JPS58183297A - Multiple heat transfer sheet for gradation recording and preparation thereof - Google Patents

Abstract

PURPOSE:To increase the number of times in transfer and to subject the density of a transfer image to linearly stable gradation recording, by a method wherein particles controlling the transfer amount of an ink are bonded by a high m.p. binder and only the ink is limited little by little to carry out transferring. CONSTITUTION:A heat transfer sheet 10 is formed by bonding porous particles 11 to condenser paper 2 in a mutually bonded state by a high m.p. binder 12 not melted at the melting temp. of a low m.p. binder. Therefore, the porous particles 11 having action limiting the transfer amount of an ink 13 are different from a conventional one and are not transferred to plain paper 7 along with the ink 13 while, even if the number of times of transfer is increased, the degree of limitation thereby is not changed and the transfer amount of the ink 13 is held stably little by little. As the result, the number of times of transfer is increased and the roughness of an image is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multi-time thermal transfer sheet capable of recording gradations used in thermal transfer recording, and a method for manufacturing the same.

As a conventional multiple thermal transfer sheet, there is one shown in FIG. A conventional thermal transfer sheet (1) is composed of a base capacitor paper (2), an adhesive layer (3), carbon black particles (4) and ink (5).

Thermal transfer using this thermal transfer sheet (1) involves heating the portion of the capacitor paper (2) corresponding to the area to be transferred with a thermal head (6), and applying the ink (5) on the upper layer.
This is done by melting the carbon black and passing the melted ink (5) between the carbon black particles (4) to transfer it to plain paper (7). Therefore, the amount of molten ink (5) passing between the carbon black particles (4), i.e. the amount of transferred ink (5), will be limited by the carbon black particles (4), thereby allowing multiple transfers. It makes it possible.

However, carbon black particles (4) are ink (
As the ink (5) melts, a part of it is transferred to the plain paper (7), and as a result, the ink (5) and carbon black particles (4) transferred to the plain paper (7) are fixed by the ink (5). ) may change suddenly and discontinuously. Therefore, with such conventional thermal transfer sheets, it is extremely difficult to perform gradation recording in which the shading of the ink (5) transferred to the plain paper (7) is linearly changed.

Furthermore, since the carbon black particles (4) are also transferred to plain paper, the image quality may become rough.

The inventors of the present invention have conducted extensive research in order to eliminate the above-mentioned drawbacks, and as a result, we have found a solution to control the amount of ink transferred.
Particles 2 with high melting point are bonded to a base of 1U (or The inventors have discovered that it is possible to linearly and stably change the shade of a transferred image, and have completed the present invention.

That is, the present invention comprises a high melting point porous layer made of porous layer forming particles and a high melting point binder on a base, and an ink filled in the voids of the porous layer, and the ink contains a colorant and a low melting point binder. The present invention relates to a multi-use thermal transfer sheet for gradation recording, characterized in that the ink is an ink consisting of or a sublimable ink as a main component.

Examples include diatomaceous earth, with a particle size of 0.5 to 50 μm, and resins, epoxy resins, ester resins, polycarbonate resins, ethyl cellulose, and polyamide-imide resins. The melting point is preferably 10,000 or higher.

Ink consists of colorants such as pigments and dyes or sublimation ink (hereinafter sometimes referred to as colorants) and a low melting point binder, and pigments and dyes include blacks such as carbon black, graphite, and acetylene black. pigments such as, oil-soluble dyes such as nigrosine base, etc.; as yellows, for example, disazo yellow pigments such as Seven Squid First Yellow OL, monoazo yellow pigments, monoazo dye lakes, basic dyes such as auramine; as cyan, for example, Pigments such as ultramarine blue, navy blue, cyanine blue, alkali blue lake, basic dyes such as Victoria blue, etc. Examples of magenta include azo pigments such as brilliant carmine 6B, basic dyes such as rhodamine base, and sublimation inks. For example, Holon Brilliant Blue (
(manufactured by Sandoz), Kayaset Black (manufactured by Nippon Kayaku),
Holon Red (manufactured by Sandoz), Sumikaron Yellow I
(manufactured by Sumitomo Chemical Co., Ltd.) etc., but the present invention is not limited to these, and commonly used colorants can also be used. The particle size of the coloring agent may be any size that can fit into the pores formed in the porous layer, but it is usually 20
It is preferably less than μ.

Examples of the low melting point binder include carnauba wax, ester wax, paraffin, and polyvinyl butyral. The melting point is from 50 to 150°c1, preferably from 50 to 100'O, but must necessarily be lower than the melting point of the high melting point binder.

The thermal transfer sheet of the present invention is produced by kneading porous forming particles and a high melting point binder, applying the resulting kneaded material to a base to form a high melting point porous layer, and then adding a coloring agent and a low melting point binder. This can be obtained by applying a mixture of the following to the porous layer to fill the voids in the porous layer.

The porous layer formed has a volume ratio of 4 pore-forming particles.
0% or less, high melting point binder 5-65%, preferably 1
The porosity is preferably 0 to 30%, and the porosity is preferably 20 to 55%.

Next, one embodiment of the multiple thermal transfer sheet for gradation recording of the present invention will be described with reference to FIG.

The thermal transfer sheet of the present invention) includes a high melting point porous layer composed of porous forming particles 0υ and a high melting point binder (b), a capacitor paper (2) as a paste, a coloring agent, etc., and a low melting point binder. Consists of ink (b).

