JP2002121434A - Aqueous color ink set for ink-jet recording and method for ink-jet recording using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous color ink set for ink-jet recording capable of sufficiently preventing occurrence of blurring between colors, having excellent color development, discharge stability and long-term preservation stability of each ink and to provide a method for ink-jet recording using the same. SOLUTION: This aqueous color ink set for ink-jet recording is characterized in that the aqueous color ink set for ink-jet recording is provided with a black ink and at least a cyan ink, a magenta ink and a yellow ink as color inks, the block ink and the color inks each contain a self-dispersible pigment, the volume-average particle diameter of the dispersed particle of the pigment is 20-150 nm, a value obtained by dividing the volume-average particle diameter by the number-average particle diameter of the dispersed particle is 1.5-3.0, the surface tension of the black ink is 25-55 mN/m and the surface tension of each color ink is 25-35 mN/m.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous color ink set for ink jet recording and an ink jet recording method using the same.

[0002]

2. Description of the Related Art Ink-jet type color printers discharge liquid or molten solid ink from nozzles, slits or porous films to record on paper, cloth, film, etc., and are small, inexpensive and quiet. It is known to have such advantages. Then, a piezo ink jet system using a piezoelectric element, a thermal ink jet system in which recording is performed by applying thermal energy to ink, and the like have been developed, and an increase in printing speed and an improvement in image resolution have been achieved. Ink jet inks used in such an ink jet recording system include those containing a water-soluble dye and those containing a pigment. In particular, various inks containing pigments have recently been developed because they are excellent in water resistance and light resistance and can obtain image quality with high optical density.

In order to increase the printing speed and improve the image resolution of a color inkjet printer, a plurality of aqueous color inks for inkjet recording used in an aqueous color ink set for inkjet recording mounted thereon are used. (1) A uniform image can be obtained at a high optical density without occurrence of bleeding in a single-color image and bleeding between colors when mixed color printing is performed; Excellent ejection stability and ejection responsiveness of the ink ejected from the ejection nozzle, no clogging of the ink at the nozzle tip, (3) excellent long-term storage stability, (4) paper It is required to have excellent scratch resistance and a sufficiently high drying speed of the ink on paper, and (5) to have high image fastness such as water resistance and light resistance.

In response to the above requirements, for example, Japanese Patent Application Laid-Open No. 7-1837 discloses that an ink containing a pH-sensitive dispersant and a pigment and that the pigment is deposited on a recording material such as paper. A water-based color ink set for ink jet recording has been proposed which prevents the occurrence of bleeding between colors at the time of mixed-color printing by combining with an ink having an advantageous pH value. Also, JP-A-10-272768 discloses that a black emulsion ink, which is a black ink, and a color ink having a higher ionic strength than the black ink cause agglomeration of the pigment to cause mixed color printing. A water-based color ink set for ink-jet recording has been proposed which prevents the occurrence of bleeding between colors.

Further, JP-A-6-1936 discloses a black ink containing a pigment as a coloring agent and having a surface tension of 40 mN / m or more, and a color containing a dye as a coloring agent and acetylene glycol as a penetrating agent. Ink-jet recording water-based color that prevents the occurrence of bleeding between colors during mixed-color printing by utilizing the difference in permeability between the black ink and the color ink with respect to the recording material by using ink. Ink sets have been proposed.

Japanese Patent Application Laid-Open No. H5-155006 discloses a color ink containing a specific pigment exhibiting each color of yellow, magenta and cyan, a water-soluble resin, and carbon black (C).
An image forming method has been proposed in which an image fastness such as water fastness and light fastness of each ink is improved by combining with a black ink containing B).

Further, JP-A-9-279069 discloses a color ink containing a surfactant, a polyvalent metal salt and a pigment, and a black ink containing a carbon black, a resin emulsion and / or an inorganic oxide colloid. There has been proposed an ink jet recording method that prevents the occurrence of bleeding between colors when mixed color printing is performed by the combination and the thickening / aggregation effect due to the contact of each ink on the recording material.

[0008] Further, as a pigment to be contained in the ink,
Various water-based pigment inks for inkjet recording with improved dispersion stability by using so-called water-dispersible pigments and reducing the amount of polymer dispersants and surfactants added to the ink Set the US Patent 557131
No. 1, JP-A-6-128517, JP-B-1-49369, JP-A-5-230410, JP-A-8-3498, JP-A-8-28
No. 3596, JP-A-11-80579, JP-A-10-110111
Nos. 1 and 2, respectively.

[0009]

SUMMARY OF THE INVENTION
In the aqueous color ink set for inkjet recording described in JP-A-7-1837, deposits such as a pH-sensitive dispersant have adhered to the nozzles, preventing smooth discharge of each ink or being discharged. There is a problem in that the flying direction of the ink droplet is disturbed. In particular, such a problem is remarkable in the thermal ink jet system,
Deposits such as a pH-sensitive dispersant tend to be formed on a heating heater to which heat stress is applied, and the dispersion stability of the pigment in the ink located near the heating heater is remarkably reduced, resulting in instability. Was.

Also, in the aqueous color ink set for ink jet recording described in JP-A-10-272768, particularly when used in a thermal ink jet system, pigment aggregates are liable to precipitate on a heater. A similar problem had occurred.

Furthermore, in the aqueous color ink set for ink jet recording described in JP-A-6-936, a dye is used in the color ink, and it is difficult to obtain sufficient water resistance and light resistance. Was.

Further, in the image forming method described in Japanese Patent Application Laid-Open No. H5-155006, since a water-soluble resin is used as a dispersant for a pigment to be contained in each ink, bubbles are easily generated. However, there is a problem that this is likely to occur. In addition, when such an ink is applied to a thermal ink jet system, as described above, aggregation of the pigment occurs due to thermal stress on the heating heater, and the smooth discharge of each ink from the nozzles. Has been problematic in that it is difficult to perform stable ejection.
Further, in this case, the long-term storage stability of each ink was insufficient.

The polyvalent metal salt, resin emulsion, and inorganic oxide colloid contained in the ink used in the ink jet recording method described in JP-A-9-279069 are all deposited on the heater as precipitates or aggregates. There is a problem that this causes the generation of an object, and in particular, when printing is performed for a long time, it becomes gradually difficult to stably eject the ink from the nozzles. Further, long-term storage stability of the ink has not been sufficiently obtained due to the influence of a polyvalent metal salt, an inorganic oxide colloid and the like contained in the ink.

Further, US Pat.
No. 28517, Japanese Patent Publication No. 1-49369, Japanese Unexamined Patent Application Publication No. H5-230410, Japanese Unexamined Patent Application Publication No. 8-3498, Japanese Unexamined Patent Application Publication No. 8-283596, Japanese Unexamined Patent Application Publication No. In the aqueous pigment ink set for inkjet recording according to the,
No studies have been made on preventing the occurrence of bleeding between colors when mixed color printing is performed, and this is insufficient.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is possible to sufficiently prevent the occurrence of bleeding between colors, and to improve the coloring properties, ejection stability, and long-term storage stability of each ink. An object of the present invention is to provide an excellent aqueous color ink set for inkjet recording and an inkjet recording method using the same.

[0016]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, as a coloring material used in black ink and color ink, it is possible to use a colorant in an ink without adding a dispersant. In the case of using a self-dispersible pigment in water that easily maintains a stable dispersion state, the particle size of the dispersed particles of the pigment in each ink is adjusted within a predetermined range, and the permeability of the black ink and the color ink By giving a predetermined difference to the permeability possessed by the ink, the degree of bleeding between colors can be reduced, and the color developability, ejection stability and long-term storage stability of each ink can be simultaneously improved. I found that it was possible.

The present invention adjusts the volume average particle diameter of the pigment dispersed particles to 20 to 150 nm, and divides the volume average particle diameter by the number average particle diameter of the pigment dispersed particles. Under the condition adjusted to 1.5 to 3.0, the permeability of the black ink and the permeability of the color ink are quantified by the measured values of the respective surface tensions. Is 25 to 55 mN / m, and when the surface tension of the color ink is 25 to 45 mN / m, the occurrence of bleeding between colors can be prevented most effectively. The inventors have found that it is possible to simultaneously improve the stability and long-term storage stability, and have reached the present invention.

That is, the aqueous color ink set for ink jet recording of the present invention is a water color ink set for ink jet recording comprising a black ink and at least a cyan ink, a magenta ink and a yellow ink as color inks. The black ink and each color ink contain a pigment that is self-dispersible in water, and the dispersed particles of the pigment have a volume average particle size of 20 to 150 nm, and the volume average particle size is dispersed. The value divided by the number average particle diameter of the particles is 1.5 to 3.0, the surface tension of the black ink is 25 to 55 mN / m, and the surface tension of each color ink is 25 to 45 mN / m.
It is characterized by being.

As described above, the coloring materials used for the black ink and the color ink are all pigments which can be self-dispersed in water,
By using an ink that satisfies the above conditions, it is possible to sufficiently prevent the occurrence of bleeding between colors and improve the color developability of each ink as compared with the conventional aqueous color ink set for inkjet recording, thereby improving image quality. In addition, the image uniformity is improved. In addition, the ejection stability and long-term storage stability of each ink are significantly improved as compared with the conventional ink using an ink in which a polymer dispersant is adsorbed and dispersed on a pigment.

