Ink composition adhesion method and liquid set

Abstract

To suppress bleeding of ink and to suppress deterioration of uniformity in a solid image.SOLUTION: The ink composition attachment method includes a first attachment step of attaching the pretreatment liquid to the medium, a first drying step of drying the pretreatment liquid from the medium after the first attachment step, a second attachment step of attaching the ink composition to the medium after the first drying step, and a second drying step of drying the ink composition from the medium after the second attachment step.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] Disclosed herein is a technique for applying an ink composition to a medium. [Background technology]

[0002] Patent Document 1 discloses a method for applying an ink composition, which includes a step of applying a pretreatment liquid to a medium and a step of applying an ink composition to the medium. In this ink composition application method, the difference between the surface tension of all components of the ink composition and the surface tension of the remaining components after the ink composition has evaporated to a predetermined evaporation rate is equal to or less than a predetermined value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-81351 Summary of the Invention [Problem to be solved by the invention]

[0004] This specification provides a novel technology for suppressing bleeding of an ink composition and suppressing a decrease in uniformity in a solid area (so-called solid uniformity) when the ink composition is applied to a non-absorbent medium or a low-absorbent medium. [Means for solving the problem]

[0005] This specification discloses an ink composition applying method. The ink composition applying method includes a first applying step of applying a pretreatment liquid to a medium, a first drying step of drying the pretreatment liquid from the medium after the first applying step, a second applying step of applying an ink composition to the medium after the first drying step, and a second drying step of drying the ink composition from the medium after the second applying step. The medium is a non-absorbent medium or a low-absorbent medium. The pretreatment liquid contains a cationic polymer flocculant. The cationic polymer has a cation concentration of 6.0 Eq / L or more. The drying rate of the pretreatment liquid after the drying step is 50% or more. The ink composition contains an anionic solid component, one or more organic solvents, a surfactant, and water. The static surface tension of all components of the ink composition is 25.2 mN / m or more and 29.3 mN / m or less. The difference between the static surface tension of all components of the ink composition and the static surface tension of the ink composition after the second drying step is 3.5 mN / m or less. The one or more organic solvents include at least one organic solvent having a static surface tension of 28.0 mN / m or more and 34.0 mN / m or less. The content of the at least one organic solvent relative to the total amount of the ink composition is 7.5 wt % or more and 24.0 wt % or less.

[0006] When an ink composition with a relatively low static surface tension (hereinafter simply referred to as surface tension) is applied to a medium, there is a risk that the ink composition will unintentionally spread on the medium. This problem is particularly pronounced when the medium is non-absorbent or low-absorbent. In the ink composition application method described above, a pretreatment liquid containing an aggregating agent with a cation concentration of 6.0 Eq / L or more is applied to the medium in advance. This allows the cationic aggregating agent contained in the pretreatment liquid to aggregate the anionic solid components contained in the ink composition when the ink composition is applied to the medium, thereby preventing the ink composition from bleeding.

[0007] However, when a solid area is formed using a relatively large amount of ink composition, even the use of the pretreatment liquid described above can result in insufficient aggregation of solid components. In this case, the ink composition used to form a solid area on a medium gradually dries on the medium. As the ink composition dries, a surface tension gradient occurs due to uneven distribution of the components in the ink composition, which can cause Marangoni convection. Marangoni convection can unintentionally shrink the ink composition or cause the coffee ring phenomenon. This can result in reduced solid uniformity. In this regard, the ink composition application method described above adjusts the difference in surface tension of the ink composition before and after drying to 3.5 mN / m or less, thereby preventing significant changes in surface tension within the ink composition during drying. This prevents reduced solid uniformity.

[0008] A liquid set comprising the above-mentioned pretreatment liquid and ink composition is also novel and useful. [Brief explanation of the drawings]

[0009] [Figure 1] 1 shows the configuration of an image forming apparatus 10. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] 10 is a comparative example for explaining that ink bleeds when it is applied to a medium 2 to which a pretreatment liquid has been applied. [Figure 4] 10A and 10B are diagrams for explaining how bleeding of ink is suppressed when ink is applied to a medium 2 on which a pretreatment liquid has been applied. [Figure 5] This is a comparative example to explain that during the drying process of the ink for forming a solid image on a medium 2 to which a pretreatment liquid is attached, a surface tension gradient occurs in the ink, resulting in a decrease in solid uniformity. [Figure 6] FIG. 10 is a diagram for explaining that during the drying process of ink for forming a solid image on a medium 2 to which a pretreatment liquid has been applied, large changes in surface tension within the ink are suppressed, and a decrease in solid uniformity is suppressed. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Configuration of image forming apparatus 10) An image forming apparatus 10 according to an embodiment will be described with reference to the drawings. As shown in FIGS. 1 and 2, the image forming apparatus 10 is a printer that uses ink to form an image on a medium 2. Specifically, the image forming apparatus 10 ejects ink toward the medium 2 according to an inkjet method to form an image on the medium 2. The image forming apparatus 10 is used while being placed on the floor or a rack. However, in other embodiments, the image forming apparatus 10 may be used while being placed on a table.

[0011] In the image forming apparatus 10, ink line heads 34a and the like equipped with nozzles 36a and the like for ejecting ink do not move. In other words, the image forming apparatus 10 is a so-called line printer. In FIGS. 1 and 2, the transport direction of the medium 2 is defined as the front-to-rear direction of the image forming apparatus 10. More specifically, the medium 2 is transported from the rear side to the front side of the image forming apparatus 10. As a result, the width direction of the medium 2 corresponds to the left-to-right direction of the image forming apparatus 10. Furthermore, the direction perpendicular to the plane of the paper in FIG. 1 corresponds to the up-to-down direction of the image forming apparatus 10.

[0012] The image forming apparatus 10 includes a housing 12, a holder 14, two pairs of conveying rollers 16 and 18, a platen 20, and a control unit 22. The control unit 22 is communicatively connected to each part of the image forming apparatus 10 and controls the operation of each part. For ease of explanation, each component housed inside the housing 12 is shown in FIG. 1, but each component does not necessarily have to be located in the position shown.

[0013] The housing 12 has an outlet 12a. The outlet 12a is provided on the front surface of the housing 12. The outlet 12a is a through-hole that penetrates the housing 12 in the front-to-rear direction. The medium 2 (see FIG. 2) on which an image is recorded is ejected from the outlet 12a.

[0014] The holder 14 supports a roll 4 on which the medium 2 is wound in a circular shape. Here, the medium 2 is a long sheet. The holder 14 is rotated by a conveyance motor (not shown). As the holder 14 rotates, the roll 4 supported by the holder 14 also rotates.

[0015] A transport path 100 through which the medium 2 passes is formed between the holder 14 and the discharge port 12a. As the medium 2 passes through this transport path 100, an image is recorded on the medium 2.

