JPH05177954A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To obtain a thermal transfer recording medium which has the high fastness of print image free of the deterioration of print quality by providing on a thermally meltable ink layer containing individually specific amounts of specific adhesiveness-imparting resin, a wax type material and a coloring agent. CONSTITUTION:40-90wt.% of an adhesiveness-imparting resin having a softening or melting point of 50-130 deg.C, a glass transition point of 15 deg.C or higher a melting viscosity of 10 to 10<5>cp at 150 deg.C and a number average molecular weight of 300-3000, 0-40wt.% of a wax type material and 10-30wt.% of a coloring agent are dissolved or dispersed in a solvent to prepare a coating solution for an ink layer. The prescribed amount of the coating solution is applied to a substrate, such as a plastic film, a condenser paper or the like and is dried to form a thermally meltable ink layer to prepare a thermal transfer recording medium. The recommended adhesiveness-imparting resins are a rosin, a modified rosin and a terpene resin. It is possible to form a peeling layer between the substrate and the ink layer consisting of a wax type material of melting point of 90-120 deg.C as a main constituent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer recording medium excellent in smear resistance, scratch resistance and alcohol resistance.

[0002]

2. Description of the Related Art Conventionally, thermal transfer recording media have been widely used for various printing applications. However, among them, in the case of thermal transfer recording media for bar code printing, label printing, etc., the robustness of the printed image [smear resistance (stain resistance), scratch resistance, etc.] is not sufficient. It's a problem.

For example, a bar code printed using these recording media is not damaged even if the image surface is rubbed to some extent during the use of the bar code, and the underlying portion is not soiled and can be reliably read by a machine. Since the stain on the surface may be wiped off with alcohol, the essential requirement that the printed image does not dissolve in alcohol is not always satisfied.

Therefore, various attempts have been made to improve the robustness. For example, a method has been proposed in which the vehicle of the ink layer is composed only of a resin composed of a mixture of glassy resin and rubbery resin (Japanese Patent Publication No. 59-37237).
Publication). However, although this method improves scratch resistance to a certain extent, it has a drawback of lowering transferability, and further has a restriction that two resins having good compatibility must be selected. In addition, a peeling layer mainly composed of wax is provided to improve transferability, and even if an attempt is made to provide a protective function after printing, the strength of the wax layer on the surface is small, so the protective effect is small. A thermal transfer recording medium satisfying both fastness and quality has not been obtained.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermal transfer recording medium which has a high printed image fastness and which does not deteriorate the quality of the printed image.

[0006]

That is, the present invention has a softening point or melting point of 50 to 130 ° C. and a glass transition point on a substrate.
15 ℃ above, the melt viscosity at 0.99 ° C. is 10 to 10 ⁵ cP, and the number average molecular weight of tackifier resin 40 to 90 wt% is 300 to 3000, 0 to 40 wt% wax-like substance and a colorant 10 The present invention relates to a thermal transfer recording medium provided with a heat-meltable ink layer consisting of ˜30% by weight.

[0007]

FUNCTION AND EXAMPLE The tackifier resin used in the ink has a softening point or melting point of 50 to 130 ° C., above all
70 to 120 ℃, glass transition temperature above 15 ℃, above all 25 ℃
Or more, is 10 to 10 ⁵ cP melt viscosity at 0.99 ° C., and a molecular weight satisfying the condition that the range of 300 to 3,000, and are selected from among the stiff alcohol-insoluble or sparingly soluble resins.

Generally, a hard resin forms a sloppy film and has low adhesion strength to a receptor, but a resin having physical properties within a specific range used in the present invention has a high adhesion strength to a receptor and the resin alone. You can meet the conditions required in.

If the softening point or glass transition point of the resin is less than the above range, there is a drawback that the back surface of the substrate and the ink surface cause blocking during storage, and if it exceeds the above range, transferability is deteriorated. It is not preferable because of its shortcomings.

If the molecular weight is less than the above range, the fastness of the printed image is not sufficient, and if it exceeds the above range, the melt viscosity becomes high and the transferability is lowered.

Since the resin under the above conditions is excellent in the melt transfer property, even if the vehicle of the heat-meltable ink is composed of this alone, transfer unevenness does not occur and a high-contrast image is provided. In addition, it has a high adhesion strength to the receptor and a hard film, which is excellent in smear resistance, abrasion resistance and alcohol resistance.

