JP2002331676A - Ink jet recorder and method for recovering discharging of recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recorder, a ink jet recording method, and a method for recovering discharging of a recording head in which high quality recording is ensured at all times by performing recovery processing, e.g. wiping, at an appropriate timing so that the mixture of ink and a liquid composition adhering to a recording head does not stick thereto. SOLUTION: Depending on the possibility that the mixture of ink and a liquid composition adheres to a plurality of recording heads 1s, 1k, 1c, 1m and 1y, respectively, conditions for recovering the discharging state of respective recording heads 1s, 1k, 1c, 1m and 1y are differentiated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus capable of always recording a high-quality image and a method for recovering the ejection of a recording head.

[0002]

2. Description of the Related Art In an ink jet recording system, recording is performed by causing ink droplets to fly and causing ink to adhere to a recording medium such as paper. For example, Japanese Patent Publication No. 61-59911, Japanese Patent Publication No. 61-59912 and Japanese Patent Publication No.
Japanese Patent No. 59914 describes an ink jet recording method in which an electrothermal converter is used as a discharge energy supply unit, and thermal energy generated from the electrothermal converter is applied to ink to generate bubbles, thereby discharging ink droplets. Have been. According to such a recording method, it is possible to easily realize a high-density multi-orifice of the recording head, and to record a high-resolution and high-quality image at a high speed.

[0003] The ink used in the conventional ink jet recording system mainly contains water, and water-soluble ink such as glycol is used for the purpose of preventing drying of the ink in the nozzle and preventing clogging of the nozzle. Those containing a high-boiling solvent are common. Therefore, when recording is performed on a recording medium using such an ink,
In some cases, sufficient fixability may not be obtained, or a problem such as generation of a non-uniform image on the surface of the recording paper as a recording medium, which is presumed to be due to non-uniform distribution of the filler and the sizing agent, may occur. On the other hand, in recent years, there has been a strong demand for high-quality images at the same level as silver halide photographs for ink-jet recorded materials.
Technical requirements for expanding the color reproduction area and improving the color uniformity of the recorded matter are extremely high.

[0004] Under such circumstances, various proposals have been made so far in order to stabilize the ink jet recording method and to improve the quality of recorded matter by the ink jet recording method. Some of the typical ones are summarized below.

(1) Method of internally adding a volatile solvent or a penetrating solvent to ink As a method of accelerating the fixability of the ink to a recording medium, Japanese Patent Application Laid-Open No. 55-65269 discloses a method in which a surfactant is incorporated into the ink. A method of adding a compound that enhances permeability, such as the above, is disclosed. Japanese Patent Application Laid-Open No. 55-66976 discloses the use of an ink mainly composed of a volatile solvent.

(2) A method of mixing a liquid composition which reacts with an ink on a recording medium to form a recorded image for the purpose of improving image density, improving water resistance, and suppressing bleeding. Prior to or after the ejection of ink, a method of applying a liquid composition for improving an image on a recording medium has been proposed.

For example, Japanese Patent Application Laid-Open No. 63-60783 discloses a method in which a liquid composition containing a basic polymer is applied to a recording medium and then recorded with an ink containing an anionic dye. . Also, JP-A-63
JP-A-2-2681 discloses a recording method in which a first liquid composition containing a reactive species and a second liquid composition containing a compound causing a reaction with the reactive species are mixed on a recording medium. A method is disclosed. Further, JP-A-63-2999
No. 71 discloses a method of applying a liquid composition containing an organic compound having two or more cationic groups per molecule on a recording medium and then performing recording with an ink containing an anionic dye. ing. Also, Japanese Unexamined Patent Publication No.
JP-A-9279 discloses a method in which an acidic liquid composition containing succinic acid or the like is applied onto a recording medium, and then recording is performed using an ink containing an anionic dye.

Japanese Patent Application Laid-Open No. 63-63185 discloses a method of applying a liquid composition for insolubilizing a dye to paper prior to applying an ink. Further, Japanese Patent Application Laid-Open No. Hei 8-224595 discloses a method of using a liquid composition containing a cationic substance having a different molecular weight distribution region together with an ink containing an anionic compound. A method is disclosed in which a liquid composition containing a cationic substance and finely divided cellulose is used together with an ink. It describes that a perfect image can be obtained.
JP-A-55-150396 discloses that after recording with a dye ink on a recording medium, water resistance of a recorded image is imparted by imparting a water-resistant agent that forms a lake with the dye. Proposed.

(3) Method of mixing ink and liquid composition containing fine particles on a recording medium JP-A-4-259590 discloses a method for recording a colorless liquid containing colorless fine particles made of an inorganic substance. A method is disclosed in which a non-aqueous recording liquid is applied after being applied onto a medium. JP-A-6-92010 discloses an ink containing a pigment, a water-soluble resin, a water-soluble solvent and water after a solution containing fine particles or a solution containing fine particles and a binder polymer is applied onto a recording medium. Is disclosed. Each of these publications describes that an image having good recording quality and coloring can be obtained regardless of the type of paper.

(Background Art) The inventors of the present invention have studied various kinds of ink jet recording techniques as described above, and as a result, although excellent effects can be confirmed for each technical problem, each of them has been replaced with each other. It has been found that other ink jet recording characteristics other than the technical problem described above may be deteriorated.

For example, a recording medium (hereinafter, also referred to as "coated paper") obtained by applying a filler or a sizing agent on the surface of a base paper of a recording medium can form a high-quality image. It is recognized as a technology. In general, it is known that in order to obtain a high-saturation image, it is necessary to leave the colorant in a monomolecular state on the surface of the recording medium without agglomeration. The porous fine particles of the coated paper have such a function. However, in order to obtain high image density and image saturation, it is indispensable to form a thick ink receiving layer that covers the base paper with a large amount of porous fine particles as a receiving layer for the coloring material in a given ink. As a result, there is a problem that the texture of the base paper is lost. The present inventors have found that the reason why such an ink-receiving layer is required to lose the texture of the base paper is that the coloring material is not efficiently adsorbed on the porous fine particles.

As a specific example, a coated paper having one ink receiving layer will be described below.

FIG. 7 schematically shows a cross section near the surface of the coated paper. In the drawing, reference numeral 901 denotes a base paper of coated paper, and 903 denotes an ink receiving layer. In general, the ink receiving layer 903 has porous fine particles 905 and an adhesive 907 for fixing them. When the ink is applied, the ink penetrates the voids between the porous fine particles 905 by capillary action to form an ink penetrating portion 909. As shown in the drawing, since the density of the porous fine particles 905 in the ink receiving layer 903 is locally different, the way of permeation of the ink by the capillary phenomenon differs depending on the place. Therefore, during the ink penetration process, the coloring material in the ink cannot uniformly contact the surface of the porous fine particles 905, and the coloring material is not efficiently adsorbed by the porous fine particles 905. Further, there are portions where ink penetration is inhibited by the adhesive 907, and there are portions in the ink receiving layer 903 where ink cannot penetrate, and portions that do not contribute to color development are generated.

For these reasons, in the conventional coated paper, the coloring material cannot be efficiently adsorbed in a monomolecular state with respect to the amount of the porous fine particles, and as a result, a high quality image is obtained. For this purpose, a large amount of porous fine particles are required, which impairs the texture of the base paper.

On the basis of the above-described new findings, the present inventors have proposed a method of using fine particles having a colorant-adsorbing action in a liquid state together with ink to efficiently adsorb or combine the colorant with the fine particles. By dispersing the fine particles in the liquid material, it is possible to cause the color material and the fine particles to react in a liquid-liquid state, and as a result, it is possible to reliably improve the density and saturation of the image. I found it.

The present inventors have further studied and found that an ink jet recording apparatus using a liquid (hereinafter, referred to as a “liquid composition”) in which fine particles having a colorant adsorbing action are dispersed together with ink is used. It has been found that a mixture of ink and a liquid composition (hereinafter, also referred to as “mixed mist”) may adhere to the vicinity of a nozzle row (ejection port surface) of a recording head for ejecting ink or liquid composition. Was. In such a case, the liquid composition and the ink react with each other to form a fixed substance, which may cause a discharge failure of the liquid composition or the ink from the recording head. In addition, the present inventors may find that ink that has landed on a recording medium rebounds and adheres to the ejection port surface of the liquid ejection recording head. It has also been found that a reaction product of the ink and the liquid composition is formed, and this reaction product causes ejection failure. Similarly, the liquid composition that has landed on the recording medium may bounce off and adhere to the ejection port surface of the ink ejection recording head. In this case, the ink and the liquid may adhere to the ejection port surface of the ink ejection recording head. A reactant with the composition is formed,
It has also been found that this reactant causes ejection failure.

[0017]

According to the present inventors,
It has been confirmed that the ink and the liquid composition come into contact with each other on the formation surface of the discharge port of the recording head (hereinafter, also referred to as “face surface” or “discharge port surface”) to cause a reaction, thereby causing the fixation thereof. did. As a result of such sticking, the ejection direction of ink droplets ejected thereafter is shifted, causing image deterioration, or causing non-ejection of ink due to clogging of ejection openings, which may have a large effect on reliability. is there. Further, such sticking is greatly affected by the cohesiveness of the liquid composition and the ink.

Conventionally, as a discharge recovery method for effectively preventing the generation of mixed mist in or around the nozzle or effectively removing the generated mixed mist and maintaining high recording quality for a long period of time, Japanese Patent Laid-Open Publication No. 11-24016
No. 5 discloses a method. The method of recovering the ejection is to vary the timing of the recovery operation by the recovery means of the recording head according to the distance between the recording heads ejecting the mutually reactive inks when using inks that react and aggregate with each other. It is. However, although the distance between the nozzles is one of the important factors for the generation of mixed mist around the nozzles of the recording head,
Investigations by the inventors have revealed that this is not enough.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object thereof is to perform wiping or the like at an appropriate timing so as not to fix a mixture of ink and a liquid composition adhered to a recording head. Ink-jet recording apparatus and recording method capable of minimizing the consumption of ink and liquid composition due to the recovery and shortening the time required for the recovery as much as possible, and always performing high-quality recording. An object of the present invention is to provide a head ejection recovery method.

[0020]

According to the present invention, there is provided an ink jet recording apparatus comprising: a plurality of ink recording heads capable of discharging ink; and a liquid capable of discharging a liquid composition containing fine particles for adsorbing a coloring material in the ink. In an ink jet recording apparatus that performs recording on a recording medium using a composition recording head, the recording head according to the possibility that a mixture of the ink and the liquid composition adheres to each of the recording heads. Are characterized by different recovery conditions for recovering the respective ejection states.

According to the present invention, there is provided a method for recovering the ejection of a recording head. A method for recovering the discharge of a recording head in an ink jet recording apparatus that performs recording on a recording medium by using a recording head, wherein a mixture of the ink and the liquid composition may adhere to each of the recording heads. Accordingly, recovery conditions for recovering the respective ejection states of the recording head are changed.

[0022]

Next, the present invention will be described in more detail with reference to preferred embodiments.

According to the present invention, a high-quality image excellent in color developability is formed by discharging a liquid composition from a nozzle of a recording head onto a recording medium, as compared with the case of forming an image using only aqueous ink. It can be applied to an ink jet recording apparatus. In particular, in the present invention, an anionic or cationic ink is used as the aqueous ink containing the colorant, and a liquid containing fine particles having a surface opposite in polarity to the aqueous ink in a dispersed state is used as the liquid composition. It is preferable to use alumina or alumina hydrate as the fine particles.

In a preferred embodiment of the method for forming a colored portion on a recording medium, (i) a step of applying an ink containing a coloring material to the recording medium, and (ii) a step of applying a liquid composition to the recording medium. And applying the ink and the liquid composition such that the ink and the liquid composition are in contact with each other in a liquid state on the surface of the recording medium. In the present invention, if the ink and the liquid composition come into contact with each other in a liquid state, the step (i) may be performed first, and then the step (ii) may be performed. On the contrary, the above-described step (ii) may be performed first, and then the above-described step (i) may be performed. As described above, by employing the ink and liquid composition as described later, the ink composition has a wider color reproduction area, is excellent in bleeding suppression, color uniformity, color developing properties, and the like. And an ink jet recorded matter having good scratch resistance can be stably obtained. Further, since the ink and the liquid composition used for recording have extremely simple configurations, high-quality and highly reliable inkjet recording can be performed.

Although it is not clear why the ink and the liquid composition used in the present invention exert the above-mentioned excellent effects, the present inventors believe that the reason is as follows.

First, the recording mechanism in the present invention will be described with reference to FIGS. Here, an aqueous ink containing a water-soluble dye having an anionic group (anionic dye) is used as the ink, and fine particles whose surface is cationically charged are included in the liquid composition in a dispersed state. The case where an aqueous liquid composition is used will be described.

Hereinafter, the recorded image according to the present invention will be described.
This will be described with reference to FIG.

First, in the present invention, the "monomolecular state" refers to a state in which a coloring material such as a dye or a pigment substantially maintains a state of being dissolved or dispersed in an ink. Even if the color material causes some aggregation, the color material is included in the “monomolecular state” as long as the color does not fall. In the case of a dye, a single molecule is considered preferable.
For convenience, coloring materials other than dyes are also referred to as "monomolecular state". In addition, "the reaction between the coloring material and the fine particles"
In addition to the covalent bond between the two, it means ionic bond, physical / chemical adsorption, absorption, adhesion, and other interactions between the two.

FIG. 8 shows a colored portion I of a recorded image according to the present invention.
Is a diagram schematically showing a state composed of a main image portion IM and its peripheral portion IS. In FIG. 8, 13
Numeral 01 indicates a recording medium, and 1302 indicates a gap generated between fibers of the recording medium 1301. Reference numeral 1303 denotes fine particles in the liquid composition, and the coloring material 1305 in the ink is chemically adsorbed. As shown in FIG. 8, in the ink-jet recorded image according to the present invention, the main image area IM includes fine particles in which the colorant 1305 is uniformly adsorbed on the surface in a state of a single molecule or a state close to a single molecule (hereinafter, referred to as a “single-molecule state”). 1303 and an agglomerate 1307 of fine particles 1303 holding the colorant 1305 in a monomolecular state. 1309 is the main image portion I
It is an aggregate of fine particles 1303 existing near the fibers of the recording medium 1301 in M. Main image section IM
Is formed by a step of physically or chemically adsorbing the fine particles 1303 to the fibers of the recording medium 1301 and a step of adsorbing the coloring material 1305 and the fine particles 1303 in a liquid-liquid state. Therefore, even in the recording medium 1301 such as plain paper in which the ink easily sinks, the image density and saturation are high, and the color reproduction range of the color material 1305 is as wide as that of coated paper. Can be formed.

