JP2675900B2 - Ink and ink jet recording method using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ink particularly suitable for an ink jet printer, and further ejects ink droplets from an orifice of a recording head by the action of thermal energy to cause non-coating. The present invention relates to an ink jet recording method for recording on paper, so-called plain paper.

[Conventional technology]

The ink jet recording method has an advantage that a high-resolution recorded image can be obtained at a high speed by using a highly integrated head with little noise during recording.

In such an ink jet recording method, as an ink, one obtained by dissolving various water-soluble dyes in water or a mixed liquid of water and an organic solvent is used.

However, when a water-soluble dye is used, these water-soluble dyes are originally inferior in light resistance, so that the light resistance of a recorded image often becomes a problem.

Further, since the ink is water-soluble, the water resistance of the recorded image often becomes a problem. That is, rain on the recorded image,
If sweat or water for eating or drinking is applied, the recorded image may be blurred or disappear.

On the other hand, stationery using a dye such as a ballpoint pen has the same problem, and various aqueous pigment inks for stationery have been proposed to solve the problems of light fastness and water resistance. As practical examples of water-based pigment inks, dispersion stability, prevention of ink solidification at the pen tip, and prevention of abrasion of balls of ball-point pens are examined as examples. JP-A-58-80368 and JP-A-61-200182 JP-A-61-247774, JP-A-61-272278, JP-A-62-568, JP-A-62.
-101671, 101672, JP-A-1-249869, 1-3017
No. 60 bulletin etc. can be mentioned. Recently, ballpoint pens and markers using water-based pigment ink have come on the market as products.

[Problems to be solved by the invention]

However, when the conventional water-based pigment ink for stationery is used in an ink jet recording apparatus of a type in which ink droplets are ejected from the orifice of the recording head by the action of thermal energy, and the recording is performed by flying, it causes a significant obstacle to ejection stability, There was a drawback that printing defects occurred. In particular, when a conventional pigment ink is used when recording is performed by applying thermal energy and ejecting droplets, when heat is applied to the ink, a pulse is applied to the ink to form a deposit on the thin film resistor. There is a case in which non-ejection occurs because the foaming is incomplete and the ejection of the droplet cannot respond to the applied pulse. That is, in order to stably eject the ink from the tip of the nozzle, the ink has the ability to foam in a desired volume on the thin film resistor, and further, it is possible to repeat foaming and defoaming at a desired time. However, since the conventional stationery inks do not satisfy these performances, the above-mentioned various inconveniences occur when the ink jet recording apparatus is filled and recording is performed.

Further, as described above, when a pigment ink using a carbon black as proposed has been used for ink jet recording, the robustness of the printed matter is remarkably improved as compared with that using the dye ink. As a result of the subsequent research, the density of the printed matter, which is one of the characteristics of ink jet recording, is inferior to that printed using dye ink. Further, in order to increase the printing density, it is possible to increase the pigment concentration, but when a high-concentration pigment ink is used in an ink jet printer, there is a drawback in that ejection stability is significantly impaired.

Generally, the printing ink can be used even if it has a very high density as compared with the ink jet recording apparatus used in the present invention, so that the printing density can be relatively easily increased. A high density can also be obtained by increasing the thickness of the ink layer to be applied, but when performing ink jet recording, especially high density recording, the nozzle size becomes very small and the amount of ejected ink is limited. To be done. Further, as described above, if the pigment concentration in the ink is increased, an undesirable situation occurs in which a precipitate is generated during long-term storage and the ink is solidified by drying at the nozzle tip to cause ejection failure.

Furthermore, among the conventional water-based pigment inks, although the ejection property is excellent in a relatively short time, the ejection becomes unstable when the driving conditions of the recording head are changed or when the continuous ejection is performed for a long time, Finally, there is a problem that ejection is stopped.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and provide an ink having a high density of a printed matter when printed on a non-coated paper. Further, the object of the present invention is to
It is an object of the present invention to provide an ink that is capable of performing stable ejection at all times even when the driving conditions change and used for a long time, and that has excellent long-term storage stability.

A further object of the present invention is to provide an ink jet recording method capable of obtaining stable and high-speed recording at all times and obtaining a printed matter excellent in fastness such as water resistance and light resistance.

[Means and actions for solving the problems]

 The above object is achieved by the present invention described below.

That is, the present invention is characterized in that the BET specific surface area in the aqueous medium is 150 m ² / g or more neutral or basic carbon black and a water-soluble resin having a weight average molecular weight in the range of 3000 to 7000. It is ink.