Regarding the effect obtained,
Although the detailed reason has not been elucidated, the fact that the occurrence of bleeding between colors can be sufficiently prevented and the color developability of each ink is also improved is described in the case of a pigment that can be self-dispersed in water and a pigment of a different color. Since the mobility of the particles is very small as compared with that of the dyes of different colors, by making all the coloring materials dispersed in each ink into pigment dispersed particles,
This is presumed to be because even if inks of different colors come into contact with each other on a recording material such as paper, the mixing of the two is effectively suppressed. Then, if the surface tension of the black ink and the surface tension of each color ink are adjusted to the above range, the difference in the permeability between the black ink, each color ink, and a recording material such as paper occurs appropriately, It is presumed that the movement of the pigment in the color ink to the black ink at the image boundary portion of the color ink is more likely to be suppressed more effectively. In addition, since the occurrence of bleeding between colors can be sufficiently prevented, a high optical density of an image can be obtained.

The improvement in long-term storage stability is due to the fact that the volume average particle size of the dispersed particles of the pigment contained in the black ink and the color ink used in the present invention and the volume average particle size of the dispersed particles are reduced. By adjusting the value divided by the number average particle diameter to the above range, the dispersion state of the dispersed particles of the pigment in each ink is more infiltrated into the recording material in the inward direction of the recording material than that of the dye, and It is presumed that this is because it is easy to adjust to a state where the permeation of the surface into the surface tends to proceed almost uniformly, and it is easy to maintain the favorable dispersion state while stabilizing it for a long period of time.

Also, compared with a conventional system in which a polymer dispersant is adsorbed and dispersed on a pigment, the ejection stability is greatly improved because the hydrophilic group chemically introduced into the pigment surface is more likely to generate heat and heat. Resistant to physical stress, ink characteristics such as ink viscosity and good dispersion state of the pigment in the ink are hardly changed in an area where heat or physical stress is applied near the nozzle orifice, and is kept almost constant. It is presumed that it is.

In the present invention, the term "pigment self-dispersible in water" in the present invention satisfies the condition based on the concentration of the pigment measured according to the procedure described below. A pigment having a soluble functional group and capable of being stably dispersed in water without using a polymer dispersant.
That is, first, the pigment was added to water so that the water content was 95% by mass and the pigment content was 5% by mass, and the pigment was dispersed in water for 5 minutes using a high-pressure homogenizer.
Leave for a time. Next, one third of the total volume of the supernatant is collected from the obtained pigment dispersion. Then, the pigment concentration in the supernatant of the dispersion is measured, and when this pigment concentration is 98% or more with respect to the pigment concentration in the dispersion immediately after dispersion, the pigment is regarded as a self-dispersible pigment in water. .

Here, in the present invention, when the volume average particle diameter of the dispersed particles of the pigment contained in the black ink and each color ink exceeds 150 nm, sedimentation of the particles is liable to occur. easy. On the other hand, when the volume average particle diameter is less than 20 nm, the interaction between the particles increases, and clogging of the nozzle easily occurs. Here, from the same viewpoint as described above, the volume average particle diameter of the dispersed particles of the pigment contained in the black ink and the color ink is preferably 20 to 70 nm.

In the present invention, when the value obtained by dividing the volume average particle size of the pigment dispersed particles by the number average particle size of the dispersed particles exceeds 3.0, the particle size distribution is large, and the nozzle clogging is prevented. And the ink ejection property tends to decrease. On the other hand, if this value is less than 1.5, the manufacturing cost will increase. Here, from the same viewpoint as above, the value obtained by dividing the volume average particle diameter of the dispersed particles of the pigment by the number average particle diameter of the dispersed particles is preferably 1.7 to 2.3.

The measured values of the volume average particle size and the number average particle size of the dispersed particles of the pigment contained in the black ink and the color ink of the present invention were measured using a Microtrac UPA particle size analyzer 9340 (Leeds & Northrup (Made by company)
Is a value measured using The measurement condition was 5 m of ink.
L was placed in a measurement cell, and the viscosity of the ink and the density of the dispersed particles of the pigment were input as measurement parameters, and the measurement was performed according to a predetermined measurement method.

In the present invention, the surface tension of the black ink used is 25 to 55 mN /
m, and the surface tension of each color ink is 25
The surface tension of the black ink is preferably kept higher than the surface tension of each color ink. This is because the bleeding of the black image and the coloring of the color image can be balanced.
In addition, the value of the surface tension of the black ink and each color ink used in the present invention is a value measured using a Wilhelmy type surface tensiometer under the measurement conditions of 23 ° C. and 55% RH.

The black ink has a surface tension of 25 m.
If it is less than N / m, the penetration into the recording paper proceeds further deeply, so that the image density tends to decrease. On the other hand, if the surface tension of the black ink exceeds 55 mN / m, the permeation becomes too slow, and the problem that the ink on the recording paper stains the back surface of the overlapped paper is likely to occur. From the same viewpoint as above, the surface tension of the black ink used in the present invention is more preferably 25 to 45 mN / m.

Further, the surface tension of the color ink is 25 mN.
When the value is less than / m, the ink penetrates deeper into the recording paper, so that the problem that the ink penetrates to the back surface of the paper in the secondary color image portion easily occurs. On the other hand, if the surface tension of the color ink exceeds 45 mN / m, the penetration into the recording paper proceeds further, so that a problem that the uniformity of the image is deteriorated easily occurs. From the same viewpoint as above, the surface tension of the color ink used in the present invention is more preferably 25 to 35 mN / m.

Further, in the aqueous color ink set for ink jet recording of the present invention, the contact angle of black ink to plain paper is 30 to 110 °, and the contact angle of each color ink to plain paper is 30 to 70 °. It is preferred that By adjusting the size of the contact angle of black ink to plain paper and the size of contact angle of each color ink to plain paper within the above range, the permeability of each ink can be more precisely adjusted. It is possible to mix different colors of pigments that occur when inks of different colors come into contact with each other on the recording paper, and a different color that occurs when different colors of ink come into contact with each other while penetrating inside the recording paper. Since color mixing of color pigments can be effectively prevented, it is possible to more reliably prevent the occurrence of bleeding between colors. Therefore, it is possible to more reliably obtain a high image optical density.

Here, from the same viewpoint as the condition of the surface tension of the ink described above, the contact angle of black ink with plain paper is always kept higher than the contact angle of each color ink with plain paper. Is preferred.

If the contact angle of the black ink with plain paper is less than 30 °, the ink tends to spread, and the bleeding of the image tends to occur. On the other hand, if the contact angle of the black ink exceeds 110 °, the ink tends to remain on the recording paper, and the abrasion resistance tends to decrease. From the same viewpoint as above, the contact angle of black ink with plain paper is 6
More preferably, it is 5 to 110 °.

Further, if the contact angle of each color ink with plain paper is less than 30 °, the ink tends to spread and the bleeding of the image tends to occur. On the other hand, if the contact angle of each color ink exceeds 70 °, the print dots do not spread, and the tendency for the color development of the secondary color image portion to decrease is increased. From the same viewpoint as above, the contact angle of each color ink with the plain paper is more preferably 30 to 65 °.

In the present invention, the term "contact angle with respect to plain paper" is used for quantifying and expressing the permeability of the ink.
Using Fuji Xerox Co., Ltd., 4.0 μL of the ink was set on the plain paper under the conditions of 23 ° C. and 55% RH, and the change with time of the dynamic contact angle from the start of measurement to 1000 seconds was measured. The measured value of the contact angle after 0.1 second at the time is shown. And, for the measurement of this contact angle, FI
BRO 1100 DAT MK II (FIBRO system) shall be used. In general, ink having a small contact angle with plain paper tends to spread on paper, and ink having a large contact angle on plain paper tends to be difficult to spread on paper.

In the aqueous color ink set for ink jet recording of the present invention, it is preferable that the surface hydrophilic group of the pigment contained in the black ink and the surface hydrophilic group of the pigment contained in each color ink are different. As a result, the occurrence of bleeding between colors is more reliably prevented. Therefore, it is possible to more reliably obtain a high image optical density. It is presumed that this is because the affinity acting between the dispersed particles of the pigments of different colors described above further decreases under these conditions. In addition, the surface hydrophilic group of the pigment described here indicates a main hydrophilic group which makes the pigment self-dispersible.

Further, the ink jet recording method of the present invention is characterized in that printing is performed using the above-described aqueous color ink set for ink jet recording of the present invention.

That is, the ink jet recording method of the present invention is an aqueous color ink set for ink jet recording comprising a black ink and at least a cyan ink, a magenta ink and a yellow ink as color inks. And each color ink contains a pigment that can be self-dispersed in water, and the dispersed particles of the pigment have a volume average particle size of 20 to 150 nm,
The value obtained by dividing the volume average particle diameter by the number average particle diameter of the dispersed particles is 1.5 to 3.0, the surface tension of the black ink is 25 to 55 mN / m, and the surface of each color ink is The aqueous color ink set for inkjet recording having a tension of 25 to 45 mN / m, or in addition to the above conditions, the contact angle of the black ink to plain paper is 30 to 1
A water-based color ink set for ink-jet recording, which satisfies the condition that the contact angle of each color ink with plain paper is 30 to 70 °, or any of the water-based color inks for ink-jet recording described above. In addition to the conditions that the set satisfies, any of the aqueous color ink sets for inkjet recording satisfying the condition that the surface hydrophilic group of the pigment contained in the black ink and the surface hydrophilic group of the pigment contained in each color ink are different. It is characterized by printing using

As described above, the use of the aqueous color ink set for ink jet recording of the present invention, which can sufficiently prevent the occurrence of bleeding between colors, and is excellent in the coloring properties, ejection stability and long-term storage stability of each ink. By performing printing, it is possible to provide an ink jet recording method capable of obtaining excellent color image quality.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the ink-jet ink of the present invention and an ink-jet recording method using the same will be described in detail below.

The aqueous color ink set for ink jet recording according to the present invention includes a black ink, and further includes at least a cyan ink, a magenta ink, and a yellow ink as the color inks. A predetermined amount is filled in each of the separate containers so as to be able to discharge.

