JP5668299B2 - Thermal transfer recording medium - Google Patents

Description

  The present invention relates to a thermal transfer recording medium having a thermal transfer layer for forming characters or images on a thermal transfer member.

  Conventionally, a sublimation thermal transfer system, a melt thermal transfer system, or the like has been adopted as a system for forming characters or images on a transfer target. For example, in the case of the sublimation type thermal transfer system, the surface of the thermal transfer recording medium provided with a thermal transfer layer containing a dye or a binder on the support, and a coated layer provided with a receiving layer for receiving the dye on another support. Dye in the thermal transfer layer is sublimated by superimposing the receiving layer surface of the thermal transfer body on each other and heating from the surface of the thermal transfer recording medium where the thermal transfer layer is not provided with a thermal head or the like that is temperature controlled by text or image information. The desired character or image is formed by transferring to the receiving layer.

  On the other hand, in the case of the melt-type thermal transfer system, the thermal transfer layer surface of the thermal transfer recording medium provided with a heat-fusible thermal transfer layer containing a pigment or wax on the support, and the thermal transfer provided with a receiving layer on another support. The receiving layer surface of the body is superposed on each other and heated by a thermal head or the like, so that the thermal transfer layer is fused and transferred to the receiving layer to form a desired character or image. Among the above methods, the sublimation thermal transfer method is widely used for monochrome printing such as characters and charts and color printing such as digital camera images or computer graphics images.

  In the case of the sublimation type thermal transfer system, the thermal transfer layer is formed by dissolving a dye and a binder resin in a solvent such as methyl ethyl ketone or toluene to form an ink, and coating the base material such as a polyethylene terephthalate film. In this case, the dye having low solubility in the solvent cannot increase the dye concentration in the ink, so that a sufficient print density may not be obtained when printing with a printer.

  Many methods have been proposed to solve the above problems. For example, Patent Document 1 proposes that by setting the weight ratio of the dye / binder resin in the thermal transfer layer to 1 or more, the thermal transfer layer can be prevented from being peeled off during thermal transfer, and an excellent image density can be provided. doing. Patent Document 2 proposes that by using porous protein particles, the proportion of the dye in the thermal transfer layer can be increased, whereby the printing density can be improved.

Japanese Patent No. 312534 Japanese Patent No. 4242704

However, in the method proposed in Patent Document 1, since the ratio of the dye becomes high, there is a concern about the precipitation of the dye. Further, in the method proposed in Patent Document 2, organic porous protein particles are used. However, in the case of organic particles, problems such as deterioration occur depending on the time and storage environment. Concerned. In addition, the durability against heat and pressure from the thermal head is low, and it drops off from the thermal transfer layer during printing, and as a result, the printing density cannot be improved, and organic protein particles are fibrous. Because there is
There is a problem that the post-process after the formation of the thermal transfer layer deforms the particles, and as a result, the print density cannot be improved.
SUMMARY OF THE INVENTION In view of the above problems, the present invention has an object of improving the print density in a thermal transfer recording medium.

The present inventors have found that the above-mentioned problems can be achieved by mixing a specific amount of inorganic porous particles in the thermal transfer layer, and have completed the present invention.
That is, the invention according to claim 1 is provided with a thermal transfer layer on at least one surface on a support, and the thermal transfer layer contains at least a sublimable dye and a polyvinyl acetal resin or polyvinyl butyral resin as a binder resin and particles. the thermal transfer recording medium der is, the ratio of the sublimable dye and a binder resin contained in the thermal transfer layer, 100 and 100: a 300, thermal transfer recording, wherein the particles are inorganic porous particles It is a medium.

  In the invention according to claim 2, when the particle size of the inorganic porous particles is r and the film thickness of the thermal transfer layer is h, the ratio [r / h] is in the range of 0.5 to 2.0. The thermal transfer recording medium according to claim 1, wherein the thermal transfer recording medium is provided.

  The invention according to claim 3 is the thermal transfer according to claim 1 or 2, wherein a blending ratio of the inorganic porous particles to the binder resin is in a range of 0.001 to 0.05. It is a recording medium.

  By using the method of the present invention, the effect that the print density can be improved in the thermal transfer recording medium is exhibited.

It is a cross-sectional schematic diagram of one embodiment of the thermal transfer recording medium of the present invention. It is a cross-sectional schematic diagram of the thermal transfer layer 3 (particles protruded) containing particles. It is a cross-sectional schematic diagram of the thermal transfer layer 3 (particles are not protruding) containing particles.

