JP2653549B2 - Thermal transfer recording medium - Google Patents

Description

The present invention relates to an improvement in a thermal transfer recording medium used in a thermal transfer recording apparatus using a thermal head such as a word processor, a facsimile, and a bar code.

More specifically, while maintaining high thermal sensitivity such as cover wrapping property on paper with low smoothness and dot reproducibility,
The present invention relates to a thermal transfer recording medium in which printing and running troubles are prevented by preventing the components of the thermal transfer layer from migrating to the back surface of the support during long-term storage at high temperature and improving storage stability.

[Conventional technology]

Conventionally, when performing output printing on low-smoothness paper by a thermal transfer method such as a word processor, facsimile, or bar code, the structure of the thermal transfer recording medium is to prevent sticking on one surface (hereinafter referred to as the back surface) of the support. Provide the intended heat-resistant protective layer, and the other side of the support (hereinafter referred to as the surface)
A first thermal transfer layer, which is a colored layer, and a second thermal transfer layer (outermost layer) made of a thermoplastic resin for the purpose of improving printability on low-smooth paper and improving adhesiveness. It is a target. In the thermal transfer recording medium having such a structure, it is necessary to use a resin having a low softening point of the outermost thermoplastic resin serving as the second thermal transfer layer in order to obtain good printing on low smooth paper.

However, in the thermal transfer recording medium having such a configuration, during high-temperature storage in a roll state or long-term storage, the components of the thermal transfer layer migrate to the heat-resistant protective layer side on the back surface, and the heat-transfer recording medium becomes a low-smooth paper due to a decrease in cover wrapping property. However, problems such as deterioration of print quality, deterioration of print quality due to thermal head dirt, occurrence of stick phenomenon, and occurrence of trouble in running the ribbon in the cassette have occurred.

That is, in the thermal transfer recording medium having such a structure, there is a problem that storability such as high temperature and long-term storage cannot be compatible with printability such as cover wrapping property on low smooth paper and dot reproducibility.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal transfer recording medium which prevents the components of the thermal transfer layer from migrating to the heat-resistant protective layer side on the back surface of the support during high-temperature and long-term storage, and provides good print quality even on low-smooth paper. Is to do.

[Means for solving the problem]

The present inventors have conducted intensive studies to solve the above-mentioned problems. As a result, the outermost layer of one or more thermal transfer layers has a specific surface area of S (m ² / g) by the BET method and an average particle size of Dμmφ
S / Dm / g contains spherical porous silica in the range of 100 × 10 ⁶ m / g> S / D> 60 × 10 ⁶ m / g, and the average particle size of the porous silica particles The diameter should be larger than the thickness of the outermost second thermal transfer layer. Furthermore, it is very effective to contain 0.5 to 50.0% by weight of porous silica particles which do not melt or soften at 300 ° C or lower. Was found. In other words, by including spherical porous silica particles having an average particle diameter larger than the thickness of the outermost layer in the outermost layer of the thermal transfer layer, direct contact between the outermost layer of the thermal transfer layer and the heat-resistant protective layer side of the back surface of the support is possible. The contact can be completely prevented, and the components of the thermal transfer layer can be prevented from migrating to the heat-resistant protective layer on the back surface of the support during high-temperature and long-term storage.

Further, the specific surface area S (m ² / g) and the particle diameter (μm) of the spherical silica particles are set to 100 × 10 ⁶ m / g> S / D> 60 × 10 ⁶ m / g. By selecting the spherical porous silica having the porous silica particles, the silica particles are anchored to the outermost layer of the thermal transfer layer by this porosity, and the porous silica particles can be rubbed with the heat-resistant protective layer in a roll state or even when running in a cassette. Is not scraped off from the outermost layer of the thermal transfer, and stable printing quality and stable running of the ribbon in the cassette are maintained even at high temperatures and after long-term storage.

