JP7426911B2 - thermal transfer media - Google Patents

Description

The present invention relates to thermal transfer media.

After filling a package with food and sealing the package, the package may be sterilized and then put on the market.
An example of the package is a bag made of laminate film.
As the laminate film, for example, a laminate is used in which a polypropylene film is laminated on the inside that contacts the food, a stretched nylon (ONY) film or a polyethylene terephthalate (PET) film is laminated on the outside, and if necessary, an aluminum foil is laminated in the middle.

The adoption of a thermal transfer printing method is being considered in order to print arbitrary characters (including symbols such as barcodes, etc., hereinafter the same) on demand on the outer surface of a package made of laminate film.
The thermal transfer printing method uses a thermal transfer medium that includes a base material and a thermal transfer layer provided on the surface of the base material so as to be thermally transferable.

Further, the thermal transfer layer generally has a laminated structure including a colored layer and an adhesive layer that are laminated in order on a base material (see Patent Documents 1 to 3, etc.).
In the thermal transfer printing method, with the thermal transfer layer of the thermal transfer medium in contact with the surface of the package, the thermal transfer layer is applied to the print pattern from the opposite side (back side) of the base material using a thermal head of a thermal transfer printer. Selectively heat as needed.

Then, the thermal transfer layer selectively melts or softens according to the heated pattern, peels off from the base material, and is thermally bonded to the surface of the package, thereby printing characters on the surface.

Japanese Patent Application Publication No. 11-334227 Japanese Patent Application Publication No. 9-86056 JP2020-69722A

Sterilization of packages filled with food is broadly classified into boil sterilization and retort sterilization. In boil sterilization, the package is boiled at a temperature below 100° C., which is the boiling point of water.
Furthermore, in retort sterilization, a package (retort pouch) filled with food and sealed is heat treated with water or steam heated to a high temperature of over 100° C., for example, under pressure.

Specifically, retort sterilization treatment is classified into semi-retort sterilization treatment, retort sterilization treatment, and high retort sterilization treatment depending on the heating temperature.
In any case, the package is exposed to high temperatures during these sterilization treatments, including boil sterilization.
Therefore, characters printed on the surface of packages etc. using the thermal transfer printing method cannot be rubbed with a paper towel after being heated to such high temperatures, agitated in high-temperature water, or exposed to a stream of high-temperature steam. High heat treatment resistance without peeling is required.

Additionally, alcohol such as ethanol or oil such as edible oil may adhere to the package during the food manufacturing process, bagging process, or after bagging or sterilization.
However, even in that case, the characters printed on the surface of the package etc. are required to have high alcohol and oil resistance so as not to melt or bleed.
An object of the present invention is to provide a heat-sensitive transfer medium capable of printing characters having high heat treatment resistance, alcohol resistance, and oil resistance on the surface of a package or the like made of a laminate film.

The present invention includes a base material and a thermal transfer layer provided on the base material so as to be thermally transferable, and the thermal transfer layer includes a colored layer and an adhesive layer laminated in this order on the base material, and the thermal transfer layer includes a colored layer and an adhesive layer laminated in this order on the base material. The colored layer contains a chlorinated polyolefin resin, a polyester resin, and an isocyanate curing agent, and the adhesive layer is a thermal transfer medium containing an acid-modified polyolefin resin.

According to the present invention, it is possible to provide a thermal transfer medium capable of printing characters having high heat treatment resistance, alcohol resistance, and oil resistance on the surface of a package or the like made of a laminate film.

As described above, the thermal transfer medium of the present invention includes a base material and a thermal transfer layer provided on the base material so as to be thermally transferable, and the thermal transfer layer includes a colored layer laminated in order on the base material, and an adhesive layer, the colored layer contains a chlorinated polyolefin resin, a polyester resin, and an isocyanate curing agent, and the adhesive layer contains an acid-modified polyolefin resin.

In the thermal transfer medium of the present invention, the chlorinated polyolefin resin contained in the colored layer is particularly difficult to dissolve in alcohol such as ethanol. Alcohol properties can be improved.
Furthermore, since the polyester resin contained in the colored layer is particularly difficult to dissolve in oil such as edible oil, the oil resistance of the characters can be improved.

Furthermore, the polyester resin can be cured with an isocyanate curing agent to increase the film strength of the colored layer, thereby further improving the alcohol resistance and oil resistance of the characters.
On the other hand, the acid-modified polyolefin resin contained in the adhesive layer is particularly excellent in thermal adhesion to the ONY film constituting the surface of a package, etc., and in adhesive strength after thermal adhesion.
Furthermore, the acid-modified polyolefin resin has appropriate thermal adhesion and adhesive strength to PET films that constitute the surfaces of packages and the like.

Therefore, the heat treatment resistance of characters printed on the surface of a package or the like by thermally transferring the thermal transfer layer including the adhesive layer can be improved compared to the current state.
Moreover, the alcohol resistance of characters can also be improved.
Therefore, according to the thermal transfer medium of the present invention, it is possible to print characters with high heat treatment resistance, alcohol resistance, and oil resistance on the surface of a package etc. due to the functions of the colored layer and adhesive layer. .

In each of Patent Documents 1 to 3, the thermal transfer layer includes a colored layer and an adhesive layer that are laminated in order on a base material, and each of the above-mentioned layers individually contains a polyester resin, a chlorinated polyolefin resin, etc. as appropriate. However, there are some good things mentioned.
Further, Patent Document 1 describes that the colored layer may contain a curing agent such as polyisocyanate.

Further, Patent Document 2 describes that when the object to be printed is a polyolefin film, particles made of a chlorinated polyolefin resin or a maleic anhydride-modified polyolefin resin are dispersed on the surface of the adhesive layer.
However, none of the thermal transfer media described in Patent Documents 1 to 3 is specialized for printing on food packages, and the resins contained in the colored layer and the adhesive layer are used in a specific combination defined by the present invention. These patent documents do not mention anything about this.

Therefore, in the thermal transfer media described in Patent Documents 1 to 3, characters having high heat treatment resistance, alcohol resistance, and oil resistance equivalent to those of the present invention are printed on the surface of the ONY film or PET film that constitutes the surface of the package etc. It cannot be printed.
This is also clear from the results of Examples and Comparative Examples described later.
《Thermal transfer medium》
As described above, the thermal transfer medium of the present invention includes a base material and a thermal transfer layer provided on the base material so as to be thermally transferable, and the thermal transfer layer includes a colored layer laminated in this order on the base material, and an adhesive layer, the colored layer contains a polyester resin, a chlorinated polyolefin resin, and an isocyanate curing agent, and the adhesive layer contains an acid-modified polyolefin resin.

By configuring the colored layer and the adhesive layer as described above, as described above, the heat treatment resistance, alcohol resistance, and oil resistance of the characters after thermal transfer can be improved compared to the current state.
Moreover, the colored layer is a so-called heat-sensitive layer that partially melts or softens and peels off from the base material in response to heat applied from the back side of the base material. By laminating it with an adhesive layer, the function of each layer can be improved individually.

In other words, by providing a colored layer separately from the adhesive layer and interposed between the adhesive layer and the base material, heat applied from the back side of the base material is transmitted to the colored layer as efficiently as possible, and the coloring is improved. The thermal sensitivity of the layer and of the thermal transfer layer as a whole during printing can be improved.
Furthermore, since the colored layer is located on the surface side after printing, it is also possible to improve the color density and color development of the characters.

On the other hand, the adhesive layer does not contain components for the colored layer, especially colorants (pigments) that interfere with thermal adhesion and film strength, so it has excellent thermal adhesion to the surface of packages, etc., and adhesive strength after thermal adhesion. It is also possible to further improve the heat treatment resistance of the characters after thermal transfer.
<Base material>
Examples of the base material include films of resins such as polysulfone, polystyrene, polyamide, polyimide, polycarbonate, polypropylene, polyester, and triacetate, thin papers such as condenser paper and glassine paper, and cellophane as in the past.

Among these, polyester films such as PET and polyethylene naphthalate are preferred from the viewpoints of mechanical strength, dimensional stability, heat resistance, cost, and the like.
Although the thickness of the base material can be arbitrarily set depending on, for example, the specifications of the thermal transfer printer, it is preferably 1 μm or more, particularly 2 μm or more, and preferably 10 μm or less, particularly 8 μm or less.

When the thickness is less than this range, the strength (tensile strength, etc.) of the base material tends to decrease.
For example, when manufacturing a thermal transfer medium by coating the surface of the base material with a coating material that is the basis of each layer constituting the thermal transfer layer, or by slitting it into a ribbon shape of a predetermined width, or when manufacturing a thermal transfer medium, When the thermal transfer medium is wound up into a roll, the base material may be easily broken.
On the other hand, if the thickness of the base material exceeds the above range, the heat applied from the back side by the thermal head cannot be efficiently transferred to the thermal transfer layer through the base material, resulting in a decrease in thermal sensitivity during printing. This may cause characters to become blurred.

In contrast, by setting the thickness of the base material within the above range, while ensuring strength, the heat applied from the back side of the base material by the thermal head of the thermal transfer printer is transferred as efficiently as possible to the thermal transfer layer through the base material. As a result, thermal sensitivity during printing can be improved.
Therefore, it is possible to print clear characters with less blurring.
<Back layer>
On the opposite side (back side) of the base material from the surface on which the thermal transfer layer is formed, a back layer is formed in the same manner as before in order to improve the heat resistance, slipperiness, scratch resistance, etc. of the back side that comes into contact with the thermal head. You may.

That is, the back layer can be formed of a silicone resin, a fluororesin, a silicone/fluorine copolymer resin, a nitrocellulose resin, a silicone-modified urethane resin, a silicone-modified acrylic resin, and may further contain a lubricant if necessary. good.
The back layer can be formed by applying a coating material in which the above-mentioned resin or the like is dissolved or dispersed in a solvent to the back surface of the base material, and then drying the coating material.

