JP2001277735A - Thermal transfer film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal transfer film wherein a void is not generated in printed matter, clear printing can be carried out, coating can be excellently and stably carried out in order to form an intermediate layer and a heat fusible coloring layer on a base material film, and a secrecy leak preventive function is provided. SOLUTION: In a heat transfer film wherein the heat fusible coloring layer is provided on the base material film via the intermediate layer, since the intermediate layer contains monomethyl itaconate and a binder resin of >=130 deg.C and <=400 deg.C in softening temperature (by measurement of a ring and ball method specified in JIS K2207-1980), though the intermediate layer is cooled to some extent while from printing to peeling, an adhesive property of the intermediate layer with the heat fusible coloring layer is decreased while the monomethyl itaconate is fused as it is by a supercooling property and the like of the monomethyl itaconate, the heat fusible coloring layer within an energy-applied area can be transferred without generating a void on paper to be transferred, and good printed matter of little void is obtained even for rough paper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer film having a heat-meltable colored layer provided on a base film via an intermediate layer. The present invention relates to a thermal transfer film which can be printed, can be applied stably in forming an intermediate layer and a heat-meltable colored layer on a base film, and has a function of preventing leakage of confidential information.

[0002]

2. Description of the Related Art Conventionally, as a thermal transfer recording medium used in thermal transfer printers, facsimile machines, etc., a thermal transfer film having a heat-fusible ink layer provided on one side of a base film has been used. Conventional thermal transfer films use a base film such as a capacitor paper or a paraffin paper having a thickness of about 10 to 20 μm, or a plastic film such as a polyester or cellophane having a thickness of about 3 to 20 μm. A colorant such as a pigment or a dye is mixed with a binder, and if necessary, a hot-melt ink containing an additive such as a low-melting agent and a plasticizer is applied to form a hot-melt ink layer. It is provided. And
From the back side of the base film, a predetermined position is heated and pressurized by a thermal head to melt the hot-melt ink layer of the hot-melt ink layer at the portion corresponding to the printing portion, and transfer it to the transfer target to print. Is what you do.

Further, as a thermal transfer film, a heat-meltable ink layer is provided on a base film via an intermediate layer. For example, Japanese Patent Application Laid-Open No. 61-144393 contains conductive powder as an intermediate layer. It is disclosed that a matte layer is used to provide matte printing, antistatic and confidential leakage prevention functions.

[0004]

As described above, when printing is performed using a thermal transfer film having an intermediate layer and a heat-meltable colored layer provided on a base film, characters and fine lines due to white spots are generated. There is a problem that the printed matter has a faint appearance, resulting in a faint appearance. Beck smoothness is 50
In order to print on rough paper that has a grain size of less than seconds without causing white spots, the colored layer in the area where energy is applied in a pixel shape by means such as a thermal head is applied to the transfer paper. It is necessary to transfer without dropout. In order to transfer the colored layer entirely to the transfer receiving paper without any slippage, the intermediate layer of the thermal transfer film provided with the colored layer via the intermediate layer on the base film is melted and a liquid with high fluidity is melted. It is effective to peel off the transfer object and the thermal transfer film in the state. However, in a device generally used in facsimile machines and the like using a thermal transfer film, the moment when printing energy is applied to the thermal transfer film after the thermal transfer film is superimposed on the thermal transfer film, the thermal transfer film is peeled off from the thermal transfer film. Even if an intermediate layer is adjusted so that it is melted by the energy for printing, there is a gap in the time until it cools down and solidifies again, or it has not solidified yet Was generally low.

The present invention improves and solves the above-mentioned drawbacks and problems, and enables clear printing without white spots on printed matter.
An object of the present invention is to provide a thermal transfer film which can be applied satisfactorily and stably in forming an intermediate layer and a heat-meltable colored layer on a base film, and further has a function of preventing secret leakage.

