JP2001158864A - Ink, bubble jet ink, ink manufacturing method, ink jet recording method, and ink jet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably suppress generation of kogation firmly adhering on a heater, to have good ink ejection characteristics, and to stably record a high-quality image. To provide an ink, a bubble jet (registered trademark) ink, an ink manufacturing method, an ink jet recording method, an ink jet recording apparatus, a recording unit, and an ink cartridge. SOLUTION: This ink is obtained by dispersing a pigment having a concentration of phosphorus as an inorganic compound of not more than 500 ppm in water or a liquid medium comprising water and a water-soluble organic solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink, an ink for bubble jet, a method for producing the ink, an ink jet recording method, and an ink jet recording apparatus.

[0002]

2. Description of the Related Art The ink jet recording method is a recording method in which ink droplets are formed by various ink ejection methods, and a part or all of the ink droplets are attached to a recording material such as paper to perform recording. As the ink used for such inkjet recording, various water-soluble dyes or pigments,
What is dissolved or dispersed in water or a liquid medium composed of water and a water-soluble organic solvent is used. As the ink jet recording method, for example, a method using mechanical energy and a method using thermal energy as energy for discharging these inks, a so-called bubble jet method, are known. .

[0003] As a phenomenon peculiar to the bubble jet method, there is a deposit of so-called "koge" on a heater surface for applying thermal energy to ink for ink jet recording. This “kog” may reduce the thermal efficiency and reduce the ink ejection efficiency. Many proposals have been made to prevent the occurrence of kogation. For example, Japanese Patent Publication No. 55555/1993 discloses a phosphorus compound contained as an impurity in a dye used as a coloring material. Is a cause of kogation, and that kogation can be prevented by reducing the phosphorus content in the ink to 4 ppm or less by dye purification or the like.
On the other hand, regarding ink containing a pigment as a coloring material, for example, Japanese Patent Application Laid-Open No. 09-183934 discusses the problem of kogation when a conventional pigment ink for stationery is ejected by the bubble jet method. It describes that the problem of kogation was solved by adjusting the composition of the ink.

[0004]

The inventors of the present invention have made various studies on pigment inks to be ejected by the bubble jet method. As a result, even when pigment ink is used, kogation adheres to the heater surface, but unlike that of dye ink, the kogation is a carbon-derived kogation having a weak adhesive force to the heater surface, and It has been found that even if such kogation adheres to the heater surface, it can be easily peeled off by cavitation at the time of foaming, and as a result, it is possible to prevent the ink ejection from being substantially affected. . However, further investigations have shown that even with such a pigment ink, kogation may be firmly adhered to the heater, and this problem is solved by using a pigment ink of high quality. We have come to recognize that this is a technical issue that must be solved in order to obtain a stable image.

A detailed analysis of the kogation firmly adhered to the heater surface revealed that the dye ink contained a phosphorus compound which was a problem. Next, as a result of further studies to investigate the origin of the phosphorus compound contained in the kogation, the occurrence of kogation differs depending on the lot of the pigment, and the result of analyzing the ink showed that kogation occurred. The pigment in the obtained ink contains a large amount of a phosphorus compound, while the pigment used in the ink in which no kogation is observed is found to contain almost no phosphorus compound. The occurrence of kogation was determined to be derived from the pigment in the ink. However, unlike dyes in which a phosphorus compound is used as a catalyst, if the present inventors recognize that there is no process of mixing phosphorus or the like during the production of a pigment unless the structure contains phosphorus. However, the presence of phosphorus derived from this pigment was a completely unexpected finding. Therefore, when this point was further investigated, groundwater was sometimes used as water used for washing the pigment during the production of the pigment, and when this groundwater contained a large amount of phosphoric acid, etc., the phosphorus in the groundwater was used. Has been found to be adsorbed on the pigment.

[0006] As described above, the present invention closely relates to the presence of phosphorus as an inorganic compound in pigments, the presence of which was not known even before, and the problem of kogation in pigment ink for bubble jet. It is based on a completely new knowledge that
An object of the present invention is to provide a pigment ink capable of stably suppressing the occurrence of kogation and a method for producing the same. Also, the present invention
Ink that can stably record high-quality images,
An object of the present invention is to provide a bubble jet ink, a method for producing the ink, an ink jet recording method, and an ink jet recording apparatus.

[0007]

The ink according to an embodiment of the present invention, which can achieve the above object, is characterized in that a pigment having a phosphorus concentration of not more than 500 ppm as an inorganic compound contained therein is mixed with water or water. It is characterized by being dispersed in a liquid medium comprising a water-soluble organic solvent.
The bubble jet ink according to an embodiment of the present invention that can achieve the above object is an ink for discharging by a bubble jet recording method, and the concentration of phosphorus as an inorganic compound is 500 ppm or less. The present invention is characterized by stably reducing the adhesion of kogation to a heater by including a certain pigment in a dispersed state in an aqueous medium.

According to one embodiment of the present invention, which can achieve the above object, there is provided a method for producing an ink, comprising the steps of: (i) selecting a pigment having a phosphorus concentration of 500 ppm or less as an inorganic compound; A) dispersing the pigment selected in the step (i) in an aqueous medium. The method for producing an ink according to another embodiment of the present invention, which can achieve the above object, includes the steps of (i) when the concentration of phosphorus as an inorganic compound is 500 pp.
m and the phosphorus concentration is 500 pp
m or less; and (ii) a step of dispersing the pigment obtained in the step (i) in an aqueous medium.

[0009] The ink jet recording method according to one embodiment of the present invention, which can achieve the above-mentioned object, is to prepare a pigment having a phosphorus content of 500 ppm or less as an inorganic compound by using water or water and a water-soluble organic solvent. And discharging the ink for ink jet recording dispersed in a liquid medium from an orifice of a recording head in accordance with a recording signal.

