JPH0318837B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a thermal printing medium, in particular, a method for thermally transferring a printed image onto a recording medium having at least a portion of its surface made of a polyvinyl chloride resin. The present invention relates to a thermal printing medium suitable for forming recorded images.

(Prior art) In recent years, non-impact thermal transfer printers have become popular because they can produce high-quality recorded images, do not generate noise, have a simple structure, are easy to maintain, and are inexpensive. It has been widely used as a type printer. This thermal transfer printer uses a thermal head to convert an electrical signal into thermal energy, and the thermal energy melts the ink on the thermal transfer ribbon that the thermal head comes into contact with and transfers it onto recording paper, thereby forming a printed image. However, the thermal transfer ribbon is usually a ribbon-shaped thermal printing medium formed by laminating an ink layer containing wax on a substrate.

A hot stamp is also known as a non-impact type image forming means, and the film for this hot stamp also employs a thermal printing medium similar to that used in the thermal transfer printer.

(Problem to be solved by the invention) However, with conventional thermal printing media, high-quality recorded images can only be formed on plain paper whose surface has been processed to be relatively smooth; It is extremely difficult to form a recorded image by thermal transfer, and even if a recorded image can be formed by thermal transfer, there is a problem that when the recorded image is rubbed, it is easily wiped off or peeled off. For this reason, it has not been put to practical use as a thermal printing medium for forming recorded images by thermal transfer on the surfaces of plastic cards, cards, and labels such as cash cards and telephone cards, which have been rapidly becoming popular in recent years. This is the current situation.

Therefore, the present invention is directed to plastic cards and labels, especially cards, labels, and sheets made of polyvinyl chloride resin, which are the predominant type of plastic cards, and which have at least a portion of their surface covered with polyvinyl chloride resin. The object of the present invention is to obtain a thermal printing medium that can form an extremely strong printed image on the surface of an article by thermal transfer.

(Means for Solving the Problem) As a means for solving this problem, the present invention, as shown in FIG. A transparent protective layer 2 made of a mixture of a donor polymer and a polyvinyl chloride resin, and a styrene-methacrylic acid ester donor polymer, polymethyl methacrylate, and a polyvinyl chloride resin laminated on the surface of the transparent protective layer 2. A thermal printing medium 4 comprising an ink layer 3 made of a mixture of a resin and a colorant.
It provides:

(Function) When the thermal printing medium according to the present invention is used, for example, as a thermal transfer ribbon of a thermal transfer printer and a printed image is formed on a recording medium made of a polyvinyl chloride resin, the thermal printing medium according to the present invention is heated from a thermal head through the substrate 1. When exposed to heat, the resins constituting the ink layer 3 and the transparent protective layer 2 are respectively melted by the heat, and at the same time, the surface of the polyvinyl chloride resin of the recording medium is also melted and softened, so that the pressing force of the thermal head is reduced. The molten thermal transfer ink is transferred onto the surface of the recording medium, and the transparent protective layer covers the ink surface on the recording medium, and is cooled and solidified. During this transfer process, the thermal transfer ink and the protective layer are transferred so as to be embedded in the surface of the recording medium, which has been thermally softened by the pressing force of the thermal head, so that after solidification, the transferred image becomes resistant to friction.

That is, the present invention does not contain any waxes, since the waxes conventionally used as components of the ink layer inhibit the adhesion of the ink to the polyvinyl chloride resin forming the surface of the recording medium. , an ink layer is formed with a component composition that easily adheres to the recording medium, while a transparent or translucent transparent protective layer is provided between the substrate and the ink layer, and the ink is transferred onto the recording medium during thermal transfer. By transferring the components of the protective layer onto the layer to protect the ink layer on the recording medium, the ink layer becomes visible through the transparent protective layer and improves the abrasion resistance of the recorded image. This is how it was done.

The substrate functions as a support for the ink layer and as a thermal conductor that transfers heat from the thermal head to the protective layer and the ink layer, and is made of polyester resin, polyethylene resin, etc.
In addition to plastic thin films conventionally used as substrates for thermal transfer ribbons, tissue paper and metal thin films can also be used.

