JP4468463B2 - Inkjet printing method - Google Patents

Description

The present invention relates to an ink jet printing method , and more particularly, a character, an image, or the like is printed on a print medium such as print paper or OHP paper by using an ink and a liquid that insolubilizes a colorant in the ink (hereinafter referred to as a treatment liquid). The present invention relates to an inkjet printing method for performing printing.

  The inkjet printing method has various advantages such as low noise, low running cost, high-speed printing, easy downsizing of the apparatus, and easy colorization, and is widely used in printers and copiers. It is a method. In such a printer or the like, in general, an ink to be used is selected from the viewpoints of print characteristics such as ejection characteristics and fixability, print image bleeding, optical reflection density, and color quality. By the way, it is widely known that inks are roughly classified into two types, dye inks and pigment inks, depending on the color materials contained therein. Among these, the pigment ink has advantages such as excellent water resistance and light resistance as compared with the dye ink, and enables clear character quality. On the other hand, the pigment ink may take a longer time to be fixed on the print medium than the dye ink, and may not have sufficient scratch resistance of the image after fixing, and the ink ejected from the nozzle by one ejection operation. Tends to reduce the size of the ink dots formed on the print medium. That is, the pigment contained in the pigment ink usually uses mainly the electric repulsive force of the polymer dispersant to overcome the intermolecular force acting between the pigment particles that causes the aggregation of the pigment particles. It is dispersed stably. Therefore, it is necessary to add a polymer dispersant in the ink according to the amount of the pigment. When such ink is printed on plain paper using the ink jet recording method, pigments aggregate due to penetration of ink such as moisture into the paper and evaporation into the air. At this time, as the behavior on paper, the larger the amount of the polymer dispersant, the stronger the cohesive force. Therefore, the diameter of the ink dots formed on the print medium by the ink having a certain volume ejected from the inkjet head is small, and the dot shape remains close to the distorted shape when colliding with the paper. Therefore, in order to obtain ink dots having a dot diameter necessary for recording that has a recording density sufficient to form an image and that does not generate white streaks, the ink ejection volume from the inkjet head is large. It is necessary to adjust to. However, even with such adjustment, coupled with a decrease in permeability into the paper due to the strong cohesion of the pigment particles adsorbed by the polymer dispersant, it causes a delay in fixing the ink to the print medium, Alternatively, the scratch resistance of the recorded image may be reduced.

  In order to increase the dot diameter and improve the fixability, it is also considered that the ink contains a penetrant for the purpose of improving the penetrability of the ink into the print medium. However, this is accompanied by phenomena that are undesirable in aiming for high-quality recorded images such as dot shape deterioration (deterioration of dot peripheral shape such as feathering) and ink permeation to the back side of paper (so-called back-through). There is a case. In addition, since the color material penetrates into the print medium, the OD of the ink dot is not so high even if the dot diameter is relatively large.

  Furthermore, an ink using a self-dispersion type pigment has been proposed. In this ink, the cohesive force of the pigment on paper is weaker than that of the ink containing the pigment dispersed by the above-described dispersant. Can be expanded, but it is not enough.

  In this way, various factors that affect the quality of the recorded image, such as ink fixability, enlargement of the ink dot diameter, uniformity of density within the ink dot, high optical density of the ink dot itself, etc. should be satisfied at a high level. New printing methods and devices are still under study.

  On the other hand, in inkjet printing technology, an ink and a treatment liquid that reacts with the ink for the purpose of further improving print quality and image quality (for example, improving water resistance and optical density (OD) of an image on a print medium) Has been proposed and put to practical use so far on the print medium so that the ink and the treatment liquid react on the print medium.

  In order to solve the problems peculiar to the pigment ink while taking advantage of the excellent characteristics of the pigment ink, the present inventor has a treatment having reactivity between the pigment ink and the pigment ink that destroys the pigment dispersibility of the pigment ink. An energetic study was carried out on the ink jet recording technology combined with the liquid. As part of the study, a recording process was performed in which a treatment liquid was applied so as to be mixed with the pigment ink on the print medium in a liquid state after the pigment ink was applied to the surface of the print medium or substantially simultaneously. The quality of the resulting image was not always satisfactory and was observed even when the quality deteriorated rather than the image formed with the pigment ink alone. Specifically, for example, a combination of a pigment ink containing a pigment dispersed in an aqueous medium with a polymer dispersant as a pigment ink and a treatment liquid that reacts with the pigment ink has a small ink dot area factor. In some cases, a decrease in OD was observed. The reason why such a phenomenon occurs is not clear, but it is thought that the aggregation of the pigment in the ink on the print medium is greatly promoted by the treatment liquid. Therefore, the area factor can be increased and the OD can be improved by increasing the amount of pigment ink applied, but in this case, it may be recognized that the fixability is inferior. In addition, dots (see 101 in FIG. 1) on a print medium obtained by a combination of a pigment ink containing a self-dispersing pigment as a pigment ink and a treatment liquid that reacts with the pigment ink are shown in FIG. A phenomenon 102 called “seepage” or “moy” was sometimes observed. FIG. 2 is a diagram for presumably explaining the occurrence mechanism of this phenomenon.

  After the pigment ink Ip containing the self-dispersing pigment and not containing the polymer dispersant is applied to the print medium P (especially plain paper) (see FIG. 2A), the treatment liquid S is applied again. Then, the production of the reaction product starts (see FIG. 2B). Then, as this reaction proceeds, as shown in FIG. 5C, a radial “bleed out” was generated from the substantially circular dots by the reaction product, and “haze” appeared around the entire dot. It becomes a state. Such “bleeding out” or “haze” is recognized in the same manner as known feathering, and thus deteriorates the print quality.

  It is presumed that the above-mentioned “bleeding out” or “haze” is the following phenomenon chemically or microscopically. The pigment ink without a dispersant has a relatively high reaction rate in the reaction with the treatment liquid, and thus the dispersed pigment instantly causes dispersion failure and generates a cluster of reactants. Particulate reactants are also produced. This particulate reactant flows out as the treatment liquid penetrates into the print medium, and as a result, the above-mentioned “bleeding out” appears.

  As described above, by simply combining the pigment ink and the treatment liquid, an event that cannot be predicted by the present inventor occurred, and it was difficult to obtain a high-quality inkjet recording image. Furthermore, it is necessary to develop further technology to achieve the intended purpose of improving the defects of the pigment ink while utilizing the advantages of the pigment ink by utilizing the ink jet recording technology using the treatment liquid. The inventor has recognized.

The present invention has been made in view of the above-described new technical knowledge, and provides an inkjet printing method for obtaining a higher quality print by utilizing an inkjet recording technique using a pigment ink treatment liquid. There is.

An inkjet printing method according to the present invention capable of achieving the above object is an inkjet printing method including a step of recording an image on a print medium.
A first step of depositing ink on a print medium using an ink jet recording method; and a second step of depositing a treatment liquid reactive with the ink on the print medium;
The ink includes a first pigment and a second pigment dispersed in an aqueous medium, and the first pigment has at least one anionic group directly or via another atomic group. A self-dispersing pigment bonded to the surface of the pigment or a self-dispersing pigment in which at least one cationic group is bonded to the surface of the first pigment directly or through another atomic group The second pigment is a pigment that can be dispersed in the aqueous medium by a polymer dispersant, and the ink is further a polymer dispersant having the same polarity as the group bonded to the surface of the first pigment. And an ink containing at least one of a nonionic polymer dispersant, and the second step is performed so that the ink and the treatment liquid are in liquid contact with each other on the print medium. It is.

According to the present invention described above, it is possible to obtain a higher quality image with a very high OD, a high edge sharpness, and various merits such as an improvement in scratch resistance and fixability. is there. The reason why the application of the treatment liquid subsequent to or substantially simultaneously with the application of the ink containing the first pigment and the second pigment brings about such an effect is not clear. However, the present inventors have confirmed the following facts through numerous experiments over the present invention. That is, when an ink containing the first pigment and the second pigment is applied to a print medium, dots having a predetermined spread are formed on the surface of the print medium P as shown in FIG. The The size (diameter: d1) of this ink dot is the same as the size (diameter: diameter) of the conventional pigment ink shown in FIG. Larger than d2) (d1> d2). The reason why such a phenomenon is observed is not clear, but is presumed to be due to the following mechanism. That is, the second pigment and the first pigment on which the polymer dispersant is adsorbed are electrically repelled in the ink, and the cohesive force of the pigment is weaker than that of at least the polymer-dispersed pigment alone. . When such ink is printed on the paper surface, since the polymer dispersant is adsorbed to the second pigment, the color material in the ink hardly penetrates in the thickness direction of the paper. On the other hand, with respect to the paper (lateral) direction, in the case of an ink containing a second pigment and a polymer dispersant, the polymers rapidly entangle with each other as the ink solvent penetrates into the paper and the moisture decreases due to evaporation. Or, the polymer is strongly agglomerated when the polymer is crosslinked between the pigments, whereas the ink of this aspect prevents the entanglement or crosslinking of the polymer due to the inclusion of the first pigment. Alternatively, the strong intermolecular force between the pigments in the ink is relieved by the repulsion between the first pigment and the polymer dispersant, and as a result, the ink easily diffuses in the lateral direction of the paper surface. Moreover, although the diffusion is moderated, it is considered that the diffusion is not disordered due to the influence of the cohesive force between the pigments.

  Then, when the treatment liquid S is applied to the ink dots that are uniformly and widely diffused on the surface of the print medium in this way (see FIGS. 2B and 2C), a reaction occurs at the interface between the ink and the treatment liquid. As described above, since the ink dots are widely diffused, there are more reaction sites with the treatment liquid than in the case of the conventional ink, and the ink dots are greatly spread. The thickness (t1) of the dots is also thinner than the thickness (t2) of the conventional ink dots on the print medium surface, and the reaction with the treatment liquid is considered to be completed in a very short time. Thus, in this embodiment, it is estimated that fixing time is shortened, fixing property is improved, and edge sharpness of ink dots is improved. From this mechanism, it will be understood that the effect exhibited by this embodiment is unique to a system in which ink is applied to the print medium prior to or substantially simultaneously with the processing liquid.

