JPH0381182A - Repeated transfer type ink sheet - Google Patents

Abstract

PURPOSE:To normally perform the transfer of ink or the release of a sheet by providing an intermediate adhesive layer and an ink layer on a base material and coating the surface of the solid fine powder in the ink layer with two kinds of EVAs different in the content of vinyl acetate. CONSTITUTION:An intermediate adhesive layer 2 and an ink layer 3 are formed on a base material 1 and the ink layer 3 is constituted of ink 4 consisting of a dye or pigment and a low m.p. material and the solid fine powder 5 mixed with the ink 4. The surface of the solid fine powder 5 is coated with an ethylene/vinyl acetate copolymer with a number average MW of 30000 or less and vinyl acetate content of 18 - 26 wt.% and an ethylene/vinyl acetate copolymer with a number average MW of 30000 or less and vinyl acetate content of 27 - 45 wt.%. By this method, a multi-ink sheet wherein the transfer of ink or the release of a sheet is normally performed not only in a case printing a usual character or mark but also in a case of solid black printing can be realized.

Description

[Detailed Description of the Invention] (Summary) Regarding thermal transfer ink sheets used in thermal printers, especially thermal transfer ink sheets that can be used repeatedly, when printing ordinary characters and symbols, it is of course possible to print solid black. The purpose of this is to provide a multi-ink sheet in which ink transfer and sheet separation occur normally even in cases where the ink layer has an intermediate adhesive layer and an ink layer formed on a base material, and the ink layer is made of dye or pigment. In a repeat transfer type ink sheet consisting of an ink composed of a low melting point material and a solid fine powder mixed into the ink, the number average molecular weight is 1300.
EVA with a vinyl acetate content of 18 to 26% by weight below 00
and a number average molecular weight of 30,000 or less and a vinyl acetate content of 2
The surface of the solid fine powder is coated with 7 to 45% by weight of EVA.

[Industrial Application Field] The present invention relates to a thermal transfer type ink sheet used in a thermal printer, and particularly to a thermal transfer type ink sheet that can be used repeatedly many times.

Thermal printers used as output devices in various electronic devices use thermal transfer ink sheets as means for printing on plain paper.

However, with ordinary thermal transfer type ink sheets, most of the ink is transferred at once, and the same ink sheet cannot be used repeatedly, resulting in high running costs. Therefore, there is a demand for the development of a thermal transfer type ink sheet (hereinafter referred to as a multi-ink sheet) that can be used repeatedly many times.

[Conventional technology]

FIG. 1 is a side sectional view showing the structure of a multi-ink sheet.

In the figure, the multi-ink sheet includes a base material 1 made of polyester or the like, an intermediate adhesive layer 2 made of polyester or the like coated on the base material 1, and an ink layer 3 coated thinly on the intermediate adhesive layer 2. The ink layer 3 is composed of an ink 4 made of a dye or pigment and a low melting point material, and a solid fine powder 5 mixed into the ink 4.

Multi-ink sheets conventionally used for thermal printers are made of ethylene vinyl acetate copolymer (hereinafter abbreviated as EVA) 6 with a number average molecular weight of 30,000 or less and a vinyl acetate content of 18 to 45% by weight, and carbon black, etc. The surface of solid fine powder 5 consisting of is covered.

When the ink N3 is heated from the back side of the base material 1 in such a multi-ink sheet, the ink 31 made of a dye or pigment and a low melting point material melts, and a part of the ink N3 is in contact with the ink layer 3. transcribed into. At this time, the EVA is melted and a portion of the solid fine powder 5 is also transferred to the printing paper.

[Problem to be solved by the invention]

FIG. 2 is a diagram showing problems in conventional multi-ink sheets.

The printing conditions of a thermal printer can only be transferred once.
It is set for so-called one-time ink sheets. For example, when printing on a solid ring in a graph ink pattern, etc., if the same printing energy is applied repeatedly, higher heat than usual is applied due to the heat storage effect of the print head, causing the ink to overmelt and not allowing normal transfer. . Therefore, when printing on a solid ring, the subsequent printing energy is reduced as shown in FIG. 2(a).

