JP2000141923A - Thermal transfer ercording medium and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a using amount of an organic solvent and to improve adhesive properties to a base material film, by providing a release layer containing at least aqueous heat meltable particles and an aqueous polyester resin having a polar group between a support and a thermal transfer ink layer. SOLUTION: In the thermal transfer recording medium, an emulsion obtained by emulsifying heat meltable particles in water is prescribed, then mixed with an aqueous polyester resin having a polar group, coating a support with the mixture to form a release layer between the support and a thermal transfer ink. In this case, an amount of the polyester resin having the polar group to the particles is 1 to 50 wt.% or preferably 3 to 25 wt.%. With this constitution, since the resin has a polarity, adhesive properties to the support is strengthened. Thus, even in a printer of an end face head or using an acceptive sheet having small surface smoothness, no pressure contact stain is brought about.

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 and a method for manufacturing the same, and more particularly, to an improvement in an intermediate layer (release layer) provided between a support of the thermal transfer recording medium and a thermal transfer ink layer. .

[0002]

2. Description of the Related Art A printing method using a thermal transfer recording medium is simpler in recording method and inexpensive than an ink-jet recording method and the like, has no blurring or blurring in an image, has a high resolution, has a high image density, and has a solid image. Because the image density is uniform, it can be used not only for recording image information and text information on general recording paper (receptive paper), but also for printing barcodes on packing materials and sticking labels for information management. Often used.

In recent years, in the market of printers using the thermal transfer recording method, the printing speed has been increased, and various measures have been taken to realize this. Technically, printers equipped with an end face head (near edge head) having a heating element having a simple mechanism at the end of the head are being widely used. The end face head (the heating element is located at the end of the head) is different from the normal flat head (the heating element is located at the center of the head plane).
Since the edge always touches the thermal transfer recording medium, the head
There has been a problem that the pressure between the platens is high, and a phenomenon (pressure contact contamination) occurs in which a part of the ink is transferred to the receiving paper only by the pressure during non-heating (non-printing). This tendency is remarkable especially in the case of receiving paper having a rough surface.

[0004] As a method for preventing the press contact stain, it is conceivable to increase the adhesive force of the thermal transfer ink layer to the support in the thermal transfer recording medium (thermal transfer ribbon). That is,
An intermediate layer (release layer) is provided between the thermal transfer ink layer of the thermal transfer recording medium and the surface of the support, and when the release layer is not heated, the adhesiveness of the thermal transfer ink layer to the support is increased. )
It is widely practiced that the thermal transfer ink layer plays a role of facilitating peeling from the support. When a release layer is used, the two characteristics of adhesion to the thermal transfer ink layer and release (transferability) to the support are important points, and the transferability is directly related to the quality of the printed image as a result.

A support generally used in a thermal transfer recording medium is a polyester film (specifically, a PET (polyethylene terephthalate) film is often used). It is conventionally known that a polyester resin is used for a release layer, paying attention to the fact that the support is a polyester film (Japanese Patent Publication No. 60-20198).
JP-A-58-132595, JP-A-59-969
No. 92). However, in this case, the polyester resin is used for both the support and the release layer, so that strong adhesion between the support and the release layer is observed, and the release property upon heating is poor. .

[0006] To correct this, Japanese Patent Publication No. 2-459
No. 97 proposes to add a lubricant to the polyester resin in the release layer for the purpose of reducing the adhesiveness between the support and the release layer and reducing the compatibility between the release layer and the ink. An intermediate product having stronger adhesiveness is used for the polyester resin. However, in this case, the amount of the polyester resin is larger than the amount of the lubricant, and the adhesiveness is still high and the transferability is insufficient. When the amount of the lubricant is made larger than the amount of the polyester resin in order to weaken the adhesiveness, the adhesiveness is weakened and the transferability is improved, but the press-contact stain is newly generated. As described above, in the prior art, it has not been possible to easily manufacture a thermal transfer recording medium that achieves both the absence of pressure contact dirt and good transferability.

