JPH0457859A - Ink and ink jet recording using the same - Google Patents

Abstract

PURPOSE:To obtain an ink which can be delivered stably and gives a recorded image excellent in water, light and marker resistances and having a high density by using, as constituents, carbon black, at most a specified amount of a water- soluble resin, specified water-soluble organic solvents, water, and a specified dye. CONSTITUTION:An ink which contains carbon black, at most 2 wt.% water-soluble resin, water-soluble organic solvents comprising a polyhydric alcohol and/or its alkyl ether and an aliphatic monohydric alcohol, water, and a dye of formula I [wherein M is an alkali metal or (organo)ammonium; R1 and R2 are each CH3, OCH3, OC2H5 or NHCOCH3; R3 to R8 are each H, OH, SO3M, OC2H3 or OC2H5; X is H, COCH3, COC6H5 or a group of formula II, III or IV; R9 and R10 are each H or a group of formula V] (e.g. a dye of formula VI)(preferably in an amount of 0.5-2.0 wt.%). This ink has such advantages that it can be delivered stably even under variable drive conditions or during long-term service and that it gives a recorded image excellent in fastness and having a high density.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an ink particularly suitable for inkjet printers, and more particularly to inkjet recording in which recording is performed by ejecting ink from an orifice of a recording head by the action of thermal energy. Regarding the method.

(Prior art) The inkjet recording method generates less noise during recording, is easily compatible with color printing, and furthermore, by using a highly integrated head, high-resolution recorded images can be obtained at high speed. It has the advantage of

In the inkjet recording method, an ink obtained by dissolving various water-soluble dyes in water or a mixture of water and an organic solvent is used. However, when water-soluble dyes are used, the light resistance of recorded images often becomes a problem because these water-soluble dyes inherently have poor light resistance.

Furthermore, since the dye is water-soluble, water resistance of recorded images often becomes a problem. In other words, if the recorded image is exposed to rain, sweat, or drinking water, the recorded image may blur or
May disappear.

On the other hand, similar problems exist in stationery using dyes such as ballpoint pens, and in order to solve the problems of light resistance and water resistance, various water-based +4 inks for stationery have been proposed. In order to put water-based pigment ink into practical use, studies are being conducted on dispersion stability, prevention of ink assimilation at the pen tip, and prevention of wear on the ball of a ballpoint pen.

For example, JP-A No. 61-246271 discloses water-soluble amine salts, ammonium salts, or An ink composition for writing instruments with improved dispersion stability and drying resistance by using a metal salt is disclosed, and JP-A-62-72774 discloses that by using a polysiloxane, the ejection down phenomenon is reduced. Disclosed is a water-based pigment ink for a ballpoint pen in which the phenomenon of ink running out does not occur.

(The problem that the invention is trying to solve) However,
As mentioned above, when pigment ink using conventional carbon black is used for inkjet recording, the fastness of printed matter is significantly improved compared to that using dye ink. A problem arose in that the density of printed matter, which is one of the characteristics of recording, was inferior to that printed using dye ink.

In addition, in order to increase the print density, it is possible to increase the pigment concentration, but when a pigment ink with a high concentration is used in an inkjet blink, there is a drawback that the ejection stability is significantly impaired.

Furthermore, when using a dispersion system called pigment ink for inkjet recording, preventing solidification at the tip of the head due to long-term storage is an important technical issue, and the composition of the ink is important in designing a reliable pigment ink. This is a great point.

Furthermore, although some conventional pigment inks have excellent ejection properties in a relatively short period of time, ejection becomes unstable if the driving conditions of the print head are changed or continuous ejection is performed for a long period of time. The problem has arisen that the liquid has become stale and eventually stops being discharged.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the problems of the prior art described above, and to provide an ink that can always be ejected stably even when driving conditions vary or when used for a long time, and an inkjet recording method using the same. There is a particular thing.

A further object of the present invention is to provide an ink that provides a recorded image with excellent fastness, particularly water resistance, light resistance, and marker resistance, and which provides a high density of the recorded image.

(Means for solving problems) The above objects are achieved by the present invention as described below.

That is, the present invention contains carbon black, a water-soluble resin, a polyhydric alcohol and/or its alkyl ether, an aliphatic monohydric alcohol, and water, and the amount of the dissolved water-soluble resin is 2% by weight or less. An ink characterized by containing a dye represented by the following general formula (A), and an inkjet that performs recording by applying thermal energy to the ink and ejecting the ink as droplets from micropores. This is a recording method.