  In this embodiment, when the treatment liquid has excellent permeability to the print medium, the fixability and the edge sharpness of the ink dots are further improved. This is presumably because the ink and the treatment liquid react on the surface of the print medium, and the solvent containing water becomes more permeable due to the penetration force of the treatment liquid and penetrates into the print medium. In general, when the coloring material penetrates into the print medium, the optical density often decreases. However, when ink is applied prior to the application of the treatment liquid as in this embodiment, the OD decreases so much. Hardly penetrates the print medium. Rather, the color material tends to stay on the surface of the print medium and the vicinity thereof by reaction with the treatment liquid, and as a result, it has been found that the OD is further improved as compared with the case where the treatment liquid is not used. Furthermore, in this embodiment, it is preferable to use a treatment liquid whose components are optimized in accordance with the types and ratios of the first pigment and the second pigment in the ink in order to further improve the image quality. It is. That is, the self-dispersing pigment seems to have a mine-like form having many beard-like polar groups (anionic groups) around the pigment particles as shown in FIG. 4A as a model. . On the other hand, a polymer compound having many cationic groups in one molecule, such as polyallylamine (PAA), is schematically shown as in FIG. When such a compound is mixed with a self-dispersing pigment, a polymer of PAA is entangled around the self-dispersing pigment as shown in FIG. However, the cationic group of PAA cannot geometrically bind to all anionic groups, and as a result, when the reaction product of the self-dispersing pigment and PAA is entirely cationic, Conceivable. Such a reaction of pigment particles having a small particle size with PAA is considered to be weak in intermolecular force, easily repelled electrically, and less likely to aggregate into a larger form. It is thought that the minute object causes a blurring around the dot. Conversely, in the case of a pigment dispersed with a polymer dispersant, the polymer dispersant itself has a large number of anionic groups or cationic groups, while one cationic group per molecule on the treatment liquid side or Even if the compound having an anionic group is contained, the dispersibility of the polymer dispersant is not completely destroyed. Therefore, for example, a polymer cationic compound such as PAA and benzalkonium chloride are used as a treatment liquid for an ink containing a first pigment having an anionic group bonded to the pigment surface and a pigment dispersed with an anionic polymer dispersant. By adding a certain amount of low molecular weight cationic compound at a predetermined ratio, the dispersibility of each pigment in the ink is surely destroyed on the print medium, and generation of unreacted cationic groups that cause fogging is suppressed as much as possible. It is what As a result, it is possible to form an extremely high-quality image having a high OD, no haze, and excellent fixability on a print medium in a short fixing time.

According to the present invention, using an ink containing a first pigment, a second pigment, and a polymer dispersant of the second pigment, and a treatment liquid that reacts with the ink, the ink is first applied to a print medium, Subsequently, the ink is applied to the print medium so that the treatment liquid and the ink are mixed in a liquid state, thereby having a high OD, excellent edge sharpness, and further, the back of the image to the print medium. An image with little penetration can be obtained. Furthermore, the slow fixing speed and the insufficient fixing property, which are the disadvantages of the conventional pigment ink, can be greatly improved.

  In addition, if an ink having a low permeation rate is used as the ink, the amount of the colorant remaining on the surface layer of the print medium can be increased even when there is a long time for the treatment liquid to be applied. The OD value can be increased. Furthermore, so-called feathering can be suppressed as an effect of using an ink having a low permeation rate. Further, according to the present invention, it is possible to extremely effectively suppress the occurrence of “seepage” or “haze” around the image dots.

When the treatment liquid is applied after the ink is applied, and when the ink is further applied, it is particularly remarkable in the improvement of the OD value, suppression of haze or feathering. Further, if the treatment liquid is highly permeable, relatively good fixability can be obtained. The rate of penetration of the treatment liquid, by _five. 0 on the ^{(ml / m 2 · msec 1/2} ) or more Ka value by Bristow method, a thing of the processing liquid is relatively high permeability, increase the fixing speed It becomes possible.

(Embodiment 1-1)
In the ink jet recording method according to an embodiment of the present invention, after the ink containing the first pigment and the second pigment is applied to the print medium, or substantially simultaneously, the treatment liquid that reacts with the ink is printed on the print medium. A step of forming image dots by applying the ink to the medium and causing the ink and the processing liquid to contact and react on the print medium in a liquid state.

(ink)
Examples of the ink that can be used in the above-described embodiment include, for example, an ink containing a first pigment and a second pigment dispersed in an aqueous medium as a coloring material, wherein the first pigment is at least A self-dispersing pigment in which one anionic group is bonded to the surface of the first pigment directly or through another atomic group or at least one cationic group is directly or through another atomic group A self-dispersing pigment bonded to the surface of the first pigment, and the second pigment can be dispersed in the aqueous medium by a polymer dispersant or a nonionic polymer dispersant The ink further includes an ink containing at least one of a polymer dispersant having the same polarity as the group bonded to the surface of the first pigment and a nonionic polymer dispersant.

Hereinafter, the ink will be sequentially described.
(First pigment)
Self-dispersing pigments are ink-jet recording technologies that maintain stable dispersion in water, water-soluble organic solvents, or liquids mixed with these without the use of dispersants such as water-soluble polymer compounds. It refers to a pigment that does not cause agglomeration of pigments in the liquid, which hinders normal ink ejection from the orifice used.
(Anionic self-dispersing CB)
As such a pigment, for example, a pigment in which at least one anionic group is bonded to the pigment surface directly or through another atomic group is suitably used. Specific examples include at least one anionic group. It includes carbon black bonded to the surface directly or through other atomic groups.

Examples of the anionic group bonded to such carbon black include, for example, —COOM, —SO ₃ M, —PO ₃ HM, —PO ₃ M _{2 and the} like (wherein M is a hydrogen atom, Represents an alkali metal, ammonium, or organic ammonium, and 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). Can be mentioned. Examples of the substituent in the case where R is a phenyl group having a substituent or a naphthyl group having a substituent include a linear or branched alkyl group having 1 to 6 carbon atoms.

  Examples of the “M” alkali metal include lithium, sodium, potassium, and the like, and examples of the “M” organic ammonium include mono to trimethyl ammonium, mono to triethyl ammonium, and mono to trimethanol ammonium. It is done.

Among these anionic groups, —COOM and —SO ₃ M are particularly preferable because they have a large effect of stabilizing the dispersion state of carbon black.

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

Specific examples of the anionic group bonded to the surface of carbon black through other atomic groups include, for example, —C ₂ H ₄ COOM, —PhSO ₃ M, —PhCOOM, etc. (where Ph represents a phenyl group) Of course, it is not limited to these.

  Carbon black in which an anionic group is bonded to the surface directly or through another atomic group as described above can be produced, for example, by the following method.

  That is, as a method for introducing —COONa into the carbon black surface, for example, a method of oxidizing a commercially available carbon black with sodium hypochlorite can be mentioned.

Further, for example, as a method of bonding an —Ar—COONa group (wherein Ar represents an aryl group) to the carbon black surface, a diazonium salt in which nitrous acid is allowed to act on an NH ₂ —Ar—COONa group is used. Of course, the present invention is not limited to this.
(Cationic self-dispersing CB)
(Cationically charged CB)
Examples of the cationically charged carbon black include those in which at least one selected from the following quaternary ammonium groups is bonded to the surface of carbon black. Quaternary ammonium group: —NH ₃ ⁺ , —NR ₃ ⁺ , —SO ₂ NH ₂ , —SO ₂ NHCOR,

  In the above formula, R represents, for example, a linear or branched alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted naphthyl group. Here, examples of the substituent of the phenyl group or naphthyl group include linear or branched alkyl groups having 1 to 6 carbon atoms.

  Examples of a method for producing a self-dispersing carbon black having a hydrophilic group bonded thereto and charged cationically include, for example, an N-ethylpyridyl group having the structure shown below:

As an example, a method of bonding carbon black is a method of treating carbon black with 3-amino-N-ethylpyridinium bromide. In this way, carbon black charged anionic or cationic by introducing a hydrophilic group to the surface of carbon black has excellent water dispersibility due to repulsion of ions, so even when it is contained in aqueous ink. A stable dispersion state is maintained without adding a dispersant or the like.

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

  By the way, 80% or more of the self-dispersing pigment contained in the ink according to the present embodiment has a particle diameter of 0.05 to 0.3 μm, particularly 0.1 to 0.25 μm. Is preferred. Such an ink adjustment method is as described in detail in the embodiments described later.

(Second pigment)
Examples of the second pigment that can be used in the ink of the present embodiment include a pigment that can be dispersed in an ink dispersion medium, specifically, an aqueous medium by the action of a polymer dispersant. That is, a pigment that can be stably dispersed in an aqueous medium for the first time as a result of the polymer dispersant adsorbing on the surface of the pigment particles is preferably used. Examples of such pigments include, for example, black pigments such as carbon black pigments such as furnace black, lamp black, acetylene black, and channel black. As specific examples of such carbon black pigments, for example, the following can be used alone or in appropriate combination.
Carbon black pigment:
・ Raven 7000, Ray Van 5750, Ray Van 5250, Ray Van 5000ULTRA, Ray Van 3500, Ray Van 2000, Ray Van 1500, Ray Van 1250, Ray Van 1200, Ray Van 1190ULTRA-II, Ray Van 1170, Ray Van 1255 (manufactured by Columbia)
Black Pearls L, Regal 400R, Regal 330R, Legal 660R, Mogul L, Monarch 700, Monak 800, Monak 880, Monak 900, Monak 1000, Monak 1100, Monak 1300 , Monak 1400, Vulcan XC-72R (above manufactured by Cabot Corporation)
-Color Black FW1, Color Black FW2, Color Black FW2V, Color Black 18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Printex 140V, Special Black 6, Special Black 5, Special Black 4A, Special Black 4 (manufactured by Degussa)
-No. 25, No. 33, No. 40, No. 47, No. 52, No. 900, No. 2300, MCF-88, MA600, MA7, MA8, MA100 (manufactured by Mitsubishi Chemical Corporation).
Examples of other black pigments include magnetic fine particles such as magnetite and ferrite, and titanium black. In addition to the black pigments described above, blue pigments, red pigments, and the like can also be used.

