JPH0421492A - Thermal transfer recording sheet - 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 Application Field] The present invention relates to a thermal transfer recording sheet used in a thermal transfer recording method in which an image is thermally transferred to an image receiving paper using a thermal head or the like, and particularly relates to a thermal transfer recording sheet used as an image receiving paper with a porous ink absorbing layer. The present invention relates to a thermal transfer recording sheet suitable for forming images having gradation expression when used in combination with a sheet provided with a gradation expression.

[Prior Art] Thermal transfer recording methods that use heat-generating elements such as thermal heads have advantages such as low printing noise, the ability to use small devices, good operability, and high reliability, and are widely used. There is.

This thermal transfer recording method uses a thermal transfer recording sheet in which a heat-fusible ink layer is applied on a base sheet such as paper or plastic film, and the heat-fusible ink layer is heated and melted by a thermal head, etc. A melt transfer method is known in which an image is obtained by transferring the image onto paper. In this method, it has been thought that it is difficult to control the amount of heat-melting ink transferred even if the amount of heat of the thermal head is changed in order to obtain a gradation image, so it is basically used for binary recording. It was used.

However, a proposal has been made to enable good gradation recording even with this melt transfer method (Japanese Patent Laid-Open No. 6O-1234
37). This proposal is an improvement on the image-receiving paper side, in which an absorbing layer capable of absorbing and retaining hot-melt ink is provided on the surface of the image-receiving paper, and the surface of this absorbing layer has a material that absorbs and retains hot-melt ink. It is characterized by containing a substance that has no adhesive force. In this method, the amount of ink that permeates into the image receiving paper is controlled by changing the amount of heat applied to the thermal head, and after recording, the heat-fusible ink layer of the thermal transfer recording sheet is separated and peeled off on the absorbing layer surface of the image receiving paper. Therefore, in the thermal transfer recording sheet used in this method, unless there is strong adhesive force between the heat-fusible ink layer and the base sheet, peeling will occur between the base sheet surface and the heat-fusible ink layer, resulting in binary It becomes a recording and gradation recording is not possible.

[Problems to be Solved by the Invention] The present invention is directed to an image-receiving paper, such as the one proposed in JP-A-61-280991 mentioned above, that is, a porous ink capable of absorbing and retaining hot-fusible ink on a base sheet. Good gradation recording is possible when used in combination with an absorbent layer provided with an image-receiving paper whose surface contains a substance that has virtually no adhesion to the hot-melt ink. The purpose is to provide a thermal transfer recording sheet.

[Means for Solving the Problems] In order to solve the above problems, the present invention interposes an intermediate adhesive layer between the base sheet of the thermal transfer recording sheet and the heat-melting ink layer to improve the adhesive force therebetween. This measure was taken.

That is, the present invention provides a thermal transfer recording sheet having a base sheet and a heat-melt ink layer laminated on the base sheet, in which between the base sheet and the heat-melt ink layer,
The present invention provides a thermal transfer recording sheet characterized by interposing an intermediate adhesive layer made of a mixture of ethylene-vinyl acetate copolymer resin and polyester resin.

The ratio of the polyester resin to the ethylene-vinyl acetate copolymer resin in the intermediate adhesive layer is preferably 2:1 to 1:2 (weight ratio).

If the content of the polyester resin is zero or its proportion is less than the above-mentioned lower limit, the adhesive strength between the base sheet and the intermediate adhesive layer will not be sufficient, and peeling will easily occur at the interface between them. On the other hand, if the proportion of the polyester resin is 100% or larger than the above upper limit, the adhesive strength between the intermediate adhesive layer and the hot-melt ink layer will not be sufficient, and peeling will easily occur at the interface between them.

[Function] By using a mixture of ethylene-vinyl acetate copolymer resin and polyester resin as the intermediate adhesive layer, the adhesive strength between the base sheet and the hot-melt ink layer can be improved, and the thermal The heat-fusible ink layer can be appropriately divided and transferred in response to changes in the amount of heat applied to the head, etc., thereby enabling good gradation recording.

[Example] Hereinafter, the present invention will be explained with reference to the illustrated embodiments.

FIG. 1 shows a cross-sectional view of a thermal transfer recording sheet according to the present invention, in which a thermal transfer recording sheet 1 consists of a base sheet 2, an intermediate adhesive layer 3 coated on the surface thereof, and this intermediate adhesive layer. It consists of a hot melt ink layer 4 laminated on one surface of a base sheet 2 with layer 3 sandwiched therebetween.

The base sheet 2 is preferably a polyester resin or a film containing polyester resin as a main component. As described above, the intermediate adhesive layer 3 is made of a mixture of ethylene-vinyl acetate copolymer resin and polyester resin.

Here, as the polyester resin, polyester resins conventionally used in adhesives such as aromatic polyester can be used. Among these, those having a glass transition temperature (Tg) of 40° C. or lower and a molecular weight of 15,000 or higher are particularly preferred because of their good adhesive properties.

There is no particular restriction on the heat-melting ink layer 4, and a combination of a heat-melting substance and a coloring material such as a pigment, which are used in conventional examples, can be used.

The image-receiving paper used in combination with the thermal transfer recording sheet of the present invention has a surface layer capable of absorbing and retaining heat-melting ink, as disclosed in JP-A-61280991 mentioned above, and has a surface layer capable of absorbing and retaining heat-melting ink. A removable substance that does not adhere to the adhesive ink, such as fluororesin, silicone resin,
A material coated with wax or the like, impregnated, dispersed, and peeled can be used as appropriate.