As described above, the black ink and each color ink contain a pigment which is self-dispersible in water. Further, the volume average particle size of the dispersed particles of the pigment is adjusted to 20 to 150 nm, and the value obtained by dividing the volume average particle size by the number average particle size of the dispersed particles is 1.5 to 3.0.
Has been adjusted. Further, the surface tension of the black ink is adjusted to 25 to 55 mN / m, and the surface tension of each color ink is adjusted to 25 to 45 mN / m.

Further, as described above, in the present invention, in order to more precisely adjust the permeability of the black ink and the permeability of each color ink to the recording material such as paper, the ordinary black ink is used. 30-1 contact angle with paper
The angle may be adjusted to 10 ° and the contact angle of each color ink with the plain paper may be adjusted to 30 to 70 °.

The water-dispersible pigment contained in each ink used in the aqueous color ink set for ink jet recording of the present invention is not particularly limited as long as it satisfies the above-mentioned conditions. For example, Cab-o- made by Cabot
jet-200, Cab-o-jet-300, IJX-55, manufactured by Orient Chemical
Commercially available self-dispersion pigments such as Microjet Black CW-1 and self-dispersion pigments sold by Nippon Shokubai may be used. In addition, the water-dispersible pigment is, for example, subjected to a surface modification treatment such as an acid / base treatment, a coupling agent treatment, a polymer graft treatment, a plasma treatment, an oxidation / reduction treatment, etc. on a normal pigment. It can be manufactured by the following.

Further, the content of the pigment self-dispersible in water in each ink is preferably from 0.5 to 10% by mass, more preferably from 1 to 5% by mass, based on the mass of the ink. preferable. If the content is less than 0.5% by mass, the optical density of a sufficient image tends not to be obtained. On the other hand, when the content exceeds 10% by mass,
The tendency that the ejection responsiveness and the ejection stability are reduced and it becomes difficult to smoothly eject the ink onto a recording medium such as plain paper increases. In addition, the tendency for nozzle clogging to occur increases.

In the present invention, the main hydrophilic group introduced on the surface of the pigment is not particularly limited.
Any of a nonionic group, an anionic group, and a cationic group may be used. Examples of such an anionic hydrophilic group include a sulfonic acid group, a carboxylic acid group, a hydroxyl group, and a phosphoric acid group. Among them, a sulfonic acid group, which is an ionic hydrophilic group easily dissociated in an aqueous medium, and a carboxylic acid group Groups and the like are preferred. When the main hydrophilic group to be introduced on the surface of the pigment is a sulfonic acid group, a carboxylic acid group, or a phosphoric acid group, it can be used as it is in the form of a free acid, but it may form a part or all of a salt. It is desirable from the viewpoint of dispersibility in ink. Compounds that form salts with these anionic hydrophilic groups include alkali metals such as sodium, potassium and lithium, aliphatic amines such as monomethylamine, dimethylamine and triethylamine, monomethanolamine, monoethanolamine and diethanolamine. Alcohol amines such as triethanolamine and diisopropanolamine, and ammonia. Among them,
It is preferable to use a basic compound of an alkali metal such as sodium, potassium and lithium. This is because a basic compound of an alkali metal is a strong electrolyte and has a large effect of promoting the dissociation of an anionic group in the ink. Examples of the cationic hydrophilic group include a quaternary ammonium group.

In the present invention, when the kind of the hydrophilic group introduced into the pigment is unknown, it can be estimated by using a general method for chemically identifying solid surface functional groups or by performing elemental analysis. It is possible. For example, when the surface hydrophilic group introduced into the pigment is a sulfonic acid group, the sulfur element in the pigment dispersion can be quantified by ICP analysis. When the surface hydrophilic group introduced into the pigment is a weakly acidic group such as a carboxylic acid group, the amount of the hydrophilic group can be confirmed by the following method, for example. That is, first, when the hydrophilic group on the pigment surface is in a free acid state, the dispersion containing a solid content of a certain weight concentration is dispersed and / or dispersed by a high-pressure homogenizer.
Alternatively, stirring is performed directly, and when the hydrophilic group on the pigment surface forms a salt, the solution is precipitated with a hydrochloric acid aqueous solution so as to have a pH of 3 or less, and then washed with pure water to obtain a free acid state. Then, a dispersion containing a solid content of a constant weight concentration is prepared, and then the mixture is dispersed and / or stirred by a high-pressure homogenizer. Then, for example, titration is performed with an alkali solution such as an aqueous sodium hydroxide solution having a known concentration, and the amount of hydrophilic groups per unit weight of the pigment is estimated from the neutralization titer. Here, the method for estimating the hydrophilic group is not limited to this, and a method can be appropriately selected depending on the type of the pigment and the type of the introduced surface hydrophilic group.

Further, in the present invention, the black pigment which is a raw material of the water-dispersible black pigment is not particularly limited, and examples thereof include carbon blacks such as furnace black, channel black, lamp black and acetylene black. Furthermore, as these specific product names, for example, Raven7000, Raven5750, Raven525
0, Raven5000 ULTRA II, Raven3500, Raven2000, Raven
1500, Raven1250, Raven1200, Raven1190 ULTRA II, Ra
ven1170, Raven1255, Raven1080, Raven1060 (all manufactured by Columbian Carbon), Regal1400R, Regal330R, R
egal660R, Mogul L, Black Pearls L, Monarch 700, Mo
narch 800, Monarch 880, Monarch 900, Monarch 100
0, Monarch 1100, Monarch 1300, Monarch 1400 (all manufactured by Cabot Corporation), Color Black FW1, Color Black FW
2, Color Black FW2V, Color Black 18, Color Black F
W200, Color Black S150, Color Black S160, Color Bl
ack S170, Printex35, Printex U, Printex V, Printex
140U, Printex140V, Special Black6, Special Black
5, Special Black 4A, Special Black 4 (from Degussa), No.25, No.33, No.40, No.47, No.52, No.90
0, No. 2300, MCF-88, MA600, MA7, MA8, MA100 (all manufactured by Mitsubishi Chemical Corporation) and the like.

Further, in the present invention, the pigment used as a raw material of the water-dispersible pigment used in each color ink is not particularly limited. Examples of the pigment of the cyan ink include CI Pigment Blue-1 and CI Pigment Blue-. 2, CIPi
gment Blue-3, CI Pigment Blue-15, CI Pigment Blue
-15: 1, CI Pigment Blue-15: 3, CI Pigment Blue-15:
4, CI Pigment Blue-16, CI Pigment Blue-22, CIP
igment Blue-60 and the like. Among these, from the viewpoint of hue, particularly CI Pigment Blue-15 and CI Pigment B
lue-15: 4 is preferably used.

The pigments of magenta ink include, for example, CI Pigment Red-5, CI Pigment Red-7, CI Pigment
gment Red-12, CI Pigment Red-48, CI Pigment Red-
48: 1, CI Pigment Red-57, CI Pigment Red-112, C.
I. Pigment Red-122, CI Pigment Red-123, CI Pigmen
t Red-146, CI Pigment Red-168, CI Pigment Red-18
4, CI Pigment Red-202 and the like. Among these, from the viewpoint of hue, it is particularly preferable to use CI Pigment Red-122.

Further, as pigments of the yellow ink, for example, CI Pigment Yellow-1, CI Pigment Yellow-2,
CIPigment Yellow-3, CIPigment Yellow-12, CIP
igment Yellow-13, CI Pigment Yellow-14, CI Pigme
nt Yellow-16 、 CIPigmentYellow-17 、 CIPigment Ye
llow-73, CI Pigment Yellow-74, CI Pigment Yellow
-75, CI Pigment Yellow-83, CI Pigment Yellow-9
3, CI Pigment Yellow-95, CI Pigment Yellow-97,
CIPigment Yellow-98, CIPigment Yellow-114, C.
I. Pigment Yellow-128, CI Pigment Yellow-129, CI
Pigment Yellow-151 and CI Pigment Yellow-154. Among them, from the viewpoint of hue, CIPi
gment Yellow-74 and CI Pigment Yellow-128 are preferably used.

As the pigment for the black ink and each color ink used in the present invention, any of the above-mentioned pigments which can be self-dispersed in water may be used. From the viewpoint of more reliably preventing occurrence,
A combination in which the main surface hydrophilic groups of the water self-dispersible pigment used in the black ink and the main surface hydrophilic groups of the water self-dispersible pigment used in the color ink are different between the black ink and each color ink. It is preferable that Further, in the present invention, from the same viewpoint as described above, when using a self-dispersible pigment in water having a hydrophilic group of the same polarity in the black ink and each color ink, particularly, sodium ion as a counter ion Ink using self-dispersible carbon black with carboxylic acid groups introduced and CIPigment with sulfonic acid groups that counter ion sodium ions and become self-dispersible
Blue-15, CIPigment Blue-15: 4, CIPigment Red-1
22, CI Pigment Yellow-74, CI Pigment Yellow-128
It is more preferable to use a combination of color inks using

Further, in the present invention, with respect to the dispersed particles of the water-dispersible pigment present in each color ink, the number of dispersed particles having a particle diameter of 0.5 μm or more present in the ink is reduced. , 1.5 × 10 ³ / μL or more. When the number of dispersed particles having a particle diameter of 0.5 μm or more is less than 1.5 × 10 ³ particles / μL,
It tends to be difficult to obtain a sufficient optical density.