Although the thickness of the back layer can be arbitrarily set according to the specifications of the thermal transfer printer, etc., it is preferable that the thickness is 0.05 g/m ² or more, especially 0.1 g/m ² or more in terms of solid content per unit area. It is preferably 0.5 g/m ² or less, particularly preferably 0.4 g/m ² or less.
If the thickness is less than this range, a continuous layer that functions well as a back layer cannot be formed on the back surface of the base material, and the above-mentioned effects of providing the back layer may not be sufficiently obtained. .

On the other hand, if the thickness of the back layer exceeds the above range, the heat applied from the back side of the base material by the thermal head cannot be efficiently transferred to the thermal transfer layer through the back layer and the base material. Thermal sensitivity during printing may be reduced, and characters may become blurred.
On the other hand, by setting the thickness within the above range, a continuous layer that functions well as a back layer is formed on the back surface of the base material, and the above-mentioned effects of providing the back layer can be sufficiently secured. be able to.

In addition, the heat applied from the back side of the substrate by the thermal head can be transmitted as efficiently as possible to the thermal transfer layer through the back layer and the substrate, improving thermal sensitivity during printing and making it difficult to cause blurring. You can also print clearly.
<Release layer>
A release layer may be provided between the base material and the thermal transfer layer.

The release layer has the function of continuing to fix the thermal transfer layer to the surface of the base material until the thermal transfer layer is thermally transferred, and also has the function of melting or softening by heating with a thermal head and peeling the thermal transfer layer from the base material. Examples include layers made of various materials.
An example of the material for forming the release layer is wax.
Further, as the wax, one or more types of wax such as polyethylene wax, carnauba wax, paraffin wax, microcrystalline wax, and Fischer-Tropsch wax can be used.

Further, a thermoplastic resin such as ethylene vinyl acetate resin (EVA) may be added to the wax in order to prevent so-called crumbling, in which the thermal transfer layer before thermal transfer peels off from the base material.
In order to satisfactorily exhibit the above-mentioned functions, the release layer preferably has a melting point of 50°C or higher, particularly 60°C or higher, and preferably 150°C or lower, particularly 120°C or lower.

In order to form a release layer having a melting point within the above range, a wax having a melting point within the above range may be selected from among waxes.
Alternatively, two or more waxes may be used in combination to adjust the melting point to fall within the above range.
The release layer can be formed by applying a coating material prepared by dissolving or dispersing wax or the like in a solvent onto the surface of the base material, and then drying the coating material.

Alternatively, a peeling layer can be formed by hot-melt coating, in which the wax or the like is heated and melted, applied to the surface of the base material, and then cooled and solidified.
The thickness of the release layer is preferably 0.1 g/m ² or more, particularly 0.2 g/m 2 or more, and 1.4 g/m ² or less, especially 1.2 g/m ² or more, expressed as solid content per unit area. It is preferable that it is less than ^m2 .

By setting the thickness above this range, it is possible to form a continuous layer on the surface of the base material that functions well as a release layer, improving the transferability of the thermal transfer layer, and preventing blurring and sharpness of characters due to poor transfer. It is possible to satisfactorily suppress the occurrence of a decrease.
In addition, by setting the thickness of the release layer within the above range, the heat applied from the back side of the substrate by the thermal head can be transmitted as efficiently as possible to the thermal transfer layer through the release layer, thereby increasing the thermal sensitivity of the thermal transfer medium. can be improved.

Therefore, it is possible to satisfactorily suppress the occurrence of blurring of characters and deterioration in sharpness due to poor transfer.
[Thermal transfer layer]
The thermal transfer layer includes a colored layer and an adhesive layer, which are laminated in order as described above, either directly on the base material or, if a release layer is provided on the surface of the base material, on the release layer.

<Colored layer>
The colored layer is a heat-sensitive layer that partially melts or softens and peels off from the base material in response to heat applied locally from the back side of the base material by a thermal head, and as mentioned above, it is a layer that is heat-sensitive and peels off from the base material. Contains polyolefin resins, polyester resins, and isocyanate hardeners.
Moreover, the colored layer may contain any coloring agent.

(chlorinated polyolefin resin)
As mentioned above, chlorinated polyolefin resin is particularly difficult to dissolve in alcohols such as ethanol, so the coloring layer and even the thermal transfer layer containing the coloring layer are thermally transferred to improve the alcohol resistance of the letters printed on the surface of the package. can do.
Specific examples of chlorinated polyolefin resins include, but are not limited to, the following various products.

C supplied as a toluene solution from the Super Chron (registered trademark) series manufactured by Nippon Paper Industries Co., Ltd. [chlorine content: 35%, viscosity: 500 to 2000 mPa・s (25 ° C.), solid content: 55%], L-206 [Chlorine content: 32%, viscosity: 50-100 mPa・s (25℃), solid content: 50%], 813A [chlorine content: 30%, viscosity: 50-250mPa・s (25℃) , solid content: 55%], 803M [chlorine content: 30%, viscosity: 1500 to 4500 mPa・s (25°C), solid content: 30%], 803MW [chlorine content: 29.5%, viscosity: 350 ~650 mPa・s (25℃), solid content: 20%], 803LT [chlorine content: 26.5%, viscosity: 50 to 120 mPa・s (25℃), solid content: 30%], 1026 [chlorine content rate: 26%, viscosity: 250-750mPa・s (25℃), solid content: 30%], 803L [chlorine content: 26%, viscosity: 1500-4500mPa・s (25℃), solid content: 30% ], or 814HS [chlorine content: 41%, viscosity in 60% toluene solution: 500 to 2000 mPa・s (25°C)], 390S [chlorine content: 36%, 50% toluene solution], supplied as a solid product. Viscosity: 200 to 600 mPa·s (25°C)], the above 803 MW solid product [chlorine content: 29.5%], and the 803 L solid product [chlorine content: 26%].

One or more of these chlorinated polyolefin resins can be used.
As the chlorinated polyolefin resin, it is particularly preferable to select and use a chlorinated polyolefin resin having a chlorine content of 29% or more from among the above.
Chlorinated polyolefin resins with a chlorine content less than this range are not sufficiently compatible with polyester resins, resulting in a decrease in the film strength of the colored layer, resulting in a decrease in alcohol resistance, oil resistance, and heat treatment resistance of letters. There is.

Furthermore, since there are few polar groups, the dispersibility of colorants (pigments) such as conductive carbon black, which will be described later, is particularly reduced, resulting in uneven dispersion, which may reduce the color density of characters.
On the other hand, by selecting and using a chlorinated polyolefin resin with a chlorine content of 29% or more, the reduction in colorant dispersibility and the accompanying decrease in the color density of the characters can be suppressed, while the characters can be improved. Alcohol resistance, oil resistance, and heat treatment resistance can be improved.

Note that the upper limit of the chlorine content is not particularly limited, and any of the various available chlorinated polyolefin resins having a chlorine content above the above range can be used.
However, chlorinated polyolefin resins with too high a chlorine content have high polarity and are particularly easily soluble in alcohol, which may reduce the alcohol resistance of letters.
Therefore, in consideration of ensuring good solubility in organic solvents, the chlorine content of the chlorinated polyolefin resin is preferably 45% or less, particularly 42% or less, even within the above range.

(polyester resin)
Polyester resin is particularly difficult to dissolve in oils such as edible oil, so it is possible to thermally transfer the colored layer, and even the thermal transfer layer containing the colored layer, to improve the oil resistance of the characters printed on the surface of the package.
Further, the polyester resin can be cured with an isocyanate curing agent to form a stronger film, thereby further improving the alcohol resistance, oil resistance, and heat treatment resistance of the characters.

Moreover, since the cured polyester resin is hard and slippery, it is also possible to improve the scratch resistance and scratch resistance of the characters printed on the surface of the package.
Specific examples of polyester resins include, but are not limited to, the following various products.
Among the polymer saturated copolymer polyester resins of the Diaclone (registered trademark) series manufactured by Mitsubishi Chemical Corporation, ER-1002 [Glass transition temperature Tg: 60°C, melting start temperature: 120°C, number average molecular weight Mn: 13500 , hydroxyl value: 5 to 10 mgKOH/g], ER-1003 [glass transition temperature Tg: 50°C, melting start temperature: 125°C, number average molecular weight Mn: 19000, hydroxyl value: 5 to 10mgKOH/g], ER-1004 [Glass transition temperature Tg: 58°C, melting start temperature: 124°C, number average molecular weight Mn: 14000, hydroxyl value: 5 to 10 mgKOH/g], ER-2001 [Glass transition temperature Tg: 15°C, melting start temperature: 83 °C, number average molecular weight Mn: 20,000, hydroxyl value: 5 to 10 mgKOH/g].

