JP4357443B2 - Thermal transfer image receiving sheet - Google Patents

Description

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

As a method of forming an image using thermal transfer, a thermal transfer sheet in which a thermal diffusion dye (sublimation dye) as a recording material is carried on a base sheet such as a plastic film, and another base such as paper or plastic film A thermal diffusion transfer system (sublimation thermal transfer system) is known in which a full-color image is formed by superimposing a thermal transfer image-receiving sheet provided with a dye receiving layer on a sheet. Since this method uses a thermal diffusion dye as the color material, the density and gradation can be freely adjusted in dot units, and a full color image as it is on the original can be clearly displayed on the image receiving sheet. It is applied to color image formation for computers. The image is of a high quality comparable to a silver salt photograph.

The receiving layer is formed of, for example, a resin made of vinyl chloride / acrylic copolymer or vinyl chloride / vinyl acetate copolymer. It has been used by adding to a solvent (see, for example, Patent Document 1 and Patent Document 2). However, there is a concern about the deterioration of the working environment due to the use of an organic solvent, and there is a demand for improved light resistance after dye diffusion in the formed receiving layer.

As a thermal transfer image receiving sheet, for the purpose of imparting heat resistance and cushioning properties, a sheet in which a layer composed of hollow particles and a binder resin is provided between a base sheet and a receiving layer has been proposed (for example, patent document). 1). However, in this laminated structure, since the receiving layer is formed by dissolving a resin in an organic solvent, the organic solvent penetrates into the hollow particles in the porous layer and dissolves and swells the hollow particles. There is a problem that the effect of hollow particles such as property is insufficient.

In order to solve this problem and to fully exhibit the effect of the hollow particles, there has been a problem that an organic solvent-resistant resin must be used as the binder resin in the porous layer. Further, in order to prevent erosion of the organic solvent from the receiving layer, a solvent barrier layer must be further provided between the porous layer and the receiving layer, resulting in a problem that the process becomes complicated and the cost is increased ( For example, see Patent Document 1.)

Since the technique described in Patent Document 2 uses natural paper as a base sheet, the coating liquid permeates the natural paper immediately after applying the porous layer forming coating liquid, resulting in density unevenness. In addition to problems, there were problems of poor smoothness and poor sensitivity and glossiness during printing.

Thermal transfer image-receiving sheet using a base material composed of a plastic skin layer containing fine voids and a plastic skin layer containing fine voids smaller than the central layer as the cushioning layer Has been proposed (see, for example, Patent Document 3).

In the thermal transfer image receiving sheet of Patent Document 3, however, the center layer and the skin layer are foamed by stretching a resin film, and the Patent Document completely describes the inclusion of hollow particles. Absent. These two layers are bonded to both sides of the PET film in the examples to form a base material, and a support such as coated paper is separately provided, so that there is a problem that the process is complicated. Further, since the PET film is rigid at the time of printing at a low temperature, there is a problem that the adhesion with the thermal head is inferior, the highlight portion is whitened and density unevenness occurs.
JP 2002-212890 ([0027], Examples) Japanese Patent Laid-Open No. 1-108090 (upper left column on page 4, example) JP-A-8-187965 (Claims 1, [0012], [0024])

In view of the above situation, the object of the present invention is to broaden the choice of binder resin material when laminating a porous layer containing hollow particles, to enable process simplification, to obtain an image with excellent sensitivity and reduced density unevenness. Furthermore, it is an object of the present invention to provide a thermal transfer image receiving sheet capable of improving high smoothness and glossiness and reducing white spots in highlight portions during low temperature printing.

The present invention relates to a thermal transfer image-receiving sheet obtained by laminating a porous layer and a receiving layer in this order on a base sheet, wherein the base sheet is formed by laminating resin layers on both sides of paper mainly composed of wood pulp. The porous layer contains high heat-resistant hollow particles and hollow particles, and comprises a high heat-resistant hollow particle layer comprising the high heat-resistant hollow particles and a binder resin (A), and the hollow particles and the binder resin (B). The hollow particle layer is a layer composed of at least two layers, wherein the receptor layer is formed using an aqueous coating liquid composed of a receptor layer forming resin, and the high heat-resistant hollow particle layer is the high heat-resistant hollow particle layer. The hollow particle layer is formed by using a porous layer coating solution in which particles and a binder resin (A) made of an ester resin or polyvinyl alcohol are dissolved or dispersed in an aqueous medium. And particles, which a binder resin and an ester-based resin or a polyvinyl alcohol (B) was formed by using a porous layer coating liquid obtained by dissolving or dispersing in an aqueous medium, wherein the high resistant hollow particles, thermal The heat transfer image-receiving sheet is characterized in that the heat-resistant temperature, which is the maximum temperature that does not break down, is 200 ° C. or higher.
The present invention is described in detail below.

The thermal transfer image receiving sheet of the present invention is obtained by laminating a porous layer and a receiving layer in this order on a base sheet.
The base sheet is a sheet in which resin layers are laminated on both sides of a base paper (sometimes referred to as “resin-coated paper” in this specification), but resin on both sides of a paper mainly composed of wood pulp. What laminated | stacked a layer is preferable.
The base sheet has a role of holding the receiving layer and heat is applied during thermal transfer. Therefore, the base sheet preferably has a mechanical strength that does not hinder handling even in a heated state.

Examples of the base paper constituting the base paper include natural pulp, synthetic pulp, and pulp paper made from a mixture thereof. Among these, paper mainly composed of wood pulp is preferable.
The base paper may be subjected to a conventionally known process such as a calendar process, which will be described later, as necessary.

The base paper preferably has a high smoothness, more preferably has a Beck smoothness of 1000 seconds or more, and more preferably has a Beck smoothness of 5000 seconds or more.
In this specification, the Beck smoothness is a value measured according to JIS P8119 using a Digibeck smoothness tester (manufactured by Toyo Seiki Co., Ltd.).
The base paper preferably has a thickness of 10 to 400 μm, and more preferably 50 to 200 μm.

