JP2015039867A - Sheet stacking device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet stacking device capable of restraining flapping of a sheet, while cooling the sheet with a simple constitution.SOLUTION: Air is blown in the horizontal direction by a plurality of nozzles 162 separated in the vertical direction toward a side surface of a sheet bundle so as to form a clearance between a plurality of sheets P of an intermediate part in the vertical direction of the sheet bundle stacked on a paper discharge tray 76. The air is passed between the sheets P of the sheet bundle. Thereby, the plurality of sheets P of the intermediate part in the vertical direction of the sheet bundle can be cooled. Since the plurality of nozzles 162 are separated in the vertical direction, the air-blowing volume is alternately different in a size in the vertical direction, so that the flapping of the sheet P can be restrained as compared with a case of setting the air-blowing volume constant in the vertical direction.

Description

  The present invention relates to a paper stacking apparatus that stacks and cools paper on which images have been recorded and heat-dried.

In inkjet printing, which performs processing at high speed, the paper is heated and dried with hot air, an infrared heater, a UV lamp, etc. to dry the paper. If the temperature of the accumulated paper is high, the printed image is caused by the weight of the paper. May stick to adjacent paper and cause image defects such as white spots and set-off, so-called blocking.
Japanese Patent Application Laid-Open No. 2004-228561 discloses an image forming apparatus having a cooling unit that blows air toward a sheet stacked on a sheet stacking unit.
Patent Document 2 discloses an image forming apparatus that blows air from a lower part to an upper part on a side surface of a sheet bundle and forms a gap between the sheets to cool the sheet bundle. In this image forming apparatus, a top plate is placed on the sheet bundle to cover the sheet bundle in order to prevent the sheet from flying up during blowing.
Patent Document 3 discloses an image forming apparatus that separates stacked sheets into sheet bundles using a separating member, and blows and cools the separated sheet bundles.

JP 2007-76864 A JP 2011-020376 A JP 2012-30913 A

However, since the image forming apparatus of Patent Document 1 blows air from the top to the bottom with respect to the stacked uppermost sheet, it can blow only to the uppermost sheet. For this reason, when the sheet processing speed is increased, the cooling time per sheet is shortened, and the sheet cooling is insufficient.
In the image forming apparatus of Patent Document 2, the top plate must be covered every time the sheet bundle is cooled, and handling is complicated.
The image forming apparatus disclosed in Patent Document 3 requires a plurality of separation members for separating the stacked sheets into a plurality of sheet bundles, and also requires a device for moving the separation members. Therefore, the number of parts is large and the structure is complicated. It becomes.

  In consideration of the above-described facts, an object of the present invention is to provide a paper stacking apparatus that can efficiently cool a paper sheet with a simple configuration, suppressing paper flapping.

  The paper stacking apparatus according to the first aspect blows air toward a side of the paper stack stacked on the paper discharge tray and the paper discharge tray that stacks the paper that has been heated and dried after the image is formed with the ink liquid. A blower that includes a blower and that varies the blown amount in the paper stacking direction alternately.

In the paper stacking apparatus according to the first aspect, the paper that has been heated and dried after the image is formed with the ink liquid is stacked on the paper discharge tray.
From the air blowing unit, air is blown toward the side surface of the sheet bundle stacked on the paper discharge table, whereby air passes between the sheets of the sheet bundle, and a plurality of sheets can be cooled. Since the air blowing unit varies the air flow rate alternately in the paper stacking direction, it becomes difficult to resonate compared to the case where the air flow rate is constant in the paper stacking direction, and fluttering of the paper can be suppressed.
In addition, the case where the air flow rate is small includes the case where the air flow rate is zero.

  The invention according to a second aspect is the paper stacking apparatus according to the first aspect, wherein the air blowing section is provided with a plurality of air ejection sections spaced apart in the vertical direction.

  In the air blowing section of the sheet stacking apparatus according to the second aspect, the plurality of air ejection sections are provided at intervals in the vertical direction, so that the air volume can be varied alternately in the vertical direction.

  According to a third aspect of the present invention, in the paper stacking apparatus according to the first aspect, the air blowing section is provided with a plurality of air ejection sections having different opening areas in the vertical direction.

