JP2018183891A - Thermal transfer image receiving sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal transfer image receiving sheet for sublimation type heat-sensitive transfer recording, capable of suppressing defective separation at dye transfer even if a content of a release agent is reduced in a dye receiving layer, while maintaining a sufficient image quality in printing by a high-speed printer.SOLUTION: A thermal transfer image receiving sheet includes: a sheet-like base material 11; a heat insulation layer 12 formed on the base material 11; a second image receiving layer 13 formed on the heat insulation layer 12; and a dye receiving layer 14 formed on the second image receiving layer 13. The second image receiving layer 13 is composed of a material including a microcapsule with an average diameter of 1 μm or less, containing a substance with a melting point of 50-60°C, and a binding material of the microcapsule. A total thickness of the dye receiving layer 14 and the second image receiving layer 13 is five or more times of an average diameter of the microcapsule.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a thermal transfer image receiving sheet used for sublimation type thermal transfer recording.

Sublimation-type thermal transfer recording is a process in which a thermal transfer sheet containing a sublimation dye is brought into close contact with the thermal transfer image-receiving sheet and heat-pressed to transfer the dye of the thermal transfer sheet to the thermal transfer image-receiving sheet, thereby forming an image, etc. Recording method.
As this thermal transfer image-receiving sheet, as described in Patent Documents 1 and 2, a sheet in which a heat insulating layer and a dye-receiving layer are laminated on a base material is known. Thermal transfer such as an ink ribbon called a so-called thermal ribbon Heat transfer is performed by heating both the recording medium (thermal transfer sheet) and the thermal transfer layer in contact with each other, thereby sublimating the ink (sublimation dye) contained in the thermal transfer layer and transferring it to the thermal transfer image-receiving sheet (printing paper). A color image or the like can be formed on the image receiving sheet.

At the time of dye transfer, the thermal transfer layer of the thermal transfer recording medium is superimposed on the dye receiving layer, pressed between a platen roller and a thermal head (transfer head), etc., and pressed, and the thermal transfer layer and the dye receiving layer are added. Heat is applied uniformly by pressure and heating.
Among thermal transfer printers, sublimation transfer printers can easily form full-color images with high-performance printers, enabling digital camera self-printing, printing of cards such as identification cards, and amusement output. Widely used for printing materials. Along with the diversification of such thermal transfer printers, there are demands for smaller, faster and lower cost printers and durability of the prints obtained.

As described in Patent Document 1, when the dye receiving layer material is a solvent type, the dye receiving layer can be formed on the substrate by evaporating the solvent after coating the material on the substrate. .
On the other hand, recently, there has been a movement to replace solvent-based materials with water-based materials from the viewpoint of environmental impact, mainly in Europe. Patent Document 2 describes that a dye transfer layer is formed by using an aqueous emulsion as a dye receiving layer material.

JP 2002-212890 (paragraph 0027, Examples) Japanese Patent Laying-Open No. 2015-189020 (0032 paragraph, examples)

  In sublimation transfer, after applying thermal pressure with a thermal head, the thermal transfer sheet is peeled from the thermal transfer image receiving sheet. Depending on the structure of the printer, there are cases where the angle (peeling angle) at the time of peeling is as narrow as 15 degrees or less. Generally, the narrower the peel angle, the harder it is to peel. The ease of peeling varies depending on the peeling angle, but also varies depending on the temperature. The temperature inside the printer that prints continuously increases. When the temperature is high, it tends to be difficult to peel off. Therefore, when continuous printing is performed using a printer having a small peeling angle, peeling problems such as abnormal noise, unevenness, and peeling failure may occur.

In order to prevent this peeling failure, there is a method of using a release agent in the dye layer and dye receiving layer of the color panel of the thermal transfer sheet (sublimation ribbon). However, there is a demand to reduce the release agent because it may increase the possibility of causing problems other than fusion.
One of the factors that increase the temperature of the thermal transfer image receiving sheet and the thermal transfer sheet is heat transmitted from the platen roller. Part of the heat generated from the thermal head during transfer passes through the thermal transfer sheet and thermal transfer image receiving sheet and is stored in the platen roller. Part of the platen roller heat is transmitted to the thermal transfer image-receiving sheet, which affects the separation between the transfer layer of the thermal transfer sheet and the dye-receiving layer of the thermal transfer image-receiving sheet. Although measures such as installing a cooling fan can be taken for the temperature inside the printer, it is often difficult to cool the platen roller directly because of the structure of the printer.

Further, due to the structure of the printer, it is inevitable that the base material of the thermal transfer image receiving sheet and the platen roller are in contact with each other. It is therefore desirable to prevent the heat of the platen roller from being transferred through the substrate to the dye receiving layer.
An object of the present invention is to provide a thermal transfer image-receiving sheet for sublimation type thermal transfer recording while maintaining a sufficient image quality at the time of printing in a high-speed printing printer, and at the time of dye transfer even if the release agent content of the dye-receiving layer is reduced. It is providing the thing which can suppress peeling malfunction.

