JPH08311381A - Ink for recording - Google Patents

Abstract

PURPOSE: To obtain ink for recording excellent in long-term stability and discharge stability and having good discharge responsiveness by treating ink for recording by passing the ink through a cation exchange resin in its production, reducing the content of zinc in ink composition to a value smaller than a specific value. CONSTITUTION: This recording ink for ink jet recording is obtained by preparing 10% aqueous solution of a commercial dye, adding sodium sulfate thereto, stirring the material, salting out the dye, filtering the salted out material, washing the material with a saturated aqueous solution of sodium sulfate, drying the solution, dissolving the dried material in a 3:1 mixed solution of ethylene glycol with N-methyl-2-pyrrolidone, filtering the solution under pressure by a membrane filter having 1μm average pore diameter, adding 60 pts.wt. water to 40 pts.wt. filtrate, stirring the solution, passing the solution through the cation exchange resin and controlling the pH of the liquid to 9.2. The ink is excellent in long-term stability and discharge stability and has good discharge responsiveness and is suitable for ink jet recording, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet recording ink, and more particularly to the content of zinc in an ink composition.

[0002]

2. Description of the Related Art Ink jet recording methods include various ink ejection methods (for example, an electrostatic suction method, a method in which a piezoelectric element is used to mechanically vibrate or displace ink, and air bubbles are generated by heating ink at that time. The ink droplets are formed by a method utilizing the pressure generated in the recording medium), and a part or all of them are attached to a recording material such as paper for recording.

As an ink composition used in such an ink jet recording system, a composition in which various water-soluble dyes or pigments are dissolved or dispersed in water or a liquid medium containing water and a water-soluble organic solvent is known. , And is used. And such ink compositions are required to have optimum performance characteristics for that purpose. For example, it does not cause precipitation or aggregation even if it is not used for a long period of time, does not cause clogging in the tip portion of the ink jet printer head and ink flow path, and has good print quality. Among them, the most required performance is clogging and sedimentation at the tip of the ink jet printer head and in the ink flow path when recording is not performed for a long time when recording is performed using the ink composition. It is liquid-stable that no matter is generated. This problem is particularly important in the inkjet method that uses thermal energy among the inkjet methods, because foreign substances are likely to deposit on the surface of the heating element due to temperature changes.

[0004]

However, in the conventional ink composition, various conditions such as ink ejection conditions, long-term storage stability, image sharpness and density during recording, surface tension, electrical properties, etc. are used. Some additives are required to satisfy the above conditions, and various impurities are contained in these additives and the dyes used. There are problems such as clogging and precipitation during long-term storage. Further, in the ink jet method using heat energy, there is a problem that deposits are generated on the surface of the heating element. This is one of the reasons why its widespread use is not rapid despite the various excellent characteristics of the inkjet recording system.

Therefore, the present invention solves the above-described problems and prevents ink from being clogged at the tip of the head of an ink jet printer or in the ink flow path during use and during long-term storage, and particularly, an ink jet using heat energy. It is an object of the present invention to provide a recording ink having excellent stability in which a precipitate is not generated on a heating element of a printer.

[0006]

In order to achieve this object, the first aspect of the present invention is characterized in that the content of zinc contained in the ink composition is less than 1 ppm.

According to a second aspect of the present invention, the recording ink is subjected to a treatment of passing a cation exchange resin in a manufacturing process thereof.

According to a third aspect, the invention is used in an ink ejecting apparatus for ejecting ink to print on a recording medium.

According to a fourth aspect of the present invention, the ink ejecting apparatus is a thermal ink jet system that ejects ink by using heat energy from a heating element provided in the ink chamber.

[0010]

According to the present invention having the above-mentioned constitution, the content of zinc contained in the ink composition is less than 1 ppm, so that the tip of the head of the ink jet printer or the ink flow path can be used even during use and long-term storage. It is possible to provide a recording ink having excellent stability in which no clogging occurs, and in particular, no precipitate is generated on the heating element of an inkjet printer which uses heat energy.