An ink jet recording unit according to one embodiment of the present invention that can achieve the above object is
The concentration of phosphorus as an inorganic compound to be contained is 500 ppm
The following pigment, an ink container containing an ink for ink-jet recording obtained by dispersing in a liquid medium composed of water or water and a water-soluble organic solvent, and a head unit for discharging the ink. It is characterized by having.

[0011] An ink cartridge according to an embodiment of the present invention, which can achieve the above object, is characterized by comprising an ink containing section for containing the above-described ink.

The ink jet recording apparatus according to one embodiment of the present invention, which can achieve the above-mentioned object, is a method for preparing a pigment having a phosphorus content of 500 ppm or less as an inorganic compound by using water or water and a water-soluble organic solvent. And a head portion for discharging the ink containing the ink for inkjet recording dispersed in a liquid medium consisting of:

[0013]

Next, the present invention will be described in more detail with reference to preferred embodiments. First, the pigment contained in the ink according to the present invention will be described. The pigment contained in the ink according to the present invention is a pigment having a phosphorus concentration of 500 ppm or less as an inorganic compound contained therein. According to the study by the present inventors, the concentration was set to 500 p.
pm or less, the generation of kogation can be effectively suppressed even after the ink has been stored for a long period of time, and the ink exhibits stable ejection characteristics, so that a high-quality image can be stably obtained. Was found to be possible. As a method of reducing the concentration of phosphorus as an inorganic compound in the pigment to 500 ppm or less, for example, washing the pigment in the following manner,
There is a method of removing phosphorus adsorbed on the pigment.

[0014] As an example of the pigment washing treatment, first, as a washing liquid that can be used, for example, pure water,
About 0.1 to 1N hydrochloric acid, sulfuric acid, nitric acid, or an acidic aqueous solution such as acetic acid; about 0.1 to 1N an alkaline aqueous solution containing a hydroxide such as sodium hydroxide, potassium hydroxide, or lithium hydroxide; An alkaline aqueous solution such as ammonia is exemplified.

Further, in order to further shorten the cleaning time by increasing the wettability between the pigment and the cleaning liquid, and to further improve the cleaning efficiency, water-soluble alcohols such as methanol, ethanol and (iso) propyl alcohol are used. Is more preferably mixed at a ratio of about 5 to 30% by weight based on the total amount of the above-mentioned cleaning liquid.

The washing treatment of the pigment with the washing liquid as described above may be repeated a plurality of times. However, when washing with an acidic aqueous solution or an alkaline aqueous solution,
After that, it is necessary to wash away with pure water until neutral.
As a specific washing method, for example, a method of filling a column or the like with a pigment and flowing a washing liquid as described above, a method of placing the pigment in a beaker or the like and repeating decantation, a method of reducing the pressure or pressure of the pigment, Examples of the method include filtration and filtration using an aspirator. In addition, washing may be performed using a reflux extraction, a Soxhlet extractor, or the like, or using a centrifuge. Further, any method other than those listed above may be used as long as it can efficiently and safely wash the pigment and remove the adsorbed phosphorus component.

The phosphorus concentration in the pigment is measured by incinating the pigment using an electric furnace or the like, dissolving the ash in a strong acid such as concentrated hydrochloric acid, and using this as a sample for measurement by inductively coupled plasma emission spectrometry. It can be quantified in the device.

In the present invention, the pigment which can be preferably used as a coloring material of the ink may be a commercially available pigment or a newly synthesized pigment as long as the pigment does not contain phosphorus in the skeleton itself. In consideration of light resistance, color tone and safety, aqueous dilute dispersibility, etc., the following may be mentioned. For example, C.I. I. Pigment Yellow (hereinafter referred to as
Abbreviated as "PY") 1, PY2, PY4, PY5, PY
6, PY7, PY8, PY12, PY13, PY14,
PY16, PY17, PY49, PY55, PY68,
PY73, PY74, PY75, PY77, PY83,
PY93, PY94, PY95, PY97, PY98,
PY114, PY117, PY120, PY124, P
Y127, PY128, PY129, PY151 and P
Y154; I. Pigment Orange (hereinafter, "P
O ") 43, PO51; Pigment Red (hereinafter abbreviated as" PR ") 48, PR3, PR4, PR6,
PR52, PR56, PR57: 1, PR58, PR6
0, PR63, PR77, PR115, PR122, P
R123, PR149, PR168, PR179, PR
184, PR189, PR190, PR200, PR2
02, PR206, PR207, PR209, PR21
0 and PR258; I. Pigment Blue (hereinafter,
15: 2, PB15: 3, PB15:
4 and PB60; I. Pigment Violet (hereinafter abbreviated as “PV”) 19, PV23, PV42 and the like are preferable, and among them, PR122, PY74, PY93,
PB15: 2, PB15: 3 and PB15: 4 are particularly preferred.

As a product name of PR122, for example, F
astogen Super Magenta R
(Dainippon Ink), Lionogen Agent
a RF (manufactured by Toyo Ink Manufacturing), Hostaperm
Pink E (Hoechst), Mondite
Rubine 3B (Zeneca), Quind
o Magenta RV-6831 and Quindo
Magenta RV-6828 (above, manufactured by Mobay Chemical) and the like. As the product name of PY74,
For example, Yellow 4633N (manufactured by Sanyo Dye), Hansa Brilliant Yellow 5GX (manufactured by Hoechst) and the like can be mentioned. As the product name of PY93, for example, Yel
low 3G (manufactured by Ciba Specialty Chemicals) and the like. As the product name of PB15: 3, for example,
Chromofine Blue 4920 (manufactured by Dainichi Seika Kogyo), Cyanine Blue KR-O (manufactured by Sanyo Pigment Co., Ltd.), Cyanine Fast Blue B (manufactured by Noma Chemical), Cyanine Blue SSK (manufactured by Nippon Pigment), FastogenBug
(Manufactured by Dainippon Ink), Bond Blue FG-7
330 (manufactured by Toyo Ink Manufacturing Co., Ltd.), Sumika prince
t Cyamine Blue GN-O (manufactured by Sumitomo Chemical), Helogen Blue L7101F (manufactured by BASF) and Heikoftal Blue G, XBT-583D (all,
But not limited to these.

