JPH07118585A - Ink for ink jet recording and water-soluble dye used in the ink - Google Patents

Abstract

PURPOSE:To provide an ink for ink jet recording which shows a reduced burning of ink on a heater in a head and a high discharge stability. CONSTITUTION:The ink comprises water, a water-soluble organic solvent and a colorant as essential components and carries out droplet formation by the action of a heat energy. The concentration of oil-soluble matters in the ink should be 150ppm or less and the concentration of silicon be in the range of 0.05-10ppm. As the colorant component of the ink, it is preferable to use a water-soluble dye whose oil-soluble matter concentration is 1,200ppm or less and whose silicon concentration is in the range of 5-200ppm, particularly a dye having 3 or more azo groups.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel ink-jet recording ink for use in an ink-jet recording apparatus which applies thermal energy to form droplets and a dye for the ink.

[0002]

2. Description of the Related Art Liquid or molten solid ink is ejected from a nozzle, a slit, a porous film, etc.
The so-called ink jet type recording device for recording on cloth, film, etc. has been vigorously studied because of its advantages such as small size, low cost, and quietness. Especially, as a black monochrome printer, so-called ordinary paper such as report paper and copy paper is used. Printers that can obtain good print quality on paper are also commercially available. The ink used in the inkjet recording apparatus is mainly composed of a solvent, a coloring material, and an additive. Dyes are often used as coloring materials. Regarding inkjet ink, 1)
High resolution, high density and uniform image without bleeding or fog on paper, 2) No clogging due to ink drying at the nozzle tip, and good ejection response and ejection stability at all times There are required characteristics such as 3) good ink drying property on paper, 4) good image fastness, and 5) good long-term storage stability.

As a measure for preventing clogging, JP-A-57-11
Removal of polyvalent metal ions by a cation exchange resin disclosed in JP-A-85366, chelation of metal ions by a chelating agent disclosed in JP-A-51-85804, JP-B-61-36876 and JP-B-62. −
No. 28828 discloses a method of increasing the solubility of a dye by using N-methyl-2-pyrrolidone or ethanolamine as a solubilizer, and Japanese Patent Publication No. 63-37830 discloses the concentration of an oil-soluble substance in an ink. A technique for reducing the amount to 100 ppm or less has been proposed. Regarding the ejection stability, the dissolved air in the ink becomes bubbles and the ejection direction is disturbed.
It is considered to cause ejection failure, and is disclosed in JP-A-53-53.
The oxygen absorber disclosed in Japanese Patent No.
In addition to the method of adding an antifoaming agent disclosed in JP-A 5-65268, a method of suppressing the generation of bubbles by degassing dissolved air is disclosed in JP-A-5-17712. Furthermore, in the case of the method of forming a droplet by applying thermal energy, which is one of the inkjet recording methods, there is a problem of burning on the heater, so-called kogation. One of the kogation is that the dye used as a coloring material is thermally decomposed, and if the product after that is insoluble in water, it is deposited on the heater, so that the decomposition product is a dye that is soluble in water. It is thought that it can be reduced by selecting. Also,
As disclosed in Japanese Examined Patent Publication Nos. 3-48950 to 3-48954, kogation is improved by reducing the amounts of iron, silicon, magnesium, calcium, etc. in the dye-derived ink. However, this alone cannot sufficiently satisfy the required characteristics.

[0004]

As described above, although measures for improving kogation and ejection stability have been conventionally proposed, a method capable of sufficiently satisfying the demand has not yet been achieved. Therefore, it is an object of the present invention to provide an ink for ink jet recording that reduces kogation of the ink on the heater in the head and has high ejection stability, and a water-soluble dye used for the ink.

[0005]

Means for Solving the Problems The inventors of the present invention have earnestly studied various physical properties of an ink jet recording ink for forming droplets by applying thermal energy, and as a result, the ink and the coloring material of the ink have been obtained. It was found that kogation is reduced and discharge stability is maintained when the contents of the oil solution and silicon contained in the water-soluble dye used are set to predetermined values, and the present invention has been completed. . That is, the ink jet recording ink of the present invention contains water, a water-soluble organic solvent, and a coloring material as essential components, and is subjected to thermal energy to form droplets, which is an oil solution contained in the ink. Is 150 ppm or less, and the silicon concentration is in the range of 0.05 to 10 ppm. Further, the water-soluble dye of the present invention is used in an ink jet recording ink which forms a droplet by applying heat energy, and the concentration of the oil solution is 1200 ppm or less,
In addition, the silicon concentration is in the range of 0.5 to 200 ppm.

