JP2832532B2 - Thermal transfer recording medium - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer recording medium suitable for printing characters or images on recording paper by utilizing the thermal fusibility of an ink layer. The present invention relates to a thermal transfer recording medium suitable for a bar code printer used in a system or the like.

2. Description of the Related Art In recent years, with the development of office automation, various terminals have been adopted. Above all, the thermal recording method has a feature that the apparatus is lightweight and small, has no noise, and is excellent in operability and maintainability, and has recently begun to be widely used.

Conventional heat melting type thermal transfer recording media are mainly composed of waxes such as paraffin wax and microcrystalline wax, and are composed of higher fatty acids such as stearic acid, higher alcohols such as stearyl alcohol, dyes, coloring agents such as pigments, and the like. A heat transfer ink layer provided on a support is known.

However, paraffin waxes and microcrystalline waxes are inferior in mechanical strength, so that the rub resistance of a transferred image is inferior. Therefore, using such a thermal transfer recording medium, for example, a bar code on a label, a product name,
After printing the price etc., creating a label of a small lot type, and then reading the barcode on the label using a light pen, for example, the form of the barcode is broken due to wear at the tip of the light pen. However, there has been a drawback that accurate information cannot be read, and a similar phenomenon occurs when a product to which a barcode-printed label is attached comes into contact with a surrounding object during handling. This was particularly noticeable when printing was performed on resin-coated paper such as mirror-coated paper, or on a film. Therefore, in the field of distribution, the emergence of a thermal transfer recording medium having excellent wear resistance has been desired.

In order to remedy this drawback, a method mainly comprising a wax having a small penetration and a method of adding a thermoplastic resin in addition to the wax component have been proposed, but the former has adhesiveness to a support, and // The ink layer peels off when handling the medium due to poor film formation, and random bridges occur in the transferred image such as characters or lines,
There was a problem that the transfer quality deteriorated. The latter has a problem that, with an increase in the resin component, the adhesive force with the support becomes strong, and the uniformity of the transferred image is deteriorated, and the image density is reduced. In addition, both have a problem that the transfer energy sensitivity is deteriorated.

 The present invention has been made in view of the above circumstances.

Therefore, an object of the present invention is to obtain a uniform screen without density unevenness, to obtain a transfer image excellent in abrasion resistance regardless of the ink receiver, and further, to provide a thermal transfer excellent in transfer energy sensitivity. A recording medium is provided.

As required items to achieve the above object of the present invention,
The following items are mentioned.

(1) The transfer ink surface has excellent mechanical strength and some degree of elasticity.

(2) When handling the medium, the ink layer must have an adhesive property and a film property that do not peel off from the support. However, the film strength of the ink layer must be such that it does not affect the resolution of the transferred image.

(3) Excellent heat sensitivity and sharp melting of heat.

(4) The transferred ink has excellent releasability from the support.

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, it has been found that the ink layer has at least a wax which is considered to be effective mainly for the quality of the transferred image, and a resistance to the ink surface mainly of the transferred ink. By including a thermoplastic resin represented by the following formula (I), which is considered to be effective mainly for thermal properties, such as a polystyrene resin which is considered effective for frictional properties and transfer energy sensitivity, the requirements of the above requirements are satisfied. It was found that satisfying the object of the present invention was achieved, and the present invention was completed.

 It was done.

That is, the present invention relates to a heat transfer recording medium comprising a heat transfer ink layer provided on a heat-resistant support, wherein the heat transfer ink layer has a penetration (JIS K2235) of 4 or less and a melting point or softening point of 130 ° C. or less. Wax, melting point or softening point of 70
Polystyrene resin in the range of -140 ° C and the following formula (I) (Wherein, n represents an integer of 50 <n <1000), wherein the content of the polystyrene resin is 1 to 25% by weight, and the content of the thermoplastic resin is The amount is from 1 to 35% by weight.

 Hereinafter, the present invention will be described in detail.

 First, the materials used in the present invention will be described.

