JP2542869B2 - Wax for thermal transfer ink - Google Patents

Description

The present invention relates to a thermal transfer ink wax, more specifically, a colorant and other additives are kneaded and applied to the surface of a heat-resistant substrate to transfer a thermal transfer recording medium. Layer (ink layer)
And a wax for heat-sensitive transfer ink capable of forming a film.

Conventional technology and its problems In recent years, various devices such as facsimiles, computer terminals, word processors, image recorders, printers, etc. are non-impact and have low noise, the mechanism of the device is simple, low cost, high reliability, small size. A thermal transfer recording medium, that is, a thermal transfer sheet is widely used in terms of weight saving and colorization. In general, the heat-sensitive transfer sheet has an ink layer formed by kneading a colorant and other additives on an ordinary temperature solid substance (low melting point substance) which becomes liquid by heat such as wax on the surface of a heat-resistant substrate such as polyester. A desired image or the like can be formed on the transfer paper by aligning the transfer paper with the ink layer and printing with a thermal head.

As the low melting point substance, natural waxes such as paraffin wax, carnauba wax, candelilla wax, and beeswax, and synthetic waxes such as polyethylene wax and modified montan wax have been conventionally used. The use of wax has the following various drawbacks as represented by carnauba wax.

First, the dispersibility of dyes and pigments as colorants is poor, and the transparency is poor, so the printing performance is reduced, and especially in the case of full-color printing in which colors are superimposed, the transparency is low and the image becomes dull. I will end up.

Secondly, since the heat of fusion is large (about 40 cal / g), a large amount of heat is required to turn the ink into a liquid, it is difficult to improve the printing sensitivity, and the printing becomes unclear.

Thirdly, conventionally used waxes generally have poor solubility in a solvent, and when a solvent-dispersed ink is applied to form a heat-sensitive transfer sheet, the ink density cannot be increased and the workability of production is poor.

Means for Solving the Problems In view of the above situation, the present inventors have solved all the drawbacks found in the conventional thermal transfer sheet of this kind, especially the low melting point substance (wax) for the ink, and in particular, the coloring agent. We have conducted intensive research to develop a new ink wax with good dispersibility, low heat of fusion, and excellent solubility.

As a result, they have found that the isocyanate polymer of lanolin fatty acid polyhydric alcohol ester has the performance as a wax that meets the above-mentioned object, and have completed the present invention.

That is, the present invention relates to a wax for heat-sensitive transfer ink, which comprises an isocyanate polymer of lanolin fatty acid polyhydric alcohol ester as an active ingredient.

The wax of the present invention eliminates all the drawbacks of the conventional waxes of this type, and has extremely excellent characteristics as a binder (binder) and dispersion medium of a thermal transfer ink.

Hereinafter, the polymer as an active ingredient of the wax of the present invention will be described in detail.

The polymer is obtained by reacting a lanolin fatty acid polyhydric alcohol ester with an isocyanate compound. The lanolin fatty acid as an acid component constituting the lanolin fatty acid polyhydric alcohol ester used here is obtained by saponification of lanolin, which is secreted from the sebaceous glands of sheep and produces a wax-like substance that adheres to sheep's hair. There are few linear fatty acid compositions, and branched fatty acids such as iso-fatty acid and anteiso-fatty acid are the main components (about 2 /
3), and a fairly large amount of hydroxy fatty acid (about 1/3)
Included in. The carbon number of iso-fatty acids is widely distributed over 9 to 34. Various lanolin fatty acids are commercially available, and they are classified into hard lanolin fatty acid, lanolin fatty acid and soft lanolin fatty acid according to the cosmetic raw material standard (Ministry of Health and Welfare Notification No. 167). Although any of the above can be used in the present invention, it is preferable to use the above hard lanolin fatty acid in order to obtain a hard wax. The lanolin fatty acid particularly suitable for the present invention has a melting point of usually
Examples thereof include those having physical properties in the range of 62 to 80 ° C, acid value of 90 to 140 ° C and saponification value of 130 to 170.

Further, as the polyhydric alcohol as an alcohol component constituting the lanolin fatty acid polyhydric alcohol ester, usual ones, for example, glycerin, diglycerin, pentaerythritol, trimethylolpropane, sorbitol, sucrose, ethylene glycol, propylene glycol, di Examples thereof include pentaerythritol and polypropylene glycol. Among them, glycerin, pentaerythritol, trimethylolpropane and the like can be preferably used.

The esterification reaction of the acid component and the alcohol component,
It can be carried out according to a conventional method by heating and dehydrating without a catalyst or using a suitable catalyst. The esterification reaction is
More specifically, it can be carried out according to the general method described in “New Edition Fatty Acid Chemistry”, Jiro Hirano et al.
Further, for example, the same conditions as those described in JP-A-59-53594 can be adopted.

Examples of the ester particularly suitable for the present invention include pentaerythritol dilanolate, pentaerythritol trilanolate, pentaerythritol tetralanolate, glycerol dilanolate and the like.