The present invention also has a weight average molecular weight of 3000 to 7000 in an aqueous medium.
An ink characterized by containing a neutral or basic carbon black having a BET specific surface area of 150 m ² / g or more adsorbed on the surface of a water-soluble resin within the range.

Furthermore, the present invention is an ink jet recording method characterized in that the ink is ejected as droplets from the fine holes by applying heat energy corresponding to a recording signal to the above ink for recording.

 Hereinafter, the present invention will be described in detail.

The present inventors have diligently studied a method of increasing the density of a printed matter by ink jet recording in an aqueous pigment ink using carbon black, and in particular, 1) as a carbon black, a BET specific surface area of 150 m ² / g or more,
Preferably, a neutral or basic carbon black of 300 m ² / g or less is used. 2) A water-soluble resin contained as a dispersant for the carbon black has a weight average molecular weight of 3000 to 7000, preferably an acid value of It was found that an ink having a high density of printed matter and good dispersion stability can be prepared by using 100 or more, and the present invention was completed.

That is, in particular, the above-mentioned carbon black is dispersed by using a dispersion resin in which the weight average molecular weight of the water-soluble resin used as the dispersion resin is 7,000 or less, and when the ink is adjusted, it is equal to or more than the case where the dye ink is used. That is, a printed matter having a higher printing density than that can be obtained.

Generally, the specific surface area of the carbon black is an index indicating the blackness of the carbon black. However, in fact, when an ink is created by dispersing a pigment with a high specific surface area to increase the print density and ejected with an ink jet recording device, the ejection state changes markedly depending on the preparation conditions of the dispersion liquid, and it is not always the surface area. It was found that a printed matter with a high print density was not obtained in proportion to.

Therefore, the present inventors have found that there is some correlation between the discharge stability and the combination of the carbon black and the dispersion resin, and as a result of diligent studies, the average molecular weight of the dispersant was found to be
It was found that when ink is prepared by dispersing using a resin of 3000 to 7000, good printing characteristics can be obtained under a wide range of driving conditions, and the present invention has been completed. Further, even if a dispersion resin capable of achieving such stable ejection is used, a desired print density cannot be obtained without the blackness of the carbon black itself.

Then, the inventors of the present invention have made earnest studies and found that the preferable range of the specific surface area of the carbon black required to obtain a preferable print density is 150 m ² / g or more. However, when dispersion is carried out with the composition of the pigment dispersion liquid used in the present invention, the dispersion becomes unstable when the specific surface area exceeds 300 m ² / g, and there is a tendency that a remarkable thickening occurs at the time of dispersion. It is considered that this is because the amount of the dispersing resin used in the present invention is relatively small with respect to the carbon black for the reason described below, and thus the pigment having a specific surface area of more than 300 m ² / g cannot be dispersed.

The reason why the neutral or basic carbon black is preferable in the present invention is that the pH of the dispersion liquid is lower than that of the neutral or basic carbon in the acidic carbon, and it is difficult to obtain a stable dispersion for a long period of time. Is mentioned.

The amount of carbon black used in the present invention is preferably 3 to 20% by weight, and more preferably 3 to 12% by weight.

As the carbon black used in the present invention, any carbon black can be used as long as it satisfies the above performance, but # 23
00, # 950, # 900, # 850, MCF88 (Made by Mitsubishi Kasei), RAVE
N2000, 1500 (made in Colombia), BLACK PEARLS MONARCK
1100,900,880 (manufactured by KYABOT), Printex95,90,85,80
Commercially available products such as (manufactured by Degussa) and products newly manufactured for this purpose can also be used.

The carbon black contained in the ink of the present invention is produced by the furnace black method.

The Furness-Brack method is a method in which natural gas or petroleum fraction is used as a raw material, which is kept in a constant temperature atmosphere and sprayed into a closed reaction furnace for thermal decomposition.

Here, the pH of the carbon black according to the present invention means a value obtained by the following measuring method.

That is, 1 to 10 g of carbon black sample is weighed in a beaker, water is added at a rate of 10 ml per 1 g of sample, covered with a watch glass, and boiled for 15 minutes (some drops of ethanol may be added to easily wet the sample. .). After boiling, the mixture is cooled to room temperature and the supernatant is removed by a gradient method or a centrifugation method to leave a mud. An electrode having a glass electrode pH is put in this mud and the pH is measured by JISZ 8802 (pH measuring method). In this case, since the measured value may change depending on the electrode insertion position, move the beaker to change the electrode position and take care so that the electrode surface and the mud surface are in sufficient contact, and the pH value is constant. Read the value when.