The washes used in the present invention have a penetration of 4 or less and a melting point or softening point of 130 ° C. or less. If the penetration is greater than 4, the friction resistance of the transfer ink surface decreases, and if the melting point or softening point is higher than 130 ° C., the thermal energy required for transfer increases, and voids may occur in the transferred image. In addition, the fixability of the ink is deteriorated.

Specific examples of these waxes include carnauba wax, candelilla wax, polyethylene wax, ester wax, montan wax, montan wax derivatives, oxidized wax, Fischer-Tropsch wax, and hardened castor oil. These can be used alone or in combination of two or more.

The wax, as described above, has a uniform image density,
It greatly affects the transfer quality such as sharpness and resolution of the image. Therefore, its content is set to 35-85% by weight, preferably 60-75% by weight. When the content is less than 35% by weight, random bridges and voids frequently occur in the transferred image, and the transfer quality is reduced. On the other hand, when the content is more than 85% by weight, the film forming property of the ink layer is deteriorated, and the ink is easily peeled off.

The polystyrene resin used in the present invention is obtained by polymerizing a styrene monomer obtained by an alkyl reaction of benzene and ethylene, a dehydrogenation reaction of ethylbenzene, or the like, by a method such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Including polystyrene generally called GP, polystyrene was graft-polymerized with rubber such as polybutadiene,
Styrene copolymers such as high impact polystyrene called HI, acrylonitrile / styrene copolymer resin, acrylonitrile / butadiene / styrene copolymer resin, styrene / methyl methacrylate copolymer resin, butadiene / styrene / methyl methacrylate copolymer resin And those having a melting point or a softening point in the range of 70 to 140 ° C.

When the melting point or the softening point is lower than 70 ° C., the storage stability of the medium is deteriorated due to blocking, and the printability in a high-temperature environment is deteriorated. On the other hand, if the temperature is higher than 140 ° C., the transfer energy sensitivity decreases, and the fixability of the ink deteriorates.
The friction resistance decreases.

As described above, the polystyrene resin greatly affects the rub resistance of the transfer ink surface. Therefore, the content is suitably 1 to 25% by weight, preferably 5 to 15% by weight.
Weight% is set. If the content is less than 1% by weight, the abrasion resistance of the transfer ink surface is reduced, and if it is more than 25% by weight, the cohesive force of the ink is increased, and a random bridge is generated in the transferred image, Or the fixability of the ink becomes poor.

The thermoplastic resin represented by the formula (I) in the present invention comprises:
Regardless of its molecular weight, it has a melting point near 60 ° C and low latent heat of fusion. Therefore, by including this resin in the ink layer, the thermal sensitivity can be sharpened. Further, it has a remarkable effect on the film forming property of the ink layer, the transfer property to resin-coated paper such as mirror-coated paper, a film, and the like, and also the dispersibility of pigment.

The content of the thermoplastic resin is suitably in the range of 1 to 35% by weight. If the amount is less than 1% by weight, the ink is liable to be peeled off because the ink layer has poor film-forming properties. On the other hand, if the content is more than 35% by weight, the adhesion to the support becomes strong, so that the transfer peeling is not carried out smoothly, which places a burden on the drive system of the apparatus, and the ink coagulates at the support / ink layer interface. It is destroyed, and uneven image density occurs.

The molecular weight of the thermoplastic resin and the adhesive force at the interface between the support and the ink layer are in a proportional relationship, and the content shown above takes these factors into consideration. For example, when n is 50, the content is suitably in the range of 15 to 35% by weight, and n is
For integers close to 1000, a range of 1 to 20% by weight is appropriate.

