JPH0410985A - Polyester film for thermal transfer recording and its manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a polyester film for thermal transfer recording provided with a heat-resistant layer. More specifically, the present invention relates to a polyester film for thermal transfer recording that allows matte printing.

[Prior Art] In recent years, thermal transfer recording, in which a transferred image is formed on plain paper using a thermal printer, thermal facsimile, etc., has become easy to maintain due to the simple mechanism of the device, and has low price and maintenance costs. In addition, it has recently been widely used because it allows for clear and robust recording with low energy, and because it is relatively easy to perform color recording by using multicolored ink sheets. In particular, the amount of monochrome thermal transfer recording films used is increasing due to the spread of thermal printers for word processors, thermal facsimiles, and the like.

[Problems to be Solved by the Invention] As the base film of the above-mentioned thermal transfer recording film, polyester, polycarbonate, polystyrene,
Films made of polypropylene, vinyl chloride, vinylidene chloride, polyimide, polyamide, etc. are known. Polyester is generally used.

However, in a thermal transfer recording film using this polyester film, the surface temperature of the thermal head becomes higher than the melting point of the polyester film during recording, and the surface of the polyester film that comes into contact with the thermal head is fused to the thermal head. As a result, the running performance of the thermal head becomes poor and printing problems occur. This is called the stick phenomenon, and a polyester film coated with a heat-resistant layer, in which one side of the polyester film is coated with a heat-resistant material, is usually used.

For example, JP-A-55-7467 discloses a base film coated on one side with a heat-resistant resin such as silicone resin, epoxy resin, or nitrocellulose. JP-A-56-155794 discloses a base film in which the lower surface is coated with a highly slippery inorganic pigment and a thermosetting or thermosetting resin material. Japanese Patent Application Publication No. 5
7-74195 discloses a base film in which a silicon oxide layer or a three-dimensional crosslinked layer of polyfunctional (meth)acrylates is coated on the lower surface of the base film.

These publications exemplify methods such as solvent coating, hot melt coating, and lamination using ready-made base films.

On the other hand, as for the polyester film for thermal transfer recording intended for matte printing of the present invention, methods are conventionally known in which various treatments are applied to the surface opposite to the surface coated with the above-mentioned heat-resistant layer. For example, as in JP-A No. 60-101084, the surface of the base film on which the heat-melting ink layer is to be provided is matted by sandblasting, or
A method of kneading fine particles and forming a film into a mat is disclosed. Also, JP-A-56-164
No. 891 discloses a method of mixing a matting agent into a heat-melting thermal ink. moreover,
JP-A-60-101083 discloses a method of providing a matte layer on a base film.

As described above, the base film is coated with a coating layer (heat-resistant layer) made of a heat-resistant material on one side and a heat-melting ink layer on the other side. When the purpose is matte printing, a matte layer is coated between the base film and the heat-melting ink layer (Japanese Patent Laid-Open No. 101083/1983). Here, three steps are required to apply each layer: a heat-resistant layer, a matte layer, and a heat-melting ink layer.

When the base film itself is subjected to sandblasting, fine particle kneading treatment (Japanese Unexamined Patent Publication No. 60-101084), or a matting agent is mixed into the heat-melting ink (Japanese Unexamined Patent Publication No. 56-164891), the heat-resistant layer, the heat-melting ink Two steps are required to apply layer after layer.

As described above, there are disadvantages in that the more manufacturing steps there are, the more complex it becomes, and the higher the cost. Furthermore, in general, when coating heat-resistant materials, many organic solvents are used, and there are problems in solvent treatment during coating.

For this reason, there has been a demand for a polyester film for thermal transfer recording that is provided with a heat-resistant layer and that can produce matte printing.

[Means for Solving the Problems] As a result of extensive research, the present inventors have provided a polyester film for thermal transfer recording that has heat resistance that allows matte printing.