However, in the case of a multi-ink sheet, since the base material and ink layer are thick, the sensitivity to printing energy is lower than that of a one-time ink sheet. As a result, when the applied printing energy is large, the melt viscosity of the ink is sufficiently reduced and the ink transfer and sheet peeling are performed normally, as shown in Fig. 2(b), but the applied printing energy is If the ink is small, as shown in Figure 2 (C), the melt viscosity of the ink will not decrease sufficiently, and the first 1 to 2 mm will be printed normally, but after that, transfer will not occur, or the sheet will be There was a problem in that it adhered to the printing paper and could not be peeled off.

An object of the present invention is to provide a multi-ink sheet in which ink transfer and sheet peeling are performed normally when printing ordinary characters and symbols as well as when printing on a solid ring.

[Means to solve the problem]

The above problem has an intermediate adhesive layer 2 formed on a base material 1 and an ink N3, an ink 4 in which the ink jW3 is composed of a dye or pigment and a low melting point material, and a solid fine powder mixed in the ink 4. 5, EVA has a number average molecular weight of 30,000 or less and a vinyl acetate content of 18 to 26% by weight, and a number average molecular weight of If 30.
000 or less with vinyl acetate content of 27-45% by weight
A is closely related to the repeat transfer type ink sheet of the present invention in which the surface of the solid fine powder 5 is coated.

[For production]

Number average molecular weight is 130,000 or less and vinyl acetate content is 18~
By coating the solid fine powder mixed in the ink with EVA of 26% by weight and EVA with a number average molecular weight of 30,000 or less and a vinyl acetate content of 27 to 45% by weight,
It is possible to realize a multi-ink sheet in which ink transfer and sheet peeling are performed normally when printing ordinary characters and symbols as well as when printing on a solid ring.

〔Example〕

Examples of the present invention will be described in detail below.

Note that FIG. 3 is an explanatory diagram of the operation of the multi-ink sheet according to the present invention.

The phenomenon of no transfer when the applied printing energy is small occurs because ink with high viscosity and weak adhesive strength cannot adhere to the printing paper side, and this phenomenon is influenced by the vinyl acetate content of EVA. That is, as shown by the solid line in FIG. 3, when the vinyl acetate content is low, there are many cases where the ink is not transferred, and as the vinyl acetate content increases, the number of cases where the ink is not transferred decreases.

Further, the phenomenon that the sheet sticks to the printing paper when the printing energy is low occurs because the ink has a high viscosity and solidifies before the sheet is peeled off, and this phenomenon also depends on the vinyl acetate content of EVA. That is, as shown by the broken line in FIG. 3, when the vinyl acetate content is low, sheets are less likely to adhere, and as the vinyl acetate content increases, sheets are more likely to adhere.

From this, in order to obtain an ink that properly transfers the ink and peels off the sheet even during solid black printing, it is necessary to use BVA with a vinyl acetate content lower than 26% by weight, where the solid line and broken line intersect in Figure 3. It is desirable to mix EVA with a vinyl acetate content higher than 26% by weight.

Example 1 20 parts by weight of carbon black, parts by weight of EVAIO with a vinyl acetate content of 19% by weight, and a vinyl acetate content of 33 parts by weight
Parts by weight of EVAIO are dispersed in a roll at 120°C and pulverized to obtain a solid fine powder whose surface is covered with EVA. Observation using an electron microscope confirmed that the surface of this solid fine powder was covered with EVA, and when the solid fine powder was mixed with toluene and stirred, a black liquid without coarse particles was obtained, and the core of the solid fine powder and It is 1i! that the carbon black is finely dispersed! It has been certified.

10 parts by weight of oil black dye, 30 parts by weight of carnauba wax
Parts by weight and 20 parts by weight of Senkun wax are kneaded at 100° C. using a roller kneader, and then the entire amount of the above solid fine powder is mixed in and kneaded for 30 minutes to obtain an ink composition liquid. The above-mentioned ink composition liquid is applied by the true melt method to a polyester film having a thickness of 6 μm, which has been previously covered with an intermediate adhesive layer, to form an ink layer having a thickness of 10 μm.

Example 2 25 parts by weight of carbon blank, 1 part by weight of EVAIO with vinyl acetate content of 25% by weight, vinyl acetate content of 41% by weight
10ti parts of EVA, and 300 parts of tetrahydrofuran
A solid fine powder coated with EVA is obtained by dispersing the weight part in a ball mill for 8 hours and evaporating the tetrahydrofuran.