The present invention will be described in detail below. The basic components of the inkjet recording ink of the present invention are known per se, and water, a water-soluble organic solvent and a coloring material are essential components. The water-soluble organic solvent is used to suppress evaporation of water in the ink. Preferred water-soluble organic solvent, for example,
Ethanol, isopropanol, butanol, alcohols such as benzyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, glycerin, polyhydric alcohols such as thiodiethanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, In addition to glycol ethers such as ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether and propylene glycol monobutyl ether, pyrrolidone, N-methyl-2-pyrrolidone, triethanolamine, dimethyl sulfoxide, Ruhoran and the like. These water-soluble organic solvents may be used alone or as a mixture of two or more kinds, and when the content thereof increases, the ink viscosity increases and the ejection stability decreases, so that the total amount of the ink is preferable. About 1 to 60% by weight, more preferably about 5 to
It is preferably 40% by weight.

A water-soluble dye is preferable as a coloring material constituting the ink of the present invention together with water and a water-soluble organic solvent, since it has the best ejection stability. Specifically, C.I. I. Direct Black-2, -4, -9, -11, -17, -19,-
22, -32, -80, -151, -154, -16
8, -171, -194, C.I. I. Direct Blue-
1, -2, -6, -8, -22, -34 -70, -7
1, -76, -78, -86, -112, -142,-
199, -200, -201, -202, -203,-
207, -218, -236, -287, C.I. I. Direct Red-1, -2, -4, -8, -9, -11,
-13, -15, -20, -28, -31, -33,-
37, -39, -51, -59, -62, -63, -7
3, -75, -80, -81, -83, -87, -9
0, -94, -95, -99, -101, -110,-
189, C.I. I. Direct Yellow-1, -2,-
4, -8, -11, -12, -26, -27, -28,
-33, -34, -41, -44, -48, -86,-
87, -88, -135, -142, -144, C.I.
I. Food Black-1, -2, C.I. I. Acid Black-1, -2, -7, -16, -24,26, -2
8, -31, -48, -52, -63, -107, -1
12, -118, -119, -121, -172, -1
94, -208, C.I. I. Acid Blue-1, -7,
-9, -15, -22, -23, -27, -29, -4
0, -43, -55, -59, -62, -78, -8
0, -81, -90, -102, -104, -111,
-185, -254, C.I. I. Acid Red-1,-
4, -8, -13, -14, -15, -18, -21,
-26, -35, -37, -249, -257, C.I.
I. Acid Yellow-1, -3, -4, -7, -1
1, -12, -13, -14, -19, -23, -2
5, -34, -38, -41, -42, -44, -5
3, -55, -61, -71, -76, -79 and the like.

These coloring materials may be used alone or in admixture of two or more. The content of the coloring material is preferably 0.1 to 20% by weight, more preferably 1 to 10% by weight based on the total amount of ink.
When the content of the color material increases, not only the amount of oil solution in the ink increases but also the clogging property when the solvent evaporates at the nozzle tip deteriorates. On the contrary, if the content is too small, it goes without saying that a sufficient image (printing) density cannot be obtained.

The oily solution referred to in the present invention is hardly soluble in water, for example, hexane (7.2), ether (7.
4), benzene (9.2), toluene (8.9), methylene chloride (9.7) etc. solubility coefficient (Solubili
ty Parameter) is 10 or less, and generally means a substance that is easily dissolved in an organic solvent used as an extractant from an aqueous solution. These oil solutions are considered to be dispersed as extremely fine particles and colloids in an aqueous solution, and although removal by filtration, ion exchange, etc. is not always sufficiently effective, extraction with the above solvent or activated carbon, activated The oil solution can be removed by adsorption or the like using alumina, activated silica or the like. The concentration of the oil solution in the ink is 150 ppm or less, preferably 70 ppm or less, more preferably 50 ppm or less. When the concentration of the oil solution in the ink becomes high, vigorous kogation occurs, the ejection amount decreases, and the image density also decreases. The oil solution in the ink is mostly derived from the coloring material, and it is considered that the oil solution is an unreacted starting material, an intermediate, or a side reaction product when the coloring material is synthesized. Therefore, the concentration of the oil solution in the ink can be lowered by sufficiently purifying the raw materials and intermediates at the stage of synthesizing the color material and suppressing side reactions to the minimum. The silicon concentration in the ink is 0.05
It is -10 ppm, preferably 0.05-7 ppm, and more preferably 0.05-5 ppm. As presented in the prior art, when the silicon concentration in the ink is high as in the case of other polyvalent metals, the deposits on the heater gradually increase during continuous ejection, which causes irregular ejection. Silicon in the ink can be separated by F
It can be removed together with polyvalent metals such as e, Mg, Ca and Al.
Further, as in the case of the oil solution, most of them are derived from the coloring material, and the silicon concentration in the ink can be lowered by minimizing the mixing of silicon at the stage of synthesizing the coloring material.

