JP3090748B2 - Thermal transfer recording medium - 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 recording medium having excellent 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 (ground stain resistance), scratch resistance, etc.) is not sufficient. It is a problem.

For example, a bar code printed using such a recording medium can be reliably read by a machine without any damage even if the printing surface is slightly rubbed during use of the bar code, and the base portion is not stained. Since the dirt on the surface may be wiped with alcohol, the essential requirement that the imprint does not dissolve in alcohol is not always satisfied.

[0004] 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 of only a resin composed of a mixture of a glassy resin and a rubbery resin (Japanese Patent Publication No. 59-37237).
No.). However, in this method, although the abrasion resistance and the like are improved to some extent, there is a drawback that the transferability is lowered, and further, there is a restriction that a resin having good compatibility must be selected as the two kinds of resins. In addition, a release layer mainly composed of wax is provided to improve transferability, and even if it is intended to provide a protection function after printing, the strength of the wax layer on the surface is small, so the protection effect is small. No thermal transfer recording medium satisfying both robustness and quality has been obtained.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermal transfer recording medium having high robustness of an image and not deteriorating the quality of the image.

[0006]

That is, according to the present invention, a softening point or melting point of 50 to 130 ° C. and a glass transition point of
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 A heat-fusible ink layer of about 30% by weight, and a melting point of 90 to 120 between the base material and the ink layer.
Α- olefin, mainly composed of polyethylene wax
TECHNICAL FIELD The present invention relates to a thermal transfer recording medium provided with a release layer that also uses thin wax .

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The tackifier resin used in the ink has a softening point or melting point of from 50 to 130.degree.
70-120 ° C, glass transition point 15 ° C or more, above all 25 ° C
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.

In general, a hard resin forms a moly film and has a low fixing strength to a receptor, but a resin having a specific range of physical properties used in the present invention has a high fixing strength to a receptor and a resin alone. Can satisfy the required conditions.

If the softening point and the glass transition point of the resin are less than the above ranges, there is a disadvantage that the back surface of the substrate and the ink surface are blocked during storage, and if it exceeds the above ranges, the transferability is reduced. It has disadvantages and is not preferred.

When the molecular weight is less than the above range, the printed image is not sufficiently fast, and when the molecular weight exceeds the above range, the melt viscosity is increased and the transferability is reduced.

Since the resin under the above conditions is excellent in the melt transferability, even if the vehicle of the hot-melt ink is constituted by itself, transfer unevenness does not occur and a high-contrast printed image is provided. In addition, the adhesive strength to the receptor is large, and a hard film is formed, so that it has excellent smear resistance, scratch resistance and alcohol resistance.

Preferred examples of the tackifier resin include natural resins such as hydrogenated rosin, disproportionated rosin, polymerized rosin, rosins such as rosin esters, rosin-modified phenolic resin, rosin-modified maleic acid resin, and the like.
Rosin-modified resins such as rosin-modified xylene resins, terpene resins obtained from polyterpenes, aromatic-modified terpenes, terpene phenols, hydrogenated terpenes, etc., terpenes
-Phenol-Terpene resins such as formaldehyde resin.

In the case of petroleum resin as a synthetic resin,
C ₅ based aliphatic or alicyclic hydrocarbon or a derivative thereof, C ₉ based aromatic or alicyclic hydrocarbon or petroleum resins consisting of derivatives, styrene or α- methylstyrene down homopolymer, copolymer resins , Dicyclopentadiene resin, aromatic addition condensation petroleum resin,
Other resins such as coumarone-indene polymer resins include xylene resins, phenolic resins, styrene-maleic anhydride resins, and ketone resins.
The rosin, rosin modified resin, terpene resin, xy
Ren-based resins and petroleum resins can be used alone or in combination
Can be used in combination. As the tackifier resin, α-methyl
Styrene or α-methylstyrene resin and rosin
Mixing with stell resin, xylene resin or terpene resin
Are preferred.

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

A wax-like substance can be added to the ink, if necessary, in order to increase the flexibility of the ink layer and improve the fixation of the ink to the receptor. Examples of waxy substances used include wood wax, beeswax,
Natural waxes such as 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, Fischer-Tropsch wax; myristic acid; Higher fatty acids such as palmitic acid, stearic acid and behenic acid; higher fatty alcohols such as stearyl alcohol and docosanol; higher fatty acid monoglycerides, fatty acid esters of sucrose, fatty acid esters of sorbitan and the like; stearic acid amide, oleyl amide and the like One or more 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 waxy substance used is preferably in the range of 0 to 40%, particularly 10 to 30% of the total solid content of the ink. If the amount used exceeds the above range, there are disadvantages in that the fastness is reduced and the transfer is poor and the ink is not transferred.