[0006]

The printing performance of a thermal transfer film using monomethyl itaconate for the intermediate layer was examined in detail.
Even if cooled to some extent, the supercooling property of monomethyl itaconate further increases the softening temperature (J
The softening temperature measured by the ring and ball method defined in IS K2207-1980) is 130 ° C. or more and 400 ° C. or less, so that the monomethyl itaconate remains molten,
The adhesiveness between the intermediate layer and the heat-meltable colored layer is reduced, and the heat-meltable colored layer in the energy-applied region can be transferred without causing the transfer-receiving paper to come off, and can be transferred to rough paper. It became clear that a good printed matter with little omission was obtained, and the invention of claim 1 of the present application was reached.

Further, the suitability for coating of the intermediate layer containing monomethyl itaconate and the suitability for overcoating of the heat-meltable colored layer on the intermediate layer were examined in detail, and the melting peak temperature and the heat fusibility of monomethyl itaconate were determined. By specifying the difference between the melting peak temperatures of the coloring layers, the invention of claim 2 of the present application was achieved. In addition, a detailed study was conducted on the suitability of the intermediate layer for coating and the suitability of the hot-melt colored layer on the intermediate layer for over-coating, without adversely affecting the supercooling property of monomethyl itaconate. A group of intermediate layer binder resins capable of improving the suitability of both colored layers has been clarified, and the inventions of claims 3 to 5 of the present application have been made.
In addition, as a result of various investigations as a method for improving the secret leakage prevention property of the thermal transfer film according to the first to fifth aspects, the invention of the sixth aspect was achieved.

[0008]

Next, embodiments of the present invention will be described in detail. The thermal transfer film of the present invention has a configuration in which a heat-meltable colored layer is provided on a base film via an intermediate layer. (A softening temperature measured) is 130 ° C or more and 400 ° C or less.

(Base Film) As the base film used in the thermal transfer film of the present invention, the same base film as used in the conventional thermal transfer film can be used as it is, and other base films can also be used. And is not particularly limited. Specific examples of preferred base film include, for example, polyester, polypropylene, cellophane, polycarbonate, cellulose acetate,
There are plastics such as polyethylene, polyvinyl chloride, polystyrene, nylon, polyimide, polyvinylidene chloride, polyvinyl alcohol, fluororesin, chlorinated rubber, ionomer, etc., papers such as condenser paper and paraffin paper, non-woven fabrics, etc. A base film may be used. The thickness of the substrate film can be appropriately changed depending on the material so that the strength and the thermal conductivity are appropriate, but the thickness is preferably, for example, 3
〜１０10 μm.

(Intermediate Layer) The intermediate layer has a monomethyl itaconate and a softening temperature (softening temperature measured by a ring and ball method specified in JIS K2207-1980) of 130 ° C. or higher and 40 ° C. or higher.
It contains a binder resin having a temperature of 0 ° C. or less. Monomethyl itaconate used in the present invention and softening temperature (JI
The binder resin having a softening temperature measured by a ring and ball method defined in SK2207-1980) of 130 ° C. or more and 400 ° C. or less contains an ester obtained by adding a methyl group to one carboxyalkyl group of itaconic acid. And
It is represented by the following structural formula.

Embedded image

The melting peak temperature of monomethyl itaconate (the melting peak temperature specified in JIS K7121-1987) is 67 ° C., and the monomethyl itaconate in the intermediate layer in the region heated by the thermal head melts.
Even when peeled off from the transfer object, the supercooling property of monomethyl itaconate keeps the molten state, and the adhesive strength between the intermediate layer and the heat-meltable colored layer in the heated area is lower than before the heating. This can reduce the occurrence of white spots in the transfer to the transfer target.

As the binder resin for the intermediate layer, JIS
The softening temperature measured by the ring and ball method specified in K2207-1980 is 130 ° C. or more and 400 ° C. or less, and when coating the heat-meltable coloring layer on the intermediate layer formed on the base film, and when printing is performed. Any resin may be used as long as the film formability is maintained without sometimes causing a low viscosity. Among them, a resin incompatible with monomethyl itaconate is preferable, and examples thereof include a polyester resin, a polybutadiene-based resin such as an SBR resin, an ABS resin, and an SBS resin;
Examples include a maleic acid resin such as a maleic anhydride copolymer, an olefin resin, an olefin copolymer, an ionomer resin, and a styrene resin, and a polyester resin is particularly preferable. As the polyester resin used as the binder resin of the intermediate layer, the main chain preferably contains an ethylenically unsaturated bond. Examples of the polyester resin containing an ethylenically unsaturated bond include a structure using fumaric acid and maleic acid as an acid component, and a structure using 2-Butene-1,4-diol as an alcohol component. it can.