In the present invention, from the viewpoint of satisfying the requirements for the ink ejection response, ejection stability, and clogging, the dispersion of the above-mentioned water-dispersible pigment present in each color ink is carried out. As for the particles, it is preferable that the number of particles having a size of 1/3 or more of the pore diameter of the prefilter provided in the head to be used is 1 × 10 ³ / μL or less. When the number of particles having a size of 1/3 or more of the pore size of the pre-filter provided in the head used exceeds 1 × 10 ³ / μL, the pressure loss of the pre-filter increases, so that the ink ejection property is reduced. The tendency for the problem of reduction to occur increases. In addition, from the same viewpoint as above, 1/3 of the hole diameter of the pre-filter provided in the head to be used.
The number of particles having the above size is more preferably 0.5 × 10 ³ particles / μL or less. The method for previously removing the coarse particles of the pigment exceeding the above numerical range from the ink is not particularly limited, and examples thereof include, for example, a commonly performed process such as centrifugation or filtration during the ink preparation process.

In the present invention, the particle size distribution of the dispersed particles of the pigment having a particle size of 0.5 μm or more dispersed in each ink is measured using an Accusizer ™ 770 Optical Pa
It measured using rticle Sizer (made by Particle Sizing Systems). At the time of measurement, as a parameter to be input to the apparatus, the density of the pigment was input as the density of the dispersed particles.
Then, dilute 2 μL of the ink in 50 mL of deionized water,
From the obtained original data of the particle size distribution, the number of particles whose particle diameter was at least 1/3 of the pore diameter of the prefilter used for the used head was read and converted to 1 μL.

Furthermore, in the present invention, the concentration of pigment-derived inorganic impurities contained in each ink used is preferably 500 ppm or less, more preferably 300 ppm or less. If the concentration of the inorganic impurities exceeds 500 ppm, kogation tends to occur on the heater due to long-term ink ejection. Therefore, when using commercially available pigment dispersions and pigments as they are, in order to remove the organic impurities and inorganic impurities contained in the pigment that is self-dispersible in water and sufficiently reduce the content thereof, these are used. At the time of surface treatment, it is desirable to carry out purification. Examples of such impurity removal treatment include water washing, ultrafiltration membrane method, ion exchange treatment, adsorption with activated carbon, zeolite, and the like.

In the present invention, in order to enhance the dispersibility of the pigment in each ink with respect to each ink, a pH adjuster may be added in accordance with the type of the hydrophilic group introduced on the surface of the pigment. . For example, the pH is preferably set to 6 to 11 in an ink using a pigment into which an anionic free radical is introduced, and the pH is preferably adjusted to an ink using a pigment into which a cationic free radical is introduced. It is preferably 3 to 6. Such pH adjuster is not particularly limited, for example, potassium hydroxide, sodium hydroxide, lithium hydroxide, ammonium hydroxide, triethanolamine, diethanolamine, ethanolamine,
2-Amino-2-methyl-1-propanol, ammonia, ammonium phosphate, potassium phosphate, sodium phosphate, lithium phosphate, sodium sulfate, acetate, lactate, benzoate, acetic acid, hydrochloric acid, nitric acid, sulfuric acid, phosphorus acid,
And propionic acid and P-toluenesulfonic acid. Further, other general pH buffers can also be used.

Further, each ink used in the present invention may contain a surfactant or the like as a penetrant. The type of such a surfactant is not particularly limited, and any of nonionic, anionic, cationic, and amphoteric surfactants may be used. As nonionic surfactants,
For example, polyoxyethylene nonyl phenyl ether,
Polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, fatty acid alkylolamide, acetylene alcohol ethylene oxide adduct, polyethylene glycol Examples include a polypropylene glycol block copolymer, a polyoxyethylene ether of glycerin ester, and a polyoxyethylene ether of sorbitol ester.

Examples of the anionic surfactant include alkyl benzene sulfonate, alkyl phenyl sulfonate, alkyl naphthalene sulfonate, higher fatty acid salt, sulfate and sulfonate of higher fatty acid ester, and higher alkyl sulfosuccinic acid. A salt or the like may be added. Furthermore, examples of the cationic surfactant include tetraalkylammonium salts, alkylamine salts, benzalkonium salts, alkylpyridium salts, imidazolium salts, and the like.More specifically, for example, dihydroxyethylstearylamine, 2-heptadecenyl-hydroxyethylimidazoline, lauryldimethylbenzylammonium chloride, cetylpyridinium chloride, stearamidomethylpyridium chloride and the like.

Further, as the amphoteric surfactant, betaine, sulfobetaine, sulfate betaine, imidazoline and the like can be used. Other examples include silicone surfactants such as polysiloxane polyoxyethylene adducts, fluorine surfactants such as oxyethylene perfluoroalkyl ether, and biosurfactants such as spiculisporic acid, rhamnolipid, and lysolecithin.

In the present invention, these surfactants can be used alone or in combination of two or more. In particular, when used for each color ink,
Among the above surfactants, it is preferable to use an acetylene glycol-based surfactant since the drying time can be shortened and a sufficient image density can be obtained.

Further, in the present invention, the content of the surfactant contained in each color ink is 0.0% with respect to the total mass of each ink from the viewpoint of the surface tension (permeability) of the ink.
It is preferably from 0.01 to 5% by mass. As a result, it is possible to make it difficult to cause a problem regarding the ink ejection property, and to reduce the influence on other ink characteristics. The content of the surfactant contained in each color ink is 0.00
If the amount is less than 1% by mass, the surface tension of each color ink becomes too high, so that the problem regarding the drying property of the ink is more likely to occur. On the other hand, when the content of the surfactant exceeds 5% by mass, excessive penetration of the ink into the recording paper occurs, and the viscosity of the ink also increases, so that a decrease in image density and a decrease in ink ejection properties occur. The tendency to do so is increased. Further, from the same viewpoint as above, the content of the surfactant contained in each color ink is more preferably 0.01 to 3% by mass based on the total mass of each ink.

Further, in the present invention, from the viewpoint of improving the permeability to the recording material, the black ink and each color ink may contain the compound shown in the following (1). Since the compound shown in the following (1) also functions as a humectant solvent, by including this in the ink, the occurrence of clogging of the ink in the nozzles can be more easily prevented. RO-XnH (1)

Here, in the formula, R is a functional group selected from alkyl, alkenyl, alkynyl, phenyl, alkylphenyl, alkenylphenyl, and cycloalkyl groups, and has 4 to 8 carbon atoms. X is
It is an oxyethylene or oxypropylene group, and n represents an integer of 1 to 4.

The compounds represented by the formula (1) include ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, diethylene glycol monohexyl ether, dipropylene glycol monobutyl ether, triethylene glycol monobutyl ether, and triethylene glycol monohexyl. Ether, diethylene glycol monocyclohexyl ether, triethylene glycol monophenylethyl ether, dioxypropyleneoxyethylene monopentyl ether, and the like,
Preferably, diethylene glycol monobutyl ether is used.

When the compound represented by the formula (1) is used alone as a penetrant, its content is preferably 0.5 to 10% by mass relative to the total mass of the ink.
More preferably, it is 5% by mass. When the content of the compound represented by the formula (1) exceeds 10% by mass, the tendency of occurrence of bleeding between colors becomes remarkable, and it becomes difficult to discharge ink from nozzles smoothly and the ink becomes unstable. Tend. On the other hand, when the content of the compound represented by the formula (1) is less than 0.5% by mass, it is difficult to obtain the effect of addition. In particular, each color ink preferably contains the compound represented by the formula (1). This is because the uniformity of the image quality is improved. When the compound represented by the formula (1) is contained in the color ink, another penetrant may be contained.

In the present invention, each ink contains a water-soluble organic solvent from the viewpoint of preventing drying (moisturizing property). Such a water-soluble organic solvent is not particularly limited as long as it is water-soluble, for example, ethylene glycol, diethylene glycol, propylene glycol, polypropylene glycol, butylene glycol, triethylene glycol, 1,5-pentanediol, 1,2, 6-hexanetriol, polyhydric alcohols such as glycerin, pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, nitrogen-containing solvents such as triethanolamine, ethanol, isopropyl alcohol, butyl alcohol, alcohols such as benzyl alcohol, Alternatively, sulfur-containing solvents such as thiodiethanol, thiodiglycerol, sulfolane and dimethylsulfoxide, propylene carbonate, ethylene carbonate and the like can be mentioned.

Further, as the water-soluble organic solvent contained in each ink used in the present invention, one kind of solvent may be used alone, or two or more kinds of solvents may be mixed and used as a mixed solvent. You may. Further, the content of the water-soluble organic solvent in each ink is preferably from 1 to 60% by mass, more preferably from 5 to 40% by mass, based on the mass of the ink. If the content of the water-soluble organic solvent is less than 1% by mass, the effect of preventing sufficient drying prevention tends to be insufficient. On the other hand, the content of the water-soluble organic solvent is 60% by mass.
When the value exceeds, the tendency that the viscosity of the ink becomes too high and the ejection property is reduced is increased.

Further, in order to adjust the optical density of the image, the uniformity of the image, the wettability to the recording material, etc., each ink used in the present invention has clogging, ejection response, ejection stability, and storage. A water-soluble resin can be added to such an extent that stability or the like does not occur. As such a water-soluble resin, a compound having a hydrophilic structure portion and a hydrophobic structure portion can be effectively used, and specific examples thereof include a condensation polymer and an addition polymer.

More specifically, the condensation polymer includes a polyester polymer, and the addition polymer includes an addition polymer of a monomer having an α, β-ethylenically unsaturated group.

Here, examples of the addition polymer include a monomer having an α, β-ethylenically unsaturated group having a hydrophilic group and a monomer having an α, β-ethylenically unsaturated group having a hydrophobic group. Those which are appropriately combined and copolymerized can be used. Further, a homopolymer of a monomer having an α, β-ethylenically unsaturated group having a hydrophilic group can also be used.

