JPH06183162A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To enhance abrasion resistance, fixing properties, heat abrasion resistance and chemical resistance, in the title recording medium having an ink layer based on an acrylic copolymer resin, by forming an internal void structure to the ink layer. CONSTITUTION:The ink layer based on a colorant and an acrylic copolymer resin containing acrylonitrile and/or methacrylonitrile as a monomer component formed on a base material is formed into an internal void structure having voids 11 therein or a porous structure and the shearing strength of the ink layer is set to 250gf/cm or less. Further, a lubricating agent is added to the ink layer or a lubricating agent layer is provided between the ink layer and the base material and an adhesive layer composed of a heat-softenable resin, for example, an acrylic resin is provided on the ink layer. The internal voids are formed by mixing a solvent inferior to compatibility with an ink soln. and drying the resulting mixture. As the lubricating agent, wax like aliphatic amide is used.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a thermal transfer recording medium,
More specifically, the present invention relates to a thermal transfer recording medium suitable for obtaining a transferred image having excellent heat resistance and chemical resistance and excellent thermal sensitivity.

[0002]

2. Description of the Related Art Conventionally, in a thermal transfer recording medium,
Many proposals have been made for obtaining a record having excellent fixability of a transferred image and excellent storage stability and abrasion resistance.
Most of such proposals relate to the binder resin used in the ink layer, and some of them are thermoplastic resins having a glass transition temperature (Tg) of 120 ° C. or higher (JP-A-3-211090), Tg50. To 70 ° C., liquefaction temperature 70 to 100 ° C., and saturated polyester resin having a molecular weight of 2000 to 8000 are used (JP-A-3-99885).
JP-A 2-5), a polyester resin having a number average molecular weight of 1,000 to 10,000 and a specific structure is used (Japanese Patent Laid-Open No. 2-5
9770). According to the thermal transfer recording medium using these binder resins in the ink layer, the transferred image is provided with good fixing property and abrasion resistance. Further, in JP-A-258295, by using a copolymer of acrylonitrile or methacrylonitrile base as a binder resin for an ink layer, fixing property and abrasion resistance are imparted to a transferred image, and heat resistance abrasion resistance is provided. There is a description of a thermal transfer recording medium which also provides the properties and chemical resistance.

[0003]

By the way, when it is attempted to obtain more excellent fixability, abrasion resistance, heat abrasion resistance and chemical resistance of a transferred image by using a thermal transfer recording medium, the glass transition point of the resin binder is Alternatively, it is necessary to increase the softening point and make the ink layer formed on the base material a stronger film. However, in the conventional thermal transfer recording medium, the ink layer may not be easily melted by heat at the time of transfer, or the shearing force of the film may be large, and as a result, the thermal sensitivity is poor. An object of the present invention is to provide a thermal transfer recording medium capable of obtaining recording excellent in fixability, abrasion resistance, heat abrasion resistance and chemical resistance.

[0004]

The thermal transfer recording medium of the present invention comprises an ink layer containing a colorant and an acrylic copolymer resin containing acrylonitrile and / or methacrylonitrile as monomer components on a substrate. It is provided that the ink layer has voids inside but has a porous structure. In the thermal transfer recording medium of the present invention, the ink layer is formed to have an internal void structure or a porous structure, preferably (i) the ink layer has a shear strength of 250 gf / cm or less, and (ii) the ink layer is A layer containing a lubrication agent or containing a lubrication agent is provided between the ink layer and the substrate, or (iii) an adhesive layer is provided on the ink layer. Two or more of the requirements (i) to (iii) may be duplicated. Hereinafter, the present invention will be described in more detail.

In the present invention, a conventionally known film or paper can be used as it is as a substrate (support) for supporting the above-mentioned ink layer, for example, polyester,
A relatively heat-resistant plastic film such as polycarbonate, triacetyl cellulose, nylon, or polyimide, cellophane, or nitric acid paper can be used. The thickness of the support is preferably 2 to 15 μm when a thermal head is considered as a heat source for thermal transfer. For example, when a heat source capable of selectively heating the thermal transfer ink layer such as laser light is used. Is not particularly limited to. When a thermal head is used as a heat source, a heat-resistant protective layer made of silicon resin, fluororesin, polyimide resin, epoxy resin, phenol resin, melamine resin, nitrocellulose, etc. on the surface of the support that contacts the thermal head. By providing the above, the heat resistance of the support can be improved, or a base material that cannot be used conventionally can be used.

