JPH1044632A - Thermal transfer recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the bonding properties of a hot-melt ink layer by setting the bonding strength of a substrate and the hot-melt ink layer and also setting the difference between the bonding strength of the substrate and the hot-melt ink layer at the curing time after heating at a specified value or above at a specified temperature. SOLUTION: A coating fluid composed of carbon black, carnauba wax, methyl methacrylate-acrilonitrile copolymer resin, a polyester and methyl ethyl ketone is so applied as to form the thickness after drying of approximately 2μm on a polyethylene terephthalate film, and dried thereon to form a hot-melt ink layer 13 as a thermal transfer recording medium 11. In that case, the bonding strength of the ink layer 13 is set at 40gf/cm at 20 deg.C or more, and the difference between the above-referred bonding strength and the bonding strength of the ink layer 13 at the time of cooling after heating is set at 30gf/cm (20 deg.C) or more. The bonding properties of the hot-melt ink layer 13 or of a layer formed by laminating a release layer and the hot-melt ink layer 13 can be improved by the arrangement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermal transfer recording medium having a heat-fusible ink layer on a support, particularly suitable for bar code printing.

[0002]

2. Description of the Related Art In recent years, a thermal transfer recording system using a thermal head has been known to be noiseless and the apparatus is relatively inexpensive.
In addition, they have come to be widely used because of their advantages such as downsizing, easy maintenance, and stable printed images. Typical examples of such a thermal transfer recording medium include (1) a heat-meltable ink layer (sometimes simply referred to as an “ink layer”) composed of a colorant and a binder provided directly on a support; One in which a heat-fusible ink layer composed of a colorant and a binder is provided on a support via a release layer containing wax as a main component, and the like.

[0003]

However, in many cases, the binder for the ink layer (1) and the binder for the release layer (2) are mainly composed of wax having low plasticity. Adhesion with a resin film such as polyethylene terephthalate (PET), which is widely used, is extremely poor, and causes a problem that the ink layer and the release layer are peeled off from the support by mechanical external force.

In order to solve such problems, the surface of the support is made uneven to increase the contact area between the ink layer and the support (Japanese Patent Application Laid-Open No. 58-16889). An intermediate adhesive layer made of a cellulosic resin, a polyester resin, or the like is provided therebetween (JP-A-59-165)
690, JP-A-60-54894, etc.), but the production method and process become complicated,
There is a disadvantage that the production cost is increased.

Also, since the binder of the ink layer of (1) and the binder of the release layer and the ink layer of (2) are mainly composed of wax having low plasticity, the shear strength and the adhesive strength of the ink layer are low. As a result, when a ladder barcode is printed by a barcode printer or the like, a dropping phenomenon (a phenomenon in which a portion to which no energy is applied by a thermal head is transferred together) occurs, resulting in unclear printing. Conversely, if a high molecular weight resin is used as the binder to increase the shear strength and the adhesive strength and eliminate the dropping phenomenon, transfer to the receiving paper becomes impossible. Therefore, in any case, there is a problem that the barcode scanner cannot read the barcode.

In view of the above circumstances, the present invention improves the adhesion of a heat-fusible ink layer or a layer formed by combining a release layer and a heat-fusible ink layer, and enhances the storage stability as a thermal transfer recording medium, and is used for barcodes. An object is to provide a suitable thermal transfer recording medium.

[0007]

According to the present invention, first, in a thermal transfer recording medium having a heat-fusible ink layer provided on a support directly or via a release layer, the support and the heat-fusible ink layer are provided. Has an adhesive strength of at least 40 gf / cm at 20 ° C.
Further, there is provided a thermal transfer recording medium characterized in that the difference between the adhesive strength of the heat-fusible ink layer and the support at the time of cooling after heating is 30 gf / cm or more at 20 ° C.

Second, in the thermal transfer recording medium described in the first aspect, both the adhesive strength and the shear strength between the support and the hot-melt ink layer during cooling after heating are 2.0 to 2.0 ° C. at 20 ° C.
A thermal transfer recording medium characterized by being in the range of 7.0 gf / cm is provided.

Third, the thermal transfer recording medium according to the first or second aspect, wherein the shear strength of the support and the heat-fusible ink layer is 40 gf / cm or more at 20 ° C. Provided.

Hereinafter, the present invention will be described in detail. The present inventors, as described above, the adhesive strength of the ink layer or the layer obtained by combining the release layer and the ink layer, the adhesive strength at the time of cooling after heating and the difference between them, and furthermore, the ink layer at the time of cooling after heating. When the adhesive strength, the shear strength, and the shear strength of the ink layer are set to specific values, the adhesion to the support is improved, and it has been found that no problem occurs even when a ladder bar code is printed, leading to the present invention. Things.

