Inkjet recording device

Abstract

The present invention provides an inkjet recording device that suppresses ink transfer to subsequent printed materials even if ink adheres to the transport roller pair, thereby avoiding a decrease in image quality. [Solution] An inkjet recording apparatus that forms an image on a recording medium by ejecting aqueous ink from a recording head onto the recording medium being transported along a predetermined transport direction, comprising a plurality of transport roller pairs provided after means for supplying thermal energy to the image-formed recording medium, which transport the image-formed recording medium by rotating in a certain direction while holding the image-formed recording medium, and wherein at least one of the transport roller pairs, the roller positioned on the image-forming surface, is provided with an ink coagulation member on at least a portion of its surface that contacts the aqueous ink to coagulate the aqueous ink.

Description

[Technical Field]

[0001] This invention relates to an inkjet recording device. [Background technology]

[0002] In an inkjet recording device, an image (ink image) can be formed by applying ink containing a colorant from a recording head to a recording medium such as paper that is transported along a predetermined transport direction. Such an inkjet recording device is provided with a pair of rollers for transporting the recording medium, and the recording medium can be nipped and transported by this pair of rollers. Furthermore, after the ink is applied from the recording head and an image is formed, the ink can be fixed to the recording medium by applying thermal energy.

[0003] However, if ink fixation is insufficient due to high-speed printing or the use of recording media with low ink absorption, the ink used for printing may transfer from the recording media to the transport rollers even after thermal energy is applied, causing the rollers to become contaminated. If the rollers become contaminated, that contaminant may transfer to subsequent printed materials, potentially causing the printed materials to become dirty.

[0004] Patent Document 1 discloses a technology in which, among a pair of transport rollers, the transport roller positioned on the side of the ink-coated recording medium is made of a material with a smooth surface and high hardness. By using this technology, it is possible to reduce the contamination of the rollers due to ink transfer from the ink-coated recording medium. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2000-238927 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, even though the material composition of the conveyance roller described in Patent Document 1 could reduce ink staining on the roller, the ink adhering to the roller had insufficient aggregation, so it was inevitable that it would be transferred to the subsequent printed matter and stain the printed matter, deteriorating the image quality of the printed matter.

[0007] Therefore, an object of the present invention is to provide an inkjet recording apparatus that can suppress the transfer of ink to a subsequent printed matter even when ink adheres to a pair of conveyance rollers and avoid deterioration of image quality.

Means for Solving the Problems

[0008] The above object is achieved by the following present invention. That is, the inkjet recording apparatus according to the present invention is provided after means for applying thermal energy to a recorded medium on which an image is formed, and has a plurality of pairs of conveyance rollers that rotate in a certain direction while sandwiching the recorded medium on which an image is formed to convey the recorded medium on which an image is formed. Among the pairs of conveyance rollers, at least on the roller arranged on the image formation surface, an ink aggregation member for aggregating the aqueous ink by contacting at least a part of the surface with the aqueous ink is provided.

[0009] Further, in the present invention, when the pairs of conveyance rollers are on the same conductor line in the conveyance direction, the content ratio of the ink aggregation member is higher on the upstream side in the conveyance of the roller arranged on the image formation surface among the pairs of conveyance rollers than on the downstream side.

[0010] Further, in the present invention, when the pairs of conveyance rollers are on the same conductor line in the conveyance direction, in the pair of conveyance rollers on the most upstream side in the conveyance, ink aggregation members are provided on both rollers.

[0011] Further, the ink aggregation member of the present invention is characterized in that it is a solid acid.

[0012] Further, the ink aggregation solid member of the present invention is characterized in that it is a hydrogen-type cation exchange resin.

[0013] Furthermore, the hydrogen-type cation exchange resin of the present invention is characterized by having a fluorine group.

[0014] Furthermore, the aqueous ink of the present invention is characterized by containing wax. [Effects of the Invention]

[0015] According to the present invention, in which at least one of the transport roller pairs, the roller positioned on the image forming surface is provided with an ink coagulation member on at least a portion of its surface that coagulates the aqueous ink upon contact with the aqueous ink, the transfer of ink to subsequent printed materials is suppressed even if ink adheres to the transport roller pair, thereby providing an inkjet recording apparatus that can avoid a decrease in image quality. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic diagram showing an example of the configuration of an inkjet recording device in one embodiment of the present invention. [Figure 2] This is a schematic diagram showing an enlarged cross-section of the main part of a conveyor roller pair in one embodiment of the present invention. [Figure 3] This is a schematic top view showing an example of the arrangement configuration of ink aggregation members provided on a transport roller pair in one embodiment of the present invention. [Figure 4] This is a schematic top view showing another example of the arrangement configuration of ink aggregation members provided on a transport roller pair in one embodiment of the present invention. [Modes for carrying out the invention]

[0017] The present invention will be described in detail below with reference to preferred embodiments.

[0018] The inkjet recording apparatus according to this embodiment is provided after means for supplying thermal energy to the image-formed recording medium, and includes a plurality of transport roller pairs that transport the image-formed recording medium by rotating in a certain direction while holding the image-formed recording medium, and at least one of the transport roller pairs, which is positioned on the image-formed surface, is provided with an ink coagulation member on at least a portion of its surface that contacts the aqueous ink to coagulate the aqueous ink.

[0019] According to the above embodiment, at least one of the transport roller pairs, the roller positioned on the image forming surface, is provided with an ink coagulation member on at least a portion of its surface that contacts the water-based ink to coagulate it. This suppresses the transfer of ink to subsequent printed materials even if ink adheres to the transport roller pair, thereby providing an inkjet recording apparatus that can avoid a decrease in image quality.

[0020] An inkjet recording apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

[0021] Figure 1 is a schematic diagram showing an example of the configuration of an inkjet recording device in one embodiment of the present invention. This inkjet recording device 100 is a sheet-fed inkjet recording device that produces a recording material by forming an ink image on a recording medium 101 using two liquids, a reaction solution and ink. In this embodiment, the X, Y, and Z directions represent the width direction (overall length direction), depth direction, and height direction of the inkjet recording device 100, respectively. The recording medium 101 is transported in the X direction indicated by the arrow.

[0022] The inkjet recording device 100 includes a feeding unit 102 capable of feeding the recording medium 101, an image forming unit 103 capable of forming an image, a drying unit 104 capable of drying the recording medium 101, a fixing unit 105 capable of fixing the image, a cooling unit 106 for cooling the recording medium 101, and an discharge unit 107 capable of discharging the recording medium 101.

[0023] <Recording medium> In this embodiment, the recording medium 101 is not particularly limited, as long as it can accept the reaction solution and ink, and any known recording medium 101 can be used. Examples of recording medium 101 include long materials wound in a roll or sheets cut to predetermined dimensions. Examples of materials include paper, plastic film, wooden board, corrugated cardboard, and metal film.

