JP6076859B2 - Image forming method and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming method and an image forming apparatus for forming an image by ejecting ink liquid onto a recording medium.

2. Description of the Related Art Conventionally, there has been known an image forming apparatus that applies a treatment liquid that agglomerates pigments dispersed in ink to a recording medium such as paper, and then forms an image by ejecting the ink liquid with an ink jet recording head. (For example, see Patent Documents 1 to 4).
Patent Document 1 discloses a technique for forming an image by applying an ink aggregation treatment liquid to a general-purpose coated paper and then ejecting the ink liquid.
In Patent Literature 2, when a coating liquid that reacts with ink to agglomerate or insolubilize ink is applied to form an image on the coated paper, the surface temperature of the coated paper is controlled to be lower than the boiling point of water. Thus, a technique for preventing the occurrence of blistering (blowing) is disclosed.
Patent Document 3 discloses an ink jet recording apparatus that ejects ink with a droplet ejection amount corresponding to the air permeability of a sheet.
Patent Document 4 describes an example in which blisters are generated on coated paper containing calcium carbonate.

JP 2012-126057 A JP 2009-285878 A JP 2008-23842 A JP 2008-1000051 A

  However, blisters may be generated by the gas generated by the reaction between the components contained in the coat layer of the coated paper and the treatment liquid for ink aggregation.

  In consideration of the above facts, the present invention provides an image forming method and an image forming apparatus capable of suppressing blisters generated by a gas generated by a reaction between a component contained in a coating layer and an aggregating treatment liquid for aggregating ink. The task is to do.

In the image forming method according to the first aspect of the present invention, an aggregation treatment liquid application step for applying an aggregation treatment liquid for aggregating the color material of the ink liquid to the coat layer of the image forming paper and the aggregation treatment liquid are applied. A drying step of heating and drying the image forming paper, and an ink dropping step of forming an image by depositing the ink liquid onto the image forming paper that has been subjected to the drying step after the aggregation treatment liquid is applied. Ink droplet ejection of the ink liquid, which is used in an image forming apparatus that performs image formation with the above-described method and can suppress blisters in the coating layer generated by a gas generated by a reaction between the aggregation processing liquid and components contained in the coating layer An amount and a maximum layer temperature of the coat layer are set in advance for each type of the image forming paper, and a maximum layer temperature T [unit: ° C] of the coat layer in the drying step is set to 80 ≦ T ≦ 100. It was .

In the image forming method according to the first aspect, in the aggregation treatment liquid application step, an aggregation treatment liquid for aggregating the color material of the ink liquid is applied to the coat layer of the image forming paper.
In the drying step, the image forming paper to which the aggregation treatment liquid is applied is heated and dried.
In the ink droplet ejection step, an image is formed by depositing the ink liquid onto the image forming paper that has been subjected to the drying step after the aggregation treatment liquid is applied. When the ink liquid is ejected onto the aggregation treatment liquid applied to the recording surface, the color material dispersed in the ink is aggregated to form a color material aggregate.
Here, in the case where a gas is generated by the reaction of the aggregating treatment liquid and the components contained in the coat layer, blisters are not generated in the coat layer if the gas permeates quickly and smoothly from the coat layer to the outside. .
However, when the amount of ink liquid adhering to the coat layer is large, the dried ink suppresses gas permeation, and the coat layer swells with gas, that is, blisters are generated. Therefore, in order to suppress the generation of blisters, it is necessary to control the ink droplet ejection amount on the coating layer.
In addition, when the coating layer to which the aggregating treatment liquid is applied is heated, a chemical reaction between the aggregating treatment liquid and the components contained in the coating layer is promoted and gas is generated in a short time, so that blisters may occur in the coating layer. is there. Therefore, in order to suppress the generation of blisters, it is also necessary to control the highest layer reachable temperature of the coat layer.
In the image forming method according to the first aspect, the droplet ejection amount of the ink liquid capable of suppressing blistering of the coating layer caused by the gas generated by the reaction between the aggregation treatment liquid and the component contained in the coating layer, and the coating layer The maximum layer temperature is set in advance for each type of image forming paper.
Therefore, at the time of image formation, an image forming sheet used for image formation can be selected from a plurality of preset image forming sheets, and the highest layer temperature reached by the coat layer corresponding to the selected image forming sheet, and By forming an image based on the droplet ejection amount of the ink liquid, blisters generated by the carbon dioxide gas generated in the coat layer can be suppressed.

The image forming method according to the second aspect of the present invention is the image forming method according to the first aspect, wherein the ink liquid is cured by being irradiated with ultraviolet rays.

In the image forming method according to the second aspect of the present invention, the ink liquid is cured by irradiation with ultraviolet rays, and the image is fixed on the image forming paper.

The image forming method according to the third aspect of the present invention is the image forming method according to the second aspect , wherein after the ink liquid is ejected, the image forming paper is irradiated with ultraviolet rays.

According to the image forming method of the third aspect of the present invention, the ink liquid can be cured by irradiating the image forming paper with ultraviolet rays after the ink liquid has been deposited.

An image forming apparatus according to a fourth aspect of the present invention includes a treatment liquid application device that applies an aggregation treatment liquid for aggregating a color material of an ink liquid to a coat layer of an image forming sheet, and the above-described aggregation treatment liquid. A drying device that heats and drys the image forming paper; an ink ejection device that forms an image by depositing the ink liquid onto the image forming paper that has been subjected to the heat drying after the aggregation processing liquid is applied; and the aggregation processing The amount of droplets of the ink liquid that can suppress blistering of the coating layer generated by the gas generated by the reaction between the liquid and the component contained in the coating layer, and the highest layer temperature of the coating layer are formed as the image. Control means that can be preset for each type of paper, and the control means heats the drying device based on a preset maximum temperature of the coat layer and a droplet ejection amount of the ink liquid. Amount, and said Controls the droplet ejection volume of ink droplet ejection device, the drying device in the heating and drying layers highest temperature T [Unit: ° C] of the coating layer, and 80 ≦ T ≦ 100.

According to the image forming apparatus of the fourth aspect of the present invention, it is possible to apply the aggregation treatment liquid for aggregating the color material of the ink liquid to the coating layer of the image forming paper with the treatment liquid application apparatus. In the drying device, the image forming paper to which the aggregation treatment liquid is applied can be heated and dried. In the ink droplet ejecting apparatus, an image can be formed by ejecting the ink liquid onto the image forming paper that has been subjected to the drying process after the aggregation treatment liquid is applied. When the ink liquid is ejected onto the aggregation treatment liquid applied to the recording surface, the color material dispersed in the ink is aggregated to form a color material aggregate.

In the image forming apparatus according to the fourth aspect of the present invention, the droplet ejection amount of the ink liquid that can suppress blistering of the coat layer caused by the gas generated by the reaction between the aggregation treatment liquid and the component contained in the coat layer, and The highest layer reaching temperature of the coat layer can be preset for each type of image forming paper.
The control means is based on the maximum reachable temperature of the coat layer capable of suppressing blistering of the coat layer caused by the gas generated by the reaction between the aggregating treatment liquid and the components contained in the coat layer, and the droplet ejection amount of the ink liquid. Then, the heating amount of the drying device and the droplet ejection amount of the ink droplet ejection device are controlled, and the maximum layer temperature T [unit: ° C] of the coating layer heated and dried by the drying device is set to 80 ≦ T ≦ 100. .
When an image forming paper to be used for image formation is selected from a plurality of preset image forming papers during image formation, the maximum layer layer reaching temperature corresponding to the selected image forming paper and the ink liquid deposition are selected. An image can be formed based on the droplet amount, and blisters generated by carbon dioxide generated in the coating layer can be suppressed.

  In the image recording method and the image recording apparatus of the present invention, blisters generated by the gas generated by the reaction between the components contained in the coat layer and the aggregation treatment liquid for ink aggregation can be suppressed.

1 is a longitudinal sectional view showing an overall configuration of an image recording apparatus according to an embodiment of the present invention. 1 is a longitudinal sectional view showing a suction plate, a chain gripper, an infrared heater and the like employed in an image forming apparatus according to an embodiment of the present invention. It is a block diagram which shows the connection state of the signal of a control apparatus and an apparatus. 5 is a table showing the relationship among paper thickness, air permeability, coat layer thickness, amount of calcium carbonate in the coat layer, calcium carbonate thickness, and carbonic acid blister occurrence concern index for each paper. It is a table | surface which shows the carbonic acid blister generation | occurrence | production situation at the time of changing a carbonic acid blister generation | occurrence | production concern index, drop amount, and temperature. It is a table | surface which shows the state of the film quality of the surface of a coating layer at the time of changing carbonic acid blister generation | occurrence | production concern index, drop amount, and temperature. It is a table | surface which shows comprehensive evaluation of the sheet | seat member at the time of changing a carbonic acid blister generation | occurrence | production concern index, drop amount, and temperature.

  An example of the image forming apparatus 10 according to an embodiment of the present invention will be described with reference to FIGS. In addition, arrow UP in a figure shows the perpendicular direction upper direction.

