JPH055073A - Production of recording liquid - Google Patents

Abstract

PURPOSE:To obtain a recording liquid capable of keeping the density, quality and light-fastness of recorded image and effective for preventing the ejection miss of ink from a recording means by using a dye purified by salting-out and adjusting the Ca ion concentration in the recording liquid to a specific level. CONSTITUTION:A water-soluble dye is purified by salting-out preferably using sodium sulfate. The calcium ion concentration in a recording liquid is adjusted to <=5ppm (preferably 0.3-5ppm, especially 0.3-3ppm) with the purified dye.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a recording liquid, which is used in a recording method in which thermal energy is applied to a recording liquid and ejected as droplets to perform recording on a recording material.

[0002]

2. Description of the Related Art Ink jet recording methods include various ink ejection methods (for example, an electrostatic attraction method, a method in which a piezoelectric element is used to mechanically vibrate or displace the ink, and the ink is heated to cause foaming. A method using pressure, etc. is known.)
t) is formed, and a part or all of them are attached to a recording material such as paper (this is abbreviated as recording paper) for recording. When a writing instrument is used, as is well known, ink is ejected from the pores and is received by the recording material for recording.

Conventionally, as the ink for such an ink jet system or writing instrument, a water-soluble dye, water as a solvent for the dye, and glycols as a drying inhibitor have been mainly used. The thing comprised as a component can be mentioned. Of these, direct dyes, acid dyes and basic dyes are preferably used as the water-soluble dye because they are excellent in fastness and color tone when recorded.
Since these are originally manufactured for dyeing fibers, they contain impurities such as inorganic salts such as sodium chloride and sodium sulfate as well as metals (ions) such as calcium, magnesium, iron and silicon. ..

If a recording ink is prepared from a dye containing such impurities, the following undesirable situation is brought about. That is, the dissolution stability of the dye in the ink is reduced, and the dye aggregates and precipitates. On the other hand, when the ink evaporates near the ink ejection orifices and the capillaries and the liquid composition changes, precipitation of salts is caused. Any of these causes the clogging of the ejection orifices and the pores that should be most avoided in the recording by the inkjet method or the writing instrument. Many countermeasures have been proposed to prevent orifice clogging, but no complete solution has been found.

If the ink is liable to cause clogging, it is necessary to lower the dye concentration, and as a result, the density of the recorded image is insufficient, the quality is poor, and the light resistance is poor.

Accordingly, the present inventor has made various attempts to find a way to eliminate clogging without limiting the dye concentration in the ink, and as a result, in particular, the calcium ion (Ca ⁺⁺ ) concentration in the ink. Have been found to be significantly involved in the occurrence of clogging.

That is, the calcium ion concentration in the ink is 5 ppm or less, especially 0.3 ppm to 5 ppm, and particularly,
If it is 3 ppm or less, and further 0.3 ppm to 3 ppm, no precipitation is observed even when the ink is stored for a long period of time, and no clogging is observed in the ejection orifices or the pores filled with the ink. It has been revealed.

[0008]

SUMMARY OF THE INVENTION The present invention has been made based on the above findings, and in particular, is a type in which thermal energy is applied to a recording liquid to eject it as droplets for recording on a recording material. When used in the inkjet recording method of No. 1, it is an object of the present invention to produce a recording liquid which does not cause deterioration of the density and quality of a recorded image and deterioration of light resistance, and which does not cause non-ejection of ink from a recording unit. And

[0009]

That is, the present invention that achieves the above-mentioned object is a method for producing a recording liquid used in a recording method in which thermal energy is applied to a recording liquid to eject it as droplets for recording on a recording material. In the recording, the method comprises the step of purifying the dye by a salting-out method and the step of adjusting the concentration of calcium ion contained in the recording liquid to 5 ppm or less by using the purified dye. Liquid manufacturing method.

According to the present invention, in particular, it effectively acts on an ink jet device of a type which applies thermal energy to a recording liquid and ejects it as a liquid droplet, and the ejection orifice is not clogged for a long period of time, and the concentration is high and high. It is possible to consistently obtain a recorded image with ink of high quality and excellent in light resistance.

The present invention will be described in detail below with reference to specific examples.

The basic components of the ink used in the present invention are firstly water-soluble dyes represented by direct dyes, acid dyes and basic dyes, and secondly solvents for these dyes. As the solvent, water (... in the following description, water means deionized water) is a main solvate component, and a mixture of water and various water-soluble organic solvents is used. It is also possible to use. Examples of the water-soluble organic solvent include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol and the like having 1 to 4 carbon atoms.
Alkyl alcohols; amides such as dimethylformamide and dimethylacetamide; ketones or keto alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol , Propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol and other alkylene groups having 2 to 6 carbon atoms; glycerin; ethylene Glycol methyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ) Lower alkyl ethers of polyhydric alcohols such as ethers; N- methyl-2-pyrrolidone,
1,3-dimethyl-2-imidazolidinone and the like can be mentioned.