Hereinafter, the present invention will be described in more detail.
FIG. 1 is a cross-sectional view of the thermal transfer recording medium (1). The thermal transfer recording medium (1) comprises a support (2) and a thermal transfer layer (3). As the support (2), a material equivalent to that conventionally used as a base material for thermal transfer recording media can be used, and it is preferable to have mechanical strength, flexibility, heat resistance and the like. Specific examples include plastic films such as polyethylene terephthalate, polyethylene naphthalate, polypropylene, cellophane, polycarbonate, polyvinyl chloride, polystyrene, polyimide, nylon, and polyvinylidene chloride, and papers such as condenser paper and paraffin paper. However, polyethylene terephthalate is particularly preferable. The thickness of the support (2) is 2 to 25 μm, more preferably 2 to 12 μm.

  Further, in order to prevent thermal contraction of the support (2) due to heat of the thermal head and breakage of the support (2) due to friction with the thermal head, the opposite side of the thermal transfer layer (3) of the support (2). A heat resistant slipping layer may be provided on the surface. Examples of materials used for the heat resistant slipping layer include cellulose resins, polyester resins, acrylic resins, vinyl resins, and polyurethane resins. For the purpose of improving the heat resistance, a crosslinking agent may be used in combination. Further, for the purpose of improving lubricity, a lubricant such as silicone oil may be used in combination, or the above-mentioned resin modified with silicone may be used.

  Moreover, in order to improve the adhesiveness between a support body (2) and a heat resistant slipping layer, an easily bonding layer may be provided on a support body (2), and a heat resistant slipping layer may be provided on it. . On the contrary, when the heat resistant slipping layer is not provided, the heat resistance and the slipperiness may be improved by adjusting the surface roughness of the surface of the support (2) in contact with the thermal head by various methods.

  In the thermal transfer layer (3), the components contained in the thermal transfer layer (3) on the thermal transfer medium are heated by a thermal head from the surface opposite to the thermal transfer layer (3) of the thermal transfer recording medium (1). The transfer body has a function of transferring the dye contained in the thermal transfer layer. The thermal transfer layer of the present invention particularly refers to a sublimable thermal transfer layer.

  The thermal transfer layer (3) contains at least a sublimable dye and a binder. As the sublimable dye, conventionally known dyes can be used. Specifically, examples of yellow include Kayaset Yellow AG, Kayaset Yellow TDN, PYT52, Plast Yellow 8040, Holon Brilliant Yellow S6GLPI, and the like. Examples of magenta include Kaya Set Red B, Kaya Set Red 130, Sele Red 7B, Macrolex Red Violet R, C.I. I. Disperse thread 60 and the like can be mentioned. Examples of cyan include Kayaset Blue 714, Ceres Blue GN, MS Blue 50, TSD-44, C.I. I. Solvent Blue 63, C.I. I. Solvent blue 36 etc. are mentioned, However, It is not limited to these.

  As the binder used for the thermal transfer layer (3) in combination with the sublimation dye, conventionally known binders can be used, such as polyvinyl acetal resin, polyvinyl butyral resin, polyester resin, phenoxy resin, styrene-acrylonitrile copolymer resin, ethyl cellulose, Resins excellent in heat resistance, dye transferability and the like such as hydroxyethyl cellulose and polycarbonate can be used.

  The glass transition temperature of the binder used in the thermal transfer layer (3) in combination with the sublimation dye is preferably 50 ° C. or higher, and when the glass transition temperature is lower than 50 ° C., the thermal transfer layer (3) is the thermal transfer body during thermal transfer. This is not preferable because it tends to be fused to each other and a problem occurs in storage stability of the thermal transfer recording medium. Furthermore, the ratio of the sublimable dye and binder contained in the thermal transfer layer (3) is preferably in the range of 100: 50 to 100: 300.

  The thermal transfer layer may be used in combination with a crosslinking agent for the purpose of improving heat resistance. By containing a cross-linking agent, heat resistance is improved and deformation of the thermal transfer recording medium can be prevented. Examples of the cross-linking agent include polyisocyanates, which are used in combinations of acrylic, urethane, and polyester polyol resins, cellulose resins, and acetal resins.

  The thermal transfer layer (3) may contain a release agent. When a release agent is contained, the releasability due to the shape of the surface of the thermal transfer layer is further improved. For example, various oils such as silicone-based, fluorine-based, and phosphate-based oils, various particles such as surfactants, metal oxides, and silica can be used. Among these, it is preferable to use silicone oil.

