JPH05185755A - Thermal transfer ink sheet usable many times - Google Patents

Abstract

PURPOSE:To make a property for coping with rough paper good by securing a required many times transferrability by a method wherein a hot-melt many times transferable ink layer and(hot-melt overcoat layer of which cohesive power is larger than that of the ink layer are successively laminated on a base material. CONSTITUTION:A coating solution is prepared by dissolving and dispersing respective components of 5-40wt.% of ethylene copolymer resin, 10-40wt.% of softener, and 30-60wt. % of coloring matter in a suitable organic solvent. A many times transferrable ink layer is formed by coating and drying the coating solution on a base material of a plastic film or the like by a coating means such as a roll coater or the like. Separately, a coating solution is prepared by dissolving and dispersing respective components of 50-90wt.% of ethylene copolymer resin and 0-50wt.% of coloring matter in a suitable organic solvent. This coating solution is applied and dried on the many times transferrable ink layer abovementioned to laminate a hot-melt overcoat layer of which cohesive power is larger than that of the ink layer, and a thermal transfer ink sheet usable many times is formed.

Description

Detailed Description of the Invention

[0001]

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 heat transfer ink sheet that can be used many times and is configured such that the heat-meltable ink layer gradually transfers to the receptor in the thickness direction each time it is heated by a heating head or the like.

[0002]

2. Description of the Related Art A thermal transfer ink sheet of this type must contain 30 to 60 parts by weight of a heat-meltable resin, 10 to 40 parts by weight of a heat-meltable substance, and 30 to 60 parts by weight of a colorant. It has been proposed to provide a heat-meltable multi-transferable ink layer contained as a component (see, for example, JP-A-2-277691).

In addition, there has been proposed a multi-transferable ink layer as described above in which the resin component content or melt viscosity is increased on the substrate side and decreased on the ink layer surface side (JP-A-61-79695). Japanese Patent Laid-Open No. 2-150385).

However, these have problems in that the printing clarity is particularly poor on paper with poor smoothness (hereinafter referred to as rough paper), and the background stain on the receiving paper is severe.
I'm not satisfied.

In view of the above points, the present invention has a desired printability for a number of times, has a good printing sharpness even on rough paper, and can be used a number of times without causing the background stain on the receiving paper. An object is to provide a possible thermal transfer ink sheet.

[0006]

According to the present invention, a heat-meltable multi-transferable ink layer is provided on a substrate, and a heat-meltable overlying layer having a larger cohesive force than the multi-transferable ink layer is further provided. The present invention relates to a thermal transfer ink sheet provided with a coat layer that can be used many times.

[0007]

OPERATION AND EXAMPLES The thermal transfer ink sheet of the present invention comprises a conventional multi-transferable ink layer (having a uniform composition in the thickness direction) and a heat-meltable overcoat layer having a larger cohesive force than that. It has a different configuration. Here, the cohesive force is
For example, it can be expressed by viscosity (larger is larger cohesive force), melting point (higher is larger cohesive force) or hardness (harder is larger cohesive force).

As described above, in the conventional multi-transferable ink layer having an inhomogeneous composition in the thickness direction, the cohesive force represented by melt viscosity and melting point on the surface side of the ink layer is reduced. ..

In the present invention, however, contrary to this, by providing a layer having a large cohesive force represented by melt viscosity, melting point, etc. on the surface side of the ink layer, the mechanism is not clear, but desired multiple times transfer While maintaining the property, it is possible to achieve a remarkable effect that the compatibility with rough paper is good and that the background stain of the receiving paper does not occur.

Since the overcoat layer in the present invention is much thinner than the multi-transferable ink layer, 1
Normally, it is thought that the overcoat layer is transferred at the second printing, and the action and effect can no longer be exerted at the second and subsequent printing. However, in the present invention, it is surprising that the second and subsequent printings are overwritten. An unexpected fact was found that the effect of the coat layer was maintained.

Next, the present invention will be specifically described.

As the multi-transferable ink layer in the present invention, any conventional multi-transferable ink layer can be used. For example, 5 to 40% by weight of ethylene copolymer resin,
Those containing 10 to 40% by weight of a softening agent and 30 to 60% by weight of a pigment are preferable from the viewpoint of multi-time printability.

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, making it 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 becomes difficult to print many times.

The softening agent has a function of reducing the cohesive force of the resin to control cohesive failure, and if the ratio is less than the above range, cohesive failure is less likely to occur 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 also has the function of controlling cohesive failure. If the ratio is less than the above range, cohesive failure is less likely to occur and printing is difficult on a large number of times. Since it becomes brittle and the thermal transfer sensitivity decreases, it becomes difficult to print many times.

