JP5846545B2 - Ink for inkjet recording - Google Patents

Description

  The present invention relates to an ink for ink jet recording, a cartridge, an ink jet recording apparatus, an image forming method, and an image formed product formed thereby.

In recent years, as an image forming method, since the process is simpler than other recording methods and full color can be easily obtained, there is an advantage that a high-resolution image can be obtained even with an apparatus having a simple configuration. Recording methods have become widespread.
Inkjet recording systems use a bubble generated by heat, or a small amount of ink to fly with pressure generated using piezo or static electricity, and adhere to an image forming body such as paper and quickly dry (or image forming body). This is an image forming apparatus that forms an image), and has been expanded to personal and industrial printers and printing applications.

In recent years, demand for industrial applications has been increasing, and high-speed printing and compatibility with various recording media (paper and other media) are desired. In particular, an ink jet printer equipped with a line head has become necessary as the speed increases.
In recent years, there has been an increasing demand for water-based inks from the viewpoints of environment and safety.
However, water-based inks are easily affected by the medium, causing various problems in the image. This is particularly noticeable when non-smooth paper is used as the medium.

In the case of water-based ink, it takes time to dry and the compatibility with the paper is good, so the permeability to the paper is high, especially in the case of uncoated relatively non-smooth paper, the coloring material penetrates into the paper. As a result, there has been a problem not seen with solvent inks in which the color density of the formed color material is low.
In particular, as high-speed printing is progressing in recent years, in order to increase the drying speed of the ink attached to the medium, means for increasing the drying speed is taken by adding a penetrant to the ink and allowing the solvent, water, to permeate the medium.
However, when a penetrant is included, the permeability of not only water but also the coloring material to the media is improved, and the problem that the image density is further lowered is noticeably different from the ink used for paints and ballpoint pens. End up.

As a method for improving the printed image density, it is proposed to oxidize acidic carbon black with hypochlorous acid to control the ratio of the surface functional group amount / specific surface area of the carbon black (Patent Document 1).
However, the treatment with hypochlorite is wet (uses water as a solvent), so dehydration and washing are necessary, resulting in high costs, and salt remains even during washing, so it is used for inkjet. In this case, the ink storage stability was not satisfactory.
In the case of non-smooth paper, the image density is not satisfactory.

For the purpose of improving the dispersion stability, it has been proposed to define the surface functional group amount / specific surface area and other characteristics of carbon black (Patent Document 2). However, this also involves wet oxidation of peroxodisulfate and the like, and for the same reason as described above, the storage stability and image density are not satisfactory.
In addition, it has been proposed to use furnace carbon black in which DBP oil absorption and acidic groups are defined (Patent Document 3).
In order to obtain the stated DBP absorption amount for furnace carbon black, it is necessary to use one having a large specific surface area, and even if acid groups are increased by oxidation, effective acidity existing on the actual carbon black surface is present. There are few groups, and storage stability and image density when used in ink are not satisfactory.

In addition, use of carbon black in which the volatile content of carbon black treated by oxidation is specified to be 25% or more has been proposed (Patent Document 4).
However, when the volatile content is high, the wettability to water is improved and the water dispersibility is improved, but the stability is decreased due to an increase in impurities during oxidation, and the compatibility with water is too high. Pigment penetration tends to occur and sufficient image density cannot be obtained.
The use of carbon black that defines the volatile content of carbon black and the CTAB surface area / iodine value has been proposed (Patent Document 5).
However, with only the above, it is difficult to achieve both image density and storage stability sufficiently.
In addition, although the water dispersibility is improved with respect to the ink jet recording inks described in Patent Documents 6 to 7 using naphthalenesulfonic acid formalin condensate as a carbon black dispersant, the compatibility with water becomes too high, so At the same time, it is easy for the pigment to penetrate into the paper, and a sufficient image density is not obtained.

Further, Patent Document 8 proposes an ink set containing a water-dispersible colorant including a surfactant-based dispersant in one of two water-based ink sets having different hues. Although bleeding is improved, the image density is not sufficient.
Further, a recording containing carbon black having a DBP oil absorption of 140 ml / 100 g or more and a pH of 6 or more and a water-soluble polymer compound having a carboxylic acid group and an acid value of 250 mg KOH / g or more in the form of a free acid. The liquid is Patent Document 9, and the recording liquid containing carbon black as a modified carbon black whose surface is coated with a metal oxide is Patent Document 10, and the physical properties of the carbon black are DBP oil absorption of 140 ml / 100 g or more. A recording liquid having carbon black having a volatile content of 4% or less, a pH of 7 to 14, and a BET specific surface area of 100 m ² / g or more has been proposed in Patent Document 11 and the like, but it cannot be said that the image density is sufficient.

  The present invention has been made in view of the above-described prior art, and provides an image forming method, ink jet recording ink, cartridge, and ink jet recording that have good ink storage stability and can achieve high image density even on smooth paper and non-smooth paper. The object is to provide an apparatus and an image formed product.

The said subject is solved by following (1)-(7) of this invention.
(1) In an inkjet recording ink containing at least water, a pigment, a dispersant, and a penetrating agent, the pigment is carbon black, ozone-oxidized, a volatile content of 10% to 20%, and a BET specific surface area of 90 to 150 m ² / carbon black CB-1 which is g 1 is dispersed in a pigment dispersion (1) in which the dispersion pH is adjusted to 6 to 8 with an alkali metal hydroxide, and particle diameter measurement by dynamic light scattering method Carbon black CB-2 having an average particle size (D50) of 50 to 180 nm and a particle size standard deviation of ½ or less of the average particle size is dispersed using a condensate of formalin naphthalene sulfonate as a dispersant. And the mass ratio of the carbon black CB-1 and the carbon black CB-2 in the ink is from 2:98 to 50:50. An ink for inkjet recording characterized in that.
(2) The ink for inkjet recording according to (1), wherein the pigment dispersion (1) and / or (2) contains a polyether type urethane having an acid value of 40 to 100 mgKOH / g.
(3) The total content of dimers, trimers and tetramers of naphthalenesulfonic acid in the condensate of naphthalenesulfonic acid formalin as the dispersant of the pigment dispersion (2) is 20% by mass to 80% by mass. The ink for inkjet recording according to (1) or (2), wherein
(4) A cartridge in which the ink for ink jet recording according to any one of (1) to (3) is contained in a container.
(5) An ink jet recording apparatus comprising the cartridge according to (4).
(6) An image forming method, wherein an image is formed using an ink jet recording apparatus provided with a head for discharging the ink for ink jet recording according to any one of (1) to (3).
(7) An image formed product printed by the ink jet recording apparatus according to (5).

  According to the present invention, an ink for ink jet recording having good ink storage stability, high image density even on non-smooth paper and smooth paper, and good ejection stability from a nozzle, and the ink jet recording ink are used. Cartridge, ink jet recording apparatus, image forming method, and image formed product can be provided.

It is the schematic of an example of the inkjet recording device of this invention. It is a schematic sectional drawing of an example of the inkjet recording device of this invention. It is the schematic of an example of the ink bag of the ink cartridge of this invention. FIG. 4 is a schematic view of an ink cartridge containing the ink bag of FIG. 3.

The present invention relates to an inkjet recording ink containing water, a pigment, a dispersant, and a penetrating agent, wherein the pigment is carbon black, ozone-oxidized, a volatile content of 10% to 20%, and a BET specific surface area of 90 to 150 m ² / g. Carbon black CB-1 was dispersed with a dispersion pH adjusted to 6-8 with an alkali metal hydroxide and dispersed, and an average particle size measured by a dynamic light scattering method A pigment dispersion in which carbon black CB-2 having a (D50) of 50 to 180 nm and a particle size standard deviation of ½ or less of the average particle size is dispersed using a condensate of naphthalene sulfonate formalin as a dispersant. (2) and is obtained.

[Pigment dispersion (1)]
The carbon black (hereinafter also referred to as CB) used in the pigment dispersion (1) of the present invention is carbon black CB-1 having a volatile content of 10% to 20% and a BET specific surface area of 90 to 150 m ² / g. Carbon black having a specific surface area of 90 to 150 m ² / g is oxidized by ozone treatment to adjust the volatile content to 10% to 20%.
Although the ozone oxidation method can be performed by a known method, a dry method performed by circulating ozone gas through carbon black is preferable because of its high oxidation treatment ability.
In the treatment using water, there is a case where sufficient oxidation cannot be performed due to the reaction between water and ozone.
The adjustment of the volatile matter of CB can be controlled by adjusting the amount of ozone and the treatment time. By increasing the amount of ozone (concentration) and lengthening the treatment time, CB having a higher volatile content can be obtained.
The relationship between the processing time and the volatile content of CB is almost linear, but when it exceeds a certain time, saturation is reached (the CB volatile content does not increase), so adjustment is required while confirming the volatile content of CB. In addition, the above conditions are different depending on the characteristics of CB before the oxidation treatment, impurities, and the like, so that adjustment may be made for convenience. Ozone can be obtained by passing air or oxygen through an ozone generator.