The ink layer of the present invention contains a colorant and a binder resin (acrylic copolymer resin containing acrylonitrile and / or methacrylonitrile as a monomer component) as main components and has voids inside.

As the colorant used in the present invention, carbon black, organic pigment,
An appropriate one can be selected and used from the inorganic pigments or dyes.

The acrylic copolymer resin used in the present invention may be one represented by the following general formula (I) containing acrylonitrile and / or methacrylonitrile as a base.

[Chemical 1] Specific examples of these copolymer resins include acrylonitrile-methyl methacrylate copolymer, acrylonitrile-methyl acrylate copolymer, acrylonitrile-ethyl methacrylate copolymer, acrylonitrile-ethyl acrylate copolymer, acrylonitrile-n-butyl methacrylate copolymer. Polymer, acrylonitrile-glycidyl methacrylate copolymer, acrylonitrile-glycidyl acrylate copolymer, acrylonitrile-2-
In addition to hydroxyethylmethacrylate copolymer, acrylonitrile-iso-butylmethacrylate copolymer, acrylonitrile-tert-butylmethacrylate copolymer, acrylonitrile-2-hydroxypropylmethacrylate copolymer, methacrylonitrile is used instead of acrylonitrile. All combinations of copolymers, if present. Among these acrylic copolymer resins, those which are particularly excellent in heat resistance, chemical resistance and abrasion resistance, and which can be easily produced industrially include acrylonitrile-glycidyl methacrylate copolymer and acrylonitrile-methyl methacrylate. Typical examples are a copolymer and an acrylonitrile-ethyl methacrylate copolymer.

In addition to the above-mentioned acrylic copolymers, various other vinyl monomers may be further copolymerized within the range not departing from the object of the present invention to form a terpolymer. Absent. Such a terpolymer is preferably represented by the following general formula (II).

[Chemical 2] (Wherein, R ^5: -H or -CH _3, R ^6: -H or _{-CH 3, -C 2 H 5,} -C 3 H 7, -C 4 H 9
Alternatively, —C ₂ H ₅ OH, 1, m, n are integers. The function of each monomer component is as follows. (Meth) acrylic ester: imparting thermoplasticity, controlling Tg, imparting chemical resistance, (meth) acrylonitrile: imparting chemical resistance, imparting mechanical strength, imparting heat resistance, glycidyl (meth) acrylate: Adhesiveness, crosslinkability, heat resistance. The composition ratio (weight ratio) of these copolymers is preferably in the following range. l: m: n = (1-80) :( 10-70) :( 1-8)
0), preferably (10-60): (20-60):
(10 to 60). 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 the acrylic copolymer in the present invention affects the melt adhesion and affects the sensitivity during thermal transfer. Therefore, the molecular weight of these copolymers is, in terms of polystyrene equivalent by GPC, a weight average molecular weight (hereinafter referred to as MW) of 2000 to 1,000,000, a number average molecular weight (hereinafter referred to as MN) of 1,000 to 500,000, and more preferably MW of 3000. ~
500,000 and MN 1500 to 250,000.

The ink layer according to the present invention has voids inside, and the form thereof is an internal void structure (FIG. 1) and a porous structure of one-dimensional single holes or three-dimensional communicating holes (FIG. 1). 2) is preferable, and a porous structure is particularly advantageous. In FIGS. 1 and 2, reference numeral 11 denotes a void (internal void structure), and 12 denotes a communicating hole (porous structure).