On the other hand, the coloring material 1305 not adsorbed on the surface of the fine particles 1303 and remaining in the ink is
Since the ink penetrates both in the lateral direction and in the depth direction with respect to 01, the ink forms a slight blur on the peripheral portion IS. In this way, the coloring material 1305 remains near the surface of the recording medium 1301,
Since slight bleeding of the ink is formed in the peripheral portion IS, even in an image area where a large amount of ink is applied, such as a shadow portion or a solid portion, white haze and color unevenness are small and color uniformity is excellent.
As shown in FIG. 8, when the recording medium 1301 has permeability of the ink and the liquid composition, the penetration of the ink component and the liquid composition component into the recording medium 1301 is not necessarily prevented. Not so, some penetration is acceptable.

Further, in the present invention, when the liquid composition is used, when the fine particle aggregate 1309 existing near the surface of the recording medium 1301 is formed, the aggregate 130
The pores of a certain size are formed inside 9. When the coloring material 1305 existing alone in the ink described above penetrates into the recording medium 1301, the coloring material 1305 penetrates into the fine pores of the fine particle aggregates 1309, and the vicinity of the entrance of the fine pore and the inner wall thereof The coloring material 1305 can be adsorbed in an ideal single-molecule state to leave more of the coloring material 1305 near the surface of the recording medium 1301. As a result, it is possible to obtain a recorded matter having more excellent coloring properties.

FIGS. 9A to 9D are explanatory diagrams of a process of forming a colored portion 1400 on a recording medium 1301 according to the present invention. Reference numeral 1401 denotes a portion (hereinafter, referred to as a “reaction portion”) corresponding to the main image portion IM in FIG.
3 with the liquid composition 1406, for example, the colorant 130
5 is a part mainly containing a reaction product of the fine particles 1303 and the fine particles 1303. Reference numeral 1402 denotes a portion corresponding to the peripheral portion IS in FIG. 8 (hereinafter, referred to as an “ink outflow portion”).
13 is a part formed by flowing out to the periphery of the reaction part 1401.

Such a colored portion 1400 is formed, for example, as follows. Reference numeral 1302 schematically represents a gap generated between fibers of the recording medium 1301.

First, a liquid composition 1406 having reactivity with the colorant 1305 is applied as droplets to the recording medium 1301 (FIG. 9A). As a result, the liquid composition 1406 is obtained.
Is formed (FIG. 9B). In the liquid reservoir 1407, the fine particles 1303 in the vicinity of the fiber surface of the recording medium 1301 are physically or chemically adsorbed on the fiber surface. At this time, the dispersion state of the fine particles 1303 becomes unstable, and the aggregate 13
It is considered that some of them form the C.09. On the other hand, it is considered that the fine particles 1303 are kept in the original dispersion state in the portion of the liquid pool 1407 away from the fibers.

Next, the ink 1413 is applied as droplets to the recording medium 1301 (FIG. 9B). As a result, first, at the interface between the ink 1413 and the liquid reservoir 1407, the coloring material 1305 is chemically adsorbed on the fine particles 1303. Since this reaction is a reaction between liquids (liquid-liquid reaction), it is considered that the coloring material 1305 is uniformly adsorbed on the surface of the fine particles 1303 in a monomolecular state (FIG. 9C). That is, it is presumed that the coloring materials 1305 on the surface of the fine particles 1303 do not agglomerate or even if they agglomerate. As a result, a large number of fine particles adsorbing the coloring material 1305 in a monomolecular state are formed on the surface layer of the reaction section 1401. As described above, since the coloring material 1305 remains in a monomolecular state on the surface layer that most affects color development, a recorded image with high image density and high saturation is formed.

Next, the fine particles 1303 to which the coloring materials 1305 are adsorbed become unstable because their dispersion state becomes unstable.
It is considered that the fine particles 1303 aggregate with each other to form an aggregate 1415 (FIG. 9C). The aggregate 1415 also holds the colorant 1305 in a monomolecular state inside.
The aggregate 1415 forms a recorded image with high image density and high chroma.

Further, a part of the unreacted coloring material 1305 diffuses in the liquid pool 1407 and is adsorbed on the surface of the unreacted fine particles 1303. As described above, since the reaction between the coloring material 1305 and the fine particles 1303 further proceeds inside the liquid reservoir 1407, an image with higher density and higher saturation is formed. A liquid pool 1407 is formed on the aggregate 1309 of the fine particles 1303 formed on the fiber surface of the recording medium 1301 described above.
Is considered to have a function of preventing the liquid phase from permeating into the recording medium 1301. Therefore, the liquid pool 1407
In this case, the fine particles 1303 in the liquid composition whose permeation is suppressed are
And the color material 1305 can be mixed more. As a result, the contact probability between the coloring material 1305 and the fine particles 1303 is increased, the reaction proceeds relatively uniformly and sufficiently, and an image excellent in image density and saturation is more uniformly formed.

The liquid composition 1406 is applied to the recording medium 1.
301 (FIG. 9 (a)) and the liquid pool 1
When the ink 1413 is applied to the ink 407 (see FIG. 9)
(B)), the dispersion medium in which the fine particles 1303 are dispersed changes, and the dispersion of the fine particles 1303 becomes unstable;
Some of them cause aggregation between the fine particles 1303 before the 05 is adsorbed. The change in the dispersion medium referred to here is a change generally observed when two or more different liquids are mixed, such as a pH of a liquid phase, a solid content concentration, a solvent composition, and a dissolved ion concentration. A change in physical properties. It is considered that when the liquid composition 1406 comes into contact with the recording medium 1301 or the ink 1413, these changes occur rapidly and in a complex manner, and the dispersion stability of the fine particles 1303 is destroyed, and aggregates are generated. These agglomerates have the effect of filling voids between fibers and the fine particles 1303 adsorbing the coloring material 1305.
Is more likely to remain near the surface of the recording medium 1301. In addition, the sump 14
Some of the aggregates formed in 07 are adsorbed on the recording medium 1301, and others are capable of moving (having fluidity) in the liquid phase. The aggregate having fluidity is formed by adsorbing the colorant 1305 in a monomolecular state on the surface of the aggregate of the fine particles 1303 in the same manner as the reaction process between the colorant 1305 and the fine particles 1303 to form a larger aggregate. It contributes to the improvement of coloring. That is, the agglomerates move with the liquid phase when the liquid phase permeates along the fiber, and fill the voids to smooth the surface of the recording medium 1301 and contribute to the formation of a more uniform and high-density image. It is thought that.

The reason why a high color image is obtained by the present invention is that the coloring material is adsorbed to the fine particles or fine particle aggregates in a monomolecular state as described above, and remains in the vicinity of the surface of the recording medium in that state. it is conceivable that. The coloring material is adsorbed in a monomolecular state, and the fine particles remaining near the surface of the recording medium are fixed on the surface of the recording medium. This improves the fastness of the image such as scratch resistance and water resistance.

Further, as shown in FIG. 9 (b), at least a part of the fine particles in the liquid composition applied to the recording medium is caused by the penetration of the liquid medium into the recording medium. It is thought that it has penetrated inside. On the other hand, FIG.
As clearly shown in (d), it can be sufficiently assumed that the coloring material is adsorbed or bonded in a monomolecular state to the fine particles that have penetrated first. As described above, it is considered that the fine particles in which the coloring material is adsorbed or bonded in a monomolecular state inside the recording medium also contributes to the improvement of the coloring property. Further, it is considered that the fixability is improved by the penetration of the liquid medium.

Further, the reason why a high color image can be obtained by the present invention will be described below. By using the liquid composition of the present invention, when the fine particle aggregate 1309 existing near the surface of the recording medium is formed, pores having a certain size are formed inside the aggregate. Pool 1407
Color material 130 that could not be completely absorbed by the fine particles 1303
No. 5 also penetrates into the fine particle aggregates 1309 through the pores together with the solvent component when penetrating into the recording medium. At this time, the coloring material 1305 is adsorbed near the entrance of the pores in the fine particle aggregates and on the inner wall of the fine pores, and only the solvent component permeates into the recording medium, so that the coloring material is more agglomerated. It can be efficiently adsorbed on the surface or inside of 1309 and can remain near the surface of the recording medium. Further, when the coloring material 1305 is a dye, since the pore diameter of the fine particle aggregates 1309 is about one to several times the molecular size existing in the ink of the coloring material 1305, the coloring material adsorbed inside the pores In the case of 1305, the aggregation of the coloring materials is extremely unlikely to occur, and an ideal single molecule state can be formed. This greatly contributes to further improvement of the color developing property, and a recorded matter having a wider color reproduction range can be obtained.

It was also found that the physical properties of the pores of the fine particle aggregates 1309 were affected not only by the fine particles contained in the liquid composition, but also by the solvent composition and the like. It has been found that the pore volume in a specific pore radius region of the fine particle aggregate has a very high correlation with the image forming ability formed on the recording medium.

Further, in the present invention, when the coloring material is anionic, the coloring material is extremely efficiently applied to the surface of the cationic fine particles by reacting the fine particles and the coloring material in a liquid phase on the surface of the recording medium. Will be adsorbed. Here, in order to achieve the same level of colorant adsorption as in the present invention in ink-jet coated paper, a large amount of cationic porous fine particles is required, and the formation of a thick ink receiving layer that covers the base paper is indispensable. Becomes For this reason, the coated paper leads to the result of impairing the texture of the base paper, but since the amount of the fine particles constituting the liquid composition of the present invention can be reduced, the printed portion and the unprinted portion can be reduced without impairing the texture of the recording medium. Thus, it is possible to form an image without feeling unnatural in texture.

Hereinafter, the liquid composition and the ink used in the present invention will be described in detail.

First, the definition of a cationic ink or an anionic ink in this specification will be described.
It is well known in the art that when referring to the ionic properties of an ink, the ink itself is uncharged and neutral in itself. The term “anionic ink or cationic ink” as used herein means a component in the ink, for example, a colorant has an anionic group or a cationic group, and in the ink, these groups are anionic or cationic. It refers to ink that has been adjusted to act as a base. The meaning of the anionic or cationic liquid composition is the same as described above.

<Liquid Composition> The liquid composition of the present invention will be described below.

[Pore Radius and Pore Volume] As described above, the pore radius of the fine particle aggregate is determined by rapid penetration of the coloring material, adsorption to the entrance of the pore or on the inner wall, and aggregation of the coloring material inside the pore. It is considered preferable that the thickness be in the range of 3 nm to 30 nm from the viewpoint of preventing the above. In addition, a certain amount of capacity is required at the same time in order to take in a color material that only contributes to the improvement of the color developing property. In addition, it is considered that the number of pores in the fine particle aggregate increases due to an increase in the pore volume. Conceivable.

Accordingly, from these viewpoints, the liquid composition suitably used in the present invention has a pore volume of 0.4 ml / g or more in a pore radius range of 3 nm to 30 nm and a pore radius exceeding 30 nm. Pore volume at 0.1 ml /
g or less. In pores having a pore radius smaller than 3 nm, the coloring material and the solvent component hardly penetrate into the pores, and the pores of the fine particle aggregates do not substantially contribute to the improvement of the coloring property. When the pore volume exceeds 0.1 ml / g in the region where the radius of the pores exceeds 30 nm, there are many pores with large light scattering, and the coloring material adsorbed near the pore entrance or on the inner wall has a color developing property. It is difficult to contribute. Further, the pore volume in the region of the pore radius is less than this range, because less coloring material and solvent component penetrate into the inside of the fine particle aggregate,
The amount of coloring material adsorbed near and inside the pores decreases,
It is not preferable because the contribution to the improvement of the coloring property is reduced.

More preferably, the pore radius is 3n.
0.4 ml / g of pore volume in the range of m to 20 nm
As described above, the pore volume in the region where the pore radius exceeds 20 nm is preferably 0.1 ml / g or less. 3 nm pores
By virtue of being present in a large range of a radius of up to 20 nm, especially when a dye is used as a coloring material, the color developability is further improved and an image having a wider color reproduction range can be formed. The pore radius and pore volume of the fine particle aggregate formed from the liquid composition vary not only with the chemical species, shape, and size of the contained fine particles, but also with the solvent species, other additives, and their composition ratios. However, it is considered that the formation state of the fine particle aggregate can be controlled by controlling these conditions.

(Fine Particles) In the present invention, the desired action of the fine particles contained in the liquid composition is as follows.
Adsorbing a coloring material; 2) when mixed with ink or applied to a recording medium, the dispersion stability is reduced and remains on the surface of the recording medium. These functions may be achieved by one or more kinds of fine particles.

As a property for satisfying the function of 1), for example, fine particles exhibit ionicity opposite to that of the coloring material. Thereby, the fine particles can electrostatically adsorb the coloring material. When the coloring material is anionic, cationic fine particles are used, and when the coloring material is cationic, anionic fine particles are used. Elements that adsorb the coloring material other than ionicity include the size and weight of the fine particles or the surface shape. For example, porous fine particles having a large number of pores on the surface exhibit unique adsorption characteristics, and can adsorb a coloring material by a plurality of factors such as the size and shape of the pores.

The function 2) is caused by the interaction with the ink and the recording medium. For this reason, what is necessary is just to achieve by each structure, For example, as a property of a fine particle,
It has the opposite ionicity to the ink composition component and the recording medium component. Also, the coexistence of an electrolyte in the ink or liquid composition affects the dispersion stability of the fine particles. In the present invention, the above 1)
It is desirable that either one of the functions 2) and 3) be obtained instantaneously. Further, it is preferable that both the effects 1) and 2) be obtained instantaneously.

Hereinafter, the liquid composition containing each ionic fine particle will be specifically described. That is, the cationic liquid composition and the anionic liquid composition applicable to the present invention will be described.

