JPH09234943A - Ink composition for ink jet recording, and recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the printing with little bleeding by containing a pigment, water-soluble resin, a water-soluble organic solvent and water and also containing a part of water-soluble resin isolatedly in the ink composition in a method in which a first liquid is made to adhere to a recording medium and then the ink composition is printed. SOLUTION: In the ink jet recording method in which a first liquid containing polyvalent metallic salt is made to adhere to a recording medium and then an ink composition is printed on the recording medium, a pigment, water-soluble resin, a water-soluble organic solvent and water are contained in the ink composition, and a part of water-soluble resin is contained isolately in the ink composition. The amount of isolated water-soluble resin is an amount effective for preventing the bleeding of printing. As the suitable amount of water-soluble resin contained isolately in the ink composition, an amount effective for setting the true roundness in the range of 1-0.9 represented by 4πS/L<2> (S represents the dot area and L represents the peripheral length of dots.) of the dots to be printed is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink composition for ink jet recording and a recording method, and more specifically, a first liquid containing the ink composition and a polyvalent metal salt is deposited on a recording medium, and then the recording is performed. The present invention relates to an ink jet recording method for printing the ink composition on a medium.

2. Background Art Ink jet recording method by ejecting droplets of an ink composition is a printing method for printing by adhering to a recording medium such as paper. This method has a feature that high-resolution and high-quality images can be printed at a high speed with a relatively inexpensive device. In general, an ink composition used for ink jet recording contains water as a main component, and contains a coloring component and a wetting agent such as glycerin for the purpose of preventing clogging.

On the other hand, as an ink jet recording method, a method of applying a polyvalent metal salt solution to a recording medium and then applying an ink composition containing a dye material having at least one carboxyl group has recently been proposed. (For example,
JP-A-5-202328). According to this method, an insoluble complex is formed from a polyvalent metal ion and a dye, and the presence of this complex can provide a high-quality image having water resistance and no color bleed.

[0004] Further, by using a color ink containing at least a surfactant or a penetrating solvent for imparting permeability and a salt, and a black ink which thickens or aggregates by the action of the salt, an image is formed. It has been proposed that a high-quality color image having a high density and no color bleed can be obtained (Japanese Patent Laid-Open No. 6-10673).
No. 5). That is, an ink jet recording method has been proposed in which a good image can be obtained by printing two liquids of a first liquid containing a salt and an ink composition.

[0005]

SUMMARY OF THE INVENTION The present inventors have recently found that in an ink jet recording method for printing such two liquids, the ink composition contains a water-soluble resin and is present in the ink composition in a free state. It was found that the functional resin is important for achieving good printing, especially printing with high roundness and less bleeding. The present invention is based on this finding.

Therefore, it is an object of the present invention to provide a method capable of realizing a good image in an ink jet recording method for printing two liquids.

The ink jet recording method according to the present invention is an ink jet recording method in which a first liquid containing a polyvalent metal salt is attached to a recording medium, and then the ink composition is printed on the recording medium. The ink composition is
A water-soluble resin that comprises a pigment, a water-soluble resin, a water-soluble organic solvent, and water, and a part of the water-soluble resin is present in the ink composition in a free state, and the free water is present. Is the amount effective for preventing the bleeding of the print.

[0008]

DETAILED DESCRIPTION OF THE INVENTION Inkjet Recording Method The inkjet recording method according to the present invention includes a step of depositing a first liquid containing a polyvalent metal salt on a recording medium, and then printing an ink composition on the recording medium. It consists of In the present invention, the ink composition contains a water-soluble resin, and the amount of the free water-soluble resin in the ink composition is the specific amount or more as described above.

Ink Composition The water-soluble resin used in the ink composition of the present invention includes not only those soluble in pure water but also resins widely soluble in aqueous solution such as alkaline aqueous solution in which amine is dissolved. Shall mean. The resin used in the present invention more preferably means a water-soluble resin that can be used as a dispersant in the ink composition.