On the other hand, in recent years, environmental issues have become more important, and attention has been paid to the handling of harmful substances on the work surface, or the discharge of harmful substances outside the factory has been restricted. In the production of a thermal transfer recording medium, a method of dissolving a resin, a lubricant or the like in an organic solvent such as toluene or methyl ethyl ketone (MEK) and applying the solution is generally employed for forming the thermal transfer ink layer and the release layer. . In addition to this, it has been considered that it is preferable that the release layer is formed into a film for the formation of the release layer. Therefore, for example, a method of dissolving a release agent in an organic solvent, applying and drying the release agent, and forming a film is used. Although used, many of the organic solvents are toxic and have a low flash point. Therefore, their use is not preferable from the viewpoint of health and safety of handlers.

[0008]

In view of the above, in the production of a thermal transfer recording medium, it is desirable to use as little organic solvent as possible and to use as little organic solvent as possible. As one of the measures, it has been proposed to apply an unmodified aqueous polyester resin emulsion liquid on a support to form a release layer. However, in this case, the unmodified polyester resin was not dissolved in the solvent but formed an emulsion with an emulsifier as a release layer forming liquid, and when this was applied to form a release layer, it remained in the coating film. Emulsifiers have a detrimental effect on the purpose of a good strengthening of the adhesion.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thermal transfer recording medium which is free from pressure contact dirt in printing with an end face head and in high-speed printing, and which can obtain a high quality printed image on a receiving paper with good transferability. is there. Another object of the present invention is to provide a thermal transfer recording medium in which the amount of solvent used is greatly reduced and environmental and safety issues are significantly reduced.

[0010]

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted various studies and studies on a thermal transfer recording medium from various angles. As a result, the base film (support) and the thermal transfer ink layer were In between, at least aqueous heat-fusible particles, by providing a release layer containing an aqueous polyester resin having a polar group, the use of an organic solvent can be reduced,
In addition, the adhesiveness to the base film, which is considered to be a weak point of the water-based release layer, is satisfied.Therefore, it is possible to eliminate press-contact stains and achieve transferability to receiving paper at the time of printing. It has been found that a thermal transfer recording material to be formed can be obtained. The present invention has been made based on this.

According to the present invention, first, in a thermal transfer recording medium having a thermal transfer ink layer provided on a support, an aqueous thermal fusible particle and a polar aqueous group-containing polar group are provided between the support and the thermal transfer ink layer. A thermal transfer recording medium provided with a release layer containing a polyester resin as a main component is provided.

Second, the particle size of the hot-melt particles is 0.1%.
２2 μm is provided.

Thirdly, the first or second thermal transfer recording medium is provided, wherein the heat-fusible particles are selected from carnauba wax and candelilla wax.

Fourth, the first, second or third thermal transfer recording medium is provided, wherein the ratio of the polyester resin to the heat-meltable particles is 1 to 50% by weight.

Fifth, the polar group of the polyester resin is any one of a sulfone group, a carboxyl group, a glycidyl group and a silyl group. A recording medium is provided.

Sixth, a coating solution containing a mixture of at least an aqueous polyester resin and an aqueous polyester resin having a polar group is coated on a support, dried to form a release layer, and then a thermal transfer ink layer is formed on the release layer. Is provided, a method for manufacturing a thermal transfer recording medium is provided.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The thermal transfer recording medium of the present invention comprises a release layer containing at least aqueous hot-melt particles and an aqueous polyester resin having a polar group, between a base film (support) and a thermal transfer ink layer. It is characterized by being provided. The “water-based hot-melt particles” in the present invention is a hot-melt particle emulsion in a state before coating, and more specifically, a hot-melt particle is emulsified in water to constitute an emulsion. . After formulating the mixture, the mixture is mixed with an aqueous polyester resin having a polar group and coated to form a release layer, whereby a thermal transfer recording medium can be obtained. The `` aqueous polyester resin having a polar group '' referred to in the present invention is a state in which the state before application is a polyester resin emulsion having a polar group, and more specifically, a polyester resin having a polar group in which a solvent is dissolved. It is emulsified in water to form an emulsion. After formulating the mixture, the mixture is mixed with the water-based heat-meltable particles and coated to form a release layer, whereby a thermal transfer recording medium can be obtained.

