JP3058993B2 - Thermal transfer ink sheet that can be used many times - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer ink sheet which can be used many times. More specifically, the present invention relates to a thermal transfer ink sheet which can be used many times, and is configured such that a heat-fusible ink layer is gradually transferred on a receptor in a thickness direction thereof every time heating is performed by a heating head or the like.

[0002]

2. Description of the Related Art A thermal transfer ink sheet of this type requires 30 to 60 parts by weight of a hot-melt resin, 10 to 40 parts by weight of a hot-melt substance, and 30 to 60 parts by weight of a colorant. There has been proposed one provided with a heat-fusible multi-transferable ink layer containing as a component (for example, see JP-A-2-77691).

In addition, there has been proposed a method in which the content or melt viscosity of the resin component in the multiple transfer ink layer as described above is increased on the base material side and lowered on the ink layer surface side (JP-A-61-79695). JP-A No. 2-150385).

[0004] However, these have problems such as inferior print clarity on paper having poor smoothness (hereinafter referred to as rough paper), and further, background soiling of receiving paper is severe.
Not satisfactory.

In view of the above, the present invention provides a desired printability for a large number of prints, has a good print definition even on rough paper, and uses the print paper many times without causing a background stain on a receiving paper. It is an object to provide a possible thermal transfer ink sheet.

[0006]

According to the present invention, there is provided a heat-fusible multi-transferable ink layer provided on a substrate, and a heat-fusible overcoat having a larger cohesive force than the multi-transferable ink layer. A multi-use thermal transfer ink sheet provided with a coat layer , wherein the multi- time transferable ink layer is an ink sheet.
5-40% by weight of a ethylene copolymer resin, 10-40 softener
% Of the pigment and 30 to 60% by weight of the pigment.
The overcoat layer is made of ethylene copolymer resin 50
-90% by weight and 0-50% by weight of pigment
Yes, the melt viscosity of the overcoat layer at 100 ° C.
Degree is 29 × 10 ² poise or more,
Melt viscosity difference between the ink layer and the ink layer at 100 ° C. is 1
0 × 10 ² poise or more at a multiple use thermal transfer Lee
Related to the link sheet .

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The thermal transfer ink sheet of the present invention is provided with a heat-meltable overcoat layer having a larger cohesive force than a conventional multiple-transfer ink layer (having a uniform composition in the thickness direction). The configuration is as follows. Where the cohesive force is
For example, it can be represented by viscosity (larger has higher cohesive strength), melting point (higher has higher cohesive strength) or hardness (harder has higher cohesive strength).

[0008] As described above, among the conventional multiple transfer ink layers, those having an inhomogeneous composition in the thickness direction reduce the cohesive force represented by the melt viscosity, melting point and the like on the surface side of the ink layer. .

However, in the present invention, the mechanism is not clear by providing a layer having a large cohesive force represented by melt viscosity and melting point on the surface side of the ink layer. While ensuring the reproducibility, the remarkable effect that the compatibility with the rough paper is good and that the receiving paper does not stain the background is produced.

In the present invention, the overcoat layer is very thin compared to the ink layer which can be transferred many times.
In general, it is considered that the overcoat layer is transferred in the second printing and the effect cannot be exhibited any more in the second and subsequent printings. An unexpected fact was found that the effect of the coat layer was maintained.

Next, the present invention will be described specifically.

As the multiple transfer ink layer in the present invention, any of the conventional multiple transfer ink layers can be used. For example, 5 to 40% by weight of an ethylene copolymer resin,
Those containing 10 to 40% by weight of a softening agent and 30 to 60% by weight of a pigment are preferred from the viewpoint of printability many times.

If the proportion of the ethylene-based copolymer resin is less than the above range, the amount of ink transferred at one time becomes large, so that it becomes difficult to print many times. On the other hand, if it exceeds the above range, cohesive failure occurs in the ink layer during transfer. It is difficult to print many times.

The softening agent has the function of reducing the cohesive force of the resin to adjust the cohesive failure. If the ratio is less than the above range, the cohesive failure hardly occurs, and it becomes difficult to print many times. If it exceeds, the amount of ink transferred at one time increases, and it becomes difficult to print many times.

