JP2823124B2 - Thermal transfer ink - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a thermal transfer ink required for a hot-melt transfer printer whose field of use is gradually expanding because it is inexpensive, has low noise, and is easy to handle. About.

[Problems to be solved by conventional technology and invention]

Conventional thermal transfer ink binders are mainly waxes such as paraffin and carnauba, and have extremely low viscosity when melted by heat.Therefore, when printing on thermal transfer paper with good smoothness, glossy clear print unique to thermal transfer can be obtained. Was giving. However, as the range of application has been expanded, various required characteristics such as printing on paper having a poorer surface smoothness, printing with printing robustness, printing with high transfer sensitivity, and printing for multiple use have been generated. As the required properties have become more advanced, it has been found that it is extremely difficult to deal with conventional inks consisting only of wax, and studies on resin-based inks are being conducted in various fields. .

Resin expected to print on rough surface paper due to high cohesive strength, resin expected to print on rough surface paper, resin expected to print with high strength and robustness, resin expected to print with high transfer sensitivity amorphous, many with strong adhesive force There are resins and the like that are expected to be used once and the possibility of application to thermal transfer is increasing. However, resins generally have a much higher melt viscosity than waxes, and this tendency is particularly remarkable when made into ink. In the thermal transfer system, the viscosity at the time of melting is an important factor in determining the formation of a transferred image on a transfer paper, and directly affects the printing quality. In the hot melt state, if the viscosity is as low as that of the wax ink, a sufficient contact area can be obtained, and high coverage printing can be achieved. In general, a low viscosity comparable to that of wax cannot be achieved during thermal transfer.

Conventionally, oil (such as butyl cellosolve, spindle oil, etc.) has been used to reduce the viscosity of the high-viscosity resin ink. But the addition of oil
If you have bleed-out or blocking issues on storage,
It was difficult to add an amount sufficient to obtain a sufficient viscosity reducing effect.

[Means for solving the problem]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, added an appropriate viscosity reducing agent according to the purpose to various hot-melt resins which could not be used conventionally due to high melt viscosity. The present inventors have found that a thermal transfer ink having excellent printing characteristics can be obtained by adjusting the viscosity by the above method, and have completed the present invention.

That is, the present invention provides a melt viscosity of 10,000 to 1,000,000 cps (120 ° C.
Is a solution-type thermal transfer ink constituted by using a resin of the formula (1) as a base binder, and having a melt viscosity of 1 to 600 cps (120 ° C.) for the purpose of reducing the melt viscosity.
At least one selected from the group consisting of resins, waxes, higher fatty acids, higher alcohols and synthetic esters which are insoluble in the solvent used (dissolved in a 100 g solvent at 40 ° C at most less than 1 g). It is intended to provide a solution-type thermal transfer ink, characterized in that it contains 13 to 250 parts by weight of a kind of a viscosity reducing agent with respect to 100 parts by weight of a base resin.

The thermal transfer ink of the present invention is obtained by adding a low-viscosity agent such as a low-viscosity resin or wax in order to reduce the viscosity of a resin-based thermal transfer ink having a relatively high melt viscosity and make good use thereof. In particular, a thermal transfer ink obtained by adding an insoluble portion of a viscosity reducing agent such as wax to a solution ink in the form of fine particles such as a slurry or a fine powder is preferable.

An existing gravure coater using the thermal transfer ink of the present invention,
By coating and drying on a substrate with a roll coater, a die coater, or the like, an ink sheet for thermal transfer can be obtained without considering the compatibility between a high-viscosity resin and a viscosity reducing agent such as wax.

The resin as a base binder that can be used in the present invention is a resin having a melt viscosity of 10,000 to 1,000,000 cps (measured at 120 ° C.), for example, a polyester resin, a polyamide resin,
Acrylic resin, polystyrene resin, polystyrene acrylic resin, vinyl chloride resin, polyvinyl butyral resin,
Examples thereof include resins having a melting point in the range of 60 to 120 ° C., such as epoxy resins, ethylene vinyl acetate resins, polyurethane resins, and polycarbonate resins, and mixtures thereof.

Examples of the low-viscosity reducing agent that can be used in the present invention include resins having a melt viscosity measured at 120 ° C. of 1 to 600 cps and being insoluble in the solvent used (dissolved in a 100 g solvent at 40 ° C. at most less than 1 g); As long as it is at least one selected from the group consisting of waxes, higher fatty acids, higher alcohols and synthetic esters, all can be used. However, more preferably, resins, waxes, higher fatty acids, higher alcohols or synthetic esters having a melt viscosity at 120 ° C. of 1 to 400 cps are desirable.

Examples of the low-viscosity resin that can be used in the present invention as a viscosity reducing agent include generally low-viscosity resins such as polyethylene resin, polyester resin, ketone resin, ethylene-α-olefin copolymer resin, α-olefin-maleic anhydride copolymer resin. Any of them can be used.

Examples of the wax that can be used in the present invention include carnauba wax, candelilla wax, oricure wax,
Natural plant waxes such as sugarcane wax and wood wax, natural animal waxes such as beeswax, whale wax, Chinese wax and wool wax, petroleum wax such as paraffin wax, microcrystalline wax, oxidized paraffin wax, oxidized microcrystalline wax, and montan wax And mineral waxes such as ozokerite, ceresin, lignite wax, and synthetic waxes such as ketone wax, Fischer-Tropsch wax, caster wax, opal wax, armor wax, and accra wax, and modified waxes thereof.

As the higher fatty acid that can be used in the present invention, any higher fatty acid that is commonly used such as palmitic acid, stearic acid, margaric acid, and behenic acid can be used.

