JP2009073102A - Thermal transfer recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal transfer recording medium equipped with a heat-resistant protective layer having sufficient heat-resistance, film forming property, and lubricating property, that prevents a heat-molten product from the heat-resistant protective layer or refuse caused by peeling or wear of the heat-resistant protective layer from adhering on a thermal head, has excellent print quality, and has superior traveling performance that expresses sufficient heat resistance and lubricating function even in high recording speed. <P>SOLUTION: In the thermal transfer recording medium provided with a thermal transfer ink layer on the surface of a base material and a heat-resistant protective layer on a surface on the back of the base material in abutment with the thermal head, the heat-resistant protective layer is formed using a cellulose derivative, zinc stearate, and a silicone-based resin, and a difference between the coefficient of dynamic friction of the ink layer and that of the heat-resistant protective layer is 0.0845 or more. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a thermal transfer recording medium, and more particularly to a thermal transfer recording medium excellent in heat resistance and lubricity when an image is formed by a thermal head.

  In recent years, with the development of office automation, thermal transfer recording systems have been adopted in various terminal devices such as facsimiles and printers. In this recording method, heat-sensitive transfer material coated with heat-meltable ink or heat-sublimation ink is superimposed on recording paper such as plain paper, and the ink is transferred from the heat-sensitive transfer material to the recording paper by heating using a thermal head. And recording.

In the recording method using the thermal head, the heat generated from the thermal head passes through the base film to melt or sublimate the thermal transfer ink and transfer the ink to the recording paper, so the ink layer melts but the base film is a plastic film or the like Must not melt.
However, since it is necessary to increase the recording speed and to record on recording paper with a rough surface, the amount of heat and pressure applied to the base film are significantly increased by increasing the heat generation amount of the thermal head or increasing the platen roll pressure. . As a result, the base film is melted and heat-sealed or damaged. As a result, there is a problem that not only normal recording cannot be performed but also the thermal head is damaged.

Conventionally, in order to improve such a phenomenon, several attempts have been proposed to provide a protective layer having excellent lubricity and heat resistance on the back surface of the base film.
For example, it is known to use silicone made of organopolysiloxane for the heat-resistant protective resin layer. Since the cohesive force of silicone is weak in this material, the adhesive strength between the base sheet made of a plastic film and the heat-resistant protective resin layer becomes insufficient. For this reason, the heat-resistant protective resin layer is peeled off from the thermal transfer sheet if a strong pressure is applied to the thermal transfer sheet while the thermal transfer sheet is running during the thermal printing process on the thermal transfer sheet. This may cause defects such as damage to the thermal head resistor, shortening its life, etc. due to falling off and adhering to the thermal head to inhibit heat dissipation of the thermal head, or reducing thermal conductivity. Have. In addition, the heat resistance is weak, and the base film melts and heat-fuses or breaks, which may cause damage to the thermal head.

  It is also known to use a silicone graft or a block acrylic copolymer for the heat-resistant protective layer. This is somewhat improved in heat resistance, but the film forming property of the acrylic component is insufficient, the heat-resistant protective layer may be peeled off from the base material, and the heat-resistant protective layer is easily worn. There is a drawback of causing poor running.

  It is also known to use a silicone graft or block acrylic copolymer mixed with a silane coupling agent in the heat-resistant protective layer. In this case, the film formation of the acrylic component is slightly improved by a partial reaction, but the unreacted silane coupling agent becomes a residue and adheres to the thermal head or is fused to dissipate heat from the thermal head. It has drawbacks such as obstructing or lowering thermal conductivity, thereby damaging the thermal head resistor and shortening its life.

  As for heat resistance, many are known which undergo a curing reaction with a hydroxyl group residue in a resin and isocyanate, melamine, epoxide, or the like. These require a heating and aging process after coating the heat-resistant protective layer, which has the disadvantage that the process becomes complicated and the cost is increased. In addition, problems such as shortening the pot life of the coating liquid have also occurred.

  Further, the above-mentioned conventional silicone has insufficient lubricity, and the ribbon winding torque is often insufficient at the time of core printing in thermal transfer recording as shown in FIG.

