JP2000239589A - Ink, ink container, ink set, ink jet recording device and ink jet printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink which gives dot diameters having proper extensions, forms dots having a high image concentration and can form images having high qualities by dispersing the first specific pigment and the second specific pigment as coloring materials in an aqueous medium. SOLUTION: This ink contains the first pigment and the second pigment as coloring materials in an aqueous medium in a dispersed state. The first pigment is a self-dispersing type pigment to whose surface one or more anionic groups are bound directly or through one or more other atomic groups or a self-dispersing type pigment to whose surface one or more cationic groups are bound directly or through one or more atomic groups. The second pigment is a pigment which can be dispersed in an aqueous medium in the presence of a polymer dispersant such as a sulfonic acid-based polymer dispersant. The ink further contains at least one of a nonionic polymer dispersant and a polymer dispersant having the same polarity as the group bound to the surface of the first pigment. The Ka value is <1 ml.m-2.msec-1/2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink, particularly to an ink used in ink jet printing and an ink jet printing method. Further, the present invention relates to an ink container, an ink set, and an ink jet recording apparatus. The present invention is applicable to all devices that can record on various recording media such as paper, cloth, leather, nonwoven fabric, and OHP paper, for example, office equipment such as printers, copiers, and facsimile machines to which an inkjet recording method is applied. It is possible.

[0002]

2. Description of the Related Art An ink jet printing system has various advantages such as low noise, low running cost, high speed printing, easy downsizing of an apparatus, and easy colorization. This method is widely used. In such a printer or the like, generally, an ink to be used is selected from the viewpoints of print characteristics such as ejection characteristics and fixability, print bleeding of a printed image, optical reflection density, and print quality such as coloration.

It is widely known that inks are roughly classified into two types, dye inks and pigment inks, depending on the coloring materials contained therein. Among them, the pigment ink has advantages such as superior water resistance and light resistance as compared with the dye ink, and enables clear character quality. The pigment contained in the pigment ink is usually stably dispersed in the ink using a dispersant such as a polymer dispersant.
Specifically, the effect is that the polymer particles are adsorbed on the polymer dispersant, and the electric repulsion force of the polymer dispersant is mainly used to cause aggregation of the pigment particles. The ink is stably dispersed in the ink by overcoming the force. Therefore, it is necessary to add a polymer dispersant to the ink according to the amount of the pigment. When such an ink is printed on plain paper using the ink jet recording method, the pigments aggregate due to the penetration of the solvent of the ink such as moisture into the paper and the evaporation into the air. At this time, the behavior on paper is such that the larger the amount of the polymer dispersant, the stronger the cohesive force. Therefore, the diameter of the ink dot formed on the print medium by the ink having a certain volume ejected from the ink jet head is small, and the ink dot has a shape close to a re-distorted shape that collides with the paper. Therefore, in order to obtain an ink dot having a recording density sufficient for forming an image and having a dot diameter necessary for recording such that white streaks and the like do not occur, the ejection volume of the ink from the inkjet head must be increased. Need to be adjusted. However, this is coupled with a decrease in the permeability of the pigment particles to which the polymer dispersant is adsorbed due to the strong cohesive force of the pigment particles, resulting in a delay in fixing of the ink to the print medium or a reduction in the scratch resistance of the recorded image. May be reduced.

[0004] In order to increase the dot diameter and improve the fixability, it has been considered to incorporate a penetrant into the ink for the purpose of improving the permeability of the ink into the print medium. However, this causes the deterioration of the dot shape (the deterioration of the dot surrounding shape such as so-called feathering) and the permeation of the ink to the back side of the paper (the so-called strike-through), and the like, which are undesirable in aiming at a high-quality recorded image. There are cases. In addition, since the coloring material permeates into the print medium, the OD of the ink dot does not often increase so much even if the dot diameter becomes relatively large.

Further, there has been proposed an ink using a self-dispersion type pigment. This ink has a lower cohesive force of the pigment on paper than the ink containing the pigment dispersed by the dispersant. Although the dot diameter can be increased, it cannot be said that it is still sufficient.

As described above, various factors that affect the quality of a recorded image, such as ink fixability, enlargement of the ink dot diameter,
It satisfies the uniformity of the density within the ink dot, the high optical density of the ink dot itself, etc. at a high level, and also satisfies the stability as an ink, especially the property that it can be stably ejected as an inkjet ink. Various inks and printing methods are still being studied for further improvement.

[0007]

One of the objects of the present invention is that an ink droplet applied to a recording medium spreads appropriately in the lateral direction of the recording medium, and does not penetrate in the thickness direction of the recording medium. Provided is an ink which is suppressed, has a dot diameter having an appropriate spread as a result, has a high and uniform image density in the dot, and is capable of giving a dot having an excellent outer shape in which almost no feathering is observed. Is to do. Another object of the present invention is to provide an ink-jet printing method capable of forming a high-quality image with high image density while suppressing the amount of ink applied to a recording medium. Another object of the present invention is to provide an ink jet recording apparatus capable of stably recording high-quality images, and an ink container and an ink set used therefor.

Another object of the present invention is to provide an ink for forming one dot or an ink for forming one pixel (a pixel including a superimposed dot portion by a dot matrix such as 3 × 3 or 4 × 4). An object of the present invention is to provide an ink for image formation and an image forming method capable of providing required image density and image quality by pursuing required characteristics.

[0009]

According to one embodiment of the present invention, which can achieve the above object, there is provided an ink in which a first pigment and a second pigment are dispersed in an aqueous medium as coloring materials. An ink containing at least one self-dispersible pigment in which the first pigment has at least one anionic group bonded directly or via another atomic group to the surface of the first pigment. A self-dispersible pigment in which one cationic group is bonded to the surface of the first pigment directly or via another atomic group, wherein the second pigment is a polymer dispersed in an aqueous medium. Wherein the ink further comprises at least one of a polymer dispersant having the same polarity as a group bonded to the surface of the first pigment and a nonionic polymer dispersant. Features.

[0010] In another embodiment of the present invention, which can achieve the above object, ink is ejected from an orifice using an ink jet recording method and applied on a print medium to form one element of an image. An ink for use in an image recording method to be formed, comprising a first pigment and a second pigment as coloring materials in a dispersed state in an aqueous medium.
Is a self-dispersible pigment in which at least one anionic group is bonded directly or via another atomic group to the surface of the first pigment, or at least one cationic group is directly or other A self-dispersible pigment that is bonded to the surface of the first pigment via an atomic group, and the second pigment is a pigment that can be dispersed in an aqueous medium by a polymer dispersant; Further comprises at least one of a polymer dispersant having the same polarity as a group bonded to the surface of the first pigment and a nonionic polymer dispersant.

An ink jet printing method as one embodiment of the present invention capable of achieving the above object is to discharge ink toward a printing medium by using an ink jet recording method and to print the ink on the printing medium. In an inkjet printing method including a step of recording an image, the ink contains a first pigment and a second pigment in a dispersed state in an aqueous medium, and the first pigment has at least one anionic group directly or A self-dispersible pigment or at least one cationic group bonded to the surface of the first pigment via another atomic group is directly or via another atomic group on the surface of the first pigment. A self-dispersed pigment that is bound, wherein the second pigment is a pigment that can be dispersed in the aqueous medium by a polymeric dispersant, and the ink further comprises Wherein the ink is an ink containing at least one of the first of the same polarity of the polymeric dispersing agent and a base coupled to the surface of the pigment and a nonionic polymer dispersant.

The image forming method as one of the embodiments of the present invention which can achieve the above object is a method for forming an image of the first pigment, wherein at least one anionic group is directly or via another atomic group. A self-dispersible pigment bonded to the surface of the first pigment or a self-dispersible pigment having at least one cationic group bonded directly or via another atomic group to the surface of the first pigment. The first ink, at least one of a polymer dispersant having the same polarity as a group bonded to the surface of the self-dispersion type pigment in the first ink and a nonionic polymer dispersant, and the polymer dispersion A second ink containing a pigment dispersible in an aqueous medium by an agent; and applying the second ink to the print medium such that the first ink and the second ink are in contact with each other in a liquid state on the surface of the print medium. hand Characterized in that it comprises a step of forming an image.

Further, the image forming method as one of the embodiments of the present invention which can achieve the above-mentioned object is characterized in that at least one anionic group is directly or via another atomic group. Including self-dispersed pigments bound to the surface of the pigment or self-dispersed pigments wherein at least one cationic group is bound to the surface of the first pigment, either directly or via another atomic group. A first ink, a pigment dispersible in the aqueous medium by a polymer dispersant, and a polymer dispersion having the same polarity as a group bonded to the surface of the self-dispersible pigment in the first ink. A second ink containing at least one of an agent and a nonionic polymer dispersant, and a third ink containing a dye having the same polarity as the group bonded to the surface of the self-dispersing pigment. The first on the surface Ink, second ink and third
And a step of applying the ink to the print medium so that the two inks come into contact with each other in a liquid state.

As described above, the present invention provides a self-dispersible pigment and a pigment which can be dispersed in an aqueous medium by a polymer dispersant in the course of research aimed at further improving the quality of an ink jet recorded image. Based on the finding that an ink mixed with a polymer dispersant satisfies various elements required for high image quality at a very high level and has excellent ink stability. Things.

That is, as the ink in a form before being discharged from the recording head, a self-dispersion type pigment (first pigment) is used.
However, since the polymer dispersant acts as a dispersant for the pigment (second pigment) that can be dispersed in the aqueous medium, the pigment in the ink is stable even when the amount of the polymer dispersant in the ink as a whole decreases. To maintain the dispersed state. On the other hand, when printing is performed on paper using this ink, the dot diameter is determined by the ink containing the second pigment and the polymer dispersant dispersing the second pigment or the ink containing only the first pigment (self-dispersible pigment). Compared to the above, it was large and diffused uniformly on the paper surface, the OD was high, and the fixability was relatively fast.