The carbon black used in the present invention has a pH of 6 to
The range of 10 is particularly preferable from the viewpoint of storage stability of the pigment ink over time.

The BET specific surface area of carbon black is calculated by Brunaur-Emmett.
-It measured by the nitrogen adsorption method (BET method) by Teller method.

Further, in the present invention, the weight average molecular weight of the water-soluble resin (dispersion resin) used for dispersing the carbon black is
Must be in the range 3000 to 7000.

That is, the ink jet recording apparatus ejects ink by using thermal energy from an ejection port whose one side is 50 μ or less.When a dispersion system such as a pigment ink is used, its viscosity and the particle diameter of the dispersion are the ejection characteristics. Have a big impact,
In order to perform stable ejection, it is desirable that the viscosity and the particle size of the dispersion be as small as possible.

Polymer-dispersed resins generally have a higher average molecular weight,
The viscosity increases when the same amount is dissolved in the aqueous solution. Further, the dispersion resin has a role of adsorbing around the carbon black when the carbon black is dispersed and stably dispersing the carbon black due to steric hindrance. Therefore, increasing the molecular weight of the dispersion resin means increasing the thickness of the adsorption layer and increasing the particle size of the dispersion.

In particular, since the carbon black used in the present invention has a large specific surface area, it is necessary to adsorb a large amount of the dispersed resin on the surface, and therefore, the amount of the dispersed resin is increased or the molecular weight of the dispersed resin is decreased. It is possible to increase the number of molecules.

However, in the ink jet recording apparatus in which the present invention is used, the amount of the dispersed resin cannot be increased for the reason described below.

Therefore, reducing the molecular weight of the dispersed resin as in the present invention,
A stable dispersion could be obtained by increasing the number of dispersion resins. Further, the ink jet recording apparatus used requires long-term storage stability for several years. Therefore, when the acid value of the dispersion resin is 100 or more, such a small molecular weight and a small addition amount make it possible to obtain long-term stability even in a system which is disadvantageous in terms of steric hindrance. It is considered that this is because the stability in the aqueous medium is increased by increasing the acid value of the resin.

The water-soluble resin contained in the ink of the present invention as a dispersant for carbon black is soluble in an aqueous solution in which an alkali is dissolved and has a weight average molecular weight of 3000 to 7000 and an acid value of
Anything can be used as long as it is 100 or more, 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 Examples thereof include polymers and salts thereof.

There are various methods for measuring the weight average molecular weight of the dispersion resin, but it is general to measure by GPC (gel permeation chromatography) or the like.

Water-soluble resin is 0.1 to 5% by weight with respect to the total amount of ink,
It is preferably contained in the range of 0.3 to 2% by weight.

The acid value of the water-soluble resin is a measured value of the acid equivalent contained in the sample, and the potassium hydroxide content required to neutralize 1 g of the sample
Expressed in mg. For detailed measurement method, see “Analysis of color materials
Test method ”See page 86, Maruzen, Color Materials Association.

Furthermore, in the ink of the present invention, preferably the entire ink is adjusted to be neutral or alkaline, whereby the solubility of the water-soluble resin is improved and the ink can be further excellent in long-term storage stability. So desirable. However, in this case, it may cause corrosion of various members used in the ink jet recording apparatus.
It is desirable that the pH range is set to.

As the pH adjuster, for example, various organic amines such as diethanolamine and triethanolamine, sodium hydroxide, lithium hydroxide, inorganic alkali agents such as alkali metal hydroxides such as potassium hydroxide, and organic acids, Mineral acid can be mentioned.

As described above, the carbon black and the water-soluble resin are dispersed or dissolved in the water-soluble medium.

A suitable aqueous medium in the ink of the present invention is a mixed solvent of water and a water-soluble organic solvent, and as the water, ink exchange water (deionized water) is used instead of general water containing various ions. Is preferred.

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, isobutyl alcohol and the like. Alkyl alcohols having 1 to 4 carbon atoms; amides such as dimethylformamide and dimethylacetamide; ketones or keto alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylenes such as polyethylene glycol and polypropylene glycol Glycols; ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol,
Alkylene glycols in which the alkylene group such as hexylene glycol and diethylene glycol contains 2 to 6 carbon atoms; glycerin; ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) Lower alkyl ethers of polyhydric alcohols such as ethers; N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like. Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether are preferable.

Among these many water-soluble organic solvents, organic amine water is contained as an essential component in the recording liquid of the present invention, preferably 0.001 to 10% by weight based on the whole recording liquid.