Among the amorphous polyester resins of the Vylon (registered trademark) series manufactured by Toyobo Co., Ltd., 200 [glass transition temperature Tg: 67 ° C., number average molecular weight Mn: 17000, hydroxyl value: 6 mgKOH/g], 220 [glass transition temperature Tg: 53°C, number average molecular weight Mn: 3000, hydroxyl value: 50mgKOH/g], 226 [glass transition temperature Tg: 65°C, number average molecular weight Mn: 8000, hydroxyl value: 20mgKOH/g], 240 [glass transition temperature Tg: 60°C, number average molecular weight Mn: 15000, hydroxyl value: 9mgKOH/g], 270 [glass transition temperature Tg: 67°C, number average molecular weight Mn: 23000, hydroxyl value: 5mgKOH/g], 280 [glass transition temperature Tg: 68°C, number average molecular weight Mn: 18000, hydroxyl value: 6mgKOH/g], 290 [glass transition temperature Tg: 72°C, number average molecular weight Mn: 22000, hydroxyl value: 5mgKOH/g], GK-250 [glass Transition temperature Tg: 60°C, number average molecular weight Mn: 10000, hydroxyl value: 11mgKOH/g], GK-360 [glass transition temperature Tg: 56°C, number average molecular weight Mn: 16000, hydroxyl value: 7mgKOH/g], GK -880 [Glass transition temperature Tg: 84°C, number average molecular weight Mn: 18000, hydroxyl value: 5mgKOH/g], 103 [glass transition temperature Tg: 47°C, number average molecular weight Mn: 23000, hydroxyl value: 5mgKOH/g] , 600 [Glass transition temperature Tg: 47°C, number average molecular weight Mn: 16000, hydroxyl value: 7mgKOH/g], GK-800 [glass transition temperature Tg: 50°C, number average molecular weight Mn: 27000, hydroxyl value: 7mgKOH/ g], 560 [glass transition temperature Tg: 7°C, number average molecular weight Mn: 19000, hydroxyl value: 8mgKOH/g], 630 [glass transition temperature Tg: 7°C, number average molecular weight Mn: 23000, hydroxyl value: 5mgKOH/ g], 670 [glass transition temperature Tg: 7°C, number average molecular weight Mn: 30000, hydroxyl value: 3mgKOH/g], GK-590 [glass transition temperature Tg: 15°C, number average molecular weight Mn: 7000, hydroxyl value: 17mgKOH/g], GK-830 [glass transition temperature Tg: 25°C, number average molecular weight Mn: 32000, hydroxyl value: 7mgKOH/g], BX-1001 [glass transition temperature Tg: -18°C, number average molecular weight Mn: 28000, hydroxyl value: 8 mgKOH/g].

Among the ELITEL (registered trademark) series manufactured by Unitika Co., Ltd., UE-3510 [glass transition temperature Tg: -25°C, hydroxyl value: 4mgKOH/g], UE-3400 [glass transition temperature Tg: -20°C, hydroxyl value :4mgKOH/g], UE-3220 [glass transition temperature Tg: 5°C, hydroxyl value: 3mgKOH/g], UE-3500 [glass transition temperature Tg: 15°C, hydroxyl value: 4mgKOH/g], UE-3210 [ Glass transition temperature Tg: 45°C, hydroxyl value: 4mgKOH/g], UE-9200 [glass transition temperature Tg: 65°C, hydroxyl value: 6mgKOH/g], UE-3600 [glass transition temperature Tg: 75°C, hydroxyl value :4mgKOH/g], UE-9800 [glass transition temperature Tg: 85°C, hydroxyl value: 4mgKOH/g], UE-9900 [glass transition temperature Tg: 101°C, hydroxyl value: 8mgKOH/g], UE-3320 [ Glass transition temperature Tg: 40°C, hydroxyl value: 60mgKOH/g], UE-9820 [glass transition temperature Tg: 52°C, hydroxyl value: 39mgKOH/g], UE-3350 [glass transition temperature Tg: 52°C, hydroxyl value :25mgKOH/g], UE-3380 [glass transition temperature Tg: 60°C, hydroxyl value: 15mgKOH/g].

One type or two or more types of these polyester resins can be used.
As the polyester resin, it is preferable to select and use a polyester resin having a number average molecular weight Mn of 10,000 or more and 33,000 or less.
Polyester resins having a number average molecular weight Mn less than this range tend to be easily soluble in alcohol and oil among polyester resins, and therefore may not be able to sufficiently improve the alcohol resistance and oil resistance of letters.

On the other hand, polyester resins with a number average molecular weight Mn exceeding the above range have low solubility in solvents, so it may not be easy to dissolve them in any solvent to prepare a coating material that will form the basis of a colored layer. .
On the other hand, by selecting and using a polyester resin with a number average molecular weight Mn within the above range, the alcohol resistance of the characters printed on the surface of the package can be improved while maintaining the ease of preparing the coating material. Oil resistance can be further improved.

Although other properties of the polyester resin are not particularly limited, the glass transition temperature Tg is preferably 20°C or higher, and preferably 90°C or lower.
Further, the hydroxyl value is preferably 50 mgKOH/g or less, particularly 20 mgKOH/g or less.
(mass ratio of both resins)
The mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer is preferably 0.1 or more, and preferably 4.5 or less.

If the mass ratio (CO)/(Ea) is less than this range, the proportion of the chlorinated polyolefin resin will be small, and the alcohol resistance of the letters, in particular, may be insufficient.
Furthermore, as will be described later, if a specific conductive carbon black is used, a certain degree of dispersibility can be ensured, but the dispersibility of the colorant such as the conductive carbon black decreases, resulting in uneven dispersion and the appearance of letters. Color density may also decrease.

On the other hand, when the mass ratio (CO)/(Ea) exceeds the above range, the proportion of the polyester resin decreases, so that the oil resistance of the letters may become insufficient.
Further, since the effect of increasing the film strength of the colored layer by curing the polyester resin cannot be obtained, the heat treatment resistance, alcohol resistance, and oil resistance of the characters may be reduced.
On the other hand, by setting the mass ratio (CO)/(Ea) within the above range, the alcohol resistance of the characters after thermal transfer is improved based on the alcohol resistance of the chlorinated polyolefin resin and the oil resistance of the polyester resin. Oil resistance can also be improved.

Further, by increasing the film strength of the colored layer by curing the polyester resin, the heat treatment resistance, alcohol resistance, and oil resistance of the characters after thermal transfer can all be further improved.
In addition, in consideration of further improving this effect, the mass ratio (CO)/(Ea) is preferably 0.2 or more, especially 0.25 or more, even within the above range, and 4.2 or less, especially It is preferable that it is 4.0 or less.

(Isocyanate curing agent)
As the isocyanate curing agent, any of various isocyanate compounds having an isocyanate group in the molecule and capable of curing the polyester resin and increasing the film strength of the colored layer can be used.
Examples of such isocyanate compounds include, but are not limited to, aliphatic isocyanates, alicyclic isocyanates, aromatic isocyanates, araliphatic isocyanates, polyisocyanate monomers (organic triisocyanates, organic tetraisocyanates, and others). is also available.

Further, as the isocyanate compound, dimers, trimers, biurets, allophanates derived from the above-mentioned isocyanate compounds, polyisocyanates having a 2,4,6-oxadiazinetrione ring, etc. can also be used.
Among the above aliphatic isocyanates, examples include the following various compounds.

Ethyl isocyanate, 2-chloroethyl isocyanate, propyl isocyanate, butyl isocyanate, t-butyl isocyanate, hexyl isocyanate, heptyl isocyanate, dodecyl isocyanate, trimethylsilyl isocyanate, 3-(triethoxysilylpropylisocyanate), trimethylene diisocyanate, tetramethylene diisocyanate, Hexamethylene diisocyanate (HDI), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanatomethyl caproate.

Examples of the alicyclic isocyanate include the following various compounds.
Cyclopentyl isocyanate, cyclohexyl isocyanate, 1,3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI, isophorone diisocyanate), 4,4'-methylenebis(cyclohexyl isocyanate), methyl 2,4-cyclohexane diisocyanate, methyl 2,6-cyclohexane diisocyanate, 1,4-bis(isocyanatomethyl)cyclohexane, 1,3-bis(isocyanatomethyl)cyclohexane .

Examples of aromatic isocyanates include the following various compounds.
Phenyl isocyanate, 4-ethyl phenyl isocyanate, 4-butylphenyl isocyanate, 4-ethoxyphenylisocyanate, phenethyl isocyanate, benzyl isocyanate, methylbenzyl isocyanate, 2-methoxyphenylisocyanate, 3-methoxyphenylisocyanate, 4-methoxyphenylisocyanate, 2 -Methylphenyl isocyanate, 3-methylphenylisocyanate, 4-methylphenylisocyanate, 3,5-dimethylphenylisocyanate, 2,6-dimethylphenylisocyanate, 2-chlorophenylisocyanate, 3-chlorophenylisocyanate, 4-chlorophenylisocyanate, 2, 3-dichlorophenylisocyanate, 2,4-dichlorophenylisocyanate, 2,5-dichlorophenylisocyanate, 2,6-dichlorophenylisocyanate, 3,4-dichlorophenylisocyanate, 3,5-dichlorophenylisocyanate, 2,4,6-trichloroisocyanate, 2 - Bromophenyl isocyanate, 3-bromophenyl isocyanate, 4-bromophenyl isocyanate, 2-fluorophenyl isocyanate, 3-fluorophenyl isocyanate, 4-fluorophenyl isocyanate, 2-(trifluoromethyl) phenyl isocyanate, 3-(trifluoro Methyl) phenyl isocyanate, 4-(trifluoromethyl) phenyl isocyanate, 1-isocyanato-3,5-bis(trifluoromethyl)benzene, 2-nitrophenyl isocyanate, 3-nitrophenyl isocyanate, 4-nitrophenyl isocyanate, 1 -(1-naphthyl)ethyl isocyanate, 1-naphthyl isocyanate, 2-biphenyl isocyanate, 2,4'-diphenylmethane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene Diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI, 2,4- or 2,6-tolylene diisocyanate, or mixtures thereof), 4,4'- Toluidine diisocyanate, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate.

Examples of the aromatic aliphatic isocyanate include the following various compounds.
1,3- or 1,4-xylylene diisocyanate or mixtures thereof, ω,ω'-diisocyanate 1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene , or a mixture thereof.
Examples of the organic triisocyanate include triphenylmethane-4,4',4''-triisocyanate, 1,3,5-triisocyanatebenzene, and 2,4,6-triisocyanatetoluene.

Examples of the organic tetraisocyanate include 4,4'-diphenyldimethylmethane-2,2'-5,5'-tetraisocyanate.
As the isocyanate curing agent, one or more of these isocyanate compounds can be used.
The proportion of the isocyanate curing agent can be set within any range that can increase the film strength of the colored layer through a curing reaction and form characters with excellent heat treatment resistance, alcohol resistance, and oil resistance.

