JPS59176367A - Black ink for ink jet printer - Google Patents

Abstract

PURPOSE:To provide a black ink for an ink jet printer, which has excellent water resistance, water repellency and aging stability and in which the contrast of a recorded image can be enhanced sufficiently, consisting of a mixture of specified dyes. CONSTITUTION:A mixture consisting of at least two members selected from among C. I. Direct Red 83, C. I. Direct Red 225, C. I. Direct Red 226, C. I. Direct Red 227, C. I. Acid Red 131 and C. I. Reactive Blue is used as the dye of a black ink for an ink jet printer. The resulting ink is a black ink which is low in brightness and is sufficiently black visually. Hence, there can be obtd. a black ink for an ink jet printer, in which no disturbance in printing is caused, good printing is made possible over a long period of time and color hardly disappears even if the print is immersed in water.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a black ink for inksheet printers, and more specifically, to a black ink for use in inksheet printers, which has excellent stability over time, water repellency, and water resistance, and has sufficient contrast in recorded images. This invention relates to a water-based ink that can be printed with high contrast and clear contrast.

(2) Background of the technology Among the colorants used in conventional black ink for inkjet printers, Color Index (C, 1,) Builef I-
(Direct) Black Nineteen dyes have been used. The ink is ejected from the nozzle of the print head of the inkjet printer toward the paper to form a print.

(3) Prior art and problems The above-mentioned commercially available C,1, Direct Black
When a water-based ink was produced using 1 to 19, the initial solubility and stability were good, but the stability over time was poor.
After 2 months, the association reaction of the dye
It is known that this causes precipitation, resulting in decreased gelation and increased viscosity, leading to loss of performance as an ink. In addition, since ink using such dyes tends to adhere to the nostle surface of an inkjet printer head, the adhered ink and the ejected ink attract each other due to surface tension, resulting in a change in the ejecting direction, resulting in irregular printing. . In addition, ink using only a black dye other than the above-mentioned dyes,
There was no product that satisfied all of the above characteristics.

When a black ink containing two or more types of dyes other than black is used, it has excellent stability over time and water resistance, but on the other hand, it is difficult to increase the color density when printed. However, in order to increase the color depth to make printing clearer, it is necessary to significantly increase the dye concentration, and increasing the dye concentration makes it easier for the dye to precipitate in the ink, causing nozzle clogging. A problem arises. Therefore, a black ink is desired that has a low dye concentration in the ink and can print with a deep color.

(4) Purpose of the Invention The present invention addresses the above-mentioned conventional problems, and uses a mixture of two or more dyes that have excellent solubility, water resistance, water repellency, and stability over time and low brightness. The objective is to provide a high-performance black ink with excellent characteristics.

(5) Structure and object of the invention According to the present invention, black ink for inksheet printers is made, and colorants are added to Color Index Direct Red 83, Color Index Direct Red 225, and Color Index Direct Red 226.
, Color Inte Nox Direct Red 227, Color Inte Nox Acid Red 131, Color Index Direct Yellow 86, and Color Index Reactive Blue 71. This is achieved by providing a black ink for blinking.

(6) Examples of the invention Examples of the present invention will be explained in detail below.

As mentioned above, conventionally, there has been no single black dye that satisfies all the characteristics of water solubility, water resistance, water repellency, and stability over time. However, the inventor of the present application does not use black dye, has all of the above characteristics, and has excellent lightness (brightness).
By mixing two or more kinds of dyes with low dyes and using them in the black ink, it was possible to obtain, through experiments, a black ink for inksheet printers that has all of the above properties and can achieve sufficient printing density even at low dye concentrations. did it.

The above dye for mixing is selected under the following conditions.

First, in order to avoid clogging, the dye concentration used in the ink should be less than h6g/100g in weight percent, and the brightness (Y value) when printed with ink with this dye concentration.
The condition for selecting a dye is that the
g/100g or more.

In addition, the print must be resistant to water, so the dye is selected by evaluating its water resistance using the following test method. In other words, the print sample is immersed in water for 10 minutes, and the degree of color fading is visually evaluated, and the water resistance condition is that the color does not fade at all. In addition, if the ink has poor water repellency, the ink tends to adhere to the nozzle surface, changing the ejection direction and causing irregular printing, so the ink must have excellent water repellency.

Therefore, water repellency is evaluated using the following method. First, a slide glass that had been ultrasonically cleaned with detergent and alcohol was immersed in the ink, and after being pulled out, the ink repellency was visually evaluated. The condition for water repellency is that it is waterproof.

Furthermore, if the viscosity of the ink changes during storage, it may cause irregular printing or inability to print, so it is necessary that the viscosity of the ink does not change even after long storage. Therefore, the condition is that the ink does not change in viscosity even if it is stored in a constant temperature bath at 60° C. for 6 months.

The inventor of the present application investigated the brightness, solubility, water resistance, water repellency, and stability over time of 50 types of dyes according to the selection conditions described above. The following table shows the survey results. Referring to the table, the O and X symbols entered in each selection condition column indicate whether the above conditions are satisfied (0) or not (0). X) respectively, and if all conditions are satisfied, 0 is written in the overall evaluation.

Therefore, according to the table above, C,1, Direct Red 83 Red, C,1
, Direct Red 225 red.

C, 1, Direct Red 226 Red, C, 1
, Direct Red 227 red.

C,1,^cid Red 131 Red, C,1,Di
'rect Yellow 86 Yellow 1C, 1, Reac
tive Blue 71 The inventor of the present application has confirmed that the seven types of blue dyes satisfy all of the above selection conditions.

Therefore, the color of the above dye, for example, C, 1, DirectR
ed 227. C, 1, Direct Yellow
86+ C, 1, Reactive Blue 71 in 1.8 ml parts, 1.2 parts by weight, 3. Oit
Mix in the proportion of 1. 70 parts by weight of ethylene glycol and 30 parts by weight of distilled water are added to this to form a 1ζ black ink.

The above-mentioned components are sufficiently mixed and melted in a container, and then filtered through a filter with a pore size of 3 μm to perform a defoaming treatment to prepare the ink. The inventor of this application used the ink to print with an inkjet printer having an on-demand head that ejects ink using a piezoelectric vibrator, and found that good printing was possible without any irregularities in printing. . After drying the print, almost no color fading was observed when the ink was immersed in water for 10 minutes, and no change in viscosity was observed when the ink was stored in a constant temperature bath at 60°C for 6 months.

(7) Effects of the Invention As explained in detail above, the present invention provides a black ink that has excellent water resistance, water repellency, and stability over time, and has low brightness, that is, it appears sufficiently black to the eye. Ink that does not cause print disturbances, enables good printing over a long period of time, has high contrast in recorded images, and does not fade even when immersed in water after printing. Sheet printers were provided, and this greatly improved the quality of ink sheets.

Claims (1)

[Claims] Use black ink for inksheet printers and add colorants to Color Index Direct Red 83, Color Index Direct Red 225, Color Index Direct Red 226, Color Intex Direct Red 227, Color Index Acid Red 131, Color - A black ink for inkjet printers characterized by being made from a mixture of two or more selected from Inte Nox Direct Yellow 86 and Color Index Reactive Blue 7I.