In the present invention, as the colorant, conventionally known inorganic and organic dyes and pigments used in printing inks, paints and the like can be used. As specific examples, as the cyan pigment, diaseritone fast brilliant blue R (trade name, manufactured by Mitsubishi Kasei Co., Ltd.), Kayaron polyester blue B-SF Conc (trade name, manufactured by Nippon Kayaku Co., Ltd.) Examples of magenta color pigments include yellow pigments such as Diaceriton Fast Red R (trade name, manufactured by Mitsubishi Kasei Co., Ltd.) and Kayaron Polyester Pink RCL-E (trade name, manufactured by Nippon Kayaku Co., Ltd.) Examples thereof include Kayaron Polyester Light Yellow 5G-S (trade name, manufactured by Nippon Kayaku Co., Ltd.) and Aizen Spiron Yellow GRH (trade name, manufactured by Hodogaya Chemical Co., Ltd.). Further, as a cyan pigment, cerulean blue, phthalocyanine blue, etc., as a magenta pigment, brilliant carmine, alzaline lake, etc., as a yellow pigment,
Examples of black pigments such as Hansa Yellow and Bisazo Yellow include carbon black, graphite, and oil black.

If necessary, a blocking inhibitor, an inorganic or organic pigment, an antioxidant, an ultraviolet absorber, an antistatic agent, a surfactant and the like may be added to the thermal transfer ink layer. In the present invention, the ink layer may have a single-layer structure or a multi-layer structure.

As the heat-resistant support in the present invention, a conventionally known film or paper can be used as it is. Specific examples thereof include various heat-resistant resin films such as polyethylene terephthalate, polyimide, polycarbonate, cellophane, and aromatic polyamide, and paper substrates such as condenser paper and sulfuric acid paper.

The thickness of the heat-resistant support is preferably about 2 to 15 μm in consideration of a thermal head as a heat source during thermal transfer. For example, the thermal transfer ink layer is selectively heated by a laser beam or the like. When using a heat source that can be used, there is no particular limitation. When a thermal head is used, a heat-resistant protective layer made of a silicone resin, a fluorine resin, a polyimide resin, an epoxy resin, a phenol resin, a melamine resin, nitrocellulose, or the like is provided on the surface of the support that comes into contact with the thermal head. Thereby, the heat resistance of the support can be improved. If necessary, pigments such as Al ₂ O ₃ , TiO ₂ , SiO ₂ , silicone additives, surfactants, and the like may be added to these protective layers.

Also, by applying a current to the heat-resistant support, generating a Joule heat and melting and transferring the thermal transfer ink layer, by making the heat-resistant support conductive or providing a conductive layer on the heat-resistant support. It can be used for thermal transfer recording.

The method for producing the thermal transfer recording medium of the present invention is not particularly limited. For example, a thermal transfer ink produced by the method described below is coated on a heat-resistant support by a hot melt coating method or a solvent coating method. It can be obtained by working.

According to the hot melt coating method, a mixture composed of the wax, the polystyrene resin, the thermoplastic resin represented by the formula (I), the coloring agent and, if necessary, various additives is kneaded in a heated and molten state by a kneader or the like. To form a thermal transfer ink, and apply the ink layer on a heat-resistant support so that the thickness of the ink layer is 0.1 to 10 μm, preferably 2 to 6 μm, to produce a thermal transfer recording medium.

According to the solvent coating method, a mixture of the wax, the polystyrene resin, the thermoplastic resin represented by the formula (I), the coloring agent, and various additives as necessary is mixed with toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone. Isopropyl alcohol, butyl cellosolve, etc., mixed in an organic solvent appropriately selected, and dispersed with a paint shaker, a ball mill, an attritor, etc. to produce a heat transferable ink, and on a heat resistant support, for example, a wire bar, etc. Thus, a thermal transfer recording medium can be prepared by coating so that the ink layer thickness falls within the above range.

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but these Examples do not limit the present invention. It should be noted that all the blending parts mean parts by weight.