[Cationic Liquid Composition] First, a cationic liquid composition, which is an example of a liquid composition applicable to the present invention, will be described. Examples of the cationic liquid composition include a liquid composition containing fine particles having a cationic group on the surface and an acid, and the fine particles are stably dispersed. In the present invention, as the cationic liquid composition, for example, those containing an acid and adjusted to a pH of 2 to 7, and those having a zeta potential of +5 to +90 mV can be suitably used.

(Regarding pH and Zeta Potential) The zeta potential of the liquid composition will be described. The basic principle of the zeta potential will be described below. In general, in a system in which a solid is dispersed in a liquid, when there is free charge on the surface of a solid phase, a charged layer having an opposite charge appears in the liquid phase near the solid phase interface so as to maintain electrical neutrality. This is called an electric double layer, and the potential difference caused by the electric double layer is called zeta potential. When the zeta potential is positive, the surface of the fine particles is cationic, and when the zeta potential is negative, it is anionic.
Generally, it is said that the higher the absolute value, the stronger the electrostatic repulsion acting between the fine particles and the better the dispersibility. At the same time, it is considered that the ionicity of the surface of the fine particles is strong. That is, the higher the zeta potential of the cationic fine particles, the stronger the cationicity,
It can be said that the power of attracting the anionic compound in the ink is strong.

Further, the present inventors have conducted intensive studies. As a result, when a liquid composition having a zeta potential in the range of +5 to +90 mV is used, the colored portion formed on the recording medium has particularly excellent color development. It has been found that it exhibits characteristics. The reason is not clear, but probably because the anionic compound (anionic colorant) does not agglomerate rapidly due to the moderate cationicity of the fine particles, the anionic compound is thinly and uniformly adsorbed on the surface of the fine particles. Therefore, it is considered that the coloring material hardly forms a huge lake, and as a result, the original coloring characteristics of the coloring material are expressed in a better state. Further, in the cationic liquid composition of the present invention, even after the anionic compound is adsorbed on the surface of the fine particles, the fine particles exhibit a weak cationic property and become in an unstable dispersion state, so that the fine particles are aggregated in the recording medium. It is considered that the ink is easily adsorbed on the surface of an anionic cellulose fiber or the like existing in the recording medium, and is likely to remain near the surface of the recording medium.

As a result, it is considered that the following excellent effects can be obtained. That is, in the image area where the amount of applied ink is large, such as a shadow portion and a solid portion, white haze and color unevenness are small, and the color uniformity is excellent. In addition, since the anionic compound is adsorbed to the fine particles and the color is extremely efficiently compared to the coated paper, the amount of the cationic fine particles can be reduced.
It does not impair the texture of the paper and has excellent scratch resistance in the printed area. As a more preferable range of the zeta potential, for example, when a liquid composition containing cationic fine particles having a zeta potential in the range of +10 to +85 mV is used, the boundary between dots becomes less noticeable when solid printing is performed, Further reduction of uneven streaks due to head scan can be achieved, and furthermore, the zeta potential is increased by +15 to +65 mV.
The use of the liquid composition containing the cationic fine particles in the range described above makes it possible to obtain an image having extremely excellent coloring properties regardless of the type of paper.

PH of the cationic liquid composition of the present invention
Is preferably in the range of 2 to 7 at around 25 ° C. from the viewpoints of storage stability and adsorptivity of the anionic compound.
Within this pH range, when mixed with an anionic ink, the stability of the anionic compound is not significantly reduced, so that strong aggregation of the anionic compounds does not occur, and the color of the recorded image does not increase. It is possible to effectively prevent the degree of the image from decreasing or becoming a dull image. Further, when the content is within the above range, the dispersion state of the cationic fine particles is good, so that the storage stability of the liquid composition and the stability of ejection from the recording head can be favorably maintained. Furthermore, when mixed with the ink, the anionic substance is sufficiently adsorbed on the surface of the cationic fine particles, so that excessive penetration of the coloring material into the recording medium is suppressed, and an ink jet recorded matter having excellent coloring properties is obtained. can get. More preferred pH
Is in the range of pH 3 to 6, and in this range,
Corrosion of the recording head due to long-term storage can be extremely effectively prevented, and the scratch resistance of the printed portion is further improved.

(Cationic Fine Particles) Next, the components constituting the cationic liquid composition of the present invention will be described. In order to achieve the above-mentioned effects, the cationic fine particles mentioned as the first component require that the surface of the particles themselves exhibit cationicity in a state of being dispersed in the liquid composition. By making the surface cationic,
When mixed with an anionic ink, the anionic coloring material is quickly adsorbed on the particle surface, and excessive penetration of the coloring material into the recording medium is suppressed, so that an inkjet recorded matter having a sufficient image density can be obtained. can get. In contrast, when the surface of the fine particles is not cationic and is present separately from the water-soluble cationic compound in the liquid composition,
The coloring material is aggregated mainly with the cationic compound, and the coloring property of the coloring material itself is impaired, so that it is difficult to achieve the coloring property comparable to the coated paper for inkjet. Therefore, the fine particles used in the liquid composition of the present invention need to have a cationic surface, but not only fine particles that are essentially cationic, but also electrostatically anionic or neutral in nature. Even certain fine particles can be used in the liquid composition of the present invention as long as the fine particles have a surface cationized by the treatment.

The cationic fine particles suitably used in the present invention are sufficient to achieve the object of the present invention as long as the fine particles formed on the recording medium have pores formed in the aggregate. For this reason, the material type of the fine particles is not particularly limited. As specific examples, for example, cationized silica, alumina, alumina hydrate, titania, zirconia, boria, silica boria, ceria,
Examples include magnesia, silica magnesia, calcium carbonate, magnesium carbonate, zinc oxide, hydrotalcite, and the like, and composite fine particles, organic fine particles, and inorganic-organic composite fine particles thereof. And in the liquid composition of the present invention, these can be used alone or in combination of two or more.

In particular, when alumina hydrate is used as the fine particles, the surface of the particles is preferably positively charged, and alumina hydrate having a boehmite structure by X-ray diffraction is particularly preferred. It is preferable in terms of properties and storage stability. Alumina hydrate is defined by the following general formula. Al2O3-n (OH) 2n.mH2O In the formula, n represents one of integers of 0 to 3, and m represents 0 to 1
It has a value of 0, preferably 0-5. The expression mH2O describes a detachable aqueous phase which is often not involved in the formation of a crystal lattice, so that m can also be a non-integer value. However, m and n do not become 0 at the same time.

In general, the crystal of alumina hydrate having a boehmite structure is a layered compound whose (020) plane forms a giant plane, and shows a diffraction peak specific to an X-ray diffraction pattern. In addition to complete boehmite, a structure called "pseudo-boehmite" containing an excess of water between layers of the (020) plane can be adopted. The X-ray diffraction pattern of this pseudo-boehmite shows a broader diffraction peak than boehmite.

Since boehmite and pseudo-boehmite cannot be clearly distinguished from each other, in the present invention, unless otherwise specified, they are referred to as alumina hydrate having a boehmite structure (hereinafter referred to as alumina hydrate). The (020) plane has an interplanar spacing and a (020) crystal thickness when the diffraction speed 2θ is 1
The peak appearing at 4 to 15 ° is measured, and from the diffraction angle 2θ of the peak and the half width B, the plane spacing can be obtained by using the Bragg equation, and the crystal thickness can be obtained by using the Scherrer equation. it can. The plane spacing of (020) can be used as a measure of the hydrophilicity / hydrophobicity of the alumina hydrate.
The method for producing the alumina hydrate used in the present invention is not particularly limited, but any method capable of producing an alumina hydrate having a boehmite structure, for example, hydrolysis of aluminum alkoxide, hydrolysis of sodium aluminate, etc. Can be produced by a known method.

As disclosed in JP-A-56-120508, a boehmite structure is obtained by heat-treating an amorphous alumina hydrate by X-ray diffraction at 50 ° C. or more in the presence of water. It can be changed and used. A method that can be particularly preferably used is a method of obtaining an alumina hydrate by adding an acid to a long-chain aluminum alkoxide and performing hydrolysis and peptization. Here, the long-chain aluminum alkoxide is, for example, an alkoxide having 5 or more carbon atoms, and further has 12 to 12 carbon atoms.
Use of the alkoxide of No. 22 is preferable because removal of the alcohol content and control of the shape of the alumina hydrate are facilitated as described later.

As the acid to be added, one or more of an organic acid and an inorganic acid can be freely selected and used. However, the reaction efficiency of hydrolysis and the shape control of the obtained alumina hydrate From the viewpoint of dispersibility and dispersibility, nitric acid is most preferred. After this step, it is also possible to control the particle size by performing hydrothermal synthesis or the like. When hydrothermal synthesis is performed using a dispersion of alumina hydrate containing nitric acid, nitric acid in the aqueous solution is incorporated as nitrate on the surface of the alumina hydrate to improve the water dispersibility of the hydrate. it can. In addition, after the hydrothermal synthesis, by appropriately adding an acid to the alumina hydrate slurry and adjusting the pH, the alumina hydrate slurry can be prepared with a small acid concentration and a very stable high solid content alumina hydrate slurry. . When such a slurry is used, a liquid composition having excellent dispersion stability of alumina hydrate fine particles can be produced without the need to separately add an acid to be described later.

The above-mentioned method of hydrolysis of aluminum alkoxide has an advantage that impurities such as various ions are hardly mixed in as compared with the method of producing alumina hydrogel or cationic alumina. Furthermore, long-chain aluminum alkoxides can be completely de-alcoholized from alumina hydrate, as compared with the case where a long-chain alcohol after hydrolysis uses, for example, a short-chain alkoxide such as aluminum isoproxide. There is also an advantage. It is preferred to set the pH of the solution at the start of the hydrolysis to less than 6. When the pH exceeds 8, the alumina hydrate finally obtained becomes crystalline, which is not preferable.

As the alumina hydrate used in the present invention, an alumina hydrate containing a metal oxide such as titanium dioxide can be used as long as it shows a boehmite structure by X-ray diffraction. . The content ratio of metal oxide such as titanium dioxide is 0.01 to 1.00 of alumina hydrate.
% By weight is preferable because the optical density is high, and more preferably 0.13 to 1.00% by weight. The adsorption speed of the coloring material is increased, and bleeding and beading are less likely to occur. Further, the titanium dioxide needs to have a valence of +4. The content of titanium dioxide can be determined by dissolving in boric acid and by the ICP method. The distribution of titanium dioxide and the valence of titanium in alumina hydrate were determined by ESC.
A can be used for analysis.

The surface of the alumina hydrate is etched with argon ions for 100 seconds and 500 seconds, and the change in the titanium content can be examined. If the valence of titanium is less than +4, the titanium dioxide may act as a catalyst to lower the weather resistance of the printed matter or to cause yellowing of the printed portion.

[0069] Titanium dioxide may be contained only in the vicinity of the surface of the alumina hydrate or may be contained up to the inside. Further, the content may change from the surface to the inside. It is more preferable that titanium dioxide is contained only in the vicinity of the surface because the electrical characteristics of alumina hydrate are easily maintained.

As a method for producing alumina hydrate containing titanium dioxide, for example, aluminum alkoxides described in “Surface Science”, 327, edited by Kenji Tamaru, ed. And a method in which a mixed solution of titanium alkoxide is hydrolyzed for production. As another method, when hydrolyzing the mixed solution of the aluminum alkoxide and the titanium alkoxide, alumina hydrate can be added as a nucleus for crystal growth to produce the mixture.

Instead of titanium dioxide, silica, magnesium, calcium, strontium, barium, zinc,
An oxide such as boron, germanium, tin, lead, zirconium, indium, phosphorus, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel, ruthenium, or the like can be used. For example, alumina hydrate containing silica is effective in improving the scratch resistance of a printed portion.

The spacing between the (020) planes of the alumina hydrate suitably used in the present invention is 0.614 nm to 0.626.
The range of nm is suitably used, and within this range, a liquid composition having good dispersion stability of alumina hydrate particles in the liquid composition and excellent storage stability and ejection stability can be obtained.
The reason for this is not clear, but if the plane spacing of the (020) plane is within the above range, the amount ratio of hydrophobicity and hydrophilicity of the alumina hydrate is within an appropriate range, so that particles in the liquid composition will It is presumed that the dispersion stability due to the appropriate repulsion and the appropriate balance of the wettability inside the discharge port improve the discharge stability of the liquid composition.

Further, the crystal thickness of the (020) plane of the alumina hydrate is preferably in the range of 4.0 to 10.0 nm. . According to the knowledge of the present inventors, since the interplanar spacing of the (020) plane and the crystal thickness of the (020) plane have a correlation, (0)
If the plane spacing of the (20) plane is within the above range, the crystal thickness of the (020) plane can be adjusted to a range of 4.0 to 10.0 nm.

The cationic fine particles as described above used in the present invention may have an average particle diameter measured by a dynamic light scattering method from the viewpoints of color development after printing, color uniformity and storage stability. Is preferably in the range of 0.005 to 1 μm. Within this range, excessive penetration into the inside of the recording medium can be effectively prevented, and a decrease in color developability and color uniformity can be suppressed. In addition, sedimentation of the cationic fine particles in the liquid composition is suppressed, and a decrease in the storage stability of the liquid composition can be effectively prevented.
More preferably, the average particle diameter is in the range of 0.01 to 0.8 μm, and if such fine particles are used, the abrasion resistance of the image after printing on the recording medium and the texture of the recorded matter are particularly high. It will be preferable. More preferably, the average particle diameter is in the range of 0.03 to 0.3 μm. This is preferable because it is easy to form the film effectively.

(Physical Properties and Shape of Pore of Cationic Fine Particles) The above-mentioned cationic fine particles used in the present invention can efficiently form fine pores of fine particle aggregates formed on a recording medium. At the same time, in order to efficiently adsorb the colorant on the surface of the fine particles themselves, the fine particles having a maximum pore radius of 2 nm to 12 nm and a total pore volume of 0.3 ml / g or more in the above nitrogen adsorption / desorption method. Is preferred.
More preferably, the maximum pore radius of the fine particles is 3 nm to 10 n.
m and the total pore volume is 0.3 ml / g or more,
The pores of the fine particle aggregates formed on the recording medium are preferable because they are easily formed effectively in the target pore radius region.