That is, in a thermal transfer recording medium in which a heat-fusible ink layer is provided directly on a support or via a release layer, the adhesive strength of the ink layer is 40 gf / c.
m (20 ° C.) or more, and the difference between the adhesive strength of the ink layer at the time of cooling after heating is 30 gf / cm (20 ° C.) or more, not only does the ink layer not fall off when not in use, but also a bar code printer. Even when a ladder bar code is printed, no drop phenomenon occurs, and it can be sufficiently read by a bar code scanner. Further, when the shear strength and the adhesive strength of the ink layer at the time of cooling after heating are 2.0 to 7.0 gf / cm, when the adhesive strength of the ink to the receiving paper is weak, particularly, a polyethylene film having a high smoothness is used. In this case, the phenomenon of so-called transfer failure in which the ink once transferred is returned to the thermal transfer recording medium side does not occur. Further, the shear strength of the ink layer is 40 gf.
/ Cm (20 ° C.) or more further increases the above-mentioned effects.

The method for measuring the adhesive strength and the shear strength in the present invention will be described with reference to the drawings. Figure 1 shows the H used for the measurement.
It is explanatory drawing of an EIDON surface property measuring apparatus, and shows the state which cut | disconnected vertically. The model used is HEIDON-14 manufactured by HEIDON
It is. A method for measuring the adhesive strength and the shear strength of the ink layer using this tester will be described. In FIG. 1, 1 is a cellophane adhesive tape (Nichiban Co., Ltd .: cellophane 18m)
m × 35 mm), 2 is a thermal transfer recording medium, and the adhesive surface of the cellophane tape 1 faces the ink layer. 2a is an ink layer and a release layer, and 2b is a support layer. Reference numeral 3 denotes a reinforcing plate, in which case a thick stainless steel plate was used. Reference numeral 4 denotes a fixture, and the medium 2 adhered with a cellophane tape was peeled off at a constant speed, and the state was observed.

Next, a method for measuring the adhesive strength and the shear strength of the ink layer at the time of cooling after heating will be described. 20 ° C using a barcode thermal transfer printer (TEC: B-30)
Under the condition of 60% RH, 19.6 mj / mm ² of energy is applied from the thermal head in a state where the receiving paper and the thermal transfer recording medium are superposed at a speed of 2 ″ / sec, thereby bonding the receiving paper and the medium. In the measurement, one end of the receiving paper and the medium adhered by the application of heat were peeled off as shown in Fig. 1, and the end of the peeled receiving paper was sandwiched by the fixture 4, peeled off at a constant speed, and the state was observed. The measurement conditions are as follows: Peeling angle: 180 ° Peeling speed: 75 mm / min Width of test piece: 6.3 mm Test environment temperature: 20 ° C. Here, the shear strength means only the peeling layer and the ink layer. Is the force applied when peeling starts when the remaining tape is peeled off to the side of the adhesive tape and the receiving paper, and the adhesive strength means the force applied when peeling.

2 and 3 are cross-sectional views of the thermal transfer recording medium according to the present invention. FIG. 2 shows an example in which an ink layer is provided directly on a support, and FIG. 3 shows an example in which the ink layer is provided via a release layer. This shows an example in which the support is provided on a support. Details of configuring these media will be described in the embodiments described below.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION As the support 12, for example, a plastic film having relatively high heat resistance such as polyester, polycarbonate, triacetyl cellulose, nylon, polyimide, etc., as well as glassine paper, condenser paper, metal foil, etc. Yes, its thickness is about 2-15 μm,
Preferably it is in the range of 3 to 10 μm. The support 1
On the surface in contact with the thermal head of No. 2 (the surface opposite to the side where the ink layer is present), if necessary, silicone resin, silicone rubber, silicone modified resin, fluororesin, polyimide resin, epoxy resin, phenol By providing the heat-resistant and / or lubricious protective layer 14 made of a resin, a melamine resin, nitrocellulose, or the like, the heat resistance and / or lubricity of the support can be improved.

Next, the heat-meltable ink layer 13 contains the same coloring agents, waxes and resins as the conventional heat-meltable layer. The colorant is appropriately selected from conventionally known dyes and pigments. Examples of waxes include paraffin wax, microcrystalline wax, oxidized paraffin wax, candelilla wax, carnauba wax, montan wax, ceresin wax, polyethylene wax, polyethylene oxide wax, caster wax, tallow hardened oil, lanolin, sorbitan stearate Sorbitan palmitate, stearyl alcohol, polyamide wax, oleylamide, hydroxystearic acid, synthetic alloy wax and the like. Examples of the resins include elastomers such as rubber, polyamide-based, polyester-based, polyurethane-based, vinyl chloride-based, petroleum-based, styrene-based, butyral-based, phenol-based, and acrylonitrile-based resins, as well as ethylene-vinyl acetate copolymer. And an ethylene-acrylic copolymer resin.