The higher alcohols usable in the present invention include palmityl alcohol, stearyl alcohol, behenyl alcohol, marganyl alcohol, myricyl alcohol,
Any higher alcohol such as eicosanol can be used.

Examples of synthetic esters that can be used in the present invention include monoesters synthesized from the above-mentioned higher fatty acids and higher alcohols, diesters synthesized from the difunctional dicarboxylic acids and the above-mentioned higher alcohols, and also bifunctional diols. And diesters synthesized from the above-mentioned higher fatty acids.

Solvents usable in the present invention include alcohols such as ethanol and isopropyl alcohol, methyl ethyl ketone,
Any solvent can be used as long as it is a solvent usually used in inks and coatings, such as ketones such as methyl isobutyl ketone and cyclohexanone, and aromatic solvents such as toluene and xylene. If necessary, these solvents may be mixed and used.

To produce a thermal transfer ink sheet using the thermal transfer ink of the present invention, at least one layer of the thermal transfer ink of the present invention is applied in contact with the substrate or a coating layer on the substrate, and may be dried. It can also be used together with other constituent layers such as an overcoat layer or a resistive layer for conducting and heating and a conductive layer.

〔Example〕

Hereinafter, the effectiveness of the present invention will be illustrated by examples, but the present invention is not limited to these examples.

Example 1 Polyester resin having a softening point of 88 ° C. (melt viscosity at 120 ° C. 2
A solvent-based thermal transfer ink composed mainly of 2000 cps) and having the following composition ratio was prepared.

Separately, fine powder of carnauba wax was added to toluene / isopropyl alcohol (2/1), kneaded with a ball mill for 12 hours, and a slurry dispersed by wet grinding was prepared.

Further, a slurry was added to the ink to prepare an ink.

These inks were applied on a 3.5 μm polyethylene terephthalate (PET) film and dried to prepare a thermal transfer ink sheet.

Printing evaluation was performed on the obtained thermal transfer ink sheet using a commercially available thermal transfer printer. The evaluation results are summarized in Table 1. As the addition amount of the carnauba wax slurry increases, the viscosity reduction effect occurs, and the transfer rate and the transfer rate are almost the same as those of the wax ink while maintaining the characteristics of the resin such as the robustness.
It can be seen that a thermal transfer image having a resolution can be obtained.

Comparative Example 1 A thermal transfer image was obtained using the ink of Example 1 under the same conditions as in Example 1.

Table 1 shows the print evaluation results. In this case, since the ink had an extremely high viscosity, sufficient transfer was not obtained, and a transferred image having a low coverage was obtained.

Example 2 Polyamide resin having a softening point of 83 ° C. (melt viscosity at 120 ° C. 170
00), polystyrene acrylic resin with a viscosity point of 100 ° C (120 ° C
Solvent-based ink composed mainly of polystyrene resin having a softening point of 48000) or a polystyrene resin having a softening point of 77 ° C (melt viscosity at 120 ° C of 10700) (all solvents are toluene / isopropyl alcohol / methyl ethyl ketone = 1/1/2) ) Was added to a polyethylene wax (12) prepared in the same manner as in Example 1.
An ink was prepared by adding 10, 20, 30, 40, 50% of a 1: 1 mixed slurry of a melt viscosity at 0 ° C. of 30 cps) and carnauba wax in a resin ratio.

When the same printing evaluation as in Example 1 was performed, the results shown in Table 2 were obtained, and it was confirmed that there was a clear viscosity reducing effect.

Example 3 Paraffin wax having a melting point of 106 ° C. (melt viscosity at 120 ° C.)
A slurry was prepared in toluene using 24 cps) and added to the polyester resin described in Example 1 at a resin weight ratio of 30% to prepare an ink. When the same printing evaluation as in Example 1 was performed, the results shown in Table 3 were obtained.

As is clear from Table 3, an ink having a sufficient viscosity reducing effect and having good printing characteristics was prepared. As described above, it has been found that even a high melting point wax having a melting point exceeding 100 ° C. exhibits a viscosity reducing effect if the melt viscosity is low.

Comparative Example 2 An ink was prepared by adding a polyester resin having a melting point of 78 ° C. (melt viscosity at 120 ° C., 2300 cps) to the resin ink used in Example 1 at a ratio of 30% to the resin. When the same printing evaluation as in Example 1 was performed, the results shown in Table 3 were obtained.

As is evident from Table 3, although a slight decrease in viscosity was observed, no viscosity-reducing effect was exhibited to give good printing characteristics. As described above, it has been proved that even a low melting point resin having a melt viscosity outside the range of the present invention has a remarkably low effect.

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masanori Minato 1334 Minato, Wakayama City, Wakayama Prefecture Within Kao Corporation (56) References JP-A-62-37189 (JP, A) JP-A-62-66992 (JP, A JP-A-63-72593 (JP, A) JP-A-64-30789 (JP, A) Patent 2644999 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41M 5/38 -5/40

Claims (2)

(57) [Claims] 1. A solution type thermal transfer ink comprising a resin having a melt viscosity of 10,000 to 1,000,000 cps (measured at 120 ° C.) as a base binder. Consists of resins, waxes, higher fatty acids, higher alcohols and synthetic esters that have a viscosity of 1 to 600 cps (measured at 120 ° C) and are insoluble in the solvent used (dissolved in a 100 g solvent at 40 ° C at most less than 1 g). At least one thinner selected from the group is added to the base resin 10
A solution-type thermal transfer ink comprising 13 to 250 parts by weight per 0 parts by weight. 2. The thermal transfer ink according to claim 1, wherein the insoluble portion of the viscosity reducing agent is contained in the form of fine particles such as slurry or fine powder.