Example 1 As an intermediate adhesive layer: - 37 parts by weight of ethylene-vinyl acetate copolymer emulsion (solid content 40%, manufactured by Bond Wax Co., Ltd.) - 40 parts by weight of polyester aqueous emulsion (solid content 37%, manufactured by Dainippon Ink ■) The composition was stirred with a propeller and coated on a polyester film with a thickness of 61 mm by wire bar coating so that the non-volatile content was 1.5 g/rd, and on top of that, a hot-melt ink having the following composition was coated with a non-volatile content of 2 g/rd. It was coated by wire bar coating to give a coating density of 5 g/rtf to form a thermal transfer recording sheet.

・Paraffin wax emulsion (solid content 40%, made by Bond Wax ■) 20 parts by weight Carnauba wax emulsion (solid content 40%, made by Bond Wax ■) 15 parts by weight ・Synthetic resin wax emulsion (solid content 40%, made by Bond Wax ■) ) 20 parts by weight of aqueous (pigment) colorant (solid content 30%, manufactured by Dainippon Seika ■) 18.3 parts by weight As the receiver paper, a commercially available mud coat film was mixed with silicone oil (manufactured by Shin-Etsu Silicone) for non-volatile content. 4. by weight.
It was coated by wire bar coating so that it was 0g1rd to obtain an image receiving paper. Using this image-receiving paper and the thermal transfer sheet described above, thermal transfer recording was performed by changing the printing energy stepwise to form a density step scale using a thermal head, and then the thermal transfer recording sheet was peeled off from the image-receiving paper.

As a result, as shown in FIG. 2, the heat-melting ink layer 4 of the thermal transfer recording sheet 1 is stably separated and peeled off at the surface peeling portion 5b of the absorbent layer 5a of the image-receiving paper 5, resulting in a stepped density gradation image. was gotten. In FIG. 2, 2 is a base sheet, 3 is an intermediate adhesive layer, 5c is a base material of the image receiving paper 5, and 6 is a thermal head.

Comparative Example 1 The same heat-melting ink as in Example 1 was applied to a thickness of 6! without applying the intermediate adhesive layer of Example 1. ! A thermal transfer recording sheet was obtained in the same manner as in Example 1, except that the coating was directly applied to the polyester film No. m. Using this thermal transfer recording sheet and the same image-receiving paper as in Example 1, recording was performed by changing the printing energy stepwise with a thermal head as in Example 1, and then the thermal transfer recording sheet was peeled from the image-receiving paper. As shown in the dotted line "A" in FIG. 3, the heat-melting ink layer 4 peels off at some places on the surface of the base sheet 2 of the thermal transfer recording sheet 1, making it impossible to obtain a stable gradation image. I couldn't. Note that the reference numerals in FIG. 3 correspond to those in FIG. 2, and the same members are designated by the same numerals.

Comparative Example 2 As an intermediate adhesive layer, only an ethylene-vinyl acetate copolymer emulsion (solid content 40%, manufactured by Bond Wax Kai) was placed on a 6-thickness polyester film with a wire bar so that the non-volatile content was 1.5 g/rd. On top of that, the same heat-melting ink as in Example 1 was applied in an amount of 2.5% by weight of non-volatile matter.
A thermal transfer recording sheet was obtained by coating with a wire bar so as to obtain g/rd. Using this thermal transfer recording sheet and the same image-receiving paper as in Example 1, recording was performed by changing the printing energy stepwise with a thermal head as in Example 1, and then the thermal transfer recording sheet was peeled from the image-receiving paper. As shown in the dotted line "A" in FIG. 3, the heat-melting ink layer 4 peels off at some places on the surface of the base sheet 2 of the thermal transfer recording sheet 1, making it impossible to obtain a stable gradation image. I couldn't do it.

[Effects of the Invention] According to the present invention, an intermediate adhesive layer made of a mixture of ethylene-vinyl acetate copolymer resin and polyester resin is interposed between the base sheet and the ink layer to improve the adhesion between them. This makes it possible to record images with good gradation on image-receiving paper whose base material is provided with porous material capable of absorbing and retaining hot-melt ink.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a thermal transfer recording sheet according to the present invention; FIG. 2 is a cross-sectional view showing a state when thermal transfer is performed on an image receiving paper using the thermal transfer recording sheet of FIG. 1; FIG. FIG. 2 is a cross-sectional view showing a state when thermal transfer is performed on an image receiving paper using a thermal transfer recording sheet without a heat transfer recording sheet. 1... Thermal transfer recording sheet, 2... Base material sheet, 3...
. . . Intermediate adhesive layer, 4. Hot-melt ink layer, 5. Receiving paper, 6. Thermal head. Applicant's representative Patent attorney Takehiko Suzue b: J. Figure Figure Figure

Claims (2)

[Claims] (1) In a thermal transfer recording sheet having a base sheet and a heat-melt ink layer laminated on the base sheet, an ethylene-vinyl acetate copolymer is formed between the base sheet and the heat-melt ink layer. A thermal transfer recording sheet characterized by interposing an intermediate adhesive layer made of a mixture of resin and polyester resin. (2) Ethylene of the polyester resin in the intermediate adhesive layer
The ratio to vinyl acetate copolymer resin is 2:1 to 1:2 (
2. The thermal transfer recording sheet according to claim 1, wherein the thermal transfer recording sheet has a weight ratio.