JP4584070B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  A recording medium using a recording head (image forming means) composed of a liquid ejection head for ejecting recording liquid droplets as an image forming apparatus such as a printer, a facsimile machine, a copying machine, a printer / fax / copier multifunction machine, etc. (Paper, recording medium, transfer material, etc. are also used interchangeably.) While transporting the recording liquid droplets (hereinafter also referred to as ink droplets) on the paper, image formation (recording, printing, printing) Are also used synonymously.) Are known.

  As described above, in the ink jet recording apparatus, since an image is formed using a recording liquid, a certain amount of time is required until the recording liquid that has landed on the recording medium dries. Until the recording liquid dries, the recording medium on which image formation has been completed is put on standby in the apparatus, or when performing duplex printing, the recording medium is once discharged onto the discharge tray and then fed again. ing.

For example, Japanese Patent Application Laid-Open No. H10-228561 describes that there is provided a means for delaying the discharge of the current recording sheet to the discharge tray for a set time when the previous dot density determination result exceeds a predetermined set value.
Japanese Patent No. 3109529

Further, Patent Document 2 describes that when performing double-sided printing, after printing on one side of a sheet, at least a part of the sheet is once discharged out of the apparatus main body so that a drying time can be secured.
Japanese Patent Publication No. 2000-001010

  By the way, in an inkjet recording apparatus, in order to implement | achieve the high-speed and high-quality recording with respect to plain paper, there exists a tendency to use a highly viscous recording liquid (high viscosity ink). In other words, especially when printing on plain paper with inkjet recording, image color reproducibility, durability, light resistance, ink drying, character bleeding (feathering), color boundary bleeding (color bleeding), duplex printing Thus, image quality deterioration problems peculiar to ink jet recording have become obvious, and when performing high-speed printing on plain paper, it is an extremely difficult task to satisfy all these characteristics for printing.

  In general, a recording liquid (ink) used in ink jet recording is generally composed mainly of water and contains a colorant and a wetting agent such as glycerin for the purpose of preventing clogging. . As the colorant, there are a dye and a pigment, and a dye-based ink is often used for the color portion from the viewpoint that excellent color developability and stability can be obtained. However, fastness such as light resistance and water resistance of an image obtained using a dye-based ink is inferior to that using a pigment as a colorant, and in particular, the water resistance has an ink absorption layer. If ink jet recording paper is used, a certain degree of improvement can be achieved, but satisfaction is not obtained when plain paper is used.

  Therefore, in order to improve the problems with the dye-based inks when using plain paper, the use of pigment-based inks using organic pigments, carbon black, etc. as colorants is considered for printing on plain paper, or It has been put into practical use. Since pigments are not soluble in water unlike dyes, they are usually used as water-based inks in a state where pigments are mixed with a dispersing agent, dispersed and stably dispersed in water.

  Since such pigment-based inks are generally high-viscosity (5 mPa · s or more) inks, when printed on plain paper, they are faster-drying than dye-based inks, but cause curling of the recording medium. There is a problem that it is easy.

  That is, in the dye-based ink, moisture permeates the back surface of the recording medium and the difference in moisture between the front and back surfaces of the recording medium is reduced. Curling due to the difference in moisture is relatively unlikely to occur.

  On the other hand, since the pigment-based ink has a quick drying property, it does not take time to dry the ink on the recording medium, but it takes time to bleed into the recording medium. Since the difference in moisture on the back side becomes large, curling due to the difference in moisture between the front and back surfaces of the recording medium is likely to occur, and when curling occurs, it dries quickly and solidifies in the curled state. become.

  As described above, if the curled paper is conveyed as it is, there is a problem that a jam occurs, the paper discharge stability is deteriorated and the paper is folded and the quality is deteriorated.

