JPH04329194A - Thermal transfer sheet - Google Patents

Abstract

PURPOSE:To provide a new thermal transfer sheet having a back layer featuring high thermal head fusion preventive, antislip and waste sticking preventive properties. CONSTITUTION:A thermal transfer sheet consists of a transferrable ink layer which melts due to heat formed on one surface of a base film and a back layer formed on the other surface of the film with which a thermal head comes in contact. The back layer is made of a silicone ionized radiation-curable resin.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a thermal transfer sheet, and more particularly, it has anti-fusing properties, slip properties, and
The present invention relates to a novel thermal transfer sheet having a back layer that is excellent in preventing slag from adhering to a thermal head.

0002

2. Description of the Related Art Conventionally, when output prints from computers, word processors, facsimile machines, etc. are printed by a thermal transfer method, a thermal transfer sheet having a heat-melting ink layer provided on one side of a base film is used. This conventional thermal transfer sheet has a thickness of 1 mm as a base film.
Using paper such as capacitor paper or paraffin paper with a thickness of 0 to 20 μm, or a plastic film such as polyester or cellophane with a thickness of 3 to 20 μm, a layer of heat-melting ink made by mixing coloring agents such as pigments and dyes with wax is applied. It is manufactured by coating. In addition, when using heat-sensitive materials such as plastic films as the base film, the thermal head may stick during printing, impairing the peeling and slipping properties of the thermal head, or causing the base film to tear. Problems such as For this reason, a method of forming a heat-resistant layer made of a highly heat-resistant thermosetting resin or the like has been proposed.

0003

[Problem that the invention is trying to solve] However,
In the case of a back layer made of thermosetting resin, excellent heat resistance can be obtained, but the back layer is very hard and causes wear on the thermal head, and furthermore, the curing process requires a relatively high temperature. Processing is required and there is a risk of damage to the base film; tens of hours of processing time is required at relatively low temperatures; and stable coating is not possible when using a two-component thermosetting resin. There is a problem in that it is difficult to form a back layer with a uniform thickness. As a method to solve the above problem, it has been proposed to form a back layer using an ionizing radiation-curable resin (see Japanese Patent Application Laid-Open No. 63-49484), but in this case, the back layer has excellent heat resistance. However, since the slip of the thermal head is insufficient, it is required to add a relatively large amount of lubricant such as a metal salt of phosphate ester or silicone powder to the back layer. As a result, problems arise, such as the thermal head being attacked by the metal salt, and additives such as silicone powder falling off when the thermal head runs and collecting as slag on the head. Therefore,
It is an object of the present invention to solve the above-mentioned drawbacks of the prior art and to provide a new thermal transfer sheet having a back layer that is excellent in preventing thermal head fusing, slipping, and slag adhesion.

0004

[Means for Solving the Problems] The above object is achieved by the following present invention. That is, the present invention provides a thermal transfer sheet in which a transfer ink layer that melts by heating is provided on one surface of a base film, and a back layer is provided on the other surface of the base film that is in contact with a thermal head. is a thermal transfer sheet characterized in that it is made of a silicone-based ionizing radiation-curable resin.

[0005]

[Function] By using a specific silicone resin as the resin forming the back layer, a new thermal transfer sheet with a back layer that is excellent in preventing thermal head fusing, slipping, and slag adhesion is provided. be done.

[0006]

[Preferred Embodiments] The present invention will now be explained in more detail with reference to preferred embodiments. As the base film used in the present invention, the same base film used in conventional thermal transfer sheets can be used as is, and other films can also be used, and there are no particular limitations. Specific examples of preferred base films include polyester, polypropylene, cellophane, polycarbonate, cellulose acetate, polyethylene, polyvinyl chloride,
Polystyrene, nylon, polyimide, polyvinylidene chloride, polyvinyl alcohol, fluororesin, chlorinated rubber,
Examples include plastic films such as ionomers, papers such as condenser paper and paraffin paper, nonwoven fabrics, and base films made of composites of these materials. The thickness of this base film can be changed as appropriate depending on the material so that its strength and thermal conductivity are appropriate, but the thickness is 0.5 to 50 μm, preferably 3 to 10 μm. .