The reason why such a phenomenon is observed is not clear, but is presumed to be due to the following mechanism. That is, the second pigment to which the polymer dispersant is adsorbed and the first pigment
Are electrically repelled in the ink, and at least the cohesive force of the pigment is weaker than that of the ink containing only the polymer-dispersed pigment. When such an ink is printed on the paper surface, the coloring material in the ink hardly permeates in the thickness direction of the paper because the polymer dispersant is adsorbed on the second pigment. On the other hand, in the case of the ink containing the second pigment and the polymer dispersant in the paper surface (horizontal) direction, the polymers are rapidly entangled with each other as the solvent of the ink permeates the paper and the water content decreases due to evaporation. In contrast, the pigment is strongly agglomerated due to the cross-linking of the polymer between the pigments, whereas the ink of the present embodiment is not entangled or cross-linked by the presence of the first pigment. Prevention or suppression, and the repulsion between the first pigment and the polymer dispersant reduces the strong intermolecular force between the pigments in the ink, and as a result, the ink is easily diffused in the lateral direction of the paper. In addition, it is considered that although the diffusion is moderated, the diffusion is not disordered due to the influence of the cohesive force between the pigments. It is considered that this results in securing a large dot diameter and roundness of dots with a small discharge amount, and conformability when a plurality of dots are connected, that is, good smoothing property. The phenomenon on the paper surface is that the Ka value of the ink in the Bristow method is 1 ml · m ⁻² · msec.
^This is particularly noticeable when the design is less than ^-1/2 , that is, when it is designed to have relatively low permeability to the print medium, and works advantageously for high image quality.

The ink of the present embodiment has good dispersion stability in the ink tank as described above, and also has a large dot diameter, high OD and good scratch resistance as printing characteristics as described above. This has a great effect such as good dot roundness.

The ink of the present invention is also good when ejected by an ink jet recording head. That is, since the viscosity is small and the refill characteristics for the nozzle are good, high-speed driving is possible. Also, regarding the discharge by the discharge method utilizing bubble formation by film boiling, the discharge speed and discharge amount are relatively large, probably because of the appropriate wetting of the discharge heater surface and / or the low viscous resistance to rapid bubbling. It does not fluctuate. That is, the ejection efficiency and the ejection stability are good.

By the way, even if an experiment is performed in which the ejection amount is controlled to be the same for various inks in consideration of the improvement in the ejection efficiency, the dot diameter of the ink of the present embodiment is sufficiently large. Therefore, the enlargement of the ink dot diameter by the ink of the present embodiment cannot be explained merely because the ejection efficiency is improved. When printing is performed with a conventional BJ recording head, the use of the ink of the present embodiment has a synergistic effect on the ejection amount, the ejection speed, and the spreadability of the ink itself, and an ink dot having a larger diameter can be formed. The fact that a sufficiently large diameter ink dot can be obtained even with a small ejection amount means that the ink is thin and spread over a wide area on the recording medium surface, and the ink dries quickly, and as a result, the time required for fixing the ink is obtained. Can be shortened.

Further, a dye having the same polarity as the group bonded to the surface of the first pigment is further added to the ink containing the first pigment, the second pigment, and the polymer dispersant, so that The cohesive force of the above pigment can be further reduced, which contributes to the further expansion of the area factor, and the occurrence of "cracks" in the recorded image of a print medium having a resin coat layer. Is more effectively suppressed.

An ink container according to an embodiment of the present invention that can achieve the above object is an ink container containing ink, wherein the ink contains a first pigment and a second pigment as coloring materials. A self-dispersing pigment, which is contained in an aqueous medium in a dispersed state, and wherein the first pigment has at least one anionic group bonded to the surface of the first pigment directly or via another atomic group, or A self-dispersible pigment in which at least one cationic group is bonded to the surface of the first pigment directly or via another atomic group;
The second pigment is a pigment that can be dispersed in the aqueous medium by a polymer dispersant, and the ink further comprises the first pigment.
Wherein at least one of a polymer dispersant having the same polarity as the group bonded to the surface of the pigment and a nonionic polymer dispersant is contained.

The ink set according to an embodiment of the present invention that can achieve the above object contains a first pigment and a second pigment as coloring materials in an aqueous medium in a dispersed state, and Is a self-dispersible carbon black in which at least one anionic group is bonded to the surface of the first pigment directly or through another atomic group, or at least one cationic group is directly or otherwise. A self-dispersible carbon black bonded to the surface of the first pigment via an atomic group of the above, wherein the second pigment can be dispersed in the aqueous medium by a polymer dispersant. A black ink containing at least one of a polymer dispersant having the same polarity as the group bonded to the surface of the first pigment and a nonionic polymer dispersant; and a known or various ink. Eroinku, characterized in that a combination of each magenta ink, and cyan ink.

An ink jet recording apparatus according to an embodiment of the present invention, which can further achieve the above object, comprises:
A first pigment and a second pigment which are dispersed in an aqueous medium as a coloring material, wherein the first pigment has at least one anionic group directly or via another atomic group; A self-dispersible carbon black bonded to the surface of the first pigment or a self-dispersible carbon black having at least one cationic group bonded directly or via another atomic group to the surface of the first pigment. Wherein the second pigment is a pigment which can be dispersed in the aqueous medium by a polymer dispersant, and the ink further comprises a polymer dispersion having the same polarity as the group bonded to the surface of the first pigment. An ink container containing a black ink containing at least one of a dispersant and a nonionic polymer dispersant; a yellow ink, a magenta ink, and a cyan ink; and the black ink and the yellow ink. , Characterized in that it comprises a means for ejecting the ink-jet printing method, each individually the magenta ink and the cyan ink. The yellow, cyan, and magenta inks used here can be known inks or inks with appropriate improvements. In particular, the Ka value in the Bristow method is 1 ml.
^{-M -2} -msec ^-1/2 or more is preferable. According to the ink container, the ink set, and the ink jet recording apparatus, it is possible to record an image that is more excellent than the conventional one for the above-described reasons.

[0024]

Next, the present invention will be described in detail based on ink as one of the embodiments capable of achieving the object of the present invention.

An example of the ink that can be used in the present invention is an ink containing a first pigment and a second pigment as colorants in a dispersed state in an aqueous medium, wherein the first pigment is at least one. A self-dispersing pigment or at least one cationic group in which one anionic group is bonded directly or via another group to the surface of the first pigment; A self-dispersible pigment bonded to the surface of the first pigment, wherein the second pigment is a pigment dispersible in the aqueous medium by a polymer dispersant or a nonionic polymer dispersant. The ink further includes an ink containing at least one of a polymer dispersant having the same polarity as the group bonded to the surface of the first pigment and a nonionic polymer dispersant.

Hereinafter, this ink will be sequentially described. (First pigment) A self-dispersing pigment is a pigment that is stably maintained in water, a water-soluble organic solvent, or a liquid mixture thereof without using a dispersant such as a water-soluble polymer compound. In addition, it refers to a pigment that does not interfere with normal ink ejection from an orifice using an ink jet recording technique and that does not generate aggregates of the pigments in the liquid. (Anionic self-dispersing CB) Such pigments include:
For example, those in which at least one anionic group is bonded to the pigment surface directly or via another atomic group are preferably used. A specific example is that at least one anionic group is directly or through another atomic group. It contains carbon black bonded to the surface via the carbon black.

Examples of such an anionic group bonded to carbon black include, for example, -COOM,
—SO ₃ M, —PO ₃ HM, —PO ₃ M _{2 and the} like (where M is a hydrogen atom, an alkali metal, ammonium, or
Represents an organic ammonium).

Examples of the alkali metal "M" include lithium, sodium, potassium and the like, and examples of the organic ammonium "M" include mono to trimethyl ammonium, mono to triethyl ammonium,
Mono to trimethanol ammonium and the like can be mentioned.

Among these anionic groups, particularly -CO
OM or -SO ₃ M because a large effect of stabilizing the dispersion state of the carbon black preferred.

Incidentally, it is preferable to use one of the above-mentioned various anionic groups bonded to the surface of carbon black via another atomic group. Examples of the other atomic group include a linear or unsubstituted alkylene group having 1 to 12 carbon atoms, a substituted or unsubstituted phenylene group, and a substituted or unsubstituted naphthylene group. Here, examples of the substituent that may be bonded to the phenylene group or the naphthylene group include a linear or branched alkyl group having 1 to 6 carbon atoms.

Specific examples of the anionic group bonded to the surface of carbon black via another atomic group include, for example, -C ₂ H ₄ COOM, -PhSO ₃ M, -PhCOO
M and the like (provided that M is defined as above and Ph represents a phenyl group), but of course is not limited thereto.

As described above, carbon black having an anionic group bonded to the surface directly or via another atomic group can be produced, for example, by the following method.

That is, -COON is applied to the carbon black surface.
As a method for introducing a, for example, a method of oxidizing commercially available carbon black with sodium hypochlorite may be mentioned.

Further, for example, -A
r-COONa group (however, Ar represents an aryl group)
Can be bonded to the surface of carbon black by using a diazonium salt in which nitrous acid acts on an NH ₂ —Ar—COONa group, but of course, the present invention is not limited to this. (Cationic Self-Dispersion CB) (Cationically Charged CB) As the cationically charged carbon black, carbon black having at least one selected from the following quaternary ammonium groups bonded to the surface of carbon black, for example: Is mentioned.

-N ⁺ H ₃ , -N ⁺ R ₃ , -SO ₂ NH ₂ , -S
O ₂ NHCOR,

[0036]

Embedded image In the above formula, R represents, for example, a linear or branched alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted naphthyl group. Here, examples of the substituent of the phenyl group or the naphthyl group include a linear or branched alkyl group having 1 to 6 carbon atoms. Examples of the substituent when R is a naphthyl group having a phenyl group or a substituent having a substituent, for example, a linear or branched alkyl group of C ₁ -C _6, and the like. As a method for producing a cationically charged self-dispersible carbon black having a hydrophilic group bonded thereto as described above, for example, an N-ethylpyridyl group having the following structure:

[0037]

Embedded image Taking carbon black as an example, a method of treating carbon black with 3-amino-N-ethylpyridium bromide may be mentioned. Since carbon black charged anionic or cationic by the introduction of a hydrophilic group on the surface of carbon black in this way has excellent water dispersibility due to repulsion of ions, even when contained in an aqueous ink, A stable dispersion state is maintained without adding a dispersant or the like.