Examples of the monomer having an α, β-ethylenically unsaturated group having a hydrophilic group include a monomer having a carboxyl group, a sulfonic acid group, a hydroxyl group, a phosphate group, and the like. , Acrylic acid, methacrylic acid,
Crotonic acid, itaconic acid, itaconic acid monoester, maleic acid, maleic acid monoester, fumaric acid, fumaric acid monoester, vinyl sulfonic acid, styrene sulfonic acid, sulfonated vinyl naphthalene, vinyl alcohol, acrylamide, methacryloxyethyl phosphate, Bismethacryloxyethyl phosphate, methacryloxyethylphenylacid phosphate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate and the like can be mentioned.

On the other hand, monomers having an α, β-ethylenically unsaturated group having a hydrophobic group include styrene derivatives such as styrene, α-methylstyrene and vinyltoluene, vinylcyclohexane, vinylnaphthalene, vinylnaphthalene derivative, acrylic acid Examples thereof include alkyl esters, phenyl acrylate, alkyl methacrylate, phenyl methacrylate, cycloalkyl methacrylate, alkyl crotonate, dialkyl itaconate, and dialkyl maleate.

The copolymer obtained by copolymerizing the above-mentioned monomer having a hydrophilic group and a hydrophobic group is as follows:
Any structure such as random, block, and graft copolymers may be used. Examples of preferred copolymers include styrene-styrenesulfonic acid copolymer, styrene-maleic acid copolymer, styrene-methacrylic acid copolymer, styrene-acrylic acid copolymer, vinylnaphthalene-maleic acid copolymer , Vinyl naphthalene-methacrylic acid copolymer, vinyl naphthalene-acrylic acid copolymer, acrylic acid alkyl ester-acrylic acid copolymer, methacrylic acid alkyl ester-methacrylic acid, styrene-methacrylic acid alkyl ester-methacrylic acid copolymer Styrene-alkyl acrylate-acrylic acid copolymer, styrene-phenyl methacrylate-methacrylic acid copolymer, styrene-cyclohexyl methacrylate-methacrylic acid copolymer, and the like.

Further, a monomer having a polyoxyethylene group and a hydroxyl group may be appropriately copolymerized with the above copolymer. Further, in order to increase the affinity with the pigment having an acidic functional group on the surface and improve the dispersion stability, a monomer having a cationic functional group, for example, N, N-dimethylaminoethyl methacrylate, N, N-dimethylamino Ethyl acrylate, N,
N-dimethylaminomethacrylamide, N, N-dimethylaminoacrylamide, N-vinylpyrrole, N-vinylpyridine, N-vinylpyrrolidone, N-vinylimidazole and the like may be appropriately copolymerized. Also, polystyrene sulfonic acid,
Polyacrylic acid, polymethacrylic acid, polyvinyl sulfonic acid, polyalginic acid, polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer, formalin condensate of naphthalene sulfonic acid, polyvinyl pyrrolidone, polyethylene imine, polyamines, polyamides, polyvinyl Cellulose derivatives such as imidazoline, aminoalkyl acrylate / acrylamide copolymer, chitosan, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid amide, polyvinyl alcohol, polyacrylamide, carboxymethyl cellulose, carboxyethyl cellulose, etc. Saccharides and their derivatives can also be used effectively.

The hydrophilic group of the water-soluble resin is not particularly limited, but is preferably, for example, a carboxyl group or a salt thereof. Thereby, particularly when a carboxyl group is used as the hydrophilic group, the degree of aggregation of the pigment on paper is easily adjusted to a level at which a sufficient optical density of an image can be obtained.

Among these water-soluble resins, the copolymer having a hydrophilic group as an acidic group is preferably used in the form of a salt with a basic compound in order to enhance water solubility. Compounds that form salts with these polymers include alkali metals such as sodium, potassium and lithium, aliphatic amines such as monomethylamine, dimethylamine and triethylamine, monomethanolamine, monoethanolamine, diethanolamine and triethanol. Amine, alcohol amines such as diisopropanolamine, ammonia and the like can be used. Among them, particularly preferred are basic compounds of alkali metals such as sodium, potassium and lithium. This is presumably because alkali metals are strong electrolytes and have an effect of promoting the dissociation of hydrophilic groups. The amount of neutralization of the water-soluble resin is preferably 60% or more of the acid value of the copolymer, more preferably 80% or more of the acid value of the copolymer. preferable. These water-soluble resins may be used alone or in combination of two or more.

Each ink used in the present invention may contain the following additives in addition to the components described above. That is, polysaccharides such as polyethyleneimine, polyamines, polyvinylpyrrolidone, polyethyleneglycol, cellulose derivatives such as methylcellulose, ethylcellulose, carboxyethylcellulose, glucose, fructose, mannitol, D-sorbitol, dextran, xanthan gum, curdlan, cycloamylose, and maltitol. And its derivatives, other polymer emulsions, cyclodextrins, macrocyclic amines, dendrimers, crown ethers, urea and its derivatives, acetamide, and the like.

Further, each ink used in the present invention may contain an antioxidant, a fungicide, a conductive agent, an ultraviolet absorber, a chelating agent, and the like, if necessary. As a chelating agent, ethylenediaminetetraacetic acid (EDT
A), iminodiacetic acid (IDA), ethylenediamine di (o-hydroxyphenylacetic acid) (EDDHA), nitrilotriacetic acid (NTA), dihydroxyethylglycine (DHEG), trans-1,2-cyclohexanediaminetetraacetic acid (CyDTA) , Diethylenetriamine-N, N, N ', N ", N" -pentaacetic acid (DTPA),
Glycol ether diamine-N, N, N ', N'-tetraacetic acid (GEDTA) and the like.

Further, each of the inks used in the present invention includes a color ink in order to increase the cohesive force of the color material on paper.
In addition to these, an electrolyte may be contained to such an extent that secondary obstacles do not occur with respect to clogging and long-term stability.

Examples of such an electrolyte include alkali metal ions such as lithium ion, sodium ion, potassium ion and the like, aluminum ion, barium ion, calcium ion, copper ion, iron ion, magnesium ion, manganese ion, nickel ion, tin ion. , Titanium ions, zinc ions and other polyvalent metal ions, hydrochloric acid, bromic acid, hydroiodic acid, sulfuric acid, nitric acid, phosphoric acid,
Thiocyanic acid, and acetic acid, oxalic acid, lactic acid, fumaric acid,
Organic carboxylic acids such as fumaric acid, citric acid, salicylic acid, and benzoic acid, and salts of organic sulfonic acids are included.
In addition, it is possible to use a substance that becomes an organic cation by dissociation in water as an electrolyte, and specifically, primary, secondary, tertiary, and quaternary amines and salts thereof, and the like. Can be

Specific examples of the electrolyte include lithium chloride, sodium chloride, potassium chloride, sodium bromide, potassium bromide, sodium iodide, potassium iodide, sodium sulfate, potassium nitrate, sodium acetate, and the like.
Salts of alkali metals such as potassium oxalate, sodium citrate and potassium benzoate, and aluminum chloride, aluminum bromide, aluminum sulfate, aluminum nitrate, sodium aluminum sulfate, potassium aluminum sulfate, aluminum acetate, barium chloride, barium bromide , Barium iodide, barium oxide, barium nitrate, barium thionate, calcium chloride, calcium bromide,
Calcium iodide, calcium nitrite, calcium nitrate, calcium dihydrogen phosphate, calcium thiocyanate, calcium benzoate, calcium acetate, calcium salicylate, calcium tartrate, calcium lactate, calcium fumarate, calcium citrate, copper chloride, bromide Copper, copper sulfate, copper nitrate, copper acetate, iron chloride, iron bromide, iron iodide, iron sulfate, iron nitrate, iron oxalate, iron lactate, iron fumarate, iron citrate, magnesium chloride, magnesium bromide, iodine Magnesium iodide, magnesium sulfate, magnesium nitrate, magnesium acetate, magnesium lactate, manganese chloride, manganese sulfate, manganese nitrate, manganese dihydrogen phosphate, manganese acetate, manganese salicylate, manganese benzoate, manganese lactate, nickel chloride, nickel bromide, Nickel sulfate, nickel nitrate Nickel acetate, tin sulfate,
Examples include salts of polyvalent metals such as titanium chloride, zinc chloride, zinc bromide, zinc sulfate, zinc nitrate, zinc thiocyanate, and zinc acetate.

Further, specific examples of the substance which becomes an organic cation when dissociated in water include tetraalkylammonium salts, alkylamine salts, benzalkonium salts,
Alkylpyridium salts, imidazolium salts, polyamines and the like, for example, isopropylamine, isobutylamine, t-butylamine, 2-ethylhexylamine,
Nonylamine, dipropylamine, diethylamine, trimethylamine, triethylamine, dimethylpropylamine, ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, tetraethylenepentamine, diethanolamine, diethylethanolamine, triethanolamine, tetramethylammonium chloride, tetraethylammonium bromide Dihydroxyethylstearylamine, 2-heptadecenyl-hydroxyethylimidazoline, lauryldimethylbenzylammonium chloride, cetylpyridinium chloride, stearamidomethylpyridium chloride, diallyldimethylammonium chloride polymer, diallylamine polymer, monoallylamine polymer and the like. .

Among the above electrolytes, aluminum sulfate, calcium chloride, calcium nitrate, calcium acetate, magnesium chloride, magnesium nitrate, magnesium sulfate, magnesium acetate, tin sulfate, zinc chloride, zinc nitrate, zinc sulfate, zinc acetate, nitrate Aluminum, a monoallylamine polymer, a diallylamine polymer, and a diallyldimethylammonium chloride polymer are preferably used from the viewpoint of the effect of cohesion.