  In the air blowing section of the paper stacking apparatus according to the third aspect, since the plurality of air ejection portions having different opening areas are provided at intervals in the vertical direction, the air volume can be varied alternately in the vertical direction. . Compared with the case where a plurality of air ejection portions having the same opening area are provided in the vertical direction, a difference in the amount of air flow in the vertical direction can be provided.

  The invention according to a fourth aspect is the paper stacking apparatus according to the first aspect, wherein the air blowing section has an air ejection opening whose opening area changes alternately in the vertical direction.

  The air blowing section of the paper stacking apparatus according to the fourth aspect has the air ejection openings whose opening areas change alternately in the vertical direction. Therefore, if the air blowing amount is different in the vertical direction by one air ejection opening, Can be made.

  The invention according to a fifth aspect is the height adjustment mechanism for changing the relative position in the vertical direction between the paper discharge table and the blower unit in the paper stacking apparatus according to any one of the first to fourth aspects. Have

  In the paper stacking apparatus according to the fifth aspect, the height adjusting mechanism can change the relative position in the vertical direction between the paper discharge platform and the air blowing unit, and thereby the air is blown to a desired position in the height direction of the paper bundle. It can be performed.

  The invention according to a sixth aspect is the paper stacking apparatus according to the fifth aspect, wherein the height detecting device detects the height of the sheet bundle stacked on the paper discharge tray, and is detected by the stacked height detecting device. And a control device for controlling the height adjusting mechanism based on the height of the sheet bundle.

In the paper stacking apparatus according to the sixth aspect, the height detection device can detect the height of the paper bundle stacked on the paper discharge tray.
The control device controls the height adjustment mechanism based on the height of the sheet bundle detected by the accumulated height detection device to change the vertical relative position between the paper discharge table and the blower. As a result, the relative position in the vertical direction between the paper discharge tray and the blower can be automatically changed.

  According to a seventh aspect of the present invention, in the paper stacking apparatus according to the fifth aspect or the sixth aspect, the height adjusting mechanism lowers the paper discharge table according to an increase in the height of the paper bundle.

  In the sheet stacking apparatus according to the seventh aspect, the height adjusting mechanism lowers the sheet discharge table in accordance with the increase in the height of the sheet bundle. Thereby, the position of the upper part of the sheet bundle can be maintained at a certain height (from the installation surface of the sheet stacking apparatus).

  According to an eighth aspect of the present invention, in the paper stacking apparatus according to the sixth aspect or the seventh aspect, the control device controls the blowing amount of the blower unit according to the stacking height of the paper.

  In the paper stacking apparatus according to the eighth aspect, the control device controls the blown amount of the blower according to the stacking height of the paper. When the integrated height is high, the cooling efficiency can be increased by increasing the air flow rate. On the other hand, when the stacking height is low, the airflow can be reduced to suppress the flapping of the paper.

  The invention according to a ninth aspect is the paper stacking apparatus according to the second aspect, wherein the sum of the vertical separation distances of the plurality of air ejection parts is A, and the uppermost air ejection part from the lower end of the lowermost air ejection part The distance C is set to 28% or more, where B is the distance in the vertical direction to the upper end of A and B is the ratio C of the distance.

  In the paper stacking apparatus according to the ninth aspect, since the separation distance ratio C is set to 28% or more, the paper bundle can be stabilized without flapping during blowing.

  The invention according to the tenth aspect is the paper stacking apparatus according to the second aspect, wherein the airflow rate of the portion with the small airflow rate is 22% or less of the airflow rate of the portion with the large airflow rate.

  In the paper stacking apparatus according to the tenth aspect, since the air flow rate of the portion with the small air flow rate is set to 22% or less of the air flow rate with the large air flow rate, the paper bundle is stabilized without flapping. I can do it.

  According to an eleventh aspect of the present invention, in the paper stacking apparatus according to the second aspect, the air ejection portions having a large opening area and the air ejection portions having a small opening area are periodically distributed in the vertical direction.

  In the paper stacking apparatus according to the eleventh aspect, since the air ejection portions are periodically distributed in the vertical direction, it is possible to stabilize the blowing.

  The invention according to a twelfth aspect is the paper stacking apparatus according to the second aspect, wherein a plurality of the air ejection portions are provided along the paper width direction, and the heights of the air ejection portions adjacent in the paper width direction are different. ing.