  The amount of the color material combining the first and second pigments is 0.1 to 15% by weight, more preferably 1 to 10% by weight, based on the total amount of ink. The ratio of the first pigment to the second pigment is preferably 5/95 to 97/3, more preferably 10/90 to 95/5. More preferably, the first pigment / second pigment = 9/1 to 4/6. Another more preferable range is a range in which the first pigment is high. In the case of such a large amount of the first pigment, not only the dispersion stability as an ink, but also the stability including the ejection stability of the head, especially the reliability due to less ejection efficiency and less wetting of the ejection port surface is exhibited. Is done. In addition, as the behavior of the ink on the paper, since the ink spreads effectively on the surface of the paper with an ink with a small amount of the second pigment adsorbed by the polymer dispersant, a uniform thin film is formed on the surface by the polymer dispersant. It is estimated that, and the effect of this also improves the scratch resistance of the image. The polymer dispersant for dispersing the second pigment in an aqueous medium has, for example, a function of adsorbing on the surface of the second pigment and stably dispersing the second pigment in the aqueous medium. Preferably used. Examples of such polymer dispersants include anionic polymer dispersants, cationic polymer dispersants, and nonionic polymer dispersants.

(Anionic polymer dispersant)
Examples thereof include a polymer of a monomer as a hydrophilic group and a monomer as a hydrophobic group and a salt thereof. Specific examples of the monomer as the hydrophilic group include, for example, styrene sulfonic acid, α, β-ethylenically unsaturated carboxylic acid, α, β-ethylenically unsaturated carboxylic acid derivative, acrylic acid, acrylic acid derivative, and methacrylic acid. Methacrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid and fumaric acid derivatives.

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

  Specific examples of the salt include hydrogen, alkali metal, ammonium ion, organic ammonium ion, phosphonium ion, sulfonium ion, oxonium ion, stibonium ion, stannonium, iodonium and other onium compounds. It is not limited to. In addition, the above polymers and salts thereof include polyoxyethylene group, hydroxyl group, acrylamide, acrylamide derivative, dimethylaminoethyl methacrylate, ethoxyethyl methacrylate, butoxyethyl methacrylate, ethoxytriethylene methacrylate, methoxypolyethylene glycol methacrylate, vinylpyrrolidone, vinylpyridine, Vinyl alcohol and alkyl ether may be appropriately added.

(Cationic polymer dispersant)
As the cationic dispersant, a tertiary amine monomer, a copolymer obtained by quaternizing these with a hydrophobic monomer, or the like is used. As the tertiary amine monomer, for example, N, N-dimethylaminoethyl methacrylate, N, N-dimethylacrylamide and the like are used. As the hydrophobic monomer, styrene, a styrene derivative, vinyl naphthalene, or the like is used. In the case of a tertiary amine, sulfuric acid, acetic acid, nitric acid and the like are used as a compound for forming a salt. Further, those quaternized with methyl chloride, dimethyl sulfate or the like can also be used.

(Nonionic polymer dispersant)
Examples of nonionic polymer dispersants include polyvinyl pyrrolidone, polypropylene glycol, vinyl pyrrolidone-vinyl acetate copolymer, and the like.

  The first pigment, the second pigment, and the polymer dispersant described above can be appropriately selected in combination, and dispersed and dissolved in an aqueous medium to obtain the ink of this embodiment. In the case of using a self-dispersing pigment in which at least one anionic group is bonded to the surface of the pigment directly or through another atomic group, an anionic polymer dispersing agent is used as the polymer dispersing agent. And at least one selected from nonionic polymer dispersants are preferable from the viewpoint of ink stability, and for the same reason, at least one cationic group is directly or other atomic group as the first pigment. In the case of using a self-dispersing pigment bonded to the surface of the pigment via a cationic dispersant or nonionic polymer dispersant as the polymer dispersant Preferably it is combined with the pigment of the first at least one selected. The ratio of the second pigment and the polymer dispersant for dispersing the second pigment in the ink is preferably 5: 0.5 to 5: 2 by weight.

(Aqueous medium)
As an aqueous medium serving as a dispersion medium for the first and second pigments, a water-soluble organic solvent is used. Examples of the water-soluble organic solvent include carbon numbers such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, and n-pentanol. 1-5 alkyl alcohols; amides such as dimethylformamide and dimethylacetamide; ketones or ketoalcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; diethylene glycol, triethylene glycol, tetraethylene glycol, di Oxyethylene or oxypropylene copolymers such as propylene glycol, tripropylene glycol, polyethylene glycol, polypropylene glycol; Alkylene glycols in which the alkylene group contains 2 to 6 carbon atoms, such as coal, propylene glycol, trimethylene glycol, triethylene glycol, 1,2,6-hexanetriol; glycerin; ethylene glycol monomethyl (or ethyl) ether; Lower alkyl ethers such as diethylene glycol monomethyl (or ethyl) ether and triethylene glycol monomethyl (or ethyl) ether; lower polyhydric alcohols such as triethylene glycol dimethyl (or ethyl) ether and tetraethylene glycol dimethyl (or ethyl) ether Dialkyl ethers; alkanolamines such as monoethanolamine, diethanolamine, triethanolamine; sulfolane, N-methyl-2-pyrrolidone, 2-pyrrole Don, 1,3-dimethyl-2-imidazolidinone. These water-soluble organic solvents can be used alone or as a mixture.

(Penetration of ink into the recording medium)
The ink according to the present embodiment containing the various components described above pays attention to the permeability to the print medium, for example, when the Ka value is adjusted to less than 1 (ml · m ⁻² · msec ^−1/2 ). By using in combination with the treatment liquid described later, it is possible to obtain an image dot having an extremely uniform density, sharp edges, and excellent fixing speed and fixability to a print medium. Hereinafter, the penetrability of the ink into the print medium will be described.

When the ink permeability is expressed by the ink amount V per 1 m ^2, the ink penetration amount V (unit: milliliter / m ² = μm) at the time t after ejecting the ink droplet is the Bristow method as shown below. It is known that

(However, t> tw)
Immediately after the ink droplets are dropped on the surface of the print medium, the ink droplets are mostly absorbed by the uneven portions of the surface (the roughness portion of the surface of the print medium) and hardly penetrate into the print medium. The time in the meantime is tw (wet time), and the amount of absorption in the concavo-convex portion is Vr. When the elapsed time after the ink droplet is dropped exceeds tw, the penetration amount V increases by an amount proportional to the half power of the excess time (t-tw). Ka is a proportional coefficient of this increase, and shows a value corresponding to the penetration rate.

  The Ka value was measured using a liquid dynamic permeability test apparatus S (manufactured by Toyo Seiki Seisakusho) by the Bristow method. In this experiment, PB paper of Canon Inc., the present applicant, was used as a print medium (recording paper). This PB paper is a recording paper that can be used for both copying machines and LBPs using an electrophotographic system and printing using an inkjet recording system.

  Similar results were obtained for PPC paper, which is an electrophotographic paper manufactured by Canon Inc.

  The Ka value is determined by the type of surfactant and the amount added. For example, ethylene oxide-2,4,7,9-tetramethyl-5-decyne-4,7-diol (ethylene oxide-2,4,7,9-tetramethyl-5-decyen-4,7-diol) By adding a nonionic surfactant called “Acetylenol” (manufactured by Kawaken Fine Chemical Co., Ltd.), the permeability is increased.

  In addition, in the case of an ink in which acetylenol is not mixed (content ratio is 0%), the permeability is low, and the ink has properties as an overlay ink specified later. Further, when acetylenol is mixed at a content ratio of 1%, it has a property of penetrating into the recording paper in a short time and has a property as a highly penetrable ink defined later. An ink in which acetylenol is mixed at a content ratio of 0.35% has a property as a semi-permeable ink intermediate between the two.

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

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

Here, the ink of the system defined as “highly penetrating ink” has an acetylenol content ratio of 0.7% or more, and is in a range in which good results regarding penetrability are obtained. As a standard of permeability to be carried on the ink of the present embodiment, it is preferable to set the Ka value of “superposition-based ink”, that is, less than 1.0 (ml · m ⁻² · msec ^−1/2 ). Is preferably 0.4 (ml · m ⁻² · msec ^−1/2 ) or less.

(Addition of dye)
A dye may be further added to the ink of the above embodiment. That is, an ink in which a dye is further added to an ink containing a dispersant for dispersing the first pigment, the second pigment, and the second pigment in an aqueous medium is more excellent when used in combination with a treatment liquid described later. Image dots can be formed on a print medium with a short fixing time. In addition, as described above, the cohesion of the second pigment is alleviated by the presence of the first pigment. However, the addition of the dye further reduces the cohesion of the second pigment by one step, and It is considered that non-uniformity in the printed image such as “cracking” that tends to occur in a recording medium having poor absorbency compared to plain paper or the like can be effectively suppressed. Examples of the dye that can be used here include an anionic dye and a cationic dye, and it is preferable to employ a dye having the same polarity as that of the group bonded to the surface of the first pigment.

(Anion, Cationic dye)
Known anionic dyes, direct dyes, reactive dyes and the like are suitably used as anionic dyes soluble in the aqueous medium that can be used in the present embodiment as described above. As the cationic dye, a known basic dye is preferably used. Particularly preferably, both dyes use a dye having a disazo or trisazo structure as a skeleton structure. It is also preferable to use two or more dyes having different skeleton structures. As the dye to be used, dyes such as cyan, magenta, and yellow may be used as long as the color tone is not significantly different from the black dye.