JIS K2207-1 for binder resin
The softening temperature measured by the ring and ball method specified in 980 is 130 ° C
If it is lower, it becomes difficult to appropriately separate the binder resin and monomethyl itaconate in the process of drying after applying the coating liquid for forming the intermediate layer on the base film, and the monomethyl itaconate is supercooled. In this state, the effect exerted is not substantially obtained, and it is difficult to transfer the hot-melt colored layer without causing the transfer-receiving paper to come off. In addition, JIS K2207-19
The binder resin whose softening temperature measured by the ring and ball method specified at 80 exceeds 400 ° C. is almost always an expensive material due to having excessive heat resistance, so that the production cost of the thermal transfer film becomes excessive. Causes malfunction.

[0014] For a transfer target such as rough paper having a low surface smoothness, white spots generated when printing is performed using a conventional thermal transfer film as described in, for example, JP-A-61-144393. After examining the cause of the occurrence, immediately after heating with the thermal head, the hot-melt colored layer immediately before peeling the thermal transfer film from the transferred body, the region where a relatively thick layer is formed, and the thin layer The heat transfer film and the object to be transferred are separated while the area where the thin layer is formed is not transferred to the object to be transferred and remains attached to the base film side of the heat transfer film. Therefore, it is clear that the area becomes an untransferred area (white area). On the other hand, when the monomethyl itaconate in the intermediate layer in the region heated by the thermal head melts and separates from the transfer object, the molten state continues due to the supercooling property of the monomethyl itaconate and the heated region The adhesive force between the intermediate layer and the heat-meltable colored layer is lower than before the heating, so that the occurrence of white spots in the transfer to the transfer-receiving member can be reduced.

In addition, as a result of a detailed study on the suitability for coating the intermediate layer containing monomethyl itaconate and the suitability for overcoating of the hot-melt colored layer on the intermediate layer, the melting peak temperature of monomethyl itaconate and the heat It is desirable that the difference between the melting peak temperatures of the fusible colored layers is 0 ° C or more and 10 ° C or less. In addition, the melting peak temperature is based on JIS K
It is measured by the method specified in 7121-1987. JIS K7121-19 of monomethyl itaconate
The melting peak temperature specified in 87 is about 67 ° C. From the above-mentioned point, by setting the melting peak temperature of the heat-fusible colored layer to 57 ° C. or more and 77 ° C. or less, the occurrence of white spots on printed matter is reduced, and Printing, an intermediate layer on the base film,
In forming the hot-melt colored layer, the coating can be performed satisfactorily and stably. It is a requirement of the present invention that the difference between the melting peak temperature of the monomethyl itaconate and the melting peak temperature of the hot-melt colored layer is 10 ° C or less, and within the range, the desired effect can be exhibited. it can. The effect is more remarkable as the difference in the melting peak temperature is smaller, and the most preferable printing result is obtained when the temperature difference is 0 ° C. If the difference in the melting peak temperature exceeds 10 ° C., the characters are liable to be crushed due to the entanglement phenomenon in printing, so that a problem that makes it difficult or impossible to determine the characters tends to occur.

When monomethyl itaconate is used for the intermediate layer, a hot-melt colored layer is hot-melt coated on the intermediate layer. It could not be manufactured. Therefore, in the present invention, J
Using a binder resin having a softening temperature of 130 ° C. or more and 400 ° C. or less as determined by the ring and ball method defined in IS K2207-1980, a resin incompatible with monomethyl itaconate, and an intermediate layer coating liquid, In the process of drying after coating on top, the number average molecular weight is preferably 15 so that the binder resin and monomethyl itaconate are appropriately separated.
It is preferable to use a polyester resin having a size of from 00 to 100,000 as the binder resin. As a result, as a result of providing an intermediate layer using monomethyl itaconate and the polyester resin in combination, a coating film is formed in a state where both layers are separated, and the polyester resin as a binder forms a non-transferable structure. Thus, a coating film was obtained in which it was considered that the space defined by the structure was filled with monomethyl itaconate. With such a configuration, hot-melt coating of the heat-meltable coloring layer is possible, and a realistic thermal transfer film can be manufactured.