By the way, various hydrophilic groups as described above are
It may be directly bonded to the surface of carbon black. Alternatively, another atomic group may be interposed between the carbon black surface and the hydrophilic group, and the hydrophilic group may be indirectly bonded to the carbon black surface. Here, specific examples of the other atomic groups include a linear or branched alkylene group having 1 to 12 carbon atoms, a substituted or unsubstituted phenylene group, and a substituted or unsubstituted naphthylene group.
Here, examples of the substituent of the phenylene group and the naphthylene group include a linear or branched alkyl group having 1 to 6 carbon atoms. As specific examples of the combination of another atomic group and the hydrophilic group, for example, _{-C 2 H 4 -COOM, -Ph-} SO 3 M, -
Ph-COOM and the like (however, Ph represents a phenyl group).

By the way, 80% or more of the self-dispersion type pigment to be contained in the ink according to the present embodiment is 0.05 to 0.05%.
It is preferable that the particles have a particle size of 0.3 μm, particularly 0.1 to 0.25 μm. Such an ink adjustment method is as described in detail in the embodiments described later. (Second Pigment) The second pigment that can be used in the ink of the present embodiment is a pigment that can be dispersed in a dispersion medium of the ink, specifically, for example, an aqueous medium by the action of a polymer dispersant. Is mentioned. That is, a pigment that can be stably dispersed in an aqueous medium only as a result of the adsorption of the polymer dispersant on the surface of the pigment particles is suitably used. And as such a pigment, for example, as a black pigment, for example, furnace black, lamp black,
And carbon black pigments such as acetylene black and channel black. Specific examples of such carbon black pigments include, for example,
Alternatively, they can be used in appropriate combination.・ Rayvan (Raven) 7000, Rayvan 57
50, Ray-Van 5250, Ray-Van 5000ULT
RA, Ray-Van 3500, Ray-Van 2000, Ray-Van 1500, Ray-Van 1250, Ray-Van 12
00, Ray-Van 1190ULTRA-II, Ray-Van 1170, Ray-Van 1255 (all manufactured by Columbia), Black Pearls L, Regal (Re
gal) 400R, legal 330R, legal 660
R, Mogul L, Monarch 700,
Monak 800, Monak 880, Monak 900, Monak 1
000, Monak 1100, Monak 1300, Monak 14
00, Valcan XC-72R (above manufactured by Cabot) ・ Color Black FW1, Color Black
FW2, Color Black FW2V, Color Black 18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170, Printtex (Printe
x) 35, PRINTEX U, PRINTEX V, PRINTEX 140U, PRINTEX 140V, Special Black 6, Special Black 5, Special Black 4A, Special Black 4
No. 25, No. 33, No. 40, No. 47, No. 52, No. 25
900, No. 2300, MCF-88, MA600, M
A7, MA8, MA100 (all manufactured by Mitsubishi Chemical Corporation) Examples of other black pigments include magnetic fine particles such as magnetite and ferrite, and titanium black.

In addition to the above-mentioned black pigments, blue pigments, red pigments and the like can also be used.

The amount of the color material including the first and second pigments is 0.1 to 15% by weight, more preferably 1 to 10% by weight, based on the total amount of the ink. The ratio of the first pigment to the second pigment is 5/95 to 97/3, more preferably 10/95 to 97/3.
The range of / 90 to 95/5 is preferred. More preferably, first pigment / second pigment = 9/1 to 4/6.
Another range that is more preferable is a range in which the first pigment is high.
When the amount of the first pigment is large, not only the dispersion stability as the ink but also the ejection stability of the head, especially the stability including the ejection efficiency and the reliability due to the small wetting of the ejection port surface are exhibited. Is done.

The behavior of the ink on the paper is such that the ink is effectively spread on the surface of the paper with the ink having a small amount of the second pigment to which the polymer dispersant is adsorbed. It is presumed to be formed, and the scratch resistance of the image is also improved by the effect. (Polymer dispersant) The polymer dispersant for dispersing the second pigment in the aqueous medium is, for example, adsorbed on the surface of the second pigment to stably disperse the second pigment in the aqueous medium. Those having a function of causing them to be used are preferably used. Examples of such polymer dispersants include anionic polymer dispersants, cationic polymer dispersants, and nonionic polymer dispersants. (Anionic polymer dispersant) Examples of the polymer include a polymer of a monomer as a hydrophilic group and a monomer as a hydrophobic group, and salts thereof. Specific examples of the monomer as the hydrophilic group include, for example, styrene sulfonic acid, α, β-ethylenically unsaturated carboxylic acid, α, β-ethylenically unsaturated carboxylic acid derivative, acrylic acid, acrylic acid derivative, methacrylic acid Methacrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid and fumaric acid derivatives.

Specific examples of the monomer as a hydrophobic component include styrene, styrene derivatives, vinyl toluene, vinyl toluene derivatives, vinyl naphthalene, vinyl naphthalene derivatives, butadiene, butadiene derivatives, isoprene, isoprene derivatives, ethylene and ethylene derivatives. , Propylene, propylene derivatives, alkyl esters of acrylic acid, alkyl esters of methacrylic acid, and the like.

Here, the salt is specifically hydrogen, alkali metal, ammonium ion, organic ammonium ion, phosphonium ion, sulfonium ion, oxonium ion, stibonium ion, stannonium,
Examples include onium compounds such as iodonium, but are not limited thereto. In addition, the polymer or a salt thereof, polyoxyethylene group, hydroxyl group, acrylamide, acrylamide derivative, dimethylaminoethyl methacrylate, ethoxyethyl methacrylate, butoxyethyl methacrylate, ethoxytriethylene methacrylate, methoxypolyethylene glycol methacrylate, vinylpyrrolidone, vinylpyridine, Vinyl alcohol, alkyl ether and the like may be appropriately added. (Cationic polymer dispersant) As the cationic dispersant, a tertiary amine monomer, and a copolymer of a quaternary product of these with a hydrophobic monomer are used. As the tertiary amine monomer, for example, N, N-dimethylaminoethyl methacrylate, N, N-dimethylacrylamide and the like are used. As the hydrophobic monomer, styrene, a styrene derivative, vinyl naphthalene, or the like is used. Also, 3
In the case of a secondary amine, as a compound for forming a salt, sulfuric acid, acetic acid, nitric acid and the like are used. Further, those quaternized with methyl chloride, dimethyl sulfate or the like can also be used. (Nonionic polymer dispersant) Examples of the nonionic polymer dispersant include polyvinylpyrrolidone, polypropylene glycol, vinylpyrrolidone-vinyl acetate copolymer and the like.

The above-mentioned first pigment, second pigment and polymer dispersant are appropriately selected in combination and dispersed and dissolved in an aqueous medium to obtain the ink of this embodiment. In the case where a self-dispersible pigment in which at least one anionic group is bonded directly or via another atomic group to the surface of the pigment is used as one pigment, an anionic high-dispersing agent is used as a polymer dispersant. It is preferable to combine at least one selected from a molecular dispersant and a nonionic polymer dispersant from the viewpoint of the stability of the ink. For the same reason, at least one cationic group may be directly or directly used as the first pigment. When a self-dispersible pigment bonded to the surface of a pigment via an atomic group is used, a cationic polymer dispersant and a nonionic It is preferred that the combination with at least one of said first pigment selected from the child dispersant. (Aqueous medium) As an aqueous medium serving as a dispersion medium for the first and second pigments, a water-soluble organic solvent is used.

For example, alkyl having 1 to 5 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol and n-pentanol. Alcohols; Amides such as dimethylformamide and dimethylacetamide; Ketones or ketoalcohols such as acetone and diacetone alcohol; Ethers such as tetrahydrofuran and dioxane; Diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene Oxyethylene or oxypropylene copolymers such as glycol, polyethylene glycol and polypropylene glycol; ethylene glycol, propylene Alkylene glycols having an alkylene group containing 2 to 6 carbon atoms, such as ethylene glycol, trimethylene glycol, triethylene glycol, 1,2,6-hexanetriol; glycerin; ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl Lower alkyl ethers such as (or ethyl) ether and triethylene glycol monomethyl (or ethyl) ether; lower dialkyl ethers of polyhydric alcohols such as triethylene glycol dimethyl (or ethyl) ether and tetraethylene glycol dimethyl (or ethyl) ether Alkanolamines such as monoethanolamine, diethanolamine and triethanolamine; sulfolane, N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3- Methyl-2-imidazolidinone. The water-soluble organic solvents as described above can be used alone or as a mixture. (Permeability of Ink into Recording Medium) The ink of this embodiment containing the various components described above has a Ka value of 1 (ml ·
m ⁻² · msec ^−1/2 ), it is possible to obtain image dots with extremely uniform density. Hereinafter, the permeability of the ink to the print medium will be described.

When the permeability of the ink is represented by the amount V of the ink per m ² , the amount V of the ink permeated at the time t after the ink droplet was ejected (unit: milliliter / m ² = μm)
Is known by the following Bristow method.

[0048]

V = Vr + Ka (t−tw) ^1/2 (where t> tw) Immediately after the ink droplet has dropped on the surface of the print medium, the ink droplet is subjected to the unevenness of the surface (the roughness of the surface of the print medium). ), And hardly penetrates into the print medium. The time during that time is tw (wet time), and the amount of absorption into the uneven portion during that time is Vr.
When the elapsed time after the drop of the ink droplet exceeds tw, the permeation amount V increases by an amount proportional to the half power of the exceeded time (t-tw). Ka is a proportional coefficient of this increase, and shows a value corresponding to the permeation speed.

The Ka value was measured using a liquid dynamic permeability tester S (manufactured by Toyo Seiki Seisakusho) by the Bristow method. In this experiment, the applicant's Canon Inc.
Paper B was used as a print medium (recording paper). This P
The B sheet is a recording sheet that can be used for both a copying machine and an LBP using an electrophotographic method and a print using an ink jet recording method.

Similar results were obtained with PPC paper, which is an electrophotographic paper from Canon Inc.

The Ka value depends on the type of surfactant, the amount added, and the like. For example, ethylene oxide
2,4,7,9-tetramethyl-5-decyne-4,7-
Diol (ethylene oxide-2,4,7,9-tetramethyl-5-decy
By adding a nonionic surfactant en-4,7-diol (trade name “acetylenol”; manufactured by Kawaken Fine Chemicals Co., Ltd.), the permeability increases.