  The thickness of the thermal transfer layer (3) is in the range of 0.2 to 5.0 μm, preferably about 0.4 to 3.0 μm. If the thickness is less than 0.2 μm, sufficient color development sensitivity cannot be obtained, and if it exceeds 5.0 μm, the color development sensitivity is deteriorated.

  The thermal transfer layer (3) described above contains at least particles (4). A cross-sectional view of the thermal transfer layer (3) containing particles is shown in FIG. The particles of the present invention are preferably porous particles. Since the particles contained in the thermal transfer layer (3) are porous particles, a large amount of dye can be held on the surface of the porous particles, and the printing density can be improved.

  The porous particles are preferably inorganic particles. In the case of inorganic particles, there is no problem such as deterioration due to aging or storage environment, and durability against heat and pressure from the thermal head when contacting with the image receiving paper during printing is improved. On the other hand, when the porous particles are organic particles, problems such as deterioration occur depending on the time and storage environment. In addition, when organic particles that are fibrous are used, the particles are deformed in a post-process after coating, and the durability against heat and pressure from the thermal head is lower than that of inorganic particles. As a result, the print density cannot be improved. In addition, printing unevenness occurs due to the dropping of the particles.

  In addition, as a feature of the present invention, it is preferable that the porous particles protrude from the surface of the thermal transfer layer and have an uneven shape. On the contrary, as shown in FIG. 3, in the case where particles exist in the thermal transfer layer (3) and have an uneven shape, many dyes held on the surface of the porous particles are not effectively used, and the printing density is improved. This is not preferable because it cannot be performed.

  The particles shown in FIG. 2 and FIG. 3 are spherical, but this is an example, and it may be spherical or non-spherical. It is sufficient that the particles protrude from the surface of the thermal transfer layer and have an uneven shape without being buried in the thermal transfer layer.

  In addition, the average particle diameter is not limited as long as the particles are not buried in the thermal transfer layer as shown in FIG. 3, but the average particle diameter may vary depending on the content of the particles contained in the thermal transfer layer ink forming the thermal transfer layer and its coating amount. Existence is different. Therefore, when the average particle diameter of the particles is r and the film thickness of the thermal transfer layer is h, the value of [r / h] preferably satisfies the range of 0.5 to 2.0. When the value of [r / h] is smaller than 0.5, the particles are often buried and the print density cannot be improved. On the other hand, when the value of [r / h] is larger than 2.0, the dropout of particles increases, and local unevenness occurs during thermal transfer, and the print density cannot be improved.

  The mixing ratio of the particles is preferably in the range of 0.001 to 0.05 with respect to the binder resin. If it is less than 0.001, the printing density cannot be improved, and if it is more than 0.05, the ratio of the particles to the binder resin becomes too large, and the printing density is lowered.

  In order to improve the adhesion between the support (2) and the thermal transfer layer (3), an easy adhesion layer may be provided as an intermediate layer. In addition, a surfactant, an antiblocking agent, an antioxidant, an ultraviolet absorber, an antistatic agent, etc. may be added to the thermal transfer layer (3) as necessary, and a layer having these functions may be added. You may laminate.

  For the thermal transfer layer (3), the coating liquid for forming the thermal transfer layer is applied onto the support 2 by a wet coating method such as bar coating, blade coating, air knife coating, gravure coating, roll coating, etc., and dried to form a thermal transfer layer. To do.

  The thermal transfer member is composed of a support and a receiving layer. The support can be the same as that used as the base material of the thermal transfer recording medium, and preferably has mechanical strength, flexibility, heat resistance and the like. Specific examples include polyesters such as polyethylene terephthalate and polyethylene naphthalate, plastic films such as polyethylene, polyvinyl chloride, polycarbonate, polyester, polysulfane, polyimide, polyvinyl alcohol, aromatic polyamide, and aramid film, fine paper, and coats. Examples thereof include paper base materials such as paper and synthetic paper. The thickness of the support is not particularly limited, but is generally 25 to 250 μm, more preferably 75 to 200 μm.