Further, the water-soluble organic solvent other than the organic amines is appropriately selected and contained in an appropriate amount as desired. Among them, polyhydric alcohols such as diethylene glycol and polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether are included. Lower alkyl ethers of alcohols are preferred. Further, the content of the polyhydric alcohol is preferably 10% or more in order to prevent solidification at the nozzle tip when the ink is used and stored in the head. Furthermore, it has been found that it is effective to add an aliphatic monohydric alcohol such as ethanol or isopropyl alcohol in an amount of 3% by weight or more in order to obtain the stability of discharge. It is considered that the ink can be more stably foamed on the thin film resistor. However, if these solvents are added excessively, the print quality of the printed matter will be impaired, so a more suitable concentration of these solvents is 3 to 10% by weight.
It is. Furthermore, as an effect of these solvents, it is possible to suppress the generation of bubbles during dispersion and perform efficient dispersion by adding these solvents to the dispersion liquid.

The content of the water-soluble organic solvent in the ink of the present invention,
10-50% by weight, preferably 10-40% by weight of the total ink
And the amount of water used is in the range of 10 to 90% by weight, preferably 30 to 70% by weight, based on the total weight of the ink.

In addition to the above components, the ink of the present invention may be added with a surfactant, an antifoaming agent, an antiseptic agent, etc. in order to obtain an ink having a desired physical property value, if necessary. It is also possible to add a water-soluble dye, etc.

As the surfactant, fatty acid salts, higher alcohol sulfate ester salts, liquid fatty acid sulfate ester salts, anionic surfactants such as alkylallyl sulfonates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, polyoxy There are nonionic surfactants such as ethylene sorbitan alkyl esters, and one or more of these can be appropriately selected and used.
The amount used depends on the dispersant, but
0.01 to 5% by weight is desirable. At this time, it is preferable to determine the amount of the activator to be added so that the surface tension of the ink is 30 dyne / cm or more. This is because the surface tension of the ink having a value smaller than this causes an undesirable situation such as printing deviation (deviation of ink droplet landing point) due to wetting of the nozzle tip in the recording method of the present invention. Is. On the other hand, a water-soluble organic solvent, a pH adjusting agent, an antifoaming agent, an antiseptic agent, etc. can be added in order to obtain an ink having desired physical properties. Further, it is possible to add a commercially available water-soluble dye or the like.

Generally, the properties required for ink jet inks include physical properties such as ink viscosity, surface tension, and pH.However, in a dispersion system such as an aqueous pigment ink, even if these physical properties are satisfied, the ink foams. Was often unstable.

Therefore, the present inventors are thermally stable with the aqueous pigment ink,
Further, as a result of earnestly researching the performance of the ink capable of optimal foaming, it was found that the amount of the water-soluble resin dissolved in the ink should be 2% by weight or less, preferably 1% by weight or less based on the total weight of the ink. It has been found that the ink accurately foams on the body even under various driving conditions, and does not cause deposits on the thin film resistor even for a long period of time. In other words, if a large amount of excess water-soluble resin is present in the ink with respect to the carbon black, the ink will not foam even if given thermal energy is applied on the thin-film resistor, or the heat generated during pulse application will prevent these inks from forming. The surplus water-soluble resin becomes an insoluble matter and is deposited on the thin film resistor, which causes ejection failure and print disorder.

The dissolved water-soluble resin refers to a resin that is not adsorbed to the pigment in the ink but is dissolved in the liquid medium.

One way to reduce the amount of such dissolved water-soluble resin is to use the weight ratio of pigment to water-soluble resin when making ink.
It is to be adjusted in the range of 3: 1 to 10: 1, preferably 10: 3 to 10: 1.

Further, the total amount of carbon black and water-soluble resin in the dispersion liquid is preferably 10% or more, and more preferably 30% or less on a weight basis. The reason is that if there is no carbon black and a water-soluble resin at a certain concentration or more in the dispersion, the dispersion can be performed efficiently and the optimum dispersion state cannot be obtained.

As a method for producing the ink of the present invention, first, a pigment is added to an aqueous solution containing at least a dispersion resin, an amine, and water, and after stirring, dispersion is performed by using a dispersion means described below, and if necessary, centrifugation is performed. Treatment is carried out to obtain the desired dispersion. Next, the above-mentioned components are added to this dispersion, and the mixture is stirred to prepare a recording liquid.