That is, the polyester film for thermal transfer recording provided by the present invention is obtained by melt-extruding polyester kneaded with inorganic fine particles of 0.1 to 3 μm, and applying a heat-resistant resin aqueous solution or the like to one side of the polyester film before crystal orientation is completed. After coating an aqueous dispersion, the film is dried, stretched, and heat-treated to form a heat-resistant layer.

Further, the method for producing a polyester film for thermal transfer recording provided by the present invention involves melt-extruding polyester kneaded with inorganic fine particles of 0.1 to 3 μm, and applying the same method to one side of the polyester film before crystal orientation is completed. This process is characterized by forming a coating layer made of the heat-resistant resin through the following steps: (1) Coating an aqueous solution of a heat-resistant resin or its aqueous dispersion; (2) Drying and stretching; and (2) Heat treatment.

Furthermore, in the polyester film for thermal transfer recording and the manufacturing method thereof of the present invention, the heat-resistant resin aqueous solution or its aqueous dispersion, the inorganic fine particles, the center surface average roughness SRa, and the 10-point average roughness SRz have the following characteristics. It is something to do.

The heat-resistant resin aqueous solution or its aqueous dispersion contains at least one selected from silicone resins, urethane resins, melamine resins, urea-formalin resins, and cellulose derivatives.
It is characterized by being a species.

The inorganic fine particles are at least one selected from silicon oxide, titanium oxide, magnesium oxide, kaolinite, aluminum hydroxide, talc, sericite, barium sulfate, spinel, and cordierite. be.

The center surface average roughness SRa of the thermal transfer recording film is 0.
15 to 1.00 μm, and the 10-point average roughness SRz is
It is characterized by having a thickness of 1.00 to 6.00 um.

The present invention will be specifically explained below.

The polyester of the present invention is a highly crystalline linear saturated polyester synthesized from an aromatic dibasic acid or its ester-forming derivative and a diol, and includes polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, polyethylene-2, 6-naphthalate and the like can be mentioned. Further, to improve slipperiness, calcium carbonate, kaolin, silica, aluminum hydroxide, etc. can be contained.

The purpose of the polyester film for thermal transfer recording of the present invention is to obtain matte printing properties, and for this purpose, inorganic fine particles are kneaded into the above-mentioned polyester to form protrusions on the surface of the film. The inorganic fine particles were selected from silicon oxide, titanium oxide, magnesium oxide, kaolinite, aluminum hydroxide, talc, sericite, barium sulfate, spinel (MgO・A1203), and cordierite (2Mg0・2A1203・5S102). It is preferable to use at least one of the following. Among these, those having a plate-like or flaky structure are particularly preferred. A material having a plate-like or flake-like structure is effective in terms of wear resistance when it comes into contact with a thermal head. However, fine particles with granular forms, such as inorganic fine particles such as silicon oxide, zirconia, titanium oxide, calcium carbonate, magnesium oxide, barium carbonate, and zinc oxide, and organic fine particles such as benzoguanamine resin particles, epoxy resin particles, and urea resin particles Fine particles may also be used together.

The surface roughness of the film into which the fine particles have been kneaded is preferably such that the center surface average roughness SRa is 0.15 to 1.00 μm. When the SRa is less than 0.15 μm, the roughness of the film surface is small, making it difficult to obtain matte printing properties.
On the other hand, when SRa exceeds 1°00 μm, matte printing properties can be obtained, but there is a drawback that the printing quality is poor.

In addition, the 10-point average roughness SRz is 1.00 to 6.00 μm
It is preferable that Similarly, SR2 is 1.00 μm
If it is less than 6.0, it is difficult to obtain matte printability due to the small roughness of the film surface;
When the thickness exceeds 0 μm, matte-like printing properties can be obtained, but there is a drawback that the printing quality is poor.