The carbon black used for oxidation may be carbon black having a BET specific surface area of 90 to 150 m ² / g, but the oil absorption (DIN ISO 787/5 method) is 230 ml / 100 g or more in terms of image density. preferable.
As carbon black, various types such as furnace black, lamp black, acetylene black, and gas black can be used, but gas black is preferable in terms of image density.
Moreover, the thing with a primary particle diameter of 30-13 nm is preferable.

  The volatile content of CB in the present invention is a value according to the measuring method described in DIN 53552, and is a percentage display of weight loss when heated at 950 ° C. for 7 minutes. The BET specific surface area is a value obtained by the measurement method described in DIN 66132.

The pigment dispersion (1) of the present invention can be obtained by dispersing the pigment, water, and if necessary, various additives using a known disperser such as a sand mill, ball mill, roll mill, bead mill, nanomizer, or homogenizer. Further, the pH of the dispersion is adjusted to 6 to 8 with an alkali metal hydroxide.
In the pigment dispersion (1), the content of carbon black CB-1 as a pigment is preferably 10% by mass to 40% by mass.
The pH of the dispersion is desirably adjusted before the dispersion, and the adjustment after the dispersion tends to be inferior in terms of dispersibility and storage stability.
Preferred examples of the alkali metal acid hydroxide include sodium hydroxide, potassium hydroxide, lithium hydroxide and the like.

Although it is unclear why the ink of the present invention can achieve both image density and storage stability, the following can be considered.
As a result of the study by the present inventors on the volatile matter of CB, when the volatile matter of CB increases, the reason is unknown, but the carbon black stays on the paper surface and the image density tends to improve. However, the improvement in the image density occurs when the volatile content exceeds about 20%, but eventually it has reached saturation and a sufficient image density cannot be obtained. It can also be seen that as the volatile content of CB increases, the hydrophilicity of carbon black increases and dispersibility improves, but impurities due to oxidation increase, and the stability of the ink as a diameter decreases. Concentration and storage stability as ink could not be compatible.
Moreover, although the specific surface area and the ratio of the volatile matter of CB were examined, it was not necessarily compatible.

Further examination revealed that the oxidation is ozone oxidation with less generation of impurities, the image density effect is still 10% to 20% of the volatile region of CB, and the BET specific surface area is 90 to 150 m ² / g. Further, by adjusting the image density and storage stability, and further adjusting the pH at the time of dispersion to 6 to 8, the image density that was insufficient can be improved.

[Pigment dispersion (2)]
The carbon black contained in the pigment dispersion (2) has an average particle size (D50) of 50 to 180 nm in particle size measurement by a dynamic light scattering method in the particle size distribution and a particle size standard deviation of 1 / average particle size. It is carbon black CB-2 which is 2 or less, and the dispersant is a condensate of formalin naphthalene sulfonate.
In addition, in the pigment dispersion (2) of the present invention, the content of carbon black CB-2 as a pigment is preferably 10% by mass to 40% by mass, and the carbon black CB-2 dispersant is carbon black 1 based on mass. Preferably, it is contained at a ratio of 0.1 or more and 2 or less. More preferably, the ratio is 0.25 to 1 with respect to carbon black 1.
By adopting such a use amount of the dispersant, the average particle size (D50) of the carbon black CB-2 of the dispersion (2) of the present invention is 50 nm or more and 180 nm or less, and the carbon black particle size distribution is The particle diameter standard deviation can be reduced to ½ or less of the average particle diameter, whereby a pigment dispersion having high image density, ejection stability, and liquid stability can be provided.

When the particle diameter (D50) is less than 50 nm, the storage stability of the pigment dispersion and the ink is poor, and as a result, the nozzle tends to be clogged. When the particle diameter (D50) exceeds 180 nm, the nozzle This is not preferable because clogging tends to occur.
Further, when the particle diameter standard deviation exceeds 1/2 of the average particle diameter, the storage stability of the pigment dispersion and the ink is inferior, and as a result, nozzle clogging tends to occur, which is not preferable.
In addition, if the amount of the dispersant used relative to the carbon black CB-2 is less than 0.1, the above effect is difficult to achieve, and the storage stability of the pigment dispersion and the ink is inferior, resulting in nozzle clogging. When the ratio is larger than 2, the viscosity of the pigment dispersion and the ink tends to be too high, and printing by the inkjet method tends to be difficult.

In the present invention, the total content of dimers, trimers and tetramers of naphthalenesulfonic acid in the naphthalenesulfonic acid sodium formalin condensate as a dispersant is preferably 20% by mass to 80% by mass. When the content is less than 20% by mass, the dispersibility is deteriorated and the storage stability of the pigment dispersion and the ink is inferior.
On the other hand, when the content of dimer to tetramer of naphthalene sulfonic acid exceeds 80% by mass, the viscosity becomes high and dispersion becomes difficult.

  Specific examples of carbon black CB-2 used in the present invention include # 10B, # 20B, # 30, # 33, # 40, # 44, # 45, # 45L, # 50, # 50 manufactured by Mitsubishi Chemical Corporation. 55, # 95, # 260, # 900, # 1000, # 2200B, # 2300, # 2350, # 2400B, # 2650, # 2700, # 4000B, CF9, MA8, MA11, MA77, MA100, MA220, MA230, MA600 Monarch 120, Monarch 700, Monarch 800, Monarch 880, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, Mogal L, Legal 99R, Legal 250R, Legal 300R, Legal 330R, Legal 400R, manufactured by Cabot Legal 500R and Legal 60R, etc .; Dexa's Printex A, Printex G, Printex U, Printex V, Printex 55, Printex 140U, Printex 140V, NIPEX60, NIPEX150, NIPEX170, NIPEX180, Special Black 4, Special Black 4A Special Black 5, Special Black 6, Special Black 100, Special Black 250, Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170, etc. Can be mentioned.

The pigment dispersion (2) of the present invention can be obtained by dispersing the pigment, dispersant, water, and various additives as necessary with a known disperser such as a sand mill, a ball mill, a roll mill, a bead mill, a nanomizer, or a homogenizer. .
In the present invention, bead mill dispersion with good dispersion efficiency is effective, and the particle diameter is easily controlled. The bead material and bead size are important for particle size control. Ceramic, glass, stainless steel, zirconia, etc. can be raised as the bead material. Among them, zirconia beads with high true specific gravity and low contamination are effective in terms of contamination and dispersion efficiency.
The bead diameter depends on the particle diameter of the target dispersion, but in the pigment dispersion (2), the range of 0.3 mm to 0.03 mm is good, especially in terms of pigment dispersion efficiency and dispersion stability. 0.03 mm is good.
The particle diameter is controlled by the rotor peripheral speed and dispersion time of the disperser, but if the rotor peripheral speed is too high, it is good in terms of dispersion efficiency. The selection of peripheral speed is important because it impairs stability. In the present invention, the optimum peripheral speed of the disperser is obtained, and further the dispersion time is adjusted to obtain the pigment dispersion (2).

The particle size measurement conditions by the dynamic light scattering method are as follows.
Dispersion, ink liquid particle size measuring condition measuring instrument: Nikkiso Co., Ltd. particle size distribution meter UPA150
Measurement conditions 1) Measurement liquid solid content concentration: 0.1 mass% water solvent
2) Transparent Pearls: Yes
3) Spherical Particles: No
4) Part. Refractive Index: 1.86
5) Part. Density: 1.86 (gm / cm ³ )
6) Fluid: Default Fluid
7) Fluid Refractive Index: 1.33
8) Viscosity High 30 ° C: 0.797 cp
9) Viscosity Low 20 ° C .: 1.002 cp
10) Display format: Volume distribution Measured under the above conditions to determine the average particle size (D50) and standard deviation (sd).

The average particle diameter (D50) is the average particle diameter (D50) (nm) when the cumulative curve is determined with the total volume of the powder (pigment) group as 100% and the cumulative curve is 50%. It is said.
The standard deviation is obtained by the following formula and is a measure of the distribution width of the measured particle size distribution, and does not mean a statistical standard deviation (statistical error).
Assuming a set of one powder (pigment) and its particle size distribution is obtained, when the cumulative curve is obtained with the total volume of the powder group as 100%, d84%: cumulative curve is 84 % Particle size (nm)
d16%: Particle diameter at the point where the cumulative curve is 16% (nm)

In the mixing of the pigment dispersions (1) and (2), the carbon black CB-1 and CB-2 have a total content of 1% by mass to 20% by mass in the inkjet ink, and the carbon black CB The mass ratio of -1 and CB-2 in the ink is preferably 2:98 to 50:50.
When the content of carbon black CB-1 is increased, the image density tends to be high, but it is not preferable because it requires a carbon oxidation treatment step, an impurity removal step, and the like, resulting in an increase in cost.
In addition, the ink of the present invention using the pigment dispersions (1) and (2) has a higher image density on plain paper (non-smooth paper) by mixing than when the pigment dispersions (1) and (2) are used alone. In addition to this, the image density on glossy paper (smooth paper) is particularly high.