The base paper can be produced by a known method, but a base paper that is calendered is preferable. When a base paper that is calendered is used for the base paper, the smoothness can be improved and the glossiness of the resulting thermal transfer image-receiving sheet can be enhanced.
The calendar process is not particularly limited, and for example, a machine calendar, a super calendar, a thermal calendar, or the like can be used.

In the substrate sheet, the resin layer may be formed on the same surface by only one layer, or may be formed by two or more layers.
When two or more resin layers are laminated, each resin layer may be made of the same resin or may be made of different types of resins.

Examples of the resin for forming the resin layer include resins having a small neck-in and good drawdown properties, such as polyolefin resins, polystyrene resins, vinyl resins, polyester resins, ionomer resins, nylon, and polyurethane. Although mentioned, polyolefin resin is preferable at the point from which the film excellent in water resistance, intensity | strength, glossiness, etc. is obtained.
Examples of the polyolefin resin include high-density polyethylene, medium-density polyethylene, low-density polyethylene, polypropylene, polybutene, and polypentene, among which high-density polyethylene, medium-density polyethylene, low-density polyethylene, and polypropylene are preferable. Polypropylene is more preferred.
The resin may contain an additive such as a modifier to improve adhesiveness. Examples of the modifying agent include olefin copolymers such as Tuffmer A (manufactured by Mitsui Chemicals).

The resin layer may be a film or sheet obtained by mixing one or more of the above resins, or a film or sheet formed by adding a pigment, a filler, or the like to the above resin. May be.
The substrate sheet can be produced by a known lamination method such as dry lamination, wet lamination, or extrusion. Each of the resin layers can be appropriately subjected to primer treatment or corona discharge treatment for the purpose of improving the interlayer adhesion.

The thermal transfer image-receiving sheet of the present invention is excellent in strength, water resistance, strain, etc. by using a resin-coated paper as a base sheet, and also contains moisture contained in the porous layer coating liquid. Can be prevented from penetrating into the paper substrate, so that an image free from density unevenness and white spots can be created.

In the thermal transfer image-receiving sheet of the present invention, the total thickness of the base sheet is usually 10 to 1000 μm, preferably 50 to 300 μm, and can be appropriately selected from the range.
The said base material sheet WHEREIN: It is preferable that the thickness of the said resin layer is 10-40 micrometers, and it is more preferable that it is 10-30 micrometers.
In addition, the thickness of the said resin layer means the total thickness of this two or more layers, when the resin layer is two or more layers.

The thermal transfer image receiving sheet of the present invention is obtained by laminating a porous layer on a base sheet. The thermal transfer image receiving sheet is formed by laminating a base sheet, a porous layer and a receiving layer described later in this order, and the porous layer is at least on the same side as the side on which the receiving layer is provided. Is provided. The porous layer can be directly laminated on the base sheet.
Since the thermal transfer image receiving sheet is a laminate of porous layers, it has excellent heat resistance and cushioning properties.

The porous layer is a layer containing highly heat-resistant particles and hollow particles.
The porous layer may have a single-layer structure, or may have a laminated structure in which two or more layers having different types, content, etc., such as highly heat-resistant particles and hollow particles, are laminated.
In the present specification, the “layer containing the high heat-resistant particles and the hollow particles” may contain the high heat-resistant particles and the hollow particles in one layer, or contains the high heat-resistant particles but the hollow particles. And a layered structure in which a layer not containing high heat-resistant particles but a layer containing hollow particles is stacked.
The “layer containing high heat resistant particles and hollow particles” in the present invention generally has a structure in which high heat resistant particles and hollow particles are supported on a binder resin.

The said hollow particle is mix | blended in order to provide heat insulation, a cushioning property, etc. to a thermal transfer image receiving sheet.
The hollow particles may be either expanded particles or non-expanded particles, and examples thereof include organic hollow particles such as a crosslinked styrene-acrylic polymer, and inorganic hollow glass bodies. When foamed particles are used, they may be either independent foamed particles or continuous foamed particles.
The hollow particles preferably have a hollow ratio of 40% or more, more preferably 50% or more, and preferably 70% or less. When the hollow ratio is less than 40%, the heat transfer image-receiving sheet may not be sufficiently provided with heat insulation and cushioning properties.
The hollow particles generally have a volume average particle size of 0.1 to 15 μm, preferably 0.1 to 10 μm. If it is less than 0.1 μm, the hollow ratio may not be within the above range, and the cost may increase. If it exceeds 15 μm, particles derived from the image may be lost in the obtained sheet.

In each layer constituting the porous layer, the hollow particles are usually 20 to 90% by mass, preferably 40 to 60% by mass. When it is less than 20% by mass, there are few voids in each layer and sufficient heat insulating properties and cushioning properties may not be obtained. When it exceeds 90% by mass, the adhesive force is insufficient and the substrate sheet may be peeled off. is there.

The high heat-resistant particles in the porous layer are added for the purpose of preventing image quality deterioration such as embossing.
When the said porous layer is a laminated structure, it may contain a high heat resistant particle in one part layer, and may contain a high heat resistant particle in all the layers.

The high heat resistant particles may be those having a heat resistant temperature of usually 200 ° C. or higher, preferably 300 ° C. or higher.
Although the said heat-resistant temperature changes according to the constituent material of particle | grains, manufacturing conditions, etc., it is so preferable that it is high, and an upper limit is not specifically limited.
In this specification, the heat-resistant temperature is the maximum temperature at which particles are not destroyed by heat, and is measured by a thermal stress strain measuring device [TMA] (name of equipment used: SSC-5200, manufactured by Seiko Electronics Industry Co., Ltd.). is there.

The high heat-resistant particles are not particularly limited, and examples thereof include those made of resin, glass, and the like.
Examples of the resin constituting the high heat resistant particles include styrene resins, (meth) acrylic resins, phenol resins, fluorine resins, polyamide resins, polyimide resins, polycarbonate resins, polyether resins, and the like. Can be mentioned.

