JP2591636B2 - Thermal transfer sheet - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thermal transfer sheet, and more particularly, to a novel thermal transfer sheet having an excellent heat-resistant slip layer made of a specific material.

(Prior Art) Conventionally, when an output print of a computer or a word processor is printed by a thermal transfer method, a thermal transfer sheet provided with a heat-fusible ink layer on one surface of a base film has been used.

This conventional thermal transfer sheet has a thickness as a base film.
Using a 10 to 20 μm capacitor paper or paraffin paper, or a 3 to 20 μm thick plastic film such as polyester or cellophane, coating a hot-melt ink layer with wax mixed with a coloring agent such as a pigment or dye. And manufactured.

Further, when a heat-sensitive material such as a plastic film is used as the base film, the thermal head sticks at the time of printing, causing problems such as peeling of the thermal head and loss of slip properties. For the purpose of forming a heat-resistant layer made of, and improving the slip property, a lubricant or the like is included in those layers.

(Problems to be Solved by the Invention) The heat-resistant slip layer in the conventional thermal transfer sheet described above,
The thermal transfer sheet needs to be formed relatively thick, and thus has a disadvantage that the sensitivity of the thermal transfer sheet is reduced. Further, in the production process, when silicone oil or silicone resin is used, the coating agent for forming the heat-resistant slip layer on the base film often causes repelling phenomena, making it difficult to form a uniform coating film.

Furthermore, organic or inorganic particles are often added to these heat-resistant slip layers in order to improve heat resistance, but there is a problem that the presence of these particles causes the thermal head to be worn.

Furthermore, since these heat-resistant slip layers are formed as relatively soft layers, wrinkles are easily generated on the thermal transfer sheet, and irregularities on the surface of the material to be transferred and irregularities of the pigment particles in the ink layer are transmitted to the thermal head. There is also a problem of promoting the wear of the thermal head.

Accordingly, an object of the present invention is to provide a thermal transfer sheet which has solved the above-mentioned disadvantages.

(Means for Solving the Problems) The above object is achieved by the present invention described below.

That is, the present invention relates to a heat transfer sheet comprising a transfer ink layer which is melted by heating on one surface of a substrate film, and a heat-resistant slip layer provided on the other surface of the substrate film contacting a thermal head. A thermal transfer sheet, wherein the slip layer is formed using polyisocyanate as a main component.

(Function) By forming the heat-resistant slip layer using polyisocyanate as a main component, a very thin heat-resistant slip layer is formed, so that a heat transfer sheet having high sensitivity is provided.

Further, the coatability of the coating solution for forming a heat-resistant slip layer on the base film is good, there is no repelling phenomenon, and a uniform and thin layer can be formed. Further, the above heat-resistant slip layer becomes a relatively hard layer due to excessive use of polyisocyanate, which suppresses the generation of wrinkles of the thermal transfer sheet, as well as the reaction of irregularities on the surface of the material to be transferred and pigment particles in the ink layer. Is cut off, and the thermal head wear is small.

(Preferred Embodiment) Next, the present invention will be described in more detail with reference to preferred embodiments.

As the substrate film used in the present invention, the same substrate film as used in the conventional thermal transfer sheet can be used as it is, and other materials can also be used, and there is no particular limitation.

Specific examples of preferred base film include, for example, polyester, polypropylene, cellophane, polycarbonate, cellulose acetate, polyethylene, polyvinyl chloride, polystyrene, nylon, polyimide, polyvinylidene chloride, polyvinyl alcohol, fluororesin, chloride rubber, ionomer, etc. Plastic, condenser paper,
There are papers such as paraffin paper, non-woven fabric, and the like, and a base film in which these are combined may be used.

The thickness of the base film can be appropriately changed depending on the material so that its strength and thermal conductivity are appropriate, but the thickness is preferably, for example, 2 to 25 μm.
It is.

The heat-resistant slip layer, which mainly characterizes the present invention, is provided on one surface of the above-mentioned base film, and is preferably used when a base film having low heat resistance such as a plastic film is used. It is.

In the present invention, the heat-resistant slip layer is formed by using polyisocyanate as a main component.