  In the paper stacking apparatus according to the twelfth aspect, a plurality of air ejection portions are provided along the paper width direction, and the heights of the air ejection portions adjacent to each other in the paper width direction are different. In the paper width direction, the air blowing amount can be varied alternately in size, and the air blowing can be stabilized.

  The paper stacking apparatus of the present invention has an excellent effect that no special member is required and the paper can be cooled while suppressing paper flapping.

1 is a longitudinal sectional view showing an overall configuration of an image recording apparatus including a paper stacking apparatus according to an embodiment of the present invention. (A) is a side view showing a paper stacking apparatus according to an embodiment of the present invention, and (B) is a side view showing a paper discharge platform lifting device provided in the paper stacking apparatus. 1 is a perspective view illustrating an overall configuration of a paper stacking apparatus. (A) is a front view which shows a 1st side jogger and a 1st shutter, (B) is a front view which shows the state which obstruct | occluded the air vent hole of the 1st side jogger with the 1st shutter. (A) is a front view of a 2nd side jogger and a 2nd shutter, (B) is a front view which shows the state which obstruct | occluded some air vent holes of the 1st side jogger with the 2nd shutter. It is. It is a longitudinal cross-sectional view which shows the paper stacking apparatus in a paper feed stand in an initial state. (A) is a plan view showing the arrangement of the nozzles of the paper stacking apparatus according to the embodiment, and (B) is a side view showing the positional relationship between the paper bundle and the nozzles in the height direction. It is a table | surface which shows an evaluation result. It is a front view which shows the nozzle which concerns on other embodiment. It is a front view which shows the nozzle which concerns on other embodiment.

  An example of the image forming apparatus 10 including the paper stacking device 77 according to an embodiment of the present invention will be described with reference to FIGS. In addition, arrow UP in a figure shows the upper direction of an up-down 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 to be processed, the processing liquid drying unit 16 for drying the image forming paper P coated with the processing liquid by the processing liquid application unit 14, and the image formation subjected to the drying processing 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 300 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 portion of the image forming paper P by the gripper 40A, so that the image forming paper P is wound around the peripheral surface while the image forming paper P is wrapped around the image forming paper P. Transport P.

<Processing liquid application part>
The processing liquid coating unit 14 mainly includes a processing liquid coating drum 42 that transports the image forming paper P, and a color material (ink liquid) in a droplet (ink liquid) 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 for aggregating the pigment 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.

(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 liquid)
A water-based UV ink is used as the ink liquid ejected from each recording head 56. The aqueous UV ink is an ink liquid that is cured by irradiating with 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. This polymer particle has a function of fixing the ink liquid by increasing the viscosity of the ink liquid by aggregating due to dispersion instability when contacted with a treatment liquid described later or a dried region thereof, and the ink liquid. The fixing property to the recording medium and the scratch resistance of the image can be further improved.

  In order to react with the aggregating agent, polymer particles having an anionic surface charge are used, and widely known latex is used as long as sufficient reactivity and droplet ejection stability are obtained. It is preferable to use dispersible 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 liquid when it comes into contact with a treatment liquid described later or a dried region thereof, and The fixability of the liquid 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 an aqueous ink liquid (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 liquid. 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 liquid adheres and dries at the ink outlet of the ejection nozzle to form an agglomerate and is used as an anti-drying agent to prevent 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>
In the paper discharge unit 24, a paper stacking device 77 is provided. The paper stacking device 77 includes a paper discharge tray 76 on which the image forming paper P irradiated with UV and released from the gripper 64B is stacked in the vertical direction and collected.
As shown in FIG. 2, a discharge tray lifting / lowering device 100 that changes the height is connected to the discharge tray 76. The paper delivery platform lifting / lowering apparatus 100 includes an endless chain 102 </ b> B that spans a pair of sprockets 102 </ b> A, and a worm wheel 104 is connected to one sprocket 102 </ b> A via a shaft 103. A worm 106 rotated by a motor 105 is engaged with the worm wheel 104. The driving of the motor 105 is controlled by the control device 88.