The back layer, which mainly characterizes the present invention, is provided on one side of the above-mentioned base film, and as the base film, for example, a material having relatively excellent heat resistance such as polyethylene terephthalate film is used. It is preferable to use In the present invention, such a back layer is formed from a silicone-based ionizing radiation-curable resin as a binder resin. The silicone-based ionizing radiation-curable resins used in the present invention include polydimethylsiloxane-based polymers and silicone-based resins having polymerizable double bonds such as vinyl groups and acrylic groups. It is preferable that the molecular weight is from 10,000 to 500,000; if the molecular weight is less than 10,000, gel formation by radiation will be insufficient and the long-term stability of the back layer will be insufficient. On the other hand, when the molecular weight exceeds 500,000, too much gel is formed due to radiation, causing problems in the smoothness of the back layer. In addition, silicone-based ionizing radiation-curable resins having polymerizable double bonds are well known, and typical examples include various silicone-based ionizing radiation-curable resins manufactured by Shin-Etsu Chemical and RC-705 and RC- manufactured by Gold Schmidt. 720 etc. are mentioned.

[0008] Furthermore, prior to forming the above-mentioned back layer,
It is also effective to form a primer layer made of polyester resin, polyurethane resin, etc. on the base film. To form the back layer, prepare a coating solution by using the silicone-based ionizing radiation-curable resin as described above or diluting it with an appropriate solvent such as acetone, methyl ethyl ketone, toluene, or xylene. It is formed by coating and curing using a conventional coating means such as a gravure coater, roll coater, wire bar, etc. Although various conventionally known additives such as lubricants can be added to the coating liquid, in the present invention, it is particularly preferable to add silicone beads. Since these beads have good adhesion to the binder, which is a silicone-based ionizing radiation-curable resin, they do not fall off later and accumulate as dregs in the thermal head. Furthermore, since the binder itself contains silicone segments, sufficient performance can be achieved with the amount of beads added of 10% by weight or less. Such silicone beads are made by spheroidizing a network resin in which polysiloxane is three-dimensionally bonded, and are available, for example, from Toshiba Silicone under the name Tospearl, and for the purpose of the present invention, particles with an average particle diameter of 0.3 to 12 μm are used. Tospearl 103, 105
, 108, 120, 130, 145, 3120, 240
etc. are particularly suitable. The coating amount, that is, the thickness of the back layer is also important, and in the present invention, it is 1.0 g/m2 on a solid content basis.
Hereinafter, a back layer having sufficient performance can be formed with a thickness of preferably 0.1 to 0.5 g/m<2>. If the back layer is too thick, the sensitivity during transfer will decrease, which is not preferable.

Conventional techniques can be used as is for the above-mentioned curing method of the coating layer. For example, in the case of electron beam curing, Cockroft-Walton type, Van de Graaff type, resonant transformer type, insulated core transformer type, linear type, dynamic type, etc. 50 to 1,000 Ke emitted from various electron beam accelerators such as Tron type and high frequency type
V, preferably an electron beam having an energy of 100 to 300 KeV, and in the case of ultraviolet curing, ultraviolet rays emitted from light sources such as ultra-high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, carbon arcs, xenon arcs, metal halide lamps, etc. used.

In the present invention, a heat-fusible ink layer is further formed on the other surface of the base film using an ink containing necessary materials. The ink for forming the hot-melt ink layer used in the present invention comprises a colorant and a vehicle, and may further contain various additives as necessary. The coloring agent is preferably an organic or inorganic pigment or dye that has good properties as a recording material, for example, one that has sufficient color density and does not discolor or fade due to light, heat, temperature, etc. Alternatively, it may be a substance that is colorless when not heated but develops color when heated, or a substance that develops color when it comes into contact with something coated on the transfer target. In addition to the colorants forming cyan, magenta, yellow, and black, colorants of various other colors can also be used. The vehicle used includes wax as a main component, and mixtures of wax with drying oil, resin, mineral oil, cellulose, rubber derivatives, and the like.

Typical examples of waxes include microcrystalline wax, carnauba wax, and paraffin wax. Furthermore, various waxes such as Fischer-Tropsch wax, various low molecular weight polyethylenes, wood wax, beeswax, spermaceti wax, privet wax, wool wax, shellac wax, candelilla wax, petrolatum, partially modified wax, fatty acid ester, fatty acid amide, etc. are used. It will be done. Further, in order to provide the hot-melt ink layer with good thermal conductivity and melt transferability, a thermally conductive substance can be blended into the hot-melt ink. Examples of this substance include carbonaceous substances such as carbon black, aluminum, copper, tin oxide, and molybdenum disulfide.

