KR100308518B1 - Thermal transfer ink ribbon - Google Patents

Abstract

The present invention relates to a melt-type thermal transfer ribbon, and more particularly, a terpolymer formed of a vinyl chloride / vinyl acetate / reactive group (—OH, —COOH) -containing acrylic monomer and a transfer ink dispersion binder component of a black ink layer. The present invention relates to a melt-type thermal transfer ribbon which improves the transfer sensitivity for printing patterns and barcodes of plastic cards and bar code label papers, and has superior print image adhesion and abrasion resistance to printing materials than conventional thermal transfer ribbons.

Description

Melt type thermal transfer ribbon {Thermal transfer ink ribbon}

The present invention relates to a melt-type thermal transfer ribbon, and more particularly, a terpolymer formed of a vinyl chloride / vinyl acetate / reactive group (—OH, —COOH) -containing acrylic monomer and a transfer ink dispersion binder component of a black ink layer. The present invention relates to a melt-type thermal transfer ribbon which improves the transfer sensitivity for printing patterns and barcodes of plastic cards and bar code label papers, and has superior print image adhesion and abrasion resistance to printing materials than conventional thermal transfer ribbons.

Recently, as the amount of personal information increases, there is a tendency to record such information on plastic cards, for example, identification cards, credit cards, etc. Personal information records are mainly printed black characters or barcodes, the print recording medium mainly used is a thermal transfer ribbon.

Meanwhile, bar codes and label printing using a thermal transfer recording medium are widely used to print bar codes necessary for manufacturing processes, product management, and the like. In addition to bar code printing, the thermal transfer printing method is widely applied to label printing such as food, medicine, paint, as well as commercial small prints such as outdoor small advertising media, election posters, stickers, brochures, calendars, and the like. As described above, the thermal transfer printing method has a very wide field of application, but the printing surface is exposed to frequent friction or abrasion, which causes problems in personal information management.

In general, thermal transfer printing is largely divided into sublimation type thermal transfer and melt type thermal transfer. Among them, the molten thermal transfer is a kind of 'Binary' in which the binder itself or the ink layer composed of the binder and the coloring material receives heat from the thermal printing head to perform melting, pressing, bonding, and cutting in a short time. (ON / OFF) by Print Mechanism '. Therefore, the technical requirements of the thermal transfer ribbon, firstly, thermal transfer compatible with the energy of the printer should be easy, and secondly, durability of the transferred printed image should be maintained for a long time. The key to transferability is the transfer efficiency that defines the transfer sensitivity and edge sharpness that determines the image quality of the transferred characters and barcodes. Therefore, the anti-abrasion of the barcode printing surface for the accurate recognition of the recorded (printed) barcode information as well as the transferability of the thermal transfer thermal ribbon is very important.

Barcode printing is possible with various printing methods, but thermal transfer printing, which is a non-impact printing method that has advantages in miniaturization, low noise, and high resolution, is most widely used. This is because it is possible to realize the resolution of the barcode surface by the point and thermal transfer method using carbon black ink which is the best barcode recognition, and is advantageous for compactness and low noise during printing.

The most important factor in barcode printing is the resolution of the printed barcode, which should be no problem when the printed side is recognized as a barcode reader. Since the barcode is a kind of information recording means, the durability of the printed barcode must also be absolutely excellent. In order to achieve such barcode transferability and durability, various ink compositions for barcode printing have been developed. In determining the ink composition, it is basically important to select the type of coloring material (Carbon Black) and the type of binder and dispersant which easily disperse the coloring material. In particular, the uniform dispersion of the coloring material actually has a direct effect on the transferability and durability.

Barcode ribbons are largely classified into resin types used as durable ribbons, wax / resin types used for high-sensitivity high-speed printing, and general purpose wax types. In the case of the resin type thermal transfer ribbon, it is excellent in the transferability with respect to polyethylene terephthalate (PET), polypropylene (PP), etc. which are synthetic vinyl papers, and the wear resistance of the printing surface is excellent also at the time of high speed printing, it is practical.