In the case of an ink in which acetylenol is not mixed (content is 0%), the ink has low permeability and has properties as an additional ink defined later. When acetylenol is mixed at a content of 1%, it has a property of penetrating into the recording paper 103 in a short time, and has a property as a highly permeable ink which will be specified later. And
An ink in which acetylenol is mixed at a content of 0.35% has a property as a semi-permeable ink that is intermediate between the two.

[0053]

[Table 1] Table 1 above shows the Ka for each of the “additional ink”, “semi-permeable ink”, and “highly permeable ink”.
Value, acetylenol content (%), surface tension (dyne
/ Cm). The greater the Ka value, the higher the permeability of each ink to recording paper as a print medium. That is, the smaller the surface tension, the higher the surface tension.

The Ka values in Table 1 were measured using the liquid dynamic permeability tester S (manufactured by Toyo Seiki Seisakusho) by the Bristow method as described above. In the experiment, the above-mentioned PB paper from Canon Inc. was used as the recording paper. Similar results were obtained with the above-described Canon PPC paper.

Here, the ink of the system defined as "highly permeable ink" has an acetylenol content of 0.7% or more, and is in a range in which good results are obtained in terms of permeability. As a criterion of the permeability to be carried by the ink of the present embodiment, the Ka value of the “additional ink”, that is, less than 1.0 (ml · m ⁻² .msec ^−1/2 ) is preferable. Is 0.4 (ml ・ m ^-2・ mse
c ^-1/2 ) or less is preferred. (Addition of Dye) A dye may be further added to the ink of the above embodiment. That is, an ink containing a first pigment, a second pigment, and an ink containing a dispersant for dispersing the second pigment in an aqueous medium, further containing a dye, has a resin layer as a coating layer on the surface as a recording medium. Fig. 1
As described above, a high-quality image having no “cracks” 1003 between the aggregates 1001 of the pigment aggregates can be formed. It is not clear why an image on a print medium provided with a resin layer formed of an ink further containing a dye can effectively prevent "cracking", but when an image is formed on a print medium using an ink further containing a dye. In addition, the aggregates of the pigments formed on the print medium are present as fine particles as shown in FIG.
The surrounding area is surrounded by the dye, and the portion where no aggregate is present is filled with the dye. Although the cohesive force of the second pigment is reduced by the presence of the first pigment as described above, the cohesive force of the second pigment is further reduced by the addition of the dye, and the It is considered that unevenness of a printed image such as "crack" which is likely to occur in a recording medium having poor absorbency compared to plain paper or the like can be effectively suppressed. Examples of the dye that can be used here include an anionic dye and a cationic dye, and it is preferable to use a dye having the same polarity as the polarity of the group bonded to the surface of the first pigment. (Anionic and cationic dyes) As the anionic dye soluble in the aqueous medium that can be used in the present embodiment as described above, known acid dyes, direct dyes, and reactive dyes are suitably used. As the cationic dye, a known basic dye is suitably used. It is particularly preferable to use a dye having a disazo or trisazo structure as a skeleton structure for both dyes. It is also preferable to use two or more dyes having different skeleton structures. As a dye to be used, a dye such as cyan, magenta, and yellow may be used as long as the color tone does not largely differ from the dye other than the black dye. (Addition amount of dye) The addition amount of the dye may be from 5% by weight to 60% by weight of the entire coloring material, but it is considered that the effect of mixing the first and second pigments is effectively utilized. Then, the content is preferably less than 50% by weight. Further, in the case where an ink is used with emphasis on the printing characteristics on plain paper, the content is preferably 5% by weight to 30% by weight. . (Recording method) The ink according to the present embodiment is applied to a print medium using a known ink applying means to form an image.

The ink application method in a preferred embodiment of the present invention is a known ink jet printing method.
That is, the ink of the present invention is suitably used in a mode in which ink is ejected from a print head to a print medium to perform printing. As a discharge method in the print head, a known method such as a piezo method can be adopted, but in a preferred embodiment, thermal energy is applied to the ink to thereby generate bubbles in the ink, and the pressure of the bubbles causes the ink to be discharged. This is a method of discharging.

The amount of ink ejected from the print head on the print medium is preferably not more than 0.014 picoliter (pl) / μm ² per unit area. More specifically, 70 at 360 dpi
pl / [mu] m ² or less, is preferably 25 pl / [mu] m ² or less at 600 dpi. This is because when an ink containing only one kind of pigment is used as a coloring material, especially in plain paper, the area factor may be insufficient and the OD may be reduced. However, according to the ink of the present embodiment, as described above, This is because the area factor can be increased, so that a large amount of driving is not required.

The ink cartridge containing the ink of the present embodiment, the ink containing section containing the ink, and the means for discharging the ink are integrated, and the recording head and the like are configured to be detachable from the ink jet printer. Is included in the embodiment of the present invention.

Further, the black ink according to the present embodiment containing the above-described self-dispersion type carbon black as a coloring material and at least one color ink selected from the group consisting of yellow ink, magenta ink and cyan ink are used. An ink set and the like stored in independent ink storage units are also included in one embodiment of the present invention.

As described above, based on the findings of the present inventors, the interaction between the first pigment, the second pigment, and the polymer dispersant reduces the cohesive force of the pigment, and the reduction of the cohesive force on the print medium. The effect of being able to form excellent images is
Of course, this can be achieved by a single ink containing these components. However, for example, the same effect can be obtained by bringing these components into a liquid state on a recording medium. . Specifically, as shown in FIG. 7, for example, a step of discharging a first ink containing a first pigment from a first inkjet head 701 and attaching the first ink to a predetermined position on a print medium, and The second ink containing the second pigment and at least one of a polymer dispersant and a nonionic polymer dispersant having the same polarity as the group bonded to the surface of the pigment and the second inkjet head 7
02 and the step of applying the first ink to the portion of the print medium 703 to which the first ink is applied or the portion of the print medium 703 to which the first ink is applied.
Inks are mixed with each other in a liquid state on the print medium, so that the area factor is large, the external shape is excellent, and the image density is high and uniform ink dots are formed within the dots. Can be formed.

Further, as shown in FIG. 8, on the one hand, the first ink containing the first pigment is ejected from the first ink jet head 801 (804), and on the other hand, the first ink from the second ink jet head 802 is ejected. A second ink containing at least one of a polymer dispersant and a nonionic polymer dispersant having the same polarity as the group bonded to the surface of the pigment and the second pigment (805); Inks ejected from inkjet heads (804, 805)
Before being attached to the print medium 803, and the ink 806 obtained by mixing the first ink and the second ink is attached to a predetermined portion of the print medium 803. It is possible to realize a state in which the first ink and the second ink are in contact with each other in a liquid state. Here, it is needless to say that the positions on the print medium 803 to which the respective inks are applied may be slightly shifted as long as these inks are in contact in a liquid state.

The Ka value of the ink obtained by mixing the first ink and the second ink in the Bristow method is 1
It is preferable to prepare each ink so as to be less than ml · m ^-2 · msec ^-1/2 .

Similarly, the effect of alleviating the cohesive force of the pigment caused by the interaction with the first pigment, the second pigment, the polymer dispersant and the dye, and providing the resin coating layer on the print medium, especially The advantage of being able to form an excellent image on a print medium is that the excellent effect exhibited by the formed image is not only a single ink containing the above four components, but also that these components are converted into a liquid on the recording medium. The same effect can be obtained by contacting in a state. That is, as shown in FIG. 9, discharging a first ink containing a first pigment from a first ink jet head 901 and attaching the first ink to a predetermined position on a print medium;
A second ink containing a second pigment containing at least one of a polymer dispersant and a nonionic polymer dispersant having the same polarity as the group bonded to the surface of the first pigment and a second pigment; Ejecting the ink from the print medium 902 to the predetermined position on the print medium 904; and applying a third dye containing a dye having the same polarity as the group bonded to the surface of the first pigment.
Discharging the third ink from the third inkjet head 903 and applying the ink to the predetermined position of the print medium 904,
Inks are mixed with each other in a liquid state on the print medium, so that the area factor is large, the external shape is excellent, and the image density is high and uniform ink dots are formed within the dots. Can be formed. Here, it is needless to say that the positions on the print medium 904 to which the respective inks are applied may be slightly shifted as long as the inks come into contact in a liquid state.

Further, as shown in FIG. 10, the first ink containing the first pigment is ejected from the first inkjet head 1001 (1002), and the surface of the first pigment is ejected from the second inkjet head 1003. The second ink containing at least one of a polymer dispersant and a nonionic polymer dispersant having the same polarity as the group bonded to the second ink and the second pigment is ejected (1004), and the third inkjet head 1005 Ejects a third ink containing a dye having the same polarity as the group bonded to the surface of the first pigment from (100)
6), the inks (1007) obtained by combining the inks ejected from the respective inkjet heads before adhering to the print medium 803 and mixing the first ink, the second ink, and the third ink with each other; The print medium 1 may be attached to a predetermined portion of the print medium
On 008, it is possible to realize a state in which the first ink, the second ink, and the third ink are in contact with each other in a liquid state. Also in this case, the Ka value of the ink mixed with the first ink, the second ink and the third ink in the Bristow method is less than 1 ml · m ⁻² · msec ^-1/2. It is preferable to prepare an ink. (Print Medium) The print medium used in the present embodiment is not particularly limited, and for example, paper, nonwoven fabric, OHP paper, leather, and the like can be used. When one ink of the embodiment of the present invention is applied to a print medium on which a resin layer is formed as a coat layer by using an ink-jet method, the above-described "crack" of an image formed on the coat layer is extremely effectively prevented. What you can do is as described above.

As an example of a print medium having a resin layer as a coat layer, a print medium in which a resin layer is provided on a plastic film such as paper or polyester is known. As a material constituting the coat layer, a water-soluble resin, a water-dispersible resin, or the like as a main component, and in addition, a cationic compound, a surfactant, a filler, and the like may be appropriately used.