For smooth paper and non-smooth paper, the smoothness of the recording material is measured, and the smooth paper and non-smooth paper are classified according to the smoothness. However, the present invention is not particularly limited to this range.
In general, non-smooth paper has a smoothness of 500 (seconds) or less and is not subjected to surface coating or the like. On the other hand, many smooth papers are surface-coated, and the smoothness is 500 (seconds) or more, and art paper, cast-coated paper, and the like can be raised.
The smoothness is measured with an Oken type measuring instrument that places a hollow head on the paper surface, depressurizes the inside, and measures the smoothness according to the time (seconds) in which a certain amount of air flows from the gap between the head and the paper surface.

Furthermore, it becomes possible to improve the storage stability while maintaining the image density by adding a polyether type polyurethane resin having an acid value of 40 to 100 mgKOH / g to the pigment dispersion (1) and / or (2). It was.
The polyurethane resin is preferably added as a polyurethane resin emulsion.
In polyurethane resin emulsions, normal polyurethane resins that are relatively hydrophilic are emulsified using an emulsifier on the outside, and functional groups that function as an emulsifier are introduced into the resin itself by means such as copolymerization. There is an emulsion type emulsion. An anionic self-emulsifying type polyurethane resin emulsion that is always excellent in dispersion stability can be used in the ink of the present invention. In this case, the polyurethane resin is preferably a polyether type rather than a polyester type or polycarbonate type in terms of pigment fixation and dispersion stability. The reason is not clear, but the non-ether type is often weak in solvent resistance, and the viscosity tends to aggregate when the ink is stored at high temperature.
The preferable content of “polyether type polyurethane” is 0.1% by mass to 10% by mass in the ink jet ink, and more preferably 0.5% by mass to 5% by mass.

The ether polyurethane resin preferably has an acid value of 40 mgKOH / g to 100 mgKOH / g and a molecular weight of 500 to 50,000. The average diameter of the primary particles of the ether polyurethane resin emulsion is preferably 20 nm or less, more preferably 15 nm or less, still more preferably 10 nm or less.
The gas black type carbon black of the present invention has good matching with the ether polyurethane resin emulsion having a small average particle diameter, and the dispersion seems to be stable. In particular, by setting the average particle size of the ether polyurethane resin emulsion to 10 nm or less, the effect of preventing trouble that ink is not ejected while the ink jet printer is operating while printing is continued is enhanced.
When ink is no longer discharged, printing can be resumed by cleaning the ink flow path including the nozzle holes of the inkjet printer, but this impedes practicality. The average particle diameter of the ether polyurethane resin emulsion in the present invention is a value measured with Nikkiso Microtrac UPA in an environment of 23 ° C. and 55% RH.

  The glass transition point of the ether polyurethane resin is preferably in the range of −50 to 150 ° C. More preferably, it is the range of -10-100 degreeC. The reason is not clear, but when the glass transition point exceeds 150 ° C., the film formation property of the ether polyurethane resin is glassy and hard, but the pigment particles and the ether polyurethane resin landed on the image support at the same time. The scratch resistance of the part is surprisingly brittle, but on the other hand, at 150 ° C. or lower, it is polyurethane-like and soft, but it has excellent scratch resistance. However, if it is less than -50 ° C, the film is too soft and the scratch resistance is poor. From the above points, at the same addition amount, the effect of scratch resistance is greater when the glass transition point is in the range of −50 to 150 ° C. In addition, the glass transition point of resin as used in the field of this invention is based on the measuring method of either DSC (differential scanning calorimeter) or TMA (thermomechanical analysis).

The ether polyurethane resin emulsion preferably has a minimum film-forming temperature of room temperature or lower, and the minimum film-forming temperature is more preferably 25 ° C. or lower. If the film formation of the ether polyurethane resin emulsion is carried out at room temperature or lower, particularly 25 ° C. or lower, the binding of paper fibers automatically proceeds without any special treatment such as heating or drying of the image-formed image support. This is preferable.
Here, the “minimum film-forming temperature (MFT)” means that the aqueous emulsion particles obtained by dispersing the ether-based polyurethane resin emulsion particles in water are cast thinly on a metal plate such as aluminum to raise the temperature. This is the lowest temperature at which a transparent continuous film is formed. In the temperature range below the minimum film-forming temperature, a white powder is formed.

  “Film-forming property” means that when resin particles are dispersed in water to form a resin emulsion, a resin film is formed when the water component, which is a continuous layer of the resin emulsion, is evaporated. means. This resin film plays a role of firmly fixing the pigment in the ink to the surface of the image support. Thus, it is considered that an image excellent in abrasion resistance and water resistance can be realized.

  In the present invention, the ether-based polyurethane resin emulsion particles do not have to be placed in advance in the pigment dispersion, and may be added later when adjusting the ink liquid.

Moreover, the ink for inkjet recording of this invention can also use dispersing agents other than the condensate of naphthalenesulfonic acid formalin in the range which does not impair the said effect.
As the dispersant, various surfactants such as an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant, and a polymer type dispersant can be used in combination.

  Examples of the anionic surfactant include alkyl sulfocarboxylates, α-olefin sulfonates, polyoxyethylene alkyl ether acetates, N-acyl amino acids and salts thereof, N-acyl methyl taurate, alkyl sulfate polyoxy Alkyl ether sulfate, alkyl sulfate polyoxyethylene alkyl ether phosphate, rosin acid soap, castor oil sulfate ester salt, lauryl alcohol sulfate ester salt, alkylphenol type phosphate ester, naphthalene sulfonate formalin condensate, alkyl type phosphate ester, Examples include alkylallylsulfone hydrochloride, diethylsulfosuccinate, and dioctylsulfosuccinate of diethylhexylsulfosuccinate.

Examples of the cationic surfactant include 2-vinylpyridine derivatives and poly-4-vinylpyridine derivatives.
Examples of amphoteric surfactants include lauryldimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, coconut oil fatty acid amidopropyldimethylaminoacetic acid betaine, polyoctylpolyaminoethylglycine and others Examples include imidazoline derivatives.

Nonionic surfactants include the following.
Ether systems such as polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene alkyl ether and polyoxyallylalkyl alkyl ether; Polyoxyethylene oleic acid, polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate and polyoxyethylene stearate Ester systems such as 2,4,7,9-tetramethyl-5-decyne-4,7-
Acetylene glycol systems such as diol, 3,6-dimethyl-4-octyne-3,6-diol, and 3,5-dimethyl-1-hexyn-3-ol

  The dispersion medium of the pigment dispersion desirably contains water, but various organic solvents may be used in combination as necessary. For example, as water-soluble organic solvents, alcohols such as methanol, ethanol, 1-propanol and 2-propanol, polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol and glycerin, N-methylpyrrolidone, 2-pyrrolidone and the like Pyrrolidone derivatives, acetone, methyl ethyl ketone lucanolamine and the like.

In addition to black ink, color ink / colorless ink can also be used in the inkjet recording system of the present invention.
Examples of the magenta pigment include Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 168, 184, 202, Pigment Violet 19, and the like. It is done.
Examples of the cyan pigment include pigment blue 1, 2, 3, 15, 15: 3, 15: 4, 16, 22, 60, and bat blue 4, 60.
Examples of the yellow pigment include pigment yellow 1, 2, 3, 12, 13, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 114, 120, 128, 129, 138, 150. 151, 154, 155, 180 and the like.
By using Pigment Yellow 74 as the yellow pigment, Pigment Red 122 and Pigment Violet 19 as the magenta pigment, and Pigment Blue 15 as the cyan pigment, it is possible to obtain a balanced ink with excellent color tone and light resistance.

The pigment concentration in the pigment dispersion or the pigment ink is preferably 0.1 to 50% by mass, particularly preferably 0.1 to 30% by mass.
These can be used by dispersing with the above-described dispersant or the like.

The ink of the present invention further contains a penetrating agent, and the pigment dispersion and the ink contain a resin, a wetting agent, a surfactant, a penetrating agent, a pH adjusting agent, an antiseptic / antifungal agent, a chelating reagent, and a rust preventing agent as necessary. Various additives such as an agent, an antioxidant, an ultraviolet absorber, an oxygen absorber, and a light stabilizer can be blended.
Examples of the wetting agent are not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include polyhydric alcohols, polyhydric alcohol alkyl ethers, polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides. , Amines, sulfur-containing compounds, propylene carbonate, ethylene carbonate, other wetting agents and the like. These may be used alone or in combination of two or more.

  Examples of polyhydric alcohols include glycerin, diethylene glycol, 1,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, propylene glycol, dipropylene glycol, trimethylolpropane, trimethylolethane, Ethylene glycol, tripropylene glycol, tetraethylene glycol, hexylene glycol, polyethylene glycol, polypropylene glycol, 1,5-pentanediol, 1,6-hexanediol, glycerol, 1,2,6-hexanetriol, 1,2, Examples include 4-butanetriol, 1,2,3-butanetriol, and petriol.

Examples of the polyhydric alcohol alkyl ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether, and the like. It is done.
Examples of polyhydric alcohol aryl ethers include ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.