[0024] <Feeding section> The feeding unit 102 is configured to feed the recording medium 101 to the image forming unit 103. Although not shown, it is sufficient if the recording medium 101 can be fed by a feeding roller or the like, and is not particularly limited.

[0025] <Image Forming Section> The image forming unit 103 includes a first transport mechanism 108 capable of transporting the recording medium 101 to the drying unit 104, and an image forming mechanism 109 capable of forming an image on the recording medium 101.

[0026] <First Conveying Mechanism> The first transport mechanism 108 comprises four first rotating shafts 110 extending in the Y direction and arranged in the X direction, and a first belt 111 wound so as to rotate in conjunction with the rotation of the rotating shafts. In the example shown in Figure 1, the first rotating shafts 110 rotate counterclockwise, causing the first belt 111 to rotate counterclockwise. As a result, the recording medium 101 is transported in the X direction indicated by the arrow. Examples of materials included in the first belt 111 include resin or metal. The first belt 111 has numerous holes. Furthermore, the first transport mechanism 108 includes a first fixing mechanism 112 positioned below the recording medium 101 on the first belt 111 and capable of fixing the recording medium 101 on the first belt 111.

[0027] An example of the first fixing mechanism 112 is a suction pump capable of generating negative pressure. By operating the suction pump, the recording medium 101 on the first belt 111 can be fixed in place by suction through the holes made in the first belt 111.

[0028] <Image Formation Mechanism> The image forming mechanism 109 includes a reaction solution application mechanism 113 capable of applying a reaction solution that reacts with ink to the recording medium 101, and an ink application mechanism 114 capable of applying ink to the recording medium 101.

[0029] <Mechanism for supplying reaction solution> The inkjet recording apparatus 100 of this embodiment has a reaction liquid application mechanism 113 that applies a reaction liquid to the recording medium 101. By contacting the ink, the reaction liquid reduces the fluidity of the ink and / or a part of the ink composition on the recording medium 101, thereby suppressing bleeding and beading during image formation by the ink. Specifically, the reactant contained in the reaction liquid (also referred to as an ink viscosity increasing component) chemically reacts with or physically adsorbs colorants, resins, etc., which are part of the composition that makes up the ink, upon contact. This causes an increase in the overall viscosity of the ink, or a local increase in viscosity due to the aggregation of some of the components that make up the ink, such as colorants, thereby reducing the fluidity of the ink and / or a part of the ink composition. In short, it can cause the ink to aggregate. The reaction liquid application mechanism 113 in Figure 1 is shown in the case of an inkjet head device.

[0030] The reaction liquid applying mechanism 113 may be any device that can apply the reaction liquid onto the recording medium 101, and various conventionally known devices can be appropriately used. Specifically, examples include a gravure offset roller, an inkjet head, a die coating device (die coater), a blade coating device (blade coater), and the like. The application of the reaction liquid by the reaction liquid applying mechanism 113 may be performed before or after the application of the ink, as long as it can be mixed (react) with the ink on the recording medium 101. Preferably, the reaction liquid is applied before the application of the ink. By applying the reaction liquid before the application of the ink, bleeding where adjacent inks applied by the inkjet method mix together and beading where the ink that landed first is attracted to the ink that landed later can be suppressed during image recording by the inkjet method.

[0031] <Reaction liquid> Hereinafter, each component constituting the reaction liquid applied to the present embodiment will be described in detail.

[0032] The reaction liquid aggregates components (such as resins and self-dispersing pigments) having an anionic group in the ink by contacting the ink and contains a reactant. Examples of the reactant include cationic components such as polyvalent metal ions and cationic resins, and organic acids.

[0033] Examples of polyvalent metal ions include divalent metal ions such as Ca 2+ 、Cu 2+ 、Ni 2+ 、Mg 2+ 、Sr 2+ 、Ba 2+ and Zn 2+ and trivalent metal ions such as Fe 3+ 、Cr 3+ 、Y 3+ and Al 3+ To contain polyvalent metal ions in the reaction liquid, polyvalent metal salts (which may be hydrates) formed by the combination of polyvalent metal ions and anions can be used. Examples of the anion include Cl - 、Br- , I - , - ClO2 - ClO3 - ClO4 - NO2 - NO3 - SO4 2- CO3 2- , HCO3 - , PO4 3- HPO4 2- , and H2PO4 - Inorganic anions such as HCOO - , (COO - )2, COOH(COO - ), CH3COO - , C2H4(COO - )2, C6H5COO - , C6H4(COO - )2 and CH3SO3 - Examples of organic anions include the following. When polyvalent metal ions are used as reactants, the content (mass%) of the polyvalent metal salt in the reaction solution is preferably 1.00% by mass or more and 20.00% by mass or less, based on the total mass of the reaction solution.

[0034] The reaction solution containing an organic acid has buffering capacity in the acidic range (pH less than 7.0, preferably pH 2.0 to pH 5.0), thereby converting the anionic groups of components present in the ink into acidic forms and causing aggregation. Examples of organic acids include monocarboxylic acids and their salts such as formic acid, acetic acid, propionic acid, butyric acid, benzoic acid, glycolic acid, lactic acid, salicylic acid, pyrrole carboxylic acid, furanic acid, picolinic acid, nicotinic acid, thiophene carboxylic acid, levulinic acid, and coumaric acid; dicarboxylic acids and their salts or hydrogen salts such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, itaconic acid, sebacic acid, phthalic acid, malic acid, and tartaric acid; tricarboxylic acids and their salts or hydrogen salts such as citric acid and trimellitic acid; and tetracarboxylic acids and their salts or hydrogen salts such as pyromellitic acid. The content (by mass) of organic acid in the reaction solution is preferably 1.00% by mass or more and 50.00% by mass or less.

[0035] Examples of cationic resins include resins having the structure of primary to tertiary amines, and resins having the structure of quaternary ammonium salts. Specifically, examples include resins having the structures of vinylamine, allylamine, vinylimidazole, vinylpyridine, dimethylaminoethyl methacrylate, ethyleneimine, and guanidine. To improve solubility in the reaction solution, cationic resins can be used in combination with acidic compounds, or the cationic resins can be subjected to quaternization treatment. When a cationic resin is used as a reactant, the content (mass%) of the cationic resin in the reaction solution is preferably 1.00% by mass or more and 10.00% by mass or less, based on the total mass of the reaction solution.

[0036] (Components other than the reactant) Other components besides the reactive agent can be the same as those listed earlier for use in inks, such as aqueous media and other additives.