As the water-soluble resin, for example, polyvinyl alcohol, anion-modified polyvinyl alcohol,
Modified products of polyvinyl alcohol such as cation-modified polyvinyl alcohol and acetal-modified polyvinyl alcohol; aqueous polyurethane; polyvinylpyrrolidone, and a copolymer of vinylpyrrolidone and vinyl acetate, a copolymer of vinylpyrrolidone and dimethylaminoethyl methacrylic acid,
Quaternized vinylpyrrolidone and dimethylaminoethyl
Modified polyvinylpyrrolidone such as methacrylic acid copolymer, vinylpyrrolidone and methacrylamidopropyl trimethylammonium chloride copolymer; cellulose-based water-soluble resins such as carboxymethylcellulose, hydroxyethylcellulose and hydroxypropylcellulose; and cationized hydroxyethylcellulose Modified cellulose; polyester, polyacrylic acid (ester), melamine resin, or a modified resin thereof, a synthetic resin such as a graft copolymer containing at least polyester and polyurethane, or albumin, gelatin, casein, starch, Examples include natural resins such as cationized starch, gum arabic, and sodium alginate.

Examples of the water-dispersible resin include polyvinyl acetate, ethylene-vinyl acetate copolymer, polystyrene, styrene- (meth) acrylate copolymer, (meth) acrylate-based polymer, Vinyl acetate- (meth) acrylic acid (ester) copolymer, poly (meth) acrylamide, (meth) acrylamide copolymer, styrene-isoprene copolymer, styrene-butadiene copolymer, styrene-propylene copolymer , Polyvinyl ether, silicon-acrylic copolymer, and the like, but are not limited thereto.

In addition to the above, a cationic compound is also suitably used as a material of a coat layer of a print medium.
This cationic compound is not particularly limited as long as it contains a cationic moiety in the molecule.
Quaternary ammonium salt-type cationic surfactants such as monoalkylammonium chloride, dialkylammonium chloride, tetramethylammonium chloride, trimethylphenylammonium chloride, ethylene oxide-added ammonium chloride, etc., or amine salt-type cationic surfactants Further, an amphoteric surfactant such as alkyl betaine, imidazolium betaine, and alanine containing a cationic moiety may be used.
Examples of the polymer or oligomer include cationically modified polyacrylamide, or a copolymer of acrylamide and a cationic monomer, polyallylamine, polyamine sulfone, polyvinylamine, polyethyleneimine, polyamide-epichlorohydrin resin, and polyvinylpyridinium halide. Can be

Further, a vinyl oxazolidone monomer alone, a copolymer with another general monomer, a vinyl imidazole monomer alone, or
Copolymers with other monomers and the like can be mentioned.

Examples of the other monomers include methacrylate, acrylate, acrylonitrile, vinyl ether, vinyl acetate, ethylene, styrene and the like. Further, cation-modified cellulose may be used.

The above-mentioned cation-modified compounds are preferably used, but, of course, the cationic compound is not limited to these.

Regarding the thickness of the coat layer, the dry weight
0.1 g / m in quantity^Two ~ 100g / m ^TwoCoated in a range of
Is preferred, and the coating layer is composed of one layer.
In addition to those formed in a multilayer structure such as a two-layer or three-layer structure
May be.

As described above, the print medium having the above-described coat layer formed thereon is particularly effective in preventing "cracking" by using the ink of the present embodiment. In addition to the above effects, the pigment itself has good wettability with respect to the coat layer, whereby the effect of compensating for the drawback of a dye having poor wettability with respect to the coat layer can be obtained. That is, by using the mixed ink of the pigment and the dye of the present embodiment, it is possible to suppress the occurrence of beading that occurs when using the ink containing only the dye as the coloring material.

[0074]

EXAMPLES Specific examples of the above embodiment will be described below. (Embodiment 1) FIG. 3 is a side view showing a schematic configuration of a full line type printing apparatus according to a first embodiment.

The printing apparatus 1 prints by discharging ink from a plurality of full-line type print heads arranged at predetermined positions along the transport direction of a recording medium as a print medium (the direction of arrow A in FIG. 1). The operation is performed under the control of a control circuit (not shown).

Each print head 10 of the head group 101g
Each of 1Bk, 101C, 101M, and 101Y has about 7,200 ink ejection orifices arranged in the width direction (direction perpendicular to the paper surface of the drawing) of the recording paper conveyed in the direction A in the drawing, and has a maximum A3 size printing. You can print on paper.

The recording paper 103 is conveyed in the direction A by the rotation of a pair of registration rollers 114 driven by a conveying motor, guided by a pair of guide plates 115, and the registration of the leading end thereof is performed. It is transported on 111. Conveyor belt 11 which is an endless belt
1 is held by two rollers 112 and 113. The rotation of the roller 113 causes the recording paper 10
3 is conveyed. The recording paper 113 is attracted to the transport belt 111 by electrostatic attraction. Roller 1
Reference numeral 13 denotes a driving source such as a motor (not shown) which is driven to rotate in a direction in which the recording paper 103 is transported in the direction of arrow A. The recording paper 103 that has been conveyed on the conveyance belt 111 and on which recording has been performed by the recording head group 101g during this time is transferred to a stocker 116.
Discharged up.

Each of the print heads of the recording head group 101g is dispersed in an aqueous medium with a black pigment (self-dispersion type carbon black) as the first pigment described in the embodiment of the present invention and a polymer dispersant. The head 101Bk containing the ink containing the second pigment to be obtained and the polymer dispersant, and the respective heads containing the color inks (cyan head 101C, magenta head 10C)
1M, the yellow head 101Y) is arranged as shown in the drawing along the transport direction A of the recording paper 103. By discharging ink of each color by each print head, printing of black characters and color images becomes possible.

The composition of the Bk ink used in this embodiment is as follows. The amounts of the respective components shown below represent parts by weight.

Pigment Dispersion 1 25 parts Pigment Dispersion 4 25 parts Glycerin 6 parts Diethylene glycol 7 parts Acetylenol EH 0.2 parts (manufactured by Kawaken Fine Chemical) Water Remaining The above pigment dispersion 1 was prepared as follows. Things. Acidic carbon black (trade name: MA-77 (p
H3.0, manufactured by Mitsubishi Chemical Corporation)) 300 g to 1000 ml of water
Then, 450 g of sodium hypochlorite (effective chlorine concentration: 12%) was added dropwise thereto, and the mixture was stirred at 100 to 105 ° C for 10 hours. The obtained slurry was applied to Toyo Filter Paper No.
2 (manufactured by Advantis), and the pigment particles were sufficiently washed with water. This pigment wet cake was redispersed in 3000 ml of water and desalted with a reverse osmosis membrane until the electric conductivity was 0.2 μs.
Further, the pigment dispersion (pH = 8 to 10) was added to a pigment concentration of 1
It was concentrated to 0% by weight. According to the above-described method, the pigment dispersion 1 in which anionic charged self-dispersible carbon black having a hydrophilic —COO— group directly bonded to the surface is dispersed.
I got

The above-described pigment dispersion 4 was prepared as follows. As a dispersant, 14 parts of a styrene-acrylic acid-ethyl acrylate copolymer (acid value 180, average molecular weight 12,000), 4 parts of monoethanolamine and 72 parts of water were mixed, and the mixture was heated to 70 ° C. in a water bath to obtain a resin. Allow the minute to completely dissolve. At this time, if the concentration of the resin to be dissolved is low, the resin may not be completely dissolved. Therefore, when dissolving the resin, a high-concentration solution may be prepared in advance and diluted to prepare a desired resin solution. Carbon black (trade name: MCF-88, pH 8.30) that can be dispersed in an aqueous medium for the first time by the action of a dispersant in this solution.
0, manufactured by Mitsubishi Chemical Corporation) and premixed for 30 minutes. Next, the following operation was performed to obtain a pigment dispersion liquid 4 in which carbon black (MCF-88) was dispersed in an aqueous medium with a dispersant.

Dispersing machine: side grinder (made by Igarashi Kikai) Grinding media: zirconia beads 1 mm diameter Filling ratio of grinding media: 50% (volume) Grinding time: 3 hours Centrifugal treatment (12000 RPM, 20 minutes) Prepared in this way Ka value of the obtained Bk ink is 0.40
(Ml ・ m^-2・ Msec ^-1/2)Met. (Example 2) As another example of Bk ink, the following
Minutes can also be used.

Pigment Dispersion 2 45 parts Pigment Dispersion 4 5 parts Glycerin 6 parts Triethylene glycol 5 parts Acetylenol EH 0.2 parts (manufactured by Kawaken Fine Chemical) Water Remaining The above pigment dispersion 2 was prepared as follows. Prepared. Surface area 230m ² / g, DBP oil absorption 70ml / 100
g of carbon black and 3.41 g of p-amino-N-benzoic acid were sufficiently mixed with 72 g of water, and 1.62 g of nitric acid was added dropwise thereto, followed by stirring at 70 ° C. After a few minutes,
A solution prepared by dissolving 1.07 g of sodium nitrite in 5 g of water was added, and the mixture was further stirred for 1 hour. The obtained slurry was applied to Toyo Filter Paper No. After filtering through a filter No. 2 (manufactured by Advantis), the pigment particles were sufficiently washed with water and dried in an oven at 90 ° C., and water was added to the pigment to prepare an aqueous pigment solution having a pigment concentration of 10% by weight. According to the above method, as represented by the following formula, Pigment Dispersion Liquid 2 in which anionic charged self-dispersible carbon black having a hydrophilic group bonded to the surface via a phenyl group was dispersed was obtained.

[0084]

Embedded image The pigment dispersion 4 was prepared in the same manner as in Example 1. The Ka value of the Bk ink thus obtained is 0.35 (ml ·
m ^-2 · msec ^-1/2 ). (Embodiment 3) As still another embodiment of the Bk ink, one having the following components can be used.

Pigment Dispersion 3 45 parts Pigment Dispersion 4 2.5 parts C.I. I. Direct Blue 199 0.25 part Glycerin 6 parts Diethylene glycol 5 parts Acetylenol EH 0.1 part Water balance The above-mentioned pigment dispersion 3 was prepared as follows.