When the BET specific surface area of the fine particles used in the present invention is in the range of 70 to 300 m 2 / g, the coloring material can be converted into a monomolecular state by a sufficient number of adsorption points of the coloring material on the surface of the fine particles. It is more likely to be left near the surface of the recording medium more effectively, which contributes to the improvement of the color developability.

The shape of the fine particles used in the present invention is as follows.
Fine particles can be dispersed in ion-exchanged water and dropped on a collodion membrane to prepare a measurement sample, which can be determined by observation with a transmission electron microscope. In the present invention, in forming fine particles in the aggregate when forming the fine particles on the recording medium, the primary particles having a needle shape, a flat plate shape, or a spherical shape have a certain direction. A non-spherical shape such as a rod shape or a necklace shape which forms secondary particles connected and held can be suitably used.

According to the findings of the present inventors, a flat plate shape has better dispersibility in water than a needle-like or hair-like bundle (ciliform), and when a fine particle aggregate is formed, This is more preferable because the pore volume increases due to random orientation. Here, the hair bundle shape refers to a state in which needle-like fine particles are in contact with each other and gather together like a bundle of hair. In particular, among the alumina hydrates that can be preferably used in the present invention, pseudo-boehmite is described in the above literature (Rocek J., etal, Applie
d Catalysis, Vol. 74, pp. 29-36, 1991), it is generally known that there are cilia-like and other shapes.

The aspect ratio of the tabular grains is 5
It can be determined by a method defined in JP-A-16015. The aspect ratio is indicated by the ratio of the diameter to the thickness of the particle. Here, the diameter indicates the diameter of a circle having an area equal to the projected area of the particles when the alumina hydrate is observed with a microscope or an electron microscope. The aspect ratio is expressed by the ratio of the diameter indicating the minimum value to the diameter indicating the maximum value of the flat plate surface observed in the same manner as the aspect ratio. In the case of the hair bundle shape, the method of obtaining the aspect ratio is to obtain the diameter and length of each of the upper and lower circles by using the individual acicular alumina hydrate particles forming the hair bundle as a cylinder. , And the ratio can be determined. The most preferred shape of alumina hydrate is a flat plate having an average aspect ratio of 3 to 10.
In the hairy bundle, the average aspect ratio is preferably in the range of 3 to 10. When the average aspect ratio is within the above range, a porous structure can be easily formed because a gap is easily formed between particles when a fine particle aggregate is formed.

The content of the cationic fine particles as described above in the liquid composition of the present invention may be appropriately determined according to the kind of the substance to be used, but may be 0.1 to 40 on a mass basis. % Is a preferable range for achieving the object of the present invention, more preferably 1 to 30%.
%, More preferably 3 to 15%. Within such a range, an image having excellent color development can be stably obtained regardless of the type of paper, and the storage stability and ejection stability of the liquid composition are particularly excellent.

(Acid) As described above, the liquid composition of the present invention preferably contains an acid and has a pH adjusted to 2 to 7. Is to ionize the surface of the cationic fine particles to increase the surface potential, thereby improving the dispersion stability of the fine particles in the liquid, improving the adsorptivity of the anionic compound (anionic coloring material) in the ink, and It plays a role in adjusting the viscosity of the composition.
The acid suitably used in the present invention is not particularly limited as long as the desired physical properties such as pH, zeta potential or fine particle dispersibility can be obtained in combination with the cationic fine particles to be used. It can be freely selected from organic acids and the like.

Specifically, examples of the inorganic acid include hydrochloric acid, sulfuric acid, sulfurous acid, nitric acid, nitrous acid, phosphoric acid, boric acid, and carbonic acid, and examples of the organic acid include carboxylic acids such as those described below. And sulfonic acids, amino acids and the like.

Examples of the carboxylic acid include formic acid, acetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, fluoroacetic acid, trimethylacetic acid, methoxyacetic acid, mercaptoacetic acid, glycolic acid, propionic acid, butyric acid, valeric acid, caproic acid and caprylic acid. Acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid,
Linoleic acid, linolenic acid, cyclohexanecarboxylic acid,
Phenylacetic acid, benzoic acid, o-toluic acid, m-toluic acid, p-toluic acid, o-chlorobenzoic acid, m-chlorobenzoic acid, p-chlorobenzoic acid, o-bromobenzoic acid, m-bromobenzoic acid , P-bromobenzoic acid, o-nitrobenzoic acid, m-nitrobenzoic acid, p-nitrobenzoic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, tartaric acid, maleic acid, fumaric acid, citric acid , Phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, p
-Hydroxybenzoic acid, anthranilic acid, m-aminobenzoic acid, p-aminobenzoic acid, o-methoxybenzoic acid,
m-methoxybenzoic acid, p-methoxybenzoic acid and the like.

Examples of the sulfonic acid include benzenesulfonic acid, methylbenzenesulfonic acid, ethylbenzenesulfonic acid, dodecylbenzenesulfonic acid,
4,6-trimethylbenzenesulfonic acid, 2,4-dimethylbenzenesulfonic acid, 5-sulfosalicylic acid, 1-
Sulfonaphthalene, 2-sulfonaphthalene, hexanesulfonic acid, octanesulfonic acid, dodecanesulfonic acid and the like can be mentioned.

The amino acids include glycine, alanine, valine, α-aminobutyric acid, γ-aminobutyric acid, and β-aminobutyric acid.
Alanine, taurine, serine, ε-amino-n-caproic acid, leucine, norleucine, phenylalanine and the like.

Then, in the liquid composition of the present invention,
These can be used alone or in combination of two or more. Among them, the primary dissociation constant pka of acid in water
Is 5 or less, which is particularly excellent in dispersion stability of the cationic fine particles and adsorptivity of the anionic compound, and thus can be suitably used. Specific examples include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, acetic acid, formic acid, oxalic acid, lactic acid, citric acid, maleic acid, and malonic acid.

In the liquid composition of the present invention, the mixing ratio of the cationic fine particles (A) and the acid (B) in the liquid composition is A: B = 200: 1 to 5: 1 on a weight basis, more preferably It is preferable that the ratio be in the range of 150: 1 to 8: 1 in order to improve the dispersion stability of the cationic fine particles and the adsorbability of the anionic compound to the surface of the fine particles.

(Other components) Next, other components constituting the cationic liquid composition will be specifically described. The cationic liquid composition of the present invention contains the above-mentioned cationic fine particles as an essential component, preferably contains the above-described acid, and, in addition, usually contains water as a liquid medium, and further contains a water-soluble organic solvent. And other additives.

The water-soluble organic solvent used in this case includes, for example, amides such as dimethylformamide and dimethylacetamide, ketones such as acetone, ethers such as tetrahydrofuran and dioxane, and polyalkylenes such as polyethylene glycol and polypropylene glycol. Glycols, ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, alkylene glycols such as diethylene glycol, ethylene glycol methyl ether, diethylene glycol monomethyl ether, triethylene glycol Lower alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl ether, ethanol, isopropyl alcohol, n Butyl alcohol, other monohydric alcohols such as isobutyl alcohol, glycerin, N
-Methyl-2-pyrrolidone, 1,3-dimethyl-imidazolidinone, triethanolamine, sulfolane, dimethyl sulfoxide and the like. The content of the water-soluble organic solvent is not particularly limited, but is preferably, for example, 5 to 60%, more preferably 5 to 40% of the total weight of the liquid composition.

The liquid composition of the present invention may further contain a viscosity adjuster, a pH adjuster, a preservative,
Additives such as various surfactants, antioxidants and evaporation promoters, water-soluble cationic compounds and binder resins may be appropriately blended. The selection of the surfactant is particularly important in adjusting the permeability of the liquid composition into the recording medium. The water-soluble cationic compound can be freely selected and added within a range that does not inhibit the effects of the present invention, for the purpose of further imparting cationicity to the liquid composition.

The binder resin can be used together with the binder resin for the purpose of further improving the scratch resistance of the cationic fine particles as long as the texture of the recording medium and the storage stability and ejection stability of the liquid composition are not impaired. For example, a water-soluble polymer, an emulsion, a latex or the like can be freely selected and used.

(Surface tension of liquid composition) The liquid composition of the present invention is more preferably colorless or white.
Toning may be performed in accordance with the color of the recording medium. Further, as a preferable range of various physical properties of the liquid composition as described above, the surface tension is 10 to 60 mN / m (dyn / cm),
More preferably, the viscosity is 10 to 40 mN / m (dyn / cm), and the viscosity is 1 to 30 mPa · s (cP).

[Anionic Liquid Composition] The liquid composition applicable in the present invention is not limited to the above-mentioned cationic liquid composition, but an anionic liquid composition is also applicable. The anionic liquid composition of the present invention is characterized in that fine particles having an anionic group on the surface are essential constituents, and the fine particles are stably dispersed. Adjusted to 7-12,
Those having a zeta potential of -5 to -90 mV are preferred.

(Regarding pH and Zeta Potential) As a result of extensive studies by the present inventors, the zeta potential of the liquid composition was -5.
Those having a range of -90 mV find that the cationic compound (cationic coloring material) in the ink is particularly efficiently adsorbed on the surface of the anionic fine particles, and exhibits particularly excellent color-forming properties on the recording medium. Was. The reason is not clear, but probably similar to the case of the cationic liquid composition described earlier, because of the moderate anionicity of the fine particles, the rapid aggregation of the cationic compound in the ink does not occur, It is considered that the coloring material does not form a huge lake by adsorbing thinly and uniformly on the surface of the fine particles, so that the original coloring characteristics of the coloring material are better exhibited. Further, in the anionic liquid composition of the present invention, the dispersion becomes unstable after the cationic compound is adsorbed on the surface of the fine particles, and the fine particles are aggregated due to a change in concentration when the solvent component penetrates on the recording medium, and the surface of the fine particles aggregates. It is thought that it is likely to remain in the vicinity.

As a result, it is considered that the following excellent effects can be obtained. That is, in the image area where the amount of applied ink is large, such as a shadow portion and a solid portion, there is little white haze and color unevenness, and the color uniformity is excellent. In addition, the cationic compound is adsorbed to the surface of the fine particles very efficiently as compared with the coated paper, and the color is formed, so that the amount of the anionic fine particles can be reduced. Scratch resistance of the printed portion is also improved. A more preferred range of the zeta potential is, for example, a zeta potential of -10.
When a liquid composition containing anionic fine particles in the range of -85 mV is used, boundaries between dots become less noticeable when solid printing is performed, and further reduction of uneven streaks due to head scanning can be achieved. Further, using a liquid composition containing anionic fine particles having a zeta potential in the range of -15 to -65 mV, regardless of the paper type,
It is possible to obtain an image having extremely excellent coloring properties.

PH of anionic liquid composition of the present invention
Is preferably in the range of 7 to 12 at around 25 ° C. from the viewpoints of storage stability and adsorptivity of the cationic compound. Within this pH range, the stability of the cationic compound does not significantly decrease when mixed with the cationic ink, so that strong aggregation of the cationic compounds does not occur, and the saturation of the recorded image is reduced. Can be effectively prevented from dropping or becoming a dull image.
Further, when the content is in the above range, the dispersibility of the anionic fine particles is good, so that the storage stability of the liquid composition and the stability of ejection from the recording head can be maintained satisfactorily. Furthermore, when mixed with the ink, the cationic substance is sufficiently adsorbed on the surface of the anionic fine particles to suppress excessive penetration of the coloring material into the inside of the recording medium. Can be The more preferable pH range of the liquid composition is from 8 to 11. When the pH is within this range, corrosion of the recording head due to long-term storage can be extremely effectively prevented, and the scratch resistance of the printing portion is further improved. improves.

(Anionic Fine Particles) Next, the components constituting the anionic liquid composition of the present invention will be described. In order to achieve the above-mentioned effects, the anionic fine particles mentioned as the first component preferably have an anionic surface when dispersed in the liquid composition. When mixed with a cationic ink by making the surface anionic, the cationic coloring material can be adsorbed on the particle surface, and the coloring material is suppressed from excessively penetrating into the recording medium. An ink jet recorded matter having an image density can be obtained. On the other hand, when the surface of the fine particles is not anionic and is present separately from the water-soluble anionic compound in the liquid composition, the coloring material causes aggregation around the anionic compound, Since the coloring properties of the coloring material itself are impaired, it is difficult to achieve coloring properties comparable to ink-jet coated paper. Therefore, the fine particles used in the liquid composition of the present invention,
It is necessary that the surface is anionically charged,
Not only fine particles that are essentially anionic, but also fine particles that are originally cationic or neutral electrostatically can be used as long as the fine particles have a surface anionized by the treatment.

The anionic fine particles suitably used in the present invention are sufficient to achieve the object of the present invention as long as the fine particles formed on the recording medium have pores formed in the aggregate. For this reason, the material type of the fine particles is not particularly limited. If a specific example is given as an example, for example, anionized, silica, titania, zirconia, boria, silica boria, ceria, magnesia, silica magnesia, calcium carbonate, magnesium carbonate, zinc oxide and the like, and composite fine particles and organic fine particles thereof, Inorganic-organic composite fine particles are exemplified. And in the liquid composition of the present invention, these can be used alone or in combination of two or more.

The anionic fine particles used in the present invention are, like the cationic fine particles described above, dynamic in view of the color development, uniformity of color and storage stability of the ink after printing. Those having an average particle diameter of 0.005 to 1 μm measured by a light scattering method are suitable. More preferably, the average particle diameter is in the range of 0.01 to 0.8 μm. When such fine particles are used, the abrasion resistance and texture after printing on a recording medium are particularly preferable. More preferably, the average particle diameter is from 0.03 to 0.1.
Such fine particles are preferred because such fine particles are easy to form effectively in the target pore radius region in the fine pores of the fine particle aggregate formed on the recording medium.

(Physical Properties and Shape of Pore of Anionic Fine Particles) The anionic fine particles as described above used in the present invention can efficiently form fine particles of fine particle aggregates formed on a recording medium. At the same time, in order to efficiently adsorb the coloring material on the surface of the fine particles themselves, the fine particles having a maximum pore radius of 2 nm to 12 nm and a total pore volume of 0.3 ml / g or more in the nitrogen adsorption / desorption method are sometimes used. preferable. More preferably, the maximum pore radius of the fine particles is 3 nm to 10 nm.
It is preferable that the total pore volume is 0.3 ml / g or more because the pores of the fine particle aggregate formed on the recording medium are easily formed effectively in the target pore radius region.