(Addition amount of dye)
The amount of the dye added may be 5% to 60% by weight of the entire coloring material, but is less than 50% by considering the effective use of the effect of mixing the first and second pigments. It is preferable that Further, in the case of using ink that emphasizes printing characteristics on plain paper, the content is preferably 5% by weight to 30% by weight.

(Processing liquid)
Next, as an example of the treatment liquid that can be used in the above embodiment, for example, if a group bonded to the surface of the first pigment in the ink is anionic, a cationic group that reacts with the anionic group is used. A treatment liquid containing the compound having is preferably used. If the group bonded to the surface of the first pigment is a cationic group, a treatment liquid containing a compound having an anionic group that reacts with the cationic group is preferably used. Examples of the cationic compound include a relatively low molecular weight cationic compound having about one cationic group in the molecule and a relatively high molecular weight cationic compound having a plurality of cationic groups in one molecule. Examples of relatively low molecular weight cationic compounds include primary to secondary to tertiary amine salt type compounds, specifically laurylamine, coconutamine, stearylamine, rosinamine and other hydrochlorides, acetates, and the like. There are quaternary ammonium salt type compounds, specifically lauryltrimethylammonium chloride, lauryldimethylbenzylammonium chloride, benzyltributylammonium chloride, benzalkonium chloride, cetyltrimethylammonium chloride, and further pyridinium salt type compounds. Include cetylpyridinium chloride, cetylpyridinium bromide, and the like, imidazoline-type cationic compounds, specifically 2-heptadecenyl-hydroxyethylimidazoline, and the like. Oxide adducts, specifically dihydroxyethyl stearylamine, and the like as a preferable example.

Furthermore, in the present invention, an amphoteric surfactant exhibiting a cationic property in a certain pH region can also be used. Specifically, there are amino acid type amphoteric surfactants, RNHCH ₂ —CH ₂ COOH type compounds, betaine type compounds, Examples thereof include stearyl dimethyl betaine and lauryl dihydroxyethyl betaine. Of course, when these amphoteric surfactants are used, the liquid composition is adjusted so that the pH is lower than their isoelectric point, or when mixed with ink on a recording medium, the pH is lower than the isoelectric point. It is preferable to take any one of the adjustment methods. Next, examples of the polymer component of the cationic substance include polyallylamine, polyaminesulfone, polyvinylamine, chitosan, and neutralized or partially neutralized products of acids such as hydrochloric acid and acetic acid.

  Moreover, as an anionic compound, an anionic surfactant etc. can be used, for example. As examples of the anionic surfactant, commonly used ones such as a carboxylate type, a sulfate type, a sulfonate type, and a phosphate type can be used. Examples of the anionic polymer include alkali-soluble resins, specifically sodium polyacrylate, or a polymer obtained by copolymerizing acrylic acid, Of course, it is not limited to these. More specifically, for example, disodium lauryl sulfosuccinate, disodium polyoxyethylene lauroyl ethanolamide ester sulfosuccinate, disodium polyoxyethylene alkylsulfosuccinate, carboxylated polyoxyethylene lauryl ether sodium salt, carboxylated polyoxyethylene lauryl ether Sodium salt, carboxylated polyoxyethylene tridecyl ether sodium salt, polyoxyethylene lauryl ether sodium sulfate, polyoxyethylene lauryl ether sulfate triethanolamine, polyoxyethylene alkyl ether sodium sulfate, polyoxyethylene alkyl ether sodium sulfate, alkyl sulfuric acid Examples include sodium and triethanolamine alkyl sulfate. But it is not limited.

  As other components constituting the treatment liquid, water, a water-soluble organic solvent and other additives may be contained in addition to the above-mentioned chaotic substances or anionic substances. Examples of water-soluble organic solvents include amides such as dimethylformamide and dimethylacetamide, ketones such as acetone, ethers such as tetrahydrofuran and dioxane, polyalkylene glycols such as polyethylene glycol and polypropylene glycol, ethylene glycol, propylene glycol and butylene. Of alkylene glycols such as glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol and diethylene glycol, polyhydric alcohols such as ethylene glycol methyl ether, diethylene glycol monomethyl ether and triethylene glycol monomethyl ether Lower alkyl ethers, ethanol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol Other monohydric alcohols such as Le, glycerin, N- methyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, triethanolamine, sulfolane, dimethyl monkey Hoki side or the like is used. Although there is no restriction | limiting in particular about content of the said water-soluble organic solvent, 5 to 60 weight% of the total liquid weight, More preferably, 5 to 40 weight% is a suitable range. In this embodiment, it is preferable to adjust the treatment liquid so as to have high penetrability with respect to the print medium in order to improve the fixing speed of the image dots on the print medium and the fixability. Is.

  In the present embodiment, the application order of the ink and the treatment liquid to the print medium is basically the predetermined order described above as long as the treatment liquid is applied after the ink is applied to the print medium as described above. The effect of can be obtained. It should be noted that even when the ink and the treatment liquid are applied to the print medium almost simultaneously at a timing such that the landing of the treatment liquid on the print medium does not precede the landing of the ink on the print medium, the above-described predetermined In order to obtain the effect, it is considered that the treatment liquid is applied after the ink is applied. With regard to a specific configuration for determining the order of application, for example, when a serial type head is used, the present invention may be applied to the case where the above-described order is realized by a plurality of times of scanning on the same area with paper feeding interposed therebetween. It is included in the range.

  As described above, the ink of the present embodiment is applied in advance of the treatment liquid, but the number of ink applied need not be limited to one drop as described above. For example, two drops of ink may be applied prior to the treatment liquid. In that case, preferably, the ratio of the second pigment to the first pigment is higher than the first pigment. In contrast, the ink applied thereafter can be such that the proportion of the first pigment is higher than that of the second pigment. Thereby, when it reacts with the process liquid provided after that, a lot of 2nd pigments react with a process liquid first, and the flow of the reaction material of a 1st pigment and a process liquid can further be suppressed by that much. As an embodiment capable of obtaining the same effect, the number of mixed inks applied prior to the treatment liquid is, for example, 3 drops, and the ratio of the second pigment is increased as the mixed ink applied later is included. Is also preferable.

  As described above, when a plurality of ink droplets are applied, the total amount of ink applied is substantially equal to that when one droplet is applied. In other words, according to the embodiment of the present invention, when the ink is applied in a plurality of divisions, the above-described predetermined effect can be obtained even if the amount of each droplet is reduced according to the number of divisions. . Next, the time difference in which the ink and the treatment liquid are applied in the present embodiment is basically the same as in the application order described above, so long as each effect of the present embodiment described above appears basically, any time difference may be applied. It is included in the range. That is, the reaction between the mixed ink and the treatment liquid occurs in various modes depending on the time from application of the ink to application of the treatment liquid. For example, even when the above time is short, the peripheral portion of the dots formed by overlapping them, that is, the edge portion, causes sufficient mixing of the pigment and the like and the treatment liquid, and each effect of this embodiment, particularly “haze”. It has also been observed that an inhibitory effect can occur at least.

  From this point, in this specification, “mixing” of the ink and the treatment liquid means not only the overall mixing but also the mixing in a part such as an edge portion. Furthermore, the case of mixing after penetrating into the print medium is also included. Further, all of these mixing modes are defined as “mixed in a liquid state”.

  The hue (type), density, and number of inks applied in the present embodiment can be arbitrarily combined as long as the application order described above is followed. For example, black (Bk), yellow (Y), magenta (M), and cyan (C) can be generally used as ink types, and dark and light inks can be used for each color. More specifically, for example, at least one of yellow ink, magenta ink, and cyan ink may be used as the mixed ink of this embodiment, and the treatment liquid may be used for the mixed ink, and may be applied in this order.

  Among such combinations to which the present invention can be applied, the most preferable form is that the mixed ink is a black ink. This is because according to this form, each effect of the present embodiment, such as an increase in OD value and suppression of “mist”, can most effectively contribute to the print quality of characters such as characters.

  Various methods for applying these inks and the like to the print medium are conceivable, such as coating, a method of applying the ink or the like by directly contacting the print medium, and any of the application methods are within the scope of the present invention. However, the most preferred form is an ink jet system using a print head. In this case, the combination of the print heads as the ejection unit and the arrangement thereof can be determined according to the combination of the application order and the ink type including the treatment liquid described above. Specifically, the above-described application order can be achieved by a configuration in which the heads of ink and processing liquid are arranged in a direction in which the print head moves relative to the print medium.

  Furthermore, as a more specific configuration of such a configuration, a so-called full multi-type print head in which ink discharge ports are arranged in a range corresponding to the entire width of the print area in the transported print medium or a print medium is scanned. Any of the serial type print heads that move for the above-described purpose enables application of the ink and the treatment liquid according to the present invention. In addition, as the ink discharge method of these print heads, any well-known method such as a piezo method can be adopted. However, the most preferable mode is to generate bubbles in the ink or the processing liquid using thermal energy. The ink or the processing liquid is ejected by the pressure of the bubbles.

  Furthermore, since the range in which the ink and the processing liquid are ejected and overlapped by each print head is normally controlled in units of pixels constituting a print image or the like, the ink or the like is ejected and overlapped at the same position. However, the application of the present invention is not limited to such a configuration. For example, a configuration in which a part of the ink dots and the processing liquid overlap to produce the predetermined effect of the present embodiment, or processing in which the processing liquid is thinned out and applied to the data of each pixel, and flows from adjacent pixels by bleeding or the like A configuration in which a liquid reacts with a pigment is also included in the scope of the present invention.

(Embodiment 1-2)
Another embodiment of the present invention will be described next. In this embodiment, the processing liquid is made highly permeable in the above-described embodiment, thereby achieving high-speed fixing. High-speed fixing is a main configuration for increasing the printing speed, that is, improving the throughput. By increasing the drive frequency of the print head and the conveyance speed of the print medium, the throughput can be directly improved. However, when the printing is completed and the ink on the discharged print medium is unfixed, the subsequent handling is inconvenient, and in the configuration in which the discharged print media are stacked, unfixed There is also a risk that other print media may be stained by ink.