Conventionally, it is known to use a polyurethane comprising a polyol and a polyisocyanate for forming various pigments, coating agents or heat-resistant slip layers, or to form a crosslinked resin layer by using a polyisocyanate compound as a crosslinker in other resin liquids. However, in these known methods, the polyisocyanate compound is merely used as a so-called simple crosslinking agent in a very small amount relative to the resin to be crosslinked.

In the present invention, unlike these conventional examples, a polyisocyanate compound is used as a main component of the heat-resistant slip layer, that is,
It has been found that the use of more than 50% by weight of the film-forming material, excluding additives, results in a coating which is very suitable as a heat-resistant slip layer.

As the polyisocyanate compound used in the present invention, a general polyisocyanate compound can also be used,
Preferred is a polyurethane polyisocyanate having a relatively high molecular weight reacted with a polyisocyanate dimer, trimer or polyol compound. In particular,
For example, cyclic trimers of 2,4-tolylene diisocyanate, cyclic trimers of 2,6-tolylene diisocyanate, trimers of diphenylmethane-4,4'-diisocyanate, 3 moles of diphenylmethane- The reaction product of 4,4'-diisocyanate with 1 mole of trimethylolpropane, the reaction product of 3 moles of 2,4-tolylene diisocyanate with 1 mole of trimethylolpropane, 3 moles of 2,6-triol Reaction product of diisocyanate with 1 mole of trimethylolpropane, reaction product of 3 moles of 2,4-tolylenediisocyanate with 1 mole of trimethylolethane, 3 moles of 2,6-tolylenediisocyanate with 1 mole Reaction product with 3 moles of trimethylolethane, 3 moles of mixed 2,4- and 2,6-tolylene diisocyanate and 1 mole of trimethylolpropane Reaction products, 2,4- and 2,6-tolylene stabilized polyisocyanate which the mixed cyclic trimer etc. and blocked with phenol or cresol isocyanate.

These polyisocyanate compounds include, for example, Takenate (manufactured by Takeda Pharmaceutical), Vernock (manufactured by Dainippon Ink and Chemicals), Coronate (manufactured by Nippon Polyurethane), Duranate (manufactured by Asahi Kasei Kogyo), DisModule (manufactured by Bayer)
And can be used in the present invention.

In the present invention, the above polyisocyanate compounds can be used alone or in combination with other binder resins.

Examples of these binder resins include cellulose resins such as ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxycellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate, cellulose acetate butyrate, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal,
Examples thereof include vinyl resins such as polyvinylpyrrolidone and polyacrylamide, and polyesters. Among these, some have reactive groups such as hydroxyl groups, such as cellulose, acetal, butyral, and polyester. Are preferred.

When the above-mentioned binder resin is used, it is preferable that the weight ratio between the binder resin and the polyisocyanate compound is such that the polyisocyanate compound becomes excessive.

In the present invention, in forming a heat-resistant slip layer from the above-mentioned materials, heat releasing agents such as waxes, higher fatty acid amides, esters, and surfactants, lubricants, and the like are used for the purpose of improving the slip property of the heat-resistant slip layer. Inorganic particles such as organic powders such as inhibitors or fluororesins, silica, clay, talc, calcium carbonate and the like can be included. Furthermore, in order to improve the antistatic property of the obtained thermal transfer sheet, a conductive property such as carbon black can be added.

To form a heat-resistant slip layer, the above-described materials are dissolved or dispersed in an appropriate solvent such as acetone, methyl ethyl ketone, toluene, and xylene to prepare a coating solution, and the coating solution is subjected to a gravure coater, a roll coater, and the like. It is formed by coating and drying by conventional coating means such as a wire bar.

The thickness of the coating amount i.e. the heat resisting slipping layer even critical, 0.5 g / m ² or less on a solids basis in the present invention, preferably heat-resistant slipping layer having sufficient performance at a thickness of 0.1 to 0.5 g / m ² Can be formed.

In the present invention, after forming the heat-resistant slip layer, unreacted isocyanate groups often remain in the layer. Therefore, it is preferable to perform a sufficient thermal treatment after the formation of the layer. By such a treatment, the heat-resistant slip layer has a pencil hardness of about H to 2H.