More specifically, the proportion of the isocyanate curing agent may be set in an optimal range depending on the functional group equivalent of the isocyanate group and the functional group equivalent of the polyester resin that undergoes a curing reaction with the isocyanate group.
(colorant)
As the colorant, one or more of various colorants can be used depending on the color of the colored layer.

In particular, pigments are preferable as the coloring agent, considering improving the weather resistance of the characters printed on the surface of the package.
For example, carbon black is preferable as a black pigment, and specific examples of carbon black include, but are not limited to, the following various carbon blacks.

Mitsubishi Chemical Corporation's MA77 powder [LFF, DBP absorption: 68cm ³ /100g], MA7 powder [LFF, DBP absorption: 66cm ³ /100g], MA7 granular [LFF, DBP absorption: 65cm ³ /100g], MA8 powder [LFF, DBP absorption: 57cm ³ /100g], MA8 granular [LFF, DBP absorption: 51cm ³ /100g], MA11 powder [LFF, DBP absorption: 64cm ³ /100g] , MA100 powder [LFF, DBP absorption: 100cm ³ /100g], MA100 granular [LFF, DBP absorption: 95cm ³ /100g], MA100R powder [LFF, DBP absorption: 100cm ³ /100g], MA100R granular [LFF, DBP absorption: 95cm ³ /100g], MA100S powder [LFF, DBP absorption: 100cm ³ /100g], MA230 powder [LFF, DBP absorption: 113cm ³ /100g], MA220 powder [LFF] , DBP absorption: 93cm ³ /100g], MA14 powder [LFF, DBP absorption: 73cm ³ /100g].

Mitsubishi Chemical Corporation #3030B (Furnace method, DBP absorption: 130cm ³ /100g), #3040B (Furnace method, DBP absorption: 114cm ³ /100g), #3050B (Furnace method, DBP absorption: 175cm ³ /100g), #3230B (Furnace method, DBP absorption: 140cm ³ /100g), #3350B (Furnace method, DBP absorption: 164cm ³ /100g), #3400B (Furnace method, DBP absorption: 175cm ³ /100g) 100g).

#5500 (Furnace method, DBP absorption: 155cm ³ /100g), #4500 (Furnace method, DBP absorption: 168cm ³ /100g), #4400 of the Toka Black (registered trademark) series manufactured by Tokai Carbon Co., Ltd. (furnace method, DBP absorption: 135 cm ³ /100g), #4300 (furnace method, DBP absorption: 142 cm ³ /100g).

Of the PRINTEX (registered trademark) series manufactured by ORION ENGINEERED CARBON, L (Furnace method, DBP absorption: 120cm ³ /100g), L6 (Furnace method, DBP absorption: 126cm ³ / 100g).
975 (furnace method, 170 cm ³ /100 g), SC (furnace method, 115 cm ³ /100 g) of the CONDUCTEX (registered trademark) series manufactured by Birla Carbon.

Of the VULCAN (registered trademark) series manufactured by CABOT, XC72 (Furnace method, DBP absorption: 174cm ³ /100g), 9A32 (Furnace method, DBP absorption: 114cm ³ /100g), manufactured by the same company 3700 of the BLACK PEARLS series (furnace method, DBP absorption: 111 cm ³ /100 g).

Among the Denka Black (registered trademark) series manufactured by Denka Co., Ltd., Denka Black granular products (acetylene method, DBP absorption amount: 160 cm ³ /100 g), FX-35 (acetylene method, DBP absorption amount: 220 cm ³ /100 g), HS-100 (acetylene method, DBP absorption: 140cm ³ /100g).
Of the KETJENBLACK (registered trademark) series manufactured by Lion Specialty Chemicals Co., Ltd., EC300J (gasification method, DBP absorption amount: 360 cm ³ /100g), EC600DJ (gasification method, DBP absorption amount: 495 cm ³ /100g).

One or more types of these carbon blacks can be used.
Among the carbon blacks mentioned above, it is preferable to select and use carbon blacks produced by a furnace method, an acetylene method, a gas method, etc. and having a DBP absorption amount of 100 cm ³ /100 g or more.
Such carbon black is generally called conductive carbon black, and has a long structure chain and high oil absorption, so it is said to have low dispersibility in resins and the like.

However, especially for polyester resins that satisfy the range of number average molecular weight Mn mentioned above, conductive carbon black has better dispersibility than ordinary carbon black for coloring such as LFF.
By uniformly dispersing as much conductive carbon black as possible in the colored layer, the characters printed on the surface of the package can be colored black with higher color density.

Although the reason for this is not clear, it is presumed that the reason is that the polyester resin has good compatibility with the conductive carbon black.
In particular, the above-mentioned polyester resin is suitable as a toner for electrophotography, has appropriate chargeability, has a high molecular weight, and has some kind of difference between the length of the structural chain of carbon black and the like. It is assumed that there is a relationship.

However, conductive carbon black with a DBP absorption of more than 300 cm ³ /100 g has a too large specific surface area, which limits the amount that can be dispersed in the resin. It may not be possible to color to a high black color.
Therefore, as the conductive carbon black, it is particularly preferable to select and use carbon black whose DBP absorption amount is 300 cm ³ /100 g or less.

Further, as the conductive carbon black, it is more preferable to use a granular conductive carbon black having a secondary particle diameter of approximately 100 μm or more and 3000 μm or less.
The proportion of carbon black is preferably 30 parts by mass or more, especially 50 parts by mass or more, and preferably 100 parts by mass or less, especially 90 parts by mass or less, per 100 parts by mass of the total amount of chlorinated polyolefin resin and polyester resin. .

If the proportion of carbon black is less than this range, the characters printed on the surface of the package may not be colored black with high color density.
On the other hand, if the proportion of carbon black exceeds the above range, the strength of the colored layer may decrease and the heat treatment resistance, alcohol resistance, and oil resistance of the characters printed on the surface of the package may become insufficient. be.

In contrast, by setting the proportion of carbon black within the above range, the characters printed on the surface of the package can be printed with high color density while suppressing the deterioration of heat treatment resistance, alcohol resistance, and oil resistance. Can be colored black.
The colored layer is formed by dissolving or dispersing chlorinated polyolefin resin and polyester resin in any solvent and dispersing carbon black, applying the coating material on the base material or release layer, and then drying it. can do.

(dispersant)
A dispersant may be added to the coating material in order to improve the dispersibility of carbon black.
Specific examples of dispersants that can be incorporated into coating materials in which the solvent is an organic solvent such as toluene or MEK include, but are not limited to, the following various products.
3000, 5000, 9000, 12000, 17000, 20000, 24000 from the Solsperse (registered trademark) series manufactured by LUBRIZOL.

U, 203 of the Anti-Terra (registered trademark) series manufactured by BYK CHEMIE, 101, 107, 110, 130, 161, and BYK of the Disperbyk (registered trademark) series. , registered trademark) series, including P104, P104S, 240S, 9077, Bykumen (registered trademark), and Lactimon (registered trademark).

One or more of these dispersants can be used.
(Thickness of colored layer)
Although the thickness of the colored layer is not limited to this, for example, it is preferably 0.5 g/m ² or more, and preferably 1.5 g/m ² or less, expressed as solid content per unit area.
If the thickness of the colored layer is less than this range, the characters printed on the surface of the package may not be colored black with high color density.

Furthermore, the heat treatment resistance, alcohol resistance, and oil resistance of the characters may become insufficient.
On the other hand, if the thickness of the colored layer exceeds the above range, the heat applied from the back side of the substrate by the thermal head cannot be efficiently transferred to the adhesive layer through the colored layer, and the entire thermal transfer layer is The thermal sensitivity during printing decreases, making it easier for characters to become blurred.
In contrast, by setting the thickness of the colored layer within the above range, the characters printed on the surface of the package can be printed with high color density while suppressing the deterioration of heat treatment resistance, alcohol resistance, and oil resistance. Can be colored black.

In addition, the heat applied from the back side of the substrate by the thermal head is transmitted as efficiently as possible to the adhesive layer through the colored layer, improving the thermal sensitivity of the entire thermal transfer layer during printing and preventing blurring. It is also possible to print clear characters by reducing the occurrence of such occurrence.
<Adhesive layer>
The adhesive layer laminated on the colored layer contains the acid-modified polyolefin resin, as described above.

Moreover, the adhesive layer may further contain polyester resin.
Polyester resin is particularly excellent in thermal adhesion to the PET film that constitutes the surface of the package and in adhesive strength after thermal adhesion.
Therefore, by using a polyester resin together with an acid-modified polyolefin resin as a resin for the adhesive layer, it is possible to further improve the alcohol resistance of the characters not only on the surface of the ONY film but also on the surface of the PET film.

(Acid-modified polyolefin resin)
Examples of acid-modified polyolefin resins include unsaturated carboxylic acid-modified polyolefin resins, maleic anhydride-modified polyolefin resins, and the like.
In particular, as the acid-modified polyolefin resin, it is preferable to select and use an unsaturated carboxylic acid-modified polyolefin resin having a carboxyl group in the molecule.

The carboxyl group in the molecule of unsaturated carboxylic acid-modified polyolefin resin has excellent affinity for the surface of ONY film and PET film, so the thermal adhesion of the thermal transfer layer to the surface and the Adhesive strength can be further improved.
Therefore, if an unsaturated carboxylic acid-modified polyolefin resin is used as the acid-modified polyolefin resin, the heat treatment resistance and alcohol resistance of the characters printed on the surface thereof by thermal transfer of the transfer layer can be further improved.

Examples of the unsaturated carboxylic acid-modified polyolefin resin include olefin-unsaturated carboxylic acid copolymers such as ethylene-acrylic acid copolymers.
The unsaturated carboxylic acid-modified polyolefin resin is mainly provided as an aqueous solution or an aqueous dispersion (including an emulsion, an emulsion, etc., hereinafter the same).
The carboxyl group also functions as a water-soluble group added to the polyolefin resin or as an emulsifier for the polyolefin resin in the aqueous solution or aqueous dispersion.

