JPH02310088A - Wax for thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To obtain high speed printability and the excellent fineness of a printing image by using an eutectic mixture of higher fatty acid and a room temp. solid substance and specifying the max. quantity of the heat of fusion thereof. CONSTITUTION:An eutectic mixture of higher fatty acid and a room temp. solid substance is contained as an effective component and the max. quantity of the heat of fusion thereof in a 5 deg.C-width measured by a differential scanning calorimeter is set to 50% or more the total quantity of the heat of fusion. As an embodiment of higher fatty acid, stearic acid, behenic acid and montan wax fatty acid are especially pref. because marked effect is obtained in the improvement of melt sharpness. As the room temp. solid substance, natural wax such as carnauba wax or synthetic wax such as behenic acid or glycerol can be designated. With respect to the mixing ratio of both of them, in case of behenic acid and carnauba wax, an eutectic mixture composition is present at two points wherein carnauba wax is about 23 pts.wt. and about 120 pts.wt. per 100 pts.wt. of behenic acid but this strict eutectic mixture composition is unnecessary and a composition in the vicinity of said composition may be used.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a wax for heat-sensitive transfer recording media, more specifically, a wax for heat-sensitive transfer recording media, which is applied alone or mixed with colorants and other additives to the surface of a heat-resistant substrate. The present invention relates to a wax for thermal transfer recording media that can form a transfer layer (ink layer), a release layer, etc. of the thermal transfer recording medium.

Conventional technology and its problems In recent years, various devices such as facsimiles, combination printers, word processors, image recorders, printers, etc. have been developed with the aim of being non-impact, making little noise, having simple device mechanisms, and low cost. Thermal transfer recording media, that is, thermal transfer sheets, are widely used because of their high reliability, small size and light weight, and ability to print in color. 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. Similarly, a low melting point substance such as wax is used for the release layer that may be formed between the ink layer and the heat-resistant base material.

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 are used; It has a serious disadvantage of being inferior. Those whose meltability is not sharp also have sharp solidification properties.
However, the assimilation of melt-transferred ink is slow, and disadvantages such as background smearing occur during high-speed printing.

Means for Solving the Problems In view of the above-mentioned current situation, the present inventors have solved the drawbacks of conventional heat-sensitive transfer recording media of this type, especially the low melting point substance (wax) that is the main component thereof, and particularly We conducted extensive research with the aim of developing a wax for thermal transfer recording media with sharp melting properties.

As a result, a eutectic mixture of a higher fatty acid and a solid substance at room temperature has a performance as a wax that meets the above criteria 1 (#I).
We have devised this idea and have now completed the present invention.

That is, the present invention 1 contains a eutectic mixture of a higher fatty acid and a room-temperature solid substance as an active ingredient, and the maximum heat of fusion in a 5°C range measured by a differential scanning calorimeter is 50% of the total heat of fusion.
The present invention relates to a wax for thermal transfer recording media characterized by the above characteristics.

The wax of the present invention eliminates all the drawbacks of conventional waxes of this type, and exhibits very excellent properties when used in the ink layer and release layer as a wax for thermal transfer recording media.

Hereinafter, the above-mentioned eutectic mixture used as an active ingredient of the wax of the present invention will be explained in detail.

The mixture is prepared by mixing and melting a higher fatty acid and a room temperature solid substance in a predetermined ratio. Examples of the higher fatty acids used here include various ordinary linear or branched saturated or unsaturated higher fatty acids, among which linear saturated fatty acids having 16 or more carbon atoms, preferably 18 to 34 carbon atoms. is suitable. Specific examples of the higher fatty acids include palmitic acid, stearic acid, elaidic acid, behenic acid, 12-hydroxystearic acid, montan wax fatty acid, rice wax fatty acid, rice plan wax fatty acid, carnauba wax fatty acid, hydrogenated castor oil fatty acid, etc. can be exemplified. One of these may be used alone, or two or more may be used in combination. Among these, stearic acid, behenic acid, montan wax fatty acid and the like are particularly preferred because they can have a remarkable effect on improving melt sharpness.

Examples of solid substances at room temperature include ordinary waxes, such as natural waxes such as carnauba wax, montan wax, castor wax, paraffin wax, ganderilla wax, rice plan wax, and beeswax, polyethylene wax, modified montan wax, and glycerol behenate. Examples include synthetic waxes such as.

The proportion of the above-mentioned higher fatty acid and room-temperature solid substance is determined as appropriate based on the combination of the two, on the premise that the mixture can form a eutectic mixture. For example, in the case of behenic acid and carnauba wax, eutectic mixture compositions exist at two points: about 23 parts by weight and about 120 parts by weight of carnauba wax based on 1001 parts of behenic acid. The wax of the present invention does not need to have such a strict eutectic mixture composition, but may have a composition around this range. Approximate values of the compositions forming the eutectic mixtures for such compositions and other combinations are as shown in the Examples below. The present inventors discovered for the first time that the above-mentioned eutectic mixture exhibits particularly sharp melting properties, and the higher the purity of the eutectic mixture, the sharper the above-mentioned melting properties become. Based on this knowledge, the present invention was completed. That's what I did. Therefore, when the heat of fusion of the mixture is measured using a differential operation calorimeter, the formation of the above-mentioned eutectic mixture can be explained by whether a peak appears at the same position as the melting peak of each component alone (i.e., the two components are simply mixed together). It can be judged by whether the peaks appear at different positions (forming a eutectic mixture). However, if the two components mentioned above are simply mixed together (), and these do not form a eutectic mixture, 1.t, it becomes difficult to obtain the sharpness of melting property characteristic of the present invention.