As described above, it has been found that the above problems can be solved by including spherical porous silica particles having an average particle diameter larger than the layer thickness in the outermost layer of the thermal transfer layer, and the present invention has been completed.

That is, the thermal transfer recording medium of the present invention is provided with a first thermal transfer layer made of a hot-melt ink on the surface of a support, and a second thermal transfer layer made of a composite of a thermoplastic resin and porous silica particles provided thereon. Wherein the outermost second thermal transfer layer is a spherical porous silica having an average particle diameter of D μm and a specific surface area of Sm ² / g, wherein S / Dm / g is 100 × 10 ⁶ m / g> S / D>
It is characterized by containing porous silica particles in the range of 60 × 10 ⁶ m / g and containing spherical porous silica particles having a particle diameter larger than the thickness of the outermost layer.

Here, a description will be given based on FIG. 1 which shows an enlarged cross section of the thermal transfer recording medium of the present invention in which the thermal transfer layer has two layers.

Support: As a substrate of the support, a plastic film having relatively high heat resistance, such as polyester, polycarbonate, and polyimide having a thickness of 2 to 20 μm, cellophane, paper, and the like can be used. If necessary, a heat-resistant protective layer or a stick prevention layer made of a silicon-modified polymer or a fluorine-based polymer may be provided on the surface in contact with the thermal head.

First Thermal Transfer Layer The first thermal transfer layer is made of a heat-meltable ink to which a coloring agent, a vehicle and various additives are added. As the colorant, carbon black, organic pigments, dyes and the like can be used alone or in combination. Preferably having a sufficient color density, light,
It is preferable to select one that does not discolor due to heat, temperature, humidity, solvent, and the like. The main component of the vehicle is a wax having a melting point of 45 to 120 ° C. A kind selected from paraffin wax, carnauba wax, microcrystalline wax, candelilla wax, polyethylene wax, wood hunting, poaching, fatty acid amide, fatty acid ester, etc. Alternatively, two or more types are used, but the present invention is not particularly limited. In addition to the above components, various additives such as a fixing agent, a dispersing agent, and a leveling agent made of a thermoplastic resin can be added to the hot-melt ink as needed.

The composition and thickness of the first thermal transfer layer are determined by the required printing density and thermal sensitivity, and the thickness is preferably 0.1 to 10.0 μm, and more preferably 2.0 to 5.0 μm.

Outermost layer (second transfer layer): The outermost layer is made of a composite of a resin and spherical porous silica particles.

As the resin, a thermoplastic resin having a softening point of about 100 ° C. is used, and one or two or more kinds can be used depending on a cover wrapping property to a low smooth paper and a required thermal sensitivity.

As the thermoplastic resin, those conventionally used as heat-sensitive adhesives can be used as they are. Although not particularly limited, for example, hydroxypropyl cellulose, ethyl cellulose, ethylene acrylic acid copolymer, acrylic resin, polystyrene, polyamide, ethylene vinyl acetate copolymer, polyvinyl alcohol, polyvinyl pyrrolidone, petroleum resin, alkyl-modified phenol resin, ketone resin , Polyvinyl butyral and the like are used alone or in combination of two or more.