Examples of the nitrogen-containing heterocyclic compound include 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, γ-butyrolactone, and the like. Is mentioned.
Examples of amides include formamide, N-methylformamide, N, N-dimethylformamide, and the like.
Examples of amines include monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, triethylamine, and the like.
Examples of the sulfur-containing compounds include dimethyl sulfoxide, sulfolane, thiodiethanol, and the like.

Other humectants are preferably sugars. Examples of saccharides include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides), polysaccharides, and the like. Specific examples include glucose, mannose, fructose, ribose, xylose, arabinose, galactose, maltose, cellobiose, lactose, sucrose, trehalose, maltotriose, and the like. Here, the polysaccharide means a saccharide in a broad sense, and is used to include a substance that exists widely in nature such as α-cyclodextrin and cellulose. Examples of derivatives of these saccharides include reducing sugars of the aforementioned saccharides (for example, sugar alcohols represented by the general formula: HOCH ₂ (CHOH) nCH ₂ OH (n = 2 to 5)), oxidized sugars ( For example, aldonic acid, uronic acid, etc.), amino acids, thioic acid and the like. Among these, sugar alcohols are preferable, and specific examples include maltitol and sorbit.
Among the above wetting agents, glycerin, diethylene glycol, triethylene glycol, 1,3-butanediol, 3-methyl-1,3-butanediol, 2-pyrrolidone, N-methyl from the viewpoint of storage stability and ejection stability. 2-pyrrolidone is particularly preferred.

The blending ratio of the pigment and the wetting agent has a great influence on the stability of ink ejection from the head. If the blending amount of the wetting agent is small even though the pigment solid content is high, the evaporation of water near the ink meniscus of the nozzle may progress, resulting in ejection failure.
The content of the wetting agent in the ink is about 20 to 35% by mass, but 22.5 to 32.5% by mass is more preferable. Within this range, the results of ink drying, storage test, reliability test and the like are very good. If the content is less than 20% by mass, the ink may easily dry on the nozzle surface, resulting in ejection failure. If the content exceeds 35% by mass, the dryness on the paper surface is poor and the character quality on plain paper is poor. May decrease.

As the surfactant, those having a low surface tension and a high leveling property are used, depending on the type of pigment and the combination with the wetting agent. For example, fluorine-based surfactants and silicone-based surfactants can be mentioned, and fluorine-based surfactants are preferable.
As the fluorine-based surfactant, those having 2 to 16 carbon atoms substituted by fluorine are preferable, and those having 4 to 16 carbon atoms are more preferable. When the fluorine-substituted carbon number is less than 2, the effect of fluorine may not be obtained, and when it exceeds 16, problems such as ink storage stability may occur.
Examples of fluorosurfactants include perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, and perfluoroalkyl ether groups in the side chain. And polyoxyalkylene ether polymer compounds. Among these, a polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain is particularly preferable because of its low foaming property.

Examples of the perfluoroalkyl sulfonic acid compound include perfluoroalkyl sulfonic acid, perfluoroalkyl sulfonate, and the like.
Examples of the perfluoroalkyl carboxylic acid compound include perfluoroalkyl carboxylic acid and perfluoroalkyl carboxylate.
Examples of the perfluoroalkyl phosphate compound include perfluoroalkyl phosphate esters, perfluoroalkyl phosphate salts, and the like.
The polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain includes a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in the side chain, and a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in the side chain. And a salt of a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in the side chain.
As counter ions of the salts in these fluorosurfactants, Li, Na, K, NH ₄ , NH ₃ CH ₂ CH ₂ OH, NH ₂ (CH ₂ CH ₂ OH) ₂ , NH (CH ₂ CH ₂ OH) ₃ etc.
As a fluorine-type surfactant, what was synthesize | combined suitably may be used, or a commercial item may be used. Examples of commercially available products include DuPont FS-300, Neos FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW, and OM-nova PF-151N. Is mentioned.

The silicone-based surfactant is not particularly limited and may be appropriately selected depending on the purpose, and those that do not decompose even at high pH are preferable. For example, side-chain modified polydimethylsiloxane, both-end modified polydimethylsiloxane, piece Examples include terminal-modified polydimethylsiloxane and side-chain both-end-modified polydimethylsiloxane, and those having a polyoxyethylene group or polyoxyethylene polyoxypropylene group as a modifying group exhibit good properties as an aqueous surfactant. preferable.
As a silicone type surfactant, you may use what was synthesize | combined suitably or may use a commercial item. Commercially available products can be easily obtained from, for example, Big Chemie, Shin-Etsu Silicone, Toray Dow Corning Silicone.
The content of the surfactant in the ink is preferably 0.01 to 3.0% by mass, and more preferably 0.5 to 2% by mass. If the content is less than 0.01% by mass, the effect of adding the surfactant may be lost. If the content exceeds 3.0% by mass, the permeability to the recording medium becomes higher than necessary, and the image density is lowered. And strikethrough may occur.

The penetrant preferably contains at least one polyol compound having a solubility in water at 20 ° C. of 0.2 to 5.0 mass%. Examples of such a polyol compound include 2-ethyl-2-methyl-1,3-propanediol, 3,3-dimethyl-1,2-butanediol, and 2,2-diethyl-1,3-propanediol. 2-methyl-2-propyl-1,3-propanediol, 2,4-dimethyl-2,4-pentanediol, 2,5-dimethyl-2,5-hexanediol, 5-hexene-1,2- Examples thereof include aliphatic diols such as diol and 2-ethyl-1,3-hexanediol.
Among these, 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol are particularly preferable.

Other penetrants that can be used in combination are not particularly limited as long as they can be dissolved in the ink and adjusted to the desired physical properties, and can be appropriately selected according to the purpose. For example, diethylene glycol monophenyl ether, ethylene Examples thereof include alkyl and aryl ethers of polyhydric alcohols such as glycol monophenyl ether, ethylene glycol monoallyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether and tetraethylene glycol chlorophenyl ether, and lower alcohols such as ethanol.
The content of the penetrant in the ink is preferably 0.1 to 4.0% by mass. If the content is less than 0.1% by mass, quick-drying may not be obtained, and a blurred image may be obtained. Or the permeability to the recording medium is unnecessarily high, and the image density may be lowered or the image may be broken through.

The pH adjuster is not particularly limited as long as it can adjust the pH to 7 to 11 without adversely affecting the ink to be prepared, and can be appropriately selected according to the purpose. And alkali metal hydroxides, ammonium hydroxides, phosphonium hydroxides, alkali metal carbonates, and the like. When the pH is less than 7 or exceeds 11, the amount of the ink-jet head or ink supply unit that melts out increases, and problems such as ink deterioration, leakage, and ejection failure may occur.
Examples of alcohol amines include diethanolamine, triethanolamine, 2-amino-2-ethyl-1,3-propanediol, and the like.
Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide.
Examples of the ammonium hydroxide include ammonium hydroxide, quaternary ammonium hydroxide, quaternary phosphonium hydroxide, and the like.
Examples of the alkali metal carbonate include lithium carbonate, sodium carbonate, and potassium carbonate.

Examples of the antiseptic / antifungal agent include sodium dehydroacetate, sodium sorbate, 2-pyridinethiol-1-oxide sodium, sodium benzoate, sodium pentachlorophenol, and the like.
Examples of the chelating reagent include sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uramil diacetate, and the like.
Examples of the rust preventive include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite and the like.

Examples of the antioxidant include phenol-based antioxidants (including hindered phenol-based antioxidants), amine-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, and the like.
Examples of phenolic antioxidants (including hindered phenolic antioxidants) include butylated hydroxyanisole, 2,6-di-tert-butyl-4-ethylphenol, stearyl-β- (3,5- Di-tert-butyl-4-hydroxyphenyl) propionate, 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 4 , 4'-butylidenebis (3-methyl-6-tert-butylphenol), 3,9-bis [1,1-dimethyl-2- [β- (3-tert-butyl-4-hydroxy-5-methylphenyl) Propionyloxy] ethyl] -2,4,8,10-tetrixaspiro [5,5] undecane, 1,1,3-to Lis (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) Benzene, tetrakis [methylene-3- (3 ′, 5′-di-tert-butyl-4′-hydroxyphenyl) propionate] methane, and the like.

  Examples of amine-based antioxidants include phenyl-β-naphthylamine, α-naphthylamine, N, N′-di-sec-butyl-p-phenylenediamine, phenothiazine, N, N′-diphenyl-p-phenylenediamine, 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butylphenol, 2,4-dimethyl-6-tert-butyl-phenol, butylhydroxyanisole, 2,2'-methylenebis (4 -Methyl-6-tert-butylphenol), 4,4'-butylidenebis (3-methyl-6-tert-butylphenol), 4,4'-thiobis (3-methyl-6-tert-butylphenol), tetrakis [methylene- 3 (3,5-di-tert-butyl-4-dihydroxyphenyl) propionate And methane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, and the like.