(In the above general formula, M represents a cation of an alkali metal, ammonium, or organic ammonium, and R and R2 represent a substituent selected from a methyl group, a methoxy group, an ethoxy group, and an acetylamino group. Show, R
,, R,, R,, R,, R, and R8 represent a substituent selected from a hydrogen atom, a hydroxyl group, a sulfonic acid group, a methoxy group, and an ethoxy group, and X represents a hydrogen atom, an acetyl group, a benzoyl group, - SO□CaHa, represents a hydrogen atom or (:2H,OH, and the sulfonic acid group is a salt of the same cation as M.) (Function) The ink of the present invention can be used in an inkjet printer using thermal energy. It has properties that are particularly suitable for

An inkjet recording method using thermal energy uses the bubbling phenomenon caused by film boiling of ink on a thin film heating resistor as a source of ejection energy, and has been put into practical use with ink using dye.

In this method, it is estimated that the ink layer on the thin film heating resistor reaches a maximum temperature of 200 DEG C. to 300 DEG C. or more, although the time taken for each signal is extremely short, 3 .mu.sec to 12 .mu.sec. Therefore, the thermal stability of ink is an extremely important requirement for imparting ejection stability.

The present inventor investigated the causes of significant problems in ejection when pigmented inks such as those proposed for stationery are used as they are in inkjet recording using thermal energy, and as a result, discovered several factors.

One is that when a pulse is applied to such stationery ink, deposits are formed on the thin film heating resistor due to the action of the heat, and the foaming of the ink is incomplete, resulting in irregular ejection or non-ejection. be.

Furthermore, even if no deposits are generated on the thin film resistor, foaming is incomplete and droplet ejection cannot respond to the applied pulse, resulting in non-ejection.

In other words, in order to eject ink stably from the nozzle tip, the ink must have the ability to foam to a desired volume on a thin film heating resistor, and to repeat foaming and defoaming in a desired amount of time. must be maintained.

However, since conventional inks for stationery do not satisfy these performance requirements, various inconveniences as described above occur when an inkjet recording device is filled with the ink and used for recording.

As a result of intensive research into the performance of a water-based pigment ink that is thermally stable and capable of optimal foaming, the inventors found that the amount of water-soluble resin not adsorbed to the pigment contained in the ink was 2% by weight. % or less, more preferably 1% by weight or less, and by using a polyhydric alcohol and/or its alkyl ether together with an aliphatic monohydric alcohol as a water-soluble organic solvent, it is possible to control the ink's behavior on the thin film heating resistor. It has been found that foaming occurs accurately even under driving conditions, and no deposits are generated on the heating resistor even over a long period of time.

Furthermore, in order to increase the density of recorded images while maintaining stable ejection, they discovered that the above-mentioned specific dyes were suitable and completed the present invention.

Note that the dissolved water-soluble resin as used in the present invention refers to a resin that is dissolved in a liquid medium that is not attached to the pigment in the ink.

(Preferred Embodiments) Next, the present invention will be described in more detail by citing preferred embodiments.

As the carbon black used in the present invention, in addition to those that are commercially available, carbon black surface-treated with a surfactant, a polymeric dispersant, etc., and grafted carbon can also be used.

The content of carbon black varies depending on the structure, but is 3 to 20% by weight, preferably 3 to 1% by weight based on the total weight of the ink.
It is used in a range of 2% by weight.

As the dispersant, water-soluble resins used for pigment dispersion can be used, and such water-soluble resins preferably have an acid value of 5.
A resin of 0 to 300, more preferably 70 to 250 is used.

The bond between the pigment and the water-soluble resin is a hydrophobic bond, so if the acid value of the resin is high (that is, it is too hydrophilic), the resin cannot be adsorbed to the pigment surface as expected, and the unadsorbed resin in the pigment solution On the other hand, the acid value of the resin is low (
In other words, if the resin has low hydrophilicity, it will not dissolve in water.

In addition, the acid value of the resin as used in the present invention refers to the KO that neutralizes the resin.
It is expressed in the amount of H (mg).

Specifically, any resin can be used as long as it is soluble in an aqueous solution containing an amine or base, including natural polymers such as lignin sulfonate and shellac.
Polyacrylic acid, styrene-acrylic acid copolymer, styrene-acrylic acid acrylic acid alkyl ester copolymer, styrene-maleic acid copolymer, styrene-maleic acid-acrylic acid alkyl ester copolymer, styrene-
Methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid half ester copolymer, vinylnaphthalene-acrylic acid copolymer, vinylnaphthalene-maleic acid copolymer, or Examples include anionic polymers such as these salts, sodium salts of β-naphthalenesulfonic acid formalin condensates, and phosphates.