(overall structure)
As shown in FIG. 1, the image forming apparatus 10 according to the present embodiment uses an aqueous UV ink (a UV (ultraviolet) curable ink using an aqueous medium) on an image forming paper P as a recording medium. This is an apparatus for forming an image by a method. The image forming apparatus 10 mainly applies a predetermined processing liquid to a paper feeding unit 12 that feeds the image forming paper P and a surface (image recording surface) of the image forming paper P fed from the paper feeding unit 12. The processing liquid application unit 14, the processing liquid drying unit 16 that performs the drying process of the image forming paper P to which the processing liquid is applied by the processing liquid application unit 14, and the image formation that has been subjected to the drying process by the processing liquid drying unit 16. An image recording unit 18 that forms an image on the surface of the sheet P, an ink drying unit 20 that performs a drying process on the image forming sheet P on which an image is formed by the image recording unit 18, and an image that is dried by the ink drying unit 20 A UV irradiation processing unit 22 that performs UV irradiation processing (fixing processing) on the forming paper P to fix the image on the image forming paper P, and a discharge that discharges the image forming paper P UV-treated by the UV irradiation processing unit 22. And a paper portion 24.

<Paper Feeder>
The paper feed unit 12 mainly includes a paper feed base 30 on which the image forming paper P is stacked, a soccer device 32 that sends out the image forming paper P, a paper feed roller 34 that transports the sent image forming paper P, and an image. A conveyance belt 36 that conveys the forming paper P, a front contact member 38 that aligns the leading end of the image forming paper P, and a paper supply drum 40 that conveys the image forming paper P while rotating are configured.

The image forming paper P used in the image forming apparatus 10 of this embodiment is so-called coated paper in which a coating layer is provided on a support. Examples of the coated paper include art paper, high-quality coated paper, medium-quality coated paper, high-quality lightweight coated paper, medium-sized lightweight coated paper, and finely coated printing paper.
Examples of the support that can be suitably used for the image forming paper P include chemical pulps such as LBKP and NBKP; mechanical pulps such as GP, PGW, RMP, TMP, CTMP, CMP, and CGP; waste paper pulps such as DIP The main component is wood pulp and pigment, and one or more additives such as binders, sizing agents, fixing agents, yield improvers, cationizing agents, paper strength enhancing agents, etc. are mixed together. Examples include base paper produced using various apparatuses such as a net paper machine and a twin wire paper machine.

The basis weight of the support is usually about 40 to 600 g / m ² , but is not particularly limited. The image forming paper P used in the image forming apparatus 10 of the present embodiment is obtained by coating 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.

  The pigment contains at least calcium carbonate. The pigment includes components other than calcium carbonate, such as kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate. , Synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, hydrous halloysite, magnesium hydroxide, inorganic pigments; styrene plastic pigment, acrylic plastic pigment, polyethylene, micro Organic pigments such as capsules, urea resins, and melamine resins may be included.

  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.

  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 sheet feeding table 30 is provided with a sheet feeding table lifting / lowering device (not shown) that raises and lowers the sheet feeding table 30 so that the height of the uppermost image forming sheet P stacked on the sheet feeding table 30 becomes a constant height. I have.

  The soccer device 32 includes a suction foot 32A that is movable up and down and swingable. The suction foot 32A sucks and holds the upper surface of the image forming paper P, and feeds the image forming paper P from the paper feed base 30. The roller 34 is sent out.

  Specifically, the suction foot 32A sucks and holds the top surface of the topmost image forming paper P stacked on the paper feed tray 30, pulls up the image forming paper P, and pulls the image forming paper P up. The leading end is sent out toward the paper feed roller 34.

  The conveyance belt 36 is disposed so as to be inclined downward on the downstream side in the conveyance direction of the sheet member (hereinafter simply referred to as the downstream side in the conveyance direction), and the image forming paper P placed on the conveyance surface is placed on the conveyance belt 36. The guide member 38 is guided along the transport surface.

  In addition, a plate-like retainer 36 </ b> B that suppresses lifting and unevenness of the image forming paper P that is transported by the transport belt 36 is disposed above the transport surface of the transport belt 36 and the transport direction of the image forming paper P and the image forming paper P. A plurality are provided side by side in the width direction (direction orthogonal to the transport direction in which the image forming paper P is transported).

  Further, a roller 36 </ b> C is provided between one retainer 36 </ b> B and the other retainer 36 </ b> B arranged in the transport direction of the image forming paper P to press the transported image forming paper P against the transport surface of the transport belt 36. Yes.

  A plurality of front contact members 38 are provided in the width direction of the image forming paper P (hereinafter simply referred to as the sheet member width direction), and the front end members 38 arranged in the width direction of the sheet member are arranged on the front contact member 38 arranged in the sheet member width direction. The posture of the image forming paper P is corrected by hitting (pushing in).

  Further, the front contact member 38 includes a swinging device (not shown) that swings the front contact member 38 so that the image forming paper P whose posture is corrected is transferred to the rotating paper feed drum 40.

  The paper feed drum 40 is formed in a cylindrical shape, and a drive source (not shown) for rotating the paper feed drum 40 is provided. Further, on the outer peripheral surface of the paper supply drum 40, a gripper 40A that holds the leading end of the image forming paper P to be conveyed is provided.

  With this configuration, the paper feed drum 40 is rotated while holding the leading end of the image forming paper P by the gripper 40A, so that the image forming paper is fed to the processing liquid application unit 14 while the image forming paper P is wound around the circumferential surface. Transport P.

<Processing liquid application part>
The processing liquid application unit 14 mainly includes a processing liquid coating drum 42 that transports the image forming paper P, and a color material (pigment) in droplets (ink) on the surface of the image forming paper P transported by the processing liquid coating drum 42. And a treatment liquid application unit 44 as an example of a treatment liquid application member for applying a treatment liquid that agglomerates particles).

  The processing liquid coating drum 42 is formed in a cylindrical shape, and a drive source (not shown) for rotating the processing liquid coating drum 42 is provided. Further, on the outer peripheral surface of the treatment liquid coating drum 42, a gripper 42A that holds the leading end portion of the image forming sheet P to be conveyed is provided.

  With this configuration, the treatment liquid application drum 42 rotates while holding the leading end portion of the image forming paper P transferred from the paper supply drum 40 by the gripper 42A, thereby winding the image forming paper P around the peripheral surface. Then, the image forming paper P is conveyed to the processing liquid drying unit 16.

  The processing liquid application unit 44 mainly pumps up the application roller 44A for applying the processing liquid to the image forming paper P, the processing liquid tank 44B for storing the processing liquid, and the processing liquid stored in the processing liquid tank 44B. And a pumping roller 44C to be supplied to the application roller 44A. With this configuration, the processing liquid application unit 44 applies the processing liquid to the surface of the image forming paper P conveyed by the processing liquid application drum 42 by a roller.

  In the present embodiment, the processing liquid application unit 14 has been described by a method using the application roller 44A. However, the present invention is not limited to this, and the processing liquid is not limited to this, but other methods such as a jetting method by jetting or a spraying method may be used. You may give using a system.

(Processing liquid)
The treatment liquid contains an aggregating agent that aggregates the components in the ink liquid.

  The aggregating agent may be a compound capable of changing the pH of the ink liquid, a polyvalent metal salt, or a polyallylamine. In the present embodiment, from the viewpoint of the cohesiveness of the ink liquid, a compound capable of changing the pH of the ink liquid is preferable, and a compound capable of lowering the pH of the ink liquid is more preferable. Preferred examples of the compound capable of lowering the pH of the ink liquid include highly water-soluble acidic substances (phosphoric acid, oxalic acid, malonic acid, citric acid, derivatives of these compounds, and salts thereof).

  As described above, as the flocculant, an acidic substance having high water solubility is preferable, and an organic acid is preferable and an organic acid having a valence of 2 or more is more preferable from the viewpoint of improving the aggregation property and fixing the entire ink. Furthermore, an acidic substance having a valence of 2 to 3 is particularly preferable. As the divalent or higher organic acid, an organic acid having a first pKa of 3.5 or less is preferable, and an organic acid of 3.0 or less is more preferable. Specifically, phosphoric acid, oxalic acid, malonic acid, Preferred examples include citric acid.

  In the flocculant, the acidic substance may be used alone or in combination of two or more. Thereby, cohesion can be improved and the whole ink can be fixed. The content of the flocculant for aggregating the ink liquid in the treatment liquid is preferably 1 to 50% by mass, more preferably 3 to 45% by mass, and still more preferably 5 to 40% by mass. . Further, it is preferable that the pH (25 ° C.) of the ink liquid is 8.0 or more and the pH (25 ° C.) of the treatment liquid is in the range of 0.5 to 4. As a result, it is possible to increase the image density, resolution, and speed of inkjet recording.

  Further, the processing liquid can contain other additives. These additives include anti-drying agents (wetting agents), anti-fading agents, emulsion stabilizers, penetration enhancers, UV absorbers, antiseptics, anti-fungal agents, pH adjusters, surface tension adjusters, antifoaming agents, Well-known additives, such as a viscosity modifier, a dispersing agent, a dispersion stabilizer, a rust preventive agent, and a chelating agent, are mentioned.

<Processing liquid drying section>
The processing liquid drying unit 16 is mainly transported by the processing liquid drying drum 46 that transports the image forming paper P, a paper transport guide 48 that is curved along the outer surface of the processing liquid drying drum 46, and the processing liquid drying drum 46. And a processing liquid drying processing unit 50 as an example of a processing liquid drying member that blows hot air on the surface of the image forming paper P to be dried to dry the processing liquid.

