JPH01126379A - Wax for heat-sensitive transfer ink - Google Patents

Abstract

PURPOSE:To obtain the titled wax capable of forming a transfer layer of a heat-transfer recording medium when kneaded with a colorant, etc., and applied to a surface of a heat-resistant substrate, by using an isocyanate polymer of a lanolin fatty acid polyhydric alcohol ester as an active component. CONSTITUTION:The objective wax contains an isocyanate polymer of a lanolin fatty acid polyhydric alcohol ester as an active component. The alcohol component constituting the ester is preferably glycerol, pentaerythritol, trimethylolpropane, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides thermal transfer recording by kneading wax for thermal transfer ink, more specifically coloring agents and other additives, and applying the mixture to the surface of a heat-resistant substrate. The present invention relates to a wax for thermal transfer ink that can form a transfer layer (ink layer) of a medium.

Conventional technology and its four points In recent years, various devices such as facsimile machines, computer terminals, word processors, image recorders, printers, etc. have been developed to have non-impact and low noise, simple mechanism, low cost, high reliability, and small size. Thermal transfer recording media, ie, heat-sensitive transfer sheets, are widely used because they are lightweight and can be colored. The heat-sensitive transfer sheet is generally made by forming an ink layer on the surface of a heat-resistant base material such as polyester, which is made by mixing coloring agents and other additives with a room-temperature solid substance (low melting point substance) such as wax that becomes liquid when heated. By aligning a transfer paper with this ink layer and printing with a thermal head, a desired image or the like can be formed on the transfer paper.

Conventionally, the low melting point substances mentioned above include natural waxes such as paraffin wax, carnauba wax, candelilla wax, and beeswax, polyethylene wax,
Synthetic waxes such as modified montan wax have been used, but the use of such waxes, as typified by carnauba wax, has the following various drawbacks.

First, the dispersibility of dyes and pigments used as colorants is poor, resulting in poor transparency, resulting in poor printing performance, and especially in full-color printing where colors are superimposed, transparency is low, resulting in images with dull colors. Put it away.

Second, since the heat of fusion is large (approximately 40 cal/g), a large amount of heat is required to liquefy the ink, making it difficult to improve the sensitivity of printing and resulting in unclear printing.

Thirdly, conventionally used waxes generally have poor solubility in solvents, and when applying a solvent-dispersed ink to make a thermal transfer sheet, the ink concentration cannot be increased and the manufacturing workability is also poor.

In view of the above-mentioned current situation, the present inventors have solved all the drawbacks of conventional heat-sensitive transfer sheets of this kind, especially the low melting point substance (wax) for ink thereof, and We conducted extensive research with the aim of developing a new ink wax that has particularly good colorant dispersibility, low heat of fusion, and excellent solubility.

As a result, the inventors discovered that an isocyanate polymer of lanolin fatty acid polyhydric alcohol ester has properties as a wax that meet the above objectives, and have now completed the present invention.

That is, the present invention relates to a wax for thermal transfer ink characterized by containing 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 conventional waxes of this type, and is a binder for thermal transfer inks (
It has very excellent properties as both a binder and a dispersion medium.

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

The polymer is obtained by reacting a lanolin fatty acid polyhydric alcohol ester with an isocyanate compound. Lanolin fatty acid as the acid component constituting the lanolin fat I-based polyhydric alcohol ester used here is obtained by saponification and decomposition of lanolin, which is secreted from the sebaceous glands of sheep and produces a wax-like substance that adheres to sheep wool. Its fatty acid composition is mainly composed of branched chain fatty acids such as isofatty acids and antiisofatty acids, with few linear fatty acids.
3) and a fairly large amount of hydroxy fatty acids (approximately 1/
Included in 3). The number of carbon atoms in secondary fatty acids is widely distributed from 9 to 34. Various types of lanolin fatty acids are commercially available, and these are based on the standards for cosmetic raw materials (Notification No. 16 of the Ministry of Health and Welfare).
According to No. 7), lanolin fatty acids are classified into hard lanolin fatty acids, lanolin fatty acids, and soft lanolin fatty acids. In the present invention,
In order to obtain such substances, it is desirable to use the above-mentioned hard lanolin fatty acids. The lanolin fatty acid particularly suitable for the present invention usually has a melting point of 62 to 8'O<0>C and an acid value of 90 to 140<0>C.
, those having physical properties in the saponification value range of 130 to 170 can be exemplified.

In addition, the polyhydric alcohol as an alcohol component constituting the lanolin fatty acid polyhydric alcohol ester is as follows:
Common examples include glycerin, diglycerin, pentaerythritol, trimethylolpropane, sorbitol, sucrose, ethylene glycol, propylene glycol, dipentaerythritol, and polypropylene glycol. Among these, glycerin, pentaerythritol, trimethylolpropane, etc. can be preferably used.