The content of these pigments in the ink is preferably 3 parts by weight based on the total weight of the ink in order to further improve the density of the printed matter and to improve the refillability of the ink.
Preferably, it is used in the range of -20% by weight. or,
The phosphorus concentration in the ink of the present invention is preferably 30 ppm or less. The reason is the same as the case where the phosphorus concentration in the pigment is 500 ppm or less.

Examples of the dispersant for dispersing the above pigment include styrene-acrylic acid copolymer, styrene-acrylic acid-alkyl acrylate copolymer,
Styrene-maleic acid copolymer, styrene-maleic acid-acrylic acid alkyl ester copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid acrylic ester copolymer, styrene-maleic acid half ester copolymer Resins such as coalesce, vinyl naphthalene-maleic acid copolymer, and salts thereof are exemplified.

In order to dissolve these resins in water or a water-soluble organic solvent containing water, it is necessary to neutralize these resins with a neutralizing agent such as an alkali compound. Preferred neutralizing agents include, for example, inorganic alkali agents such as hydroxides of alkali metals such as potassium hydroxide, sodium hydroxide and lithium hydroxide; and organic acids such as monoethanolamine, diethanolamine, triethanolamine and aminomethylpropanol. Amines; ammonia and the like.
In addition, the amount of the neutralizing agent required to neutralize the above resin,
It is obtained from the following equation. In practice, it is preferable to neutralize with a neutralizing agent of about 1.0 to 1.2 times the value calculated from this formula.

(Equation 1)

The resin used as a dispersant for the above-mentioned pigment may be added to the total weight of the ink in order to further improve the abrasion resistance of the printed matter and the long-term preservability of the ink, and to keep the ink followability better. On the other hand, the content is preferably in the range of 0.05 to 3% by weight.

In addition to the above dispersants, for example, polyoxyethylene tridecyl ether phosphate, sodium polyoxyethylene lauryl ether phosphate, sodium polyoxyethylene cetyl ether phosphate, sodium polyoxyethylene oleyl ether phosphate, etc. Or a phosphate ester-based surfactant, or polyurethane, polyester, or the like.

A preferred liquid medium as a component of the ink according to the present invention is a mixed solvent of water and a water-soluble organic solvent. As the water, it is preferable to use ion-exchanged water instead of general water containing various ions.

Examples of the water-soluble organic solvent used by mixing with water include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol and isobutyl alcohol. Alkyl alcohols having 1 to 4 carbon atoms such as alcohol; amides such as dimethylformamide and dimethylacetamide; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol, propylene glycol, triethylene glycol, diethylene glycol, dipropylene glycol ,
Thiodiglycol, 1,2,6-hexanetriol,
Polyols such as hexylene glycol and glycerin; lower alkyl ethers of polyhydric alcohols such as ethylene glycol monoethyl (butyl) ether, diethylene glycol monoethyl (butyl) ether and triethylene glycol monoethyl (butyl) ether;
Non-proton-donating polar solvents such as N-methyl-2-pyrrolidone, 2-pyrrolidone, dimethylsulfoxide, sulfolane and dimethylformamide. In general, the content of the water-soluble organic solvent in the ink according to the present invention is preferably in the range of 13 to 50% by weight based on the total weight of the ink.
It is preferably in the range of 0% by weight.

The ink according to the present invention may contain, in addition to the above components, a surfactant, an antifoaming agent, a preservative, and the like, if necessary, in order to obtain an ink having desired physical properties. It is also possible to add a commercially available water-soluble dye or the like.

As a method of preparing the ink according to the present invention described above, for example, the following method can be mentioned.
That is, first, as described above, the phosphorus concentration is adjusted to 5 by washing or the like.
After the pigment having a concentration of 00 ppm or less is mixed with an aqueous solution containing a pigment dispersant such as an alkali-soluble resin made alkaline by adding a predetermined amount of an alkali compound, the resultant is subjected to a dispersion treatment using a disperser described below. The dispersion is added with the above-mentioned water-soluble solvent, water, or the like, and the pH of the ink is adjusted to a range of 7 or more using a pH adjuster or the like. Also, if necessary, a water-soluble organic solvent in this dispersion,
An antifoaming agent, a preservative, or the like may be added, and the dispersion itself may be used as the ink. Furthermore, classification processing by centrifugation or the like may be performed as necessary.

The disperser preferably used in the above-mentioned dispersion treatment may be any commonly used disperser, and examples thereof include a ball mill, a roll mill and a sand mill. Among them, a high-speed sand mill is preferable. For example, a super mill, a sand grinder, a bead mill, an agitator mill, a Glen mill, a Tyno mill, a pearl mill, and a Kobol mill (all are trade names)
And the like.

The pigment used in the present invention can be made to have a desired particle size distribution by reducing the size of the pulverized media of the disperser, increasing the filling rate of the pulverized media, increasing the processing time, Examples of the method include a method of slowing down the discharge speed, a method of classifying with a filter or a centrifuge after pulverization, and a method of combining those methods.