It is also effective to form a primer layer made of polyurethane resin or the like before forming the heat-resistant slip layer.

In the present invention, a heat-meltable ink layer is formed on the other surface of the base film from an ink containing necessary materials.

The ink for forming a hot-melt ink layer used in the present invention comprises a colorant and a vehicle, and may further contain various additives as necessary.

As the coloring agent, among organic or inorganic pigments or dyes, those having good characteristics as a recording material, for example, those having a sufficient coloring density and not discoloring due to light heat, temperature and the like are preferable.

Further, a substance which is colorless when not heated but develops a color when heated, or a substance which develops a color when it comes into contact with a substance applied to a transfer-receiving body may be used. In addition to the colorants that form cyan, magenta, yellow, and black, colorants of various other colors can also be used.

As the vehicle, a mixture of wax as a main component, and other components such as a wax and a derivative of a drying oil, a resin, a mineral oil, cellulose, and rubber is used.

Representative examples of wax include microcrystalline wax, carnauba wax, paraffin wax and the like. Furthermore, various waxes such as Fischer-Tropsch wax, various low molecular weight polyethylenes, wood wax, beeswax, spermaceti, Ibota wax, wool wax, shellac wax, candelilla wax, petrolatum, partially modified wax, fatty acid ester, fatty acid amide and the like are used. Can be

In addition, a heat conductive substance can be added to the heat fusible ink in order to provide the heat fusible ink layer with good heat conductivity and melt transferability. Examples of this substance include carbonaceous substances such as carbon black, aluminum, copper, tin oxide, and molybdenum dioxide.

As a method for forming a hot-melt ink layer directly or indirectly on a base film, a hot-melt coat, a hot lacquer coat, a gravure coat, a gravure reverse coat, a roll coat, and the like are applied by various methods. And the like. The thickness of the ink layer to be formed should be determined so as to balance the required density with the thermal sensitivity, and is in the range of 0.1 to 30 μm, preferably 1 to 20 μm.

In the present invention, a surface layer can be further formed on the ink layer. The surface layer forms part of a transfer film,
It forms a surface on the side in contact with the paper to be transferred, has a function of stopping the printed portion of the paper at the time of transfer, preventing other stains, and improving the adhesion of the ink layer to the paper to be transferred.

The wax used for forming the surface layer is the same as the wax used for the above-mentioned hot-melt ink layer.

The surface layer made of the wax is formed by applying and cooling a wax melt, applying and drying an organic solvent solution containing the wax, and further applying and drying an aqueous dispersion containing the wax particles.

Coating of the surface layer can also be performed by various techniques as in the formation of the ink layer. In order to prevent the sensitivity from being insufficient even when the printing energy is low as in a high-speed type printer, the thickness of this layer is preferably 0.
1 μm or more and less than 5 μm.

It is recommended that an appropriate amount of extender be added to the surface layer. As a result, bleeding and tailing of the print can be more favorably prevented.

A thermal transfer image generally has a glossy print and is beautiful, but on the other hand, matte printing may be desirable because the document may be difficult to read. In such a case, for example, as proposed by the applicant (Japanese Patent Application No. 58-208306), an inorganic pigment such as silica, calcium carbonate or the like dispersed in a suitable solvent is dispersed on a base film. It is preferable to form a thermal transfer sheet by coating and providing a mat layer, and then coating a hot-melt ink layer. Alternatively, the base film itself may be used after mat processing (the technique of Japanese Patent Application No. 58-208307 also proposed by the applicant).

Needless to say, the present invention can be applied to a thermal transfer sheet for color printing, and a multicolor thermal transfer sheet is also included in the scope of the present invention.

(Effects) According to the present invention as described above, since the formed heat-resistant slip layer is a very thin layer, the sensitivity of the thermal transfer sheet is hardly reduced, and excellent printing is possible.

Also, unlike the conventional silicone resin and the like, when forming the heat-resistant slip layer, the coating liquid does not undergo repelling during coating, and can be formed as a very uniform layer despite being a thin layer. it can.