The pigment is a colorant and has an action of controlling cohesive failure. When the ratio is less than the above range, the cohesive failure hardly occurs and printing is difficult many times. Since it becomes brittle and the thermal transfer sensitivity is lowered, it becomes difficult to print many times.

The ethylene copolymer resin includes a copolymer of ethylene and another vinyl monomer. Examples of the other vinyl monomer include vinyl acetate, vinyl butyrate, (meth) acrylic acid, and alkyl (meth) acrylate. Esters (alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, dodecyl, hexadecyl, etc.)
Acrylonitrile, acrylamide, N-methylolacrylamide, styrene and the like. These vinyl monomers may be used alone or in combination. In the case of an ethylene copolymer in which the other vinyl monomer is vinyl acetate or vinyl butyrate, a partially saponified product can also be used. The content of the vinyl monomer in the ethylene copolymer resin is preferably about 10 to 90% by weight. These ethylene copolymer resins may be used alone or in combination of two or more. Preferred ethylene copolymer resins are an ethylene-vinyl acetate copolymer and an ethylene-alkyl acrylate copolymer, and an ethylene-vinyl acetate copolymer is particularly preferred.

Examples of the softener include a wax-like substance and an oil-like substance.

The waxy substance includes natural waxes such as wood wax, beeswax, carnauba wax, candelilla wax, montan wax and ceresin wax;
Petroleum waxes such as paraffin wax and microcrystalline wax; synthetic waxes such as oxidized wax, ester wax, low molecular weight polyethylene, and Fischer-Tropsch wax; higher fatty acids such as myristic acid, palmitic acid, stearic acid, and behenic acid; stearyl alcohol, docosanol Esters such as higher fatty acid monoglycerides, fatty acid esters of sucrose, and fatty acid esters of sorbitan;
Examples include amides such as oleylamide and bisamides. Preferred waxy substances are paraffin wax and microcrystalline wax.

The oily substances include rapeseed oil, castor oil, coconut oil, sunflower oil, corn oil, linseed oil, natural oils such as safflower oil, lanolin, fish oil, squalane, jojoba oil, liquid paraffin, petrolatum, Petroleum oils such as spindle oil and motor oil, sorbitan oleate, surfactants such as polyoxyethylene fatty acid ester, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ether, dioctyl phthalate, tributyl acetyl citrate, dioctyl azelate And plasticizers such as dioctyl sebacate, diethyl phthalate and dibutyl phthalate; and oleic acid, lauric acid, linoleic acid, linoleic acid and isostearic acid. Preferred oily substances are lanolin, petrolatum and liquid paraffin.

These waxy substances and oily substances may be used alone or in combination of two or more.

The pigment includes an inorganic pigment and an organic pigment. A typical example of the inorganic pigment is carbon black,
This is preferably used in the present invention. Examples of the organic pigment include the following.

Yellow pigments include naphthol yellow S, Hansa yellow 5G, Hansa yellow 3G, Hansa yellow G, Hansa yellow GR, Hansa yellow A, Hansa yellow RN, Hansa yellow R, benzidine yellow G, benzidine yellow GR, permanent yellow NCG, quinoline yellow lake and the like.

Magenta pigment Permanent Red 4R, Brilliant Fast Scarlet, Brilliant Carmine BS, Permanent Carmine FB, Risor Red, Permanent Red F5
R, brilliant carmine 6B, pigment scarlet 3B, rhodamine lake B, rhodamine lake Y, alizarin lake and the like.

Cyan pigments Victoria Blue Lake, metal-free phthalocyanine blue, phthalocyanine blue, fast sky blue and the like can be mentioned.

In addition to the above-mentioned components, a dispersant for improving the dispersibility of the pigment, a filler such as diatomaceous earth, talc, silica powder and calcium carbonate, and other additives are required in the multiple transfer ink layer. May be blended according to.

The overcoat layer is a layer having a larger cohesive force (for example, higher in viscosity and / or melting point) than the above-mentioned multiple transfer ink layer, and is compatible with the multiple transfer ink layer.