10 parts by weight of carbon black (pigment), microcrystalline wax (manufactured by Nikko Fine Products) 35
55 parts by weight of the above solid fine powder in 400 parts by weight of toluene
Parts by weight are added and kneaded in a ball mill for 4 hours to obtain an ink composition liquid. The above ink composition liquid is applied to a 6 μm thick polyester film on which an intermediate adhesive layer has been applied in advance to form an ink layer with a thickness of 10 μm.

The ink sheet created in Example 1 or Example 2 was printed on a thermal printer (Fujitsu word processor).
When the printer was attached to the Oasis Lite (FROMIID) and printed, the solid black print was normal and clear, just like normal characters and symbols, and there were no problems such as sheets adhering to the printing paper.

In this way, EVA with a number average molecular weight of 30,000 or less and a vinyl acetate content of 18 to 26% by weight, and a number average molecular weight of 30
EV with vinyl acetate content of 27 to 45% by weight below 000
By coating the solid fine powder mixed in with the ink, A is a multi-layer printer that allows ink transfer and sheet peeling to occur normally, not only when printing regular characters and symbols, but also when printing in solid black. An ink sheet can be realized.

In addition, as reference example 1, an EV with a vinyl acetate content of 19% by weight
A, EV with vinyl acetate content of 33% by weight as Reference Example 2
A, EV with vinyl acetate content of 25% by weight as Reference Example 3
In the case of solid fine powder formed by using A alone and covering the surface of carbon black, both have advantages and disadvantages, and ink transfer occurs normally during solid black printing, and the sheet peels off normally. Could not get multi-ink sheet done.

The printing characteristics of these examples and reference examples are shown in Tables 1 and 2.

Table 1 Ink fixation: No stains.

(Evaluation of stains caused by light rubbing with a finger) As shown in Table 1, there are no particular problems with character pattern printing in either the Examples or the Reference Examples.

For the solid ring in Table 2, a strip pattern with a length of 150 mm was printed, and the print densities at the left end and right end were compared.

As a result, in Reference Example 1, the first 1+m was printed, but no density was produced thereafter. This is thought to be because the vinyl acetate content of EVA is low, so the ink does not melt sufficiently during solid black printing, and when the ribbon is peeled off, the ink has already solidified, and the ink, which has low adhesive strength, is not transferred. .

Further, in Reference Example 2, after about Ioms of printing, the ribbon adhered to the paper and it became impossible to wind it up. This is EV, contrary to reference example 1.
This is because A has a high vinyl acetate content and has too strong adhesive strength. Furthermore, in Reference Example 3, the density was initially high between 2 and 3 when printed, and thereafter the density became low.

In contrast to these Reference Examples 1 to 3, in the case of Examples 1 and 2, the 150 mm strip pattern was able to obtain sufficient density over the entire area. The print density value in the table is O.
This is the D value (optical reflection density), and if the OD value is about 0.8, it can be said that the density as a printed matter is sufficient.

(Effects of the Invention) As described above, the present invention provides a multi-ink sheet in which ink transfer and sheet peeling are performed normally when printing ordinary characters and symbols as well as when printing on a solid ring. be able to.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing the structure of a multi-ink sheet, FIG. 2 is a diagram showing problems in the conventional multi-ink sheet, and FIG. 3 is a diagram illustrating the operation of the multi-ink sheet according to the present invention. In the figure, 1 represents a base material, 2 represents an intermediate adhesive layer, 3 represents an ink layer, 4 represents ink, 5 represents solid fine powder, and 6 represents EVA. M) Inverted cross-section showing the straightening of the V-ch ink sheet Σ Figure 1 EVA vinyl acetate-Wt Explanatory diagram of the action of the T-wobble multi-ink sheet in the present invention (C)

Claims (1)

[Claims] An ink (4) comprising an intermediate adhesive layer (2) and an ink layer (3) formed on a base material (1), the ink layer (3) comprising a dye or pigment and a low melting point material; and a repeatable transfer type ink sheet consisting of the solid fine powder (5) mixed in the ink (4), with a number average molecular weight of 30,000.
The solid fine powder ( 5) A repeatable transfer type ink sheet, characterized in that the surface of item 5) is coated.