JPS61113671A - Recording liquid - Google Patents

Abstract

PURPOSE:To obtain a recording liquid for ink jet system or writing utensils, free from nozzle clogging, development of sediments and foreign substance settling on heating head, by regulating to a level below specified value the content of the multivalent metal(s) as an impurity present in an ink composition containing water-soluble dye. CONSTITUTION:The objective recording liquid, being a liquid composition containing a water-soluble dye, can be obtained by regulating the content of the multivalent metal(s) present in said composition to a level <=20ppm. This recording liquid is used, for example, in ink jet recording system operating by applying thermal energy. For said regulation, one of the processes is as follows : sodium sulfate is added to an aqueous dye solution to subject the dye to salting-out. The resulting precipitate deposited is collected by filtration, being washed with aq. Na2SO4 solution and dried. The solid thus obtained is dissolved in a water-soluble organic solvent followed by filtration. The resultant filtrate is incorporated with water followed by passing the liquid through cation exchange resin layer. To this filtrate, is incorporated, if needed, with an additive.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a recording liquid ( (hereinafter referred to as ink)
Regarding.

(Prior Art) The inkjet recording method forms ink droplets using various ink ejection methods, and performs recording by attaching some or all of them to a recording material such as paper. As inks used in such inkjet recording methods, inks in which various water-soluble dyes or pigments are dissolved or dispersed in water or a liquid medium consisting of water and a water-soluble organic solvent are known and used. ing.

Further, inks similar to those described above are also used as inks for writing instruments such as fountain pens, felt pens, and ballpoint pens.

(Problem to be solved by the invention) It is natural that various performances are required of conventional inks such as those mentioned above, but the most required performance is that of recording using ink. The stability of the liquid means that there will be no clogging or sedimentation in the nozzle, orifice or pen tip of the recording device when recording is interrupted or when recording is not performed for a long period of time. This problem is particularly important in inkjet systems that use thermal energy because foreign matter tends to deposit on the surface of the heat generating head due to temperature changes. However, in the case of conventional ink, the ink ejection conditions,
Several additives are required to satisfy various conditions such as long-term storage stability, image clarity during recording, density, surface tension, and electrical properties, and the dyes used also contain various impurities. These substances cause a number of problems, such as clogging of the nozzles and orifices of inkjet devices, deposits on the surface of heating heads, and sedimentation during long-term storage. Despite its various excellent properties, this is one of the reasons why it has not spread rapidly.

Therefore, the main object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to avoid clogging of nozzles, orifices, etc., even during use and long-term storage, despite the high dye concentration.
In particular, it is an object of the present invention to provide an ink with excellent stability that does not cause sedimentation in the heat-generating head of an inkjet device that uses thermal energy.

As a result of intensive research to achieve the above object, the present inventor has found that commercially available dyes contain many impurities (e.g., various organic and inorganic substances such as dispersants and leveling agents) in addition to dyes. It has been found that these impurities primarily cause the above-mentioned problems. Furthermore, among these impurities, divalent or higher-valent metal ions or their compounds contained in the ink can clog nozzles and orifices, or form sediments during ink storage, especially in inkjet systems that use thermal energy. The present invention was completed based on the discovery that this is the biggest cause of foreign matter depositing on the heating head.

(Disclosure of the Invention) That is, the present invention provides a liquid composition containing a water-soluble dye, in which the total content of divalent or higher-valent metals contained in the composition is adjusted to 20 ppm or less. This is a distinctive ink.

To explain the present invention in more detail, 1. The basic components constituting the ink of the present invention are already known, and dyes include direct dyes, acid dyes, basic dyes, 1. water-soluble dyes such as reactive dyes, etc. It is a dye, and is particularly suitable as an ink for inkjet recording methods, and has excellent clarity, water solubility, stability,
As for those that meet light resistance and other required performance,
For example, C,1, Direct Black 17.19.32
．． 51.71, 108.146; C, 1, Direct Blue 6.22.25.71.86.90.106.19
9; C, 1, Direct Red 1.4.17.28.8
3. C, 1, Direct Niro 12.24.26.98
．． C, 1, Direct Orange 34.39.44.46
．． 60; C, 1, Direct Violet 47.48;
C, 1, Direct Brown 109; C, 1, Direct Green s9; C, R, Acid Black 2.7.2
4.26.31.52.63.112.118;C,1
, acid blue 9.22.40.59.93.102
．． 104.113.117.120.167.229.
234;C.

■, Acid Red 1.6.32.35.37.51.
52.80.85.87.92.94.115, 18
0, 256, 317, 315;C.