[0011]

EXAMPLES The basic composition itself of the ink composition in the present invention is already known, and as the dye, a water-soluble dye represented by a direct dye, an acid dye, a basic dye, a reactive dye or the like can be used. Particularly suitable as an ink for an inkjet recording system, and those which satisfy the required performances such as sharpness, water solubility, stability, light resistance, etc. include C.I.
I. Direct Black 17, 19, 32, 51, 7
1, 108, 146; C.I. I. Direct Blue 6, 2
2, 25, 71, 86, 90, 106, 199; C.I.
I. Direct Red 1, 4, 17, 28, 83; C.I.
I. Direct Yellow 12, 24, 26, 86, 9
8, 142; C.I. I. Direct Orange 34, 39,
44, 46, 60; C.I. I. Direct violet 4
7, 48; C.I. I. Direct Brown 109; C.I.
I. Direct Green 59; C.I. I. Acid Black 2, 7, 24, 26, 31, 52, 63, 112, 1
18; C.I. I. Acid Blue 9, 22, 40, 59,
93, 102, 104, 117, 120, 167, 22
9, 234; C.I. I. Acid Red 1, 6, 32, 3
7, 51, 52, 80, 85, 87, 92, 94, 11
5, 180, 256, 315, 317; C.I. I. Acid Yellow 11, 17, 23, 25, 29, 42, 6
1, 71; C.I. I. Acid Orange 7, 19; C.I.
I. Acid Violet 49; C.I. I. Basic Black 2; C.I. I. Basic Blue 1, 3, 5, 7,
9, 24, 25, 26, 28, 29; C.I. I. Basic Red 1, 2, 9, 12, 13, 14, 37; C.I.
I. Basic Violet 7, 14, 27; C.I. I.
Food Black 1, 2 etc. are mentioned. The above dyes are particularly preferable for the ink composition applicable to the recording method of the present invention, but the present invention is not limited to these dyes.

Such a water-soluble dye is generally used in a conventional ink composition in an amount of about 0.1 to 20% by weight, but in the present invention, it is used within the above range. Needless to say, the stability of the ink composition is exhibited even when the amount used is larger than the conventional amount used, and no precipitate is generated.

The solvent used in the ink composition of the present invention is water or a mixed solvent of water and a water-soluble organic solvent,
Particularly preferred is a mixed solvent of water and a water-soluble organic solvent, which contains a polyhydric alcohol having an effect of preventing ink drying as a water-soluble organic solvent. Further, as the water, it is desirable to use deionized water instead of general water containing various ions.

As the water-soluble organic solvent used by mixing with water, for example, methyl alcohol, ethyl alcohol,
n-propyl alcohol, isopropyl alcohol, n
-Butyl alcohol, sec-butyl alcohol, te
Lower alcohols such as r-butyl alcohol, amides such as dimethylformamide and dimethylacetamide, ketones or keto alcohols such as acetone and diacetone alcohol, ethers such as tetrahydrofuran and dioxane, polyglycol such as polyethylene glycol and polypropylene glycol. Alkylene glycols, ethylene glycol, propylene glycol, butylene glycol,
Alkylene glycols such as diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, thiodiglycol and hexylene glycol, ethylene glycol monomethyl ether,
Ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether,
Lower alkyl ethers of polyhydric alcohols such as triethylene glycol monoethyl ether and triethylene glycol monobutyl ether, glycerin, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-
2-imidazolidinone etc. are mentioned. Among these, alkylene glycols such as glycerin and diethylene glycol, and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monoethyl ether are particularly preferable.

The content of the water-soluble organic solvent in the ink composition is generally 0% by weight based on the total weight of the ink.
The range is from 95 to 95% by weight, preferably from 10 to 80% by weight, more preferably from 20 to 50% by weight.