When the BET specific surface area of the fine particles used in the present invention is in the range of 70 to 300 m 2 / g, the coloring material can be more effectively used in a monomolecular state due to sufficient adsorption of the coloring material on the surface of the fine particles. Therefore, it is easy to remain near the surface of the recording medium, which contributes to the improvement of the coloring property.

The shape of the fine particles used in the present invention is as follows.
Fine particles can be dispersed in ion-exchanged water and dropped on a collodion membrane to prepare a measurement sample, which can be determined by observation with a transmission electron microscope. In the present invention, the primary particles having a needle-like, plate-like, or spherical primary particle shape have a certain direction in that pores are formed in the aggregate when the fine-particle aggregate is formed on the recording medium. A non-spherical shape such as a rod-like or necklace-like shape that forms secondary particles connected together can be suitably used. According to the findings of the present inventors, the flat shape has better dispersibility in water than the needle shape, and the pore volume is small because the orientation of the fine particles becomes random when the fine particle aggregate is formed. It is more preferable because it becomes larger.

The content of the above-mentioned anionic fine particles in the liquid composition depends on the kind of the substance to be used.
The optimum range may be determined as appropriate, but is preferably 0.
The range of 1 to 40% by weight is a preferable range for achieving the object of the present invention, more preferably 1 to 30% by weight, and further preferably 3 to 15% by weight. Within such a range, an image with excellent color development can be stably obtained regardless of the type of paper, and the storage stability and ejection stability of the liquid composition are particularly excellent.

(Base) As described above, the anionic liquid composition of the present invention preferably contains a base and is adjusted to have a pH of 7 to 12. Base ionizes the anionic fine particle surface,
By increasing the surface potential, the dispersion stability in the liquid is improved, and at the same time, the function of improving the adsorptivity of the cationic compound (cationic colorant) in the ink and adjusting the viscosity of the liquid composition is achieved. The base suitably used in the present invention is not particularly limited as long as physical properties such as desired pH, zeta potential and fine particle dispersibility can be obtained when combined with the anionic fine particles to be used. It can be used by freely selecting from various inorganic compounds and organic compounds.

Specifically, for example, sodium hydroxide,
Lithium hydroxide, sodium carbonate, ammonium carbonate,
Ammonia, sodium acetate, ammonium acetate, morpholine, monoethanolamine, diethanolamine,
Triethanolamine, ethyl monoethanolamine,
Alkanolamines such as normal butyl monoethanolamine, dimethylethanolamine, diethylethanolamine, ethyldiethanolamine, normal butyldiethanolamine, dinormalbutylethanolamine, monoisopropanolamine, diisopropanolamine, and triisopropanolamine can be used. Among these, particularly, a base having a primary dissociation constant pkb of 5 or less in water is preferably used because it is particularly excellent in dispersion stability of anionic fine particles and adsorptivity of a cationic compound (cationic coloring material). .

The mixing ratio of the anionic fine particles (A) and the base (B) in the liquid composition of the present invention is based on weight: B =
200: 1 to 5: 1, more preferably 150: 1 to 8:
If it is in the range of 1, the dispersion stability of the anionic fine particles,
It is preferable because the adsorption of the cationic compound on the surface of the fine particles is excellent.

(Other Components) Next, other components constituting the anionic liquid composition will be specifically described. The anionic liquid composition of the present invention contains the above-described anionic fine particles as an essential component, preferably contains the above-described base, and, in addition, usually contains water as a liquid medium, and further contains a water-soluble organic solvent. And other additives, for example, a viscosity adjuster, a pH adjuster, a preservative, various surfactants, an antioxidant, an evaporation promoter, a water-soluble anionic compound and a binder resin or the like. I don't care.

(Surface tension of liquid composition) The anionic liquid composition of the present invention is more preferably colorless or white, but may be toned in accordance with the color of the recording medium. Further, as a preferable range of various physical properties of the liquid composition as described above, the surface tension is set to 10 to 60 mN / m (dyn /
cm), more preferably 10 to 40 mN / m (dyn /
cm) and a viscosity of 1 to 30 mPa · s (cP).

(Method for Producing Liquid Composition) As a method for producing the liquid composition of the present invention containing the fine particles, any one of methods generally used for dispersion and the like can be used. Specifically, a dispersing machine such as a roll mill, a sand mill, a homogenizer, an ultrasonic homogenizer, an ultrahigh-pressure emulsifier (eg, Nanomizer, etc.) in order to make the average particle size and particle size distribution of the fine particles in the liquid composition fall within the above ranges. Dispersion treatment using, or classification treatment by centrifugation, ultrafiltration, or the like is suitably used, and the dispersion means of the fine particles in the liquid composition can be made uniform by these treatment means.

<Aqueous Ink> [Anionic Ink] Next, an aqueous anionic ink constituting the ink set of the present invention in combination with the cationic liquid composition described above will be described. Here, the ink set refers to a combination of the liquid composition of the present invention and at least one or more anionic inks containing an anionic substance (anionic colorant). Further, a combination of at least one type of ink obtained by removing the liquid composition of the present invention from this ink set is referred to as an ink subset. The anionic ink used in the present invention uses a water-soluble dye containing an anionic group as a coloring material or, in the case where a pigment is used as a coloring material, a combination of an anionic compound (also in the present invention). (Referred to as an anionic coloring material). The anionic ink as described above used in the present invention further includes water, a water-soluble organic solvent and other components such as a viscosity adjuster, a pH adjuster, a preservative, a surfactant, and an antioxidant. An agent and the like are included as necessary. Hereinafter, each component of these inks will be described.

(Water-soluble dye) Examples of the water-soluble dye having an anionic group used in the present invention include water-soluble acid dyes, direct dyes, and reactive dyes described in Color Index. There is no particular limitation as long as it exists. Also, even those not listed in the color index,
There is no particular limitation as long as it has an anionic group such as a sulfone group and a carboxyl group. The water-soluble dyes mentioned here include those having a pH dependence of solubility.

(Pigment) As another form of the aqueous anionic ink, a pigment and an anionic compound are used in place of the water-soluble dye having an anionic group as described above.
The ink may include water, a water-soluble organic solvent, and other components such as a viscosity adjuster, a pH adjuster, a preservative, a surfactant, and an antioxidant, if necessary. Here, the anionic compound may be a dispersant for the pigment, or when the dispersant for the pigment is not anionic, an anionic compound other than the dispersant may be added. Of course, even when the dispersant is an anionic compound, the dispersant may further contain another anionic compound.

The pigment that can be used in the present invention is not particularly limited. For example, the following pigments can be suitably used.

First, the carbon black used in the black pigment ink is a carbon black produced by a furnace method or a channel method and has a primary particle size of 15 to 40.
m μm, specific surface area by BET method is 50 to 300 m 2 /
g, DBP oil absorption of 40 to 150 ml / 100 g, volatile matter of 0.5 to 10% by weight, and pH of 2 to 9 are preferable.

For example, No. 1
2300, no. 900, MCF88, No. 40, N
o. 52, MA7, MA8, No. 2200B (or more,
Mitsubishi Kasei), RAVEN1255 (Colombia), REGAL
400R, REGAL660R, MOGUL L (above, made by Cabot), Color Black FW1, Color Black FW18, Color
Black S170, Color Black S150, Printex 35,
Commercial products such as Printex U (all manufactured by Degussa) can be used. Further, a prototype newly manufactured for the present invention may be used.

Examples of the pigment used in the yellow ink include CI Pigment Yellow 1 and CI Pigment Yel.
low 2, CI Pigment Yellow 3, CI Pigment Yellow
13, CI Pigment Yellow 16, CI Pigment Yellow
83 and the like.

Examples of the pigment used as the magenta ink include CI Pigment Red 5 and CI Pigment Red.
7, CI Pigment Red 12, CI Pigment Red 48 (C
a), CI Pigment Red 48 (Mn), CI Pigment Red
57 (Ca), CI Pigment Red 112, CI Pigment Re
d 122 and the like.

Examples of the pigment used as the cyan ink include CI Pigment Blue 1 and CI Pigment Blue.
2, CI Pigment Blue 3, CI Pigment Blue 15:
3, CI Pigment Blue 16, CI Pigment Blue 22,
CIVat Blue 4, CIVat Blue 6, and the like.

[0119] Regarding the color materials of any of the above colors,
Newly manufactured ones for the present invention can also be used.

(Pigment Dispersant) As a pigment dispersant that can be used in the ink used in the present invention, a water-soluble dispersant having a function of stably dispersing the pigment in water or an aqueous medium due to the presence of an anionic group. Any resin can be used. In particular, the weight average molecular weight is 1,000
Those having a range of up to 30,000 are preferred. More preferably, it is in the range of 3,000 to 15,000. Specifically, for example, hydrophobic monomers such as styrene, styrene derivatives, vinyl naphthalene, vinyl naphthalene derivatives, aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, or acrylic acid, acrylic acid derivatives, Maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, block copolymers, graft copolymers or random copolymers of two or more monomers selected from fumaric acid and fumaric acid derivatives, or these And the like. These resins are alkali-soluble resins that are soluble in an aqueous solution in which a base is dissolved.

Further, a homopolymer comprising a hydrophilic monomer or a salt thereof may be used. Also, polyvinyl alcohol,
Water-soluble resins such as carboxymethylcellulose and condensates of naphthalenesulfonic acid formaldehyde can also be used. However, when an alkali-soluble resin is used, there is an advantage that the viscosity of the dispersion can be reduced and the dispersion is easy. The water-soluble resin is preferably used in the range of 0.1 to 5% by weight based on the total amount of the ink.

The pigment ink which can be used in the present invention is constituted by dispersing or dissolving the pigment and the water-soluble resin as described above in a water-soluble medium. An aqueous medium suitable for the pigment-based ink that can be used in the present invention is a mixed solvent of water and a water-soluble organic solvent. ) Are preferably used.

When the dispersant is not an anionic polymer, it is preferable to further add an anionic compound to the ink containing the pigment described above. Examples of the anionic compound suitably used in the present invention include, in addition to the high-molecular substances such as the alkali-soluble resins described in the section of the pigment dispersant, low-molecular-weight anionic surfactants as described below. it can.

Specific examples of the low molecular weight anionic surfactant include, for example, disodium lauryl sulfosuccinate, disodium polyoxyethylene lauroylethanolamide ester sulfosuccinate, disodium polyoxyethylene alkyl sulfosuccinate, carboxylation Polyoxyethylene lauryl ether sodium salt, carboxylated polyoxyethylene tridecyl ether sodium salt, polyoxyethylene lauryl ether sodium sulfate, polyoxyethylene lauryl ether triethanolamine sulfate, polyoxyethylene alkyl ether sodium sulfate, sodium alkyl sulfate, alkyl Examples include, but are not limited to, triethanolamine sulfate. The preferred amount of the anionic substance as described above is in the range of 0.05 to 10% by weight, and more preferably 0.05 to 5% by weight, based on the total amount of the ink.

(Self-dispersing Pigment) As a pigment that can be used in anionic ink, a self-dispersing pigment that can be dispersed in water or an aqueous medium without using a dispersant can also be used. . The self-dispersion type pigment has at least one kind of anionic hydrophilic group bonded directly or via another atomic group to the pigment surface. Examples of the anionic hydrophilic group include, for example, at least one kind selected from the following hydrophilic groups, and further another atomic group is an alkyl group having 1 to 12 carbon atoms, a substituent. And a phenyl group optionally having a substituent or a naphthyl group optionally having a substituent.

-COOM, -SO3M, -SO2NH
2, -PO3HM, -PO3M2 (M in the above formula represents a hydrogen atom, an alkali metal, ammonium, or an organic ammonium.) The pigment thus anionically charged by introducing a hydrophilic group to the pigment surface Has excellent water dispersibility due to the repulsion of ions, and thus maintains a stable dispersion state even when added to an aqueous ink without adding a dispersant or the like. It is particularly preferable when the pigment is carbon black.

(Additional Components in Ink) In addition to the above components, a surfactant, an antifoaming agent, a preservative, or the like may be added to the ink in order to obtain an ink having desired physical properties as required. And a commercially available water-soluble dye or the like can be further added.

Examples of the surfactant include anionic surfactants such as fatty acid salts, higher alcohol sulfates, liquid fatty oil sulfates, alkyl allyl sulfonates, polyoxyethylene alkyl ethers, and polyoxyethylene alkyl esters. , Polyoxyethylene sorbitan alkyl esters, acetylene alcohol, acetylene glycol, and other nonionic surfactants, and one or more of these can be appropriately selected and used. The amount used depends on the amount of the dispersant added,
Desirably, the content is 0.01 to 5% by weight based on the total amount of the ink.
At this time, the surface tension of the ink is 30 mN / m (dyn / c
It is preferable to determine the amount of the activator to be added so as to satisfy m) or more. This is because, in the ink jet recording method used in the present invention, the occurrence of printing distortion (deviation of the impact point of the ink droplet) due to the wetting of the nozzle tip can be effectively suppressed.

As a method for preparing a pigment-based ink as described above, first, a pigment is added to an aqueous solution containing at least a pigment-dispersing resin and water, and the mixture is stirred.
Dispersion is performed using a dispersing means described later, and centrifugation is performed as needed to obtain a desired dispersion. Next, the above-mentioned components are further added to the dispersion and stirred to form an ink.

When an alkali-soluble resin is used, it is necessary to add a base to dissolve the resin. At this time, the amount of the amine or the base for dissolving the resin must be at least one time the amount of the amine or the base obtained by calculation from the acid value of the resin. The amount of the amine or the base can be calculated by the following equation.

[0131]

(Equation 1)

If premixing is carried out for 30 minutes or more before the aqueous solution containing the pigment is subjected to the dispersion treatment, the dispersion efficiency of the pigment is improved. This premixing operation improves the wettability of the pigment surface and promotes the adsorption of the dispersant on the pigment surface.