The high heat resistant particles may be hollow as long as they have a heat resistant temperature within the above range. In the present specification, hereinafter, the high heat-resistant particles that are hollow may be referred to as “high heat-resistant hollow particles”. In the present specification, the “hollow particles” contained separately from the high heat resistant particles in the porous layer are a concept that does not include the high heat resistant hollow particles.
The hollow ratio of the high heat-resistant hollow particles may be smaller than the hollow ratio of the hollow particles or less than 40% when contained in a single layer together with the hollow particles.
In the present invention, when the high heat resistant particles and the hollow particles are contained in a single layer, the hollow particles have a hollow ratio of 40% or more, and the high heat resistant particles have a hollow ratio of the hollow ratio of the hollow particles. It is more preferable that it is smaller.

In the present invention, when the high heat resistant particles and the hollow particles are contained in a single layer, the high heat resistant particles are usually 20 to 40% by mass, preferably 30% of the total amount of the high heat resistant particles and the hollow particles. It can be set to -35 mass%.
In the present invention, the voids of the layer constituting the porous layer need only exist as much as formed when the hollow particles are contained within the above range. When the layer constituting the porous layer contains high heat-resistant hollow particles as the high heat-resistant particles, the voids are formed by the hollow particles and the high heat-resistant hollow particles, so that the high heat-resistant particles and the hollow particles are a single layer. Even if contained, the heat-resistant hollow particles may be contained in a larger amount than the hollow particles. For example, when the hollow ratio is 30%, the high heat-resistant hollow particles may be contained in an amount of 300% by mass or less of the hollow particles, or may be contained in an amount of 400% by mass or less. .

The porous layer may have a layer made of a binder resin containing highly heat-resistant particles and hollow particles.
In the layer, the hollow particles and the high heat-resistant particles can be contained in a range not exceeding 90% by mass.
When it is assumed that the hollow particles have a fine structure (cubic fine structure, hexagonal fine structure, or a mixed structure thereof), the layer has a structure in which voids formed between hollow particles are filled with high heat resistant particles. It is preferable to have.

In the present invention, when the high heat resistant particles and the hollow particles are contained in a single layer, the high heat resistant particles have a volume average particle size that is usually not more than the volume average particle size of the hollow particles used, and the hollow It is preferably about 1/3 or less of the volume average particle diameter of the particles.
In the above layer, the ratio (V ₁ : V ₂ ) of the volume (V ₁ ) occupied by the high heat resistant particles and the volume (V ₂ ) occupied by the hollow particles is preferably 20:80 to 40:60. 20:80 to 30:70 is more preferable.
When V ₂ is larger than the above range, when printing is performed by mixing three colors, the print density may be reduced and defects such as embossing may occur in the image. When V ₂ is smaller than the above range, the image receiving layer The sensitivity of the image quality may decrease, and the image quality may deteriorate.
In the present invention, when the high heat-resistant particles and the hollow particles are contained in a single layer, a receiving layer with high smoothness is formed, and a high-quality image without density unevenness or missing dots can be obtained during image formation. Thus, it is particularly preferable that the volume average particle diameter of the high heat-resistant particles is 1/3 or less of the volume average particle diameter of the hollow particles, and the ratio (V ₁ : V ₂ ) is in the above range.

Examples of the binder resin in the porous layer include urethane resins; ester resins; vinyl resins such as vinyl acetate and polyvinyl alcohol; acrylic resins; cellulose resins; The resin may be dissolved in water, dispersed, or may form an emulsion. In the present invention, since the receiving layer is formed using an aqueous coating solution composed of a receiving layer forming resin described later, unlike the conventional case where the receiving layer is formed using an organic solvent, the binder resin in the porous layer is used as a binder resin. Need not be limited to solvent-resistant resins, and can be widely selected.
In the porous layer, the binder resin may be composed of one kind or a mixture of two or more kinds of binder resins.
The binder resin is preferably an ester resin from the viewpoint of adhesiveness to the base sheet.

In addition to the hollow particles, the high heat resistant particles, and the binder resin, the porous layer is a known stabilizer, antistatic agent, ultraviolet absorber, fluorescent whitening as long as it does not impair properties such as heat insulation and cushioning properties. An additive such as an agent, a processing aid, and a plasticizer may be appropriately blended.

The porous layer may have a laminated structure as described above.
The porous layer includes, for example, a three-layer structure composed of a high heat-resistant particle layer / hollow particle layer / high heat-resistant particle layer, a three-layer structure composed of a high heat-resistant particle layer / general-purpose resin layer / hollow particle layer, and a high heat-resistant particle layer / hollow. A three-layer structure composed of a particle layer / a high heat-resistant particle / hollow particle mixed layer may be used. Among them, the high heat-resistant particle layer composed of the high heat-resistant particles and the binder resin (A), and the hollow particles And a hollow particle layer consisting of at least two layers of a binder resin (B) is preferable, and the hollow particle layer and the high heat-resistant particle layer are laminated on the base sheet in this order from the base sheet side. A two-layer structure is more preferable.
Examples of the binder resin (A) and the binder resin (B) include the above-described binder resins, and the binder resins may be of the same type or different types. .

The thickness of the porous layer is preferably 5 to 40 μm in total after drying. If it is less than 5 μm, the heat insulating properties and cushioning properties tend to be insufficient. If it exceeds 40 μm, the thermal transfer image-receiving sheet as a whole may become too thick depending on the application.
When the porous layer has a laminated structure, the thickness of the hollow particle layer after drying is preferably 5 to 36 μm, and more preferably 10 to 20 μm. The high heat-resistant particle layer preferably has a post-drying film thickness of 4 to 12 μm, and more preferably 5 to 10 μm.

In the thermal transfer image-receiving sheet of the present invention, the receptor layer is formed using an aqueous coating liquid (hereinafter sometimes referred to as “receptor layer coating liquid”) made of a receptor layer-forming resin.
The receptor layer may be formed directly on the porous layer described above, or may be formed on an intermediate layer formed on the porous layer described above.

