JPH04236274A - Method for dispersing pigment - Google Patents

Abstract

PURPOSE:To enable the dispersion of increased amount of copper phthalocyanine blue or carbon black compared with conventional method in a hot-melt medium for thermal transfer ink. CONSTITUTION:A metal phthalocyanine compound, especially an iron phthalocyanine or tin phthalocyanine is used as a dispersing agent. A thermal transfer ink having a melt viscosity comparable to or lower than that of conventional ink can be produced even by dispersing an increased amount of a coloring pigment.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method for dispersing pigments in a hot melt medium for thermal transfer inks.

0002

BACKGROUND OF THE INVENTION Thermal transfer inks are manufactured by dispersing pigments such as carbon black in a heat-melting medium (hereinafter referred to as vehicle) mainly consisting of wax. It is desirable that the pigment be dispersed in the vehicle at as high a concentration as possible in order to improve production efficiency and the coloring power of the ink. However, increasing the concentration of pigment in the vehicle increases the viscosity of the ink when melted, creating a problem that it becomes difficult to apply a uniform thin film. This tendency is particularly noticeable in the case of copper phthalocyanine blue and carbon black, which have small particle sizes.

0003

SUMMARY OF THE INVENTION An object of the present invention is to provide a pigment dispersion method for solving the above-mentioned conventional problems and for obtaining a thermal transfer ink having a low melt viscosity even when the pigment concentration in a vehicle is high. With the goal.

0004

[Means for Solving the Problems] The present invention provides copper phthalocyanine, characterized in that a metal phthalocyanine compound is used as a dispersant when copper phthalocyanine blue or carbon black is dispersed in a heat-melting medium for thermal transfer ink. Concerning a method for dispersing blue or carbon black.

[0005]

[Operations and Examples] The present invention provides the following advantages: when dispersing the pigment copper phthalocyanine blue or carbon black in a vehicle for thermal transfer ink, a metal phthalocyanine compound, especially iron phthalocyanine or tin phthalocyanine, is used as a dispersant. Surprisingly, this work was completed based on the new discovery that the viscosity of the ink when melted decreases and the dispersibility improves.

The pigment used in the present invention is copper phthalocyanine blue, carbon black, or a mixture thereof (hereinafter referred to as colored pigment).

[0007] The particle size of the colored pigment is desirably small from the viewpoint of coloring power and resolution; for example, it is preferable that the average particle size of the primary particles is about 0.02 to 0.06 μm. In the present invention, even if a pigment with such a small particle size is used, an ink with low viscosity and good fluidity when melted can be obtained.

In the present invention, a metal phthalocyanine compound is used as a dispersant for dispersing the colored pigment in a vehicle. Various metals are known as the central metal atom of the compound, and among these, iron phthalocyanine and tin phthalocyanine are particularly preferred.

[0009] The metal phthalocyanine compound can be synthesized by a generally well-known method. In the case of iron phthalocyanine and tin phthalocyanine, one or two chlorine atoms may be bonded to the central iron or tin atom depending on the synthesis method. Compounds are also included.

[0010] The dispersant is used in an amount of 5 to 20 parts, preferably 10 to 1 part, per 100 parts (by weight, the same applies hereinafter) of the color pigment.
5 copies will be used. If the amount of dispersant used is less than the above range,
The effect of improving the dispersibility of the colored pigment is not sufficiently achieved, and the viscosity of the ink is not sufficiently reduced. On the other hand, if the amount of the dispersant used exceeds the above range, the influence on the hue of the final ink will increase, which is not preferable.

[0011] In the present invention, as the material of the vehicle in which the colored pigment is to be dispersed, the heat-melting materials used in conventional thermal transfer inks can be used as they are. For example, paraffin waxes such as paraffin wax and polyethylene wax, natural waxes such as tree wax, beeswax, carnauba wax, microcrystalline wax, and ceresin wax, as well as oxidized waxes, ester waxes, and higher fatty acids such as oleic acid and stearic acid. waxy substances such as vinyl chloride-vinyl acetate copolymers, ethylene-vinyl acetate copolymers, vinyl chloride-vinyl acetate-maleic acid terpolymers, alpha-olefin-maleic anhydride copolymers, synthetic polymers such as polyvinyl butyral, petroleum resins, etc. used. These materials may be used alone or in combination of two or more.