Therefore, the aqueous solution or aqueous dispersion of the unsaturated carboxylic acid-modified polyolefin resin is stable, and when preparing a coating material containing the aqueous solution or aqueous dispersion, or when applying the coating material to form an adhesive layer. It is also possible to improve the ease of handling.
An aqueous solution or aqueous dispersion of an unsaturated carboxylic acid-modified polyolefin resin can be obtained by, for example, neutralizing an olefin-unsaturated carboxylic acid copolymer such as the above-mentioned ethylene-acrylic acid copolymer with an alkali to generate carboxyl groups in the molecule. It is prepared by letting.

Examples of the neutralizing agent used for alkali neutralization include ammonia, alkanolamine, sodium hydroxide, and the like.
Examples of alkanolamines include diethylamine, triethylamine, monoethanolamine, dimethylethanolamine, diethylethanolamine, and the like.

Unsaturated carboxylic acid-modified polyolefin resins prepared using these neutralizing agents are excellent in improving the heat treatment resistance and alcohol resistance of characters printed on the surface of ONY film or PET film.
Specific examples of aqueous solutions or aqueous dispersions of unsaturated carboxylic acid-modified polyolefin resins include, but are not limited to, the following various products.

Among the Zaixen (registered trademark) series manufactured by Sumitomo Seika Co., Ltd., A-GH [self-emulsifying aqueous solution, solid content concentration: 24%, neutralizing agent: ammonia, pH: 8-10], AC [translucent aqueous solution] or emulsion, solid content concentration: 29-30%, neutralizing agent: ammonia, pH: 8-10], A [translucent aqueous solution or emulsion, solid content concentration: 24-25%, neutralizing agent: Ammonia, pH: 8-10], AC-HW-10 [emulsion, solid concentration: 29-30%, neutralizing agent: ammonia, pH: 8-10], L [translucent aqueous solution or emulsion , solid content concentration: 27-29%, neutralizing agent: dimethylethanolamine, pH: 8-10], NC [translucent aqueous solution, solid content concentration: 27-29%, neutralizing agent: sodium hydroxide, pH: 8.5-10.5], N [translucent aqueous solution, solid concentration: 24-25%, neutralizing agent: sodium hydroxide, pH: 8-10], Primacol (registered trademark) manufactured by SK Sogo Kagaku Co., Ltd. ) series, P-5990L [aqueous dispersion, solid content concentration: 20%].

Examples of unsaturated carboxylic acid-modified polyolefin resins include AC 540, 540A, 580, 5120, OS-540, and OS-580 manufactured by Honeywell Performance Additives, which are solid, powdery, granular, or granular. etc. can also be used.
On the other hand, specific examples of maleic anhydride-modified polyolefin resins include, but are not limited to, the following various products.

Among the Arrowbase (registered trademark) series manufactured by Unitika Co., Ltd., SB-1200 [aqueous dispersion, polyethylene type, solid content concentration: 25% by mass, pH: 9-11, melting point: 80°C], SE-1200 [ Aqueous dispersion, polyethylene type, solid content concentration: 20% by mass, pH: 9 to 11, melting point: 95°C], SD-1200 [aqueous dispersion, polyethylene type, solid content concentration: 20% by mass, pH: 9 to 11. Melting point: 105°C], DA-1010 [aqueous dispersion, polypropylene type, solids concentration: 25% by mass, pH: 9-12, melting point: 75°C], DB-4010 [aqueous dispersion, polypropylene type, Solid content concentration: 25% by mass, pH: 9-12, melting point: 155°C], YA-4010 [aqueous dispersion, polypropylene type, solid content concentration: 20% by mass, melting point: 148°C].

Further, as the maleic anhydride-modified polyolefin resin, for example, A-C 596P, 597A, 597P, 950A, 950P, 1325P manufactured by Honeywell Performance Additives, etc., which are solid and have a powder, granular or granular shape, may be used. can.
One or more of these acid-modified polyolefin resins can be used.
(polyester resin)
As mentioned above, when using an acid-modified polyolefin resin provided as an aqueous solution or an aqueous dispersion as the acid-modified polyolefin resin, a polyester resin supplied as an aqueous solution or an aqueous dispersion may be used as the polyester resin.

Specific examples of the polyester resin supplied as an aqueous solution or aqueous dispersion include, but are not limited to, the following various products.
KA-0134 [Glass transition temperature Tg: 40°C, number average molecular weight Mn: 9000, water dispersion type, solid content concentration: 30% by mass, pH: 7-10], KA-0134 from the ELITEL series manufactured by Unitika Co., Ltd. 5034 [Glass transition temperature Tg: 67°C, number average molecular weight Mn: 9000, water dispersion type, solid content concentration: 30% by mass, pH: 7-10], KA-6137 [Glass transition temperature Tg: 71°C, number average Molecular weight Mn: 5000, water dispersion type, solid content concentration: 30% by mass, pH: 7 to 10], KA-3556 [glass transition temperature Tg: 80°C, number average molecular weight Mn: 8000, water dispersion type, solid content concentration : 30% by mass, pH: 7-10], KT-0507 [Glass transition temperature Tg: -25°C, number average molecular weight Mn: 17000, water dispersion type, solid content concentration: 25% by mass, pH: 7-10] , KT-8904 [Glass transition temperature Tg: 8°C, number average molecular weight Mn: 17000, water dispersion type, solid content concentration: 30% by mass, pH: 7-10], KT-8701 [Glass transition temperature Tg: 15°C , number average molecular weight Mn: 13000, water dispersion type, solid content concentration: 30% by mass, pH: 6 to 8], KT-9204 [glass transition temperature Tg: 18 ° C., number average molecular weight Mn: 17000, water dispersion type, Solid content concentration: 30% by mass, pH: 7-10], KT-8803 [Glass transition temperature Tg: 65°C, number average molecular weight Mn: 15000, water dispersion type, solid content concentration: 30% by mass, pH: 7- 10].

Among the Vylonal (registered trademark) series manufactured by Toyobo Co., Ltd., MD-1100 [glass transition temperature Tg: 40°C, number average molecular weight Mn: 20000, hydroxyl value: 5mgKOH/g, aqueous dispersion, solid content concentration: 30% ], MD-1200 [Glass transition temperature Tg: 67°C, number average molecular weight Mn: 15000, hydroxyl value: 6 mgKOH/g, aqueous dispersion, solid content concentration: 34%], MD-1245 [Glass transition temperature Tg: 61 °C, number average molecular weight Mn: 20000, hydroxyl value: 5 mgKOH/g, aqueous dispersion, solid content concentration: 30%], MD-1335 [glass transition temperature Tg: 4 °C, number average molecular weight Mn: 8000, hydroxyl value: 13mgKOH/g, aqueous dispersion, solid concentration: 30%], MD-1480 [glass transition temperature Tg: 20°C, number average molecular weight Mn: 15000, hydroxyl value: 6mgKOH/g, aqueous dispersion, solid concentration: 25%], MD-1500 [glass transition temperature Tg: 77°C, number average molecular weight Mn: 8000, hydroxyl value: 14 mgKOH/g, aqueous dispersion, solid content concentration: 30%], MD-1930 [glass transition temperature Tg : -10°C, number average molecular weight Mn: 20000, hydroxyl value: 5mgKOH/g, aqueous dispersion, solid content concentration: 31%], MD-1985 [glass transition temperature Tg: -20°C, number average molecular weight Mn: 25000 , hydroxyl value: 4mgKOH/g, aqueous dispersion, solid content concentration: 27%], MD-2000 [glass transition temperature Tg: 67°C, number average molecular weight Mn: 18000, hydroxyl value: 6mgKOH/g, aqueous dispersion, Solid content concentration: 40%].

One type or two or more types of these polyester resins can be used.
As the polyester resin, it is particularly preferable to select and use a polyester resin having a glass transition temperature Tg of 40° C. or higher and 75° C. or lower.
A polyester resin having a glass transition temperature Tg below this range has a low softening temperature or melting start temperature, specifically, about less than about 100° C., so that the heat treatment resistance of characters may be reduced.

On the other hand, polyester resins whose glass transition temperature Tg exceeds the above range have a softening temperature or melting start temperature that is too high, and therefore tend to have lower thermal sensitivity.
Then, when printing characters, the thermal transfer layer may peel off from the base material to the area surrounding the characters adjacent to the area of the characters to be thermally transferred, which is so-called excessive peeling.
In contrast, by selecting and using a polyester resin whose glass transition temperature Tg falls within the above range, heat treatment of characters printed on the surface of a package made of laminate film can be achieved while suppressing a decrease in thermal sensitivity during printing. Decrease in resistance can be suppressed.

Although other properties of the polyester resin are not particularly limited, the number average molecular weight Mn is preferably 5,000 or more, and preferably 18,000 or less.
(mass ratio of both resins)
When the adhesive layer contains a polyester resin together with an acid-modified polyolefin resin, the mass ratio (AO)/(Eb) of the acid-modified polyolefin resin (AO) to the polyester resin (Eb) is preferably 0.4 or more, It is preferably 6.0 or less.

In addition, when using an aqueous solution or aqueous dispersion as each resin, the mass ratio (AO)/(Eb) is the solid content of the acid-modified polyolefin resin or polyester resin contained in the aqueous solution or aqueous dispersion. Mass ratio converted to solid content.
Furthermore, as described above, when using a solid acid-modified polyolefin resin, the mass ratio (AO)/(Eb) may be determined based on the total amount of the acid-modified polyolefin resin.

If the mass ratio (AO)/(Eb) is less than the above range, the proportion of acid-modified polyolefin resin will decrease, the thermal adhesion and adhesive strength of printing will decrease, and the heat treatment resistance of characters will become insufficient, especially ONY. The alcohol resistance of the letters on the surface of the film may be reduced.
On the other hand, if the mass ratio (AO)/(Eb) exceeds the above range, the proportion of the polyester resin will be relatively small, and the polyester resin will have particularly good thermal adhesion and adhesive strength to the surface of the PET film. The effect of improving this may not be sufficient.