In the ink composition used in the present invention, a part of the water-soluble resin is present in a free state (hereinafter, "the water-soluble resin present in a free state in the ink composition" is simply referred to as "water-soluble resin"). Sometimes called "free water-soluble resin"). Here, "is present in the ink composition in a free state."
The term "water-soluble resin" means that the water-soluble resin is in a state of being dissolved in the ink composition without being adsorbed by particle components such as pigments. That is, it means that the ink composition of the present invention contains the water-soluble resin in an amount exceeding the amount required for dispersing the particle component such as the pigment. Therefore, the amount of the free water-soluble resin in the ink composition is determined by separating the ink composition from the supernatant by precipitating the particle components such as pigments together with the water-soluble components adsorbed to the ink composition by centrifugation or the like. It can be determined by measuring the amount of water-soluble resin.

In the present invention, the amount of the free water-soluble resin is an amount effective for preventing bleeding of printing. According to a preferred embodiment of the present invention, the amount of free water-soluble resin in the ink composition is 4πS / L of the printed dots.
² (where S is the dot area and L is the perimeter of the dot), the roundness is set in the range of 1 to 0.9, preferably in the range of 1 to 0.95. It is supposed to be an effective amount. Further, according to a preferred embodiment of the present invention, the amount of the free water-soluble resin is 0.3% by weight or more, preferably 0.3 to 5% by weight, more preferably 0.5 to 3% by weight based on the ink composition.
% By weight.

In the present invention, the water-soluble resin is added to the ink composition when the ink composition is produced by using the pigment dispersion as a starting material and adding other ink composition components to the pigment dispersion. Alternatively, it may be substantially performed by controlling the amount of the water-soluble resin as a dispersant contained in the pigment dispersion liquid. Further, not only the water-soluble resin derived from the pigment dispersion but also a water-soluble resin may be added. In the latter case, the water-soluble resin added later may be the same as or different from the water-soluble resin contained in the pigment dispersion liquid.

Examples of water-soluble resins preferably used in the present invention include natural polymers such as lignin sulfonic acid and shellac, polyacrylic acid, styrene-acrylic acid copolymers, styrene-acrylic acid-acrylic acid alkyl ester copolymers. Polymer, styrene-maleic acid copolymer, styrene-maleic acid-acrylic acid alkyl ester copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid half Ester copolymers, vinylnaphthalene-acrylic acid copolymers, vinylnaphthalene-maleic acid copolymers or salts thereof, sodium salts of β-naphthalenesulfonic acid formalin condensates, anionic polymers such as phosphates, etc. Can be given.

The range of the molecular weight of such a water-soluble resin is not particularly limited, but the range of 3,000 to 50,000 is preferable, and the range of 7,000 to 15,000 is more preferable.

It is also possible to use a commercially available water-soluble resin, for example, John Cryl 62 (styrene-acrylic resin manufactured by Johnson Polymer Co., Ltd.), Movinyl S-100A (modified vinyl acetate resin manufactured by Hoechst Synthesis Co., Ltd.). , Jurimer AT-210 (polyacrylic acid ester copolymer manufactured by Nippon Pure Chemical Co., Ltd.) and the like. Of these, a resin containing a carboxyl group is preferable.

The ink composition of the present invention may contain a resin emulsion. Such a resin emulsion is
It means an emulsion in which the continuous phase is water and the dispersed phase is the following resin component. As the resin component of the dispersed phase,
Acrylic resins, vinyl acetate resins, styrene-butadiene resins, vinyl chloride resins, acryl-styrene resins, butadiene resins, styrene resins and the like.

According to a preferred embodiment of the present invention, this resin is preferably a polymer having both a hydrophilic portion and a hydrophobic portion. Further, the particle size of these resin components is not particularly limited as long as an emulsion is formed.
It is preferably not more than about 5 nm, more preferably about 5 to 100 nm.