In particular, in order to reduce the amount of unadsorbed resin to 2% or less, an aqueous solution containing resin, amine and water is added in the production method to 60%.
It is necessary to completely dissolve the resin in advance by stirring at a temperature of not lower than 0 ° C. for 3 minutes or longer.

Further, it is necessary to add 1.2 times or more of the amount of amine that dissolves the resin, to the amount of amine calculated by the acid value of the resin. The amount of this amine is calculated by the following formula.

It is also necessary to carry out premixing for 30 minutes or more before dispersing the aqueous solution containing the pigment.

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

As amines added to the dispersion, organic amines such as monoethanolamine, diethanolamine, triethanolamine, aminomethylpropanol, and ammonia are preferable.

On the other hand, the disperser used in the present invention may be any disperser generally used, and examples thereof include a ball mill, a roll mill and a sand mill.

Among them, a high speed type sand mill is preferable, for example, a super mill, a sand grinder, a bead mill,
Agitator mills, Glen mills, Dyno mills, Pearl mills, Cobol mills (all are trade names) and the like.

In the present invention, as a method of obtaining a pigment having a desired particle size distribution, the size of the pulverized media of the disperser is reduced, the filling rate of the pulverized media is increased, the treatment time is lengthened, and the discharge speed is slowed. After crushing, a method such as classification with a filter or a centrifugal separator is used.
Alternatively, a combination of these techniques may be used.

As a method for measuring the amount of unadsorbed resin according to the present invention, a pigment component and a resin component adsorbed to the pigment are precipitated using an ultracentrifuge or the like, and the amount of residual resin contained in the supernatant liquid is determined. TOC (Total Organic Carbon),
A gravimetric method (a method in which the supernatant is evaporated to dryness and the amount of resin is measured) or the like is preferably used.

The recording liquid of the present invention is particularly suitable for use in an ink jet recording method in which droplets are ejected by the action of heat energy for recording, but it goes without saying that it can also be used for general writing instruments.

A recording apparatus suitable for recording using the ink of the present invention is an apparatus which applies thermal energy corresponding to a recording signal to a recording liquid in a chamber of a recording head and generates a droplet by the energy.

An example of the head structure, which is the main part, is shown in FIG.
(B) is shown in FIG.

The head 13 is a glass having a groove 14 through which ink passes, a ceramics plate, a plastic plate or the like, and a heating head 15 (thin film head is shown in the figure, but not limited to this) used for thermal recording. It is obtained by bonding.
The heating head 15 is a protective film 16 formed of silicon oxide or the like.
It is composed of aluminum electrodes 17-1 and 17-2, a heating resistor layer 18 made of nichrome, a heat storage layer 19, and a substrate 20 having a good heat dissipation property such as alumina.

The ink 21 reaches the discharge orifice (fine holes) 22 and forms a meniscus 23 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 generates heat rapidly, and bubbles are generated in the ink 21 in contact with the area, and the meniscus is generated by the pressure.
23 protrudes, the ink 21 is ejected, and becomes a recording droplet 24 from the orifice 22, and flies toward the recording medium 25. FIG. 2 is an external view of a multi-head in which a number of heads shown in FIG. 1 (a) are arranged. The multi-head is made by bonding a glass plate 27 having multi-grooves 26 and a heat-generating head 28 similar to that described in FIG. 1 (a).

It should be noted that FIG. 1A shows a head 13 along the ink flow path.
FIG. 1 (b) is a cross-sectional view of FIG.
It is a cutting plane along a line.

FIG. 3 shows an example of an ink jet recording apparatus incorporating the head according to FIG.

In FIG. 3, reference numeral 61 denotes a blade as a wiping member, one end of which is held by a blade holding member to become a fixed end, which is in the form of a cantilever. blade
Reference numeral 61 is arranged at a position adjacent to the recording area of the recording head, and in the case of this example, it is held in a protruding form in the moving path of the recording head. 62 is a cap and blade
It is provided in a home position adjacent to 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. Further 63 is blade 61
Is an ink absorber provided adjacent to the blade 61.
Similarly to the above, the recording head is held in a protruding form in the moving path of the recording head. The blade 61, the cap 62, and the absorbent body 63 constitute a discharge recovery section 64, and the blade 61 and the absorbent body 63.
Thus, water, dust, etc. on the surface of the ink ejection port are removed.

Reference numeral 65 denotes a recording head which has ejection energy generating means and discharges ink on a recording material facing the ejection port surface where the ejection ports are arranged to perform recording, and 66 denotes a mounting of the recording head 65 and movement of the recording head 65. Carriage for doing. Carriage
66 is slidably engaged with a guide shaft 67, and a part of the carriage 66 is connected (not shown) to a belt 69 driven by a motor 68. As a result, the carriage 66 can move along the guide shaft 67, and the recording head 65 can move the recording area and the area adjacent thereto.