As such an overcoat layer, for example, 50 to 90% by weight of an ethylene copolymer resin and pigment 0
Those containing about 50 to 50% by weight, especially 10 to 30% by weight are preferred.

If the proportion of the ethylene-based copolymer resin is less than the above range, the printing clarity on rough paper is not improved, and the effect of preventing background stain is not sufficiently exhibited. If the proportion exceeds the above range, the initial print density becomes low.

The pigment is not necessarily required to be incorporated in the overcoat layer, but is preferably incorporated from the viewpoint of increasing the initial print density. 10-30% by weight if mixed
Is more preferable, and when it exceeds 50% by weight, background soiling is likely to occur.

In a preferred embodiment of the present invention, the melt viscosity of the overcoat at 100 ° C. (hereinafter simply referred to as melt viscosity) is 29 × 10 ² poise or more, especially 10 ×.
Is 10 ³ poise or more, is further melt viscosity difference between the overcoat layer and the multiple rotation copy ink layer 10 × 10 ² poise or more, inter alia 50 × 10 ² poise or more. If the melt viscosity of the overcoat layer is lower than the above range, the cohesive force of the overcoat layer is insufficient, and the rough paper compatibility tends to be poor. If the difference in melt viscosity between the two layers is smaller than the above range, there is a tendency that rough paper compatibility and background stain resistance are not sufficiently exhibited.

As the ethylene copolymer resin for the overcoat layer, the same ethylene copolymer resin for the multiple transfer ink layer is used, and the same type as the multiple transfer ink layer is used. And different types may be used.

In addition to the above components, a softener, a dispersant, a filler, and the like may be added to the overcoat layer as required. As these compounding agents, those similar to those for the multiple transfer ink layer can be used.

As the pigment to be added to the overcoat layer as needed, the same pigment as the pigment for the multiple transfer ink layer can be used. Usually, the pigment used for the overcoat layer is of the same type as the pigment used for the multiple transfer ink layer.

The multiple transfer ink layer is coated with a coating solution prepared by dissolving and dispersing the above-mentioned components in an appropriate organic solvent or another coating solution in the form of an aqueous dispersion or emulsion. For example, it can be formed by applying to a substrate using a roll coater, a gravure coater, a reverse coater, a bar coater or the like, and drying.
Moreover, you may form by hot melt coating. The overcoat layer can be formed in the same manner.

The thickness of the multiple transfer ink layer is preferably about 6 to 12 g / m ² from the viewpoint of ensuring desired multiple printability. The thickness of the overcoat layer is 0.2 to 1.5 g / m
^{About 2} is preferred. If the thickness of the overcoat layer is less than the above range, the function and effect of the overcoat layer are not sufficiently exhibited, and the print clarity on rough paper is reduced, and background stain tends to occur. If it exceeds the above range, the initial print density decreases.

The substrate in the present invention includes polyester films such as polyethylene terephthalate film and polyethylene naphthalate film, polyamide films, aramid films, and other various types of films generally used as a substrate film for this type of ink sheet. Plastic films can be used. When such a plastic film is used, a silicone resin, a fluororesin, a nitrocellulose resin, or various kinds of lubricating and heat-resistant resins modified with these resins, or a heat-resistant resin on the back surface (the surface that is in contact with the heating head). It is desirable to prevent the stick phenomenon of the heating head on the base film by providing a conventionally known stick prevention layer composed of a mixture of a lubricant and a lubricant. The base material and the stick prevention layer may contain an antistatic agent and the like. Alternatively, high-density thin paper such as condenser paper may be used as the base material. The thickness of the substrate is preferably about 1 to 9 μm, particularly preferably about 2 to 6 μm, from the viewpoint of improving heat conduction.

Next, the present invention will be described with reference to Examples and Comparative Examples.

Examples 1-4 Amount of dry coating consisting of silicone-modified urethane resin on the back surface
4.5 μm with 0.1 g / m ² stick prevention layer
m, a coating liquid prepared by dissolving and dispersing the composition shown in Table 1 in a mixed solvent of benzene and ethyl acetate was applied to the surface of the polyester film, dried and transferred a number of times having the physical properties shown in Table 1. A hydrophilic ink layer was formed.

