JPH06435B2 - Ink for thermal transfer - Google Patents

Description

The present invention relates to an ink for forming an ink layer for thermal transfer in a thermal transfer sheet, that is, an ink for thermal transfer.

[Prior Art] A thermal transfer ink layer of a thermal transfer sheet used in a thermal transfer recording method is formed by an ink obtained by melting and kneading a colorant into a binder component composed of a wax such as a natural wax or a synthetic wax. It was common.

[Problems to be solved by the invention]

By the way, the thermal transfer ink containing the wax and the colorant as composition components, the wax in the ink component is a mixture of compounds having different molecular weights, and thus the thermal transfer ink layer formed of the thermal transfer ink. The binder component therein has a wide temperature range (melting point width) of 5 to 10 ° C. from the start of melting by heating to the completion of melting,
Therefore, in the thermal recording method using the thermal transfer sheet having the thermal transfer ink layer with the thermal transfer ink, not only the thermal transfer becomes insufficient depending on the temperature of the thermal head used, but also the vicinity of the printed portion The bleeding of printing that is caused by the melting of wax components having a relatively low melting point in the thermal transfer ink layer is inevitable,
It has a drawback that it is difficult to transfer it to a character or shape having a clear contour.

Furthermore, when natural wax is used as the wax component in the thermal transfer ink, the composition thereof varies depending on the place of origin, weather conditions, etc., and thus it is difficult to mass-produce thermal transfer ink of a certain quality. Have.

Also, wax is soft at room temperature and easily scratched,
It also has the drawback of being complicated to handle.

On the other hand, the thermal transfer ink of the present invention does not contain the wax component in the composition components, is excellent in thermal transfer property, and is capable of obtaining a thermal transfer layer having clear characters and shapes with a clear contour. is there.

[Means for solving problems]

In the thermal transfer ink of the present invention, the binder component in the ink is represented by the general formula CH ₂ ═C (R ¹ ) COOR ² [wherein R ¹ is H, CH
₃ , C ₂ H ₅ or C ₃ H ₇ and R ² represents a long-chain alkyl group having 17 or more carbon atoms] or a homopolymer of a radical-polymerizable unsaturated monomer represented by It is composed of a copolymer of saturated monomers and has a melting point of 50 ° C. or higher and lower than 100 ° C. and a melting point width of 4.5 ° C. or lower.

The vinyl polymer having a melting point of 50 ° C. or higher and lower than 100 ° C. usually has a molecular weight of about 1,000 to 100,000 and a melt viscosity of about 10 to 3,000 cp.

Further, since the vinyl polymer as a binder component in the thermal transfer ink of the present invention has a melting point width of 4.5 ° C. or less, a polymer having a substantially uniform molecular weight is used.

Formula ^{_{CH 2 = C (R 1)}} COOR 2 [ In the formula, ^{R 1} represents _H, a CH _3, C 2 _{H 5} or _C 3 _{H 7,} ^{R 2} is a more long chain alkyl group 17 carbon atoms] The vinyl-based polymer composed of the polymer of the radical-polymerizable unsaturated monomer represented by (3) has a very sharp melting point, that is, has a narrow melting point width.

This property of the polymer is due to the fact that the crystallinity in the molecule of the polymer is extremely high because the alkyl group involved in the ester bond in the molecule is a long chain having 17 or more carbon atoms, and the alkyl group is heated during heating. It is presumed that this is due to the disappearance of crystallinity and fluidity.

Formula ^{_{CH 2 = C (R 1)}} COOR 2 [ In the formula, ^{R 1} represents _H, a CH _3, C 2 _{H 5} or _C 3 _{H 7,} ^{R 2} is a more long chain alkyl group 17 carbon atoms] Radical-polymerizable unsaturated monomers represented by are, for example, heptadecyl alcohol, stearyl alcohol, nonadecyl alcohol,
Alcohols such as eicosyl alcohol, hene eicosyl alcohol, docosyl alcohol, tricosyl alcohol, and tetracosyl alcohol, and the general formula CH ₂ = C
(R ¹ ) COOH [wherein R ¹ is H, CH ₃ , C ₂ H ₅
Or C ₃ H ₇ ] is an ester of acrylic acid or α-alkylacrylic acid.

The vinyl polymer used as the binder component of the thermal transfer ink of the present invention can be obtained by ordinary solution polymerization, emulsion polymerization, pearl polymerization or the like with the radically polymerizable unsaturated monomer.