Examples of the receiving layer forming resin include polyolefin resin, polyvinyl resin, polyester resin, polycarbonate resin, polyamide resin, poly (meth) acrylic acid resin, cellulose derivative resin, and polyether resin.
The receiving layer coating liquid may contain only one type of receiving layer forming resin, or may contain two or more types of receiving layer forming resins having different monomer compositions, average molecular weights, and the like. There may be.

As the above-mentioned receiving layer forming resin, a polyvinyl resin is particularly preferable.
Examples of the polyvinyl resins include vinyl chloride / vinyl acetate copolymers, vinyl chloride / acrylic compound copolymers, ethylene / vinyl chloride / acrylic ester copolymers, ethylene / vinyl acetate / vinyl chloride copolymers, and the like. It is done.

The vinyl chloride / vinyl acetate copolymer is not particularly limited as long as it is a copolymer composed of vinyl chloride and vinyl acetate, and can be copolymerized with these essential monomers in addition to vinyl chloride and vinyl acetate. The polymer may be obtained by polymerizing a small amount, but is preferably a vinyl chloride / vinyl acetate binary copolymer.

The vinyl chloride / acrylic compound copolymer is not particularly limited as long as it is a copolymer composed of vinyl chloride and an acrylic compound, and can be copolymerized with these essential monomers in addition to vinyl chloride and an acrylic compound. The polymer may be a copolymer of a small amount, but is preferably a vinyl chloride / acrylic compound binary copolymer.
In the present specification, “acrylic compound” means (meth) acrylic acid and / or an alkyl ester thereof.
Examples of the acrylic compound include acrylic acid; acrylic acid salts such as calcium acrylate, zinc acrylate, magnesium acrylate, and aluminum acrylate; methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and 2-ethoxyethyl. Acrylic esters such as acrylate, 2-hydroxyethyl acrylate, n-stearyl acrylate, tetrahydrofurfuryl acrylate, trimethylolpropane triacrylate; methacrylic acid; methyl methacrylate, ethyl methacrylate, t-butyl methacrylate, tridecyl methacrylate, Cyclohexyl methacrylate, triethylene glycol dimethacrylate, 1,3-butylene dimethacrylate, trimethylol trimethacrylate Methacrylic acid esters of bread and the like.

The ethylene / vinyl chloride / acrylic acid ester copolymer and the ethylene / vinyl acetate / vinyl chloride copolymer (hereinafter, each copolymer is collectively referred to as “ethylene / vinyl chloride copolymer”). The copolymer is not particularly limited as long as it is a copolymer obtained by polymerizing at least three monomers of ethylene, vinyl chloride and acrylate, or three monomers of ethylene, vinyl acetate and vinyl chloride. A small amount of a small amount of monomer may be copolymerized in addition to the seed monomer, but ethylene / vinyl chloride / acrylic acid ester terpolymer or ethylene / vinyl acetate / vinyl chloride ternary copolymer. A polymer is preferred.
The ethylene / vinyl acetate / vinyl chloride copolymer may be a copolymer of ethylene / vinyl acetate copolymer [EVA] and vinyl chloride. As the EVA / vinyl chloride copolymer, EVA may be chlorinated. It may be one obtained by graft copolymerization of vinyl, or one obtained by graft copolymerization of EVA with polyvinyl chloride. EVA includes those in which all or part of vinyl acetate units in the copolymer is saponified.

In the present invention, “acrylic acid ester” constituting the ethylene / vinyl chloride / acrylic acid ester copolymer is a concept including a methacrylic acid ester in addition to the acrylic acid ester. Examples of the acrylic acid ester include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-ethoxyethyl acrylate, 2-hydroxyethyl acrylate, n-stearyl acrylate, tetrahydrofurfuryl acrylate, and trimethylolpropane triacrylate. Examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, t-butyl methacrylate, tridecyl methacrylate, cyclohexyl methacrylate, triethylene glycol dimethacrylate, 1,3-methacrylic acid 1,3- Examples include butylene and trimethylolpropane trimethacrylate.

The receptor layer-forming resin preferably has a glass transition temperature of 20 ° C. or higher.
In the present invention, when the receptor layer-forming resin having a glass transition temperature within the above range is included as the receptor layer, a thermal transfer image-receiving sheet particularly excellent in releasability can be obtained.
The glass transition temperature is more preferably 30 ° C. or higher, and still more preferably 40 ° C. or higher.

The receiving layer coating solution is not particularly limited as long as it is an aqueous coating solution made of a receiving layer forming resin, and the aqueous coating solution usually contains a receiving layer forming resin and water. For example, the receptor layer-forming resin may be dispersed in water, or the receptor layer-forming resin may be dissolved in water, but is preferably composed of a receptor layer-forming resin emulsion.
The emulsion may contain, for example, an emulsifier such as a nonionic surfactant, a cationic surfactant, and an anionic surfactant.
In the emulsion, the emulsifier is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of each copolymer.
In addition to the above-mentioned receptor layer-forming resin and the above-mentioned emulsifier, the above emulsion may be formed by blending known additives for the purpose of storage stability and the like.
Examples of the emulsion include a vinyl chloride / vinyl acetate copolymer emulsion, a vinyl chloride / acrylic compound copolymer emulsion, an ethylene / vinyl chloride / acrylate copolymer emulsion, or an ethylene / vinyl acetate / vinyl chloride copolymer. A polymer emulsion etc. are mentioned.
In the present invention, as the emulsion, for example, commercially available products such as VINYBRAN 601 and VINYBRAN 276 (all manufactured by Nissin Chemical Industry Co., Ltd.), SE1320, and S-830 (all manufactured by Sumika Chemtex) can be used. it can.

In the present invention, the receiving layer coating liquid may also contain a release agent in order to prevent thermal fusion with the thermal transfer sheet during image formation.
Examples of the release agent include known ones such as silicone oil, phosphate ester compounds, and fluorine compounds, but silicone oil is particularly preferable.
Examples of the silicone oil include epoxy-modified silicone oil, alkyl-modified silicone oil, amino-modified silicone oil, fluorine-modified silicone oil, phenyl-modified silicone oil, epoxy / polyether-modified silicone oil, vinyl-modified silicone oil, hydrogen-modified silicone oil, etc. Modified silicone oil is preferred.
The release agent is preferably added so as to be about 0.5 to 30 parts by mass with respect to 100 parts by mass of each of the above-mentioned copolymers.