In addition, as shown in Patent Document 1, the invention uses a weight ratio of 50:50 to 80:20 of a silicone-modified acrylic resin and a silicone-modified urethane resin for a back layer made of a heat-resistant resin, and as shown in Patent Document 2, a heat-resistant slip property. The invention is an invention comprising a melamine resin, an organic silane compound, and a heat-resistant lubricant, each of which forms a crosslinked structure independently, and as shown in Patent Document 3, the thermal transfer ink layer contains a polyol resin, and the back layer comprises a polyol resin and a crosslinking agent. And the invention using a copolymer of a reactive silicone and a vinyl monomer and a self-crosslinking acrylic resin in a heat-resistant slipping layer as shown in Patent Document 4 are known. .
JP 2003-63155 A JP 2004-249663 A JP-A-2005-144852 JP 2001-171248 A

  The present invention has been made in view of the above-mentioned conventional problems, and does not particularly require steps such as heating and aging, and the heat-resistant protective layer has sufficient heat resistance, film formability, sliding properties immediately after coating and drying. It is possible to prevent hot melt from the heat-resistant protective layer or debris from the heat-resistant protective layer from being attached to the thermal head, and the print quality is good, even at high recording speeds. It is an object of the present invention to provide a thermal transfer recording medium that exhibits sufficient heat resistance and lubricity and is excellent in running performance.

  In order to solve the above problems, the invention described in claim 1 is a thermal transfer recording medium in which a thermal transfer ink layer is provided on the surface of a base material, and a heat-resistant protective layer is provided on a surface of the back surface of the base material that contacts the thermal head. The heat-resistant protective layer is formed using a cellulose derivative, zinc stearate, and a silicone-based resin, and the difference between the dynamic friction coefficient of the ink layer and the dynamic friction coefficient of the heat-resistant protective layer is 0.0845 or more. Features a medium.

  According to a second aspect of the present invention, in the thermal transfer recording medium according to the first aspect, the cellulose derivative used for forming the heat-resistant protective layer is cellulose acetate propionate or ethyl hydroxyethyl cellulose.

  According to a third aspect of the present invention, there is provided a silicone-modified acrylic copolymer obtained by polymerizing a reactive silicone and a vinyl monomer, wherein the silicone resin used for forming the heat-resistant protective layer is the vinyl monomer. Is an acrylic or methacrylic resin.

  The invention according to claim 4 is the invention according to claim 3, wherein the silicone-modified acrylic copolymer is obtained by using a vinyl monomer further having a hydrolyzable silyl group as the vinyl monomer. It is characterized by being able to.

  The invention described in claim 5 is characterized in that, in the invention described in claim 4, the vinyl monomer having a hydrolyzable silyl group is used in an amount of less than 1%.

  According to a sixth aspect of the present invention, in the thermal transfer recording medium according to any one of the first to fifth aspects, the zinc stearate is contained in the heat-resistant protective layer in the form of particles, and the average particle size is 0.00. It is the range of 1-0.5 micrometer.

  A seventh aspect of the present invention is the thermal transfer recording medium according to any one of the first to sixth aspects, wherein the thickness X of the base material is in a range represented by 3.5 μm ≦ X <4.5 μm. It is characterized by being.

  The invention according to claim 8 is the thermal transfer recording medium according to any one of claims 1 to 7, wherein the heat-resistant protective layer is in a range of 0.01 to 2.00 μm.

  According to the present invention, it is possible to prevent the occurrence of debris due to peeling or abrasion of the hot melt from the heat-resistant protective layer or the heat-resistant protective layer, thereby preventing the adhesion to the thermal head, leading to excellent print quality, and lubricity. In addition, it is possible to obtain a thermal transfer recording medium that is excellent in running property with less peeling of the heat-resistant protective layer from the substrate and wear of the heat-resistant protective layer.

Hereinafter, embodiments of the thermal transfer recording medium of the present invention will be described in detail.
As described above, the present invention relates to a thermal transfer recording medium in which a thermal transfer ink layer is provided on the surface of a substrate, and a heat-resistant protective layer is provided on the surface of the substrate that is in contact with the thermal head. It is characterized by comprising zinc acid and a silicone resin, and the difference between the dynamic friction coefficient of the ink layer and the dynamic friction coefficient of the heat-resistant protective layer as the back layer is 0.0845 or more.