Methods for directly or indirectly forming a heat-melting ink layer on a base film include hot melt coating, hot lacquer coating, gravure coating,
Examples include methods of applying the above ink by gravure reverse coating, roll coating, and many other methods. The thickness of the ink layer formed should be determined to balance the required concentration and thermal sensitivity, and is in the range of 0.1 to 30 μm, preferably in the range of 1 to 20 μm. In the present invention, a surface layer can be further formed on the ink layer. The surface layer forms a part of the transfer film, forms the surface in contact with the transfer paper, seals the printed area of the transfer paper during transfer, prevents scumming, and prevents the ink layer from being covered. It has the function of improving adhesion to transfer paper. The wax used to form the surface layer is the same substance as the wax used in the hot-melt ink layer described above. The surface layer made of the wax is coated with a wax melt and cooled.
It is formed by applying and drying an organic solvent solution containing the above-mentioned wax, and further by applying and drying an aqueous dispersion containing the above-mentioned wax particles. The coating of the surface layer, as well as the formation of the ink layer, can also be done by various techniques. In the present invention, the thickness of this layer is preferably 0.1 μm or more and less than 5 μm so that sensitivity is not insufficient even when printing energy is low as in a high-speed printer.

[0013] It is recommended that an appropriate amount of extender pigment be added to the above surface layer. This is because bleeding and trailing of printed characters can be better prevented. Thermal transfer images generally have glossy and beautiful prints, but the documents may become difficult to read, so matte prints are sometimes desirable. In such a case, for example, as proposed by the applicant (Japanese Patent Application No. 58-208306), an inorganic pigment such as silica or calcium carbonate may be dispersed in a suitable solvent on a base film. It is preferable to form a thermal transfer sheet by coating a matte layer and then coating a heat-melting ink layer. Alternatively, the base film itself may be matted and used. It goes without saying that the present invention can be applied to thermal transfer sheets for color printing, so multicolor thermal transfer sheets are also included within the scope of the present invention.

[0014]

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples. In the text, parts or percentages are based on weight unless otherwise specified.

Example 1 Ultraviolet curing silicone resin (manufactured by Shin-Etsu Silicone, X)
0.5 μm on one side of a polyester film (thickness: 4.5 μm, made of diamond foil) using a gravure reverse coater.
After coating at a rate of g/m2, 1
Under a high pressure mercury lamp of 60W/cm at 50m/min. The resin was cured to form a back layer. Separately, a transfer ink composition having the composition shown below was kneaded using a blade kneader for 6 hours while being heated to 100°C. Ink composition for forming transfer ink layer Paraffin wax

Part 10 Carnauba wax

10 parts Ethylene/vinyl acetate copolymer (Sumitate HC-10, manufactured by Sumitomo Chemical) 1 part Carbon black (Sheet 3
, made by Tokai Electrode)
2 parts The above ink composition is heated at a temperature of 100°C, and the coating amount is about 5.0 g/m2 on the other surface of each base film on which the back layer is formed by hot melt roll coating. A thermal transfer ink layer was formed by coating in the same manner as above to obtain a thermal transfer sheet of the present invention.

Example 2 A silicone electron beam curable resin (RC-705, manufactured by Gold Schmidt) was used in place of the ultraviolet curable resin in Example 1, and an electron curtain type EB device (ESI) was used. A thermal transfer sheet of the present invention was obtained in the same manner as in Example 1 except that the coating film was cured by irradiating with 3 Mrad of electron beam. Example 3 A thermal transfer sheet of the present invention was obtained in the same manner as in Example 1 except that 3% of silicone beads (Tospar 120, manufactured by Toshiba Silicone) were added to the ultraviolet curable resin in Example 1. Using the thermal transfer sheet of the present invention obtained above, an output of 1 W/
Dot, pulse width 0.3 to 4.5 msec. Printing was performed on plain paper at a dot density of 3 dots/mm, and the thermal adhesion prevention property, slip property, and print quality were examined, and good results were obtained in all cases.

[0017]

Effects of the Invention According to the present invention as described above, by using a silicone-based ionizing radiation-curable resin as the resin forming the back layer, the fusion prevention property of the thermal head can be improved.
A novel thermal transfer sheet having a back layer with excellent slip properties etc. is provided.

Claims (2)

[Claims] 1. A thermal transfer sheet comprising a transfer ink layer that melts when heated on one side of a base film, and a back layer provided on the other side of the base film that comes into contact with a thermal head, wherein the back layer is A thermal transfer sheet characterized by being made of a silicone-based ionizing radiation-curable resin. 2. The thermal transfer sheet according to claim 1, wherein the back layer contains silicone fine particles.