JPS59133274A - Black water-based ink for ink jet printer - Google Patents

Abstract

PURPOSE:To provide the titled black ink having excellent solubility, water resistance, water repellency and prolonged stability, containing a coloring material obtd. by mixing specified red, yellow and blue dyes. CONSTITUTION:A coloring material composed of 0.4-1.6wt% C.I. Direct Red 225, 0.6-2.4wt% C.I. Direct Yellow 50 and 1.0-4.0wt% C.I. Reactive Blue 71 is dissolved in water. EFFECT:There can be obtd. ink jet recording in which uneveness in printing is not caused. It is possible to conduct good printing over a long period of time, and a printed image is not faded after printing even when wetted with water.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a black ink for inkjet printers, and particularly to an aqueous ink having excellent stability over time, water repellency, and water resistance.

(2) Prior Art and Problems Among the colorants used in conventional black ink for inkjet printers, C, which has the best overall color tone, water resistance, solubility, etc. Direct BAack19 has been used. However, commercially available C, I, Direct f
When a water-based ink is produced using 31ack 19,
Initial solubility and stability are good, but stability over time is lacking, and after 1 to 2 months, an association reaction of the dye occurs.
It is known that the gelation phenomenon and increase in viscosity lead to precipitation, resulting in a loss of performance as an ink (JP-A-57
-115468).

Ink using this dye has poor water repellency, so it tends to adhere to the nozzle surface of the inkjet printer head, so the adhering ink and the injected ink attract each other due to surface tension, causing the ejection direction to change and cause print irregularities. There were drawbacks. Also, no other black dye satisfies the above characteristics and -fC.

Therefore, as mentioned above, single dyes have poor solubility, color tone, water resistance,
It has not been possible to create a black ink for inkjet printers that satisfies all the characteristics of water repellency and stability over time.

(3) Purpose of the Invention The present invention provides a high-performance black water-based ink that is excellent in all of the above characteristics by using a mixture of three colors of red, blue, and yellow dyes that are excellent in solubility, water resistance, water repellency, and stability over time. Our goal is to provide the following.

(4) Structure of the invention In the inkjet recording ink, the colorant is CI
, Direct Red 225 and (:, 1.p
direct Yellow 50 and C, I, Re
This is achieved with an aqueous black ink characterized by being a mixture of active Blue 71.

In the present invention, a black ink is produced by selecting one dye each from red, blue, and yellow that has excellent properties as described above, and mixing them without using a black dye.

(5) Examples of the invention The present invention will be described below with reference to Examples.

First, we will show the process of selecting three dye colors. If the dye has low solubility in the ink solvent, the color density cannot be increased when printing, and the dye tends to precipitate in the ink, increasing the risk of clogging in the printer head nozzle. . Therefore, the dye is a bit expensive at least 69/,! A solubility of 9 or higher is required. Therefore, the dye used is 69/
The condition was that it had a solubility higher than or equal to the above.

Furthermore, since printing by an inkjet printer must be resistant to water, it is necessary to use ink that hardly fades even when immersed in water. The test method was to print using ink, dry it, then immerse the print in water for 10 minutes, and visually evaluate the degree of color fading. The condition for water resistance is that the color does not fade.

If the water repellency of the ink is poor, it will easily adhere to the nozzle surface of the printer head, causing irregular printing.

Therefore, inks with good water repellency were evaluated using the following method. A slide glass that had been ultrasonically cleaned with detergent and alcohol was immersed in the evaluation ink, and after being pulled up, the ink repellency was visually evaluated. Water repellency was defined as repelling more than half of the ink leaking area.

If the viscosity of ink changes during storage, it will cause irregular printing or printing problems, so it is necessary that the ink does not change in viscosity for six months. Therefore, the condition for an ink with excellent stability over time was that the viscosity did not change for 6 months.

According to the above evaluation method, red - 10 types, blue - 11 types, yellow - 10 types
Table 1 shows the results of the species investigation.

From Table 1, the one that satisfies all the characteristics is red-1)
irect Red 225, yellow-Dtrect Ye
low50, blue-Reactive Biue 7
It was 1. Therefore, by mixing these in an appropriate mixing ratio to obtain a black color, it was possible to obtain a black aqueous ink for inkjet printers that satisfies all of the above characteristics.

Example I C,I, Direct Red 225 1.2
IJ measurement section, 1. Djrect Ye IIow 50
1.8pi part C, 1, Reactive Blue
71 3.0 parts by weight Ethylene glycol 70 parts by weight Distilled water 30 parts by weight The above components were thoroughly mixed and dissolved in a container, and the pore size was 3 μm.
The ink was adjusted using a P-filtration filter, treated with bubbles. Using this ink, an inkjet printer with an on-demand head that ejects the ink through a piezoelectric vibrator was able to print well without any disturbances. Also, after drying the print, soak it in water.
When the sample was soaked for 0 minutes and pulled out, almost no color change was observed. Further, no increase in viscosity was observed after this ink was stored at room temperature for 6 months.

The black ink of the present invention may have a composition other than Example 1, such as C, I
, Direct Red 225 0.4~
1.6 Weight part C, 1, Direct Yellow
w 50 0.6-2.4 parts by weight C, Reac
tiveBlue 71 1. C1-4, the color tone is C, I in the composition range of the OM placement part, Direct: 31a
It can be mixed and used in almost the same way as ck 19.

(6) Effects of the Invention According to the present invention, it is possible to supply black ink with excellent water repellency, stability over time, and water resistance, so that printing irregularities do not occur and good printing is possible over a long period of time. Also, it has the effect of realizing inkjet recording that hardly loses color even if it leaks into water after printing.

Claims (2)

[Claims] (1) In the inkjet recording ink, the colorants are C1, Direct Red 225 and C,1, Dir.
ect ”fe#ow50 and C, 1, Reactive
A water-based black ink for inkjet printers, characterized in that it is a mixture of BAiue 71. (2) C, 1, Direct Red 225
is 0.4 to 1.6 parts by weight C, I, D 1rect
Yelllavt 5()AZ O, 6-2.4 parts by weight C, I, Reactive BAiue 71
1. The aqueous black ink for inkjet printers according to claim 1, wherein the amount is 1.0 to 4.0 parts by weight.