[0016] Each of the two transport roller pairs 16, 18 includes a transport roller 16a, 18a and a pinch roller 16b, 18b. The transport rollers 16a, 18a come into contact with the pinch rollers 16b, 18b to form a nip. The transport roller pairs 16, 18 are rotated by a transport motor (not shown). The first transport roller pair 16 rotates while nipping the medium 2, thereby transporting the medium 2 fed from the roll 4 forward. In the transport path 100, the second transport roller pair 18 is located downstream of the first transport roller pair 16. The second transport roller pair 18 rotates while nipping the medium 2, thereby transporting the medium 2 to the discharge opening 12a. The number and arrangement of each transport roller pair 16, 18 are not particularly limited.

[0017] A platen 20 is disposed between the first conveying roller pair 16 and the second conveying roller pair 18. The platen 20 supports the medium 2.

[0018] The image forming apparatus 10 further includes a frame 24 and a pretreatment liquid line head 26. The frame 24 supports the pretreatment liquid line head 26. A plurality of nozzles 28 are open on the underside of the pretreatment liquid line head 26. The plurality of nozzles 28 are arranged along the width direction (i.e., the left-right direction) of the medium 2. The control unit 22 drives a piezoelectric element (not shown) corresponding to each nozzle 28 to selectively eject the pretreatment liquid toward the medium 2 passing through the transport path 100. This causes the pretreatment liquid to adhere to the medium 2. Note that the number and arrangement of the nozzles 28 are not particularly limited.

[0019] The image forming apparatus 10 further includes a drying device 30. The drying device 30 is disposed downstream of the pretreatment liquid line head 26 in the transport path 100. The drying device 30 is, for example, a dryer, an oven, or an IR heater. The control unit 22 controls the drying device 30 to dry the pretreatment liquid adhered to the medium 2 passing through the transport path 100. Note that the drying device 30 may be a dryer, an oven, or an IR heater, and may be a combination of two or more of these.

[0020] The image forming apparatus 10 further includes four frames 32a, 32b, 32c, and 32d and four ink line heads 34a, 34b, 34c, and 34d. Each frame 32a to 32d supports a corresponding ink line head 34a to 34d. The four ink line heads 34a to 34d eject cyan ink, magenta ink, yellow ink, and black ink, respectively. In the transport path 100, the four ink line heads 34a to 34d are disposed downstream of the drying device 30. The four ink line heads 34a to 34d are disposed at intervals along the transport direction (i.e., the front-to-rear direction) of the medium 2. Because the four ink line heads 34a to 34d have the same configuration, the following description focuses on one ink line head 34a.

[0021] A plurality of nozzles 36a are opened on the bottom surface of the ink line head 34a. The plurality of nozzles 36a are arranged along the width direction (i.e., the left-right direction) of the medium 2. The control unit 22 drives a piezoelectric element (not shown) corresponding to each nozzle 36a to selectively eject ink toward the medium 2 passing through the transport path 100. In this way, an image is formed on the medium 2. Note that the number and arrangement of the nozzles 36a are not particularly limited.

[0022] The image forming apparatus 10 further includes a drying device 38. The drying device 38 is disposed downstream of the ink line heads 34a to 34d in the transport path 100. The drying device 38 is, for example, a dryer, an oven, or an IR heater. The control unit 22 controls the drying device 38 to dry the ink adhered to the medium 2 passing through the transport path 100. Note that the drying device 38 may be one type of device selected from the group consisting of a dryer, an oven, and an IR heater, or two or more types may be used in combination.

[0023] (medium) The medium 2 is a non-absorbent medium or a low-absorbent medium. Examples of non-absorbent media include plastic films that have not been surface-treated for inkjet printing (i.e., do not have an ink-absorbing layer), media such as paper coated with plastic, and media such as paper with a plastic film adhered to it. Examples of plastics include polypropylene, polyethylene, polyethylene terephthalate, polyvinyl chloride resin, and polycarbonate. Examples of low-absorbent media include art paper, coated paper, and matte paper. Coated paper is, for example, plain paper made primarily of pulp, such as high-grade printing paper or medium-grade printing paper, coated with a coating agent to improve smoothness, whiteness, gloss, etc. Specific examples include high-grade coated paper and medium-grade coated paper.

[0024] The non-absorbent medium and the low-absorbent medium are described above as examples. However, in addition to the above-described exemplary media, for example, a medium having a low absorbency of 30 msec from the start of contact in the Bristow method may be used. 1 / 2 Water absorption up to 10mL / m 2 The following media are also included in the non-absorbent media and low-absorbent media. The Bristow method referred to here is, for example, Standard No. 51 "Paper and paperboard - Liquid absorbency test method - Bristow method" of "JAPAN TAPPI Paper and Pulp Testing Method 2000 Edition."

[0025] (Pretreatment liquid) The pretreatment liquid contains a cationic flocculant and water. The cationic flocculant can flocculate anionic solid components in the ink when the pretreatment liquid and the ink come into contact with each other on the medium 2.

[0026] Examples of cationic flocculants include cationic polymers. Cationic polymers may be either natural or synthetic. Cationic polymers are polymers having cationic groups or groups that can be ionized into cationic groups (e.g., primary amino groups, secondary amino groups, tertiary amino groups, quaternary ammonium groups, etc.), and include amphoteric polymers that are cationic as a whole. Examples of cationic polymers include ammonium-containing polymers, amine-containing polymers, polyallylamine, polydiallylamine, polytriallylamine, polyvinylamine, polyimine, polyvinylpyrrolidone, polyethyleneimine, polyvinylpyridine, aminoacetalized polyvinyl alcohol, ionene polymers, polyvinylimidazole, polyvinylbenzylphosphonium, polyalkylallylammonium, polyamidine, polyamine sulfone, and polymethyldiallylamine. One type of cationic polymer may be used alone, or two or more types may be used in combination.

[0027] From the viewpoint of the aggregating ability of the anionic solid components contained in the ink, it is preferable to use polyallylamine as the cationic polymer. As used herein, polyallylamine refers to a polymer containing repeating units derived from allylamine. Examples of polyallylamine include polymers containing allylamine and / or its derivatives as repeating units, polymers containing diallylamine and / or its derivatives as repeating units, and polymers containing polytriallylamine-derived and / or its derivatives as repeating units.

[0028] From the viewpoint of the aggregating property of the anionic solid components contained in the ink, it is more preferable to use a polymer containing at least one repeating unit represented by formula (1) to formula (4) among the above-mentioned allylamines. [ka] [ka] [ka] [ka]

[0029] In formula (1), R1 and R2 each represent hydrogen or an alkyl group. The number of carbon atoms in the alkyl group is, for example, 1 to 10, or 1 to 5. The alkyl group may have a substituent such as a carboxy group, and may be linear or branched.

[0030] In formula (2), R3 is hydrogen or an alkyl group. The number of carbon atoms in the alkyl group is, for example, 1 to 10, or 1 to 5. The alkyl group may have a substituent such as a carboxy group, and may be linear or branched.