At 5 ° C., 1.58 g of anthranilic acid was added to a solution of 5 g of concentrated hydrochloric acid in 5.3 g of water.
This solution was constantly stirred for 10 minutes in an ice bath.
A solution obtained by adding 1.78 g of sodium nitrite to 8.7 g of water at 5 ° C. was added while keeping the temperature at not more than 0 ° C. After further stirring for 15 minutes, the surface area was 320 m ² / g and the DBP oil absorption was 120
20 g of carbon black (ml / 100 g) was added in a mixed state. Thereafter, the mixture was further stirred for 15 minutes. The obtained slurry was applied to Toyo Filter Paper No. 2 (Advantis)
After thoroughly washing the pigment molecules with water and drying in an oven at 110 ° C., water is added to the pigment to obtain a pigment concentration of 10%.
A weight percent aqueous pigment solution was prepared. According to the above method, as represented by the following formula, Pigment Dispersion Liquid 3 in which anionic charged self-dispersible carbon black having a hydrophilic group bonded through a phenyl group was dispersed on the surface was obtained. The pigment dispersion 4 was prepared in the same manner as in Example 1.

[0087]

Embedded image The Ka value of the Bk ink thus obtained is 0.33 (ml · m
^-2 · msec ^-1/2 ). Comparative Example 1 As a comparative example with respect to Examples 1 to 3 described above, an ink having the following components was prepared using only the pigment dispersion 4 prepared in the same manner as in Example 1.

Pigment dispersion 4 50 parts Ethylene glycol 8 parts Glycerin 5 parts Isopropyl alcohol 4 parts Water 33 parts (Evaluation) Using the inks of Examples 1 to 3 and Comparative example 1, a recording head having a resolution of 360 dpi was provided. Using an inkjet printer, printing was performed at an ejection frequency of 7.2 kHz and at an interval of 720 dpi in the main scanning direction. Here, the ejection amount per ink droplet from the recording head was about 25 picoliters, and recording was performed by ejecting one ink droplet to one pixel which was formed at a resolution of 360 dpi × 720 dpi. OD of the image by printing solid image and character pattern, etc.
The dot peripheral shape, solid uniformity, strikethrough, smoothing, and roundness were evaluated. As a print medium, PB paper manufactured by Canon Inc. was used.

Here, OD is a value obtained by measuring a 5 mm square solid pattern portion. -For the dot peripheral shape, the sharpness of the edge portion of the line image was visually checked with a loupe. A: The edges of the lines are connected in a straight line. ：: Although the linearity of the line edge is slightly lost, there is no practical problem. X: The linearity of the line edge is lost. The solid uniformity was visually confirmed by checking the uniformity of density in a 5 mm square solid pattern. ◎: No white part was observed. ：: white spots were observed, but not noticeable,
There is no practical problem. ×: The white portion is conspicuous and affects the image quality.・ The strike-through property is to visually check the part where the solid pattern is printed from the back side to see if the pattern can be seen through,
The optical density of the corresponding portion on the back surface was measured using a Macbeth densitometer. A: Almost no see-through, and optical density measured by Macbeth densitometer is less than 0.2. ：: Though slightly transparent, it was hardly noticeable, and the optical density measured by a Macbeth densitometer was 0.2 or more and less than 0.25. -For roundness, the shape of an ink dot formed on a print medium with one drop of ink was observed with a loupe. ：: Most dots are close to a perfect circle from a statistical point of view. ：: Statistically, the dot circularity is broken, but there is no problem in image formation. Δ: From a statistical viewpoint, the roundness of a considerable number of dots is broken, and irregularly shaped dots are formed.

The results are shown in Table 2 below.

[0091]

[Table 2] When an ink containing only the first pigment was prepared and recorded and evaluated in the same manner as in the above-described example, all the inks were evaluated as ○ according to the above evaluation criteria, and there was no practical problem. However, the ink according to the present embodiment exhibits performance exceeding that, and the usefulness and superiority of the present invention are apparent.

Next, using the ink of the third embodiment,
A solid image of a predetermined size was printed on a transparency film (trade name: CF102) on which a coat layer made by Canon Inc. of the present applicant was formed by using the apparatus described above, and evaluated by the presence or absence of “cracks”. However, "cracking" was not confirmed. On the other hand, in the case of using the ink of Comparative Example 1, the phenomenon of "cracking" was confirmed.

The same ink was used to print on a transparency film (trade name: CF101) manufactured by Canon Inc. on which a coat layer was formed, and evaluated by the presence or absence of “cracks”. In the case of using CF, the phenomenon of "cracking" was more remarkably recognized than when printing was performed on CF102. However, Example 3
No "crack" was observed when the ink was used. (Other Embodiments) FIG. 4 is a schematic perspective view showing the structure of a serial type printing apparatus 5 showing another apparatus which can use the ink according to each of the above embodiments of the present invention. In FIG. 4, the same elements as those shown in FIG. 3 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The recording paper 103 serving as a print medium is inserted from the paper supply 105 and discharged through the print unit 126. In the print unit 126, the carriage 107
The print heads 101Bk, 101C, 101M, and 101Y are mounted, and are configured to be able to reciprocate along the guide rail 109 by the driving force of a motor (not shown). The print head 101Bk discharges the black ink according to the present embodiment. The print head 10
1C, 101M, and 101Y discharge cyan ink, magenta ink, and yellow ink, respectively, and are driven to discharge ink on the recording paper 103 in this order.

Each of the heads has a corresponding ink tank 108Bk, 108 containing ink to be ejected.
Ink is supplied from C, 108M, and 108Y, and at the time of ink ejection, a drive signal is supplied to an electrothermal transducer (heater) provided for each ejection port of each head.
The thermal energy is applied to the ink to generate bubbles, and the pressure at the time of the foaming is used to discharge the ink. Each head is provided with 64 ejection ports at a density of 360 dpi, and these are arranged in substantially the same direction as the transport direction Y of the recording paper 103, that is, in a direction substantially perpendicular to the scanning direction by each head. . The discharge amount of each discharge port is 23 pl.

In the above configuration, the head-to-head distance for each color ink is 1/2 inch and the head 101B
The distance Di between k and 101C is 1 inch, the print density in the scanning direction is 720 dpi, and the ejection frequency of each head is 7.2 kHz.

FIG. 5 is a view for explaining a printing process by the serial type printing apparatus shown in FIG. 4, and schematically shows a state where the printing unit 126 is viewed from above. In FIG. 5, the carriage 107 reciprocates above the recording paper 103 to be conveyed in the X direction substantially perpendicular to the conveyance direction Y. The black discharge unit 101Bk and the color discharge units (101C, 101C) mounted on the carriage 107
M, 101Y) are opened in a direction for discharging ink to the recording paper 103 (indicated by dots in the drawing).

Each of the ejection sections scans the recording paper 10 by one scan.
The ejection ports are arranged so that recording with a width d can be performed along the conveyance direction Y of No.3. Also, the black discharge unit 101Bk
In order to provide a time lag between the ejection of the color ink and the ejection of the color ink, the black ejection unit 101Bk and the color ink ejection unit are arranged at positions displaced from each other in the transport direction by the distance of the print width d. The ejection time difference is a time when the black ink has almost completely penetrated into a predetermined range in the thickness direction of the recording paper. With this configuration,
Black discharge unit 101 at a predetermined position on recording paper 103
The ejection of the Bk ink and the ejection of the color ink are performed at a predetermined time difference as described above, with a shift of one scan of the carriage 107 (scanning cycle is set to 1.5 seconds). The problem of bleeding at the boundary of can be solved.

FIG. 6 is a perspective view showing another example of an ink jet printer according to still another embodiment. Elements similar to those shown in FIGS. 3 and 4 are denoted by the same reference numerals.
The description is omitted. As shown in FIG. 6, the ink according to an embodiment of the present invention can be used as a black ink in a monocolor printer.

[0100]

As is apparent from the above description, according to the present invention, a pigment (second pigment) which can be dispersed in an aqueous medium only by the action of a self-dispersing pigment (first pigment) and a dispersing agent. Pigment) and the ink containing the dispersant, the second pigment is contained in the ink even if the content of the dispersant is small, probably because the first pigment itself functions as a dispersant for the second pigment. To obtain an ink having excellent storage stability. On the other hand, when this ink is used for printing, for example, the aggregation of the pigment caused by the interaction between the second pigment and the dispersant generated on the recording medium is alleviated by the first pigment. Excellent in peripheral and external shape, having a dot diameter with a suitable diameter, dispersed uniformly in ink dots and having an appropriate spread, and with almost no feathering etc. Ink dots can be obtained.

Further, the ink containing the first pigment, the second pigment, the dispersant, and the dye according to another embodiment of the present invention may be used on a recording medium because the cohesive force of the pigment is further reduced by the dye. The pigment aggregates are in the form of fine particles. On the other hand, the dye takes in the surroundings of the particulate pigment, and as a whole, the printed image is one in which unevenness due to aggregation is suppressed.
The effect is most remarkable in that the occurrence of "cracks" in ink dots can be extremely effectively suppressed or prevented even when this ink is inkjet-recorded on a print medium having poor ink absorption. Can be observed.

In this specification, “parts” or “%” is based on weight unless otherwise specified.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a “crack” phenomenon of a pigment ink, which is a problem to be solved by the present invention.

FIG. 2 is a diagram illustrating a result of printing using ink according to an embodiment of the present invention.

FIG. 3 is a side view illustrating a schematic configuration of an inkjet printing apparatus according to an embodiment of the present invention.

FIG. 4 is a perspective view showing an ink jet printer according to another embodiment of the present invention.

FIG. 5 is a diagram illustrating a printing operation in the printer shown in FIG.

FIG. 6 is a perspective view showing an inkjet printer according to still another embodiment of the present invention.

FIG. 7 is a schematic explanatory diagram of an image forming method according to an embodiment of the present invention.

FIG. 8 is a schematic explanatory view of an image forming method according to another embodiment of the present invention.

FIG. 9 is a schematic explanatory view of an image forming method according to an embodiment of the present invention.

FIG. 10 is a schematic explanatory view of an image forming method according to another embodiment of the present invention.