These resin emulsions can be obtained by mixing resin particles with water, optionally together with a surfactant. For example, an acrylic resin or styrene-acrylic resin emulsion is prepared by adding (meth) acrylic acid ester or styrene, (meth) acrylic acid ester, and optionally (meth) acrylic acid ester, and a surfactant to water. It can be obtained by mixing. The mixing ratio of the resin component and the surfactant is usually preferably about 10: 1 to 5: 1. When the amount of the surfactant used is in the above range, better water resistance and permeability of the ink can be obtained. The surfactant is not particularly limited, but preferable examples include anionic surfactants (eg, sodium dodecylbenzenesulfonate, sodium laurate, ammonium salt of polyoxyethylene alkyl ether sulfate, etc.), nonionic surfactants ( Examples thereof include polyoxyethylene alkyl ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine, polyoxyethylene alkylamide, etc. A mixture of two or more species can be used.

The ratio of the resin as the disperse phase component to water is 60 to 400 parts by weight of water, preferably 100 to 200 parts by weight, relative to 100 parts by weight of the resin.

It is also possible to use a commercially available resin emulsion, for example, Microgel E-100.
2, E-5002 (styrene-acrylic resin emulsion, manufactured by Nippon Paint Co., Ltd.), Boncoat 4001
(Acrylic resin emulsion, manufactured by Dainippon Ink and Chemicals, Inc.) Boncoat 5454 (styrene-acrylic resin emulsion, manufactured by Dainippon Ink and Chemicals, Inc.), SAE-1014 (styrene-acrylic resin emulsion, Nippon Zeon Co., Ltd.) Made), Cybinol S
K-200 (acrylic resin emulsion, manufactured by Saiden Chemical Co., Ltd.) and the like.

The ink composition used in the present invention comprises a resin emulsion whose resin component is 0.1 to 0.1% of that of the ink composition.
The content is preferably 40% by weight, more preferably 1 to 25% by weight.

The resin emulsion has the effect of suppressing the permeation of the coloring component by the interaction with the polyvalent metal ion and further promoting the fixing to the recording medium. Also, depending on the type of resin emulsion, a film is formed on the recording medium,
It also has the effect of improving the abrasion resistance of the printed matter.

In the present invention, an inorganic pigment or an organic pigment can be used without particular limitation as the pigment. As the inorganic pigment, in addition to titanium oxide and iron oxide, carbon black produced by a known method such as a contact method, a furnace method, and a thermal method can be used. The organic pigments include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, etc.), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazines). Pigments, thioindigo pigments, isoindolinone pigments, quinofuraron pigments, etc.), dye chelates (for example, basic dye type chelates,
Acid dye type chelates), nitro pigments, nitroso pigments, aniline black, etc. can be used.

According to a preferred embodiment of the present invention, these pigments are preferably added to the ink composition as a pigment dispersion obtained by dispersing them in an aqueous medium with a dispersant.
As a preferable dispersant, a dispersant which is commonly used for preparing a pigment dispersion, for example, a polymer dispersant or a surfactant can be used. It will be apparent to those skilled in the art that the dispersant and the surfactant contained in this pigment dispersion will also function as the surfactant of the ink composition described later.

The amount of the pigment added to the ink composition is 0.5.
Is preferably about 25 to 25% by weight, more preferably 2 to 15
It is about% by weight.

The organic solvent is preferably a low boiling point organic solvent, and preferred examples thereof include methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-butanol, sec-butanol and tert.
-Butanol, iso-butanol, n-pentanol and the like. A monohydric alcohol is particularly preferable. The low boiling point organic solvent has the effect of shortening the ink drying time.

The ink composition used in the present invention may contain a surfactant. Examples of surfactants include:
The above-mentioned surfactant and acetylene glycol (olefin Y, and Surfynol 82, 104, 44
0, 465, and 485 (all Air Products and
Chemicals Inc.))).

According to a preferred embodiment of the present invention, the ink composition preferably contains sugar. Examples of saccharides include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides) and polysaccharides, preferably glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucosyl Sorbitol, maltose, cellobiose, lactose, sucrose, trehalose, maltotriose, and the like. Here, the polysaccharide means a sugar in a broad sense, and is used to include a substance widely existing in nature such as alginic acid, α-cyclodextrin, and cellulose.