Means for forming an ink layer having an internal void structure include an ink liquid containing an acrylic copolymer resin containing acrylonitrile and / or methacrylonitrile as a constituent resin of the present invention as a monomer component and a colorant as main components. What,
It is formed by mixing a solvent having poor compatibility with the resin, dispersing and drying. The addition of a poorly compatible solvent causes the resin to agglomerate during dry operation to form an internal void structure. Examples of the "solvent having poor compatibility" here include alcohols such as methanol, ethanol and isopropyl alcohol. On the other hand, as a means for forming the ink layer in a porous structure, water is mixed into an ink solution using an organic solvent having a higher evaporation rate than water, and the difference in the evaporation rate of the organic solvent and water is used to make the ink layer porous. Form a structure.

Whether the ink layer has the above-mentioned internal void structure or the above-mentioned porous structure depends on the amount of alcohols or water in the ink liquid, and its form also differs. Increasing the content of alcohols promotes internal void structuring, and increasing the content of water promotes porous structuring. However, when too much alcohol or water is contained with respect to the blending amount of the resin and colorant in the ink liquid, the resin causes gelation or precipitation, and in addition, the dispersibility of the colorant deteriorates. There is. Considering these, the forms of the internal void structure and the porous structure can be arbitrarily formed.

The ink layer is preferably adjusted to have a shear strength of 250 gf / cm or less, preferably 220 gf / cm or less. This can be adjusted by setting arbitrary drying conditions in the preparation of the ink liquid and the formation of the ink layer. If the shear strength is 250 gf / cm or less, problems such as ink layer dropout and blocking may occur.

In the present invention, it is desirable to provide a lubricant or a layer containing the lubricant in the ink layer or between the substrate and the ink layer. The term "lubrication agent" as used herein means a substance that can improve the lubricity of the surface of a heat-transferred image, and this lubricity reduces the abrasion coefficient for all objects such as metal, corrugated paper and wood. This is to prevent stress concentration on the ink in the image area.

As described above, the lubricity imparting agent acts to impart lubricity to the acrylic copolymer resin according to the present invention. For example, a wax-like fatty acid amide, a phosphoric acid ester or the like lubricant, or a natural lubricant. Waxes such as paraffin wax, candelilla wax and carnauba wax, oils such as silicone oil and perfluoroalkyl ether, oils such as silicone resin and perfluoroalkyl ether, resins such as silicone resin and fluoroalkyl ether resin, Examples thereof include particles imparting lubricity such as PTFE, SiC, and SiO ₂ . Of these, carnauba wax is the most effective substance for achieving both mechanical strength and lubricity of the ink layer. When the lubricity-imparting agent is added to the ink layer, the addition amount is appropriately 1 to 30% by weight based on the acrylic copolymer resin.

The above-mentioned lubricity-imparting agent may be added to the ink layer and used, but as a measure for further improving the function,
As described above, it is preferable to provide the lubrication agent layer between the base material and the ink layer. The above-mentioned lubrication agent substances are used for this lubrication agent layer, but paraffin wax and carnauba wax are most preferable. For example, when carnauba wax is used, a layer having a thickness of 0.3 to 2.0 μm can sufficiently exhibit its function. In order to impart elasticity to the lubrication agent layer (improve adhesion between the thermal transfer recording medium and the transfer target (recording paper)), for example, isopropylene rubber, butadiene rubber, ethylene propylene rubber, butyl rubber, nitrile Rubbers such as rubber may be added, and / or in order to provide the lubrication agent layer with adhesiveness to the substrate (prevents the lubrication agent layer from falling off), for example, ethylene-vinyl acetate copolymer. , Ethylene-ethyl acrylate copolymer, ethylene-vinyl chloride copolymer may be added. When transferring this layer, it is preferable that waxes having an appropriate melting point are blended in an amount of 30 to 90% by weight.

In addition, a flexibility-imparting agent, a heat sensitivity adjusting agent, etc. can be used as an additive for the ink layer. As examples thereof, a plasticizer such as DOP, a softening agent such as EVA, EEA, synthetic rubber or the like, a thermoplastic resin such as an acrylic resin or a polyester resin which does not deteriorate wear resistance, or the like can be used.

The thickness of the ink layer is appropriately set depending on the smoothness of the recording paper as in the adhesive layer described later. 1.0 for infinite smoothness such as polyester film
When the thickness is up to 2.5 μm, a sufficiently tough image can be formed and the thermal sensitivity is also good. For coated paper and high-quality paper, 2.
It is preferable in terms of image quality to have a thickness of about 5 to 4.0 μm, and about 1.5 to 3.0 μm is preferable for a type in which an adhesive layer is provided on the ink layer.