Reference numeral 51 is a paper feed unit for inserting a 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 discharge port surface of the recording head, and as the recording progresses, a discharge roller 53 is formed.
Is discharged to the paper discharge unit where.

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 head recovery unit 64 is retracted from the moving path of the recording head 65,
61 protrudes into the movement route. As a result, the recording head
The ejection port surface of 65 is wiped. When the cap 62 comes into contact with the ejection surface of the recording head 65 to perform the capping, the cap 62 moves so as to project into the moving 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 above wiping position. As a result, even during this movement, the ejection port surface of the recording head 65 is wiped.

To move the recording head to the home position described above,
Not only at the end of recording or at the time of ejection recovery, while the recording head moves in the recording area for recording, it moves to the home position adjacent to the recording area at a predetermined interval, and the wiping is performed along with this movement. Be seen.

FIG. 4 is a diagram showing an example of an ink cartridge containing ink supplied to the head through the ink supply tube. Here, reference numeral 40 denotes an ink bag storing the supply ink, and a rubber stopper 42 is provided at the tip of the ink bag. By inserting a needle (not shown) into the stopper 42, the ink in the ink bag 40 can be supplied to the head. 44
Is an ink absorber for receiving waste ink.

The ink jet recording apparatus used in the present invention is not limited to the above-described head and ink cartridge which are separate bodies, and an integrated one as shown in FIG. 5 is also preferably used. .

In FIG. 5, reference numeral 70 denotes an ink jet cartridge, which contains an ink absorber impregnated with ink, and which receives ink from a head portion 71 having a plurality of orifices. It is configured to be ejected as ink droplets.

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

The ink jet cartridge 70 is used in place of the recording head 65 shown in FIG. 3, and is attachable to and detachable from the carriage 66.

〔Example〕

 Next, the present invention will be described specifically with reference to examples.

Example 1 (Preparation of pigment dispersion liquid) Styrene-acrylic acid-butyl acrylate copolymer (acid value 116, weight average molecular weight 3700) 2 parts Monoethanolamine 1 part Ion-exchanged water 73 parts Diethylene glycol 5 parts The above components are mixed. Then, heat to 70 ° C with a water bath,
Dissolve the resin completely. To this solution, 14 parts of carbon black (MCF88 manufactured by Mitsubishi Kasei) and 5 parts of isopropyl alcohol were added, and after premixing for 30 minutes, dispersion treatment was carried out under the following conditions.

Dispersing machine Sand grinder (Igarashi Machinery Co., Ltd.) Grinding media Zirconium beads 1mm diameter Packing ratio of grinding media 50% (volume) Grinding time 3 hours Centrifugation treatment (12000RPM, 20 minutes) is performed to remove coarse particles and dispersion liquid. And

(Preparation of Ink) Dispersion 30 parts Diethylene glycol 15 parts Isopropyl alcohol 5 parts Ion-exchanged water 50 parts The above components were mixed and the pH was adjusted to 8 to 10 with monoethanolamine to prepare ink (A). .

Example 2 (Preparation of Pigment Dispersion) Styrene-acrylic acid-butyl acrylate copolymer (acid value 120, weight average molecular weight 6100) 5 parts Triethanolamine 2 parts Ion-exchanged water 66 parts Diethylene glycol 5 parts Mix the above components Then, heat to 70 ° C with a water bath,
Dissolve the resin completely. To this solution, 15 parts of carbon black (Printex95, manufactured by Degussa) and 7 parts of ethanol were added, and after premixing for 30 minutes, dispersion treatment was carried out under the following conditions.

Disperser Pearl Mill (manufactured by Ashizawa) Grinding media Glass beads 1 mm diameter Filling ratio of grinding media 50% (volume) Discharge rate 100 ml / min. Centrifugation treatment (12000 RPM, 20 minutes) is performed to remove coarse particles and dispersion liquid. And

(Preparation of ink) 30 parts of the above dispersion liquid Diethylene glycol 10 parts Ethylene glycol 10 parts Ethanol 5 parts Ion-exchanged water 45 parts The above components are mixed and the pH is adjusted to 8 to 10 with triethanolamine. ).