[0031] In formula (3), each of R4, R5, and R6 is hydrogen or an alkyl group. The number of carbon atoms in the alkyl group is, for example, 1 to 10, or 1 to 5. The alkyl group may have a substituent such as a carboxy group, and may be linear or branched. In formula (3), X1 - is an anion. X1 - Examples of the cations include methyl sulfate ion, ethyl sulfate ion, chloride ion, sulfate ion, acetate ion, phosphate ion, citrate ion, and amidosulfate ion.

[0032] In formula (4), each of R6 and R7 is hydrogen or an alkyl group. The number of carbon atoms in the alkyl group is, for example, 1 to 10, or 1 to 5. The alkyl group may have a substituent such as a carboxy group, and may be linear or branched. In formula (4), X2 - is an anion. X2 -Examples of the cations include methyl sulfate ion, ethyl sulfate ion, chloride ion, sulfate ion, acetate ion, phosphate ion, citrate ion, and amidosulfate ion.

[0033] As the cationic polymer, for example, commercially available products may be used. Examples of commercially available products include "PAS-M-1A," a methyldiallylamine acetate polymer manufactured by Nittobo Medical Co., Ltd., and "PAA-U5000," a partially methoxycarbonylated allylamine polymer. "PAS-M-1A" is a cationic polymer containing methyldiallylamine as a repeating unit, represented by formula (4), in which R7 is hydrogen, R8 is a methyl group, and X2 - is an acetate ion. "PAA-U5000" is a cationic polymer containing allylamine as a repeating unit, represented by formula (1), where R1 is hydrogen and R2 is hydrogen. Note that part of R2 may be a methoxycarboxy group.

[0034] When the cationic polymer is water-soluble, the cation concentration of the cationic polymer is, for example, 6.0 Eq / L or more, for example, 7.0 Eq / L or more, for example, 7.5 Eq / L or more, or for example, 8.0 Eq / L or more. From the viewpoint of the coagulation properties of the anionic solid components contained in the ink, the cation concentration of the cationic polymer is preferably 7.5 Eq / L or more. The cation concentration can be measured, for example, by colloid titration using a polyvinyl potassium sulfate reagent. The cation concentration of the aforementioned "PAS-M-1A" is 7.5 Eq / L, and the cation concentration of "PAA-U5000" is 6.0 Eq / L.

[0035] The weight average molecular weight of the cationic polymer is, for example, 600 to 20,000, or, for example, 900 to 15,000, or, for example, 1,200 to 10,000.

[0036] The content of the cationic flocculant relative to the total amount of the pretreatment liquid is, for example, in the range of 0.1% by weight to 5% by weight, or, for example, in the range of 0.5% by weight to 3% by weight, or, for example, in the range of 0.75% by weight to 2% by weight.

[0037] The water is preferably ion-exchanged water or pure water. The content of water relative to the total amount of the pretreatment liquid is, for example, the remainder of the components other than water.

[0038] The pretreatment liquid may further contain a known water-soluble organic solvent, such as a polyhydric alcohol, a polyhydric alcohol derivative, an alcohol, an amide, a ketone, a ketoalcohol, an ether, a nitrogen-containing solvent, a sulfur-containing solvent, propylene carbonate, ethylene carbonate, or 1,3-dimethyl-2-imidazolidinone.

[0039] The pretreatment liquid may further contain known additives as needed. Examples of additives include surfactants, pH adjusters, viscosity adjusters, surface tension adjusters, antioxidants, and antifungal agents. Commercially available surfactants may be used. Examples of commercially available surfactants include Olfine (registered trademark) E1010, Olfine (registered trademark) E1006, Olfine (registered trademark) E1004, Silface SAG503A, and Silface SAG002 manufactured by Nissin Chemical Industry Co., Ltd. The surfactant content relative to the total amount of the pretreatment liquid is, for example, 3% by weight or less, 2% by weight or less, or 1% by weight or less. Examples of viscosity adjusters include polyvinyl alcohol, cellulose, and water-soluble resins.

[0040] The pretreatment liquid can be prepared, for example, by uniformly mixing a cationic flocculant, water, and, if necessary, other additive components by a known method, and then removing insoluble matter with a filter or the like.

[0041] (ink) The ink contains resin particles, a coloring material, an organic solvent, a surfactant, and water, and is an aqueous ink in which the resin particles, the coloring material, and the organic solvent are dissolved or dispersed in water.

[0042] The lower limit of the static surface tension (hereinafter simply referred to as surface tension) of all the components of the ink is, for example, 25.2 mN / m, or, for example, 26.6 mN / m, or, for example, 27.0 mN / m. The upper limit of the surface tension of all the components of the ink is, for example, 29.3 mN / m, or, for example, 28.2 mN / m, or, for example, 28.0 mN / m. The range of the surface tension can be set by appropriately combining the above upper and lower limits, and is, for example, from 25.2 mN / m to 29.3 mN / m, or, for example, from 26.6 mN / m to 28.2 mN / m. The surface tension can be measured, for example, using a surface tensiometer by the Wilhelmy method using a platinum plate in an environment of 25°C.

[0043] The resin particles may contain, for example, at least one of methacrylic acid and acrylic acid as a monomer, and commercially available products may be used. The resin particles may further contain, for example, styrene, vinyl chloride, etc. as a monomer. The resin particles may be contained in, for example, an emulsion. The emulsion is composed of, for example, resin particles and water. The resin particles are not dissolved in water, but are dispersed in water within a specific particle size range. Examples of resin particles include acrylic acid-based resins, maleic acid ester resins, vinyl acetate-based resins, carbonate-based resins, polycarbonate-based resins, styrene-based resins, ethylene-based resins, polyethylene-based resins, propylene-based resins, polypropylene-based resins, urethane-based resins, polyurethane-based resins, polyester-based resins, and copolymer resins thereof. The resin particles may include anionic resin particles, nonionic resin particles, or nonionic resin particles. One type of resin particle may be used alone, or two or more types may be used in combination.

[0044] The glass transition temperature (Tg) of the resin particles is not particularly limited, but is, for example, 0°C or higher and 200°C or lower, or, for example, 20°C or higher and 180°C or lower, or, for example, 30°C or higher and 150°C or lower.

[0045] The emulsion may be, for example, a commercially available product, such as "Superflex (registered trademark) 870" and "Superflex (registered trademark) 150" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., "Mowinyl (registered trademark) DM774" and "Mowinyl (registered trademark) 6969D" manufactured by Japan Coating Resins Co., Ltd., and "Hi-Loss-X (registered trademark) KE-1062" and "Hi-Loss-X (registered trademark) QE-1042" manufactured by Seiko PMC Corporation.

[0046] The average particle diameter of the resin particles is not particularly limited, but is, for example, 30 nm to 200 nm, or, for example, 50 nm to 160 nm. The average particle diameter can be measured as an arithmetic mean diameter using, for example, a dynamic light scattering particle size distribution analyzer "LB-550" manufactured by Horiba, Ltd.

[0047] The solid content of the resin particles relative to the total amount of ink is, for example, in the range of 0.1% by weight to 30% by weight, or, for example, in the range of 0.5% by weight to 20% by weight, or, for example, in the range of 1.0% by weight to 15.0% by weight.