As shown in FIGS. 2 and 3, a guide plate 108 made of a plate material is disposed on the UV irradiation processing unit side (the direction of arrow A in the drawing) of the paper discharge tray 76. The guide plate 108 includes a horizontal portion 108A that is horizontally disposed, and a paper back guide 108B that is disposed on the discharge tray side of the horizontal portion 108A and extends downward. The horizontal portion 108A and the paper back guide 108B are smoothly connected via the arc portion 108C.
A large number of slits 110 are formed in the horizontal portion 108A and the arc portion 108C, and a plurality of air vent openings 112 are formed in the paper back guide 108B at intervals in the horizontal direction.

As shown in FIG. 3, the first side wall frame 114 is arranged on the side of the paper discharge tray 76 in the direction of the drawing arrow L, and the second side wall frame 116 is arranged on the side of the drawing arrow R direction.
The motor 104 (not shown in FIG. 3; see FIG. 2) of the above-described discharge table lifting apparatus 100 is attached to the first side wall frame 114.

  Further, the first side wall frame side of the paper discharge tray 76 is brought into contact with the end portion of the image forming paper P stacked on the paper discharge tray 76 so that the positions in the arrow R direction side and the arrow L direction side are aligned. There are provided a first side jogger 118 and a side jogger driving mechanism 120 that moves the first side jogger 118 in a direction (arrow R direction and arrow L direction) to contact and separate from the image forming paper P. The structure of the side jogger drive mechanism 120 is not particularly limited, and a linear actuator, a cam mechanism, a link mechanism, a rack / pinion mechanism, or the like can be used.

As shown in FIG. 4A, the first side jogger 118 has a rectangular plate shape elongated in the lateral direction, and a plurality of air vent holes 122 are formed in the longitudinal direction and the vertical direction.
A first shutter plate 126 that is moved up and down by a first actuator 124 is disposed on the opposite side of the first side jogger 118 from the paper discharge platform side. As shown in FIG. 4B, the plurality of air vent holes 122 formed in the first side jogger 118 are closed by lowering the first shutter plate 126 and facing the first side jogger 118. Can do.
The shape of the air vent hole 122 is not limited to a round shape, but may be other shapes such as a rectangle, a polygon, and a slit.

  As shown in FIG. 3, a second side jogger 128 that abuts the end of the image forming paper P accumulated on the paper discharge tray 76 is attached to the second side wall frame 116 of the paper discharge tray 76. Yes. Note that the second side jogger 128 has the same configuration as the first side jogger 118.

On the opposite side of the second side jogger 128 from the paper discharge platform side, as shown in FIG. 5A, a second shutter plate 132 that is moved up and down by the second actuator 130 is disposed. The second shutter plate 132 is formed in substantially the same size as the second side jogger 128, and a notch 134 for venting air is formed in the central portion in the longitudinal direction.
As shown in FIG. 5B, when the second shutter plate 132 is lowered, the second side jogger 128 facing the notch 134 in the plurality of air vent holes 122 formed in the second side jogger 128 is shown. The air vent hole 122 formed in the vicinity of the center in the longitudinal direction is not closed, and the air vent hole 122 not opposed to the notch 134 is closed.
Note that the end of the image forming paper P can be brought into contact with the second side jogger 128 by pressing the image forming paper P placed on the paper discharge tray 76 by the first side jogger 118.

As shown in FIG. 3, on the side opposite to the arrow A direction of the paper discharge tray 76, a first support member 138 that bridges the first side wall frame 114 and the second side wall frame 116, and a second A support member 140 is provided.
A reflected light type photoelectric sensor 142 that detects the upper end of the sheet bundle on the paper discharge tray 76 is attached to the first support member 138. The photoelectric sensor 142 includes a light source such as an LED or a laser diode that emits light, and a light receiving sensor such as a photodiode that receives reflected light reflected by the light irradiation target (image forming paper P). This photoelectric sensor 142 is connected to the control device 88.
The photoelectric sensor 142 is arranged at a predetermined distance above the uppermost nozzle 162 described later.
As a sensor capable of detecting the upper end of the sheet bundle, another sensor such as a transmitted light type photoelectric sensor or an electrostatic sensor may be used instead of the photoelectric sensor 142.