The number average molecular weight of the binder resin used in the intermediate layer is preferably 1500 or more and 100000 or less. When used together with monomethyl itaconate, the two are incompatible and the coating film is formed in a state of layer separation. You. If the number average molecular weight of the binder resin of the intermediate layer is less than 1500, the binder resin and monomethyl itaconate are appropriately separated in the process of applying a coating solution for forming the intermediate layer on the base film and then drying. It is difficult to transfer the heat-meltable colored layer to the transfer-receiving paper without causing the effect to be exhibited substantially because monomethyl itaconate is in a supercooled state. Become. Also, when the number-average molecular weight of the binder resin of the intermediate layer is larger than 100,000, the binder resin and monomethyl itaconate can be appropriately removed in the process of drying after applying the coating liquid for providing the intermediate layer on the base film. It becomes difficult to separate the monomethyl itaconate from the supercooled state, and the effect exerted by the supercooled state is not substantially obtained. Becomes

Further, by blending carbon black into the intermediate layer, the printed content can be read from the thermal transfer film after printing. It is difficult to read the content printed on the thermal transfer film from the copied material), and it is possible to additionally provide a function for preventing confidential leakage. In order to form the intermediate layer, the above-mentioned materials and a dispersant such as a higher aliphatic alcohol, a phosphoric acid ester and a metal salt thereof, an organic carboxylic acid and a derivative thereof, a low-melting wax, and various surfactants are optionally used. , And dissolved or dispersed in an appropriate solvent such as methyl ethyl ketone, toluene, alcohols, water, etc. to prepare a coating liquid, and the coating liquid is applied by a conventional coating means such as a gravure coater, a roll coater, and a wire bar. Work and dry. The coating amount of the intermediate layer is 0.1 to 1.0 on a dry solids basis.
g / m ² is preferred. When the coating amount is less than 0.1 g / m ² , it is difficult to obtain a clear printed matter with no white spots. On the other hand, when the coating amount exceeds 1.0 g / m ² , the intermediate layer is If the thickness is too large, the printing sensitivity at the time of transfer decreases, which is not preferable.

(Heat-meltable colored layer) In the present invention, a heat-meltable colored layer is provided on the above-mentioned intermediate layer. The hot-melt colored layer is a hot-melt ink layer and is made of a conventionally known colorant and binder. If necessary, mineral oil, vegetable oil, higher fatty acids such as stearic acid, plasticizer, antioxidant, filling What added various additives, such as an agent, is used. Examples of the wax component used as the binder include microcrystalline wax, carnauba wax, and paraffin wax. Furthermore, Fischer-Tropsch wax, various low molecular weight polyethylenes, wood wax, beeswax, whale wax, Ibota wax, wool wax, shellac wax, candelilla wax, petrolactam, polyester wax, partially modified wax,
Various waxes such as fatty acid esters and fatty acid amides are used. Among them, those having a melting point of 50 to 85 ° C are particularly preferable. If the temperature is lower than 50 ° C., there arises a problem in storage stability.

The resin component used as a binder includes, for example, polyester, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, polyethylene, polystyrene, polypropylene, polybutene, petroleum resin, vinyl chloride resin, vinyl chloride -Vinyl acetate copolymer, polyvinyl alcohol, vinylidene chloride resin, methacrylic resin, polyamide, polycarbonate,
Fluororesin, polyvinyl formal, polyvinyl butyral, acetylcellulose, nitrocellulose, polyvinyl acetate, polyisobutylene, ethylcellulose or polyacetal, and the like, and particularly a relatively low softening point conventionally used as a heat-sensitive adhesive, for example, , 5
Those having a softening point of 0 to 80 ° C are preferred.

The colorant can be appropriately selected from known organic or inorganic pigments or dyes.
For example, having a sufficient coloring density, discoloration by light, heat, etc.
Those that do not fade are preferred. Further, it may be a substance that develops color by heating or a substance that develops color when it comes into contact with a component applied to the surface of the transfer-receiving body. Further, the color of the colorant is not limited to cyan, magenta, yellow, and black, and various colors of colorants can be used.

