JP3405051B2 - Ink composition for thermal transfer recording, thermal transfer ribbon using the same, image receiving material for thermal transfer, and transfer recorded material - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a thermal transfer recording ink composition, a ribbon using the same, a thermal transfer image-receiving material, and a transfer recorded product.

[0002]

2. Description of the Related Art The heat-sensitive transfer recording ink used for heat-sensitive transfer recording medium (heat-sensitive transfer ribbon and image-receiving material for heat-sensitive transfer) comprises a heat-melting resin and a solvent, and if necessary, a pigment or dye as a colorant, It can be obtained by dispersing and kneading additives such as a dispersant and wax by a ball mill or a sand mill. The heat-sensitive transfer recording medium can be obtained by applying one or more layers of heat-sensitive transfer recording ink on a substrate such as paper or plastic film.

Ink for thermal transfer recording is polyester,
It contains a heat-melting resin such as acrylic or polyamide as a binder, but if the solid content concentration is lowered to apply a thin film of several μm evenly, it will have a low viscosity like a solvent (Viscosity of Zahn Cup No. 3). Is often about 11 seconds), and unevenness in light and shade called streaks and swimming is likely to occur on the coated surface. Further, in the case of an ink having a poor pigment dispersibility, the fluidity exhibits thixotropy, and in many cases a good coated surface cannot be obtained.

Further, when the heat-sensitive transfer recording ink is applied to the substrate, the viscosity of the ink is kept constant in order to easily control the application amount at the time of application. However, especially for inks with a low solid content concentration, the viscosity does not increase even if the solid content concentration increases due to evaporation of the solvent, making it difficult to control the coating amount, and the film at the start of coating and at the end of coating. It causes adverse effects such as different thickness. Since the thermal transfer recording ink is used for thermal transfer recording with a thermal transfer printer after coating it on a substrate, if a thin and uniform coating film cannot be formed, uneven density may occur in the transferred image, and transfer sensitivity may deteriorate. This has caused a remarkable change, and has been a cause of significantly lowering the image quality of the transferred recorded matter.

In order to obtain a thin, uniform and precise coated surface, the fluidity and viscosity of the thermal transfer recording ink are important characteristics, and the fluidity of the ink is preferably Newtonian fluid. The viscosity of ink is generally controlled by adding finely divided silica, bentonite, ethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose and the like. However, these have many problems such as impairing the dispersion of the pigment and poor compatibility with the resin, so that the ink has an extremely high yield value in the fluidity characteristics.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to improve the coating suitability of an ink without sacrificing the heat-sensitive characteristics (thermal response) and the dispersion stability of the ink of the heat-sensitive transfer recording ink, and to make the ink thin and thin. An object of the present invention is to provide an ink composition for thermal transfer recording that can be applied uniformly. Another object of the present invention is to provide a heat-sensitive transfer ribbon and a heat-sensitive transfer image-receiving material which eliminates unevenness in the density of a transferred recorded matter and improve transfer quality. Further, it is an object of the present invention to provide a transfer recorded product which is free from uneven density and has excellent transfer quality.

[0007]

That is, the present invention comprises a binder resin, a solvent and a fluidity adjusting agent, and the fluidity adjusting agent has a number average molecular weight of 1.5 × 10 ^{5 to} 3.
0 × 10 ⁵ or weight average molecular weight 3.5 × 10 ⁵
Nitrocellulose having a concentration of 6.0 × 10 ⁵ and a nitrogen content of 11.5 to 12.2% by weight is used in an amount of 0.1 to 25% by weight based on the total resin content of the ink composition. An ink composition for thermal transfer recording is provided. The present invention also provides a heat-sensitive transfer ribbon in which the above ink composition is applied to one surface of a substrate. Furthermore, the present invention provides an image-receiving material for heat-sensitive transfer, wherein one surface of a substrate is coated with the above ink composition. Furthermore, the present invention provides a transfer recording material obtained by performing thermal transfer recording on the above-mentioned image receiving material for thermal transfer using the above thermal transfer ribbon.