A shaft 146 whose both ends are rotatably supported by the first side wall frame 114 and the second side wall frame 116 is disposed on the side opposite to the arrow A direction side of the first support member 138.
The shaft 146 has a plurality of (four in this embodiment) front joggers 148 that are in contact with the end of the image forming paper P stacked on the paper discharge tray 76 on the side opposite to the arrow A direction. Are arranged at intervals in the longitudinal direction. The front jogger 148 has an upper end fixed to the shaft 146 and extends downward from the shaft 146. Note that knobs 149 for moving the front jogger 148 away from the paper are attached to both ends of the shaft 146.

  A first bevel gear 150 is attached to the central portion of the shaft 146 in the longitudinal direction. A motor 154 is attached to the first support member 138. The motor 154 is connected to and controlled by the control device 88. A second bevel gear 156 is attached to the rotation shaft of the motor 154, and the second bevel gear 156 meshes with the first bevel gear 150. Therefore, by rotating the motor 154, the shaft 146 can be rotated to swing the front jogger 148, and the end of the image forming paper P placed on the paper discharge tray 76 is moved by the front jogger 148. By pressing, the opposite end of the image forming paper P can be brought into contact with the paper back guide 108B.

A blower 158 is provided on the side opposite to the arrow A direction side of the paper discharge tray 76.
The air blower 158 of this embodiment includes two blowers 160 that are connected to and controlled by the control device 88. Each blower 160 includes a total of six nozzles 162, two rows in the horizontal direction and three rows in the vertical direction. The nozzle 162 corresponds to the air ejection part of the present invention.
The nozzle 162 extends horizontally toward the paper discharge platform, and air is ejected horizontally from the tip of the nozzle 162 in the direction of arrow A. The nozzle 162 of the present embodiment has a rectangular shape with the opening at the tip being elongated in the direction of the arrow R and the direction of the arrow L, and all have the same shape.
Note that the lower end of the front jogger 148, the lower end of the first side jogger 118, and the lower end of the second side jogger 128 are located below the lowest nozzle 162.

  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 to the processing liquid coating unit 14 by the paper feed drum 40.

  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 conveyance 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 process).

  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 coated with the processing liquid) 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 liquid) 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 configuration, the image forming apparatus 10 supplies the processing liquid to an ink storage tank that supplies ink liquid to the recording heads 56C, 56M, 56Y, and 56K, and the processing liquid application unit. 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.
The control device 88 is further connected to a display device 90 capable of displaying the type of image forming paper P, the state of the device, and the like, an operation panel 92 for performing various operations of the device, and the like.
The control device 88 stores in advance the weight and thickness of each type of image forming paper P (per sheet), and the image forming paper P can be selected by selecting the type of image forming paper P on the operation panel 92. Control of each part is performed correspondingly. Details of the control will be described later.

(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 coated with the processing liquid is conveyed along the outer peripheral surface of the processing liquid drying drum 46 and dried by heating.
In the image recording unit 18, the recording heads 56 C, 56 M, 56 Y, and 56 K for each color eject droplets (ink liquid) onto the recording surface (coat layer) of the image forming paper P conveyed by the image recording drum 52. An image is formed on the image forming paper P. At that time, the ink liquid comes into contact with the processing liquid previously applied to the recording surface by the processing liquid coating unit 14, and the pigment and resin particles dispersed in the ink 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 liquid 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 performing image formation, the operation panel 92 is operated to select one to be used from a plurality of types of image forming paper P set in advance.
The control device 88 controls each device based on various setting values corresponding to the selected image forming paper P.

Hereinafter, the operation of the paper discharge unit 24 will be described in detail.
(1) Before the image forming paper P is stacked for the first time, the control device 88 controls the paper discharge platform lifting device 100, and the upper surface of the paper discharge tray 76 is placed from the lowermost nozzle 162 as shown in FIG. Is also positioned downward by a preset distance.

(2) When the heat-dried image forming paper P is discharged to the paper discharge tray 76, the control device 88 controls the side jogger drive mechanism 120 and the motor 154 to control the first side jogger 118, and The end of the image forming paper P is pressed by the front jogger 148. As a result, the image forming paper P is pressed against the second side jogger 128 and the paper back guide 108B of the guide plate 108. Every time the image forming paper P is stacked, the end of the image forming paper P is pressed by the first side jogger 118 and the front jogger 148 so that the image forming paper P is stacked while being aligned.
Here, when the image forming paper P is initially stacked, the air is weakly blown from the nozzles 162 of the blower 160. The blowing amount at this time is stored in the controller 88 in advance. Note that when the image forming paper P is initially stacked, the weight acting on the lower image forming paper P is relatively small, so that blocking does not occur.