[0048] The colorant is a pigment that can be dispersed in water, for example, with a pigment dispersing resin (resin dispersant) or by self-dispersion. Examples of pigments include carbon black, inorganic pigments, and organic pigments. Examples of carbon black include furnace black, lamp black, acetylene black, and channel black. Examples of inorganic pigments include titanium oxide, iron oxide-based inorganic pigments, and carbon black-based inorganic pigments. Examples of organic pigments include azo pigments, polycyclic pigments, dye lake pigments, nitro pigments, nitroso pigments, and aniline black daylight fluorescent pigments. Examples of azo pigments include azo lake, insoluble azo pigments, condensed azo pigments, and chelate azo pigments. Examples of polycyclic pigments include phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments. Dye lake pigments include, for example, basic dye lake pigments and acid dye lake pigments. Other pigments include, for example, CI Pigment Black 1, 6, 7, CI Pigment Yellow 1, 2, 3, 12, 13, 14, 15, 16, 17, 55, 73, 74, 75, 78, 83, 93, 94, 95, 97, 98, 114, 128, 129, 138, 150, 151, 154, 155, 180, 185, 194, CI Pigment Orange 31, 43, and CI Pigment Red 2, 3, 5, 6, 7, 12, 15, 16, 48, 48:1, 48:3, and 53:1. , 57, 57:1, 112, 122, 123, 139, 144, 146, 149, 150, 166, 168, 175, 176, 177, 178, 184, 185, 190, 202, 209, 221, 222, 224, 238, 254, CI Pigment Violet 19, 196, CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 16, 22, 60, CI Pigment Green 7, 36, and solid solutions of these pigments. The colorant may be an anionic colorant, a nonionic colorant, or may contain a nonionic colorant. One type of colorant may be used alone, or two or more types may be used in combination.

[0049] The content of the solid pigment content of the coloring material relative to the total amount of ink is, for example, 0.1% by weight to 20.0% by weight, and for example, 1.0% by weight to 15.0% by weight.

[0050] The ink contains at least one of anionic resin particles and anionic coloring material as an anionic solid component. From the viewpoint of the aggregating properties of the anionic solid component contained in the ink, for example, when the polarity of the resin particles contained in the ink is anionic, the polarity of the coloring material contained in the ink is preferably anionic or nonionic.

[0051] The organic solvent includes an organic solvent having a predetermined surface tension. The lower limit of the predetermined surface tension is, for example, 28.0 mN / m, or 28.5 mN / m, or 29.0 mN / m. The upper limit of the surface tension is, for example, 34.0 mN / m, or 33.5 mN / m, or 33.0 mN / m. The range of the surface tension can be set by appropriately combining the above upper and lower limits, and is, for example, from 28.0 mN / m to 34.0 mN / m, or from 28.5 mN / m to 33.5 mN / m, or from 29.0 mN / m to 33.0 mN / m. Examples of organic solvents having the predetermined surface tension include tripropylene glycol (surface tension: 34.00 mN / m), triethylene glycol monobutyl ether (surface tension: 31.85 mN / m), 1,2-hexanediol (surface tension: 28.14 mN / m), etc. One type of organic solvent having the predetermined surface tension may be used alone, or two or more types may be used in combination.

[0052] The lower limit of the content of the organic solvent having a predetermined surface tension relative to the total amount of ink is, for example, 7.5 wt %, 8.5 wt %, or 10.0 wt %. The upper limit of the content of the organic solvent having a predetermined surface tension relative to the total amount of ink is, for example, 24.0 wt %, 21.0 wt %, 18.0 wt %, or 15.0 wt %. The content range can be set by appropriately combining the above upper and lower limits, and is, for example, 7.5 wt % to 24.0 wt % or less, 8.5 wt % to 21.0 wt % or less, 10.0 wt % to 18.0 wt %, or 8.0 wt % to 15.0 wt %. Note that, from the viewpoint of suppressing the occurrence of Marangoni convection during drying of the ink, the content of the organic solvent is preferably 10.0 wt % to 18.0 wt %.

[0053] As the organic solvent, at least one organic solvent having the above-mentioned predetermined static surface tension is used. The type of organic solvent is not particularly limited as long as the content of the organic solvent relative to the total amount of ink is within the predetermined range. As an example, the organic solvent may further contain an organic solvent other than the organic solvent having the above-mentioned predetermined surface tension (e.g., propylene glycol (surface tension: 37.08 mN / m), methyl alcohol (surface tension: 22.60 mN / m), ethyl alcohol (surface tension: 22.55 mN / m), glycerin (static surface tension: 63.40 mN / m), ethyl ether (surface tension: 16.96 mN / m), etc.).

[0054] The surfactant is not particularly limited, and any surfactant can be used. For example, commercially available surfactants may be used. Examples of commercially available surfactants include "Olfine (registered trademark) E1010," "Olfine (registered trademark) E1006," "Olfine (registered trademark) E1004," "Silface SAG503A," and "Silface SAG002" manufactured by Nissin Chemical Industry Co., Ltd. The content of the surfactant relative to the total amount of ink is not particularly limited, but is, for example, 0.01% by weight to 5.0% by weight, for example, 0.05% by weight to 4.0% by weight, or for example, 0.1% by weight to 3.0% by weight.

[0055] The ink may further contain known additives as needed. Examples of additives include pH adjusters, viscosity adjusters, surface tension adjusters, preservatives, and antifungal agents. Examples of viscosity adjusters include polyvinyl alcohol, cellulose, and water-soluble resins.

[0056] The water is preferably ion-exchanged water or pure water. The content of water relative to the total amount of ink is, for example, the remainder of the components other than water.

[0057] The ink can be prepared, for example, by uniformly mixing resin particles, a colorant, an organic solvent, a surfactant, water, and, if necessary, other additives, using a known method, and then removing any insoluble matter using a filter or the like.

[0058] (Image forming method) Next, an image forming method using the image forming apparatus 10 will be described. The image forming method includes a first adhering process, a first drying process, a forming process, and a second drying process. The adhering process, first drying process, forming process, and second drying process are performed in this order. The control unit 22 performs each process in response to, for example, an external command to form an image input to the image forming apparatus 10. When the command is input, the control unit 22 controls each unit, such as the first conveying roller pair 16 and the second conveying roller pair 18, to convey the medium 2 on the conveying path 100.

[0059] (Attachment process) In the adhesion step, the control unit 22 adheres the pretreatment liquid to the surface of the medium 2 being transported along the transport path 100. The control unit 22 controls piezoelectric elements (not shown) or the like corresponding to the plurality of nozzles 28 to selectively eject the pretreatment liquid from each nozzle 28 toward the medium 2 passing below the pretreatment liquid line head 26. This causes the pretreatment liquid to adhere to the surface of the medium 2.

[0060] (First drying step) In the first drying step, the pretreatment liquid is dried from the medium 2. The control unit 22 controls the drying device 30 to dry the pretreatment liquid adhering to the surface of the medium 2 passing under the drying device 30.

