JP2009226907A - Image forming method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable high-quality image formation by preventing blocking and curling of a recording medium in a two-liquid agglomerating system that uses an ink and a processing liquid. <P>SOLUTION: An image forming method for forming an image on the recording medium by using both the ink which contains a coloring material and the processing liquid which contains a component to agglomerate the coloring material includes a processing liquid giving process of giving the processing liquid onto the recording medium, an ink droplet striking process of striking droplets of the ink on the recording medium to which the processing liquid is given, an ink drying process of heating and drying an ink layer formed on the recording medium by the ink droplet striking process, and a solvent removing process of removing a remaining solvent by bringing a solvent removing means into contact with the remaining solvent left on the recording medium after the ink drying process is carried out. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming method and an image forming apparatus, and more particularly to a technique for preventing curling and blocking of a recording medium in a two-liquid aggregation method in which an image is formed on a recording medium using ink and a processing liquid.

  The ink jet recording method is a method of recording by discharging ink droplets from a plurality of nozzles formed on an ink jet head toward a recording medium. The noise during the recording operation is low, the running cost is low, and the high resolution is achieved. Images and high-quality image recording are possible. Ink ejection methods include a piezoelectric method using displacement of a piezoelectric element and a thermal method using thermal energy generated by a heating element.

  In the ink jet recording method, when ink droplets are continuously ejected so that adjacent ink droplets (ink dots) overlap on the recording medium, these ink droplets are united by the surface tension, and the desired ink droplets are combined. There is a problem of bleeding (landing interference) in which dots cannot be formed. In the case of dots of the same color, the dot shape collapses, and in the case of dots between different colors, a problem of color mixing also occurs. In particular, when recording is performed by a single pass method using a line head, the landing time difference between adjacent ink droplets is short, so that landing interference is likely to occur and it is difficult to form a sharp image.

  On the other hand, a technique for improving the image quality by applying a so-called treatment liquid on a recording medium prior to ink and reacting with the ink is generally known. When pigment particles are used as the colorant, the treatment liquid has a function of neutralizing the Coulomb repulsive force of the pigment particles and aggregating the particles to thicken the ink liquid. Thereby, interference between droplet ejection dots is suppressed, and a sharp image can be recorded without density unevenness.

In such a high-speed printing method, the drawn ink needs to be dried. If the drying is insufficient, ink transfer or blocking (paper sticking) may occur when the recording medium is discharged. Become. In particular, when water-based ink is used, curling of the paper due to insufficient drying is also a serious problem. On the other hand, a technique for solving these problems by heating and drying after applying ink to a recording medium is known (see, for example, Patent Documents 1 and 2).
JP 2007-160839 A JP 2003-048317 A

  However, so-called coated paper for printing used in offset printing or the like has a slow paper penetration because the paper surface is hydrophobic. When a treatment liquid is applied to such a substrate and then ink droplets are ejected and the ink is heated and dried, stickiness occurs on the ink surface even if the drying is performed sufficiently. It was found that blocking would occur.

  In general, in an ink jet recording system using water-based ink containing water as a main component, it is necessary to add at least about 10 to 30% by mass of a high boiling point solvent in order to prevent clogging of nozzles due to drying. These wetting agents have a relatively low viscosity in the state of an aqueous solution, but when moisture is evaporated to increase the concentration, the viscosity increases and the permeability to paper decreases. For this reason, it remains in the ink layer and causes stickiness.

  By delaying the time from ink ejection to drying, it is possible to allow the high-boiling point solvent to penetrate into the paper in the form of an aqueous solution, but the printing productivity decreases and the curling deteriorates due to the delay in drying. It is not preferable.

  The present invention has been made in view of such circumstances, and in a two-liquid aggregation method using ink and processing liquid, an image forming method capable of preventing a recording medium from blocking or curling and enabling high-quality image formation. An object of the present invention is to provide an image forming apparatus.

  In order to achieve the above object, an image forming method according to the present invention forms an image on a recording medium using an ink containing a color material and a treatment liquid containing a component for aggregating the color material. An image forming method comprising: a treatment liquid application step for applying the treatment liquid onto the recording medium; an ink ejection step for ejecting the ink onto the recording medium provided with the treatment liquid; and the ink An ink drying step for heating and drying the ink layer formed on the recording medium by the droplet ejection step, and after the ink drying step, a solvent removing means is brought into contact with the residual solvent remaining on the recording medium. And a solvent removal step of removing the residual solvent.

  According to the present invention, not only is the ink layer formed on the recording medium dried by heating to evaporate the solvent component (mainly moisture) contained in the ink layer, but also the residual remaining on the recording medium. By removing the residual solvent (particularly a high boiling point solvent) by bringing the solvent removal means into contact with the solvent, curling and blocking of the recording medium can be prevented, and high-quality image formation is possible.

  In the present invention, it is preferable that the time from when the ink is deposited on the recording medium to when the ink layer is heated and dried is within 10 seconds (preferably within 1 second). The amount of moisture penetrating the recording medium can be suppressed, and the curling of the recording medium can be surely prevented.

  In the present invention, the solvent removal step is preferably performed such that the solvent content of the ink layer after the solvent removal by the solvent removal means is 50% or less. By reducing the amount of the high boiling point solvent contained in the ink layer on the recording medium, stickiness of the ink layer can be reduced, and blocking of the recording medium can be surely prevented.

  In the present specification, the “solvent content of the ink layer” refers to the ratio of the solvent weight to the solid weight of the ink layer.

  In the present invention, it is preferable to further include a treatment liquid drying step in which the treatment liquid applied on the recording medium is heated and dried. The amount of moisture penetrating the recording medium can be reduced, and the curling prevention effect of the recording medium can be enhanced.

  In the present invention, it is preferable that the method further includes a fixing step of fixing the ink layer on the recording medium by applying heat and pressure after the solvent removing step. The abrasion resistance of the image is improved.

  The recording medium used in the present invention is not particularly limited, but a particularly preferable result can be obtained for a coated paper for printing in which the penetration of the ink solvent is slow. That is, if the ink layer on the coated paper for printing (slowly osmotic medium) is only heated and dried to evaporate the water, the ink layer remains on the recording medium due to an increase in the viscosity of the high boiling point solvent, and the ink layer tends to become sticky. If the ink layer is not heated and dried, moisture permeates the recording medium and curling is likely to occur. On the other hand, according to the present invention, the solvent component (mainly moisture) of the ink layer on the recording medium is evaporated by heating and the high boiling point solvent is removed from the recording medium. And blocking can be prevented reliably.

  In order to achieve the above object, an apparatus invention is provided. That is, the image forming apparatus according to the present invention is an image forming apparatus that forms an image on a recording medium using an ink containing a color material and a treatment liquid containing a component that aggregates the color material. The processing liquid applying means for applying the processing liquid onto the recording medium, the ink droplet ejecting means for ejecting the ink onto the recording medium to which the processing liquid is applied, and the recording by the ink droplet ejecting means. An ink drying unit that heat-drys the ink layer formed on the medium, and the residual solvent that comes into contact with the residual solvent remaining on the recording medium after the ink layer is heated and dried by the ink drying unit. And a solvent removing means for removing the solvent.

  According to the present invention, not only is the ink layer formed on the recording medium dried by heating to evaporate the solvent component (mainly moisture) contained in the ink layer, but also the residual remaining on the recording medium. By removing the residual solvent (particularly a high boiling point solvent) by bringing the solvent removal means into contact with the solvent, curling and blocking of the recording medium can be prevented, and high-quality image formation is possible.

  According to the present invention, not only is the ink layer formed on the recording medium dried by heating to evaporate the solvent component (mainly moisture) contained in the ink layer, but also the residual remaining on the recording medium. By removing the residual solvent (particularly a high boiling point solvent) by bringing the solvent removal means into contact with the solvent, curling and blocking of the recording medium can be prevented, and high-quality image formation is possible.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  First, the ink and the treatment liquid used in the present invention will be described.

〔ink〕
The ink used in the present invention is a water-based pigment ink containing a pigment that is a coloring material (coloring agent) or polymer fine particles as a solvent-insoluble material.

The concentration of the solvent-insoluble material is preferably 1 wt% or more and 20 wt% or less considering a viscosity of 20 mPa · s or less suitable for ejection. More preferably, the pigment concentration is 4 wt% or more in order to obtain the optical density of the image.
The surface tension of the ink is preferably 20 mN / m or more and 40 mN / m in consideration of ejection stability.

  The color material used in the ink can be a pigment or a mixture of a dye and a pigment. From the viewpoint of aggregability at the time of contact with the treatment liquid, a pigment in a dispersed state in the ink is preferable because it aggregates more effectively. Among the pigments, a pigment dispersed by a dispersant, a self-dispersing pigment, a pigment whose surface is coated with a resin (microcapsule pigment), and a polymer graft pigment are particularly preferable. From the viewpoint of pigment aggregation, a form modified with a carboxyl group having a low dissociation degree is more preferable.

  The resin of the microcapsule pigment is not limited, but is preferably a high molecular compound having a self-dispersibility or solubility in water and an anionic group (acidic). This resin usually has a number average molecular weight of about 1,000 to 100,000, and particularly preferably about 3,000 to 50,000. Further, it is preferable that this resin is dissolved in an organic solvent to form a solution. When the number average molecular weight of the resin is within this range, the function as a coating film in the pigment or as a coating film in the ink composition can be sufficiently exhibited.

  The resin may be self-dispersible or soluble, or may have a function added by some means. For example, it may be a resin in which an anionic group such as a carboxyl group, a sulfonic acid group, or a phosphonic acid group is introduced by neutralization with an organic amine or an alkali metal. Further, it may be a resin into which one or two or more anionic groups of the same type or different types are introduced. In the present invention, a resin in which a carboxyl group is introduced by neutralization with a base is preferably used.

  Although it does not specifically limit as a pigment used for this invention, As a specific example, as a pigment for orange or yellow, C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 180, C.I. I. And CI Pigment Yellow 185. Examples of red or magenta pigments include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of the pigment for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

  Examples of black pigments include C.I. I. Pigment black 1, C.I. I. Pigment black 6, C.I. I. Pigment black 7 and the like.

  In the colored ink liquid according to the present invention, it is preferable to add polymer fine particles not containing a colorant as a component that reacts with the treatment liquid. The polymer fine particles can enhance the thickening action and aggregation action of the ink by reaction with the treatment liquid, and can improve the image quality. In particular, a highly safe ink can be obtained by incorporating anionic polymer fine particles into the ink.

  By using polymer fine particles that react with the treatment liquid and cause thickening and aggregating action in the ink, the quality of the image can be improved. At the same time, depending on the type of polymer fine particles, the polymer fine particles form a film on the recording medium. It also has the effect of improving the scratch resistance and water resistance of the image.