The bases added to the dispersion when the alkali-soluble resin is used include, for example, organic amines such as monoethanolamine, diethanolamine, triethanolamine, amine methylpropanol and ammonia, potassium hydroxide, and the like. It is preferable to use an inorganic base such as sodium hydroxide.

On the other hand, the dispersing machine used for preparing the pigment ink may be any commonly used dispersing machine, and examples thereof include a ball mill and a sand mill.
Among them, a high-speed sand mill is preferable, for example,
Examples thereof include a super mill, a sand grinder, a bead mill, an agitator mill, a Glen mill, a dyno mill, a pearl mill, a Kobol mill (all trade names) and the like.

The ink used in the present invention may contain, if necessary, a water-soluble organic solvent, a surfactant,
Additives such as an H preparation agent, a rust inhibitor, a fungicide, an antioxidant, an evaporation promoter, a chelating agent, and a water-soluble polymer may be added.

The liquid medium for dissolving or dispersing the coloring material which can be used in the present invention is preferably a mixture of water and a water-soluble organic solvent. Specific water-soluble organic solvents, for example, methyl alcohol, ethyl alcohol,
n-propyl alcohol, isopropyl alcohol, n
-Butyl alcohol, sec-butyl alcohol, te
C 1-4 alkyl alcohols such as rt-butyl alcohol; amides such as dimethylformamide and dimethylacetamide; ketones such as acetone; ethers such as tetrahydrofuran and dioxane; Alkylene groups such as alkylene glycols, ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol and diethylene glycol contain 2 to 6 carbon atoms Lower alkyl ethers of polyhydric alcohols such as alkylene glycols, glycerin, ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether S, N- methyl-2-pyrrolidone,
1,3-dimethyl-2-imidazolidinone, sulfolane, dimethyl sulfoxide, 2-pyrrolidone, ε
And cyclic amide compounds such as caprolactam and imide compounds such as succinimide.

In general, the content of the water-soluble organic solvent is preferably from 1% to 40% by weight, more preferably from 3% to 30% by weight based on the total weight of the ink. Further, when the content of water in the ink is in the range of 30 to 95% by weight, the solubility of the coloring material is good, the increase in the viscosity of the ink can be suppressed, and the fixing property is sufficient. Can be satisfied.

Although the anionic ink used in the present invention can be used as a general aqueous writing instrument, it is particularly suitable when applied to an ink jet recording method of a type in which the ink is ejected by the bubbling phenomenon of the ink by thermal energy. It is characterized in that the ejection becomes extremely stable and no satellite dots are generated. However, in this case, the thermal properties (for example, specific heat, thermal expansion coefficient, and thermal conductivity) may be adjusted.

[Cationic Ink] Next, the aqueous cationic ink constituting the ink set of the present invention in combination with the anionic liquid composition described above will be described. Here, the ink set refers to a combination of the liquid composition of the present invention and at least one or more inks containing a cationic substance (cationic colorant). Also, a combination of at least one or more inks excluding the liquid composition of the present invention from this ink set is called an ink subset. In the cationic ink used in the present invention, a water-soluble dye containing a cationic group is used as a coloring material, or when a pigment is used as a coloring material, a cationic compound is used in combination. The combination is also referred to as a cationic coloring material). The ink as described above used in the present invention further includes water, a water-soluble organic solvent and other components such as a viscosity modifier,
An adjuster, a preservative, a surfactant, an antioxidant and the like are included as necessary. Hereinafter, each component of these inks will be described.

(Water-soluble dye) The water-soluble dye having a cationic group used in the present invention is not particularly limited as long as it is a water-soluble dye described in, for example, Color Index. In addition, there is no particular limitation on those not described in the color index as long as they have a cationic group. The water-soluble dyes mentioned here include those having a pH dependency of solubility.

(Pigment) As another form of the ink used in the present invention, a pigment and a cationic compound are used in place of the above-mentioned water-soluble dye having a cationic group, and water, a water-soluble organic solvent and other Components, such as viscosity modifiers,
The ink may include a pH adjuster, a preservative, a surfactant, an antioxidant, and the like as necessary. Here, the cationic compound may be a dispersant for the pigment, or if the dispersant for the pigment is not cationic, a cationic compound other than the dispersant may be added. Of course, even when the dispersant is a cationic compound, another cationic compound may be further added. The pigment that can be used in the present invention is not particularly limited, and the pigment described in the section of the anionic ink can be suitably used.

(Pigment Dispersant) The pigment dispersant in the ink used in the present invention may be any water-soluble resin having a function of stably dispersing the pigment in water or an aqueous medium due to the presence of a cationic group. Can be used. As a specific example, what is necessary is just what is obtained by superposition | polymerization of a vinyl monomer, and at least one part of the obtained polymer has cationic property. Examples of the cationic monomer for constituting the cationic moiety include salts of the following tertiary amine monomers and quaternized compounds thereof. N, N-dimethylaminoethyl methacrylate [CH2 = C (CH3) -COO-C2H4N (CH3)
2], N, N-dimethylaminoethyl acrylate [CH2 = CH-COO-C2H4N (CH3) 2], N, N-dimethylaminopropyl methacrylate [CH2 = C (CH3) -COO-C3H6N (CH3) 2], N, N-dimethylaminopropyl acrylate [CH2 = CH-COO-C3H6N (CH3) 2], N, N-dimethylacrylamide [CH2 = CH-CON (CH3) 2], N, N-dimethylmethacrylamide [CH2 = C (CH3) -CON (CH3) 2], N, N-dimethylaminoethylacrylamide [CH2 = CH-CONHC2H4N (CH3) 2], N, N-dimethylaminoethylmethacrylamide [CH2 = C (CH3) -CONHC2H4N (CH3)
2], N, N-dimethylaminopropylacrylamide [CH2 = CH-CONH-C3H6N (CH3) 2], N, N-dimethylaminopropylmethacrylamide [CH2 = C (CH3) -CONH-C3H6N (CH3)
2]

In the case of tertiary amines, compounds for forming salts include hydrochloric acid, sulfuric acid and acetic acid, and compounds used for quaternization include methyl chloride, dimethyl sulfate, benzyl chloride, and the like. Epichlorohydrin and the like. Among them, methyl chloride, dimethyl sulfate and the like are preferable in preparing the dispersant used in the present invention. The tertiary amine salt or the quaternary ammonium compound as described above behaves as a cation in water, and under neutralized conditions, acidity is a stable dissolution region.
The content of these monomers in the copolymer is preferably in the range of 20 to 60% by weight.

Examples of other monomers used in the constitution of the polymer dispersant include 2-hydroxyethyl methacrylate, acrylic acid esters having a hydroxy group such as acrylic acid esters having a long ethylene oxide chain in the side chain, and styrene. Examples of hydrophobic monomers such as series monomers and water-soluble monomers soluble in water near pH 7 include acrylamides, vinyl ethers, vinylpyrrolidones, vinylpyridines, and vinyloxazolines. As the hydrophobic monomer, a hydrophobic monomer such as styrene, a styrene derivative, vinyl naphthalene, a vinyl naphthalene derivative, an alkyl ester of (meth) acrylic acid, or acrylonitrile is used. In the polymer dispersant obtained by copolymerization, a water-soluble monomer is used in order to make the copolymer stably exist in an aqueous solution.
The hydrophobic monomer is used in an amount of 20 to 4% by weight in order to enhance the dispersing effect of the copolymer on the pigment.
It is preferable to use it in the range of 0% by weight.

(Self-dispersing Pigment) In the case of a cationically charged pigment, at least one hydrophilic group bonded directly or via another atomic group is selected from the following quaternary ammonium groups. Are combined. However, the present invention is not limited to these.

[0146]

Embedded image

In the above formula, R represents 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. In addition, in the above-mentioned cationic group, for example, NO3- and CH3COO- exist as counter ions.

As a method for producing a cationically-charged self-dispersion pigment having a hydrophilic group bonded thereto as described above, for example, a method of bonding an N-ethylpyridyl group having the following structure is exemplified. To explain, 3
-Amino-N-ethylpyridinium bromide.

[0149]

Embedded image

The pigment charged cationically by the introduction of a hydrophilic group on the surface of the pigment has excellent water dispersibility due to repulsion of ions. Therefore, even when the pigment is contained in an aqueous ink, the dispersing agent can be used. A stable dispersion state is maintained without adding any of these. In particular, it is preferable that the pigment is carbon black.

(Surface Tension of Ink) Further, the cationic ink used in the present invention has the following properties in order to improve the ink permeability of the printed matter recorded on plain paper or the like and the good matching with the ink jet head. As the physical properties of the ink itself, a surface tension at 25 ° C. of 30 to 68 mN
/ M (dyn / cm), viscosity 15 mPa · s (cP)
The pressure is preferably adjusted to 10 mPa · s (cP) or less, more preferably 5 mPa · s (cP) or less.

<Concentration of Aqueous Ink> The mass concentration of the coloring material component contained in the above-mentioned anionic and cationic inks is appropriately selected according to the repair of the coloring material such as aqueous dyes, pigments and self-dispersible pigments. However, with respect to the mass of the ink, 0.
The range is preferably from 1 to 20% by mass, particularly preferably from 0.1 to 12% by mass.

When the mass concentration of the coloring material component is in the range of 0.3 to 7% by mass, the relationship between the concentration of the fine particles in the liquid composition and the concentration of the coloring material in the ink is determined on a mass basis. When the color material is 1.2 or less, particularly 1.0 or less with respect to 1, the coloring property of an image formed under ordinary two-liquid recording conditions becomes particularly excellent.

<Inkjet Recording Apparatus> FIG. 4 is a perspective view showing a schematic configuration of an inkjet printer as an example of an inkjet recording apparatus to which the present invention can be applied.

The printer of this embodiment has a carriage 2, on which a recording head 1s for discharging the liquid composition s, a recording head 1k for discharging the black ink k, and a recording head 1c for discharging the cyan ink c. , A recording head 1 m for ejecting magenta ink m, and a recording head 1 y for ejecting yellow ink y. Further, the printer transmits an electric signal from the printer body to the recording head 1.
It has a flexible cable 3 for sending to s, 1k, 1c, 1m and 1y, a cap unit 4 as a recovery mechanism, and a paper feed tray 8 for feeding paper 7 as a recording medium. The cap unit 4 is formed of cap members 5s, 5k, 5c, 5m, and 5y corresponding to the recording heads 1s, 1k, 1c, 1m, and 1y, and members such as rubber, and the recording heads 1s, 1k, 1c, and 1 are formed.
wiper blades 6s, 6k, 6 corresponding to m, 1y
m, 6y. These wiper blades are provided so as to be able to advance and retreat with respect to the movement path of the recording head. In a normal state, these wiper blades protrude beyond the surfaces of the respective cap members, so that the discharge port surfaces of the corresponding print heads can be wiped as the print head moves. Further, each cap member can cap the recording head by moving with respect to the recording head facing each other.

In the printer having such a configuration, the recording heads 1s, 1k, 1c, 1m, and 1y are serially scanned in a direction (main scanning direction) B orthogonal to the conveying direction (sub-scanning direction) A of the sheet 7. Then, printing is performed with a width corresponding to the number of nozzles described later. Then, while the recording head repeats the main scanning in this way, the paper 7 is conveyed by a feed amount equal to the recording width corresponding to the number of nozzles, thereby sequentially recording on the paper 7. Recording heads 1s, 1k, 1c, 1
Each of m and 1y has 64 nozzles at a density of 360 per inch, and each nozzle ejects about 40 ng of the liquid composition or ink. Therefore, the recording density in the sub-scanning direction is 360 dpi,
Accordingly, the recording density in the main scanning direction is set to be 360 dpi.

FIG. 5 is a block diagram showing the control system of such an ink jet printer.

In FIG. 5, reference numeral 301 denotes a system controller for controlling the entire apparatus. The system controller 301 includes a microprocessor (MPU), a ROM containing a control program, and a ROM for processing by the microprocessor. A RAM or the like used as a work area is provided. The system controller 301 also performs recovery control described later according to a control program. In addition,
Main control of the printer of this embodiment, including this recovery control, may be executed under the control of the host computer 306.

Reference numeral 302 denotes a driver, which is a motor 304 for moving the carriage 2 on which the recording head is mounted.
Drive control. A driver 303 controls driving of a motor 305 for transporting the sheet 7 in the sub-scanning direction.

A host computer 306 transfers recording data and the like to the printer of this embodiment. 307
Is a reception buffer for temporarily storing data from the host computer 306, and accumulates data until the system controller 301 reads the data. 308 (308k, 308c, 308m, 308
y) is a frame memory provided for each ink color (k, c, m, y) in order to develop print data into image data, and has a memory size necessary for printing. ing. Frame memory 308 of this example
(308k, 308c, 308m, 308y) have a memory size capable of recording print data for one sheet. The present invention is, of course, not limited to the size of the frame memory 308. 309 (309
k, 309c, 309m, 309y) are buffers for temporarily storing print data for one scan of the print head, and are provided for each ink color (k, c, m, y). . The buffer 309 stores one scan of print data created by subjecting print data received from the host computer 306 to processing such as color conversion and density correction and binarization processing. Along with the generation of the recording data, based on the recording data, liquid composition ejection data (hereinafter, “liquid composition data”
Is also created. The liquid composition data is stored in the buffer 309s. The rules for creating the liquid composition data include, for example, ink color (y,
m, c, k) corresponding to each of the recording data,
When each data is "1" (discharge), a rule that the liquid composition data is also "1" (discharge) can be adopted.

Reference numeral 310 denotes a print control unit for controlling the print head under the control of the system controller 301. That is, the recording control unit 310 controls the recording speed, the number of recording data, and the like, and also creates data for discharging the liquid composition as described above. The print control unit 310 also counts a print duty of an image printed by one scan of the print head. Reference numeral 311 denotes a driver, which is a recording head 1s for discharging the liquid composition s,
Then, the recording heads 1y, 1m, 1c and 1k for ejecting the respective inks y, m, c and k are driven. The driver 311 is controlled by a control signal from the recording control unit 310.