Assuming that the specific surface area of the porous particles is S (m ² / g) by the BET method and the average particle diameter is D μm, S / Dm / g is 100 × 10 ⁶ m / g> S / D
> 60 × 10 ⁶ m / g in the range of spherical porous particles having an average particle size in the range of 0.1 to 10.0 μm and basically 100
It is a porous silica particle that does not melt and soften at a temperature of not more than ℃, and one or more kinds can be used as needed. The porous silica particles need to have an average particle diameter larger than the thickness of the second thermal transfer layer (outermost layer).
If the average particle diameter of the porous silica particles is smaller than the thickness of the second thermal transfer layer (outermost layer), the porous silica particles will be buried in the second thermal transfer layer (outermost layer) and the second thermal transfer layer (outermost layer) Direct contact with the heat-resistant protective layer on the back side of the support cannot be prevented, especially when the resin component of the second thermal transfer layer (outermost layer) is transferred to the heat-resistant protective layer when stored for a long time in an environment at 60 ° C or higher. As a result, running defects during printing and deterioration in print quality occur. Therefore, the average particle diameter of the porous silica particles must be larger than the thickness of the second thermal transfer layer. The specific surface area Sm ² / g of the porous silica particles is 100 × 10 ⁶ m / g> S / DT>
If it is not within the range of 60 × 10 ⁶ m / g, the particles uniformly dispersed in the second thermal transfer layer (outermost layer) are not anchored to the second thermal transfer layer (outermost layer), and the particles are not transferred to the outermost thermal transfer layer. (The outermost layer), which easily causes a running defect in the cassette. Therefore, the specific surface area of the porous silica particles can be calculated from the average particle diameter range and the specific surface area range for application to the second thermal transfer layer, from 60 × 10 ⁶ m / g <(specific surface area) / (average particle diameter). ) <100 × 1
It is necessary in the range of 0 ⁶ m / g. The addition amount of the porous silica particles is closely related to the print quality and the storage stability. If the amount of the porous silica particles is less than 0.5% by weight in the second thermal transfer layer (outermost layer), the initial print quality is good but the temperature is high. If the storability is poor, and if it exceeds 50.0% by weight, the high-temperature storability is good, but the initial printability tends to be poor. Therefore, the addition amount of the porous silica particles is 0.1 to achieve both print quality and storage stability.
5 to 50.0% is good.

Heat-resistant protective layer: The heat-resistant protective layer is preferably one having both slipperiness and heat resistance, such as a silicone-modified polymer coating agent and a fluorine coating agent, and the material is not particularly limited.

(Examples) Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. Parts of the composition are by weight.

(Example 1) After preparing a first thermal transfer layer ink and an outermost thermal transfer layer ink having the following composition on the surface of a 3.5 μm pet film as a support and an ink for a heat-resistant protective layer on the back surface of the support, respectively. The resultant was applied and dried by the above-mentioned means to obtain a thermal transfer recording medium of the present invention.

Heat-resistant protective layer Silicone copolymer elastomer: 100 parts Polyisocyanate: 15 parts Methyl ethyl ketone: 500 parts Toluene: 400 parts Ink of the above composition is applied to the back surface of the support at 100 ° C. by a gravure roll coating method, and dried. , A 0.3 μm heat-resistant protective layer was formed.

First thermal transfer layer: Paraffin wax: 45 parts Ethylene-vinyl acetate copolymer: 30 parts Carbon black: 15 parts Dispersant: 10 parts An ink having the above composition was prepared using a three roll ink for ink heated to 100 ° C. This was coated on the surface of the support with a hot melt gravure roll so as to have a thickness of 3.5 μm to form a first thermal transfer layer.

Second thermal transfer layer (outermost layer): Polyamide resin ... 2 parts Ketone resin ... 70 parts Porous silica (SD-8, manufactured by Nittetsu Mining) ... 1 part (average particle size = 8 ± 2 µm, specific surface area = 600 [m ^2] / g] or more) Ethyl alcohol: 600 parts Ethyl acetate: 300 parts Ink of the above composition is applied on the first thermal transfer layer by a gravure roll coating method, dried at 90 ° C., and has a thickness of 1.0 μm.
Of the second thermal transfer layer (outermost layer).

Even after the heat transfer recording medium thus obtained was wound up in a roll state and stored at 60 ° C. for 24 hours, no transfer of the components of the second heat transfer layer (outermost layer) to the heat-resistant protective layer side was observed. As a result of performing thermal transfer printing with a commercial thermal printer at room temperature, from smooth paper with a Beck smoothness of 200 seconds or more,
Good print quality was obtained up to rough paper with a Beck smoothness of about 20 seconds, and no troubles such as running of the ribbon in the cassette and contamination of the head occurred.