As the cellulose derivative used in the present invention, cellulose derivatives having a softening temperature of 142 ° C. or more such as cellulose acetate, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, etc. are used. Among them, cellulose acetates (cellulose acetate or derivatives thereof; cellulose acetate, cellulose) Examples thereof include acetate butyrolate and cellulose acetate propionate, and cellulose acetate propionate is particularly desirable.
Among cellulose acetates, cellulose acetate having an acetylation degree of 50 to 55% is desirable because it has a low viscosity in terms of solution viscosity. An acetic acid content of 47.7 to 55.9% is desirable because of its excellent solubility in organic solvents. Moreover, the said cellulose derivative may be used independently and may use 2 or more types together.

The zinc stearate used in the present invention is commercially available and can be handled, but a melting point in the range of 115 to 125 ° C. is desirable. When the temperature is lower than 115 ° C., it is difficult to form a particulate structure when the heat-resistant protective layer is formed. When the temperature exceeds 125 ° C., it is difficult to melt by heat from the thermal head during thermal transfer recording, and the function as a lubricant is difficult to be exhibited.
The zinc stearate used in the present invention is preferably in the form of particles, and the particle size is more preferably in the range of 0.2 to 0.4 μm.

  The silicone resin used in the heat-resistant protective layer of the present invention is basically a compound having a siloxane bond, and typical examples include compounds represented by the following general formula (1).

The silicone resin represented by the general formula (1) is oily, waxy or resinous (including rubbery) depending on the type of R, the degree of polymerization, the skeleton structure, and the like. It does not necessarily have to have a siloxane bond as a skeleton of the main chain (that is, a linear silicone compound), and may have a siloxane bond in the side chain or be branched. R is independently an alkyl group, phenyl group, hydrogen atom, fluorine atom, hydroxyl group, hydroxyl group-containing substituent, carboxyl group, carboxyl group-containing substituent, ether bond-containing substituent, epoxy group, epoxy group-containing substituent, amide It represents a monovalent substituent such as a bond-containing substituent, an amino group and an amino group-containing substituent, and a monovalent atom such as a hydrogen atom and a fluorine atom, and n is usually in the range of 10 to 10,000. In the case where the silicone resin represented by the general formula (1) has a siloxane bond as a side chain or is branched, the R group which is a side chain group has a siloxane bond (— (Si (R ₂ )). O) _n- : where R is the same as R in the general formula.
Furthermore, what mix | blended a thickener or an additive with these can be used. In addition, a modified copolymer such as a copolymer of reactive silicone and a vinyl monomer can be used, and a silicone-modified acrylic copolymer is particularly preferably used.

  Examples of the reactive silicone include a silicone compound having a functional group such as an OH group and an epoxy group at one end, a polyalkylsiloxane compound having a radically polymerizable unsaturated group at least one end, and the molecular weight thereof is 100. About 50,000 is preferable. These compounds may be used alone or in combination of two or more. In particular, the film strength can be increased by using a reactive silicone having a molecular weight of less than 5000. The amount of reactive silicone in the whole modified polymer is preferably in the range of 5 to 50% by weight, particularly preferably in the range of 10 to 40% by weight.

Examples of the vinyl monomer include methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, and tetrahydrofur Furyl acrylate, stearyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, tetrahydrofurfuryl methacrylate, stearyl methacrylate , Aliphatic such as lauryl methacrylate Or nitrile monomers such as cyclic acrylate, acrylonitrile, methacrylonitrile, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, acrylamide, methacrylamide, N, N-methylolacrylamide, N, N-dimethylacrylamide, Amides such as diacetone acrylamide and methyl acrylamide glycolate methyl ether, N, N-dimethylaminoethyl methacrylate, N, N-diethylaminoethyl methacrylate, N, N-dimethylaminopropyl methacrylate, N, N-dimethylaminoethyl acrylate, Amino group-containing monomers such as N, N-diethylaminoethyl acrylate and N, N-dimethylaminopropyl acrylate, and epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate Body, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate. These monomers such as acrylic acid and methacrylic acid are used alone or in combination. The above examples are not intended to limit the present invention.
In particular, methyl methacrylate (polymer Tg: 105 ° C.), methacrylic acid (polymer Tg: 130 ° C.) and the like (polymer) are used as monomers in terms of glass transition temperature and copolymerization reactivity. It is preferable to form a polymer. The amount of the vinyl monomer in the modified copolymer is preferably about 10 to 85% by weight.