Further, a heat conductive substance may be blended as a filler for the binder in order to provide the heat melt colored layer with good heat conductivity and heat melt transferability. Examples of such a filler include carbonaceous substances such as carbon black, and metals and metal compounds such as aluminum, copper, tin oxide, and molybdenum disulfide. The formation of the hot-melt colored layer is performed by adding the colorant component and the binder component as described above, and further, if necessary, a mineral oil, a vegetable oil, a higher fatty acid such as stearic acid, a plasticizer, an antioxidant, and a filler. A hot melt coat, a hot lacquer coat, a gravure coat, a gravure reverse, and a hot melt coat, a hot lacquer coat, a gravure coat, a gravure coat Coating, roll coating, etc. are performed. Also, there is a method of forming using an aqueous or non-aqueous emulsion coating liquid. The thickness of the hot-melt colored layer should be determined so as to balance the required printing density with the thermal sensitivity, and is preferably in the range of 0.5 to 6.5 g / m ² , A range of 5 to 4.5 g / m ² is particularly preferred.

(Heat-resistant lubricating layer) A heat-resistant lubricating layer can be provided on the other surface of the substrate film in order to prevent sticking of the thermal head and improve the slipperiness. The heat-resistant lubricating layer is formed by suitably using a binder resin to which a slip agent, a surfactant, inorganic particles, organic particles, a pigment and the like are added. Binder resin used in the heat-resistant lubricating layer, for example, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose resin such as nitrified cotton, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, Examples include vinyl-based resins such as polyvinyl acetal, polyvinyl pyrrolidone, acrylic resin, polyacrylamide, acrylonitrile-styrene copolymer, polyester resin, polyurethane resin, silicone-modified or fluorine-modified urethane resin.

Among them, those having several reactive groups, for example, those having a hydroxyl group are used, and as a crosslinking agent,
It is preferable to use a crosslinked resin in combination with a polyisocyanate or the like. The means for forming the heat-resistant lubricating layer is, as described above, a material obtained by adding a slipping agent, a surfactant, inorganic particles, organic particles, a pigment, etc. to a binder resin, by dissolving or dispersing the same in a suitable solvent, A working liquid is prepared, and the coating liquid is applied and dried by a conventional coating means such as a gravure coater, a roll coater, and a wire bar.

As the heating means in the image formation using the above-mentioned thermal transfer film, any conventionally known method capable of controlling the amount of heating in accordance with image information from a computer can be used. For example, a thermal head used for a word processor, a facsimile, or the like, a laser head used for a laser printing printer, or the like can be used. Further, when an electric heating layer is provided on the back side of the thermal transfer film, it is also possible to use an electric heating type energizing head for a fusion transfer method. Needless to say, the thermal transfer film of the present invention can be applied to color printing, and a multicolor thermal transfer film is also included in the scope of the present invention. Note that the thermal transfer film of the present invention is not limited to the above embodiment of the present invention. Further, the transfer object used in combination with the thermal transfer film of the present invention can be any conventionally known transfer object.

[0026]

The present invention will be described more specifically with reference to examples and comparative examples. In the text, "part" or "%" means
Unless otherwise specified, it is based on mass. (Heat-meltable colored layer ink) The materials shown in Table 1 were heated to 120 ° C., melt-mixed, and vigorously stirred with steel beads, so that the heat-meltable color used in Examples 1 to 25 and Comparative Examples 1 to 11 were obtained. Layer inks 1 to 5 were prepared. Table 1 shows the results of measuring the melt viscosities of the obtained hot-melt colored inks 1 to 5 at 100 ° C. In addition, the measurement of the melt viscosity was performed with the following measuring device and measuring conditions.

Apparatus name: Viscoelasticity measuring apparatus Rotovisco R
V20 (manufactured by HAKKE) ・ Measurement head: M5 ・ Sensor system: Sensor system cone plate PK5 (opening angle 0.5 °, cone plate radius 25m)
m, and the set temperature was 100 ° C. The melting peak temperature is measured according to JIS K7121-
The measurement was performed according to the rules of 1987. However, when a plurality of melting peak temperatures are observed, the temperature having the largest endothermic amount is defined as the melting peak temperature defined in the present invention.

