JP3121334B2 - 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 capable of obtaining an image having improved abrasion resistance and heat resistance.

[Prior Art] Conventionally, as a thermal transfer recording medium, one having an ink layer composed of an epoxy resin having a softening temperature of 60 to 110 ° C. and a coloring agent has been known (Japanese Patent Publication No. Sho 60-5919). According to this method, it is possible to obtain a recording having primary coloring on various recording surfaces such as plain paper, plastic and metal foil, and also having excellent storage stability and abrasion resistance.

In addition, the first layer is provided with a release layer, the second layer is provided with a colored layer containing no wax, and the third layer is provided with an adhesive layer made of a polyamide resin having a softening point of 90 to 180 ° C. to improve smear resistance. 63-78791). Alternatively, an ink comprising a thermoplastic resin having a glass transition point of 50 to 110 ° C. as a main component, a lubricant and a coloring agent as a main component of the ink and having improved abrasion resistance and chemical resistance of the image (Japanese Patent Laid-Open No. 63-230392) is proposed. Have been.

However, in the above-mentioned thermal transfer recording medium, the epoxy resin constituting the ink layer has a softening point of 60 to 110 ° C., and thus has a drawback that the thermal abrasion resistance is poor. That is, when an image exposed to a high temperature, for example, 70 ° C. is rubbed with, for example, corrugated paper, the image is disturbed and it is difficult to read the image.

Further, the image surface of the ink using the epoxy resin has a defect that the lubricating property is inferior and easily falls off when it comes into contact with a highly hard material such as a metal edge or a nail.

Therefore, it has been found that the above problem can be solved by employing a methyl methacrylate / acrylonitrile-based copolymer and a lubricating agent as constituent materials of the ink layer, and has already filed an application.

That is, (1) a thermal transfer recording medium comprising an ink layer containing, as a main component, a lubricating agent, a colorant, and a copolymer mainly composed of a methyl methacrylate monomer and an acrylonitrile monomer on a base material; (2)
A thermal transfer recording medium comprising an ink layer mainly composed of a lubricating agent, a colorant and a copolymer mainly composed of a methyl methacrylate monomer and an acrylonitrile monomer, which are mainly laminated on a substrate. ,
(3) A thermal transfer recording medium in which an adhesion enhancer layer is provided on a substrate, and the layers described in (1) and (2) are further formed thereon.

By using the thermal transfer recording medium having the above configuration, an image having improved abrasion resistance and heat resistance can be obtained.
However, a large applied energy is required to obtain a good image having a low thermal sensitivity and no fine line breakage. Printing speed 100 mm / sec, when printing by the printer platen pressure 150 g / cm, whereas good images are obtained at 20 mJ / mm ² in the case of printing onto highly smooth recording material such as a film, In the case of coated paper having lower smoothness than a film such as mirror coated paper, a good image cannot be obtained unless the applied energy is 25 mJ / mm ² . If the applied energy necessary to obtain a good image of the thermal transfer recording medium of the general wax as a main component is 13 mJ / mm ² in the film is 16 mJ / mm ² by the mirror-coated paper.

The softening point of the surface of the thermal transfer recording
When the main component is a material having a temperature of 150 ° C. or a glass transition point exceeding 70 ° C., the thermal sensitivity is low. If a material such as wax for improving the thermal sensitivity is added to solve this problem, the abrasion resistance and heat resistance deteriorate.

In order to solve the above-mentioned problem, it has been proposed to laminate a sensitivity enhancer layer containing a branched polyester resin as a main component on the ink layer, and has previously filed an application. As a result, printing with lower applied energy became possible as compared with the case where the sensitivity enhancer layer was not provided. However, heat resistance, abrasion resistance and chemical resistance were slightly deteriorated.

[Problems to be Solved by the Invention] The present invention aims to improve heat resistance and wear resistance without deteriorating thermal sensitivity. Further, when the heat resistance and the wear resistance are limited, the selection range of the material is expanded.

[Means for Solving the Problems] The constitution of the present invention for solving the above problems is as follows: (1) an ink layer mainly composed of a lubricating agent, a coloring agent and the following resin (I), Next, the following resin (II)
A heat-sensitive transfer recording medium in which each layer is formed in the order of a sensitivity enhancer layer containing as a main component.

