JP5676328B2 - Image forming method - Google Patents

Description

  The present invention relates to an image forming method.

The ink jet recording method is a method of performing recording by ejecting droplet-shaped ink from a large number of nozzles formed on an ink jet recording head toward a recording medium and fixing the ink to the recording medium. In order to obtain a high-definition and high-quality image, a processing liquid (also referred to as a fixing liquid or a reaction liquid) containing a compound that promotes ink aggregation is studied as a technique for quickly fixing ink to a recording medium. Has been.
For example, an ink set is disclosed in which a treatment liquid containing a polyvalent organic acid and at least one of polyphosphoric acid and metaphosphoric acid is combined with an ink composition containing a pigment (for example, Patent Document 1).
Also, a method for applying a treatment liquid to a recording medium has been studied. For example, a proposal has been made to apply a treatment liquid containing an acidic compound at a predetermined application speed by a roller application method (for example, Patent Document 2). .

JP 2010-188661 A JP 2010-240862 A

In the ink jet recording method, when an image is formed using a processing liquid and an ink composition containing a component aggregated by the processing liquid, the image may have insufficient abrasion resistance. In particular, when a treatment liquid containing an inorganic acidic compound is used for the purpose of suppressing the occurrence of uneven glossiness in the image area, the abrasion resistance of the image may be insufficient. It was suspected that the insufficient abrasion resistance of the image was caused by the acidic compound contained in the processing liquid damaging the recording medium.
Therefore, in order to obtain a high-quality image, it is necessary to realize an effective acid concentration on the recording medium for agglomerating ink while suppressing damage to the recording medium by the processing liquid.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming method that is excellent in ink cohesion, suppresses occurrence of gloss unevenness in an image area, and suppresses adverse effects of a processing liquid on a recording medium. Examples of adverse effects on the recording medium include roughness on the surface of the recording medium and deterioration in adhesion of the image area.

<1> water, organic acidic compounds, and contain an inorganic acidic compound containing at least phosphoric acid, the 50 content of 5 mol% or more of the inorganic acidic compound to the content of the organic acidic compound containing at least malonic acid A treatment liquid applying step of applying a treatment liquid having a mol% of not more than 25 and a pH of 0.5 to 2.0 at 25 ° C. to the recording medium, and 0.5 seconds after the treatment liquid is applied to the recording medium. Drying is started within ² seconds, and after applying the treatment liquid to the recording medium, a drying step of drying the recording medium to a moisture content of 1.0 g / m ² or less within 5 seconds, and after the drying step, An ink application step of forming an image by applying an ink composition containing at least one of a colorant and polymer particles to the recording medium.
<2> The image forming method according to <1>, wherein the treatment liquid has a phosphoric acid content with respect to a malonic acid content of 5 mol% or more and 50 mol% or less.
< 3 > The image forming method according to <1> or <2> , wherein the treatment liquid has a pH at 25 ° C. of 0.5 to 1.5.
< 4 > The drying step starts within 0.5 seconds to 1.5 seconds after the treatment liquid is applied to the recording medium, and within 3 seconds after the treatment liquid is applied to the recording medium. The image forming method according to any one of <1> to < 3 >, wherein the recording medium is dried to a moisture content of 1.0 g / m ² or less.
< 5 > The image forming method according to any one of <1> to < 4 >, wherein the recording medium has a coat layer containing calcium carbonate.

  According to the present invention, it is possible to provide an image forming method that is excellent in ink cohesion, suppresses the occurrence of uneven glossiness in the image area, and suppresses the adverse effect of the treatment liquid on the recording medium. Examples of adverse effects on the recording medium include roughness on the surface of the recording medium and deterioration in adhesion of the image area.

Hereinafter, although the form for implementing this invention is demonstrated in detail, this invention is not limited to this, A various deformation | transformation can be implemented within the range of the meaning.
In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

The image forming method of the present invention comprises:
A treatment liquid applying step of applying a treatment liquid containing at least one of water, an organic acidic compound, and at least one inorganic acidic compound and having a pH of 0.5 to 2.0 at 25 ° C. to a recording medium; ,
Drying is started within 0.5 to 2 seconds after the treatment liquid is applied to the recording medium, and the water content is reduced to 1.0 g / m ² or less within 5 seconds after the treatment liquid is applied to the recording medium. A drying step of drying the recording medium;
An ink application step of forming an image by applying an ink composition containing at least one of a colorant and polymer particles to the recording medium after the drying step.
With such a configuration, the image forming method of the present invention is excellent in ink cohesiveness, suppresses occurrence of uneven glossiness in the image area, and suppresses adverse effects of the processing liquid on the recording medium. The image forming method of the present invention is excellent in image abrasion resistance by suppressing the adverse effect of the treatment liquid on the recording medium.

≪Processing liquid application process≫
In the present invention, the treatment liquid application step records a treatment liquid containing at least one of water, at least one organic acidic compound, and at least one inorganic acidic compound and having a pH at 25 ° C. of 0.5 to 2.0. To the medium.

  In the present invention, the treatment liquid application step is provided before the ink application step. That is, before the ink composition is applied on the recording medium, a treatment liquid for aggregating the color material and / or polymer particles in the ink composition is applied in advance, and the processing applied on the recording medium. An ink composition is applied so as to come into contact with the liquid to form an image. Thereby, for example, image formation by an ink jet method can be accelerated, and an image with high density and resolution can be obtained even if high-speed recording is performed.

  In the treatment liquid application step, the treatment liquid can be applied by applying a known method such as a coating method, an ink jet method, or an immersion method. The coating method may be a known coating method using a roller, bar coater, extrusion die coater, air doctor coater, blade coater, rod coater, knife coater, squeeze coater, reverse roll coater, or the like. The ink jet method may be an ink jet method (details will be described later) applied to the ink application step in the present invention. In the present invention, roller coating using a coating roller is preferable from the viewpoint of coating uniformity. The application roller is not particularly limited, and for example, it can be performed using a liquid application apparatus having a structure described in FIG. 7 of JP-A-2009-61645.

  The area to which the treatment liquid is applied may be the entire area application to the entire recording medium or the partial application to be partially applied to the area where ink jet recording is performed in the ink application process. In the present invention, from the viewpoint of uniformly adjusting the application amount of the processing liquid, uniformly recording fine lines and fine image portions, and suppressing density unevenness such as image unevenness, a recording medium is applied by application using an application roller or the like. The entire surface is preferably applied to the entire surface.

  Examples of the method of applying the treatment liquid by controlling the application amount of the treatment liquid include a method using an anilox roller. An anilox roller is a roller with a ceramic-sprayed roller surface processed with a laser to give it a pyramid shape, a diagonal line, a turtle shell shape, or the like. The treatment liquid enters the concave portion formed on the roller surface, and is transferred when it comes into contact with the recording medium, and is applied in a coating amount controlled by the concave portion of the anilox roller.

The application amount of the treatment liquid can be appropriately selected according to the total droplet ejection amount of the ink composition. Conversely, the total droplet ejection amount of the ink composition may be selected according to the coating amount of the treatment liquid. In the present invention, from the viewpoint of the cohesiveness of the ink composition, the average application amount of the acidic compound in the region on the recording medium to which the treatment liquid has been applied is preferably 0.1 to 1.0 g / m ² on average. 0.15-0.70 g / m ² is more preferable, and 0.25-0.55 g / m ² is even more preferable.
When the applied amount of the treatment liquid is 0.1 g / m ² or more as the applied amount of the acidic compound, the ink composition to be ejected can be effectively aggregated and fixed, and a higher resolution image is recorded. be able to. On the other hand, when the application amount of the treatment liquid is 1.0 g / m ² or less as the application amount of the acidic compound, an adverse effect on the recording medium can be suppressed, and a decrease in abrasion resistance can be suppressed. In particular, when a recording medium having a coating layer containing calcium carbonate is used, from the viewpoint of suppressing adverse effects on the coating layer, the amount of treatment liquid applied is 1.0 g / m ² or less as the amount of acidic compound applied. It is preferable that

<Processing liquid>
The treatment liquid in the present invention contains water, at least one organic acidic compound, and at least one inorganic acidic compound, and has a pH at 25 ° C. of 0.5 to 2.0. When the treatment liquid having such a configuration comes into contact with an ink composition containing at least one kind of colorant and polymer particles, the dispersed particles in the ink composition can be aggregated.
In the present invention, by using a treatment liquid containing at least one organic acidic compound and at least one inorganic acidic compound, the ink cohesiveness is excellent and the occurrence of uneven glossiness in the image area is suppressed.
Hereinafter, the organic acidic compound and the inorganic acidic compound may be collectively referred to as “acidic compound”.

(Organic acidic compounds)
The organic acidic compound contained in the treatment liquid can aggregate the components in the ink composition.
The organic acidic compound contained in the treatment liquid is not particularly limited as long as it is an organic compound having at least one acidic group. Examples of the acidic group include a phosphoric acid group, a phosphonic acid group, a phosphinic acid group, a sulfuric acid group, a sulfonic acid group, a sulfinic acid group, and a carboxy group. In the invention, the acidic group is preferably a phosphoric acid group or a carboxy group, more preferably a carboxy group, from the viewpoint of the aggregation rate of the ink composition.

  Organic compounds having a carboxy group (organic carboxylic acid) are polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid (preferably DL-malic acid), maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid. Acid, citric acid, tartaric acid, phthalic acid, 4-methylphthalic acid, lactic acid, sulfonic acid, orthophosphoric acid, pyrrolidone carboxylic acid, pyrone carboxylic acid, pyrrole carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, Nicotinic acid, derivatives of these compounds, or salts thereof (for example, polyvalent metal salts) are preferred. These compounds may be used alone or in combination of two or more.

  The organic carboxylic acid is preferably a divalent or higher carboxylic acid (hereinafter also referred to as polyvalent carboxylic acid) from the viewpoint of the aggregation rate of the ink composition, and malonic acid, malic acid, maleic acid, and succinic acid. , Glutaric acid, fumaric acid, tartaric acid, 4-methylphthalic acid, and citric acid are more preferable, and malonic acid, malic acid, tartaric acid, and citric acid are particularly preferable.