The receiving layer coating solution is also formed by appropriately blending known additives such as an antioxidant, an ultraviolet absorber, a light stabilizer, a filler, a pigment, an antistatic agent, a plasticizer, and a hot-melt material. It may be a thing.

Examples of the antioxidant include chroman compounds, coumarone compounds, phenol compounds, hydroquinone derivatives, hindered amine derivatives, spiroindane compounds, sulfur compounds, phosphorus compounds, and the like known compounds for improving image durability. Can be mentioned.

Examples of the ultraviolet absorber and the light stabilizer include known compounds described in JP-A-1-204788.
Examples of the filler include inorganic compound fine particles and organic compound resin particles.
Examples of the inorganic compound fine particles include silica gel, calcium carbonate, titanium oxide, acidic clay, activated clay, and alumina. Examples of the organic compound resin particles include fluorine resin particles, guanamine resin particles, acrylic resin particles, silicon. Examples thereof include resin particles such as resin particles.

Examples of the pigment include known compounds such as titanium white, calcium carbonate, zinc oxide, barium sulfate, silica, talc, clay, kaolin, activated clay, and acid clay.
Examples of the antistatic agent include known compounds such as a cationic surfactant, an anionic surfactant, a nonionic surfactant, a polymer antistatic agent, and conductive fine particles.

The plasticizer and the heat-meltable substance are usually added to promote transfer of the obtained thermal transfer image-receiving sheet.
Examples of the plasticizer include known compounds such as phthalic acid plasticizers, phosphate ester plasticizers, and polyester plasticizers.
Examples of the hot-melt material include known compounds having an action of promoting transfer, such as alcohols, ketones, and higher fatty acid esters.

The receiving layer coating solution usually has a solid content concentration of 5% by mass or more. The upper limit of the solid content concentration is usually 50% by mass or less because if the concentration becomes too high, the storage stability may decrease and the viscosity may increase.

As described above, the thermal transfer image receiving sheet of the present invention may be formed by laminating an intermediate layer in addition to the receiving layer and the porous layer. The intermediate layer can be provided, for example, between the receiving layer and the porous layer.
The thermal transfer image-receiving sheet of the present invention may be excellent in, for example, cushioning properties, barrier properties, interlayer adhesion properties, whiteness properties, concealing properties, antistatic properties, etc. by providing the intermediate layer. However, even if a resin film such as a polyethylene terephthalate [PET] resin film is not used, the strength is excellent, and it is not necessary to use such a resin film. An image without unevenness can be obtained. The thermal transfer image-receiving sheet of the present invention can also be excellent in interlayer adhesion between the porous layer and the receiving layer without using a primer as the intermediate layer.

Examples of the resin forming the intermediate layer and other polymers include gelatin, casein and the like in addition to the resins exemplified as the resin constituting the porous layer.
Since the conventional thermal transfer image-receiving sheet is formed by dissolving the resin in the organic solvent in the receiving layer, the resin forming the intermediate layer is limited to the solvent-resistant resin, but the thermal transfer image-receiving sheet of the present invention Since the receiving layer is formed using the above-described receiving layer-forming resin and a coating solution containing water, the resin for forming the intermediate layer should be selected without being limited to the solvent-resistant resin. Can do.

The intermediate layer may be a layer to which a water-soluble polymer is added, for example.
Examples of the water-soluble polymer include polysaccharides such as cellulose resin, starch and agar; proteins such as casein and gelatin; polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer. Vinyl resins such as vinyl acetate- (meth) acrylic copolymer, vinyl acetate-veova copolymer, (meth) acrylic resin, styrene- (meth) acrylic copolymer, styrene resin; melamine resin, urea resin, Polyamide resins such as benzoguanamine resins; polyesters; polyurethanes and the like.
In the present invention, the water-soluble polymer is completely dissolved in an aqueous solvent (particle size 0.01 μm or less), colloidal dispersion (particle size 0.01 to 0.1 μm), emulsion (particle size 0.1 to 1 μm). Or the polymer which will be in the state of a slurry (particle size of 1 micrometer or more) is meant.

When an adhesive layer containing urethane resin, polyester resin or the like as a constituent component is provided as the intermediate layer, a thermal transfer image receiving sheet having excellent interlayer adhesion can be obtained.
Moreover, when the thermoplastic resin having active hydrogen and a curing agent such as an isocyanate compound are used in combination as the intermediate layer, a thermal transfer image-receiving sheet having further excellent interlayer adhesion can be obtained.

For example, when a fluorescent brightener is added to the intermediate layer, white color can be imparted to the thermal transfer image receiving sheet.
The fluorescent brightening agent is not particularly limited, and conventionally known fluorescent brightening agents can be used. For example, stilbene fluorescent brighteners, distilbene fluorescent brighteners, benzoxazole fluorescent brighteners, styryl- Oxazole fluorescent whitening agent, pyrene-oxazole fluorescent whitening agent, coumarin fluorescent whitening agent, aminocoumarin fluorescent whitening agent, imidazole fluorescent whitening agent, benzimidazole fluorescent whitening agent, pyrazoline fluorescent whitening Examples include whitening agents, distyryl-biphenyl fluorescent whitening agents, and the like.
In the thermal transfer image-receiving sheet of the present invention, the whiteness can be adjusted by appropriately selecting the type and amount of the fluorescent whitening agent.

When titanium oxide is added to the intermediate layer, it is possible to obtain a thermal transfer image receiving sheet that conceals glare and unevenness of the base sheet.
Examples of the titanium oxide include rutile type titanium oxide and anatase type titanium oxide, and anatase type titanium oxide is preferable in terms of whiteness.
When the intermediate layer is made of the water-soluble resin described above, the titanium oxide may be added with a hydrophilic treatment applied to the surface, or a dispersant such as a surfactant may be appropriately added and dispersed.