The water content at this time is determined in a wide range depending on the kind of the solvent component, its composition, or the desired properties of the ink, but is generally 10 to the total weight of the ink. The range is 95% by weight, preferably 10 to 70% by weight, more preferably 20 to 70% by weight.

The basic composition of the ink composition of the present invention is as described above, but various other conventionally known additives such as dispersants, surfactants, viscosity modifiers, surface tension modifiers, pH modifiers and anti-corrosion agents. A fungicide or the like can be added if necessary. For example, polyvinyl alcohol, celluloses, viscosity modifiers such as water-soluble resins, cations, anions,
Examples thereof include various nonionic surfactants, pH adjusting agents such as diethanolamine and triethanolamine. When an ink composition used in an inkjet recording method of charging a recording liquid is prepared, a resistivity adjusting agent such as an inorganic salt such as ammonium chloride is added.

The method for adjusting the zinc content in the ink composition according to the present invention will be specifically described below.

First, sodium sulfate is added to an aqueous dye solution having a desired concentration to salt out the dye. Next, the deposited precipitate is collected by filtration, washed with a saturated aqueous solution of sodium sulfate, and then dried. After dissolving a predetermined amount of the obtained dry solid in a water-soluble organic solvent, the aqueous solution is filtered to obtain a filtrate. In this case, the water-soluble organic solvent may be any solvent as long as it is a poor solvent for sodium sulfate and a good solvent for the dye, and the solvent may be arbitrarily selected in the structure of the dye to be treated. it can. Usually, alcohols, glycols and glycol ethers are preferred water-soluble organic solvents.

Next, a predetermined amount of water is added to the obtained filtrate, and the mixture is stirred and then passed through a cation exchange resin. The solution subjected to cation exchange treatment should be adjusted to pH 7
After standing for 10 days, it is filtered. Then, if necessary, additives and the like are added, and after filtering, an ink composition is obtained. Then, determine the zinc content in the ink to 1 p using an atomic absorption spectrophotometer.
Confirm that it is less than pm and use it.

In the treatment procedure described above, the first salting-out treatment is a treatment to remove sodium chloride, which is a typical impurity contained in many commercially available dyes. The subsequent treatment with a water-soluble organic solvent is a treatment performed to remove both sodium sulfate originally contained as an impurity in the dye and sodium sulfate added in a large amount in the salting-out treatment. Subsequent cation exchange resin treatment and static treatment are one of the methods for reducing the zinc content in the ink composition of the present invention, and the cation exchange resin treatment is for removing ionized zinc. The static treatment is effective for removing colloidal zinc.

Although a typical method for adjusting the zinc content in the ink composition has been described above, the adjusting method is not limited to this method, and ionized zinc or colloidal zinc compound is used. Any method that can remove the like can be effectively used. For example, an aeration method, a coagulation precipitation method using a coagulant, a filtration method, a lime softening method, an electrolysis method and the like can be mentioned.

The source of zinc as an impurity may be water used in addition to the dye. However, the use of distilled water, ion-exchanged water, or the like as the water for preparing the ink makes it possible to avoid zinc contamination. it can. The largest source of zinc contamination is dyes, especially when the dyes are commercial products, the zinc content is often large, and some of the analysis examples show that the dye powder reaches several thousand ppm. Has been.

Although the removal of the zinc component contained in the ink composition has been mainly described above, it is preferable to remove sodium, iron, calcium, barium and the like in addition to the removal of zinc.

Next, examples and comparative examples of the present invention will be described.