[0028]

[Table 1]

(Examples 1 to 25) As a base film,
Using a 4.5 μm thick polyethylene terephthalate film (manufactured by Toray Industries, Inc.),
An intermediate layer coating solution having a composition shown in Table 2 below is applied by a gravure coating method so as to have a coating amount shown in Table 2,
After the solvent was dried with hot air at 100 ° C., it was wound up. Next, on each intermediate layer, the heat-meltable colored layer ink shown in Table 1 was heated to 120 ° C., and dried to a thickness of 4.5 μm by a hot melt coating method using a roll coat. To form a hot-melt colored layer by applying
Twenty-five thermal transfer films were made. However, on the other surface of the base film, a heat-resistant lubricating layer coating solution having the following composition was applied by a roll coater and dried, and a heat-resistant lubricating layer having a thickness of 0.1 μm when dried was previously provided.

[0030]

[Table 2]

(Heat-resistant lubricating layer coating liquid) Polyvinyl butyral resin 20 parts (ESREC BX-1 manufactured by Sekisui Chemical Co., Ltd.) Talc (Microace L-1 manufactured by Nippon ALC Co., Ltd.) 30 parts Melamine resin fine particles (Nippon Shokubai Chemical Co., Ltd.) Industrial Co., Ltd. eposter S) 30 parts Polyisocyanate (Takeda Pharmaceutical Co., Ltd. Takenate A-3) 40 parts Toluene / methyl ethyl ketone (mass ratio 1/1) 900 parts

(Comparative Examples 1 to 11) The coating liquid for the intermediate layer and the ink for the hot-melt colored layer were changed to the compositions shown in Tables 1 and 2 above, and coated so as to have the respective coating amounts shown in Table 2. Except having performed, the thermal transfer film of Comparative Examples 1-11 was produced like Example.

The thermal transfer films obtained in the above Examples and Comparative Examples were evaluated for the suitability of the intermediate layer, the suitability of the hot-melt colored layer by the following evaluation methods.
Print quality and confidential leakage prevention were evaluated. (Coating Suitability of Intermediate Layer) The coating suitability when applying the intermediate layer on the substrate film was evaluated according to the following evaluation criteria. A: The intermediate layer after drying the solvent does not show any tack when touched with a finger, and the base film surface after winding and the intermediate layer adhere to each other by the tack of the intermediate layer. There was no. B: A slight tack was observed when the intermediate layer after drying the solvent was touched with a finger, but it was found that the substrate film surface after winding and the intermediate layer adhered due to the tack of the intermediate layer. Did not. C: Tack was observed when the intermediate layer after drying the solvent was touched with a finger, and a state in which the substrate film surface after winding and the intermediate layer were adhered by the tack of the intermediate layer was observed. .

(Coating Suitability of Hot Melt Colored Layer) The coating suitability when applying the hot melt colored layer coating solution on the intermediate layer was evaluated according to the following evaluation criteria. A: A coating surface of the same high quality as that obtained when the coating liquid for the hot-melt colored layer was directly coated on the base film was stably obtained. B: As compared with the case where the coating liquid for the hot-melt colored layer was directly coated on the substrate film, a coating surface with more conspicuous unevenness was obtained. C: A coated surface which was so uneven that it could not be practically used as a thermal transfer film was obtained.

(Printing quality) Using a facsimile (Telecopier 7033) manufactured by Fuji Xerox Co., Ltd.
Printing in copy mode (document type: text, print density: normal) on Xerox printer paper (# 4024, Beck smoothness 32 seconds) using the thermal transfer films obtained in the above Examples and Comparative Examples Was performed. In order to be able to change the printing energy of the thermal head to an arbitrary value, the facsimile was appropriately modified so that an arbitrary voltage could be externally applied between the common electrode and the ground electrode of the thermal head mounted on the facsimile. Used for evaluation. The manuscript to be copied includes an Oki Electric printer (MICROLINE 900 PSI).
ILT) with Fuji Xerox Co., Ltd. copy paper (W
R-100) was used as an 8-point size uppercase alphabet (courier typeface).