The modified copolymer used for forming the heat-resistant protective layer constituting the thermal transfer recording medium of the present invention needs to contain a vinyl monomer having a hydrolyzable silyl group.
Examples of vinyl monomers having such hydrolyzable silyl groups include γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, and γ-methacryloxypropylmethyldidisilane. Silane coupling agents such as ethoxysilane, γ-methacryloxypropylmethoxyethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane can be used.
The amount of the vinyl monomer having a hydrolyzable silyl group in the modified copolymer is preferably about 1 to 20% by weight.
In addition, for the formation of the heat-resistant protective layer, the composition ratio of the monomer having a hydrolyzable silyl group in the silicone-modified acrylic copolymer as a raw material for the formation is preferably 1% or less in terms of heat resistance and film formability. . The thermal transfer recording medium of the present invention having a heat-resistant protective layer obtained using a coating solution from such a raw material is excellent in heat resistance and weather resistance (water resistance).

  The blending ratio of the cellulose derivative, zinc stearate, and silicone resin for forming the heat-resistant protective layer constituting the thermal transfer recording medium of the present invention is the ratio of the dynamic friction coefficient between the ink layer and the heat-resistant protective layer of the back layer. If a difference is 0.0845 or more, it will not restrict | limit in particular and it can be used by a desired structure ratio. Desirably, cellulose derivative / zinc stearate / silicone resin (weight ratio) = (80 to 85) / (5 to 7) / (5 to 10).

  For the formation of the heat-resistant protective layer constituting the thermal transfer recording medium of the present invention, a coating solution obtained by dissolving or dispersing the silicone resin or the modified copolymer in a solvent such as methyl ethyl ketone is used using a coating means such as a wire bar. Then, it may be applied to the back surface of the substrate and dried. As a drying temperature, the range of 50-100 degreeC is preferable, and 70-100 degreeC is especially preferable. The thickness of the heat-resistant protective layer constituting the thermal transfer recording medium of the present invention is preferably from 0.01 to 2.00 μm, particularly preferably from 0.04 to 0.6 μm.

  As the base material used in the thermal transfer recording medium of the present invention, polycarbonate, polyarylate, polyetherimide, polysulfone, polyphenyl ether, polyamideimide, polyimide, polyethylene naphthalate, polyphenyl sulfide, polyether ether ketone, fluororesin In addition to films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polybutylene naphthalate (PBN), polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, nylon (polyamide resin), etc. Can be used. A film having biaxial orientation is preferred. The thickness of the substrate is preferably 6 μm or less from the viewpoint of sensitivity in thermal transfer recording. In particular, from the viewpoint of recording speed, it is more desirable that the thickness X of the base material satisfies 3.5 μm ≦ X <4.5 μm.

  As the thermal transfer ink layer in the thermal transfer recording medium of the present invention, a conventionally known ink layer is used as it is, and is not particularly limited. That is, the thermal transfer ink layer used in the present invention is composed of colorants, waxes, resins, lubricants, additives such as surfactants, and the like. In this case, as the colorant, for example, carbon black, Bengala, Rayleigh C, Fast Sky Blue, Benzidine Yellow, Phthalocyanine Green, Phthalocyanine Blue, direct dye, oily dye, basic dye and other pigments, dyes and the like are used. .

  As waxes, for example, natural wax such as carnauba wax, oricuri wax, candelilla wax, Japan wax, cane wax, montan wax, ozokerite, microcrystalline wax, ceresin wax, paraffin wax, Fischer-Tropsch wax, Synthetic waxes such as low molecular weight polyethylene, oxidized wax, hydrogenated wax and the like can be mentioned.