  The treatment liquid drying drum 46 is formed in a cylindrical shape, and a drive source (not shown) for rotating the treatment liquid drying drum 46 is provided. Further, on the outer peripheral surface of the processing liquid drying drum 46, a gripper 46A that holds the leading end of the image forming sheet P to be conveyed is provided.

  With this configuration, the processing liquid drying drum 46 holds the leading end portion of the image forming paper P transferred from the processing liquid coating drum 42 by the gripper 46A and rotates, thereby winding the image forming paper P around the peripheral surface. The image forming sheet P is conveyed to the image recording unit 18.

  Two processing liquid drying processing units 50 are arranged inside the processing liquid drying drum 46, and include a heater 50A and a fan 50B that blows air heated by the heater 50A onto the surface of the image forming paper P. Yes.

Here, an infrared thermometer 51 that measures the temperature of the recording surface (coat layer) of the image forming paper P in a non-contact manner is disposed in the paper transport guide 48. The infrared thermometer 51 is connected to a control device 88 (see FIG. 3) to be described later that controls the image forming apparatus 10.
Based on the temperature information sent from the infrared thermometer 51, the control device 88 appropriately adjusts the temperature and air volume of the hot air blown from the processing liquid drying processing unit 50 toward the image forming paper P, thereby providing various drying conditions. Can be realized.

<Image recording unit>
The image recording unit 18 mainly includes an image recording drum 52 that conveys the image forming paper P, and a pressing roller 54 that presses the image forming paper P that is conveyed by the image recording drum 52 and closely contacts the peripheral surface of the image recording drum 52. Recording heads 56C, 56M, 56Y, and 56K as examples of image forming members that eject droplets (ink droplets) of C, M, Y, and K on the image forming paper P; An in-line sensor 58 that reads the formed image information, a mist filter 60 that captures ink mist, and a drum cooling unit 62 that cools the image recording drum 52 are configured. In the following description, Y, M, C, and K are omitted when there is no need to distinguish between Y, M, C, and K.

  The image recording drum 52 is formed in a cylindrical shape, and a drive source (not shown) for rotating the image recording drum 52 is provided. Further, on the outer peripheral surface of the image recording drum 52, a gripper 52A that holds the leading end portion of the image forming sheet P to be conveyed is provided.

  With this configuration, the image recording drum 52 rotates while holding the leading end portion of the image forming paper P delivered from the processing liquid drying drum 46 by the gripper 52A, so that the image forming paper P is wound around the circumferential surface. The image forming paper P is conveyed to the ink drying unit 20.

  The image recording drum 52 and the above-described processing liquid drying drum 46 of the present embodiment are provided with grippers 52A and 46A at two locations on the outer peripheral surface, and convey two image forming sheets P by one rotation. It is configured to be able to.

  A number of suction holes (not shown) are formed on the peripheral surface of the image recording drum 52. The image forming paper P wound around the peripheral surface of the image recording drum 52 is transported while being sucked and held on the peripheral surface of the image recording drum 52 by being sucked from the suction holes.

  The pressure roller 54 is disposed in the vicinity of the sheet member receiving position of the image recording drum 52 (the position where the image forming paper P is received from the processing liquid drying drum 46). The pressing roller 54 is composed of a rubber roller and is arranged so as to be pressed against the peripheral surface of the image recording drum 52. As a result, the image forming paper P is brought into close contact with the peripheral surface of the image recording drum 52 by passing through the sandwiching portion between the pressing roller 54 and the image recording drum 52.

  Each of the recording heads 56 is arranged at a constant interval on the downstream side in the conveyance direction with respect to the pressing roller 54, and is a full line head corresponding to the sheet member width. Further, the recording head 56 is provided with a nozzle surface (not shown) on which nozzles for ejecting droplets are formed so as to face the peripheral surface of the image recording drum 52.

(ink)
A water-based UV ink is used as the ink liquid ejected from each recording head 56. The aqueous UV ink is an ink that is cured by irradiating ultraviolet rays (UV) after droplet ejection.

  The ink liquid in the present embodiment contains a pigment, and can be configured using a dispersant, a surfactant, and other components as necessary. The ink liquid contains at least one pigment as a color material component. There is no restriction | limiting in particular as a pigment, According to the objective, it can select suitably, For example, any of an organic pigment and an inorganic pigment may be sufficient. Since the pigment is almost insoluble or hardly soluble in water, the pigment is preferable in terms of ink colorability and durability. The pigment is preferably a water-dispersible pigment in which at least a part of its surface is coated with a polymer dispersant.

  The ink liquid of the present embodiment can contain at least one dispersant. The dispersant for the pigment may be either a polymer dispersant or a low molecular surfactant type dispersant. The polymer dispersant may be either a water-soluble dispersant or a water-insoluble dispersant.

  The weight average molecular weight of the polymer dispersant is preferably 3,000 to 100,000, more preferably 5,000 to 50,000, still more preferably 5,000 to 40,000, particularly preferably. 10,000 to 40,000.

The acid value of the polymer dispersant is preferably 100 KOHmg / g or less from the viewpoint of good aggregation when the treatment liquid comes into contact. Furthermore, the acid value is more preferably 25 to 100 KOH mg / g, further preferably 25 to 80 KOH mg / g, and particularly preferably 30 to 65 KOH mg / g. When the acid value of the polymer dispersant is 25 or more, the stability of self-dispersibility is improved.
The oxidation of the polymer was determined by the method described in JIS standard (JIS K0070: 1992).

  The polymer dispersant preferably contains a polymer having a carboxyl group from the viewpoint of self-dispersibility and aggregation rate when the treatment liquid comes into contact, and the polymer dispersant has a carboxyl group and an acid value of 25 to 80 KOHmg / g. More preferably.

  In the present embodiment, from the viewpoints of image light resistance and quality, the ink liquid preferably contains a pigment and a dispersant, more preferably an organic pigment and a polymer dispersant, and further includes an organic pigment and a carboxyl. It is particularly preferred to contain a polymer dispersant containing groups. Moreover, it is preferable that a pigment is coat | covered with the polymer dispersing agent which has a carboxyl group from a cohesive viewpoint, and is water-insoluble. Furthermore, from the viewpoint of cohesiveness, it is preferable that the acid value of the self-dispersing polymer particles described below is smaller than the acid value of the polymer dispersant.

  The average particle diameter of the pigment is preferably 10 nm to 200 nm, more preferably 10 nm to 150 nm, and even more preferably 10 nm to 100 nm. When the average particle diameter is 200 nm or less, the color reproducibility is good, and the droplet ejection characteristics when droplets are ejected by the ink jet method are good, and when it is 100 nm or less, the light resistance is good. Further, the particle size distribution of the color material is not particularly limited, and may be either a wide particle size distribution or a monodisperse particle size distribution. Two or more color materials having a monodisperse particle size distribution may be mixed and used.

  The average particle size and particle size distribution of the color material (pigment particles) are measured by the dynamic light scattering method using Nanotrac particle size distribution analyzer UPA-EX150 (manufactured by Nikkiso Co., Ltd.). Is required.

  You may use a pigment individually by 1 type or in combination of 2 or more types. As content in the ink liquid of a pigment, it is preferable that it is 1-25 mass% with respect to an ink liquid from a viewpoint of image density, 2-20 mass% is more preferable, and 5-20 mass% is further. Preferably, 5 to 15% by mass is particularly preferable.

  The ink liquid in the present embodiment can contain at least one kind of polymer particles. The polymer particles have a function of fixing the ink liquid by increasing the viscosity of the ink by aggregating by dispersion instability when contacted with a treatment liquid described later or a region where the liquid is dried. Fixability to a recording medium and image scratch resistance can be further improved.

  In order to react with the flocculant, polymer particles having an anionic surface charge are used, and widely known latexes are used as long as sufficient reactivity and droplet ejection properties are obtained. It is preferable to use polymer particles.

  The ink liquid in the present embodiment preferably contains at least one kind of self-dispersing polymer particles as polymer particles. This self-dispersing polymer has a function of fixing the ink liquid by destabilizing and agglomerating and thickening the ink when it comes into contact with a treatment liquid described later or a dried area thereof, The fixing property to the recording medium and the scratch resistance of the image can be further improved. Self-dispersing polymers are also preferred resin particles from the viewpoint of droplet ejection stability and liquid stability (particularly dispersion stability) of a system containing the pigment.

Self-dispersing polymer particles are water-insoluble polymers that can be dispersed in an aqueous medium by the functional groups (especially acidic groups or salts thereof) of the polymer itself in the absence of other surfactants. Means water-insoluble polymer particles which do not contain free emulsifiers.
The self-dispersing polymer is described in detail in paragraphs [0063] to [0088] of JP 2010-69805 A, and the self-dispersing polymer particles described herein can be suitably used in the present invention. .

  The acid value of the self-dispersing polymer in the present embodiment is preferably 50 KOHmg / g or less from the viewpoint of good cohesion when the treatment liquid comes into contact. Further, the acid value is more preferably 25 to 50 KOH mg / g, and further preferably 30 to 50 KOH mg / g. When the acid value of the self-dispersing polymer is 25 or more, the stability of the self-dispersing property is improved.