  The organic acidic compound contained in the treatment liquid preferably has a low pKa. Dispersion stability is reduced by bringing the surface charge of particles such as pigments and polymer particles in the ink composition, which is stabilized by a weakly acidic functional group such as a carboxy group, into contact with an organic acidic compound having a lower pKa. Can be reduced.

  The organic acidic compound contained in the treatment liquid preferably has a low pKa, a high solubility in water, and a valence of 2 or more, and a functional group that stabilizes the particles in the ink composition (for example, A divalent or trivalent acidic substance having a high buffering capacity in a pH region lower than the pKa of a carboxy group or the like is more preferable.

(Inorganic acidic compounds)
The inorganic acidic compound contained in the treatment liquid can aggregate the components in the ink composition.
Examples of the inorganic acidic compound contained in the treatment liquid include phosphoric acid, nitric acid, nitrous acid, sulfuric acid, and hydrochloric acid, but are not particularly limited thereto. As the inorganic acidic compound, phosphoric acid is most preferable from the viewpoint of suppressing the occurrence of uneven glossiness in the image area and the ink aggregation rate.

  Phosphoric acid has a low water solubility (25 ° C.) of 0.0018 g / 100 g of water when a calcium salt (calcium phosphate) is used. Therefore, when the inorganic acidic compound contained in the processing liquid is phosphoric acid, the calcium salt is not dissolved but is fixed, and the effect of suppressing the occurrence of uneven gloss on the surface of the image area is high. In particular, when a recording medium having a coating layer containing calcium carbonate is used as the recording medium, phosphoric acid is advantageous as the inorganic acidic compound contained in the treatment liquid.

The total amount of acidic compounds contained in the treatment liquid is not particularly limited, but is preferably 5 to 40% by mass and more preferably 10 to 30% by mass from the viewpoint of the aggregation rate of the ink composition.
The content ratio of the organic acidic compound to the inorganic acidic compound is preferably 5 to 50 mol% of the content of the inorganic acidic compound with respect to the content of the organic acidic compound from the viewpoint of aggregation rate and suppression of uneven gloss. More preferably, it is -40 mol%, and it is still more preferable that it is 15-35 mol%.

(water)
The treatment liquid contains water. The water content is preferably 50 to 90% by mass and more preferably 60 to 80% by mass with respect to the total mass of the treatment liquid.

(Water-soluble organic solvent)
The treatment liquid preferably contains at least one water-soluble organic solvent.
The water-soluble organic solvent is not particularly limited as long as it is an organic solvent capable of dissolving 5 g or more in 100 g of water at 20 ° C. Specifically, a water-soluble organic solvent that can be contained in the ink composition described later can be used in the treatment liquid as well. Among them, from the viewpoint of curling suppression, polyalkylene glycol or a derivative thereof is preferable, diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, dipropylene glycol, tripropylene glycol monoalkyl ether, polyoxypropylene glyceryl ether, and More preferably, it is at least one selected from polyoxyethylene polyoxypropylene glycol.

  As content in the processing liquid of a water-soluble organic solvent, it is preferable that it is 3-20 mass% with respect to the whole processing liquid from viewpoints of applicability | paintability etc., and it is more preferable that it is 5-15 mass%.

(Surfactant)
The treatment liquid may contain at least one surfactant. The surfactant can be used as a surface tension adjusting agent. Examples of the surface tension adjusting agent include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants, and the like. Among these, nonionic surfactants or anionic surfactants are preferable from the viewpoint of the aggregation rate of the ink composition.

  As the surfactant, JP-A-59-157636, pages 37 to 38 and Research Disclosure No. The compounds listed as surfactants in 308119 (1989) are also included. Further, fluorine (fluorinated alkyl) -based surfactants and silicone-based surfactants described in JP-A Nos. 2003-322926, 2004-325707, and 2004-309806 are also included.

  Although there is no restriction | limiting in particular as content of surfactant in a processing liquid, It is preferable that it is content so that the surface tension of a processing liquid will be 50 mN / m or less, Content which will be 20-50 mN / m It is more preferable that the content is 30 to 45 mN / m.

(Other additives)
The treatment liquid can be configured to contain other additives in addition to the acidic compound and the water-soluble organic solvent. Other additives in the treatment liquid are the same as other additives in the ink composition described later.

(Physical properties of processing solution)
The treatment liquid has a pH of 0.5 to 2.0 at 25 ° C. (± 1 ° C.) from the viewpoint of the aggregation rate of the ink composition. If the pH of the treatment liquid is less than 0.5, the adverse effect on the recording medium, for example, the roughness of the paper surface increases, and the adhesion of the image area deteriorates. On the other hand, if the pH of the treatment liquid exceeds 2.0, the aggregation rate is too slow, and dot coalescence occurs and the graininess deteriorates. The pH (25 ° C. ± 1 ° C.) of the treatment liquid is more preferably 0.5 to 1.5.

  The viscosity of the treatment liquid is preferably in the range of 0.5 to 10 mPa · s, more preferably in the range of 1 to 5 mPa · s, from the viewpoint of the aggregation rate of the ink composition. The viscosity is measured under a condition of 25 ° C. using a VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD).

  The surface tension of the treatment liquid at 25 ° C. (± 1 ° C.) is preferably 60 mN / m or less, more preferably 20 to 50 mN / m, and still more preferably 30 to 45 mN / m. When the surface tension of the treatment liquid is within the above range, the occurrence of curling in the recording medium is advantageously suppressed. The surface tension of the treatment liquid is measured under a condition of 25 ° C. by the plate method using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).

≪Drying process≫
In the present invention, the drying step starts drying within 0.5 to 2 seconds after the treatment liquid is applied to the recording medium, and the moisture content is 1.0 g within 5 seconds after the treatment liquid is applied to the recording medium. The recording medium is dried to / m ² or less. The moisture content (g) of the recording medium is obtained by punching the paper into a size of 3 cm × 3 cm and using a trace moisture measuring device CA-200 (Karl Fischer moisture meter manufactured by Mitsubishi Chemical Analytech Co., Ltd.) according to the specifications of the moisture meter. It is to be measured. The measured moisture content (g) is divided by the punched area to calculate the moisture content (g / m ² ) per unit area.
The image forming method of the present invention has such a drying step between the treatment liquid application step and the ink application step, so that the ink cohesion is excellent, and the adverse effect on the recording medium by the treatment liquid is suppressed, and the image resistance. Excellent friction.

In the drying step, drying is started at 0.5 to 2 seconds after the application of the treatment liquid to the location is completed at the location where the application of the treatment liquid on the recording medium is completed.
When drying of the treatment liquid application portion is started within 0.5 seconds after the treatment liquid is applied to the recording medium, it is supplied to a treatment liquid application means (for example, an application roller) disposed near the treatment liquid application portion. The treated liquid may also be dried. In this case, the treatment liquid may be concentrated in the treatment liquid application means or the components of the treatment liquid may be deposited, making it difficult to apply a desired amount of the acidic compound in the treatment liquid to the recording medium.
On the other hand, when drying is started after 2 seconds have passed after applying the treatment liquid to the recording medium, a neutralization reaction between the acidic compound contained in the treatment liquid and a component (eg, calcium carbonate) contained in the recording medium proceeds, and the ink composition The effective acid concentration causing aggregation to the product becomes too low, and the aggregation property of the ink applied later deteriorates, which is not preferable.

In the drying step, the recording medium is dried to a moisture content of 1.0 g / m ² or less within 5 seconds from the end of the application of the treatment liquid to the location at the location where the application of the treatment liquid on the recording medium is completed. Neutralization and water content advances neutralization reaction between the components (e.g., calcium carbonate) contained in the acidic compounds and the recording medium contained in the treatment liquid exceeds 1.0 g / m ^2, to 1.0 g / m ² or less The reaction can be suppressed. In order to further suppress the neutralization reaction, the water content is preferably 0.7 g / m ² or less, and most preferably 0.3 g / m ² or less. After the treatment liquid is applied to the recording medium, if the time required for drying the recording medium to a moisture content of 1.0 g / m ² or less is more than 5 seconds, the acidic compound contained in the treatment liquid and the recording medium are included. The neutralization reaction with a component (for example, calcium carbonate) proceeds, the effective acid concentration causing aggregation in the ink composition becomes too low, and the cohesiveness of the ink applied later deteriorates, which is not preferable.

The drying step starts drying within ² seconds after applying the treatment liquid to the recording medium, and reduces the water content to 1.0 g / m ² or less within 5 seconds after applying the treatment liquid to the recording medium. By drying the recording medium, the neutralization reaction is suppressed, and the effective acid concentration is prevented from becoming too low. Therefore, it is not necessary to apply a large amount of acidic compound to the recording medium in order to ensure the effective acid concentration, and there is little adverse effect on the recording medium.

From the viewpoint that the drying process is excellent in the cohesiveness of the ink, and from the viewpoint that the adverse effect on the recording medium by the processing liquid is suppressed and the image is excellent in abrasion resistance, 0.5 seconds after the processing liquid is applied to the recording medium. It is preferable to start drying within 1.5 seconds and dry the recording medium to a moisture content of 1.0 g / m ² or less within 3 seconds after applying the treatment liquid to the recording medium.

In the drying method of the drying step, at least a part of water in the processing liquid is removed, and the recording medium is dried to a water content of 1.0 g / m ² or less within 5 seconds after the processing liquid is applied to the recording medium. However, a method of removing the solvent by heat drying is preferable.
Heating and drying can be performed by a known heating means such as a heater, a blowing means using blowing air such as a dryer, or a combination of these. As the heating method, for example, a method of applying heat with a heater or the like from the side opposite to the treatment liquid application surface of the recording medium, a method of applying warm air or hot air to the treatment liquid application surface of the recording medium, an infrared heater was used. The heating method etc. are mentioned, You may heat combining these two or more.