  The dispersion method in the polymer ink is not limited to emulsion, and it may be dissolved or exist in a colloidal dispersion state.

  The polymer fine particles may be obtained by dispersing the polymer fine particles using an emulsifier, or may be dispersed without using an emulsifier. As the emulsifier, a low molecular weight surfactant is usually used, but a high molecular weight surfactant can also be used as an emulsifier. It is also preferable to use capsule type polymer fine particles (core / shell type polymer fine particles having different compositions at the center and outer edge of the particle) whose outer shell is made of acrylic acid, methacrylic acid or the like.

  As a dispersion method, polymer fine particles not using a low molecular weight surfactant are called soap-free latex, including polymer fine particles using a high molecular weight surfactant and polymer fine particles not using an emulsifier. For example, a polymer having a water-soluble group such as a sulfonic acid group or a carboxylic acid group described above (a polymer in which a solubilizing group is graft-bonded, a monomer having a solubilizing group, and an insoluble portion) Polymer fine particles using a block polymer obtained from a monomer as an emulsifier are also included.

  In the present invention, it is particularly preferable to use this soap-free latex. The soap-free latex, compared with polymer fine particles polymerized using a conventional emulsifier, inhibits the reaction aggregation and film formation of the polymer fine particles, or the free emulsifier. However, it moves to the surface after forming the polymer fine particles, and there is no concern that the adhesiveness between the aggregate in which the pigment and the polymer fine particles are mixed and the recording medium is lowered.

  Examples of the resin component added to the ink as polymer fine particles include acrylic resins, vinyl acetate resins, styrene-butadiene resins, vinyl chloride resins, acrylic-styrene resins, butadiene resins, styrene resins, and the like.

  From the viewpoint of imparting high-speed cohesiveness to the polymer fine particles, those having a carboxylic acid group having a low dissociation degree are more preferable. Since the carboxylic acid group is easily affected by pH change, the dispersion state is easily changed and the cohesiveness is high.

  The change of the dispersion state with respect to the pH change of the polymer fine particles can be adjusted by the content ratio of the constituent component in the polymer fine particles having a carboxylic acid group such as an acrylate ester, and the like depending on the anionic surfactant used as the dispersant. Can also be adjusted.

  The resin component of the polymer fine particles is preferably a polymer having both a hydrophilic portion and a hydrophobic portion. By having the hydrophobic portion, the hydrophobic portion is oriented inside the polymer fine particle, the hydrophilic portion is efficiently oriented outside, and the effect of increasing the dispersion state with respect to the pH change of the liquid is greater, and aggregation is caused. Done more efficiently.

  Examples of commercially available polymer fine particles include Jonkrill 537, 7640 (styrene-acrylic resin emulsion, manufactured by Johnson Polymer Co., Ltd.), Microgel E-1002, E-5002 (styrene-acrylic resin emulsion, Nippon Paint Co., Ltd.). Manufactured), Boncoat 4001 (acrylic resin emulsion, manufactured by Dainippon Ink & Chemicals, Inc.), Boncoat 5454 (styrene-acrylic resin emulsion, manufactured by Dainippon Ink & Chemicals, Inc.), SAE-1014 (styrene-acrylic resin) Emulsion, manufactured by Nippon Zeon Co., Ltd., Jurimer ET-410, FC-30 (acrylic resin emulsion, manufactured by Nippon Pure Chemicals Co., Ltd.), Aron HD-5, A-104 (acrylic resin emulsion, manufactured by Toagosei Co., Ltd.) ), Cybino Le SK-200 (acrylic resin emulsion, manufactured by Saiden Chemical Industry Co., Ltd.), Zaikthene L (acrylic resin emulsion, manufactured by Sumitomo Seika Chemicals Co., Ltd.) and the like, not limited to this.

  The weight ratio of the polymer fine particle addition amount to the pigment is preferably 2: 1 to 1:10, more preferably 1: 1 to 1: 3. If the weight ratio of the amount of polymer fine particles added to the pigment is less than 2: 1, the cohesive force of the aggregate due to resin fusion will not be improved effectively. Moreover, even if the addition amount is more than 1:10, the viscosity of the ink becomes too high, and the discharge properties and the like deteriorate.

  The molecular weight of the polymer fine particles added to the ink is preferably 5,000 or more in view of the adhesive force when fused. If it is less than 5,000, the effect of improving the internal cohesive force of the ink aggregate when aggregated, fixing the image on the recording medium, and the effect of improving the image quality are insufficient.

  The volume average particle diameter of the polymer fine particles is preferably in the range of 10 nm to 1 μm, more preferably in the range of 10 to 500 nm, still more preferably in the range of 20 to 200 nm, and particularly preferably in the range of 50 to 200 nm. If the thickness is 10 nm or less, the effect of improving the image quality and the improvement of transferability cannot be expected even if they are aggregated. When the thickness is 1 μm or more, there is a concern that the ejection properties of the ink from the head and the storage stability may deteriorate. Moreover, there is no restriction | limiting in particular regarding the volume average particle diameter distribution of a polymer particle, What has a wide volume average particle diameter distribution or a thing with a monodispersed volume average particle diameter distribution may be sufficient.

  Further, two or more kinds of polymer fine particles may be mixed and used in the ink.

  As the pH adjuster added to the ink of the present invention, an organic base or an inorganic alkali base can be used as a neutralizing agent. The pH adjusting agent is preferably added so that the inkjet ink has a pH of 6 to 10 for the purpose of improving the storage stability of the inkjet ink.

  The ink of the present invention preferably contains a water-soluble organic solvent for the purpose of preventing clogging of the nozzles of the inkjet head due to drying. Such water-soluble organic solvents include wetting agents and penetrants.

  Examples of the water-soluble organic solvent include polyhydric alcohols, polyhydric alcohol derivatives, nitrogen-containing solvents, alcohols, sulfur-containing solvents and the like, as in the case of the treatment liquid. Specific examples of polyhydric alcohols include ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,5-pentanediol, 1,2,6-hexanetriol, and glycerin. Examples of polyhydric alcohol derivatives include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, and diglycerin. Examples include ethylene oxide adducts. Examples of nitrogen-containing solvents include pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, and triethanolamine. Examples of alcohols include alcohols such as ethanol, isopropyl alcohol, butyl alcohol, and benzyl alcohol. Thiodiethanol, thiodiglycerol, sulfolane, dimethyl sulfoxide and the like. In addition, propylene carbonate, ethylene carbonate, or the like can be used.

  The ink of the present invention can contain a surfactant.

  Examples of surfactants include fatty acid salts, alkyl sulfate esters, alkyl benzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate ester salts, naphthalene sulfonate formalin condensates, Anionic surfactants such as oxyethylene alkyl sulfate esters, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkylamines Nonionic surfactants such as glycerin fatty acid ester and oxyethyleneoxypropylene block copolymer are preferred. Further, SURFYNOLS (Air Products & Chemicals), which is an acetylene-based polyoxyethylene oxide surfactant, is also preferably used. An amine oxide type amphoteric surfactant such as N, N-dimethyl-N-alkylamine oxide is also preferred.

  Further, pages (37) to (38) of JP-A-59-157636, Research Disclosure No. The surfactants described in 308119 (1989) can also be used. In addition, fluorine (fluorinated alkyl) and silicone surfactants as described in JP-A Nos. 2003-322926, 2004-325707, and 2004-309806 are also used. Can do. These surface tension modifiers can also be used as antifoaming agents, and fluorine-based, silicone-based compounds, chelating agents represented by EDTA, and the like can also be used.

  The surface tension can be lowered to increase the wettability on the solid or semi-solid solution aggregation treatment agent layer, and the spreading rate can be increased.

  The surface tension of the ink of the present invention is preferably 10 to 50 mN / m, and from the viewpoint of compatibility between the permeability to the permeable recording medium, the formation of fine droplets, and the ejection property, 15 to 45 mN. More preferably, it is / m.

  The viscosity of the ink of the present invention is preferably 1.0 to 20.0 cP.

  In addition, a pH buffer, an antioxidant, a fungicide, a viscosity modifier, a conductive agent, an ultraviolet absorber, and the like can be added as necessary.

[Treatment solution]
The treatment liquid (aggregation treatment liquid) according to the present invention is preferably a treatment liquid that agglomerates the pigment and polymer fine particles contained in the ink by changing the pH of the ink to produce an aggregate.

  Treatment liquid components include polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid, lactic acid, sulfonic acid, orthophosphoric acid, pyrrolidone It is preferably selected from carboxylic acid, pyrone carboxylic acid, pyrrole carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, derivatives of these compounds, or salts thereof.

  A preferable example of the treatment liquid according to the present invention is a treatment liquid to which a polyvalent metal salt or polyallylamine is added. These compounds may be used alone or in combination of two or more.

  The treatment liquid according to the present invention preferably has a pH of 1 to 6, more preferably 2 to 5, and particularly preferably 3 to 5 from the viewpoint of pH aggregation performance with the ink. .

  In the treatment liquid according to the present invention, the addition amount of the component for aggregating the pigment and polymer fine particles of the ink is preferably 0.01% by weight or more and 20% by weight or less with respect to the total weight of the liquid. When the amount is 0.01% by weight or less, concentration dispersion does not proceed sufficiently when the treatment liquid and the ink are in contact with each other, and an agglomeration effect due to pH change may not occur sufficiently. On the other hand, if it is 20% by weight or more, the dischargeability from the ink jet head may deteriorate.

  The treatment liquid according to the present invention preferably contains water and other additive-soluble organic solvents for the purpose of preventing clogging of the nozzles of the inkjet head due to drying. Such water and other additive-soluble organic solvents include wetting agents and penetrants.

  These solvents can be used alone or in combination with water and other additives.

  The content of water and other additive-soluble organic solvents is preferably 60% by weight or less based on the total weight of the treatment liquid. When the amount is more than 60% by weight or more, the viscosity of the treatment liquid increases, and the dischargeability from the inkjet head may deteriorate.

  The treatment liquid may further contain a resin component in order to improve fixability and abrasion resistance. The resin component may be any resin component that does not impair the ejection properties from the head when the treatment liquid is ejected by the ink jet method and has storage stability, and water-soluble resins and resin emulsions can be used freely.