  The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus in which curling is reduced even when plain paper printing is performed using a high viscosity recording liquid.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A recording head for discharging droplets of recording liquid ;
In the apparatus main body, one surface of the recording medium on which image formation by the recording head has been completed is held by a guide plate, and the recording medium is conveyed from both sides of the recording medium with a roller and a spur constrained respectively. Conveying means for
Control means for controlling the recording medium that has been subjected to the image formation to be stopped in a state in which the recording medium is restrained by the conveying means and to wait .
The control means includes
During the curl suppression waiting time until curling due to the droplets landing on the recording medium is less likely to occur, the recording medium is made to wait in the restrained state,
Means for changing the curl suppression standby time according to at least one of the amount of droplets driven into the recording medium and the absolute humidity in the apparatus main body.
The configuration.

Here, the changing means may be configured to change the curl suppression standby time according to at least one of the amount of droplets driven into the recording medium and the absolute humidity in the apparatus main body and the type of the recording medium. .
The image forming apparatus according to claim 1.

According to the image forming apparatus of the present invention, one surface of the recording medium on which image formation by the recording head has been completed is held by the guide plate in the apparatus main body, and is covered by a roller and a spur from both sides of the recording medium. comprising conveying means for conveying the recording medium in a state of being restrained, and a control means for performing remains controlled to wait is stopped in a state in which the recording medium on which image formation has ended restraint by the conveying means has been performed, the control The means waits in a state where the recording medium is constrained for a curling suppression standby time until curling due to droplets landing on the recording medium is less likely to occur, and the curling suppression standby time is driven into the recording medium. since the configuration includes a means for changing in accordance with at least one of the absolute humidity of saliva drop volume and the apparatus body, plain paper print curling is suppressed as much as possible mosquito even when conducted Le is reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. An example of an image forming apparatus according to the present invention will be described with reference to FIGS. 1 is a schematic configuration diagram showing the overall configuration of the image forming apparatus, FIG. 2 is a plan explanatory view of an image forming unit and a sub-scanning conveying unit of the apparatus, FIG. 3 is a side explanatory view, and FIG. FIG. 4 is an explanatory diagram of a main part of a paper transport unit 7.

  This image forming apparatus has an image forming part (means) 2 for forming an image, a sub-scanning conveying part (means) 3, etc. in the inside (enclosure) of the apparatus main body 1. The paper 5 is fed one by one from the paper feed unit (means) 4 provided, and the paper 5 is conveyed by the image forming unit 2 while the sub-scanning conveying unit 3 conveys the paper 5 at a position facing the image forming unit 2. In the case of single-sided printing, a sheet 5 is placed on a paper discharge tray 8 formed on the upper surface of the apparatus main body 1 through a paper discharge conveyance unit (means). In the case of paper discharge and double-sided printing, the paper is transported from the middle of the paper discharge transport unit 7 to the double-sided unit 10 provided at the bottom of the apparatus main body 1 to perform switchback transport and feed the sub-scan transport unit 3 again. After forming images on both sides, the paper is discharged onto the paper discharge tray 8.

  The image forming apparatus also has an image reading unit (scanner) for reading an image above the discharge tray 8 above the apparatus main body 1 as an input system for image data (print data) formed by the image forming unit 2. Part) 11. The image reading unit 11 includes a scanning optical system 15 including an illumination light source 13 and a mirror 14 and a scanning optical system 18 including mirrors 16 and 17. The scanned document image is read as an image signal by the image reading element 20 disposed behind the lens 19, and the read image signal is digitized and subjected to image processing, and the image-processed print data is printed. be able to.

  Further, this image forming apparatus uses an information processing apparatus such as an external personal computer, an image reading apparatus such as an image scanner, and an imaging apparatus such as a digital camera as an input system for image data (print data) formed by the image forming unit 2. For example, print data including image data from the host side can be received via a cable or a network, and the received print data can be processed and printed.

  Here, as shown in FIG. 2, the image forming unit 2 of the image forming apparatus holds the carriage 23 movably in the main scanning direction by the guide rod 21 and a guide stay (not shown), and is driven by the main scanning motor 27. It moves and scans in the main scanning direction via a timing belt 29 spanned between the pulley 28A and the driven pulley 28B.