  Further, as the receiving layer, when a sublimation dye is used for the thermal transfer layer, for example, butyral resin having a dyeing property, polyethylene, polyurethane, polypropylene, polyvinyl chloride, polybutadiene, polyvinyl acetate, vinyl chloride-vinyl acetate. Uses thermoplastic resins such as copolymers, ethylene-vinyl acetate copolymers, polyamides, polyesters, polycaprolactones, polyvinyl acetals, epoxies, ketones, modified resins and blends thereof, and cross-linked products thereof. can do. These may be used alone or in combination of two or more. If the film thickness of the image receiving layer is too thin, the reflection density of the image is lowered and it becomes difficult to form a sufficient image. On the other hand, if the thickness is too large, image quality such as color bleeding is deteriorated. Therefore, it is generally 1 to 30 μm, preferably 3 to 10 μm. In this case, the image receiving layer preferably contains various release agents for the purpose of preventing thermal fusion to the thermal transfer recording body during image formation. As such a release agent, a known release agent can be appropriately selected and used. For example, various oils such as silicone-based, fluorine-based, and phosphate-based oils, various particles such as surfactants, metal oxides, silica, and the like can be used. Among these, silicone oil is preferably used. The amount added varies depending on the constituent conditions of the image-receiving layer, but generally it is preferably 1 to 30% by weight.

Hereinafter, although an embodiment of the present invention is described in detail about an example, the present invention is not limited to these examples.
<Example 1>
An ink composition for a thermal transfer layer having the following composition was prepared and applied to a 4.5 μm thick polyethylene terephthalate film having a heat-resistant slip treatment on the back so that the thickness of the thermal transfer layer after drying was 1.0 μm. It was dried to obtain the thermal transfer recording medium of the present invention. Among the ink compositions for the thermal transfer layer, inorganic porous particles having an average particle size of 0.5 μm were used.
[Ink for thermal transfer layer]
・ C. I. Solvent Blue 63 2.5 parts C.I. I. Solvent Blue 36 2.5 parts, polyvinyl acetal resin 5 parts, inorganic porous particles (average particle size: 0.5 μm) 0.005 parts, methyl ethyl ketone 60 parts, toluene 30 parts

Next, a foamed polypropylene film (thickness: 50 μm) / adhesive resin layer / coated paper (coating amount: 108 g / m ² ) / adhesive resin layer / foamed polypropylene film (thickness: 50 μm) was used as the base sheet. On the surface, the following receiving layer ink was applied and dried so that the film thickness after drying was 4 μm, and then subjected to aging at 45 ° C. for 1 week to obtain a thermal transfer member with a receiving layer.
(Receptive layer ink)
・ Vinyl chloride-vinyl acetate copolymer (manufactured by Nissin Chemical Industry Co., Ltd., Solvein A) 50.0 parts ・ Silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., KF393) 2.0 parts ・ Methyl ethyl ketone 25.0 parts ・ Toluene 25 .0 part

<Example 2>
A thermal transfer recording medium was obtained in the same manner as in Example 1 except that the average particle size of the inorganic porous particles in the thermal transfer layer ink composition was set to 2.0 μm.

<Example 3>
A thermal transfer recording medium was obtained in the same manner as in Example 1 except that the amount of inorganic porous particles in the thermal transfer layer ink composition was 0.25 parts.

<Example 4>
A thermal transfer recording medium was obtained in the same manner as in Example 2 except that the amount of inorganic porous particles in the thermal transfer layer ink composition was 0.25 parts.

<Example 5>
A thermal transfer recording medium was obtained in the same manner as in Example 1 except that the amount of the inorganic porous particles in the thermal transfer layer ink composition was 0.001 part.

<Example 6>
A thermal transfer recording medium was obtained in the same manner as in Example 5 except that the average particle size of the inorganic porous particles in the thermal transfer layer ink composition was 2.0 μm.

<Example 7>
A thermal transfer recording medium was obtained in the same manner as in Example 1 except that the amount of inorganic porous particles in the thermal transfer layer ink composition was 0.50 part.

<Example 8>
A thermal transfer recording medium was obtained in the same manner as in Example 7 except that the average particle size of the inorganic porous particles in the thermal transfer layer ink composition was 2.0 μm.

<Example 9>
In the thermal transfer layer ink composition, a thermal transfer recording medium was obtained in the same manner as in Example 1 except that the average particle size of the inorganic porous particles was 0.3 μm.

<Example 10>
A thermal transfer recording medium was obtained in the same manner as in Example 9 except that the amount of inorganic porous particles in the thermal transfer layer ink composition was 0.25 parts.

<Example 11>
A thermal transfer recording medium was obtained in the same manner as in Example 1 except that the average particle size of the inorganic porous particles in the thermal transfer layer ink composition was 2.5 μm.

<Example 12>
A thermal transfer recording medium was obtained in the same manner as in Example 11 except that the amount of inorganic porous particles in the thermal transfer layer ink composition was 0.25 parts.

<Comparative Example 1>
A thermal transfer recording medium was obtained in the same manner as in Example 1 except that the inorganic porous particles in the thermal transfer layer ink composition were changed to organic porous particles.