  Examples of the resin component include acrylic, urethane, polyester, vinyl, and styrene. In order to sufficiently develop the function of improving the fixing property, it is necessary to add a relatively high polymer to a high concentration of 1% by weight to 20% by weight. However, if it is attempted to dissolve the above material in a liquid and add it, the viscosity becomes high, and the discharge property is lowered. In order to add an appropriate material at a high concentration and suppress an increase in viscosity, a means of adding as a latex is effective. Latex materials include alkyl acrylate copolymers, carboxy-modified SBR (styrene-butadiene latex), SIR (styrene-isoprene) latex, MBR (methyl methacrylate-butadiene latex), NBR (acrylonitrile-butadiene latex), and the like. Conceivable. The glass transition point Tg of the latex is a value that has a strong influence upon fixing in the process, and is preferably 50 ° C. or higher and 120 ° C. or lower in order to achieve both stability at room temperature storage and transferability after heating. Further, the minimum film-forming temperature MFT is a value that has a strong influence upon fixing in the process, and is 100 ° C. or lower, more preferably 50 ° C. or lower in order to obtain sufficient fixing at a low temperature.

  The coagulability may be further enhanced by adding polymer fine particles having a polarity opposite to that of the ink to the treatment liquid and aggregating with the pigment and polymer fine particles in the ink.

  In addition, a curing agent corresponding to the polymer fine particle component contained in the ink is contained in the treatment liquid, and after the two liquids contact, the resin emulsion in the ink component aggregates and crosslinks or polymerizes to increase the cohesiveness. Also good.

  The treatment liquid according to the present invention can contain a surfactant.

  Examples of surfactants include fatty acid salts, alkyl sulfate esters, alkyl benzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate ester salts, naphthalene sulfonate formalin condensates, Anionic surfactants such as oxyethylene alkyl sulfate esters, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkylamines Nonionic surfactants such as glycerin fatty acid ester and oxyethyleneoxypropylene block copolymer are preferred. Further, SURFYNOLS (Air Products & Chemicals), which is an acetylene-based polyoxyethylene oxide surfactant, is also preferably used. An amine oxide type amphoteric surfactant such as N, N-dimethyl-N-alkylamine oxide is also preferred.

  Further, pages (37) to (38) of JP-A-59-157636, Research Disclosure No. The surfactants described in 308119 (1989) can also be used. In addition, fluorine (fluorinated alkyl) and silicone surfactants as described in JP-A Nos. 2003-322926, 2004-325707, and 2004-309806 are also used. Can do. These surface tension modifiers can also be used as antifoaming agents, and fluorine-based, silicone-based compounds, chelating agents represented by EDTA, and the like can also be used.

  This is effective in reducing the surface tension and increasing the wettability on the recording medium. Further, even when ink is ejected in advance, the wettability on the ink is enhanced, and the cohesive action is effectively promoted by increasing the contact area of the two liquids.

  The surface tension of the treatment liquid according to the present invention is preferably 10 to 50 mN / m. From the viewpoint of coexistence of penetrability into a permeable recording medium, fine droplet formation, and dischargeability, 15 More preferably, it is -45 mN / m.

  The viscosity of the treatment liquid according to the present invention is preferably 1.0 to 20.0 cP.

  In addition, pH buffering agents, antioxidants, fungicides, viscosity modifiers, conductive agents, ultraviolet rays, absorbents, and the like can be added as necessary.

〔recoding media〕
The recording medium used in the present invention is not particularly limited, but a particularly preferable result can be obtained with respect to the coated paper for printing in which the penetration of the ink solvent is slow.

  Examples of the support that can be suitably used for coated paper include: chemical pulp such as LBKP and NBKP; mechanical pulp such as GP, PGW, RMP, TMP, CTMP, CMP, and CGP; wood pulp such as waste paper pulp such as DIP And a pigment as a main component, and one or more kinds of additives such as a binder, a sizing agent, a fixing agent, a yield improver, a cationizing agent, and a paper strength enhancer are mixed together to produce a long net paper machine, circular net paper machine. Base paper manufactured using various machines such as a machine, twin-wire paper machine, base paper provided with size press or anchor coat layer using starch, polyvinyl alcohol, etc., or of these size press or anchor coat layer Examples thereof include coated paper such as art paper, coated paper, cast coated paper and the like, on which a coating layer is provided.

  In the method of the present invention, these base papers or coated papers may be used as they are, or for example, a calendar process is performed using a machine calendar, a TG calendar, a soft calendar, or the like, and the flattening is controlled. May be used.

The basis weight of the support is usually about 40 to 300 g / m ² , but is not particularly limited. The coated paper used in the present invention is coated with a coating layer on the support as described above. The coating layer is composed of a coating composition mainly composed of a pigment and a binder, and is coated on at least one layer on the support.

  As the pigment, a white pigment can be preferably used. Examples of such white pigments include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, Inorganic pigments such as diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, hydrous halloysite, magnesium hydroxide; styrene plastic pigments, Examples thereof include organic pigments such as acrylic plastic pigment, polyethylene, microcapsule, urea resin, melamine resin.

Examples of the binder include starch derivatives such as oxidized starch, etherified starch, and phosphate esterified starch; cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; casein, gelatin, soybean protein, polyvinyl alcohol or derivatives thereof; various saponification degrees Polyvinyl alcohol or various derivatives thereof such as silanol-modified products, carboxylated products, and cationized products thereof; conjugated diene copolymer latexes such as polyvinylpyrrolidone, maleic anhydride resin, styrene-butadiene copolymer, and methyl methacrylate-butadiene copolymer Acrylic polymer latex such as polymer or copolymer of acrylic acid ester and methacrylic acid ester; vinyl polymer latex such as ethylene vinyl acetate copolymer; Functional group-modified polymer latex with functional group-containing monomers such as xy groups; water-based adhesives such as thermosetting synthetic resins such as melamine resins and urea resins; acrylics such as polymethyl methacrylate; acid esters; Polymer or copolymer resin; Synthetic resin adhesives such as polyurethane resin, unsaturated polyester resin, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, alkyd resin, and the like.
The blending ratio of the pigment and binder in the coating layer is 3 to 70 parts by weight, preferably 5 to 50 parts by weight, based on 100 parts by weight of the pigment. When the blending ratio of the binder with respect to 100 parts by weight of the pigment is less than 3 parts by weight, the coating strength of the ink receiving layer made of such a coating composition may be insufficient. On the other hand, when the blending ratio exceeds 70 parts by weight, the absorption of the high boiling point solvent becomes extremely slow.

  Further, the coating layer includes, for example, a dye fixing agent, a pigment dispersant, a thickener, a fluidity improver, an antifoaming agent, a foam suppressor, a release agent, a foaming agent, a penetrating agent, a coloring dye, a coloring pigment, Various additives such as a fluorescent whitening agent, an ultraviolet absorber, an antioxidant, an antiseptic, an antibacterial agent, a water resistant agent, a wet paper strength enhancer, and a dry paper strength enhancer can be appropriately blended.

The coating amount of the ink receiving layer varies depending on the required gloss, ink absorbability, type of support, etc., and cannot be generally stated, but is usually 1 g / m ² or more. Further, the ink receiving layer may be applied by dividing a certain coating amount into two portions. When coating is performed in two steps in this way, the gloss is improved as compared with the case where the same coating amount is applied once.

  Coating of the coating layer is performed by using various devices such as various blade coaters, roll coaters, air knife coaters, bar coaters, rod blade coaters, curtain coaters, short dwell coaters, and size presses on-machine or off-machine. be able to. Further, after coating the coating layer, the ink receiving layer may be flattened using a calendar device such as a machine calendar, a TG calendar, or a soft calendar.

  In addition, the number of coat layers can be appropriately determined as necessary.

  Coated paper includes art paper, high-quality coated paper, medium-quality coated paper, high-quality lightweight coated paper, medium-sized lightweight coated paper, and fine-coated printing paper. The coating amount of the coating layer is about 40 g / m2 on both sides of art paper. High-quality coated paper and medium-sized coated paper have a double-sided surface of about 20 g / m2, and high-quality lightweight coated paper and medium-sized and lightweight coated paper have a double-sided surface of about 15 g / m2. Examples of art paper include Tokuhishi Art, Ulite as high-quality coated paper, Tohoku Art (made by Mitsubishi Paper Industries), satin Kinto (made by Oji Paper Co., Ltd.), etc. as art paper, Examples of coated paper include OK Top Coat (Oji Paper Co., Ltd.), Aurora Coat (Nippon Paper Co., Ltd.), and Recycle Coat T-6 (Nippon Paper Co., Ltd.). , New V mat (Mitsubishi Paper Co., Ltd.), New Age (Oji Paper Co., Ltd.), Recycle Mat T-6 (Nihon Paper Co., Ltd.), Pisum (Nihon Paper Co., Ltd.). Examples of the fine coated printing paper include Aurora L (manufactured by Nippon Paper Industries Co., Ltd.), Kinmari Hi-L (manufactured by Hokuetsu Paper Industries Co., Ltd.) and the like. Further, examples of the cast coated paper include SA Kanto Plus (manufactured by Oji Paper Co., Ltd.), Hi McKinley Art (manufactured by Gojo Paper Co., Ltd.), and the like.

[Image forming apparatus]
First, a basic process of the image forming method according to the present invention will be described with reference to FIG. FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus according to the present invention.

  An image forming apparatus (inkjet recording apparatus) 10 shown in FIG. 1 mainly includes a processing liquid application section 14, a processing liquid drying section 16, and an ink ejection section in order from the upstream side in the transport direction (sub-scanning direction) of the recording medium 12. 18 and an ink drying unit 20 and a contact solvent removing unit 22.

  The recording medium 12 is held on an endless conveying belt 28 that is stretched between rollers 24 and 26, and is conveyed from left to right in FIG. The conveyance method of the recording medium is not limited to the belt method as shown in FIG. 1. For example, various methods such as a method of conveying the recording medium in close contact with the surface (circumferential surface) of the drum-like member are applied. Is possible.

  The treatment liquid application unit 14 applies the treatment liquid onto the recording medium 12 before the ink droplets are ejected by the ink ejection unit 18 arranged on the downstream side in the sub-scanning direction. The method for applying the treatment liquid is not particularly limited, and for example, a coating method using a coating roller or the like, a spray method, an ink jet recording method, and other various methods can be applied. Among these, an embodiment in which a treatment liquid (droplet) is ejected using an ink jet recording type recording head (inkjet head) is preferable, and the treatment liquid can be selectively applied to a position where ink is ejected. , Drying time can be shortened and heating energy can be reduced.

  The processing liquid drying unit 16 is disposed downstream of the processing liquid application unit 14 in the sub-scanning direction, and heats and drys the processing liquid applied to the recording medium 12. At this time, it is preferable that the drying is performed so that a solid or semi-solid aggregation treatment agent layer (a thin film layer obtained by drying the treatment liquid) is formed on the surface of the recording medium 12. As will be described later, it is possible to prevent image degradation due to color material movement. The method for drying the treatment liquid is not particularly limited. For example, a method (hot air drying method) that includes a hot air dryer capable of controlling the temperature and air volume within a predetermined range and blows hot air onto the treatment liquid on the recording medium 12. ) Is preferred. Further, in combination with or alone with the hot air drying method, a heater (for example, a flat plate heater) 30 is provided inside the conveyor belt 28 and is heated from the back surface (the surface opposite to the image forming surface) of the recording medium 12. A method (back surface heating method) is also suitable.