The formed heat-resistant slip layer is a hard layer having a high cross-linking density, exhibits high heat resistance and high slip properties, and is caused by irregularities of the material to be transferred and various particles in the ink layer and the heat-resistant slip layer. The wear of the thermal head is small, and since it is a hard layer, wrinkles do not occur during printing.

(Examples) Hereinafter, the present invention will be described more specifically with reference to examples. In the description, parts and% are based on weight unless otherwise specified.

Example 1 An ink composition for a heat-resistant slip layer having the following composition was prepared and used as a base film.
And 12.0 μm polyester film (trade name “Lumirror” manufactured by Toray Industries, Inc.) on one surface,
The coating amount of the ink composition was 0.5 g / m ² (solid content) using No. 4.
Then, it was dried with warm air after coating.

Ink composition for heat-resistant slip layer (I) Polyvinyl butyral resin (S-REC BX-1, manufactured by Sekisui Chemical Co., Ltd. 2.2 parts Toluene 35.4 parts Methyl ethyl ketone 53.0 parts Polyisocyanate (Bernock D-750, manufactured by Dainippon Ink and Chemicals, Inc.) 6.8 parts Phosphate ester (Plysurf A-208S, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 1.6 parts Sorbitan fatty acid ester (Reodol SP-030, manufactured by Kao Corporation) 0.6 parts Talc (Microace L-1, Nippon Talc) (Co.) 0.
4 parts Amine catalyst (Desmorapid PP, manufactured by Sumitomo Bayer Urethane Co., Ltd.) 0.02 parts The obtained film was further heated in an oven at 60 ° C. for 5 days to perform a curing treatment to form a heat-resistant slip layer.
The ratio of NCO / OH between the polyisocyanate and the thermoplastic resin in the ink composition for a heat-resistant slip layer was 1.8.

Separately, a transfer ink composition having the following composition was kneaded for 6 hours while heating to 90 ° C. using a blade kneader.

Ink composition for forming transfer ink layer Paraffin wax 10 parts Carnauba wax 10 parts Polybutene (VH-100, manufactured by Nippon Oil Co., Ltd. 1 part Carbon black (Seast 3, manufactured by Tokai Electrode Co., Ltd.) 2
Part The above ink composition is heated at a temperature of 100 ° C., and is applied to the other surface of the substrate film by a roll coating method using a hot melt so that an application amount is about 5.0 g / m ² , and a thermal transfer ink layer is formed. Was formed to obtain a thermal transfer sheet of the present invention.

Example 2 The ink composition for a heat-resistant slip layer was prepared using the following composition (II)
A thermal transfer sheet of the present invention was formed in the same manner as in Example 1 except that the heat transfer sheet was replaced with Example 1.

Ink composition for heat-resistant slip layer (II) Polyvinyl butyral resin (ESREC BX-1, manufactured by Sekisui Chemical Co., Ltd. 3.0 parts Toluene 44.53 parts Methyl ethyl ketone 44.53 parts Polyisocyanate (Bernock D-750, manufactured by Dainippon Ink and Chemicals, Inc.) 4.2 parts Phosphate ester (Plysurf A-208S, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 2.2 parts Sorbitan fatty acid ester (Reodol SP-030, manufactured by Kao Corporation) 0.9 part Talc (Microace L-1, Nippon Talc) (Co.) 0.
6 parts Amine catalyst (Desmorapid PP, manufactured by Sumitomo Bayer Urethane Co., Ltd.) 0.04 parts The NCO / OH ratio of the polyisocyanate to the thermoplastic resin in the above composition was 0.8.

Example 3 An ink composition for a heat-resistant slip layer was prepared using the following composition (II
A thermal transfer sheet of the present invention was formed in the same manner as in Example 1 except that I) was replaced.