At the time of printing, when the above-mentioned original is copied with the thermal transfer films prepared in Examples 1 to 25 and Comparative Examples 1 to 11, the minimum voltage at which the distinction between capital letters E and B can be visually recognized. It was decided to print. Then, the printing result of the uppercase alphabet at the time of printing at the lowest voltage was visually observed, and the loss of characters and thin lines due to the occurrence of white spots was evaluated according to the following criteria. A: Defects of characters and fine lines due to the occurrence of white spots were hardly observed, and extremely good printed matter was obtained. B: Defects in characters and fine lines due to occurrence of white spots were slightly observed, but good printed matter was obtained. C: The loss of characters and fine lines due to the occurrence of white spots was remarkably observed, and a printed matter having an appearance in which the characters and fine lines were remarkably blurred was obtained.

(Protection of Security Leakage) The surface of the heat-meltable colored layer of the thermal transfer film after printing under the same printing conditions as the printing quality described above was subjected to a Fuji Xerox copier (Vision 675) manufactured by Fuji Xerox Co., Ltd. Copied on copy paper (WR-100) manufactured by Co., Ltd. The density setting for copying was "automatic". Visually observe the image copied on the copy paper, whether the contents printed on the thermal transfer film can be read, according to the following criteria,
An evaluation was performed. A: The printed content could not be read. B: The printed content could hardly be understood. C: The printed contents could be easily read.

(Evaluation Results) The evaluation results are shown in Table 3 below.

[0039]

[Table 3]

[0040]

As described above, according to the thermal transfer film of the present invention, while the monomethyl itaconate remains molten, the adhesiveness between the intermediate layer and the heat-meltable colored layer is reduced, and the area to which energy is applied is reduced. It is possible to transfer the heat-meltable colored layer of the transfer-receiving paper without causing a dropout,
A good printed matter with little omission was obtained even on rough paper. In addition, when the hot melt coating method is applied to the base film provided with the intermediate layer with a hot-melt coloring layer, the intermediate layer containing monomethyl itaconate is excellent in coating suitability of the intermediate layer containing monomethyl itaconate.
Even when the heat-meltable colored layer ink is melted by the heat of the heat-melted colored layer ink to form a low-viscosity liquid, the hot-meltable colored layer ink can be stably overcoated with good surface quality. Also,
By adding carbon black to the intermediate layer,
It becomes difficult to read the printed content from the thermal transfer film after printing, and it is also possible to have an effect of preventing confidential leakage.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mitsuru Maeda 1-1-1, Ichigaya-Kagacho, Shinjuku-ku, Tokyo Inside Dai Nippon Printing Co., Ltd. (72) Inventor Fumihiko Mizukami 1-chome, Ichigaya-cho, Shinjuku-ku, Tokyo No. 1 Dai Nippon Printing Co., Ltd. F-term (reference) 2H111 AA14 AA26 AA33 BA07 BA34 BA53 BA55 BA61 BA71 BB06

Claims (6)

[Claims] 1. A thermal transfer film having a heat-meltable colored layer provided on a base film via an intermediate layer, wherein the intermediate layer is composed of monomethyl itaconate and a softening temperature (JIS K
A thermal transfer film comprising a binder resin having a softening temperature (measured by a ring and ball method specified in 2207-1980) of 130 ° C. or more and 400 ° C. or less. 2. The melting peak temperature of the monomethyl itaconate (the melting peak temperature defined in JIS K7121-1987) and the melting peak temperature of the hot-melt colored layer (JIS).
2. The thermal transfer film according to claim 1, wherein the difference in the melting peak temperature defined in K7121-1987 is 0 ° C. or more and 10 ° C. or less. 3. The number average molecular weight of the binder resin is as follows:
The thermal transfer film according to claim 1, wherein the thermal transfer film has a number of 1500 or more and 100000 or less. 4. The thermal transfer film according to claim 1, wherein said binder resin is a polyester resin. 5. The thermal transfer film according to claim 4, wherein the main chain of the polyester resin contains an ethylenically unsaturated bond. 6. The thermal transfer film according to claim 1, wherein carbon black is blended in the intermediate layer.