The aqueous polyester resin having a polar group is
At the time of non-printing (at the time of non-heating), it has a function of adhering the base film and the thermal transfer ink layer so as not to be peeled off, and not inhibiting the transfer function at the time of printing (at the time of heating). On the other hand, the water-based hot-melt particles exhibit a sharp decrease in melt viscosity at or above the melting point, and have a function of melting during printing (heating) to separate (peel) the ink from the support.

In the present invention, the amount of the water-based polyester resin having a polar group with respect to the water-based hot-melt particles is from 1 to 5;
0% by weight, preferably 3 to 25% by weight. 1% by weight
Below, the adhesiveness is too weak to easily cause press-contact dirt. Conversely, if it is 50% by weight or more, the adhesiveness becomes too strong and the transferability becomes weak. As described above, it is preferable that the amount of the water-based hot-melt particles is larger than the amount of the water-based polyester resin having a polar group, whereby sufficient transferability at the time of printing (heating) is exhibited, especially in high-speed printing. Desirable printing quality is obtained. Further, by setting the glass transition temperature (Tg) of the polyester resin having a polar group to -10 ° C to + 20 ° C, a more desirable release layer can be obtained.

In the release layer of the present invention, since the water-based polyester resin has a polar group, the water-based polyester resin has stronger adhesiveness to a support than conventional non-modified polyester resin and is rich in hot-melt particles. In addition, it has a proper adhesiveness to the support, and therefore does not cause pressure contact stains even in a printer equipped with an end face head and in the use of receiving paper having a small surface smoothness. In addition, in the present invention, by using the water-based hot-melt particles and the water-based polyester resin having a polar group in combination, it is possible to eliminate the press-contact stain, which has been considered difficult, and to obtain good transferability (good print quality). It is compatible.

The aqueous polyester resin having a polar group used in the present invention is obtained by condensing or adding an -OH residue or an unsaturated bond of the polyester, or one having a polar group in a part of the monomer. It is obtained by partially polymerizing and adding a polar group. As the type of the polar group, a carboxyl group, a glycidyl group, a sulfone group, and a silyl group are preferable. In particular, the sulfone group is most effective for achieving both the smearing of the pressure contact and the printing quality. The reason is presumed as follows.

That is, in contrast to an aqueous polyester resin having no polar group, an aqueous polyester resin having a polar group has a stronger chemical attraction to the support, has a higher affinity for water, and has a semi-dissolved state with water. As a result, the emulsion is stable, and the use of an emulsifier is unnecessary. Further, since the use of an emulsifier can prevent the adhesion of the polyester resin particles to each other at the time of dry film formation, the adhesion to the PET film is much better than that of the unmodified polyester resin emulsion.

The heat-fusible particles used in the present invention include paraffin wax, microcrystalline wax, carnauba wax, ceresin wax, oxidized wax, ester wax, polyethylene wax, candelilla wax, wood wax, beeswax, and montan wax. Examples include, but are not limited to, waxes, other natural waxes, and synthetic waxes. Among them, the use of carnauba wax, canterilla wax, etc. is excellent in terms of printed images. In the present invention, these heat-meltable particles are used in the form of an aqueous emulsion.