  One aspect of the present invention is a thermal transfer image-receiving sheet used for sublimation thermal transfer recording, a sheet-like base material, a heat insulating layer formed on the base material, and a second image receiving image formed on the heat insulating layer. And a dye receiving layer formed on the second image receiving layer. The second image receiving layer is formed of a material including a microcapsule having an average diameter of 1 μm or less containing a substance having a melting point of 50 ° C. or more and 60 ° C. or less and a binder for the microcapsules. Further, the total thickness of the dye receiving layer and the second image receiving layer is at least 5 times the average diameter of the microcapsules.

  According to the present invention, as a thermal transfer image-receiving sheet for sublimation type thermal transfer recording, while maintaining sufficient image quality at the time of printing in a high-speed printing printer, even when the release agent content of the dye receiving layer is reduced, the dye transfer layer can be used at the time of dye transfer. What can suppress a peeling defect is provided.

It is sectional drawing which shows the thermal transfer image receiving sheet of embodiment. It is sectional drawing which shows the example of the thermal transfer sheet which transfers dye to a thermal transfer image receiving sheet. It is a schematic block diagram which shows an example of a thermal transfer apparatus. It is a partial expanded sectional view of FIG. It is a graph which shows the temperature transition in the thermal transfer apparatus at the time of printing. It is a figure which shows the relationship between energy and temperature before and after a phase transition state.

Hereinafter, although embodiment of this invention is described, this invention is not limited to embodiment shown below. In the embodiment described below, a technically preferable limitation is made for carrying out the present invention, but this limitation is not an essential requirement of the present invention.
[Constitution]
As shown in FIG. 1, the thermal transfer image receiving sheet 10 of the present embodiment includes a sheet-like base material 11, a heat insulating layer 12, a second image receiving layer 13, and a dye receiving layer sequentially formed on one surface 11 a of the base material 11. 14.

<Base material>
Examples of the base material 11 include, for example, a film made of a synthetic resin, high-quality paper, medium-quality paper, coated paper, art paper, and resin-laminated paper. Examples of the synthetic resin include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene and polyethylene, polyvinyl chloride, polycarbonate, polyvinyl alcohol, polystyrene, and polyamide. As the substrate 11, one of these films and papers may be used alone, or two or more may be used in combination as a composite.

The thickness of the substrate 11 is preferably 25 μm or more and 250 μm or less, for example, and more preferably 50 μm or more and 200 μm or less, but is not limited to this range.
If the thickness of the base material 11 is in the above range, the elasticity, strength and heat resistance required for the printed material can be sufficiently obtained when the printed material is formed.

<Insulation layer>
The heat insulation layer 12 is made of, for example, a material containing hollow particles and a resin, or made of a porous film.
When the heat insulation layer 12 is formed of a material containing hollow particles and a resin, examples of the hollow particles used include acrylic porous particles having a large number of fine cavities inside the particles, and silica particles having a hollow structure. (Hollow silica).

The average particle diameter of the hollow particles is, for example, 0.3 μm or more and 5.0 μm or less. The average particle diameter of the hollow particles can be measured by a laser diffraction method using a particle size distribution measuring device.
In this case, the resin constituting the heat insulating layer 12 fills the gaps between the hollow particles to bind the hollow particles to each other, and bonds the base material 11 and the heat insulating layer 12 together.
Examples of such resins include gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, styrene butadiene latex, acrylic, polyester, and the like. The ratio between the hollow particles and the resin is such that sufficient heat insulation is obtained for the heat insulating layer 12, the base material 11 is not thermally deformed or melted during thermal transfer, sufficient image quality is obtained, and sufficient strength is obtained. Is within the range that can be obtained.

  When the heat insulation layer 12 consists of a porous film, an adhesive layer and a porous film can be laminated | stacked and the base material 11 can be bonded together. Such an adhesive layer can be a polyolefin resin layer. Examples of the polyolefin resin layer include high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), polypropylene, ethylene-acrylic acid copolymer, ethylene- Methyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, ethylene-vinyl acetate copolymer, ethylene-maleic acid copolymer, ethylene-maleic anhydride copolymer, ethylene -A fumaric acid copolymer is preferably used.

Among these, polyethylene and polypropylene are more preferable. These polyolefin resins can be used in combination of two or more. Furthermore, examples of the material for forming the adhesive layer include urethane resins, acrylic resins, polyester resins, and the like in addition to polyolefin resins.
Also, for polyolefin resins, adhesion improving resins, organic fine particles, inorganic fine particles, organic-inorganic fine particles, antioxidants, fluorescent brighteners, ultraviolet absorbers, antistatic agents, light stabilizers, heat as necessary You may mix and use a stabilizer etc.