Hot-melt ink, which has been widely used in the related art, has been pointed out as a disadvantage in barcode printing due to its relatively low wear resistance and relatively low adhesion to the printing surface. Several methods have been tried to compensate for this drawback. For example, wax can be added to compensate for surface lubricity and scratch resistance, or a cohesive hard binder is used, or a hard granular inorganic filler is mixed in appropriately to improve durability of the printing surface. Various methods of raising have been applied.

However, polymer binders used for improving durability tend to rather reduce the transferability (or transfer sensitivity). In order to compensate for the deterioration of transferability and at the same time increase the wear resistance of the printing surface, it is basically a proper blending formulation of a binder, a uniform dispersion technique of a wax or an inorganic pillar, a black ink layer (coloring material layer) and the releasability of the layer ( The release layer structure design (interlayer thickness control) for improvement (from the substrate) is very important. The binder used for the black ink layer effectively has a low melt viscosity and good fluidity, so that the binder easily penetrates onto the printed substrate surface and adhesion occurs. In this case, in order to improve the adhesion, compatibility between the binders used in the black ink layer and the receiving layer should be good. In addition, the cohesive force of the black ink layer may be small, so that the break between the molten portion and the unmelted portion may be better, thereby increasing the edge resolution of the printing surface.

Also in the pigment dispersion of the black ink layer, the selection of the binder provides a great influence on the degree of dispersion and dispersion stability. Therefore, the selection of the ink dispersing binder used for the black ink layer is very important in producing the thermal transfer ribbon having excellent physical properties. Vinyl chloride / vinyl acetate binary copolymers (containing 2-25 mol% of vinyl acetate), which have been widely used as ink dispersing binders in the past, are due to high fluidity and solubility parameters for PVC cards and synthetic vinyl labels. It has been known to provide good adhesion. However, the binary copolymer has a problem of somewhat insufficient physical properties in terms of pigment dispersibility and adhesion of the print image.

The present invention is an ink dispersing binder component constituting the black ink layer of the thermal transfer ribbon, the weight average molecular weight is relatively low (M _w : 10,000 ~ 50,000), soft point or softening point (T _g : 50 ~ 90 ℃), When a terpolymer composed of a third acrylic monomer containing a reactive group (-OH, -COOH) other than vinyl chloride and vinyl acetate is used, the transferability is increased, and the printing surface transferred by thermal curing of the reactive group is increased. The present invention was completed by confirming that the wear resistance (increasing the adhesion between the substrate and the printing surface) is greatly improved.

Particularly, in the present invention, when the polymer plasticizer and polyethylene wax of the polyester-based oligomer based on adipic acid together with the terpolymer are contained in the black ink layer in an appropriate content ratio, a thermal transfer ribbon having excellent physical properties can be obtained. .

Accordingly, an object of the present invention is to provide a thermal transfer ribbon having excellent physical properties such as transferability, wear resistance, and adhesion to a substrate, as compared with a conventional thermal transfer ribbon.

Figure 1 shows the structure of a typical melt thermal transfer ribbon,

1a is a cross-sectional view of a molten thermal transfer ribbon having a two-layer structure in which a release layer and a black ink layer are sequentially stacked on a base film,

1b is a cross-sectional view of a three-layer melt thermal transfer ribbon in which an undercoat layer, a release layer, and a black ink layer are sequentially stacked on a base film.

FIG. 2 is a cross-sectional view of a PVC card thermally transferred a fused thermal transfer ribbon. FIG.

<Description of the symbols for the main parts of the drawings>

1: base film 2a: release layer

2b: black ink layer 2c: undercoat layer

3: Transfer Equipment (PVC Card)

The invention relates to a melt thermal transfer ribbon having a release layer and a black ink layer formed on a base film or an undercoat layer, a release layer and a black ink layer formed on a base film, wherein the black ink layer has a transfer ink dispersion binder. And a melt type thermal transfer ribbon containing a terpolymer of an acrylic monomer containing vinyl chloride / vinyl acetate / reactive group (-OH, -COOH).

Referring to the present invention in more detail as follows.