Example 1 A 10% aqueous solution of a commercial dye "Special Black 7984" (manufactured by Bayer) was prepared, sodium sulfate was added, and the mixture was stirred to salt out the dye. The precipitate was collected by filtration, washed with a saturated aqueous solution of sodium sulfate, and dried.
A predetermined amount of the dried solid matter was weighed so that the dye concentration in the obtained ink was 3%, and this was dissolved in a 3: 1 mixed solution of ethylene glycol and N-methyl-2-pyrrolidone. Next, this aqueous solution is pressure-filtered with a membrane filter having an average pore size of 1 μm, and 60 parts of water is added to 40 parts of the filtrate and stirred to obtain a cation exchange resin “C-464”.
(Made by Sumitomo Chemical Co., Ltd.). Thereafter, the pH was adjusted to 9.2 with triethanolamine, and the mixture was allowed to stand in a plastic container for 10 days. Then, the mixture was filtered through a 0.7 μm membrane filter to obtain an ink composition. When the zinc content in this ink composition was measured by an atomic absorption spectrophotometer,
It was 0.7 ppm.

An on-demand type multi-head (ejection orifice diameter 35 μm, heating resistor resistance value 150 ohms) in which thermal energy is applied to ink in a recording head to generate droplets by using this ink composition for recording. The following examinations (1) to (3) were carried out with an inkjet printer having a driving voltage of 30 V and a frequency of 2 kHz), and good results were obtained in all cases.

(1) Long-term stability: No precipitation of insoluble matter was observed even after the ink composition was sealed in a heat-resistant glass bottle and stored at −30 ° C. and 60 ° C. for 6 months, and the physical properties and color tone of the liquid were almost the same. There was no change.

(2) Discharge stability: 5 ° C, 20 ° C, 40 ° C
Although continuous ejection was performed for 24 hours at each ambient temperature, stable and high-quality recording could be performed under all conditions.

(3) Discharge responsiveness: intermittent discharge for 1 minute and 2
The ejection after leaving for a month was examined, and in any case, stable and uniform recording was performed without clogging at the tip of the head of the inkjet printer or in the ink flow path.

Comparative Example 1 When an ink composition was prepared in Example 1 without the cation exchange resin treatment and the standing treatment, the zinc content in the ink composition was 2.5 ppm. When the same examination as in Example 1 was conducted using this ink composition,
In (2), ejection failure of ink was often seen. At that time, when the surface of the heating element was observed with a microscope, the presence of deposits was confirmed.

Example 2 An ink composition was prepared in the same manner as in Example 1 by using a commercially available dye "Water Yellow 6" (manufactured by Orient Chemical Industry Co., Ltd.). The zinc content in the ink composition was 0. It was 9 ppm. When the same examination as in Example 1 was carried out using this ink composition, good results were obtained as in Example 1.

Comparative Example 2 When an ink composition was prepared without carrying out the cation exchange resin treatment and the standing treatment in Example 2, the zinc content in the ink composition was 5.3 ppm. When the same examination as in Example 1 was conducted using this ink composition,
In (1), a small amount of precipitate was observed, and the conductivity of the liquid was reduced. In addition, in (2), ejection failure of ink was often observed, and in (3), after leaving for 2 months, clogging occurred at the tip of the head of the inkjet printer, and ejection was impossible. At that time, when the surface of the heating element was observed with a microscope, the presence of deposits was confirmed.

Example 3 An ink composition was prepared in the same manner as in Example 1 using a commercially available dye "Cyrus Supra Red F3B" (manufactured by Bayer). The zinc content in the ink composition was 0.07 ppm. Met. When the same examination as in Example 1 was carried out using this ink composition, good results were obtained as in Example 1.

Comparative Example 3 When an ink composition was prepared without carrying out the cation exchange resin treatment and the standing treatment in Example 3, the zinc content in the ink composition was 1.8 ppm. When the same examination as in Example 1 was conducted using this ink composition,
The color tone changes after storage at -30 ° C in (1), and the difference is Δ
E = 4.5. A printing test was conducted in the same manner as in Example 3 using this ink composition.
Compared to the case where E is the ink composition before storage, 6.
The change was 0, and the difference was clearly visible.