By providing an adhesive layer containing a thermosoftening resin as a main component on the ink layer, it is possible to further improve the fixability of the image. As the heat softening substance, an acrylic resin, a polyamide resin, an epoxy resin, or a polyester resin, which has a strong adhesive force to the transferred material, can be used,
A branched polyester resin is particularly preferable. Further, in order to improve the surface property of the adhesive layer and to cope with printing on low-smoothness paper, even if a heat-melting substance such as carnauba wax, paraffin wax, candelilla wax, polyethylene wax, fatty acid amide is added. Good. The heat-fusible substance may be used alone, but if the waxes alone are formed on the ink layer, the abrasion resistance may be deteriorated. Therefore, the composition of the waxes alone is not preferable, and the above-mentioned heat softening is not preferable. It is advisable to use a hydrophilic resin together. The ratio of the heat fusible substance / the heat softening substance is in the range of 95/5 to 0/100, and 50/50 to 0/100 is desirable in order to provide more fixing property. For the purpose, the thickness of the adhesive layer is sufficient if it is the minimum thickness necessary for adhesion, and is 0.1 to 1.5 μm, more preferably 0.3 to 1.0 μm.

[0021]

EXAMPLES The present invention will be described more specifically by way of examples. The parts here are based on weight. In each of the following examples and comparative examples, an ink layer or the like was applied onto a polyester film (base material) having a thickness of about 4.5 μm to prepare a thermal transfer recording medium.

Example 1 Carbon black 5 parts Acrylonitrile-methyl methacrylate-glycidyl methacrylate copolymer (weight ratio 25/55/20, MW = 6100, MN = 3300) 20 parts Carnauba wax 5 parts Methyl ethyl ketone 55 parts Methanol 15 parts After the ink liquid consisting of is applied on the substrate, it is dried at 60 ° C. for 2 minutes to form an ink layer having an internal void structure (about 2.0 μm thick).
A thermal transfer recording material was formed on which a film was formed.

Example 2 Carbon black 5 parts Acrylonitrile-methyl methacrylate-glycidyl methacrylate copolymer (weight ratio 25/55/20, MW = 6100, MN = 3300) 20 parts Carnauba wax 5 parts Methyl ethyl ketone 35 parts Methanol 35 parts Was applied onto a substrate and dried at 60 ° C. for 2 minutes to prepare a thermal transfer recording medium having an ink layer (about 2.0 μm thick) having an internal void structure.

Example 3 Carbon black 5 parts Acrylonitrile-methyl methacrylate-glycidyl methacrylate copolymer (weight ratio 25/55/20, MW = 6100, MN = 3300) 20 parts Carnauba wax 5 parts Methyl ethyl ketone 65 parts Water 5 parts An ink liquid consisting of the above was applied onto a substrate and then dried at 60 ° C. for 2 minutes to prepare a thermal transfer recording medium having an ink layer (about 2.0 μm thick) having a porous structure.

Example 4 Carbon black 5 parts Acrylonitrile-methyl methacrylate-glycidyl methacrylate copolymer (weight ratio 25/55/20, MW = 6100, MN = 3300) 20 parts Carnauba wax 5 parts Methyl ethyl ketone 35 parts Water 15 parts An ink liquid consisting of the above was applied onto a substrate and then dried at 60 ° C. for 2 minutes to prepare a thermal transfer recording medium on which an ink layer (about 2.0 μm thick) having a porous structure was formed.

Examples 5 to 8 The lubrication agent layer shown below was provided on the substrate so that the thickness after drying would be about 1.0 μm. Carnauba wax 9 parts Ethylene-vinyl acetate copolymer resin 1 part Toluene 90 parts Examples 1 to 4 ink layers are provided on this lubrication agent layer,
Four types of thermal transfer recording media were prepared in order as Examples 5 to 8.