The wax for thermal transfer recording media of the present invention (is a eutectic mixture of the above-mentioned higher fatty acids and a solid material at room temperature) which can be used as an alternative to the conventional solid material at room temperature for this kind of thermal transfer recording media to produce thermal transfer inks, release layers, etc. A heat-sensitive transfer recording medium can be prepared. A second-class heat-sensitive transfer recording medium can be prepared according to a conventional method except for using the sock of the present invention. For example, the heat-sensitive transfer ink can be prepared by using the sock of the present invention with carbon silk, phthalocyanine green, carbon silk, phthalocyanine green, Coloring agents such as brilliant carmine 6B, other additives, film quality modifiers such as ethylene vinyl acetate resin, acrylic resin, vinyl chloride-vinyl acetate copolymer resin, plasticizers such as liquid paraffin, DOP, castor oil, etc. It can be prepared by pre-mixing with a solvent such as 1-helene, xylene, ethyl acetate, etc., and then kneading and dispersing using a dispersing machine such as a ball mill, a sand mill, an A1-lighter, or a three-roll mill.

In preparing the above thermal transfer ink, the wax l of the present invention
j1, usually) about 5 to 95 to the solid content of the ink
% by weight, preferably in the range of about 10-90% by weight.

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

Effects of the Invention The wax of the present invention has a sharp melting property and is commercially available. By using it, thermal transfer inks, etc. can be easily prepared, and the resulting thermal transfer recording medium can be heated easily with the thermal head. The response is excellent, and it is possible to print 1q with excellent sensitivity even at high speed printing.

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

Example 1 Stearic acid (manufactured by NOF Corporation, stearic acid NAΔ-1
80) 20Ω of Rice Plan wax (manufactured by Noda Wax Co., Ltd.) was added to 80 g, and the mixture was heated and stirred to 100° C. to prepare the wax of the present invention.

Examples 2 to 9 In the same manner as in Example 1, the waxes of the present invention shown in Table 1 were prepared using the following higher fatty acids and normal temperature solid substances in predetermined ratios.

Behenic acid: manufactured by Crowder Chemical, 85/90 Behenic acid hydrogenated castor oil fatty acid: Carnauba wax (No. 1) manufactured by Ito Oil Co., Ltd.: Montan wax manufactured by Yamaguchi Kasei Co., Ltd.
"Hex 1-Wax S" manufactured by Hex 1~ Co., Ltd. Castor wax: Manufactured by Toyota Oil Co., Ltd. The following physical properties and performance as a wax for thermal transfer recording media were measured and evaluated for the waxes obtained in each of the above examples. .

0 melting point: According to JIS K 2235 5.3.

0 Total heat of fusion and 5°C width Heat of fusion: Differential scanning calorimeter (Matsukuxience DS (-3100)
Measurements are made at a heating rate of 10° C./min to create a DSC curve. The sample to be measured is 2 to 3 mg.

The total heat of fusion is calculated from the area of the portion surrounded by the DSC curve and its baseline.

The 5°C width heat of fusion is calculated by drawing two straight lines parallel to the vertical axis with a 5°C width on the above DSC curve, and taking the area surrounded by the equal straight lines, the above DSC curve, and the baseline. . The maximum heat of fusion in the 5°C width is defined as the maximum heat of fusion in the 5°C width.

0 Melting sharpness: 5° C. maximum heat of fusion or 50% or more of the total heat of fusion is defined as good sharpness.

0 Printability: Measure and evaluate according to the following method.

(1) Preparation details of thermal transfer recording sheet 50% of the wax sample obtained in each of the above examples and 0.20% of ethylene vinyl acetate resin (Evaflex 45, manufactured by Mitsui Dupontbo 1 No Chemical Co., Ltd.) were placed in a 7Qm12 stainless steel cylindrical cup. Add 20g of toluene to dissolve it, and add carbon black (MAiooo) to it.
(manufactured by Mitsubishi Kasei Corporation) 1.5C] and crow beads 20Q with a diameter of 1 mm were added and dispersed for 30 minutes using a disk type stirrer to prepare a test ink. This ink was applied onto a polyethylene film with a thickness of 6 μm using a bar plater to form a 10 μm thick film.
The coating was applied to a coating thickness of η and dried with hot air at 100'C for 2 minutes to prepare a thermal transfer recording sheet I.

(2) Measurement/Evaluation of Printability Each sheet obtained in (1) above was printed on thermal transfer paper (#8785, manufactured by Epson Sales Co., Ltd.) using an Epson Word Punk LX King. The presence or absence of fading and background smearing is visually determined, and those without such markings are considered to have good printability.

) The results obtained are not shown in Table 1 below.

For comparison, Table 1 also lists the same characteristic values for a mixture of stearic acid and castor wax in a composition that does not form a eutectic mixture, and for each of carnauba wax, castor wax, and montan wax alone. .

Furthermore, DSC charts of each of the above sample waxes are shown in FIGS. 1 to 14.

From the above results, it can be seen that the wax #J of the present invention is extremely excellent as a wax for thermal transfer recording media.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 - Figure 13 4', A DSC diagram showing the melting properties measured by differential scanning calorimeter for each of the inventive waxes prepared in the examples and the comparative waxes. It is.

(that's all) (S/120 field)　○S.

(S/1120 field) ○50 (S/120 field) ○5O (S/190 field) ○S0 (S/190 mountain) ○50 (S/190 field) ○5O (S/190LLl) 0S0 (S/1eOLU) ○SO (S/190tJJ) :) SO (s/1eouJ) ○5O (S/190 field) ○S0

Claims (1)

[Claims] 1 Contains a eutectic mixture of higher fatty acids and room temperature solid substances as an active ingredient, and has a temperature of 5°C as measured by a differential scanning calorimeter.
A wax for thermal transfer recording media, characterized in that the maximum heat of fusion in width is 50% or more of the total heat of fusion.