However, the resin (I) is one or a combination of two or more of the following resins, and has a glass transition temperature of 70 to 180 ° C.

a) a copolymer mainly composed of a methyl methacrylate monomer and an acrylonitrile monomer, b) a terpolymer of methyl methacrylate / acrylonitrile / glycidyl methacrylate, c) a polyester resin, and the resin (II) are the following acids and diols: A resin having a glass transition temperature of 30 to 60 ° C., which is composed of one or a combination of two or more of polyesters formed of condensates by an arbitrary combination selected from the above.

(Acid) Fumaric acid, isophthalic acid, terephthalic acid, phthalic anhydride, tetrabromophthalic anhydride, tetrachlorophthalic anhydride, alkylbenzene polycarboxylic acid, succinic acid, sebacic acid, heptic acid, adipic acid, (diol) alkyl polyalcohol , Ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, trimethylene glycol, trimethylolpropane, hydrogenated bisphenol A, bisphenol A hydroxypolyoxy alcohol copolymer, allyl glycidyl ether, 1,6-hexanediol (2) The above (1), wherein instead of the ink layer in the above item (1), a lubricating agent layer is formed, and then a laminate comprising an ink layer containing a colorant and a resin (I) as main components is formed. Heat transfer It is a copy recording medium.

The sensitivity enhancer layer must adhere to the recording medium with low applied energy and have chemical resistance and mechanical strength. However, in general, a substance that adheres to a recording medium with low applied energy is a heat-meltable substance such as wax (a substance that changes from a solid to a liquid of 5000 cps or less at the boundary of the melting point). If it exceeds this, the viscosity becomes low, so there is no heat resistance, the adhesive strength to the transfer receiving body is small, and the mechanical strength and the chemical resistance to oil and the like are weak. On the other hand, a material with high heat resistance and high mechanical strength is generally called a resin, which has a low thermal sensitivity because it has no melting point, such as a hot-melt substance. And weak in chemical resistance.

Therefore, as a result of research, the glass transition point of the sensitivity enhancer layer was 30
It was found that by using a resin at 60 ° C. as a main component, abrasion resistance and heat resistance can be improved without deteriorating thermal sensitivity. Also, it was found that chemical resistance can be improved by using a polyester resin composed of a condensate of any of the following acids and diols as the main component.

As other characteristic values, a material having a flow start temperature of 70 to 120 ° C and a melt viscosity of 1000 to 3000 poise (at 140 ° C) is preferable.

The glass transition temperature of the main component of the ink layer is 70 to 18
An image excellent in abrasion resistance and heat resistance can be obtained by using a resin, a lubricating agent and a coloring agent at 0 ° C.

When one or a combination of the following resins is used as the resin, an image having excellent chemical resistance can be obtained.

a. A copolymer mainly composed of a methyl methacrylate monomer and an acrylonitrile monomer.

b. Terpolymer of methyl methacrylate / acrylonitrile / glycidyl methacrylate.

In addition to the above, a material having excellent mechanical strength and relatively high chemical resistance such as a polyester resin can be used in a mixed form.

As the substrate for supporting the above-mentioned ink layer in the present invention, a conventionally known film or paper can be used as it is, for example, polyester, polycarbonate, triacetyl cellulose, nylon, polyimide and the like having relatively high heat resistance. A plastic film, cellophane, parchment paper, or the like can be suitably used. The thickness of the support is preferably 2 to 15 μm when considering a thermal head as a heat source at the time of thermal transfer.For example, when a heat source that can selectively heat a thermal transferable ink layer such as a laser beam is used. Is not particularly limited. When a thermal head is used, a heat-resistant protective layer made of silicon resin, fluorine resin, polyimide resin, epoxy resin, phenol resin, melamine resin, nitrocellulose, etc. is provided on the surface of the support that comes into contact with the thermal head. The heat resistance of the support can be improved, or a substrate that could not be used conventionally can be used.

Further, as the colorant used in the present invention, an appropriate one can be selected from carbon black, an organic pigment, an inorganic pigment, or a dye according to a required color tone or the like.

In the copolymer based on methyl methacrylate / acrylonitrile used in the present invention, besides methyl methacrylate and acrylonitrile, any other vinyl monomer can be optionally used as a comonomer without departing from the object of the present invention. Glycidyl methacrylate is particularly preferred as such a vinyl monomer.

 This copolymer can be represented by the following general formula.

The function of each comonomer is as follows.