(3) After the upper end of the sheet bundle is detected by the photoelectric sensor 142, the height of the image forming sheets P sequentially discharged onto the sheet bundle is set in advance (the control device 88 is the control device 88). This value is calculated by the thickness of the image forming paper P set in step x the number of ejected image forming paper P. As an example, when the value reaches 1 mm, the control device 88 controls the paper discharge platform lifting device 100. Then, the discharge tray 76 is lowered by a preset dimension (for example, 1 mm). Thereby, the upper end of the sheet bundle is kept at a fixed position.
(3) As shown in FIG. 2A, when the image forming sheets P are stacked and the height of the sheet bundle is increased, the controller 88 increases the amount of air blown from the nozzles 162 of the blower 160 and opens the nozzles 162. A gap is formed between the image forming paper P and the image forming paper P by allowing air to pass between the image forming paper P and the image forming paper P positioned in front of the image forming unit. Note that the control device 88 can calculate the height of the sheet bundle from the thickness of the image forming sheet P and the accumulated number of sheets, and can determine the timing for increasing the blowing amount.
Thereby, a plurality of image forming sheets P facing the front of the opening of the nozzle 162 can be simultaneously and efficiently cooled.
Further, by separating the plurality of nozzles 162 in the vertical direction and separating a large portion of the air flow rate without continuing in the vertical direction, the image forming paper P positioned above the nozzles 162 is difficult to resonate, Flutter can be suppressed.
The cause of the fluttering of the image forming paper P is that the nozzle 162 is continuously provided in the vertical direction, so that the air blown area between the papers in the paper bundle becomes long in the vertical direction. It is considered that the weight of the elastic body and the image forming paper P becomes a mass, and the paper bundle resonates due to air blowing.
Note that the air that has passed between the image forming paper P and the image forming paper P in the sheet bundle passes through the opening 112 (not shown in FIG. 2A) formed in the paper back guide 108B of the guide plate 108. Through the paper discharge unit 24.

  Further, since the weight of the sheet bundle positioned above the front of the opening of the uppermost nozzle 162 is kept within a certain range, the weight acting on the image forming surface of the image forming sheet P of the sheet bundle has a weight. The occurrence of blocking can be suppressed without becoming excessive.

  The image forming paper P positioned below the front of the opening of the lowermost nozzle 162 is not blown from the side, and the image forming paper is near the lower end of the lowermost nozzle 162. Each time the P falls, the end of the sheet is pressed by each jogger, so that the image forming sheets P of the sheet bundle accumulated below the lowermost nozzle 162 are not displaced. Further, since the image forming paper P positioned below the front of the opening of the lowermost nozzle 162 is sufficiently cooled, no blocking occurs even if a large weight is applied.

  As described above, in the image forming apparatus 10 of the present embodiment, the image forming paper P can be efficiently cooled and fluttering of the image forming paper P can be suppressed. Sticking and folding can be suppressed.

Here, for example, the gap size of the image forming paper P formed by blowing is narrow on the first side jogger 118 side and widened on the second side jogger 128, and the upper surface of the paper bundle is the second side jogger 128. When the first side jogger 118 side is lower than the side, the gap size of the image forming paper P can be made constant and the inclination of the paper bundle can be corrected as follows.
As shown in FIGS. 4B and 5B, the first shutter plate 126 and the second shutter plate 132 are moved down to block all the air vent holes 122 of the first side jogger 118, and The plurality of air vent holes 122 of the second side jogger 128 are not blocked. As a result, part of the air that has entered between the image forming sheets P of the sheet bundle is discharged from the non-blocked air vent hole 122 of the second side jogger 128, and the image forming sheet P on the second side jogger 128 side is discharged. The inclination of the sheet bundle can be corrected by narrowing the interval.