Examples of the ethylene-based copolymer resin include copolymers of ethylene and other vinyl monomers, and other vinyl monomers include vinyl acetate, vinyl butyrate, (meth) acrylic acid, and alkyl (meth) acrylate. Ester (As alkyl group, methyl, ethyl, propyl, butyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, dodecyl, hexadecyl, etc.
Examples include acrylonitrile, acrylamide, N-methylol acrylamide, and styrene. These vinyl monomers may be used alone or in combination. When the other vinyl monomer is an ethylene copolymer such as vinyl acetate or vinyl butyrate, a partially saponified product can be used. The content of vinyl monomer in the ethylene copolymer resin is preferably about 10 to 90% by weight. These ethylene-based copolymer resins may be used alone or in combination of two or more kinds. Preferred ethylene copolymer resins are ethylene-vinyl acetate copolymers and ethylene-alkyl acrylate copolymers, and ethylene-vinyl acetate copolymers are particularly preferred.

Examples of the softening agent include wax-like substances and oil-like substances.

Examples of the waxy substance include 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 oxidation wax, ester wax, low molecular weight polyethylene, Fischer-Tropsch wax; higher fatty acids such as myristic acid, palmitic acid, stearic acid, behenic acid; stearyl alcohol, docosanol Higher fatty alcohols such as; higher fatty acid monoglycerides, sucrose fatty acid esters, sorbitan fatty acid esters, and other esters;
Examples thereof include amides such as oleylamide and bisamides. Preferred waxy substances are paraffin wax and microcrystalline wax.

Examples of the oily substance include rapeseed oil, castor oil, coconut oil, sunflower oil, corn oil, linseed oil, safflower oil, lanolin, fish oil, squalane, jojoba oil, and other natural oils, liquid paraffin, petrolatum, Spindle oil, petroleum oil such as motor oil, sorbitan oleate, polyoxyethylene fatty acid ester, surfactant such as polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ether, dioctyl phthalate, tributyl acetyl citrate, dioctyl azelate , 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 wax-like substances and oil-like substances may be used alone or in combination of two or more kinds.

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

Yellow pigments 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 rake and the like.

Magenta Pigment Permanent Red 4R, Brilliant Huast Scarlet, Brilliant Carmine BS, Permanent Carmine FB, Resole Red, Permanent Red F5
R, Brilliant Carmine 6B, Pigment Scarlet 3B, Rhodamine Lake B, Rhodamine Lake Y, Alizarin Lake, and the like.

Examples of cyan pigments include Victoria blue lake, metal-free phthalocyanine blue, phthalocyanine blue, and fast sky blue.

In addition to the above components, the multi-transferable ink layer requires a dispersant for improving the dispersibility of the pigment, a filler such as diatomaceous earth, talc, silica powder, calcium carbonate, and other additives. You may mix | blend according to.

The overcoat layer has a higher cohesive force (for example, a higher viscosity and / or a higher melting point) than the multi-transferable ink layer and is compatible with the multi-transferable ink layer.

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

When the proportion of the ethylene-based copolymer resin is less than the above range, the printing sharpness on rough paper is not improved and the background stain preventing effect is not sufficiently exhibited, and when it exceeds the above range, the initial print density is lowered.

It is not always necessary to add a pigment to the overcoat layer, but it is preferable to add it from the viewpoint of increasing the initial print density. 10 to 30% by weight when blended
Is preferable, and if it exceeds 50% by weight, scumming 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 ×.
The porosity is set to 10 ³ poise or more, and the difference in melt viscosity between the overcoat layer and the multi-transferable ink layer is set to 10 × 10 ² poise or more, particularly 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 compatibility with rough paper tends to be poor. When the difference in melt viscosity between the two layers is smaller than the above range, compatibility with rough paper and resistance to scumming tend to be insufficiently exhibited.

As the ethylene-based copolymer resin for the overcoat layer, the same ethylene-based copolymer resin for the multi-transferable ink layer is used, and the same type as the multi-transferable ink layer is used. Alternatively, different types may be used.

In addition to the above-mentioned components, a softener, a dispersant, a filler and the like may be added to the overcoat layer as required. As these compounding agents, the same ones as those for the multi-transferable ink layer can be used.

As the pigment to be added to the overcoat layer as required, the same pigments as those for the multi-transferable ink layer can be used. Usually, the pigment used in the overcoat layer is of the same type as the pigment used in the multi-transferable ink layer.

For the multi-transferable ink layer, a coating solution prepared by dissolving and dispersing each of the above components in an appropriate organic solvent, or a coating solution in the form of an aqueous dispersion, emulsion or the like is applied by an appropriate coating means. For example, it can be formed by coating on a substrate using a roll coater, a gravure coater, a reverse coater, a bar coater, etc., and drying.
It may also be formed by hot melt coating. The overcoat layer can be formed in the same manner.