Example 1 Carnauba wax (mp 83 ° C., penetration 1 or less) 79 parts Polystyrene resin (sp 85 ° C.) 15% MEK solution 113 parts [Sumitomo Chemical Co., Ltd., trade name Esbrite 500SB] Heat represented by formula (I) Plastic resin (n = 300-500) 17 parts [Placcel H-4, manufactured by Daicel Chemical Co., Ltd.] Colorant: carbon black 17 parts Solvent: toluene / MEK = 50/50 774 parts Glass in the above mixture After adding the beads and dispersing for 2 hours with an attritor, a 6 μm-thick polyethylene terephthalate film was coated by a solvent coating method so that the coating thickness after drying was 4.0 μm,
A thermal transfer recording medium was obtained. Drying conditions were 100 ° C. for 2 minutes.

Example 2 Montanic acid wax (mp80 ° C., penetration 1 or less) 85 parts Polystyrene resin (sp85 ° C.) 15% MEK solution 113 parts [Dainippon Ink Chemical Company, trade name Dick Styrene MH
−6700] 11 parts of a thermoplastic resin represented by the formula (I) (n = 600 to 900) [Placcel H-7 manufactured by Daicel Chemical Co., Ltd.] Colorant: carbon black 17 parts Solvent: toluene / MEK = 50/50 774 parts A thermal transfer recording medium was obtained in the same manner as in Example 1 using the above mixed liquid.

Example 3 85 parts of montanic acid ester wax (mp 78 ° C., penetration 1) Polystyrene resin (sp 85 ° C.) 15% MEK solution 113 parts [manufactured by Dainippon Ink and Chemicals, trade name: Dick Era Styrene # 200] Formula (I) 11 parts [Placcel H-7, manufactured by Daicel Chemical Co., Ltd.] Colorant: carbon black 17 parts Solvent: toluene / MEK = 50/50 774 parts Using the mixed solution, a thermal transfer recording medium was obtained in the same manner as in Example 1.

Example 4 Polyethylene wax (mp 103 ° C., penetration 1 or less) 85 parts Acrylonitrile / styrene copolymer resin 15% MEK solution 113 parts [trade name TTR-02, manufactured by Fujikura Kasei Co., Ltd.] Thermoplastic represented by formula (I) Resin (n = 600-900) 11 parts [Placcel H-7, manufactured by Daicel Chemical Co., Ltd.] Colorant: carbon black 17 parts Solvent: toluene / MEK = 50/50 774 parts Using the above mixture, A thermal transfer recording medium was obtained in the same manner as in Example 1.

Comparative Example 1 Carnauba wax (mp83 ° C, penetration 1 or less) 14 parts Paraffin wax (mp55 ° C, penetration 14) 67 parts Microcrystalline wax (mp75 ° C, penetration 12) 14 parts Additive: oleic acid 17 Part Colorant: carbon black 17 parts Solvent: toluene / MEK = 50/50 870 parts A thermal transfer recording medium was obtained in the same manner as in Example 1 using the above mixed liquid.

Comparative Example 2 Carnauba wax (mp 83 ° C., penetration 1 or less) 96 parts Thermoplastic resin represented by the formula (I) (n = 300 to 500) 17 parts Colorant: carbon black 17 parts Solvent: toluene / MEK = 50 / 50 870 parts A thermal transfer recording medium was obtained in the same manner as in Example 1 using the above mixed liquid.

Comparative Example 3 Carnauba wax (mp 83 ° C, penetration 1 or less) 96 parts Polystyrene resin (sp85 ° C) 15% MEK solution 113 parts [Sbright 500SB manufactured by Sumitomo Chemical Co., Ltd.] Colorant: carbon black 17 parts Solvent: Toluene / MEK = 50/50 774 parts A thermal transfer recording medium was obtained in the same manner as in Example 1 using the above mixed liquid.

Comparative Example 4 Polyethylene wax 79 parts (sp136 ° C., penetration 1 or less) Polystyrene resin (sp85 ° C.) 15% MEK solution 113 parts [Sumitomo Chemical Co., Ltd. brand name Esbrite 500SB] Thermoplastic represented by formula (I) Resin (n = 300-500) 17 parts Colorant: carbon black 17 parts Solvent: toluene / MEK = 50/50 774 parts A thermal transfer recording medium was obtained in the same manner as in Example 1 using the above mixed liquid.

