JPS63268693A - Multitime use type thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To prevent generation of ghost, even in repeated printing, and enable clear printing, by enabling a surface of a porous structure to be releasably adhered to a receptor. CONSTITUTION:An ink-maintaining layer 3 is provided on a base 2. The layer 3 has a heat-fusible colored ink 6 contained in pores 5 of a porous structure 4, and a surface 4a of the structure 4 is releasably adhered to a receptor at the time of thermal transfer. At the time of thermal transfer, the peripheral parts of the pores 5 of the structure 5 in printing areas are closed by adhesion of the surface 4a to the receptor 21, the colored ink 6 caused to flow out of the pores 5 by heating moves toward the receptor 21, and does not remain on the surface of the layer 3. Further, since the surface of the porous structure is releasably adhered to the receptor, generation of ghost is prevented even when the same part of this thermal transfer recording medium is repeatedly used.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a multi-use type thermal transfer recording medium used in a thermal melt transfer method, and more specifically, the present invention relates to a multi-use type thermal transfer recording medium used in a thermal melt transfer method. The present invention relates to a multi-use thermal transfer recording medium having an ink retaining layer containing a colored ink having a melt-transferable property.

[Problems to be solved by conventional technology and invention]

As a recording medium of this kind, Japanese Patent Application Laid-Open No. 55-10'557
A method disclosed in Japanese Patent No. 9 is known, but when printing using a conventional recording medium, a phenomenon called a ghost occurs.

The ghost is a phenomenon in which the outline of the first printed image pattern (for example, the letter W) is lightly transferred during the next printing (for example, the letter I), as shown in Fig. 4. When this phenomenon occurs, the printed image immediately becomes unclear.

The cause of this phenomenon was initially thought to be due to the pressure-sensitive transferability of the colored ink, and attempts were made to raise the melting point of the ink to reduce the pressure-sensitive transferability, but this resulted in a significant decrease in transfer density. It was not put into practical use.

The present invention fundamentally solves this problem by investigating its cause.

[Means for solving problems]

The present invention provides a multi-use thermal transfer recording medium having an ink retaining layer in which a porous structure contains a colored ink that can be melted and transferred to a receptor by heating, wherein the surface of the porous structure is The present invention relates to a multi-use thermal transfer recording medium that can be releasably adhered to a receptor.

[Function and Examples]

As a result of detailed research on the ghost phenomenon, it is assumed that it occurs through the following mechanism. This mechanism will be explained with reference to FIG.

In FIG. 5, al) is a conventional multi-use thermal transfer recording medium, which has an ink retaining layer 03 provided on a base 02), and the ink retaining layer has a porous structure 04). The hot-melt colored ink 00 is contained in the pores of the ink. Figure 5 shows the state of the recording medium after the recording medium 01) is heated from the back side of the base 02) using a heating head ■, etc. to melt and transfer the colored ink 0■ to the receiver, and then the receiver is separated. It is something.

As shown in FIG. 5, it was found that ink (1ea) remained on the surface of the ink retaining layer (13) at the boundary between the heated area (A) and the non-heated area (B) during printing.

It has come to be believed that the ink (lea) remaining on this surface is transferred to the receptor by pressure contact from a heating head, an energizing head, etc. during the next printing, causing ghosts.

Therefore, in the present invention, in order to eliminate such residual ink, the surface of the porous structure can be releasably adhered to the receptor.

Next, the operation of the configuration of the present invention will be explained based on the drawings.

FIG. 1 is a schematic partial sectional view showing an embodiment of the recording medium of the present invention. In FIG. 1, (1) is a recording medium, which has an ink retaining layer (3) on a base (z), and the ink retaining layer (3) has a porous structure (4).
A hot-melt colored ink (6) is contained in the pores (5). Then, the surface of the porous structure (4) (
4a) is configured such that it can be releasably adhered to the receiver at least during thermal transfer.

When using the above configuration, as shown in FIG. 2, during thermal transfer, the area around the holes (5) of the porous structure (4) on the surface of the ink retaining layer (3) at the printing location is heated by the heating head (2). The surface (4a) of the porous structure (4) is closed by adhering to the receptor (21), and therefore the colored ink (6) that melts due to heating and overflows from the pores (5) is attached to the receptor +211. Move only in the direction of hole (5
), and as a result, the colored ink (6) does not remain on the surface of the ink retaining layer (3) at the boundary between the heated area and the non-heated area during printing. Ta.