The particle size of the heat-fusible particles is preferably from 0.1 to
2 μm. When the thickness is 0.1 μm or less, cracks (cracks) tend to occur in the release layer during the formation of the thermal transfer ink layer.
Conversely, if the thickness is 2 μm or more, the resolution of the printed image is reduced. Further, since the heat-fusible particles of the present invention are used in an aqueous emulsion, the effects of the particles are exhibited. That is,
When a solvent is used, most of the heat-fusible substance dissolves in the solvent, so that when applied, it forms a continuous, if not complete, film. For this reason, the cut of the ink layer in the horizontal direction becomes poor during printing, and there is no block of heat propagation at the particle interface, and the transferred image is not sharp. On the other hand, in the case of the water-based hot-melt particle emulsion, since some particles remain, the residual heat portion is shut out by the gap between the particles, so that a sharper printed image can be obtained.

The release layer may contain a pigment or dye for coloring, a plasticizer, an antifoaming agent, a surfactant and the like, if necessary. 0.5 ~
Good about 2 g / m ^2, too strong adhesiveness at 2 g / m ² or more, inhibits heat transfer to the ink, 0.5 g / m ²
Below, the effect on adhesiveness and peelability is poor.

The thermal transfer ink layer in the present invention mainly comprises a heat-fusible substance, a resin and a colorant. As the heat-fusible substance, the heat-fusible substance described in the description of the release layer is used as it is. As the resin, acrylic resin, polyester resin, polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, urethane resin, cellulose resin, vinyl chloride-vinyl acetate copolymer, petroleum resin, rosin resin, and these At least one of the derivatives, polyamides and the like may be appropriately selected. As the colorant, one or more colorants selected from carbon black, organic pigments, inorganic pigments and various dyes are used.

The thermal transfer ink layer and the release layer are formed by a known coating method. Examples include wire bar coating, gravure coating, burr bar, curtain call, and the like, but are not particularly limited.

As the support, a known film or paper may be used, and polyester films such as PET, and plastic films such as polycarbonate, triacetyl cellulose, polyimide, and polyamide are preferably used.
ET is particularly valuable.

It is desirable to provide a heat-resistant lubricating layer on the back surface of the support in order to protect the support from high temperatures caused by the thermal head and to ensure the transportability of the thermal head. This heat-resistant lubricating layer may be formed of a thin film of silicone oil, silicone rubber, silicone resin, polyimide, epoxy resin, phenol resin, melamine resin, or cellulose.

[0030]

Next, the present invention will be described more specifically with reference to examples. All percentages and parts herein are based on weight.

Examples 1 to 12 and Comparative Examples 1 to 3 (Formation of release layer) A release layer forming solution having the following formulation was dried on a commercially available PET film (support) having a thickness of about 3 μm, and the dry adhesion amount was 7.7 g. / M ² (dry weight) by hand coating with a wire bar and drying with warm air at 40 ° C. to form a release layer. [Release layer forming liquid] Aqueous emulsion of polyester resin (see Table 1) (solid content 20%) (Note 1) x part Carnauba wax / candelilla wax = 5/5 aqueous emulsion (solid content 40%) 6 1.5 parts Ethanol 1.0 part Water Appropriate amount (Note 2) (Note 1) In preparing each stripping solution of the aqueous polyester resin having a polar group shown in Table 1, it was diluted to 20% for convenience. (Note 2) An appropriate amount is added depending on the amount of the aqueous emulsion (solid content: 20%) of the polyester resin. The above composition was sufficiently mixed with a ball mill to prepare a release layer forming liquid.

(Formation of Thermal Transfer Ink Layer) On the above-mentioned release layer, a thermal transfer ink layer forming liquid having the following formulation was applied with a wire bar so as to have a dry adhesion amount of about 1.3 g / m ² , and heated at 40 ° C. with warm air. And dried to form a thermal transfer ink layer. [Thermal transfer ink layer forming liquid] Carbon black 1.5 parts Candelilla wax (Note 3) 3.0 parts Ethylene-vinyl acetate copolymer (vinyl acetate content 28%) 4.0 parts Rosin ester resin (melting point 125 ° C) 1.5 parts Toluene 67 parts (Note 3) Candelilla wax is used after melting to some extent with toluene. The above composition was dispersed by a ball mill until the particle size became about 6 μm to prepare a thermal transfer ink layer forming liquid.