The content of these water-soluble resins varies depending on the type of pigment and water-soluble resin used, but the amount of water-soluble resin that is not adsorbed to the pigment in the ink is 2% by weight or less, preferably 1% by weight.
It is sufficient if the amount is less than % by weight, and the ratio of pigment to water-soluble resin is 3=2 to 10:1 by weight. Preferably 3:1
The amount is preferably from 10:1 to 10:1, more preferably from 10:3 to 10:1.

Polyhydric alcohols and/or alkyl ethers thereof used in the present invention include polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1.2.6-hexane Alkylene glycols in which the alkylene group contains 2 to 6 carbon atoms such as triol, thiodiglycol, hexylene glycol, diethylene glycol; glycerin; ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl)
Examples include lower alkyl ethers of polyhydric alcohols such as ethers.

The content of these polyhydric alcohols and/or their alkyl ethers is 10 to 5oMIk%, more preferably 20
~40% by weight, and if the content is less than 10% by weight, it is not sufficient to prevent clogging at the nozzle tip (
, 50% by weight, the print quality of the printed matter will deteriorate.

Examples of aliphatic monohydric alcohols include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, 5ec
-C1-C4 alkyl alcohols such as -butyl alcohol, tert-butyl alcohol, and isobutyl alcohol.

Among these, ethyl alcohol is particularly preferred since it greatly improves the ejection stability of the ink.

The content of aliphatic monohydric alcohol ranges from 3 to 15% by weight, preferably from 3 to 10% by weight, with a content of 3% by weight
If it is less than 15% by weight, stable ejection cannot always be obtained against changes in printer driving conditions, and if it exceeds 15% by weight, the quality of the printed matter tends to be impaired.

The water content is 10 to 60% by weight, more preferably 10 to 60% by weight.
It is in the range of 50% by weight.

The dye represented by the general formula (A) used in the present invention is a dye with good coloring properties, and preferred specific examples are shown below.

(M=NH3C2H,0H) The above dyes can be produced according to the synthesis of known azo dyes. Examples of syntheses of the dyes (1) and (2) above will be given as examples.

1-Amino-2-ethoxynaphthalene-6-sulfonic acid is diazotized by a conventional method and coupled with K acid at pH 4 to 5. 1-Naphthylamine-7-sulfonic acid is diazotized by a conventional method, coupled with dimethoxyaniline, and further diazotized with sodium nitrite. Add this diazotized solution to the above reaction solution, and adjust the pH to 8 to 9 and the temperature to 5 to 10°C.
Stir for 4 hours. The process of adding lithium chloride to salt out the dye and filtering it out is repeated several times to remove impurities and at the same time convert the counter ion of the dye into a lithium ion. The dye of (1) was obtained by desalting and purification using an ultrafiltration device (manufactured by Sartorius).

1-Naphthylamine-6-sulfonic acid is diazotized by a conventional method and coupled with H acid at pH 4 to 5. Separately, H acid is diazotized by a conventional method and coupled with 5-methyl-0-anisidine to further diazotize the product.

Add this diazotized solution to the above reaction solution and adjust the pH to 8-9 under water cooling.
Stir for 3 hours. Salt is added to salt out the dye, and an ultrafiltration device (manufactured by Sartorius) is used to desalt and purify. The sulfonic acid group in the dye molecule was converted into a free acid form using a strongly acidic ion exchange resin, and the dye of (11) was obtained by neutralizing with monoethanolamine.

In the above manufacturing method, the SO and H groups in each compound may be an alkali metal salt, an ammonium salt, or an organic amine salt depending on the conditions.

-8 The content of the compound of formula (A) in the ink is 0.5 to
2.0% by weight is preferable; if it is less than 0.5% by weight, it will not be effective as a coloring agent, and if it exceeds 2.0% by weight, it will cause a decrease in the fastness of the printed matter, especially water resistance and light resistance.

The main components constituting the ink of the present invention are as described above, and in addition, water-soluble organic solvents, surfactants,
A pH adjuster, preservative, etc. may also be used.

Usable water-soluble organic solvents include amides such as dimethylformamide and dimethylacetamide; acetone;
Ketones or keto alcohols such as diacetone alcohol; ethers such as tetrahydrofuran and dioxane; N
-Methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, and the like.

Examples of surfactants include aliphatic salts, higher alcohol sulfate ester salts, liquid fatty oil sulfate ester salts, anionic surfactants such as alkylaryl sulfonates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, There are nonionic surfactants such as polyoxyethylene sorbitan alkyl esters, and one or more of these can be selected and used as appropriate.The amount used varies depending on the dispersant, but is 0.0% based on the total amount of ink.
1 to 5% by weight is desirable. At this time, it is preferable to determine the amount of surfactant added so that the surface tension of the ink is 35 dyne/cm or more. This is because if the surface tension of the ink is smaller than this value, in a recording method like the present invention, printing may occur due to wetting of the nozzle tip (
This is because undesirable situations such as deviation of the landing point of ink droplets on the recording paper may occur.