Ink composition for heat-resistant slip layer (III) Polyvinyl butyral resin (ESREC BX-1, manufactured by Sekisui Chemical Co., Ltd. 1.8 parts Toluene 44.04 parts Methyl ethyl ketone 44.04 parts Polyisocyanate (Bernock D-750, manufactured by Dainippon Ink and Chemicals, Inc.) 7.9 parts Phosphate ester (Plysurf A-208S, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 1.3 parts Sorbitan fatty acid ester (Reodol SP-030, manufactured by Kao Corporation) 0.54 parts Talc (Microace L-1, Nihon Talc) (Co.) 0.
36 parts Amine-based catalyst (Desmorapid PP, manufactured by Sumitomo Bayer Urethane Co., Ltd.) 0.02 parts The NCO / OH ratio of the polyisocyanate to the thermoplastic resin in the above composition was 2.5.

When the IR spectrum of the film surface on which the heat-resistant slip layer of the thermal transfer sheet of the present invention obtained as described above was formed was measured, an absorption based on the NCO group was observed at around 2,272 cm ⁻¹ , and the residual amount was determined from the magnitude of this absorption. The amount of isocyanate appears to be quite high. If this is stored under high temperature and high humidity,
It has been found that the moisture in the air and the residual isocyanate react as shown in the following formula, and a high-density crosslinked product is formed at 60 ° C. for 3 to 5 days.

Example 4 Prior to forming a heat-resistant slip layer on a polyester film, a primer layer was formed using an ink composition for a primer layer having the following composition, and then a heat-resistant slip layer was formed on the heat-resistant layer. In the same manner as in Example 1, a thermal transfer sheet of the present invention was produced.

Ink composition for primer layer Acrylic polyol (Acryt 6416MA, 45% solution, manufactured by Taisei Kako Co., Ltd. 41.2 parts Toluene 26.3 parts Methyl ethyl ketone 26.3 parts Polyisocyanate (Coronate L, 45% acetate solution, manufactured by Nippon Polyurethane Co., Ltd.) 6.2 Part The above composition was applied on a polyester film using a Miyabar # 8 so that the coating amount was 1.0 g / m ² (solid content), and then dried with warm air.
A heat-resistant slip layer was provided in the same manner as described above, and an ink for forming a thermal transfer ink layer was applied on the opposite surface of the polyester film.

When a printing test was performed using a printer, the thermal transfer sheet according to Example 1 without a primer layer showed that when the printing energy was increased to 6 mJ / dot or more, the film was stretched due to heat, causing wrinkles and leaving marks on the printing surface. However, in the thermal transfer sheet according to the present example provided with the primer layer, no wrinkles were observed even when a printing energy of 6 mJ / dot was applied.

Comparison of test results The samples obtained in the above Examples 1 to 4 and those without the heat-resistant slip layer were prepared as comparative examples, and the head running state and the state after printing when printing was performed under the following conditions were prepared. Observed.

Printing equipment used: Thin-film thermal head Printing energy: 1 mJ / dot (area per dot is 4 × 10 ^-4 cm ³ ) Example 4: 6 mJ / dot Transferred object: Fine paper (Sanyo Kokusaku Pulp, KKYP4) 135k
g) In the above, the evaluation was performed after the first printing.

Further, the heat-resistant sheet according to the present invention obtained as described above, when printing under the above-described printing conditions, the heat-resistant slip layer ink composition necessary for smooth conveyance without generation of wrinkles is possible. 0.2 g / m ²
Turned out to be enough. 5.0g of ink composition applied
/ When a m ^2, and the order to obtain a sufficient print density in the transfer ink layer, it is necessary printing energy of 1.0 mJ / dot, when the coating amount of the heat resisting slipping layer and 0.2 g / m ^2, 0.7 mJ
/ Dot is sufficient and can reduce printing energy by about 30%.

Claims (3)

(57) [Claims] 1. A heat transfer sheet comprising: a transfer ink layer which is melted by heating on one surface of a substrate film; and a heat resistant slip layer provided on the other surface of the substrate film contacting a thermal head. A thermal transfer sheet, wherein the layer is formed mainly of polyisocyanate. 2. The thermal transfer sheet according to claim 1, wherein the heat-resistant slip layer is formed mainly of a binder and a polyisocyanate, and the polyisocyanate accounts for 50% by weight or more of the film-forming component. 3. The thermal transfer sheet according to claim 1, wherein the heat-resistant slip layer has a thickness of 0.5 μm or less.