  The self-dispersing polymer particles in the present embodiment preferably contain a polymer having a carboxyl group from the viewpoint of self-dispersibility and agglomeration speed when the treatment liquid comes into contact, and have a carboxyl group and an acid value of 25. It is more preferable to include a polymer having ˜50 KOH mg / g, and it is more preferable to include a polymer having a carboxyl group and an acid value of 30 to 50 KOH mg / g.

  The molecular weight of the water-insoluble polymer constituting the self-dispersing polymer particles is preferably 3,000 to 200,000, more preferably 5,000 to 150,000 in terms of weight average molecular weight, and 10,000 to 10,000. More preferably, it is 100,000. By setting the weight average molecular weight to 3,000 or more, the amount of water-soluble components can be effectively suppressed. Moreover, self-dispersion stability can be improved by making a weight average molecular weight into 200,000 or less.

  The weight average molecular weight is measured by gel permeation chromatography (GPC). For GPC, HLC-8220GPC (manufactured by Tosoh Corporation) is used, and as columns, TSKgeL SuperHZM-H, TSKgeL SuperHZ4000, TSKgeL SuperHZ2000 (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) are used as eluents. Use THF (tetrahydrofuran). As conditions, the sample concentration was 0.35 / min. The flow rate is 0.35 ml / min. The sample injection volume is 10 μl, the measurement temperature is 40 ° C., and an IR detector is used.

  In addition, calibration curves are manufactured by Tosoh Corporation, “Standard sample TSK standard, polysrene”, “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”. , “A-2500”, “A-1000”, “n-propylbenzene”.

  The average particle size of the self-dispersing polymer particles is preferably in the range of 10 nm to 400 nm, more preferably in the range of 10 nm to 200 nm, and still more preferably in the range of 10 to 100 nm. When the volume average particle size is 10 nm or more, the production suitability is improved, and when it is 1 μm or less, the storage stability is improved.

  The average particle size and particle size distribution of the self-dispersing polymer particles are measured by the dynamic light scattering method using Nanotrac particle size distribution analyzer UPA-EX150 (manufactured by Nikkiso Co., Ltd.). Is required.

  The self-dispersing polymer particles can be used singly or in combination of two or more. The content of the self-dispersing polymer particles in the ink liquid is preferably 1 to 30% by mass, and preferably 5 to 15% by mass with respect to the ink liquid from the viewpoints of the aggregation speed and the glossiness of the image. It is more preferable that

  The content ratio of the pigment and the self-dispersing polymer particles in the ink liquid (for example, water-insoluble pigment particles / self-dispersing polymer particles) is 1 / 0.5 from the viewpoint of image scratch resistance. It is preferably ˜1 / 10, more preferably 1/1 to ¼.

The ink liquid in the present embodiment can contain at least one water-soluble polymerizable compound that is polymerized by active energy rays.
As the polymerizable compound, a nonionic or cationic polymerizable compound is preferable in that the reaction between the flocculant, the pigment, and the polymer particles is not hindered. The term “water-soluble” means that it can be dissolved in water at a certain concentration or higher, and it can be dissolved in water-based ink (preferably uniformly). Further, the solubility may be increased by adding a water-soluble organic solvent, and it may be dissolved (desirably uniformly) in the ink. Specifically, the solubility in water is preferably 10% by mass or more, and more preferably 15% by mass or more.

  As the polymerizable compound, a nonionic or cationic polymerizable compound is preferable in that it does not interfere with the reaction between the flocculant, the pigment, and the polymer particles, and the solubility in water at 25 ° C. is 10% by mass or more (further 15 (Mass% or more) polymerizable compound is preferable.

  As the polymerizable compound in the present embodiment, a polyfunctional monomer is preferable from the viewpoint of enhancing scratch resistance, and a bifunctional to hexafunctional monomer is preferable, and from the viewpoint of compatibility between solubility and scratch resistance, bifunctional to 4 Functional monomers are preferred. A polymeric compound can be contained individually by 1 type or in combination of 2 or more types.

  The content of the polymerizable compound in the ink liquid is preferably 30 to 300% by mass, more preferably 50 to 200% by mass, based on the total solid content of the pigment and the self-dispersing polymer particles. When the content of the polymerizable compound is 30% by mass or more, the image strength is further improved and the image has excellent scratch resistance, and when it is 300% by mass or less, it is advantageous in terms of pile height.

  At least one of the ink liquid and the treatment liquid further includes an initiator that initiates polymerization of the polymerizable compound by active energy rays.

  The ink liquid in the present embodiment can contain at least one initiator that initiates polymerization of the polymerizable compound by active energy rays with or without being contained in the treatment liquid. A photoinitiator can be used individually by 1 type or in mixture of 2 or more types or using together with a sensitizer.

  The initiator can contain a compound capable of initiating a polymerization reaction by active energy rays as appropriate. For example, the initiator starts generation of active species (radicals, acids, bases, etc.) by radiation or light, or electron beams. An agent (for example, a photopolymerization initiator) can be used.

  When the initiator is contained, the content of the initiator in the ink liquid is preferably 1 to 40% by mass and more preferably 5 to 30% by mass with respect to the polymerizable compound. When the initiator content is 1% by mass or more, the scratch resistance of the image is further improved, which is advantageous for high-speed recording, and when it is 40% by mass or less, it is advantageous in terms of droplet ejection stability.

  The ink liquid in the present embodiment can contain at least one water-soluble organic solvent. By containing the water-soluble organic solvent, it is possible to obtain the effect of preventing drying, wetting or promoting penetration. In order to prevent drying, the ink adheres and dries at the ink outlet of the ejection nozzle to form an aggregate and is used as a drying preventing agent that prevents clogging. A water-soluble organic solvent having a vapor pressure lower than that of water is preferable for preventing drying and wetting. Further, for penetration promotion, it can be used as a penetration enhancer that enhances ink permeability to paper.

  The drying inhibitor is preferably a water-soluble organic solvent having a vapor pressure lower than that of water. Anti-drying agents may be used alone or in combination of two or more. The content of the drying inhibitor is preferably in the range of 10 to 50% by mass in the ink liquid.

  The ink liquid contains water, but the amount of water is not particularly limited. Among these, the preferable content of water is 10 to 99% by mass, more preferably 30 to 80% by mass, and still more preferably 50 to 70% by mass.

  The ink liquid in the present embodiment can be configured using other additives in addition to the above components. Other additives include, for example, anti-drying agents (wetting agents), anti-fading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, anti-fungal agents, pH adjusters, surface tension adjusters, Well-known additives, such as a foaming agent, a viscosity modifier, a dispersing agent, a dispersion stabilizer, a rust preventive agent, a chelating agent, are mentioned.

  As shown in FIG. 1, the in-line sensor 58 is arranged at a constant interval on the downstream side in the transport direction with respect to the recording head 56 so as to read image information formed on the image forming paper P by the recording head 56 of each color. It has become. Further, a contact prevention plate 59 for preventing the image forming paper P from coming into contact with the inline sensor 58 is installed on the downstream side in the transport direction of the inline sensor 58. The contact prevention plate 59 prevents the image forming paper P from coming into contact with the inline sensor 58 when the image forming paper P is lifted due to a conveyance failure or the like.

  The mist filter 60 is disposed between the recording head 56 and the in-line sensor 58, and sucks air around the image recording drum 52 to capture ink mist. As a result, the ingress of ink mist to the in-line sensor 58 is suppressed, and the occurrence of poor reading and the like is prevented.

  The drum cooling unit 62 is provided to face the lower peripheral surface of the image recording drum 52, and mainly includes an air conditioner (not shown) and a duct 62A for blowing cool air supplied from the air conditioner to the peripheral surface of the image recording drum 52. And.

<Ink drying section>
The ink drying unit 20 mainly includes a chain gripper 64 as an example of a conveying member that conveys the image forming paper P on which an image is formed, and a suction plate 72 that applies tension to the image forming paper P conveyed by the chain gripper 64. And an ink drying processing unit 68 for drying the image forming paper P conveyed by the chain gripper 64.

  The chain gripper 64 includes a first sprocket 63A installed in the vicinity of the image recording drum 52, a second sprocket 63B installed in the paper discharge unit 24 and made rotatable, and the first sprocket 63A and the second sprocket 63B. The chain body 64A includes an endless chain 63C wound around and a plurality of chain guides (not shown) for guiding the travel of the chain 63C. The first sprocket 63A is provided with a drive source (not shown) that rotates the first sprocket 63A.

  Two chain bodies 64A are provided at an interval in the width direction of the image forming paper P, and a holding member for holding the leading end of the image forming paper P to be conveyed so as to straddle the pair of chain bodies 64A. A plurality of grippers 64B as an example are provided (see FIG. 2).

  That is, the chain gripper 64 includes a pair of chain bodies 64A and a plurality of grippers 64B.

  The chain guide is arranged at a predetermined position, and the chain 63C guides the predetermined route so that it can travel. In the image forming apparatus 10 of the present embodiment, the second sprocket 63B is disposed at a position higher than the first sprocket 63A. For this reason, a travel route in which the chain 63C is inclined in the middle is formed. Specifically, the path of the chain 63C includes a first horizontal transfer path 70A having the same height as the first sprocket 63A, an inclined transfer path 70B, and a second horizontal transfer path 70C having the same height as the second sprocket 63B. It consists of For this reason, a chain guide (not shown) is provided at the intersection of the paths whose traveling direction changes.