  In this specification, “solid or semi-solid solution aggregation treatment agent (aggregation treatment agent layer)” means a range in which the solvent content of the aggregation treatment agent (aggregation treatment agent layer) defined below is 0 to 70%. Refers to things.

  The “aggregation treatment agent” is used not only in a solid or semi-solid solution but also in a broad concept including other liquids, and particularly in a liquid state with a solvent content of 70% or more. The aggregating agent thus obtained is referred to as “aggregating treatment liquid” or simply “treatment liquid”.

  As a method for calculating the solvent content of the aggregating agent, a paper having a predetermined size (for example, 100 mm × 100 mm) is cut out, and the total weight after applying the treatment liquid (paper + pre-drying treatment liquid) and the total after the treatment liquid is dried. The weight (paper + post-drying treatment liquid) is measured, and the solvent reduction amount (solvent evaporation) due to drying is obtained from the difference between them. Moreover, what is necessary is just to use the calculated value calculated | required from the preparation prescription of a process liquid as the amount of solvents contained in the process liquid before drying. The solvent content can be obtained from these calculation results.

  As shown in FIG. 2A, when the ink droplet 42 is ejected in a state where the liquid layer (processing liquid layer) 40 of the processing liquid exists on the surface of the recording medium 12, the processing liquid layer 40 enters the processing liquid layer 40. The ink color material (ink dot) 44 floats and moves, causing deterioration in image quality. On the other hand, as shown in FIG. 2B, before the ink droplet 42 is ejected, the treatment liquid on the recording medium 12 is heated and dried to form a solid or liquid on the surface of the recording medium 12. By forming the semisolid solution aggregation treatment agent layer 40 ′, the ejected ink droplets 42 land on the solid or semisolid solution aggregation treatment agent layer 40 ′, and from the contact surface thereof. Since the agglutination reaction is started, sufficient adhesion can be obtained, and image deterioration due to color material movement (dot floating) can be prevented.

  Here, Table 1 shows the evaluation results of the color material movement when the solvent content of the treatment liquid (aggregation treatment agent layer) on the recording medium 12 is changed.

  As shown in Table 1, when the treatment liquid is not dried (Experiment 1), image degradation occurs due to color material movement.

  On the other hand, when the treatment liquid is dried (Experiments 2 to 5), when the treatment liquid is dried until the solvent content of the treatment liquid becomes 70% or less, the color material movement becomes inconspicuous, and further 50%. It was confirmed that when the treatment liquid was dried to the following level, the color material movement could not be confirmed by visual observation, and it was effective in preventing image deterioration.

In this way, heat drying is performed until the solvent content of the treatment liquid (aggregation treatment agent) on the recording medium 12 is 70% or less (preferably 50% or less), and the solid or semi-solid solution is formed on the recording medium 12. By forming the aggregating agent layer, it is possible to prevent image deterioration due to color material movement and obtain a high-quality image.
The ink droplet ejecting section 18 is an inkjet recording head (hereinafter referred to as “ink ejection head”) 18C corresponding to each color ink of cyan (C), magenta (M), yellow (Y), and black (K). 18M, 18Y, and 18K are provided, and corresponding color ink droplets are ejected from the nozzles of the respective ink ejection heads 18C, 18M, 18Y, and 18K in accordance with input image data. In this example, the ejection volume (droplet ejection amount) of the ink droplets ejected from each nozzle is 2 pl, and the main scanning direction (direction perpendicular to the conveyance direction of the recording medium 12) and the sub-scanning direction (of the recording medium 12). The recording density (droplet ejection density) in the transport direction is 1200 dpi.

  The ink drying unit 20 is disposed on the downstream side in the sub-scanning direction of the ink droplet ejection unit 18 and heats and drys the ink layer on the recording medium 12. The ink drying method is not particularly limited, but a method of blowing hot air onto the ink layer on the recording medium 12 (hot air drying method) is preferable, as with the treatment liquid drying unit 16. Further, in combination with the hot air drying method, or alone, a heater (for example, a flat plate heater) 32 is provided on the back surface (surface opposite to the image forming surface) side of the recording medium 12, and from the back surface side of the recording medium 12. A heating method (back surface heating method) is also suitable. In this example, while the back surface side of the recording medium 12 is heated to 60 ° C. using the heater 32, hot air of 70 ° C. is blown onto the surface side of the recording medium 12 for 2 seconds from the hot air dryer (blower). Dry the upper ink layer.

  The contact solvent removing unit 22 is brought into contact with an ink layer on the recording medium 12 by bringing a solvent removing roller (corresponding to “contact type solvent removing means” of the present invention) whose surface is formed of a porous member into contact with the ink layer on the recording medium 12. Absorb and remove residual solvent (especially high boiling point solvent) remaining on the top. In this example, a metal roller (roller diameter φ40 mm) coated with a porous member (Ecolon sheet manufactured by Tosho Rubber Co., Ltd .; hole diameter φ10 μm, thickness 3.0 mm) is used as the solvent removal roller. The nip pressure of the solvent removal roller with respect to the recording medium 12 is 0.3 MPa.

  A mode in which a fixing unit (not shown) is provided downstream of the contact solvent removing unit 22 in the sub-scanning direction is also preferable. For example, the image formed on the recording medium 12 is fixed while the recording medium 12 is heated and pressurized with a heating roller whose temperature can be controlled within a predetermined range. Thereby, the abrasion resistance of the image can be improved, and a preferable image quality can be obtained. The heating temperature of the heating roller is preferably set according to the glass transition temperature of the polymer fine particles contained in the treatment liquid or ink. Further, a plurality of heating rollers may be provided to fix the image formed on the recording medium 12 in a stepwise manner.

  Next, the operation of the image forming apparatus 10 shown in FIG. 1 will be described with reference to FIG. FIG. 3 is a diagram schematically showing a state from the application of the treatment liquid to the recording medium until the fixing is performed, and a part of the state in which the ink aggregate (coloring material aggregate) is formed. Exaggerated expression. Note that FIG. 3 shows a case where coated paper for printing is used as the recording medium, and shows a state in which a part of the solvent component of the treatment liquid or ink penetrates into the recording medium.

  First, the recording medium 12 held on the conveyance belt 28 is conveyed in the sub-scanning direction (the direction from the left to the right in FIG. 1) and passes through the treatment liquid application unit 14, so that the treatment liquid is placed on the recording medium 12. Is applied (treatment liquid application step). Subsequently, when the recording medium 12 passes through the processing liquid drying unit 16, the processing liquid on the recording medium 12 is heated and dried, and the solvent component (mainly moisture) of the processing liquid on the recording medium 12 evaporates ( Treatment liquid drying step). As a result, as shown in FIG. 3A, a treatment liquid layer (preferably a solid or semi-solid aggregation treatment agent layer) 50 is formed on the recording medium 12.

  Next, when the recording medium 12 passes through the ink ejection heads 18C, 18M, 18Y, and 18K in the ink droplet ejection unit 18, the ink droplets of the respective colors are ejected from the ink ejection heads 18C, 18M, 18Y, and 18K. Are ejected onto the recording medium 12 (ink ejection step). As a result, as shown in FIG. 3B, an ink layer (a liquid layer made of a mixture of ink and processing liquid) 52 is formed on the recording medium 12. At this time, an ink aggregate (color material aggregate) 54 is formed in the ink layer 52 by reaction with the treatment liquid.

  When a solid or semi-solid aggregation treatment agent layer is formed on the surface of the recording medium 12, ink droplets ejected from the respective ink ejection heads 18C, 18M, 18Y, 18K It lands on the surface of the solid or semi-solid agglomeration treatment agent layer formed in (1). At this time, due to the balance between the flying energy and the surface energy, the contact surface between the ink droplet and the aggregating agent layer lands in a predetermined area. The aggregation reaction starts immediately after the ink droplets land on the aggregation treatment agent layer, and the aggregation reaction starts from the contact surface between the ink droplets and the aggregation treatment agent layer. The agglomeration reaction occurs only in the vicinity of the contact surface, and the color material in the ink is agglomerated in a state where the adhesive force is obtained with a predetermined contact area at the time of ink landing, so that the color material movement is suppressed.

  Even if other ink droplets land adjacent to this ink droplet, the color material of the ink that has landed first is already agglomerated, so the color materials do not mix with the ink that landed later, Bleed is suppressed. After the color material is aggregated, the separated ink solvent spreads, and a liquid layer (ink layer) in which the aggregation treatment agent is dissolved is formed on the recording medium 12.

  Next, when the recording medium 12 passes through the ink drying unit 20, the ink layer 52 on the recording medium 12 is heated and dried, and the ink layer 52 on the recording medium 12 is dried as shown in FIG. The solvent component (mainly moisture) evaporates (ink drying process). At this time, the high boiling point solvent in the ink layer 52 is increased in concentration without evaporating, the viscosity increases, and the permeability to the recording medium 12 decreases. For this reason, the high boiling point solvent does not penetrate into the recording medium 12 and remains in the ink layer 52 to cause stickiness and cause blocking. On the other hand, if the time (interval) from ink ejection to heat drying is increased, the high-boiling point solvent can penetrate into the recording medium in the form of an aqueous solution, but the productivity is greatly increased. It becomes a factor to decrease.

  Therefore, in the present invention, after the ink layer 52 on the recording medium 12 is heated and dried as described above, the recording medium 12 further passes through the contact solvent removing unit 22 disposed on the downstream side in the sub-scanning direction. At this time, as shown in FIG. 3D, the solvent removing roller 56 is brought into contact with the ink layer 52 of the recording medium 12 and the capillary force of the porous body constituting the surface of the solvent removing roller 56 is used to record the recording medium. The residual solvent (especially high boiling point solvent) remaining on 12 is absorbed and removed (contact solvent removal step). The solvent component removed by the contact solvent removing unit 22 is not limited to the high boiling point solvent, and other solvent components (such as moisture) remaining on the recording medium 12 without being evaporated by the ink drying unit 20 are also included. included.

  As described above, in the present invention, by heating and drying the ink layer 52 on the recording medium 12, the amount of moisture penetrating into the recording medium 12 can be suppressed and curling of the recording medium 12 can be prevented. Further, since the residual solvent (particularly the high boiling point solvent) remaining on the recording medium 12 is absorbed and removed by the solvent removal roller 56, stickiness of the ink layer (ink image) 52 caused by the high boiling point solvent is suppressed, and the recording medium 12 is removed. Can be prevented.