(Formation of heat-resistant lubricating layer) A silicone resin (manufactured by Toray Dow Silicone Co., Ltd., SD7260) was applied to the back surface of the PET film for coating the thermal transfer ink layer with a dry adhesion of 0.
A heat-resistant lubricating layer was formed by coating and drying with a wire bar so as to obtain a heat transfer recording sheet at a weight of 05 g / m ² .

[0034]

[Table 1]

The thermal transfer recording media were evaluated, and the results are shown in Table 2. The evaluation was performed on the press contact dirt and rough paper transferability.

(1) Pressure contact dirt Receiving paper (coated paper having a thickness of 260 μm) and the above-prepared thermal transfer recording sheet are set on a Ricoh B572 printer equipped with an end face head manufactured by TEC at 40 ° C.
The thermal head is pressed against the surface of the thermal transfer recording sheet under an environment of 50% RH, and left as it is for 1 minute. The evaluation is 最 も from the best ◎ sequentially ○,
Δ, Δ ×, and × represent the transition from good to bad, and Δ is an unacceptable level.

(2) Rough paper transferability Ricoh B572 equipped with an end face head manufactured by TEC
Using a receiving paper (rough paper) and the thermal transfer recording sheet prepared above with a printer, the printed image was visually observed after printing. ：: No white spots etc. △: Some white spots but no problem (acceptable level) ×: Many white spots and problems in use

[0038]

[Table 2]

[0039]

(1) According to the first aspect of the present invention, a release layer containing aqueous hot-melt particles and an aqueous polyester resin having a polar group is provided between the support and the thermal transfer ink layer. As a result, the amount of the organic solvent used during the production of the thermal transfer recording medium can be reduced, and the smear due to pressure contact can be suppressed as much as possible, so that a high quality printed image can be obtained. (2) According to the second aspect of the invention, by setting the size of the heat-fusible particles to 0.1 to 2 μm, a printed image is further improved. (3) According to the third aspect of the present invention, the use of carnauba wax and candelilla wax for the heat-meltable particles improves the printed image. (4) According to the invention of claim 4, the ratio of the water-based polyester resin having a polar group to the water-based hot-melt particles is 1 to 5.
By setting the content to 50% by weight, good thermal transferability to the receiving paper can be obtained. (5) According to the fifth aspect of the present invention, by selecting the type of the polar group contained in the aqueous polyester resin, it is possible to obtain less press contact stains and good print quality. (6) According to the invention of claim 6, the thermal transfer recording medium of the present invention can be easily manufactured.

Continued on the front page (72) Inventor Kazuyoshi Inamura 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. 2C068 AA06 BB08 BB11 BB22 BB27 2H111 AA01 BA07 BA53 BA54 BA55 BA62 BA76

Claims (6)

[Claims] 1. A thermal transfer recording medium in which a thermal transfer ink layer is provided on a support, wherein the thermal transfer recording medium contains aqueous hot-melt particles and an aqueous polyester resin having a polar group as main components between the support and the thermal transfer ink layer. A thermal transfer recording medium provided with a release layer. 2. The heat fusible particles have a particle size of 0.1 to 2 μm.
2. The thermal transfer recording medium according to claim 1, wherein m is m. 3. The thermal transfer recording medium according to claim 1, wherein the heat-fusible particles are selected from carnauba wax and candelilla wax. 4. The thermal transfer recording medium according to claim 1, wherein a ratio of the polyester resin to the heat-fusible particles is 1 to 50% by weight. 5. The thermal transfer recording medium according to claim 1, wherein the polar group of the polyester resin is any one of a sulfone group, a carboxyl group, a glycidyl group, and a silyl group. 6. A coating solution obtained by mixing at least an aqueous polyester resin and an aqueous polyester resin having a polar group on a support, followed by drying to form a release layer, and then providing a thermal transfer ink layer on the release layer. A method for producing a thermal transfer recording medium, comprising: