JPH05156192A - Color recording ink - Google Patents

Abstract

PURPOSE:To obtain a color recording ink which is lowly viscous, undergoes less thickening due to the evaporation of water after the lapse of time and can be stably delivered without bending by specifying the surface tensions and viscosities of the respective color inks each comprising an aqueous solution containing a water-soluble dye, a polyalcohol and its derivative. CONSTITUTION:A color ink for jet recording comprising aqueous solutions each containing a water-soluble dye, a polyalcohol and its derivative, wherein the surface tensions of the respective constituent inks of colors Y, M and C are such that the surface tension of C is higher than that of Y, the surface tension of M is higher than that of C, and the viscosities of the respective inks are 3-7cP at 20 deg.C, and their pHs are 5-10 at 20 deg.C. As the water-soluble dyes, any dyes that do not change in their colors and do not precipitate when other ink components are added thereto and do not change markedly in surface tension can be used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording color ink used in an ink jet recording apparatus.

[0002]

2. Description of the Related Art Conventionally, as a recording color ink used in an ink jet recording apparatus, ink clogging in nozzles does not occur for all colors, a sufficient contrast is provided for recording, and physical properties of ink change by storage. Alternatively, it is necessary to have various characteristics such as not forming a precipitate.

The inks conventionally used as ink-jet recording color inks are roughly classified into water-based inks and non-water-based inks. Non-aqueous ink is difficult to use except for low-priced products or special applications. Therefore, almost all water-based inks are used as ink-jet recording inks that require high-quality printing on paper.

[0004]

However, a drawback of the water-based ink is that it has a high freezing point and easily freezes because the solvent is water. If the freezing point of the ink is high, there is a problem that the head such as a glass material is cracked due to volume expansion due to freezing of the ink in a cold region. Therefore, lowering the freezing point is not effective unless more polyhydric alcohol or the like is added, but since the ink viscosity increases, the ink meniscus is restored at the ejection port in the formation of the ink drop. The time may be delayed, the ink may not be ejected properly, the flight may be bent, and stable printing may not be obtained.

In the color ink jet recording apparatus, it is difficult to secure the overall reliability of the apparatus as compared with the monochrome recording apparatus. In particular, for all colors of color ink with different characteristics, the above-mentioned clogging, defects in the ink itself such as ink storability, and problems with ink ejection such as flight bending, oblique or satellite occurrence in the ink are all color inks. It is necessary to solve in.

Clogged with water-based color ink,
Further, the present inventor conducted an experiment that the ink components, composition, etc. often cause the basic problems of the inkjet recording ink, such as changes in the physical properties of the ink or the formation of precipitates, etc. upon storage. Confirmed by. This is because water in the ink evaporates from the nozzle at room temperature or high temperature, the viscosity increases due to the change in the ink composition due to the solvent ratio in the ink, the pH of the ink decreases, the solubility of the dye in the ink component decreases, etc. Is affected.
Then, the ink cannot be ejected due to an increase in the viscosity of the ink, or the ink drop may scatter or fly even when ejected, so that stable ink ejectability cannot be obtained.

Further, in the color ink jet recording apparatus, it is difficult to secure the overall reliability of the apparatus as compared with the monochrome recording apparatus. Especially, in all color inks with different characteristics, the clogging as described above,
It is necessary to solve problems with ink of all colors, such as defects in ink alone such as ink storability, and problems in ink ejection such as flight bending, oblique or satellite generation in the ink. Further, as a drawback in color printing, since the heads are arranged in the order of Y, M, and C, there is no problem in single-color printing, but when performing heavy-color printing such as red printing, ink ejection is performed in forward printing. The order is Y +
In the backward printing, the ink ejection order is M + Y. Therefore, when ink is fixed on the paper, there is a drawback that the color is changed in the bidirectional printing due to the influence of the ink ejected later. Therefore, the printing direction is always Y, M, C, or one-way printing is performed by moving the head in a certain direction by the heads arranged in the order C, M, Y, but the printing speed is slow. There was a flaw.

The present invention is intended to solve the above problems, and its purpose is to provide a low viscosity, a small increase in viscosity due to evaporation of water over time, and excellent discharge stability without bending. is there. It is another object of the present invention to provide a color ink for recording that enables color printing such that double-color printing in color printing recording does not result in different print colors in reciprocal printing.

[0009]

In order to solve the above-mentioned problems, the present invention provides a recording color ink used in an ink jet recording apparatus for recording by jetting from a nozzle,
The surface tension of each ink composed of the Y, M, and C color inks of the recording color ink made of an aqueous solution containing a water-soluble dye, a polyhydric alcohol and its derivative is higher than C and higher than C. Is high, the viscosity of each ink at that time is 20 ° C
Is 3 to 7 cP, and the ink pH is 5 to 10 at 20 ° C.

[0010]

The water-soluble dye having the above-mentioned constitution is a dye such as a dye which does not cause a change in color tone or the formation of precipitates by addition of other ink components, or a dye which does not cause a great variation in surface tension. If it can be used. As a further example, C.I. I. Direct Yellow 12, 26, 86, 130 C.I. I. Direct Red 9, 13, 17, 227 C.I. I. Direct Blue 78,86,90,199 C.I. I. Acid Yellow 23, 25 C.I. I. Acid Red 254,289 C.I. I. Acid Blue 9,254 and the like, which are used alone or in combination of two or more. If the addition amount is less than 0.5% by weight, the required color tone and contrast are difficult to appear, and if it is 5% by weight or more, clogging due to water vaporization easily occurs in the injection nozzle.
Weight percent is suitable.

Further, although not described in addition to the above water-soluble dyes, they can be appropriately used if they meet the conditions. Next, an aqueous solution containing a polyhydric alcohol and its derivative is used to prevent ink evaporation, ink penetration into paper,
It is added to lower the freezing point of the ink,
Specifically, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol,
Polyethylene glycol, glycerin, ethylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether, ethylene glycol diethyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol isopropyl ether, ethylene glycol monobutyl ether, ethylene glycol dibutyl ether, ethylene Glycol monobutyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, diethylene glycol dimethyl ether, di Chi glycol diethyl ether, diethylene glycol acetate, triethylene glycol monoethyl ether, diethylene glycol monomethyl ether or the like is mainly used. The amount added is
If the amount is less than 15% by weight, it is less effective in preventing ink clogging in the ejection nozzle and lowering the freezing point of the ink. If the amount is 55% by weight or more, the ink viscosity becomes too high and the ink flying speed becomes slow, resulting in positional accuracy. Therefore, 15 to 55% by weight is suitable. Then, in the present invention, a color ink is prepared by adjusting the ink surface tension value of the solvent described below including glycerin as the solvent without using a surfactant. Further, in addition to the above-mentioned components, an antifungal agent, an antiseptic agent, a pH adjusting agent and the like may be appropriately added to the recording color ink of the present invention.

[0012]

EXAMPLES Examples of the present invention will be described below. (Example 1) First, triethylene glycol and diethylene glycol monobutyl ether were mixed with ion-exchanged water and dissolved in an aqueous solution containing a polyhydric alcohol and its derivative. I. Direct Y
ellow86 / C. I. Direct Red9 /
C. I. Using Direct Blue 199, color inks having different surface tensions having the following compositions were prepared. Proxel (manufactured by ICI) was added as an antiseptic to the following inks.

The physical properties of the ink at 20 ° C. are 5.2 cP and 5.2-10, respectively. In addition, the ink surface tension was adjusted with diethylene glycol monobutyl ether so as to be the measured value described in the following color ink composition. When the physical properties of the obtained ink were measured, the viscosity was 5.2 cP (20 ° C.), the ink pH was 10, and the surface tension was 28 dyne / cm (20 ° C.). When the physical properties of the obtained ink were measured, the viscosity was 5.2 cP (20 ° C.), the ink pH was 7.5, and the surface tension was 38 dyne / cm (20 ° C.). When the physical properties of the obtained ink were measured, the viscosity was 5.2 cP (20 ° C.), the ink pH was 6.5, and the surface tension was 34 dyne / cm (20 ° C.).

Even when the color inks set as described above are allowed to stand for one month at room temperature, no foreign matters or precipitates are generated, and the basic characteristic of the ink jet ink is that all color inks are recorded in the color ink jet recording apparatus. The ink is highly reliable as an inkjet ink, for example, it is sucked, printed, left for 1 month without a cap, and then printed, without printing defects such as missing dots, resulting in extremely stable printing results. Met.

In particular, as a confirmation experiment for double-color printing in color print recording, first, color inks having the same surface tension were sucked into an inkjet recording apparatus, and reciprocal printing was performed as double-color printing on an inkjet paper. Showed different printing colors in the forward and backward printing. This is because the ink ejected first is fixed on the inkjet paper and begins to penetrate, and the next ink is ejected and fixed on the paper, so that the ink ejected later penetrates further, The influence of the ink colors of # 1 to # 4 will result in different colors in heavy color printing.

Therefore, when the color ink of the present invention is sucked into the ink jet recording apparatus of the present invention and Y + M or Y + C, or M + C is printed in one direction and reciprocating direction as the multicolor printing on the ink jet paper, either printing is performed. In the direction as well, it was possible to perform color printing with the same color as visual confirmation. This is because, for example, when performing red print recording, ink is ejected by Y + M in forward pass printing of reciprocal printing and M + Y in forward pass printing, so from a conventional perspective, M ink in forward pass printing and Y ink in backward pass printing should affect. is there. However, in the forward printing, the Y ink fixed on the inkjet paper has a low ink permeability due to the high surface tension of the M ink, and the fixed Y ink is fixed.
Permeates cleanly around the ink dots, making red printing possible. Further, in the backward pass printing, since the M ink fixed on the inkjet paper has a high surface tension, the permeation time is delayed, and the next Y ink is overlapped during the permeation, so that the permeability of the M ink is As a result, the red print record that is comparable to the forward print can be made even in the backward print. As for the color of the printed matter, the method of visually confirming it is the best, but since it was also confirmed in the observation field of view of the CIE colorimetric system with a Macbeth CE7000 spectrophotometer, it is shown in Table 1 below for reference. The color measurement samples shown in Table 1 below are those recorded at a printing rate of 100%.

[0017]

[Table 1]

The measured values shown in Table 1 are described as a reference because they differ depending on the measurement accuracy, the measurement conditions, etc., but it can be confirmed that they show extremely close colors. Example 2 First, diethylene glycol and diethylene glycol monoethyl ether were mixed with ion-exchanged water and dissolved in an aqueous solution containing a polyhydric alcohol and a derivative thereof, and C.I. I. Direct Ye
low 86 / C. I. Direct Red227 /
C. I. Using Direct Blue 199, color inks having different surface tensions having the following compositions were prepared. Proxel (manufactured by ICI) was added as an antiseptic to the following inks.

The physical properties of the ink at 20.degree. C. are 4.5 cP and pH is 6.5-10. When the physical properties of the obtained ink were measured, the viscosity was 4.5 cP (20 ° C.), the ink pH was 10, and the surface tension was 25 dyne / cm (20 ° C.). When the physical properties of the obtained ink were measured, the viscosity was 4.5 cP (20 ° C.), the ink pH was 7.8, and the surface tension was 38 dyne / cm (20 ° C.). When the physical properties of the obtained ink were measured, the viscosity was 4.5 cP (20 ° C.), the ink pH was 6.5, and the surface tension was 30 dyne / cm (20 ° C.).

Even when each color ink set as described above is allowed to stand for one month at room temperature, no foreign matter or precipitate is generated, and the basic characteristics of the ink jet ink are all colors in the color ink jet recording apparatus. The ink is highly reliable as an inkjet ink, for example, it is sucked, printed, left for 1 month without a cap, and then printed, without printing defects such as missing dots, resulting in extremely stable printing results. Met.