The thermal transfer recording ink composition of the present invention comprises:
High molecular weight nitrocellulose that does not show heat melting characteristics
Since it is contained in a small amount as a flow control agent, not as the main binder of the ink, the fluidity is improved without impairing the thermal transfer property.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The ink composition for heat-sensitive transfer recording of the present invention contains a heat-meltable resin having excellent heat-sensitive properties, a solvent and a fluidity modifier, and if necessary, a colorant, a dispersant, a wax, Includes various additives. Since the wax and various additives may remarkably reduce the resistance of the transferred recorded matter, it is desirable to include them in the ink composition in an amount of less than 10% by weight. Among the components other than the fluidity adjusting agent in the ink composition, those existing in a dissolved state are preferably compatible with nitrocellulose used as the fluidity adjusting agent.

The number average molecular weight used as a fluidity modifier is 1.5 × 10 ^{5 to} 3.0 × 10 ^5, or the weight average molecular weight is 3.5 × 10 ^{5 to} 6.0 × 10 ⁵ or more and the nitrogen content is 1.
1.5 to 12.2% by weight of nitrocellulose (hereinafter referred to as high molecular weight nitrocellulose) adjusts the viscosity and fluidity of the thermal transfer recording ink composition to a suitable range. When the number average molecular weight and the weight average molecular weight of nitrocellulose are out of the above ranges, the viscosity and fluidity of the resulting thermal transfer recording ink composition cannot be adjusted to suitable ranges. Further, if the nitrogen content of nitrocellulose is lower than 11.5% by weight, the solubility in the solvent used in the ink composition is poor, and if it is higher than 12.2% by weight, the risk of spontaneous combustion increases, and therefore it cannot be used.

The amount of the high molecular weight nitrocellulose used as the fluidity modifier is appropriately set within the range of 0.1 to 25% by weight based on the total resin content in the ink composition. If the amount of the high-molecular-weight nitrocellulose used is less than 0.1% by weight, the fluidity adjusting effect will not be exhibited, and the viscosity of the resulting thermal transfer recording ink composition will remain the same as that of the solvent, so during coating. In addition, light and shade unevenness called streaks and swimming is likely to occur. Furthermore, even if the solid content concentration increases due to the evaporation of the solvent during coating, the viscosity of the ink composition does not increase, making it difficult to control the coating amount of the ink composition by the viscosity, and the start and end In some cases, this may cause adverse effects such as different ink application amounts. On the other hand, when the amount of the high-molecular-weight nitrocellulose used exceeds 25% by weight, a phenomenon called whitening may occur when the ink composition is dried, the coating film has no gloss, and the adhesion to the substrate is poor. Further, there arises a problem that the film strength is significantly reduced.

The thermal transfer recording ink composition of the present invention comprises:
By using high molecular weight nitrocellulose as a flow control agent, Zahn cup No. 3 (made by Riaisha, hole diameter 3
It is preferable to adjust the viscosity according to (mm) to be 12 to 24 seconds. Furthermore, in order to improve the circulation of the ink composition by the pump provided in the coater and to improve the leveling of the ink composition during drying, it is more preferable to adjust the viscosity to 12 seconds to 18 seconds. .

As the binder resin, a heat-meltable resin that is hard at room temperature and solid or has no tackiness is suitable. Such resins generally have a glass transition temperature (hereinafter,
(Abbreviated as Tg) is -30 to 80 ° C, or the softening point or melting point is in the range of 40 to 180 ° C.
Is -10 to 50 ° C, or the softening point or melting point is 50 to
A 150 ° C. resin is preferred. A resin having a Tg, a softening point or a melting point lower than the above range generally exhibits tackiness or fluidity at room temperature, and tends to cause troubles such as blocking with time after being processed as a thermal transfer ribbon or an image receiving material for thermal transfer. On the other hand, a resin having a Tg, a softening point or a melting point higher than the above range is inferior in sensitivity to heat, and thus tends to cause transfer failure during thermal transfer recording.