The thickness of the multi-transferable ink layer is preferably about 6 to 12 g / m ² from the viewpoint of ensuring desired multi-printability. Overcoat layer thickness is 0.2-1.5 g / m
^{About 2} is preferable. If the thickness of the overcoat layer is less than the above range, the action and effect of the overcoat layer are not sufficiently exhibited, the print definition on rough paper is lowered, and scumming tends to occur. When it exceeds the above range, the initial print density is lowered.

The substrate in the present invention includes polyester films such as polyethylene terephthalate film and polyethylene naphthalate film, polyamide film, aramid film, and various other films generally used as a substrate film for ink sheets of this type. A plastic film can be used. When using such plastic film, silicone resin, fluororesin, nitrocellulose resin, or various slip heat resistant resins modified by these, or heat It is desirable to prevent the sticking phenomenon of the heating head with respect to the base material film by providing a conventionally known sticking prevention layer composed of a mixture of a functional resin and a lubricant. An antistatic agent and the like may be contained in the base material and the stick prevention layer. Further, a high density thin paper such as a condenser paper may be used as a base material. The thickness of the base material is preferably about 1 to 9 μm, more 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 to 4 Dry coating amount of silicone modified urethane resin on the back surface
4.5 μm with a 0.1 g / m ² stick prevention layer
A coating solution prepared by dissolving and dispersing the composition shown in Table 1 in a benzene-ethyl acetate mixed solvent was applied onto the surface of the polyester film of m, and dried to obtain a multi-transfer method having physical properties shown in Table 1. The ink layer was formed.

Then, the compositions shown in Table 2 were dissolved and dispersed in a toluene-methyl cellosolve mixed solvent to prepare a coating solution,
This was coated on the transferable ink layer a number of times and dried to form an overcoat layer having the physical properties shown in Table 2 to obtain 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 conducted 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 multi-time printability, print quality and background stain, and a Beck smoothness of 30 seconds was used for rough paper compatibility. The results are shown in Table 3.

(1) Multiple times printability It was determined how many times printing at a predetermined density or more could be made using the same location on the ink sheet, and the following evaluation values were shown.

3 ... Printing with an OD value of 0.7 or more was obtained four times. 2 ... Printing with an OD value of 0.7 or more was obtained twice. 1 ... Printing with an OD value of 0.7 or more was not obtained more than once.

(2) Printing Quality The printing obtained on the receiving paper (smooth paper) was visually evaluated, and the following evaluation values were shown.

3 ... Clear and bleed-free printing was obtained. 2 ... Although there was bleeding, legible prints were obtained. 1 ... Only unreadable prints were obtained.

(3) Background stain The background stain on the receiving paper (smooth paper) was visually evaluated, and the following evaluation value was shown.

3 ... None at all. 2 ... Slightly soiled, but not to the extent that print quality was affected. 1 ... A lot of stains were found and the print quality was significantly impaired.

(4) Rough paper compatibility The prints obtained on the receiving paper (rough paper) were visually evaluated, and the following evaluation values were shown.

3 ... Clear printing was obtained without voids or print defects. 2 ... Although there were 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]

INDUSTRIAL APPLICABILITY In a thermal transfer ink sheet which can be used many times, compatibility with rough paper and scumming are improved while ensuring printability many times.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Katsuhiro Yoshida, Inventor Katsuhiro Yoshinakajima, Nishiyodogawa-ku, Osaka 4-14, Fujikopian Co., Ltd.Technical Center Technology Center Co., Ltd.

Claims (4)

[Claims] 1. A multiple number of times in which a heat-fusible multi-transferable ink layer is provided on a substrate, and a heat-meltable overcoat layer having a cohesive force larger than that of the multi-time transferable ink layer is provided thereon. Thermal transfer ink sheet that can be used. 2. The multi-transferable ink layer is a layer containing 5 to 40% by weight of an ethylene copolymer resin, 10 to 40% by weight of a softening agent and 30 to 60% by weight of a pigment, and the overcoat layer is Ethylene copolymer resin 50 to 90% by weight and pigment 0
The multi-use thermal transfer ink sheet according to claim 1, which is a layer containing about 50% by weight. 3. The multi-use thermal transfer ink sheet according to claim 2, wherein the pigment is carbon black. 4. The melt viscosity of the overcoat layer at 100 ° C. is 29 × 10 ² poise or more, and the difference in melt viscosity between the overcoat layer and the ink layer at 100 ° C. is 10.
The thermal transfer ink sheet according to claim 2 or 3, which has a density of × 10 ² poise or more.