In particular, as a confirmation experiment for double-color printing in color printing recording, first, color inks having the same surface tension were sucked into an ink jet recording apparatus, and reciprocal printing was performed on the ink jet paper as double color printing. Showed different printing colors in the forward and backward printing. This is because the ink ejected first is fixed on the inkjet paper and begins to penetrate, and the next ink is ejected and fixed on the paper, so that the ink ejected later penetrates further, The influence of the ink colors of # 1 to # 4 will result in different colors in heavy color printing.

Therefore, when the color ink of the present invention is sucked into the ink jet recording apparatus of the present invention and Y + M or Y + C, or M + C is printed in one direction and reciprocating direction as a multicolor print on the ink jet paper, either print is performed. In the direction as well, it was possible to perform color printing with the same color as visual confirmation. This is because, for example, when performing green print recording, Y + C is ejected in C + Y in forward print of forward and backward print, and C ink in forward print should affect C ink in forward print and Y ink in return print. Is. However, in the forward printing, the Y ink fixed on the inkjet paper is affected by the high surface tension of the C ink, the ink permeability is reduced, and the Y ink fixed permeates around the dots of the fixed Y ink neatly, and red print recording is possible. Become. Also, in the backward pass printing, the C ink fixed on the inkjet paper has a high surface tension, so the permeation time is delayed, and the next Y ink overlaps during the permeation, so that the permeability of the C ink is As a result, it is possible to perform green print recording that is comparable to the forward print even in the backward print. As for the color of the printed matter, the method of visually confirming is the best, but since the Macbeth CE7000 spectrophotometer confirmed the samples of each double-colored printing (printing rate 100%) even in the observation field of 10 ° of the CIE color system. For reference, see Table 2 below.

[0023]

[Table 2]

It can be confirmed that the measured values shown in Table 2 show very close colors although they differ depending on the measurement accuracy and the measurement conditions. As described above, the recording color ink of the present invention has been described in the examples, but it goes without saying that other than the described color ink composition and components, it can be appropriately used. Needless to say, in addition to the ink physical property values set in the examples, particularly the surface tension value can be appropriately used in the claims.

[0025]

INDUSTRIAL APPLICABILITY As described above, the recording color ink of the present invention is a recording color ink used in an ink jet recording apparatus which is ejected from a nozzle to perform recording. The surface tension of each ink composed of the Y, M, and C color inks of the recording color inks containing the aqueous solution contains C is higher than Y and M is higher than C. The viscosity of each ink at that time is 20 ° C.
By setting the ink pH to be 3 to 7 cP and the ink pH to be 5 to 10 at 20 ° C., the nozzle clogging due to the evaporation of the solvent, which is a drawback of the water-based ink, can be eliminated, and the change in the ink physical properties due to the ink storability or the precipitation There is no such occurrence.

Further, it is excellent in ejection stability without bending. Furthermore, it has become possible to carry out color printing in double-color printing in color printing recording such that the printing colors in reciprocal printing do not differ.

Claims (5)

[Claims] 1. A recording color ink used in an ink jet recording apparatus for recording by being ejected from a nozzle, wherein each of Y and M of the recording color inks is an aqueous solution containing a water-soluble dye, a polyhydric alcohol and a derivative thereof. , C
The surface tension of each color ink is C rather than Y.
Is high, M is higher than C, and the viscosity of each ink at that time is 2
A recording color ink having a pH of 3 to 7 cP at 0 ° C. and an ink pH of 5 to 10 at 20 ° C. 2. The recording color ink according to claim 1, wherein the surface tension of the color ink composed of the Y, M and C color inks is in the range of 25 to 50 dyne / cm. 3. The surface tension of the Y ink is 25 to 40 d.
The color ink for recording according to claim 1, which is in the range of yne / cm. 4. The surface tension of the M ink is 28 to 50 d.
The color ink for recording according to claim 1, which is in the range of yne / cm. 5. The surface tension of the C ink is 26 to 45 d.
The color ink for recording according to claim 1, which is in the range of yne / cm.