(Recording Apparatus) Next, an example of an ink jet recording apparatus suitable for performing ink jet recording using the ink according to the present invention will be described below. First, as a first embodiment, an ink jet recording apparatus to which a method of ejecting ink by applying thermal energy to ink will be described as an ink ejection method.
FIGS. 1, 2 and 3 show examples of the configuration of a head which is a main part of the apparatus.

The head 13 includes a glass, ceramic or plastic plate having a groove 14 through which ink passes, and a heating head 15 (a thin film head is shown in the figure, but is not limited to this). Is not obtained.) The heating head 15 includes a protective film 16 made of silicon oxide or the like, aluminum electrodes 17-1 and 17-2, and a heating resistor layer 1 made of nichrome or the like.
8, heat storage layer 19 and substrate 20 having good heat dissipation such as alumina
Consists of

The ink 21 has a discharge orifice (fine hole) 2
2, and the meniscus 23 is formed by the pressure P. Now, when electric signal information is applied to the aluminum electrodes 17-1 and 17-2, the area of the heating head 15 indicated by n rapidly generates heat, and bubbles are generated in the ink 21 in contact with the area. The meniscus 23 protrudes, the ink 21 is ejected to form an ink droplet 24, and flies from the ejection orifice 22 toward the recording material 25.

FIG. 3 is an external view of a multi-head in which many heads shown in FIG. 1 are arranged. The multi-head is manufactured by closely contacting a glass plate 27 having a multi-groove 26 and a heating head 28 similar to that described with reference to FIG. still,
FIG. 1 is a cross-sectional view of the head 13 along the ink flow path, and FIG. 2 is a cross-sectional view taken along line AB in FIG.

FIG. 4 shows an example of an ink jet recording apparatus incorporating the above head. In FIG. 4, 61 is
A blade as a wiping member, one end of which is held by a blade holding member to serve as a fixed end, in the form of a cantilever. The blade 61 is connected to the recording head 6.
5, and is held in a form protruding into the movement path of the recording head 65 in this example.

Reference numeral 62 denotes a cap on the ejection port surface of the recording head 65, which is disposed at a home position adjacent to the blade 61 and moves in a direction perpendicular to the direction in which the recording head 65 moves, so that the ink ejection port surface is A configuration is provided for abutting and capping. Further, reference numeral 63 denotes an ink absorber provided adjacent to the blade 61, and is held in a form protruding into the movement path of the recording head 65, similarly to the blade 61.

The blade 61, the cap 62, and the ink absorber 63 constitute an ejection recovery unit 64, and the blade 61 and the ink absorber 63 remove moisture, dust, and the like from the ink ejection port surface. 65 is a recording head which has an ejection energy generating means, and performs recording by ejecting ink to a recording material facing an ejection port surface provided with ejection ports.
Reference numeral 66 denotes a carriage on which the recording head 65 is mounted and moved. The carriage 66 is slidably engaged with the guide shaft 67, and a part of the carriage 66 is
8 (not shown). Accordingly, the carriage 66 can move along the guide shaft 67, and the recording head 65 can move the recording area and the adjacent area.

Reference numeral 51 denotes a paper feed unit for inserting a recording material, and reference numeral 52 denotes a paper feed roller driven by a motor (not shown). With such a configuration, the recording material is fed to a position facing the discharge port surface of the recording head 65, and is discharged to a discharge section provided with a discharge roller 53 as recording proceeds.

In the above configuration, when the recording head 65 returns to the home position at the end of recording or the like, the cap 62 of the ejection recovery section 64 is retracted from the moving path of the recording head 65, but the blade 61 protrudes into the moving path. ing. As a result, the ejection port surface of the recording head 65 is wiped. When capping is performed with the cap 62 in contact with the ejection surface of the recording head 65, the cap 62 moves so as to protrude into the movement path of the recording head.

When the recording head 65 moves from the home position to the recording start position, the cap 62 and the blade 61 are at the same position as the position at the time of wiping described above. As a result, the ejection port surface of the recording head 65 is also wiped during this movement. The movement of the print head 65 to the home position is performed not only at the end of printing or at the time of ejection recovery, but also at the home position adjacent to the printing area at a predetermined interval while the printing head 65 moves through the printing area for printing. And the wiping is performed with this movement.

FIG. 5 is a diagram showing an example of an ink cartridge 45 containing ink supplied to the head via an ink supply member, for example, a tube. Where 4
0 is an ink storage unit that stores the supply ink, for example,
The ink bag is provided with a rubber stopper 42 at the tip. By inserting a needle (not shown) into the stopper 42, the ink in the ink bag 40 can be supplied to the head. An ink absorber 44 receives the waste ink. It is preferable for the present invention that the ink container has a surface in contact with the ink made of polyolefin, particularly polyethylene.

The ink jet recording apparatus using the ink according to the present invention is not limited to the one in which the head and the ink cartridge are separated as described above, but the one in which they are integrated as shown in FIG. Is also preferably used. In FIG. 6, reference numeral 70 denotes a recording unit, in which an ink storage unit storing ink, for example, an ink absorber is stored, and a head unit having a plurality of orifices in which the ink in the ink absorber is stored. It is configured to be ejected from 71 as ink droplets.

As the material of the ink absorber, it is preferable to use polyurethane, cellulose, polyvinyl acetate or polyolefin. Reference numeral 72 denotes an atmosphere communication port for communicating the inside of the recording unit with the atmosphere. The recording unit 70 is used in place of the recording head shown in FIG. 4, and is detachable from the carriage 66.

Next, as an embodiment of the second ink jet recording apparatus, an ink jet recording apparatus to which a method of ejecting ink by applying a mechanical energy to the ink as an ink discharging method will be described. As a recording head which is a main part of such an apparatus, a nozzle forming substrate having a plurality of nozzles, a piezoelectric material disposed to face the nozzles, a pressure generating element made of a conductive material, An on-demand ink jet recording head that includes ink that fills the surroundings, displaces a pressure generating element by an applied voltage, and discharges small droplets of ink from a nozzle can be given. FIG. 7 shows a configuration example of such a recording head.