(Test Example 1)
Testing how the height dimension (z) of the air blowing area, the aperture ratio (a) of the air blowing area, and the air volume (q) of each air blowing area affect the paper cooling temperature, occurrence of blocking, and paper fluttering Went.
The test conditions are as follows.
Paper: Eye vest W (manufactured by Nippon Paper Industries), paper weighing 310 gsn, paper thickness 0.34 mm, paper size 750 × 530 mm.
-Number of printed sheets: 1000 sheets.
-Paper temperature: Paper is discharged to a paper discharge tray at 55 ° C.
External environment: room temperature 23 ° C, humidity 50% RH.
As shown in FIGS. 7A and 7B, a total of 20 nozzles 162 were arranged in four rows in the horizontal direction and five rows in the vertical direction.
Air blow region total height Z (vertical dimension from the lower end of the opening of the bottom of the nozzle 162 to the upper end of the opening of the top of the nozzle 162) is 25 mm, 20 mm width _{w 1} of the opening of the nozzle 162, the lateral spacing _{w 2} of the opening of the nozzle 162 was set to 60 mm. Each nozzle 162 adjusted the air volume by adjusting the aperture ratio at the tip. The air volume was calculated by measuring the wind speed in each nozzle and multiplying the cross-sectional area.

The evaluation index is as follows.
-Paper cooling temperature: Insert a thermocouple into the cooled paper bundle and measure the paper temperature.
A: Paper temperature ≦ 40 ° C
B: 40 ° C <paper temperature ≦ 45 ° C
C: 45 ° C. <paper temperature / blocking: A solid image is printed on both sides, and after standing overnight, the paper is turned over and visually evaluated for blocking (image peeling).
A: No blocking occurrence B: Minor blocking (Slight image peeling, but no problem in practical use)
C: Occurrence of blocking / fluttering of paper: Visual evaluation of fluttering of paper during blowing.
A: No fluttering B: There is some fluttering, but there is no practical problem.
C: Fluctuation is large, and the paper is scratched or broken.
The evaluation results were as shown in FIG.
In the table of FIG. 8, “weak air blowing area distance sum (A: mm)” = z2 + z4, “ratio of separation distance (C:%)” = (z2 + z4) / 25 in the table of FIG. 8, FIG. In the table, “ratio of the air volume in the separation part (%)” = {(q2 + q4) / 2} / {(q1 + q3 + q5) / 3}.

[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.
In the above embodiment, the upper end position of the sheet bundle is directly detected using the photoelectric sensor 142, but the upper end position of the sheet bundle can be indirectly detected by other methods.
For example, a weight sensor is provided on the paper discharge tray 76, and the control device 88 is based on the weight of the image forming paper P detected by the weight sensor, the weight per thickness of the image forming paper P known in advance, and the thickness. The height of the sheet bundle can be calculated.

  In the embodiment described above, the vertical distance h from the upper end of the uppermost nozzle 162 to the upper end of the sheet bundle is kept constant by changing the height position of the paper discharge tray 76, but the present invention is not limited to this. By connecting an actuator that moves the blower 160 in the vertical direction to the blower 160 and increasing the position of the nozzle 162 as the height of the sheet bundle increases, the vertical distance h can be kept constant.

  In the air blower 158 of the above embodiment, the two blowers 160 are used. However, the number of the blowers 160 is not limited to two, and may be provided for each nozzle 162. You may distribute it.

In the blower 158 of the above embodiment, the two blowers 160 are used. However, the number of the blowers 160 is not limited to two, and may be provided for every 12 nozzles 162. You may distribute to 12 nozzles 162.
When the blower 160 is provided for each nozzle, for example, SanAce B97 (maximum static pressure 1280 Pa, maximum air volume 1.61 m ³ / min) manufactured by Sanyo Denki Co., Ltd. can be used. When distributing to the nozzles 162, for example, EM-125M2 (maximum static pressure 1670 Pa, maximum air volume 33 m ³ / min) manufactured by Showa Denki Co., Ltd. can be used for the blower 160.
In order to secure a sufficient air volume for allowing the image forming paper P to sufficiently float, the static pressure is preferably 500 Pa or more, and more preferably 1000 Pa or more. Further, in order to sufficiently cool the image forming paper P, the air volume is preferably 8 m ³ / min or more, and more preferably 15 m ³ / min or more.
In the above embodiment, the accumulated image forming paper P is cooled by blowing air, but the image forming paper P being conveyed may be cooled.