The transparent protective layer is thermally transferred onto the recording medium made of polyvinyl chloride resin together with the ink of the ink layer, but it covers the surface of the ink that has been thermally transferred and firmly adheres to the recording medium. In addition, it is necessary to see through the ink layer transferred onto the substrate, but as a result of implementation, these requirements can be protected with a thin layer made of a mixture of styrene-methacrylic acid ester copolymer and polyvinyl chloride resin. It has become clear that this can be achieved by forming a layer.

Examples of the polyvinyl chloride resin used as a component of the transparent protective layer include vinyl chloride homopolymer, vinyl chloride-acrylic acid ester copolymer, vinyl chloride-vinyl acetate copolymer, and vinyl chloride-ethylene copolymer. These resins can be used alone or in combination of two or more. Furthermore, after the protective layer is transferred with the ink, it is necessary to see through the ink underneath, so it is desirable that the protective layer be transparent or semi-transparent.
Furthermore, it is desirable that the material be colorless or light-colored.

A small amount of lubricant may be added to the composition of the protective layer in order to improve the abrasion resistance. As the lubricant, for example, a lubricant that is fixed at room temperature such as stearic acid or AC polyethylene can be used.

In order to improve the adhesion to the recording medium, the ink layer uses a mixture of three components, styrene-methacrylic acid ester copolymer, polymethyl methacrylate resin, and polyvinyl chloride resin, as the matrix resin. Although the blending ratio of these resins can be set arbitrarily, a composition containing styrene-methacrylic acid ester and polymethyl methacrylate resin as main components and a polyvinyl chloride resin as a secondary component is preferable.

As with the protective layer, the polyvinyl chloride resin that is a component of the ink layer includes vinyl chloride homopolymer, vinyl chloride-acrylic acid ester copolymer,
One or more resins selected from the group consisting of vinyl chloride-vinyl acetate copolymers and vinyl chloride-ethylene copolymers can be used. Moreover, plasticity may be added as necessary.

A coloring agent is added to the matrix resin of the ink layer in order to obtain a desired color tone, and any known coloring agent may be used. Note that a dispersant may be added to uniformly disperse the colorant in the colorant matrix, and an oily substance such as castor oil or mink oil may be added to improve the fluidity of the ink during thermal transfer. Also good. However, the addition of waxes conventionally added to the ink layer, such as carnauba wax and polyethylene wax, is undesirable because the abrasion resistance of the printed image after transfer is greatly reduced.

The thermal printing medium according to the present invention basically has a three-layer structure as described above, but in order to improve the releasability from the substrate during thermal transfer, if necessary, the thermal printing medium has a three-layer structure between the substrate and the protective layer. A release layer may be provided in between. This release layer is usually formed of a mixture containing a silicone release agent, a resin such as polyamide, and a lubricant such as stearic acid. These may be commercially available.

The thickness of each layer of the substrate, transparent protective layer, and ink layer is not particularly limited, but when obtaining a clear image as a printing medium for a thermal transfer printer, the thickness of the substrate is 3 to 15 μm, and the thickness of the protective layer is 0.5 μm. ~5μ, the ink layer is
The thickness is preferably in the range of 0.5 to 7.5μ, and the protective layer is preferably thinner than the ink layer.

The thermal printing medium having the above structure is manufactured by sequentially laminating a protective layer and an ink layer on a substrate, and any method such as a conventionally known solvent casting method or hot melt casting method may be used for this purpose. can.

The present invention was made for the purpose of forming a printed image on the surface of a plastic recording medium by thermal transfer. Those formed from polyvinyl chloride resins such as vinyl-acrylic acid ester copolymers, vinyl chloride-vinyl acetate copolymers, vinyl chloride-ethylene copolymers, and polyvinylidene chloride resins are suitable. These recording bodies may be formed of the polyvinyl chloride resin alone or a mixture thereof,
Further, depending on the purpose, the material may contain a plasticizer, a flexibility modifier such as rubber or rubber-based resin, a coloring agent, or a filler.