For example, when a conductive inorganic filler, an organic conductive agent or the like is added to the intermediate layer, a thermal transfer image-receiving sheet having antistatic properties can be obtained.

The thermal transfer image-receiving sheet of the present invention has a back layer on the surface opposite to the receiving layer-forming side of the base sheet for the purpose of improving the mechanical transportability of the sheet, preventing curling, writing properties, preventing charging, etc. There may be.
In the thermal transfer image-receiving sheet of the present invention, the back layer may be composed of only one layer, or may be composed of two or more layers having different compositions and the like. .

The said back surface layer can be formed from the resin similar to what was illustrated as resin which forms the said intermediate | middle layer, and another polymer.
When forming the back layer, for example, (1) In addition to the above-exemplified resins, etc., an appropriate amount of organic filler or inorganic filler is added, or (2) a resin having high lubricity, such as a polyolefin resin or a cellulose resin. When used, it is possible to obtain a thermal transfer image receiving sheet with improved transportability during printing.

When the back layer is formed, curling of the obtained thermal transfer image-receiving sheet can be prevented when a water-holding resin such as polyvinyl alcohol or polyethylene glycol is used as a main component.
When the back layer is formed, when fillers, pigments, and the like exemplified as additives in the above-described receiving layer are blended, writing property can be imparted to the resulting thermal transfer image-receiving sheet.

In order to obtain an antistatic function, the back layer is made by adding a conductive resin such as an acrylic resin and / or various antistatic agents such as fatty acid ester, sulfate ester, phosphate ester, and ethylene oxide adduct. There may be.
The amount of the antistatic agent used varies depending on the layer to which the antistatic agent is added, the antistatic agent used, and the like, but the surface electrical resistance value of the thermal transfer image-receiving sheet is 10 ¹³ in order to prevent paper feeding troubles. Usually, it is preferable to use the coating amount so as to be an amount of 0.01 to 3 g / m ² after drying so as to be Ω / cm ² or less.

If the coating amount is 3 g / m ² or less as a whole after drying, the above-mentioned back layer can usually exhibit various intended effects.

The thermal transfer image-receiving sheet of the present invention has, for example, (1) a laminate of the porous layer on a substrate sheet, and (2) a laminate of a receiving layer on the porous layer or an intermediate layer laminated on the porous layer. Can be created.

(1) The porous layer is laminated by preparing a porous layer coating solution prepared by dissolving or dispersing the binder resin and hollow particles and / or high heat resistant particles in an aqueous medium. Can be carried out by coating on a substrate sheet and drying.

The porous layer coating liquid preferably has a binder resin solid content of 10 to 30 parts by mass with respect to 100 parts by mass of the solid content of the hollow particles. When the binder resin solid content is 10 parts by mass or less, the strength of the porous layer may be weakened and peel off. When the binder resin solid content is 30 parts by mass or more, voids in the porous layer are reduced. As a result, the heat insulating property and cushioning property of the porous layer may deteriorate.
Examples of the aqueous medium in the porous layer coating liquid include water and alcohols such as ethanol and propanol.

The porous layer coating solution can be applied by a general method such as roll coating, bar coating, gravure coating, gravure reverse coating, comma coating, die coating, or lip coating.
The porous layer coating liquid is preferably applied such that the porous layer has a thickness within the above-mentioned range.
In the coating of the porous layer, drying is preferably performed at a temperature of 50 to 150 ° C., although it varies depending on the composition of the coating solution used.

(2) Lamination of the receiving layer can be performed, for example, by preparing the above-described receiving layer coating solution and coating the receiving layer coating solution on the porous layer or the intermediate layer.

Application | coating of the said coating liquid for receiving layers can be performed by the above-mentioned general method.
The receiving layer coating solution is preferably applied such that the receiving layer has an amount of 0.5 to 10 g / m ² after drying.
In the coating of the receptor layer, drying is preferably performed at a temperature of 50 to 150 ° C., although it varies depending on the composition of the coating solution used.

The method for forming the intermediate layer and the back layer in the thermal transfer image-receiving sheet of the present invention is not particularly limited. For example, a method of preparing and applying a coating liquid comprising the above-described constituents, drying and baking, etc. Can be mentioned.
In the above-described coating of the intermediate layer and the back layer, as a solvent for preparing the coating liquid, for example, in addition to those exemplified with respect to the above-mentioned porous layer coating liquid, aromatics such as toluene, xylene, chlorobenzene, etc. Ketones such as acetone and methyl ethyl ketone; ester solvents such as ethyl acetate and butyl acetate; ethers such as tetrahydrofuran and dioxane; chlorinated solvents such as chloroform and trichloroethylene; nitrogen-containing compounds such as dimethylformamide and N-methylpyrrolidone Solvents such as system solvents; dimethyl sulfoxide;

In each coating for forming each layer in the present invention, a known resin surface modification such as primer treatment may be performed after coating in order to smooth the layer surface.

The method for forming an image on the image receiving surface of the thermal transfer image receiving sheet of the present invention is not particularly limited, and can be performed by a known thermal diffusion transfer method (sublimation thermal transfer method).
The thermal transfer sheet used for the image formation is not particularly limited. For example, a conventional thermal transfer sheet in which a dye layer containing a thermal diffusion dye (sublimation dye) is provided on a base sheet is used. Can do.
In particular, the thermal transfer sheet is preferably composed of a dye layer made of a polyacetal resin and a base sheet made of a polyester resin.

The thermal transfer image receiving sheet of the present invention may be formed by transferring a protective layer to the image forming surface after forming an image on the image receiving surface of the thermal transfer image receiving sheet. By transferring the protective layer, the light resistance of the obtained sheet can be further improved, and the durability such as sebum resistance can be improved.

The protective layer can be formed from a known protective layer forming resin such as a thermoplastic resin, a heat crosslinkable resin, or an ionizing radiation crosslinkable resin.
Examples of the thermoplastic resin include polyester resins, polycarbonate resins, urethane resins, epoxy resins, phenoxy resins, and resins obtained by modifying these resins with silicone.
The protective layer may be formed by blending one or more thermoplastic resins, thermally crosslinkable resins, and ionizing radiation crosslinked resins.
In addition to the resin, the protective layer may be formed by appropriately blending the additives described for the receiving layer, such as an ultraviolet blocking resin, an ultraviolet absorber, a conductive resin, and a filler, as necessary. .