Thermal transfer in the present invention is performed by heating the capacitor paper (2) with a thermal head (6) to melt the low melting point binder in the ink, and then transferring the melted ink to the plain paper (7). It is the same as the conventional one. However, in the thermal transfer sheet α of the present invention, the porous forming particles 0υ are connected to each other and/or to the capacitor paper (2) by a high melting point binder (b) that does not melt at the melting temperature of the low melting point binder. Porous forming particles (rivers) that act to limit the amount of transfer (to ink) are different from conventional ones, and are not transferred to plain paper (7) together with ink (b), and even if the number of transfers increases The degree of restrictions imposed by them changes7.
Therefore, the amount of ink (b) transferred can be kept stable little by little. Since the transfer amount of ink can be stably supplied in this way, transfer can be performed more than 10 times using the same thermal transfer sheet, whereas conventionally it could only be performed about 3 times. Moreover, the roughness of the image quality due to the transfer of the porous forming particles (11) is eliminated.

Furthermore, by changing the temperature of the thermal head (6) by changing the applied voltage, the amount of ink (13) transferred can be changed linearly, making it possible to perform gradation recording where the density can be freely adjusted. Become.

Note that when a sublimable ink is used as an ink component, the low melting point binder is not transferred, and only the sublimable ink is vaporized and transferred.

As a base, not only capacitor paper but also a heat-resistant plastic film, such as a polyimide film, can be used.

Furthermore, in the embodiment described above, a porous state with a high melting point is formed by the high melting point binder and the porous forming particles, but this state is formed by a porous substance that is not transferred by the heating of the thermal head and has ink retention properties. may be created.

As described above, the thermal transfer sheet of the present invention can be subjected to 10 or more transfers, and has extremely excellent effects in that it can linearly and stably record the gradation of the transferred image.

Next, the present invention will be explained with reference to Examples, but the present invention is not limited to these Examples.

Example 1 10 parts of ethyl cellulose (by weight, the same applies hereinafter) was dissolved in 70 parts of ethyl alcohol, and this was put in a ball mill with 27 parts of diatomaceous earth and kneaded for 6 hours, resulting in a concentration of 20 p/m on a 10μ capacitor paper. A high melting point porous layer with a porosity of 40% was formed.

Separately, 15 parts of carbon black, paraffin (melting point 12
5°y) 20 parts and 65 parts of carnauba wax to 90 parts
An ink was prepared by dispersing carbon black in carnauba wax using three rolls heated to 0°C.

15. The obtained ink is applied onto the porous layer using a hot melt coater. /m, then 100°C
The thermal transfer sheet of the present invention was manufactured by passing the sheet over two to three rolls heated to 2 to 30 degrees to allow the ink to penetrate into the porous layer.

Example 2 A high melting point porous layer with a porosity of 35% was formed in the same manner as in Example 1 using 23 parts of talc, 12 parts of polycarbonate and 75 parts of methylene chloride as high melting point porous layer forming materials, and carbon black 12 1 part, Sudan Sheep Black (manufactured by BASF), 3 parts of Hoechst Wax]
? ) A thermal transfer sheet of the present invention was produced by infiltrating a porous layer in the same manner as in Example 1.

Example 3 6 parts of Kayaset Black 922-D (Nippon Kakamibu), 14 parts of polyvinyl butyral, and 80 parts of ethyl alcohol were mixed as ink components, and the resulting mixture was applied to the porous layer formed in Example 2. The thermal transfer sheet of the present invention was manufactured by coating.

Example 4 10 parts of polyamideimide resin was dissolved in a mixed solvent of 50 parts of ethyl alcohol and 90 parts of toluene, and diatomaceous earth 2
The mixture was put in a ball mill with 7 parts and kneaded for 3 hours, and then coated on a 10 μm polyimide film at a ratio of 20p, /++a2 to form a high melting point porous layer with a porosity of 50%.

Next, the ink obtained in the same manner as in Example 1 was used as Example 1.
The thermal transfer sheet of the present invention was produced by infiltrating the porous layer in the same manner as described above.

Next, thermal transfer recording was performed using the thermal transfer sheets obtained in Examples 1 to 4, respectively.

For thermal transfer recording, images were transferred onto plain paper using a thermal facsimile (MEL7AS, manufactured by Mitsubishi Electric ■) equipped with a single-color line head.

The resulting transferred image had no unevenness in density, and the 12th transferred image had the same density as the first transferred image. When the temperature of the head was varied by changing the head voltage stepwise, a transferred image with a density corresponding to the temperature of the head was obtained without unevenness in density.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional multiple thermal transfer sheet, and FIG. 2 is an explanatory diagram of a multiple thermal transfer sheet for gradation recording of the present invention. (Main symbols in the drawing) (1): Capacitor paper (7): Plain paper (6): Thermal head (12): High melting point binder (11): Porous forming particles (10): Multiple thermal transfer for gradation recording Seat (13)
:ink

Claims (1)

[Scope of Claims] 1 Consists of a high melting point porous layer made of porous layer forming particles and a high melting point binder on a base, and an ink filled in the voids of the porous layer, and the ink has a coloring agent and a low melting point binder. 1. A multi-use thermal transfer sheet for gradation recording, characterized in that the ink is an ink consisting of a binder and a sublimable ink as a main component. 2. Forming a high melting point porous layer consisting of porous forming particles and a high melting point binder on the base, then applying an ink consisting of a colorant etc. and a low melting point binder or an ink whose main component is sublimation ink, A method for producing a multi-time thermal transfer sheet for gradation recording, characterized by allowing ink to seep into a porous layer.