Example 3 (Preparation of Pigment Dispersion) Styrene-acrylic acid-ethyl acrylate copolymer (acid value 138, weight average molecular weight 5600) 4 parts Aminomethyl propanol 2 parts Ion-exchanged water 69 parts Diethylene glycol 5 parts Mix the above components Then, heat to 70 ° C with a water bath,
Dissolve the resin completely. To this solution, 15 parts of carbon black (MCF88, manufactured by Mitsubishi Kasei) and 5 parts of ethanol were added, and after premixing for 30 minutes, dispersion treatment was carried out under the following conditions.

Disperser Pearl Mill (manufactured by Ashizawa) Grinding media Glass beads 1 mm diameter Filling ratio of grinding media 50% (volume) Discharge rate 100 ml / min. Centrifugation treatment (12000 RPM, 20 minutes) is performed to remove coarse particles and dispersion liquid. And

(Preparation of Ink) Dispersion 50 parts Triethylene glycol 15 parts Ethylene glycol 5 parts Ethanol 5 parts Ion-exchanged water 25 parts The above components are mixed and adjusted to pH 8 to 10 with aminomethyl propanol, Ink (C) was obtained.

Example 4 (Preparation of pigment dispersion) Styrene-maleic acid half ester-maleic anhydride copolymer (acid value 188, weight average molecular weight 5600) 3 parts Monoethanolamine 1 part Ion-exchanged water 71 parts Ethylene glycol 5 parts Above Mix the ingredients and heat to 70 ° C with a water bath,
Dissolve the resin completely. To this solution, 15 parts of carbon black (manufactured by Monarch 900 Cab) and 5 parts of ethanol were added, and after premixing for 30 minutes, dispersion treatment was carried out under the following conditions.

Disperser Sand grinder (Igarashi Kikai) Grinding media Zirconium beads 0.5 mm diameter Packing ratio of grinding media 40% (volume) Grinding time 3 hours Centrifugation treatment (12000RPM, 20 minutes) is carried out to disperse coarse particles. It was designated as liquid (D).

(Preparation of Ink) 30 parts of the above dispersion, 20 parts of thiodiglycol, 5 parts of ethylene glycol, 4 parts of ion-exchanged water, 41 parts of the above components were mixed and stirred for 1 hour to obtain an ink (D).

Reference Example 1 A dispersion liquid was prepared by using the following dispersion resin in the ink of Example 1, and other inks were prepared in the same manner as ink (E).

Styrene-maleic acid half ester copolymer (acid value 180, weight average molecular weight 10,000) Reference Example 2 The carbon black contained in the dispersion of Example 2 was made into RE.
Ink (F) was obtained by replacing the GAL660R (manufactured by KYABOT) with an ink having the same formulation.

Reference Example 3 An ink (G) was obtained by preparing a dispersion liquid using the following dispersion resin in the ink of Example 4, and preparing an ink in the same manner as in the other cases.

Styrene-acrylic acid-butyl acrylate copolymer (acid value 88, weight average molecular weight 13000) An on-demand type ink jet device that ejects ink by applying thermal energy corresponding to a recording signal to the ink using each of the above inks. The following tests were conducted using an ink jet recording apparatus having a recording head.

T1: Drive condition and ejection stability Set the drive voltage to 25V, and the frequency of each voltage is 2KHz, 4
Printing was performed at room temperature under two conditions of KHz, and the presence or absence of print disturbance, chipping, non-ejection, etc. was observed to evaluate the ejection stability.

A: Discharges cleanly from the first character, during continuous printing, no discharge,
There is no chipping or printing disorder.

B: The character portion was ejected cleanly, but several ejection failures occurred in the solid print portion.

C: Even in the character portion, when several characters are printed, ejection failure occurs, and the characters are disturbed so that the characters cannot be read.

T2: Optical density of the printed matter The printed matter printed on the NP-DK paper and the XEROX4024 paper using the BJ130 printer (manufactured by Canon) is the Macbeth densitometer (RD91
Measured using 8). The average value of two papers was used for evaluation.

T3: Long-term ink storage test After each ink was stored at 40 ° C. for 4 weeks, the amount of the precipitate attached to the bottom of the storage bottle was visually observed.

A: No precipitate is seen.

B: A slight precipitate is seen at the bottom of the bottle, but there is no problem in practical use.

C: A large amount of precipitate is generated.

T0: Amount of dissolved water-soluble resin The ink obtained was ultra-high-speed cooled centrifuge (manufactured by Beckmann)
At 55000 rpm for 5 hours, the pigment component and the resin component adsorbed to the pigment are allowed to settle, and a fixed amount of the supernatant is collected,
Dry and solidify in a vacuum dryer (60 ° C, 24 hours). The percentage of the amount of the resin to the charged ink is calculated and defined as the residual resin concentration.