In the above arrangement, the image data transferred from the host computer 306 is
7 is temporarily stored. The stored image data is read by the system controller 301,
After the above processing is performed, the buffer 309
Will be expanded to. Then, the recording control unit 310 controls the operation of the recording head based on the recording data in the buffer 309 and the data for the liquid composition.

Next, an example of preparing a liquid composition will be described.

After the following components were mixed and dissolved, the mixture was filtered under pressure through a membrane filter having a pore size of 1 μm (trade name, Fluoropore Filter, manufactured by Sumitomo Electric Industries, Ltd.) to obtain a liquid composition.

<Composition of liquid composition> Glycerin 10.0 parts by weight Diethylene glycol 7.5 parts by weight Alumina hydrate slurry A 50.0 parts by weight Water 32.5 parts by weight Emulsifying and dispersing the above components TK Robomix (Special Machinery Industries
The mixture was mixed at 3,000 rpm for 30 minutes using a centrifugal separator (4000 rpm, 15 minutes) to remove coarse particles to obtain a liquid composition. Alumina hydrate is
It could be synthesized as follows.

(Synthesis Example of Alumina Hydrate) Aluminum dodexide was produced by the method described in US Pat. No. 4,242,271. Next, U.S. Pat.
Aluminum dodoxide was hydrolyzed by the method described in JP-A-02,870 to produce an alumina slurry. The solid content of alumina hydrate is 8.
Water was added to 2%. The pH of the alumina slurry was 9.7. The pH was adjusted by adding a 3.9% nitric acid solution, and a colloidal sol was obtained under the aging conditions shown in Table 1 below.
The pH of the colloidal sol was adjusted with the acids shown in Table 1 below,
The slurry was concentrated to a solid content of 20% to prepare A to D alumina hydrate slurries. The surface of the alumina hydrate in these slurries is positively charged in water and shows cationicity.
Further, these alumina hydrate slurries were diluted and dispersed in ion-exchanged water, and then dropped on a collodion film to prepare a measurement sample. Observation with a transmission electron microscope revealed that the particles were all flat plate-shaped fine particles.

[0167]

[Table 1]

Next, an example of producing a combination of black, yellow, magenta, and cyan inks as an ink subset 1 will be described.

The following components were mixed, sufficiently stirred and dissolved, and filtered under pressure through a Fluoropore filter having a pore size of 0.45 μm (trade name, manufactured by Sumitomo Electric Industries, Ltd.) to obtain black, yellow, Magenta and cyan dye inks Bk1, Y1, M1 and C1 were prepared, and a combination of these dye inks was used as ink subset 1.

[Black Ink Bk1] (pH = 7.0) C.I. I. Direct Black 195 2.5 parts-2-Pyrrolidone 10 parts-Glycerin 5 parts-Isopropyl alcohol 4 parts-Sodium hydroxide 1 part-Ammonium sulfate 0.45 part-Water balance [Yellow ink Y1] (pH = 8.0)-Projet Fast Yellow 2 (Zeneca) 2.0 parts I. Direct Yellow 86 1.0 part ・ Thiodiglycol 8 parts ・ Ethylene glycol 8 parts ・ Acetyleneol EH (manufactured by Kawaken Chemicals) 0.2 part ・ Isopropyl alcohol 4 parts ・ Water remainder [Magenta ink M1] (pH = 8.0)・ Projet Fast Magenta 2 (Zeneca) 3 parts ・ Glycerin 7 parts ・ Urea 7 parts ・ Acetyleneol EH (Kawaken Chemicals) 0.2 parts ・ Isopropyl alcohol 4 parts ・ 10% LiOH 1 part ・ Water remaining [Cyan Ink C1] (pH = 7.5) I. Direct Blue 199 3 parts ・ Ethylene glycol 7 parts ・ Diethylene glycol 10 parts ・ Acetyleneol EH (manufactured by Kawaken Chemicals) 0.3 parts ・ Water remaining

The present invention considers the case where the above-described liquid composition or ink mist adheres to the ejection port surface of the recording head, and minimizes the decrease in recording speed while maintaining the ink and liquid composition accompanying recovery. By executing the recovery processing while minimizing the consumption of the object, it is possible to reduce the ejection failure of the recording head and to secure the reliability of recording for a long time. That is, the greater the number and amount of the recovery operation, the more the liquid composition or ink, or the mixture of the liquid composition and the ink, can be reduced from adhering to the ejection opening surface of the recording head. As the time required for the recovery operation increases, the consumption of the liquid composition and ink used for the recovery operation increases.
Therefore, in the present invention, as will be described later, in order to reduce the adhesion of the liquid composition or the ink, or the mixture of the liquid composition and the ink to the ejection port surface of the recording head, the number and amount of the recovery operation are simply reduced. Instead of increasing the number of recovery operations, the number and amount of the recovery operations are changed according to the possibility that the liquid composition or the ink or the mixture of the liquid composition and the ink adheres to the ejection opening surface.

Next, an embodiment of the recovery processing will be described.

(First Example of Recovery Processing) When the recording head ejects ink and liquid composition, fine mist-like ink and liquid composition are used in addition to the main ink droplet and liquid composition droplet. (Hereinafter referred to as “mist”). This mist is so small that it floats between the recording medium and the recording head without landing on the recording medium. Further, it has been confirmed that this mist also adheres to the face surface of the recording head, that is, the surface on which the discharge port is formed (discharge port surface). On the face surface, the mist of the ink and the mist of the liquid composition are mixed. It has been confirmed that they cause a change such as sticking or the like and cause a discharge failure.

Further, as to the binding between the dye molecules in the ink and the fine particles of the liquid composition as described above, all of the characteristics and the like have not been clarified. But,
The present inventor's research has revealed that the pH greatly contributes to the relationship between the ejection failure and the deposit. FIG. 2 is a diagram showing the zeta potential of the liquid composition (oxide sol) used in this example. The vertical axis in the figure indicates the fluidity of the liquid. As is clear from the figure, the fluidity decreases as the pH value increases. Since the higher the fluidity, the lower the viscosity, and the lower the flowability, the higher the viscosity. From this figure, it can be seen that the viscosity increases (increases) as the pH value increases. Thus, that the change in pH is deeply involved in viscosity, p
It can be seen from FIG. 2 that the viscosity increases (increases) as the value of H increases. Then, as the viscosity increases, the recovery operation such as wiping or wiping for maintaining the ejection reliability of the recording head does not function sufficiently. Therefore, paying attention to the pH of the ink and the liquid composition, It is determined whether or not the mixture has a property of being easily fixed (whether the viscosity of the mixture is high or low). If the viscosity of the mixture is high, the recovery operation is set to be performed frequently. That is, the pH value of the mixture is roughly known by considering the pH of the ink and the pH of the liquid composition. When one type of liquid composition is used, the pH of the liquid composition is a fixed value. Differences in pH are due to differences in viscosity of the mixture. Therefore, focusing only on the pH of the ink, it can be predicted that if the pH of the ink is large, the pH of the mixture will be large and the viscosity will be large.
If the pH is small, it can be predicted that the pH of the mixture will be low and the viscosity will also be low. What is necessary is to set the number of times of the recovery operation of the ink head for discharging the ink to a small value.

In consideration of the above points, in this example, the number of times of ink ejection (hereinafter, also referred to as “dot count”) in each of the ink recording heads 1k, 1c, 1m, and 1y is counted. Further, each of the recording heads 1k, 1c, 1
A threshold corresponding to the pH of the ejected ink is determined for each of m and 1y. Then, the ink recording heads 1k, 1c, 1m,
When any one of the count values of the dot count of 1y (hereinafter, referred to as “dot count value”) exceeds a threshold,
A recovery process is performed on the ink recording head and the liquid composition recording head 1s.

In this example, the threshold value t for black ink, cyan ink, magenta ink, and yellow ink is used.
k, tc, tm, and ty were set as follows. tk = 9504000 tc = 6336000 tm = 6336000 ty = 8448000

The higher the pH, the more easily the viscosity changes when agglomerated.
It is predicted that the larger the difference in H, the more likely the ink is to cause aggregation. Then, with respect to an ink recording head that ejects an ink having a large pH difference with such a liquid composition, the threshold value is set small so that the recovery operation is performed frequently. For example, the above-mentioned liquid composition having a pH of 3.9 and p
When each of the black, yellow, magenta, and cyan dye inks Bk1, Y1, M1, and C1 having H of 7.0, 8.0, 8.0, and 7.5 is used, black ink, cyan ink, The threshold values tk, tc, tm, and ty for the magenta ink and the yellow ink can be set as described above. Then, when the dot count value in any of the ink recording heads exceeds a threshold,
Recovery processing by wiping is performed only on the recording head for ink and the recording head for liquid composition. And
The dot count value in the ink recording head on which the wiping has been performed is initialized.

FIG. 6 is a flowchart for explaining such a recovery process.

In the case of this example, every time one scan of the print head is completed, the print heads 1k, 1c, 1m, 1y for ink are used.
Dot count values ck, cc, cm, cy and threshold value t
k, tc, tm, and ty are compared (step S1,
2, 5, 8, 11). When the dot count value ck of the recording head 1k exceeds the threshold tk, the recording head 1k and the liquid composition recording head 1s are wiped, and then the dot count value ck is cleared (steps S2, S3). 4). When the dot count value cc of the recording head 1c exceeds the threshold value tc, the recording head 1c
After wiping c and the liquid composition recording head 1s, the dot count value cc is cleared (step S).
5, 6, 7). When the dot count value cm of the recording head 1m exceeds the threshold value tm, the recording head 1m
Wiping the liquid composition recording head 1s and
Clear the dot count value cm (step S8,
9, 10). When the dot count value cy of the recording head 1y exceeds the threshold value ty, the recording head 1y and the liquid composition recording head 1s are wiped, and then the dot count value cy is cleared (steps S11 and S1).
2, 13).

By performing the recovery process in this way, it is possible to prevent a certain amount or more of mixed mist from adhering to any of the recording heads. In addition, a decrease in throughput due to wiping can be minimized.

In this example, the recording heads 1k,
The distances dk, dc, dm, and dy between each of the recording heads 1c, 1m, and 1y and the liquid composition recording head 1s are 0.5 inches, 1.0 inches, 1.5 inches, and 2.
0 inches. That is, each print head is arranged as shown in FIG. 1A, and the distances dk, dc, dm, and dy between the discharge ports of each print head in the main scanning direction are set to 0.
5 inches, 1.0 inches, 1.5 inches, and 2.0 inches. In FIG. 1A, 1k, 1c, 1m, 1y
May be used as a discharge unit to form the recording head 1.

As described above, according to the first recovery example, paying attention to the pH of the ink and the pH of the liquid composition, the more the ink head ejects the ink having a higher pH,
On the other hand, the frequency of the recovery operation corresponds to the tendency of the mixture of the ink and the liquid composition to be stuck to the discharge port surface because the frequency of the recovery operation is smaller in the ink head that discharges the ink having a lower pH. As a result, the consumption of the ink and the liquid composition due to the recovery can be reduced as much as possible, and the formation of the mixture of the ink and the liquid composition on the ejection port surface can be reduced. Also in the head (1s), the recording head for ink (1k, 1
c, 1m, 1y), a stable ejection operation can be realized.

(Second Example of Recovery Processing) As one of the causes of the contact between the ink and the liquid composition on the discharge port surface of the recording head, the ink or the liquid composition was discharged toward the recording medium. Bounce from the recording medium which occurs at the time can be mentioned. Hereinafter, different forms of the bouncing phenomenon in the recording process will be described with reference to FIGS. 3 (a), 3 (b) and 3 (c).

FIG. 3A is a diagram showing a state of rebound generated when the ink 51 or the liquid composition 51 discharged from the recording head lands on the recording medium 50. FIG. As is clear from the figure, the small droplets 52 generated by the rebound fly in the direction opposite to the recording medium 50, that is, in the direction toward the ejection port surface of the recording head. As shown in FIG. 1A, the recording heads are arranged side by side in the main scanning direction, and after the liquid composition 51 is ejected from the recording head 1s in the main scanning direction, the recording heads 1k, 1c, 1m, 1y are used. Is ejected, the small liquid droplets 52 rebounding from the recording medium 50 in FIG.

FIG. 3B is a view showing a state of rebound generated when the ink 54 is applied after the liquid composition 53 is applied on the recording medium 50. in this case,
The ink 54 is applied to the layer of the liquid composition 53 previously applied.
Is given. At this time, similarly to FIG. 3A, the small droplet 55 due to the rebound is moved in the opposite direction to the recording medium 50,
That is, it flies in the direction toward the ejection port surface of the recording head.

FIG. 3 (c) shows the case where the ink 54 is applied after the liquid composition 53 has been applied to the recording medium 50 and a longer time has elapsed than in the case shown in FIG. 3 (b). It is a figure which shows the mode of the bouncing which arises. In this case, since the ink 54 is applied after the previously applied layer of the liquid composition 53 permeates the recording medium 50, the small droplets due to the rebound are compared with the case of FIG. The amount of flight of 53 is reduced. As described above, the amount of the small droplets 53 generated by the rebound depends on the elapsed time from when the liquid composition 53 is ejected to when the ink 54 is ejected.

In this example, by arranging the recording heads side by side in the main scanning direction as shown in FIG. 1A, the black ink k is ejected first after the liquid composition s is ejected on the recording medium. (See FIG. 1B). Therefore, when the recording head 1k discharges the black ink k, since the elapsed time from the discharge of the liquid composition s is relatively short, the amount of small droplets generated by the rebound is large. On the other hand, when the recording head 1y ejects the yellow ink y, the amount of small droplets generated by the rebound is reduced because the elapsed time from the ejection of the liquid composition s is relatively long.

From this point of view, in the case of the present example, the shorter the elapsed time from the ejection of the liquid composition onto the recording medium to the ejection of the ink at the landing position of the liquid composition, the shorter the recording head. The threshold values tk, tc, tm, and ty of the above-described dot count value are set so that the recovery operation is frequently performed. In other words, in this example, the frequency of performing the recovery operation is in the order of the ink recording heads 1k>1c>1m> 1y.
The threshold is set as tk <tc <tm <ty. The threshold can be set based on the distance between the recording heads and the moving speed of the carriage, as described later.