Examples 9 to 16 In the same manner as in Examples 1 to 8, an ink layer or an adhesive layer made of the following composition was dried on a substrate provided with an ink layer or a lubrication agent layer and an ink layer. After thickness is about 0.5
It was provided so as to have a thickness of μm, and was set to Examples 9 to 16 in order 8
A variety of thermal transfer recording media were made. Polyester resin 9 parts Carnauba wax 1 part Toluene 90 parts

Comparative Example 1 Carbon black 5 parts Acrylonitrile-methyl methacrylate glycidyl methacrylate copolymer (weight ratio 25/55/20, MW = 6100, MN = 3300) 20 parts Carnauba wax 5 parts Methyl ethyl ketone 70 parts Ink liquid Was coated on a substrate and then dried at 60 ° C. for 2 minutes to prepare a comparative thermal transfer recording medium on which an ink layer (about 2.0 μm thick) was formed. FIG. 3 shows a state in which the ink of the ink layer has a continuous layer structure.

COMPARATIVE EXAMPLE 2 Carbon black 5 parts Methyl methacrylate-glycidyl tacrylate copolymer (weight ratio 50/56, MW = 6700, MN = 3700) 20 parts Carnauba wax 5 parts Methyl ethyl ketone 55 parts Methanol 15 parts Ink The liquid was applied on a substrate and then dried at 60 ° C. for 2 minutes to prepare a comparative thermal transfer recording medium having an ink layer (about 2.0 μm thick) formed thereon.

Comparative Example 3 5 parts of carbon black Acrylonitrile-methyl methacrylate-glycidyl methacrylate copolymer (weight ratio 25/55/20, MW = 6100, MN = 3300) 25 parts Methyl ethyl ketone 55 parts Methanol 15 parts After coating on a substrate, it was dried at 60 ° C. for 2 minutes to prepare a comparative thermal transfer recording medium on which an ink layer (about 2.0 μm thick) was formed.

A print test was performed on 19 types of thermal transfer recording media prepared as described above. The transfer paper used in this test is a label-shaped polyester film (PET) that is glued to the release surface, and mirror-coated paper (coated paper).
Was used. The printing conditions are as follows. (Printing conditions) Thermal head: Thin film line head type Platen pressure: 150 g / cm Draw-out angle of thermal transfer recording medium: 30 with respect to transfer target paper
Degree, peeling torque value: 200 g Applied energy: 10-30 mJ / mm ² Printing speed: 125: mm / sec

Subsequently, the following test was conducted on the transferred image. Thermosensitivity: Applied energy that does not cause fine line blur in mirror-coated paper. Abrasion resistance: Place a printed sample on a glass plate in a bath set at 100 ° C, and print the surface with corrugated paper 60 g / cm ²
50 reciprocating rub test was performed at a load of 30 cm / sec. Metal edge wear resistance: A rub test was conducted in the same manner with a stainless edge objective of about 1 t / cm ² . Chemical resistance: 0.5 g of various solvents (ethanol, kerosene, brake oil, toluene) contained in a cotton swab, 10 g / m
A love test was performed under a load of m ² . The printed image used here was printed on PET. Evaluation criteria: ⊚-The image is not destroyed at all. ○ -The image is hardly destroyed. Δ-The image is slightly destroyed. X-The image is completely destroyed.

Table 1 shows the measurement results of thermal sensitivity and ink layer shearing force of Examples 1 to 4 and Comparative Example 1. The shear force of the ink layer was measured by a tensile tester manufactured by Minebea. Table 2 shows the evaluation results of heat resistance wear resistance, metal edge wear resistance, and chemical resistance for Examples 1 to 16 and Comparative Examples 1 to 3.
It was shown to. FIG. 4 shows the internal void structure in Example 1, and FIG.
FIG. 6 shows the porous structure in Example 3, and FIG. 6 shows Comparative Example 1
3 is a surface photograph (× 2000) of each ink layer of the continuous layer structure in FIG. From these photographs, it was confirmed that the irregularities were the particles of carnauba wax, but the internal void structure could consist of aggregates or a porous structure.