In addition, the alcohol resistance of the characters on the surface of the PET film may deteriorate.
On the other hand, by setting the mass ratio (AO)/(Eb) within the above range, both the thermal adhesion and adhesive strength to the surfaces of ONY film and PET film can be improved, and packages made of these films can be improved. The heat treatment resistance of characters printed on the surface of the paper can be further improved.
Furthermore, the alcohol resistance of characters on both the surfaces of ONY film and PET film can be improved.

In addition, in consideration of further improving this effect, it is preferable that the mass ratio (AO)/(Eb) is 1.0 or more even within the above range.
The adhesive layer can be formed by applying an acid-modified polyolefin resin or a coating material containing an acid-modified polyolefin resin and a polyester resin onto the previously formed colored layer, and then drying the coating material.

When using an aqueous solution or dispersion of an acid-modified polyolefin resin, or an aqueous solution or dispersion of an acid-modified polyolefin resin and a polyester resin, the coating material is at least one selected from the group consisting of water and a water-soluble organic solvent. It can be prepared using an aqueous solvent.
As the water-soluble organic solvent, for example, one or more alcohols such as methanol, ethanol, 1-propanol, and 2-propanol can be used, and methanol is particularly preferred.

(thickness of adhesive layer)
Although the thickness of the adhesive layer is not limited to this, for example, it is preferably 0.1 g/m ² or more, and preferably 1 g/m ² or less, expressed as solid content per unit area.
If the thickness is less than this range, the thermal adhesion of the adhesive layer and the adhesive strength after thermal adhesion will decrease, resulting in insufficient heat treatment resistance, alcohol resistance, and oil resistance for characters printed on the surface of packages, etc. There is.

On the other hand, if the thickness exceeds the above range, the adhesive layer becomes difficult to tear, and excessive peeling may occur when printing characters or the like by thermally transferring the thermal transfer layer.
In contrast, by setting the thickness of the adhesive layer within the above range, it is possible to suppress the occurrence of excessive peeling, improve the thermal adhesion of the adhesive layer and the adhesive strength after thermal adhesion, and print on the surface of packages, etc. It is possible to further improve the heat treatment resistance, alcohol resistance, and oil resistance of letters, etc.

The structure of the thermal transfer medium of the present invention is not limited to the examples described above.
For example, the back layer may be omitted, and the thermal transfer layer may have a multilayer structure of three or more layers.
Alternatively, the release layer may be omitted by subjecting the surface of the base material to a release treatment.
In order to release the surface of the base material, for example, the surface may be subjected to fluorination, chlorination, or the like, or a release layer containing silicone resin, fluororesin, etc. may be formed.

In addition, various changes can be made without changing the gist of the present invention.

The present invention will be further explained below based on Examples and Comparative Examples, but the configuration of the present invention is not limited to these examples.
<Example 1>
(base material and back layer)
A PET film with a thickness of 4.5 μm is used as the base material, and a silicone resin with a solid content of 0.5 μm per unit area is coated on the opposite surface (back surface) of the base material to the surface on which the thermal transfer layer is formed. A back layer of 1 g/m ² was applied.

(Peeling layer)
40 parts by mass of carnauba wax, 40 parts by mass of paraffin wax (melting point: 65°C), and 20 parts by mass of EVA [Ultracene (registered trademark) 685 manufactured by Tosoh Corporation, melting temperature: 77°C] were mixed in toluene and methyl ethyl ketone. A coating material having a solid content concentration of 20% by mass was prepared by dissolving it in a mixed solvent at a mass ratio of 2/1.

Next, this coating material was applied to the surface of the base material and dried to form a release layer having a solid content of 1.0 g/m ² per unit area.
(colored layer)
As the resins, 42.86 parts by mass of the following chlorinated polyolefin resin and 57.14 parts by mass of polyester resin were used.

Chlorinated polyolefin resin: Superchron 814HS manufactured by Nippon Paper Industries Co., Ltd. [solid product, chlorine content: 41%, viscosity in 60% toluene solution: 500 to 2000 mPa・s (25°C)]
Polyester resin [Diaclone ER-1002 manufactured by Mitsubishi Chemical Corporation, polymer saturated copolymer type, glass transition temperature Tg: 60°C, melting start temperature: 120°C, number average molecular weight Mn: 13500, hydroxyl value: 5 ~ 10mgKOH/g]
Next, each of the following components and MEK as a solvent were added to a total of 100 parts by mass of the resin to prepare a coating material for a colored layer.

表１中の各成分は、下記のとおり。
カーボンブラック：三菱ケミカル(株)製の＃３４００Ｂ〔ファーネス法、ＤＢＰ吸収量：１７５ｃｍ^３／１００ｇ〕
イソシアネート硬化剤：ＤＩＣ（株）製のバーノック（登録商標）Ｄ－８００
分散剤：ルーブリゾール社製のソルスパース２００００
そして調製した塗材を、先に形成した剥離層の上に塗布したのち乾燥させて、単位面積あたりの固形分量が１ｇ／ｍ^２である着色層を形成した。

Each component in Table 1 is as follows.
Carbon black: #3400B manufactured by Mitsubishi Chemical Corporation [furnace method, DBP absorption: 175 cm ³ /100 g]
Isocyanate curing agent: Burnock (registered trademark) D-800 manufactured by DIC Corporation
Dispersant: Solsperse 20000 manufactured by Lubrizol
The prepared coating material was applied onto the previously formed release layer and dried to form a colored layer having a solid content of 1 g/m ² per unit area.

The mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
(Adhesive layer)
A coating material for the adhesive layer was prepared by blending the following acid-modified polyolefin resin (65 parts by mass in terms of solid content) and polyester resin (35 parts by mass in terms of solid content) with methanol as a solvent.

Acid-modified polyolefin resin: Zaixen L manufactured by Sumitomo Seika Co., Ltd. [carboxyl group-containing polyolefin resin, translucent aqueous solution or emulsion, solid content concentration: 27-29%, neutralizing agent: dimethylethanolamine, pH: 8 ~10]
Polyester resin: ELITEL KA-5034 manufactured by Unitika Co., Ltd. [Glass transition temperature Tg: 67°C, number average molecular weight Mn: 9000, water dispersion type, solid content concentration: 30% by mass, pH: 7-10]
The prepared coating material was applied onto the previously formed colored layer and dried to form an adhesive layer having a solid content of 0.5 g/m ² per unit area, thereby producing a heat-sensitive transfer medium.

The mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
<Example 2>
As the acid-modified polyolefin resin, Zaixen AC manufactured by Sumitomo Seika Co., Ltd. [carboxyl group-containing polyolefin resin, translucent aqueous solution or emulsion, solid content concentration: 29-30%, neutralizing agent: ammonia, pH: 8- A coating material for an adhesive layer was prepared in the same manner as in Example 1 except that 10] were blended so that the solid content was the same, an adhesive layer was formed, and a thermal transfer medium was produced.

The mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
Moreover, the mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
<Example 3>
As the acid-modified polyolefin resin, Zaixen N manufactured by Sumitomo Seika Co., Ltd. [carboxyl group-containing polyolefin resin, translucent aqueous solution, solid content concentration: 24-25%, neutralizing agent: sodium hydroxide, pH: 8-10] A coating material for an adhesive layer was prepared in the same manner as in Example 1 except that the following were blended so that the solid content was the same, an adhesive layer was formed, and a heat-sensitive transfer medium was produced.

The mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
Moreover, the mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
<Example 4>
As acid-modified polyolefin resin, Arrowbase SB-1200 manufactured by Unitika Co., Ltd. [maleic anhydride-modified polyolefin resin, aqueous dispersion, polyethylene type, solid content concentration: 25% by mass, pH: 9 to 11, melting point: 80 ° C. A coating material for an adhesive layer was prepared in the same manner as in Example 1, except that the following were blended so that the solid content was the same, an adhesive layer was formed, and a heat-sensitive transfer medium was produced.

The mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
Moreover, the mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
<Example 5>
As a polyester resin, ELITEL KT-9204 manufactured by Unitika Co., Ltd. [glass transition temperature Tg: 18 ° C., number average molecular weight Mn: 17000, water dispersion type, solid content concentration: 30% by mass, pH: 7 to 10], A coating material for an adhesive layer was prepared in the same manner as in Example 1 except that the solid content was blended in the same amount, and an adhesive layer was formed to produce a heat-sensitive transfer medium.

The mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
Moreover, the mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
<Example 6>
As a polyester resin, ELITEL KA-0134 manufactured by Unitika Co., Ltd. [glass transition temperature Tg: 40 ° C., number average molecular weight Mn: 9000, water dispersion type, solid content concentration: 30% by mass, pH: 7 to 10], A coating material for an adhesive layer was prepared in the same manner as in Example 1 except that the solid content was blended in the same amount, and an adhesive layer was formed to produce a heat-sensitive transfer medium.

The mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
Moreover, the mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
<Example 7>
As a polyester resin, ELITEL KT-8803 manufactured by Unitika Co., Ltd. [glass transition temperature Tg: 65 ° C., number average molecular weight Mn: 15000, water dispersion type, solid content concentration: 30% by mass, pH: 7 to 10], A coating material for an adhesive layer was prepared in the same manner as in Example 1 except that the solid content was blended in the same amount, and an adhesive layer was formed to produce a heat-sensitive transfer medium.

The mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
Moreover, the mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
<Example 8>
As a polyester resin, ELITEL KA-6137 manufactured by Unitika Co., Ltd. [glass transition temperature Tg: 71 ° C., number average molecular weight Mn: 5000, water dispersion type, solid content concentration: 30% by mass, pH: 7 to 10], A coating material for an adhesive layer was prepared in the same manner as in Example 1 except that the solid content was blended in the same amount, and an adhesive layer was formed to produce a heat-sensitive transfer medium.

The mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
Moreover, the mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
<Example 9>
As a polyester resin, ELITEL KA-3556 manufactured by Unitika Co., Ltd. [glass transition temperature Tg: 80 ° C., number average molecular weight Mn: 8000, water dispersion type, solid content concentration: 30% by mass, pH: 7 to 10], A coating material for an adhesive layer was prepared in the same manner as in Example 1 except that the solid content was blended in the same amount, and an adhesive layer was formed to produce a heat-sensitive transfer medium.

The mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
Moreover, the mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
<Comparative example 1>
A coating material for an adhesive layer was prepared in the same manner as in Example 1, except that no acid-modified polyolefin resin was blended and the amount of polyester resin was 100 parts by mass in terms of solid content, and an adhesive layer was formed. , a thermal transfer medium was prepared.

The mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
<Example 10>
A coating material for the adhesive layer was prepared in the same manner as in Example 1, except that the amount of acid-modified polyolefin resin was 30 parts by mass in terms of solid content, and the amount of polyester resin was 70 parts by mass in terms of solid content. Then, an adhesive layer was formed to produce a heat-sensitive transfer medium.

The mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 0.43.
Moreover, the mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
<Example 11>
A coating material for the adhesive layer was prepared in the same manner as in Example 1, except that the amount of acid-modified polyolefin resin was 50 parts by mass in terms of solid content, and the amount of polyester resin was 50 parts by mass in terms of solid content. Then, an adhesive layer was formed to produce a heat-sensitive transfer medium.

The mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.00.
Moreover, the mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
<Example 12>
A coating material for the adhesive layer was prepared in the same manner as in Example 1, except that the amount of acid-modified polyolefin resin was 80 parts by mass in terms of solid content, and the amount of polyester resin was 20 parts by mass in terms of solid content. Then, an adhesive layer was formed to produce a heat-sensitive transfer medium.

The mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 4.00.
Moreover, the mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
<Example 13>
A coating material for the adhesive layer was prepared in the same manner as in Example 1, except that the amount of acid-modified polyolefin resin was 85 parts by mass in terms of solid content, and the amount of polyester resin was 15 parts by mass in terms of solid content. Then, an adhesive layer was formed to produce a heat-sensitive transfer medium.

The mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 5.67.
Moreover, the mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
<Example 14>
A coating material for an adhesive layer was prepared in the same manner as in Example 1, except that the amount of acid-modified polyolefin resin was 100 parts by mass in terms of solid content, and no polyester resin was blended, and an adhesive layer was formed. , a thermal transfer medium was prepared.

The mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
<Example 15>
A coating material for a colored layer was prepared in the same manner as in Example 1, except that the same amount of a solid product of Super Chron 803L (chlorine content: 26%) manufactured by Nippon Paper Industries Co., Ltd. was blended as the chlorinated polyolefin resin. Then, a colored layer was formed to produce a heat-sensitive transfer medium.

The mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
In addition, the mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
<Example 16>
A coating material for a colored layer was prepared in the same manner as in Example 1, except that the same amount of Super Chron 803MW solid product [chlorine content: 29.5%] manufactured by Nippon Paper Industries Co., Ltd. was blended as the chlorinated polyolefin resin. was prepared, a colored layer was formed, and a heat-sensitive transfer medium was produced.

The mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
In addition, the mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
<Example 17>
As the chlorinated polyolefin resin, Superchlorne C manufactured by Nippon Paper Industries Co., Ltd. [chlorine content: 35%, toluene solution, viscosity: 500 to 2000 mPa·s (25°C), solid content: 55%] 77.92 parts by mass A coating material for a colored layer was prepared in the same manner as in Example 1 except that (solid content: 42.86 parts by mass) was blended, a colored layer was formed, and a heat-sensitive transfer medium was produced.

The mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
In addition, the mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
<Example 18>
Same as Example 1 except that the same amount of Vylon GK-830 manufactured by Toyobo Co., Ltd. [glass transition temperature Tg: 25 ° C., number average molecular weight Mn: 32000, hydroxyl value: 7 mgKOH/g] was blended as the polyester resin. A coating material for a colored layer was prepared, a colored layer was formed, and a heat-sensitive transfer medium was produced.

The mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
In addition, the mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
<Example 19>
Same as Example 1 except that the same amount of Vylon GK-880 manufactured by Toyobo Co., Ltd. [glass transition temperature Tg: 84 ° C., number average molecular weight Mn: 18000, hydroxyl value: 5 mgKOH/g] was blended as the polyester resin. A coating material for a colored layer was prepared, a colored layer was formed, and a heat-sensitive transfer medium was produced.

The mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
In addition, the mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
<Example 20>
The same procedure as in Example 1 was carried out except that the same amount of Vylon 220 (glass transition temperature Tg: 53°C, number average molecular weight Mn: 3000, hydroxyl value: 50 mgKOH/g) manufactured by Toyobo Co., Ltd. was blended as the polyester resin. A coating material for a colored layer was prepared, a colored layer was formed, and a heat-sensitive transfer medium was produced.

The mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
In addition, the mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
<Comparative example 2>
Except that 100 parts by mass of acrylic resin [Dyanal (registered trademark) BR-106 manufactured by Mitsubishi Chemical Corporation] was blended in place of the chlorinated polyolefin resin and polyester resin, and no isocyanate curing agent was blended. A coating material for a colored layer was prepared in the same manner as in Example 1, and a colored layer was formed to produce a heat-sensitive transfer medium.

The mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
<Comparative example 3>
A coating material for a colored layer was prepared in the same manner as in Example 1 except that the chlorinated polyolefin resin was not blended and the amount of polyester resin was 100 parts by mass, the colored layer was formed, and a thermal transfer medium was coated. Created.

The mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
<Example 21>
A coating material for a colored layer was prepared in the same manner as in Example 1, except that the amount of chlorinated polyolefin resin was 10.20 parts by mass and the amount of polyester resin was 89.80 parts by mass, and a colored layer was formed. A thermal transfer medium was prepared.

The mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.11.
Moreover, the mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
<Example 22>
A coating material for a colored layer was prepared in the same manner as in Example 1, except that the amount of chlorinated polyolefin resin was 20.41 parts by mass and the amount of polyester resin was 79.59 parts by mass, and a colored layer was formed. A thermal transfer medium was prepared.

The mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.26.
Moreover, the mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
<Example 23>
A coating material for a colored layer was prepared in the same manner as in Example 1, except that the amount of chlorinated polyolefin resin was 79.59 parts by mass and the amount of polyester resin was 20.41 parts by mass, and a colored layer was formed. A thermal transfer medium was prepared.

The mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 3.90.
Moreover, the mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
<Example 24>
A coating material for a colored layer was prepared in the same manner as in Example 1, except that the amount of chlorinated polyolefin resin was 81.63 parts by mass and the amount of polyester resin was 18.37 parts by mass, and a colored layer was formed. A thermal transfer medium was prepared.

The mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 4.44.
Moreover, the mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
<Comparative example 4>
A coating material for a colored layer was prepared in the same manner as in Example 1 except that the amount of chlorinated polyolefin resin was 100 parts by mass and the polyester resin and isocyanate curing agent were not blended, and a colored layer was formed. A thermal transfer medium was prepared.

The mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
<Example 25>
A coating material for a colored layer was prepared in the same manner as in Example 1, except that the same amount of Denka Black FX-35 (acetylene method, DBP absorption: 220 cm ³ /100 g) manufactured by Denka Co., Ltd. was blended as carbon black. A thermal transfer medium was prepared by forming a colored layer.

The mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
In addition, the mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
<Example 26>
A coating material for a colored layer was prepared in the same manner as in Example 1, except that the same amount of MA100 granules [LFF, DBP absorption: 95 cm ^/ 100 g] manufactured by Mitsubishi Chemical Corporation was blended as carbon black, A colored layer was formed to produce a thermal transfer medium.

The mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
In addition, the mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
<Example 27>
As carbon black, an attempt was made to blend the same amount of KETJENBLACK EC300J (gasification method, DBP absorption amount: 360 cm ³ /100 g) manufactured by Lion Specialty Chemicals Co., Ltd. as in Example 1, but the entire amount was not uniformly mixed into the resin. could not be distributed to

Therefore, a coating material for a colored layer was prepared by blending 32.66 parts by mass, which is half of that in Example 1, and a colored layer was formed to produce a heat-sensitive transfer medium.
The mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.
In addition, the mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.

<Comparative example 5>
A coating material for a colored layer was prepared in the same manner as in Example 1 except that no isocyanate curing agent was blended, and a colored layer was formed to produce a heat-sensitive transfer medium.
The mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer was 0.75.

In addition, the mass ratio (AO)/(Eb) of acid-modified polyolefin resin (AO) to polyester resin (Eb) in the adhesive layer was 1.86 in terms of solid content.
<Heat treatment resistance evaluation>
The thermal transfer media produced in each example and comparative example were slit into ribbons of a predetermined width, wound into a roll, and used in a thermal transfer printer [label printer B-SX4T manufactured by Toshiba Tec Corporation, resolution: 300 dpi]. I set it to

In addition, a laminate film of a biaxially stretched nylon film (ONY) and a linear low-density polyethylene film (LLDPE) was prepared as a model for a food package.
Next, a barcode was printed on the ONY side surface of the laminate film using the thermal transfer printer, followed by retort sterilization treatment by heating to 120° C. under pressure.
Then, the state of the barcode after the retort sterilization treatment was observed, the barcode was read using a barcode reader, and the heat treatment resistance was evaluated based on the following criteria.

○: No change was observed in the barcode, and it could be read correctly with a barcode reader.
Δ: Although slight chipping or peeling was observed in the barcode, it could be read correctly with a barcode reader.
×: Chips and peeling of the barcode were observed, and the barcode could not be read correctly with a barcode reader.