Methyl methacrylate: imparting thermoplasticity, increasing Tg,
Acrylonitrile: imparts chemical resistance, imparts mechanical strength, glycidyl methacrylate: imparts adhesiveness, imparts crosslinkability, imparts heat resistance The composition ratio of these comonomers is as follows: Is preferred.

Methyl methacrylate: acrylonitrile: other vinyl monomer weight ratio = (20-80) :( 10-50) :( 0-5
0), more preferably (40-60) :( 20-40) :( 0
~ 30).

If the composition is out of balance, sufficient mechanical strength cannot be ensured, and problems such as deterioration of chemical resistance and curling of the ink layer occur.

The molecular weight of these copolymers affects the melt viscosity and affects the sensitivity during thermal transfer. Therefore, the melt viscosity is used as a measure of the molecular weight. Its melt viscosity was measured by a B-type rotary viscometer.
It is preferably 1000 to 50,000 cps at 0 ° C.

The preparation of the copolymer can be easily carried out by a known method.
For example, it is obtained by using a radical initiator such as benzoyl peroxide or azobisisobutyronitrile as a polymerization initiator and polymerizing the mixture at an appropriate temperature and in a solvent.

When a terpolymer having a curable functional group obtained by using glycidyl methacrylate or the like as the third monomer is used, an appropriate thermosetting agent may be contained in the ink layer. Typical examples are phenols,
For example, phenolic resins, primary amines, secondary amines, complex compounds of amines (Lewis acids, especially complex compounds of boron trifluoride with amines, such as BF ₃ .C ₂ H ₅ .NH ₂ ), organic acids, and organic acids Anhydrides and the like. The amount of these used is theoretically sufficient if a curing agent having an amount equivalent to a glycidyl group or the like of the terpolymer to be cured and a functional group having a chemical equivalent is used.

The lubricating agent is a substance capable of improving the lubricity of the thermally transferred image surface. This lubricity serves to reduce the coefficient of wear on all objects, such as metal, corrugated cardboard and wood, and to reduce the concentration of stress on the ink in the image area.

As described above, the lubricating agent functions to impart lubricity to the above-mentioned copolymer, and includes, for example, a lubricant such as wax-like fatty acid amide and phosphate ester, natural paraffin wax, candelilla wax, and carnauba. Waxes such as waxes, silicone oils, oils such as perfluoroalkyl ethers, silicone resins, oils such as perfluoroalkyl ethers, silicone resins, resins such as fluoroalkyl ether resins, PTFE,
And lubricating particles such as SiC and SiO ₂ . Of these, carnauba wax is the most effective substance for achieving both mechanical strength and lubricity of the ink. The addition amount is suitably from 1 to 30% by weight based on the copolymer.

The above-mentioned lubricating agent may be added to the ink layer and used. However, as a measure for further improving the function, it is preferable to provide a lubricating agent layer between the base material and the ink layer. As the lubricating agent layer, the above-mentioned substances are used. For example, when carnauba wax is used, a layer having a thickness of 0.3 to 2.0 μm can sufficiently exhibit its function.

A flexibility imparting agent, a thermal sensitivity adjuster, and the like can be used as additives to the main components of the ink layer described above. As examples thereof, plasticizers such as DOP, softeners such as EVA, EEA and synthetic rubber, and thermoplastic resins can be used.

The thickness of the ink layer is appropriately set depending on the smoothness of the recording paper to be recorded. For a film having an infinite smoothness such as a polyester film, a sufficiently strong image can be formed at 1.0 to 2.5 μm, and the thermal sensitivity is good. Further, it is good in terms of image quality to have about 2.5 to 4.0 μm for coated paper and high quality paper.

The thermal transfer recording medium of the present invention, which is formed by laminating the above ink layer or lubricating agent layer and ink layer, can be printed at a low temperature,
In order to prevent the ink from falling off during printing under an environment of ° C., an adhesion improver layer can be provided between the base material and the ink layer or between the base material and the lubricating agent layer. The adhesion improver layer may be thermally transferred or may remain on the substrate. As the adhesion improver, a substance exhibiting flexibility near normal temperature is preferable, and examples thereof include resins such as ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl chloride copolymer, polyvinyl butyral, natural rubber, and synthetic rubber. Used.
When thermally transferring this layer, waxes having an appropriate melting point, such as paraffin wax and carnauba wax, are used.
What is necessary is just to blend 30-70 weight%. An appropriate thickness is 0.2 to 1.0 μm.