<Comparative example 2>
A thermal transfer recording medium was obtained in the same manner as in Example 1 except that the inorganic porous particles in the thermal transfer layer ink composition were changed to inorganic nonporous particles.

<Comparative Example 3>
A thermal transfer recording medium was obtained in the same manner as in Example 1 except that the ink composition for thermal transfer layer was adjusted not to add inorganic porous particles.

  The thermal transfer layer surface of the obtained thermal transfer recording medium and the receiving layer surface of the transfer target were overlapped, the dye was transferred using a thermal head, and a solid pattern image was printed.

The following evaluation was performed on the obtained image. The results are shown in Table 1.
〔Evaluation item〕
・ Print density The print density of the obtained image is measured by optical density measurement with the density measurement status A of X-Rite 528 densitometer (manufactured by X-Rite). If the print density is less than 1.4, the print density is x. The evaluation was evaluated as Δ for 1.4 or more and less than 1.5, and ○ for 1.5 or more.
-Print unevenness The print unevenness of the obtained image was visually evaluated. When there was no printing unevenness, it was evaluated as ◯, when there was printing unevenness, Δ when there was no problem in practical use, and × when there was a level of printing unevenness that would cause practical problems.

  As described above, by using the thermal transfer recording medium of the present invention, it was possible to improve the print density of the printed image on the thermal transfer recording medium. From Examples 1 to 4, the ratio [r / h] of the average particle diameter r of the particles contained in the thermal transfer layer to the film thickness h of the thermal transfer layer satisfies 0.5 to 2.0, and the inorganic porous particles When the blending ratio with respect to the binder resin satisfies 0.001 to 0.05, it has been confirmed that a sufficiently high printing density can be obtained and printing unevenness does not occur.

  From Examples 5 and 6, when the blending ratio of the inorganic porous particles to the binder resin is less than 0.001, the printing density is somewhat increased, but it cannot be improved to a sufficient value. It could be confirmed.

  From Examples 7 and 8, when the mixing ratio of the inorganic porous particles to the binder resin is larger than 0.50, the ratio of the particles to the binder resin becomes too large, and conversely the printing density is improved. It was confirmed that was not sufficient.

  From Examples 9 and 10, when [r / h] is less than 0.5, the number of particles embedded in the thermal transfer layer increases, and the print density slightly increases, but it is improved to a sufficient value. It was confirmed that it was not possible.

  From Examples 11 and 12, when [r / h] is greater than 2.5, more particles are dropped and the print density is somewhat increased, but it cannot be improved to a sufficient value. Was confirmed. Moreover, it was confirmed that the printing unevenness of a level causing no problem in practice occurred due to the omission.

  From Comparative Example 1, by using organic porous particles, the printing density is improved by dropping the particles from the thermal transfer layer due to the deformation of the particles in the post-process after coating and the heat and pressure from the thermal head. I couldn't. In addition, it was confirmed that printing unevenness at a level causing a practical problem occurred due to the dropping of the particles.

  From Comparative Example 2, it was confirmed that by using inorganic non-porous particles, a large amount of dye could not be held on the surface, and the printing density could not be improved.

From Comparative Example 3, it can be confirmed that the printing density cannot be improved by not adding the particles to the ink composition for the thermal transfer layer, and that printing unevenness occurs by sticking to the image receiving paper at the time of printing. It was.

  The thermal transfer recording medium of the present invention can be widely applied to monochrome prints such as characters and diagrams, and color prints such as digital camera images or computer graphics images.

1 ... thermal transfer recording medium 2 ... support 3 ... thermal transfer layer 4a ... particle 4b ... particle 4c ... particle 4d ... particle 4e ... particle 4f ... particle 4a '... particle 4b' ... particle 4c '... particle 4d' ... particle 4e '... Particle 4f '... particle

Claims (3)

The thermal transfer layer provided on at least one surface of the support, wherein the thermal transfer layer of polyvinyl acetal resin or a polyvinyl butyral resin as at least sublimable dye and a binder resin, and Ri thermal transfer recording medium der containing particles, the thermal transfer layer The thermal transfer recording medium characterized in that the ratio between the sublimable dye and the binder resin contained is 100: 50 to 100: 300, and the particles are inorganic porous particles.   The ratio [r / h] is in the range of 0.5 to 2.0, where r is the particle size of the inorganic porous particles and h is the film thickness of the thermal transfer layer. 2. The thermal transfer recording medium according to 1.   The thermal transfer recording medium according to claim 1, wherein a blending ratio of the inorganic porous particles to the binder resin is in a range of 0.001 to 0.05.