[0012] In the present invention, in order to obtain an ink by dispersing the colored pigment in the vehicle, for example, the vehicle 10
To 0 parts, add 4 to 50 parts, preferably 7 to 20 parts, of a color pigment, a dispersant in the above proportion, and a slight amount of other additives as necessary, and heat it to about 90 to 100 °C and mill it in a roll mill or sand mill. The mixture is kneaded by passing it through a kneader such as a kneader several times. If necessary, the pigment and dispersant may be first dispersed in a portion of the vehicle, and then the remaining vehicle may be added and mixed uniformly to form an ink.

In the present invention, as a result of using a metal phthalocyanine as a dispersant, it is possible to uniformly disperse a larger amount of color pigment than before and to obtain an ink having a low melt viscosity. As described above, since the ink obtained by the present invention has a low melt viscosity, it is possible to apply a thin film onto a substrate.
As a result, it is possible to obtain a thermal transfer recording medium that provides an image with high density, high resolution, and excellent scratch resistance.

The present invention will be explained below with reference to Examples, but the present invention is not limited thereto.

Example 1 7 parts of copper phthalocyanine blue (average particle size 0.04 μm
), 1 part of iron phthalocyanine was added to a mixture consisting of 25 parts of paraffin wax, 10 parts of petroleum resin, and 10 parts of carnauba wax, and a three-roll mill heated to 90°C was heated to
A circulation distribution process was performed. Further, 47 parts of paraffin wax was added and mixed uniformly to prepare a cyan color thermal transfer ink.

The viscosity of the obtained cyan thermal transfer ink was measured. The results are shown in Table 1. The viscosity measurement method is as follows.

Viscometer used: Parallel plate viscometer conditions
: 90°C x 60 seconds Measurement method: Fill ink into the sample filling hole (diameter 10mmφ, volume 0.5ml) of a viscometer that has been kept at 90±1°C in advance and hold for about 5 minutes. Next, the sample is pushed up with the piston knob, and at the same time the load plate is dropped, and the expanded diameter of the sample is read 60 seconds after this point and recorded in mm.

Examples 2 to 4 A cyan thermal transfer ink was prepared in the same manner as in Example 1 except that the amount of copper phthalocyanine blue and the amount and type of dispersant were changed. The viscosity was measured in the same manner.

Table 1 shows the composition of the ink and the results of measuring the viscosity of the obtained ink.

Comparative Example 1 An ink was prepared in the same manner as in Example 1 except that no dispersant was added, and the viscosity was measured.

Table 1 shows the composition of the ink and the results of measuring the viscosity of the obtained ink.

[0022]

[Table 1]

Example 5 14 parts of carbon black, 22 parts of paraffin wax,
Adding 1.6 parts of iron phthalocyanine to a mixture consisting of 8.5 parts of petroleum resin and 9.0 parts of carnauba wax;
Dispersion treatment was carried out by passing it through a three-roll mill heated to 90° C. five times. Further, 44.9 parts of paraffin wax was added and mixed uniformly to prepare a black thermal transfer ink.

The viscosity of the obtained black thermal transfer ink was measured in the same manner as in Example 1. The results are shown in Table 2.

Examples 6 to 8 Black thermal transfer ink was prepared in the same manner as in Example 5, except that the amount of carbon black and the amount and type of dispersant were changed. The viscosity was measured.

Table 2 shows the composition of the ink and the results of measuring the viscosity of the obtained ink.

Comparative Example 2 11 parts of carbon black, 25 parts of paraffin wax,
A mixture of 9.0 parts of petroleum resin and 9.5 parts of carnauba wax was heated to 90°C in a three-roll mill for 5 minutes.
A circulation dispersion process was performed. Further, 45.5 parts of paraffin wax was added and mixed uniformly to prepare a black thermal transfer ink, and the viscosity was measured in the same manner as in Example 1. The results are shown in Table 2.

[0028]

[Table 2]

From the results in Tables 1 and 2, it is clear that according to the method of the present invention, a thermal transfer ink containing 20 to 50% more pigment dispersed can be obtained than when metal phthalocyanine is not used as a dispersant. It can be seen that the melt viscosity of the ink is equal to or lower than that of the ink not produced by the method of the present invention.

[0030]

According to the method of the present invention, phthalocyanine blue or carbon black can be dispersed in a heat-melting medium for thermal transfer ink in a larger amount than in conventional products, and an ink with a high pigment concentration can be obtained.

Claims (2)

[Claims] 1. A method for dispersing copper phthalocyanine blue or carbon black, which comprises using a metal phthalocyanine compound as a dispersant when dispersing copper phthalocyanine blue or carbon black in a heat-melting medium for thermal transfer ink. 2. The dispersion method according to claim 1, wherein the metal phthalocyanine compound used as the dispersant is iron phthalocyanine or tin phthalocyanine.