  A recording head 24 including a droplet discharge head for discharging droplets of each color is mounted on the carriage 23, the carriage 23 is moved in the main scanning direction, and the sheet 5 is transferred to the sheet by the sub-scanning conveyance unit 3. A shuttle type is used in which droplets are ejected from the recording head 24 while feeding in the transport direction (sub-scanning direction) to form an image. A line-type head can also be used.

  The recording head 24 has two droplet discharge heads 24k1 and 24k2 that discharge black (Bk) ink, respectively, and one each that discharges cyan (C) ink, magenta (M) ink, and yellow (Y) ink. Each of the sub-tanks 25 mounted on the carriage 23 is composed of a total of five liquid droplet ejection heads (hereinafter referred to as “recording head 24” when the colors are not distinguished). Of ink is supplied.

  On the other hand, as shown in FIG. 1, a recording liquid cartridge containing black (Bk) ink, cyan (C) ink, magenta (M) ink, and yellow (Y) ink from the front of the apparatus main body 1 to the cartridge mounting portion. Each color ink cartridge 26 can be detachably mounted, and ink is supplied from each color ink cartridge 26 to each color sub-tank 25. The black ink is supplied from one ink cartridge 26 to the two sub tanks 25.

  The recording head 24 uses a piezoelectric element as a pressure generating means (actuator means) for pressurizing the ink in the ink flow path (pressure generation chamber) to deform the vibration plate that forms the wall surface of the ink flow path. A so-called piezo type that discharges ink droplets by changing the volume in the flow channel, or discharges ink droplets with a pressure generated by heating the ink in the ink flow channel using a heating resistor to generate bubbles. The so-called thermal type, the diaphragm that forms the wall surface of the ink flow path and the electrode are placed opposite to each other, and the diaphragm is deformed by the electrostatic force generated between the vibration plate and the electrode, thereby the ink flow path inner volume It is possible to use an electrostatic type or the like that discharges ink droplets by changing the above.

  Further, as shown in FIG. 2, a maintenance / recovery device 121 for maintaining and recovering the nozzle state of the recording head 24 is disposed in the non-printing area on one side in the scanning direction of the carriage 23. The maintenance / recovery device 121 includes five moisturizing caps 122k2, 122k1, 122c, 122m, and 122y for capping the nozzle surfaces of the five recording heads 24 (“moisturizing caps” when colors are not distinguished). 122 ”), a single suction cap 123, a wiper blade 124 for wiping the nozzle surface of the recording head 24, and discharge (empty discharge) of droplets that do not contribute to recording (image formation). For example, an empty discharge receiving member 125 is provided.

  Further, as shown in FIG. 2, in the non-printing area on the other side of the carriage 23 in the scanning direction, droplets that do not contribute to recording (image formation) (empty discharge) are discharged from the five recording heads 24. An empty discharge receiving member 126 is provided. The empty discharge receiving member 126 has five openings 127k2, 127k1, 127c, 127m, and 127y corresponding to the recording head 24 (referred to as “openings 127” when colors are not distinguished).

  As shown in FIG. 3, the sub-scanning conveyance unit 3 is a driving roller for conveying the paper 5 fed from below by changing the conveyance direction by approximately 90 degrees and facing the image forming unit 2. An endless transport belt 31 laid between the transport roller 32 and a driven roller 33 which is a tension roller, and a charging means to which a high voltage as an alternating voltage is applied from a high voltage power source in order to charge the surface of the transport belt 31 A charging roller 34, a guide member 35 that guides the conveyance belt 31 in a region facing the image forming unit 2, and a pressing roller (pressure roller) that presses the paper 5 against the conveyance belt 31 at a position facing the conveyance roller 32. 36 and a separation claw 37 for separating the paper 5 on which the image is formed by the image forming unit 2 from the transport belt 31.

  The transport belt 31 of the sub-scan transport unit 3 is rotated in the paper transport direction (sub-scan direction) in FIG. 2 by rotating the transport roller 32 from the sub-scan motor 131 through the timing belt 132 and the timing roller 133. It is configured to do. The transport belt 31 includes, for example, a surface layer that is a sheet adsorption surface formed of a pure resin material that is not subjected to resistance control, such as ETFE pure material, and a back layer that is subjected to resistance control using carbon with the same material as the surface layer. Although a two-layer structure (medium resistance layer, earth layer) is used, the present invention is not limited to this, and a one-layer structure or a structure of three or more layers may be used.