Engineering 6 Acid Erotic-LL, 17.23.25.29.4
2.61.7i; c, r, acid orange 7.19.
C, 1, Acid Violet 49, C, 1, Basic Black 2. C, I, Basic Blue 1.3.5
．． 7.9.24.25.26.28.29; C, 1, Basic Red 1.2, 9.12.13.14.37;
C.I.

Examples include Basic Violet 7.14.27; C, I Food Black 2, and the like. The above six examples of dyes are particularly preferred in the present invention, but the present invention is not limited to these dyes.

Such water-soluble dyes are generally used in a proportion of about 0.11 to 20% by weight in conventional inks, but in the present invention, based on the knowledge of the present invention, they are used within the above range. Of course, even when used in an amount greater than the conventional ink composition, the ink composition exhibits better liquid stability than conventional ink compositions and does not produce any precipitates.

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, and particularly preferred is a mixed solvent of water and a water-soluble organic solvent. It contains polyhydric alcohol which has an anti-drying effect.

In addition, as water, it is preferable to use deionized water rather than ordinary water containing various ions.As for the water-soluble organic solvent used in combination with water, for example, methyl alcohol, ethyl alcohol, etc. , n-propyl alcohol, isopropyl alcohol, n-butyl alcohol,
Alkyl alcohols with 1 to 4 carbon atoms such as 5ec-butyl alcohol, tart-butyl alcohol, and isobutyl alcohol; amides such as dimethylformamide and dimethylacetamide; ketone or keto alcohols such as acetone and diacetone alcohol; tetrahydrofuran, dioxane, etc. ethers; polyalkylene glycols such as polyethylene glycol and polypropylene glycol: ethylene glycol, propylene glycol,
Butylene glycol, triethylene glycol, l, 2
゜Alkylene glycols in which the fullylene group contains 2 to 6 carbon atoms such as 6-hexandriol, thiodiglycol, hexylene glycol, diethylene glycol; 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 ether; N-methyl-2-pyrrolidone, 1.3
-dimethyl-2-imidazolidinone and the like. Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl)ether are preferred.

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

The water content at this time is determined within a wide range depending on the type of solvent component, its composition, and the desired properties of the ink, but is generally 10-10% of the total weight of the ink.
0% by weight, preferably 10 to 70% by weight, more preferably 20 to 70% by weight.

The basic components of the ink composition of the present invention are as described above, but the main feature of the present invention is that the total content of divalent or higher metals included in the ink composition is 20
It was set to be less than ppm.

The inventor of the present invention conducted intensive research on the stability of ink compositions and found that since the dyes used in conventional ink compositions were originally manufactured for dyeing fibers, various additives were added. For example, it contains a large number of impurities such as surfactants, leveling agents, sodium chloride, and sodium sulfate, and it is known that these impurities cause various problems in inkjet recording and writing instruments. The present inventor also diligently removed these impurities to obtain a highly pure dye and used this to create an ink composition, which solved the problem to a considerable extent, but the inkjet method, especially the use of thermal energy, In the inkjet method, it was not always possible to sufficiently prevent foreign matter from depositing on the thermal head. As a result of further detailed research, the present inventor found that there is a considerable amount (several tens of pp) in commercially available dyes.
(ppm to several hundred ppm) of divalent or higher valent metal ions or metal compounds, such as ions of calcium, magnesium, manganese, iron, aluminum, silicon, etc., or these compounds (e.g., colloids of oxides and hydroxides) ), etc., and it was discovered that these are the main causes of deposits on the surface of the thermal head and have the greatest influence on the generation of foreign matter, leading to the present invention.

A method for adjusting the content of the above-mentioned harmful substances in the ink composition will be specifically explained below.

That is, first, sodium sulfate is added to an aqueous dye solution of a desired concentration to salt out the dye. Next, the precipitate is collected by filtration, washed with a saturated 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.

The water-soluble organic solvent in this case 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 can be selected arbitrarily to the one that is most suitable for the structure of the dye to be treated. Usually, alcohols, glycols, and glycol Φ ethers can be preferably used. The filtrate thus obtained was 1
Let stand for ~3 days and refilter.

Next, a predetermined amount of water is added to the obtained filtrate, stirred, and then passed through a cation exchange resin layer. Thereafter, additives are added as needed and stirred to prepare the ink. Then, the content of divalent or higher metals in the ink is measured using an atomic absorption spectrophotometer or an induced plasma emission spectrometer to confirm whether the total amount of divalent or higher metals contained is 20 ppm or less, put it into use.