The weight ratio of each material constituting the ink layer 13 is as follows: colorant / wax / resin = 5 to 3
0/5 to 30/30 to 90 are suitable.

The adhesive strength of the ink layer 13 is at least 40 gf / cm at 20 ° C., the difference from the adhesive strength of the ink layer at the time of cooling after heating is at least 30 gf / cm (20 ° C.), and the ink at the time of cooling after heating. The bond strength and shear strength of the layer are 2.0
In order that the shear strength of the ink layer is not less than 7.0 gf / cm (20 ° C.) and the ink layer has a shear strength of 40 gf / cm (20 ° C.) or more, a copolymer based on acrylonitrile or methacrylonitrile should be used. Is preferred.

Specific examples thereof include acrylonitrile-methyl methacrylate, acrylonitrile-methyl acrylate, acrylonitrile-ethyl methacrylate, acrylonitrile-ethyl acrylate, acrylonitrile-n-butyl methacrylate, acrylonitrile-glycidyl methacrylate, acrylonitrile-glycryl acrylonitrile-glycryl acrylonitrile-glycryl acrylonitrile-glycryl acrylonitrile-glycryl acrylonitrile-glycryl acrylonitrile glycidyl acrylate. -Hydroxyethyl methacrylate, acrylonitrile-iso-butyl methacrylate, acrylonitrile-tert-butyl methacrylate, acrylonitrile-2-hydroxypropyl methacrylate, and a copolymer of all the above combinations in which acrylonitrile is changed to methacrylonitrile.

In addition to the above, a small amount (30 ° C. or less) of a plasticizer such as a fatty acid ester, a glycol ester, a phosphoric acid ester, or an epoxidized linseed oil, or an oil may be added to the ink layer 13.

The ink layer 13 can be formed by coating in a state of being dissolved or dispersed in a hot melt or a solvent and then drying, and has a thickness of 1 to 10 μm, preferably 2 to 6 μm.
(In the case of FIG. 2) and 1 to 3 μm (in the case of FIG. 3). If the thickness of the ink layer is thinner than 1 μm, insufficient density or lack of printing on paper having relatively low smoothness occurs, and conversely, 10 μm
If it exceeds, the adhesive strength is reduced, and the ink layer peels off. In addition, if the thickness of the ink layer is too large, the shear strength increases, which may result in poor transfer.

The release layer 15 is mainly formed at 40 to 100 ° C.
Paraffin wax, microcrystalline wax, paraffin oxide wax, candelilla wax, carnauba wax, montan wax, ceresin wax, polyethylene wax, polyethylene oxide wax, caster wax, tallow hardened oil, lanolin, wood wax, sorbitan steer having a melting point of Wax, sorbitan palmitate, stearyl alcohol, polyamide wax, oleylamide, stearylamide, hydroxystearic acid, synthetic ester wax, synthetic alloy wax, etc. Elastomer, polyvinyl butyral, vinyl chloride-vinyl acetate copolymer resin, nitrocellulose, epoxy resin, ethylene-vinyl acetate copolymer resin, ethylene-α-ole Fin copolymer resin, alpha-olefin - maleic anhydride copolymer resin, ethylene - methacrylic acid copolymer resin, one or more kinds, such as ethyl cellulose may be mixed in an appropriate amount.

[0023]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. In addition, all the parts and% shown below are based on weight.

Example 1 A coating liquid of the following component A was dried on a PET film having a thickness of about 4.5 μm to a thickness of about 2 μm.
Was applied using a wire bar and dried to form a heat-meltable ink layer to obtain a thermal transfer recording medium. <Component A> Carbon black 20 parts Carnauba wax 20 parts Methyl methacrylate-acrylonitrile copolymer resin 60 parts Polyester 40 parts Methyl ethyl ketone 900 parts

Example 2 A coating solution of the following component B was dried on a PET film having a thickness of about 4.5 μm to a thickness of about 1.5.
μm is applied using a wire bar, dried to form a release layer, and a coating solution comprising the following C component is further applied thereon using a wire bar such that the thickness after drying is about 2 μm. To form a heat-meltable ink layer to obtain a thermal transfer recording medium. <Component B> Carnauba wax 95 parts Ethylene-vinyl acetate copolymer resin 5 parts Toluene 700 parts Methyl ethyl ketone 200 parts <Component C> Carbon black 30 parts Methyl methacrylate-acrylonitrile copolymer resin 40 parts Polyester 30 parts Methyl ethyl ketone 900 parts