[0061] In this image forming method, the drying rate of the pretreatment liquid after the first drying step is 100%. If the drying rate is 100%, it is possible to prevent the ink from mixing with the pretreatment liquid when the ink is applied to the medium 2 in the forming step performed after the first drying step, and it is possible to effectively prevent the ink from bleeding. The drying rate of the pretreatment liquid can be calculated based on the change in weight of the pretreatment liquid before and after drying. The drying rate of the pretreatment liquid is calculated, for example, as the weight ratio of the pretreatment liquid reduced by drying to the total amount (100% weight) of evaporated components in the pretreatment liquid.

[0062] (Formation process) In the formation process, the control unit 22 causes ink to adhere to the surface of the medium 2 being transported along the transport path 100. The control unit 22 controls piezo elements (not shown) and the like corresponding to the multiple nozzles 36a to 36d, thereby selectively ejecting ink from each of the nozzles 36a to 36d toward the medium 2 passing below the four ink line heads 34a to 34d. In this way, an image is formed on the surface of the medium 2.

[0063] (Second drying process) In the second drying step, the ink is dried from the medium 2. The control unit 22 controls the drying device 38 to dry the ink adhering to the surface of the medium 2 passing below the drying device 38. After the second drying step, a predetermined amount of the water-containing component contained in the ink has evaporated. This predetermined amount can be changed as appropriate, and is, for example, 80% by weight of the water-containing component contained in the ink, or 90% by weight of the water-containing component contained in the ink, or 95% by weight of the water-containing component contained in the ink, or 100% by weight of the water-containing component contained in the ink.

[0064] The upper limit of the difference between the surface tension of all ink components and the surface tension of the ink components after the second drying step is, for example, 3.5 mN / m, such as 3.0 mN / m, 2.5 mN / m, 2.0 mN / m, 1.5 mN / m, or 1.0 mN / m. The surface tension of the ink components after the second drying step can be measured, for example, by measuring the surface tension of the ink present on the medium 2 after passing through the drying device 38. Alternatively, as in this embodiment, the surface tension of the ink adjusted by mixing the remaining components of the ink, excluding the water-containing component, may be measured as the surface tension of the ink components after the second drying step. This is because the components that evaporate as the ink dries are considered to be the water-containing components contained in the ink, and the remaining components, excluding the water-containing components, can be considered to be the components of the ink after the second drying step. In this case, the water-containing component contained in the ink corresponds to a case where 100% by weight of the water-containing component has evaporated, and the above-mentioned predetermined amount corresponds to 100% by weight of the water-containing component contained in the ink. The water-containing component includes water, components contained in water, and components containing water. A component contained in water refers to a component that contains a relatively large amount of water and in which an active ingredient is dispersed in water. A component containing water refers to a component that contains a relatively small amount of water and in which water is present among the active ingredients. If the difference between the surface tension of all components of the ink and the surface tension of the components in the ink after the second drying step is 3.5 mN / m or less, local changes in the surface tension of the ink can be suppressed during the drying process of the ink.

[0065] As shown in FIG. 3, when ink with a relatively low surface tension (for example, 25.2 mN / m or more and 29.3 mN / m or less) is applied to the medium 2, there is a risk that the ink will unintentionally spread on the medium 2. This problem becomes particularly pronounced when the medium 2 is a non-absorbent medium or a low-absorbent medium. In the image forming method described above, a pretreatment liquid containing a flocculant with a cation concentration of 6.0 Eq / L or more is applied to the medium 2 in advance. As a result, as shown in FIG. 4, when the ink is applied to the medium 2, the cationic flocculant contained in the pretreatment liquid can flocculate the anionic solid components contained in the ink, thereby preventing the ink from bleeding.

[0066] However, when forming a so-called solid image using a relatively large amount of ink, even using the above-mentioned pretreatment liquid may result in insufficient aggregation of solid components. In this case, the ink used to form the solid image on the medium 2 gradually dries on the medium 2. As the ink dries, a surface tension gradient occurs due to uneven distribution of the ink components, which can cause Marangoni convection. Marangoni convection may unintentionally shrink the ink or cause the coffee ring phenomenon (see Figure 5). In other words, it may reduce the uniformity of the solid image. In this regard, the image recording method described above adjusts the difference in the surface tension of the ink before and after drying to 3.5 mN / m or less, thereby preventing significant changes in the surface tension within the ink during drying. This reduces the reduction in the uniformity of the solid image, as shown in Figure 6.

[0067] In this embodiment, the formation process is performed using ink line heads 34a to 34d. This line head method can form an image on the medium 2 at higher speeds than the serial head method, and therefore ejects a larger amount of ink per unit time. As a result, a larger amount of ink adheres to the medium 2 per unit time. Therefore, in the line head method, as in the case of forming a solid image described above, it is necessary to control the surface tension within the ink during the ink drying process. In this regard, in the image recording method described above, for example, the difference in the surface tension of the ink before and after drying is adjusted to be 3.5 mN / m or less, which is thought to prevent a large change in the surface tension within the ink while the ink is drying, and thus prevent a decrease in solid uniformity.

[0068] (Correspondence) The image recording method is an example of an "ink composition applying method." The ink is an example of an "ink composition." The applying step is an example of a "first applying step." The forming step is an example of a "second applying step."

[0069] Examples and Comparative Examples Next, the pretreatment liquid and ink will be specifically described with reference to examples and comparative examples, although the present invention is not limited to these examples in any way.

[0070] (Preparation of pretreatment liquid and ink) Pretreatment liquids 1 to 7 were prepared by mixing the components shown in Table 1. Inks 1 to 13 were prepared by mixing the components shown in Table 2. The numerical value in each column for each component in each table indicates the content of that component relative to the total amount of the pretreatment liquid or ink, and is expressed in weight percent. The cation concentration of the flocculant in Table 1 was measured by colloid titration using potassium polyvinyl sulfate reagent. The detailed procedure is as follows: First, a cationic polymer was placed in a conical beaker, and a 10 ppm aqueous solution of the cationic polymer was prepared using pure water. Four to five drops of toluidine blue indicator (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added to the aqueous solution, which was then titrated with N / 400 potassium polyvinyl sulfate reagent (N / 400PVSK) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). 100 μL of N / 400PVSK was added dropwise during the titration. The endpoint of the titration was the point at which the color of the test solution changed from blue to purple and remained that way for at least 10 seconds. The cation concentration (Eq / L) was calculated using the following formula: Cation concentration = 1 / 400 × (N / 400PVSK titration amount) / total amount of cationic polymer in the test solution

[0071] The resin particle content in Table 2 is shown as a solid content. The colorant content in Table 2 is shown as a pigment solid content. Regarding (A) the static surface tension of all the components in the ink, the prepared inks 1 to 13 were measured using a surface tensiometer at 25°C by the Wilhelmy method using a platinum plate. Regarding (B) the static surface tension of the components in the dried ink, the water-free ink prepared by mixing the remaining components, excluding the water-containing component, from the components contained in each ink 1 to 13 was measured using a surface tensiometer at 25°C by the Wilhelmy method using a platinum plate. That is, in this example, the water-free ink of each ink 1 to 13 was considered to be the ink obtained by drying each ink 1 to 13, and the static surface tension of the components in the dried ink was measured. For each ink 1 to 13, water, Movinyl 6969D, and magenta pigment were considered to be the water-containing components.