[Examples] The present invention will be described in more detail with reference to Examples. Inks were prepared at 20% solids in methyl ethyl ketone unless otherwise specified.

Example 1 The following components were used as ink layer components.

Colorant: carbon black 20 parts by weight Copolymer: methyl methacrylate / acrylonitrile copolymer (weight ratio 70:30) [melt viscosity: 16500 cps (140
° C)] [Glass transition temperature: 108 ° C] 70 parts by weight Lubricant: carnauba wax 10 parts by weight A 4.5 µm-thick polyester film was used as a base material. The above composition was applied to this substrate so as to have an ink layer of 3.0 μm and dried.

As a sensitivity enhancer layer, 100 parts by weight of a polyester resin (glass transition temperature: 45 ° C.) composed of a polycondensate of terephthalic acid, isophthalic acid as an acid and ethylene glycol and neopentyl glycol as diols is 1.0 μm above the ink layer.
The above composition was applied and dried to obtain a thermal transfer recording medium.

Example 2 An ink layer was formed in the same manner as in Example 1, except that the copolymer in the composition of Example 1 was changed to the following substances.

Copolymer: methyl methacrylate / acrylonitrile (weight ratio: 50:50) Melt viscosity: 28000 cps (140 ° C.) Glass transition temperature: 120 ° C. Example 3 The following components were used as ink layer components.

Colorant: 20 parts by weight of carbon black Copolymer: 76 parts by weight of the same components as in Example 1 Lubricant: 4 parts by weight of silicone oil 3. Ink layer on the same material as the base material used in Example 1.
It is applied to a thickness of 0 μm and dried to form a sensitivity improver layer. A. A polyester resin (glass) made of a polycondensate of fumaric acid, phthalic anhydride, ethylene glycol, bisphenol A hydride, neopentyl glycol as an acid B. Polyester resin (glass transition temperature 53 ° C) consisting of polycondensate of adipic acid and phthalic anhydride as acid and 1,6-hexanediol, ethylene glycol, and trimethylol glycol as diols. = 70:30 parts by weight, 0.5 on the ink layer
The resultant was coated and dried to a thickness of μm to obtain a thermal transfer recording medium.

Example 4 A lubricating agent layer was formed on the same base material as in Example 1 by a coating liquid in which a mixed wax of carnauba wax and paraffin wax (weight ratio 1: 1) was dispersed in toluene.
It was formed by coating and drying so as to have a thickness of 1.0 μm.

On this layer, a composition from which the lubricant was removed from the ink composition used in Example 1 was applied as an ink layer component to a thickness of 2.5 μm and dried to form a sensitivity enhancer layer in the same manner as in Example 1.

Example 5 On the same base material as in Example 1, a 1: 1 weight ratio of ethylene-vinyl acetate copolymer (40% vinyl acetate, melt index 150) and carnauba wax was dispersed in toluene as an adhesion promoter layer. The liquid was obtained by coating and drying to a thickness of 0.5 μm.

On this layer, the same ink composition as in Example 1 was applied to a thickness of 2.5 μm.
m, and dried by drying to further form the same sensitivity improving layer as in Example 3.

The thermal transfer recording medium was checked for ink drop-off by hand fogging, but remained almost on the substrate, confirming the effect of the adhesion improver layer.

Example 6 The following components were used as ink layer components.

Colorant: 20 parts by weight of carbon black Terpolymer: l: m: n (weight ratio) of general formula (I) = 55: 2
5:20 [melt viscosity: 14000 cps (140 ° C)] Glass transition temperature 85
° C 70 parts by weight Lubricant: Carnauba wax 10 parts by weight The other conditions were the same as in Example 1.

Example 7 An ink layer was formed in the same manner as in Example 6, except that the terpolymer in Example 6 was replaced with the following substances.

Terpolymer: l: m: n of general formula (I) = 45: 30: 25 [melt viscosity: 18000 cps (140 ° C.)] Glass transition temperature 97 ° C. Example 8 Example 6 is used as an ink layer component Was. A thermal transfer recording medium was obtained in the same manner as in Example 6 except that 1.5 parts by weight of a latent heat curing agent BF ₃ C ₂ H ₅ —NH ₂ was added to the composition.

Comparative Example 1 As an ink layer component, the following component containing a so-called heat-fusible wax as a main component was used.