Further, not only does the oil solution and silicon in the ink cause kogation, but when the silicon concentration is outside the predetermined range in the coexistence state of both, bubbles tend to be generated over time, It lowers the ejection stability and leads to missing or disturbed images. As described above, by reducing the concentration of the oil solution and the concentration of silicon in the ink, it is possible to reduce kogation, minimize the generation of bubbles, and maintain the ejection stability. In particular, when the ink of the present invention is used in a high-resolution inkjet printer of 300 dpi or more, the drop amount is reduced and bubbles are liable to affect the image, so that the above-described improvement effect is significant.

As the coloring material for the ink, a water-soluble dye is generally used as exemplified above, but a dye having three or more azo groups of trisazo or higher, such as C.I. I.
Direct Black-2, -4, -9, -11, -1
9, -22, -32, -80, -151, -154,-
168, -171, C.I. I. Direct Blue-34,
-70, -71, -78, -112, -287, C.I.
I. Direct Red-80, -94, C.I. I. Acid black-208 and the like contain a large amount of oil solution. It is considered that as the number of azo couplings increases, the types of unreacted raw materials, intermediates and by-products increase, and the molecular weight also increases, so that the oil solution easily adheres to the dye. In the present invention, the oil solution concentration in the water-soluble dye is
It is 1200 ppm or less, preferably 500 ppm or less, more preferably 300 ppm or less. When the oil solution concentration in the dye becomes higher than this, as a result, the oil solution concentration in the ink becomes too high and vigorous kogation occurs.
The concentration of silicon in the water-soluble dye is 0.5 to 200 pp.
m, preferably 0.5 to 140 ppm, more preferably 0.5 to 100 ppm. The silicon concentration in the dye is 20
When it is higher than 0 ppm, as a result, the silicon concentration in the ink is too high to cause kogation, while when it is lower than 0.5 ppm, bubbles are remarkably generated after standing and the ejection stability is deteriorated. Further, when both the oil solution concentration and the silicon concentration are high, not only kogation but also discharge instability due to bubbles occurs.

The oil solution concentration is difficult to detect even if the ink and the water-soluble dye are directly analyzed by HPLC or GC, but it can be determined by measuring the weight after extraction with a solvent and drying. Also, many of these oil solutions are colored,
In that case, if the relationship between the oil solution concentration and the absorbance of the extract is known, the concentration can be determined by measuring the absorbance. The silicon concentration of both ink and dye is determined by atomic absorption spectrometry or high frequency inductively coupled plasma emission spectrometry (ICP-AE).
It can be determined using S). In the examples and comparative examples described below, the oil solution concentration in the ink was about 30 for 30 minutes at 60 ° C. using 5 ml of toluene for 20 ml of the ink.
After stirring under the condition of 0 rpm, the mixture was allowed to stand and separated into two layers,
Then, the toluene layer as the supernatant was taken out and the absorbance was measured, and the absorbance was determined from the previously measured relationship between the oil solution concentration and the extract absorbance. FIG. 1 shows a correlation graph between the absorbance at a wavelength of 435 nm and the oil solution concentration of a certain ink jet recording ink. The oil solution concentration in the dye is 1
Using 20 ml of toluene for 20 ml of dye aqueous solution prepared as 0% aqueous solution, at 300C for 30 minutes at about 300 rp.
After stirring under the condition of m, the absorbance was measured and determined from the relationship between the oil solution concentration and the absorbance in the same manner as in the measurement of the ink.
The silicon concentration was measured by the above ICP-AES for the ink as it was and for the dye in the state of a 10% aqueous solution.

In the present invention, a penetrant that enhances penetration into the paper in order to accelerate the drying time of the ink and a surfactant may be added to further stabilize the dissolved or dispersed state of the coloring material. Good. The surfactant may be a nonionic, anionic, cationic or amphoteric surfactant. For example, as nonionic surfactants, polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene / polyoxypropylene block copolymer, polyoxyethylene fatty acid ester,
Examples thereof include polyoxyethylene sorbitan fatty acid ester, sorbitan fatty acid ester, and fatty acid alkylolamide. As the anionic surfactant, alkylbenzene sulfonate, alkylnaphthalene sulfonate,
Formalin condensate of alkylnaphthalene sulfonate,
Higher fatty acid salts, sulfate salts of higher fatty acid esters,
Examples thereof include sulfonic acid salts of higher fatty acid esters, sulfuric acid ester salts of higher alcohol ethers, sulfonic acid salts of higher alcohol ethers, alkylcarboxylic acid salts of higher alkylsulfonamide, sulfosuccinates, sulfosuccinic acid ester salts and the like. Examples of the cationic surfactant include primary to tertiary amine salts and quaternary ammonium salts. Examples of the amphoteric surfactant include betaine, sulfobetaine, sulfate betaine and the like.

In addition, solubilizers such as urea and acetamide, and pH adjusters such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid,
Acids such as citric acid, sodium hydroxide, potassium hydroxide,
A base such as ammonia and various buffers are used.
Further, as the physical property adjusting agent, polyethyleneimine, polyamines, polyvinylpyrrolidone, polyethylene glycol, cellulose derivatives and the like, as an inclusion compound, cyclodextrin, macrocyclic amines, crown ethers and the like may be contained in the ink, An antifungal agent may be contained if necessary.

[0015]

As described above, the ink jet recording ink of the present invention having an oil solution concentration of 150 ppm or less and a silicon concentration of 0.05 to 10 ppm has reduced kogation, small change in drop amount, and Less bubbles are generated and discharge is less disturbed. That is, in the case of kogation of the dye itself, it undergoes a process of decomposition and insolubilization by heat and is deposited on the head to become kogation, whereas in the case of an oil solution, it is stably dispersed in an aqueous solution. There is no problem in this case, but once it adheres to the heater, it deposits as it is as an insoluble matter, so it is considered that even a small amount has a strong influence on kogation. When the oil solution concentration in the ink is 150 ppm or less, the mechanism that makes kogation difficult is not always clear, but it is considered that since it has high dispersion stability, it is hard to adhere to the heater. On the other hand, it is considered that silicon exists as an insoluble substance in the ink in the form of SiO ₂ or the like and affects kogation. Also, regarding the generation of bubbles,
In the coexistence state of the oil solution and silicon, it is considered that the affinity with the dissolved air is strong, or the dissolved air gathers around these as nuclei to form bubbles, and the silicon concentration is particularly 0.05.
When it is in the range of 10 ppm, the bubbles disappear without being stabilized, and it is considered that the problem of dischargeability does not occur. However, if the silicon concentration is too low, the bubbles are stabilized and remain without disappearing. On the contrary, if the silicon concentration is too high, the amount of bubbles generated increases, and as a result, the ejection stability is considered to deteriorate.

[0016]

EXAMPLES The present invention will be described in more detail below with reference to examples. In addition, "part" indicating the composition amount of the ink means "part by weight". Example 1 Inorganic impurities were removed by filtration through a reverse osmosis membrane, and an oil solution was further removed by adsorption with activated carbon. I. Prepared by dissolving 2 g of powder of Direct Black 168 in water 10
When 20 ml of toluene was added to 20 ml of a wt% aqueous solution and the oil solution was extracted by stirring at 23 ° C. for 30 minutes, the absorbance was measured to obtain the oil solution concentration.
It was m. Further, the silicon concentration in the 10 wt% dye aqueous solution was determined by ICP-AES, and when converted into the value per dye powder, it was 90 ppm. With this dye,
An ink was prepared by thoroughly mixing and dissolving the components shown below and pressurizing and filtering with a 0.45 μm filter. C. I. Direct Black 168 Lot 1 3 parts Diethylene glycol 20 parts Pure water 80 parts The above ink has a viscosity of 2.0 cP and a surface tension of 56 dyn.
Was / cm. To 20 ml of this ink, 5 ml of toluene was used to extract the oil solution, and the absorbance was measured. The concentration of the oil solution was 12 ppm. The silicon concentration in the ink was 3 ppm as determined by ICP-AES.

Example 2 C. I. Inorganic impurities in Direct Black 168 were removed as in Example 1 and oil solubles were removed at different levels. The oil solution concentration and silicon concentration in the dye were determined in Example 1
It was 285 ppm and 90 ppm, respectively. Using this dye, the following components were sufficiently mixed and dissolved, and pressure-filtered with a 0.45 μm filter to prepare an ink. C. I. Direct Black 168 Lot 2 3 parts Diethylene glycol 20 parts Pure water 80 parts The above ink has a viscosity of 2.0 cP and a surface tension of 56 dyn.
Was / cm. When the oil solution concentration in the ink was determined in the same manner as in Example 1, it was 38 ppm, and the silicon concentration was 3 p.
It was pm.

Example 3 C. I. Inorganic impurities in Direct Black 168 were removed as in Example 1 and oil solubles were removed at different levels. The oil solution concentration and silicon concentration in the dye were determined in Example 1
It was 450 ppm and 90 ppm, respectively. Using this dye, the following components were sufficiently mixed and dissolved, and pressure-filtered with a 0.45 μm filter to prepare an ink. C. I. Direct Black 168 Lot 3 3 parts Diethylene glycol 20 parts Pure water 80 parts The above ink has a viscosity of 2.0 cP and a surface tension of 56 dyn.
Was / cm. When the oil solution concentration in the ink was determined in the same manner as in Example 1, it was 55 ppm, and the silicon concentration was 3 p.
It was pm.

Comparative Example 1 C. I. The inorganic impurities in Direct Black 168 were removed in the same manner as in Example 1, but the oil solution was not removed.
When the oil solution concentration and the silicon concentration in the dye were determined in the same manner as in Example 1, they were 1540 ppm and 90, respectively.
It was ppm. Using this dye, the following components were sufficiently mixed and dissolved, and pressure-filtered with a 0.45 μm filter to prepare an ink. C. I. Direct Black 168 Lot 4 3 parts Diethylene glycol 20 parts Pure water 80 parts The above ink has a viscosity of 2.0 cP and a surface tension of 56 dyn.
Was / cm. When the oil solution concentration in the ink was determined in the same manner as in Example 1, it was 172 ppm, and the silicon concentration was 3
It was ppm.

Comparative Example 2 C. I. The inorganic impurities in Direct Black 168 were removed at a level different from that of Example 1, and the oil solution was removed at the same level. The oil solution concentration and the silicon concentration in the dye were determined in the same manner as in Example 1 to find that each was 130 pp.
m and 300 ppm. Using this dye, the following components were sufficiently mixed and dissolved, and pressure-filtered with a 0.45 μm filter to prepare an ink. C. I. Direct Black 168 Lot 5 3 parts Diethylene glycol 20 parts Pure water 80 parts The above ink has a viscosity of 2.0 cP and a surface tension of 56 dyn.
Was / cm. When the oil solution concentration in the ink was determined in the same manner as in Example 1, it was 15 ppm, and the silicon concentration was 12
It was ppm.

Comparative Example 3 C. I. The inorganic impurities in Direct Black 168 were removed at a level different from that of Example 1, and the oil solution was not removed. The oil solution concentration and the silicon concentration in the dye were determined in the same manner as in Example 1 and found to be 1510 ppm each.
And 300 ppm. Using this dye, the following components were sufficiently mixed and dissolved, and pressure-filtered with a 0.45 μm filter to prepare an ink. C. I. Direct Black 168 Lot 6 3 parts Diethylene glycol 20 parts Pure water 80 parts The above ink has a viscosity of 2.0 cP and a surface tension of 56 dyn.
Was / cm. When the oil solution concentration in the ink was determined in the same manner as in Example 1, it was 160 ppm, and the silicon concentration was 1
It was 2 ppm.

Ink evaluation 1) Ink surface tension It was measured using a Wilhelmy type surface tensiometer in an environment of 20 ° C. and 50% RH. 2) Ink viscosity 20 ° C., 50% RH environment, shear rate 1400
It was measured at s ^-1 . 3) Head kogation test For the prepared ink, a resolution of 30 was made for evaluation.
1 using a 0 dpi thermal inkjet printer
Discharge of × 10 ⁸ pulses was performed, and the change in discharge amount during that period was measured. A: Change in ejection amount less than 15% B: Change in ejection amount 15% or more and less than 25% X ... Change in ejection amount 25% or more 4) Clogging test The resolution of the prepared ink for trial evaluation Thirty
Using a 0 dpi thermal ink jet printer, the image disorder was observed when the discharge was resumed after left for 1 week in a capped state after the discharge was stopped, and evaluated according to the following criteria. ○
・ ・ ・ Image dropout, no disturbance △ ・ ・ ・ Image dropout, turbulence, etc. defect less than 5% × ・ ・ ・ Image dropout, turbulence, etc. defect 5% or more 5) Ejection stability test Evaluate the prepared ink After filling in an ink cartridge prototyped for use, the ink cartridge was left at 10 ° C. for 1 week, then left at 40 ° C. for 1 week to change to an environment of 20 ° C., and then the generation state of bubbles was observed. Also, the resolution is 300 dpi
A4 paper 5 using the thermal inkjet printer
0 sheets were continuously ejected, and image disturbance during that period was evaluated according to the following criteria. ○: No air bubbles were generated and no white spots were found in the image. △: Small bubbles were visible to the naked eye, and defects such as white spots in the image were less than 5%. 5% or more of defects such as white spots

The above results are shown in Table 1.

[Table 1]

Example 4 Inorganic impurities were removed and an oil solution was further removed. I.
The oil solution concentration of Direct Black 151 was determined in the same manner as in Example 1, and it was 170 ppm. The silicon concentration in the dye was 65 ppm. With this dye,
The components shown below were thoroughly mixed and dissolved, and pressure-filtered with a 0.45 μm filter to prepare an ink. C. I. Direct Black 151 2 parts Glycerin 10 parts Diethylene glycol monobutyl ether 10 parts Pure water 80 parts The above ink has a viscosity of 2.0 cP and a surface tension of 36 dyn.
Was / cm. When the oil solution concentration in the ink was determined in the same manner as in Example 1, it was 15 ppm, and the silicon concentration was 2 p.
It was pm. On the other hand, the change in the ejection amount in the head kogation test was 5%, and the results of the clogging test and the ejection stability test were ◯.

Example 5 Inorganic impurities were removed and an oil solution was further removed. I.
The oil solution concentration of Direct Black 19 was determined in the same manner as in Example 1, and it was 375 ppm. The silicon concentration in the dye was 52 ppm. Using this dye, the following components were sufficiently mixed and dissolved, and pressure-filtered with a 0.45 μm filter to prepare an ink. C. I. Direct Black 19 4 parts Ethylene glycol 25 parts Pure water 75 parts The above ink has a viscosity of 2.4 cP and a surface tension of 54 dyn.
Was / cm. When the oil solution concentration in the ink was determined in the same manner as in Example 1, it was 32 ppm, and the silicon concentration was 2 p.
It was pm. On the other hand, the change in the ejection amount in the head kogation test was 13%, and the results of the clogging test and the ejection stability test were O.

Example 6 Inorganic impurities were removed and an oil solution was further removed. I.
The oil solution concentration of Direct Black 171 was determined in the same manner as in Example 1, and it was 230 ppm. The silicon concentration in the dye was 80 ppm. With this dye,
The components shown below were thoroughly mixed and dissolved, and pressure-filtered with a 0.45 μm filter to prepare an ink. C. I. Direct Black 171 4 parts Propylene glycol 20 parts Acetic acid 0.1 parts NaOH 0.07 parts Pure water 75 parts The above ink has a viscosity of 2.0 cP and a surface tension of 54 dyn.
Was / cm. When the oil solution concentration in the ink was determined in the same manner as in Example 1, it was 24 ppm, and the silicon concentration was 4 p.
It was pm. On the other hand, the change in the ejection amount in the head kogation test was 11%, and the results of the clogging test and the ejection stability test were O.

Example 7 Inorganic impurities were removed, and then an oil solution was removed. I.
The oil solution concentration of Direct Blue 287 was determined in the same manner as in Example 1, and it was 130 ppm. The silicon concentration in the dye was 75 ppm. Using this dye, the following components were sufficiently mixed and dissolved, and pressure-filtered with a 0.45 μm filter to prepare an ink. C. I. Direct Blue 287 3 parts Triethylene glycol 15 parts Pure water 75 parts The above ink has a viscosity of 1.8 cP and a surface tension of 52 dyn.
Was / cm. When the oil solution concentration in the ink was determined in the same manner as in Example 1, it was 18 ppm, and the silicon concentration was 4 p.
It was pm. On the other hand, the change in the ejection amount in the head kogation test was 7%, and the results of the clogging test and the ejection stability test were ◯.

Example 8 Inorganic impurities were removed and an oil solution was further removed. I.
The following components were sufficiently mixed and dissolved using Acid Blue 9 and pressure-filtered with a 0.45 μm filter to prepare an ink. C. I. Acid Blue 9 2 parts Ethylene glycol 30 parts Pure water 70 parts The above ink has a viscosity of 2.9 cP and a surface tension of 51 dyn.
Was / cm. When the oil solution concentration in the ink was determined in the same manner as in Example 1, it was 2 ppm, and the silicon concentration was 2 pp.
It was m. On the other hand, the change in the ejection amount in the head kogation test was 4%, and the results of the clogging test and the ejection stability test were ◯.

Example 9 C. Inorganic impurities were removed, and an oil solution was further removed. I.
The components shown below were sufficiently mixed and dissolved using Direct Blue 70, and pressure-filtered with a 0.45 μm filter to prepare an ink. C. I. Direct Blue 70 2 parts 2-Pyrrolidone 25 parts Pure water 75 parts The above ink has a viscosity of 2.5 cP and a surface tension of 53 dyn.
Was / cm. When the oil solution concentration in the ink was determined in the same manner as in Example 1, it was 1.2 ppm, and the silicon concentration was 2
It was ppm. On the other hand, the change in the ejection amount in the head kogation test was 3%, and the results of the clogging test and the ejection stability test were ◯.

Example 10 Inorganic impurities were removed and oil solution was further removed. I. The following components were thoroughly mixed and dissolved using Acid Red 249, and pressure-filtered with a 0.45 μm filter to prepare an ink. C. I. Acid Red 249 3 parts N-methyl-2-pyrrolidone 20 parts Potassium dihydrogen phosphate 0.3 parts Disodium hydrogen phosphate 0.3 parts Pure water 75 parts The above ink has a viscosity of 2.0 cP and a surface tension of 49 dyn.
Was / cm. When the oil solution concentration in the ink was determined in the same manner as in Example 1, it was 0.6 ppm, and the silicon concentration was 3
It was ppm. On the other hand, the change in the ejection amount in the head kogation test was 2%, and the results of the clogging test and the ejection stability test were ◯.

Example 11 Inorganic impurities were removed, and oil solution was further removed. I. Using Food Black 2, the components shown below were thoroughly mixed and dissolved, and pressure-filtered with a 0.45 μm filter to prepare an ink. C. I. Food Black 2 4 parts Glycerin 15 parts _{HO (C 2 H 4 O)} a (C 3 H 6 O) b (C 2 H 4 O) c H 0.5 parts (oxypropylene block molecular weight 1800, polyoxyethylene content 20 %, Average molecular weight about 2250) Diethylene glycol monobutyl ether 10 parts Pure water 70 parts The above ink has a viscosity of 3.0 cP and a surface tension of 35 dyn.
Was / cm. When the oil solution concentration in the ink was determined in the same manner as in Example 1, it was 2.6 ppm, and the silicon concentration was 5
It was ppm. On the other hand, the change in the ejection amount in the head kogation test was 4%, and the results of the clogging test and the ejection stability test were ◯.

Example 12 Inorganic impurities were removed and oil solution was further removed. I. Using Direct Yellow 144, the components shown below were thoroughly mixed and dissolved, and pressure-filtered with a 0.45 μm filter to prepare an ink. C. I. Direct Yellow 144 3 parts Polyethylene glycol (molecular weight 200) 10 parts HO (C ₂ H ₄ O) _a (C ₃ H ₆ O) _b (C ₂ H ₄ O) _c H 1 part (oxypropylene block molecular weight 1800, oxyethylene) Content 40%, average molecular weight about 3000) N, N, -bis (2-hydroxyethyl) -2-aminoethanesulfonic acid 0.6 part NaOH 0.06 part Pure water 85 parts Viscosity of the above ink is 1.8 cP , Surface tension is 37 dyn
Was / cm. When the oil solution concentration in the ink was determined in the same manner as in Example 1, it was 0.4 ppm, and the silicon concentration was 6
It was ppm. On the other hand, the change in the ejection amount in the head kogation test was 10%, and the results of the clogging test and the ejection stability test were ◯.