  Further, since the water is evaporated from the ink layer 52 on the recording medium 12 to improve the cohesive force of the color material, the solvent removal roller 56 absorbs and removes the residual solvent. Material adhesion can be prevented. As a result, it is possible to prevent image deterioration due to redeposition of the color material from the solvent removal roller 56 to the recording medium 12.

  In the case where a fixing unit (not shown) is provided on the downstream side in the sub-scanning direction of the contact solvent removing unit 22, the residual solvent on the recording medium 12 is absorbed and removed by the solvent removing roller 56 and then the fixing unit. When the recording medium 12 passes through the recording medium 12, as shown in FIG. 3E, the heating roller 58 heats and presses the recording medium 12, and the image formed on the recording medium 12 is fixed (fixing). Process).

  In the present invention, it is preferable that the time (ink droplet ejection / drying interval) from when an ink droplet is deposited on the recording medium 12 to when heat drying is performed is as short as possible. By quickly evaporating the solvent component (mainly moisture) of the ink layer 54 on the recording medium 12, the amount of moisture permeating into the recording medium 12 can be reduced, and curling of the recording medium 12 can be reliably prevented. According to the results of an evaluation experiment described later, the ink droplet ejection / drying interval is within 10 seconds, more preferably within 1 second.

  In the present invention, the solvent of the ink layer (ink image) 52 on the recording medium 12 after the contact solvent removing step is performed (that is, after the residual solvent on the recording medium 12 is absorbed and removed by the solvent removing roller 56). The content is preferably as low as possible, and the recording medium 12 can be reliably prevented from blocking. According to the results of the evaluation experiment described later, the preferable range of the solvent content of the ink layer is 50% or less (more preferably 30% or less, still more preferably 20% or less).

  As described above, the recording medium used in the present invention is not particularly limited, but a particularly preferable result can be obtained with respect to the coated paper for printing in which the penetration of the ink solvent is slow. That is, if the ink layer on the coated paper for printing (slowly osmotic medium) is only heated and dried to evaporate the water, the ink layer remains on the recording medium due to an increase in the viscosity of the high boiling point solvent, and the ink layer tends to become sticky. If the ink layer is not heated and dried, moisture permeates the recording medium and curling is likely to occur. On the other hand, according to the present invention, the solvent component (mainly moisture) of the ink layer on the recording medium is evaporated by heating, and the high boiling point solvent is removed from the recording medium. Blocking can be reliably prevented.

[Evaluation experiment]
Next, an evaluation experiment related to the present invention will be described.

  The composition of the treatment liquid and ink used in this evaluation experiment is shown below.

<Processing liquid>
-10 parts by weight of malonic acid-1.8 parts by weight of sodium hydroxide-20 parts by weight of diethylene glycol monoethyl ether-1 part by weight of surfactant 1-remainder of ion-exchanged water The above-mentioned surfactant 1 is represented by the following chemical formula Is done.

<Ink>
-Pigment 1 4 parts by mass-Dispersant polymer 1 2 parts by mass-Resin emulsion 8 parts by mass-Glycerin 15 parts by mass-Surfactant 2 1 part by mass-Remaining ion-exchanged water The details of each of the above components are as follows: is there.

Pigment 1: Cromophtal jet Magenta DMQ (PR-122)
(Ciba Specialty Chemicals)
Dispersant polymer 1:
Benzyl methacrylate / methyl methacrylate / methacrylic acid
60/30/10 (mass ratio)
Resin emulsion 1:
Methyl methacrylate / Phenoxyethyl acrylate / Acrylic acid
60/35/5 (mass ratio)
Surfactant 2: Olfine E1010 (manufactured by Nissin Chemical Industry)
Moreover, the experimental conditions of this evaluation experiment are shown below.

Recording medium (base material): Tokishi Art, manufactured by Mitsubishi Paper Industries Co., Ltd. Treatment liquid application: Injecting treatment liquid with an inkjet head (treatment liquid application amount per unit area 2.5 g / m ² )
Treatment liquid drying: Backside heater 40 ° C. + Blower (hot air dryer) Heat drying for 2 seconds at 70 ° C. Ink droplet ejection: Ink droplet ejection with an inkjet head (ink application amount 10.0 g / m ² per unit area)
Ink drying: Heat drying for 5 seconds at an air temperature of 70 ° C. and a back surface heater temperature of 60 ° C. Contact solvent removal: a metal roller (roller diameter φ40 mm) and a porous member (Ecolo sheet manufactured by Tosho Rubber Co., Ltd .; pore diameter φ40 mm, thickness 3. 0 mm) is contacted with a solvent removal roller (porous roller) coated with NIP time (pressurization time) of 10 msec. The evaluation results of this evaluation experiment are shown in FIGS. Evaluation methods and evaluation criteria for the respective evaluation items shown in FIGS. 4 to 7 are shown below.

<Roller color material adhesion>
After 1000 sheets of solid images drawn with an ink application amount of 10.0 g / m ² per unit area were passed through and the contact solvent was removed, the optical density on the surface of the solvent removal roller was measured using an optical densitometer Xrite 938. The color material adhesion amount was evaluated (with reference to the light reflectance before use of 1).

A: Optical density of 0.04 or less (color material adhesion does not occur at all, which is very preferable)
○: Optical density 0.07 or less (color material adhesion hardly occurs)
Δ: Optical density 0.07 to 0.1 (There is some color material adhesion, but it is a practical level)
X: Optical density 0.1 (Color material adhesion is large, roller durability is insufficient)
<Blocking>
A solid image drawn with an ink application amount of 10.0 g / m ² per unit area is printed, and a plain paper is layered on the image immediately after printing, and sandwiched between two acrylic plates and pressed with a 10 kG weight from above. . After leaving for 1 hour, the acrylic plate was removed, and the degree of color material transfer and adhesion was confirmed while peeling the stacked samples by hand. The paper was A4 size and was performed in an environment of 23 ° C. and 50 RH.

A: Color material transfer and paper adhesion do not occur at all. ○: Color material transfer and paper adhesion are very slight. Occurs and the surface of the printed surface deteriorates, or the paper does not adhere and peel off <Curl>
In a solid part drawn with an ink application amount of 10.0 g / m ² per unit area, the paper is cut into 50 mm × 5 mm (the short direction is along the eyes of the paper fibers) in an environment of 23 ° C. and 50 RH. Left for 3 hours. The curvature R [m] of the subsequent paper was measured, and the curl value was calculated as C = 1 / R.

A: C <5 (curling does not occur at all, which is very preferable)
○: C <10 (curl is hardly generated and there is no problem in quality)
Δ: 10 <C <30 (curling slightly generated)
×: 30 <C (large curl generation)
<Abrasion resistance>
In a solid portion drawn with an ink application amount of 10.0 g / m ² , a special diamond art paper is covered from above in an environment of 25 ° C. and 50 RH, and rubbed 20 times with a load of 1.5 kg / cm ² , and the color of the coated sample The material peeling state was visually evaluated.

◎: Color material peeling at the rubbed part is not known at all ○: Color material peeling is hardly seen at the rubbed part, and there is no problem in appearance △: Color material peeling is recognized at the rubbed part, but is allowed Range x: There is a portion exposed to the white background of the art paper surface, outside the allowable range. FIG. 4 shows the evaluation results when the presence or absence of the ink drying step and the contact solvent removal step and the order are changed. In FIG. 4, “droplet-to-dry interval” represents the time (ink droplet / dry interval) from when an ink droplet is deposited onto a recording medium until the ink layer is heated and dried. “Contact solvent removal” represents a contact solvent removal step, and “heat drying” represents an ink drying step. For example, Comparative Example 4 is performed in the order of the contact solvent removal step and the ink drying step. Example 1 means that the ink drying step and the contact solvent removal step are performed in this order.

  Comparative Example 1 is a case where neither the ink drying process nor the contact solvent removing process is performed, and the occurrence of blocking and paper curling was remarkable.

  Comparative Example 2 is a case where only the ink drying process is performed, and paper curl can be reduced by evaporating moisture, but blocking is caused by the influence of the high boiling point solvent remaining in the ink layer.

  Comparative Example 3 was a case where the contact solvent removal step was performed without performing the ink drying step, and the result was that the color material adhesion to the solvent removal roller deteriorated. This is presumably because the ink layer has a high solvent content and the ink aggregate structure is in a fragile state. Comparative Example 4 is a case where the contact solvent removal step and the ink drying step are performed in this order, and the result is that coloring material adheres to the solvent removal roller for the same reason as in Comparative Example 3.

  On the other hand, Example 1 is a case where the ink drying step and the contact solvent removing step are performed in this order, and all the favorable results are shown for the evaluation items of roller coloring material adhesion, blocking, and paper curl. I understood that. The reason why the color material adheres well to the solvent removal roller is considered to be because the water in the ink layer is evaporated by heat drying and aggregation is progressing. Regarding blocking, it is considered that the stickiness of the ink layer is eliminated by absorbing and removing the high boiling point solvent remaining in the ink layer.

  Further, in FIG. 4, the effect when the ink droplet ejection / drying interval is changed is also evaluated.

  In the case where the ink drying process and the solvent removal process are performed in this order, when the ink droplet ejection / drying interval is 1 second, paper curling hardly occurs (Example 1). Further, when the ink droplet ejection / drying interval is 10 seconds, the paper curl slightly occurs but is within an allowable range (Example 2). On the other hand, when the ink ejection / drying interval was 60 seconds, paper curling was greatly generated (Comparative Example 5). This is presumably because the amount of moisture penetrating into the paper increases before drying.

  As described above, according to the present invention, after ink droplets are deposited on a recording medium, the ink layer on the recording medium is heated and dried to evaporate the solvent component (mainly moisture) of the ink layer. Therefore, the amount of moisture penetrating into the recording medium can be reduced, and curling of the recording medium can be prevented. Further, after the ink layer on the recording medium is heated and dried, the residual solvent remaining on the recording medium (particularly, the high boiling point solvent) is absorbed and removed by a solvent removal roller, whereby the ink layer caused by the high boiling point solvent is removed. The occurrence of stickiness can be suppressed, and as a result, blocking of the recording medium can be prevented.

  In addition, the residual solvent is contacted and removed by the solvent removal roller in a state where the water in the ink layer is evaporated by heat drying and the aggregation of the ink coloring material is advanced, so that the coloring material is prevented from adhering to the solvent removal roller. Can do. For this reason, it is possible to prevent image deterioration due to reattachment of the color material from the solvent removing means to the recording medium.

  Further, the ink droplet ejection / drying interval is preferably within 10 seconds (more preferably within 1 second), the amount of moisture penetrating into the recording medium can be suppressed, and the curling prevention effect of the recording medium can be enhanced.