[0037] <Ink application mechanism> The inkjet recording apparatus 100 of this embodiment has an ink application mechanism 114 that applies ink to the recording medium 101. On the recording medium 101, the reaction liquid and the ink are mixed, and an ink image is formed by the reaction liquid and the ink.

[0038] In this embodiment, an inkjet head is used as the ink dispensing device 114 that dispenses ink. Examples of inkjet heads include those that eject ink by causing film boiling in the ink using an electro-thermal converter to form bubbles, those that eject ink using an electro-mechanical converter, and those that eject ink using static electricity. In this embodiment, known inkjet heads can be used. Among these, those using an electro-thermal converter are particularly preferred from the viewpoint of high-speed and high-density printing. The drawing receives an image signal and dispenses the required amount of ink at each position.

[0039] In this embodiment, the inkjet head is a full-line head extending in the Y direction, and the nozzles are arranged to cover the width of the image recording area of ​​the largest usable recording medium. The inkjet head has an ink ejection surface on its lower surface (the recording medium 101 side) where the nozzles open, and the ink ejection surface faces the surface of the recording medium 101 with a small gap (about a few millimeters) between them.

[0040] The amount of ink applied can be expressed by the density value of the image data or the ink thickness, but in this embodiment, the average value obtained by multiplying the mass of each ink dot by the number of dots applied and dividing by the printing area is used as the amount of ink applied (g / m²). 2 ) was defined as follows. Furthermore, the maximum ink application amount in the image area is defined as at least 5 mm within the area used as information of the ejected medium, from the viewpoint of removing liquid components from the ink. 2 This shows the amount of ink applied to the area described above.

[0041] The ink application mechanism 114 may have multiple inkjet heads to apply each color ink onto the recording medium 101. For example, when forming color images using yellow ink, magenta ink, cyan ink, and black ink, the ink application mechanism 114 will have four inkjet heads, each ejecting one of the four types of ink onto the recording medium 101. These inkjet heads are arranged in a line in the X direction.

[0042] <ink> The following describes in detail each component that makes up the ink applied to this embodiment.

[0043] (Colorants) Pigments and dyes can be used as colorants. The colorant content in the ink is preferably 0.5% by mass or more and 15.0% by mass or less, and more preferably 1.0% by mass or more and 10.0% by mass or less, based on the total mass of the ink.

[0044] Specific examples of pigments include inorganic pigments such as carbon black and titanium dioxide; and organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolon, diketopyrrolopyrrole, and dioxazine.

[0045] As for the dispersion method of the pigment, resin-dispersed pigments using a resin as a dispersant, and self-dispersing pigments in which hydrophilic groups are bonded to the surface of the pigment particles can be used. In addition, resin-bonded pigments in which organic groups containing resin are chemically bonded to the surface of the pigment particles, and microcapsule pigments in which the surface of the pigment particles is coated with resin or the like can be used.

[0046] As a resin dispersant for dispersing pigments in an aqueous medium, it is preferable to use one that can disperse pigments in the aqueous medium through the action of anionic groups. Preferably, as the resin dispersant, a resin as described later can be used, and more preferably, a water-soluble resin can be used. The pigment content (mass%) is preferably 0.3 times or more and 10.0 times or less in mass ratio (pigment / resin dispersant) to the resin dispersant content.

[0047] Self-dispersing pigments can be those in which anionic groups such as carboxylic acid groups, sulfonic acid groups, and phosphonic acid groups are bonded directly to the surface of the pigment particles or via other atomic groups (-R-). The anionic group may be either acidic or salt-type, and if it is salt-type, it may be in a partially dissociated state or a fully dissociated state. Examples of cations that become counterions when the anionic group is salt-type include alkali metal cations, ammonium, and organic ammonium. Specific examples of other atomic groups (-R-) include linear or branched alkylene groups with 1 to 12 carbon atoms, arylene groups such as phenylene and naphthylene groups, carbonyl groups, imino groups, amide groups, sulfonyl groups, ester groups, and ether groups. Combinations of these groups may also be used.

[0048] It is preferable to use dyes that have anionic groups. Specific examples of dyes include azo, triphenylmethane, (aza)phthalocyanine, xanthene, and anthrapyridone.

[0049] (resin) The ink may contain resin. The resin content (by mass) in the ink is preferably 0.1% by mass or more and 20.0% by mass or less, and more preferably 0.5% by mass or more and 15.0% by mass or less, based on the total mass of the ink.

[0050] Resins can be added to ink for reasons such as (i) stabilizing the dispersion state of pigments, i.e., as resin dispersants or their auxiliary agents as described above, and (ii) improving various properties of the recorded image. Examples of resin forms include block copolymers, random copolymers, graft copolymers, and combinations thereof. The resin may be dissolved in an aqueous medium as a water-soluble resin, or dispersed in an aqueous medium as resin particles. The resin particles do not need to contain colorants.

[0051] In this invention, a resin is considered water-soluble if, when neutralized with an equivalent amount of alkali to its acid value, it does not form particles whose particle size can be measured by dynamic light scattering. Whether or not a resin is water-soluble can be determined according to the following method. First, a liquid containing the resin (resin solids content: 10% by mass) is prepared, neutralized with an alkali equivalent to its acid value (such as sodium hydroxide or potassium hydroxide). Next, the prepared liquid is diluted 10 times (by volume) with pure water to prepare a sample solution. Then, when the particle size of the resin in the sample solution is measured by dynamic light scattering, if no particles with a particle size are measured, the resin can be determined to be water-soluble. The measurement conditions can be set, for example, as follows: SetZero: 30 seconds, Number of measurements: 3 times, Measurement time: 180 seconds. As a particle size distribution analyzer, a particle size analyzer using dynamic light scattering (for example, product name "UPA-EX150", manufactured by Nikkiso) can be used. Of course, the particle size distribution analyzer and measurement conditions used are not limited to those described above.

[0052] The acid value of the resin is preferably 100 mg KOH / g or more and 250 mg KOH / g or less for water-soluble resins, and preferably 5 mg KOH / g or more and 100 mg KOH / g or less for resin particles. The weight-average molecular weight of the resin is preferably 3,000 or more and 15,000 or less for water-soluble resins, and preferably 1,000 or more and 2,000,000 or less for resin particles. The volume-average particle diameter of the resin particles, measured by dynamic light scattering (measurement conditions are the same as above), is preferably 100 nm or more and 500 nm or less.

[0053] Examples of resins include acrylic resins, urethane resins, and olefin resins. Among these, acrylic resins and urethane resins are preferred.

[0054] As for acrylic resins, those having hydrophilic units and hydrophobic units as constituent units are preferred. Among these, resins having hydrophilic units derived from (meth)acrylic acid and hydrophobic units derived from at least one of a monomer having an aromatic ring and a (meth)acrylic acid ester monomer are preferred. In particular, resins having hydrophilic units derived from (meth)acrylic acid and hydrophobic units derived from at least one of a monomer of styrene and α-methylstyrene are preferred. Because these resins readily interact with pigments, they can be suitably used as resin dispersants for dispersing pigments.