The derivatives of these saccharides include reducing sugars of the aforementioned saccharides (for example, sugar alcohols (general formula H
OCH ₂ (CHOH) n CH ₂ OH (where n = 2
Represented by an integer of 5), oxidized sugars (eg, aldonic acid, uronic acid, etc.), amino acids, thiosugars and the like. In particular, sugar alcohols are preferred, and specific examples include maltitol and sorbitol.

The content of these saccharides is 0.1 to 0.1% of the ink.
A range of 40% by weight, preferably 0.5 to 30% by weight is suitable.

Further, according to a preferred embodiment of the present invention, the ink composition used in the present invention preferably further comprises a high boiling point organic solvent. Preferred examples of the high boiling point organic solvent agent include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, propylene glycol, butylene glycol, 1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerin, Polyhydric alcohols such as triethylene glycol, trimethylolethane, and trimethylolpropane,
Alkyl of polyhydric alcohols such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether Ethers, urea, 2-pyrrolidone, N-methyl-2
-Pyrrolidone, 1,3-dimethyl-2-imidazolidinone, triethanolamine and the like.

The amount of these wetting agents added is preferably 0.5 to 40% by weight of the ink composition, more preferably 2 to 2%.
The range is 0% by weight. Further, the amount of the low-boiling organic solvent to be added is preferably 0.5 to 10% by weight of the ink, more preferably 1.5 to 6% by weight.

In addition, a pH adjusting agent, a preservative, a fungicide, etc. may be added, if necessary.

First Liquid The first liquid used in the present invention basically comprises a polyvalent metal salt, water, and preferably a high boiling point organic solvent.

In the present invention, the polyvalent metal salt contained in the first liquid is composed of a polyvalent metal ion having a valence of 2 or more and preferably a nitrate ion or a carboxylate ion which binds to these polyvalent metal ions. , Soluble in water.

Here, the carboxylate ion is preferably derived from a carboxylic acid selected from the group consisting of a saturated aliphatic monocarboxylic acid having 1 to 6 carbon atoms and a carbocyclic monocarboxylic acid having 7 to 11 carbon atoms. It is something. Carbon number 1
Preferred examples of the saturated aliphatic monocarboxylic acid of to 6 include formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, pivalic acid and hexanoic acid. Particularly, formic acid and acetic acid are preferable.

The hydrogen atom on the saturated aliphatic hydrocarbon group of this monocarboxylic acid may be substituted with a hydroxyl group, and a preferable example of such a carboxylic acid is lactic acid.

Further, preferred examples of the carbocyclic monocarboxylic acid having 6 to 10 carbon atoms include benzoic acid and naphthoic acid, and benzoic acid is more preferred.

On the other hand, specific examples of polyvalent metal ions include:
Examples thereof include divalent metal ions such as Ca ²⁺ , Cu ²⁺ , Ni ²⁺ , Mg ²⁺ , Zn ²⁺ and Ba ^2+, and trivalent metal ions such as Al ³⁺ , Fe ³⁺ and Cr ³⁺ .

In particular, the metal salt composed of the above anion and Ca ²⁺ or Mg ²⁺ gives preferable results from the two viewpoints of the pH of the first liquid and the quality of the printed matter obtained.

The concentration of these polyvalent metal salts in the first liquid may be appropriately determined within the range where the effects of printing quality and clogging prevention can be obtained, but it is preferably about 0.1 to 40% by weight, and It is preferably about 5 to 25% by weight.

Preferred examples of the high boiling point organic solvent include those described in the section of the ink composition. The high-boiling organic solvent prevents head clogging by preventing the first liquid from drying.

The amount of the high boiling point organic solvent added is not particularly limited, but is preferably about 0.5 to 40% by weight, more preferably about 2 to 20% by weight.