Since the recording head reciprocates in the main scanning direction as described above, the recording head does not move at a constant speed. However, when recording is performed on a recording medium, the recording head moves at a substantially constant speed. Assume that you are moving. The moving speed is a value that changes depending on the type of recording operation mode of the printer. In this example, two recording speeds are set. Coefficients that fluctuate according to the two recording speeds are v1 and v2,
It is expressed as j (j = 1, 2). Further, FIG.
As shown in (a), each ink recording head 1k,
The distances between 1c, 1m, 1y and the liquid composition head 1s are dk, dc, dm, and dy, which are di (i
= K, c, m, y).

Based on the coefficient vj and the distance di, the recording heads 1k, 1c, 1 are calculated by the following equation (1).
The thresholds tk, tc, tm, and ty for m and 1y are set.
The thresholds tk, tc, tm, ty are ti (i =
k, c, m, y). ti = k × di / vj (1) In the above equation (1), k is a predetermined constant.

Then, as in the first example of the recovery processing described above, any one of the dot count values ck, cc, cm, and cy of the ink recording heads 1k, 1c, 1m, and 1y corresponds to the threshold value ti (tk , Tc, tm, ty), recovery processing by wiping is performed only on the recording head for ink and the recording head for liquid composition. Then, the dot count value corresponding to the wiped ink recording head is initialized. In the case of this example, the dot count value is compared with the threshold value each time one scan of the recording head is completed, as in the first example described above. Therefore, the recovery processing in the present example can be described by a flowchart similar to that of FIG. 6 described above. For example,
When the dot count value ck of the recording head 1k exceeds the threshold value tk, the recording head 1k and the liquid composition recording head 1s are wiped, and then the dot count value ck is obtained.
Clear

By performing the recovery process in this manner, it is possible to prevent a certain amount of mixed mist from adhering to any of the recording heads. In addition, a decrease in throughput due to wiping can be minimized.

In this example, the recording heads 1k,
The distances dk, dc, dm, and dy between each of the recording heads 1c, 1m, and 1y and the liquid composition recording head 1s are 0.5 inches, 1.0 inches, 1.5 inches, and 2.
0 inches. That is, each print head is arranged as shown in FIG. 1A, and the distances dk, dc, dm, and dy between the discharge ports of each print head in the main scanning direction are set to 0.
5 inches, 1.0 inches, 1.5 inches, and 2.0 inches. Further, in this example, the constant k in the above equation (1) used for calculating the threshold is set to 122672000, and dk,
The values of dc, dm, and dy are 5, 10, 15, and 20, respectively.
And

As described above, according to the second recovery example, the frequency of the recovery operation is set to increase as the ink recording head having a shorter physical distance from the liquid composition head. Therefore, the frequency of the recovery operation corresponds to the degree to which the mixture of the ink and the liquid composition is formed on the ejection port surface, and as a result, the consumption of the ink and the liquid composition due to the recovery can be minimized. The formation of the mixture of the ink and the liquid composition on the discharge port surface can be reduced, and both the liquid composition head (1s) and the ink recording head (1k, 1c, 1m, 1y) are stable. A discharge operation can be realized.

(Others) The recovery process of the recording head includes wiping, wiping of the recording head by a wiping member, suction recovery process of sucking and discharging ink from the discharge port of the recording head, or image recovery from the discharge port of the recording head. For example, any one of the ejection recovery processing for ejecting ink that does not contribute to the recording may be used, or at least two of them may be combined. In the suction recovery process, the cap members 5s, 5k, 5c, 5m, and 5y in the capping state are used.
A negative pressure is introduced into the recording heads 1s, 1k,
This can be performed by sucking and discharging the liquid composition and the ink from the discharge ports 1c, 1m, and 1y. In addition, the ejection recovery processing includes the cap members 5s, 5k, 5c, 5m, and 5y.
Inward, the corresponding recording heads 1s, 1k, 1c,
It can be carried out by discharging the liquid composition and the ink from the discharge ports of 1 m and 1y.

Further, in such a recording head recovery process, not only the number of recovery processes but also the amount of recovery processes can be varied depending on the possibility of the mixture of the ink and the liquid composition adhering. For example, the recovery conditions for recovering the respective ejection states of the recording heads include the distance between the recording head for ejecting ink and the recording head for ejecting the liquid composition,
It can be varied according to the moving speed of the recording head, the dye concentration of the ink, the physical properties of the ink, and the distance between the recording medium and the recording head. Preferably, as the distance between the recording head for discharging the ink and the recording head for discharging the liquid composition is shorter and the moving speed of the recording head is higher, the number of times of the recovery processing and the processing amount are increased. Also, the higher the dye concentration of the ink, the greater the number and amount of recovery processing. Further, as the physical properties of the ink, the greater the difference in pH from the liquid composition, the greater the number and amount of recovery processing. Further, as the distance between the recording medium and the recording head is shorter, the number of times of the recovery processing and the processing amount are increased. Further, it is preferable that the conditions of such a recovery process are made different depending on the type of the ink or liquid composition to be ejected. The greater the cohesiveness of the ink, the greater the number and the amount of the recovery process. in this way,
The higher the possibility of adhesion of the mixture of the ink and the liquid composition, the greater the number and amount of recovery processing.

As the recording head, those of various ejection systems can be adopted. For example, a method of discharging ink or a liquid composition using a piezo element or an electrothermal converter can be employed. In the case of a discharge method using an electrothermal converter, an electrothermal converter is provided in a liquid passage communicating with the discharge port, and thermal energy generated by the electrothermal converter causes film boiling in the ink and the liquid composition. Then, the ink and the liquid composition are ejected from the ejection port by the foaming energy.

The recording head may be configured separately for discharging ink and discharging liquid composition, or may be configured to integrally include a discharging section for discharging ink and a discharging section for discharging liquid composition. Good.

As the combination of the ink and the liquid composition, for example, an anionic or cationic aqueous ink containing a coloring material and fine particles having a surface opposite in polarity to the aqueous ink are dispersed. And an aqueous liquid composition contained in a state. In that case, the state of adhesion of the mixture can be predicted from the cohesiveness of the mixture of the ink and the liquid composition. Further, the cohesiveness of the mixture of the ink and the liquid composition can be associated with the pH of the ink. Further, the cohesiveness of the mixture of ink and liquid composition depends on the relationship between the distance between the ejection port for ejecting the ink and the ejection port for ejecting the liquid composition, and the ejection frequency of the ink or liquid composition. Can be assigned. In that case, the ejection frequency of the ink or liquid composition can correspond to the moving speed of the recording head.

[0200]

As described above, according to the present invention,
Depending on the possibility that the mixture of the ink and the liquid composition adheres to each of the plurality of recording heads, the ink attached to the recording head is changed by changing recovery conditions for restoring the ejection state of each of the recording heads. A recovery process such as wiping is performed at an appropriate timing so that the mixture of the liquid composition and the liquid composition is not fixed, so that high-quality recording can be always performed. By doing so, only the head that needs a recovery process can be recovered as needed, and the ink and liquid composition can be applied to the ejection opening surface of the head while reducing the consumption of ink and liquid composition during recovery. Can be prevented from being fixed, and a stable discharge operation can be realized.

In particular, while maintaining the texture of plain paper, it is possible to obtain, as a recorded image on the plain paper, excellent color developability and color uniformity comparable to that of coated ink-jet paper, and to obtain a solid image portion in the recorded image. A recorded image with less streaks and excellent scratch resistance can be obtained. Further, an ink or liquid composition having optimum recording characteristics can be employed regardless of the degree of the adhesion of the mixture of the ink and the liquid composition. As a result, the ink and the liquid composition are excellent in storability, and have excellent printability with respect to the recording head, that is, the reliability of the ejection of the first ink or liquid composition ejected from the recording head, and the nozzles of the recording head. Those that do not cause clogging can be employed.

[Brief description of the drawings]

FIG. 1A is a diagram of a configuration example of a recording head viewed from an ejection port side, and FIG. 1B is an explanatory diagram of an example of dot formation by the recording head.

FIG. 2 is a diagram showing the relationship between pH and viscosity of a liquid composition used in an embodiment of the present invention.

FIGS. 3A, 3B, and 3C are explanatory diagrams of different forms of a bouncing phenomenon in a recording process. FIGS.

FIG. 4 is a schematic perspective view of an ink jet printer as an embodiment of the present invention.

FIG. 5 is a block diagram for explaining a configuration example of a control system in the inkjet printer of FIG.

FIG. 6 is a flowchart illustrating a recovery process in the inkjet printer of FIG. 4;

FIG. 7 is a schematic cross-sectional view of a colored portion of an image on coated paper on which inkjet recording has been performed.

FIG. 8 is a schematic sectional view of a colored portion of an image recorded by the inkjet recording device according to the present invention.

FIGS. 9A, 9B, 9C, and 9D are illustrations of a process for forming a colored portion of an image recorded by the inkjet recording apparatus according to the present invention.

[Explanation of symbols]

 1s, 1k, 1c, 1m, 1y Recording head 2 Carriage 3 Flexible cable 4 Cap unit 5s, 5k, 5c, 5m, 5y Cap member 6s, 6k, 6c, 6m, 6y Wiper blade 7 Paper (recording medium) 8 Supply Paper tray 50 Recording medium 51, 54 Ink 52, 55 Small droplet 53 Liquid composition

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masao Kato 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Kentaro Yano 3-30-2 Shimomaruko, Ota-ku, Tokyo Non-corp. F term (reference)

Claims (19)

[Claims] 1. Recording is performed by using a plurality of ink recording heads capable of discharging ink and a liquid composition recording head capable of discharging a liquid composition containing fine particles for adsorbing a coloring material in the ink. In an inkjet recording apparatus that performs recording on a medium, a recovery condition for recovering a discharge state of each of the recording heads according to a possibility that a mixture of the ink and the liquid composition adheres to each of the recording heads. An ink jet recording apparatus characterized in that: 2. The ink is an anionic or cationic aqueous ink containing a coloring material, and the liquid composition contains fine particles whose surface is oppositely charged to the aqueous ink in a dispersed state. The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus is an aqueous liquid composition containing the composition. 3. The ink jet recording apparatus according to claim 1, wherein the recovery condition is changed according to the cohesiveness of a mixture of the ink and the liquid composition. 4. The ink recording head according to claim 1, wherein the cohesiveness corresponds to a pH of the ink, and a recovery operation of the ink recording head that discharges the ink having the higher pH as compared with an ink recording head that discharges the ink having the lower pH. The ink jet recording apparatus according to claim 3, wherein the frequency of the ink jet recording is increased. 5. The cohesiveness corresponds to a distance between an ejection port of the recording head for ink and an ejection port of the recording head for liquid composition, and the distance from the recording head for liquid composition is large. 4. The ink jet recording apparatus according to claim 3, wherein a frequency of a recovery operation of the ink recording head, which has a smaller distance from the liquid composition recording head than the ink recording head, is increased. 5. . 6. The cohesiveness corresponds to a relationship between a distance between an ejection port of the ink recording head and an ejection port of the liquid composition recording head and an ejection frequency of the ink recording head. The inkjet recording apparatus according to claim 3, wherein the recording is performed. 7. A method according to claim 6, wherein a predetermined value is set for each of said plurality of printheads in accordance with the possibility of adhesion, and when the number of ejections counted for each of said plurality of printheads exceeds a predetermined value for each of said printheads. 7. The inkjet recording apparatus according to claim 1, wherein an ejection state recovery process is performed on a recording head in which at least the number of ejections exceeds the predetermined value. 8. The ink jet recording according to claim 1, wherein the number of times of recovery processing for recovering the ejection state of the recording head is changed according to the possibility of the adhesion. apparatus. 9. The ink jet printer according to claim 1, wherein a processing amount of a recovery process for recovering an ejection state of the recording head is changed according to the possibility of the adhesion. Recording device. 10. A process for recovering an ejection state of the recording head includes at least wiping of the recording head, wiping operation of the recording head, and ink or liquid composition not contributing to recording of an image from the recording head. The ink jet recording apparatus according to claim 1, further comprising one of an ejection operation and an operation of sucking and discharging ink or liquid composition from the recording head. 11. The recording head according to claim 1, wherein the recording head has an electrothermal converter that generates thermal energy used for discharging an ink or a liquid composition. Ink jet recording device. 12. The ink jet recording apparatus according to claim 2, wherein said fine particles are alumina or alumina hydrate. 13. Recording is performed using a plurality of ink recording heads capable of discharging ink and a liquid composition recording head capable of discharging a liquid composition containing fine particles for adsorbing a coloring material in the ink. A recording head ejection recovery method in an ink jet recording apparatus that performs recording on a medium, wherein a mixture of the ink and the liquid composition adheres to each of the recording heads. An ejection recovery method for a print head, wherein recovery conditions for recovering an ejection state are changed. 14. The ink is an anionic or cationic aqueous ink containing a coloring material, and the liquid composition contains fine particles whose surface is oppositely charged to the aqueous ink in a dispersed state. 14. The method according to claim 13, wherein the aqueous liquid composition contains an aqueous liquid composition. 15. The method according to claim 14, wherein the fine particles are alumina or alumina hydrate. 16. The method according to claim 13, wherein the recovery condition is changed according to the cohesiveness of a mixture of the ink and the liquid composition. . 17. The ink cohesiveness corresponds to the pH of the ink, and a recovery operation of the ink recording head that discharges the ink having the higher pH as compared with an ink recording head that discharges the ink having the lower pH. 17. The ejection recovery method for a recording head according to claim 16, wherein the frequency of the ejection is increased. 18. The ink according to claim 18, wherein the cohesiveness corresponds to a magnitude of a difference between the pH of the ink and the pH of the liquid composition, and the ink ejecting an ink having a small pH difference between the pH of the liquid composition and the ink. 17. The frequency of a recovery operation of an ink recording head that ejects an ink having a pH having a large difference from the pH of the liquid composition as compared with a recording head for recording is increased. A method for recovering the ejection of the recording head. 19. The cohesiveness corresponds to a distance between an ejection port of the ink recording head and an ejection port of the liquid composition recording head, and the distance from the liquid composition recording head is large. 17. The recording head according to claim 16, wherein the frequency of the recovery operation of the recording head for ink whose distance from the recording head for liquid composition is small as compared to the recording head for ink is large. Discharge recovery method.