The above-described electrolyte and cationic substance may be used alone or in combination of two or more in each color ink. The content of the electrolyte and / or the cationic substance contained in each color ink is preferably 0.01 to 10% by mass in total with respect to the total mass of the ink,
More preferably, it is 0.01 to 5% by mass. When the content of the electrolyte and / or the cationic substance is less than 0.01% by mass, the cohesive force of the pigment on a recording material such as paper tends to be insufficient. On the other hand, when the content of the electrolyte and / or the cationic substance exceeds 5% by mass, clogging or the like in the nozzle is likely to occur.

Hereinafter, a preferred embodiment of the ink jet recording method of the present invention will be described. The inkjet recording method of the present embodiment is not particularly limited as long as it is a method of printing using the above-described inkjet ink of the present invention. For example, a known method such as a piezo inkjet method or a thermal inkjet method is used. It may be. However, from the viewpoint of realizing an improvement in image resolution while maintaining a sufficiently high printing speed of the inkjet printer, each ink used in the aqueous color ink set for inkjet recording of the present invention may cause bleeding between colors. It is preferable to employ a thermal ink jet recording method because the ink can be sufficiently prevented, and each ink is excellent in color development, ejection stability and long-term storage stability. The apparatus used in the ink jet recording method of the present invention is not particularly limited, for example, a normal ink jet recording apparatus, a recording apparatus equipped with a heater or the like for controlling ink drying, an intermediate transfer mechanism It is also possible to use a recording device that is mounted and transfers a recording material onto a recording medium such as paper after printing a recording material on an intermediate.

When the thermal ink jet recording method is employed in the ink jet recording method of the present invention, it is preferable to apply the present invention to an ink jet recording method in which ink droplets are ejected from an orifice in accordance with a recording signal to perform recording. In this case, it is preferable that the adjustment is performed such that the mass of the ink droplets ejected at a time of each color ink is smaller than the mass of the ink droplets ejected at a time of the black ink. Thereby, the balance between the gradation of the color image and the black density is improved. Here, if the mass of the ink droplets ejected at one time for each color ink is smaller than the mass of the ink droplets ejected at one time for the black ink, the dots of the color inks become larger, so that the overlap between the colors becomes larger. Bleeding easily occurs.

Further, in this case, the mass of the ink droplet ejected at one time for each color ink is preferably 20 ng or less, more preferably 1 to 10 ng. By controlling the mass of ink droplets ejected at one time for each color ink within the range of 20 ng or less, printing is performed by appropriately controlling the penetration of the ink into the recording medium and the diffusion toward the surface of the recording medium. Thus, it is possible to easily adjust the optical density to a level at which a sufficient optical density and a sufficient quick-drying property can be obtained. Here, if the mass of the ink droplets ejected at one time for each color ink exceeds 20 ng, there is a tendency that bleeding between colors becomes remarkable.

[0088]

EXAMPLES The aqueous color ink set for ink jet recording of the present invention and the contents of the ink jet recording method using the same will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. It is not limited.

First, the following 16 types of pigment dispersions were prepared, and any one of these was used to prepare an aqueous color ink set for ink jet recording of the present invention having the following composition. Example inks and 10 inks for use in comparative examples were prepared. Table 1 shows the physical property values indicating the characteristics of each of these inks.

Next, by combining the prepared inks,
The aqueous color ink set for inkjet recording of Examples 1 to 5 and the aqueous color ink set for inkjet recording of Comparative Examples 1 to 5 were prepared.

<Black Pigment Dispersion 1> Pigment Special Bla
ck 4 (manufactured by Degussa) treated with 3-amino-N-ethylpyridium bromide, and then added with a pH adjuster to give a solid concentration of 10%.
The mixture was mixed with pure water so as to obtain a weight%, and dispersed with a high-pressure homogenizer for 10 minutes while stirring. The obtained dispersion was subjected to a centrifugal separation treatment (5000 rpm × 10 minutes), and a supernatant liquid of 80% by weight based on the whole amount was collected. When the pigment was examined for self-dispersibility by the method described in the text, it was confirmed that the pigment was self-dispersible.

<Black Pigment Dispersion 2> A pigment dispersion liquid Cabojet 200 (manufactured by Cabot Corporation) which can be self-dispersed in water is mixed with pure water so that the solid content concentration becomes 10% by weight, stirred, and then centrifuged (5,000 rpm). × 10 minutes), and a supernatant of 80% by weight based on the total amount was collected. When the pigment was examined for self-dispersibility by the method described in the text, it was confirmed that the pigment was self-dispersible.

<Black Pigment Dispersion 3> A pigment dispersion liquid Cabojet 300 (manufactured by Cabot) self-dispersible in water was mixed with pure water so that the solid content concentration became 10% by weight, stirred, and then centrifuged (5,000 rpm). × 10 minutes), and a supernatant of 80% by weight based on the total amount was collected. When the pigment was examined for self-dispersibility by the method described in the text, it was confirmed that the pigment was self-dispersible.

<Cyan Pigment Dispersion 1> Cyan pigment (C.I.
I. Pigment Blue 15: 3) is treated with sulfanilic acid and sodium nitrite, and the surface is treated with C6H4SO.
A treated color pigment having a 3-Na + group was obtained. After purification
The resulting dispersion was mixed with pure water so that the solid content concentration became 10% by weight, and the resulting dispersion was subjected to centrifugal separation (5000 rpm × 20 minutes) to collect a supernatant of 80% by weight based on the total amount. When the pigment was examined for self-dispersibility by the method described in the text, it was confirmed that the pigment was self-dispersible.

<Cyan Pigment Dispersion 2> Cyan pigment (C.I.
I. Pigment Blue 15: 3) is treated with anthranilic acid and sodium nitrite, and the surface is treated with C6H4CO.
A treated color pigment having O-Na + groups was obtained. After purification
The resulting dispersion was mixed with pure water so that the solid content concentration became 10% by weight, and the resulting dispersion was subjected to centrifugal separation (5000 rpm × 20 minutes) to collect a supernatant of 80% by weight based on the total amount. When the pigment was examined for self-dispersibility by the method described in the text, it was confirmed that the pigment was self-dispersible.

<Magenta Pigment Dispersion 1>
Pigment Red-122 was treated with sulfanilic acid and sodium nitrite to obtain a treated color pigment having a C6H4SO3-Na + group on the surface. After the purification treatment, the solid content was mixed with pure water so as to have a concentration of 10% by weight, and the obtained dispersion was subjected to a centrifugation treatment (5000 rpm × 20 minutes) to collect a supernatant liquid of 80% by weight based on the total amount. When the pigment was examined for self-dispersibility by the method described in the text, it was confirmed that the pigment was self-dispersible.

<Magenta Pigment Dispersion 2>
Pigment Red-122 was treated with anthranilic acid and sodium nitrite to give a treated color pigment having a C6H4COO-Na + group on the surface. After the purification treatment, the solid content was mixed with pure water so as to have a concentration of 10% by weight, and the obtained dispersion was subjected to a centrifugation treatment (5000 rpm × 20 minutes) to collect a supernatant liquid of 80% by weight based on the total amount. When the pigment was examined for self-dispersibility by the method described in the text, it was confirmed that the pigment was self-dispersible.

<Yellow Pigment Dispersion 1>
Pigment Yellow-74 was treated with sulfanilic acid and sodium nitrite to obtain a treated color pigment having a C6H4SO3-Na + group on the surface. After purification treatment, solid content concentration is 10% by weight
And the resulting dispersion was subjected to centrifugation (5000 rpm × 20 minutes) to collect a supernatant of 80% by weight based on the total amount. When the pigment was examined for self-dispersibility by the method described in the text, it was confirmed that the pigment was self-dispersible.

<Yellow Pigment Dispersion 2>
Pigment Yellow-74 was treated with anthranilic acid and sodium nitrite to obtain a treated color pigment having C6H4COO-Na + groups on the surface. After purification treatment, solid content concentration is 10% by weight
And the resulting dispersion was subjected to centrifugation (5000 rpm × 20 minutes) to collect a supernatant of 80% by weight based on the total amount. When the pigment was examined for self-dispersibility by the method described in the text, it was confirmed that the pigment was self-dispersible.

<Black Pigment Dispersion A> A dispersant aqueous solution neutralized by adding 4 parts by mass of potassium hydroxide to 20 parts by mass of a styrene / acrylic acid copolymer (copolymerization ratio: 50/50 mol, polymerization average molecular weight: 8000). Created. Pure water in 40 parts by mass of dispersant aqueous solution
After adding 190 parts by mass and stirring, 40 parts by mass of a pigment Black pearls L (manufactured by Cabot) were added with stirring. After stirring for 10 minutes, the mixture was dispersed with a high-pressure homogenizer for 20 minutes while stirring. The resulting dispersion is centrifuged (5000 rpm × 10
), And a supernatant liquid of 80% by weight based on the total amount was collected. The pigment concentration of this pigment dispersion was calculated by dry-up, and diluted with pure water so that the pigment concentration became 10% by weight.

<Cyan Pigment Dispersion A> A dispersant aqueous solution neutralized by adding 4 parts by mass of potassium hydroxide to 20 parts by mass of a styrene / acrylic acid copolymer (copolymerization ratio: 50/50 mol, polymerization average molecular weight: 8000). Created. Pure water 19 in 40 parts by mass of dispersant aqueous solution
0 parts by mass were added, and after stirring, the pigment CI Pigment Blue-15 was added to 40 parts.
Parts by mass were charged with stirring. After stirring for 10 minutes, the mixture was dispersed with a high-pressure homogenizer for 20 minutes while stirring. The obtained dispersion was subjected to a centrifugation treatment (5000 rpm × 20 minutes), and a supernatant of 80% by weight based on the whole amount was collected. The pigment concentration of this pigment dispersion was calculated by dry-up, and diluted with pure water so that the pigment concentration became 10% by weight.