According to a preferred embodiment of the present invention, it is preferable to add triethylene glycol monobutyl ether and glycerin as the high boiling point organic solvent. In addition to these, it is also preferable to add triethanolamine for pH adjustment. When adding these in combination,
The addition amount of triethylene glycol monobutyl ether and glycerin is preferably about 10 to 20% by weight and about 1 to 15% by weight, respectively, and when triethanolamine is further added, the addition amount is 0 to 2.0% by weight. A degree is preferable.

In addition, various pH adjusting agents, preservatives, fungicides and the like may be added, if necessary.

Further, the first liquid may be colored by adding a color coloring agent and may also have a function of the ink composition.

The ink jet recording apparatus connexion below the ink jet recording apparatus for practicing the ink jet recording method according to the present invention will be described with reference to the drawings.

The ink jet recording apparatus shown in FIG. 1 is a mode in which an ink composition and a first liquid are stored in a tank, and the ink composition and the first liquid are supplied to a recording head via an ink tube. That is, the recording head 1 and the ink tank 2 are connected by the ink tube 3. Here, the inside of the ink tank 2 is partitioned, and the ink composition,
In some cases, a room for a plurality of color ink compositions and a room for the first liquid are provided.

The recording head 1 moves along the carriage 4
It is moved by the timing belt 6 driven by the motor 5. On the other hand, the paper 7 as a recording medium is placed at a position facing the recording head 1 by the platen 8 and the guide 9. In this embodiment, a cap 10 is provided. A suction pump 11 is connected to the cap 10 to perform a so-called cleaning operation. The sucked ink composition is supplied to the waste ink tank 13 via the tube 12.
Is stored in.

FIG. 2 is an enlarged view of the nozzle surface of the recording head 1. The portion indicated by 1b is the nozzle surface of the first liquid, and the nozzle 21 for discharging the first liquid is provided in the vertical direction. On the other hand, the portion indicated by 1c is the nozzle surface of the ink composition, and from the nozzles 22, 23, 24, and 25, the yellow ink composition, the magenta ink composition, the cyan ink composition, and the black ink composition are respectively provided. Discharged.

Further, an ink jet recording method using the recording head shown in FIG. 2 will be described with reference to FIG. The recording head 1 moves in the direction of arrow A. During that move,
The first liquid is ejected from the nozzle surface 1b to form a band-shaped first liquid adhesion region 31 on the recording medium 7. Next, the recording medium 7 is transported by a predetermined amount in the paper feed direction arrow B. During that time, the recording head 1 moves in the direction opposite to the arrow A in the figure, and returns to the position on the left end of the recording medium 7. Then, the ink composition is printed on the first liquid adhering area where the first liquid is already adhering, and the printing area 32 is formed.

Further, as shown in FIG. 4, in the recording head 1, all the nozzles can be arranged in the horizontal direction. In the figure, 41a and 41b are discharge nozzles of the first liquid, respectively, from the nozzles 42, 43, 44 and 45, a yellow ink composition, a magenta ink composition,
A cyan ink composition and a black ink composition are ejected. In the recording head of such a mode, the recording head 1 can print on both the forward path and the return path that reciprocate on the carriage, and at a speed faster than that when the recording head shown in FIG. 2 is used. Printing can be expected.

Further, in some ink jet recording apparatuses, replenishment of the ink composition is performed by replacing a cartridge which is an ink tank. This ink tank may be integrated with the recording head.

FIG. 5 shows a preferred example of an ink jet recording apparatus using such an ink tank. In the figure, the same members as those of the apparatus of FIG. 1 are denoted by the same reference numerals. In the embodiment of FIG. 5, the recording heads 1a and 1b
Is integrated with the ink tanks 2a and 2b.
The recording head 1a or 1b discharges the ink composition and the first liquid, respectively. The printing method may be basically the same as that of the apparatus shown in FIG. In this embodiment, the recording head 1a and the ink tank 2a and the recording head 1a and the ink tank 2b move on the carriage 4.