[0055] Hydrophilic units are units that have hydrophilic groups, such as anionic groups. Hydrophilic units can be formed, for example, by polymerizing hydrophilic monomers that have hydrophilic groups. Specific examples of hydrophilic monomers that have hydrophilic groups include acidic monomers having carboxylic acid groups, such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid, and anionic monomers such as anhydrides and salts of these acidic monomers. Cations that constitute salts of acidic monomers include ions such as lithium, sodium, potassium, ammonium, and organic ammonium. Hydrophobic units are units that do not have hydrophilic groups, such as anionic groups. Hydrophobic units can be formed, for example, by polymerizing hydrophobic monomers that do not have hydrophilic groups, such as anionic groups. Specific examples of hydrophobic monomers include monomers having aromatic rings, such as styrene, α-methylstyrene, and benzyl (meth)acrylate; and (meth)acrylic acid ester monomers, such as methyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0056] Urethane resins can be obtained, for example, by reacting polyisocyanate with a polyol. Alternatively, they may be obtained by further reacting with a chain extender. Examples of olefin resins include polyethylene and polypropylene.

[0057] (aqueous medium) The ink may contain an aqueous medium, which is water or a mixed solvent of water and a water-soluble organic solvent. Deionized water or ion-exchanged water is preferred as the water. The water content (mass%) in the aqueous ink is preferably 50.0% to 95.0% by mass, based on the total weight of the ink. Furthermore, the water-soluble organic solvent content (mass%) in the aqueous ink is preferably 3.0% to 50.0% by mass, based on the total weight of the ink. As the water-soluble organic solvent, any solvent suitable for inkjet inks, such as alcohols, (poly)alkylene glycols, glycol ethers, nitrogen-containing compounds, and sulfur-containing compounds, can be used.

[0058] (wax particles) It is preferable that the ink contains wax-formed particles (wax particles).

[0059] As will be described later, in this embodiment, at least the rollers of the first transport roller pair 123 of the cooling unit 106 and the second transport roller pair 124 of the discharge unit 107 that are positioned on the image forming surface are provided with an ink coagulation member 125 on at least a portion of their surface that contacts the water-based ink to coagulate it. As a result, even if ink adheres to the first transport roller pair 123 and the second transport roller pair 124, the transfer of the ink to the subsequent recording medium 101 is suppressed, and a decrease in image quality can be avoided.

[0060] However, as the ink aggregates and accumulates on the surfaces of the first conveyor roller pair 123 and the second conveyor roller pair 124, the sliding performance of the first conveyor roller pair 123 and the second conveyor roller pair 124 may decrease, potentially leading to an increase in torque. Therefore, by including wax in the ink, a portion of the wax is exposed on the surface of the ink when it aggregates, thus suppressing the decrease in sliding performance and the increase in torque of the first conveyor roller pair 123 and the second conveyor roller pair 124.

[0061] Furthermore, it is desirable to include wax in order to improve the scratch resistance of printed materials.

[0062] The wax may be a composition containing ingredients other than wax, or it may be wax itself. The wax particles may be dispersed by a dispersant such as a surfactant or resin.

[0063] In the narrow sense, wax is an ester of a higher monohydric or dihydric alcohol that is insoluble in water and a fatty acid. This includes animal waxes and plant waxes, but does not include oils and fats. In the broader sense, it includes high-melting-point fats, mineral waxes, petroleum waxes, and various wax formulations and modified products. In the recording method of the present invention, any wax in the broad sense can be used without particular limitation. Wax in the broad sense can be classified into natural waxes, synthetic waxes, formulations thereof (blended waxes), and modified products thereof (modified waxes).

[0064] Examples of natural waxes include animal-based waxes such as beeswax, whale wax, and wool wax (lanolin); plant-based waxes such as wood wax, carnauba wax, sugarcane wax, palm wax, candelilla wax, and rice wax; mineral waxes such as montane wax; and petroleum-based waxes such as paraffin wax, microcrystalline wax, and petrolatum. Examples of synthetic waxes include hydrocarbon waxes such as Fischer-Tropsch wax and polyolefin wax (e.g., polyethylene wax, polypropylene wax). Blended wax is a mixture of the above-mentioned waxes. Modified wax is obtained by modifying the above-mentioned waxes through oxidation, hydrogenation, alcohol modification, acrylic modification, urethane modification, etc. It is preferable that the wax is at least one selected from the group consisting of microcrystalline wax, Fischer-Tropsch wax, polyolefin wax, paraffin wax, and modified or blended products thereof. In particular, it is even more preferable that it be a blend of multiple types of waxes, and especially preferable that it be a blend of petroleum-based wax and synthetic wax.

[0065] The wax is preferably solid at room temperature (25°C). The melting point (°C) of the wax is preferably between 40°C and 120°C, and more preferably between 50°C and 100°C. The melting point of the wax can be measured in accordance with the test method described in JIS K2235:1991 (Petroleum Wax) 5.3.1 (Melting Point Test Method). In the case of microcrystalline wax, petrolatum, and mixtures of multiple types of wax, the test method described in 5.3.2 can be used for more accurate measurement. The melting point of the wax is easily affected by properties such as molecular weight (higher molecular weight means higher melting point), molecular structure (linear molecular structure means higher melting point, branching lowers it), crystallinity (higher crystallinity means higher melting point), and density (higher density means higher melting point). Therefore, by controlling these properties, it is possible to produce a wax with a desired melting point.

[0066] (Other additives) In addition to the components listed above, the ink may also contain various additives as needed, such as defoamers, surfactants, pH adjusters, viscosity adjusters, rust inhibitors, preservatives, fungicides, antioxidants, and reduction inhibitors.

[0067] <Drying section> The drying unit 104 is configured to dry the image-formed recording medium 101 while fixing it in place and to transport it to the fixing unit 105. In this embodiment, the drying unit 104 includes a second transport mechanism 115 and a first blower mechanism 116. The second transport mechanism 115 includes a second fixing mechanism 117 that can fix the recording medium 101 while maintaining its smooth surface, and a first heating mechanism 118 that can heat the recording medium 101.

[0068] By drying the image-formed recording medium 101 with the first blowing mechanism 116 and the first heating mechanism 118, the evaporation of liquid components contained in the ink is promoted, and cockling can be suppressed by the second fixing mechanism 117.