  The suction plate 72 is disposed along a conveyance path along which the image forming paper P is conveyed by the chain gripper 64. Specifically, it is disposed along a chain 63C that travels along the first horizontal conveyance path 70A and the inclined conveyance path 70B.

  Further, a fan 82 is provided inside the suction plate 72, and a suction force for sucking the back surface of the image forming paper P is generated on the suction surface 72 </ b> A (surface facing the chain gripper 64 side) of the suction plate 72. It has become.

  As a result, the image forming paper P that is conveyed while its leading end is held by the chain gripper 64 is conveyed while being in sliding contact with the suction surface 72A of the suction plate 72, and tension is generated in the image forming paper P. Yes.

  The ink drying processing unit 68 is arranged on the opposite side of the suction plate 72 arranged in the first horizontal conveyance path 70A across the image forming paper P to be conveyed, and hot air is applied to the surface of the image forming paper P to be conveyed. Are provided with a plurality of infrared heaters 78 for heating and drying the image forming paper P.

  The configuration of the ink drying unit 20 will be described later in detail.

<UV irradiation processing part>
The UV irradiation processing unit 22 includes a UV irradiation unit 74 as an example of an ultraviolet lamp that irradiates the image forming paper P conveyed by the chain gripper 64 with ultraviolet rays. As a result, the UV irradiation unit 74 irradiates the image formed on the image forming paper P with ultraviolet rays (UV) to fix the image on the image forming paper P.

<Output section>
The paper discharge unit 24 includes a paper discharge tray 76 on which the image forming paper P irradiated with UV and released from the gripper 64B is stacked and collected. In addition, the paper discharge tray 76 includes an elevating device (not shown) for always positioning the uppermost image forming paper P stacked on the paper discharge tray 76 at a constant height. As a result, in the paper discharge unit 24, the image forming paper P on which a series of image recording processing has been performed is stacked on the paper discharge tray 76 and collected.

  With the above configuration, when forming an image on the surface of the image forming paper P, in the paper feeding unit 12, the image forming paper P stacked on the paper feeding base 30 is one by one in order from the top by the soccer device 32. The paper is pulled up and fed to the paper feed roller 34. The image forming paper P fed to the paper feed roller 34 is sent out toward the transport belt 36 and placed on the transport belt 36.

  The image forming paper P placed on the transport belt 36 is transported by the circulating transport belt 36. In the conveyance process, the image forming paper P is pressed against the conveyance surface of the conveyance belt 36 by the retainer 36B, and the unevenness is corrected. The inclination of the image forming paper P conveyed by the conveying belt 36 is corrected by the front end of the image forming paper P being applied to the front contact member 38. Thereafter, the image forming paper P is delivered to the paper supply drum 40. Then, it is transported by the paper feed drum 40 to the processing liquid application unit 14.

  In the processing liquid application unit 14, the image forming paper P delivered from the paper supply drum 40 is received by the processing liquid application drum 42. The processing liquid coating drum 42 holds the leading end portion of the image forming paper P with the gripper 42A and rotates, so that the image forming paper P is wound around the circumferential surface and conveyed. In this conveying process, the application roller 44A is pressed against the surface of the image forming paper P, and the processing liquid is applied to the surface of the image forming paper P (processing liquid application step).

  In the processing liquid drying unit 16, the image forming paper P delivered from the processing liquid coating drum 42 is received by the processing liquid drying drum 46. The processing liquid drying drum 46 conveys the image forming paper P by rotating the image forming paper P while holding the leading end of the image forming paper P with the gripper 46A. At this time, the processing liquid drying drum 46 conveys the surface of the image forming paper P (the surface to which the processing liquid is applied) inward.

  In the course of being conveyed by the processing liquid drying drum 46, the image forming paper P is dried by hot air blown from the processing liquid drying processing unit 50 installed inside the processing liquid drying drum 46 (processing liquid drying process). ).

  In the image recording unit 18, the image forming paper P delivered from the processing liquid drying drum 46 is received by the image recording drum 52. The image recording drum 52 conveys the image forming paper P by holding the leading end of the image forming paper P with the gripper 52A and rotating. The image forming paper P delivered to the image recording drum 52 is brought into close contact with the peripheral surface of the image recording drum 52 by passing through the pressing roller 54. At the same time, the image forming sheet P is sucked and held on the outer peripheral surface of the image recording drum 52 by being sucked from the suction holes of the image recording drum 52.

  The image forming paper P is conveyed in this state, and passes through a position facing the recording head 56 of each color. Then, during the passage, droplets (ink) are ejected from the recording heads 56 of the respective colors onto the surface, and a color image is formed on the surface (image forming process).

  The image forming paper P on which an image is formed by the recording head 56 of each color passes through a position facing the inline sensor 58. Then, image information formed on the surface of the image forming paper P when the inline sensor 58 passes is read. The reading of the image information is performed as necessary, and an inspection for defective droplet ejection is performed from the read image. Thereby, for example, an abnormality such as a droplet ejection defect can be detected immediately, and the response can be performed quickly.

  In the ink drying unit 20, the image forming paper P delivered from the image recording drum 52 is received by the chain gripper 64. The chain gripper 64 holds the leading end portion of the image forming paper P with the gripper 64 </ b> B and transports the image forming paper P along the suction plate 72.

  The image forming paper P delivered to the chain gripper 64 is transported through the first horizontal transport path 70A. In the process of being transported along the first horizontal transport path 70A, the image forming paper P is heated and dried by the infrared heater 78 (droplet drying process).

  In the UV irradiation processing unit 22, ultraviolet light is irradiated from the UV irradiation unit 74 onto the surface of the image forming paper P that is transported through the inclined transport path 70 </ b> B by the chain gripper 64. Thereby, the UV irradiation process is performed on the image formed on the image forming paper P, and the image is fixed on the image forming paper P (light irradiation process).

  In the paper discharge unit 24, the image forming paper P irradiated with UV and released from the gripper 64B is stacked on the paper discharge tray 76 and collected. In this way, the image forming paper P that has undergone a series of image recording processes is stacked on the paper discharge tray 76 and collected.

Next, the configuration of the ink drying unit 20 and the like will be described in detail.
As shown in FIG. 2, the suction plate 72 includes a box-shaped housing 80 having a large number of suction holes and discharge holes formed on the outer peripheral surface, and a suction surface 72A of the housing 80 (facing the chain gripper 64 side). And the above-described fan 82 for generating a suction force on the surface).

  With this configuration, the back surface of the image forming sheet P conveyed while the leading end is held by the gripper 64B of the chain gripper 64 is adsorbed to the adsorption surface 72A. As a result, the image forming paper P is transported while being in sliding contact with the suction surface 72A of the suction plate 72, and tension is generated on the image forming paper P to pull the image forming paper P in the transport direction of the image forming paper P. ing.

  That is, the tension applying device 86 as an example of a tension applying unit that generates tension in the conveyance direction of the image forming paper P on the image forming paper P includes the chain gripper 64 and the suction plate 72.

  Here, the suction force of the suction surface 72A and the transport force of the chain gripper 64 are determined so that the tension generated in the image forming paper P is 100 N / m to 1000 N / m.

  Further, as shown in FIG. 1, as described above, the infrared heater 78 provided in the ink drying processing unit 68 is provided on the opposite side of the suction plate 72 across the image forming paper P to be conveyed. A plurality are provided side by side in the conveyance direction of P.

Further, the image forming paper P is heated and dried by all the infrared heaters 78 so that the residual water amount of the image forming paper P is 3 g / m ² or less in a state where the tension is applied to the image forming paper P by the tension applying device 86. Thus, the output of each infrared heater 78 is determined.

Here, the residual water amount is the residual water amount of the ink moisture, and the moisture originally contained in the image forming paper P is not taken into consideration. For example, when the ink moisture content is 10 g / m ² at the time of droplet ejection, the ink moisture content is reduced to 3 g / m ² or less by drying the image forming paper P.

  On the other hand, the grain of the image forming paper P used in the image forming apparatus 10 of the present embodiment is orthogonal to the conveying direction of the image forming paper P as an example. That is, the image forming paper P is given a tension in a direction perpendicular to the paper grain. Here, the paper grain refers to the direction in which paper fibers are arranged.

Although not shown, in addition to the above-described configuration, the image forming apparatus 10 supplies processing liquid to the ink storage tank that supplies ink to the recording heads 56C, 56M, 56Y, and 56K, and the processing liquid applying unit 14. And a head maintenance unit for cleaning the recording heads 56C, 56M, 56Y, and 56K (nozzle surface wiping, purging, nozzle suction, etc.) and a position for detecting the position of the image forming paper P on the medium conveyance path A detection sensor, a temperature sensor for detecting the temperature of each part of the device, and the like are provided, and these are connected to the control device 88 shown in FIG.
The control device 88 is further connected with a display device 90 capable of displaying the type of image forming paper P, the state of the device, etc., an operation panel 92 for performing various operations of the device, and an infrared thermometer 51. .
Further, the storage device (not shown) of the control device 88 has a value of Oken-type air permeability p corresponding to a plurality of image forming sheets P, an ink droplet ejection amount, and a treatment liquid after application. A map (condition) for controlling each device showing the relationship such as the temperature of the coat layer when the image forming paper P is dried by heating is stored in advance.