Example 4 An ink composition was prepared in the same manner as in Example 1 by using a commercially available dye "Levacell Fast Blue HS" (manufactured by Bayer Co.), and the zinc content in the ink composition was 0. It was 5 ppm. When the same examination as in Example 1 was carried out using this ink composition, good results were obtained as in Example 1.

Comparative Example 4 When an ink composition was prepared without carrying out the cation exchange resin treatment and the standing treatment in Example 4, the zinc content in the ink composition was 2.0 ppm. When the same examination as in Example 1 was conducted using this ink composition,
In (3), after left for 2 months, clogging occurred at the tip of the head of the inkjet printer, and ejection was impossible. At that time, when the surface of the heating element was observed with a microscope, the presence of deposits was confirmed.

Example 5 Commercial dye "Supranol First Black VLG"
When an ink composition was prepared using (manufactured by Bayer) in the same manner as in Example 1, the zinc content in the ink composition was 0.1 ppm. When the same examination as in Example 1 was carried out using this ink composition, good results were obtained as in Example 1.

Comparative Example 5 When an ink composition was prepared in Example 5 without the cation exchange resin treatment and the standing treatment, the zinc content in the ink composition was 1.9 ppm. When the same examination as in Example 1 was conducted using this ink composition,
Ink ejection failure was often observed in the intermittent ejection for 1 minute of (2) and (3). At that time, when the surface of the heating element was observed with a microscope, the presence of deposits was confirmed.

Example 6 In Examples 2 to 5, the ink of Example 2 was used as the yellow ink, the ink of Example 3 was used as the magenta ink, the ink of Example 4 was used as the cyan ink, and the ink of Example 5 was used as the black ink. A full-color photograph was reproduced with the same inkjet recording device as the one used.
The resulting image was extremely clear in each color and had good color reproduction.

Comparative Example 6 As in Example 6, the ink of Comparative Example 2 was used as the yellow ink, the ink of Comparative Example 3 was used as the magenta ink, the ink of Comparative Example 4 was used as the cyan ink, and the ink of Comparative Example 5 was used as the black ink. When trying to reproduce a full-color photograph, many missing dots were seen and a clear image could not be obtained. The color reproducibility was also poor.

In each of the ink compositions of Examples 1 to 6, which had good long-term stability, ejection stability, and ejection response, the zinc content was less than 1 ppm.

On the other hand, in Comparative Examples 1 to 6 in which problems in long-term stability, ejection stability and ejection response occurred, the zinc content in the ink composition was 1 ppm or more.

As described above, in Examples 1 to 6, since the zinc content in the ink composition was less than 1 ppm, recording inks excellent in long-term stability, ejection stability and ejection response were obtained. Obtainable.

In Examples 1 to 6 and Comparative Examples 1 to 6,
An ink jet head having an on-demand type multi-head for recording by applying heat energy to ink in the recording head to generate droplets has been used. However, the Kaiser type disclosed in Japanese Patent Publication No. 53-12138. As a result of conducting the same examination as in the example using the recording ink under the above conditions in the shear mode type ink jet head disclosed in JP-A-2-150355, the same effect was obtained.

[0046]

According to the recording ink of the present invention having the above-mentioned constitution, since the zinc content in the ink composition is less than 1 ppm, the long-term stability as an ink is good. In the ink ejecting apparatus using, the ink can be ejected favorably without being clogged in the ejection port and the ink flow path through which the ink is ejected.

Claims (4)

[Claims] 1. A recording ink, wherein the content of zinc contained in the ink composition is less than 1 ppm. 2. The recording ink according to claim 1, wherein the recording ink is subjected to a treatment of passing a cation exchange resin in a manufacturing process thereof. 3. The recording ink according to claim 1, wherein the recording ink is used in an ink ejecting device that ejects ink from an ejection port to print on a recording medium. 4. The recording ink according to claim 3, wherein the ink ejecting device is a thermal ink jet system that ejects the ink by using thermal energy from a heating element provided in the ink chamber.