Furthermore, the recording medium does not necessarily have to be entirely made of the polyvinyl chloride resin, but may be made of metal, paper, or any other material whose surface is at least partially coated with the polyvinyl chloride resin. It's okay if it's hot.

Examples of the present invention will be described below.

Example 1 A commercially available polyester film (thickness: 12 μm) was used as a substrate, and a transparent protective layer forming composition having the following composition was gravure printed on one surface of the film, and then dried to form a transparent layer with a thickness of 0.2 μm. A protective layer was formed.

Next, a separately prepared thermal transfer ink layer composition having the following composition was laminated on the surface of the transparent protective layer by gravure printing and dried to form a 1.5 μm thick ink layer, and a 13.7 μm thick thermal transfer ink layer composition was laminated on the surface of the transparent protective layer by gravure printing. A print medium was obtained.

(Composition for forming a transparent protective layer) Styrene-methacrylic acid ester copolymer (manufactured by Taisei Kako Co., Ltd., 7450MB) 1.0 parts by weight Polyvinyl chloride resin (manufactured by Showa Kobunshi Co., Ltd., Vinyroll K-2) 0.15 Part by weight AC polyethylene (Lubricant manufactured by Nippon Polycon Co., Ltd., A-
20) 0.15 parts by weight Toluene 59 parts by weight Ethyl acetate 59 parts by weight (composition for forming thermal transfer ink layer) Carbon black (MA-100, manufactured by Mitsubishi Kasei Corporation)
8 parts by weight Styrene-methacrylic acid ester copolymer (7450MB) 4 parts by weight Dyanaru LR-174 (trade name, Mitsubishi Rayon Co., Ltd.)
Polymethyl methacrylate resin) 3 parts by weight Vinyroll K-2 (trade name, manufactured by Showa Kobunshi Co., Ltd., vinyl chloride resin) 1 part by weight BYK130 (trade name, amide dispersant manufactured by Bitskumarinkrodt) 1 weight 1 part mink oil (manufactured by Nikko Rica) 85 parts by weight Solvent (toluene:ethyl acetate = 1:1) A transparent polyvinyl chloride resin film (50 μm) made by adding 5 parts by weight of methacrylate-butadiene-styrene copolymer as a modifier and 2 parts by weight of dioctyl phthalate as a plasticizer is layered so as to be in contact with the surface. When the material was supplied to a commercially available thermal transfer printer modified to print at a temperature 60°C higher and thermal transfer recording was performed, clear black print with a density of 1.30 was obtained.

When this printed transparent polyvinyl chloride resin film was set in a friction tester and rubbed against high-quality paper under a load of 2 kg, no change was observed in the print even after 100 times of rubbing. Also, when I stroked the printed surface with my finger, it was smooth.
Even when scratched with a fingernail, no peeling of the print occurred.

Example 2 The same procedure as Example 1 was repeated except that a red pigment (Shimura First Magenta RH, manufactured by Dainippon Ink Co., Ltd.) was used instead of carbon black to prepare a composition for forming a thermal transfer ink layer. A thermal printing medium was obtained in the same manner.

This thermal printing medium was placed on top of a white card made of polyvinyl chloride resin and titanium oxide so that its thermal transfer ink layer was in contact with the surface of the card, and the temperature was increased to 130°C.
When the sample was supplied to a commercially available hot stamp device set at ℃ and thermal transfer recording was performed, a clear red print with a density of 1.25 was obtained.

When the printed surface of this card was subjected to a friction resistance test in the same manner as in Example 1, no change was observed in the printed image. Further, when the printed surface was stroked with a finger, it was smooth, and even when scratched with a fingernail, no peeling of the printed character occurred.

Comparative Example The polyester film used in Example 1 was used as a base, and the thermal transfer ink layer forming composition prepared in Example 1 was directly gravure printed on the surface of the base and dried to form a 1.5 μm ink layer. A thermal printing medium was obtained.