  FIG. 5 shows the evaluation results when the solvent content of the ink layer after the contact solvent removing step is changed. Here, as in the first and second embodiments shown in FIG. 4, the ink drying step and the contact solvent removal step are performed in this order, and the residual solvent by the solvent removal roller is controlled by controlling the contact time of the solvent removal roller. The solvent content of the ink layer after the removal of was changed. The contact time of the solvent removal roller can be controlled by controlling the nip pressure (nip area) of the solvent removal roller with respect to the recording medium. In addition, regarding the measurement of the solvent content of the ink layer, the ink layer after printing was scraped off with a knife, the high boiling point solvent was extracted, and quantified by gas chromatography.

  In FIG. 5, Example 3 is a case where the solvent content of the ink layer after removal of the solvent is 80%. Although blocking occurs somewhat, a more preferable result is obtained as compared with Comparative Example 2 shown in FIG. Obtained. This is considered to be because, although the total amount of the high boiling point solvent removed is never large, the stickiness is reduced by reducing the high boiling point solvent on the outermost surface of the ink layer.

  Examples 4 to 6 are cases where the solvent content of the ink layer after contact removal was 50%, 30%, and 17%, respectively. Thus, when the solvent content of the ink layer is reduced to 50% or less (more preferably 30% or less, and still more preferably 20% or less), a favorable result regarding blocking can be obtained.

  FIG. 6 shows the evaluation results when the presence or absence of the treatment liquid drying step is changed. Example 1 in FIG. 6 is a reproduction of Example 1 in FIG.

  In FIG. 6, Example 7 is a case where the treatment liquid drying step was performed, and a more preferable result than Example 1 could be obtained. Here, as the treatment liquid drying step, heat drying was performed for 1 second at an air temperature of 70 ° C. and a back surface heater temperature of 40 ° C.

  Regarding the color material adhering to the solvent removal roller, the processing liquid on the recording medium is heated and dried to evaporate the solvent component (mainly water) of the processing liquid. This is presumably because the adhesion of the recording medium (base material) is strong. Regarding paper curl, it is considered that curling is further improved by drying the treatment liquid before moisture contained in the treatment liquid penetrates into the recording medium.

  FIG. 7 shows the evaluation results when the presence or absence of the contact solvent removal step and the fixing step is changed. Note that Example 1 in FIG. 7 is a reprint of Example 1 in FIG. Here, as a fixing process, a hot-pressing roller (a metal roller having a diameter of 40 mm and covered with silicon rubber having a thickness of 1 mm) was pressed at a roller temperature of 80 ° C. and a pressure of 1.2 MPa. In the fixing step, the purpose is to make the ink layer into a film by applying pressure while melting the resin emulsion in the ink so as to have abrasion resistance.

  In FIG. 7, Example 1 is a case where the fixing step (hot pressure fixing) is not performed, and in the ink drying step, the ink layer is formed to some extent, so that a certain rub resistance is ensured. .

  In Example 8, the ink drying step and the contact removal step were sequentially performed, and further the fixing step (hot-pressure fixing) was performed. Compared to Comparative Example 6, better abrasion resistance was obtained. This is presumably because the high-boiling point solvent in the ink layer was removed by the contact solvent removal step, and thus the ink layer was more firmly formed at the time of heating and pressurization by the heating roller. Also, from the viewpoint of print image quality, a good printed material with a more glossy feeling was obtained.

[Other Embodiments]
FIG. 8 is a schematic configuration diagram showing another embodiment of the image forming apparatus according to the present invention.

  An image forming apparatus (inkjet recording apparatus) 100 shown in FIG. 8 is a recording apparatus to which a two-liquid aggregation method for forming an image on a recording medium 114 using ink and a processing liquid (aggregation processing liquid) is applied. The image forming apparatus 100 mainly includes a paper supply unit 102 that supplies a recording medium 114, a processing liquid application unit 104 that applies a processing liquid to the recording medium 114, and ink droplets that eject color ink onto the recording medium 114. Part (printing part) 106, solvent removing part 108 for removing the solvent component (liquid component) on the recording medium 114, fixing part 110 for fixing the image formed on the recording medium 114, and an image are formed. And a paper discharge unit 112 that conveys and discharges the recording medium 114.

  The paper feed unit 102 is provided with a paper feed stand 120 on which the recording media 114 are stacked. A feeder board 122 is connected in front of the paper feed tray 120 (left side in FIG. 1), and the recording media 114 stacked on the paper feed tray 120 are sent to the feeder board 122 one by one in order from the top. The recording medium 114 sent to the feeder board 122 is transferred to the pressure drum (processing liquid drum) 126a of the processing liquid application unit 104 via the transfer cylinder 124a.

  Although not shown, a holding claw (gripper) that holds the tip of the recording medium 114 and a suction port are formed on the surface (circumferential surface) of the pressure drum 126a, and the pressure drum 126a is transferred from the transfer drum 124a to the pressure drum 126a. The recorded recording medium 114 is rotated in the direction of rotation of the impression cylinder 126a (in FIG. 1 opposite to that of the impression cylinder 126a) while being in close contact with the surface of the impression cylinder 126a while being held by the holding claws. (Clockwise direction). The same configuration is applied to other impression cylinders 126b to 126d described later.

  In the treatment liquid application unit 104, a sheet preheating unit 128 and a treatment liquid discharge head 130 are disposed at positions facing the surface of the pressure drum 126 a in order from the upstream side in the rotation direction of the pressure drum 126 a (counterclockwise direction in FIG. 8). , And a processing liquid drying unit 132 are provided.

  The paper preheating unit 128 and the treatment liquid drying unit 132 are each provided with a hot air dryer capable of controlling temperature and air volume within a predetermined range. When the recording medium 114 held on the impression cylinder 126a passes through a position facing the paper preheating unit 128 and the processing liquid drying unit 132, the air heated by the hot air dryer (hot air) is processed liquid on the recording medium 114. It is configured to be sprayed on.

  The treatment liquid ejection head 130 ejects treatment liquid onto the recording medium 114 held by the pressure drum 126a. Each of the ink ejection heads 136C, 136M, 136Y, 136K of the ink ejection section 106, which will be described later, The same configuration as 136R, 136G, and 136B is applied.

  In this example, an inkjet head is applied as a means for applying the treatment liquid to the surface of the recording medium 114. However, the present invention is not limited to this, and various methods such as a spray method and a coating method can also be applied. It is.

  The treatment liquid used in this example is contained in the ink ejected toward the recording medium 114 from each of the ink ejection heads 136C, 136M, 136Y, 136K, 136R, 136G, and 136B disposed in the ink ejection unit 106 at the subsequent stage. It is the acidic liquid which has the effect | action which agglomerates the coloring material which is made.

  The treatment liquid drying unit 132 is provided with a hot air dryer capable of controlling the temperature and the air volume within a predetermined range, and the recording medium 114 held on the impression cylinder 126a faces the hot air dryer of the treatment liquid drying unit 132. When passing through the position, air heated by a hot air dryer (hot air) is sprayed onto the processing liquid on the recording medium 114. In this example, the treatment liquid is dried by hot air at 80 ° C.

  The temperature and air volume of the hot air dryer are adjusted so that the processing liquid applied on the recording medium 114 is dried by the processing liquid discharge head 130 disposed on the upstream side in the rotation direction of the impression cylinder 126 a, and the solid on the surface of the recording medium 114 Or a semi-solid solution aggregation treatment agent layer (thin film layer in which the treatment liquid is dried) is set to such a value.

  As in this example, it is preferable that the recording medium 114 be preheated by the paper preheating unit 128 before the treatment liquid is applied onto the recording medium 114. In this case, the heating energy required for drying the treatment liquid can be kept low, and energy saving can be achieved.

  Following the treatment liquid application unit 104, an ink droplet ejection unit 106 is provided. A transfer cylinder 124b is provided between the pressure drum (processing liquid drum) 126a of the treatment liquid application unit 104 and the pressure drum 126b of the ink droplet ejection unit (drawing drum) 106 so as to be in contact with them. As a result, the recording medium 114 held on the pressure drum 126a of the treatment liquid application unit 104 is applied with the treatment liquid to form a treatment liquid layer (preferably a solid or semi-solid aggregation treatment agent layer). Then, the ink is transferred to the pressure drum 126b of the ink droplet ejection unit 106 via the transfer drum 124a.

  The ink ejection unit 106 corresponds to the seven colors of CMYKRGB at positions facing the surface of the pressure drum 126b in order from the upstream side in the rotation direction (counterclockwise direction in FIG. 8) of the pressure drum 126b. Ink discharge heads 136C, 136M, 136Y, 136K, 136R, 136G, and 136B are provided side by side.

  As each of the ink discharge heads 136C, 136M, 136Y, 136K, 136R, 136G, and 136B, an ink jet recording head (ink jet head) is applied in the same manner as the processing liquid discharge head 130 described above. That is, each of the ink discharge heads 136C, 136M, 136Y, 136K, 136R, 136G, and 136B discharges the corresponding color ink droplets toward the recording medium 114 held by the pressure drum 126b.

  The ink storage / loading unit (not shown) includes an ink tank that stores ink supplied to each of the ink ejection heads 136C, 136M, 136Y, 136K, 136R, 136G, and 136B. Each ink tank communicates with a corresponding head through a required flow path, and supplies a corresponding ink to each ink discharge head. The ink storage / loading unit includes notifying means (display means, warning sound generating means) for notifying when the remaining amount of liquid in the tank is low, and has a mechanism for preventing erroneous loading between colors. ing.

  Ink is supplied from each ink tank of the ink storage / loading unit to each of the ink discharge heads 136C, 136M, 136Y, 136K, 136R, 136G, and 136B, and 136C, 136M, 136Y, 136K, 136R, and 136G according to the image signal. The corresponding color ink is ejected from 136B onto the recording medium 114.

  Each of the ink discharge heads 136C, 136M, 136Y, 136K, 136R, 136G, and 136B has a length corresponding to the maximum width of the image forming area in the recording medium 114 held by the pressure drum 126b, and its ink discharge surface Is a full line type head in which a plurality of nozzles for ink ejection (not shown in FIG. 8, indicated by reference numeral 161 in FIG. 9) are arranged over the entire width of the image forming area. Each of the ink ejection heads 136C, 136M, 136Y, 136K, 136R, 136G, and 136B is fixedly installed so as to extend in a direction orthogonal to the rotation direction of the impression cylinder 126b (conveying direction of the recording medium 114).

  According to the configuration in which a full line head having a nozzle row covering the entire width of the image forming area of the recording medium 114 is provided for each ink color, the recording medium 114 and each ink in the transport direction (sub-scanning direction) of the recording medium 114 The primary image is formed on the image forming area of the recording medium 114 by performing the operation of relatively moving the ejection heads 136C, 136M, 136Y, 136K, 136R, 136G, and 136B only once (that is, in one sub-scan). Can be recorded. As a result, printing can be performed at a higher speed than when a serial (shuttle) type head that reciprocates in the direction (main scanning direction) orthogonal to the conveyance direction (sub-scanning direction) of the recording medium 114 is applied. Can be improved.