Examples of the sulfur-based antioxidant include dilauryl-3,3′-thiodipropionate, distearyl thiodipropionate, lauryl stearyl thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl. -Β, β'-thiodipropionate, 2-mercaptobenzimidazole, dilauryl sulfide and the like.
Examples of the phosphorus antioxidant include triphenyl phosphite, octadecyl phosphite, triisodecyl phosphite, trilauryl trithiophosphite, and trinonylphenyl phosphite.

Examples of the ultraviolet absorber include a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, a salicylate ultraviolet absorber, a cyanoacrylate ultraviolet absorber, and a nickel complex ultraviolet absorber.
Examples of benzophenone-based ultraviolet absorbers include 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone and the like can be mentioned.
Examples of the benzotriazole ultraviolet absorber include 2- (2′-hydroxy-5′-tert-octylphenyl) benzotriazole, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- ( 2'-hydroxy-4'-octoxyphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole and the like.
Examples of salicylate-based ultraviolet absorbers include phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate, and the like.
Examples of the cyanoacrylate ultraviolet absorber include ethyl-2-cyano-3,3′-diphenyl acrylate, methyl-2-cyano-3-methyl-3- (p-methoxyphenyl) acrylate, and butyl-2- And cyano-3-methyl-3- (p-methoxyphenyl) acrylate.
Examples of the nickel complex ultraviolet absorber include nickel bis (octylphenyl) sulfide, 2,2′-thiobis (4-tert-octylferrate) -n-butylamine nickel (II), 2,2′-thiobis ( 4-tert-octylferrate) -2-ethylhexylamine nickel (II), 2,2′-thiobis (4-tert-octylferrate) triethanolamine nickel (II), and the like.

The inkjet recording ink containing the pigment used in the present invention is a known method, for example, a pigment dispersion, water, a water-soluble organic solvent, a surfactant, etc., sand mill, ball mill, roll mill, bead mill, nanomizer, homogenizer, ultrasonic dispersion. It is obtained by stirring and mixing using a machine, etc., filtering coarse particles with a filter, a centrifugal separator or the like, and deaeration as necessary.
The concentration of the pigment in the ink is preferably 1 to 20% by mass with respect to the total amount of the ink. If the amount is less than 1% by mass, the image density is low and the printed image lacks sharpness. If the amount is more than 20% by mass, not only the viscosity of the ink tends to increase but also nozzle clogging tends to occur.
The content of the water-soluble organic solvent is 50% by mass or less, preferably 5 to 40% by mass, and more preferably 10 to 35% by mass with respect to the total amount of the ink.
In addition, the ink may be blended with additives similar to the materials described for the additive to the pigment dispersion, if necessary.

The ink for inkjet recording can be accommodated in a container and used as a cartridge.
As a printing method, there are a continuous jet type and an on-demand type, and examples of the on-demand type include a piezo method, a thermal method, and an electrostatic method.

An example of the image forming method of the present invention and an ink jet recording apparatus for carrying out the method will be described with reference to the drawings.
-Recording device-
The ink of the present invention can be suitably used for various recording apparatuses using an ink jet recording system, such as an ink jet recording printer, a facsimile apparatus, a copying apparatus, a printer / fax / copier multifunction machine, and the like.

The outline of the ink jet recording apparatus used in the examples will be described below.
The ink jet recording apparatus shown in FIG. 1 has an apparatus main body (101), a paper feed tray (102) for loading paper mounted on the apparatus main body (101), and an image mounted on the apparatus main body (101). A paper discharge tray (103) for stocking the formed paper and an ink cartridge loading section (104) are provided. On the upper surface of the ink cartridge loading section (104), an operation section (105) such as operation keys and a display is arranged. The ink cartridge loading unit (104) has an openable / closable front cover (115) for attaching and detaching the ink cartridge (200). (111) is the upper cover, and (112) is the front surface of the front cover.

In the apparatus main body (101), as shown in FIG. 2, a carriage (133) is mainly composed of a guide rod (131) and a stay (132) which are guide members horizontally mounted on left and right side plates (not shown). It is slidably held in the scanning direction and moved and scanned by a main scanning motor (not shown).
The carriage (133) includes a plurality of recording heads (134) including four inkjet recording heads that discharge ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk). Are arranged in a direction crossing the main scanning direction, and the ink droplet ejection direction is directed downward.
As an inkjet recording head constituting the recording head (134), a piezoelectric actuator such as a piezoelectric element, a thermal actuator that utilizes a phase change caused by liquid film boiling using an electrothermal transducer such as a heating resistor, and a temperature change A shape memory alloy actuator using a metal phase change, an electrostatic actuator using an electrostatic force, or the like provided as energy generating means for discharging ink can be used.
The carriage (133) is equipped with a sub tank (135) for each color for supplying ink of each color to the recording head (134). The sub tank (135) is supplied with ink according to the ink set of the present invention from the ink cartridge (200) of the present invention loaded in the ink cartridge loading section (104) via an ink supply tube (not shown). To be replenished.

On the other hand, as a paper feeding unit for feeding the paper (142) stacked on the paper stacking unit (pressure plate) (141) of the paper feed tray (102), 1 sheet (142) is fed from the paper stacking unit (141). Opposite to the half-moon roller [sheet feeding roller (143)] for separating and feeding one sheet at a time, and the sheet feeding roller (143), a separation pad (144) made of a material having a large friction coefficient is provided, and this separation pad (144) is It is biased toward the paper feed roller (143).
A conveying belt (151) for electrostatically adsorbing and conveying the paper (142) as a conveying unit for conveying the paper (142) fed from the paper feeding unit below the recording head (134). A counter roller (152) for conveying the paper (142) sent from the paper supply unit via the guide (145) between the conveying belt (151) and a paper (substantially vertically upward) ( 142) and a leading guide roller 153 urged toward the conveying belt (151) by the holding member (154). (155) and a charging roller (156) which is a charging means for charging the surface of the conveyor belt (151).

The conveyance belt (151) is an endless belt, is stretched between the conveyance roller (157) and the tension roller (158), and can circulate in the belt conveyance direction. The transport belt (151) includes, for example, a surface layer serving as a sheet adsorbing surface formed of a resin material having a thickness of about 40 μm without resistance control, for example, a copolymer of tetrafluoroethylene and ethylene (ETFE), It has the same material as the surface layer and a back layer (medium resistance layer, earth layer) that has been subjected to resistance control by carbon. On the back side of the conveyance belt (151), a guide member (161) is arranged corresponding to the printing area by the recording head (134). As a paper discharge unit for discharging the paper (142) recorded by the recording head (134), a separation claw (171) for separating the paper (142) from the transport belt (151), and paper discharge A roller (172) and a paper discharge roller (173) are provided, and a paper discharge tray (103) is arranged below the paper discharge roller (172).
A double-sided paper feeding unit (181) is detachably attached to the back surface of the apparatus main body (101). The double-sided paper feeding unit (181) takes in the paper (142) returned by the reverse rotation of the transport belt (151), reverses it, and feeds the paper again between the counter roller (152) and the transport belt (151). To do. A manual paper feed unit (182) is provided on the upper surface of the double-sided paper feed unit (181).

In this ink jet recording apparatus, the sheet (142) is separated and fed one by one from the sheet feeding unit, and the sheet (142) fed substantially vertically upward is guided by the guide (145) and the transport belt (151). ) And the counter roller (152). Further, the leading end is guided by the conveying guide (153) and pressed against the conveying belt (151) by the leading end pressure roller (155), and the conveying direction is changed by about 90 °.
At this time, the conveyance belt (157) is charged by the charging roller (156), and the paper (142) is electrostatically adsorbed to the conveyance belt (151) and conveyed. Therefore, by driving the recording head (134) according to the image signal while moving the carriage (133), ink droplets are ejected onto the stopped sheet (142) to record one line, and the sheet ( 142), the next line is recorded after a predetermined amount is conveyed. Upon receiving a recording end signal or a signal that the rear end of the paper (142) has reached the recording area, the recording operation is finished and the paper (142) is discharged to the paper discharge tray (103).

When a near-end ink remaining amount in the sub tank (135) is detected, a required amount of ink is supplied from the ink cartridge (200) to the sub tank (135).
In this ink jet recording apparatus, when the ink in the ink cartridge (200) is used up, the casing of the ink cartridge (200) can be disassembled and only the ink bag inside can be replaced. Further, the ink cartridge (200) can supply ink stably even when the ink cartridge (200) is vertically placed and has a front loading configuration. Therefore, even when the upper part of the apparatus main body (101) is closed and installed, for example, even when it is stored in a rack or an object is placed on the upper surface of the apparatus main body (101), the ink The cartridge (200) can be easily replaced.
Here, an example is described in which the present invention is applied to a serial (shuttle type) ink jet recording apparatus that is scanned by a carriage, but the present invention can be similarly applied to a line type ink jet recording apparatus having a line type head.