[0069] <Second Conveying Mechanism> The second transport mechanism 115 comprises four second rotating shafts 119 extending in the Y direction and arranged in the X direction, and a second belt 120 wound so as to rotate in conjunction with the rotation of the rotating shafts. Examples of materials included in the second belt 120 include resin or metal. When a suction pump is used as a method for fixing the recording medium 101, numerous holes must be made in the second belt 120. This allows the recording medium 101 to be fixed using a second fixing mechanism 117 located below the recording medium 101 on the second belt 120.

[0070] <Second fixing mechanism> The second fixing mechanism 117 can be any mechanism as long as it can fix the recording medium 101 in a position that maintains its smoothness while the recording medium 101 is being heated. Various conventionally known mechanisms can be used as the second fixing mechanism 117 as appropriate. The method for fixing the recording medium 101 is preferably by suction or adhesive fixing. Among these, suction fixing using a suction pump is preferred from the viewpoint of cost and energy efficiency.

[0071] For example, if a suction pump is used as the second fixing mechanism 117, the suction pump is positioned below the second belt 120, which has numerous holes. By operating the suction pump and generating negative pressure, the recording medium 101 on the second belt 120 can be sucked in and fixed through the holes in the second belt 120.

[0072] <First heating mechanism> The first heating mechanism 118 is configured to heat and dry the recording medium 101. As described above, when heating the recording medium 101, cockling can also be suppressed by fixing the recording medium 101. The first heating mechanism 118 can be any mechanism that can heat the recording medium 101 and further allows adjustment of its heating temperature.

[0073] For example, various conventionally known mechanisms can be used as appropriate. A preferred example of the first heating mechanism 118 is a radiant heater. There are no particular restrictions on the type of heater. It can be appropriately selected and applied from known heaters. Among these, electric heating wires or infrared heaters are preferred when considering safety and energy efficiency. A heat roller with a heat source inside may be used as the first heating mechanism 118. The heating temperature of the first heating mechanism 118 when heating the recording medium 101 is preferably 40°C to 100°C. A more preferred heating temperature is 60°C to 80°C.

[0074] <First air blowing mechanism> The first blowing mechanism 116 is configured to blow air onto the recording medium 101 to which ink has been applied by the ink application mechanism 114, thereby drying it. The blowing mechanism 116 can be any mechanism as long as it can dry the recording medium 101 and its airflow can be adjusted. A preferred example of the first blowing mechanism 116 is a hot air dryer. There are no particular restrictions on the type of hot air dryer, and any known hot air dryer can be appropriately selected and applied.

[0075] The air temperature is preferably between 40°C and 100°C, and more preferably between 60°C and 80°C. The airflow rate is, for example, 50 m³. 3 / min or more 200m 3 Within a range of / min or less, the value should be determined according to the type of recording medium 101 (for example, basis weight).

[0076] <Fixing section> The fixing unit 105 is configured to heat and solidify the ink applied to the recording medium 101. In the fixing unit 105, a film is formed by the resin particles contained in the ink by heating the recording medium 101 on which the image has been formed. The fixing unit 105 is not particularly limited, and various conventionally known devices can be used as appropriate. The fixing unit 105 preferably includes a fixing roller or a fixing belt. In this embodiment, it includes a fixing roller 121.

[0077] To bring the fixing roller 121 into close contact with the image on the recording medium 101, the solid components contained in the ink forming the image (more specifically, solid components with a softening point, such as resin particles) are softened by heat, and a temperature and pressure are applied that allows them to adhere to the fixing roller 121. The fixing roller 121 has a heat source, such as a halogen heater, inside the roller and is heated to a predetermined temperature. The fixing roller 121 may be a system in which a heat source, such as a halogen heater, is inside the heating and pressing roller and the fixing belt is heated to a predetermined temperature, or a system in which a heat source, such as an IR heater, is outside the roller and the fixing roller is heated to a predetermined temperature, or a system in which there are heat sources both inside and outside the roller.

[0078] Here, the predetermined temperature is a temperature above the softening point of the solid components mentioned above, and is the temperature at which the ink image softens. For example, the surface temperature of the fixing roller 121 immediately before contact with the recording medium 101 is preferably 60°C to 120°C. More preferably, it is 70°C to 100°C.

[0079] In this way, the ink forms a film on the recording medium 101, resulting in a high-quality image with excellent scratch resistance. In addition, the fixing unit 105 improves the surface smoothness of the image formed on the recording medium 101, resulting in a highly glossy image and a high-quality image with excellent scratch resistance. In short, by going through the fixing process, an inkjet recorded image with good durability and color reproduction can be obtained.

[0080] <Cooling section> The cooling unit 106 is configured to cool the recording medium 101 heated in the fixing unit 105 and transport it to the discharge unit 107. In this embodiment, the cooling unit 106 includes a second blower mechanism 122 and a first transport roller pair 123.

[0081] If the heated recording medium 101 is left unattended after ink fixing without cooling, curling may occur over time as the dry recording medium 101 absorbs moisture from the surrounding air. Therefore, rapid cooling can suppress the occurrence of curling.

[0082] <Second air blowing mechanism> The second blowing mechanism 122 can be any mechanism that can cool the recording medium 101 heated in the fixing unit 105 and allows for adjustment of its airflow. Preferred examples of the second blowing mechanism 122 include air coolers and blowers, with blowers being more preferred. There are no particular restrictions on the type of blower, and any known blower can be appropriately selected and applied.

[0083] Furthermore, the airflow rate should be adjusted so that the temperature of the recording medium 101 when it is discharged to the discharge section 107 by the airflow is 50°C or lower, more preferably 40°C or lower. The airflow rate can be, for example, 50 m³. 3 / min or more 200m 3 You can decide on the appropriate value within the range of / min or less.

[0084] <First pair of conveyor rollers> Multiple pairs of first transport rollers 123 are arranged at intervals in the Y direction and the X direction of transport, allowing the recording medium 101 to be nipped and transported to the discharge section. Of the first pairs of transport rollers 123, the roller that contacts the image forming surface after fixing and the roller opposite it may both be drive rollers, or one of them may be a drive roller and the other a driven roller. Examples of materials included in the first pairs of transport rollers 123 include resin, elastic rubber, and metal, but resin and elastic rubber are preferred.

[0085] Furthermore, as shown in Figure 2, at least the rollers positioned on the image-forming surface of the first transport roller pair 123 are provided with an ink-coagulating member 125 on at least a portion of their surface that contacts the water-based ink to agglomerate it. This suppresses the transfer of ink to the subsequent recording medium 101 even if ink adheres to the first transport roller pair 123, thus preventing a decrease in image quality.