By the way, center surface average roughness SRa and 10 point average roughness S
Rz is measured according to a measurement method according to JIS B 0601. The definition of center surface average roughness SRa is as follows. From the roughness curved surface, the area S on its center plane
If we extract the M part and place orthogonal coordinate axes, X axis, and Y axis on the central plane of this extracted part and express the axis perpendicular to the central plane as the Z axis, we can express the value given by the following formula in μm. .

However, SM = LX XLY.

Furthermore, the definition of the 10-point average roughness SRz is as follows. Input and convert the distance between the average of the 1st to 5th peaks from the highest and the average of the 1st to 5th valleys from the deepest of the planes parallel to the average line of the part extracted from the curved surface by the standard area. expressed in μm.

In addition to the fine particles kneaded together with the polyester, antistatic agents, antioxidants, ultraviolet absorbers, foaming agents, etc. may be added as necessary.

The polyester film for thermal transfer recording of the present invention is coated with a heat-resistant resin as an aqueous solution or dispersion on one side, and the polyester film is selected from silicone resin, urethane resin, melamine resin, urea-formalin resin, and cellulose derivative. It is preferable to use at least one of the following. The melting point of polyester is 260°C, and it is a material that does not fuse to the thermal head, and is higher than the melting point of polyester.
Or, the decomposition temperature is 260°C or higher, preferably 280°C
There is no limitation to the use of other materials as long as they meet the above requirements.

The thickness of the coated layer coated with the heat-resistant resin is 0.05 to 3.0 μm, preferably 0.05 μm to 3.0 μm after stretching.
It is 1 to 2.0 μm. If it is less than the lower limit of 0.05 μm, there is no effect on heat resistance (and if it exceeds 3.0 μm, there is a drawback of poor printing performance.

The polyester film for thermal transfer recording of the present invention is obtained by melt-extruding polyester kneaded with inorganic fine particles, coating with a heat-resistant resin material, drying, stretching, and heat-treating, and the surface of the film is matte. It has a heat-resistant layer on one side. Therefore, a thermal transfer recording sheet can be prepared from the obtained polyester film for thermal transfer recording by simply coating the surface opposite to the surface coated with the heat-resistant layer with a heat-melting ink. Heat-resistant layer on existing polyester film,
Compared to the conventional method in which each matte layer was applied individually, this method saves labor in the process, which is a huge advantage.

The method for producing the polyester film for thermal transfer recording of the present invention is a so-called in-line coating method, and specifically, the above-mentioned polyester raw material is melt-extruded using an ordinary film-forming machine, cooled, and then A heat-resistant resin aqueous solution or aqueous dispersion is applied to a longitudinally stretched film that has been uniaxially stretched to ~5 times. After coating, it is dried, the longitudinally stretched film is stretched 3 to 5 times in the transverse direction, and then heat treated to produce a biaxially stretched polyester film. In this method, heat-resistant resin is coated, dried, and immediately stretched.
The coated surface can have a uniform and thin film thickness.

The method for coating the heat-resistant resin may be any commonly used method, and for example, coaters such as a rod coater, gravure coater, reverse roll coater, direct roll coater, knife coater, etc. can be used.

The thickness of the polyester film for thermal transfer recording of the present invention is:
The thickness is 3 to 18 μm, preferably 4 to 8 μm.

In the polyester film for thermal transfer recording of the present invention,
A heat-melt ink is coated on the opposite side of the heat-resistant layer coated side to form a heat transfer recording sheet.
It mainly consists of colorants, waxes, and resins.

As the coloring agent, for example, benzidine yellow G for yellow, rhodamine lake Y for magenta, phthalocyanine blue for cyan, and carbon black for black are used.

As waxes, for example, paraffin wax, carnauba wax, microcrystalline wax, low molecular weight polyethylene wax, oxidized polyethylene wax, synthetic wax, etc. are used.

As the resin, for example, ethylene vinyl acetate copolymer, ethylene ethyl acrylate copolymer, fatty acid hydrocarbon resin, aromatic hydrocarbon resin, etc. are used.