In the present invention, as a transfer ink dispersing binder component contained in the black ink layer composition constituting the thermal transfer ribbon, a vinyl chloride / vinyl acetate / reactive group (-OH,- The main technique is to use terpolymers in which COOH) -containing acrylic monomers are copolymerized at a ratio of 75 to 90/3 to 20/1 to 20 mol%.

In general, the curable binder may cause shrinkage of the binder after curing, thereby weakening the interface adhesive force, and therefore, the curing degree needs to be adjusted to a low level. Therefore, in the present invention, a terpolymer containing a small amount of a hydroxyl group (-OH), a carboxy group (-COOH), or a reactive monomer in which these are simultaneously substituted with a reactive group is used as an ink dispersion binder. As the reactive monomer, maleic acid or a hydroxyacrylic compound is preferably used.

The terpolymer according to the present invention has good pigment dispersibility, low weight average molecular weight (M _w : 10,000-50,000), low softening point or softening point (T _g : 50-90 ° C.), and is excellent in improving transferability. High meltability and good adhesion to substrates provide excellent adhesion to PVC cards and synthetic vinyl labels. Furthermore, the reactive group, carboxyl group or hydroxyl group, included in the terpolymer is combined with another binder (Physical Interlocking or Chemical Bonding) included in the resin layer to increase the binding force of the print image (improved wear resistance).

1 is a cross-sectional view showing a general structure of a thermal transfer ribbon, and may have a two-layer structure in which a release layer and a black ink layer are sequentially stacked on a base film, or an undercoat layer, release layer, and black ink on a base film. It is possible to form a three-layer structure in which the layers are stacked in sequence. The transfer ink composition according to the present invention can be applied to both the thermal transfer ribbon of the two-layer structure or the three-layer structure described above.

Hereinafter, each layer constituting the thermal transfer ribbon according to the present invention will be described in detail.

As the base film, a polyester film is particularly preferably a polyethylene terephthalate (PET) film. Prior to use, the base film may be a gravure coating process having a thickness of about 1 μm or less on a rear surface of a composition solution containing a cellulose binder and a release agent (modified silicone polymer) to form a heat / lubricating layer.

The undercoating layer is introduced as needed between the base film and the release layer in a thickness of 0.01 to 1 μm as required. Mechanical cracking of the black ink layer generated during thermal transfer printing and cohesive failure of the black ink layer during transfer It controls the transcriptional role. The binder mainly used for the undercoat layer is saturated polyester (trade name Vylon) and has a very strong adhesive force with a PET base film. In general, the undercoat layer may contain a polyester binder in a concentration of about 0.01 to 10% by weight, preferably 0.01 to 0.5% by weight.

The release layer is introduced by coating 0.1-1 μm thick between the base film and the black ink layer or between the undercoat layer and the black ink layer. In the case of the release layer, when the black ink layer exhibits strong adhesion to the base film, the adhesion force is reduced to increase the release property of the black ink layer, and at the same time, the black ink layer serves as a protective layer of the printed image, thereby improving scratch resistance and wear resistance. Since the terpolymer used as the binder component of the black ink layer as in the present invention has excellent adhesion to the PET base film, it is difficult to release the black ink layer unless a release layer is introduced to effectively inhibit the adhesion. The transferability is reduced. The release layer composition mainly contains an acrylic binder having a weight average molecular weight (M _w ) of 5,000 to 50,000, and in addition, 5 to 40 parts by weight of a polymeric plasticizer of a polyester oligomer based on adipic acid based on 100 parts by weight of the acrylic binder ( Solids content) and 1 to 30 parts by weight (based on solids content) of polyethylene wax.

Since the transferability and wear resistance required for the thermal transfer thermal ribbon are almost dependent on the black ink layer, optimization of the black ink composition is most important.