  That is, among the various factors that contribute to the increase in the printing speed, the one that is directly recalled is the speed at which the print medium that has been printed is discharged, as described above. It depends on the conveyance speed of the medium or the scanning speed of the print head. That is, in an apparatus using a so-called full multi-type print head, the conveyance speed of the print medium in the printing operation means the discharge speed as it is, and in an apparatus using a serial type print head, scanning is performed. As a result, the speed is related to the discharge speed of the print medium that has been printed. The print medium conveyance speed or the like correlates with the ink ejection cycle for the pixel through the print resolution, that is, the dot density. That is, in a configuration in which one pixel is printed with ink ejected from a plurality of print heads, when the resolution is fixed, the ejection cycle for the pixel correlates with the transport speed and the like.

  On the other hand, when considering the respective technical problems related to the reaction between the pigment ink and the processing liquid, it is desirable to take as long as possible the time from discharging the ink to discharging the processing liquid. This is because when the pigment ink permeates into the print medium and reacts with the treatment liquid, the above-described phenomenon is difficult to occur. In other words, it can be said that the above-described problem in printing using pigment ink and treatment liquid also hinders the increase in printing speed. In particular, when a pigment ink having a low permeation speed is used in order to improve the OD value, the problem of impairing the speed increase becomes particularly significant.

  In the present embodiment, after the ink is applied to the print medium, by applying a treatment liquid having a high penetration speed, each effect described in the first embodiment is generated, and the ink has a relatively low penetration speed. However, with these, the penetration rate is increased. That is, when the permeation speeds of the mixed ink and the processing liquid into the print medium are v1 and v2, respectively, v1 <v2 is satisfied. FIG. 6 presumably shows the phenomenon in this case. FIG. 6 shows a case where the mixed ink Im and the treatment liquid S are applied to the print medium P in this order. In this case, a reaction product starts to be generated between the processing liquid S and the mixed ink Im in contact with the boundary thereof, but the permeation speed of the mixture of the processing liquid S and the mixed ink is faster than that of the mixed ink alone. Thus, as a whole, high speed fixing is possible by increasing the speed of the mixed ink more than the permeation speed in the case of a single ink. In the present embodiment, by using a treatment liquid having a high penetration rate, relatively fast fixing can be achieved even when a mixed ink having a low penetration rate is employed for improving the OD value.

(Embodiment 1-3)
Yet another embodiment of the present invention relates to the application order of ink and treatment liquid. That is, in this embodiment, after applying the mixed ink, the treatment liquid is applied, and the mixed ink is further applied. According to this embodiment, among the effects described above, it is particularly remarkable in the improvement of the OD value, the suppression of “haze” or feathering. Further, if the treatment liquid applied between the inks is highly permeable, better fixability can be obtained. The above operations and effects of the present embodiment are that the amount of ink is relatively small in the reaction between the mixed ink first applied and the treatment liquid, so that fluidization due to the reaction is small, and the treatment liquid When ink is applied later, the viscosity increases to some extent due to the reaction between the first treatment liquid and the ink, and the penetration of the ink or the like is also progressing. .

(Processing liquid selectivity)
The composition of the treatment liquid is as described above, but it is important to optimize the composition of the treatment liquid according to the types and amounts of the first pigment, the second pigment, and the polymer dispersant in the ink. This is preferable in order to maximize the effects of the invention. This point will be described below with a specific example. Self-dispersing carbon black having an anionic group bonded to the surface as the first pigment, general carbon black as the second pigment, and styrene-acrylic acid-ethyl acrylate copolymer (acid) as the polymeric dispersant And a treatment liquid containing benzalkonium chloride (EBK) as a low molecular weight cationic compound and polyarylamine (PAA) as a high molecular weight cationic compound. When the ratio of EBK and PAA in the processing liquid is fixed to (PAA: 4%, EBK: 0.5%), and the ratio of the self-dispersing carbon in the ink to normal carbon black is changed. Then, the characteristics of the obtained image were evaluated (note that the amount of the polymer dispersant was increased or decreased in accordance with the increase or decrease of the usual amount of carbon black). FIG. 7A is a graph schematically showing a change in the OD of an image obtained when the composition of the treatment liquid is fixed and the weight ratio between the first pigment and the second pigment in the ink is changed. It is. As can be seen from this graph, the OD shows a maximum when the ratio of the first pigment and the second pigment is a predetermined value. In FIG. 7B, the OD of the image obtained when the composition of the treatment liquid is fixed and the weight ratio of the first pigment to the second pigment in the ink is changed is measured from the back side of the print medium. It is measured by a change in OD (back OD), and it can be seen that there is a predetermined correlation between the ratio of the first pigment and the second pigment and the back OD. FIG. 7C shows a case where the edge sharpness of the image obtained when the composition of the treatment liquid is fixed and the weight ratio of the first pigment to the second pigment in the ink is changed is visually observed. The evaluation results are graphed, and similarly, it is understood that the degree of edge sharpness is the best when the ratio of the first pigment and the second pigment is a predetermined value.

  Next, the same experiment was performed by changing the ratio of EBK and PAA in the treatment liquid. As a result, when the EBK is increased, each curve shifts in a direction in which the ratio of the self-dispersing carbon black in the ink is high, and when the PAA ratio is increased, the dispersion of the polymer dispersant in the ink is increased. The ratio of carbon black shifts in the higher direction. From this fact, it is estimated that there is a close relationship between PAA and polymer dispersant-dispersed carbon black, and between EBK and self-dispersing carbon black. This is considered to be explained by the following estimation mechanism.

  That is, the self-dispersing pigment schematically has the form shown in FIG. 4A as described above, and the cationic polymer PAA is as shown in FIG. 4B. A string-like substance having a plurality of cationic groups in one molecule. Here, when only PAA is contained in the treatment liquid, when the self-dispersing pigment and PAA are mixed, a polymer of PAA is entangled around the self-dispersing pigment as shown in FIG. However, since the cationic group of PAA is geometrically difficult to bind to the anion group of all pigments, the bonded group as shown in FIG. 5 is in the form of a cationic state as a whole. It is thought that. In other words, the dispersibility of the pigment is not sufficiently destroyed. When the surroundings of fine pigment particles and the like are surrounded by cationic groups in the ink, the electric repulsive force acts more strongly than the intermolecular force, preventing the aggregation of fine pigment particles, and The tendency to penetrate inside rather than remain on the surface is promoted. As a result, it acts in a direction that hinders improvement in OD and edge sharpness. Here, when EBK having a form as shown in FIG. 4C is present in the processing liquid, the reaction between the self-dispersing carbon black and PAA becomes a competitive reaction with the reaction between the self-dispersing carbon black and EBK. The rate of formation of a black / PAA conjugate decreases. On the other hand, in the second pigment, the polymer dispersant adhering to the surface and PAA in the treatment liquid are easily entangled. As a result, the dispersibility of the pigment in the ink is sufficiently destroyed, and the pigment tends to remain on the surface of the print medium. Therefore, it is considered that OD and edge sharpness are improved.

  More specifically, for example, the ratio of polyarylamine to benzalkonium chloride (PAA: 3.. 6%, EBK: 0.5%), and a combination of processing solutions having high permeability, an image having excellent fixability and particularly excellent edge sharpness can be obtained. In addition, the ratio of polyarylamine and benzalkonium chloride to the ink in which the ratio of the self-dispersing carbon black and the carbon black dispersed with the polymer dispersant is 9: 1 (PAA: 0%, EBK: 4%) In addition, when a processing solution having high permeability is combined, an image having both high-speed fixability and excellent image quality can be obtained. The reason why this mode can achieve both high-speed fixing and high image quality is that the thickness of the ink dots on the print medium can be made particularly thin, and that the treatment liquid does not contain a polymer compound, For example, the viscosity of the reaction solution is small due to the small amount of the polymer dispersant.

( Reference Embodiment 1 )
In the first embodiment, the form using the ink containing the first pigment and the second pigment is mainly described. However, the form in which the first pigment and the second pigment are contained in separate inks is referred. As an embodiment.

( Reference embodiment 1-1)
In this aspect, the first ink containing the first pigment, the second ink containing the second pigment, and the treatment liquid that reacts with the first and second inks are brought into contact with each other in the liquid state on the print medium surface. It is given to do. At that time, it is preferable to perform at least one of the first ink and the second ink prior to application of the treatment liquid. Thereby, substantially the same effects as the various effects of the present invention described above can be obtained.

As a combination of the order of application, (1) first ink → second ink → treatment liquid,
(2) Second ink → first ink → processing liquid,
(3) First ink → processing liquid → second ink,
(4) There are four types: second ink → processing liquid → first ink.

Embodiments and reference examples of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to such examples, and these are further combined, and other fields of technology including similar problems. It can also be applied to.

(Example 1-1)
FIG. 8 is a side view showing a schematic configuration of the full line type printing apparatus according to the first embodiment. The printing apparatus 1 uses a plurality of full-line type print heads (ejection units) arranged at predetermined positions along a conveyance direction of a recording medium as a print medium (the direction of arrow A in FIG. 1) to process ink or processing liquid. An ink jet printing method is employed in which printing is performed by discharging the ink, and the operation is controlled by a control circuit of FIG.

  Each of the print heads 101Bk1, 101Bk2, 101S, 101C, 101M, and 101Y of the head group 101g has about 7200 pieces in the width direction of the recording paper 103 conveyed in the direction A in the drawing (a direction perpendicular to the drawing sheet). It is possible to print on recording paper of maximum A3 size by arranging ink discharge ports. The recording paper 103 is conveyed in the A direction by the rotation of a pair of registration rollers 114 driven by a conveyance motor, and is guided by a pair of guide plates 115 to be registered at the leading end, and then is conveyed by a conveyance belt 111. Be transported. The conveying belt 111 as an endless belt is held by two rollers 112 and 113, and the vertical displacement of the upper portion thereof is regulated by the platen 104. The recording sheet 103 is transported by rotating the roller 113. Note that the recording paper 113 is attracted to the transport belt 111 by electrostatic attraction. The roller 113 is rotationally driven in a direction in which the recording paper 103 is conveyed in the direction of arrow A by a driving source such as a motor (not shown). The recording paper 103 conveyed on the conveying belt 111 and recorded during this time by the recording head group 101g is discharged onto the stocker 116.