In addition, as an additive, a pigment dispersant, oil, etc. can be added as necessary.

The hot melt ink is applied by hot melt coating or solvent coating using a rod coater, gravure coater, reverse roll coater, direct roll coater, or the like.

Although heat-melting ink is illustrated here, there is no limitation in that it may be replaced with heat-sublimable ink.

[Function] The polyester film for thermal transfer recording of the present invention is capable of matte printing and is coated with a heat-resistant layer, and its manufacturing method is a so-called in-line coating method. A thermal transfer recording sheet manufactured using this polyester film for thermal transfer recording has excellent heat resistance when printed with a thermal head, and can produce a matte-like recorded image. This is because inorganic fine particles are kneaded into the polyester when stretching the polyester film, making it easier to obtain matte prints. Furthermore, since the coating is applied during molding of the polyester film, it is thought that the heat resistance results from a uniform heat-resistant layer.

[Example] The present invention will be specifically described below with reference to Examples.

Example 1 Polyethylene terephthalate with an intrinsic viscosity of 0.66 containing 10% by weight of aluminum hydroxide having a flaky structure with an average particle size of 0.3 microns as inorganic fine particles was melted at 285°C and heated to 60°C. It was extruded onto a cooling drum to obtain an unstretched film with a thickness of 80 microns. The film was then stretched 3.5 times in the machine direction at 83° C. to obtain a uniaxially stretched film.

- Melamine resin (manufactured by Sumitomo Chemical Co., Ltd.) on the axially stretched film;
Coat product name violet resin 613) and immediately apply 1
It was stretched 3.5 times in the transverse direction at 10°C and heat treated at 210°C to obtain a polyester film for thermal transfer recording having a coating layer thickness of 0.2 μm and a base polyester film thickness of 7 μm. Regarding this film, the center surface average roughness SRa and the 10-point average roughness SRz were measured using a three-dimensional roughness measuring instrument 5E-3AK manufactured by Koita Research Institute Co., Ltd. As a result, SRa was 0.51 μm and SRz was 4°17 μm.

The following heat-melt ink was applied to the thus obtained polyester film for thermal transfer recording using a hot melt coater at a coating density of 4 g/rrr.

Carbon black 15 parts by weight Black dye 5 parts by weight Paraffin wax 40 parts by weight Carnauba wax 30 parts by weight Ethylene-vinyl acetate resin 10 parts by weight or more A thermal transfer recording sheet was printed in solid black using a Matsushita Densen facsimile UF-82H. was printed in send mode. The 60 degree glossiness of the solid black portion of the obtained printed image was measured using Gloss checker IG-310 manufactured by Horiba, Ltd. 60 degree gloss is 1
6, and a matte-like printed image could be obtained.

Example 2 Polyethylene terephthalate with an intrinsic viscosity of 0.66 containing 5% by weight of titanium oxide with an average particle size of 0.1 microns as inorganic fine particles was melted at 285°C.
It was extruded onto a cooling drum at 60°C to obtain an unstretched film with a thickness of 80 microns.

The film was then stretched 3.5 times in the machine direction at 83° C. to obtain a uniaxially stretched film.

An aqueous liquid consisting of 2 parts by weight of 2.4.6-tris(dimethylaminomethyl)phenol per 10 parts by weight of a polyfunctional epoxy compound (manufactured by Nagashio Kasei Co., Ltd., trade name Dinacol EX-614) was applied to a uniaxially stretched film. Apply and immediately apply 1
Stretched 3.5 times in the transverse direction at 10°C and heat-treated at 210°C to reduce the thickness of the coating layer to 0. A polyester film for thermal transfer recording with a thickness of 7 μm and a polyester film having a base material of 2 μm was obtained. Regarding this film, the center surface average roughness SRa and the 10-point average roughness SRz were measured using a three-dimensional roughness measuring instrument 5E-3AK manufactured by Koita Research Institute Co., Ltd. As a result, SRa was 0.23 μm and 1SRz was 2.55 μm.