As the colorant, various inorganic and organic pigments and dyes which have conventionally been used as colorants for hot-melt transfer inks, magnetic powders, metal powders, fluorescent pigments and dyes, and the like are suitable. Can be used for

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

Further, in the present invention, if necessary, extenders and other additives can be contained in a small amount, for example, in a proportion of 10% or less of the solid matter of the ink layer.

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

The release layer in the present invention facilitates release of the ink layer from the substrate during printing, and has a melting point of 90 to 90.
Polyethylene wax scan a 120 ° C. mainly, alpha-OH
Refin wax is used in combination .

[0022] Po triethylene wax is used particularly preferably as the main component wax. In other words, polyethylene wax has a high melting point, so there is no so-called reverse transfer in which the ink once transferred to the ribbon is returned. The low viscosity makes the transferability good, and the molecular weight is large, so that the solvent resistance is excellent. In addition, the α-olefin wax gives a sharp image because the edge of the transferred wax is good. Further, it is preferable to use a resin such as ethylene-vinyl acetate copolymer (EVA) in addition to the wax in order to improve the adhesiveness on a substrate such as polyethylene terephthalate.

To provide a release layer, a wax-like substance to be applied is dissolved in a solvent (which may be a single solvent or a mixed solvent), and the solution is applied to a substrate and dried, or Hot melt coating can be used. The coating amount of the release layer 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 other plastic films generally used as a substrate film for this type of ink ribbon can be used. . Further, a high-density thin paper such as a condenser paper may be used as a base material.

When the plastic film is used, a silicone resin, a fluororesin, a nitrocellulose resin, or various kinds of lubricating heat-resistant resins modified with these resins are provided on the back surface (the surface on the side sliding on the thermal head).
Alternatively, a conventionally known stick prevention layer made 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 thermal conductivity.

When the thermal transfer recording medium of the present invention is heated from the side of the substrate by the thermal head, each layer is melted and transferred to the receptor. The transferred image is in the order of the ink layer and the release layer from the side of the receiver, and the transferred ink layer itself is mainly composed of a hard tackifier resin, so that high smear resistance, scratch resistance and Alcohol resistance,
Particularly useful for barcode printing. In addition, it is also useful for label printing and the like, and can of course be used well for printing on plain paper.

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

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

On the release layer, inks having the compositions shown in Table 1 were respectively applied using a gravure coater to produce a thermal transfer recording medium. The physical property values of the tackifier resin and the waxy 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. Table 3 shows the evaluation results.

The evaluation items and evaluation methods are as follows.

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

○ Printing is possible at less than 20 mJ / mm ² . △ Printing is possible in the range of ^{20 to} 25mJ / mm2. × 25 mJ / mm ² than can be printed in.

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

○ No stain is seen on the white background. △ Dirt is slightly seen on the white background. C: The stain on the white background is apparent.

(3) Scratch resistance The bar code image obtained under the conditions of (1) was applied with a pressure of 250 g / cm on the image using a scratch resistance tester (Lab Tester manufactured by Yasuda Seiki Co., Ltd.). ^{In step 2} , the state of slippage when the sand slag was reciprocated 10 times was evaluated.

○ No deviation is observed in the imprint. Δ: The image is slightly distorted. C: The image shift is apparent.

(4) Alcohol resistance The barcode image obtained under the conditions of (1) was applied with a clock meter (manufactured by Atlas, USA) to apply a pressure of 5% 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 (particularly, a white background portion) was evaluated.

○ No stain is seen on the image-printed surface. △ Stain is slightly seen on the image surface. C: The stain on the printing surface is apparent.

[0044]

[Table 3]

From Table 3, it can be seen that the images obtained by using the thermal transfer recording medium of the present invention have excellent sensitivity and a good balance of smear resistance, scratch resistance and alcohol resistance.

[0046]

The thermal transfer recording medium of the present invention has excellent transfer sensitivity, and the obtained image has a good balance of smear resistance, scratch resistance and alcohol resistance.

Continuation of the front page (56) References JP-A-63-162287 (JP, A) JP-A-61-244591 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5 / 38-5/40

Claims (3)

(57) [Claims] 1. A softening point or melting point of 50 to 130 on a substrate.
° C., a glass transition point of 15 ℃ or higher, 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 3,000, wax-like substance 0-4
A hot-melt ink layer comprising 0% by weight and a colorant of 10 to 30% by weight is provided, and between the base material and the ink layer, mainly a polyethylene wax having a melting point of 90 to 120 ° C , A thermal transfer recording medium provided with a release layer using an α-olefin wax in combination . 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 2, wherein the tackifier resin comprises an α-methylstyrene resin or a mixture of an α-methylstyrene resin and a rosin ester resin, a xylene resin or a terpene resin.