Furthermore, since the surface of the porous structure is designed to be releasably adhesive to the receptor, the adhesion of the porous structure to the receptor is retained in the ink retaining layer indefinitely and maintains connectivity. Therefore, even if the same location on the recording medium is used repeatedly, such a function is repeatedly exhibited and the occurrence of ghosts is completely prevented.

Next, the configuration of the present invention will be specifically explained.

The ink retaining layer is generally provided on the base. The base material is a film made of synthetic resin such as polyester, polyamide, polycarbonate, polyimide, etc., with a thickness of about 1-15mm, or a film with a thickness of 5mm thick, such as condenser paper, glassine paper, India paper, etc.
It is possible to use various base materials conventionally known for use in this type of recording medium, such as paper with a weight of about 1.5 to 25 mm.

Note that, in order to prevent the stick phenomenon, the base may be provided with a conventionally known stick prevention layer on the back surface (head contact surface).

Further, a conductive material may be mixed into the base to form a heating resistance layer using an electric transfer method, or to provide a static electricity removal function. Furthermore, it is also a preferable embodiment to provide an undercoat layer on the surface of the base to enhance bonding strength with the porous structure.

Next, the ink retaining layer will be explained.

The ink retaining layer is composed of a porous structure and colored ink contained therein. The appropriate thickness of the ink retaining layer is about 3 to 20 mm. When the thickness is less than 3 mm, the ink content decreases, resulting in extremely poor multi-time transfer properties, while when it exceeds 2011 mm, the initial density tends to decrease.

As the porous structure, any conventionally known porous structure can be employed, such as one made only of resin or one in which porous powder is bonded with resin.

The resin used should be heat resistant so that it will not decompose or change in quality even when heated during image formation, and even once heated, it will not transfer from the base to the receptor or cause layer separation. Preferably, the material has adhesiveness to the base and internal cohesive strength such that it does not cause any damage.

Examples of the resin include styrene-isoprene copolymer resin, styrene-butadiene copolymer resin, 1.2
- One or a mixture of polybutadiene resin, polyester resin, polyvinyl butyral resin, vinyl chloride-vinyl acetate copolymer resin, ethyl cellulose resin, cellulose acetate resin, etc., can be used.

Further, as the porous powder, diatomaceous earth, silica, and the like having an average particle size of about 0.3 to 30 mm can be used.

As means for imparting adhesion to the receptor on the surface of the porous structure, there are two methods: 1. Using a resin component that adheres to the receptor as a resin component constituting the porous structure, 2. Another method is to bloom a material that is adhesive to the receptor.

It is sufficient that the surface of the porous structure has adhesion to the receptor at least during thermal transfer, and it does not matter whether or not it has adhesion under normal conditions.

Among the resin components mentioned above, styrene-butadiene copolymer resin, 1,2-polybutadiene resin, styrene-isoprene copolymer resin, etc. can be suitably used as the resin that can be used in the above-mentioned means (2).

As a material that can be used for the above method (2), it is preferable to use an adhesive resin that is incompatible with the resin that mainly constitutes the porous structure, but can be dispersed and mixed with the resin. It is appropriate to add about 0.2 to 3.0 parts by weight to 10 parts by weight of the main resin component.

The adhesive resin for blooming is ethylene-
Vinyl acetate copolymer resin, ethylene-ethyl acrylate copolymer resin, styrene-butadiene copolymer resin,
One type of styrene-isoprene copolymer resin, 1,2-polybutadiene resin, ethyl cellulose resin, cellulose acetate resin, acrylic resin, or a mixture of a plurality of these resins can be used. However, since the adhesiveness of the resin component may vary depending on the surface properties of the receptor, other resins may be used depending on the receptor.

In the blooming process, adhesive resin is dissolved in a solvent that has a boiling point higher than that of a volatile solvent that dissolves the main resin of the porous structure and does not substantially dissolve the main resin, and when dried, the main resin component is first dissolved. It is appropriate to evaporate the solvent and then evaporate the solvent of the adhesive resin so that the adhesive resin stands out on the surface.

Table 1 shows preferred combinations of the main resin of the porous structure and the adhesive resin in an embodiment in which the adhesive resin is bloomed onto the surface of the porous structure.

[Margin below]

Ethylene-vinyl acetate copolymer is preferable as the adhesive resin for blooming, especially when the content of vinyl acetate is 15 to 50% by weight and <30 to 4% by weight.
0% weight is preferred.

The colored ink has a vehicle that is substantially incompatible with the resin constituting the porous structure.