In the treatment procedure described above, the first salting-out treatment is mainly aimed at removing sodium chloride, which is a typical impurity often contained in ordinary commercially available dyes, and the first treatment with a water-soluble organic solvent is After the filtrate after the zero-order filtration, which is carried out for the purpose of removing both the sodium sulfate originally contained as an impurity in the dye and the sodium sulfate added in a large amount in the salting-out treatment, is left standing for a long time. The main purpose of the filtration treatment is to remove colloidal substances containing divalent or higher valent metals contained in the solution. The subsequent treatment with a cation exchange resin is intended to remove the ions of divalent or higher valent metals contained therein.

Although one method for adjusting the content of divalent or higher valent metal in the ink composition has been described above, the adjustment method is not limited to this method, and the ionized divalent or higher valent metal or colloid Any method that can remove divalent or higher valent metal compounds, etc., is effective *IJf! t6. :&7′″″6・
M, tlf, @%? 1. Examples include the coagulation-sedimentation method, filtration method, lime softening method, and electrolytic method using 8 m and j.

In addition to impurities in dyes, the source of contamination of divalent or higher-valent metal ions or their compounds as impurities is considered to be the water used, but distilled water, ion-exchanged water, or a combination of these may be used as water for ink. By using treated water, it is possible to avoid contamination of divalent or higher valent metals. The biggest source of contamination with divalent or higher metals is the dye used, and especially when the dye used is a commercially available product, the content is often very large.

The above explanation has mainly focused on the removal of divalent or higher valent metals contained in the ink, but in practice, it is recommended to remove various inorganic salts such as common salt and sodium sulfate in addition to removing divalent or higher valent metals. Common.

The basic composition of the ink of the present invention is as described above, and in addition, various conventionally known dispersants, surfactants, viscosity modifiers,
A surface tension adjuster and the like can be added as necessary.

For example, viscosity modifiers such as polyvinyl alcohol, celluloses, and water-soluble resins; various cationic, anionic, or nonionic surfactants; surface tension modifiers such as jetanolamine, diethanolamine, and reethanolamine; (Can include regulators, antifungal agents, etc.)

Further, in order to prepare a recording liquid used in an inkjet recording method of a type in which the recording liquid is charged, a resistivity adjusting agent such as inorganic salts such as lithium chloride, ammonium chloride, and sodium chloride is added. Note that when applied to a type of inkjet system that ejects recording liquid by the action of thermal energy, the thermal properties (e.g., specific heat, coefficient of thermal expansion, thermal conductivity, etc.) may be adjusted. be.

The ink of the present invention obtained as described above has sufficiently solved the problems of the prior art, and has recording properties (signal response, droplet formation stability, ejection stability, Excellent and well-balanced in terms of continuous time recording, ink ejection stability after long periods of non-operation), storage stability, fixation to recording materials, and light resistance and weather resistance of recorded images. It is useful as an ink for various types of inkjet recording or as an ink for writing instruments, and is particularly suitable as an ink for inkjet recording that uses thermal energy, where the generation of deposits is least desirable.

Next, the present invention will be further explained with reference to Examples. Note that "%" or "%" in the text is based on weight.

Example 1 "Adjustment of ink" Commercially available dye; "Direct Fast Yellow RJ"
(manufactured by Susumu Kagaku Kogyo ■) was prepared, and sodium sulfate was then added to the aqueous solution and stirred to salt out the dye. The precipitate was collected by filtration, washed with a saturated pure aqueous solution of sodium sulfate, and dried. A predetermined amount of the dry solid was weighed so that the dye concentration in the resulting ink was 3%, and this was mixed with ethylene glycol and N-methyl-2-
This aqueous solution of pyrrolidone dissolved in a 3:1 mixture was filtered under pressure through a Teflon filter with an average pore size of 1 micron, and the filtrate was sealed in a plastic container and allowed to stand in a cool, dark place for 3 days. Then, filter again using a 1 micron Teflon filter. 60 parts of water was added to 40 parts of the obtained filtrate and stirred to form an ink.The ink was then passed through a layer of cation exchange resin rC-464J manufactured by Sumitomo Chemical Co., Ltd. After that, the first passing liquid was adjusted to p) 19.8 with an O, IN caustic soda aqueous solution, and the total amount of divalent or higher metals in this recording liquid was measured using an induced plasma emission spectrometer, and it was found to be a 20pp layer. . Using this ink, thermal energy is applied to the ink in the recording head to generate droplets to perform recording. With a recording device having a frequency of 30 ports and a frequency of 2 KHz, the following TI
-T5 were investigated and good results were obtained in all cases.