<Cyan Pigment Dispersion B> A dispersant aqueous solution neutralized by adding 4 parts by mass of potassium hydroxide to 20 parts by mass of a styrene / acrylic acid copolymer (copolymerization ratio: 50/50 mol, polymerization average molecular weight: 8,000). Created. Pure water 19 in 40 parts by mass of dispersant aqueous solution
0 parts by mass were added, and after stirring, the pigment CI Pigment Blue-15 was added to 40 parts.
Parts by mass were charged with stirring. After stirring for 10 minutes, the mixture was dispersed with a high-pressure homogenizer for 15 minutes while stirring. The obtained dispersion was subjected to a centrifugal separation treatment (5000 rpm × 10 minutes), and a supernatant liquid of 80% by weight based on the whole amount was collected. The pigment concentration of this pigment dispersion was calculated by dry-up, and diluted with pure water so that the pigment concentration became 10% by weight.

<Magenta Pigment Dispersion A> An aqueous solution of a dispersant neutralized by adding 4 parts by mass of potassium hydroxide to 20 parts by mass of a styrene / acrylic acid copolymer (copolymerization ratio: 50/50 mol, polymerization average molecular weight: 8,000) was added. Created. Pure water in 40 parts by mass of dispersant aqueous solution
After adding 190 parts by mass and stirring, the pigment CI Pigment Red-122 is added.
40 parts by mass were charged with stirring. After stirring for 10 minutes, the mixture was dispersed with a high-pressure homogenizer for 20 minutes while stirring. The obtained dispersion was subjected to a centrifugation treatment (5000 rpm × 20 minutes), and a supernatant of 80% by weight based on the whole amount was collected. The pigment concentration of this pigment dispersion was calculated by dry-up, and diluted with pure water so that the pigment concentration became 10% by weight.

<Magenta Pigment Dispersion B> A dispersant aqueous solution neutralized by adding 4 parts by mass of potassium hydroxide to 20 parts by mass of a styrene / acrylic acid copolymer (copolymerization ratio: 50/50 mol, polymerization average molecular weight: 8000). Created. Pure water in 40 parts by mass of dispersant aqueous solution
After adding 190 parts by mass and stirring, the pigment CI Pigment Red-122 is added.
40 parts by mass were charged with stirring. After stirring for 10 minutes, the mixture was dispersed with a high-pressure homogenizer for 15 minutes while stirring. The obtained dispersion was subjected to a centrifugal separation treatment (5000 rpm × 10 minutes), and a supernatant liquid of 80% by weight based on the whole amount was collected. The pigment concentration of this pigment dispersion was calculated by dry-up, and diluted with pure water so that the pigment concentration became 10% by weight.

<Yellow Pigment Dispersion A> An aqueous solution of a dispersant neutralized by adding 4 parts by mass of potassium hydroxide to 20 parts by mass of a styrene / acrylic acid copolymer (copolymerization ratio: 50/50 mol, polymerization average molecular weight: 8,000) was used. Created. Pure water in 40 parts by mass of dispersant aqueous solution
After adding 190 parts by mass and stirring, the pigment CI Pigment Yellow-74
Was added while stirring. After stirring for 10 minutes, the mixture was dispersed with a high-pressure homogenizer for 20 minutes while stirring. The obtained dispersion was subjected to a centrifugation treatment (5000 rpm × 20 minutes), and a supernatant of 80% by weight based on the whole amount was collected. The pigment concentration of this pigment dispersion was calculated by dry-up, and the pigment concentration was 10% by weight.
And diluted with pure water.

<Yellow Pigment Dispersion B> A dispersant aqueous solution neutralized by adding 4 parts by mass of potassium hydroxide to 20 parts by mass of a styrene / acrylic acid copolymer (copolymerization ratio: 50/50 mol, polymerization average molecular weight: 8000). Created. Pure water in 40 parts by mass of dispersant aqueous solution
After adding 190 parts by mass and stirring, the pigment CI Pigment Yellow-74
Was added while stirring. After stirring for 10 minutes, the mixture was dispersed with a high-pressure homogenizer for 15 minutes while stirring. The obtained dispersion was subjected to a centrifugal separation treatment (5000 rpm × 10 minutes), and a supernatant liquid of 80% by weight based on the whole amount was collected. The pigment concentration of this pigment dispersion was calculated by dry-up, and the pigment concentration was 10% by weight.
And diluted with pure water.

[Ink for Examples] Using the above-described black pigment dispersions 1 to 3, cyan pigment dispersions 1 and 2, magenta pigment dispersions 1 and 2, and yellow pigment dispersions 1 and 2, Example inks having compositions, black inks 1-3, cyan inks 1 and 2, magenta ink 1
And 2, and the yellow inks 1 and 2 were prepared so that the total mass was 100 parts by mass. When preparing each of these inks, other components were added to each pigment dispersion at a predetermined concentration, mixed, stirred and then filtered through a 2 μm filter,
Each ink was obtained.

<Black Ink 1> Black Pigment Dispersion 1 30 parts by mass Diethylene glycol 10 parts by mass Propylene glycol 10 parts by mass Surfynol 465 (manufactured by Nissin Chemical Co., Ltd.) 3 parts by mass Ethanol 2 parts by mass urea 6 Parts by mass Water: balance

<Black Ink 2 and 3> Black inks 2 and 3 were prepared in the same composition as black ink 1 except that the pigments were black pigment dispersions 2 and 3, respectively.

<Cyan Ink 1> Cyan Pigment Dispersion 1 30 parts by weight Diethylene glycol 18 parts by weight Diethylene glycol monobutyl ether 1 part by weight Surfynol 465 (manufactured by Nissin Chemical Co., Ltd.) 1 part by weight Ethanol 2 parts by weight urea 6 parts by mass Water: balance

<Cyan ink 2, magenta ink 1, and
2. Yellow inks 1 and 2> The same composition as that of cyan ink 1 was used except that the pigments were cyan pigment dispersion 2, magenta pigment dispersions 1 and 2, and yellow pigment dispersions 1 and 2, respectively.

[Ink for Comparative Example] The above-mentioned black pigment dispersion A, cyan pigment dispersions A and B, magenta pigment dispersions A and B, yellow pigment dispersions A and B, black pigment dispersion 1, cyan pigment dispersion Using Pigment Dispersion 1, Magenta Pigment Dispersion 1, and Yellow Pigment Dispersion 1, comparative inks having the following compositions, black ink A, cyan inks A to C, magenta inks A to C, Yellow inks A to C were prepared so that the total mass was 100 parts by mass. In preparing each of these inks, other components are added to each pigment dispersion at a predetermined concentration, and after mixing and stirring, when each color pigment dispersion A is used, 2 μm is used, and each color pigment dispersion B is used. In the case where the ink was present, filtration was performed with a 5 μm filter to obtain each ink. Note that black ink A, cyan inks A to C,
The compositions of the magenta inks A to C and the yellow inks A to C were prepared so as to be classified as follows by the symbols of “A to C”.

<Each ink A or B> Each pigment dispersion A or B: 30 parts by mass Diethylene glycol: 10 parts by mass Diethylene glycol monobutyl ether: 2.5 parts by mass Surfynol 465 (manufactured by Nissin Chemical Co., Ltd.): 2.5 parts by mass Ethanol ... 2 Parts by weight Urea: 6 parts by weight Water: balance

<Each color ink C> Each pigment dispersion 1: 30 parts by weight Diethylene glycol: 10 parts by weight Propylene glycol: 10 parts by weight Surfynol 104 (manufactured by Nissin Chemical Co., Ltd.): 0.05 parts by weight Ethanol: 2 parts by weight urea: 6 parts by mass Water: balance

Table 1 shows the physical properties of these inks.
The physical properties of each ink shown in Table 1 were measured by the following measurement methods. (1) Ink pH was measured using a glass electrode in an environment of 23 ° C. and 55% RH. (2) Surface tension of the ink In an environment of 23 ° C. and 55% RH, the ink was measured using a Wilhelmy surface tensiometer. (3) In an environment with a contact angle of 23 ° C and 50% RH, 4.0μl of each ink was set on plain paper FX-L paper (manufactured by Fuji Xerox) and FIBRO 1100 DAT
The dynamic contact angle was measured from the start of measurement to 1000 seconds using an MKII (manufactured by FIBRO system) device. 0.1 from the start of measurement
The second value was read.

(4) Ink viscosity A Rheomat 115 (manufactured by Contraves) device was used. 23 measurements
C., the shear rate was 1400 s-1. (5) The average particle size of the dispersed particles of the pigment in the ink.
UPA particle size analyzer 9340 (manufactured by Leeds & Northrup) was used. For the measurement, 5 mL of the ink was put into a measurement cell, and the viscosity was measured at 23 ° C. by inputting the viscosity of the ink as the viscosity and the density of the pigment as the density of the dispersed particles as input parameters.

(6) Number of Coarse Particles in Ink The particle size distribution of the region of 0.5 μm
cusizerTM770 OpticalParticles Sizer (Particle Sizi
ng Systems). When measuring Accusizer, enter the density of the pigment as the
2 μl were diluted in 50 ml of deionized water and measured. The desired number of particles was read from the original data table of the obtained particle size distribution, and the number of particles was converted to 1 μL. Since the pore size of the filter closest to the discharge port used for the recording head used for black ink is 15 μm, the number of particles of 5 μm or more, which is 1/3 the size of black ink, is used for color ink Since the pore diameter of the filter closest to the discharge port used in Example 2 was 6 μm, the number of particles of 2 μm or more, which is 1 / of each color ink, was read.