[0072] [Table 1]

[0073] [Table 2]

[0074] Using each prepared pretreatment liquid and each ink, ruggedness evaluation and mottle evaluation were performed by the following methods. The drying rate of the pretreatment liquid in Tables 3 and 4 was calculated as the weight ratio of the pretreatment liquid reduced by drying to the total amount of water in the pretreatment liquid (100% by weight), with water in the pretreatment liquid considered as the evaporated component.

[0075] (Ruggedness rating) Each sample was prepared according to the conditions (pretreatment liquid, ink, medium, drying rate of pretreatment liquid) for each example shown in Tables 3 and 4. Specifically, the pretreatment liquid was applied to Medium 2, the pretreatment liquid was dried, and then an inkjet recording device "MFC-J7100CDW" manufactured by Brother Industries, Ltd. was used to apply ink to Medium 2 and form a one-dot line (resolution 600 dpi × 600 dpi) to prepare each sample. The ruggedness of these samples was measured using a handheld image evaluation system "PIAS (registered trademark)-II" manufactured by Quality Engineering Associates (QEA) and evaluated according to the following criteria. The evaluation results are shown in Tables 3 and 4. Ruggedness is the line ruggedness defined by ISO-13660. A rugged line refers to a state in which the line edge is wavy, rather than the ideal line edge that should be smooth and straight. AA: Ruggedness less than 0.004 mm A: Ruggedness is 0.004mm or more and less than 0.005mm B: Ruggedness is 0.005mm or more and less than 0.006mm C: Ruggedness is 0.006 mm or more

[0076] (Mottle Rating) Each sample was prepared under the conditions (pretreatment liquid, ink, medium, drying rate of pretreatment liquid) for each example shown in Tables 3 and 4. Specifically, the pretreatment liquid was applied to medium 2, dried, and then ink was applied to medium 2 using an inkjet recording device "MFC-J7100CDW" manufactured by Brother Industries, Ltd. to form a solid image (resolution 600 dpi × 600 dpi, 300% duty) to prepare each sample. The mottle of these samples was measured using the aforementioned "PIAS (registered trademark)-II" and evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 3 and 4. In Tables 3 and 4, PET refers to a 38 μm polyethylene terephthalate film (manufactured by Toppan Printing Co., Ltd.), PP refers to a 40 μm polypropylene film (manufactured by Futamura Chemical Co., Ltd.), and coated paper refers to a 145 μm coated paper (manufactured by Oji Tack Co., Ltd.). A: Mottle is 3.0 or less B: Mottle is 3.1 or more and 10.0 or less C: Mottle is 10.1 or more

[0077] [Table 3]

[0078] [Table 4]

[0079] (Ruggedness results) It can be said that the smaller the ruggedness of the measured sample, the less the wavyness of the line edge of the one-dot line formed on the medium 2, i.e., the less the ink bleeds on the medium 2. On the other hand, the greater the ruggedness of the measured sample, the greater the wavyness of the line edge of the one-dot line formed on the medium 2, i.e., the greater the ink bleeds on the medium 2. Hereinafter, a relatively small degree of ink bleed, as in Figure 4, will be referred to as having excellent ink bleed properties, and a relatively large degree of ink bleed, as in Figure 3, will be referred to as having poor ink bleed properties.

[0080] As shown in Tables 3 and 4, it was confirmed that Examples 1 to 15 had excellent ink bleeding properties. On the other hand, it was confirmed that Comparative Examples 7 and 8 had poor ink bleeding properties. In Comparative Examples 7 and 8, the type of cationic flocculant contained in the pretreatment liquid was changed compared to Examples 1 and 7. Comparing these Examples and Comparative Examples, it was confirmed that Examples 1 and 7, in which a cationic polymer was contained as a flocculant in the pretreatment liquid, had excellent ink bleeding properties.

[0081] In Examples 1 and 7 and Comparative Example 9, the cation concentration of the cationic polymer contained in the pretreatment liquid was changed. Comparing these Examples and Comparative Examples, it was confirmed that Examples 1 and 7, which used "PAS-M-1A" and "PAA-U5000," each with a cation concentration of 6.0 Eq / L or higher, exhibited excellent ink bleeding properties. Furthermore, it was confirmed that Example 1, which used "PAS-M-1A," with a cation concentration of 7.5 Eq / L, exhibited better ink bleeding properties than Example 7, which used "PAA-U5000," with a cation concentration of 6.0 Eq / L. This is thought to be because the cationic polymer had a larger number of cationic groups, which allowed it to effectively aggregate anionic solid components.

[0082] In Examples 1, 14, and 15, the content of "PAA-U5000" relative to the total amount of pretreatment liquid was varied. Comparing these Examples, it was confirmed that the greater the content of "PAA-U5000" relative to the total amount of pretreatment liquid, the better the ink bleeding properties tended to be. This is thought to be because the presence of a larger amount of cationic polymer allowed the anionic solid components to be effectively aggregated.

[0083] The surface tension of all ink components was changed in Examples 1 to 6 and 13 and Comparative Examples 1, 2 and 6. Comparing these Examples and Comparative Examples, it was confirmed that the ink bleeding properties were excellent in Examples 1 to 6 and 13, in which the surface tension of all ink components was 25.2 mN / m or more and 29.3 mN / m or less.

[0084] The type of organic solvent contained in the ink was changed in Examples 1, 5, and 6 and Comparative Examples 2 and 4. Comparing these Examples and Comparative Examples, it was confirmed that Examples 1, 5, and 6, which used ink containing an organic solvent with a surface tension of 28.0 mN / m or more and 34.0 mN / m or less, had excellent ink bleeding properties.

[0085] The content of triethylene glycol monobutyl ether relative to the total amount of ink was changed in Examples 1, 3, 4, and 13 and Comparative Examples 1, 5, and 6. Comparing these Examples and Comparative Examples, it was confirmed that Examples 1, 3, 4, and 13, in which the content was 7.5% by weight or more and 24.0% by weight or less, had excellent ink bleeding properties.

[0086] The drying rate of the pretreatment liquid was changed in Examples 1, 10, and 11 and Comparative Example 10. Comparing these Examples and Comparative Examples, it was confirmed that Examples 1, 10, and 11, in which the drying rate of the pretreatment liquid was 50% or more, had excellent ink bleeding properties. This is thought to be because drying the pretreatment liquid until the drying rate reaches 50% or more makes it possible to prevent the ink from mixing with the pretreatment liquid when the ink is subsequently applied to the medium 2, and as a result, makes it possible to prevent the ink from bleeding.