A hot melt ink was applied in the same manner as in Example 1, and
When the 60 degree glossiness of the printed image was measured, the 60 degree glossiness of the printed image was 20, indicating a matte tone.

Examples 3 to 4 and Comparative Examples 1 to 2 A polyester film for thermal transfer recording was prepared in the same manner as in Example 1, except that the inorganic fine particles of Example 1, their particle sizes, and the amount of inorganic fine particles added to be mixed with polyethylene terephthalate were changed. A thermal transfer recording sheet was produced.

The polyester film for thermal transfer recording and the thermal transfer recording sheet obtained here were evaluated, and the results are shown in Table 1.

In Comparative Example 2, the 60 degree glossiness was as high as 45, and a matte image could not be obtained.

[Effects of the Invention] The polyester film for thermal transfer recording of the present invention is finished by coating a heat-resistant material made of an aqueous solution of a heat-resistant resin or a dispersion thereof in the manufacturing process of the polyester film. The practical effects of the present invention are extremely large, since labor can be saved in the production of coated thermal transfer recording sheets capable of printing with a matte appearance.

From the results in Table 1, in Examples 3 and 4, the 60 degree glossiness was 8 and 3, respectively, and a matte image could be obtained. Comparative Example 1 had a low 60 degree gloss of 1, but
The printed image had white spots and was well received. This is S
This is due to the large roughness of Ra of 1.66 μm and 1SRz of 7.52 μm.

Claims (1)

[Claims] 1. Polyester kneaded with inorganic fine particles of 0.1 to 3 μm is melt-extruded, and a heat-resistant resin aqueous solution or its aqueous dispersion is coated on one side of the polyester film before crystal orientation is completed. A polyester film for thermal transfer recording, which is obtained by drying, stretching, and heat-treating the film to form a heat-resistant layer. 2. The thermal transfer recording according to claim 1, wherein the heat-resistant resin aqueous solution or its aqueous dispersion is at least one selected from silicone resins, urethane resins, melamine resins, urea-formalin resins, and cellulose derivatives. Polyester film for use. 3 The inorganic fine particles include silicon oxide, titanium oxide, magnesium oxide, kaolinite, aluminum hydroxide, talc,
The polyester film for thermal transfer recording according to claim 1, characterized in that it is at least one selected from sericite, barium sulfate, spinel, and cordierite. 4. Claim 1, wherein the polyester film for thermal transfer recording has a central surface average roughness SRa of 0.15 to 1.00 μm and a 10-point average roughness SRz of 1.00 to 6.00 μm. The polyester film for thermal transfer recording described above. 5 Melt-extrude polyester kneaded with inorganic fine particles of 0.1 to 3 μm, and apply an aqueous heat-resistant resin solution or its aqueous dispersion to one side of the polyester film before crystal orientation is completed. (2) Drying and stretching step (3) Heat treatment step to form a coating layer made of the heat-resistant resin. A method for producing a polyester film for thermal transfer recording. 6. The thermal transfer recording according to claim 5, wherein the heat-resistant resin aqueous solution or its aqueous dispersion is at least one selected from silicone resins, urethane resins, melamine resins, urea-formalin resins, and cellulose derivatives. Method for producing polyester film for use. 7 The inorganic fine particles include silicon oxide, titanium oxide, magnesium oxide, kaolinite, aluminum hydroxide, talc,
6. The method for producing a polyester film for thermal transfer recording according to claim 5, wherein the polyester film is at least one selected from sericite, barium sulfate, spinel, and cordierite. 8. Claim 5, wherein the polyester film for thermal transfer recording has a central surface average roughness SRa of 0.15 to 1.00 μm, and a 10-point average roughness SRz of 1.00 to 6.00 μm. The method for producing the polyester film for thermal transfer recording described above.