[Explanation of symbols]

101g Head group 101Bk, 101C, 101M, 101Y Print head 103 Recording paper 111 Conveyor belt 112 Roller 113 Roller 114 Registration roller 115 Guide plate 116 Stocker 701, 801 First ink jet head 702, 802 Second ink discharge Inkjet heads 703, 803 Print media

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshihisa Takizawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Sadayuki Sugama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside the corporation

Claims (87)

[Claims] 1. An ink containing a first pigment and a second pigment as a coloring material in a dispersed state in an aqueous medium, wherein the first pigment has at least one anionic group directly or another atom. A self-dispersing pigment or at least one cationic group bonded to the surface of the first pigment via a group, or bonded to the surface of the first pigment directly or via another atomic group. A self-dispersible pigment, wherein the second pigment is a pigment that can be dispersed in the aqueous medium by a polymer dispersant, and the ink further comprises a group bonded to the surface of the first pigment. An ink comprising at least one of a polymer dispersant having the same polarity as the above and a nonionic polymer dispersant. 2. The ink according to claim 1, wherein the Ka value of the ink in the Bristow method is less than 1 ml · m ⁻² .msec ^−1/2 . Wherein the anionic group bonded to the surface of the _{pigment, -COOM, -SO 3 M, -PO} 3 HM and -P
At least one anionic group selected from the group consisting of O ₃ M ₂ , wherein M is a hydrogen atom, an alkali metal,
The ink of claim 1 representing ammonium or organic ammonium. 4. The method according to claim 1, wherein the other atomic group is a substituted or unsubstituted alkylene group having 1 to 12 carbon atoms, a substituted or unsubstituted phenylene group, or a substituted or unsubstituted naphthylene group. ink. 5. A pigment having a particle size of at least 80% of the first pigment.
The ink according to any one of claims 1 to 4, wherein the thickness is from 0.5 to 0.3 µm. 6. A pigment having a particle size of at least 80% of the first pigment.
The ink according to claim 5, which has a thickness of 1 to 0.25 µm. 7. The ink according to claim 1, wherein the second pigment is dispersed by adsorbing a polymer dispersant on the surface of the second pigment. 8. The ink according to claim 1, wherein the polymer dispersant is at least one of a sulfonic acid polymer dispersant and a carboxylic acid polymer dispersant. 9. The ink according to claim 1, wherein the second pigment contains at least two kinds of pigments having different structures. 10. The method according to claim 1, wherein the ratio of the first pigment to the second pigment is in the range of 5/95 to 97/3.
The ink according to any one of the above. 11. The ink according to claim 10, wherein a ratio between the first pigment and the second pigment is in a range of 10/90 to 95/5. 12. The ink according to claim 11, wherein a ratio between the first pigment and the second pigment is in a range of 9/1 to 4/6. 13. The ink according to claim 1, wherein the amount of the first pigment is larger than that of the second pigment. 14. The ink according to claim 1, wherein at least one of the first and second pigments is carbon black. 15. The ink of claim 1, wherein the ink further comprises a dye of the same polarity as the group attached to the surface of the first pigment.
15. The ink according to any one of items 14 to 14. 16. The ink according to claim 15, wherein the dye is an anionic dye or a cationic dye. 17. The ink according to claim 16, wherein the anionic dye is at least one selected from an acid dye, a direct dye and a reactive dye. 18. The ink according to claim 16, wherein the anionic dye has a disazo skeleton or a trisazo skeleton. 19. An ink used in an image recording method for discharging an ink from an orifice using an ink jet recording method and applying the ink onto a print medium to form one element of an image, wherein the first pigment and the second pigment are used as coloring materials. A self-dispersible pigment, wherein the first pigment is dispersed in an aqueous medium, and the first pigment has at least one anionic group bonded directly or via another atomic group to the surface of the first pigment. Or a self-dispersible pigment in which at least one cationic group is bonded directly or via another atomic group to the surface of the first pigment, wherein the second pigment is a polymer dispersant. The ink can further be dispersed in an aqueous medium, and the ink further comprises at least one of a polymer dispersant having the same polarity as a group bonded to the surface of the first pigment and a nonionic polymer dispersant. An ink comprising: 20. Ka of the ink in the Bristow method
20. The value is less than 1 ml · m ^-2 · msec ^-1/2.
The ink described. 21. anionic group bonded to the first surface of the _{pigment, -COOM, -SO 3 M, -PO} 3 HM
And at least one selected from the group consisting of -PO ₃ M ₂
20. The ink of claim 19, wherein there are two anionic groups, wherein M represents a hydrogen atom, an alkali metal, ammonium or organic ammonium. 22. The method according to claim 19, wherein the other atomic group is a substituted or unsubstituted alkylene group having 1 to 12 carbon atoms, a substituted or unsubstituted phenylene group, or a substituted or unsubstituted naphthylene group. ink. 23. The ink according to claim 19, wherein 80% or more of the first pigment has a particle size of 0.05 to 0.3 μm. 24. The ink according to claim 23, wherein 80% or more of the first pigment has a particle size of 0.1 to 0.25 μm. 25. The ink according to claim 19, wherein the second pigment is a pigment which is dispersed by adsorbing the polymer dispersant on a surface thereof. 26. The ink according to claim 19, wherein the polymer dispersant is at least one of a sulfonic acid-based polymer dispersant and a carboxylic acid-based polymer dispersant. 27. The ink according to claim 19, wherein the second pigment includes at least two pigments having different structures. 28. The ink according to claim 19, wherein the ratio of the first pigment to the second pigment is in the range of 5:95 to 97: 3. 29. The ink according to claim 28, wherein the ratio of the first pigment to the second pigment is in the range of 10/90 to 95/5. 30. The ink according to claim 29, wherein a ratio of the first pigment to the second pigment is in a range of 9/1 to 4/6. 31. The ink according to claim 19, wherein the proportion of the first pigment is higher than that of the second pigment. 32. The ink according to claim 19, wherein at least one of the first pigment and the second pigment is carbon black. 33. An ink-jet printing method comprising discharging an ink toward a print medium using an ink-jet recording method to record an image on the print medium, wherein the ink comprises a first pigment and a second pigment. A self-dispersing pigment comprising a pigment dispersed in an aqueous medium, wherein the first pigment has at least one anionic group bonded directly or via another atomic group to the surface of the first pigment; A pigment or a self-dispersible pigment in which at least one cationic group is bonded to the surface of the first pigment directly or via another atomic group, wherein the second pigment is a polymer dispersant; A pigment dispersible in the aqueous medium, wherein the ink further comprises a polymer dispersant having the same polarity as the group bonded to the surface of the first pigment and a nonionic polymer dispersant. An ink-jet printing method, characterized in that the ink comprises at least one ink. 34. The Ka of the ink in the Bristow method
34. The value is less than ¹ ml.m- ^2.msec- 1 / ^2.
3. The ink-jet printing method according to item 1. 35. The ink-jet printing method according to claim 33, further comprising a step of applying thermal energy to the ink to discharge the ink from an orifice toward the print medium. 36. anionic group bonded to the first surface of the _{pigment, -COOM, -SO 3 M, -PO} 3 HM
And at least one selected from the group consisting of -PO ₃ M ₂
The ink-jet printing method according to claim 33, wherein there are two anionic groups, wherein M represents a hydrogen atom, an alkali metal, ammonium or organic ammonium. 37. The inkjet according to claim 36, wherein the other atomic group is a substituted or unsubstituted alkylene group having 1 to 12 carbon atoms, a substituted or unsubstituted phenylene group, or a substituted or terminally substituted naphthylene group. Printing method. 38. The inkjet printing method according to claim 33, wherein 80% or more of the first pigment has a particle size of 0.05 to 0.3 μm. 39. The ink-jet printing method according to claim 33, wherein 80% or more of the first pigment has a particle size of 0.1 to 0.25 μm. 40. The ink jet printing method according to claim 33, wherein the second pigment is dispersed by adsorbing a polymer dispersant on a surface of the second pigment. 41. The ink according to claim 33, wherein the polymer dispersant is at least one of a sulfonic acid-based polymer dispersant and a carboxylic acid-based polymer dispersant. 42. The inkjet printing method according to claim 33, wherein the second pigment includes two or more pigments having different structures. 43. The method according to claim 33, wherein the ratio of the first pigment to the second pigment is in the range of 5:95 to 97: 3.
The inkjet printing method according to any one of the above. 44. The ink-jet printing method according to claim 43, wherein a ratio of the first pigment to the second pigment is in a range of 10/90 to 95/5. 45. The ink-jet printing method according to claim 44, wherein a ratio of the first pigment to the second pigment is in a range of 9/1 to 4/6. 46. The ink jet printing method according to claim 33, wherein the proportion of the first pigment is higher than that of the second pigment. 47. The method according to claim 33, wherein at least one of the first pigment and the second pigment is carbon black.
7. The inkjet printing method according to any one of 6. 48. The ink of claim 3, wherein the ink further comprises a dye of the same polarity as the group attached to the surface of the first pigment.
48. The inkjet printing method according to any one of items 3 to 47. 49. The ink jet printing method according to claim 48, wherein the dye is an anionic dye or a cationic dye. 50. The ink jet printing method according to claim 49, wherein the anionic dye is at least one selected from an acid dye, a direct dye and a reactive dye. 51. The ink-jet printing method according to claim 50, wherein the anionic dye has a disazo skeleton or a trisazo skeleton. 52. The ink-jet recording method according to claim 33, wherein the ink-jet recording method includes a step of applying thermal energy to the ink to discharge the ink using bubble formation by film boiling. Printing method. 53. An image is recorded on the outer surface of the coat layer by discharging ink toward the outer surface of the coat layer of a print medium having a coat layer containing a resin on the surface by using an ink jet recording method. In an ink-jet printing method comprising the steps of:
A self-dispersible pigment, wherein the first pigment is dispersed in an aqueous medium, and the first pigment has at least one anionic group bonded directly or via another atomic group to the surface of the first pigment. Or a self-dispersible pigment in which at least one cationic group is bonded directly or via another atomic group to the surface of the first pigment, wherein the second pigment is a polymer dispersant. Wherein the ink further comprises at least one of a polymer dispersant having the same polarity as a group bonded to the surface of the first pigment and a nonionic polymer dispersant. An ink-jet printing method, comprising: an ink containing a dye bonded to the surface of the first pigment and a dye having the same polarity as a group bonded to the surface of the first pigment. 54. The Ka of the ink in the Bristow method
Claim the value is less than 1ml · m ^-2 · msec ^-1/2 53