≪Ink application process≫
In the ink application process, an ink composition including at least one of a colorant and polymer particles is applied to a recording medium to which a treatment liquid has been applied to form an image. The method for applying the ink composition to the recording medium is not particularly limited, but among these, the ink jet method is preferable because it has advantages such as a simple printing mechanism and no noise.

The inkjet method is not particularly limited, and is a known method, for example, a charge control method that discharges ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that uses vibration pressure of a piezoelectric element, an electric method An acoustic ink jet system that converts a signal into an acoustic beam, irradiates the ink with ink and ejects the ink using radiation pressure, and a thermal ink jet (bubble jet (registered trademark)) that heats the ink to form bubbles and uses the generated pressure. )) Any method may be used. As an ink jet method, in particular, the method described in Japanese Patent Application Laid-Open No. Sho 54-59936 causes an abrupt volume change of the ink subjected to the action of thermal energy, and the ink is ejected from the nozzle by the action force due to this state change. Ink jet method can be used effectively.
The ink jet method includes a method for ejecting a large number of low-density inks called photo inks in a small volume, a method for improving image quality using a plurality of inks having substantially the same hue and different concentrations, and colorless and transparent inks. The method using is included.

An ink jet head used in the ink jet method may be an on-demand method or a continuous method. In addition, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electro-thermal conversion method (for example, a thermal type) Specific examples include an ink jet type, a bubble jet (registered trademark) type, an electrostatic suction type (for example, an electric field control type, a slit jet type, etc.) and a discharge type (for example, a spark jet type). However, any discharge method may be used.
There is no restriction | limiting in particular about an ink nozzle etc., According to the objective, it can select suitably.

  As an ink jet method, a short serial head is used, and a shuttle system that performs recording while scanning the head in the width direction of the recording medium, and a line head in which recording elements are arranged corresponding to the entire area of one side of the recording medium There is a line system using. In the line system, an image can be recorded on the entire surface of the recording medium by scanning the recording medium in a direction orthogonal to the arrangement direction of the recording elements, and a carriage system such as a carriage for scanning a short head is not necessary. Further, since complicated scanning control of the carriage movement and the recording medium is not required, and only the recording medium is moved, the recording speed can be increased as compared with the shuttle system. The image forming method of the present invention can be applied to any of these, but generally, when applied to a line system that does not use a dummy jet, the effect of improving ejection accuracy and image scratch resistance is great.

  The ink application step is preferably started within 3.0 seconds after the drying step from the viewpoint of speeding up image formation. Here, “starting within 3.0 seconds after the drying step” means that the time from the end of the drying step until the first ink droplets land on the recording medium is within 3.0 seconds. means.

<Ink composition>
The ink composition according to the present invention includes at least one of a coloring material and polymer particles, and may include a water-soluble organic solvent, a surfactant, and other additives as necessary.

(Color material)
When the ink composition is colored, it contains at least one coloring material. The color material is preferably a water-insoluble color material. By containing a water-insoluble color material, the colorability of the ink becomes good, and a visible image with good color density and hue can be recorded.
The water-insoluble colorant refers to a colorant that is almost insoluble or hardly soluble in water, and specifically means that the amount dissolved in water at 25 ° C. is 0.5% by mass or less. .

As the color material component constituting the water-insoluble color material, known dyes, pigments and the like can be used without particular limitation. Among these, from the viewpoint of the colorability of the ink, a color material that is almost insoluble or hardly soluble in water is preferable. Specific examples include various pigments, disperse dyes, oil-soluble dyes, and dyes that form J aggregates, and pigments are more preferable from the viewpoint of light resistance.
In the present invention, the ink composition may contain a water-insoluble pigment itself or a water-insoluble pigment surface-treated with a dispersant as a water-insoluble colorant.

There are no particular restrictions on the type of the pigment, and conventionally known organic and inorganic pigments can be used.
Examples of the organic pigment include azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Among these, azo pigments and polycyclic pigments are more preferable. Examples of the azo pigments include azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments. Examples of the polycyclic pigment include phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments. Examples of the dye chelates include basic dye chelates and acidic dye chelates.
Specific examples of the organic pigment that can be used in the present invention include pigments described in paragraph numbers 0142 to 0145 of JP-A-2007-100071.
Examples of the inorganic pigment include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, and carbon black. Among these, carbon black is particularly preferable. In addition, as said carbon black, what was manufactured by well-known methods, such as a contact method, a furnace method, and a thermal method, is mentioned, for example.

-Dispersant-
When a pigment is contained as a coloring material, it is preferably dispersed in an aqueous solvent by a dispersant. The dispersant may be a polymer dispersant or a low molecular surfactant type dispersant. Further, the polymer dispersant may be either a water-soluble dispersant or a water-insoluble dispersant.
The low molecular surfactant type dispersant (hereinafter sometimes referred to as “low molecular dispersant”) can stably disperse an organic pigment in an aqueous solvent while maintaining a low viscosity of the ink. The low molecular dispersant herein is a low molecular dispersant having a molecular weight of 2000 or less. Moreover, 100-2000 are preferable and, as for the molecular weight of a low molecular dispersing agent, 200-2000 are more preferable.

  The low molecular weight dispersant has a structure including a hydrophilic group and a hydrophobic group. One or more hydrophilic groups and hydrophobic groups may be independently contained in one molecule, and each of them may have plural kinds of hydrophilic groups and hydrophobic groups. In addition, a linking group for linking a hydrophilic group and a hydrophobic group can be appropriately included.

Examples of the hydrophilic group include an anionic group, a cationic group, a nonionic group, and a betaine type combining these.
The anionic group is not particularly limited as long as it has a negative charge, but may be a phosphoric acid group, a phosphonic acid group, a phosphinic acid group, a sulfuric acid group, a sulfonic acid group, a sulfinic acid group, or a carboxylic acid group. Preferably, it is a phosphoric acid group or a carboxylic acid group, and more preferably a carboxylic acid group.
The cationic group is not particularly limited as long as it has a positive charge, but is preferably an organic cationic substituent, more preferably a cationic group containing nitrogen or phosphorus, and still more preferably a cationic group containing nitrogen. . Among these, a pyridinium cation or an ammonium cation is particularly preferable.
The nonionic group is not particularly limited as long as it has no negative or positive charge, and examples thereof include polyalkylene oxide, polyglycerin, and a part of sugar unit.

In the present invention, the hydrophilic group is preferably an anionic group from the viewpoint of dispersion stability and aggregation of the pigment.
Moreover, when a low molecular weight dispersing agent has an anionic hydrophilic group, it is preferable that the pKa is 3 or more from a viewpoint of making it contact with an acidic process liquid and promoting aggregation reaction. The pKa of the low molecular dispersant in the present invention is determined experimentally from a titration curve by titrating a solution of 1 mol / L of the low molecular dispersant in a tetrahydrofuran-water = 3: 2 (V / V) solution with an acid or alkaline aqueous solution. It is the value obtained in
Theoretically, if the pKa of the low molecular dispersant is 3 or more, 50% or more of the anionic groups are in a non-dissociated state when in contact with a treatment solution having a pH of about 3. Accordingly, the water solubility of the low molecular weight dispersant is remarkably lowered, and an agglutination reaction occurs. That is, the aggregation reactivity is improved. From this viewpoint, it is preferable that the low molecular dispersant has a carboxylic acid group as an anionic group.

On the other hand, the hydrophobic group may have any structure such as hydrocarbon, fluorocarbon, and silicone, but is particularly preferably hydrocarbon. Further, the hydrophobic group may have a linear structure or a branched structure. The hydrophobic group may have a single-chain structure or two or more chain structures, and may have a plurality of types of hydrophobic groups in the case of a structure having two or more chains.
The hydrophobic group is preferably a hydrocarbon group having 2 to 24 carbon atoms, more preferably a hydrocarbon group having 4 to 24 carbon atoms, and still more preferably a hydrocarbon group having 6 to 20 carbon atoms.

Among the polymer dispersants, hydrophilic polymer compounds can be used as the water-soluble dispersant, natural hydrophilic polymer compounds, hydrophilic polymer compounds chemically modified from natural products, and synthetic water-soluble dispersants. Any of the functional polymer compounds may be used.
Examples of natural hydrophilic polymer compounds include, for example, plant polymers such as gum arabic, tragan gum, guar gum, karaya gum, locust bean gum, arabinogalactone, pectin, quince seed starch, and seaweed systems such as alginic acid, carrageenan, and agar. Examples thereof include polymer polymers, animal polymers such as gelatin, casein, albumin and collagen, and microbial polymers such as xanthene gum and dextran.
Examples of hydrophilic polymer compounds that are chemically modified from natural products include fiber polymers such as methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, starches such as sodium starch glycolate and sodium starch phosphate And seaweed polymers such as propylene glycol alginate and the like.

  Synthetic hydrophilic polymer compounds include vinyl polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, and polyvinyl methyl ether, polyacrylamide, polyacrylic acid or alkali metal salts thereof, acrylic resins such as water-soluble styrene acrylic resins, Water-soluble styrene maleic acid resin, water-soluble vinyl naphthalene acrylic resin, water-soluble vinyl naphthalene maleic resin, polyvinyl pyrrolidone, polyvinyl alcohol, alkali metal salts of β-naphthalene sulfonic acid formalin condensate, cations such as quaternary ammonium and amino group And a high molecular compound having a salt of a functional functional group in the side chain.

  Among these, from the viewpoint of pigment dispersion stability and aggregation, a polymer compound containing a carboxy group is preferable. For example, an acrylic resin such as a water-soluble styrene acrylic resin, a water-soluble styrene maleic acid resin, and a water-soluble vinyl naphthalene. High molecular compounds containing a carboxy group such as an acrylic resin and a water-soluble vinyl naphthalene maleic resin are particularly preferred.