The protective layer may be composed of only one layer, or may be composed of two or more layers having different compositions and the like.
The protective layer may have an adhesive layer in order to improve transferability to the thermal transfer image-receiving sheet (printed material), adhesion, and the like.
Although the said contact bonding layer can be formed from a conventionally well-known thing, it is more preferable to form from a thermoplastic resin whose glass transition temperature (Tg) is 50-80 degreeC.
Examples of the thermoplastic resin include those having a glass transition temperature within the above range from polyester resin, vinyl chloride-vinyl acetate copolymer resin, acrylic resin, butyral resin, epoxy resin, polyamide resin, vinyl chloride resin, and the like. It is preferable to select. In terms of adhesiveness, the thermoplastic resin preferably has a smaller average molecular weight.
The said protective layer is 0.1-30 micrometers normally in the whole layer, Preferably it can be set as the thickness of 0.5-5 micrometers.

Since the thermal transfer image-receiving sheet of the present invention has the above-described configuration, it can be widely selected without being limited to the solvent-resistant resin in the intermediate layer and the porous layer, and blocks the organic solvent used in the conventional receiving layer. It is possible to obtain an image with excellent sensitivity, glossiness and smoothness, and reduced density unevenness and white spots in highlight areas. is there.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.
In the text, “part” or “%” is based on mass unless otherwise specified.

Example 1
1. Preparation of base sheet White base paper (thickness: 168 g / m ² , manufactured by Mitsubishi Paper Industries Co., Ltd.) was smoothed with a super calendar to give a Beck smoothness of 2000 seconds, and then a polypropylene resin (product name: Sun Allomer PHA03A, Sun Allomer Co., Ltd.) is laminated with an extrusion coater to a thickness of 30 μm after drying, and the other surface is dried with a high-density polyethylene resin (product name: J-Rex KH578A, manufactured by Nippon Polyolefin Co., Ltd.) on the extrusion coater. A base sheet was prepared by laminating to a thickness of 30 μm.
2. Formation of porous layer (1) On the base material sheet, a coating liquid for porous layer A having the following composition was applied by gravure coating so as to be 5 g / m ^2, and then dried (110 ° C., 1 Minutes) to form a porous layer A.
(Coating solution composition for porous layer A)
・ Acrylic hollow particles (Product name: Ropaque HP-1055, non-crosslinked type, hollow ratio 55%, hollow particle diameter 1.0 μm, solid content 26.50%, manufactured by Rohm and Haas) 100 parts ・ Polyvinyl alcohol [PVA ] (Product name: KM-11 solid content 10%, manufactured by Nippon Synthetic Chemical Co., Ltd.) 29.4 parts, water 5 parts, isopropyl alcohol [IPA] 10 parts hollow particles / binder resin ratio = 9/1
(2) Subsequently, on the obtained porous layer A, a coating solution for porous layer B having the following composition was applied by gravure coating so as to be ² g / m ² after drying, and dried (110 ° C., 1 minute) ) To form a porous layer B.
(Coating solution composition for porous layer B)
Highly crosslinked styrene-acrylic polymer hollow particles (Product name: AE-866, highly crosslinked type, solid content 20%, hollow ratio 30%, volume average particle size 0.3 μm, heat resistant temperature 300 ° C., manufactured by JSR)
100 parts polyester resin (Product name: AP-40, solid content 20%, manufactured by Dainippon Ink & Chemicals, Inc.)
25 parts / water 5 parts / IPA 10 parts hollow particle / binder resin ratio = 4/1

3. Preparation of Receiving Layer On the porous layer B, a receiving layer coating liquid (I) having the following composition was applied by gravure coating so as to have an amount of 4.0 g / m ² after drying and dried (110 ° C., 1 minute) to obtain the thermal transfer image-receiving sheet of the present invention.
(Coating fluid for receiving layer (I) composition)
・ Vinyl chloride / vinyl acetate copolymer emulsion (Viniblanc 601, solid concentration 43%; manufactured by Nissin Chemical Industry Co., Ltd.) 100 parts ・ Polyether modified silicone (Product name: SH-3771, Toray Dow Corning Silicone) 2.5 parts ・ Curing agent (Smiles Resin 613, manufactured by Sumitomo Chemical Co., Ltd.) 0.5 parts ・ Catalyst A (For Sumires Resin 613, manufactured by Sumitomo Chemical Co., Ltd.) 0.1 parts ・ Water 10 parts

Example 2
A thermal transfer image receiving sheet was obtained in the same manner as in Example 1, except that the receiving layer coating solution (II) was used instead of the receiving layer coating solution (I).

(Coating fluid for receiving layer (II) composition)
Polyester resin emulsion (MD-1200, solid content concentration 43%; manufactured by Toyobo Co., Ltd.)
100 parts polyether modified silicone (product name: SH-3771, manufactured by Toray Dow Corning Silicone) 1.75 parts curing agent (Smiles Resin 613, manufactured by Sumitomo Chemical Co.) 0.35 parts Catalyst A (For Sumire's Resin 613, manufactured by Sumitomo Chemical Co., Ltd.) 0.07 parts, water 10 parts

Example 3
A thermal transfer image receiving sheet was obtained in the same manner as in Example 1 except that the porous layer B was coated on the porous layer B after the porous layer B was coated on the substrate sheet.

Comparative Example 1
A thermal transfer image receiving sheet was obtained in the same manner as in Example 1 except that the porous layer A was applied instead of the porous layer B.

Comparative Example 2
A thermal transfer image receiving sheet was obtained in the same manner as in Example 1 except that the porous layer B was applied instead of the porous layer A.