Regarding the adhesion of the first liquid to the recording medium, either the method of selectively adhering the first liquid only to the place where the ink composition is adhered or the method of adhering the first liquid to the entire surface of the paper is used. It may be a mode. The former is economical because it can minimize the consumption of the first liquid,
A certain degree of accuracy is required for the position where both the first liquid and the ink composition are attached. On the other hand, in the latter, the requirement for the accuracy of the adhesion position of the first liquid and the ink composition is relaxed compared to the former, but a large amount of the first liquid is adhered to the entire surface of the paper, and the paper curls during drying. Cheap. Therefore, which method is adopted may be determined in consideration of the combination of the ink composition and the first liquid.

[0056]

The present invention will be described in more detail with reference to the following examples, but it should not be construed that the invention is limited thereto.

In producing the ink composition, first, the pigment, a predetermined amount of the pigment dispersant, and water are mixed and stirred using a jet mill until the average particle diameter of the pigment becomes 1 μm or less, to prepare a pigment dispersion liquid. . Then, after adding other ingredients and mixing, 3
An ink composition was produced by pressure filtration with a μm membrane filter.

Ink Composition Ink 1 Carbon Black Raven 1080 5 wt% (manufactured by Columbian Carbon Co., Ltd.) Styrene-acrylic acid copolymer (dispersant) 1 wt% Microgel E-5002 4 wt% (styrene-acrylic -Based resin emulsion, resin component 29.2%, MFT = about 80 ° C., manufactured by Nippon Paint Co., Ltd.) Sucrose 0.7% by weight Maltitol 6.3% by weight Glycerin 10% by weight 2-Pyrrolidone 2% by weight Ethanol 4% by weight John Kryl 62 0.5 wt% (manufactured by Johnson Polymer Co., resin component 34%) Pure water remaining amount The amount of free water-soluble resin in this ink was 0.3 wt%.

Ink 2 Carbon black Raven 1080 2% by weight (Colombian Carbon Co., Ltd.) Styrene-acrylic acid copolymer (dispersant) 1% by weight Microgel E-5002 7% by weight (styrene-acrylic resin emulsion) , Resin component 29.2%, MFT = about 80 ° C., manufactured by Nippon Paint Co., Ltd.) Sucrose 0.7% by weight Maltitol 6.3% by weight Glycerin 10% by weight 2-Pyrrolidone 2% by weight Ethanol 4% by weight Mobile S- 100A 3% by weight (modified vinyl acetate resin, resin component 50%, Hoechst Synthetic Co., Ltd.) Pure water remaining amount The amount of free water-soluble resin in this ink was 1.6% by weight.

Ink 3 KETBLUEEX-1 2% by weight (Dainippon Ink and Chemicals, Inc.) Styrene-acrylic acid copolymer (dispersant) 1% by weight Boncoat 4001 2% by weight (acrylic resin emulsion, resin component 50% MFT = about 5 ° C., manufactured by Dainippon Ink and Chemicals, Inc.) Sucrose 0.7% by weight Maltitol 6.3% by weight Glycerin 10% by weight 2-Pyrrolidone 2% by weight Ethanol 4% by weight Julimer AT-210 5% by weight (poly) Acrylic ester copolymer, resin component 30%, manufactured by Nippon Pure Chemical Co., Ltd. Pure water remaining amount The amount of free water-soluble resin in this ink was 1.5% by weight.

Ink 4 Carbon Black Raven 1080 5 wt% (manufactured by Columbian Carbon Co., Ltd.) Styrene-acrylic acid copolymer (dispersant) 1 wt% Microgel E-5002 10 wt% (styrene-acrylic resin emulsion) , Resin component 29.2%, MFT = about 80 ° C., manufactured by Nippon Paint Co., Ltd.) Sucrose 0.7% by weight Maltitol 6.3% by weight Glycerin 10% by weight 2-Pyrrolidone 2% by weight Ethanol 4% by weight Pure water remaining Amount The amount of free water-soluble resin in this ink was 0.15% by weight.