Examples of preferable tackifier resins include natural resins such as hydrogenated rosins, asymmetric rosins, polymerized rosins, rosins such as rosin esters, rosin-modified phenolic resins, rosin-modified maleic acid resins, and the like.
A terpene resin obtained from rosin-modified resins such as rosin-modified xylene resin, polyterpenes, aromatic-modified terpenes, terpene phenols, hydrogenated terpenes, and terpenes
-Phenol- terpene resin such as formaldehyde resin.

In the petroleum resin system as a synthetic resin,
Petroleum resin comprising C ₅ -based aliphatic or alicyclic hydrocarbon or its derivative, C ₉ -based aromatic or alicyclic hydrocarbon or their derivative, homopolymer of styrene, α-methylstyrene or isopropyltoluene ,
Copolymer resin, dicyclopentadiene resin, aromatic addition condensation type petroleum resin, coumarone-indene polymer resin, and other resins include xylene resin, phenol resin, styrene-maleic anhydride resin and ketone resin. Be done.

The amount of tackifier resin used is preferably 40 to 90% (% by weight, the same applies hereinafter) of the total solid amount of the ink, and more preferably about 40 to 70%. If the amount of the tackifier resin is less than the above range, a coating having the required hardness cannot be obtained, and if it is more than the above range, the amount of the coloring pigment becomes too small and the density of the transferred image becomes small, so that it cannot be used. Absent.

If desired, a wax-like substance may be added to the ink in order to increase the flexibility of the ink layer and improve the adhesion of the ink to the receptor. Examples of the wax-like substance used include wood wax, beeswax,
Natural waxes such as carnauba wax, candelilla wax, montan wax, 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; myristic acid, Higher fatty acids such as palmitic acid, stearic acid and behenic acid; higher aliphatic alcohols such as stearyl alcohol and docosanol; higher fatty acid monoglycerides, fatty acid esters of sucrose, fatty acid esters of sorbitan, stearic acid amide, oleyl amide, etc. One or more kinds of amides and bisamides can be used. As these wax-like substances, those having a melting point of 70 to 90 ° C. are preferable from the viewpoint of thermal transfer sensitivity.

The amount of the wax-like substance used is preferably in the range of 0 to 40%, especially 10 to 30% of the total solid amount of the ink. If the amount used exceeds the above range, there are disadvantages that the robustness is lowered, or transfer failure occurs and the ink is not transferred.

As the colorant, various inorganic and organic pigments and dyes, which are conventionally used as colorants for heat-fusible transfer inks, magnetic powder, metal powder, fluorescent pigments and dyes are suitable. Can be used for

The amount of the colorant used is 10 to 30 of the total solid amount of the ink.
% Is preferable.

Further, in the present invention, if necessary, an extender pigment and other additives may be contained in a small amount, for example, 10% or less of the solid content of the ink layer.

In order to form the ink layer, the ink components are dissolved or dispersed in a solvent and applied using a bar coater or a gravure coater. The coating amount is usually preferably in the range of 1.8 to 2.6 g / m ² in terms of solid content after drying.

The release layer in the present invention facilitates the release of the ink layer from the substrate during printing, and is mainly composed of a wax-like substance.

As the wax-like substance, any of the wax-like substances used in the ink can be used. The waxy substances may be used alone or as a mixture. Among them, polyethylene wax, α-olefin wax, Fischer-Tropsch wax and the like are particularly preferably used as the main wax. That is, since the polyethylene wax and the Fischer-Tropsch wax have high melting points, there is no so-called reverse transfer in which the ink once transferred returns to the ribbon, the viscosity is low, the transferability is good, and the molecular weight is large, so that the solvent resistance is excellent. In addition, the α-olefin wax gives a clear image because the edges of the α-olefin wax are sharp when transferred. Further, in order to improve the adhesion to a substrate such as polyethylene terephthalate, it is preferable to use a resin such as ethylene-vinyl acetate copolymer (EVA) in addition to the wax.

To provide the release layer, the wax-like substance to be coated is dissolved in a solvent (either a single solvent or a mixed solvent) and the solution is coated on a substrate and dried, or the wax-like substance is applied. It can be by hot melt coating. The amount of the release layer applied on the substrate is about 1.0 to 2.
It is preferably 0 g / m ² .

As the substrate in the present invention, a polyester film such as polyethylene terephthalate, a polycarbonate film, a polyamide film, and various plastic films which are generally used as a substrate film for an ink ribbon of this type can be used. .. It is also preferable to use a high density thin paper such as a condenser paper as a base material.