[0034]

[Table 1]

[0035]

[Table 2]

As is clear from Table 1, in comparison with Comparative Example 1 in which the ink layer is a continuous layer, Example 1 having an internal void structure is used.
2 and 2, and Examples 3 and 4 having a porous structure have improved thermal sensitivity. In addition, the shearing force of the ink layer is 250 gf /
The heat sensitivity of Examples 2 and 4 having a value of cm or less is higher than that of Examples 1 and 3 having a large shearing force. Then, as is clear from Table 2, the lubrication agent is better in Example 1 in which the ink layer contains the lubrication agent and in Examples 5 to 8 in which the lubrication agent layer is provided between the base material and the ink layer. Further, it is more excellent in image resistance such as heat abrasion resistance, metal edge resistance, and chemical resistance than Comparative Example 3 having no lubricity imparting agent layer. Furthermore, again
Examples 9 to 16 in which the adhesive layer is provided on the ink layer are more excellent in image resistance than Examples 1 to 8 in which the adhesive layer is not provided.

[0037]

According to the first and second aspects of the invention, since the ink layer has an internal void structure or a porous structure, the thermal sensitivity is improved without impairing the heat resistance and heat resistance of the transferred image. According to the invention of claim 3, the shearing force of the ink layer is 2
Since it is 50 gf / cm or less, the heat sensitivity is further improved. According to the inventions of claims 4 and 5, since the lubrication agent is contained in the ink layer or is provided between the ink layers using the lubrication layer as a base material, the transferred image is provided with lubricity and abrasion resistance. Further improve. According to the sixth aspect of the invention, since the adhesive layer containing a thermosoftening resin as a main component is provided on the ink layer, the fixing property of the transferred image is improved and the abrasion resistance is further improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing that an ink layer has an internal void structure.

FIG. 2 is a schematic diagram showing that the ink layer has a porous structure.

FIG. 3 is a schematic diagram showing that the ink layer has a continuous layer structure (without an internal void structure or a porous structure).

FIG. 4 is a surface photograph (× 2000) of an ink layer in Example 1, taken with an electron microscope.

FIG. 5 is a surface photograph (× 2000) of an ink layer in Example 2, taken with an electron microscope.

FIG. 6 is a surface photograph (× 2000) of an ink layer in Comparative Example 1, taken by an electron microscope.

[Explanation of symbols]

 11 voids (internal void structure) 12 communicating holes (porous structure)

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[Procedure amendment]

[Submission date] January 6, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a schematic diagram showing that an ink layer has an internal void structure.

FIG. 2 is a schematic diagram showing that the ink layer has a porous structure.

FIG. 3 is a schematic diagram showing that the ink layer has a continuous layer structure (without an internal void structure or a porous structure).

FIG. 4 is a photograph (× 2000) showing the particle structure of the ink layer in Example 1 under an electron microscope.

FIG. 5 is a photograph (× 2000) showing the particle structure of the ink layer in Example 2 under an electron microscope.

FIG. 6 is a photograph (× 2000) showing the particle structure of the ink layer in Comparative Example 1 taken with an electron microscope.

[Explanation of symbols] 11 voids (internal void structure) 12 communicating holes (porous structure)

Claims (6)

[Claims] 1. An ink layer comprising, as a main component, a colorant and an acrylic copolymer resin containing acrylonitrile and / or methacrylonitrile as a monomer component on a substrate, wherein the ink layer is internally formed. A thermal transfer recording medium having a void structure. 2. An ink layer comprising, as a main component, a colorant and an acrylic copolymer resin containing acrylonitrile and / or methacrylonitrile as a monomer component on a substrate, wherein the ink layer is porous. A thermal transfer recording medium having a quality structure. 3. The shear strength of the ink layer is 250 gf /
The thermal transfer recording medium according to claim 1 or 2, having a size of not more than cm. 4. The thermal transfer recording medium according to claim 1, 2 or 3, wherein the ink layer further contains a lubricity imparting agent. 5. The thermal transfer recording medium according to claim 1, wherein a layer containing a lubricant is provided between the base material and the ink layer. 6. The thermal transfer recording medium according to claim 1, wherein an adhesive containing a thermosoftening resin as a main component is provided on the ink layer.