  The image forming apparatus 100 of this example is capable of recording up to a recording medium (recording paper) of a maximum chrysanthemum half size, and a drum having a diameter of 810 mm corresponding to a recording medium width of 720 mm is used as the impression cylinder (drawing drum) 126b. It is done. The drum rotation peripheral speed at the time of ink ejection is 530 mm / sec. The ink discharge volumes of the respective ink discharge heads 136C, 136M, 136Y, 136K, 136R, 136G, and 136B are 2 pl, and the recording density is the main scanning direction (width direction of the recording medium 114) and the sub-scanning direction (recording medium 114). The transporting direction) is 1200 dpi.

  In this example, the configuration of seven colors of CMYKRGB is illustrated, but the combination of ink colors and the number of colors is not limited to this embodiment, and light ink, dark ink, and special color ink are added as necessary. May be. For example, it is possible to add a head for ejecting light ink such as light cyan and light magenta, and the arrangement order of the color heads is not particularly limited.

  A solvent removal unit 108 is provided following the ink ejection unit 106. A transfer drum 124c is provided between the pressure drum (drawing drum) 126b of the ink droplet ejection unit 106 and the pressure drum (solvent removal drum) 126c of the solvent removal unit 108 so as to be in contact therewith. As a result, the recording medium 114 held on the pressure drum 126b of the ink ejection unit 106 is transferred to the pressure drum 126c of the solvent removal unit 108 via the transfer drum 124c after each color ink is applied.

  In the solvent removal unit 108, an ink drying unit 138 and a solvent removal roller 140 are arranged in a position facing the surface of the pressure drum 126c in order from the upstream side in the rotation direction (counterclockwise direction in FIG. 8) of the pressure drum 126c. Is provided.

  The ink drying unit 138 includes a hot air dryer capable of controlling the temperature and the air volume within a predetermined range, like the paper preheating unit 128 and the processing liquid drying unit 132 described above. By blowing hot air heated to a predetermined temperature (for example, 70 ° C.) by the hot air dryer of the ink drying unit 138 onto the surface of the recording medium 114, the solvent component (mainly moisture) of the ink layer on the recording medium 114 is evaporated. Let Thereby, the amount of moisture penetrating into the recording medium 114 can be suppressed, and curling of the recording medium 114 can be prevented.

  The same configuration as the solvent removal roller of the contact solvent removal unit 22 shown in FIG. 1 is applied to the solvent removal roller 140. That is, the solvent removal roller 140 is a roller-like member having a porous surface, and the residual solvent remaining on the recording medium 114 by bringing the solvent removal roller 140 into contact with the ink layer on the recording medium 114. (Mainly high boiling point solvent) is removed. Thereby, the stickiness of the ink layer (that is, the ink image) due to the high boiling point solvent can be suppressed, and blocking of the recording medium 114 can be prevented. Further, the solvent component (mainly moisture) of the ink layer on the recording medium 114 is evaporated before the residual solvent (mainly high boiling point solvent) is removed by the solvent removal roller 140, so that the processing liquid and The cohesive force of the ink aggregate (color material aggregate) formed by this reaction is improved, and the color material adhesion to the solvent removal roller 140 can be prevented.

  A fixing unit 110 is provided following the solvent removal unit 108. A transfer drum 124d is provided between the pressure drum (solvent removal drum) 126c of the solvent removing unit 108 and the pressure drum (fixing drum) 126d of the fixing unit 110 so as to be in contact with them. Accordingly, the recording medium 114 held on the pressure drum 126c of the solvent removing unit 108 is delivered to the pressure drum 126d of the fixing unit 110 via the transfer drum 124d after each color ink is applied.

  In the fixing unit 110, print detection is performed by reading the print result of the ink droplet ejection unit 106 at a position facing the surface of the pressure drum 126 c in order from the upstream side in the rotation direction (counterclockwise direction in FIG. 8) of the pressure drum 126 d. A portion 144 and heating rollers 148a and 148b are provided.

  The print detection unit 144 captures an image sensor (line sensor or the like) for imaging a print result of the ink droplet ejection unit 106 (a droplet ejection result of each of the ink ejection heads 136C, 136M, 136Y, 136K, 136R, 136G, and 136B). In addition, it functions as a means for checking nozzle clogging and other ejection defects from the droplet ejection image read by the image sensor.

  The heating rollers 148a and 148b are rollers whose temperature can be controlled within a predetermined range (for example, 100 ° C. to 180 ° C.), and heating and pressurizing the recording medium 114 sandwiched between the heating roller 148 and the impression cylinder 126d. Then, the image formed on the recording medium 114 is fixed.

  In this example, the heating temperature of the heating rollers 148a and 148b is set to 110 ° C., and the surface temperature of the impression cylinder 126d is set to 60 ° C. The nip pressure of the heating rollers 148a and 148b is 1 MPa. The heating temperature of the heating rollers 148a and 148b is preferably set according to the glass transition temperature of the polymer fine particles contained in the treatment liquid or ink.

  Subsequent to the fixing unit 110, a paper discharge unit 112 is provided. The paper discharge unit 112 includes a paper discharge drum 150 that receives the recording medium 114 on which an image is fixed, a paper discharge tray 152 on which the recording medium 114 is loaded, and a sprocket and a paper discharge tray 152 provided on the paper discharge drum 150. And a paper discharge chain 154 provided with a plurality of paper discharge grippers.

  Next, the structure of the ink ejection heads 136C, 136M, 136Y, 136K, 136R, 136G, and 136B arranged in the ink droplet ejection unit 106 will be described in detail. Since the structures of the ink discharge heads 136C, 136M, 136Y, 136K, 136R, 136G, and 136B are the same, the ink discharge head (hereinafter simply referred to as “head”) is denoted by reference numeral 160 below. Is also present).

  9A is a perspective plan view showing an example of the structure of the head 160, FIG. 9B is an enlarged view of a part thereof, and FIG. 9C is a plan view showing another example of the structure of the head 160. FIG. FIG. 10 is a cross-sectional view (a cross-sectional view taken along line XX in FIGS. 9A and 9B) showing a three-dimensional configuration of the ink chamber unit.

  In order to increase the dot pitch formed on the recording medium 114, it is necessary to increase the nozzle pitch in the head 160. As shown in FIGS. 9A and 9B, the head 160 of this example includes a plurality of ink chamber units 163 including nozzles 161 serving as ink droplet ejection holes, pressure chambers 162 corresponding to the nozzles 161, and the like. Are arranged in a staggered matrix (two-dimensionally) so that the projection is substantially performed so as to be aligned along the head longitudinal direction (main scanning direction orthogonal to the recording medium conveyance direction). High density of nozzle spacing (projection nozzle pitch) is achieved.

  The form in which one or more nozzle rows are configured over a length corresponding to the entire width of the recording medium 114 in a direction substantially orthogonal to the conveyance direction of the recording medium 114 is not limited to this example. For example, instead of the configuration of FIG. 9A, as shown in FIG. 9C, short head blocks 160 ′ in which a plurality of nozzles 161 are two-dimensionally arranged are arranged in a staggered manner and joined together. A line head having a nozzle row having a length corresponding to the entire width of the recording medium 114 may be configured. Although not shown, a line head may be configured by arranging short heads in a line.

  The pressure chamber 162 provided corresponding to each nozzle 161 has a substantially square planar shape, and the nozzle 161 and the supply port 164 are provided at both corners on the diagonal line. Each pressure chamber 162 communicates with a common flow path 165 through a supply port 164. The common flow path 165 communicates with an ink supply tank (not shown) as an ink supply source, and the ink supplied from the ink supply tank is distributed and supplied to each pressure chamber 162 via the common flow path 165.

  A piezoelectric element 168 having an individual electrode 167 is joined to a diaphragm 166 that constitutes the top surface of the pressure chamber 162 and also serves as a common electrode, and the piezoelectric element 168 is applied by applying a drive voltage to the individual electrode 167. Deformation causes ink to be ejected from the nozzle 161. When ink is ejected, new ink is supplied from the common channel 165 to the pressure chamber 162 through the supply port 164.

  In this example, the piezoelectric element 168 is applied as an ejection force generation unit for ink ejected from the nozzles 161 provided in the head 160. However, a heater is provided in the pressure chamber 162, and the pressure of film boiling caused by heating of the heater is used. It is also possible to apply a thermal method that ejects ink.

  As shown in FIG. 9B, the ink chamber units 163 having such a structure are arranged in a fixed manner along the row direction along the main scanning direction and the oblique column direction having a constant angle θ that is not orthogonal to the main scanning direction. By arranging a large number of patterns in a lattice pattern, the high-density nozzle head of this example is realized.

  That is, with the structure in which a plurality of ink chamber units 163 are arranged at a constant pitch d along the direction of an angle θ with respect to the main scanning direction, the pitch P of the nozzles projected in the main scanning direction is d × cos θ. Thus, in the main scanning direction, each nozzle 161 can be handled equivalently as a linear array with a constant pitch P. With such a configuration, it is possible to realize a high-density nozzle configuration in which 2400 nozzle rows are projected per inch (2400 nozzles / inch) so as to be aligned in the main scanning direction.

  In the implementation of the present invention, the nozzle arrangement structure is not limited to the illustrated example, and various nozzle arrangement structures such as an arrangement structure having one nozzle row in the sub-scanning direction can be applied.

  Further, the application range of the present invention is not limited to a printing method using a line-type head, and a short head that is less than the length in the width direction (main scanning direction) of the recording medium 114 is scanned in the width direction of the recording medium 114. Printing in the width direction is performed, and when printing in one width direction is completed, the recording medium 114 is moved by a predetermined amount in a direction (sub-scanning direction) perpendicular to the width direction of the recording medium 114, and the recording medium 114 in the next printing area is moved. A serial method may be applied in which printing in the width direction is performed and printing is performed over the entire printing area of the recording medium 114 by repeating this operation.

  FIG. 11 is a principal block diagram showing the system configuration of the image forming apparatus 100. The image forming apparatus 100 includes a communication interface 170, a system controller 172, a memory 174, a motor driver 176, a heater driver 178, a print control unit 180, an image buffer memory 182, a head driver 184, and the like.

  The communication interface 170 is an interface unit that receives image data sent from the host computer 186. As the communication interface 170, a serial interface such as USB (Universal Serial Bus), IEEE 1394, Ethernet (registered trademark), a wireless network, or a parallel interface such as Centronics can be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted. Image data sent from the host computer 186 is taken into the image forming apparatus 100 via the communication interface 170 and temporarily stored in the memory 174.