  The thickness of the polyolefin resin layer serving as the adhesive layer is preferably 8 μm or more and 80 μm or less, and more preferably 10 μm or more and 60 μm or less. The thermal transfer image-receiving sheet 10 can be formed, for example, by bonding the base material 11 and a porous film together through a polyolefin resin layer by extrusion sandwich lamination. For this reason, when the thickness of the polyolefin resin layer is 8 μm or more, the strength and heat resistance of the substrate 2 are improved, and the arithmetic of the surface facing the anchor layer of the porous film after the porous film is bonded together The average roughness (SRa) is reduced. Moreover, since the usage-amount of polyolefin material can be decreased when the thickness of a polyolefin resin layer is 80 micrometers or less, manufacturing cost can be reduced.

  In the porous film used as the heat insulating layer 12 in this case, the arithmetic average roughness (SRa) of the surface facing the dye receiving layer 14 or the anchor layer described later is adjusted to 0.8 μm or less, for example. The porous film is formed of a conventionally known material, for example, using a foamed film such as a foamed polypropylene film or a foamed polyethylene terephthalate film, or a composite film provided with a skin layer on one or both sides of the foamed film. The porous film which was used can be mentioned. Among these, it is particularly preferable to use a composite film in which a skin layer is provided on one side or both sides of a foam film. The thickness of the porous film is preferably 10 μm or more and 80 μm or less, and more preferably 20 μm or more and 60 μm or less.

In addition, you may give conventionally well-known various processes to the base material 11, the polyolefin resin layer used as an adhesive layer, and the porous film used as the heat insulation layer 12 as needed for adhesive improvement. For example, the adhesion can be improved by subjecting the base material 11 to corona treatment, the polyolefin resin layer to ozone treatment, and the porous film to easy adhesion treatment.
The thickness of the heat insulating layer 12 is a range in which sufficient heat insulating properties can be obtained as the heat insulating layer 12 in any configuration, and the elasticity required for the printed material can be obtained in a printed state. To do. Moreover, the density of the heat insulation layer 12 shall be the range from which sufficient heat insulation is acquired.
Although the thermal transfer image receiving sheet 10 of this embodiment has one heat insulating layer 12, it may have two or more heat insulating layers 12 having different states and compositions.

<Dye-receiving layer>
The dye receiving layer 14 is formed of a material containing an emulsion of a vinyl chloride resin having a vinyl chloride ratio of 50% by mass or more. The glass transition temperature of this vinyl chloride resin is 30 ° C. or higher and 100 ° C. or lower. Vinyl chloride is inexpensive but has high dyeing properties and many glass transition temperatures (Tg), and is suitable as a dye-receiving layer material.

As the vinyl chloride resin for the dye receiving layer 14, for example, a vinyl chloride-acrylate copolymer having a glass transition temperature (Tg) of 30 ° C. or higher and 100 ° C. or lower is preferably used.
The glass transition temperature (Tg) is a value measured by differential scanning calorimetry (DSC) of a sample that has been dried under reduced pressure and solidified.

As a vinyl chloride-acrylic acid ester copolymer having a glass transition temperature (Tg) of 30 ° C. or higher and 100 ° C. or lower, for example, a vinyl chloride monomer and a (meth) acrylic monomer or a (meth) acrylic acid ester are conventionally known. Those obtained by polymerization by the method can be used.
Examples of the acrylate ester include methyl acrylate, ethyl acrylate, butyl acrylate, -2-ethylhexyl acrylate, hydroxyethyl acrylate, and 2-hydroxypropyl acrylate. Examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, butyl methacrylate, propyl methacrylate and the like.

When the dye receiving layer 14 contains a vinyl chloride-acrylic acid ester copolymer having a glass transition temperature (Tg) of 30 ° C. or higher and 100 ° C. or lower, the dye receiving layer 14 has excellent color developability and has sufficient image quality. Can be formed. Moreover, the deterioration of the surface property of the base material 11 is prevented, curling due to the shrinkage of the base material 11 does not occur, and problems such as cracking of the heat insulating layer 12 do not occur.
At the same time, under high-temperature and high-humidity environments, image quality defects are likely to occur due to the formation state of the ink film containing the emulsion, but this is prevented and the film formation state of the ink film containing the emulsion is changed by the printing heat. In this case, sufficient image quality can be obtained in a high temperature and high humidity environment. In addition, it is possible to prevent image quality defects (cracking and cracking) after storage of a printed matter which is considered to be caused by the state of ink film formation.

The dye receiving layer 14 may contain a release agent.
Examples of the release agent include various oils such as silicon-based, fluorine-based, and phosphate-based oils, various fillers such as emulsions, surfactants, metal oxides, and silica, and waxes. Among these release agents, it is preferable to use silicon oil.
These release agents may be used alone or in combination of two or more.