The esterification reaction between the acid component and the alcohol component can be carried out by heating and dehydrating without a catalyst or using a suitable catalyst according to a conventional method. The esterification reaction can be carried out in more detail according to the general method described in "New Edition Fatty Acid Chemistry" written by Futabe et al. Hirano, published by Koshobo, pp. 161-165, and also as described in, for example, Japanese Patent Application Laid-Open No. 59-53594. This can be carried out using conditions similar to those described.

Examples of the above-mentioned esters particularly suitable for the present invention include pentaerythritol syralate, pentaerythritol syralt, pentaerythritol tetraralt, glycerol syralate, and the like.

The lanolin fatty acid polyhydric alcohol ester obtained as described above has a hydroxyl group or carboxyl group derived from lanolin fatty acid and a hydroxyl group derived from polyhydric alcohol as active hydrogen in its molecule, and the active ingredient of the present invention is It is produced by reacting these equally active hydrogen atoms with isocyanate. The incyanate used here is not particularly limited as long as it can react with the above active hydrogen to form a urethane bond, urea bond, billet bond, allophanate bond, etc., but usually, for example, tolylene diisocyanate (TDI), tolydine diisocyanate, etc. (T.O.D.
I>, diphenylmethane-4,4'-diisocyanate (MDI), 1,5-naphthalene diisocyanate, xylene diisocyanate, triphenylmethane triisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, and the like. Among these, TDI,
MDI, xylene diisocyanate, etc. are preferred.

The reaction between the lanolin fatty acid polyhydric alcohol ester and the isocyanate can be carried out by employing a heating stirring operation according to a conventional method. If the heating temperature is too high, the resulting product will be markedly colored, and if it is too low, the reaction time will be prolonged, so it is desirable to select the heating temperature in the usual range of 70 to 150°C. In addition, the above reaction can be carried out using a metal salt catalyst,
For example, stannic chloride, ferric chloride, potassium oleate,
The use of dibutyltin dilaurate and the like allows the process to proceed relatively quickly at lower temperatures. It is appropriate that the reaction time is usually about 0.5 to 5 hours.

The amount of isocyanate used in the above reaction is appropriately selected depending on the type of each raw material used, reaction conditions, etc., but it is usually about 0.1 to 40% by weight, preferably about 0.1 to 30% by weight based on the ester. The desired polymerization reaction can proceed within this range, and a wax having desired properties can be produced.

In this way, a desired polymer to be used as an active ingredient in the present invention can be produced. The polymer has the following physical properties and can be suitably used as the wax for thermal transfer of the present invention.

Melting point = 40~100℃ Acid value: 20 or less Viscosity 20.6~500 poise (100℃) Penetration: 0
~20 Heat of fusion: 10 to 30 Ca1/q The wax for thermal transfer ink of the present invention can be prepared by directly utilizing the reaction mixture containing the isocyanate polymer of lanolin fatty acid polyhydric alcohol ester obtained as described above. Of course, the above-mentioned polymer can also be isolated and purified from the reaction mixture according to a conventional method to obtain the wax of the present invention.

A thermal transfer ink can be prepared by using the wax of the present invention in part or in whole in place of a conventional room-temperature solid material as a binder and dispersant for this type of thermal transfer ink. This thermal transfer ink can be prepared according to a conventional method except for using the wax of the present invention. For example, the wax of the present invention may be added with coloring agents such as carbon black, phthalocyanine green, and brilliant carmino 6B, and other additives, such as ethylene vinyl acetate resin, acrylic resin, vinyl chloride-vinyl acetate copolymer resin, etc., for film quality modification. liquid paraffin, DOP, plasticizers such as castor oil, toluene,
After premixing with solvents such as xylene and ethyl acetate,
A desired thermal transfer ink can be prepared by kneading and dispersing using a dispersing machine such as a ball mill, sand mill, attritor, or three-roll mill.

In preparing the above thermal transfer ink, the wax of the present invention is suitably used in an amount of about 5 to 95% by weight, preferably about 10 to 90% by weight, based on the solid content of the ink normally obtained.

The ink thus obtained is applied to a heat-resistant substrate such as polyester, polypropylene, polystyrene, polycarbonate, polyimide, other heat-resistant plastic films, paper, metal foil, etc. to form an ink layer according to a conventional method. , it can be put to practical use as a thermal transfer recording medium.

The wax of the present invention has a low heat of fusion and excellent dispersibility of coloring agents such as pigments, and by its use, thermal transfer inks can be easily prepared and can be obtained in this way. Adds homogeneity, smooth coating film formation, good coating properties, etc. to the ink,
Further, by using a thermal transfer recording medium using the ink, it is possible to obtain good printing with excellent transparency, sharpness, multicolor reproducibility, sensitivity, etc. Furthermore, the wax of the present invention has excellent solubility in solvents, and therefore has the advantage that a solvent-type ink suitable for, for example, gravure printing can be easily prepared with good workability.

EXAMPLES Hereinafter, the present invention will be explained in more detail by referring to examples of manufacturing the wax for thermal transfer ink of the present invention.