  Examples of the resins include polyacrylic acid, polyacrylic acid ester, polymethacrylic acid, polymethacrylic acid ester, polyacrylamide, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, polyvinyl chloride, poly Vinyl resins such as vinylidene chloride, cellulose resins such as ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxy cellulose, hydroxypropyl cellulose, methyl cellulose, and cellulose acetate, polyester resins, polyacetal resins, epoxy resins, terpene resins, rosin resins, fluorine resins, silicones Resin etc. are mentioned. As additives, fatty acids, fatty acid metal salts, fatty acid esters, fatty acid amides, inorganic salts, nonionic surfactants, cationic surfactants, anionic surfactants, amphoteric surfactants, and the like can be used. It is not limited. The thermal transfer ink layer can be formed by a known method.

  According to the thermal transfer recording medium of the present invention described above, the thermal melt from the heat-resistant protective layer or the residue due to peeling or abrasion of the heat-resistant protective layer is prevented from adhering to the thermal head, and the print quality is excellent. In addition, it is possible to obtain a thermal transfer recording medium having good lubricity, and excellent in running properties with less peeling of the heat-resistant protective layer from the substrate and wear of the heat-resistant protective layer.

  In addition, according to the present invention, a thermal transfer recording medium having a heat-resistant protective layer using cellulose acetate propionate can provide a thermal transfer recording medium having good coating properties during production and excellent print quality. it can.

  Further, according to the present invention, a copolymer from a vinyl monomer having a hydrolyzable silyl group is used in addition to the reactive silicone and the vinyl monomer as the silicone resin of the heat-resistant protective layer. A thermal transfer recording medium having excellent lubricity and excellent print quality can be obtained.

  According to the present invention, the thermal transfer recording medium obtained by using less than 1% of the hydrolyzable silyl group monomer composition in the copolymer for forming the heat-resistant protective layer is excellent in ribbon heat resistance.

  Further, according to the present invention, zinc stearate is contained in the heat-resistant protective layer in the form of dispersed particles, and the average particle diameter thereof is 0.1 to 0.5 μm. A medium can be obtained.

  Further, according to the present invention, since the thickness X of the base material of the thermal transfer recording medium is 3.5 μm ≦ X <4.5 μm, a thermal transfer recording medium that can cope with a printing speed up to 12 ips or more can be obtained. .

  Hereinafter, the thermal transfer recording medium of the present invention will be described more specifically with reference to examples and comparative examples. The parts, percentages and ratios shown below are all based on weight.

Ethyl hydroxyethyl cellulose 85 parts Zinc stearate (average particle size 0.1 μm) 5 parts Silicone resin 10 parts of MEK / cyclohexanone = 95/5 in 9% solution Polyethylene terephthalate (PET) film about 4.5 μm thick The back surface of this was coated with a wire bar and dried at 100 ° C. for 5 seconds to form a heat-resistant protective layer having a thickness of about 0.4 μm. Further, the following thermal transfer ink component dispersion was applied to the surface of the film and dried to provide a thermal transfer ink layer having an adhesion amount of about 2.8 g / m ² to obtain a thermal transfer recording medium.
Thermal transfer ink component Carnauba wax 6 parts Paraffin wax 8 parts Carbon black 4 parts Toluene 82 parts

Cellulose acetate propionate 85 parts Zinc stearate (average particle size 0.1 μm) 5 parts Silicone resin 10 parts of MEK / cyclohexanone = 95/5 in 9% solution Polyethylene terephthalate (PET) film about 4.5 μm thick The back surface of this was coated with a wire bar and dried at 100 ° C. for 5 seconds to form a heat-resistant protective layer having a thickness of about 0.4 μm. Further, the same thermal transfer ink layer as that of Example 1 was provided on the surface of the film to obtain a thermal transfer recording medium.

Cellulose acetate propionate 85 parts Zinc stearate (average particle size 0.1 μm) 5 parts Reactive silicone (molecular weight 10,000) 3 parts Methyl methacrylate 6 parts γ-methacryloxypropylmethyldiethoxysilane 1 part MEK / cyclohexanone = 95 Apply a 9% solution at 5/5 to the back of a polyethylene terephthalate (PET) film with a thickness of about 4.5μm with a wire bar and dry at 100 ° C for 5 seconds to form a heat-resistant protective layer with a thickness of about 0.4μm did. Further, the same thermal transfer ink layer as in Example 1 was provided on the surface of the film to obtain a thermal transfer recording medium. The monomer ratio at this time is 1.2%.