Comparative Example 3
After the two porous layers A are applied, a polyethylene terephthalate [PET] film (manufactured by Toray Industries, Inc., thickness 25 μm) is pressure-bonded at 130 ° C. with a liminator to form a PET layer on the PET layer. A primer coating solution having the following composition is applied after drying to 2 g / m ² , dried (110 ° C., 1 minute) to form a primer layer, and then a receiving layer is applied to obtain a thermal transfer image receiving sheet. It was.
(Primer coating solution)
WR-905 (polyester resin, solid content 20%, manufactured by Nippon Synthetic Chemical Co., Ltd.)
100 parts, water 5 parts, IPA 10 parts

Test Example The thermal transfer image-receiving sheet obtained from each example and each comparative example was evaluated by the following method.
<Evaluation method>
1. Measurement of dyeing property (sensitivity) (1) Yellow (Y), Magellan (M) using sublimation transfer printer CP-200 (manufactured by Canon) and thermal transfer sheet for sublimation transfer printer CP-200 (manufactured by Canon) ), Cyan (C), and protective layer in this order, a gradation image was formed under the following conditions.
(Print printing conditions)
Gradation printing: The duty ratio of each divided pulse is fixed at 40%, and the number of pulses per line period is increased by 17 from 0 to 255, thereby controlling 16 gradations from 1 to 16 steps. A gradation pattern consisting of gradation was printed. The printing environment was set to 25 ° C. and humidity 40%.
Transfer of protective layer: The number of pulses per line period was fixed at 210, solid printing was performed, and the protective layer was transferred to the entire print surface.

(2) About each printed matter, the maximum reflection density (measurement range: 3 Bk) was measured using the chromaticity meter (Macbeth densitometer RD-918; Macbeth company make).
2. Density unevenness (1) The above 1. except that the number of pulses per line period is fixed to 210 and a gray solid print is printed. A printed material was prepared under the same conditions as in (1).
(2) The obtained printed matter was visually evaluated based on the following criteria.
○: Conspicuous density unevenness was not confirmed.
X: Density unevenness was observed in each part.

3. White spot 1. (1) and 2. The printed matter obtained from (1) was visually evaluated based on the following evaluation criteria as to whether white spots had occurred. Further, the above 1. except that the printing environment is 0 ° C. and normal pressure. (1) and 2. Printing was performed in the same manner as in (1), and the obtained printed matter was also visually evaluated in the same manner.
○: No white spots could be confirmed in both solid print and gradation print.
X: White spots were confirmed in either the solid print or the gradation print.
Table 1 shows the results.

From each evaluation result, a resin that is not resistant to organic solvents can be used as the binder resin in the porous layer, and in the examples, white spots did not occur even at low-temperature printing.
It was found that the printed matter (thermal transfer image-receiving sheet of Example 1 and Example 2) in which a hollow particle layer and a highly heat-resistant hollow particle layer (highly crosslinked type) were laminated in order from the base sheet side was particularly excellent in sensitivity. . On the other hand, the thermal transfer image-receiving sheet of Comparative Example 1 in which the porous layer contains only hollow particles causes density unevenness during printing, and the thermal transfer image-receiving sheet of Comparative Example 2 in which the porous layer contains only high heat-resistant particles is used during printing. It has been found that the thermal transfer image-receiving sheet of Comparative Example 3 in which the porous layer is composed only of hollow particles has a low sensitivity, and a PET film is provided, and white spots are produced in low-temperature printing.

Since the thermal transfer image-receiving sheet of the present invention has the above-described configuration, it can be widely selected without being limited to the solvent-resistant resin in the intermediate layer and the porous layer, and blocks the organic solvent used in the conventional receiving layer. It is possible to obtain an image with excellent sensitivity, glossiness and smoothness, and reduced density unevenness and white spots in highlight areas. is there.

Claims (7)

In the thermal transfer image receiving sheet formed by laminating the porous layer and the receiving layer in this order on the base sheet,
The base sheet is formed by laminating resin layers on both sides of paper mainly composed of wood pulp,
The porous layer contains high heat-resistant hollow particles and hollow particles, and includes a high heat-resistant hollow particle layer composed of the high heat-resistant hollow particles and a binder resin (A), and a hollow particle composed of the hollow particles and the binder resin (B). A layer composed of at least two layers,
The receiving layer is formed using an aqueous coating solution made of a receiving layer forming resin,
The high heat-resistant hollow particle layer was formed using a porous layer coating solution obtained by dissolving or dispersing the high heat-resistant hollow particles and a binder resin (A) made of an ester resin or polyvinyl alcohol in an aqueous medium. Is,
The hollow particle layer is formed using a coating liquid for a porous layer in which the hollow particles and a binder resin (B) made of an ester resin or polyvinyl alcohol are dissolved or dispersed in an aqueous medium,
The high heat resistant hollow particles have a heat resistant temperature of 200 ° C. or higher. The hollow particles have a hollow ratio of 40% or more,
The thermal transfer image receiving sheet according to claim 1, wherein the high heat-resistant hollow particles have a hollowness smaller than that of the hollow particles. The thermal transfer image receiving apparatus according to claim 1 or 2, wherein the porous layer has a two-layer structure in which the hollow particle layer and the high heat resistant hollow particle layer are laminated in this order from the substrate sheet side on the substrate sheet. Sheet. The receiving layer is made of a vinyl chloride / vinyl acetate copolymer emulsion, a vinyl chloride / acrylic compound copolymer emulsion, an ethylene / vinyl chloride / acrylic ester copolymer emulsion, or an ethylene / vinyl acetate / vinyl chloride copolymer emulsion. The thermal transfer image receiving sheet according to claim 1, wherein the thermal transfer image receiving sheet is formed by using the thermal transfer image receiving sheet. The thermal transfer image-receiving sheet according to any one of claims 1 to 4, wherein the paper mainly composed of wood pulp is a base paper having a Beck smoothness of 1000 seconds or more. The thermal transfer image receiving sheet according to claim 1, wherein the resin layer has a thickness of 10 to 40 μm. The thermal transfer image receiving sheet according to any one of claims 1 to 6, wherein an image is formed on the image receiving surface of the thermal transfer image receiving sheet, and then a protective layer is transferred to the image forming surface.