Example 1 Hard lanolin fatty acid (lanolin fatty acid HH, acid value 105
, melting point 74°C (manufactured by Yoshikawa Oil Co., Ltd.) to 1,000 liters, pentaerythritol 140C] was added to 140C under reduced pressure.
Esterification reaction was carried out by heating and stirring at 50'C for 10 hours.

Tolylene diisocyanate (TDI) was then added to the reaction mixture.
-80, manufactured by Nippon Polyurethane Industry Co., Ltd.>100CI
was added, and the mixture was heated and stirred at 120°C for 4 hours to obtain the wax of the present invention.

Example 2 Glycerin 16 to lanolin fatty acid 1-IHlooOQ
0C] and 12C1 of potassium hydroxide, and 2C under reduced pressure.
Esterification reaction was carried out by heating and dehydrating at 30° C. for 8 hours. After the reaction was completed, a strong acid type ion exchange resin (Amberlite IR-120 (H>TG, manufactured by Rohm and Haas)>100CI was added to the reaction mixture to neutralize it, and the mixture was filtered to remove the catalyst.

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

Example 3 Using pentaerythritol 800 and tolylene diisocyanate 50Q, an esterification reaction and a polycondensation reaction were carried out in the same manner as in Example 1 to obtain a wax of the present invention.

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

The following physical properties were measured for each wax or ester obtained on each side.

0 Appearance: Measured with the naked eye.

0 acid value...according to JIS K 0070.

0 melting point...according to JIS K 2235 5.3.

○Viscosity...J Is K 2283 (100'
According to C).

Q Penetration - J Is K 2235 5-4 (2
5°C). -0@Antipyretic...Differential scanning calorimeter (PerkinElmer DSC-2>
The measurement was carried out at a heating rate of 10° C./min.

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

Further, the waxes and esters, paraffin waxes, and carnauba waxes obtained on each side were tested for their solubility in toluene as follows.

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

○・・・Flowing △・・・If you take a photo lightly, it will flow ×・・・Solidizes The results obtained are shown in Table 2 below.

Table 2 <Colorant dispersibility test> Contents: 5 g of the wax sample obtained on each side in a 70 mQ stainless steel cylindrical cup and 0.0 g of ethylene vinyl acetate resin [Evaflex 45, DuPont Mitsui Polychemical Co., Ltd. 1]. 2CI was taken and 20g of toluene was added to dissolve it. 1.50 of the following colorant (pigment) and glass peas 20Q with a diameter of 1 mm were placed in this and dispersed for 30 minutes using a disk type stirrer to obtain a test ink.

○Test pigment Black...Carbon black MA-100 (manufactured by Mitsubishi Kasei Corporation) Yellow...Disashi Yellow (manufactured by Hoechst, Permanent Yellow DHG> Red...Brilliant Carmine 6B (manufactured by Fuji Shiki Co., Ltd.)
Fuji Carmine 6B> Green... Phthalocyanine Green (manufactured by Sanyo Shiki Co., Ltd., Phthalocyanine Green 5AX) One drop of each of the above test inks was placed on a slide glass plate, the solvent was dried, and then melted on a hot plate and covered. A glass was placed and the dispersion state of the sample was comparatively observed using a microscope (x200x) and evaluated according to the following criteria.

0 Dispersibility evaluation criteria ○... Pigment particles are uniformly dispersed without agglomeration △... Slight aggregation is observed X... Agglomeration and voids are observed. Melt welding, cooling naturally without placing a cover glass, and compare the surface gloss and color tone with the naked eye 11! and evaluated based on the following criteria.

0 Gloss color tone evaluation standard O... The surface is glossy, transparent, and has a clear color tone. △... It has a slightly dull color tone. X... It is opaque and cloudy, and the color tone is dull and whitish. The results of the above tests obtained using each colorant (pigment) are shown in Table 3 below.

Table 3 (Thermal transfer ink performance test) A thermal transfer recording sheet was prepared by the following method using the thermal transfer ink containing carbon black as a colorant of Example 1 prepared in the above colorant dispersion test.

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

Further, 20 CJ of the present wax obtained in Example 3 and 1 q of ethylene vinyl acetate resin were placed in a stainless steel cylindrical cup with a content of 70 ml, and 20 g of glass beads with a diameter of 1 mm and 4 g of brilliant carmine 6B were added therein.
The mixture was melted by heating to 100° C. and dispersed for 30 minutes using a disc type stirrer to obtain a red ink. This ink was applied to a 6-μm-thick polyester film to a thickness of 2 μm to obtain a thermal transfer sheet.

Each sheet obtained in this way is stored in Epson Word Bank L.
Thermal transfer paper (product of Epson Sales Co., Ltd., #
8785).

As a result, no matter which sheet was used, clear, glossy prints with firm outlines were obtained.

From the above results, it can be seen that the wax of the present invention can exhibit remarkable effects as a wax for thermal transfer ink.

(that's all)

Claims (1)

[Claims] (1) A wax for thermal transfer ink characterized by containing an isocyanate polymer of lanolin fatty acid polyhydric alcohol ester as an active ingredient.