Cellulose acetate propionate 85 parts Zinc stearate (average particle size 0.1 μm) 5 parts Reactive silicone (molecular weight 10,000) 3 parts Methyl methacrylate 5 parts Methacrylic acid 1 part γ-Methacryloxypropylmethyldiethoxysilane 1 part MEK / Cyclohexanone = 95/5 in 9% solution, coated on the back of polyethylene terephthalate (PET) film with a thickness of approximately 4.5 μm with a wire bar, dried at 100 ° C. for 5 seconds, and heat resistant with a thickness of approximately 0.4 μm A protective layer was formed. Further, the same thermal transfer ink layer as in Example 1 was provided on the surface of the film to obtain a thermal transfer recording medium. The monomer ratio at this time is 0.2%.

Cellulose acetate propionate 85 parts Zinc stearate (average particle size 0.5 μm) 5 parts Silicone resin 10 parts of MEK / cyclohexanone = 95/5 in 9% solution Polyethylene terephthalate (PET) film about 4.5 μm thick The back surface of this was coated with a wire bar and dried at 100 ° C. for 5 seconds to form a heat-resistant protective layer having a thickness of about 0.4 μm. Further, the same thermal transfer ink layer as that of Example 1 was provided on the surface of the film to obtain a thermal transfer recording medium.

Cellulose acetate propionate 85 parts Zinc stearate (average particle size 0.5 μm) 5 parts Silicone resin 10 parts of MEK / cyclohexanone = 95/5 in 9% solution Polyethylene terephthalate (PET) film about 3.5 μm thick The back surface of this was coated with a wire bar and dried at 100 ° C. for 5 seconds to form a heat-resistant protective layer having a thickness of about 0.4 μm. Further, the same thermal transfer ink layer as that of Example 1 was provided on the surface of the film to obtain a thermal transfer recording medium.

[Comparative Example 1]
Reactive silicone (molecular weight 10,000) 30 parts Methyl methacrylate 65 parts polyethylene terephthalate having a thickness of about 4.5 μm in a 5% solution with MEK / ethanol = 5/5 A (PET) film was coated on the back surface with a wire bar and dried at 100 ° C. for 5 seconds to form a heat-resistant protective layer having a thickness of about 0.4 μm. Further, the same thermal transfer ink layer as that of Example 1 was provided on the surface of the film to obtain a thermal transfer recording medium.

[Comparative Example 2]
Reactive silicone (molecular weight 10,000) 30 parts Methyl methacrylate 70 parts is polymerized so that the weight average molecular weight is 30000, 5 parts of γ-methacryloxypropylmethyldiethoxysilane are mixed, and MEK / ethanol = 5/5. A 5% solution was applied to the back surface of a polyethylene terephthalate (PET) film having a thickness of about 4.5 μm with a wire bar and dried at 100 ° C. for 5 seconds to form a heat-resistant protective layer having a thickness of about 0.4 μm. Further, the same thermal transfer ink layer as that of Example 1 was provided on the surface of the film to obtain a thermal transfer recording medium.

〔Evaluation test〕
Printing is performed using the thermal transfer recording media obtained in the above examples and comparative examples, and the thermal head is soiled [the presence or absence of hot melt adhering to the thermal head surface (hot melt adhering), and physically falling off. The presence / absence of adhesion of debris to the surface of the thermal head (deposition of debris)] was evaluated. The printing conditions and evaluation criteria are shown below.

Printing conditions Thermal head: Thin film line thermal head (density 12 / mm) (Kyocera)
Applied energy: 25 mJ / mm ²
Printing speed: 100mm / sec and 300mm / sec
Platen pressing: 350 gf / cm
Receiving paper: Cast coat (manufactured by Lintec)
Printing pattern: under printing conditions of a code width of 30 mm and a length of about 40 mm
CODE39 vertical bar code (Narrow2: Wide6dot)
The thermal transfer printing is performed continuously for 100 m under the printing conditions of the above, the presence or absence of hot melt adhering to the thermal head heating element (head fusing property: ribbon heat resistance), and to the thermal head heating element that is physically dropped The presence or absence of adhesion (head residue adhesion) was confirmed and evaluated.