Table 1 shows the performance of the carbon black used in this experiment. Further, the evaluation results are shown in Table 2. Regarding the evaluation in the table, the results based on the above-mentioned criteria for the ejection stability of T1, the reflection density of the printed matter for T2, and the results of visual observation for T3 are shown.

[Effects] As described above, the ink of the present invention, when applied to an ink jet printer, is not only excellent in the fastness of the printed matter, but also has a high density of the printed matter, fluctuation of driving conditions and long-term Even if it is used, it is possible to always perform stable ejection, and it has an effect of excellent long-term storage stability.

[Brief description of the drawings]

1 (a) and 1 (b) are a longitudinal sectional view and a transverse sectional view of a head portion of an ink jet recording apparatus. FIG. 2 is an external perspective view of a head obtained by multiplying the head shown in FIG. FIG. 3 is a perspective view showing an example of the ink jet recording apparatus. FIG. 4 is a longitudinal sectional view of the ink cartridge. FIG. 5 is a perspective view of an ink jet cartridge. 61 ...... Wiping member 62 ...... Cap 63 ...... Ink absorber 64 ...... Ejection recovery section 65 ...... Recording head 66 ...... Carriage

Claims (20)

(57) [Claims] 1. A neutral or basic carbon black having a BET specific surface area of 150 m ² / g or more and a weight average molecular weight in an aqueous medium.
An ink containing a water-soluble resin in the range of 3000 to 7000. 2. The ink according to claim 1, wherein the water-soluble resin has an acid value of 100 or more. 3. The ink according to claim 1, wherein the amount of the water-soluble resin dissolved in the ink is 2% by weight or less. 4. The ink according to claim 1, wherein the aqueous medium contains water and a water-soluble organic solvent. 5. The ink according to claim 4, wherein the water-soluble organic solvent contains a polyhydric alcohol and / or its alkyl ether and an aliphatic monohydric alcohol. 6. A weight average molecular weight of 3,000 to 7,000 in an aqueous medium.
An ink containing a neutral or basic carbon black having a BET specific surface area of 150 m ² / g or more adsorbed on the surface of a water-soluble resin within the range of. 7. The ink according to claim 6, wherein the amount of the water-soluble resin dissolved in the ink is 2% by weight or less. 8. The ink according to claim 6, wherein the water-soluble resin has an acid value of 100 or more. 9. The ink according to claim 6, wherein the aqueous medium contains water and a water-soluble organic solvent. 10. The ink according to claim 9, wherein the water-soluble organic solvent contains a polyhydric alcohol and / or its alkyl ether and an aliphatic monohydric alcohol. 11. An ink jet recording method for recording by ejecting ink as droplets from fine holes by applying thermal energy to the ink according to a recording signal,
The BET specific surface area of the ink in an aqueous medium is 150 m ² / g or more and the weight average molecular weight of neutral or basic carbon black.
An ink jet recording method comprising a water-soluble resin in the range of 3000 to 7000. 12. The ink jet recording method according to claim 11, wherein the water-soluble resin has an acid value of 100 or more. 13. The ink jet recording method according to claim 11, wherein the amount of the water-soluble resin dissolved in the ink is 2% by weight or less. 14. The ink jet recording method according to claim 11, wherein the aqueous medium in the ink contains water and a water-soluble organic solvent. 15. The ink jet recording method according to claim 14, wherein the water-soluble organic solvent contains a polyhydric alcohol and / or its alkyl ether and an aliphatic monohydric alcohol. 16. An ink jet recording method for recording by ejecting ink as droplets from fine holes by applying thermal energy to the ink according to a recording signal,
BET specific surface area 1 in which the water-soluble resin having a weight average molecular weight of 3000 to 7000 in the aqueous medium is adsorbed on the surface of the ink.
An ink jet recording method comprising a neutral or basic carbon black of 50 m ² / g or more. 17. The ink jet recording method according to claim 16, wherein the water-soluble resin has an acid value of 100 or more. 18. The ink jet recording method according to claim 16, wherein the amount of the water-soluble resin dissolved in the ink is 2% by weight or less. 19. The ink jet recording method according to claim 16, wherein the aqueous medium in the ink contains water and a water-soluble organic solvent. 20. The ink jet recording method according to claim 19, wherein the water-soluble organic solvent contains a polyhydric alcohol and / or its alkyl ether and an aliphatic monohydric alcohol.