Among these many water-soluble organic solvents,
Preferred are polyhydric alcohols such as diethylene glycol and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether.

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

The water content at this time is determined in a wide range depending on the kind of the solvent component, the composition thereof or the desired characteristics of the ink, but is generally 10 to 100 relative to the total weight of the ink. %, Preferably 10 to 70%, more preferably 20 to 70%.

The specific method for adjusting the calcium ion concentration in the above ink composition is as follows. That is,
First, sodium sulfate is added to a dye aqueous 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 [... Removal of calcium (ion) contained in the original dye in the above process. Is done. ]. After dissolving a predetermined amount of the obtained dried solid matter (purified dye) in a water-soluble organic solvent, the solution is filtered, a predetermined amount of water and, if necessary, an additive are added to the filtrate and stirred. The ink is prepared.

Then, the calcium ion concentration in the ink is measured by an atomic absorption spectrophotometer, and it is confirmed whether it is 5 ppm or less, and the ink is used. By the way, when an ink having a dye concentration of about 1 to 5% is prepared by the above ink preparation method, the calcium ion concentration in the ink should be 5
Adjustment to ppm is easy and can be surely achieved.

The above-obtained ink thus obtained by itself has recording characteristics in the ink jet system (signal responsiveness, droplet formation stability, ejection stability, long-term continuous recording property, long-term recording ability). Ink ejection stability after suspension of operation) Storage stability, fixability on recording material, light resistance of recorded image, weather resistance, etc. are well balanced and excellent.

Now, the present invention will be described in more detail with reference to the above-described embodiment of the method for producing an ink, and the effects will be illustrated together.

[0020]

【Example】

Example 1 <Preparation of Ink> Commercial Dye; Water Black 187
Sodium sulfate was added to a 20% L (manufactured by Orient Chemical Co.) aqueous solution and stirred to salt out the dye. The precipitate was collected by filtration and washed with a saturated aqueous solution of sodium sulfate,
Dried. The concentration of dye in the obtained ink is 3% by weight (w
A predetermined amount of the dried solid substance was weighed so as to be t)%, and this was dissolved in a 3: 1 mixture of diethylene glycol and N-methyl-2-pyrrolidone. Next, this solution was subjected to pressure filtration with a Teflon filter having an average pore size of 1 μm, and water (60 parts by weight) was added to 40 parts by weight of the filtrate to stir to obtain an ink. When the calcium ion concentration in this ink was measured by an atomic absorption spectrophotometer, it was 1.8 ppm.

Examples 2 to 5 Inks were prepared in the same manner as in Example 1 using the commercially available dyes shown in Table 1 below.

[0022]

[Table 1]

Reference Example 1 An on-demand type multi-head (ejection orifice diameter 35 μ, heating resistor resistance value) in which thermal energy is applied to ink in a recording head to generate droplets using the inks in Table 1 for recording 150Ω, drive voltage 30V, frequency 2K
When the following T _{1 to} T ₅ were examined with a recording device having a frequency of 10 Hz, excellent results were obtained in all cases.

(T ₁ ) Long-term storability: The ink was sealed in a plastic film bag and stored at −30 ° C. and 60 ° C. for 6 months, no precipitation of insolubles was observed, and the physical properties and color tone of the liquid were confirmed. There was no change.

(T ₂ ) Discharge stability: room temperature, 5 ° C, 40 ° C
In each atmosphere, continuous ejection was performed for 24 hours, and stable high-quality recording could be performed from beginning to end under any conditions.

(T ₃ ) Ejection responsiveness: An intermittent ejection every 2 seconds and an ejection after left for 2 months were examined, and in any case, stable and uniform recording was performed without clogging at the tip of the orifice.

(T ₄ ) Quality of recorded image: The images recorded on the recording materials listed in the table below had high density and were clear. The rate of decrease in concentration after exposure to room light for 6 months was 1% or less.

(T ₅ ) Fixability on various recording materials: After printing on the recording materials in Table 2 for 15 seconds, the printed portion was rubbed with a finger and the presence or absence of image misalignment and bleeding was determined. In all cases, there was no image shift or blurring, and excellent fixing properties were exhibited.

[0029]

[Table 2]

Reference Example 2 In Reference Example 1, 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 used. The obtained image was very clear in each color and had good color reproduction.

Comparative example

[0032]

[Outer 1]

The above components were mixed and dissolved, and then pressure-filtered with a Teflon filter having an average pore size of 1 μ to obtain an ink. When the calcium ion concentration in this ink was measured, it was 7 ppm.

Claims (1)

Claim: What is claimed is: 1. A method for producing a recording liquid used in a recording method, wherein thermal energy is applied to a recording liquid to eject it as droplets to perform recording on a recording material. And a step of adjusting the concentration of calcium ions contained in the recording liquid to 5 ppm or less by using the purified dye. 2. The calcium ion concentration is 0.3 p
The method for producing a recording liquid according to claim 1, wherein the recording liquid is pm-5 ppm. 3. The method for producing a recording liquid according to claim 1, wherein sodium sulfate is used in the salting-out method.