Example 13 C. Inorganic impurities were removed and the oil solution was removed. I. Using Direct Blue 199, the following components were thoroughly mixed and dissolved, and pressure-filtered with a 0.45 μm filter to prepare an ink. C. I. Direct Blue 199 3 parts Glycerin 10 parts Sulfolane 2 parts Pure water 85 parts The above ink has a viscosity of 1.8 cP and a surface tension of 55 dyn.
Was / cm. When the oil solution concentration in the ink was determined in the same manner as in Example 1, it was 3 ppm, and the silicon concentration was 3 pp.
It was m. The change in the ejection amount in the head kogation test was 6%, and the results of the clogging test and the ejection stability test were O.

Example 14 Inorganic impurities were removed and the oil solution was further removed. I. The oil solution concentration of direct black 154 was determined in the same manner as in Example 1, and it was 820 ppm. The silicon concentration in the dye was 85 ppm. Using this dye, the following components were sufficiently mixed and dissolved, and pressure-filtered with a 0.45 μm filter to prepare an ink. C. I. Direct Black 154 5 parts Diethylene glycol 10 parts Isopropanol 3 parts Pure water 80 parts The above ink has a viscosity of 1.7 cP and a surface tension of 45 dyn.
Was / cm. When the oil solution concentration in the ink was determined in the same manner as in Example 1, it was 90 ppm, and the silicon concentration was 8 p.
It was pm. On the other hand, the change in the ejection amount in the head kogation test was 19%, the result of the clogging test was ◯, and the result of the ejection stability test was Δ.

Comparative Example 4 Inorganic impurities were removed, but oil solution was not removed.
I. The oil solution concentration of direct black 154 was determined in Example 1
It was 1400 ppm when determined in the same manner as. The silicon concentration in the dye was 65 ppm. Using this dye, the following components were thoroughly mixed and dissolved to give 0.45 μm
An ink was prepared by pressure filtration with a filter. C. I. Direct Black 154 5 parts Glycerin 15 parts 1,5-Pentanediol 5 parts Pure water 75 parts The above ink has a viscosity of 2.8 cP and a surface tension of 49 dyn.
Was / cm. When the oil solution concentration in the ink was determined in the same manner as in Example 1, it was 82 ppm, and the silicon concentration was 3 p.
It was pm. On the other hand, the change in the ejection amount in the head kogation test was 29%, and the result of the ejection stability test was Δ, but the result of the clogging test was x.

[0036]

INDUSTRIAL APPLICABILITY According to the present invention, the contents of oil solution and silicon contained in the water-soluble dye are reduced to a predetermined range. When used in a method of forming droplets by applying thermal energy, which is one of the above, the charring on the heater, so-called kogation, is reduced, so the drop amount change is small and the number of bubbles is small. Is less disturbed, storage stability is good and clogging does not occur. Furthermore, a good image can be obtained over a long period of time.

[Brief description of drawings]

FIG. 1 Wavelength 435n of inkjet recording ink
The correlation graph of the light absorbency in m and an oil solution concentration is shown.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Bunkyo Koide 1600 Takematsu, Minamiashigara-shi, Kanagawa Fuji Xerox Co., Ltd. (72) Inventor Ken Hashimoto 1600 Takematsu, Minamiashigara-shi, Kanagawa Fuji Xerox Co., Ltd.

Claims (2)

[Claims] 1. An ink for ink jet recording in which water, a water-soluble organic solvent, and a coloring material are used as essential components to apply heat energy to form droplets, and the concentration of the oil solution contained in the ink is 150 ppm or less. And the concentration of silicon is in the range of 0.05 to 10 ppm. 2. In a water-soluble dye used in an ink jet recording ink which forms a droplet by applying heat energy, the concentration of an oil solution contained in the dye is 1200.
ppm or less and a silicon concentration of 0.5 to 200 ppm
Is a water-soluble dye.