Comparative Example 1 A heat-resistant protective layer and a first thermal transfer layer were prepared and coated on the same support as in Example 1 in the same manner as in Example 1, and a porous silica ratio was applied to the second thermal transfer layer (outermost layer). A coating material having a surface area of 7 m ² / g or less was prepared and coated in the same manner as in Example 1 except that the following composition was used.

Second thermal transfer layer (outermost layer) Polyamide resin ... 2 parts Ketone resin ... 70 parts Porous silica (SH-4, manufactured by Nittetsu Mining) ... 1 part (average particle size = 4 ± 1 µm, specific surface area = 7 [m ² / g] The following) Ethyl alcohol: 600 parts Ethyl acetate: 300 parts The thus obtained thermal transfer recording medium is wound into a roll and stored at 60 ° C. for 24 hours.
Transfer of the components of the thermal transfer layer (outermost layer) was observed. 60 ° C-24
Thermal transfer printing of the ribbon after storage at room temperature with a commercial thermal printer at room temperature resulted in background staining on smooth paper with a Beck smoothness of 200 seconds or more, and dot reproduction on rough paper with a Beck smoothness of about 20 seconds. Good printing quality was not obtained due to poor properties. In addition, the pulling force of the ribbon during the running of the ribbon in the cassette increased, and a sticking tendency was occasionally observed and the running was unstable. In addition, troubles such as head contamination occurred.

(Comparative Example 2) On the same support as in Example 1, a heat-resistant protective layer and a first thermal transfer layer were prepared and coated in the same manner as in Example 1, and an average of silica was contained in the second thermal transfer layer (outermost layer). Particles having a particle diameter of not more than 0.1 μm and a specific surface area of not less than 100 [m ² / g] were prepared and coated in the same composition as in Example 1.

The second thermal transfer layer (outermost layer) Polyamide resin ... 2 parts Ketone resin ... 70 parts of silica ... 1 part (average particle size = 0.007, specific surface area = 380 [m ² / g]) ethyl alcohol ... 600 parts of ethyl acetate ... 300 parts The thus obtained thermal transfer recording medium is wound into a roll and stored at 60 ° C. for 24 hours.
Transfer of the components of the thermal transfer layer (outermost layer) was observed. 60 ° C-24
Thermal transfer printing of the ribbon after storage at room temperature with a commercial thermal printer at room temperature resulted in background staining on smooth paper with a Beck smoothness of 200 seconds or more, and dot reproduction on rough paper with a Beck smoothness of about 20 seconds. Good printing quality was not obtained due to poor properties. In addition, the pulling force of the ribbon during the running of the ribbon in the cassette increased, and the stick tended to be seen occasionally. In addition, troubles such as head contamination occurred.

〔The invention's effect〕

With the use of the thermal transfer recording medium according to the present invention, the effect of the porous silica particles makes it possible to completely prevent the components of the thermal transfer layer from migrating to the back surface of the support or the heat-resistant protective layer during high-temperature and long-term storage, as compared with conventional thermal transfer recording media. And good printing with excellent dot reproducibility is obtained even after storage, and good ribbon running properties are obtained.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view of the thermal transfer recording medium of the present invention, wherein 1 is a support, 2 is a first thermal transfer layer, 3 is a second thermal transfer layer (outermost layer), and 4 is a heat-resistant protective layer.

Claims (1)

(57) [Claims] 1. A thermal transfer recording medium comprising: a first thermal transfer layer comprising a heat-meltable ink on a surface of a support; and a second thermal transfer layer comprising a composite of a thermoplastic resin and porous silica particles provided thereon. The average particle diameter Dμ is applied to the outermost second thermal transfer layer.
m, spherical porous silica having a specific surface area of Sm ² / g, wherein S / Dm /
g is in the range of 100 × 10 ⁶ m / g> S / D> 60 × 10 ⁶ m / g, and the outermost second thermal transfer layer is an average of the porous silica particles. A thermal transfer recording medium characterized by being thinner than the particle diameter.