When this thermal printing medium was used to print on a transparent polyvinyl chloride resin film by thermal transfer under the same conditions as in Example 1 and a friction resistance test was performed, the ink gradually shifted after the 10th printing, and the image was disordered.

Comparative Example 2 Same as Example 1 except that 1.5 parts by weight of magnesium silicate was used instead of the polyvinyl chloride resin in the composition for forming a thermal transfer ink layer. A thermal printing medium was obtained in exactly the same manner.

When this thermal printing medium was used to print on a transparent polyvinyl chloride resin film by thermal transfer under the same conditions as in Example 1 and a friction resistance test was conducted, the ink suddenly shifted after the 30th printing. The image is distorted.

Comparative Example 3 The polyester film used in Example 1 was used as a base, and 1.5 parts by weight of magnesium silicate was used instead of the polyvinyl chloride resin in the composition for forming a thermal transfer ink layer of Example 1 to form a thermal transfer ink layer. A composition was prepared, and this composition was directly gravure printed on the surface of the substrate and dried to form an ink layer with a thickness of 1.5 μm, thereby obtaining a thermal printing medium.

Using this thermal printing medium, printing was performed on a transparent polyvinyl chloride resin film under the same conditions as in Example 1,
When a friction resistance test was performed, there was no disturbance of the image due to ink displacement, but the printed characters were raised from the surface of the polyvinyl chloride resin film that was the recording medium, and the surface of the printed characters was rough, and it was difficult to scratch with a fingernail. When scratched, the ink layer cracked and easily peeled off. This is presumably because the ink has poor thermal fluidity and poor adhesion.

Comparative Example 4 A thermal printing medium was prepared in exactly the same manner as in Example 1, except that a composition for forming a transparent protective layer prepared by removing the polyvinyl chloride resin from the composition for forming a transparent protective layer was used. I got it.

When this thermal printing medium was used to print on a transparent polyvinyl chloride resin film by thermal transfer under the same conditions as in Example 1 and a friction resistance test was performed, no image disturbance due to ink displacement occurred. The problem was that the protective layer easily peeled off when scratched with a fingernail.

(Effects of the Invention) As is clear from the above description, according to the present invention, the thermal printing medium has a three-layer structure in which an ink layer and a protective layer are sequentially laminated, and the ink layer and the protective layer are formed by polychlorinating the recording medium. By being made of a material that easily adheres to vinyl resin, it is possible to make plastic articles that are not possible with conventional thermal printing media, especially articles made of polyvinyl chloride resin, such as cash cards, etc.
In addition to cards such as telephone cards, labels,
Barcodes, letters, numbers, symbols, and other arbitrary images can be formed on articles whose surfaces are made of polyvinyl chloride resin, such as OHP sheets, resin-coated paper, packaging films, and cases. Further, the thermal printing medium according to the present invention can be used not only as a thermal transfer ribbon or sheet for a thermal transfer type printer or a thermal transfer type printer, but also as a thermal printing medium for a hot stamp, and other excellent effects can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a thermal printing medium according to the present invention. 1 - Substrate, 2 - Transparent protective layer, 3 - Thermal transfer ink layer.

Claims (1)

[Scope of Claims] 1. A substrate, a transparent protective layer laminated on one surface of the substrate and made of a mixture of a styrene-methacrylic acid ester copolymer and a polyvinyl chloride resin, and a transparent protective layer laminated on one surface of the substrate; 1. A thermal printing medium comprising an ink layer laminated on a surface thereof and comprising a mixture of a styrene-methacrylic acid ester copolymer, polymethyl methacrylate, a polyvinyl chloride resin, and a colorant. 2. The polyvinyl chloride resin is one selected from the group consisting of vinyl chloride homopolymer, vinyl chloride-acrylic acid ester copolymer, vinyl chloride-vinyl acetate copolymer, and vinyl chloride-ethylene copolymer. or the thermal printing medium according to claim 1, which is two or more kinds of resins.