The method for incorporating the colored ink into the porous structure is as follows: (1) Dispersing and mixing the colored ink and the resin component of the porous structure in an incompatible state in an appropriate solvent, and using the dispersion-mixed coating material. (1) A method in which a coating obtained by dispersing and mixing a porous powder impregnated with the colored ink and a resin component in an appropriate solvent is applied on the base and dried; A base coating material obtained by lightly mixing a uniform powder obtained by crushing colored ink with a solvent solution of a resin component (use a solvent that does not dissolve the colored ink) to the extent that the solid powder does not become too fine. It is appropriate to use a method such as coating and drying.

The colored ink may be similar to conventional heat-melting transfer ink, and is a mixture of colorants such as dyes and pigments dispersed in a vehicle mainly composed of natural or synthetic wax or low-melting thermoplastic resin. It is solid or gel-like.

The adhesive strength of the surface of the ink retaining layer thus obtained was determined by an average peel strength of 1 in a 180' peel test against thermal transfer paper.
Approximately 0 to 50 g[' is appropriate.

The measurement conditions for the 180' peel test are as follows.

Peeling tester: Shinsha Kagaku ■ surface property measuring machine 11EIDON
= 14-type receptor: thermal transfer paper (TRW-7 manufactured by Jujo Paper Industries) test piece; A test ribbon of 8.35+a width was placed on the receptor, and the ribbon was printed using a thermal head with a printing energy of 0.4V. It was produced by solid printing all over the inside.

The peel strength is lOg! If it is smaller than 50gf, the ghost prevention effect tends to be poor, while if it is larger than 50gf, the separation between the recording medium and the receptor after printing will not be smooth, and problems such as hindering the feeding of the recording medium will tend to occur. be.

Note that the upper limit of the peel strength mentioned above depends on the surface condition of the receptor, the tensile strength of the ribbon, the magnitude of the peeling force, etc. Therefore, even if the value is higher than this, it can be used without any problem. There are many cases.

Next, the recording medium of the present invention will be described with reference to Examples.

Example 1 Ethylene-vinyl acetate copolymer (vinyl acetate content 35% by weight) as adhesive resin 1 part (parts by weight, the same applies hereinafter)
was dissolved in 9 parts of toluene, and on the other hand, 9 parts of vinyl chloride-vinyl acetate copolymer (vinyl acetate content: 17% by weight) as the main resin having a porous structure was dissolved in 45 parts of methyl ethyl ketone.

The above two types of solutions were mixed, and 7 parts of microcrystalline wax, 1 part of sorbitol stearate, and 5 parts of colored pigment as colored ink components were dissolved and dispersed therein.

After drying, apply the resulting mixed solution onto a polyester film with a thickness of 6JIM so that the thickness becomes 8JM, and then! 10
evaporate the methyl ethyl ketone by drying at 1
A recording medium obtained by drying at 00°C to evaporate the remaining solvent and having an ink-retaining layer containing a blue ink in a porous structure and blooming ethylene-vinyl acetate copolymer on the surface of the porous structure. I got it.

Examples 2 to 3 Recording media were produced in the same manner as in Example 1, except that the following ethylene-vinyl acetate copolymer was used instead of the ethylene-vinyl acetate copolymer in Example 1.

Example 2: Vinyl acetate content 33% by weightExample 3: Vinyl acetate content 32% by weightExample 4 1 part of ethylene-ethyl acrylate copolymer (ethyl acrylate content 35% by weight) as adhesive resin Polyvinyl butyral resin (butyral group content: 68
(mol%) was dissolved in 40 parts of methyl ethyl ketone.

The above two types of solutions were mixed, and 7 parts of microcrystalline wax, 1 part of sorbitol stearate, and 5 parts of colored pigment as colored ink components were dissolved and dispersed therein.

The resulting mixed solution was applied onto a polyester film with a thickness of 6 parts m so that the thickness after drying would be 8 mm, first dried at 80°C to evaporate the methyl ethyl ketone, and then
The remaining solvent was evaporated by drying at ℃ to obtain a recording medium having an ink retaining layer containing colored ink in a porous structure and blooming ethylene-ethyl acrylate copolymer on the surface of the porous structure. .

Example 5 Styrene-isoprene copolymer (styrene/isoprene-21/79 (ffI ffI
(ratio)) was dissolved in 9 parts of toluene, and on the other hand, 9 parts of polyvinyl butyral resin (butyral group content: about 88 mol%) as the main resin with a porous structure was dissolved in 4 parts of methyl ethyl ketone.
It was dissolved in 5 parts.