Examples of the binder resin include polyvinyl acetate, vinyl chloride / vinyl acetate copolymer, polyethylene, polypropylene, polyacetal, ethylene / vinyl acetate copolymer, ethylene / (meth) acrylic acid copolymer, α- Olefin / maleic anhydride copolymer, α
-Olefin / maleic anhydride copolymer esterification product, polystyrene, poly (meth) acrylic acid ester,
α-olefin / maleic anhydride / vinyl group-containing monomer copolymer, styrene / maleic anhydride copolymer, styrene / (meth) acrylic acid ester copolymer, polyamide, epoxy resin, xylene resin, ketone resin, petroleum resin , Rosin or its derivatives, coumarone indene resin, terpene resin, polyurethane resin, styrene / butadiene rubber, polyvinyl butyral, nitrile rubber, acrylic rubber, ethylene / propylene rubber, and other synthetic rubber,
Examples thereof include polyester resins, cellulose derivatives other than nitrocellulose, and sucrose esters, and one or more of these may be used.

The binder resin may be selected appropriately according to the required thermal transfer characteristics, the dispersibility of the pigment used, and the required quality. Polyester, acrylic resin, cellulose derivative except nitrocellulose,
Sucrose ester and polyurethane have excellent compatibility with high molecular weight nitrocellulose, and are preferably used.

The solvent dissolves or stably disperses the above binder resin, and must completely dissolve nitrocellulose added as a flow regulator. Further, the solvent is preferably one which has excellent drying property during coating. Examples of the solvent include toluene, xylene, n
Hydrocarbon solvents such as hexane, n-heptane, cyclohexane and turpentine oil, alcohol solvents such as methyl alcohol, ethyl alcohol, isopropyl alcohol and butyl alcohol, acetone, methyl ethyl ketone,
Ketone solvents such as methyl isobutyl ketone and cyclohexanone, methyl acetate, ethyl acetate, butyl acetate, acetic acid
Ester solvents such as ethylene glycol monomethyl ether, acetic acid and ethylene glycol monoethyl ether,
Examples include ether solvents such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether, tetrahydrofuran, and the like, and one or more of these are used. In the case of a mixed solvent composed of a plurality of solvents, it is sufficient that the mixed solvent has the above-mentioned characteristics.

As the colorant, carbon black, azo lake type, insoluble azo type, condensed azo type, phthalocyanine type, quinacridone type, dioxazine type, isoindolinone type, benzimidazolone type, anthraquinone type, perylene type, perinone type, Pigments and dyes such as thioindigo type, quinophthalone type, aniline black type, diketopyrrolopyrrole type and nigrosine type are generally used.

Specific examples of the pigment include carbon black, fast yellow, cadmium yellow, yellow iron oxide, iron oxide black, chromophthal yellow, anthrapyridine yellow, isoindolinone yellow, nickel azo yellow, copper azomethine yellow,
Benzimidazolone yellow, quinophthalone yellow,
Nickel dioxin yellow, nickel dioxin yellow, flavans yellow, yellow lead, titanium yellow, disazo yellow, benzimidazolone orange, pyranthrone orange, perinone orange, para red, lake red, naphthol red, pyrazolone red, permanent red, madder lake, Thioindigo Bordeaux, Bengala, Red Gold, Cadmium Red, Quinacridone Magenta, Perylene Vermillion, Perylene Red, Chromophthal Scarlet, Anse Anthlon Red, Gianthraquinolyl Red, Perylene Maroon, Benzimidazolone Carmine, Perylene Scarlet, Quinacridone Red, Pyran Slon Red, Manganese Violet, Dioxazine Violet, Phthalocyanine Blue, Navy Blue, Cobalt Bu Over, ultramarine blue, indanthrone blue, phthalocyanine green, Pigment Green, chromium oxide, viridian, benzimidazolone Brown,
Examples thereof include bronze powder, white lead, zinc white, lithopone, titanium oxide, and pearl pigment, and one or more of these may be used. As the dye, one kind or two or more kinds of conventionally known dyes such as azo type, anthraquinone type and nigrosine type dyes are used alone or in combination with a pigment.

The thermal transfer recording ink composition of the present invention comprises:
Usually, it is produced by mixing and dispersing the raw materials using a kneading machine such as a ball mill, an attritor, a sand mill and a high speed agitator. Further, in the case of containing a pigment as a colorant, in order to improve the dispersion, after premixing the pigment, the resin and the dispersant,
A high-concentration pigment dispersion in the form of a paste or solid chips is produced using a three-roll, two-roll or the like, and then wet-dispersed by the above-mentioned kneading machine to produce. High molecular weight nitrocellulose is preferably dissolved in the above solvent in advance and added to the thermal transfer recording ink composition.

Next, the thermal transfer ribbon and the thermal transfer image receiving material of the present invention will be described. The heat-sensitive transfer ribbon and the heat-sensitive transfer image-receiving material can be obtained by applying the heat-sensitive transfer recording ink composition of the present invention to one surface of a substrate. Examples of the substrate include polyester (polyethylene terephthalate, polyethylene naphthalate, etc.) film, polyamide (nylon, etc.) film, polyolefin (polypropylene, etc.) film, cellulose-based (triacetate, etc.) film, vinyl chloride, polyimide,
A conventionally known plastic film such as polycarbonate or paper is used.

The base material of the heat-sensitive transfer ribbon is heat resistant,
A polyester film is preferably used in terms of mechanical strength, tensile strength, thermal conductivity and the like. The thinner the substrate, the better the thermal conductivity, but it is most preferably 3 to 50 μm in terms of strength and ease of coating the thermal transfer recording ink composition. Also, on the surface of the substrate opposite to the thermal transfer recording ink layer,
A back coat layer (heat resistant layer) made of a heat resistant resin may be provided.

The thermal transfer ribbon may be provided with a release layer between the base material and the thermal transfer recording ink layer for the purpose of improving the releasability of the thermal transfer recording ink layer from the base material. Further, a top coat layer (adhesive layer) may be provided on the thermal transfer recording ink layer for the purpose of improving the transferability of the thermal transfer recording ink layer and the adhesion to the image receiving material. No colorant is particularly required for the release layer or the top coat layer, and the binder resin and the wax may be used alone or in combination of two or more of them.

The thermal transfer recording ink composition of the present invention comprises:
As an image-receiving layer on the base material of the image-receiving material for heat-sensitive transfer, for the purpose of improving not only coloring but also transfer sensitivity of the heat-sensitive transfer ribbon, adhesion with the image-receiving material, scratch resistance of the transferred recorded matter, weather resistance, etc. One layer or two or more layers are coated.

By carrying out thermal transfer recording on the image-receiving material for heat-sensitive transfer of the present invention using the heat-sensitive transfer ribbon of the present invention, it is possible to obtain a transfer-recorded material which is free from uneven density and has excellent transfer quality. When performing thermal transfer recording with a thermal transfer printer,
Energy (heat) from the surface of the thermal transfer ribbon opposite to the ink layer (hereinafter referred to as the transfer layer) by the printer head
Is applied, the transfer layer at that portion is peeled off from the substrate, and transferred to the image receiving layer on the image receiving material. The heat from the printer head is transferred from the base material to the transfer layer and reaches the image receiving layer.However, since the latent heat of fusion of the transfer layer removes the heat, only the surface layer of the image receiving layer melts and the image receiving layer is transferred to the thermal transfer ribbon side. On the contrary, it is not transcribed.

[0025]

The present invention will be described in more detail with reference to the following examples. “Parts” and “%” in each example represent “parts by weight” and “% by weight”, respectively. Table 1 shows the nitrogen content, number average molecular weight, and weight average molecular weight of the nitrocellulose used in the examples.

[0026]

[Table 1]

Example 1 (containing 20.0% of nitrocellulose A based on the total resin content) An ink composition for a heat-sensitive transfer ribbon having the following composition was wet-dispersed in a sand mill for about 1 hour, except for components except for nitrocellulose varnish. , And was adjusted by adding nitrocellulose varnish after dispersion. As the nitrocellulose varnish, a solution prepared by dissolving nitrocellulose at a solid concentration of 5% in a mixed solvent of methyl ethyl ketone: toluene: isopropyl alcohol = 45.35: 47.50: 2.15 was used. The composition shown below is the composition of the final ink composition. Carbon black 4.8 parts Polyester resin 4.0 parts Nitrocellulose A 1.0 part Isopropyl alcohol 0.7 parts Methyl ethyl ketone 44.3 parts Toluene 45.0 parts

Example 2 (containing 16.0% of nitrocellulose B relative to the total resin content) In the same manner as in Example 1, an ink composition for a thermal transfer ribbon having the following composition was prepared. Carbon black 4.8 parts Polyester resin 4.2 parts Nitrocellulose B 0.8 parts Isopropyl alcohol 0.4 parts Methyl ethyl ketone 44.6 parts Toluene 45.0 parts

Example 3 (containing 8.3% of nitrocellulose C based on the total resin content) In the same manner as in Example 1, an ink composition for a thermal transfer ribbon having the following composition was prepared. Carbon black 4.8 parts Polyester resin 4.4 parts Nitrocellulose C 0.4 parts Isopropyl alcohol 0.2 parts Methyl ethyl ketone 45.0 parts Toluene 45.0 parts

Example 4 (containing 8.3% of nitrocellulose D based on the total resin content) In the same manner as in Example 1, a thermal transfer ribbon ink composition having the following composition was prepared. Carbon black 4.8 parts Polyester resin 4.4 parts Nitrocellulose D 0.4 parts Isopropyl alcohol 0.2 parts Methyl ethyl ketone 45.0 parts Toluene 45.0 parts

Comparative Example 1 (without nitrocellulose) In the same manner as in Example 1, an ink composition for a thermal transfer ribbon having the following composition was prepared. Carbon black 5.0 parts Polyester resin 5.0 parts Methyl ethyl ketone 45.0 parts Toluene 44.8 parts

Comparative Example 2 (Containing 27.0% of nitrocellulose E based on the total resin content) In the same manner as in Example 1, an ink composition for a thermal transfer ribbon having the following composition was prepared. Carbon black 5.0 parts Polyester resin 3.7 parts Nitrocellulose E 1.4 parts Isopropyl alcohol 0.6 parts Methyl ethyl ketone 45.0 parts Toluene 44.2 parts

Comparative Example 3 (containing 25.0% of nitrocellulose E based on the total resin content) In the same manner as in Example 1, an ink composition for a thermal transfer ribbon having the following composition was prepared. Carbon black 5.0 parts Polyester resin 3.8 parts Nitrocellulose E 1.2 parts Isopropyl alcohol 0.6 parts Methyl ethyl ketone 45.0 parts Toluene 44.2 parts

The viscosity and dispersion stability of the ink compositions for thermal transfer ribbons prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were evaluated. Further, a heat-sensitive transfer ribbon was produced using the ink composition for heat-sensitive transfer ribbon prepared in Examples and Comparative Examples, and the uniformity of the coated surface of the ink composition for heat-sensitive transfer ribbon was evaluated. Further, the ink surface of the obtained thermal transfer ribbon and the image receiving material (transparent polyethylene terephthalate film having a thickness of 100 μm) are superposed, and a transfer recording material is prepared by heating the surface of the heat resistant layer of the thermal transfer ribbon with a thermal head. The image clarity was evaluated. The results are shown in Table 2.

The thermal transfer ribbon is coated with a release layer ink having the following composition at a speed of 100 m / min to a thickness of about 1 μm on the surface opposite to the heat resistant layer of a substrate (6 μm polyester film having a heat resistant layer on one side). After being dried with hot air of 60 ° C., the ink composition for a thermal transfer ribbon prepared in Examples and Comparative Examples is further applied thereto at a speed of 100 m / min for about 1 minute.
It was manufactured by applying a coating having a thickness of μm and sufficiently drying it with warm air of 60 ° C. The ink composition is coated by Heliocushograph 250 line (cell: Elongate 120 °).
Direct gravure method using the gravure plate of. The WET coating amount of this plate was about 9 to 10 μm. Ethylene-vinyl acetate copolymer resin 3 parts Carnauba wax 22 parts Toluene 50 parts Isopropyl alcohol 25 parts

The evaluation method is shown below. (1) Viscosity Zahn cup No. The viscosity of the ink was measured with No. 3 (manufactured by Riaisha Co., Ltd., hole diameter 3 mm). (2) Dispersion stability The ink composition was left at room temperature, and the separation and sedimentation of the pigment was visually confirmed. ◯: Pigment does not sediment even after 1 week and is stably dispersed Δ: Pigment begins to sediment after 3 days ×: Pigment has settled in 1 day

(3) Uniformity of coated surface The state of the coated surface of the ink composition for a thermal transfer ribbon was visually evaluated. ◯: Uniform application surface without unevenness in density such as swimming and streaks Δ: Application surface with slight unevenness in density such as swimming and streaks ×: Non-uniform application with unevenness in density such as swimming and streaks Surface (4) Image sharpness The image sharpness of the transfer recording material was visually determined. ◯: The image on the transfer portion is clear. Δ: Partial blurring or poor resolution. ×: Remarkably poor resolution (blurring, swelling of the image, etc.).

[0038]

[Table 2]

Example 5 (containing 3% of nitrocellulose D based on the total resin content) An ink composition for an image receiving material having the following composition was prepared in the same manner as in Example 1. Polyester resin 9.7 parts Nitrocellulose D 0.3 parts Isopropyl alcohol 0.2 parts Methyl ethyl ketone 44.4 parts Toluene 44.4 parts

Comparative Example 4 (No Nitrocellulose) An ink composition for an image receiving material having the following composition was prepared in the same manner as in Example 1. Polyester resin 10.0 parts Methyl ethyl ketone 45.0 parts Toluene 45.0 parts

The ink compositions for image receiving materials prepared in Example 5 and Comparative Example 4 were evaluated for viscosity and dispersion stability. Further, the ink composition for an image receiving material prepared in Example 5 and Comparative Example 4 was applied to one surface of a transparent polyethylene terephthalate film having a thickness of 80 μm at a speed of 25 m / min to a thickness of about 1 μm, and 60 An image receiving material for thermal transfer was produced by sufficiently drying with warm air at ℃, and the uniformity of the coated surface of the ink composition for the image receiving material was evaluated. Furthermore, the image-receiving layer of the image-receiving material for heat-sensitive transfer and the ink surface of the heat-sensitive transfer ribbon previously produced by using the ink composition for heat-sensitive transfer ribbon prepared in Example 4 were superposed to each other to obtain heat resistance of the heat-sensitive transfer ribbon. A transfer recording material was prepared by heating from the surface of the layer with a thermal head, and the image sharpness was evaluated. The results are shown in Table 3. The evaluation was performed by the same method as the evaluation of the ink composition for thermal transfer ribbon.

[0042]

[Table 3]

[0043]

EFFECT OF THE INVENTION The ink composition for heat-sensitive transfer recording of the present invention has good dispersion stability and coating suitability, so that it is possible to obtain a heat-sensitive transfer ribbon having a uniform coating surface and a heat-sensitive transfer image-receiving material. Furthermore, by using a thermal transfer ribbon coated with the thermal transfer recording ink composition of the present invention on a substrate and an image receiving material for thermal transfer, it is possible to obtain a transfer recorded product having no unevenness in density and excellent transfer quality. You can

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-6-24161 (JP, A) JP-A-4-115991 (JP, A) JP-A-3-247491 (JP, A) JP-A-63- 135291 (JP, A) JP-A-52-136014 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B41M 5/38-5/40 C09D 11/00-13/00

Claims (4)

(57) [Claims] 1. A binder resin, a solvent and a fluidity adjusting agent, wherein the fluidity adjusting agent has a number average molecular weight of 1.5.
× 10 ^{5 to} 3.0 × 10 ⁵ or a weight average molecular weight of 3.
5 × 10 ^{5 to} 6.0 × 10 ⁵ with a nitrogen content of 11.5 to 1
An ink composition for thermal transfer recording, wherein 2.2% by weight of nitrocellulose is used in the range of 0.1 to 25% by weight based on the total resin content in the ink composition. 2. A heat-sensitive transfer ribbon in which the ink composition according to claim 1 is coated on one surface of a substrate. 3. An image receiving material for thermal transfer, wherein one surface of a base material is coated with the ink composition according to claim 1. 4. A transfer recording material obtained by performing thermal transfer recording on the image receiving material for thermal transfer according to claim 3 using the thermal transfer ribbon according to claim 2.