Examples of pH adjusting agents include various organic amines such as jetanolamine and triethanolamine, inorganic alkaline agents such as alkali metal hydroxides such as sodium hydroxide, lithium hydroxide, and potassium hydroxide, and organic acids. and mineral acids.

The method for preparing the ink of the present invention is to first add a pigment to an aqueous solution containing at least a dispersion resin, an amine or a base, and water, stir it, and then disperse it using the dispersion means described below. Perform centrifugation to obtain the desired dispersion. Next, a solution containing the above-mentioned components and completely dissolving the dye is added to this dispersion and stirred to form an ink.

In particular, in order to reduce the amount of unadsorbed resin to 2% by weight or less, in the preparation method, it is necessary to completely dissolve the resin in advance by stirring an aqueous solution containing the resin, amine or base, and water at 60 ° C. or higher for 30 minutes or more. is necessary.

Further, it is necessary to add the amount of amine or base that dissolves the resin at least 1.2 times the amount of amine or base calculated from the acid value of the resin.

The amount of amine or base is determined by the following formula.

Amount of amine or base (g)= Furthermore, it is also necessary to carry out premixing for at least 30 minutes before dispersing the aqueous solution containing the pigment.

This premixing operation improves the wettability of the pigment surface and promotes adsorption of the resin onto the pigment surface.

The amines added to the dispersion include monoethanolamine, jetanolamine, triethanolamine,
Organic amines such as aminomethylpropertool and ammonia are preferred.

Further, as the base added to the dispersion liquid, a non-contact alkali agent such as an alkali metal hydroxide such as sodium hydroxide, lithium hydroxide, potassium hydroxide, etc. is preferable.

On the other hand, the dispersing machine used in the present invention may be any commonly used dispersing machine, and includes, for example, a ball mill, a roll mill, a sand mill, and the like.

Among them, high-speed star [・D sand mills are preferred, and examples include super mills, sand grinder bead mills, agitator mills, grain mills, guino mills, burr mills, and cobol mills (all trade names).

In the present invention, methods for obtaining a pigment having a desired particle size distribution include reducing the size of the grinding media of the dispersion machine, increasing the filling rate of the grinding media, lengthening the processing time, and slowing down the discharge speed. Methods such as pulverization and classification using a filter or centrifuge are used. Or
Examples include combinations thereof.

In addition, as a method for measuring the amount of unadsorbed resin according to the present invention, the pigment component and the resin component adsorbed to the pigment are precipitated using an ultracentrifuge, and the amount of residual resin contained in this supernatant liquid is determined. TOC (Total OrganicC:arbon
, total organic carbon meter), gravimetric method (evaporate the supernatant to dryness,
A method for measuring the amount of resin) is preferably used.

The ink of the present invention is particularly suitable for use in an inkjet recording method in which recording is performed by ejecting droplets under the action of thermal energy, but it goes without saying that it can also be used for general writing instruments.

Apparatuses suitable for performing recording using the ink of the present invention include an apparatus that applies thermal energy corresponding to a recording signal to the ink in the chamber of a recording head, and generates droplets using the thermal energy.

Examples of the head configuration, which is the main part, are shown in Figures 1-a and 1-b.
As shown in FIG.

The head 13 is made by bonding a glass, ceramic, or plastic plate, etc., having grooves 14 through which ink passes, and a heat-generating head 15 (the head is shown in the figure, but is not limited thereto) used for thermal recording. It can be obtained by

The heat generating head 15 has a protective film 1 formed of silicon oxide or the like.
6. It consists of aluminum electrodes 17-1, 17-2, a heating resistor layer 18 made of nichrome or the like, a heat storage layer 19, and a substrate 20 with good heat dissipation properties such as alumina.

The ink 21 has reached a discharge orifice (micropore) 22, and a meniscus 23 is formed by the pressure P.

Now, when an electric signal is applied to the electrodes 17-1 and 17-2, the area indicated by n of the heating head 15 suddenly generates heat, bubbles are generated in the ink 21 in contact with this area, and the pressure causes a meniscus. 23 protrudes, the ink 21 is ejected, becomes a recording droplet 24 from the orifice 22, and flies toward the recording material 25. FIG. 2 shows an external view of a multi-head in which two heads like those shown in FIG. 1-a are arranged. The multi-head is manufactured by closely adhering a glass plate 27 having multi-grooves 26 and a heating head 28 similar to that explained in FIG. 1-a.