A control procedure performed by the control device 88 will be described below.
The dimension when the amount of calcium carbonate in the coat layer is expressed in thickness is tca [unit: μm], the Wangken air permeability of the image forming paper P is p [unit: sec], and the blister carbonate on the image forming paper P The occurrence concern index is y = tca × p / 1000 [unit: μm · sec], the highest layer temperature reached in the coating layer in the treatment liquid drying step is T [unit: ° C], and the ink liquid droplet is 1 square inch. 1.44 × 10 ⁶ droplets per droplet The average droplet ejection amount per droplet of ink liquid is V [unit: pl (picoliter)], V1 = − (1.5 / 10) [unit : Pl / ° C] × (T-100) [unit: ° C] +2.8 [unit: pl] Carbonic acid blister generation concern index 23 ≦ y [unit: μm · sec] ≦ 609, V [Unit: pl (picoliter)] ≤ min (V1, 4.3) [Calculate The value of V1 and 4.3 is smaller. ] And 80 ≦ T [unit: ° C] ≦ 100, the average droplet ejection amount V of the ink liquid and the highest layer temperature T of the coating layer are set. The average droplet ejection amount V includes ink liquids of C, M, Y, and K colors.

Here, tca represents a thickness obtained by analyzing the coat layer of the image forming paper P in advance and forming only the calcium carbonate in the coat layer, and the value for each image forming paper P is the control device 88. Stored in advance.
As the carbonic acid blister generation concern index y, a value for each image forming sheet P obtained by calculating tca × p / 1000 is stored in the controller 88 in advance.
Further, the maximum layer temperature T of the coating layer in the drying step of the treatment liquid is set in the range of 80 ≦ T [unit: ° C] ≦ 100, and the carbonic acid blister generation concern index y is 23 ≦ y ≦ 609 [unit: μm. In the control device 88, the range is set to the range of sec], and the average droplet ejection volume V is calculated to be equal to or smaller than the smaller value of V1 and 4.3.
The Oken air permeability p is measured in advance for each image forming paper P used in the apparatus by using the Oken air permeability tester, and the controller 88 makes the Oken air permeability for each image forming paper P. The air permeability p is stored in advance.
As the Oken type air permeability tester, Asahi Seiko Co., Ltd. Oken type air permeability and smoothness tester EYO type 5 was used.

  In the image forming apparatus 10 of the present embodiment, before the image formation, the operation panel 92 is operated to select a preset type of image forming paper P. When the type of the image forming paper P is selected, the control device 88 controls each unit so that processing is performed while satisfying a preset condition.

(Function, effect)
Next, the operation and effect of the image forming apparatus 10 of this embodiment will be described.
As shown in FIG. 1, the image forming paper P fed from the paper feed unit 12 is conveyed along the outer peripheral surface of the rotating paper feed drum 40 and the processing liquid coating drum 42.
In the treatment liquid application unit 14, the treatment liquid application unit 44 applies the treatment liquid (ink aggregation treatment liquid) to the recording surface (coat layer) of the image forming paper P conveyed along the outer peripheral surface of the treatment liquid application drum 42. To do.

Further, the image forming paper P to which the processing liquid has been applied is conveyed along the outer peripheral surface of the processing liquid drying drum 46 and is heated and dried.
In the image recording unit 18, the recording heads 56 C, 56 M, 56 Y, and 56 K of the respective colors eject ink liquid onto the recording surface (coat layer) of the image forming paper P that is conveyed by the image recording drum 52 to form the image forming paper P. An image is formed on. At that time, the ink liquid comes into contact with the processing liquid previously applied to the recording surface by the processing liquid applying unit 14, and the pigment and resin particles dispersed in the ink liquid aggregate to form an aggregate. Thereby, the pigment flow on the image forming paper P is prevented, and an image is formed on the recording surface of the image forming paper P.

  Further, the image forming paper P on which an image is formed on the recording surface is conveyed to the ink drying unit 20. In the ink drying unit 20, the recording surface of the image forming paper P is heated by the infrared heater 78, so that the water contained in the image forming paper P is dried after the ink liquid is deposited (the solvent separated by the aggregating action). To reduce the water content in).

Further, the heat-dried image forming paper P is conveyed to the UV irradiation processing unit 22. In the UV irradiation processing unit 22, the image formed with the ink is cured by the ultraviolet rays irradiated from the UV irradiation unit 74 and fixed on the image forming paper P.
The image forming paper P on which image fixing has been completed is discharged to a paper discharge tray 76.

In the image forming apparatus 10 of the present embodiment, before the image formation, the operation panel 92 is operated to select a preset type of image forming paper P.
The control device 88 sets various setting values corresponding to the selected image forming paper P (carbonic acid blister generation concern index y = tca × p / 1000 [unit: μm · sec], layer of coat layer in drying process liquid) The maximum reached temperature is T [unit: ° C], and the average droplet ejection amount per droplet of ink liquid when an ink droplet of 1.44 × 10 ⁶ droplets is ejected per square inch is V [ Unit: pl (picoliter)], V1 =-(1.5 / 10) [unit: pl / ° C] × (T-100) [unit: ° C] +2.8 [unit: pl] In addition, carbonic acid blister generation concern index 23 ≦ y [unit: μm · sec] ≦ 609, V [unit: pl (picoliter)] ≦ min (V1, 4.3) [calculated value of V1 and 4.3 The smaller value is expressed.], And 80 ≦ T [unit: ° C] ≦ 100 is satisfied. Within such a range, the maximum layer reaching temperature T and the average droplet ejection amount V of the ink liquid are set, and image formation processing is performed using the set maximum layer reaching temperature T and the average droplet ejection amount V of the ink liquid. Do.
As described above, the image forming apparatus 10 performs processing by optimally setting the ink droplet ejection amount V and the coat layer maximum temperature T according to the image forming paper P, and thus occurs in the coat layer. The blistering of the coating layer due to the carbon dioxide gas can be suppressed.

Note that the average droplet ejection amount V of the ink liquid, the highest layer reachable temperature T of the coating layer, and the like can be appropriately changed within this range as long as preset conditions are satisfied. Further, the highest layer reachable temperature T of the coat layer may be fixed to a temperature set in advance for each image forming sheet, or may be appropriately changed within a set range.
For example, by selecting the type of the image forming paper P on the operation panel 92, the preset layer maximum temperature T (fixed value) of the coat layer is displayed, and the layer maximum temperature T of the coat layer is displayed. The control device 88 can control the infrared heater 78 so as to be a value.
In addition, by selecting the type of image forming paper P on the operation panel 92, the range of the highest layer temperature T that has been set in advance is displayed, and a desired temperature is set from the displayed temperature range. By doing so, the control device 88 can also control the infrared heater 78 so as to achieve the set desired temperature.
The average droplet ejection volume V of the ink liquid is preferably set to a lower limit of 2.8 [unit: pl]. If the average droplet ejection amount V of the ink liquid is less than 2.8 [unit: pl], the solid portion density is lowered and may be outside the practical range.

<Relationship between paper, ink droplet ejection amount, and processing liquid drying temperature>
Table 1 in FIG. 4 shows the thickness of the image forming paper P, the type of paper, the Oken air permeability p (unit: sec), the thickness of the coat layer (unit: μm), and the amount of calcium carbonate in the coat layer ( %), A value tca (unit: μm) obtained by converting the amount of calcium carbonate into thickness, and a carbonic acid blister concern index y = tca × p / 1000 (unit: μm · sec).
Table 2 in FIG. 5 shows the carbon dioxide blister generation concern index y, the maximum temperature reached by the coating layer of the image forming paper P when dried after the treatment liquid is applied, and the average droplet amount per droplet of ink liquid (unit: It is the result of sensory evaluation in three stages of the state of carbonic acid blister generation when pl picoliter) was changed. In the evaluation, OK (no problem) was 3, 2 within the allowable range, and 1 outside the allowable range.
Table 3 in FIG. 6 shows the carbon dioxide blister generation concern index y, the maximum temperature reached by the coating layer of the image forming paper P during drying after the treatment liquid is applied, and the average droplet amount per droplet of ink liquid (unit: This is a result of sensory evaluation of the film quality on the surface of the coating layer of the image forming paper P in three stages when changing (pl picoliter). As for the film quality, a weight was placed on the image forming surface, the image forming paper P was dragged against the weight, and the image forming surface was visually inspected. In the evaluation, OK (no problem) was 3, 2 within the allowable range, and 1 outside the allowable range.
Table 4 in FIG. 7 shows the results of comprehensive evaluation of the occurrence of carbonic acid blisters on the image forming paper P and the film quality on the surface of the coat layer. In the evaluation, OK (no problem) was 3, 2 within the allowable range, and 1 outside the allowable range.