  As the water-insoluble dispersant among the polymer dispersants, a polymer having both a hydrophobic part and a hydrophilic part can be used. For example, styrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer, (meth) acrylic acid ester- (meth) acrylic acid copolymer, polyethylene glycol ( Examples thereof include a meth) acrylate- (meth) acrylic acid copolymer and a styrene-maleic acid copolymer.

  The weight average molecular weight of the polymer dispersant is preferably 3,000 to 200,000, more preferably 5,000 to 100,000, still more preferably 5,000 to 80,000, and particularly preferably 10,000 to 60. , 000. The weight average molecular weight can be measured, for example, by gel permeation chromatography (GPC).

  Further, the mixing mass ratio of the pigment and the dispersant (pigment: dispersant) is preferably in the range of 1: 0.06 to 1: 3, more preferably in the range of 1: 0.125 to 1: 2. Preferably it is 1: 0.125 to 1: 1.5.

When a dye is used as the color material, a material in which the dye is held on a water-insoluble carrier can be used as the water-insoluble color material. As the dye, known dyes can be used without particular limitation. For example, the dyes described in JP-A-2001-115066, JP-A-2001-335714, JP-A-2002-249677 and the like can be used in the present invention. It can be used suitably. The carrier is not particularly limited as long as it is insoluble in water or hardly soluble in water, and inorganic materials, organic materials, and composite materials thereof can be used. Specifically, the carriers described in JP-A-2001-181549, JP-A-2007-169418, etc. can be suitably used in the present invention.
The carrier holding the dye (water-insoluble colorant) can be used as an aqueous dispersion using a dispersant. As the dispersant, the above-described dispersants can be suitably used.

The colorant preferably contains a pigment and a dispersant, more preferably contains an organic pigment and a polymer dispersant, from the viewpoint of light resistance and quality of the image, and the polymer dispersant contains an organic pigment and a carboxy group. It is particularly preferred that Among them, the water-insoluble colorant is preferably a water-insoluble colorant in which the colorant (preferably a pigment) is coated with a polymer dispersant (preferably having a carboxy group) from the viewpoints of cohesiveness and thus ink fixability. Furthermore, a water-insoluble pigment in which a pigment is coated with an acrylic polymer is preferable. As the acrylic polymer, for example, an acrylic resin such as a water-soluble styrene acrylic resin, a water-soluble styrene maleic acid resin, a water-soluble vinyl naphthalene acrylic resin, and a water-soluble vinyl naphthalene maleic resin are preferable.
Furthermore, from the viewpoint of cohesiveness, it is preferable that the acid value of the polymer dispersant is larger than the acid value of the polymer particles (preferably self-dispersing polymer particles) described later.

The volume average particle diameter of the color material is preferably 10 to 200 nm, more preferably 10 to 150 nm, and still more preferably 10 to 100 nm. When the volume average particle size is 200 nm or less, the color reproducibility is good, and in the case of the ink jet method, the droplet ejection characteristics are good. Moreover, light resistance becomes favorable because a volume average particle diameter is 10 nm or more.
The particle size distribution of the color material is not particularly limited, and may be either a wide particle size distribution or a monodispersed particle size distribution. Two or more color materials having a monodisperse particle size distribution may be mixed and used.
The volume average particle size of the coloring material is determined by measuring the particle size distribution by a dynamic light scattering method using a nanotrack particle size distribution measuring device UPA-EX150 (manufactured by Nikkiso Co., Ltd.). .

The content of the color material in the ink composition is preferably 1 to 25 mass%, more preferably 2 to 20 mass%, and more preferably 5 to 20 mass% with respect to the ink composition from the viewpoint of image density. Is more preferable, and 5 to 15% by mass is particularly preferable.
A color material may be used individually by 1 type and may be used in combination of 2 or more type.

(Polymer particles)
The ink composition in the invention preferably contains at least one polymer particle. By including the polymer particles, fixability and scratch resistance of the formed image are improved.

  Examples of polymer particles include thermoplastic, thermosetting or modified acrylic, epoxy, polyurethane, polyether, polyamide, unsaturated polyester, phenol, silicone, or fluorine resins, chlorides, and the like. Polyvinyl resins such as vinyl, vinyl acetate, polyvinyl alcohol, or polyvinyl butyral, polyester resins such as alkyd resins and phthalic resins, melamine resins, melamine formaldehyde resins, amino alkyd co-condensation resins, amino materials such as urea resins, Or the particle | grains of resin which has anionic groups, such as those copolymers or a mixture, are mentioned. Among these, anionic acrylic resins include, for example, an acrylic monomer having an anionic group (anionic group-containing acrylic monomer) and, if necessary, other monomers copolymerizable with the anionic group-containing acrylic monomer. Obtained by polymerization in a solvent. Examples of the anionic group-containing acrylic monomer include an acrylic monomer having one or more selected from the group consisting of a carboxy group, a sulfonic acid group, and a phosphonic group. Among them, an acrylic monomer having a carboxy group (for example, acrylic acid) Methacrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, fumaric acid and the like), and acrylic acid or methacrylic acid is particularly preferred.

As the polymer particles, self-dispersing polymer particles are preferable from the viewpoints of ink ejection stability and liquid stability (particularly dispersion stability) when the above-described coloring materials (particularly pigments) are used, and have a carboxy group. Self-dispersing polymer particles are more preferred. Self-dispersing polymer particles are water-insoluble polymers that can be dispersed in an aqueous medium by the functional groups (particularly acidic groups or salts thereof) of the polymer itself in the absence of other surfactants, By means of water-insoluble polymer particles containing no free emulsifier.
The dispersed state is both an emulsified state (emulsion) in which a water-insoluble polymer is dispersed in a liquid state in an aqueous medium and a dispersed state (suspension) in which a water-insoluble polymer is dispersed in a solid state in an aqueous medium. Is included. The water-insoluble polymer in the present invention is preferably a water-insoluble polymer that can be in a dispersed state in which the water-insoluble polymer is dispersed in a solid state from the viewpoint of aggregation speed and fixing property when an ink composition is used.

  The dispersion state of the self-dispersing polymer particles refers to a solution in which 30 g of a water-insoluble polymer is dissolved in 70 g of an organic solvent (for example, methyl ethyl ketone), a neutralizing agent that can neutralize the salt-forming group of the water-insoluble polymer 100% If the group is anionic, sodium hydroxide, acetic acid if it is cationic) and 200 g of water are mixed and stirred (apparatus: stirring apparatus with stirring blades, rotation speed 200 rpm, 30 minutes, 25 ° C.), and then mixed. Even after removing the organic solvent from the liquid, it means that the emulsified state or the dispersed state exists stably at 25 ° C. for at least one week, and the occurrence of precipitation cannot be visually confirmed.

  The water-insoluble polymer means a polymer having a dissolution amount of 10 g or less when the polymer is dried at 105 ° C. for 2 hours and then dissolved in 100 g of water at 25 ° C., and the dissolution amount is preferable. Is 5 g or less, more preferably 1 g or less. The dissolution amount is the dissolution amount when 100% neutralized with sodium hydroxide or acetic acid according to the type of salt-forming group of the water-insoluble polymer.

  The aqueous medium is configured to contain water, and may contain a hydrophilic organic solvent as necessary. In the present invention, it is preferably composed of water and 0.2% by mass or less of a hydrophilic organic solvent with respect to water, and more preferably composed of water.

  The main chain skeleton of the water-insoluble polymer is not particularly limited. For example, a vinyl polymer or a condensation polymer (epoxy resin, polyester, polyurethane, polyamide, cellulose, polyether, polyurea, polyimide, polycarbonate, etc.) is used. it can. Of these, vinyl polymers are particularly preferred.

Preferable examples of the vinyl polymer and the monomer constituting the vinyl polymer include those described in JP-A Nos. 2001-181549 and 2002-88294. In addition, radical transfer of vinyl monomers using dissociable groups (or substituents that can be induced to dissociable groups), polymerization initiators, and iniferters, or dissociable groups on either initiators or terminators. A vinyl polymer in which a dissociable group is introduced at the end of a polymer chain by ionic polymerization using a compound having (or a substituent that can be derived from a dissociable group) can also be used.
Moreover, as a suitable example of the monomer which comprises a condensation type polymer and a condensation type polymer, what is described in Unexamined-Japanese-Patent No. 2001-247787 can be mentioned.

  From the viewpoint of self-dispersibility, the self-dispersing polymer particles are preferably composed of a water-insoluble polymer containing a hydrophilic structural unit and a structural unit derived from an aromatic group-containing monomer.

The hydrophilic structural unit is not particularly limited as long as it is derived from a hydrophilic group-containing monomer, and even if it is derived from one kind of hydrophilic group-containing monomer, it contains two or more hydrophilic groups. It may be derived from a monomer. The hydrophilic group is not particularly limited, and may be a dissociable group or a nonionic hydrophilic group.
In the present invention, the hydrophilic group is preferably a dissociable group and more preferably an anionic dissociable group from the viewpoint of promoting self-dispersion and the stability of the formed emulsified or dispersed state. Examples of the dissociable group include a carboxy group, a phosphoric acid group, and a sulfonic acid group. Among them, a carboxy group is preferable from the viewpoint of fixability when an ink composition is configured.

The hydrophilic group-containing monomer is preferably a dissociable group-containing monomer from the viewpoint of self-dispersibility and aggregability, and is preferably a dissociable group-containing monomer having a dissociable group and an ethylenically unsaturated bond. .
Examples of the dissociable group-containing monomer include an unsaturated carboxylic acid monomer, an unsaturated sulfonic acid monomer, and an unsaturated phosphoric acid monomer.

Specific examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid. Specific examples of the unsaturated sulfonic acid monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylate, and bis- (3-sulfopropyl) -itaconate. It is done. Specific examples of unsaturated phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2- Examples include acryloyloxyethyl phosphate.
Among the dissociable group-containing monomers, unsaturated carboxylic acid monomers are preferable and acrylic acid and methacrylic acid are more preferable from the viewpoints of dispersion stability and ejection stability.