Note that FIG. 1-a is a sectional view of the head 13 along the ink flow path, and FIG. 1-b is a cross-sectional view taken along line A-B in FIG. 1-a.

FIG. 3 shows an example of an ink jet recording apparatus incorporating such a head.

In FIG. 3, 61 is a blade as a wiping member, one end of which is held by a blade holding member and becomes a fixed end, forming a cantilever shape. The blade 61 is disposed adjacent to the recording area of the recording head, and in this example, is held in a protruding form in the movement path of the recording head. A cap 62 is disposed at a home position adjacent to the blade 61, and is configured to move in a direction perpendicular to the moving direction of the recording head and come into contact with the ejection port surface to perform capping. Furthermore, 63 is an ink absorber provided adjacent to the blade 61;
Like the blade 61, it is held in a protruding form in the movement path of the recording head. The blade 61 and cap 62
The absorber 63 constitutes an ejection recovery section 64, and the blade 61 and the absorber 63 remove moisture, dust, etc. from the ink ejection orifice surface.

Reference numeral 65 is a recording head that has an ejection energy generating means and performs recording by ejecting ink onto a recording material facing the ejection orifice surface on which ejection ports are arranged, and 66 is a recording head that mounts the print head 65 and moves the print head 65. It is a carriage for carrying out. The carriage 66 is slidably engaged with a guide shaft 67, and a portion of the carriage 66 is connected to a belt 6 driven by a motor 68.
9 (not shown). As a result, carriage 6
6 can be moved along the guide shaft 67, and the recording head 65 can move the recording area and its adjacent area.

Reference numeral 51 is a paper feeder for inserting recording material, and 52 is a paper feed roller driven by a motor (not shown). With these configurations, the recording material is fed to a position facing the ejection opening surface of the recording head, and as recording progresses, the recording material is discharged to a paper discharge section provided with a paper discharge roller 53.

In the above configuration, when the recording head 65 returns to the home position after recording is completed, the cap 62 of the head recovery section 64
is retracted from the moving path of the recording head 65, but the blade 61 protrudes into the moving path. As a result, the ejection port surface of the recording head 65 is wiped. Note that when the cap 62 contacts the ejection surface of the recording head 65 to perform capping, 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 in the same position as the wiping position described above. As a result,
During this movement as well, the ejection orifice surface of the recording head 65 is wiped.

The above-mentioned movement of the print head to the home position is not limited to the end of printing or recovery of ejection, but also the movement of the print head to the home position adjacent to the print area at predetermined intervals while the print head moves across the print area for printing. However, along with this movement, the above-mentioned wiping is performed.

FIG. 4 is a diagram showing an example of an ink cartridge containing ink supplied to the head via an ink supply tube. Here, 40 is an ink bag containing supply ink, and a rubber stopper 42 is provided at the tip of the ink bag. By inserting a needle (not shown) into this plug 42,
The ink in the ink bag 40 can be supplied to the head. 44 is an ink absorber that receives waste ink.

The inkjet recording device used in the present invention includes:
It can be suitably used not only in the case where the head and ink cartridge are separate bodies as described above, but also in one in which they are integrated as shown in FIG.

In FIG. 5, 70 is an inkjet cartridge, which houses an ink absorber impregnated with ink. It is configured to be discharged as

Reference numeral 72 denotes an atmosphere communication port for communicating the inside of the cartridge with the atmosphere.

This inkjet cartridge 70 is used in place of the recording head shown in FIG. 3, and is detachable from the carriage 66.

(Example) Next, the present invention will be explained in more detail by giving examples and comparative examples. It should be noted that the terms in the text or % are based on weight unless otherwise specified.

Example 1 (Preparation of pigment dispersion) Styrene-maleic acid-methyl methacrylate copolymer (
Acid value 155, average molecular weight 13000) 5 parts monoethanolamine 2 parts ion exchange water 63 parts ethylene glycol 5 parts The above components were mixed and heated to 70°C in a water bath to completely dissolve the resin component. At this time, if the concentration of the resin to be dissolved is low, it may not be completely dissolved, so when dissolving the resin, a high concentration solution may be prepared in advance and diluted to prepare the desired resin solution. Carbon black (MCF-88,
After adding 20 parts of Mitsubishi Kasei ■ and 5 parts of ethanol and performing premixing for 30 minutes, dispersion treatment was performed under the following conditions.

Dispersion machine: Burl mill (manufactured by Ashizawa ■) Grinding media: Glass beads (0.8-1.2 mm diameter) Grinding media filling rate: 50% (volume) Discharge speed: 10
0mρ/min.

Furthermore, centrifugation treatment (1200 rpm, 15 minutes) was performed to remove coarse particles and obtain a dispersion liquid.

