following inventions.

[0155] [1] A thermal transfer image receiving sheet comprising a paper substrate, an insulating layer, and a receiving layer in this order in the thickness direction, The biomass content of the thermal transfer imaging sheet is 75% or more. The thickness of the aforementioned paper substrate is 60 μm or more and 300 μm or less. A thermal transfer image receiving sheet wherein the heat insulating layer comprises at least one of the following resins: vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, chlorinated polypropylene, and polypropylene. [2] The thermal transfer image receiving sheet according to [1], wherein the ratio of the thickness of the paper substrate to the thickness of the thermal transfer image receiving sheet is 80% or more. [3] The thermal transfer image receiving sheet according to [1] or [2], wherein the thickness of the thermal insulation layer is 3 μm or more and 40 μm or less. [4] The thermal transfer image receiving sheet according to [1], wherein the thermal insulation layer contains a resin derived from biomass. [5] The thermal transfer image receiving sheet according to [4], wherein the proportion of the biomass-derived resin to the total resin components in the heat insulating layer is 55% by mass or more. [6] The paper substrate has a resin layer on at least one surface, The aforementioned resin layer contains a biomass-derived resin, The thermal transfer image receiving sheet according to [1] to [5], wherein the proportion of the biomass-derived resin to the total resin components in the resin layer is 55% by mass or more. [Explanation of Symbols]

[0156] 1… Thermal transfer imaging sheet 2 … Paper base material 3. Insulation layer 4… Receptive layer 5. Primer layer 6… Back layer 7… Resin layer

Claims

1. A thermal transfer image receiving sheet comprising a paper substrate, an insulating layer, and a receiving layer in this order in the thickness direction, The biomass content of the thermal transfer image receiving sheet is 75% or more. The thickness of the aforementioned paper substrate is 60 μm or more and 300 μm or less. A thermal transfer image receiving sheet wherein the heat insulating layer comprises at least one of the following resins: vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, chlorinated polypropylene, and polypropylene.

2. The thermal transfer image receiving sheet according to claim 1, wherein the ratio of the thickness of the paper substrate to the thickness of the thermal transfer image receiving sheet is 80% or more.

3. The thermal transfer image receiving sheet according to claim 1, wherein the thickness of the heat insulating layer is 3 μm or more and 40 μm or less.

4. The thermal transfer image receiving sheet according to claim 1, wherein the heat insulating layer contains a resin derived from biomass.

5. The thermal transfer image receiving sheet according to claim 4, wherein the proportion of the biomass-derived resin to the total resin components in the heat insulating layer is 55% by mass or more.

6. The paper substrate has a resin layer on at least one surface, The aforementioned resin layer contains a biomass-derived resin, The thermal transfer image receiving sheet according to claim 1, wherein in the resin layer, the proportion of the biomass-derived resin to the total resin components is 55% by mass or more.

Images