The lanolin fatty acid polyhydric alcohol ester obtained as described above has a lanolin fatty acid-derived hydroxyl group and a carboxyl group and a polyhydric alcohol-derived hydroxyl group as active hydrogen in its molecule, and the active ingredient of the present invention is It is produced by reacting an isoactive hydrogen atom with an isocyanate. As the isocyanate used here, a urethane bond, a urea bond, by reacting with the active hydrogen,
There is no particular limitation as long as it can form a buret bond, an allophanate bond, etc., but usually for example tolylene diisocyanate (TDI), tolidine diisocyanate (TODI), diphenylmethane-4,4'-diisocyanate (MDI), 1,
Examples thereof include 5-naphthalene diisocyanate, xylene diisocyanate, triphenylmethane triisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate and isophorone diisocyanate. Among them, TDI, MDI, xylene diisocyanate and the like are preferable.

The reaction between the lanolin fatty acid polyhydric alcohol ester and the isocyanate can be carried out by employing a heating and stirring operation according to a usual method. If the heating temperature is too high, the coloration of the obtained product will be remarkable, and if it is too low, the reaction time will be long. Therefore, it is usually desirable to select a range of about 70 to 150 ° C. Further, the above reaction can be allowed to proceed relatively quickly at a lower temperature by using a metal salt catalyst such as stannic chloride, ferric chloride, potassium oleate and dibutyltin dilaurate. It is suitable that the reaction time is usually 0.5 to 5 hours.

The amount of isocyanate used in the reaction is appropriately selected depending on the type of each raw material used, reaction conditions, etc.
Usually about 0.1 to 40% by weight relative to the ester, preferably about
It is preferably selected from the range of 0.1 to 30% by weight, in which the desired polymerization reaction proceeds and a wax having desired properties can be produced.

Thus, the desired polymer as the active ingredient in the present invention can be produced. The polymer usually has the following physical properties and can be suitably used as the heat-sensitive transfer wax of the present invention.

Melting point: 40 to 100 ° C Acid value: 20 or less Viscosity: 0.6 to 500 poise (100 ° C) Penetration: 0 to 20 Heat of fusion: 10 to 30 cal / g The wax for thermal transfer ink of the present invention is The reaction mixture containing the isocyanate polymer of the lanolin fatty acid polyhydric alcohol ester thus obtained can be prepared as it is.Of course, the polymer is isolated and purified from the reaction mixture according to a conventional method, It can also be an inventive wax.

The wax of the present invention can be used to prepare a thermal transfer ink by substituting a part or all of the conventional solid substance at room temperature as a binder and a dispersant for this type of thermal transfer ink. The preparation of this thermal transfer ink can be carried out according to a usual method except that the wax of the present invention is used. For example, the wax of the present invention is used as a colorant such as carbon black, phthalocyanine green, and brilliant carmine 6B, and other additives such as ethylene vinyl acetate resin, acrylic resin, vinyl chloride-vinyl acetate copolymer resin, and other film quality modifiers. , Liquid paraffin, DOP, plasticizer such as castor oil, solvent such as toluene, xylene, ethyl acetate, etc., and then kneading and dispersing with a disperser such as ball mill, sand mill, attritor, or triple roll. The desired heat-sensitive transfer ink can be prepared.

In the preparation of the above thermal transfer ink, the wax of the present invention is appropriately used in the range of about 5 to 95% by weight, preferably about 10 to 90% by weight, based on the solid content of the ink usually obtained.

The ink thus obtained is applied to a heat-resistant substrate, for example, polyester, polypropylene, polystyrene, polycarbonate, polyimide, other heat-resistant plastic film, paper, metal foil, etc. according to a conventional method to form an ink layer. It can be practically used as a thermal transfer recording medium.

EFFECTS OF THE INVENTION The wax of the present invention has a low heat of fusion and is excellent in the dispersibility of a colorant such as a pigment. By using the wax, a heat-sensitive transfer ink can be easily prepared, and the ink thus obtained can be uniformly and evenly coated. By providing a film-forming property, good coatability, and the like, and by using a thermal transfer recording medium using the ink, excellent printing such as transparency, sharpness, multicolor reproducibility, and sensitivity can be obtained. Obtainable. Furthermore, the wax of the present invention is
It is also excellent in solubility in a solvent. Therefore, this has an advantage that a solvent type ink suitable for eg gravure printing can be easily prepared with good workability.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to production examples of the wax for thermal transfer ink of the present invention.

Example 1 Hard lanolin fatty acid (lanolin fatty acid HH, acid value 105,
140 g of pentaerythritol was added to 1000 g of a melting point of 74 ° C., manufactured by Yoshikawa Oil Co., Ltd., and the mixture was heated and stirred under reduced pressure at 250 ° C. for 10 hours to carry out an esterification reaction.

The reaction mixture is then added to tolylene diisocyanate (TDI
-80, manufactured by Nippon Polyurethane Industry Co., Ltd.) 100 g,
The wax of the present invention was obtained by heating and stirring at 120 ° C. for 4 hours.