In order to examine the transfer energy sensitivity, transfer image density and transfer image quality of the thermal transfer recording media of each of the above Examples and Comparative Examples, a thermal gradient tester (HG-100 manufactured by Toyo Seiki Seisaku-sho, Ltd.)
Temperature setting: 60-140 ° C, pressure: 2kg / cm, thermocompression bonding time: 3
Seconds), high-density thermal printer (printer with a thermal head of 8 dots / mm; printing speed: 60 characters / second,
Applied energy: 0.15 ~ 0.66mJ / dot, 0.03mJ / dot interval)
The experiment was performed using.

Further, in order to examine the friction resistance of the transfer ink surface obtained by the above experiment, a rough paper having a smoothness of 5 to 10 seconds was measured using a paperboard abrasion tester (manufactured by Kumagaya Riki Kogyo Co., Ltd.). Abrasion resistance was tested under constant conditions of room temperature: 20 ° C., load: 500 gw / cm, and number of friction: 100 reciprocations. As receiving paper,
Thermal transfer paper, mirror coated paper, and OHP sheets were used. The results are summarized in Table 1.

Transfer image quality: The image was evaluated for density unevenness, uniformity, sharpness, random bridges, and the occurrence of voids.
Each evaluation is a visual evaluation using an enlarged photograph or the like.

：: All of the evaluation items are satisfied. ：: One of the evaluation items has a problem. X: Two or more of the evaluation items have a problem. Abrasion resistance: ：: No change. A little adheres to the paper, but does not affect the transferred image. ×: The ink in the transferred image area adheres significantly to the friction paper and affects the transferred image. Transfer energy sensitivity: Transfer energy when transfer image density is saturated Transfer Image density: Saturated image reflection density value of solid printing portion (measurement machine: Macbeth reflection densitometer) Effect of the Invention As described above, the thermal transfer recording medium of the present invention has at least mainly a transfer image quality in the thermal transfer ink layer. A thermoplastic resin represented by the formula (I) which is considered to be effective mainly for thermal properties such as a wax which is considered to be effective, a polystyrene resin which is thought to be mainly effective for abrasion resistance of a transfer ink surface, and a transfer energy sensitivity. Since it has a configuration containing a conductive resin, a uniform transfer image without unevenness in density can be obtained, and a transfer image excellent in body friction can be obtained regardless of the ink receiver.
Further, the thermal transfer recording medium of the present invention has excellent transfer energy sensitivity. Therefore, the thermal transfer recording medium of the present invention
It can be particularly suitably used for barcode printers and the like.

Continuation of the front page (72) Inventor Hitoshi Tsukada 3-1 Yomibacho, Shizuoka-shi, Shizuoka Pref. In the Technical Research Laboratory of Tomoegawa Paper Mill Co., Ltd. (56) References JP-A-61-297186 (JP, A) JP-A-62-5888 (JP, A) JP-A-62-25887 (JP, A) JP-A-60-122194 (JP, A) JP-A-62-59089 (JP, A) JP-A-62-142687 (JP, A) JP-A-62-148289 (JP, A) JP-A-62-196185 (JP, A) JP-A-62-5884 (JP, A) 60-165291 (JP, A) JP-A-62-89777 (JP, A)

Claims (1)

(57) [Claims] 1. A thermal transfer recording medium comprising a heat transfer ink layer provided on a heat-resistant support, wherein the thermal transfer ink layer comprises:
A wax having a penetration of at least 4 (JISK2235) and a melting point or softening point of 130 ° C. or less, a polystyrene resin having a melting point or softening point in the range of 70 to 140 ° C., and the following formula (I) (Wherein, n represents an integer of 50 <n <1000), wherein the content of the polystyrene resin is 1 to 25% by weight, and the content of the thermoplastic resin is A thermal transfer recording medium having an amount of 1 to 35% by weight.