Furthermore, you may add additives, such as colloidal silica, an inorganic polymer, resin, a leveling agent, and surfactant, to the dye receiving layer 14 as needed.
If the release agent and additives to be added are too large, the adhesion between the dye receiving layer 14 and the adjacent layer is lowered, and there is a possibility that the thermal transfer image receiving sheet 10 is wrinkled during printing. However, since the manufacturing cost increases, it is preferable to reduce the addition amount as much as possible. By providing the second image receiving layer 13, the content of the release agent in the dye receiving layer 14 can be reduced, and the release agent can be made unnecessary.

The thickness of the dye receiving layer 14 is preferably 0.1 μm or more and 10 μm or less, and more preferably 0.2 μm or more and 8 μm or less.
If the thickness of the dye receiving layer 14 is 0.1 μm or more, sufficient mechanical strength can be obtained in the dye receiving layer 14, and image quality is unlikely to occur. On the other hand, if the thickness of the dye receiving layer 14 is 10 μm or less, the cost merit is large.

The 5 ° reflectance at a wavelength of 550 nm on the surface of the dye receiving layer 14 is adjusted to, for example, 1% to 8%.
Regarding the measurement of the reflectance, the measurement is performed based on the method described in JIS K5602. The reason for selecting the measurement condition as 5 ° reflectance at a wavelength of 550 nm is the wavelength determined by the International Commission on Illumination (CIE), which has the highest spectral visible efficiency that makes people feel brightest. This is because it was considered preferable to measure at a low incident angle that is near the region (555 nm) and the roughness of the surface is easy to see.

  In addition, glossiness is mentioned as another method of measuring the reflection of the surface of the dye receiving layer 14. There seems to be a correlation between the reflectance and the glossiness under some measurement conditions, but the correlation between the reflectance and the glossiness under this measurement condition is not clear. According to the 2007 Niigata Industrial Technology Research Report, there is a difference between the absolute value of the glossiness calculated from the reflectance of the spectrophotometer and the glossiness measured by the glossometer. .

<Second image receiving layer 13>
The second image receiving layer 13 is formed of a material including a microcapsule and a binding material for the microcapsule. When the diameter of the microcapsule is large, unevenness due to the microcapsule is generated on the surface of the dye receiving layer 14 formed on the second image receiving layer 13. As a result of detailed experiments in this regard, it was found that there is no practical problem if the total thickness of the dye receiving layer 14 and the second image receiving layer 13 is 5 times or more the diameter of the microcapsules.

As described above, the thickness of the dye-receiving layer 14 is desirably 10 μm or less, and the second image-receiving layer 13 has a small contribution to the dye transfer performance. Therefore, the second image-receiving layer 13 is desirably thin. Therefore, the diameter of the microcapsule is desirably 1 μm or less.
As a microcapsule manufacturing method, there are various methods such as an ultrasonic method, an interfacial polymerization method, and an in-situ method. For the capsule outer wall material, gelatin, wax, solvent or the like is used. In some cases, the surface treatment is performed depending on whether the microcapsule capsule is desired to be dispersed or aggregated.

The encapsulating material of the microcapsule may be any material having a melting point of 50 ° C. or higher and 60 ° C. or lower, but is preferably a material having a large heat of fusion. As a preferable material for the encapsulation material of the microcapsule, for example, cetyl alcohol (melting heat 224 kJ / kg) having a melting point of 49 ° C. can be mentioned.
As the base material (microcapsule binder) of the second image receiving layer 13, it is preferable to use a material having high adhesion to both the heat insulating layer 12 and the dye receiving layer 14. The binder of the microcapsule is preferably the same as the vinyl chloride resin in which the vinyl chloride ratio contained in the material forming the dye receiving layer is 50% by mass or more. That is, the second image receiving layer 13 is preferably formed of a material containing microcapsules and the above-described vinyl chloride resin emulsion as a binder for the microcapsules.

<Anchor layer>
The thermal transfer image receiving sheet 10 according to the present embodiment includes the thermal transfer image receiving sheet according to the present embodiment, either or both between the heat insulating layer 12 and the second image receiving layer 13 and between the second image receiving layer 13 and the dye receiving layer 14. An anchor layer may be provided as long as the performance of the sheet 10 is not impaired.
The thickness of the anchor layer is preferably 0.1 μm or more and 6 μm or less, and more preferably 0.2 μm or more and 5 μm or less.

  If the thickness of the anchor layer is 0.1 μm or more, not only the film thickness adjustment of the anchor layer is easy, but also the print density does not easily vary. In addition, adhesion between the anchor layer and the heat insulating layer 12, the dye receiving layer 14, and the second image receiving layer 13 is sufficient. On the other hand, when the thickness of the anchor layer is 6 μm or less, the printing density at the time of high-speed printing does not decrease. Also, from the viewpoint of cost, the thickness of the anchor layer is preferably 6 μm or less.

As the resin used for the anchor layer, conventionally known resins can be used, and examples thereof include gelatin, polyvinyl alcohol, acrylic, polyester, styrene butadiene latex, and polyvinyl pyrrolidone.
Furthermore, at least a binder resin and a white pigment can be contained as the anchor layer. In this case, as the binder resin used for the anchor layer, for example, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate copolymer resin, polyvinyl acetal resin, polyvinyl butyral resin, polyvinyl alcohol resin, epoxy resin, ethylene -Vinyl acetate copolymer resin, polyurethane resin, acrylic resin, polyester resin, cellulose resin, polycarbonate resin, polystyrene resin, polyamide resin, polyolefin resin and the like.

As the white pigment used for the anchor layer, known inorganic pigments such as titanium oxide, calcium carbonate, zinc oxide, talc and kaolin can be used, and among these, titanium oxide is more preferable.
The anchor layer has an isocyanate compound within a range that does not impair the concealability by the white pigment contained in the anchor layer, the adhesion between the anchor layer and the heat insulating layer 12, and the adhesion between the anchor layer and the second image receiving layer 13. Known additives such as a crosslinking agent such as a fluorescent brightener, a silane coupling agent, a dispersant, a viscosity modifier, and a stabilizer can be used.

<Back layer>
In the thermal transfer image receiving sheet 10 of this embodiment, a back surface layer may be formed on the other surface (the surface opposite to the surface on which the heat insulating layer 12 is formed) 11 b of the base material 11. The purpose of providing this back layer is to improve printer transportability, prevent blocking with the dye receiving layer 14, prevent curling in the thermal transfer image receiving sheet 10 before and after printing, and improve writing performance.

Examples of the material for forming the back layer include polyolefin resins such as polyethylene resins and polypropylene resins, acrylic resins, polycarbonate resins, polyvinyl alcohol resins, polyvinyl acetal resins, polyester resins, polystyrene resins, and binder resins such as polyamides. Etc.
Moreover, you may add well-known additives, such as a filler and an antistatic agent, to the material which forms a back layer as needed. Further, as the back surface layer, a back extrusion resin layer, a back film layer, a back surface layer, and printing that imparts characters, designs, and the like may be provided. The order of lamination of the back-extruded resin layer, the back film layer, the back layer, and the printing layers to which characters, designs, etc. are applied is appropriately selected. Moreover, a conventionally well-known material can be used for the printing material which provides a back extrusion resin layer, a back film layer, a back layer, a character, a design, etc.

[Production method]
Next, a method for manufacturing the thermal transfer image receiving sheet 10 of this embodiment will be described.
First, the heat insulating layer 12 is laminated on the one surface 11 a of the base material 11.
When the heat insulating layer 12 is formed of a material containing hollow particles and a resin, first, a polyolefin resin layer is formed on the one surface 11a of the substrate 11 as an adhesive layer by a melt extrusion method or the like. Next, a heat insulating layer coating solution containing hollow particles and a resin is applied onto the polyolefin resin layer to form a coating film, and the coating film is dried.

  When using a porous film as the heat insulation layer 12, the base material 11 and the porous film are bonded together by an extrusion sandwich lamination method through an adhesive layer made of a polyolefin resin. In this method, the molten polyolefin resin is extruded into a film shape between the substrate 11 and the porous film, and the porous film is supplied via the molten polyolefin resin and cooled by a cooling roll. As a result, the polyolefin resin is solidified to form an adhesive layer.

Here, as the cooling roll, a mirror roll or a semi-matt roll can be used. The arithmetic average roughness (Ra) of the surface of the cooling roll facing the porous film is preferably 1.0 μm or less, and more preferably 0.8 μm or less. The nip pressure during extrusion sandwich lamination is adjusted to 3 kg / cm ^{2 to} 50 kg / cm ² , preferably 4 kg / cm ^{2 to} 50 kg / cm ² . Furthermore, in the bonding step, the thickness of the solidified polyolefin resin layer is adjusted uniformly to 8 μm to 80 μm, preferably 10 μm to 60 μm. Thereby, the arithmetic mean roughness (SRa) of the surface which opposes the anchor layer of a porous film can be 0.8 micrometer or less.

Next, if necessary, an anchor layer is formed by applying and drying an anchor layer coating solution containing a binder resin and a white pigment on the surface of the heat insulating layer 12 opposite to the substrate 11.
Next, the second image receiving layer 13 is formed by applying the second image receiving layer coating solution onto the heat insulating layer 12 or the anchor layer and drying it. The second image-receiving layer coating solution comprises a microcapsule having an average diameter of 1 μm or less containing a substance having a melting point of 50 ° C. or more and 60 ° C. or less, and a binder of the microcapsules (glass transition temperature of 30 ° C. or more and 100 ° C. or less. And vinyl chloride resin emulsion having a vinyl chloride ratio of 50% by mass or more.

Next, the dye receiving layer coating liquid is applied onto the second image receiving layer 13 and dried to form the dye receiving layer 14. The dye-receiving layer coating solution contains an emulsion of a vinyl chloride resin having a glass transition temperature of 30 ° C. or more and 100 ° C. or less and a vinyl chloride ratio of 50% by mass or more.
The dye-receiving layer coating liquid may be applied onto the second image-receiving layer coating liquid film (an anchor layer coating liquid film when an anchor layer is provided) formed on the heat insulating layer 12 before drying.

  Furthermore, the anchor layer coating solution and the dye receiving layer coating solution include wetting agents, dispersants, thickeners, antifoaming agents, colorants, antistatic agents, preservatives and the like used in general coated paper production. Various adjuvants can also be added as appropriate. Examples of the coating method for the anchor layer coating solution and the dye receiving layer coating solution include known wet coating methods such as bar coating, blade coating, air knife coating, gravure coating, roll coating, and die coating.

Further, at the time of applying the anchor layer coating solution and the dye receiving layer coating solution, the anchor layer coating solution and the dye receiving layer coating solution may be applied to each layer, or two or more layers may be coated and dried simultaneously.
Through these steps, the thermal transfer image receiving sheet 10 in the present embodiment is manufactured.
According to the manufacturing method of the thermal transfer image receiving sheet 10 in the present embodiment, the thermal transfer image receiving sheet 10 having the second image receiving layer 13 can be easily manufactured.

[Image forming method]
Next, an example of a printing (image forming) method using the thermal transfer image receiving sheet 10 of this embodiment will be described. In this example, the thermal transfer sheet 20 shown in FIG. 2 and the thermal transfer apparatus shown in FIG. 3 are used.
As shown in FIG. 2, in the thermal transfer sheet 20, color layers 23, 24, and 25 containing a sublimation dye are formed on one surface of a substrate 21, and a back coat layer 22 is formed on the opposite surface. . The color layer 23 is yellow, the color layer 24 is magenta, and the color layer 25 is cyan. A color image is formed by combining these colors. In addition to the panel for forming a color image, an overlay for protecting the color image formed on the thermal transfer image receiving sheet 10 may be provided.

As shown in FIG. 3, the thermal transfer device 30 includes a supply roll 31 that supplies the thermal transfer sheet 20, a transfer head 32, a platen roller 34, a release plate 35, a take-up roller 36, and a control unit 37. Have.
In the thermal transfer device 30, a thermal transfer sheet 20 that is a sublimation transfer medium is supplied from a supply roll 31. The thermal transfer image receiving sheet 10 is also supplied from the other path, and the dye receiving layer 14 of the thermal transfer image receiving sheet 10 and the color layers 23, 24, and 25 of the thermal transfer sheet 20 overlap in the vicinity of the transfer head 32, and these are the transfer head 32 and the platen roller 34. And is sandwiched at a predetermined pressure. The thermal transfer sheet 20 and the thermal transfer image receiving sheet 10 are set so as to be conveyed in synchronization. First, the yellow color layer 23 of the thermal transfer sheet 20 is formed so that an image set in accordance with these movements is formed. The dye of each panel of the panel portion, and then the magenta color layer 24 and the cyan color layer 25 is transferred to form a color image on the thermal transfer image receiving sheet 10 which is an image receiving paper.

When the sublimation dye is transferred from the thermal transfer sheet 20 to the thermal transfer image receiving sheet 10 that is a transfer target, the back coat layer 22 that contacts the transfer head 32 has heat resistance and low friction performance because it is exposed to a high temperature momentarily. It is supposed to have both.
The transfer head 32 is lined with minute heating elements, and the size of one minute heating element is about several tens of μm. An electric current is instantaneously passed through the minute heating element in units of several ms to heat to several hundred degrees Celsius. This heat is received by the thermal transfer sheet 20 and further transferred to the dye receiving layer 14 of the thermal transfer image receiving sheet 10, and the diffusion coefficient of the dye receiving layer 14 is increased. As a result, the sublimation dye is more easily transferred to the dye receiving layer 14 than the color layers 23, 24, and 25 in contact with the dye receiving layer 14, and the dye is transferred to the dye receiving layer 14. Since this heating is very short, subsequent dye diffusion in the dye receiving layer 14 hardly occurs.

  In this way, first, one line of the print image is printed. Thereafter, in order to print the next line, the thermal transfer sheet 20 and the thermal transfer image receiving sheet 10 are fed by one line. When printing at 300 dpi, approximately one line is about 85 μm. After the thermal transfer sheet 20 and the thermal transfer image receiving sheet 10 are sent, the above printing procedure is repeated. In this flow, the entire print image is printed. Many printers employ a roll-shaped thermal transfer image-receiving sheet for ease of handling. After printing, the print portion of the thermal transfer image receiving sheet 10 is cut out and discharged. The thermal transfer sheet 20 is peeled off from the thermal transfer image receiving sheet 10 by the peeling plate 35 and then wound around the winding roller 36.

[Function and effect]
The vicinity of the peeling plate 35 will be described in detail with reference to FIG. By changing the path of the thermal transfer sheet 20 with the release plate 35, the paths of the thermal transfer image receiving sheet 33 and the thermal transfer sheet 38 are angled. However, the release plate 35 does not cause the release, and the transfer head 32 peels off the heating element. Separation occurs between the plates 35. For this reason, the peel angle is very small. If the peel angle is small, the film tends to be difficult to peel. In addition to this, if the temperature of the thermal transfer image receiving sheet becomes high, it becomes difficult to peel off, and problems are likely to occur.

  As shown in FIG. 5, the temperature in the printer during printing changes. The peaks 41, 42, and 43 are caused by heat generated when the dye of the thermal transfer sheet 20 is transferred to the dye receiving layer of the thermal transfer image receiving sheet 10. Usually, since a sublimation heat transfer sheet uses a dye panel of yellow, magenta, and cyan, peak 41 is caused by transferring yellow, peak 42 is magenta, and peak 43 is caused when cyan dye is transferred.

Part of the heat generated from the transfer head 32 during dye transfer is diffused to the platen roller, and part of the heat is diffused from the jig or the like that fixes the transfer head 32 to the printer body, or may be diffused into the air. Most of the heat stored in the platen roller is transferred to the printer body through the axis of the platen roller, so the temperature of the platen roller is saturated.
The saturation temperature is approximately 70 degrees. In this case, the saturation temperature indicates the baseline in FIG. In many cases, problems occur due to an instantaneous temperature rise (peaks 41, 42, 43) at the time of transfer. Therefore, if the instantaneous temperature increase is not transmitted, the problem can be suppressed. it can.

As shown in FIG. 6, when the substance changes from the solid phase to the liquid phase, the temperature hardly changes near the transition temperature (melting point) 51 even if energy is given to the substance. This is because in the solid phase, molecules and atoms constituting the substance are in a bound state, and the given energy is used to release the bound state and is not transmitted to the molecules and atoms.
Since the second image receiving layer 13 is formed of a material including a microcapsule that encloses a substance having a melting point of 50 ° C. or higher and 60 ° C. or lower, the melting point temperature of the inclusion of the microcapsule (50 ° C. or higher and 60 ° C. or lower). In the transition state from the solid phase to the liquid phase, the inclusion does not rise in temperature. That is, while in this transition state, the thermal energy transferred from the heat insulating layer 12 to the second image receiving layer 13 is consumed as transition energy from the solid phase to the liquid phase of the inclusions of the microcapsules. Therefore, not only the heat of the base material 11 is weakened by the heat insulating layer 12 but also the heat is hardly transmitted from the heat insulating layer 12 to the second image receiving layer 13 while the inclusions of the microcapsules are in the transition state.

  Therefore, according to the thermal transfer image receiving sheet 10 in the present embodiment, when the thermal transfer sheet is peeled from the dye receiving layer 14 at the time of dye transfer, the substrate 11 is compared with the thermal transfer image receiving sheet not having the second image receiving layer 13. From the heat to the dye receiving layer. Therefore, even if the release agent content of the dye receiving layer 14 is reduced, the thermal transfer sheet 20 can be easily peeled from the thermal transfer image receiving sheet 10.

  Further, by setting the total thickness of the dye receiving layer 14 and the second image receiving layer 13 to 5 times or more the diameter of the microcapsules, unevenness due to the microcapsules is less likely to occur on the surface of the dye receiving layer 14. Furthermore, when the dye receiving layer 14 contains an emulsion of a vinyl chloride-acrylic acid ester copolymer having a glass transition temperature of 30 ° C. or higher and 100 ° C. or lower, it is excellent in color developability and sufficient image quality can be formed. Therefore, according to the thermal transfer image receiving sheet 10 in the present embodiment, it is possible to maintain a sufficient image quality when printing with a high-speed printing printer.

Examples of the present invention and comparative examples will be described below.
The thermal transfer image receiving sheet 10 of the embodiment was produced by the following method.
The materials used in each example are shown below. In the text, “part” is based on mass unless otherwise specified. The present invention is not limited to the following examples.
[Example]
As the base material 11, high-quality paper (Shiraoi basis weight 127.9 g / m ² made by Nippon Paper Industries Co., Ltd.) having a corona treatment on both sides is prepared, and melt extrusion method is applied to the other surface 11 b of the base material 11. Thus, a back layer made of a low-density polyethylene resin (LC600A made by Nippon Polyethylene) having a thickness of 30 μm was formed.

  Next, the heat insulation layer 12 which consists of a porous film was formed in one surface (surface opposite to the surface in which the back surface layer was formed) 11a. Specifically, a low-density polyethylene resin (LC600A manufactured by Nippon Polyethylene Co., Ltd.) obtained by melting a foamed polypropylene film having a thickness of 30 μm (Econage NW-2 manufactured by Mitsui Chemicals, Inc.) on one surface 11a of the substrate 11 is used. Bonding was performed by the extrusion sandwich lamination method used.