The ink-jet printing method as described above. 55. The ink-jet printing method according to claim 53, wherein the ink-jet recording method includes a step of applying thermal energy to the ink to discharge the ink using bubble formation due to film boiling. 56. anionic group bonded to the surface of the first pigment, -COOM, -SO ₃ M, at least one selected from the group consisting of -PO ₃ HM and -PO ₃ M ₂ 54. The inkjet printing method according to claim 53, wherein M is an anionic group, and M represents a hydrogen atom, an alkali metal, ammonium or organic ammonium. 57. The inkjet according to claim 53, wherein the other atomic group is a substituted or unsubstituted alkylene group having 1 to 12 carbon atoms, a substituted or unsubstituted phenylene group, or a substituted or unsubstituted naphthylene group. Printing method. 58. The ink jet printing method according to claim 53, wherein 80% or more of the first pigment has a particle size of 0.05 to 0.3 μm. 59. The ink jet printing method according to claim 58, wherein 80% or more of the first pigment has a particle size of 0.1 to 0.25 μm. 60. The ink jet printing method according to claim 53, wherein the second pigment is dispersed by adsorbing the polymer dispersant on the surface. 61. The ink-jet printing method according to claim 53, wherein the polymer dispersant is at least one of a sulfonic acid-based polymer dispersant and a carboxylic acid-based polymer dispersant. 62. The ink jet printing method according to claim 53, wherein the second pigment contains two or more dyes having different structures. 63. The ratio of the first pigment to the second pigment is in the range of 5:95 to 97: 3.
3. The inkjet printing method according to any one of 2. 64. The ink according to claim 53, wherein the ratio of the first pigment to the second pigment is in the range of 10/90 to 95/5. 65. The ink according to claim 64, wherein the ratio of the first pigment to the second pigment is in the range of 9/1 to 4/6. 66. The ink according to claim 53, wherein the ink contains more of the first pigment than the second pigment. 67. The inkjet printing method according to claim 53, wherein at least one of the first pigment and the second pigment is carbon black. 68. The ink jet printing method according to claim 53, wherein the resin contained in the coat layer contains a water-soluble resin or a water-dispersible resin. 69. The water-soluble resin may be polyvinyl alcohol, anion-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, acetal-modified polyvinyl alcohol, aqueous polyurethane, polyvinylpyrrolidone, vinylpyrrolidone / vinyl acetate copolymer, vinylpyrrolidone / dimethylaminoethyl. Methacrylic acid copolymer, quaternized vinylpyrrolidone / dimethylaminoethyl methacrylic acid copolymer, vinylpyrrolidone / methacrylamidopropyl trimethylammonium chloride copolymer, carboxymethylcellulose, hydroxyethylcellulose,
From hydroxypropylcellulose, cationized hydroxyethylcellulose polyester, polyacrylic acid, polyacrylate, melamine resin, graft copolymer containing polyester and polyurethane, albumin, gelatin, casein, starch, cationized starch, gum arabic and sodium alginate 69. The ink-jet printing method according to claim 68, which is at least one resin selected. 70. The water-dispersible resin is polyvinyl acetate,
Ethylene-vinyl acetate copolymer, polystyrene, styrene-acrylate copolymer, styrene-methacrylate copolymer, acrylate copolymer,
Methacrylic acid ester copolymer, vinyl acetate / acrylic acid copolymer, vinyl acetate / acrylic acid ester copolymer, vinyl acetate / methacrylic acid copolymer, vinyl acetate
Methacrylic acid ester copolymer, polyacrylamide,
69. The inkjet print according to claim 68, comprising at least one selected from polymethacrylamide, acrylamide copolymer, methacrylamide copolymer, styrene / isoprene copolymer, polyvinyl ether, and silicon / acrylic copolymer. Method. 71. A self-dispersing pigment or at least one cationic group, wherein at least one anionic group is bonded to the surface of the first pigment directly or via another atomic group. A first ink containing a self-dispersing pigment bonded to the surface of the first pigment via another atomic group; and a first ink bonded to the surface of the self-dispersing pigment in the first ink. A second ink containing at least one of a polymer dispersant having the same polarity as the group and a nonionic polymer dispersant, and a pigment dispersible in an aqueous medium by the polymer dispersant. 3. An image forming method according to claim 1, further comprising a step of applying an image to a print medium so that the first ink and the second ink are in contact with each other in a liquid state. 72. A step of applying the first ink and the second ink to the print medium such that the first ink and the second ink are in contact with each other in a liquid state on the surface of the print medium. The first ink and the second ink are mixed before the first ink and the second ink adhere to the print medium surface, and the first ink and the second ink are mixed. 72. The image forming method according to claim 71, further comprising a step of applying the mixed ink to the print medium. 73. The image according to claim 72, wherein the ink obtained by mixing the first ink and the second ink has a Ka value in a Bristow method of less than 1 ml · m ⁻² · msec ^-1/2. Forming method. 74. A step of applying the first ink and the second ink to the print medium such that the first ink and the second ink are in contact with each other in a liquid state on the surface of the print medium. A first step of applying the first ink to a predetermined position on the print medium, and a second step of applying the second ink to a position at least partially overlapping the predetermined position on the print medium. 72. The image forming method according to claim 71, wherein the first step and the second step are performed such that the first ink and the second ink come into contact with each other in a liquid state on a recording medium surface. 75. A self-dispersible pigment or at least one cationic group, wherein at least one anionic group is bonded to the surface of the first pigment directly or via another atomic group. A first ink containing a self-dispersible pigment bonded to the surface of the first pigment via another atomic group, a pigment dispersible in the aqueous medium by a polymer dispersant, and A second ink containing a group bonded to the surface of the self-dispersion type pigment in the first ink and at least one of a polymer dispersant of the same polarity and a nonionic polymer dispersant; A third ink containing a dye of the same polarity as the group bonded to the surface of the pigment of the type, wherein the first ink, the second ink and the third ink are both liquid on the surface of the print medium. Print media to be in contact with the state An image forming method comprising the step of: 76. A method in which the first ink, the second ink, and the third ink are mixed on the surface of a print medium in a state where the first ink, the second ink, and the third ink are all in a liquid state. The step of applying to the print medium so as to be in contact with the print medium comprises the first step.
Mixing the first ink, the second ink, and the third ink before the first ink, the second ink, and the third ink adhere to the print medium surface; 78. The image forming method according to claim 75, further comprising a step of applying to the print medium an ink in which the first ink, the second ink, and the third ink are mixed. 77. The Ka value of the ink mixed with the first ink, the second ink and the third ink in the Bristow method of less than 1 ml · m ⁻² · msec ^-1/2. Item 78. The image forming method according to Item 76. 78. A method in which the first ink, the second ink, and the third ink are mixed in a liquid state on the surface of a print medium in a state where the first ink, the second ink, and the third ink are all in a liquid state. The step of applying to the print medium so as to be in contact with the print medium comprises the first step.
A first ink which is applied to a predetermined position of the print medium.
A second step of applying the second ink to a position at least partially overlapping the predetermined position of the print medium, and applying the third ink to at least one of the predetermined positions of the print medium. Third given to the position where the parts overlap
Wherein the first step, the second step, and the third step are performed when the first ink, the second ink, and the third ink are in a liquid state on a recording medium surface. The image forming method according to claim 75, wherein the image forming method is performed so as to be in contact with the image. 79. An ink container containing ink, the ink comprising a first pigment and a second pigment dispersed in an aqueous medium as coloring materials, wherein the first pigment comprises at least one anion. A self-dispersible pigment wherein at least one cationic group is bonded to the surface of the first pigment directly or via another atomic group, or the at least one cationic group is directly or via another atomic group. A self-dispersible pigment bonded to the surface of the first pigment, wherein the second pigment is a pigment which can be dispersed in the aqueous medium by a polymer dispersant, and the ink further comprises An ink container comprising at least one of a polymer dispersant having the same polarity as a group bonded to the surface of a pigment and a nonionic polymer dispersant. 80. A coloring material comprising a first pigment and a second pigment in a dispersed state in an aqueous medium, wherein the first pigment has at least one anionic group directly or via another atomic group. A self-dispersible carbon black bonded to the surface of the first pigment or a self-dispersed carbon black bonded to the surface of the first pigment directly or through another atomic group. Carbon black, wherein the second pigment is a pigment that can be dispersed in the aqueous medium by a polymer dispersant, and the ink further has the same group as that bonded to the surface of the first pigment. An ink set comprising a combination of a black ink containing at least one of a polar polymer dispersant and a nonionic polymer dispersant, and a yellow ink, a magenta ink, and a cyan ink. . 81. The black ink further comprises a dye of the same polarity as the group attached to the surface of the first pigment.
The described ink set. 82. The black ink according to the Bristow method
An ink set whose Ka value is less than 1 ml · m ^-2 · msec ^-1/2 . 83. The Ka of each of the yellow ink, the magenta ink and the cyan ink in the Bristow method
81. The ink set according to claim 80, wherein the value is 1 ^{mlm- 2} msec- ^{1 / 2} or more. 84. A colorant comprising a first pigment and a second pigment dispersed in an aqueous medium, wherein the first pigment has at least one anionic group directly or via another atomic group. A self-dispersible carbon black bonded to the surface of the first pigment or a self-dispersed carbon black bonded to the surface of the first pigment directly or through another atomic group. Carbon black, wherein the second pigment is a pigment that can be dispersed in the aqueous medium by a polymer dispersant, and the ink further has the same group as that bonded to the surface of the first pigment. A black ink containing at least one of a polar polymer dispersant and a nonionic polymer dispersant, and an ink storage unit containing a yellow ink, a magenta ink, and a cyan ink, and the black ink, Means for individually ejecting the yellow ink, the magenta ink, and the cyan ink by an ink-jet printing method. 85. The ink jet recording apparatus according to claim 84, wherein the black ink further contains a dye having the same polarity as the group bonded to the surface of the first pigment. 86. The black ink according to the Bristow method
Ka value is 1ml ・ m ^-2・ Msec^-1/2Claims that are less than
84. The ink jet recording apparatus according to 84 or 85. 87. Ka of each of the yellow ink, the magenta ink and the cyan ink in the Bristow method
^85. The ink jet recording apparatus according to claim 84, wherein the value is 1 ^{mlm- 2} msec- ^{1 / 2} or more.