The black ink layer contains a terpolymer composed of carbon black, which is a coloring material, and an acrylic monomer containing vinyl chloride / vinyl acetate / reactive group (—OH, —COOH) as a transfer ink dispersion binder component. In particular, the control of the content ratio of the carbon black coloring material and the binder in the transfer and wear resistance is a major variable. Therefore, in the present invention, the black ink layer contains 20 to 80% by weight of carbon black coloring material and 20 to 80% by weight of terpolymer binder based on the solid content, so that the transferability decreases when the relative content of the binder is increased. If the content is small, the transferability is greatly increased, but the wear resistance and the resolution of the transfer surface are reduced.

In addition, the black ink layer uses a polymer plasticizer and a wax together to complement and improve the properties of the existing thermal transfer ribbon. In the case of the polymeric plasticizer, the melting point may be added to improve the transfer sensitivity. In the present invention, in consideration of compatibility with the terpolymer binder, adipic acid-based polyester oligomer may be added to 100 parts by weight of the binder. 50 parts by weight or less, preferably 5 to 50 parts by weight, and particularly preferably 10 to 40 parts by weight. In particular, the uniform dispersion degree of the coloring material directly affects the transferability and durability of the thermal transfer ribbon. Therefore, in the present invention, a predetermined polymer plasticizer is used in combination with the terpolymer binder as described above to transfer the transferability. Further improve.

In addition, various types of waxes, such as polyethylene wax, microcrystalline wax, paraffin wax, amide wax, ester wax, oxide wax, etc., may be used to improve the surface durability (scratch resistance) of the printing surface which is insufficient of the conventional thermal transfer ribbon. Can be used. Among the waxes, in particular, the use of polyethylene wax having a general suitable melting point (100 to 130 ° C.) can improve the transfer sensitivity and the surface properties. The wax is contained 20 parts by weight or less, preferably 1 to 20 parts by weight, based on 100 parts by weight of the binder.

In addition, the pigment dispersibility, that is, the influence of the thermal head of the printer varies depending on the size and the degree of dispersion of the dispersed particles affects the transferability. Therefore, the dispersion state should be adjusted so that the particle size is not at least twice larger than the thickness of the black ink layer. In the present invention, the pigment particle size is dispersed to 1 μm or less and used. Pigment dispersion of the black ink layer is dispersed about 1 hour to 3 hours at a speed of 1500 rpm to 2200 rpm using a mechanical mixer (Sand Mill).

Various coating methods are applicable to the coating process for forming each layer of the thermal transfer ribbon using the composition as described above. For example, various coating methods such as gravure coating, bar coating, comma coating, roll coating, and knife coating can be applied in a suitable coating thickness range.

As described above, the present invention relates to a transfer ink composition constituting a melt type thermal transfer ribbon of a single black patch, and is widely applied to printing black images on PVC cards or synthetic vinyl labels as described above.

As described above, the present invention will be described in more detail based on the following examples and comparative examples, but the present invention is not limited thereto.

Examples 1-4 and Comparative Examples 1-2

The heat-resistant / lubricated coating layer was formed in advance with a coating amount of 0.5 g / m 2 on the rear surface of the thermally transferable polyethylene terephthalate (PET) film having a thickness of 4.5 μm. The heat / lubrication coating layer was gravure-coated by mixing 5 parts by weight of a modified silicone binder (Shin-Etsu, X-24-3544A) as a release agent to 100 parts by weight of a nitrocellulose binder (ICI, LX grade). Then, using the composition of the following Table 1, as shown in the following Table 2, the undercoat layer, the release layer, the black ink layer was sequentially coated with gravure to prepare a thermal transfer ribbon. The undercoat layer was coated at about 0.2 g / m 2 or less, the release layer at 0.5 to 1.0 g / m 2, and the black ink layer at a coating amount of about 4 g / m 2. The release layer was prepared by preparing an acrylic binder, polyethylene wax, and a polymer plasticizer in the composition of Table 2 below, and coating the undercoating layer. In the case of the binder component of the black ink layer, examples include terpolymer, vinyl chloride / vinyl acetate / maleic anhydride terpolymer (VMCA ™, Union Carbide) or vinyl chloride / vinyl acetate / hydroxyacrylic terpolymer (VROH ™). , Union Carbide Co.), and a vinyl chloride / vinyl acetate binary copolymer (VYHD ™, Union Carbide Co., Ltd.) were used for the comparative example.