[0086] Figure 2(a) is a schematic diagram in which an ink agglutinating member 125 is provided on a portion of the surface of the roller positioned on the image forming surface of the first transport roller pair 123, and Figure 2(b) is a schematic diagram in which an ink agglutinating member 125 is provided on a portion of the surface of both rollers of the first transport roller pair 123. The roller containing the ink agglutinating member 125 is referred to as the ink agglutinating member-containing roller 126, and the roller without the ink agglutinating member is referred to as the ink agglutinating member-free roller 127.

[0087] (Ink aggregation member) Here, the ink coagulation member 125 refers to a component that, upon contact with the water-based ink, chemically reacts to increase the overall viscosity of the ink, or to cause a local increase in viscosity due to the coagulation of some of the components that make up the ink, such as colorants, thereby reducing the fluidity of part of the ink and / or ink composition.

[0088] The ink agglutination member 125 exhibits the same effect as the reaction solution described above, but the ink agglutination member 125 can be a solid, not a liquid.

[0089] Examples of the solid ink agglomeration and solidification member 125 include inorganic solid acids and organic solid acids. Examples of inorganic solid acids include clay minerals, zeolites, activated carbon, metal oxides, metal sulfides, and metal salts. Examples of organic solid acids include hydrogen-type cation exchange resins. In this embodiment, it is preferable to use a hydrogen-type cation exchange resin, which is an organic solid acid, from the viewpoint of moldability and other factors.

[0090] Hydrogen-type (H-type) cation exchange resins are primarily resins capable of exchanging cations containing hydrogen atoms between a matrix structure and ion exchange groups. For example, a matrix structure consisting of a styrene-divinylbenzene copolymer and a resin having ion exchange groups such as carboxylic acid groups (-COOH) or sulfonic acid groups (-SO3H) is one such example. In addition, acrylic acid-divinylbenzene copolymers and methacrylic acid-divinylbenzene copolymers can also be used as the matrix structure for hydrogen-type cation exchange resins.

[0091] The structural formula below represents a resin containing sulfonic acid groups in a styrene-divinylbenzene copolymer.

[0092] [ka]

[0093] Hydrogen-type cation exchange resins generate hydrogen ions upon contact with water, thus possessing acidic properties. Furthermore, the inclusion of fluorine groups in hydrogen-type cation exchange resins enhances their acidic properties, further improving ink aggregation performance. Examples of hydrogen-type cation exchange resins containing fluorine groups include Nafion (DuPont), Flemion (Asahi Glass Co.), Aquivion (Solvay), and Aciplex (Asahi Kasei). The structural formula shown below is that of Nafion.

[0094] [ka]

[0095] As for the formation method, for example, a dispersion of the ink agglutinating member 125 can be coated onto an ink agglutinating member-free roller 127, and then dried to form the material. Various conventional methods can be used as appropriate for coating the dispersion, such as die coating, blade coating, gravure rollers, offset rollers, spray coating, etc. Alternatively, a pre-formed film of the ink agglutinating member 125 can be bonded and held onto the ink agglutinating member-free roller 127 with various adhesives to form the material over the entire surface. Furthermore, a mixture of the ink agglutinating member 125 and resin or rubber in a certain proportion can be processed and molded into a roller shape, and the ink agglutinating member 125 can be exposed on the surface by surface polishing.

[0096] Figure 3 is a schematic diagram viewed from above in the Z direction, showing that an ink aggregation member 125 is provided on a portion of the surface of the roller positioned on the image forming surface among the first transport roller pair 123 in Figure 2(a), illustrating how the image-formed recording medium 101 is transported to the cooling unit 106 and the discharge unit 107 after fixing. The first transport roller pair 123 are arranged on the same conductor in the X direction of transport, and the second blowing mechanism 122 is not shown so that the arrangement of the first transport roller pair 123 can be seen.

[0097] In this case, if ink fixation is insufficient due to high-speed printing or the use of a recording medium with low ink absorption, the first transport roller pair 123a, which is the first to come into contact with the image forming surface, will have the most ink adhering to it. Therefore, it is preferable that the proportion of ink agglomerating member 125 in the first transport roller pair 123a is greater than that of the subsequent first transport roller pairs 123b and 123c on the same conductor. That is, among the transport roller pairs on the same conductor in the transport direction, the upstream side has a higher proportion of ink agglomerating member 125 than the downstream side, and it is preferable that the order from highest to lowest is: first transport roller pair 123a > first transport roller pair 123b ≥ first transport roller pair 123c.

[0098] Figure 4 is a schematic diagram viewed from above in the Z direction, showing that ink aggregation members 125 are provided on a portion of the surface of both rollers of the first transport roller pair 123 in Figure 2(b), illustrating how the image-formed recording medium 101 is transported to the cooling section 106 and the discharge section 107 after fixing. The first transport roller pair 123 are arranged on the same conductor in the X direction of transport, and the second blowing mechanism 122 is not shown so that the arrangement of the first transport roller pair 123 can be seen.

[0099] Similarly, if ink fixation is insufficient due to high-speed printing or the use of a recording medium with low ink absorption, the first pair of transport rollers 123a that first contact the image-forming surface will have the most ink adhering to it. For this reason, it is preferable that both rollers of the first pair of transport rollers 123a on the upstream side of the transport roller pairs on the same conductor in the transport direction are ink-coagulating member-containing rollers 126. If the ink-coagulating member-containing rollers 126 are only placed on the image-forming surface, if the amount of ink adhering becomes large, the ink-coagulating member 125 will not be able to completely agglomerate the ink. However, if the opposing rollers are also ink-coagulating member-containing rollers 126, the first pair of transport rollers 123 continues to rotate in contact even when the recording medium 101 is not passing through, so the ink-coagulating member 125 of the opposing rollers can agglomerate the ink, thereby suppressing ink transfer to the subsequent recording medium 101.

[0100] <Discharge section> The recording medium 101, which has been transported from the cooling section 106 to the discharge section 107, is loaded into the discharge section 107 while being transported by the second pair of transport rollers 124.

[0101] <Second conveyor roller pair> Multiple pairs of second transport rollers 124 are arranged at intervals in the Y direction and the X direction of transport, allowing the recording medium 101 to be nipped, transported, and loaded inside. Since the second pairs of transport rollers 124 are the same as the first pairs of transport rollers 123 described above, a detailed explanation is omitted.

[0102] Figure 3 is a schematic diagram viewed from above in the Z direction, showing that an ink aggregation member 125 is provided on a portion of the surface of the roller positioned on the image forming surface among the first transport roller pair 124 in Figure 2(a), illustrating how the image-formed recording medium 101 is transported to the cooling unit 106 and the discharge unit 107 after fixing. The second transport roller pair 124 is arranged on the same conductor in the X direction of transport.