  The memory 174 is a storage unit that temporarily stores an image input via the communication interface 170, and data is read and written through the system controller 172. The memory 174 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The system controller 172 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire image forming apparatus 100 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. . That is, the system controller 172 controls the communication interface 170, the memory 174, the motor driver 176, the heater driver 178, and the like, performs communication control with the host computer 186, read / write control of the memory 174, etc. A control signal for controlling the motor 188 and the heater 189 is generated.

  The memory 174 stores programs executed by the CPU of the system controller 172 and various data necessary for control. Note that the memory 174 may be a non-rewritable storage means, or may be a rewritable storage means such as an EEPROM. The memory 174 is used as a temporary storage area for image data, and is also used as a program development area and a calculation work area for the CPU.

  Various control programs are stored in the program storage unit 190, and the control programs are read and executed in accordance with instructions from the system controller 172. The program storage unit 190 may use a semiconductor memory such as a ROM or an EEPROM, or may use a magnetic disk or the like. An external interface may be provided and a memory card or PC card may be used. Of course, you may provide several recording media among these recording media. The program storage unit 190 may also be used as a recording unit (not shown) for operating parameters.

  The motor driver 176 is a driver that drives the motor 188 in accordance with an instruction from the system controller 172. In FIG. 11, a motor (actuator) arranged at each part in the apparatus is represented by reference numeral 188. For example, the motor 188 shown in FIG. 11 includes motors that drive the pressure drums 126a to 126d, the transfer drums 124a to 124d, and the paper discharge drum 150 shown in FIG.

  The heater driver 178 is a driver that drives the heater 189 in accordance with an instruction from the system controller 172. In FIG. 11, a plurality of heaters provided in the image forming apparatus 100 are represented by reference numeral 189. For example, the heater 189 shown in FIG. 11 includes the paper preheating unit 128, the treatment liquid drying unit 132, the heater built in the hot air dryer of the ink drying unit 138, and the like shown in FIG.

  The solvent removal control unit 179 controls the nip pressure (pressing force) and the nip time (pressurization time) of the solvent removal roller 140 in accordance with an instruction from the system controller 172. The optimum nip pressure, nip time, etc. of the solvent removal roller 140 are obtained in advance for each type of recording medium 114 and each type of ink, and are converted into a data table and stored in a predetermined memory (for example, the memory 174). When the information 114 and the information on the ink used are acquired, the nip pressure and the nip time of the solvent removal roller 140 are controlled with reference to the memory.

  The print control unit 180 has a signal processing function for performing various processes and corrections for generating a print control signal from the image data in the memory 174 in accordance with the control of the system controller 172. The generated print data This is a control unit that supplies (dot data) to the head driver 184. Necessary signal processing is performed in the print control unit 180, and the ejection droplet amount (droplet ejection amount) and ejection timing of the head 192 are controlled via the head driver 184 based on the image data. Thereby, a desired dot size and dot arrangement are realized. In FIG. 11, a plurality of heads (inkjet heads) provided in the image forming apparatus 100 are represented by reference numeral 192. For example, the head 192 shown in FIG. 8 includes the processing liquid discharge head 130 and the ink discharge heads 136C, 136M, 136Y, 136K, 136R, 136G, and 136B shown in FIG.

  The print control unit 180 is provided with an image buffer memory 182, and image data, parameters, and other data are temporarily stored in the image buffer memory 182 when image data is processed in the print control unit 180. Also possible is an aspect in which the print controller 180 and the system controller 172 are integrated and configured with one processor.

  The head driver 184 generates a drive signal to be applied to the piezoelectric element 168 of the head 192 based on the image data given from the print control unit 180, and applies the drive signal to the piezoelectric element 168 to drive the piezoelectric element 168. Including a driving circuit. Note that the head driver 184 shown in FIG. 11 may include a feedback control system for keeping the driving conditions of the head 192 constant.

  As described with reference to FIG. 8, the print detection unit 144 is a block including a line sensor. The print detection unit 144 reads an image printed on the recording medium 114, performs necessary signal processing, etc. And the detection result is provided to the print control unit 180. The print control unit 180 performs various corrections on the head 192 based on information obtained from the print detection unit 144 as necessary.

  Next, the operation of the image forming apparatus 100 of this embodiment will be described.

  First, when the recording medium 114 is sent from the sheet feeding table 120 of the sheet feeding unit 102 to the feeder board 122, the recording medium 114 is held on the pressure drum 126a of the treatment liquid applying unit 104 via the transfer drum 124a. Preheating is performed by the paper preheating unit 128, and the processing liquid is ejected by the processing liquid discharge head 130. Subsequently, heat drying by the treatment liquid drying unit 132 is performed, and the solvent component (mainly moisture) of the treatment liquid layer formed on the recording medium 114 is evaporated. At this time, heat drying is preferably performed so that a solid or semi-solid aggregation treatment agent layer is formed on the recording medium 114, and image deterioration due to color material movement can be prevented.

  After the treatment liquid layer (preferably a solid or semi-solid aggregation treatment agent layer) is formed on the recording medium 114, the recording medium 114 held on the pressure drum 126a of the treatment liquid application unit 104 is transferred to the transfer cylinder 124b. Then, the ink is transferred to the pressure drum 126b of the ink droplet ejection unit 106. Corresponding color inks are ejected from the respective ink ejection heads 136C, 136M, 136Y, 136K, 136R, 136G, and 136B on the recording medium 114 held on the impression cylinder 126b in accordance with the input image data. . As a result, an ink layer (a liquid layer made of a mixture of ink and processing liquid) is formed on the recording medium 114.

  After the ink layer is formed on the recording medium 114, the recording medium 114 held on the pressure drum 126b of the ink ejection unit 106 is transferred to the pressure drum 126c of the solvent removing unit 108 via the transfer cylinder 124c. . When the recording medium 114 held on the pressure drum 126c passes through a position facing the ink drying unit 138, the solvent component (mainly moisture) of the ink layer on the recording medium 114 is heated and dried by the ink drying unit 138. Evaporate. Further, residual solvent (particularly high boiling point solvent) remaining on the recording medium 114 is absorbed and removed by the solvent removal roller 140. Accordingly, the amount of moisture penetrating into the recording medium 114 can be suppressed, so that the occurrence of curling can be suppressed, and the high boiling point solvent is removed from the recording medium 114, so that blocking of the recording medium 114 is also prevented. Can do.

  After the solvent component is removed from the ink layer on the recording medium 114 in this way, the recording medium 114 held on the impression cylinder 126c is transferred to the impression cylinder 126d of the fixing unit 110 via the transfer cylinder 124d. The recording medium 114 held on the pressure drum 126d is formed on the recording medium 114 by the heating and pressurization by the heating rollers 148a and 148b after the printing result of the ink ejection unit 106 is read by the printing detection unit 144. The fixed image is fixed.

  The recording medium 114 on which the image is fixed is transferred from the pressure drum 126 d to the paper discharge drum 150, conveyed above the paper discharge tray 152 by the paper discharge chain 154, and stacked on the paper discharge tray 152.

  The image forming method and the image forming apparatus of the present invention have been described in detail above. However, the present invention is not limited to the above examples, and various improvements and modifications are made without departing from the gist of the present invention. Of course it is also good.

1 is a schematic configuration diagram showing an embodiment of an image forming apparatus according to the present invention. The figure which showed a mode that an ink droplet landed on the recording medium to which the process liquid was provided. A diagram schematically showing the state from the application of the treatment liquid on the recording medium to the fixing. The figure which showed the evaluation result when the presence or absence of execution of the ink drying process and the solvent removal process and the order were changed The figure which showed the evaluation result when changing the solvent content rate of the ink layer after a contact solvent removal process was performed Evaluation results when the presence or absence of the treatment liquid drying process is changed Evaluation results when the presence or absence of the contact solvent removal process or fixing process is changed Schematic configuration diagram showing another embodiment of the image forming apparatus according to the present invention. Plane perspective view showing a configuration example of an ink discharge head Sectional view showing the three-dimensional configuration of the ink chamber unit FIG. 8 is a principal block diagram showing the system configuration of the image forming apparatus shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 12 ... Recording medium, 14 ... Processing liquid application part, 16 ... Processing liquid drying part, 18 ... Ink drop part, 20 ... Ink drying part, 22 ... Contact solvent removal part, 56 ... Solvent removal roller, 100 ... Image forming apparatus , 102 ... paper feeding unit, 104 ... treatment liquid application unit, 106 ... ink ejection unit, 108 ... solvent removal unit, 110 ... fixing unit, 112 ... paper discharge unit, 114 ... recording medium, 130 ... treatment liquid ejection head, 132 ... Processing liquid drying unit, 136 ... Ink discharge head, 138 ... Ink drying unit, 140 ... Solvent removal roller, 160 ... Head, 161 ... Nozzle, 162 ... Pressure chamber, 168 ... Piezoelectric element, 179 ... Solvent removal control unit, 180 .. print control unit

Claims (7)

An image forming method for forming an image on a recording medium using an ink containing a color material and a treatment liquid containing a component that aggregates the color material,
A treatment liquid application step of applying the treatment liquid onto the recording medium;
An ink droplet ejection step of ejecting the ink onto the recording medium to which the treatment liquid has been applied;
An ink drying step of heating and drying the ink layer formed on the recording medium by the ink droplet ejection step;
A solvent removal step of removing the residual solvent by bringing a solvent removal means into contact with the residual solvent remaining on the recording medium after the ink drying step;
An image forming method comprising:   2. The image forming method according to claim 1, wherein the time from when the ink is deposited onto the recording medium to when the ink layer is heated and dried is within 10 seconds.   3. The image forming method according to claim 1, wherein the solvent removing step is performed such that a solvent content of the ink layer after the solvent removal by the solvent removing unit is 50% or less.   The image forming method according to claim 1, further comprising a treatment liquid drying step of drying the treatment liquid provided on the recording medium by heating.   5. The method according to claim 1, further comprising a fixing step of fixing the ink layer on the recording medium by heating and pressurizing after the solvent removing step is performed. 6. Image forming method.   The image forming method according to claim 1, wherein the recording medium is a coated paper for printing. An image forming apparatus that forms an image on a recording medium using an ink containing a color material and a treatment liquid containing a component that aggregates the color material,
Treatment liquid application means for applying the treatment liquid on the recording medium;
Ink droplet ejection means for ejecting the ink onto the recording medium to which the treatment liquid has been applied;
An ink drying means for heating and drying an ink layer formed on the recording medium by the ink droplet ejection means;
A solvent removing means for removing the residual solvent by contacting the residual solvent remaining on the recording medium after the ink layer is heated and dried by the ink drying means;
An image forming apparatus comprising:

Images