Experimental Example

Evaluation of physical properties of each thermal transfer ribbon coated with the composition of the above Examples and Comparative Examples was compared according to the following evaluation items. Table 3 shows the results of the physical property evaluation.

(1) transferability

The transfer material was evaluated using a Cheetah II printer manufactured by Fargo, USA, and the Easycoder 401 printer manufactured by UBI, Inc., with a label (PET, YUPO). The main evaluation items were low printability (characteristics) and barcode resolution, which were evaluated while changing printing speed and energy.

(2) resolution

Using UBI's barcode printer, Easycoder 401, after printing at 4IPS print speed and 0.7 mJ / dot thermal head energy, the print surface resolution was measured with an optical microscope, and the degree of comparison was compared. Evaluated.

(3) adhesion

Using UBI's barcode printer, Model Easycoder 401, after printing at 4IPS printing speed and 0.7 mJ / dot thermal head energy, the adhesive force was compared and evaluated by the number of times applied when the image was peeled off with a spectula.

(4) wear resistance

The taber abraser equipped with CS-10 grift wheel was worn 100 times per minute on the card side and 30 times per minute on the label side under a 1 kg load, and then the degree of wear was measured by optical reflectance density measurement using a Macbeth photometer. .

(5) scratch resistance

The label surface printed under the printer condition was rubbed with a fingernail to measure the degree of surface damage.

As described above, in the present invention, a terpolymer composed of vinyl chloride / vinyl acetate / reactive group-containing acrylic monomer is contained as an ink dispersing binder in the composition of the black ink layer of the melt type thermal transfer ribbon. The polymer plasticizer and the wax are contained together in a certain content ratio to obtain excellent print image adhesion and wear resistance. Therefore, the thermal transfer ribbon of the present invention can be applied to a melt type thermal transfer ribbon having excellent wear resistance by improving transferability and adhesion of a transfer image with a PVC card or a synthetic vinyl label.

Claims (9)

In the molten thermal transfer ribbon in which a release layer and a black ink layer are formed on a base film, or an undercoat layer, a release layer, and a black ink layer are formed on a base film, And the black ink layer contains a terpolymer of a vinyl chloride / vinyl acetate / reactive group (-OH, -COOH) -containing acrylic monomer as a transfer ink dispersion binder. The transfer ink composition of claim 1, wherein the reactive group-containing acrylic monomer constituting the terpolymer is a maleic acid or a hydroxyacrylic compound. The melt according to claim 1 or 2, wherein the terpolymer is copolymerized with vinyl chloride / vinyl acetate / reactive group-containing acrylic monomer at a ratio of 75 to 90/3 to 20/1 to 20 mol%. A transfer ink composition for a type thermal transfer ribbon. The melt thermal transfer ribbon according to claim 1, wherein the terpolymer has a weight average molecular weight (M _w ) of 10,000 to 50,000 and a softening point (T _g ) of 50 to 90 ° C. The melt-type thermal transfer ribbon according to claim 1, wherein the black ink layer contains 20 to 80% by weight of carbon black colorant and 20 to 80% by weight of the terpolymer binder based on the solid content. According to claim 1, wherein the black ink layer 5 to 50 parts by weight of a polymeric plasticizer of a polyester-based oligomer based on adipic acid based on 100 parts by weight of the terpolymer binder based on the solids content and polyethylene wax 1 to 20 Melted thermal transfer ribbon, characterized in that it contains a weight part. The melt-type thermal transfer ribbon according to claim 1, wherein the release layer contains an acrylic binder having a weight average molecular weight (M _w ) of 5,000 to 50,000. According to claim 1 or 7, wherein the release layer based on the solids content based on 100 parts by weight of the acrylic binder, 5 to 40 parts by weight of a polymeric plasticizer of a polyester-based oligomer based on adipic acid and polyethylene wax 1 ~ Melt type thermal transfer ribbon, characterized in that it contains 30 parts by weight. The melt-type thermal transfer ribbon according to claim 1, wherein the undercoating layer contains a saturated polyester binder.