Colorant: carbon black 20 parts by weight Binder: paraffin wax (melting point 68 ° C) 40 parts by weight Carnauba wax (melting point 81 ° C) 20 parts by weight Ethylene / vinyl acetate copolymer (vinyl acetate 28%, melt index 250) 10 parts by weight The above composition Was prepared at 15% solids in toluene.

Using the same base material as in Example 1, 3.0 μm as an ink layer
The above composition was applied and dried so as to be thick, and a thermal transfer recording medium as a comparative example was obtained.

Comparative Example 2 So-called thermoplastic resin as an ink layer component
60-59159 described below) as main components were used.

Coloring agent: carbon black 20 parts by weight Binder: bisphenol A type epoxy resin (Epicoat 1002, softening point 77-78 ° C., manufactured by Shell Chemical Co., Ltd.) 80 parts by weight The composition was applied and dried to a thickness of 3.0 μm to obtain a thermal transfer recording medium as a comparative example.

[Comparison Evaluation Results] In the printing test, a label-shaped polyester film (PET) and a mirror-coated paper (coated paper), which were glued on the release surface, were used. The printing conditions are as follows.

<Print conditions> Thermal head: Partial glaze thin film head type Platen pressure: 150 g / cm Peeling angle of thermal transfer recording medium: 30 degrees to transfer paper Peeling torque value: 200 g Applied energy: 10 to 30 mJ / mm ² printing Speed: 10 cm / sec Various performances evaluated comparatively are as follows.

Thermal sensitivity: applied energy that does not cause thin wire blurring in the mirror coat Thermal wear resistance: A printed sample is placed on a glass plate in a bath set at 70 ° C, and the printed surface is made of cardboard paper with a load of 60 g / cm ² . Three
A reciprocating love test was performed at a speed of 0 cm / sec, and the number of times the image became unreadable was recorded.

Hardness 2H abrasion: A rub test was performed with an objective having a hardness of 2H of about 2 t / cm ² , and the number of times the transfer paper surface was exposed was recorded.

Metal edge abrasion resistance: Using a stainless steel edge of about 2 t / cm ² as an object, a rub test was performed in the same manner, and the number of times the transferred paper surface was exposed was recorded.

Chemical resistance: A cotton swab is immersed in 0.5 ml of various solvents listed below.
A rub test was performed under a load of 0 g / mm ² , and the number of times required to expose the transfer paper surface was recorded. The image printed on PET was used.

[Evaluation results] [Effects of the Invention] As described above, according to the present invention, it is possible to provide a heat-sensitive transfer recording medium capable of forming an image excellent in abrasion resistance, heat resistance, and chemical resistance without lowering the thermal sensitivity. .

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-63-162287 (JP, A) JP-A-1-141788 (JP, A) JP-A-3-36096 (JP, A) (58) Investigation Field (Int.Cl. ⁷ , DB name) B41M 5/26

Claims (2)

(57) [Claims] 1. An ink layer comprising a lubricating agent, a coloring agent and the following resin (I) as main components on a substrate,
A heat-sensitive transfer recording medium, wherein each layer is formed in the order of a sensitivity improver layer containing (I) as a main component. However, the resin (I) is one or a combination of two or more of the following resins, and has a glass transition temperature of 70 to 180 ° C. a) a copolymer mainly composed of a methyl methacrylate monomer and an acrylonitrile monomer, b) a terpolymer of methyl methacrylate / acrylonitrile / glycidyl methacrylate, c) a polyester resin, and the resin (II) are the following acids and diols: Consisting of one or a combination of two or more of polyesters composed of condensates by an arbitrary combination selected from among them, having a glass transition temperature of
30-60 ° C resin. (Acid) Fumaric acid, isophthalic acid, terephthalic acid, phthalic anhydride, tetrabromophthalic anhydride, tetrachlorophthalic anhydride, alkylbenzene polycarboxylic acid, succinic acid, sebacic acid, heptic acid, adipic acid, (diol) alkyl polyalcohol , Ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, trimethylene glycol, trimethylolpropane, hydrogenated bisphenol A, bisphenol A hydroxypolyoxy alcohol copolymer, allyl glycidyl ether, 1,6-hexanediol , 2. The ink layer according to claim 1, wherein
2. A thermal transfer recording medium according to claim 1, wherein a layer comprising a lubricating agent layer, and then an ink layer containing a colorant and a resin (I) as main components is formed.