The above two solutions were mixed, and 7 parts of microcrystalline wax, 1 part of sorbitol stearate, and 5 parts of a color pigment as colored ink components were dissolved and dispersed therein.

Thicken the resulting mixture to a thickness of 4. - After drying, the film was coated on condenser paper to a thickness of 5 layers, first dried at 60°C to evaporate the methyl ethyl ketone, and then dried at 100°C to evaporate the remaining solvent, forming a porous structure. A recording medium was obtained which had an ink retaining layer containing a colored ink and a styrene-isoprene copolymer blooming on the surface of a porous structure.

Example 6 1.2- as main resin with porous structure and adhesive resin
9 parts of polybutadiene (breaking strength 100 kg/cd) was dissolved in 45 parts of toluene, and 10 parts of microcrystalline wax as a colored ink component and 5 parts of a colored pigment were added to the solution.
part was dissolved and dispersed.

The resulting mixed solution was applied onto a polyester film with a thickness of 6 mm to a thickness of 10 mm after drying, and dried at 90°C to evaporate the solvent, resulting in the colored ink being contained in the porous structure. A recording medium having an ink retaining layer whose entire porous structure is composed of an adhesive resin was obtained.

Comparative Example 9 parts of the same vinyl chloride-vinyl acetate copolymer used in Example 1 was dissolved in 45 parts of methyl ethyl ketone, and 6 parts of
Microcrystalline wax as a color ink component 7
1 part of sorbitol stearate and 5 parts of blue pigment were dissolved and dispersed.

The resulting mixture was applied onto a polyester film with a thickness of 6 cm to a dry thickness of 8 cm, dried at 80°C to evaporate the solvent, and the colored ink was deposited in the porous structure. A recording medium having an ink retaining layer contained therein was obtained.

For each recording medium obtained, the adhesive force (180' peel strength) of the surface of the ink retaining layer to the receptor was measured.

Further, using each of the above-mentioned recording media, printing was carried out with a thermal printer (WO-55 model manufactured by Sharp ■), and multi-time transferability and occurrence of ghost were examined.

These results are shown in Table 2. 1. The multiple transferability in Table 2 is expressed as the number of times printing is performed until the print density decreases to 0.5 when printing is repeatedly performed on the same location on the recording medium.

Further, each of the recording media was used to print once using the thermal printer, and then the surface condition of each recording medium was photographed and observed using a scanning electron microscope. FIG. 3 is a sketch diagram based on an electron micrograph J:4 (magnification: 1000 times) of the recording medium in Example 1. In FIG. 3, the upper half is an unused portion, and the lower half is a used portion. As shown in Figure 3, there is some fuzz-like material in the used area. This is because the adhesive resin on the surface of the porous structure became fluffy because the receptor adhered to the surface of the porous structure during thermal transfer was peeled off after the transfer.

Similar fuzziness was observed in the used areas of the recording media of Examples 2 to 6, but since the surface of the porous structure of the recording media of Comparative Examples was not adhesive to the receptor, such fuzziness was observed in the used areas. No fluff was observed.

Table 2 [Effects of the Invention] When printing using a multi-use thermal transfer recording medium, ghosts do not occur even if printing is repeated at the same location, so even if printing is performed many times, it is not the case for the first time. A similarly clear impression can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic partial sectional view showing an embodiment of the multi-use thermal transfer recording medium of the present invention, FIG. 2 is an explanatory view showing the state when thermal transfer printing is performed using the recording medium, and FIG. Scanning electron micrograph of the surface of the recording medium after use (magnification: 1
Figure 4 is an explanatory diagram showing the ghost phenomenon that occurs when using a conventional multi-use thermal transfer recording medium, and Figure 5 is a schematic diagram showing the ghost generation mechanism. be. (Main symbols in the drawings) (3): Ink retaining layer. (4): Porous structure (6) Two-color ink 21: Receptor

Claims (1)

[Scope of Claims] 1. A multi-use thermal transfer recording medium having an ink retaining layer in which a porous structure contains a colored ink that can be melted and transferred to a receptor upon heating. A multi-use thermal transfer recording medium, the surface of which is adapted to releasably adhere to the receptor. 2. The porous structure is composed of a resin as a main component and an adhesive resin that is incompatible with the resin and has adhesive properties to the receptor, and the surface of the porous structure is covered with the adhesive resin. A multi-use thermal transfer recording medium according to claim 1, which is covered. 3. The multi-use thermal transfer recording medium according to claim 1 or 2, wherein the adhesion to the receptor is developed by heating during thermal transfer.