The composition components other than the binder component of the thermal transfer ink of the present invention are no different from the composition components in the conventional thermal transfer ink using wax as a binder. For example, as the colorant as a composition component in the thermal transfer ink, among organic or inorganic dyes or pigments, those having characteristics as an ink for forming the thermal transfer ink layer, for example, exhibiting sufficient coloring density However, it is preferable that it does not discolor or fade due to photothermal humidity or the like. Further, as a colorant or a colorant-equivalent substance, it is colorless when not heated, but it has a property of developing color by heating and maintaining its hue as it is, or contacting with a substance coated on the surface of a transfer target. As a matter of course, a material having a property of causing the surface of the transferred material to be colored can be used. The ratio of the colorant to the vinyl polymer as a binder component in the thermal transfer ink is 1 to 80% by weight of the colorant: 99 to 20% by weight of the binder component, preferably 2 to 20% by weight of the colorant: The binder component is about 98 to 80% by weight.

Further, as other composition components added as necessary to constitute the thermal transfer ink of the present invention, for example, a softening agent such as mineral oil or vegetable oil, a thermal conductivity improver such as metal powder, Microsilica, extender pigments such as calcium carbonate or kaolin, transferability improving agents such as polyhydric alcohols, xylene, toluene, trichlene,
Solvents or diluents such as white spirit, ethyl acetate, n-butyl acetate, methanol, ethanol, isopropanol, n-butanol, ethylcyclohexane, ethylcellosolve, butylcellosolve, cyclohexanone, etc. are present.

The constitution of the heat-sensitive transfer sheet obtained by using the heat-transfer ink of the present invention having the above constitution will be described below.

The substrate on which the thermal transfer ink layer is formed by the thermal transfer ink of the present invention, that is, the substrate in the thermal transfer sheet, is a substrate in a conventional thermal transfer sheet, for example, polyester resin, polypropylene resin, cellulose triacetate resin, Starting with resin films made of polystyrene resin, polycarbonate resin, polyimide resin, etc.,
Cellophane, glassine paper, condenser paper, form paper,
Indian paper, metal foil, composites of the above-mentioned base materials, etc. can be used. Further, as a concrete example of the composite, for example, an aluminum / paper composite, a metal vapor-deposited paper, a metal vapor-deposited plastic film or the like is used. Further, the thickness of the base material is preferably thinner from the viewpoint of thermal conductivity to the thermal transfer ink layer formed by the thermal transfer ink, but is 2 μm.
If the amount is less than 50%, not only the strength is insufficient, but also the handleability is deteriorated, and if it exceeds 50 μm, the resolution of the printed portion which is the thermal transfer layer obtained by the thermal transfer recording method is deteriorated. Therefore, those having a thickness of about 2 to 50 μm are usually used.

It should be noted that one side of the substrate, that is, the side in contact with the thermal head when used as a thermal transfer sheet, is provided with a slip agent such as silicone oil to impart slip characteristics, or when a heat resistant resin layer is formed and used. In order to provide anti-sticking performance by adding thermal head adhesion to the base material (staining), or by adding and mixing a lubricant such as talc or fluorine-based resin powder in the heat-resistant resin layer. It goes without saying that means such as further enhancement may be added.

Examples of the method for applying the thermal transfer ink of the present invention to one surface of the base material include a hot melt coating method in which the composition constituting the thermal transfer ink is heated and applied while being melted, gravure coating, roll coating. , Air knife coat, kiss coat, spray coat, pouring coat, deep coat, spinner coat, wheeler coat, brush coat, silk screen solid coat, wire bar coat, flow coat, etc., coating means, gravure printing, gravure offset printing, Printing methods such as lithographic offset printing, dilithographic printing, intaglio printing and silk screen printing can be used. The thickness of the thermal transfer ink layer formed by applying the thermal transfer ink to one surface of the substrate is 0.1 μm.
If it is less than 30 μm, the density of the printed portion, which is the heat transfer layer obtained by the heat sensitive transfer recording method, may be insufficient, so that the purpose of recording may not be achieved in many cases. For the reason that heat transfer to the entire layer becomes insufficient and the purpose of thermal transfer recording is not achieved, etc., it is usually 0.1 to 30 μm, preferably 1 to 2 μm.
The thickness is about 0 μm.

[Work]

In the thermal transfer ink of the present invention, the binder component in the thermal transfer ink is represented by the general formula CH ₂ = C (R ¹ ) COOR ² [wherein R ¹ is H, CH ₃ , C ₂ H ₅ or C ₃ H ₇ , R ² represents a long-chain alkyl group having 17 or more carbon atoms] from a homopolymer of a radically polymerizable unsaturated monomer or a copolymer of the radically polymerizable unsaturated monomers described above. And the melting point is 5
It is a vinyl-based polymer having a melting point width of 4.5 ° C. or less and 0 ° C. or more and less than 100 ° C.