The ribbon transportability was confirmed by carrying the thermal transfer recording medium in the state shown in FIG. 1 in the recording apparatus and printing in a low temperature environment (0 ° C., 30%). At this time, (transport ribbon length) / (receiving paper label length) = transport rate (%).
Near the end of use of the thermal transfer ribbon, the winding diameter of the used ribbon becomes large, so the torque of the printer take-up shaft tends to be insufficient, and if the sliding between the heat-resistant protective layer and the thermal head is insufficient, poor conveyance is likely to occur ( (See FIG. 1).
・ ANSI is a numerical value and grade representing the barcode reading quality determined by the American National Standards Institute, and is divided into five grades as shown in Table 1 below. A quick check QC500B was used for the measurement.
For lubricity, a dynamic friction coefficient was measured using a HEIDON surface property tester (manufactured by Shinto Kagaku Co., Ltd.) under measurement conditions of a load of 50 gf, a point contact, and an objective 9.5 mm diameter SUS ball.
Moreover, the presence or absence (conveyability) of the trouble at the time of conveyance on the said printing conditions was confirmed and evaluated.
The evaluation results are shown in Table 2.

Evaluation criteria and head fusing properties (◎: None at all △: Slightly but no trouble in printing ×: Large amount of adhesion)
・ Coating property <viscosity (25 ° C.)> (◯: 1 to 10 cp Δ: 11 to 25 cp ×: 26 cp or more)
The coatability represents the uniformity of the back layer coating film. The lower the viscosity, the easier the coating film is formed. Moreover, if the coating property is not sufficient, the thickness of the coating film tends to be non-uniform, which affects the head fusing property (ribbon heat resistance) and the like.
・ ANSI grade and numerical values

  From Table 2 above, by forming the ink layer according to the present invention and defining the difference between the dynamic friction coefficient of the ink layer and the dynamic friction coefficient of the back layer to be 0.0845 or more, the coating property is good, and the head fusion and the head residue adhesion It can be seen that a good thermal transfer recording medium with less printed images can be provided.

It is a figure for demonstrating the use condition and conveyance property of a thermal transfer ribbon, (a) shows the use start of a thermal transfer ribbon, (b) shows the completion | finish use of a thermal transfer ribbon.

Claims (8)

A thermal transfer recording medium in which a thermal transfer ink layer is provided on the surface of the substrate, and a heat-resistant protective layer is provided on the surface of the back surface of the substrate that contacts the thermal head,
The heat-resistant protective layer is formed using a cellulose derivative, zinc stearate, and a silicone resin, and the difference between the dynamic friction coefficient of the ink layer and the dynamic friction coefficient of the heat-resistant protective layer is 0.0845 or more. Thermal transfer recording medium.   2. The thermal transfer recording medium according to claim 1, wherein the cellulose derivative used for forming the heat-resistant protective layer is cellulose acetate propionate or ethyl hydroxyethyl cellulose.   The silicone resin used for forming the heat-resistant protective layer is a silicone-modified acrylic copolymer polymerized from a reactive silicone and a vinyl monomer, and the vinyl monomer is an acrylic or methacrylic resin. The thermal transfer recording medium according to claim 1, wherein the thermal transfer recording medium is a recording medium.   4. The thermal transfer recording medium according to claim 3, wherein the silicone-modified acrylic copolymer is obtained by using a vinyl monomer further having a hydrolyzable silyl group as the vinyl monomer.   The thermal transfer recording medium according to claim 4, wherein the vinyl monomer having a hydrolyzable silyl group is used in an amount of less than 1%.   6. The zinc stearate is contained in the heat-resistant protective layer in the form of particles, and the average particle size is in the range of 0.1 to 0.5 [mu] m. Thermal transfer recording medium.   7. The thermal transfer recording medium according to claim 1, wherein the thickness X of the base material is in a range represented by 3.5 μm ≦ X <4.5 μm.   The thermal transfer recording medium according to claim 1, wherein the heat-resistant protective layer has a range of 0.01 to 2.00 μm.

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