Next, the above black ink and color ink were combined as described below to form a color ink set.

Example Color Ink Set Example 1 Black ink 1, cyan ink 1, magenta ink 1, and yellow ink 1 were combined.

Example 2 Black ink 2, cyan ink 1, magenta ink 1, and yellow ink 1 were combined.

(Example 3) Black ink 2, cyan ink 2, magenta ink 2, and yellow ink 2 were combined.

Example 4 Black ink 3, cyan ink 1, magenta ink 1, and yellow ink 1 were combined.

(Example 5) Black ink 3, cyan ink 2, magenta ink 2, and yellow ink 2 were combined.

[Comparative Example Color Ink Set] (Comparative Example 1) Black ink A, cyan ink A, magenta ink A, and yellow ink A were combined.

(Comparative Example 2) Black ink A, cyan ink 1, magenta ink 1, and yellow ink 1 were combined.

Comparative Example 3 Black ink 1, cyan ink A, magenta ink A, and yellow ink A were combined.

Comparative Example 4 A black ink A, a cyan ink C, a magenta ink C, and a yellow ink C were combined.

(Comparative Example 5) Black ink 3, cyan ink B, magenta ink B, and yellow ink B were combined.

[Characteristic evaluation test of aqueous color ink set for inkjet recording] (1) Long-term storage stability For each ink provided in the aqueous color ink set for inkjet recording of the above Examples and Comparative Examples, each ink was made of glass. Place in a tube to a height of 9 cm and seal tightly.
Stored for months. Sample the ink up to 3 cm from the top, dilute it 3000 times with pure water, measure the transmittance at 600 nm with a U-3210 type recording spectrophotometer (manufactured by Hitachi, Ltd.), and determine the long-term storage stability of each ink That is, the long-term storage stability of the aqueous color ink set for inkjet recording provided with each of these inks was compared. The measured values of each of the obtained inks were as follows: ；: the difference in transmittance before and after storage was within 2%,
X: Each ink was evaluated under the evaluation criteria that the difference in transmittance before and after storage exceeded 2%. Table 2 shows the results.

Then, based on the evaluation of each of the obtained inks, the long-term storage stability of the aqueous color ink set for ink jet recording of the examples and comparative examples was evaluated. The evaluation criteria at this time were as follows: ○: All of the provided inks were evaluated as に お い て in the evaluation criteria of long-term stability in Table 2. X: At least one of the provided inks was as shown in Table 2. Of the long-term stability evaluation criterion was evaluated as “Poor”. Table 3 shows the results.

Next, printing was actually performed using the aqueous color ink set for ink jet recording of the above Examples and Comparative Examples, the degree of bleeding between colors when printing was performed, Printing characteristics such as color development and ink ejection stability were evaluated. The evaluation of the printing characteristics was 23
The test was performed in a thermal ink jet printing apparatus capable of full-color printing under an environment of 55 ° C. and 55% RH. Printing was performed by applying a plurality of pulses to the ink to form one drop. Recording head 400dpi, 160 nozzles, 800dpi
m and 160 nozzles were prepared. The former head was used for black ink, and the latter head was used for color ink.

Here, with respect to all of the aqueous color ink sets for ink jet recording of the Examples and Comparative Examples used, it was confirmed that the ejection weight per discharge was larger for the black ink than for each color ink. . The filter closest to the discharge port used in the former head has a pore size of 15 μm, and the filter in the latter head has a pore size of 6 μm.
μm one was used.

(2) Color developing property of each ink-1: Optical density of single-color portion image A solid image of 2 cm × 10 cm was printed on plain paper FX-L paper (Fuji Xerox) and 4024 paper (Xerox). After printing and standing for one day, five arbitrary points were measured using an optical densitometer X-Rite MODEL404 (manufactured by X-Rite), and the average value was determined. And about the measured value of each obtained ink, 、: 1.0 or more,
X: Each ink was evaluated under the evaluation criteria of less than 1.0. Table 2 shows the results.

Based on the evaluation of each of the obtained inks, the aqueous color ink sets for ink jet recording of Examples and Comparative Examples were evaluated. The evaluation criteria at this time were as follows: ○: All of the provided inks were evaluated as に お い て in the optical density evaluation criterion in Table 2, x: At least one of the provided inks was in Table 2. It was determined that the evaluation of × was obtained in the evaluation criteria of the optical density. Table 3 shows the results.

(3) Color developing property of each ink-2: Uniform color image uniformity A solid image of 2 cm × 10 cm is printed on plain paper FX-L paper (Fuji Xerox Co., Ltd.) and 4024 paper (Xerox Co., Ltd.). Then, sensory evaluation was performed to determine whether or not there was color unevenness. In this case,
；: No color unevenness ×: Each ink was evaluated under the evaluation criteria that there was color unevenness. Table 2 shows the results.

Based on the evaluation of each of the obtained inks, the aqueous color ink sets for ink jet recording of Examples and Comparative Examples were evaluated. At this time, the evaluation criteria were as follows: ；; all of the provided inks were evaluated as に お い て in the evaluation criteria of the single-color portion image uniformity in Table 2. x: At least one of the provided inks Table 2
In the evaluation criteria for the uniformity of the single-color portion, the evaluation of × was obtained. Table 3 shows the results.

(4) Intercolor bleed A pattern in which each color ink was printed on plain paper FX-L paper (manufactured by Fuji Xerox Co., Ltd.) and 4024 paper (manufactured by Xerox Co., Ltd.) with 10-point black characters as the background was created. When printing was performed using the aqueous color ink set for ink jet recording of Examples and Comparative Examples, bleeding of a character portion was sensory evaluated. In this case, ○: all kanji and hiragana are reproduced without any problem; Δ; some of the kanji are not reproduced, but some are readable ×; kanji and hiragana cannot be read,
The water-based color ink set for inkjet recording was evaluated under the following evaluation criteria. Table 3 shows the results.

(5) Discharge stability -1: Degree of occurrence of clogging Using a prototype ink jet recording apparatus, after the discharge was stopped, the nozzle was left in an environment of 23 ° C. and 50% RH without capping the nozzle surface. Then, when the ejection was restarted, the standing time until image disturbance due to clogging of the nozzle for each ink was measured. The ejection stability of each ink was evaluated on the basis of the evaluation criteria of the obtained measurement time, that is, ；: 15 seconds or more, Δ: 5 seconds to less than 15 seconds, ×: less than 5 seconds. Table 2 shows the results.

Based on the evaluation of each of the obtained inks, the aqueous color ink sets for ink jet recording of Examples and Comparative Examples were evaluated. At this time, the evaluation criteria were as follows: ；: All of the provided inks were evaluated as に お い て in the evaluation criteria of the degree of clogging occurrence in Table 2. X: At least one of the provided inks In the evaluation criteria for the degree of clogging in Table 2,
Or, it was determined that the evaluation of × was obtained. Table 3 shows the results.

(6) Ejection stability-2: Evaluation of kogation Using a prototype printing apparatus, 1 × 108 pulses were continuously ejected per nozzle, and the initial dot diameter on FX-L paper (Fuji Xerox) was measured. The rate of change with respect to the dot diameter was measured. With respect to the obtained measurement values, the ejection stability of each ink was evaluated based on the evaluation criteria of ○: less than 5%, Δ: 5% or more and less than 10%, ×: 10% or more. Table 2 shows the results.

Then, based on the evaluation of each of the obtained inks, the aqueous color ink sets for ink jet recording of Examples and Comparative Examples were evaluated. The evaluation criteria at this time were as follows: ○: All of the provided inks were evaluated as に お い て in the evaluation criteria of the kogation evaluation in Table 2. X: At least one of the provided inks was in Table 2.
Or × in the evaluation criteria for kogation evaluation in
Has been evaluated. Table 3 shows the results. In Table 3, Bk indicates black ink, C indicates cyan ink, M indicates magenta ink, and Y indicates yellow ink.

[0142]

[Table 1]

[0143]

[Table 2]

[0144]

[Table 3]

[0145]

As described above, according to the present invention, it is possible to sufficiently prevent the occurrence of bleeding between colors, and it is possible to form an ink for ink jet recording which is excellent in color development, ejection stability and long-term storage stability of each ink. An aqueous color ink set and an inkjet recording method using the same can be provided.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Ken Hashimoto 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture F-Xerox Co., Ltd.F-term (reference) 2C056 EA13 FC02 2H086 BA04 BA53 BA55 BA60 4J039 BA04 BC09 BC10 BC11 BC13 BC14 BC15 BC34 BC54 BE01 BE12 BE15 BE22 CA06 EA29 EA42 EA44 EA46 EA47 GA24

Claims (4)

[Claims] 1. An ink jet recording aqueous color ink set comprising a black ink and at least a cyan ink, a magenta ink, and a yellow ink as color inks, wherein the black ink and each of the color inks are provided. Contains a self-dispersible pigment in water, and the dispersed particles of the pigment have a volume average particle diameter of 20 to 150 nm.
And the value obtained by dividing the volume average particle diameter by the number average particle diameter of the dispersed particles is 1.5 to 3.0, and the surface tension of the black ink is 25 to 55 mN / m, The aqueous color ink set for inkjet recording, wherein the surface tension of each color ink is 25 to 45 mN / m. 2. The contact angle of the black ink to plain paper is 30 to 110 °, and the contact angle of each color ink to plain paper is 30 to 70 °. 2. The aqueous color ink set for inkjet recording according to item 1. 3. The inkjet recording according to claim 1, wherein a surface hydrophilic group of the pigment contained in the black ink is different from a surface hydrophilic group of the pigment contained in each of the color inks. Water-based color ink set. 4. An ink jet recording method comprising printing using the aqueous color ink set for ink jet recording according to claim 1.