The recording head includes an ink flow path 80 communicating with an ink chamber (not shown), an orifice plate 81 for discharging ink droplets of a desired volume, a vibrating plate 82 for directly applying pressure to the ink, A piezoelectric element 83 joined to the vibration plate 82 and displaced by an electric signal;
3, a base 84 for supporting and fixing the orifice plate 81, the diaphragm 82 and the like.

In FIG. 7, an ink flow path 80 is formed of a photosensitive resin or the like, and an orifice plate 81 has a discharge port 85 formed by electroforming a metal such as stainless steel or nickel or by punching by press working. The plate 82 is formed of a metal film such as stainless steel, nickel and titanium, and a highly elastic resin film, and the piezoelectric element 83 is formed of a dielectric material such as barium titanate and PZT.

In the recording head having the above-described structure, a pulse-like voltage is applied to the piezoelectric element 83 to generate a strain stress, and the energy thereof deforms the diaphragm joined to the piezoelectric element 83, and the ink flow is reduced. The ink in the path 80 is vertically pressed, and an ink droplet (not shown) is discharged from the discharge port 85 of the orifice plate 81 to perform recording. Such a recording head is used by being incorporated in a recording apparatus similar to that shown in FIG. The detailed operation of the recording apparatus may be performed in the same manner as described above.

[0048]

Next, the present invention will be described more specifically with reference to examples. In the following description, “parts” and “%” are based on weight unless otherwise specified. Example 1 (Pigment washing treatment 1) Pigment PR122 (trade name: Host)
aperm Pink E, Hoechst) was charged into a column, and a 5% aqueous solution of 1N hydrochloric acid / ethanol was flowed about 30 times the volume of the filled pigment. Then, a 10% aqueous solution of ethanol was further passed through the washing liquid. The pH was flushed until neutral and the pigment was washed. The flow rate of the cleaning liquid is 10 m
1 / min. It was as follows. Thereafter, the pigment was taken out of the column and dried in a thermostat at 100 ° C.

(Measurement of Phosphorus Concentration in Pigment) About 1 g of the pigment powder before and after the washing was put into a porcelain crucible, respectively.
The lid was lightly covered and incinerated by heating at 700 ° C. for 2 hours in an electric furnace. After cooling, a few drops of concentrated hydrochloric acid were added to dissolve the ash, and then diluted with pure water to 10 ml, and the phosphorus content was quantified in an inductively coupled plasma emission spectrometer. The phosphorus concentration in 1 g of the pigment before washing was 1,500 ppm, whereas that after washing was 40 ppm.

[0050] Mix the above ingredients and heat to 70 ° C in a water bath,
The resin was completely dissolved. To this solution, 15 parts of the pigment subjected to the above-mentioned washing treatment and 5 parts of ethanol were added, and after premixing for 30 minutes, a dispersion treatment was carried out under the following conditions.

Disperser: Sand grinder (made by Igarashi Kikai) Grinding media: zirconium beads 1 mm diameter Filling ratio of crushed media: 60% by volume Grinding time: 3 hours Further, the above dispersion liquid is subjected to centrifugation treatment (20,000 rpm)
m, 20 minutes) to remove coarse particles and obtain a pigment dispersion, which was used for the preparation of the next ink.

[0052] The above components were mixed and stirred for 1 hour to obtain Ink 1 having a pH of 9.8.

(Measurement of Phosphorus Concentration in Ink) The ink prepared as described above was diluted 5-fold with pure water, and the phosphorus content was quantified in an inductively coupled plasma emission spectrometer (ICP). As a result, the phosphorus concentration in the ink was 2 ppm
Met.

Example 2 (Pigment washing treatment 2) Pigment PR122 (trade name: Host)
aperm Pink E, Hoechst) was placed in a beaker, 1N sodium hydroxide / 5% ethanol aqueous solution was added, the mixture was stirred with a magnetic stirrer for 60 minutes, left to stand, the supernatant was discarded, and 1N sodium hydroxide A 5% aqueous ethanol solution was added, and the same operation was repeated 5 times. Next, the washing solution was replaced with a 10% aqueous ethanol solution, and the same operation was repeated until the pH of the supernatant became neutral, thereby washing the pigment. After that, wash the pigment with 10
It was dried in a thermostat at 0 ° C.

(Measurement of Phosphorus Concentration in Pigment) The phosphorus concentration in the pigment used above and the pigment after washing were measured in the same manner as in Example 1.
pm, and 50 ppm after washing.

(Preparation of Pigment Dispersion and Ink) Ink 2 was obtained in the same manner as in Example 1 except that the pigment whose phosphorus content had been removed in the above-mentioned washing treatment 2 was used. The phosphorus concentration in the ink was 2 ppm.

Example 3 (Pigment washing treatment 3) Pigment PR168 (trade name: Host)
aperm Scarlet GO, manufactured by Hoechst) was charged into a column, and a 5% aqueous 1N potassium hydroxide / ethanol solution was flowed about 30 times the volume of the filled pigment, and then a 10% aqueous ethanol solution was passed through the washing liquid. P
The H was allowed to flow until neutral, and the pigment was washed. The flow rate of the washing solution was 10 ml / min. It was as follows. Thereafter, the pigment was taken out of the column, and the washed pigment was dried in a thermostat at 100 ° C.

(Measurement of Phosphorus Concentration in Pigment) The phosphorus concentration in the pigment used above and the pigment after washing were measured in the same manner as in Example 1.
pm, and 50 ppm after washing.