  The water-insoluble polymer is preferably a polymer having a carboxy group from the viewpoint of self-dispersibility and the aggregation rate when contacted with the treatment liquid, and has a carboxy group and an acid value of 25 to 100 mgKOH. More preferably, the polymer is / g. Furthermore, the acid value is more preferably from 25 to 80 mgKOH / g, and further preferably from 30 to 65 mgKOH / g, from the viewpoints of self-dispersibility and aggregation rate when contacted with the treatment liquid. If the acid value is 25 mgKOH / g or more, the stability of self-dispersibility is good, and if it is 100 mgKOH / g or less, the cohesiveness when contacting with the treatment liquid is improved.

The aromatic group-containing monomer is not particularly limited as long as it is a compound containing an aromatic group and a polymerizable group. The aromatic group may be a group derived from an aromatic hydrocarbon or a group derived from an aromatic heterocycle. In the present invention, an aromatic group derived from an aromatic hydrocarbon is preferable from the viewpoint of particle shape stability in an aqueous medium.
Further, the polymerizable group may be a condensation polymerizable polymerizable group or an addition polymerizable polymerizable group. In the present invention, from the viewpoint of particle shape stability in an aqueous medium, an addition polymerizable polymerizable group is preferable, and a group containing an ethylenically unsaturated bond is more preferable.

  The aromatic group-containing monomer is preferably a monomer having an aromatic group derived from an aromatic hydrocarbon and an ethylenically unsaturated bond. An aromatic group containing monomer may be used individually by 1 type, or may be used in combination of 2 or more type.

Examples of the aromatic group-containing monomer include phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, phenyl (meth) acrylate, and a styrene monomer. Of these, aromatic group-containing (meth) acrylate monomers are preferred from the viewpoint of the balance between the hydrophilicity and hydrophobicity of the polymer chain and the ink fixability, and include phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, and phenyl (meth). At least one selected from acrylates is more preferable, and phenoxyethyl (meth) acrylate and benzyl (meth) acrylate are more preferable.
“(Meth) acrylate” means acrylate or methacrylate.

The content of the structural unit derived from the aromatic group-containing (meth) acrylate monomer contained in the self-dispersing polymer particles is preferably 10 to 95% by mass. When the content of the aromatic group-containing (meth) acrylate monomer is 10 to 95% by mass, the stability of the self-emulsification or dispersion state is improved, and further the increase in ink viscosity can be suppressed.
In the present invention, from the viewpoints of stability in a self-dispersing state, stabilization of particle shape in an aqueous medium due to hydrophobic interaction between aromatic rings, and reduction in the amount of water-soluble components due to appropriate hydrophobicization of particles. More preferably, it is -90 mass%, It is more preferable that it is 15-80 mass%, It is still more preferable that it is 25-70 mass%.

  The water-insoluble polymer can be constituted using, for example, a structural unit derived from an aromatic group-containing monomer and a structural unit derived from a dissociable group-containing monomer. Furthermore, other structural units may be further included as necessary.

The monomer that forms the other structural unit is not particularly limited as long as it is a monomer copolymerizable with the aromatic group-containing monomer and the dissociable group-containing monomer. Among these, an alkyl group-containing monomer is preferable from the viewpoint of flexibility of the polymer skeleton and ease of control of the glass transition temperature (Tg).
Examples of the alkyl group-containing monomer include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, alkyl (meth) acrylates such as t-butyl (meth) acrylate, hexyl (meth) acrylate, ethylhexyl (meth) acrylate; hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) Ethylenically unsaturated monomers having a hydroxyl group such as acrylate, 4-hydroxybutyl (meth) acrylate, hydroxypentyl (meth) acrylate, hydroxyhexyl (meth) acrylate; Dialkylaminoalkyl (meth) acrylates such as ru (meth) acrylate; N-hydroxyalkyl (meth) such as N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N-hydroxybutyl (meth) acrylamide Acrylamide; N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N- (n-, iso) butoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, N-ethoxyethyl (meta And (meth) acrylamides such as N-alkoxyalkyl (meth) acrylamides such as acrylamide and N- (n-, iso) butoxyethyl (meth) acrylamide.

  The molecular weight of the water-insoluble polymer is preferably 3000 to 200,000, more preferably 5000 to 150,000, and still more preferably 10,000 to 100,000 in terms of weight average molecular weight. When the weight average molecular weight is 3000 or more, the amount of water-soluble components can be effectively suppressed, and when it is 200,000 or less, stabilization of self-dispersibility can be enhanced.

  The weight average molecular weight is measured by gel permeation chromatography (GPC). GPC uses HLC-8020GPC (manufactured by Tosoh Corporation), and TSKgel and Super Multipore HZ-H (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) are connected in series as an eluent. Use THF (tetrahydrofuran). As conditions, the sample concentration is 0.35% by mass, the flow rate is 0.35 ml / min, the sample injection amount is 10 μl, the measurement temperature is 40 ° C., and an IR detector is used. In addition, the calibration curve is “standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, It is prepared from 8 samples of “A-2500”, “A-1000”, “n-propylbenzene”.

  From the viewpoint of controlling the hydrophilicity / hydrophobicity of the polymer, the water-insoluble polymer has a structural unit derived from an aromatic group-containing (meth) acrylate monomer as a copolymerization ratio of 15 to 80% by mass, and a structural unit derived from a carboxy group-containing monomer. And a structural unit derived from an alkyl group-containing monomer (preferably a structural unit derived from an alkyl ester of (meth) acrylic acid), and a structural unit derived from phenoxyethyl (meth) acrylate and / or benzyl A structural unit derived from (meth) acrylate as a copolymerization ratio of 15 to 80% by mass, a structural unit derived from a carboxy group-containing monomer, and a structural unit derived from an alkyl group-containing monomer (preferably (meth) acrylic acid More structural units derived from alkyl esters having 1 to 4 carbon atoms) More preferably, the acid value is preferably 25 to 100 mgKOH / g and the weight average molecular weight is preferably 3000 to 200,000, the acid value is 25 to 95 mgKOH / g and the weight average molecular weight is 5000 to More preferably, it is 150,000.

  Specific examples (Exemplary Compounds B-01 to B-19) of the water-insoluble polymer are given below. However, the present invention is not limited to these. The values in parentheses represent the mass ratio of the copolymer component.

B-01: Phenoxyethyl acrylate / methyl methacrylate / acrylic acid copolymer (50/45/5)
B-02: Phenoxyethyl acrylate / benzyl methacrylate / isobutyl methacrylate / methacrylic acid copolymer (30/35/29/6)
B-03: Phenoxyethyl methacrylate / isobutyl methacrylate / methacrylic acid copolymer (50/44/6)
B-04: Phenoxyethyl acrylate / methyl methacrylate / ethyl acrylate / acrylic acid copolymer (30/55/10/5)
B-05: benzyl methacrylate / isobutyl methacrylate / methacrylic acid copolymer (35/59/6)
B-06: Styrene / phenoxyethyl acrylate / methyl methacrylate / acrylic acid copolymer (10/50/35/5)
B-07: benzyl acrylate / methyl methacrylate / acrylic acid copolymer (55/40/5)
B-08: Phenoxyethyl methacrylate / benzyl acrylate / methacrylic acid copolymer (45/47/8)
B-09: Styrene / phenoxyethyl acrylate / butyl methacrylate / acrylic acid copolymer (5/48/40/7)
B-10: benzyl methacrylate / isobutyl methacrylate / cyclohexyl methacrylate / methacrylic acid copolymer (35/30/30/5)
B-11: Phenoxyethyl acrylate / methyl methacrylate / butyl acrylate / methacrylic acid copolymer (12/50/30/8)
B-12: benzyl acrylate / isobutyl methacrylate / acrylic acid copolymer (93/2/5)
B-13: Styrene / phenoxyethyl methacrylate / butyl acrylate / acrylic acid copolymer (50/5/20/25)
B-14: Styrene / butyl acrylate / acrylic acid copolymer (62/35/3)
B-15: Methyl methacrylate / phenoxyethyl acrylate / acrylic acid copolymer (45/51/4)
B-16: Methyl methacrylate / phenoxyethyl acrylate / acrylic acid copolymer (45/49/6)
B-17: Methyl methacrylate / phenoxyethyl acrylate / acrylic acid copolymer (45/48/7)
B-18: Methyl methacrylate / phenoxyethyl acrylate / acrylic acid copolymer (45/47/8)
B-19: Methyl methacrylate / phenoxyethyl acrylate / acrylic acid copolymer (45/45/10)

  There is no particular limitation on the method for producing the water-insoluble polymer constituting the self-dispersing polymer particles. For example, a method in which emulsion polymerization is carried out in the presence of a polymerizable surfactant to covalently bond the surfactant and the water-insoluble polymer. Examples thereof include a method of copolymerizing a monomer mixture containing the hydrophilic group-containing monomer and the aromatic group-containing monomer by a known polymerization method such as a solution polymerization method or a bulk polymerization method. Among the polymerization methods, a solution polymerization method is preferable and a solution polymerization method using an organic solvent is more preferable from the viewpoint of aggregation rate and droplet ejection stability when an ink composition is used.

  The self-dispersing polymer particles include a polymer synthesized in an organic solvent from the viewpoint of the aggregation rate, and the polymer has a carboxy group (preferably having an acid value of 20 to 100 mgKOH / g). It is preferable that some or all of the carboxy groups of the polymer are neutralized and prepared as a polymer dispersion having water as a continuous phase. That is, the production of the self-dispersing polymer particles in the present invention includes a step of synthesizing a polymer in an organic solvent, and a dispersion step of preparing an aqueous dispersion in which at least a part of the carboxy group of the polymer is neutralized. It is preferable to do so.