<Alcohol resistance evaluation (ONY)>
The thermal transfer media produced in each example and comparative example were slit into ribbons of a predetermined width, wound up into a roll, and set in the same thermal transfer printer used in the heat treatment resistance evaluation.
Next, a barcode was printed on the ONY side surface of the same laminate film used in the heat treatment resistance evaluation using the above thermal transfer printer.

Then, a cotton swab impregnated with ethanol was brought into contact with the surface of the laminate film on which the barcode was printed, and the swab was moved back and forth 50 times under a load of 1N, and then the condition of the barcode was observed.
At the same time, the barcode was read using a barcode reader, and the alcohol resistance of the surface of the ONY film was evaluated based on the following criteria.

○: The barcode was not melted, smeared, scratched, or washed away, and could be read correctly with a barcode reader.
△: Although the barcode was slightly melted and smeared, scratched, or ran, it could be read correctly by the barcode reader.
×: The barcode was noticeably melted, blurred, blurred, or washed out, and could not be read correctly with a barcode reader.

<Alcohol resistance evaluation (PET)>
The alcohol resistance of the surface of the PET film was evaluated in the same manner as in the alcohol resistance evaluation (ONY) except that a laminate film of a biaxially stretched PET film and aluminum foil was used as a model of a food package.
That is, the thermal transfer media produced in each Example and Comparative Example were slit into ribbons of a predetermined width, wound up into a roll, and set in the same thermal transfer printer used in the heat treatment resistance evaluation.

Next, a barcode was printed on the PET side surface of the laminate film using the thermal transfer printer.
Then, a cotton swab impregnated with ethanol was brought into contact with the surface of the laminate film on which the barcode was printed, and the swab was moved back and forth 50 times under a load of 1N, and then the state of the barcode was observed.

At the same time, the barcode was read using a barcode reader, and the alcohol resistance of the surface of the PET film was evaluated based on the following criteria.
○: The barcode was not melted, smudged, scratched, or washed away, and could be read correctly with a barcode reader.
△: Although the barcode was slightly melted and smeared, scratched, or ran, it could be read correctly by the barcode reader.

×: The barcode was noticeably melted, blurred, blurred, or washed out, and could not be read correctly with a barcode reader.
<Oil resistance evaluation>
The thermal transfer media produced in each example and comparative example were slit into ribbons of a predetermined width, wound up into a roll, and set in the same thermal transfer printer used in the heat treatment resistance evaluation.

Next, a barcode was printed on the ONY side surface of the same laminate film used in the heat treatment resistance evaluation using the above thermal transfer printer.
Then, a cotton swab impregnated with edible oil was brought into contact with the surface of the laminate film on which the barcode was printed, and the swab was moved back and forth 50 times under a load of 1N, and then the condition of the barcode was observed.

At the same time, the barcode was read using a barcode reader, and the oil resistance was evaluated based on the following criteria.
○: The barcode was not melted, smudged, scratched, or washed away, and could be read correctly with a barcode reader.
△: Although the barcode was slightly melted and smeared, scratched, or ran, it could be read correctly by the barcode reader.

×: The barcode was noticeably melted, blurred, blurred, or washed out, and could not be read correctly with a barcode reader.
<Evaluation of thermal sensitivity during printing>
The thermal transfer media produced in each example and comparative example were slit into ribbons of a predetermined width, wound up into a roll, and set in the same thermal transfer printer used in the heat treatment resistance evaluation.

Then, on the ONY side surface of the same laminate film used in the heat treatment resistance evaluation, a thin line with a line width of 1 dot was continuously printed over a predetermined length using the above thermal transfer printer, and printed according to the following criteria. The thermal sensitivity was evaluated.
Good: A thin line could be printed over the entire length with a line width of 1 dot without any problem.
Δ: The line width became thinner in some areas, but the thin line could be printed over the entire length without interruption.

×: There were many breaks in thin lines in the middle.
<Print color density evaluation>
The thermal transfer media produced in each example and comparative example were slit into ribbons of a predetermined width, wound up into a roll, and set in the same thermal transfer printer used in the heat treatment resistance evaluation.
Then, solid printing was performed on the ONY side surface of the same laminate film used in the heat treatment resistance evaluation using the above thermal transfer printer, and the color density was measured using a density measuring device (Macbeth Densitometer RD-918 ). The color density was evaluated based on the following criteria.

○: Color density was 1.5 or more.
Δ: Color density was 1.0 or more and less than 1.5.
×: Color density was less than 1.0.
The above results are shown in Tables 2 to 9.
In each table, the codes in the column for the type of acid-modified polyolefin resin are as follows.
CP-Ea: carboxyl group-containing polyolefin resin, neutralizing agent: dimethylethanolamine CP-Am: carboxyl group-containing polyolefin resin, neutralizing agent: ammonia CP-Na: carboxyl group-containing polyolefin resin, neutralizing agent: sodium hydroxide MP :Maleic anhydride modified polyolefin resin

表２～表９の各実施例、比較例の結果より、熱転写層を構成する着色層が塩素化ポリオレフィン樹脂、ポリエステル樹脂、イソシアネート硬化剤を含み、接着層が酸変性ポリオレフィン樹脂を含むことにより、ラミネートフィルムからなるパッケージ等の表面に、高い熱処理耐性、耐アルコール性、および耐油性を有する文字を印刷できる感熱転写媒体を提供できることが判った。

From the results of the Examples and Comparative Examples in Tables 2 to 9, it is clear that the colored layer constituting the thermal transfer layer contains a chlorinated polyolefin resin, a polyester resin, and an isocyanate curing agent, and the adhesive layer contains an acid-modified polyolefin resin. It has been found that it is possible to provide a thermal transfer medium capable of printing characters having high heat treatment resistance, alcohol resistance, and oil resistance on the surface of a package or the like made of a laminate film.

From the results of Examples 1 and 15 to 17, considering that the alcohol resistance and oil resistance are improved while suppressing the decrease in the color density of the characters, the chlorinated polyolefin resin contained in the colored layer has a chlorine content of It was found that 29% or more is preferable.
From the results of Examples 1 and 18 to 20, considering that the alcohol resistance and oil resistance of letters can be improved while maintaining the ease of preparing the coating material, the polyester resin contained in the colored layer is It has been found that the molecular weight Mn is preferably 10,000 to 33,000.

From the results of Examples 1 and 21 to 24, considering that the heat treatment resistance, alcohol resistance, and oil resistance of the characters are all further improved, it was found that chlorinated polyolefin resin (CO) and polyester in the colored layer The mass ratio (CO)/(Ea) to the resin (Ea) is 0.1 or more, especially 0.2 or more, especially 0.25 or more, and 4.5 or less, especially 4.2 or less, especially 4.0. It has been found that the following is preferable.

From the results of Examples 1 and 25 to 27, considering that as much carbon black as possible is uniformly dispersed in the colored layer to color the characters in black with higher color density, the above carbon black has a DBP absorption property. It has been found that an amount of 100 to 300 cm ³ /100g is preferred.
From the results of Examples 1 and 14, considering that the alcohol resistance of the characters not only on the surface of the ONY film but also on the surface of the PET film is further improved, the adhesive layer contains not only the acid-modified polyolefin resin but also the polyester resin. I found it preferable to stay.

Furthermore, from the results of Examples 1 and 10 to 13, considering that the combination system of acid-modified polyolefin resin and polyester resin further improves heat treatment resistance, alcohol resistance, and oil resistance, acid-modified polyolefin resin (AO) It has been found that the mass ratio (AO)/(Eb) of the polyester resin and the polyester resin (Eb) is preferably 0.4 or more, particularly 1.0 or more, and preferably 6.0 or less.

From the results of Examples 1 to 4, it was found that an unsaturated carboxylic acid-modified polyolefin resin is preferable as the acid-modified polyolefin resin contained in the adhesive layer, in order to further improve the heat treatment resistance and alcohol resistance of the characters. Ta.
Furthermore, from the results of Examples 1 and 5 to 9, considering that the reduction in heat treatment resistance of characters is suppressed while suppressing the reduction in thermal sensitivity during printing, the glass transition temperature Tg of the polyester resin contained in the adhesive layer is It has been found that a temperature of 40 to 75°C is preferred.

Claims (8)

The thermal transfer layer includes a base material, and a thermal transfer layer provided on the base material so as to be thermally transferable, and the thermal transfer layer includes a colored layer and an adhesive layer laminated in this order on the base material, and the colored layer includes: , a chlorinated polyolefin resin, a polyester resin, and an isocyanate curing agent, and the adhesive layer includes an acid-modified polyolefin resin. The thermal transfer medium according to claim 1, wherein the chlorinated polyolefin resin contained in the colored layer is a chlorinated polyolefin resin having a chlorine content of 29% or more. 3. The thermal transfer medium according to claim 1, wherein the polyester resin included in the colored layer has a number average molecular weight Mn of 10,000 or more and 33,000 or less. Claims 1 to 3, wherein the mass ratio (CO)/(Ea) of the chlorinated polyolefin resin (CO) to the polyester resin (Ea) in the colored layer is 0.1 or more and 4.5 or less. The thermal transfer medium according to any one of the items. 5. The thermal transfer medium according to claim 1, wherein the colored layer further contains carbon black having a DBP absorption of 100 cm ³ /100 g or more and 300 cm ³ /100 g or less. The thermal transfer medium according to any one of claims 1 to 5, wherein the adhesive layer further contains a polyester resin. 7. The adhesive layer has a mass ratio (AO)/(Eb) of the acid-modified polyolefin resin (AO) and the polyester resin (Eb) of 0.4 or more and 6.0 or less. Thermal transfer medium. 8. The thermal transfer medium according to claim 1, wherein the acid-modified polyolefin resin contained in the adhesive layer is an unsaturated carboxylic acid-modified polyolefin resin.