(Preparation of Pigment Dispersion and Ink) Ink 3 was obtained in the same manner as in Example 1, except that the pigment from which phosphorus was removed in the above-mentioned washing treatment 3 was used. The phosphorus concentration in the ink was 2 ppm.

Example 4 (Pigment washing treatment 4) Pigment PR168 (trade name: Host)
aperm Scarlet GO (available from Hoechst) was placed in a funnel of a vacuum filter, and a 10% aqueous isopropyl alcohol solution was flowed about 50 times the weight of the pigment to wash the pigment. Thereafter, the pigment was taken out from the funnel, and the washed pigment was dried in a thermostat at 100 ° C.

(Measurement of Phosphorus Concentration in Pigment) The phosphorus concentration in the pigment used above and the pigment after washing were measured in the same manner as in Example 1.
pm, and 500 ppm after washing.

(Preparation of Pigment Dispersion and Ink) A pigment dispersion was prepared in the same manner as in Example 1 by using the pigment from which phosphorus was removed in the above-mentioned washing treatment 4. An ink was prepared in the same manner as in Example 1 except that the pigment dispersion was changed to 40 parts and the pure water was changed to 32 parts, to obtain an ink 4. The phosphorus concentration in the ink was 30 ppm.

Example 5 (Pigment washing treatment 5) Pigment PY151 (trade name: Host)
aperm Yellow H4G, manufactured by Hoechst) was placed in a column, and a 5% aqueous solution of 0.1N hydrochloric acid, which was 20 times the weight of the pigment, was allowed to flow. And the pigment was washed. The flow rate of the washing solution was 10 ml / m
in. It was as follows. Thereafter, the pigment was taken out of the column, and the washed pigment was dried in a thermostat at 100 ° C.

(Measurement of Phosphorus Concentration in Pigment) When the phosphorus concentration in the pigment used above and the pigment after washing were measured in the same manner as in Example 1, it was 900 ppm before washing.
On the other hand, it was 100 ppm after washing.

(Preparation of Pigment Dispersion Liquid and Ink) Ink 5 was obtained by performing the same treatment as in Example 1 except that the pigment from which phosphorus was removed in the above-mentioned washing treatment 5 was used. The phosphorus concentration in the ink was 5 ppm.

Example 6 (Pigment washing treatment 6) Powder of pigment PB15: 3 (trade name: Liogen Blue L7101F, manufactured by BASF) was placed in a large beaker, and a 10% aqueous solution of ethanol was added to the weight of the pigment. It was poured about 20 times and stirred with a magnetic stirrer for 60 minutes. Thereafter, the contents of the beaker were placed in a centrifuge tube, and centrifuged at 12,000 rpm for 10 minutes using a centrifuge (18PR-52, manufactured by Hitachi). After the treatment, the supernatant was removed, a 10% aqueous solution of ethanol was poured, and the mixture was stirred and centrifuged again under the above conditions to remove the supernatant. Thereafter, the pigment was taken out, and the washed pigment was dried in a thermostat at 100 ° C.

(Measurement of Phosphorus Concentration in Pigment) The phosphorus concentration in the pigment used above and the pigment after washing were measured in the same manner as in Example 1, and 600 ppm before washing.
On the other hand, it was 300 ppm after washing.

(Preparation of Pigment Dispersion Liquid and Ink) Ink 6 was obtained by performing the same treatment as in Example 1 except that the pigment from which phosphorus was removed in the above-mentioned cleaning treatment 6 was used. The phosphorus concentration in the ink was 14 ppm.

Example 7 A pigment dispersion having the following composition was used, except that
The same operation as in Example 1 was performed to obtain Ink 7. (Composition of pigment dispersion) ・ Polyoxyethylene tridecyl ether phosphate ester salt (Phosphanol RS410, Toho Chemical) 5 parts ・ Potassium hydroxide 0.5 part ・ Ion exchange water 70 parts ・ Diethylene glycol 5 parts Organic phosphorus Was used, the concentration of inorganic phosphorus in the ink was measured by the following method.

(Measurement of Inorganic Phosphorus Concentration in Ink) One drop of 50% hydrochloric acid was added to 10 g of pigment ink to coagulate the pigment, filtered using Toyo Filter Paper 5C, and washed with pure water to remove the coagulated substance. The solution was washed until it became neutral. Further, the dispersant in the aggregate was extracted by reflux, decantation, and Soxhlet using tetrahydrofuran, chloroform, or the like, and then dried in a constant temperature bath at 40 ° C. The dried pigment powder was placed in a magnetic crucible, covered lightly, and heated at 700 ° C. for 2 hours in an electric furnace to completely incinerate. After cooling, a few drops of concentrated hydrochloric acid were added dropwise to dissolve the ash, then diluted to 10 ml with pure water, and quantitatively measured for phosphorus in an inductively coupled plasma emission spectrometer (ICP). The inorganic phosphorus concentration in the ink was 2 ppm.

Comparative Example 1 Unwashed pigment PR122 (trade name: Hostaperm)
A comparative ink 1 was obtained by performing the same process as in Example 1 except that powder of E.Pink E (manufactured by Hoechst) was used. The phosphorus concentration in the ink was 68 ppm.

Comparative Example 2 Unwashed pigment PR168 (trade name: Hostaperm)
Comparative ink 2 was obtained in the same manner as in Example 1, except that powder of Scarlet GO (manufactured by Hoechst) was used. The phosphorus concentration in the ink was 54 ppm.

(Evaluation) (1) Ejection Durability The inks prepared in Examples 1 to 7 and Comparative Examples 1 and 2 were each used for a large-capacity bottle of a bubble jet printer BJ-W7000 (manufactured by Canon) and a BC20 (manufactured by Canon). The ink cartridges were filled with the ink cartridges, respectively, and mounted in a bubble jet printer BJ-W7000 (manufactured by Canon Inc.). When a predetermined pattern was printed, stable printing of 200 sheets was possible. With respect to the ejection durability, the following items were evaluated.