Example 2 To 1000 g of lanolin fatty acid HH, 160 g of glycerin and 12 g of potassium hydroxide were added, and the mixture was heated and dehydrated under reduced pressure at 230 ° C. for 8 hours to carry out an esterification reaction. After the reaction was completed, a strong acid type ion exchange resin (Amberlite IR-120 was added to the reaction mixture.
(H) TG, manufactured by Rohm and Haas Co., Ltd.) (100 g) was added for neutralization, and the catalyst was removed by passing.

To the thus obtained esterified product, 10 g of TDI-80 was added and stirred at 100 ° C. for 4 hours to obtain the wax of the present invention.

Example 3 Esterification reaction and polycondensation reaction were carried out in the same manner as in Example 1 using 80 g of pentaerythritol and 50 g of tolylene diisocyanate to obtain the wax of the present invention.

Comparative Example 1 The same reaction as the first half (esterification reaction) of Example 1 was repeated to obtain a pentaerythritol ester of lanolin fatty acid.

The following physical properties were measured for the wax or ester obtained in each of the above examples.

Appearance: Measured visually.

Acid value: According to JIS K 0070.

Melting point ... according to JIS K 2235 5.3.

Viscosity: According to JIS K 2283 (100 ° C).

Penetration ... According to JIS K 2235 5.4 (25 ° C).

Heat of fusion ... Differential scanning calorimeter (Perkin Elmer DSC-
In 2), the heating rate was 10 ° C./min.

The results obtained are shown in Table 1 below. Table 1 also shows
For comparison, the same characteristic values for paraffin wax and carnauba wax are also shown.

Also, the wax and ester obtained in each of the above examples, the paraffin wax and the carnauba wax were tested for their solubility in toluene as follows.

That is, 3 g of each sample was heated and dissolved in 7 g of toluene, left to stand in a room at 25 ° C. and allowed to cool naturally, and the liquid temperature at which the liquid began to become turbid as the temperature decreased was measured as a cloud point. The fluidity of each sample was examined 24 hours after the above test, and evaluated according to the following criteria.

◯: Flows Δ: Flows when shaken lightly ×: Solidifies The obtained results are shown in Table 2 below.

<Colorant dispersibility test> 5 g of the wax sample and the like obtained in each of the above examples and 0.2 g of ethylene vinyl acetate resin [Eva Flex 45, manufactured by Mitsui DuPont Polychemical Co., Ltd.] in a 70 ml stainless steel cylindrical cup, 20 g of toluene was added and dissolved.
1.5 g of the following colorant (pigment) and 20 g of glass beads having a diameter of 1 mm were put in this and dispersed for 30 minutes with a disk-type stirrer to obtain a test ink.

Test pigment Black ... Carbon black MA-100 (manufactured by Mitsubishi Kasei Co., Ltd.) Yellow ... Disazo yellow (Hoechst, permanent yellow DHG) Red ... Brilliant carmine 6B (Fuji dye, Fujicarmine 6B) Green ... Phthalocyanine green (Sanyo dye) (Phthalocyanine Green SAX manufactured by the company) 1 drop of each of the above test inks is placed on a slide glass plate, the solvent is dried, and then melted on a hot plate,
A cover glass was placed, and the dispersed state of the sample was compared and observed with a microscope (× 200), and evaluated according to the following criteria.

Criteria for dispersibility ○: Pigment particles are uniformly dispersed without agglomerating Δ: Slight agglomeration is observed × ... Agglomeration is observed and a cover glass is put on the glass plate after melting. Without cooling, the surface gloss and color tone were compared and visually observed and evaluated according to the following criteria.

Gloss color evaluation criteria ○… Glossy, transparent and clear color tone on the surface △… Slightly dull color tone ×… Opaque and cloudy, and the color tone is dull and whitish The results of the above tests obtained by using the above are shown in Table 3 below.

<Thermal Transfer Ink Performance Test> A thermal transfer recording sheet was prepared by the following method for the thermal transfer ink containing carbon black of Example 1 as a colorant prepared in the above colorant dispersion test.

That is, the above ink was applied onto a polyester film having a thickness of 6 μm so as to have a coating film thickness of 10 μm using a barcolator, and dried with hot air at 100 ° C. for 2 minutes to prepare a thermal transfer recording sheet.

In addition, 20 g of the wax of the present invention obtained in Example 3 and 1 g of ethylene vinyl acetate resin were placed in a stainless steel cylindrical cup having a content of 70 ml, and 20 g of glass beads having a diameter of 1 mm and 4 g of Brilliant Carmine 6B were added thereto, and the temperature was 100 ° C. Was heated and melted, and dispersed with a disk stirrer for 30 minutes to obtain a red ink. This ink was applied to a polyester film having a thickness of 6 μm to a thickness of 2 μm to obtain a thermal transfer sheet.

Epson Word Bank
Thermal transfer paper (product of Epson Sales Co., Ltd., # 8)
785).

As a result, no matter which sheet was used, clear printing with a firm contour and gloss was obtained.

From the above results, it is understood that the wax of the present invention can exert a remarkable effect as a wax for thermal transfer ink.

Claims (1)

(57) [Claims] 1. A wax for a heat-sensitive transfer ink, which contains an isocyanate polymer of a lanolin fatty acid polyhydric alcohol ester as an active ingredient.