The heat-sensitive transfer sheet having the heat-transfer ink layer formed by the heat-transfer ink of the present invention has a high resolution because the vinyl polymer as a binder component in the heat-transfer ink layer has a narrow melting point width and is sharp. Characters and figures of sex are reproduced extremely faithfully by the heat pattern from the thermal head.

〔Example〕

Hereinafter, the specific constitution of the thermal transfer ink of the present invention will be described with reference to Examples, and the performance of the thermal transfer sheet having the thermal transfer ink layer formed of the ink will be mentioned.

Example 1 The following composition [i] was refluxed for 2 hours to obtain a vinyl polymer [A] as a binder component in the thermal transfer ink of the present invention.

Composition [i] Stearyl acrylate: 100 parts by weight Toluene: 150 parts by weight α, α'-azobisisobutyronitrile: 0.2 parts by weight In addition, the obtained vinyl polymer [A] is The average molecular weight is 2000, the melting point is 53 ° C, and the melting point width is 4.0 ° C.

Then, the following composition [ii] is stirred at room temperature with a ball mill,
Viscosity at 25 ° C 300C. P. Gravure ink [a] was obtained as an example of the thermal transfer ink of the present invention.

Composition [ii] Vinyl polymer [A] 25 parts by weight Red pigment (CI.15850) 5 parts by weight Toluene 70 parts by weight Further, the base material of the heat-sensitive transfer sheet has a thickness of 6 μm. The above gravure ink [a] is applied to one surface of the polyester film (1) by a gravure coating method and dried,
A thermal transfer sheet was obtained by forming a thermal transfer ink layer having a thickness of 3 μm.

Using the heat-sensitive transfer sheet thus obtained, printing was performed with a printing machine equipped with a thermal head [F1610 manufactured by Toko Co., Ltd.], and red printing with a clear contour was obtained.

Example 2 The following composition [iii] was refluxed for 2 hours to obtain a vinyl polymer [B] as a binder component in the thermal transfer ink of the present invention.

Composition [iii] Behenyl acrylate: 100 parts by weight Toluene: 100 parts by weight α, α'-azobisisobutyronitrile: 0.2 parts by weight The vinyl polymer [B] thus obtained is The average molecular weight is 3000, the melting point is 60 ° C, and the melting point width is 3.5 ° C.

Then, the following composition [iv] is stirred at room temperature with a ball mill,
Viscosity at 25 ° C 300C. P. A gravure ink [b] was obtained as an example of the thermal transfer ink of the present invention.

Composition [iv] Vinyl-based polymer [B] 25 parts by weight Blue pigment (CI.74160) 5 parts by weight Toluene 70 parts by weight Further, the base material of the heat-sensitive transfer sheet has a thickness of 6 μm. The above-mentioned gravure ink [b] was applied to one surface of the polyester film (1) by a gravure coating method and dried to form a thermal transfer ink layer having a thickness of 3 μm to obtain a thermal transfer sheet.

Using the heat-sensitive transfer sheet thus obtained, printing was carried out by a printer equipped with a thermal head [F1610 manufactured by Toshiba Corp.], and blue printing with clear contours was obtained.

〔effect〕

In the thermal transfer ink of the present invention, the binder component in the thermal transfer ink is represented by the general formula CH ₂ = C (R ¹ ) COOR ² [wherein R ¹ is H, CH ₃ , C ₂ H ₅ or C ₃ H ₇ , R ² represents a long-chain alkyl group having 17 or more carbon atoms] from a homopolymer of a radically polymerizable unsaturated monomer or a copolymer of the radically polymerizable unsaturated monomers described above. And the melting point is 5
A heat-sensitive transfer sheet having a thermal transfer ink layer formed of the thermal transfer ink is obtained by using a vinyl polymer having a melting point width of 4.5 ° C. or less and a temperature of 0 ° C. or more and less than 100 ° C. , It has an extremely excellent effect on thermal transfer characteristics.

Claims (1)

[Claims] 1. A general formula CH ₂ ═C (R ¹ ) COOR ² [wherein R ¹ is H, CH ₃ , C ₂ H ₅ or C ₃ H].
₇ , R ² represents a long-chain alkyl group having 17 or more carbon atoms]
Consisting of a homopolymer of a radical-polymerizable unsaturated monomer represented by or a copolymer of the radical-polymerizable unsaturated monomers, a melting point of 50 ℃ or more, less than 100 ℃, and
A thermal transfer ink comprising a vinyl polymer having a melting point width of 4.5 ° C. or less as a binder component.