  Each print head of the recording head group 101g includes two heads 101Bk1 and 101Bk2 that discharge black ink described in the first embodiment, a processing liquid head 101S that discharges processing liquid, and each head for color ink (cyan head 101C). , Magenta head 101M and yellow head 101Y) are arranged as shown in the drawing along the conveyance direction A of the recording paper 103. Then, it is possible to print black characters and color images by ejecting each color ink and processing liquid from each print head.

  FIG. 9 is a block diagram showing a control configuration of the full-line type printing apparatus 1 shown in FIG.

  The system controller 201 includes a microprocessor, a ROM that stores a control program executed by the apparatus, a RAM that is used as a work area when the microprocessor performs processing, and executes control of the entire apparatus. . The drive of the motor 204 is controlled via the driver 202, and the roller 113 shown in FIG. 8 is rotated to convey the recording paper.

  The host computer 206 transfers information to be printed to the printing apparatus 1 of this embodiment and controls the printing operation. The reception buffer 207 temporarily stores data from the host computer 206 and stores the data until the data is read by the system controller 201. The frame memory 208 is a memory for expanding data to be printed into image data, and has a memory size necessary for printing. In this embodiment, the frame memory 208 is described as being capable of storing one sheet of recording paper, but the present invention is not limited by the capacity of the frame memory.

  The buffers 209S and 209P temporarily store data to be printed, and the storage capacity varies depending on the number of ejection ports of the print head. The print control unit 210 is for appropriately controlling the drive of the print head according to a command from the system controller 201. The print control unit 210 controls the drive frequency, the number of print data, and the like, and further data for discharging the processing liquid. Also create. The driver 211 performs ejection driving of the print head 101S for ejecting the processing liquid and the print heads 101Bk1, 101Bk2, 101C, 101M, and 101Y for ejecting the respective inks. Controlled by signal.

  In the above configuration, print data is transferred from the host computer 206 to the reception buffer 207 and temporarily stored. Next, the stored print data is read by the system controller 201 and developed in the buffers 209S and 209P. Further, paper jam, ink out, paper out, etc. can be detected by various detection signals from the abnormality sensor 222.

The print control unit 210 creates processing liquid data for discharging the processing liquid based on the image data developed in the buffers 209S ^and 209P. Then, the ejection operation of each print head is controlled based on the print data and processing liquid data in each buffer 209S, 209P.

  In this embodiment, for the black ink ejected from the heads 101Bk1 and 101Bk2, an ink having a slow permeation speed (hereinafter referred to as an overlay ink in this embodiment) is used and ejected from the heads 101S, 101C, 101M, and 101Y, respectively. The treatment liquid and the cyan, magenta, and yellow inks used were treatment liquids and inks (hereinafter referred to as “highly permeable inks” in the present example) that have high permeation speeds. The composition of the treatment liquid and each ink used in this example is as follows. In addition, the ratio of each component is shown by the weight part.

[Treatment solution]
Glycerin: 7 parts Diethylene glycol: 5 parts acetylenol EH: 2 parts (manufactured by Kawaken Fine Chemicals)
Polyallylamine: 4 parts (molecular weight: 1500 or less, average value of about 1000)
Acetic acid: 4 parts Benzalkonium chloride: 0.5 part Triethylene glycol monobutyl ether: 3 parts Water: remainder [Yellow (Y) ink]
C. I. Direct yellow 86: 3 parts glycerin: 5 parts diethylene glycol: 5 parts acetylenol EH: 1 part (manufactured by Kawaken Fine Chemicals)
Water: remaining [Magenta (M) ink]
C. I. Acid Red 289: 3 parts glycerin: 5 parts diethylene glycol: 5 parts acetylenol: EH 1 part (manufactured by Kawaken Fine Chemicals)
Water: remaining [cyan (C) ink]
C. I. Direct Blue 199: 3 parts glycerin: 5 parts diethylene glycol: 5 parts acetylenol EH: 1 part (manufactured by Kawaken Fine Chemicals)
Water: remaining [Black (Bk) ink]
Pigment dispersion 1: 25 parts Pigment dispersion 2: 25 parts Glycerin: 6 parts Diethylene glycol: 5 parts Acetylenol EH: 0.1 part (manufactured by Kawaken Fine Chemicals)
Water: remainder The Ka value of this black ink was 0.33. The pigment dispersions 1 and 2 are as follows.

[Pigment dispersion 1]
10 g of carbon black having a surface area of 230 m ² / g and a DBP oil absorption of 70 ml / 100 g and 3.41 g of p-aminobenzoic acid were mixed well with 72 g of water, and then 1.62 g of nitric acid was added dropwise thereto at 70 ° C. Stir. Several minutes later, a solution prepared by dissolving 1.07 g of sodium nitrite in 5 g of water was added, and the mixture was further stirred for 1 hour. The obtained slurry was Toyo Filter Paper No. 2 (manufactured by Advantis), the pigment particles were sufficiently washed with water and dried in an oven at 90 ° C., and water was added to the pigment to prepare a pigment aqueous solution having a pigment concentration of 10% by weight. By the above method, as shown in the following formula, a pigment dispersion in which an anionically charged self-dispersing carbon black having a hydrophilic group bonded thereto via a phenyl group was dispersed was obtained.

[Pigment dispersion 2]
The pigment dispersion 2 is prepared as follows. As a dispersant, 14 parts of a styrene-acrylic acid-ethyl acrylate copolymer (acid value 180, average molecular weight 12000), 4 parts of monoethanolamine and 72 parts of water are mixed, and heated to 70 ° C. in a water bath, Dissolve the resin completely. At this time, if the concentration of the resin to be dissolved is low, the resin may not be completely dissolved. Therefore, when the resin is dissolved, a high concentration solution may be prepared in advance and diluted to prepare a desired resin solution. To this solution, 10 parts of carbon black (trade name: MCF-88, pH 8.0, manufactured by Mitsubishi Chemical) that can be dispersed in an aqueous medium for the first time by the action of a dispersant is added, and premixing is performed for 30 minutes under the following conditions. It was. Subsequently, the following operation was performed to obtain a pigment dispersion 2 in which carbon black (MCF-88) was dispersed in an aqueous medium with a dispersant.

Dispersing machine: Side grinder (Igarashi Machine)
Grinding media: Filling ratio of zirconia beads 1 mm diameter grinding media: 50% (volume)
Grinding time: Centrifugation for 3 hours (12000 RPM, 20 minutes)
By using the black ink according to the present embodiment as described above, the self-dispersing carbon black and the carbon black dispersible with the polymer dispersant and the polymer dispersant are mixed and dispersed. A treatment liquid containing two kinds of different polar cationic compounds (polyarylamine, benzalkonium chloride) reacts.

In this embodiment, the ink discharge ports of each print head are arranged at a density of 600 dpi, and printing is performed at a dot density of 600 dpi in the recording paper conveyance direction. As a result, the dot density of an image or the like printed in this embodiment is 600 dpi in both the row direction and the column direction. The ejection frequency of each head is 4 KHz, and therefore the recording paper conveyance speed is about 170 mm / sec. Further, the distance D _i (see FIG. 8) between the mixed ink heads 101Bk1 and 101Bk2 and the processing liquid head 101S is 80 mm. Therefore, after the black pigment ink is discharged, the processing liquid is discharged. It takes about 0.48 sec.

  The discharge amount of each print head was 15 pl (picoliter) per discharge except for the Bk head, and each Bk head was about 10 pl per discharge. Therefore, the ink application amount per pixel when the two heads Bk1 and Bk2 are used is about 20 pl. In addition, similar results could be obtained in the case where an additional test was performed up to 0.1 seconds from the discharge of the black ink Bk to the discharge of the treatment liquid S.

(Example 1-2)
The experiment was performed in the same manner as in Example 1-1 except that the composition of the treatment liquid and the black ink in Example 1-1 was changed as follows.
[Treatment solution]
Glycerin: 7 parts Diethylene glycol: 5 parts acetylenol EH: 2 parts (manufactured by Kawaken Fine Chemicals)
Benzalkonium chloride: 4 parts Triethylene glycol monobutyl ether: 3 parts Water: remainder [Black (Bk) ink]
Pigment dispersion 1: 45 parts Pigment dispersion 2: 5 parts Glycerin: 6 parts Diethylene glycol: 5 parts Acetylenol EH: 0.1 part (manufactured by Kawaken Fine Chemicals)
Water: balance In addition, Ka value of this black ink was 0 _33..

(Example 1-3)
In Example 1-1, an experiment was performed in the same manner as in Example 1-1 except that the composition of the treatment liquid and the black ink was changed as follows.

[Treatment solution]
Glycerin: 7 parts Diethylene glycol: 5 parts acetylenol EH: 2 parts (manufactured by Kawaken Fine Chemicals)
Polyallylamine: 0.5 part (molecular weight: 1500 or less, average value of about 1000)
Acetic acid: 0.5 part Benzalkonium chloride: 4 parts Triethylene glycol monobutyl ether: 3 parts Water: remainder [Black (Bk) ink]
Pigment dispersion 1:45 parts Pigment dispersion 2: 2.5 parts C.I. I. Food Black 2: 0.25 parts Glycerin: 6 parts Diethylene glycol: 5 parts Acetylenol _EH:. 0 1 part (manufactured by Kawaken Fine Chemicals Co., Ltd.)
Water: balance In addition, Ka value of this black ink was 0 _33..