The dispersion step preferably includes the following step (1) and step (2).
Step (1): Step of stirring a mixture containing a polymer (water-insoluble polymer), an organic solvent, a neutralizing agent, and an aqueous medium Step (2): Step of removing the organic solvent from the mixture

The step (1) is preferably a treatment in which a polymer (water-insoluble polymer) is first dissolved in an organic solvent, then a neutralizing agent and an aqueous medium are gradually added, mixed and stirred to obtain a dispersion. In this way, by adding a neutralizing agent and an aqueous medium to a water-insoluble polymer solution dissolved in an organic solvent, a self-dispersing polymer having a particle size with higher storage stability without requiring strong shearing force. Particles can be obtained.
There is no restriction | limiting in particular in the stirring method of this mixture, Dispersing machines, such as a generally used mixing stirring apparatus and an ultrasonic disperser, a high-pressure homogenizer, can be used as needed.

Preferred examples of the organic solvent include alcohol solvents, ketone solvents, and ether solvents.
Examples of the alcohol solvent include isopropyl alcohol, n-butanol, t-butanol, ethanol and the like. Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. Examples of ether solvents include dibutyl ether and dioxane. Among these solvents, ketone solvents such as methyl ethyl ketone and alcohol solvents such as isopropyl alcohol are preferable. It is also preferable to use isopropyl alcohol and methyl ethyl ketone in combination for the purpose of moderating the polarity change during the phase inversion from oil to water. By using the solvent in combination, it is possible to obtain self-dispersing polymer particles having a fine particle size with high dispersion stability without aggregation and sedimentation and fusion between particles.

  The neutralizing agent is used so that a part or all of the dissociable group is neutralized and the self-dispersing polymer forms a stable emulsified or dispersed state in water. When the self-dispersing polymer has an anionic dissociation group (for example, carboxy group) as a dissociable group, examples of the neutralizing agent used include basic compounds such as organic amine compounds, ammonia, and alkali metal hydroxides. It is done. Examples of organic amine compounds include monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monopropylamine, dipropylamine, monoethanolamine, diethanolamine, triethanolamine, N, N-dimethyl-ethanolamine, N, N-diethyl-ethanolamine, 2-dimethylamino-2-methyl-1-propanol, 2-amino-2-methyl-1-propanol, N-methyldiethanolamine, N-ethyldiethanolanine, monoisopropanolamine, di Examples include isopropanolamine and triisopropanolamine. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Among these, sodium hydroxide, potassium hydroxide, triethylamine, and triethanolamine are preferable from the viewpoint of stabilizing the dispersion of the self-dispersing polymer particles in water.

  These basic compounds are preferably used in an amount of 5 to 120 mol%, more preferably 10 to 110 mol%, still more preferably 15 to 100 mol%, based on 100 mol% of the dissociable group. . By setting it as 5 mol% or more, the effect which stabilizes dispersion | distribution of the particle | grains in water expresses, and there exists an effect which reduces a water-soluble component by setting it as 120 mol% or less.

  In the step (2), the aqueous dispersion of the self-dispersing polymer particles is obtained by distilling off the organic solvent from the dispersion obtained in the step (1) by a conventional method such as distillation under reduced pressure and phase-inversion into an aqueous system. A dispersion can be obtained. The organic solvent in the obtained aqueous dispersion has been substantially removed, and the amount of the organic solvent is preferably 0.2% by mass or less, more preferably 0.1% by mass or less.

The average particle size of the polymer particles (particularly self-dispersing polymer particles) is preferably in the range of 10 to 400 nm, more preferably in the range of 10 to 200 nm, still more preferably in the range of 10 to 100 nm, and particularly preferably in terms of volume average particle size. It is the range of 10-50 nm. Manufacturability is improved by having an average particle diameter of 10 nm or more. Moreover, storage stability improves by being an average particle diameter of 400 nm or less. Moreover, there is no restriction | limiting in particular regarding the particle size distribution of a polymer particle, Any of what has a wide particle size distribution or a monodispersed particle size distribution may be sufficient. Further, two or more water-insoluble particles may be mixed and used.
The average particle size and particle size distribution of the polymer particles are obtained by measuring the volume average particle size by a dynamic light scattering method using a nanotrack particle size distribution analyzer UPA-EX150 (manufactured by Nikkiso Co., Ltd.). It is.

The content of the polymer particles (particularly self-dispersing polymer particles) in the ink composition is preferably 1 to 30% by mass with respect to the total mass of the ink composition from the viewpoint of image glossiness and the like. 5 to 15% by mass is more preferable.
The polymer particles (particularly self-dispersing polymer particles) can be used singly or in combination of two or more.

(water)
The ink composition preferably contains water. There is no restriction | limiting in particular in the quantity of the water to contain. The preferable content of water in the ink composition is 10 to 99% by mass, more preferably 30 to 80% by mass, and still more preferably 50 to 70% by mass.

(Water-soluble organic solvent)
The ink composition preferably contains at least one water-soluble organic solvent. By containing a water-soluble organic solvent, it is possible to prevent drying and promote penetration. When a water-soluble organic solvent is used as an anti-drying agent, nozzle clogging that may occur due to ink drying at the ink discharge port is effectively prevented when an ink composition is discharged by an inkjet method to record an image. be able to.

In order to prevent drying, a water-soluble organic solvent having a vapor pressure lower than that of water is preferable. Specific examples of water-soluble organic solvents suitable for preventing drying include ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol, thiodiglycol, dithiodiglycol, 2-methyl-1,3-propanediol, 1,2 , 6-hexanetriol, acetylene glycol derivative, glycerin, polyhydric alcohols represented by trimethylolpropane, ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monoethyl (or butyl) ) Lower alkyl ethers of polyhydric alcohols such as ethers, heterocyclic rings such as 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, N-ethylmorpholine, Horan, dimethyl sulfoxide, sulfur-containing compounds such as sulfolane, diacetone alcohol, polyfunctional compounds such as diethanolamine, and urea derivatives.
Of these, polyhydric alcohols such as glycerin and diethylene glycol are preferred. Moreover, these may be used individually by 1 type, or may use 2 or more types together. These water-soluble organic solvents are preferably contained in the ink composition in an amount of 10 to 50% by mass.

  In order to promote penetration, a water-soluble organic solvent is preferably used from the viewpoint of allowing the ink composition to penetrate better into the recording medium. Specific examples of water-soluble organic solvents suitable for promoting penetration include alcohols such as ethanol, isopropanol, butanol, di (tri) ethylene glycol monobutyl ether, 1,2-hexanediol, sodium lauryl sulfate, and sodium oleate. And nonionic surfactants. A good effect is acquired by containing these 5-30 mass% in an ink composition. Further, these water-soluble organic solvents are preferably used within a range of addition amounts that do not cause printing / image bleeding and paper loss (print-through).

In addition to the above, the water-soluble organic solvent can be used for adjusting the viscosity. Specific examples of water-soluble organic solvents that can be used to adjust the viscosity include alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, t-butanol, pentanol, hexanol, Cyclohexanol, benzyl alcohol), polyhydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, Thiodiglycol), glycol derivatives (eg, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether) Tellurium, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether, ethylene glycol diacetate, ethylene glycol monomethyl ether acetate, Triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, ethylene glycol monophenyl ether), amine (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, Tylenediamine, diethylenetriamine, triethylenetetramine, polyethyleneimine, tetramethylpropylenediamine) and other polar solvents (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, sulfolane, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, acetonitrile, acetone).
In addition, you may use a water-soluble organic solvent individually by 1 type or in mixture of 2 or more types.

(Surfactant)
The ink composition preferably contains at least one surfactant. The surfactant is used as a surface tension adjusting agent. Examples of the surface tension adjusting agent include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants, and the like. In the present invention, from the viewpoint of aggregation rate, an anionic surfactant or a nonionic surfactant is preferable, and an anionic surfactant is more preferable.

The surfactant preferably contains an amount capable of adjusting the surface tension of the ink composition to 25 mN / m or more and less than 40 mN / m in order to eject droplets well by the ink jet method. Among them, the content of the surfactant is preferably an amount capable of adjusting the surface tension to 27 to 37 mN / m.
The surface tension of the ink composition is measured under conditions of 25 ° C. by the plate method using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).

  Specific examples of surfactants include fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate esters, naphthalene sulfonate formalin condensation in hydrocarbons Products, anionic surfactants such as polyoxyethylene alkyl sulfates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxy Nonionic surfactants such as ethylene alkylamine, glycerin fatty acid ester and oxyethyleneoxypropylene block copolymer are preferred. Orphine (Nissin Chemical Industry Co., Ltd.) and SURFYNOLS (Air Products & Chemicals), which are acetylene-based polyoxyethylene oxide surfactants, are also preferably used. An amine oxide type amphoteric surfactant such as N, N-dimethyl-N-alkylamine oxide is also preferred.

Further, pages 37 to 38 of JP-A-59-157636 and Research Disclosure No. The surfactants described in 308119 (1989) can also be used.
In addition, fluorine (fluorinated alkyl-based) surfactants, silicone-based surfactants and the like described in JP-A Nos. 2003-322926, 2004-325707, and 2004-309806 are also included. Scratch resistance can also be improved.

  These surface tension modifiers can also be used as antifoaming agents, and fluorine compounds, silicone compounds, chelating agents represented by EDTA, and the like can also be used.

(Other additives)
The ink composition can further contain other additives in addition to the above components. Examples of other additives include antifading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, antiseptics, antifungal agents, pH adjusters, antifoaming agents, viscosity modifiers, dispersants, and dispersion stabilizers. And known additives such as rust preventives and chelating agents. These various additives may be added directly after the ink composition is prepared, or may be added when the ink composition is prepared.

  By containing an ultraviolet absorber, image storability can be improved. Examples of the ultraviolet absorber include benzotriazoles described in JP-A Nos. 58-185677, 61-190537, JP-A-2-782, JP-A-5-97075, JP-A-9-34057, and the like. Compounds, benzophenone compounds described in JP-A No. 46-2784, JP-A No. 5-194433, US Pat. No. 3,214,463, etc., JP-B Nos. 48-30492, 56-211141, and JP-A No. 10-2 Cinnamic acid compounds described in JP-A-88106 and the like, JP-A-4-298503, JP-A-8-53427, JP-A-8-239368, JP-A-10-182621, JP-A-8-501291 Triazine compounds described in the above, Research Disclosure No. The compounds described in No. 24239, compounds that emit fluorescence by absorbing ultraviolet rays typified by stilbene and benzoxazole compounds, so-called fluorescent brighteners can also be used.