(1-1) Measurement of Change in Discharge Amount Change in discharge amount was measured from the number of pulses and the reduced weight of ink when printing the fifth and 200th sheets. A: The change in the weight of the ejection amount is ± 5% or less, and the density of the printed matter on the fifth and 200th sheets is almost equal visually. B: Change in weight of discharge amount exceeds ± 5% and ± 10
5% and 200%
The difference in the density of the printed matter on the sheet is of no concern. C: The change in the weight of the ejection amount exceeds ± 10%, and the difference in density between the fifth and 200th printed matter is clearly visible.

(1-2) Visual evaluation of kogation of heater The ink jet head after printing 200 sheets (in the comparative example, ink was not ejected) was disassembled, and the heater was taken out. After water was dropped and washed, the heater surface was observed with an optical microscope. A: No deposit is observed on the heater surface. B: Slight deposits are observed around the center of the heater surface. C: The entire heater surface is covered with the deposit.

(1-3) Analysis of kogation on heater The ink jet head after printing 200 sheets (in the comparative example, ink was not ejected) was disassembled, and the deposit on the heater was subjected to electron beam microanalysis (EPMA). ), And the phosphorus intensity was measured. The analysis conditions were an acceleration voltage of 15 kV and a beam diameter of 20 microns. If the phosphorus concentration is less than 0.5%, the effect of the kogation on the ejection characteristics is not a problem. A: The ratio of phosphorus to all elements in the deposit on the heater analyzed by characteristic X-ray (Kα) is less than 0.3%. B: The ratio of phosphorus to all elements in the deposit on the heater analyzed by characteristic X-ray (Kα) is 0.3% or more and 0.5% or more.
Is less than. C: The ratio of phosphorus in all the elements in the deposit on the heater analyzed by characteristic X-ray (Kα) is 0.5% or more.

(Evaluation Results) The evaluation results of the discharge durability are shown in Table 1.

[0078]

[Table 1]

From the above results, in the embodiment in which the phosphorus concentration as the inorganic compound in the ink is low, the change in the discharge amount is small, the discharge durability is good, and the carbon kogation that can be easily removed by pure water is obtained. In Example 4 where the kogation was the largest, only a slight amount of adhered substance was observed on the heater surface after cleaning. However, in the comparative example having a high phosphorus concentration, the ink was not ejected, and
A strong kogation that could not be peeled off by washing was confirmed on the entire heater. As a result of analyzing the kogation on the heater before cleaning by EPMA, as the amount of kogation that cannot be removed by cleaning increases, the phosphorus concentration in the kogation increases, and further, the phosphorus concentration in the used ink is high. There was found. In other words, it was found that when the inks of the examples were used, carbon kogation that could be peeled or redispersed due to cavitation was generated, but that phosphorus-derived kogation that would affect ejection was not formed. On the other hand, when the ink of the comparative example was used, not only carbon kogation but also kogation derived from phosphorus were formed in a large amount, and it was found that the ejection characteristics were affected.

The mechanism by which a small amount of phosphorus in the pigment ink promotes kogation on the heater and rapidly reduces the ejection amount can be considered as follows. The inorganic phosphorus compound in the ink is heated by the heater in the nozzle to form a compound with calcium eluted from the ink or a material in contact with the ink such as the nozzle or the tank, and adheres to the heater. Phosphorus and calcium compounds (calcium phosphate, hydroxyapatite, etc.) are very hard and poorly soluble,
Once deposited on the heater without re-decomposition or peeling, the scorched pigment ink that has been peeled off or re-dispersed by cavitation tends to adhere to the heater. As a result, carbon scorch accumulation that did not occur in the absence of kogation due to phosphorus occurs at an accelerated rate,
It is considered that the foaming is hindered, and a rapid decrease in the discharge amount occurs. It is not clear why the charring of small amounts of phosphorus and calcium promotes the charring adhesion, but it is presumed that the charring of phosphorus and calcium causes fine irregularities on the heater, and the charred carbon enters the heater. Is done.

(2) Dischargeability of Ink Cartridge After Long-Term Storage Next, the following methods and standards were used for each of the inks of Examples 1 to 7 for which good results were obtained in the above-mentioned ink discharge durability test. The ejection characteristics after long-term storage were evaluated. (2-1) Measurement of Pigment Concentration in Cartridge The ink was filled in a BC20 (Canon) ink cartridge, the nozzle was fixed upward, and stored in a 60 ° C. constant temperature bath for 2 months. Then, after cooling to room temperature, a hole was made in the lower side of the ink cartridge (where it was downward during storage) and on the side near the nozzle (where it was upward during storage), and 0.5 g of ink was drawn. After diluting with pure water in Examples 1, 2, 3, 4, 5 and 7 in Example 1, and 2000 in Example 6, the absorbance was measured with a spectrophotometer, and λ _max ( Colorant absorption) was measured.

(2-2) Measurement of Change in Discharge Amount The ink was filled in an ink cartridge BC20 (manufactured by Canon), the nozzle was fixed upward, and stored in a 60 ° C. constant temperature bath for 2 months. This ink cartridge is mounted on a bubble jet printer BJC5500 / BJC5500J (manufactured by Canon), and is mounted at 360 dpi × 360 dpi.
When a predetermined pattern is printed at 10 kHz,
100 prints were possible. So the 5th and 10th
The change in the ejection amount was measured from the number of pulses at the time of printing the 0th sheet and the reduced weight of the ink, and evaluated according to the following criteria. A: The change in weight of the ejection amount is ± 5% or less, and the density of the printed matter on the fifth and 100th sheets is almost the same visually. B: The change in the weight of the ejection amount is more than ± 5% and not more than ± 10%, and the difference in density between the fifth printed sheet and the 100th printed sheet is visually insignificant. C: The change in the weight of the discharge amount exceeds ± 10%, and the difference in density between the fifth and 100th printed matter is clearly visible.