(Comparative Example 1)
As comparative examples for Examples 1-1 to 1-3, inks having the following components were prepared using only pigment dispersion 2 prepared in the same manner as Example 1-1. Next, using this ink, printing was performed under the same conditions as in Example 1-1. In this comparative example, no treatment liquid was used.
Pigment dispersion 2: 50 parts ethylene glycol: 8 parts glycerin: 5 parts isopropyl alcohol: 4 parts water: balance (Comparative Example 2)
Comparative Example, except that ink prepared in the same manner as in Comparative Example 1 was used, a head having an ink discharge amount of about 15 pl per discharge was used for the Bk1 head and Bk2 head, and the ink application amount per pixel was 30 pl. Printing was performed in the same manner as in 1. The evaluation results of the printed matter obtained in Examples 1-1 to 1-3, Comparative Example 1 and Comparative Example 2 are shown in Table 2 below.

  The printing in each of the examples and comparative examples is obtained by printing a predetermined image on PB paper manufactured by Canon Inc. and measuring the OD value or the like. In addition, among the evaluation items in Table 2, the OD value was measured using a Macbeth concentration measuring machine, and the water resistance expression time was almost visually recognized when the water was dropped after printing. Furthermore, the fixability is the time when there is no show-through when the printed matter is discharged. Further, in the feathering, the ink dots are observed with a loupe, and the presence or absence of a haze-like portion around the dots and the presence or absence of feathering are observed. If they are not observed, “A”, and if they are observed, “B”. It was evaluated. Furthermore, with regard to the edge sharpness of the solid portion, the edge portion of the solid line image is observed with a magnifying glass, and “A” indicates that the line edge is connected in a straight line. The case where there was no practical problem although it was slightly damaged was evaluated as “B”, and the case where the linearity of the edge of the line was lost was evaluated as “C”.

  As is clear from Table 2, in the case of the system of this example, compared with the printed matter using the conventional pigment ink, a printed matter having excellent OD value, water resistance expression time and fixing property can be obtained. Is understood.

Regarding this OD value, in the case of this example in which a treatment liquid is applied to an ink in which a pigment that does not require a dispersant, a pigment that is dispersed by the dispersant, and a polymer dispersant are mixed, the above-described effects of the mixing thereof And a higher OD value can be obtained than when the treatment liquid is applied only to the pigment or the dye. Further, the suppression of feathering (“haze” and “bleed out”) and the sharpness of the edge portion are also superior to the comparative example when compared by the time from the ejection of the head 101Bk to the ejection of the head 101S. I can understand that. Incidentally, in the case where the time until the processing liquid S is ejected from it is ejected black ink Bk in Table 2 as _0. 1 second, obtained almost the same evaluation results.

  The full multi-type printing apparatus described above is used in a state where the print head is fixed in the printing operation, and the time required for transporting the recording paper is almost the time required for printing. is there. Therefore, by applying the present invention to such a high-speed printing device, the high-speed printing function can be further improved, and high-quality printing with a high OD value and no bleeding or smearing is possible.

  The printing apparatus according to the present embodiment is most commonly used as a printer, but is not limited thereto, and can of course be configured as a printing unit such as a copying apparatus or a facsimile. The effect of the present embodiment described with reference to Table 2 above is not limited to the configuration in which two heads are used for the black mixed ink as in the present embodiment, but when one head is used and the ejection amount is 20 pl. The same effect can be obtained.

(Example 2)
FIG. 10 is a schematic perspective view showing the configuration of a serial type printing apparatus 5 according to the second embodiment of the present invention. That is, it is obvious that the printing apparatus that discharges and reacts the treatment liquid after applying ink to the print medium is not limited to the above-described full line type, but can also be applied to a serial type apparatus. The same elements as those shown in FIG. 8 are denoted by the same reference numerals, and detailed description thereof is omitted. A recording sheet 103 as a print medium is inserted from the paper feeding unit 105 and discharged through the printing unit 126. In this embodiment, an inexpensive plain paper that is generally widely used is used as the recording paper 103. In the print unit 126, the carriage 107 is mounted with print heads 101Bk, 101S, 101C, 101M, and 101Y, and is configured to be reciprocated along the guide rail 109 by a driving force of a motor (not shown). The print head 101Bk discharges the black mixed ink described in the above embodiment. The print heads 101S, 101C, 101M, and 101Y eject processing liquid, cyan ink, magenta ink, and yellow ink, respectively, and are driven to eject ink or processing liquid onto the recording paper 103 in this order. .

  Each head is supplied with ink or processing liquid from the corresponding ink tank 108Bk, 108S, 108C, 108M, 108Y, and is driven by an electrothermal transducer, that is, a heater provided for each ejection port of each head when ink is ejected. A signal is supplied, thereby causing thermal energy to act on the ink or processing liquid to generate bubbles, and the ink or processing liquid is ejected using the pressure at the time of foaming. Each head is provided with 64 ejection openings at a density of 360 dpi, which are arranged in substantially the same direction as the conveyance direction Y of the recording paper 103, that is, in a direction substantially perpendicular to the scanning direction by each head. . And the discharge amount for each discharge port is 25 pl.

  In the above configuration, the distance between the heads is ½ inch. Therefore, the distance between the heads 101Bk and 101S is 1 inch, the print density in the scanning direction is 720 dpi, and the ejection frequency of each head is 7.2 KHz. Therefore, the time from when the pigment ink of the head 101Bk is ejected until the treatment liquid of the head 101S is ejected is 0.05 sec.

FIGS. 11A to 11C are diagrams schematically showing an ejection port array, showing other examples of the head configuration in the serial printing apparatus as shown in FIG. As shown in FIG. 6A _, there are two discharge units that discharge black ink using ink (discharge units 101Bk1 _and 101Bk2), and a discharge unit 101S that discharges processing liquid is disposed between them. It may be. In this case, after the black ink is applied, the treatment liquid is applied, and then the black ink is further applied.

The head configuration shown in FIG. 11 including FIG. 11A is an integrated head structure for several inks or processing liquids. Of course, in an integrated head unit, ink and The discharge ports and the liquid chambers communicating with the treatment liquids are separated from each other for each processing liquid. Accordingly, each ejection unit is the same as each ink or processing liquid head.

FIG. 11B shows an example having two ejection units that eject black ink using ink, as in the example shown in FIG. 11A, but these ejection units 101Bk1 and 101Bk2 can be ejected prior to the processing liquid. It is arranged as follows. According to this configuration, the post-treatment liquid is applied after two drops of black ink. FIG. 11C shows the same arrangement and number of the ejection unit 101Bk that ejects black ink and the ejection unit 101S that ejects the processing liquid as in the embodiment shown in FIG. The structure of the ejection part for each of the C, M, and Y inks is different. Two discharge portions for each of the C, M, and Y inks are provided (discharge portions 101C1, 101C2, discharge portions 101M1, 101M2, discharge portions 101Y1, 101Y2), and discharge portions 101C1 for each ink in a direction perpendicular to the scanning direction. , 101M1, 101Y1 and the ejection units 101C2, 101M2, 101Y2 are respectively arranged. In the case of this head configuration, the C, M, and Y inks are superimposed by a plurality of scans sandwiching the conveyance of the recording paper. In addition, the two ejection portions of each ink are for mutually ejecting dark _and light inks.

  As shown in FIGS. 11 (a) and 11 (b), when there are, for example, two black ink discharge portions, the content ratio of the first pigment and the second pigment in the ink discharged from each of them is as follows. Are the same in any of the discharge parts, but this may be changed. For example, the ratio of the first pigment to the second pigment may be (1: 1) for the discharge unit 101Bk1 and (9: 1) for the discharge unit 101Bk2. On the contrary, the discharge unit 101Bk1 may be (9: 1) and the discharge unit 101Bk2 may be (1: 1).

(Example 3)
In still another embodiment of the present invention, as shown in FIG. 11A, for example, print heads or ejection units are arranged. That is, in FIG. 11A, the black ink is ejected from the ejection units 101Bk1 and 101Bk2, and the processing liquid is ejected from the ejection unit 101S. That is, ejection is performed in the order of ink, processing liquid, and ink. In this embodiment, each discharge portion has discharge ports arranged at a density of 600 dpi, the discharge amount is about 15 pl, and the interval between each discharge portion is ½ inch as in the second embodiment. The ejection frequency is 10 KHz, and the print resolution is 600 dpi in both the sub-scanning direction and the scanning direction. Thereby, the discharge interval between the ink and the treatment liquid is 30 msec. The treatment liquid has a high permeability of 2% acetylenol. According to the configuration of the above embodiment, the OD value of printing, such as black character can get about _1.5 or more high OD values, also for fluidization of the reaction product by the treatment liquid is little, "also It is possible to prevent the occurrence of “ya” and feathering. In addition, since a highly permeable processing solution is used as described above, better fixability can be realized.

( Reference Example 1 )
When the embodiment shown in FIGS. 8 and 9 is applied not to the mixed ink but to the form in which the first pigment and the second pigment are individually ejected, each print head of the recording head group 101g is made of black. The first pigment ink head 101Bk1 _{, the} black second pigment ink head 101Bk2, the processing liquid head 101S for discharging the processing liquid, and the color ink heads (cyan head 101C, magenta head 101M, yellow head 101Y). The recording paper 103 is arranged as shown in the drawing direction A. Then, it is possible to print black characters and color images by ejecting each color ink and processing liquid from each print head.

In this reference example, the black first pigment ink and the second pigment ink ejected from the heads 101Bk1 and 101Bk2, respectively, are superposed inks having a low permeation speed, and the heads 101S, 101C, 101M, and 101Y are used. The treatment liquid and cyan _, magenta _{, and} yellow inks to be ejected use a treatment liquid and a highly permeable ink, respectively, which have a high penetration speed.

The compositions of the first and second inks and the treatment liquid used in this reference example are as follows.

[Treatment solution]
Glycerin: 7 parts Diethylene glycol: 5 parts acetylenol EH: 2 parts (manufactured by Kawaken Fine Chemicals)
Polyallylamine: 4 parts (molecular weight: 1500 or less, average value of about 1000)
Acetic acid: 4 parts Benzalkonium chloride: 0.5 parts Triethylene glycol monobutyl ether: 3 parts Water: remainder [Black (Bk) first pigment ink]
Pigment dispersion 1:50 parts Glycerin: 6 parts Jiri Ethylene glycol: 5 parts Acetylenol _EH:. 0 1 part (manufactured by Kawaken Fine Chemicals)
Water: balance In addition, Ka value of this black ink was 0 _33.. The pigment dispersions 1 and 2 are as follows.