  By containing the anti-fading agent, the storability of the image can be improved. As the antifading agent, various organic and metal complex antifading agents can be used. Examples of organic anti-fading agents include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, heterocycles, etc. There are nickel complexes and zinc complexes. More specifically, Research Disclosure No. No. 17643, Nos. VII to I, J; 15162, ibid. No. 18716, page 650, left column, ibid. No. 36544, page 527, ibid. No. 307105, page 872, ibid. The compounds described in the patent cited in Japanese Patent No. 15162 and the compounds represented by the general formulas and compound examples of the representative compounds described on pages 127 to 137 of JP-A-62-215272 can be used.

  Examples of the antifungal agent include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, p-hydroxybenzoic acid ethyl ester, 1,2-benzisothiazolin-3-one and salts thereof. These are preferably used in the ink composition in an amount of 0.02 to 1.00% by mass.

  As the pH adjuster, a neutralizer (organic base, inorganic alkali) can be used. From the viewpoint of improving the storage stability of the ink composition, the pH adjuster is preferably added so that the pH of the ink composition is 6 to 10, and more preferably added so that the pH is 7 to 10. . The pH is measured at 25 ° C. (± 1 ° C.).

(Physical properties of ink composition)
From the viewpoint of storage stability, the ink composition preferably has a pH at 25 ° C. (± 1 ° C.) of 6 to 10, more preferably 7 to 10.

  The viscosity of the ink composition is preferably in the range of 1 to 30 mPa · s, more preferably in the range of 1 to 20 mPa · s, from the viewpoint of ejection stability when ejected by the inkjet method and the aggregation rate when using the treatment liquid. More preferably, the range of 2-15 mPa * s is still more preferable, and the range of 2-10 mPa * s is especially preferable. The viscosity is measured using a VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD) under conditions where the temperature of the ink composition is 25 ° C.

<Recording medium>
The image forming method of the present invention forms an image on a recording medium.
The recording medium to be used is not particularly limited, but so-called coated paper used for general offset printing is suitable. The coated paper is provided with a coating layer (also referred to as a coating layer) containing an inorganic pigment or the like on the surface of high-quality paper, neutral paper or the like, which is generally not surface-treated, mainly composed of cellulose as a support. Is. The coated paper is likely to cause uneven gloss in the image area, but according to the image forming method of the present invention, it is possible to effectively suppress the occurrence of uneven gloss in the image area. Specifically, art paper, coated paper, lightweight coated paper, or finely coated paper is preferable.

  The inorganic pigment contained in the coating layer is not particularly limited, but from the viewpoint that the effect of suppressing the occurrence of uneven glossiness in the image area is more remarkably exhibited, silica, carion, clay, fired clay, zinc oxide , Tin oxide, magnesium sulfate, aluminum oxide, aluminum hydroxide, pseudoboehmite, calcium carbonate, satin white, aluminum silicate, smectite, zeolite, magnesium silicate, magnesium carbonate, magnesium oxide, and diatomaceous earth Are preferable, and calcium carbonate, silica, and carion are more preferable. In particular, when calcium carbonate is contained in the coating layer, when an image is formed by the image forming method of the present invention, the occurrence of uneven gloss in the image area and the adverse effect of the treatment liquid on the recording medium are remarkable.

  As the recording medium, commercially available media can be used. For example, “OK Prince Quality” manufactured by Oji Paper Co., Ltd., “Shiraoi” manufactured by Nippon Paper Industries Co., Ltd., and Nippon Paper Industries Co., Ltd. Fine paper (A) such as “New NPI Fine” manufactured by Oji Paper Co., Ltd., “OK Everlight Coat” manufactured by Oji Paper Co., Ltd., and “Aurora S” manufactured by Nippon Paper Industries Co., Ltd., Oji Paper Co., Ltd. Lightweight coated paper (A3) such as “OK Coat L” manufactured by Nippon Paper Industries Co., Ltd. and “Aurora L” manufactured by Nippon Paper Industries Co., Ltd. “OK Top Coat +” manufactured by Oji Paper Co., Ltd. and Nippon Paper Industries Co., Ltd. Coated paper (A2, B2) such as “Aurora Coat” manufactured by Oji Paper Co., Ltd. Art paper (A1) such as “OK Kanto +” manufactured by Oji Paper Co., Ltd. and “Tokuhishi Art” manufactured by Mitsubishi Paper Industries Co., Ltd. Can be mentioned. It is also possible to use various photographic papers for ink jet recording.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “parts” and “%” represent mass standards.

  The weight average molecular weight was measured by gel permeation chromatography (GPC). GPC uses HLC-8020GPC (manufactured by Tosoh Corporation), TSKgel Super Multipore HZ-H (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) as a column, and THF (tetrahydrofuran) as an eluent. Using. The conditions were as follows: the sample concentration was 0.35%, the flow rate was 0.35 ml / min, the sample injection amount was 10 μl, the measurement temperature was 40 ° C., and an IR detector was used. In addition, the calibration curve is “standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, It produced from eight samples of "A-2500", "A-1000", and "n-propylbenzene".

<Preparation of ink composition>
(Synthesis of polymer dispersant P-1)
To a 1000 ml three-necked flask equipped with a stirrer and a condenser tube, 88 g of methyl ethyl ketone was added and heated to 72 ° C. in a nitrogen atmosphere. Here, 50 g of methyl ethyl ketone was mixed with 0.85 g of dimethyl 2,2′-azobisisobutyrate and 60 g of benzyl methacrylate. Then, a solution in which 10 g of methacrylic acid and 30 g of methyl methacrylate were dissolved was dropped over 3 hours. After completion of the dropwise addition, the reaction was further continued for 1 hour, and then a solution of 0.42 g of dimethyl 2,2′-azobisisobutyrate in 2 g of methyl ethyl ketone was added, heated to 78 ° C. and heated for 4 hours. The obtained reaction solution was reprecipitated twice in a large excess amount of hexane, and the precipitated resin was dried to obtain 96 g of a polymer dispersant P-1.
The composition of the obtained resin was confirmed by ¹ H-NMR. The weight average molecular weight (Mw) determined in terms of polystyrene by GPC was 44600. The acid value determined by the method described in the JIS standard (JISK0070: 1992) was 65.2 mgKOH / g.

(Preparation of cyan pigment dispersion)
Pigment Blue 15: 3 (phthalocyanine blue A220, manufactured by Dainichi Seika Co., Ltd.), 5 parts of the polymer dispersant P-1, 42 parts of methyl ethyl ketone, 5.5 parts of 1N NaOH aqueous solution, 87.2 parts of ion-exchanged water was mixed and dispersed with a bead mill using 0.1 mmφ zirconia beads for 2 to 6 hours.
Methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed. Then, using a high-speed centrifugal cooler 7550 (manufactured by Kubota Seisakusho), a 50 mL centrifuge was used and 8000 rpm. The mixture was centrifuged for 30 minutes, and the supernatant other than the precipitate was collected. Thereafter, the pigment concentration was determined from the absorbance spectrum, and a dispersion (cyan pigment dispersion) of resin-coated pigment particles (pigment coated with a polymer dispersant) having a pigment concentration of 10.2% was obtained.

(Preparation of magenta pigment dispersion)
In the preparation of the cyan pigment dispersion, resin-coated pigment particles (coated with a polymer dispersant) were prepared in the same manner as in the preparation of the cyan pigment dispersion, except that Pigment Red 122 was used instead of Pigment Blue 15: 3. Pigment) dispersion (magenta pigment dispersion) was prepared.

(Preparation of yellow pigment dispersion)
In the preparation of the cyan pigment dispersion, resin-coated pigment particles (coated with a polymer dispersant) were prepared in the same manner as in the preparation of the cyan pigment dispersion except that Pigment Yellow 74 was used instead of Pigment Blue 15: 3. Pigment) dispersion (yellow pigment dispersion) was prepared.

(Preparation of black pigment dispersion)
In the preparation of the cyan pigment dispersion, resin-coated pigment particles (polymer) were prepared in the same manner as in the preparation of the cyan pigment dispersion, except that carbon black (NIPEX 160-IQ manufactured by Degussa) was used instead of Pigment Blue 15: 3. A dispersion (black pigment dispersion) of a pigment coated with a dispersant was prepared.

(Preparation of self-dispersing polymer particles B-01)
360.0 g of methyl ethyl ketone was charged into a 2 liter three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, and the temperature was raised to 75 ° C. under a nitrogen atmosphere. While maintaining the temperature in the reaction vessel at 75 ° C., 180.0 g of phenoxyethyl acrylate, 162.0 g of methyl methacrylate, 18.0 g of acrylic acid, 72 g of methyl ethyl ketone, and “V-601” (manufactured by Wako Pure Chemical Industries, Ltd.) A mixed solution consisting of 44 g was added dropwise at a constant speed so that the addition was completed in 2 hours. After completion of the dropwise addition, a solution consisting of 0.72 g of “V-601” and 36.0 g of methyl ethyl ketone was added, stirred for 2 hours at 75 ° C., and then a solution consisting of 0.72 g of “V-601” and 36.0 g of isopropanol was added. After stirring at 75 ° C. for 2 hours, the temperature was raised to 85 ° C. and stirring was further continued for 2 hours. About the obtained copolymer, the weight average molecular weight (Mw) calculated | required by GPC by polystyrene conversion was 64000. The acid value determined by the method described in JIS standard (JISK0070: 1992) was 38.9 mgKOH / g.
Next, 668.3 g of the polymerization solution was weighed, 388.3 g of isopropanol and 145.7 ml of 1 mol / L NaOH aqueous solution were added, and the temperature in the reaction vessel was raised to 80 ° C. Next, 720.1 g of distilled water was added dropwise at a rate of 20 ml / min to disperse in water. Thereafter, the temperature in the reaction vessel was maintained at 80 ° C. for 2 hours, 85 ° C. for 2 hours, and 90 ° C. for 2 hours under atmospheric pressure, and then the reaction vessel was depressurized, and isopropanol, methyl ethyl ketone, and distilled water totaled 913. 7 g was distilled off to obtain an aqueous dispersion (emulsion) of self-dispersing polymer particles B-01 having a solid content concentration of 28.0%.