[0087] In addition to the above, it was confirmed that the ink bleeding properties were better in the order of Example 10, Example 11, and Example 1. The drying rate of the pretreatment liquid increased in the order of Example 10, Example 11, and Example 1. That is, the higher the drying rate of the pretreatment liquid, the better the ink bleeding properties. This is thought to be because the higher the drying rate of the pretreatment liquid before the ink is applied to the medium 2, the more effectively it is possible to suppress mixing of the ink with the pretreatment liquid when the ink is applied to the medium 2. Furthermore, when Examples 12 and 13 were compared, Example 13, which had a higher drying rate of the pretreatment liquid, showed better ink bleeding properties. This is the same result as above.

[0088] (Mottle results) The smaller the mottle of the evaluation sample, the less color unevenness occurs in the solid image formed on the medium 2, i.e., the higher the uniformity (solid uniformity) of the solid image, as shown in Figure 6. On the other hand, the larger the mottle of the evaluation sample, the more color unevenness occurs in the solid image formed on the medium 2, i.e., the lower the solid uniformity, as shown in Figure 6.

[0089] As shown in Tables 3 and 4, it was confirmed that Examples 1 to 15 had excellent solid uniformity. On the other hand, it was confirmed that Comparative Example 3 had poor solid uniformity. In Comparative Example 3, the difference in the surface tension of the ink before and after drying was changed compared to Examples 1 to 6 and 13. Comparing these Examples and Comparative Examples, it was confirmed that Examples 1 to 6 and 13, in which the difference in the surface tension of the ink before and after drying was 3.5 mN / m or less, had excellent solid uniformity. This is thought to be because by suppressing large changes in surface tension within the ink while the ink is drying, it is possible to suppress Marangoni convection within the ink caused by a surface tension gradient, and as a result, it is possible to suppress a decrease in solid uniformity.

[0090] The surface tension of all ink components was changed in Examples 1 to 6 and 13 and Comparative Example 2. Comparing these Examples and Comparative Examples, it was confirmed that Examples 1 to 6 and 13, in which the surface tension of all ink components was 25.2 mN / m or more and 29.3 mN / m or less, had excellent solid uniformity.

[0091] In Examples 1, 5, and 6 and Comparative Example 4, the surface tension of the organic solvent contained in the ink was varied. Comparing these Examples and Comparative Examples, it was confirmed that Examples 1, 5, and 6, which used inks containing organic solvents with surface tensions of 28.0 mN / m or more and 34.0 mN / m or less, exhibited excellent solid image uniformity. It is believed that water-containing components evaporate as the ink dries. This is because water evaporates more easily than other components (e.g., organic solvents) contained in the ink. The drying rate of the ink edges used to form a solid image on the medium 2 is faster than the drying rate of the ink center. Therefore, it is believed that the organic solvent accounts for a larger proportion of the ink at the ink edges, while the water accounts for a larger proportion at the ink center. Therefore, when an organic solvent with a surface tension within the above range is contained in the ink, it is possible to increase the wettability of the ink edges, where the organic solvent accounts for a larger proportion, thereby suppressing Marangoni convection.

[0092] In Examples 1, 3, 4, and 13, and Comparative Example 5, the content of triethylene glycol monobutyl ether (surface tension: 31.85 mN / m) relative to the total amount of ink was varied. Comparing these Examples and Comparative Examples, it was confirmed that Examples 1, 3, 4, and 13, in which the content was 7.5 wt % or more and 24.0 wt % or less, exhibited excellent solid uniformity. This is believed to be because a consistent amount of organic solvent can be maintained throughout the ink during the ink drying process, preventing uneven distribution of the organic solvent in the ink. This prevents uneven distribution of surfactants, which tend to be present near the organic solvent. This reduces the surface tension gradient within the ink, which is believed to suppress Marangoni convection caused by this gradient. Furthermore, if the organic solvent having a surface tension in the range of 28.0 mN / m or more and 34.0 mN / m or less is contained in an amount of 7.5 wt % or more and 24.0 wt % or less relative to the total amount of ink, the presence of a constant amount of organic solvent throughout the ink during the drying process can increase the wettability at the edges of the ink, and it is thought that Marangoni convection can be effectively suppressed.

[0093] In addition to the above, it was confirmed that Examples 1 and 3, in which the content of triethylene glycol monobutyl ether relative to the total amount of ink was 10% by weight or more and 18% by weight or less, had better solid uniformity than Examples 4 and 13. This is thought to be because the inclusion of a larger amount of organic solvent in the ink makes it possible to suppress uneven distribution of the organic solvent and surfactants that have a high affinity with the organic solvent during the ink drying process.

[0094] In Examples 1, 8, and 9, medium 2 was changed. Comparing these Examples, it was confirmed that when a non-absorbent medium (here, polyethylene terephthalate, polypropylene) or a low-absorbent medium (here, coated paper) was used as medium 2, both ink bleeding resistance and solid uniformity were excellent. Therefore, it can be said that any non-absorbent medium or low-absorbent medium can be used as medium 2.

[0095] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. Modifications of the above embodiments are listed below.

[0096] (Variation 1) In the above-described embodiment, the ink does not need to contain a colorant. For example, a clear ink that does not contain a colorant may be used instead of the ink. The clear ink is used to impart gloss, protect the printed image, and improve the print image quality. The clear ink is a water-based ink that contains resin particles as a solid content. In this modification, the clear ink is an example of an "ink composition."

[0097] (Variation 2) The drying rate of the pretreatment liquid after the first drying step may be lower than 100%. The drying rate may be, for example, 90% or higher, 80% or higher, 70% or higher, 60% or higher, or 50% or higher. The drying rate can be appropriately set by controlling the drying temperature, drying time, drying pressure, etc.

[0098] (Variation 3) In the above-described embodiment, the image forming apparatus 10 may be provided with an ink serial head instead of the ink line heads 34a to 34d. That is, the forming process may be performed by a serial head instead of the ink line heads 34a to 34d. In other words, the image forming apparatus 10 may be a serial printer instead of a line printer.

[0099] (Variation 4) In the above-described embodiment, the image forming apparatus 10 may include a stamp, a brush, a roller, or the like, instead of the pretreatment liquid line head 26. In other words, the application step may be performed using, for example, a stamp, a brush, a roller, or the like, instead of the pretreatment liquid line head 26. Furthermore, in the application step, the pretreatment liquid may be selectively applied only to a necessary portion of the medium 2, or the pretreatment liquid may be applied to the entire surface of the medium 2.

[0100] (Variation 5) In the above-described embodiment, the image forming apparatus 10 may not be equipped with the drying device 38. In this case, as an example, after the ink is applied to the medium 2 in the image forming apparatus 10, the ink may be dried from the medium 2 in a drying device configured separately from the image forming apparatus 10. Alternatively, after the ink is applied to the medium 2 in the image forming apparatus 10, the medium 2 may be left to stand for a predetermined period of time to evaporate a predetermined amount of water-containing components contained in the ink. In other words, after the ink is applied to the medium 2 in the image forming apparatus 10, the medium 2 may be allowed to dry naturally without using the drying device 38.