(Preparation of ink) Specific example of 40 parts of the above dispersion (
2) Dye 1.5 parts glycerin
5 parts ethylene glycol
3 parts ethanol
5 parts diethylene glycol 10 parts ion-exchanged water 35.5 parts Of the above ingredients, remove the dispersion (mix the ingredients and stir. After the dye is completely dissolved, add the prescribed amount of the dispersion and stir for 1 hour. The ink of the present invention was obtained.

Example 2 With the composition of Example 1, the dye of Example (2) was replaced with the dye of Example (6), and dispersion and centrifugation were performed under the conditions of Example 1 to obtain a black ink of the present invention.

Example 3 (Preparation of pigment dispersion) a-methylstyrene-styrene-acrylic acid copolymer (
Acid value 195, average molecular weight 17,000) 4 parts Aminomethylpropanol 2 parts Ion exchange water 65.5 parts Diethylene glycol 5 parts Nikkor BL-9EX
(manufactured by Nikko Chemicals ■) 0.5 parts The above ingredients were mixed and heated to 70°C in a water bath.
Completely dissolve the resin. To this solution were added 16 parts of carbon black (MA-100, Mitsubishi Kasei ■g) and 7 parts of ethanol, and after premixing for 30 minutes, dispersion treatment was performed under the following conditions.

Dispersion machine: Sand grinder (manufactured by Igarashi Kikai ■) Grinding media: Zirconium beads (1 mm diameter) Filling rate of grinding media: 50% (volume) Grinding time: 5 hours Further centrifugation treatment (1200 Orpm, 20 minutes) is performed to coarsely The particles were removed to prepare a dispersion.

(Preparation of ink) Specific example of 50 parts of the above dispersion (
4) Dye 1.5 parts glycerin
5-part diethylene glycol
7.5 parts ethanol
1.5 parts polyethylene glycol (PEG300) 5 parts ion-exchanged water 29.5 parts The above components except for the dispersion were mixed.

Stir. After the dye was completely dissolved, a predetermined amount of the dispersion was added and stirred for 1 hour to obtain the ink of the present invention.

Example 4 (Preparation of pigment dispersion) Styrene-maleic acid-methyl methacrylate copolymer (
Acid value 165, average molecular weight 8200) 7 parts monoethanolamine 3 parts ion-exchanged water 60 parts ethylene glycol 5 parts The above components were mixed and heated to 70°C in a water bath to completely dissolve the resin component. At this time, if the concentration of the resin to be dissolved is low, it may not be completely dissolved, so when dissolving the resin, a high concentration solution may be prepared in advance and diluted to prepare the desired resin solution. Carbon black (MCF-”
88, manufactured by Mitsubishi Kasei ■) and 5 parts of ethanol,
After premixing for 30 minutes, dispersion treatment was performed under the following conditions.

Dispersion machine: Sand grinder (manufactured by Igarashi Kikai ■) Grinding media: Zirconium beads (2 mm diameter) Filling rate of grinding media: 40% (volume) Grinding time: 3 hours Further centrifugation treatment (1200 Orpm, 20 minutes) is performed to coarsely The particles were removed to prepare a dispersion.

(Preparation of ink) Specific example of 40 parts of the above dispersion (
2) Dye 1.5 parts diethylene glycol 12.5 parts ethanol
1. 5 parts polyethylene glycol (PE
G300) 5 parts ion exchange water 39
．． 5 parts Among the above components, the components except the dispersion are mixed and stirred. After the dye was completely dissolved, a predetermined amount of the dispersion was added and stirred for 1 hour to obtain the ink of the present invention.

Example 5 (Preparation of pigment dispersion) Styrene-acrylic acid-methyl methacrylate copolymer (
Acid value: 180, average molecular weight: 10,000) 6 parts monoethanolamine 2 parts ion-exchanged water 64 parts ethylene glycol 5 parts The above ingredients are mixed and heated to 70°C in a water bath to completely dissolve the resin component. At this time, if the concentration of the resin to be dissolved is low, it may not be completely dissolved, so when dissolving the resin, a high concentration solution may be prepared in advance and diluted to prepare the desired resin solution. Add carbon black (MCF-88) to this solution.
, manufactured by Mitsubishi Kasei ■), 5 parts of ethanol were added, and 30
After premixing for a minute, dispersion treatment was performed under the following conditions.

Dispersion machine: Sand grinder (manufactured by Igarashi Kikai ■) Grinding media: Glass beads (1 mm diameter) Filling rate of grinding media: 50% (volume) Grinding time: 3 hours Further centrifugation treatment (1200 Orpm, 20 minutes) is performed to coarsely grind The particles were removed to prepare a dispersion.