[Black second pigment ink]
Pigment dispersion liquid 2: 50 parts Ethylene glycol: 8 parts Glycerin: 5 parts Isopropyl alcohol: 4 parts Water: balance The above-described black first pigment ink and second pigment ink according to this reference example were used to The treatment liquid containing the compound of different polarity reacts with the state of the liquid in which the first pigment having the polarity, the second pigment, and the polymer dispersant are mixed and dispersed. .

In this reference example, the distance Di (see FIG. 8) between the pigment ink head 101Bk1 and the treatment liquid head 101S is 80 mm. Therefore, after the black first or second pigment ink is ejected. The time until the processing liquid is discharged is about 0.48 sec. The discharge amount of each print head was 15 pl per discharge except for the Bk head, and each Bk head was about 10 pl per discharge. Therefore, when one pixel is formed by the Bk1 and Bk2 heads, about 20 pl of Bk ink is applied in total. When printed materials obtained using such an apparatus and ink were evaluated in the same manner as in Examples 1-1 to 1-3, almost the same results were obtained.

( Reference Example 2 )
FIG. 12 is a schematic perspective view showing a configuration of a serial type printing apparatus 5 that can be used in a process in which a first pigment ink and a second pigment ink are mixed on a print medium and then reacted with a treatment liquid. . That is, it is obvious that the printing apparatus that can be used in such a process is not limited to the above-described full line type, but can also be applied to a serial type apparatus. Note that the same elements as those shown in FIG. 8 are denoted by the same reference numerals, and detailed description thereof will be omitted. A recording sheet 103 as a print medium is inserted from the paper feeding unit 105 and discharged through the printing unit 126. In this reference example, an inexpensive plain paper that is generally widely used is used as the recording paper 103. In the printing unit 126, the carriage 107 is mounted with print heads 101Bk1, 101Bk2, 101S, 101C, 101M, and 101Y, and is configured to be reciprocally movable along the guide rail 109 by a driving force of a motor (not shown). The print head 101Bk1 ejects the first black pigment ink, and the print head 101Bk2 ejects the second black pigment ink. The print heads 101S, 101C, 101M, and 101Y eject processing liquid, cyan ink, magenta ink, and yellow ink, respectively, and are driven to eject ink or processing liquid onto the recording paper 103 in this order. .

  Each head is supplied with ink or processing liquid from the corresponding ink tank 108Bk1, 108Bk2, 108S, 108C, 108M, 108Y, and at the time of ink ejection, an electrothermal converter (heater) provided for each ejection port of each head. A drive signal is supplied to the ink or the processing liquid, thereby generating a bubble by applying thermal energy to the ink or the processing liquid, and the ink or the processing liquid is discharged using the pressure at the time of foaming. Each head is provided with 64 ejection openings at a density of 360 dpi, which are arranged in substantially the same direction as the conveyance direction Y of the recording paper 103, that is, in a direction substantially perpendicular to the scanning direction by each head. . The discharge amount of the Bk ink discharge port is 15 pl, and the discharge amounts of the other ink and processing liquid discharge ports are 23 pl.

  In the above configuration, the distance between the heads is ½ inch. Therefore, the distance between the heads 101Bk1 and 101S is 1 inch, the print density in the scanning direction is 720 dpi, and the ejection frequency of each head is 7.2 KHz. Therefore, the time from when the pigment ink of the head 101Bk1 is ejected until the treatment liquid of the head 101S is ejected is 0.1 sec.

( Reference Example 3 )
In still another reference example of the present invention, in the serial type inkjet printing apparatus shown in FIG. 12, the arrangement order of the print heads is changed, and the black first pigment ink, the second pigment ink, and the treatment liquid are changed accordingly. The order of granting is different. That is, in FIG. 12, the arrangement order of the print heads is the head 101Bk1 and the head 101Bk2 (the other heads are the same as in Reference Example 2 ), whereby the first black pigment ink, the processing liquid, and the second black The pigment inks are ejected onto the print medium in this order. The distance between the heads, the ejection frequency of each head, and the like are the same as in the second embodiment. According to this reference example, the fluidization of the reaction product between the ink and the treatment liquid can be reduced compared to the case where the treatment liquid is applied after the first pigment ink and the second pigment ink are applied. Can be further suppressed. In the above description, the black first pigment ink is ejected from the head 101Bk1, and the black second pigment ink is ejected from the head 101Bk2. On the contrary, the black first pigment ink is ejected from the head 101Bk1. 2 pigment ink may be ejected, and the black first pigment ink may be ejected from the head 101 </ b> Bk <b> 2, and the same effect as described above can also be obtained by this configuration.

It is a conceptual diagram presumably explaining a “bleeding out” phenomenon of a reaction product when ink and a treatment liquid are reacted. FIG. 6 is a conceptual diagram for presumably explaining dot formation when a treatment liquid is reacted after ink is applied to a print medium in an embodiment of the present invention. (A) It is a schematic explanatory drawing of the state by which the ink concerning this invention was provided to the print medium surface. (B) It is a schematic explanatory drawing of the state in which the conventional pigment ink was provided to the print medium surface. (A) It is a conceptual diagram of an anionic self-dispersion type pigment molecule. (B) It is a conceptual diagram of a cationic polymer compound molecule. (C) It is a conceptual diagram of a cationic surfactant molecule. It is a schematic diagram showing the reaction form in the boundary part of two anionic self-dispersion type pigments which a cationic polymer interposes. FIG. 5 is a conceptual diagram presumably explaining dot formation when pigment ink and dye ink are mixed on a print medium and then reacted with a treatment liquid in an embodiment of the present invention. (A) It is a graph which shows roughly the change which the ratio change of the 1st pigment in an ink and the 2nd pigment gives to OD of an image. (B) It is a graph which shows roughly the change which the ratio change of the 1st pigment in an ink and the 2nd pigment gives to the back OD of an image. (C) It is a graph which shows roughly the change which the ratio change of the 1st pigment in an ink and the 2nd pigment gives to the edge sharpness of an image dot. 1 is a side view illustrating a schematic configuration of a printing apparatus according to an embodiment of the present invention. FIG. 9 is a block diagram illustrating a control configuration of the printing apparatus illustrated in FIG. 8. It is a perspective view which shows the structure of the printing apparatus which concerns on the other Example of this invention. It is a schematic diagram which shows the head structure of the printing apparatus which concerns on the further another Example of this invention. It is a perspective view which shows the structure of the printing apparatus which concerns on another reference example.

Explanation of symbols

_Id dye ink P Print medium S Treatment liquid I _p Pigment ink _Im Mixed ink v ₁ Penetration speed of pigment ink to the print medium v ₂ Penetration speed of the dye ink to the print medium v ₃ Penetration speed of the treatment liquid to the print medium coefficient t elapsed time V permeation amount tw wet time D distance 1 printing apparatus between the head of the head and processing liquid _I pigment ink 5 printing apparatus 101g head group 101 (Bk1, Bk2, S, C, M, Y, C1 , C2, M1, M2, Y1, Y2) Print head (discharge unit)
103 Recording paper 104 Platen 105 Paper feed unit 107 Carriage 108 (Bk, 108S, 108C, 108M, 108Y) Ink tank 109 Guide rail 111 Conveying belt 112, 113 Roller 114 Registration roller 115 Guide plate 116 Stocker 126 Printing unit 201 System controller 202 Driver 204 Motor 206 Host computer 207 Reception buffer 208 Frame memory 209S, 209P Buffer 210 Print control unit 211 Driver 222 Error sensor

Claims (9)

In an inkjet printing method comprising a step of recording an image on a print medium,
A first step of depositing ink on a print medium using an ink jet recording method; and a second step of depositing a treatment liquid reactive with the ink on the print medium;
The ink includes a first pigment and a second pigment dispersed in an aqueous medium, and the first pigment has at least one anionic group directly or via another atomic group. A self-dispersing pigment bonded to the surface of the pigment or a self-dispersing pigment in which at least one cationic group is bonded to the surface of the first pigment directly or through another atomic group The second pigment is a pigment that can be dispersed in the aqueous medium by a polymer dispersant, and the ink is further a polymer dispersant having the same polarity as the group bonded to the surface of the first pigment. And an ink containing at least one of a nonionic polymer dispersant, and the second step is performed so that the ink and the treatment liquid are in contact with each other in a liquid state on the print medium. How to print.   The inkjet print according to claim 1, further comprising a third step of applying the ink onto the print medium so that the ink is mixed in a liquid state with a mixed liquid of the ink and the treatment liquid on the print medium. Method. The inkjet printing method according to claim 1, wherein the anionic group is at least one selected from the following anionic groups.
_{-COOM, -SO 3 M, -PO 3} HM and -PO ₃ M ₂
(These M's independently represent a hydrogen atom, an alkali metal, ammonium, or organic ammonium.)   The atomic group is an alkyl group having 1 to 12 carbon atoms, a phenyl group which may have a substituent, or a naphthyl group which may have a substituent. Inkjet printing method.   The ink jet printing method according to any one of claims 1 to 4, wherein a ratio of the first pigment to the second pigment is in a range of 9/1 to 4/6.   The ink jet printing method according to claim 1, wherein the first pigment is contained in a larger amount than the second pigment.   The ink-jet printing method according to any one of claims 1 to 6, wherein the ink further contains a dye having the same polarity as the group bonded to the surface of the first pigment.   The treatment liquid has a first compound having one group having a polarity opposite to the group bonded to the surface of the first pigment, and a polarity opposite to the group bonded to the surface of the first pigment. The inkjet printing method according to any one of claims 1 to 7, comprising a second compound having a plurality of groups.   The ink jet printing method according to claim 8, wherein the first compound is benzalkonium chloride and the second compound is polyallylamine.

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