As shown in Table 2 of FIG. 5, when the carbonic acid blister generation concern index y is large, the maximum temperature reached by the coating layer of the image forming paper P is high, and the amount of ink droplets deposited is large, carbonic blisters are likely to occur. I understand that The lower limit of the ink droplet ejection amount is set to 2.8 pl. When the ink droplet ejection amount is less than 2.8 pl, the solid area density of the image is low and the practical range is narrow. Because it is. The reason why the upper limit of the ink droplet ejection amount is 4.3 pl is that when the ink droplet ejection amount exceeds 4.3 pl, carbon dioxide blisters are likely to occur, and more ink is used than necessary. It is. Further, if the maximum temperature reached by the coating layer of the image forming paper P is too high (for example, when the temperature exceeds 100 ° C.), carbonic acid blisters are likely to be generated even if the ink droplet ejection amount is reduced.
Average droplet ejection amount V1 per droplet of ink liquid V1 = − (1.5 / 10) [unit: pl / ° C.] × (T−100) [unit: ° C] +2.8 [unit: pl ] Is derived from experimental results in order to make the evaluation based on the generation of carbonic acid blisters to be 2 or more.

As shown in Table 3 of FIG. 6, when the maximum temperature reached by the coating layer of the image forming paper P is low (for example, 70 ° C. or less), a large amount of moisture penetrates the image forming paper P, and the amount of paper deformation is small. It becomes larger and the film quality deteriorates.
Therefore, in order to suppress the generation of carbonic acid blisters and ensure the film quality, the carbonic acid blister generation concern index y, the maximum temperature at which the coating layer is reached when the treatment liquid is dried, and the ink liquid droplet amount must be optimally controlled. I understand that.
From the evaluation results, it can be seen that by setting y to be 351 or less, it is possible to keep all blisters within an allowable range.
As described above, the evaluation results in Table 4 in FIG. 7 are “3: OK (no problem)” and “2: Within an acceptable range”, and the average droplet deposition amount V, and the highest layer reachable temperature of the coating layer. By setting T according to the image forming paper P, the occurrence of blisters can be suppressed.
Although not shown in the table, if the ink droplet ejection amount is set to zero, the occurrence of carbonic acid blisters is naturally suppressed, and there is no problem in film quality.

The test conditions conducted for the evaluation in the above table are as follows.
<Ink liquid adjustment>
Hereinafter, the adjustment of the ink liquid will be described in detail, but is not limited to the following examples. Unless otherwise specified, “part” is based on mass.

[Preparation of Polymer Dispersant 1 Solution]
In a reaction vessel, 6 parts of styrene, 11 parts of stearyl methacrylate, 4 parts of styrene macromer AS-6 (manufactured by Toagosei Co., Ltd.), 5 parts of Bremer PP-500 (manufactured by NOF Corporation), 5 parts of methacrylic acid, 2 -0.05 part of mercaptoethanol and 24 parts of methyl ethyl ketone were added to prepare a mixed solution. Meanwhile, in a dropping funnel, 14 parts of styrene, 24 parts of stearyl methacrylate, 9 parts of styrene macromer AS-6 (manufactured by Toagosei Co., Ltd.), 9 parts of Blenmer PP-500 (manufactured by NOF Corporation), 10 parts of methacrylic acid 2-mercaptoethanol (0.13 parts), methyl ethyl ketone (56 parts), and 2,2′-azobis (2,4-dimethylvaleronitrile) (1.2 parts) were added to prepare a mixed solution.
Thereafter, the mixed solution in the reaction vessel was heated to 75 ° C. with stirring in a nitrogen atmosphere, and the mixed solution in the dropping funnel was gradually dropped over 1 hour. Two hours after the completion of the dropwise addition, a solution obtained by dissolving 1.2 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) in 12 parts of methyl ethyl ketone was added dropwise thereto over 3 hours. After the dropwise addition, the mixture was aged at 75 ° C. for 2 hours, and further aged at 80 ° C. for 2 hours to obtain a polymer dispersant 1 solution.

  A part of the obtained polymer dispersant 1 solution was collected, and the solvent was removed. The obtained solid content was diluted to 0.1% by mass with tetrahydrofuran, and TSKgeL SuperHZM-H, TSKgeL SuperHZ4000, and TSKgeL SuperHZ2000 were analyzed with high-speed GPC (gel permeation chromatography) HLC-8220GPC (manufactured by Tosoh Corporation). (Tosoh Co., Ltd.) 3 were connected in series, and the weight average molecular weight of the polymer dispersant 1 was measured. The weight average molecular weight of the measured polymer dispersant 1 was 25,000 in terms of polystyrene. Moreover, the acid value of the polymer dispersing agent 1 calculated | required by the method as described in JIS specification (JISK0070: 1992) was 99 mgKOH / g.

[Preparation of pigment dispersion M]
5.0 g of the obtained polymer dispersant 1 solution in terms of solid content, 10.0 g of magenta pigment (Pigment Red 122, manufactured by Dainichi Seika Co., Ltd.), 40.0 g of methyl ethyl ketone, 1 mol / L (liters; the same applies hereinafter) 8.0 g of sodium hydroxide and 82.0 g of ion-exchanged water were supplied to a vessel together with 300 g of 0.1 mm zirconia beads, and dispersed at 1000 rpm for 6 hours using a ready mill disperser (manufactured by IMEX Co., Ltd.). The obtained dispersion was concentrated under reduced pressure using an evaporator until methyl ethyl ketone could be sufficiently distilled off, and further concentrated until the pigment concentration became 10% by mass to prepare pigment dispersion M of resin-coated magenta pigment.
The volume average particle diameter (secondary particles) of the obtained pigment dispersion M is subjected to dynamic light scattering using a Microtrac particle size distribution analyzer (trade name: Version 10.1.2-211BH, manufactured by Nikkiso Co., Ltd.). It was 84 nm when measured by the method.

[Preparation of pigment dispersion Y]
In the preparation of Pigment Dispersion Liquid M, Pigment Red 122 was used as a pigment, except for using Irgalite Yellow GS (Pigment Yellow 74, manufactured by BASF Japan Ltd.) instead of Pigment Red 122. In the same manner as in the preparation of the pigment dispersion M, a pigment dispersion Y of a resin-coated yellow pigment was obtained. The volume average particle diameter (secondary particles) of the pigment dispersion Y measured by the same method as in the case of the pigment dispersion M was 75 nm.

[Preparation of pigment dispersion K]
In the preparation of Pigment Dispersion Liquid M, Pigment Red 122 was used as a pigment, except that Carbon Black MA-100 (manufactured by Mitsubishi Chemical Corporation) was used instead of Pigment Red 122. In the same manner as in the preparation of M, a pigment dispersion K of a resin-coated black pigment was obtained. The volume average particle diameter (secondary particles) of the pigment dispersion K measured by the same method as in the case of the pigment dispersion M was 80 nm.

[Preparation of pigment dispersion C]
As the pigment dispersion C, CABO-JET250C (cyan pigment dispersion, pigment: Pigment Blue 15: 4 (PB15: 4), manufactured by CABOT Co., Ltd.) was prepared. The pigment dispersion C is a pigment dispersion of a resin-coated cyan pigment in which PB15: 4 is coated with a resin. The volume average particle diameter (secondary particles) of the pigment dispersion C measured by the same method as in the case of the pigment dispersion M was 110 nm.

[Synthesis of (Meth) acrylamide M-1]
As a polyfunctional polymerizable compound, the following (meth) acrylamide M-1 (hereinafter referred to as “multivalent (meth) acrylamide M-1”) was synthesized according to the following method.

-First step-
To a 1 L three-necked flask equipped with a stirrer bar was added 121 g (1 equivalent) of tris (hydroxymethyl) aminomethane (manufactured by Tokyo Chemical Industry Co., Ltd.), 84 ml of a 50 mass% potassium hydroxide aqueous solution, and 423 ml of toluene. The mixture was stirred and the reaction system was maintained at 20 ° C. to 25 ° C. in a water bath, and 397.5 g (7.5 equivalents) of acrylonitrile was added dropwise over 2 hours. After dropping, the mixture was stirred for 1.5 hours. Thereafter, 540 ml of toluene was added to the reaction system, the reaction mixture was transferred to a separatory funnel, and the aqueous layer was removed. The remaining organic layer was dried over magnesium sulfate, filtered through Celite, and the solvent was distilled off under reduced pressure to obtain an acrylonitrile adduct. The analysis results by 1H-NMR and MS of the obtained substance (acrylonitrile adduct) showed good agreement with known substances, and thus were used for the next reduction reaction without further purification.

-Second step-
In an autoclave having a volume of 1 L, 24 g of the obtained acrylonitrile adduct, 48 g of Ni catalyst (Raney nickel 2400, manufactured by WR Grace & Co.), and 600 ml of 25% by mass aqueous ammonia solution (water: methanol = 1: 1) were placed. The reaction vessel was sealed by suspending. 10 Mpa of hydrogen was introduced into the reaction vessel and reacted at a reaction temperature of 25 ° C. for 16 hours.
The disappearance of the raw materials was confirmed by 1H-NMR, the reaction mixture was filtered through Celite, and the Celite was washed several times with methanol. The filtrate was evaporated under reduced pressure to obtain a polyamine compound. The obtained substance (polyamine body) was used in the next reaction without further purification.