(Preparation of ink) Specific example of 50 parts of the above dispersion (
1) Dye 1.5 parts diethylene glycol 12.5 parts ethanol
1.5 parts polyethylene glycol (PE6
300) 5 parts ion exchange water 29.
5 parts Among the above components, the components except the dispersion are mixed and stirred. After the dye was completely dissolved, a predetermined amount of the dispersion was added and stirred for 1 hour to obtain the ink of the present invention.

Example 6 (Preparation of pigment dispersion) Styrene-acrylic acid-butyl methacrylate copolymer (
Acid value 179, average molecular weight 18000) 2 parts monoethanolamine 2 parts ion-exchanged water 70 parts ethylene glycol 5 parts The above components were mixed and heated to 70°C in a water bath to completely dissolve the resin component. At this time, if the concentration of the resin to be dissolved is low, it may not be completely dissolved, so when dissolving the resin, a high concentration solution may be prepared in advance and diluted to prepare the desired resin solution. Add carbon black (MCF-88) to this solution.
, manufactured by Mitsubishi Kasei ■) and 5 parts of ethanol were added, and 30
After premixing for a minute, dispersion treatment was performed under the following conditions.

Dispersing machine: Sand grinder (manufactured by Igarashi Kikai ■) Grinding media: Zirconium beads (1 mm diameter) Filling rate of grinding media: 50% (volume) Grinding time = 5 hours Further centrifugation treatment (1200 Orpm, 20 minutes) was performed to coarsely The particles were removed to prepare a dispersion.

(Preparation of ink) Specific example of 30 parts of the above dispersion (
3) Dye 1.5 parts glycerin
5-part diethylene glycol
7.5 parts isopropyl alcohol 1
．． 5 parts polyethylene glycol (PEG300) 5 parts ion-exchanged water 29.5 parts The above components except for the dispersion are mixed and stirred. After the dye was completely dissolved, a predetermined amount of the dispersion was added and stirred for 1 hour to obtain the ink of the present invention.

Comparative Example 1 A black ink for comparison was obtained by removing the dye from the composition of Example 1 above, and further increasing the concentration of carbon black to 12 parts and carrying out a dispersion treatment.

Comparative Example 2 A comparative black ink was obtained by changing the dye to Direct Black 19 in the composition of Example 2 and carrying out a dispersion treatment.

Comparative Example 3 A comparative black ink was obtained by carrying out a dispersion treatment using the composition of Example 1 but excluding ethanol.

Using the inks of the above Examples and Comparative Examples, the following study was carried out using an on-demand type multi-head recording device (Canoward α-50 manufactured by Canon Inc.) that ejects ink by applying thermal energy. went. The results are shown in Table 1 below.

T1; Fastness of printed matter (light resistance) Print samples made using the above ink were measured using a xenon fade meter (black panel 63°C, humidity 75%).
for 100 hours, and the change in chromaticity (color difference) before and after treatment (color difference) is measured by the distance of 11 fl.

(Water resistance) The printed sample is immersed in tap water for 5 minutes, and the change in optical density of the printed matter before and after treatment is measured.

(Marking resistance) Apply a commercially available marking pen (highlighter) over the printed sample.
to evaluate the degree of contamination of the printed matter.

○: There is no stain such as tailing on the dark side of the seal.

×: Severe trailing on the printed surface and severe contamination of the printed matter.

T2; Optical density of printed matter The printed matter was measured using a Macbeth densitometer (RD918).

T3: Clogged when reprinting after stopping printing After filling the printer with the specified ink and printing alphanumeric characters continuously for 10 minutes, printing was stopped and the printer was left for 10 minutes without a cap, etc. After that, alphanumeric characters were printed again and judged based on the presence or absence of defects such as faded characters or missing characters (20 copies were left at 5°C and 50 copies were left at 10% RH).

○: 1: No defective parts from the characters.

Δ: 1: Part of the letters are faded or missing.

×: The first character cannot be printed at all.

T4: Recovery from clogging when reprinting after a long printing stop After filling the printer with the specified ink and printing alphanumeric characters continuously for 10 minutes, stop printing and leave it without a cap for 7 days. After that, the nozzle clogging recovery operation was performed, and the number of recovery operations until normal printing without blurring or missing characters was possible was determined (60℃, 10±5
%RH).

○: Normal printing is possible after 1 to 5 recovery operations.

△: Normal printing is possible after 6 to 9 recovery operations.

x: Normal printing is possible after 11 or more recovery operations.

T: Discharge stability Continuous discharging was performed at 5° C. and 40° C., and the time at which non-discharging occurred was measured.