(Preparation of ink composition)
Using the pigment dispersion of each color obtained above and the aqueous dispersion of self-dispersing polymer particles B-01, each component was mixed so as to have the composition shown in Table 1 below, and the plastic disposable syringe was used. Filtration was performed with a PVDF 5 μm filter (Millex SV manufactured by Millipore, diameter 25 mm) to obtain ink compositions C, M, Y, and K.
About the ink composition of each color, pH (25 degreeC) was measured using the Toa DKK Co., Ltd. product pH meter WM-50EG. Further, the surface tension at 25 ° C. was measured with an Automatic Surface Tensionmeter CBVP-Z manufactured by Kyowa Interface Science Co., Ltd. The results are shown in Table 1 below.

<Preparation of treatment liquid>
The processing liquids 1-11 were produced by mixing materials with the composition shown in Table 2 below.
About each process liquid, pH (25 degreeC) was measured using the Toa DKK Co., Ltd. product pH meter WM-50EG. Further, the surface tension at 25 ° C. was measured with an Automatic Surface Tensionmeter CBVP-Z manufactured by Kyowa Interface Science Co., Ltd. The results are shown in Table 2 below.

Example 1
<Image recording>
A printer for evaluation equipped with a GELJET GX5000 printer head (full line head manufactured by Ricoh) was prepared, and the storage tank connected thereto was refilled with the inks C, M, Y, and K obtained above. As a recording medium, an OK top coat (manufactured by Oji Paper Co., Ltd.) was prepared, and the following treatment liquid application step, drying step, and ink application step were sequentially performed to form an image on the recording medium.

(Processing liquid application process)
An OK top coat is fixed on a stage that can move at a speed of 500 mm / second in a predetermined linear direction that is the sub-scanning direction during recording, and each of the treatment liquids obtained above is fixed to about 1.7 g with a wire bar coater. / M ² to apply.

(Drying process)
At the place where the application of the treatment liquid is completed, drying of the recording medium is started under the condition of 50 ° C. using a dryer after 1.5 seconds from the end of the application of the treatment liquid to the place. The drying was finished 3.5 seconds after the end of the application of the. The drying time at this time is 2 seconds.
-Measurement of moisture content of recording medium-
The recording medium was extracted for measuring the moisture content, and the moisture content of the recording medium was measured by the following method.
The paper was punched to a size of 3 cm × 3 cm, and a moisture content (g) was measured using a trace moisture measuring device CA-200 (Karl Fischer moisture meter manufactured by Mitsubishi Chemical Analytech Co., Ltd.) according to the specifications of the moisture meter. . The measured water content (g) was divided by the area of the sample to calculate the water content (g / m ² ) per unit area. The measurement was performed three times for one sample, and the average value of the water content was determined to be 0.2 g / m ² .

(Ink application process)
After the drying process performed under the same conditions as the above drying process, ink ejection was started within 2 seconds by the following method.
-Drip ejection method-
The GELJET GX5000 printer head is fixed so that the direction of the line head in which the nozzles are aligned (main scanning direction) is inclined by 75.7 ° with respect to the direction orthogonal to the moving direction of the stage (sub scanning direction) on the same plane. A solid image is ejected by a line system under the ejection conditions of an ink droplet amount of 2.8 pL, an ejection frequency of 24 kHz, a resolution of 1200 dpi × 1200 dpi, and a stage speed of 50 mm / s while moving the recording medium at a constant speed in the sub-scanning direction. Was printed. Immediately after printing, the sample was dried at 60 ° C. for 3 seconds, passed between a pair of fixing rollers heated to 60 ° C., and subjected to a fixing process at a nip pressure of 0.25 MPa and a nip width of 4 mm to obtain an evaluation sample.

<Evaluation>
The following evaluation items were evaluated. The results are shown in Table 3 below.
(Ink cohesion)
The ink composition C was drawn as halftone dots to obtain a cyan monochrome dot image. Separately, the ink composition M is drawn as a uniform solid image, and the ink composition C is drawn as halftone dots under the same conditions as the above-mentioned single color dot, and a cyan dot (secondary color dot) image on the magenta solid is drawn. Obtained.
About 100 cyan single color dots and 100 secondary color dots, the equivalent circle diameter was measured using a dot analyzer DA-6000 manufactured by Oji Scientific Instruments, and the average value of 100 dots was defined as the dot diameter. The difference between the cyan monochrome dot diameter and the secondary color dot diameter (Δ dot diameter) was calculated, and the ink cohesiveness was evaluated according to the following evaluation criteria. The smaller the Δ dot diameter is, the more preferable it is because the dot diameter of each color is uniform and a homogeneous image can be drawn.

~Evaluation criteria~
A: Δ dot diameter is from 0 μm to less than 0.5 μm B: Δ dot diameter is from 0.5 μm to less than 1 μm C: Δ dot diameter is from 1 μm to less than 2 μm D: Δ dot diameter is from 2 μm to less than 3 μm E: Δ dot diameter is 3μm or more

(Gloss unevenness)
For a print sample in which the ink composition M was drawn as a uniform solid image, the solid image portion was touched with a finger for 30 seconds and then allowed to stand at room temperature for 5 minutes. Gloss unevenness was visually observed in the peripheral image area touched with a finger and evaluated according to the following evaluation criteria.
~Evaluation criteria~
A: Uneven gloss is not seen.
B: Some gloss unevenness is seen in the peripheral part touched by the finger.
C: Gloss unevenness in the peripheral area touched by the finger is conspicuous, which causes a practical problem.

(Roughness of the paper surface)
The roughness of the surface of the non-image part (the processing solution is applied) of the print sample was visually observed and evaluated according to the following evaluation criteria.
A: No roughness is seen at all.
B: A change in the shape of the surface is observed when viewed with a microscope, but no roughness is visually observed.
C: Roughness is visually observed.

(Image adhesion)
Using the ink composition M and the ink composition K, a magenta and black secondary color solid image was drawn at 2 cm × 10 cm. Immediately after printing, a cellophane tape was affixed to a part of the image portion and peeled off after 5 seconds, and the image portion was visually observed. Further, the print sample was left in an environment of 25 ° C. and 50% RH for 24 hours, and the print sample after being left was subjected to the same procedure as described above, and the image portion was observed. From the observation results, image adhesion was evaluated according to the following evaluation criteria.
~Evaluation criteria~
A: Immediately after printing and after leaving for 24 hours, no peeling of the image is observed and the adhesion is excellent.
B: Slight image peeling is observed immediately after printing, but no image peeling is observed after standing for 24 hours.
C: Slight peeling of the image is observed immediately after printing and after standing for 24 hours.
D: The level at which the image peels off immediately after printing and after standing for 24 hours, causing a problem in practical use.

<< Example 2 >>
In the same manner as in Example 1, except that the treatment liquid 7 was used and the drying process conditions were changed as described in Table 4 below by appropriately adjusting the temperature of the dryer, the air volume, the distance to the recording medium, and the like. An image was formed. And it evaluated similarly to Example 1. FIG. The results are shown in Table 4 below.

Example 3
Materials were mixed at the following composition ratios to prepare treatment liquids A1 to A5. Images were formed using the treatment liquids A1 to A5 in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 5 below.

“Composition ratio of treatment liquids A1 to A5”
・ Malonic acid (organic acidic compound) ...... Content shown in Table 5 below ・ Phosphoric acid (Inorganic acidic compound) ...... Content shown in Table 5 below ・ Diethylene glycol monoethyl ether ...... 4%
・ Tripropylene glycol monomethyl ether …… 4%
-Ion-exchanged water: Remaining amount of 100% in total The pH (25 ° C) of each treatment solution was measured using a pH meter WM-50EG manufactured by Toa DKK Co., Ltd. Further, the surface tension at 25 ° C. was measured with an Automatic Surface Tensionmeter CBVP-Z manufactured by Kyowa Interface Science Co., Ltd. The results are shown in Table 5 below.

Example 4
Using the apparatus having the structure described in FIG. 1 of Japanese Patent Application Laid-Open No. 2009-61645 as an ink jet recording apparatus, setting was performed so as to satisfy the drying process conditions of the present invention, and the effects of the present invention were obtained. It was confirmed that

Claims (5)

Water, at least an organic acidic compound containing malonic acid, and at least contains an inorganic acidic compound containing phosphoric acid, wherein the content of the inorganic acidic compound to the content of the organic acidic compound is 5 mol% to 50 mol% , and the treatment liquid applying step pH at 25 ° C. is the processing liquid is 0.5 to 2.0, is applied to a recording medium,
Drying is started within 0.5 to 2 seconds after the treatment liquid is applied to the recording medium, and the water content is reduced to 1.0 g / m ² or less within 5 seconds after the treatment liquid is applied to the recording medium. A drying step of drying the recording medium;
After the drying step, an ink application step of forming an image by applying an ink composition containing at least one of a colorant and polymer particles to the recording medium;
An image forming method comprising: The image forming method according to claim 1, wherein the treatment liquid has a phosphoric acid content of 5 mol% or more and 50 mol% or less with respect to the content of malonic acid. The image forming method according to claim 1, wherein the processing liquid has a pH at 25 ° C. of 0.5 to 1.5. In the drying step, drying is started between 0.5 seconds and 1.5 seconds after the treatment liquid is applied to the recording medium, and the water content is 1 within 3 seconds after the treatment liquid is applied to the recording medium. The image forming method according to claim 1, wherein the image forming method is a step of drying the recording medium to 0.0 g / m ² or less. The image forming method according to claim 1 , wherein the recording medium has a coat layer containing calcium carbonate.