Example 3 A thermal transfer recording medium was produced in the same manner as in Example 2 except that the component B was changed to the following component D. <Component D> Carnauba wax 90 parts Epoxy resin 10 parts Toluene 700 parts Methyl ethyl ketone 200 parts

Example 4 A thermal transfer recording medium was produced in the same manner as in Example 2, except that the component B was changed to the following component E. <E component> 95 parts of carnauba wax 5 parts of vinyl chloride-vinyl acetate copolymer resin 700 parts of toluene 200 parts of methyl ethyl ketone

Example 5 A thermal transfer recording medium was produced in the same manner as in Example 2 except that the component B was changed to the following component F in Example 2. <F component> Carnauba wax 85 parts Ethylene-methacrylic acid copolymer resin 15 parts Toluene 700 parts Methyl ethyl ketone 200 parts

Comparative Example 1 A thermal transfer recording medium was produced in the same manner as in Example 2 except that the component B was changed to the following component G in Example 2. <G component> 97 parts of carnauba wax 3 parts of ethylene-vinyl acetate copolymer resin 700 parts of toluene 200 parts of methyl ethyl ketone

Comparative Example 2 A thermal transfer recording medium was produced in the same manner as in Example 2 except that the component B was changed to the following component H. <H component> Carnauba wax 100 parts Styrene-butadiene copolymer resin 10 parts Toluene 700 parts Methyl ethyl ketone 200 parts

Comparative Example 3 A thermal transfer recording medium was prepared in the same manner as in Example 2 except that the component B was changed to the following component I. <I component> Carnauba wax 100 parts Toluene 700 parts Methyl ethyl ketone 200 parts

With respect to the thermal transfer recording media of the examples and comparative examples obtained as described above, the results of measuring the adhesive strength and the like between the support and the heat-fusible ink layer are shown in Table 1.

[0033]

[Table 1] (Note 1) The transferability was evaluated based on whether or not the bar code portion was clearly printed. ：: The bar code portion is clearly printed and transferred. X: There is a bar code in which the bar code portion is unclearly printed and is not partially transferred. (Note 2) The reading rate of the ladder bar code is the laser check LC-2811 (SYMBOL TECHNOLOG
IES, INC.), The laser was scanned 100 times and the number of readings was expressed as a percentage.

According to Table 1, when the adhesive strength and the shear strength of the ink layer are less than 40 gf / cm (20 ° C.) and the difference between the adhesive strength and the adhesive strength upon cooling after heating is less than 30 gf / cm (20 ° C.), It can be seen that the ink layer tends to fall off during use, and that a drop phenomenon occurs when a ladder bar code is printed by a bar code printer. Further, it can be seen that when the shear strength and the adhesive strength of the ink layer at the time of cooling after heating exceed 7.0 gf / cm, the transferability deteriorates. In any case, it can be seen that the prescribed conditions of the present invention are extremely limited.

[0035]

As described above, according to the present invention, the adhesion strength and the shear strength of the layer obtained by combining the support and the hot-melt ink layer or the release layer and the hot-melt ink layer are determined. It is possible to obtain a thermal transfer recording medium free from the dropping of the ink layer during use, the occurrence of a dropping phenomenon during ladder bar code printing, and the occurrence of so-called transfer failure when using smooth receiving paper.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a measuring machine used for measuring characteristics of a thermal transfer recording medium of the present invention.

FIG. 2 is a schematic sectional view showing an example of the thermal transfer recording medium of the present invention.

FIG. 3 is a schematic sectional view showing another example of the thermal transfer recording medium of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cellophane tape 2 Thermal transfer recording medium 2a Ink layer and release layer 2b Support 3 Reinforcement plate 4 Fixture 11 Thermal transfer recording medium 12 Film support 13 Ink layer 14 Heat resistance and / or lubricity layer 15 Release layer

Claims (3)

[Claims] In a thermal transfer recording medium in which a heat-fusible ink layer is provided directly or via a release layer on a support, the adhesive strength between the support and the heat-fusible ink layer is 40 g at 20 ° C.
f / cm or more, and the difference between the adhesive strength of the heat-fusible ink layer and the support at the time of cooling after heating is 30 gf /
cm or more. 2. The thermal transfer recording medium according to claim 1, wherein the adhesive strength and the shear strength between the support and the heat-meltable ink layer at the time of cooling after heating are both 2.0 to 7.0 gf / at 20 ° C.
cm, a thermal transfer recording medium. 3. The thermal transfer recording medium according to claim 1, wherein the shear strength between the support and the hot-melt ink layer is 40 gf / cm or more at 20 ° C.