(T1) Long-term stability;
″′＋liH″V″′・−°°12°°11°”1.1
Even after storage, no precipitation of insoluble matter was observed, and there was no change in the physical properties or color tone of the liquid.

(T2) Ejection stability: Continuous ejection was performed for 24 hours in an atmosphere of room temperature, 5° C., and 40° C. Under all conditions, stable high-quality recording was possible from beginning to end.

(T3) Ejection responsiveness: Initial ejection for 2 seconds and ejection after 2 months of standing were investigated, and in both cases, there was no clogging at the orifice tip, and recording was stable and uniform.

(T4) Quality of recorded images: The images recorded on the recording materials listed in Table 1 below had high density and were clear. After six months of exposure to indoor light, the rate of decrease in concentration was less than 1%.

(T5) Fixability on various recording materials: After 15 seconds of printing on the recording materials listed in Table 1 below, rub the printed area with your finger to prevent image shift.
The presence or absence of bleeding was determined, and all showed excellent fixing properties with no image shift or bleeding.

Examples 2 to 5 Inks were prepared using the commercially available dyes shown in Table 2 below in the same manner as in Example 1, and 1 to T5 were examined in the same manner as in Example 1 for each ink. All of these showed excellent results similar to Example 1.

Example 6 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, and the inks were ejected by a piezo vibrator. On-demand recording head (discharge orifice diameter: 50 microns, piezoelectric vibrator drive voltage: 60 volts, frequency: 4KH)
z), T1
~T5 was studied. All of these showed excellent results.

Examples The ink of Example 2 as a yellow ink, the ink of Example 3 as a magenta ink, the ink of Example 4 as a cyan ink, and the ink of Example 5 as a black ink were used in Examples 2 to 5. A full-color photograph was reproduced using an inkjet recording device similar to the original. The resulting image had extremely clear colors and good color reproduction.

Example 8 Each colored ink prepared in Examples 2 to 5 was individually filled into felt-tip pens, the caps of each were removed and the pens were left for 10 days. When the pens were written on paper, there was no ink smearing.
I was able to write smoothly.

Comparative Example A saturated aqueous solution of the dye "Direct Fast Yellow R" shown in Example 1 was prepared, then sodium sulfate was added to the aqueous solution, stirring was performed, and the dye was salted out.The precipitate was collected by filtration. This was washed with a pure aqueous solution of sodium sulfate and dried.

A predetermined amount of the dry solid was weighed so that the dye concentration in the resulting ink was 3%, and this was dissolved in a 3:1 mixture of ethylene glycol and N-methyl-2-pyrrolidone. This solution was filtered under pressure using a Teflon filter with an average pore size of 1 micron, and 40% of the filtrate was mixed with 60% water.
was added and stirred to prepare a sample ink.

The content of divalent or higher valent metals in this ink was measured using an atomic absorption spectrophotometer and was found to be 30 pp. When this ink was examined at T1 to T5 in the same manner as in Example 1, precipitation of insoluble matter was observed in the ink after one month of ink storage. In addition, in (T2), when the surface of the zero-heating head, which was forced to change the drive voltage (voltage up) due to frequent failure to eject ink, was observed under a microscope, brown precipitates were found attached. was seen.

In (T3), it was observed that the orifice portion was clogged and the ink ejection was unstable after being left for one month. Furthermore, regarding this dye, for the ink that was processed by removing only the static treatment step from the treatment process of Example 1, and the ink that was processed by removing only the cation exchange resin treatment, each of the divalent or higher valences in the ink was When the total metal content was measured, the former was 23 ppm and the latter was 25 ppm.

When testing T1 to T5 was similarly conducted for these, results were obtained that were inferior to the performance of Example 1, in which no treatment steps were omitted.

One-dan list - 1-j Yani Tatsu 1 Shi Lk - Bun Ichisuke 2 Manufacturer Gin Tamaki High quality paper Choyo Kokusaku Pulp ■ Seven Stars High quality paper Hokuetsu Paper ■ White Botan Medium quality paper Honshu Paper ■ Toyo Roshi No. 4 non-size paper Toyo Roshi ■-Self-view-U More than 2 valent mackerel in ink Moxibustion-1-1-sword Shikaku 1 Capture 2 Water Yellow 6
19PPI13 Chuganoru Fast Red 3B 20p.

Claims (2)

[Claims] (1) A liquid composition containing a water-soluble dye, wherein the total content of divalent or higher metals contained in the composition is 20 ppm.
A recording liquid characterized by being adjusted as follows. (2) The recording liquid according to claim (1), which is used in an inkjet recording method in which thermal energy is applied.