When the above plastic film is used, a silicone resin, a fluororesin, a nitrocellulose resin, or various slip heat resistant resins modified by these, on the back surface (the surface on the side that slides on the thermal head),
Alternatively, a conventionally known stick-preventing layer composed of a mixture of a heat-resistant resin and a lubricant may be provided.

The thickness of the substrate is preferably about 2 to 10 μm, more preferably about 3 to 7 μm from the viewpoint of improving the thermal conductivity.

When the thermal transfer recording medium of the present invention is heated by the thermal head from the substrate side, each layer is melted and transferred to the receptor. The transferred image is in the order of the ink layer and the peeling layer from the side of the receptor, and since the transferred ink layer itself contains a hard tackifier resin as a main component, high smear resistance, abrasion resistance and Has alcohol resistance,
It is especially useful for printing barcodes. In addition, it is useful for printing labels, and of course, can be favorably used for printing on plain paper.

The present invention will be further described below with reference to examples, but the present invention is not limited thereto.

Examples 1 to 8 and Comparative Examples 1 to 2 A polyethylene terephthalate film having a thickness of 4.5 μm was used as a base material, and a release layer having the composition shown in Table 1 was provided thereon. The coated amount was 1.2 g / m ² in terms of solid content after drying.

Inks having the compositions shown in Table 1 were coated on the release layer using a gravure coater to produce a thermal transfer recording medium. The physical property values of the tackifier resin and wax-like substance used are as shown in Table 2.

The coating amount of each layer was 2.2 g / m ² in terms of solid content after drying.

[0032]

[Table 1]

[0033]

[Table 2]

The obtained thermal transfer recording medium was evaluated. The evaluation results are shown in Table 3.

The evaluation items and evaluation methods are as follows.

(1) Transferability (sensitivity) Bar code printer (Tokyo Electric Co., Ltd., B-30)
Was used to print on art paper (Beck's smoothness of about 500 seconds), and the transferability (sensitivity) was evaluated from the applied energy when a printed image readable by a scanner was obtained.

○ Printing is possible at less than 20 mJ / mm ² . Possible to print in the range of ^{20 to} 25 mJ / mm ² . Printable at over 25 mJ / mm ² .

(2) Smear resistance (stain resistance) The bar code image obtained under the conditions of (1) is printed by using a rubbing resistance tester (Lab tester manufactured by Yasuda Seiki Co., Ltd.). The state of contamination when the cardboard was reciprocated 100 times at a pressure of 250 g / cm ² was evaluated.

○ No stain is found on the white background. △ Some dirt is seen on the white background. × The stain on the white background is obvious.

(3) Scratch resistance With respect to the bar code image obtained under the condition of (1), a pressure of 250 g / cm was applied on the image using a scratch resistance tester (Rab tester manufactured by Yasuda Seiki Co., Ltd.). ^{In 2} , the misalignment state was evaluated when the sand crusher was reciprocated 10 times.

○ There is no deviation in the printed image. △ There is some misalignment in the printed image. × The deviation of the printed image is clear.

(4) Alcohol resistance With respect to the barcode image obtained under the condition (1), a clock meter (manufactured by Atlas, USA) was used and pressure was applied on the image.
When the cloth moistened with alcohol was reciprocated 10 times at 00 g / cm ² , the stain state of the image surface (in particular, the white background portion) was evaluated.

○ No stain is found on the image side. △ The image surface has some stains. × The stain on the printed surface is obvious.

[0044]

[Table 3]

It can be seen from Table 3 that the printed images obtained by using the thermal transfer recording medium of the present invention have excellent sensitivity and well-balanced smear resistance, scratch resistance and alcohol resistance.

[0046]

The thermal transfer recording medium of the present invention has excellent transfer sensitivity, and the obtained printed image has a well-balanced smear resistance, scratch resistance and alcohol resistance.

Claims (3)

[Claims] 1. A softening point or melting point of 50 to 130 on a substrate.
° C., a glass transition point of 15 ℃ or more and is 10 to 10 ⁵ cP melt viscosity at 0.99 ° C., and a number average molecular weight of tackifier resin 40 to 90 wt% is 300 to 3,000, wax-like substance 0
A thermal transfer recording medium provided with a heat-meltable ink layer comprising 40% by weight and 10 to 30% by weight of a colorant. 2. The thermal transfer recording medium according to claim 1, wherein the tackifier resin is one or more selected from rosins, rosin-modified resins, terpene resins, xylene resins and petroleum resins. .. 3. The thermal transfer recording medium according to claim 1, further comprising a release layer mainly composed of a wax-like substance having a melting point of 90 to 120 ° C. provided between the base material and the ink layer.