In the above embodiment, the nozzles 162 are arranged in a matrix in the vertical direction and the paper width direction. However, the present invention is not limited to this, and the height of the plurality of nozzles 162 and the separation distance in the vertical direction can be set in the paper width direction. For example, a plurality of nozzles 162 may be arranged in a staggered manner.
The plurality of nozzles 162 may have different opening areas.

  In the above embodiment, air is blown using a plurality of nozzles 162 whose openings are rectangular. However, the present invention is not limited to this, and for example, the width is set to be approximately the same as the size in the paper width direction. A single nozzle 162 as shown in FIG. 9 is used, and a large-diameter air jet 162A with a large air flow rate and a small-diameter air jet 162B with a small air flow rate are provided at the tip of the nozzle 162 in the vertical direction. Alternatively, it may be formed alternately. The shapes of the air outlet 162A and the air outlet 162B shown in FIG. 9 are circular, but may be other shapes such as a triangle, a polygon, a rectangle, and an ellipse.

As shown in FIG. 10, a single nozzle 162 is used, a plurality of horizontal slits 162C extending in the paper width direction are formed in the vertical direction, and the horizontal slits 162C are connected to each other by vertical slits 162D extending in the vertical direction. The opening area may be changed alternately in the vertical direction by one air ejection opening.
In any of the nozzles 162 shown in FIGS. 9 and 10, the amount of air blown in the vertical direction can be set alternately.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 76 Paper discharge stand 77 Paper stacking device 88 Control apparatus 100 Paper discharge stand raising / lowering device (height adjustment mechanism)
142 Photoelectric sensor (height detection device)
158 Air blower 162 Nozzle (air blower, air blower)
162A Air outlet (blower, air outlet)
162B Air outlet (blower, air outlet)
162C Horizontal slit (air blower, air outlet opening)
162D Upper and lower slits (blower, air outlet opening)
P Image forming paper

Claims (12)

A paper discharge tray for stacking paper that has been heat-dried after an image is formed with ink liquid;
A blower that includes a blower that blows air toward the side of the bundle of sheets stacked on the paper discharge table, and that has a different amount of blown air in the paper stacking direction; and
A paper stacking apparatus.   The paper stacking apparatus according to claim 1, wherein the air blowing unit is provided with a plurality of air ejection units spaced in the vertical direction.   The paper stacking apparatus according to claim 1, wherein the blower unit is provided with a plurality of air ejection units having different opening areas in the vertical direction.   The paper stacking apparatus according to claim 1, wherein the air blowing section has an air ejection opening whose opening area changes alternately in the vertical direction.   5. The sheet stacking apparatus according to claim 1, further comprising a height adjustment mechanism that changes a relative position in the vertical direction between the sheet discharge table and the air blowing unit. A height detecting device for detecting the height of the sheet bundle accumulated on the paper discharge table;
A control device that controls the height adjustment mechanism based on the height of the sheet bundle detected by the integrated height detection device;
The paper stacking apparatus according to claim 5.   The paper stacking apparatus according to claim 5, wherein the height adjustment mechanism lowers the paper discharge table in accordance with an increase in the height of the paper bundle.   The paper stacking device according to claim 6 or 7, wherein the control device controls a blowing amount of the blower according to a stacking height of the paper.   The sum of the vertical separation distances of the plurality of air ejection portions is A, the vertical distance from the lower end of the lowermost air ejection portion to the upper end of the uppermost air ejection portion is B, and the ratio C of the separation distances is A The sheet stacking apparatus according to claim 2, wherein the ratio C of the separation distance is set to 28% or more when / B is set.   The paper stacking apparatus according to claim 2, wherein a blown amount of a portion with a small blown amount is 22% or less of a blown amount of a portion with a large blown amount.   The paper stacking apparatus according to claim 2, wherein the air ejection portion having a large opening area and the air ejection portion having a small opening area are periodically arranged in the vertical direction. A plurality of the air ejection portions are provided along the paper width direction,
The paper stacking apparatus according to claim 2, wherein heights of the air ejection portions adjacent in the paper width direction are different.

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