Next, the composition shown in Table 2 was dissolved and dispersed in a mixed solvent of toluene and methyl cellosolve to prepare a coating liquid.
This was coated on the transferable ink layer many times and dried to form an overcoat layer having the physical properties shown in Table 2, thereby obtaining a thermal transfer ink sheet.

[0040]

[Table 1]

[0041]

[Table 2]

COMPARATIVE EXAMPLE A thermal transfer ink sheet was obtained in the same manner as in Example 2 except that the same multi-transferable ink layer as in Example 2 was formed on the polyester film, and no overcoat layer was formed thereon.

Using each of the thermal transfer ink sheets obtained above, a printing test was performed with a thermal transfer printer (PCPR printer manufactured by NEC Corporation), and the following items were evaluated. As the receiving paper, a paper having a Beck smoothness of 300 seconds was used for multiple printability, print quality, and background stain, and a paper having a Beck smoothness of 30 seconds was used for rough paper compatibility. Table 3 shows the results.

(1) Printability Many Times The number of times printing at a predetermined density or more can be performed using the same portion of the ink sheet was determined, and the result was shown by the following evaluation value.

3: Four prints with an OD value of 0.7 or more were obtained. 2: Two prints with an OD value of 0.7 or more were obtained. 1: Two or more prints with an OD value of 0.7 or more were not obtained.

(2) Print Quality The print obtained on the receiving paper (smooth paper) was visually evaluated and indicated by the following evaluation values.

3: A clear and blur-free print was obtained. 2: Legible prints were obtained with some bleeding. 1: Only unreadable printing was obtained.

(3) Background dirt Background dirt on the receiving paper (smooth paper) was visually evaluated and indicated by the following evaluation values.

3 ... Nothing at all. 2: Slightly stained, but not to affect print quality. 1: There were many stains and the printing quality was significantly impaired.

(4) Correspondence to rough paper The print obtained on the receiving paper (rough paper) was visually evaluated and indicated by the following evaluation values.

3: Clear printing was obtained without voids or lack of printing. 2: Despite the presence of voids, readable prints with few print defects were obtained. 1: There were many print defects, and it was difficult to read the print.

[0052]

[Table 3]

[0053]

As described above, in a thermal transfer ink sheet that can be used many times, compatibility with rough paper and background stain can be improved while ensuring printability many times.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsuhiro Yoshida 5-4-14 Mundeshima, Nishiyodogawa-ku, Osaka-shi Fujikopian Corporation Technical Center (72) Inventor Naohiro Ikeda 4-14, Motejima, Nishiyodogawa-ku, Osaka-shi Fujikopian (56) References JP-A-2-150385 (JP, A) JP-A-61-112691 (JP, A) (58) Fields studied (Int. Cl. ⁷ , DB name) B41M 5 / 38-5/40

Claims (3)

(57) [Claims] 1. A multi-time printing method comprising: providing a heat-fusible multi-transferable ink layer on a base material; and providing a heat-fusible overcoat layer having a larger cohesive force than the multi-transferable ink layer. A usable thermal transfer ink sheet ,
The transferable ink layer is made of an ethylene copolymer resin 5 to 4
0% by weight, 10 to 40% by weight of softener and 30 to 6 pigments
0% by weight, wherein the overcoat layer is
50 to 90% by weight of ethylene copolymer resin and pigment 0
A layer containing 50% by weight, wherein the overcoat layer
Has a melt viscosity of 29 × 10 ² poise or more at 100 ° C.
And 100 of the overcoat layer and the ink layer.
Melt viscosity difference at 10 ° C. is 10 × 10 ² poise or more
Thermal transfer ink sheet that can be used many times . 2. The ink layer has a thickness of 6 to 12 g / g.
m ² , the thickness of the overcoat layer is 0.2 to 1.5 g
The thermal transfer ink sheet according to claim 1, wherein the thermal transfer ink sheet has a ratio of / m ² . 3. A process according to claim 1 or 2 multiple use thermal transfer ink sheet according the pigment is carbon black.