Table 2 shows the results of the evaluation of the dischargeability of the ink cartridge after the long-term storage.

[0084]

[Table 2]

From the above measurement of λ _max , it was confirmed that the pigment concentration was distributed in the ink cartridge by storing the ink cartridge for a long period of time. It is suggested that the concentration of phosphorus as a possible inorganic compound is also distributed in the ink cartridge. However, even if such an ink cartridge is used, there is almost no change in the ejection amount except for the fourth embodiment.
Visually, the difference in image density of the printed matter was not noticeable. In other words, it was confirmed that even when an ink cartridge that is considered to have a partial increase in the phosphorus concentration due to long-term storage was used, kogation that would affect the ejection amount and the visual evaluation of printed matter did not occur. .

[0086]

As described above, according to the present invention,
The generation of kogation that adheres firmly to the heater is stably suppressed,
Good ejection characteristics can be maintained, and high-quality images can be stably recorded.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a head of an ink jet recording apparatus.

FIG. 2 is a cross-sectional view of a head of the inkjet recording apparatus.

FIG. 3 is an external perspective view of a head of the inkjet recording apparatus.

FIG. 4 is a perspective view showing an example of an ink jet recording apparatus.

FIG. 5 is a longitudinal sectional view of the ink cartridge.

FIG. 6 is a perspective view showing an example of a recording unit.

FIG. 7 is a schematic diagram showing a configuration of an ink jet recording head using a piezoelectric element.

[Explanation of symbols]

 13: Head 14: Ink groove 15: Heating head 16: Protective film 17-1, 17-2: Aluminum electrode 18: Heating resistor layer 19: Heat storage layer 20: Substrate 21: Ink 22: Discharge orifice (fine hole) 23 : Meniscus 24: Recording droplet 25: Recording material 26: Multi-groove 27: Glass plate 28: Heating head 40: Ink storage part 42: Plug 44: Ink absorber 45: Ink cartridge 51: Supply part 52: Feed roller 53 : Discharge roller 61: blade 62: cap 63: ink absorber 64: discharge recovery section 65: recording head 66: carriage 70: recording unit 71: head section 72: atmosphere communication port 80: ink flow path 81: orifice plate 82: diaphragm 83: piezoelectric element 84: base 85: discharge port

Claims (22)

[Claims] 1. An ink comprising a pigment having a phosphorus concentration of not more than 500 ppm as an inorganic compound contained therein, dispersed in water or a liquid medium comprising water and a water-soluble organic solvent. 2. The ink according to claim 1, wherein the concentration of phosphorus as an inorganic compound in the ink is 30 ppm or less. 3. The ink according to claim 1, further comprising at least one pigment dispersant selected from an alkali-soluble resin and a surfactant. 4. The ink according to claim 1, wherein the ink is an ink jet recording ink. 5. The ink according to claim 4, wherein the ink for ink jet recording is an ink for bubble jet recording. 6. An ink to be ejected by a bubble jet recording method, wherein a pigment having a phosphorus concentration of 500 ppm or less as an inorganic compound is contained in an aqueous medium in a dispersed state, whereby kogation to a heater is reduced. Bubble jet ink characterized in that adhesion is stably reduced. 7. A method for producing an ink, comprising: (i) a step of selecting a pigment having a phosphorus concentration of an inorganic compound of 500 ppm or less; and (ii) an aqueous medium containing the pigment selected in the step (i). A method for producing an ink. 8. A method for producing an ink, comprising: (i) washing a pigment having a phosphorus concentration as an inorganic compound higher than 500 ppm to reduce the phosphorus concentration to 500 ppm or less; and (ii) the step. A process of dispersing the pigment obtained in (i) in an aqueous medium. 9. The method according to claim 7, wherein the ink is an ink jet recording ink. 10. An ink jet recording method, comprising the step of discharging the ink according to claim 4 from an orifice of a recording head according to a recording signal. 11. The ink jet recording method according to claim 10, wherein the ink is ejected by applying mechanical energy to the ink. 12. An ink jet recording method, comprising the step of ejecting the ink according to claim 5 by applying thermal energy from an orifice of a recording head according to a recording signal. 13. An ink jet printer, comprising: an ink storage unit that stores the ink according to claim 1; and a head unit that discharges the ink. Recording unit. 14. The ink jet recording unit according to claim 13, wherein the head section is a head for ejecting the ink by applying thermal energy to the ink. 15. The ink jet recording unit according to claim 13, wherein the head section is a head for ejecting the ink by applying a mechanical energy to the ink. 16. The ink absorber in the ink storage section is made of polyurethane, cellulose, polyvinyl acetate or polyolefin resin.
16. The ink jet recording unit according to any one of items 15 to 15. 17. An ink cartridge, comprising: an ink storage section that stores the ink according to claim 1. Description: 18. The ink cartridge according to claim 17, wherein the ink container has a liquid contact surface formed of polyolefin. 19. An ink jet recording apparatus, comprising: an ink storage section for storing the ink according to claim 1; and a head section for discharging the ink. apparatus. 20. The ink-jet recording apparatus according to claim 19, wherein the head portion is a head for ejecting the ink by applying thermal energy to the ink. 21. The ink jet recording apparatus according to claim 19, wherein the head section is a head for ejecting the ink by applying a mechanical energy to the ink. 22. The ink absorber in the ink containing section is made of polyurethane, cellulose, polyvinyl acetate or polyolefin resin.
22. The inkjet recording apparatus according to any one of 21.