At this time, the coating thickness of the low density polyethylene (that is, the thickness of the polyolefin resin layer) was adjusted to 8 μm. A mirror roll having a surface arithmetic average roughness (Ra) of 0.2 μm was used as a cooling roll used during extrusion sandwich lamination. In addition, the nip pressure in the cooling roll peripheral surface and 3kg weight / cm ^2.
Next, after applying a heat-insulating layer coating liquid having the following composition on the surface of the heat-insulating layer 12 made of a foamed polypropylene film opposite to the base material 11, a dye-receiving layer coating liquid having the following composition was applied. Next, the base material 11 on which both coating solutions are coated on the heat insulating layer 12 is put in an oven and dried at 100 ° C. for 5 minutes. The thickness after drying is 2 μm for the second image receiving layer 13, and the dye receiving layer. 14 was 3 μm.

<Second image-receiving layer coating solution>
Emulsion of vinyl chloride-acrylic acid ester copolymer (Tg: 80 ° C., minimum film forming temperature of about 100 ° C.) (trade name: Vinibrand 690, manufactured by Nissin Chemical Industry Co., Ltd., vinyl chloride ratio 50 mass%, solid content 50 mass %): 49.8 parts by mass Silicon oil (trade name: KF-354L, manufactured by Shin-Etsu Chemical Co., Ltd.): 0.2 parts by mass Microcapsules (inclusion is cetyl alcohol: melting point 51 ° C., outer shell is paraffin): 50 masses Part

<Dye-receiving layer coating solution>
Emulsion of vinyl chloride-acrylic acid ester copolymer (Tg: 80 ° C., minimum film forming temperature of about 100 ° C.) (trade name: Vinibrand 690, manufactured by Nissin Chemical Industry Co., Ltd., vinyl chloride ratio 50 mass%, solid content 50 mass %): 99.7 parts by mass Silicon oil (trade name: KF-354L, manufactured by Shin-Etsu Chemical Co., Ltd.): 0.3 parts by mass

[Comparative example]
After the dye receiving layer coating solution having the same composition as that of the example was applied to the surface of the heat insulating layer 12 made of a foamed polypropylene film on the side opposite to the base material 11, the base material 11 was placed in an oven at 5O 0 C at 5 ° C. The thickness of the dye receiving layer 14 after drying was 5 μm. Except for this point, a thermal transfer image-receiving sheet of a comparative example was obtained in the same manner as in the example. That is, the thermal transfer image receiving sheet of the comparative example does not have the second image receiving layer 13 of the thermal transfer image receiving sheet 10 of FIG. 1, and the dye receiving layer having the total thickness of the second image receiving layer 13 and the dye receiving layer 14 is on the heat insulating layer 12. It is formed.

The thermal transfer image receiving sheets of Examples and Comparative Examples thus obtained are continuously printed using a digital color printer (CP-D70) manufactured by Mitsubishi Electric Corporation, and the performance of the thermal transfer image receiving sheet occurs at the time of peeling. A test was conducted to check for abnormal noise. The printing conditions were L size (89 × 127 mm) and about 7.7 seconds.
The test results are shown in Table 1.

なお、表１において、「○」は異音の発生無し、「×」は異音の発生ありを示している。

In Table 1, “◯” indicates that no abnormal noise is generated, and “X” indicates that abnormal noise is generated.

  As can be seen from the results shown in Table 1, in the thermal transfer image-receiving sheet of the comparative example that does not include the second image-receiving layer 13, noise was generated although it was small when 10 sheets were printed, and then the noise became more intense and 20 sheets. A remarkable noise was generated. In contrast, in the thermal transfer image-receiving sheet 10 of the example having the second image-receiving layer 13, only a small noise was finally generated in 30 continuous prints.

  Further, the image quality printed on the thermal transfer image receiving sheets of the comparative example and the example was preferable because a sufficient print density was obtained.

DESCRIPTION OF SYMBOLS 10 ... Thermal transfer image receiving sheet 11 ... Base material 12 ... Heat insulation layer 13 ... 2nd image receiving layer 14 ... Dye receiving layer 20 ... Thermal transfer sheet 35 ... Release plate

Claims (2)

A thermal transfer image receiving sheet used for sublimation type thermal transfer recording,
A sheet-like substrate;
A heat insulating layer formed on the substrate;
A second image receiving layer formed on the heat insulating layer;
A dye-receiving layer formed on the second image-receiving layer;
With
The second image receiving layer is formed of a material including a microcapsule having an average diameter of 1 μm or less containing a substance having a melting point of 50 ° C. or more and 60 ° C. or less, and a binder for the microcapsule,
A thermal transfer image-receiving sheet, wherein the total thickness of the dye-receiving layer and the second image-receiving layer is at least 5 times the average diameter of the microcapsules.   2. The thermal transfer image-receiving sheet according to claim 1, wherein the dye-receiving layer is formed of a material containing a vinyl chloride resin emulsion having a glass transition temperature of 30 ° C. to 100 ° C. and a vinyl chloride ratio of 50% by mass or more. .

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