[0101] Furthermore, the technical elements described in this specification or drawings may exhibit technical utility either alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings may achieve multiple objectives simultaneously, and achieving one of those objectives is itself technically useful.

[0102] In the scope of the claims at the time of filing, even if each claim depends on only some of the claims, it is not limited to the fact that each claim can depend on only those some of the claims. To the extent that there is no technical contradiction, each claim can also depend on other claims that were not dependent at the time of filing. In other words, the technology of each claim can be combined in various ways as follows: (Item 1) 1. A method for applying an ink composition, comprising: a first application step of applying a pretreatment liquid to a medium; a first drying step of drying the pretreatment liquid from the medium after the first applying step; a second applying step of applying the ink composition to the medium after the first drying step; a second drying step of drying the ink composition from the medium after the second applying step; Equipped with the medium is a non-absorbent medium or a low-absorbent medium; the pretreatment liquid contains a cationic polymer flocculant, The cationic polymer has a cation concentration of 6.0 Eq / L or more; the drying rate of the pretreatment liquid after the drying step is 50% or more; The ink composition includes an anionic solid component, one or more organic solvents, a surfactant, and water; the static surface tension of all components of the ink composition is 25.2 mN / m or more and 29.3 mN / m or less; a difference between the static surface tension of all components of the ink composition and the static surface tension of components in the ink composition after the second drying step is 3.5 mN / m or less; the one or more organic solvents include at least one organic solvent having a static surface tension of 28.0 mN / m or more and 34.0 mN / m or less; the content of the at least one organic solvent relative to the total amount of the ink composition is 7.5% by weight or more and 24.0% by weight or less; Method for depositing ink composition. (Item 2) Item 2. The ink composition applying method according to item 1, wherein the drying rate of the pretreatment liquid after the first drying step is 70% or more. (Item 3) 3. The ink composition applying method according to item 2, wherein the drying rate of the pretreatment liquid after the first drying step is 100%. (Item 4) 4. The method for applying an ink composition according to any one of items 1 to 3, wherein the cationic polymer is a polyallylamine. (Item 5) The polyallylamine is a methyldiallylamine acetate polymer, 5. The ink composition applying method according to item 4, wherein the cation concentration of the polyallylamine is 7.5 Eq / L or more. (Item 6) 6. The ink composition applying method according to claim 1, wherein the content of the at least one organic solvent relative to the total amount of the ink composition is 10% by weight or more and 18% by weight or less. (Item 7) 7. The ink composition applying method according to claim 1, wherein the second applying step is performed by a line head that ejects the ink composition. (Item 8) 1. A fluid set for depositing an ink composition on a medium, the medium being a non-absorbent medium or a low-absorbent medium, comprising: a pretreatment liquid to be applied to the medium; an ink composition to be applied to the medium and then dried after the pretreatment liquid has been applied to the medium; Equipped with the pretreatment liquid contains a cationic polymer flocculant, The cationic polymer has a cation concentration of 6.0 Eq / L or more; The ink composition includes an anionic solid component, one or more organic solvents, a surfactant, and water; the static surface tension of all components of the ink composition is 25.2 mN / m or more and 29.3 mN / m or less; the difference between the static surface tension of all components of the ink composition and the static surface tension of the components in the dried ink composition is 3.5 mN / m or less; the one or more organic solvents include at least one organic solvent having a surface tension of 28.0 mN / m or more and 34.0 mN / m or less; the content of the at least one organic solvent relative to the total amount of the ink composition is 7.5% by weight or more and 24.0% by weight or less; Liquid set. [Explanation of symbols]

[0103] 2: medium, 4: roll, 10: image forming device, 12: housing, 14: holder, 16, 18: pair of conveying rollers, 20: platen, 22: control unit, 24: frame, 26: pretreatment liquid line head, 28: nozzle, 30: drying device, 32a to 32d: frame, 34a to 34d: ink line head, 36a to 36d: nozzle, 38: drying device, 100: conveying path

Claims

1. 1. A method for depositing an ink composition, comprising: a first application step of applying a pretreatment liquid to a medium; a first drying step of drying the pretreatment liquid from the medium after the first applying step; a second applying step of applying the ink composition to the medium after the first drying step; a second drying step of drying the ink composition from the medium after the second applying step; Equipped with the medium is a non-absorbent medium or a low-absorbent medium; the pretreatment liquid contains a cationic polymer flocculant, the cation concentration of the cationic polymer is 6.0 Eq / L or more; the drying rate of the pretreatment liquid after the drying step is 50% or more; the ink composition includes an anionic solid component, one or more organic solvents, a surfactant, and water; the static surface tension of all components of the ink composition is 25.2 mN / m or more and 29.3 mN / m or less; a difference between the static surface tension of all components of the ink composition and the static surface tension of components in the ink composition after the second drying step is 3.5 mN / m or less; the one or more organic solvents include at least one organic solvent having a static surface tension of 28.0 mN / m or more and 34.0 mN / m or less, the content of the at least one organic solvent relative to the total amount of the ink composition is 7.5% by weight or more and 24.0% by weight or less; Method for depositing ink composition.

2. The ink composition applying method according to claim 1 , wherein the drying rate of the pretreatment liquid after the first drying step is 70% or more.

3. The ink composition applying method according to claim 2 , wherein the drying rate of the pretreatment liquid after the first drying step is 100%.

4. 2. The method of applying an ink composition according to claim 1, wherein the cationic polymer is a polyallylamine.

5. The polyallylamine is a methyldiallylamine acetate polymer, 5. The method for applying an ink composition according to claim 4, wherein the cation concentration of the polyallylamine is 7.5 Eq / L or more.

6. 2. The method for applying an ink composition according to claim 1, wherein the content of the at least one organic solvent relative to the total amount of the ink composition is 10% by weight or more and 18% by weight or less.

7. The ink composition applying method according to claim 1 , wherein the second applying step is performed by a line head that ejects the ink composition.

8. 1. A fluid set for depositing an ink composition on a medium, the medium being a non-absorbent medium or a low-absorbent medium, comprising: a pretreatment liquid to be applied to the medium; an ink composition to be applied to the medium and then dried after the pretreatment liquid has been applied to the medium; Equipped with the pretreatment liquid contains a cationic polymer flocculant, the cation concentration of the cationic polymer is 6.0 Eq / L or more; the ink composition includes an anionic solid component, one or more organic solvents, a surfactant, and water; the static surface tension of all components of the ink composition is 25.2 mN / m or more and 29.3 mN / m or less; a difference between the static surface tension of all components of the ink composition and the static surface tension of components in the dried ink composition is 3.5 mN / m or less; the one or more organic solvents include at least one organic solvent having a surface tension of 28.0 mN / m or more and 34.0 mN / m or less, the content of the at least one organic solvent relative to the total amount of the ink composition is 7.5% by weight or more and 24.0% by weight or less; Liquid set.

Images