-Ink cartridge-
Each ink constituting the ink set of the present invention can be accommodated in a container and used as an ink cartridge, and other members appropriately selected as necessary may be attached.
The container is not particularly limited, and its shape, structure, size, material, etc. can be appropriately selected according to the purpose. For example, the container has an ink bag formed of an aluminum laminate film, a resin film, etc. Etc. are preferable.
The ink cartridge will be described with reference to FIGS. Here, FIG. 3 is a schematic diagram illustrating an example of the ink bag 241 of the ink cartridge of the present invention, and FIG. 4 is a schematic diagram illustrating the ink cartridge 200 in which the ink bag 241 of FIG. 3 is accommodated in the cartridge case 244. is there.

As shown in FIG. 3, ink is filled into the ink bag 241 from the ink inlet 242 and air remaining in the ink bag is exhausted, and then the ink inlet 242 is closed by fusion. In use, the needle of the apparatus main body is pierced into the ink discharge port 243 made of a rubber member and supplied to the apparatus. The ink bag 241 is formed of a packaging member such as a non-permeable aluminum laminate film. As shown in FIG. 4, it is usually housed in a plastic cartridge case 244 and used as an ink cartridge 200 detachably mounted on various ink jet recording apparatuses.
The ink cartridge of the present invention is particularly preferably used by being detachably mounted on the above-described ink jet recording apparatus of the present invention.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these Examples.
In Examples and Comparative Examples, pigment dispersions were prepared and inks were prepared using the pigment dispersions. Moreover, the pre-processing liquid was created, respectively. In the examples, “parts” and “%” are based on mass.

Example 1
<Preparation of oxidized carbon black (1)>
200 g of Degussa carbon black PRINTEX-U is put into a cylindrical ozone treatment device, ozone is generated with an ozone generator (KQS-120, manufactured by Kotohira Kogyo Co., Ltd.), and the treatment temperature is under an ozone atmosphere. An oxidation treatment was carried out for 2 hours while maintaining the temperature at about 30 ° C. to obtain oxidized carbon black (1).
When the CB volatilization amount of the obtained oxidized carbon black (1) was measured, it was 10%. The BET specific surface area was 110 m ² / g.

<Preparation of pigment dispersion (1-1)>
・ Oxidized carbon black (1) 20.0 parts ・ Distilled water 70.0 parts After adjusting pH to 7.0 by adding NaOH 20% aqueous solution to the above, the total amount of the dispersion is 100 parts by mass with distilled water. Distilled water was added for adjustment.
The NaOH 20% aqueous solution used was 1.2 parts.
After pre-mixing the materials of the above formulation, disperse for 5 minutes at a peripheral speed of 10 m / s and a liquid temperature of 10 ° C. using 0.3 mm zirconia beads with a disk-type bead mill (KDL type batch type manufactured by Shinmaru Enterprises). did.
Coarse particles were separated by a centrifugal separator (Model 3600 manufactured by Kubota Corporation) to obtain a carbon black pigment dispersion (1-1) having an average particle diameter of about 125 nm and a standard deviation of 60.2 nm.

<Preparation of pigment dispersion (2-1)>
・ Carbon black NIPEX150
(Degussa: Gas Black) 200 parts ・ Naphthalene sulfonate sodium formalin condensate (A-45-PN, Takemoto Yushi Co.)
(Naphthalenesulfonic acid dimer, trimer, tetramer total content: 20%) 50 parts • Distilled water 750 parts After premixing the above mixture, the premixed bead mill disperser (UAM manufactured by Kotobuki Kogyo Co., Ltd.) -015) was dispersed with 0.03 mm zirconia beads (density 6.03 × 10 ⁻⁶ g / m ² ) at a peripheral speed of 10 m / s and a liquid temperature of 25 ° C. for 40 minutes, and then a centrifuge (Kubota Corporation) Coarse particles were centrifuged with Model-3600) to obtain a dispersion (2-1) shown in Table 1 having an average particle diameter of 50.4 nm and a standard deviation of 18.3 nm of the carbon black dispersion.

<Creation of Ink of Example 1>
The material having the following formulation was mixed and stirred for 30 minutes to prepare the ink of Example 1.
(Ink formulation of Example 1)
-Pigment dispersion (1-1) (pigment concentration 20%) 4.0 parts-Pigment dispersion (2-1) (pigment concentration 20%) 36.0 parts-Glycerol 5.5 parts-1,3-butane Diol 16.5 parts ・ 2-ethyl-1,3-hexanediol 2.0 parts ・ Fluorosurfactant (solid content 40%) 2.5 parts (manufactured by DuPont: Zonyl FS-300)
Fluoroethylene / vinyl ether alternating copolymer (solid content 50%) 6.0 parts (Asahi Glass Co., Ltd .: Lumiflon FE4300, average particle size 150 nm,
MFT 30 ℃ or less)
27.4 parts of distilled water After that, 0.1 part of 2-amino-2-ethyl-1,3-propanediol (40% aqueous solution) was added and the pH of the ink was adjusted to 10, followed by mixing and stirring for 30 minutes. The ink of Example 1 was made.

Examples 2-9
<Creation of oxidized carbon black (2) to (9)>
In the production of oxidized carbon black (1) of Example 1, carbon black PRINTEX-U manufactured by Degussa was changed to pre-oxidized carbon black described in Table 1, respectively, and the ozone generation amount / treatment time was adjusted, and the volatile content was adjusted. Except for the adjustment, oxidized carbon blacks (2) to (9) were prepared in the same manner as the oxidized carbon black (1).

<Preparation of pigment dispersions (1-2) to (1-9)>
In the preparation of the pigment dispersion (1-1) in Example 1, instead of the oxidized carbon black (1), the oxidized carbon black (2) to (9) was used, and the addition amount of the NaOH aqueous solution was adjusted to adjust the dispersion pH. The pigment dispersions (1-2) to (1-9) shown in Table 1 were obtained in the same manner as in the preparation of the pigment dispersion (1-1) except that was adjusted to 7.

<Preparation of pigment dispersions (2-2) to (2-3)>
The pigment dispersion (2) was changed to a pigment dispersion (2) except that the naphthalenesulfonic acid dimer, trimer, and tetramer total content was changed to 50% and 80% naphthalenesulfonic acid. The pigment dispersions (2-2) to (2-3) shown in Table 1 were obtained in the same manner as in the preparation of -1).

<Creation of inks of Examples 2 to 9>
In the preparation of the ink of Example 1, instead of the pigment dispersion (1-1) (pigment concentration 20%), the pigment dispersions (1-2) to (1-9) (pigment concentration 20%) and the pigment Instead of dispersion (2-1) (pigment concentration 20%), pigment dispersions (2-2) to (2-3) (pigment concentration 20%) were used, and pigment dispersions (1) and (2) The inks of Examples 2 to 9 described in Table 1 were prepared in the same manner as in Example 1 except that the total amount of

Examples 10-11
<Preparation of pigment dispersions (1-10) to (1-11)>
In preparation of the pigment dispersion (1-1) of Example 1, instead of oxidized carbon black (1), oxidized carbon black (2) was used, the amount of NaOH aqueous solution was adjusted, and the dispersion pH was listed in Table 1. Pigment dispersions (1-10) to (1-11) were obtained in the same manner as in the preparation of the pigment dispersion (1-1) except that the pH was adjusted.

<Preparation of pigment dispersion (2-4)>
The dispersion time of the pigment dispersion (2-2) was adjusted to obtain the pigment dispersion (2-4) shown in Table 1 having an average particle diameter of 131.8 nm and a standard deviation of 55.1 nm of the carbon black dispersion.

<Creation of inks of Examples 10 to 11>
In the preparation of the ink of Example 2, instead of pigment dispersion (1-2) (pigment concentration 20%), pigment dispersions (1-10) to (1-11) (pigment concentration 20%) and pigments Example 10 shown in Table 1 was carried out in the same manner as Example 2 except that instead of Dispersion (2-2) (pigment concentration 20%), Pigment Dispersion (2-4) (pigment concentration 20%) was used. ~ 11 inks were made.

Example 12
<Preparation of pigment dispersion (1-12)>
(Pigment dispersion (1-12) formulation)
-20.0 parts of oxidized carbon black (1)-70.0 parts of distilled water After adjusting pH to 7.0 by adding NaOH 20% aqueous solution to the above, the dispersion becomes 93 parts by mass with distilled water. Distilled water was added to adjust. The NaOH 20% aqueous solution used was 1.2 parts.
After pre-mixing the materials of the above formulation, disperse for 5 minutes at a peripheral speed of 10 m / s and a liquid temperature of 10 ° C. using 0.3 mm zirconia beads with a disk-type bead mill (KDL type batch type manufactured by Shinmaru Enterprises). did. Next, 7.0 parts of a polyether type polyurethane resin (acid value 80 mg KOH / g solid content 28%, manufactured by Mitsui Chemicals, Inc.) was added, and after stirring well, coarse particles were obtained using a centrifuge (Model 3600 manufactured by Kubota Corporation). Were separated to obtain a carbon black pigment dispersion (1-12) shown in Table 1.

<Creation of Ink of Example 12>
The material of the following formulation was mixed and stirred for 30 minutes to prepare the ink of Example 12.
(Ink formulation of Example 12)
-Pigment dispersion (1-12) (pigment concentration 20%) 4.0 parts-Pigment dispersion (2-1) (pigment concentration 20%) 36.0 parts-Glycerin 5.5 parts-1,3-butane Diol 16.5 parts ・ 2-ethyl-1,3-hexanediol 2.0 parts ・ Fluorosurfactant (solid content 40%) 2.5 parts (manufactured by DuPont: Zonyl FS-300)
Fluoroethylene / vinyl ether alternating copolymer (solid content 50%) 6.0 parts (Asahi Glass Co., Ltd .: Lumiflon FE4300, average particle size 150 nm,
MFT 30 ℃ or less)
-27.4 parts of distilled water 0.1 parts of 2-amino-2-ethyl-1,3-propanediol (40% aqueous solution) was then added, and after adjusting the ink pH to 10, the mixture was stirred for 30 minutes. The ink of Example 12 was made.

Examples 13-20
<Creation of oxidized carbon black (13) to (20)>
In the production of oxidized carbon black (1) of Example 1, carbon black PRINTEX-U manufactured by Degussa was changed to pre-oxidized carbon black described in Table 1, respectively, and the ozone generation amount / treatment time was adjusted, and the volatile content was adjusted. Except for the adjustment, oxidized carbon blacks (13) to (20) were prepared in the same manner as the oxidized carbon black (1).

<Creation of pigment dispersions (1-13) to (1-20)>
In preparation of the pigment dispersion (1-12) of Example 12, oxidized carbon black (13) to (20) was used instead of oxidized carbon black (1), and the addition amount of NaOH aqueous solution was adjusted to obtain dispersion pH. Pigment dispersions (1-13) to (1-20) were obtained in the same manner as in the preparation of the pigment dispersion (1-12) except that was adjusted to 7.

<Creation of inks of Examples 13 to 20>
In preparing the ink of Example 12, instead of pigment dispersion (1-12) (pigment concentration 20%), pigment dispersions (1-13) to (1-20) (pigment concentration 20%) were used. Example 12 except that the pigment dispersion described in Table 1 was used as the pigment dispersion (2) without changing the total amount of the pigment dispersions (1) and (2) and using the ratio in the ratio described in Table 1. Similarly, inks of Examples 13 to 20 shown in Table 1 were prepared.

Examples 21-22
<Preparation of Pigment Dispersions (1-21) to (1-22)>
In the preparation of the pigment dispersion (1-12) of Example 12, oxidized carbon black (2) was used instead of oxidized carbon black (1), the amount of NaOH aqueous solution was adjusted, and the dispersion pH was listed in Table 1. The pigment dispersions (1-21) to (1-22) shown in Table 1 were obtained in the same manner as in the preparation of the pigment dispersion (1-12) except that the pH was adjusted to.

<Creation of inks of Examples 21 to 22>
In the preparation of the ink of Example 12, pigment dispersions (1-25) to (1-26) (pigment concentration 20%) were used instead of pigment dispersion (1-12) (pigment concentration 20%). Example 12 except that the pigment dispersion described in Table 1 was used as the pigment dispersion (2) without changing the total amount of the pigment dispersions (1) and (2) and using the ratio in the ratio described in Table 1. In the same manner, inks of Examples 21 to 22 described in Table 1 were prepared.

Examples 23-26
<Preparation of Pigment Dispersions (1-23) to (1-26)>
In preparation of the pigment dispersion (1-12) of Example 12, the oxidized carbon black (2) was used instead of the oxidized carbon black (1), and a polyether type polyurethane resin (manufactured by Mitsui Chemicals, acid value 80 mgKOH / (g, solid content 28%) in place of the polyether type polyurethane resin with acid value shown in Table 1 (manufactured by Mitsui Chemicals, solid content 28% diluted product), and adjusting the amount of NaOH aqueous solution to adjust the dispersion pH The pigment dispersions (1-23) to (1-26) shown in Table 1 were obtained in the same manner as in the preparation of the pigment dispersion (1-12) except that the pH was adjusted to the pH shown in Table 1.

<Creation of inks of Examples 23 to 26>
In the preparation of the ink of Example 12, the pigment dispersions (1-23) to (1-26) (pigment concentration 20%) were used instead of the pigment dispersion (1-12) (pigment concentration 20%). Example 12 except that the pigment dispersion described in Table 1 was used as the pigment dispersion (2) without changing the total amount of the pigment dispersions (1) and (2) and using the ratio in the ratio described in Table 1. In the same manner, inks of Examples 23 to 26 shown in Table 1 were prepared.

Example 27
<Preparation of pigment dispersion (1-27)>
In preparing the pigment dispersion (1-12) of Example 12, oxidized carbon black (2) was used instead of oxidized carbon black (1), and instead of NaOH aqueous solution (20%), LiOH 20% aqueous solution (20 %), And the addition amount was adjusted and the dispersion pH was adjusted to the pH shown in Table 1, in the same manner as in the preparation of the pigment dispersion (1-12), the pigment dispersion (1-27) shown in Table 1 was used. Got.

<Creation of Ink of Example 27>
In preparing the ink of Example 12, instead of the pigment dispersion (1-12) (pigment concentration 20%), the pigment dispersion (1-27) (pigment concentration 20%) was used, and the pigment dispersion (2 As in Example 12, except that the total amount of the pigment dispersions (1) and (2) was not changed and the ratio was used in the ratio described in Table 1. The ink of Example 27 was prepared.

Example 28
<Preparation of pigment dispersion (2-5)>
The pigment dispersion (2-1) except that the dispersant of the pigment dispersion (2-1) is naphthalenesulfonic acid having a total content of naphthalenesulfonic acid dimer, trimer and tetramer of 10%. The pigment dispersion (2-5) shown in Table 1 was obtained in the same manner as in the above.
<Creation of Ink of Example 28>
In Example 12, the ink of Example 28 was prepared in the same manner as in Example 12 except that the pigment dispersion (2-5) was used instead of the pigment dispersion (2-1).

Example 29
<Preparation of pigment dispersion (2-6)>
The pigment dispersion (2-1) except that the dispersant for the pigment dispersion (2-1) is naphthalenesulfonic acid having a total content of naphthalenesulfonic acid dimer, trimer and tetramer of 90%. The pigment dispersion (2-6) shown in Table 1 was obtained in the same manner as in the preparation of
<Creation of Ink of Example 29>
In Example 12, the ink of Example 29 was prepared in the same manner as in Example 12 except that the pigment dispersion (2-6) was used instead of the pigment dispersion (2-1).

Comparative Examples 1-10
<Creation of oxidized carbon black (30) to (39)>
In the preparation of the acid value carbon black (1) of Example 1, carbon black PRINTEX-U manufactured by Degussa was changed to pre-oxidation carbon black described in Table 2, and the ozone generation amount / treatment time was adjusted, and the volatile content The oxidized carbon blacks (30) to (39) were prepared in the same manner as in the preparation of the acid value carbon black (1) except that was adjusted.

<Preparation of pigment dispersions (1-30) to (1-39)>
In the preparation of the pigment dispersion (1-1) in Example 1, instead of the oxidized carbon black (1), the oxidized carbon black (30) to (39) was used, and the added amount of the NaOH aqueous solution was adjusted to adjust the dispersion pH. Pigment dispersions (1-30) to (1-39) were obtained in the same manner as in the preparation of the pigment dispersion (1-1) except that was adjusted to 7.

<Creation of inks of Comparative Examples 1 to 10>
In creating the ink of Example 1, pigment dispersions (1-30) to (1-29) (pigment concentration 20%) were used in place of pigment dispersion (1-1) (pigment concentration 20%). Except that, inks of Comparative Examples 1 to 10 were prepared in the same manner as in Example 1.

Comparative Example 11
<Preparation of oxidized carbon black (40)>
Carbon black PRINTEX-U (100 g) manufactured by Degussa was mixed with 500 g of distilled water. While stirring, 1000 g of sodium hypochlorite solution (12%) was added dropwise and boiled for 6 hours for wet oxidation.
Then, it filtered by glass fiber filtration, and also wash | cleaned with distilled water, and made it dry in a 100 degreeC high temperature tank.
When the volatilization amount of the obtained oxidized carbon black (40) was measured, it was 13%. The BET specific surface area was 110 m ² / g.

<Preparation of pigment dispersion (1-40)>
In preparation of the pigment dispersion (1-1) of Example 1, the oxidized carbon black (40) was used instead of the oxidized carbon black (1), and the added amount of the NaOH aqueous solution was adjusted to adjust the dispersion pH to 7. Except that, pigment dispersion (1-40) was obtained in the same manner as in the preparation of pigment dispersion (1-1).

<Creation of Ink of Comparative Example 11>
Example 1 is the same as Example 1 except that pigment dispersion (1-1) (pigment concentration 20%) was used instead of pigment dispersion (1-1) (pigment concentration 20%). Similarly, the ink of Comparative Example 11 was prepared.

Comparative Example 12
<Preparation of oxidized carbon black (41)>
Carbon black PRINTEX-U (100 g) manufactured by Degussa was mixed with 500 g of distilled water, 600 g of peroxodisulfuric acid Na solution (10%) was added dropwise with stirring, and the mixture was boiled for 6 hours for wet oxidation.
Then, it filtered by glass fiber filtration, and also wash | cleaned with distilled water, and made it dry in a 100 degreeC high temperature tank.
When the volatilization amount of the obtained oxidized carbon black (41) was measured, it was 13%. The BET specific surface area was 110 m ² / g.

<Preparation of pigment dispersion (1-41)>
In preparation of the pigment dispersion (1-1) of Example 1, the oxidized carbon black (41) was used instead of the oxidized carbon black (1), and the amount of NaOH aqueous solution was adjusted to adjust the dispersion pH to 7. A pigment dispersion (1-41) was obtained in the same manner as in the preparation of the pigment dispersion (1-1) except that.

<Creation of Ink of Comparative Example 11>
In the preparation of the ink of Example 1, Example 1 was used except that instead of the pigment dispersion (1-1) (pigment concentration 20%), the pigment dispersion (1-41) (pigment concentration 20%) was used. Similarly, an ink of Comparative Example 12 was prepared.

Comparative Examples 13-14
<Preparation of pigment dispersions (1-42) to (1-43)>
In preparation of the pigment dispersion (1-1) of Example 1, oxidized carbon black (3) was used instead of oxidized carbon black (1), the amount of NaOH aqueous solution was adjusted, and dispersion pH was described in Table 2. Pigment dispersions (1-42) to (1-43) were obtained in the same manner as in the preparation of the pigment dispersion (1-1) except that the pH was adjusted.

<Creation of Inks of Comparative Examples 13-14>
In creating the ink of Example 1, pigment dispersions (1-42) to (1-43) (pigment concentration 20%) were used in place of pigment dispersion (1-1) (pigment concentration 20%). Except that, inks of Comparative Examples 13 to 14 were prepared in the same manner as Example 1.

Comparative Examples 15-17
<Creation of Inks of Comparative Examples 15 to 17>
Comparative Examples 15 to 17 are the same as Examples 1 to 3 except that the pigment dispersion in the preparation of the inks of Examples 1 to 3 is 40.0 parts only for the pigment dispersions (1-1) to (1-3) Created ink.
Comparative Examples 18-20
<Creation of Inks of Comparative Examples 18-20>
Comparative Examples 18-20 were the same as Examples 12-14 except that the pigment dispersions in the preparation of the inks of Examples 12-14 were 40.0 parts only for the pigment dispersions (1-12)-(1-14). Created ink.

Comparative Examples 21-26
<Creation of Inks of Comparative Examples 21 to 26>
Inks of Comparative Examples 21 to 26 were prepared in the same manner as in Example 1 except that only the pigment dispersion (2) shown in Table 3 was used in the preparation of the ink of Example 1 at 40.0 parts.
In addition, in dispersions 2-7 to 2-9, 7.0 parts of polyether type polyurethane resin (acid value 80 mg KOH / g solid content 28%, manufactured by Mitsui Chemicals, Inc.) was added to dispersions 2-1 to 2-3. Is.
Comparative Examples 27-35
<Creation of Inks of Comparative Examples 27 to 35>
Similar to Example 1 except that the pigment dispersions (1-1) and (2-1) in the preparation of the ink of Example 1 were changed to the pigment dispersions (1) and (2) shown in Table 4. Ink of Comparative Examples 27 to 35 was prepared.

  The storage stability of the inks of the above examples and comparative examples was evaluated by the following method, and the inks of the above examples and comparative examples were further filled into cartridges and mounted on the ink jet printer shown in FIG. Image density and storage stability were evaluated as follows. The results are shown in Tables 5-8.

1 is printed on Xerox PPC paper 4024 (non-smooth paper) and glossy paper (EPSON MC glossy paper), and the color measurement of the solid image of the image sample is measured with an Xrite 938 densitometer.
[PPC paper 4024 manufactured by Xerox Corporation]
A: 1.31 or more B: 1.21 to 1.30
Δ: 1.11 to 1.20
×: 1.10 or less [MC glossy paper manufactured by EPSON]
A: 1.81 or more B: 1.71 to 1.80
Δ: 1.61-1.70
X: 1.60 or less

(2) Ink storage stability After measuring the initial viscosity of the ink liquid, 50 g of the liquid was sealed in a Nidec Denka Co. sample bottle SV-50, stored at 70 ° C. for 2 weeks, and the rate of change was calculated according to the following formula. , Rank.
The viscosity was an average value measured three times in an environment of 22 ° C. and 65% humidity.
Viscometer: Toyo Seiki RE500
Change rate (%) = (viscosity after 2 weeks at 70 ° C.−initial viscosity) / initial viscosity × 100
: Change rate is less than 5% (best)
○: Change rate is 5% or more and less than 10% (good level)
○: Change rate is 10% or more and less than 15% (a level that is not problematic in practical use)
Δ: Change rate of 15 to less than 20% (problem level)
×: Change rate is 20% or more (problem level)

(3) Discharge stability With respect to the discharge stability, after printing the printed matter, the printer was left in a 50 ° C. environment for one month with the printer head capped. Whether the discharge state of the printer after being left is restored to the initial discharge state was evaluated by the following number of cleaning operations.
A: Printing was possible without cleaning.
○: Recovered by one operation.
○ △: Recovered by two operations.
Δ: Recovered by three operations.
×: No recovery was observed even after three or more movements

The inks for inkjet recording of the present invention have high image densities on non-smooth paper (plain paper) and smooth paper (glossy paper). Examples 1 to 11, Comparative Examples 1 to 17, Comparative Examples 21 to 23, It is clear by comparison with Comparative Examples 27 to 35. In addition, it can be seen from Examples 12 to 27 that by containing a polyether type urethane having an acid value of 40 to 100 mgKOH / g, ink storage stability and ejection stability are improved.
The total content of dimers, trimers and tetramers of naphthalenesulfonic acid in the condensate of naphthalenesulfonic acid formalin as a dispersant for the pigment dispersion (2) is 20% by mass to 80% by mass. As a result, it is apparent in Examples 12 to 24 and Examples 28 and 29 that ink storage stability and ejection stability are improved.

DESCRIPTION OF SYMBOLS 101 Main body 102 Paper feed tray 103 Paper discharge tray 104 Ink cartridge loading part 105 Operation part 111 Upper cover 112 Front cover front 115 Front cover 131 Guide rod 132 Stay 133 Carriage 134 Recording head 135 Sub tank 141 Paper placement part 142 Paper 143 Feed roller 144 Separator pad 145 Guide 151 Transport belt 152 Counter roller 153 Transport guide 154 Pressing member 155 Pressure roller 156 Charging roller 157 Transport roller 158 Tension roller 161 Guide member 171 Separating claw 172 Paper discharge roller 173 Paper discharge roller 181 Double-sided feeding Paper unit 182 Manual paper feed unit 200 Ink cartridge 241 Ink bag 242 Ink inlet 243 Ink outlet 244 Cartridge case

JP 2000-319572 A JP 2004-224955 A Japanese Patent Laid-Open No. 10-324818 JP 2001-164148 A JP 11-349849 A JP 2009-0697907 JP 2009-149815 A JP 2008-260926 A JP 2000-290554 A Japanese Patent No. 4389348 Japanese Patent No. 3907263

Claims (7)

In an inkjet recording ink containing at least water, a pigment, a dispersant, and a penetrant, the pigment is carbon black, is ozone-oxidized, has a volatile content of 10% to 20%, and a BET specific surface area of 90 to 150 m ² / g. Pigment dispersion (1) in which carbon black CB-1 is dispersed with an alkali metal hydroxide adjusted to a dispersion pH of 6 to 8, and an average particle size in particle size measurement by a dynamic light scattering method A pigment dispersion in which carbon black CB-2 having a (D50) of 50 to 180 nm and a particle diameter standard deviation of ½ or less of the average particle diameter is dispersed using a condensate of formalin naphthalene sulfonate as a dispersant. And the mass ratio of the carbon black CB-1 and the carbon black CB-2 in the ink is 2:98 to 50:50. Jet recording ink, characterized in that.   The ink for inkjet recording according to claim 1, wherein the pigment dispersion (1) and / or (2) contains a polyether type urethane having an acid value of 40 to 100 mgKOH / g.   The total content of dimers, trimers and tetramers of naphthalenesulfonic acid in the condensate of naphthalenesulfonic acid formalin as a dispersant for the pigment dispersion (2) is 20% by mass to 80% by mass. The ink for inkjet recording according to claim 1 or 2.   A cartridge characterized in that the ink for ink jet recording according to claim 1 is contained in a container.   An ink jet recording apparatus comprising the cartridge according to claim 4.   An image forming method comprising: forming an image using an ink jet recording apparatus provided with a head for discharging the ink for ink jet recording according to claim 1. An image formed product printed by the ink jet recording apparatus according to claim 5.

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