[0103] In this case, if ink fixation is insufficient due to high-speed printing or the use of a recording medium with low ink absorption, the second transport roller pair 124a, which is the first to come into contact with the image forming surface, will have the most ink adhering to it. Therefore, it is preferable that the ratio of ink agglomerating member 125 in the second transport roller pair 124a is greater than that of the subsequent first transport roller pairs 124b and 124c on the same line. That is, among the transport roller pairs on the same line in the transport direction, it is preferable that the ratio of ink agglomerating member 125 increases from the upstream side to the downstream side, in the order of second transport roller pair 124a > second transport roller pair 124b ≥ first transport roller pair 124c.

[0104] Figure 4 is a schematic diagram viewed from above in the Z direction, showing that ink aggregation members 125 are provided on a portion of the surface of both rollers of the second transport roller pair 124 in Figure 2(b), illustrating how the image-formed recording medium 101 is transported to the cooling unit 106 and the discharge unit 107 after fixing. The second transport roller pair 124 are arranged on the same conductor in the X direction of transport.

[0105] Similarly, if ink fixation is insufficient due to high-speed printing or the use of a recording medium with low ink absorption, the second transport roller pair 124a, which is the first to contact the image-forming surface, will have the most ink adhering to it. For this reason, it is preferable that both rollers of the upstream second transport roller pair 124a, among the transport roller pairs that are on the same line in the transport direction, are ink-coagulating member-containing rollers 126. If the ink-coagulating member-containing rollers 126 are only placed on the image-forming surface, if the amount of ink adhering becomes large, the ink-coagulating member 125 will not be able to completely agglomerate the ink. However, if the opposing rollers are also ink-coagulating member-containing rollers 126, the first transport roller pair 123 continues to rotate in contact even when the recording medium 101 is not passing through, so the ink-coagulating member 125 of the opposing rollers can agglomerate the ink, thereby suppressing ink transfer to the subsequent recording medium 101. [Examples]

[0106] The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited in any way by the following examples unless it exceeds the gist of the invention. In the following examples, "parts" refers to mass unless otherwise specified.

[0107] <Manufacturing of conveyor roller components> (Laura 1) An EPDM roller substrate was used, and an inorganic solid acid, sulfated zirconia (SO4 / ZrO2 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)), was used as the ink agglomerating component 125. The mixture was kneaded in an amount of 15 parts by mass relative to the roller substrate, and an ink agglomerating component-containing roller 126 was formed by molding or other means. It was confirmed that SO4 / ZrO2 was exposed on a portion of the roller surface.

[0108] (Laura 2) An ink-coagulating component 125 was formed by mixing EPDM as the roller base material and a strongly acidic cation exchange resin No. 6 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), which is a divinylbenzene-styrene-ethyl(vinyl)benzene polymer sulfonate (H type), with the water removed, in an amount of 15 parts by mass with the roller base material, kneading the mixture, and then molding or otherwise forming an ink-coagulating component-containing roller 126. It was confirmed that the strongly acidic cation exchange resin No. 6 was exposed on a portion of the roller surface.

[0109] (Laura 3) EPDM was prepared as the roller substrate. Next, Nafion powder (35-60 mesh, manufactured by Sigma-Aldrich) was sieved so that the particle size was 300 μm or less. The EPDM was mixed with 15 parts by mass of the above 300 μm or less Nafion powder and kneaded, and an ink-coagulating member-containing roller 126 was formed by molding or other means. It was confirmed that Nafion was exposed on a part of the roller surface.

[0110] (Laura 4) A roller 126 containing an ink agglomerating member was formed in the same manner, except that the amount of Nafion powder in roller 3 was 25 parts by mass. Similarly, it was confirmed that Nafion was exposed on a portion of the roller surface.

[0111] (Laura 5) A roller 126 containing an ink agglomerating member was formed in the same manner, except that the amount of Nafion powder in roller 3 was 5 parts by mass. Similarly, it was confirmed that Nafion was exposed on a portion of the roller surface.

[0112] (Laura 6) Using EPDM as the roller base material, an ink-free roller 127 was formed by molding or other means.

[0113] Table 1 shows a list of the rollers produced as described above.

[0114] [Table 1]

[0115] <Arrangement of conveyor roller pairs> Based on the rollers fabricated above, roller pairs were formed to create the first conveyor roller pair 123 and the second conveyor roller pair 124. As shown in Figures 3 and 4, the first conveyor roller pair 123 was arranged in two rows in the Y direction and three rows in the X direction at equal intervals, with the three rows in the X direction placed on the same conductor. Similarly, the second conveyor roller pair 124 was arranged in three rows in the Y direction and three rows in the X direction at equal intervals, with the three rows in the X direction placed on the same conductor. Note that the three rows in the X direction of the first conveyor roller pair 123 and the three rows in the X direction of the second conveyor roller pair 124 are not placed on the same conductor.

[0116] Table 2 shows a list of the configurations of the first conveyor roller pair 123 and the second conveyor roller pair 124 arranged therein.

[0117] [Table 2]

[0118] <Preparation of reaction solution> (Reaction solution) A mixture of 21.0 parts by mass of glutaric acid, 2.0 parts by mass of potassium hydroxide, 5.0 parts by mass of glycerin, 5.0 parts by mass of surfactant (product name: Megafac F444 (manufactured by DIC)), and 67.0 parts by mass of deionized water was thoroughly stirred, and then the mixture was pressure-filtered through a 3.0 μm pore size microfilter (manufactured by Fujifilm) to prepare the reaction solution.

[0119] <Preparation of Pigment Dispersion> (Pigment dispersion) Ten parts of carbon black (product name: Monac 1100, manufactured by Cabot), fifteen parts of resin aqueous solution (styrene-ethyl acrylate-acrylic acid copolymer, acid value 150, weight-average molecular weight (Mw) 8,000, an aqueous solution with a resin content of 20.0% by mass neutralized with potassium hydroxide aqueous solution), and seventy-five parts of pure water were mixed and charged into a batch-type vertical sand mill (manufactured by Imex). Two hundred parts of 0.3 mm diameter zirconia beads were added, and the mixture was dispersed for five hours while being cooled with water. After centrifuging the dispersion to remove coarse particles, a black pigment dispersion with a pigment content of 10.0 parts by mass was prepared.