To: The obtained ink was centrifuged at 5+5000 rpm for 5 hours using an ultra-high-speed refrigerated centrifuge (manufactured by Beckman) to precipitate the pigment and the resin adsorbed on the pigment, and then a certain amount of the supernatant was collected. , dry and solidify in a vacuum dryer (60°C, 24 hours). The percentage of this resin amount to the charged ink is calculated and determined as the residual resin concentration.

The evaluation results are shown in Table 1 below. Regarding the evaluation in the table,
Regarding the light resistance of T1, the results of each color difference are described, regarding the water resistance, the dye residual rate calculated from the density of the printed matter before and after treatment, and for T2, the reflection density of the printed matter is described.

(Margin below) (Effects of the Invention) As explained above, when the ink of the present invention is applied to an inkjet printer, it does not cause ink assimilation at the tip of the head even if it is left for a long time. Not only is it excellent in robustness, but it also has the advantage of being highly reliable, with high density prints, and stable ejection at all times even when driving conditions vary or long-term use.

[Brief explanation of drawings]

1-a and 1-b are a vertical cross-sectional view and a cross-sectional view of a head section of an inkjet recording apparatus. FIG. 2 is an external perspective view of a multi-head head shown in FIG. 1. FIG. 3 is a perspective view showing an example of an inkjet recording apparatus. FIG. 4 is a longitudinal sectional view of the ink cartridge. Figure 5 is a perspective view of the inkjet cartridge (paper used for printing: Xerox 4024 paper. Tg: 5°C in the upper row)
, lower row 40°C). 61: Wiping member 62: Cap 63: Ink absorber 64: Ejection recovery section 65: Recording head 66: Carriage Fig. 1-a Fig. 2 Fig. 4 Fig. 5

Claims (11)

[Claims] (1) An ink containing carbon black, a water-soluble resin, a polyhydric alcohol and/or its alkyl ether, an aliphatic monohydric alcohol, and water, in which the amount of dissolved water-soluble resin is 2% by weight or less. An ink characterized by containing a dye represented by the following general formula (A). ▲There are mathematical formulas, chemical formulas, tables, etc.▼(A) (In the above general formula, M represents a cation of an alkali metal, ammonium, or organic ammonium, and R_1 and R_2 represent a methyl group, a methoxy group, or an ethoxy group. R_3, R_4, R_5, R_6, R_7 and R_8
represents a substituent selected from a hydrogen atom, a hydroxyl group, a sulfonic acid group, a methoxy group, and an ethoxy group;
There are tables, etc. ▼, R_9 and R_1_0 represent hydrogen atoms or C_2H_4OH, and the sulfonic acid group is M
It is a salt of the same cation as . ) (2) The ink according to claim 1, wherein the dye content is in the range of 0.5 to 2.0% by weight. (3) The ink according to claim 1, wherein the aliphatic monohydric alcohol is ethyl alcohol. (4) Content of aliphatic monohydric alcohol is 3 to 15% by weight
The ink according to claim 1, which is within the range of . (5) The ink according to claim 1, wherein the content of the polyhydric alcohol and/or its alkyl ether is in the range of 10 to 50% by weight. (6) In an inkjet recording method in which recording is performed by applying thermal energy to ink and ejecting the ink as droplets from micropores, the ink is carbon black, a water-soluble resin, a polyhydric alcohol, and/or an alkyl ether thereof. contains an aliphatic monohydric alcohol and water, the amount of dissolved water-soluble resin is 2% by weight or less, and is characterized by containing a dye represented by the following general formula (A). Inkjet recording method. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(A) (In the above general formula, M represents a cation of an alkali metal, ammonium, or organic ammonium, and R_1 and R_2 represent a methyl group, a methoxy group, or an ethoxy group. and acetylamino group, R_2, R_4, R_5, R_6, R_7 and R_8
represents a substituent selected from a hydrogen atom, a hydroxyl group, a sulfonic acid group, a methoxy group, and an ethoxy group;
There are tables, etc. ▼, R_9 and R_1_0 represent hydrogen atoms or C_2H_4OH, and the sulfonic acid group is M
It is a salt of the same cation as . ) (7) The inkjet recording method according to claim 6, wherein the recording method is an on-demand type recording method. (8) The inkjet recording method according to claim 6, wherein the content of the dye is in the range of 0.5 to 2.0% by weight. (9) The inkjet recording method according to claim 6, wherein the aliphatic monohydric alcohol is ethyl alcohol. (10) The inkjet recording method according to claim 6, wherein the content of the aliphatic monohydric alcohol is in the range of 3 to 15% by weight. (11) The inkjet recording method according to claim 6, wherein the content of the polyhydric alcohol and/or its alkyl ether is in the range of 10 to 50% by weight.