[0062] The first liquid first liquid of the following composition, the following components were mixed, at room temperature for 1
The mixture was stirred for an hour, and then the composition was suction-filtered with a 5 μm membrane filter at room temperature to prepare. Magnesium nitrate hexahydrate 25% by weight Triethylene glycol monobutyl ether 5% by weight Glycerin 20% by weight Ion-exchanged water Remaining amount print evaluation test : Roundness Using an inkjet printer MJ-700V2C (manufactured by Seiko Epson Corp.) Xerox 4024
3R 721 (manufactured by Xerox Co., Ltd.) and Xerox
Printing was performed on two sheets of R (manufactured by Xerox Co., Ltd., recycled paper). The printing was performed by printing the first liquid with 100% duty and then printing dots with the ink composition.

The circularity of dots formed by the ink composition is 4π.
When defined as S / L ² (where S is the dot area and L is the dot perimeter), the roundness was evaluated as follows. When both papers are 1 to 0.9 ... ◎ Either or both papers are 0.9 to 0.8 ... ○ Either or both papers are less than 0.8 ... × The results are as shown in Table 1. there were.

[0064]

[Brief description of drawings]

FIG. 1 is a diagram showing an inkjet recording apparatus for carrying out a method according to the present invention, in which a recording head and an ink tank are independent from each other, and an ink composition and a first liquid are formed by an ink tube. Is supplied to.

FIG. 2 is an enlarged view of the nozzle surface of the recording head, showing 1b.
Is the nozzle surface of the first liquid, and 1c is the nozzle surface of the ink composition.

FIG. 3 is a diagram illustrating inkjet recording using the recording head of FIG. 2; In the figure, reference numeral 31 denotes a first liquid adhering area, and reference numeral 32 denotes a printing area where the ink composition is printed on the first liquid adhering.

FIG. 4 is a diagram showing another aspect of the recording head, in which all the ejection nozzles are arranged in the horizontal direction.

FIG. 5 is a view showing an ink jet recording apparatus for carrying out the method according to the present invention. In this embodiment, the recording head and the ink tank are integrated.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Recording head 2 Ink tank 3 Ink tube 21 First liquid discharge nozzle 22, 23, 24, 25 Ink composition discharge nozzle 31 First liquid adhesion area 32 Printing area

Claims (7)

[Claims] 1. An ink jet recording method, comprising depositing a first liquid containing a polyvalent metal salt on a recording medium, and then printing the ink composition on the recording medium, wherein the ink composition comprises a pigment. A water-soluble resin, a water-soluble organic solvent, and water, and a part of the water-soluble resin is present in the ink composition in a free state, and the amount of the water-soluble resin present in the free state is A method comprising an amount effective for preventing bleeding of printing. 2. The amount of the water-soluble resin present in the ink composition in a free state is 4πS / L ^{2 of the} dots to be printed (where S is the dot area and L is the perimeter of the dot). The method according to claim 1, wherein the circularity represented by (a) is in an amount effective to set the circularity in the range of 1 to 0.9. 3. The method according to claim 1, wherein the amount of the water-soluble resin present in the ink composition in a free state is 0.3% by weight or more based on the ink composition. 4. The ink composition according to claim 1, wherein the ink composition further comprises a resin emulsion. 5. An ink composition for use in an ink jet recording method, comprising depositing a first liquid containing a polyvalent metal salt on a recording medium, and thereafter printing the ink composition on the recording medium, which comprises a pigment. A water-soluble resin, a water-soluble organic solvent, and water are contained, and a part of the water-soluble resin is present in the ink composition in a free state, and the amount of the free water-soluble resin is printed. An ink composition comprising an amount effective to prevent bleeding. 6. The amount of the water-soluble resin present in the ink composition in a free state is 4πS / L ^{2 of the} dots to be printed (where S is the dot area and L is the perimeter of the dot). The ink composition according to claim 5, wherein the amount is an amount effective to keep the circularity represented by (a) in the range of 1 to 0.9. 7. The ink composition according to claim 5, wherein the amount of the water-soluble resin present in the ink composition in a free state is 0.3% by weight or more based on the ink composition.