[0120] <Preparation of resin particle dispersion> (Resin particle dispersion) 20 parts ethyl methacrylate, 3 parts 2,2'-azobis-(2-methylbutyronitrile), and 2 parts n-hexadecane were mixed and stirred for 0.5 hours. 75 parts by mass of an 8% aqueous solution of styrene-butyl acrylate-acrylic acid copolymer (acid value: 130 mg KOH / g, weight-average molecular weight (Mw): 7,000) were added dropwise to this mixture and stirred for 0.5 hours. Next, the mixture was irradiated with ultrasound for 3 hours using an ultrasonic irradiator. Subsequently, a polymerization reaction was carried out at 80°C for 4 hours under a nitrogen atmosphere, and after cooling to room temperature, the mixture was filtered to prepare a resin particle dispersion with a resin content of 25.0 parts by mass. The resin content of the resin particle dispersion can be adjusted by dilution or concentration as needed. The softening point of this resin is 90°C. This softening point was measured in accordance with JIS K 6828-2 "Method for determining the minimum film-forming temperature". Specifically, the resin dispersion was heated under an appropriate temperature gradient, and the boundary temperature between the transparent film-forming portion and the non-film-forming portion was measured. The minimum film-forming temperature of the resin dispersion was measured using a minimum film-forming thermometer (product name: MFTTB90, manufactured by RHOPOINT INSTRUMENTS).

[0121] <Ink adjustment> (Ink 1) After thoroughly stirring a mixture of 4.0 parts by mass of the pigment dispersion obtained above, 7.0 parts by mass of the resin particle dispersion, 7.0 parts by mass of glycerin, 1.0 part by mass of polyethylene glycol (number average molecular weight (Mn): 1,000), 0.5 parts by mass of surfactant (acetylenol® E100, manufactured by Kawaken Fine Chemical Co., Ltd.), and 80.5 parts of ion-exchanged water, ink 1 was prepared by pressure filtration through a microfilter with a pore size of 3.0 μm (manufactured by Fujifilm Corporation).

[0122] (Ink 2) Ink 2 was prepared in the same manner as Ink 1, except that 6.0 parts by mass of the resin particle dispersion of Ink 1 was used, and 1.0 part by mass of wax (Hi-Mic-2095 (manufactured by Nippon Seiro Co., Ltd.) microcrystalline wax (melting point: 103°C)) was added.

[0123] <Print> In this example, the inkjet recording device 100 shown in Figure 1 was used.

[0124] The transport speed is set to 0.5 m / s, and the recording medium 101 is Magno Satin (manufactured by Sappi, basis weight 300 g / m²). 2 I used A4 size paper.

[0125] The reaction solution dispensing mechanism 113 uses an inkjet head that dispenses the reaction solution on demand using an electrical-to-thermal conversion element, and the amount of reaction solution 1 dispensed as described above is 1 g / m². 2 That's what I decided.

[0126] The ink application mechanism 114, like the reaction liquid application mechanism 113, uses an inkjet head that ejects ink on demand using an electrical-to-thermal conversion element, and uses either ink 1 or ink 2 adjusted above, with an ink application amount of 12 g / m². 2 That's what I decided.

[0127] Next, in the drying section 104 for drying the ink, a hot air dryer was used and set to a surface temperature of 80°C for the recording medium 101. In the fixing section 105, a fixing roller 121 was used, which has a halogen heater heat source inside the heating and pressing roller and heats to a predetermined temperature. The temperature of the fixing roller 121 immediately before contact with the recording medium 101 was set so that the contact temperature with the recording medium 101 was 90°C. In the cooling section 106, a blower was used and the airflow was set so that the temperature of the recording medium 101 after fixing was 50°C or lower.

[0128] Under the above printing conditions, using an image of a checkerboard pattern with each square measuring 1 cm vertically and 1 cm horizontally, 1,000 sheets were printed in 50 consecutive runs, resulting in a total of 50,000 printed sheets.

[0129] [evaluation] Under the conditions described above, the evaluation was performed using the following evaluation method. The evaluation results are shown in Table 3. In this invention, A to B in the evaluation criteria for each of the evaluation items below are considered desirable levels, and C is considered an unacceptable level.

[0130] <Stains on the surface of printed materials> We checked whether ink stains occurred in the white areas of the checkerboard pattern image due to ink adhering to the transport rollers being transferred. The evaluation criteria are as follows: A: No ink stains were visible to the naked eye. B: A slight ink stain was visible to the naked eye, but it was at a level that would not cause any problems in actual use. C: Ink stains were clearly visible to the naked eye and were at a level that would cause problems in actual use.

[0131] <Increase in torque of the conveyor roller pair> The torque of each transport roller pair was measured before and after printing to determine how much the torque increased after printing compared to the torque before printing. For each printing condition, the highest torque increase rate among each transport roller pair was compared and evaluated according to the following evaluation criteria.

[0132] A: The maximum torque increase was less than 2%.

[0133] B: The maximum torque increase was between 2% and 5%.

[0134] C: The maximum torque increase rate was 5% or more.

[0135] The evaluation results are shown in Table 3.

[0136] [Table 3] [Explanation of symbols]

[0137] 100 Inkjet Recording Devices 101 Recording media 102 Feeding section 103 Image forming unit 104 Drying section 105 Fixing section 106 Cooling section 107 Discharge section 108 First conveying mechanism 109 Image Formation Mechanism 110 First axis of rotation 111 The First Belt 112 First fixing mechanism 113 Reaction solution supply mechanism 114 Ink application mechanism 115 Second conveying mechanism 116 First blower mechanism 117 Second fixing mechanism 118 First heating mechanism 119 Second axis of rotation 120 The second belt 121 Fixing roller 122 Second blower mechanism 123 First conveyor roller pair 124 Second conveyor roller pair 125 Ink aggregation member 126 Ink agglomeration component-containing roller 127 Rollers that do not contain ink agglomerating material

Claims

1. An inkjet recording apparatus for forming an image on a recording medium that is transported along a predetermined transport direction by ejecting aqueous ink from a recording head, wherein the apparatus comprises a plurality of transport roller pairs provided after means for supplying thermal energy to the image-formed recording medium, and which transport the image-formed recording medium by rotating in a certain direction while holding the image-formed recording medium, and at least one of the transport roller pairs, which is positioned on the image-forming surface, is provided with an ink-coagulating member on at least a portion of its surface that contacts the aqueous ink to agglomerate the aqueous ink.

2. The inkjet recording apparatus according to claim 1, characterized in that, when the transport roller pair is on the same conductor in the transport direction, the transport upstream side of the transport roller pair, which is arranged on the image forming surface, has a higher ink aggregation member content than the transport downstream side.

3. The inkjet recording apparatus according to claim 1, characterized in that, when the transport roller pair is on the same conductor in the transport direction, the transport roller pair on the upstream side of the transport roller pair is provided with the ink agglomerating member on both rollers.

4. The inkjet recording apparatus according to claim 1, characterized in that the ink agglomerating member is a solid acid.

5. The inkjet recording apparatus according to claim 4, characterized in that the ink aggregation solidification member is a hydrogen-type cation exchange resin.

6. The inkjet recording apparatus according to claim 5, characterized in that the hydrogen-type cation exchange resin has a fluorine group.

7. The inkjet recording apparatus according to claim 1, characterized in that the aqueous ink contains wax.

Images