-Third step-
To a 2 L three-necked flask equipped with a stirrer, 30 g of the polyamine obtained, 120 g of sodium hydrogen carbonate (14 equivalents), 1 L of dichloromethane and 50 ml of water were added, and 92.8 g (10 equivalents) of acrylic acid chloride in an ice bath. ) Was added dropwise over 3 hours. After dropping, the mixture was stirred at room temperature for 3 hours. After confirming disappearance of the raw material by 1H-NMR, the reaction mixture was evaporated under reduced pressure. Subsequently, the reaction mixture was dried over magnesium sulfate, filtered through celite, and the solvent was distilled off under reduced pressure. Finally, it was purified by column chromatography (ethyl acetate / methanol = 4: 1) to obtain a polyvalent (meth) acrylamide M-1 solid at room temperature. The yield of polyvalent (meth) acrylamide M-1 obtained through the above three steps was 40%.
The polyvalent (meth) acrylamide M-1 is a compound having the following structure in which R1 = H, R2 = C3H6, R3 = CH2, and X = Y = Z = 0 in the general formula (1). It was.

[Synthesis of self-dispersing polymer particles P-1 (polymer particles)]
360.0 g of methyl ethyl ketone was charged into a 2 L three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, and the temperature was raised to 75 ° C. Thereafter, while maintaining the temperature in the flask at 75 ° C., 151.2 g of benzyl methacrylate, 172.8 g of methyl methacrylate, 36.0 g of methacrylic acid, 72 g of methyl ethyl ketone, and “V-601” (manufactured by Wako Pure Chemical Industries, Ltd.) A mixed solution consisting of 1.44 g was added dropwise at a constant speed so that the addition was completed in 2 hours. After completion of the dropwise addition, a solution consisting of 0.72 g of “V-601” and 36.0 g of methyl ethyl ketone was added thereto, followed by stirring at 75 ° C. for 2 hours, and further comprising 0.72 g of “V-601” and 36.0 g of isopropanol. The solution was added and stirred at 75 ° C. for 2 hours. Thereafter, the temperature was raised to 85 ° C., and stirring was further continued for 2 hours to obtain a polymer solution of a benzyl methacrylate / methyl methacrylate / methacrylic acid (= 42/48/10 [mass ratio]) copolymer.
The weight average molecular weight (Mw) of the obtained benzyl methacrylate / methyl methacrylate / methacrylic acid copolymer measured by the same method as in the case of the polymer dispersant 1 was 58000, and the acid value was 32.6 mgKOH / g. Met.

  Next, 668.3 g of the obtained polymer solution was weighed, 388.3 g of isopropanol and 145.7 ml of 1 mol / L sodium hydroxide aqueous solution were added thereto, and the temperature in the reaction vessel was raised to 80 ° C. Next, 720.1 g of distilled water was dropped at a rate of 20 ml / min to disperse in water, and then the atmospheric temperature was changed to 80 ° C. for 2 hours, 85 ° C. for 2 hours, and 90 ° under atmospheric pressure. Hold at ℃ for 2 hours. Thereafter, the pressure in the reaction vessel was reduced, and 913.7 g of isopropanol, methyl ethyl ketone, and distilled water were distilled off in total, and self-dispersing polymer particles P-1 (polymer) having a solid content concentration (polymer particle concentration) of 28.0% by mass. An aqueous dispersion of particles) was obtained.

Among the constituents of the self-dispersing polymer particles P-1, the constituents derived from benzyl methacrylate, the constituents derived from methyl methacrylate, and the constituents derived from methacrylic acid are hereinafter referred to as “constituent component A”, Also referred to as “component B” and “component C”.
In addition, the mass ratio of the constituent component A, the constituent component B, and the constituent component C [the mass of the constituent component A / the mass of the constituent component B / the mass of the constituent component C] is hereinafter referred to as the mass ratio [A / B of the constituent components]. / C].

  It was 90 degreeC when the glass transition temperature (Tg) of the self-dispersing polymer particle P-1 obtained above was measured with the following method.

-Measurement of glass transition temperature (Tg)-
An aqueous dispersion of self-dispersing polymer particles having a solid content of 0.5 g was dried under reduced pressure at 50 ° C. for 4 hours to obtain a polymer solid content. Using the obtained polymer solid content, Tg was measured with a differential scanning calorimeter (DSC) EXSTAR 6220 manufactured by SII Nanotechnology. A sample amount of 5 mg was sealed in an aluminum pan, and the DSC peak top value in the measurement data at the second temperature increase in the following temperature profile in a nitrogen atmosphere was defined as Tg.
30 ° C to -50 ° C (cooled at 50 ° C / min)
−50 ° C. → 120 ° C. (temperature rising at 20 ° C./min)
120 ° C to -50 ° C (cooled at 50 ° C / min)
−50 ° C. → 120 ° C. (temperature rising at 20 ° C./min)
[Experiment 1]
[Preparation of ink liquid 1]
Components having the following composition were mixed, coarse particles were removed through a membrane filter (pore diameter 0.5 μm), and ink liquid 1 (hereinafter referred to as “ink 1” as appropriate) was prepared as a black ink.

<Composition of ink liquid 1>
・ Pigment dispersion K: 2.0% by mass
・ Pigment dispersion M: 0.5% by mass
-Pigment dispersion C: 0.5% by mass
・ Hydroxyethylacrylamide: 5.0% by mass
(Manufactured by Kojin Film & Chemicals Co., Ltd.)
・ Multivalent (meth) acrylamide M-1 ... 8.0 mass%
1- [4- (2-hydroxyethoxy) -phenyl]
-2-Hydroxy-2-methyl-1-propan-1-one ・ ・ ・ 3.0% by mass
("IRGACURE2959", manufactured by BASF Japan Ltd., polymerization initiator)
Compound (III) -1 ... 1.0% by mass
(Exemplary compounds and additives of the compound represented by the general formula (III))
・ 2-Pyrrolidone: 7.0% by mass
(Specific examples of compounds represented by formula (B), water-soluble solvent)
・ Glycerin: 2.0% by mass
・ Orphine E1010 (surfactant, manufactured by Nissin Chemical Industry Co., Ltd.) ... 1.0% by mass
-Self-dispersing polymer particles (P-1) ... 2.0 mass%
・ Snowtex XS (Colloidal silica, manufactured by Nissan Chemical Co., Ltd.) ・ ・ ・ 0.3% by mass
-BYK-024 (antifoaming agent, manufactured by Big Chemie Japan Co., Ltd.) ... 0.01% by mass
・ Triethanolamine: 0.2% by mass
・ Ion-exchanged water: Remaining amount when 100% by mass as a whole

<Preparation of treatment solution>
The processing liquid was prepared by mixing components having the following composition. The pH of the treatment liquid was 1.1.
~ Composition of treatment liquid ~
・ Malonic acid (Wako Pure Chemical Industries, Ltd.) ... 25%
・ Diethylene glycol monomethyl ether (Wako Pure Chemical Industries, Ltd.) 20%
・ Emulgen P109 (Kao Co., Ltd., nonionic surfactant) 1%
・ Ion exchange water 54%
Application amount of treatment liquid: 1.5 g / m ² ± 10%

<Other embodiments>
As mentioned above, although one Embodiment of this invention was described, it cannot be overemphasized that this invention is not limited to said Example at all, and can implement in a various aspect in the range which does not deviate from the summary of this invention.

10 Image Forming Device 18 Image Recording Unit (Ink Drop Device)
22 Irradiation processing unit (ultraviolet irradiation device)
44 Treatment liquid application unit (treatment liquid application device)
46 Treatment liquid drying drum (drying equipment)
51 Infrared thermometer 56 Recording head (ink ejection device)
88 Control device 90 Display device 92 Operation panel P Image forming paper

Claims (4)

An aggregation treatment liquid application step for applying an aggregation treatment liquid for aggregating the color material of the ink liquid to the coat layer of the image forming paper;
A drying step of heating and drying the image forming paper provided with the aggregation treatment liquid;
An ink droplet ejection step for forming an image by ejecting the ink liquid onto the image forming paper that has been subjected to the drying step after the aggregation treatment liquid has been applied;
Is used in an image forming apparatus that performs image formation,
The amount of droplets of the ink liquid that can suppress blistering of the coating layer caused by the gas generated by the reaction between the aggregating treatment liquid and the component contained in the coating layer, and the highest layer reachable temperature of the coating layer Preset for each type of image forming paper ,
The image forming method , wherein a layer maximum temperature T [unit: ° C] of the coat layer in the drying step is 80 ≦ T ≦ 100 . The image forming method according to claim 1, wherein the ink liquid is cured by being irradiated with ultraviolet rays. The image forming method according to claim 2, further comprising an ultraviolet irradiation step of irradiating the image forming surface of the image forming paper with ultraviolet rays by an ultraviolet irradiation device after the ink droplet ejection step.
A treatment liquid application device for applying an aggregation treatment liquid for aggregating the color material of the ink liquid to the coat layer of the image forming paper;
A drying device for heating and drying the image forming paper to which the aggregation treatment liquid is applied;
An ink droplet ejecting apparatus that forms an image by ejecting the ink liquid onto the image forming paper that has been subjected to the heat drying after the aggregation treatment liquid is applied;
The amount of droplets of the ink liquid that can suppress blistering of the coating layer caused by the gas generated by the reaction between the aggregating treatment liquid and the component contained in the coating layer, and the highest layer reachable temperature of the coating layer Control means that can be preset for each type of image forming paper,
The control means controls the heating amount of the drying device and the droplet ejection amount of the ink droplet ejection device based on the preset maximum layer temperature of the coat layer and the droplet ejection amount of the ink liquid , An image forming apparatus , wherein a layer maximum temperature T [unit: ° C] of the coat layer that is heated and dried by a drying device is 80 ≦ T ≦ 100 .

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