  In addition, a cleaning unit (mylar is used here) 135 for removing paper dust and the like adhering to the surface of the conveyor belt 31 between the driven roller 33 and the charging roller 34, and the surface of the conveyor belt 31. And a static elimination brush 136 for removing electric charges.

  The paper feed unit 4 can be inserted / removed from the front side of the apparatus main body 1. The paper feed cassette 41 that stacks and stores a large number of sheets 5 and the sheets 5 in the sheet feed cassette 41 are separated and sent out one by one. For this purpose, a feed roller 42 and a friction pad 43 are provided.

  In addition, the paper feed unit 4 includes a manual feed tray 46 for loading and storing the paper 5, a manual feed roller 47 for feeding the paper 5 one by one from the manual feed tray 46, and a lower side of the apparatus main body 1. A transport roller 48 for transporting paper 5 fed from an optional paper feed cassette or duplex unit 10 and a transport roller 49 for feeding the fed paper 5 to the sub-scanning transport unit 3 are provided. ing. A member for feeding the sheet 5 to the sub-scanning conveying unit 3 such as the sheet feeding roller 42 is rotationally driven by a sheet feeding motor (driving means) 45 including an HB type stepping motor via a sheet feeding clutch (not shown).

  As shown in FIG. 4, the paper discharge conveyance unit 7 includes a conveyance roller 71 that feeds the paper 5 separated by the separation claw 37 of the sub-scanning conveyance unit 3, a spur 72 that faces the conveyance roller 71, and a lower side of the paper 5. A guide plate 170A for guiding and holding, an upper guide plate 170B facing the guide plate 170A, transport rollers 73 and 74 for transporting the paper 5, and for transporting the paper 5 and restraining the paper 5 from above and below. Are provided with conveying rollers 171 to 173 and spurs 174 to 176 opposed thereto, a conveying roller pair 76 for sending the paper 5 to the paper discharge tray 8, and a paper discharge roller pair 77. A conveyance path for discharging the paper 5 to the paper discharge tray 8 is a discharge conveyance path 70.

  The duplex unit 10 receives a sheet 5 conveyed by being guided by the branch plate 60 from the side surface of the apparatus main body 1 and conveys the sheet 5 downward, and includes a vertical conveyance unit 101a that constitutes a vertical duplex conveyance path 90c, and a vertical duplex conveyance path 90c. Subsequently, a horizontal feeding conveyance path 90a that conveys in the horizontal direction and a horizontal conveyance section 101b that constitutes a switchback conveyance path 90b are integrally provided.

  The vertical double-sided conveyance path 90c is provided with a double-sided entrance roller pair 91 for conveying the fed paper 5 downward and a conveyance roller pair 92 for sending it out to the horizontal taking-in conveyance path 90a. 93, and the switchback conveyance path 90b includes a double-sided exit roller 94 composed of a reverse roller for reversing and refeeding the sheet 5 fed from the take-in conveyance path 90a and three double-sided conveyance roller pairs 95. Yes.

  Further, the branch plate 96 for switching between the conveyance path of the sheet 5 from the take-in conveyance path 90a to the switchback conveyance path 90b and the conveyance path for refeeding from the switchback conveyance path 90b to the conveyance roller pair 48 can be swung. Provided. The branch plate 96 can swing between a switchback side position shown by a solid line in FIG. 1 and a refeeding side position shown by a broken line.

  Note that the branch plate 60 is disposed at the discharge side position indicated by the solid line in FIG. 1 in order to switch the conveyance direction of the sheet 5 to the discharge tray 8 direction and the duplex conveyance unit 10 side on the downstream side of the discharge conveyance roller pair 75. The paper 5 can be swung between the double-sided position shown in the broken line, and when the paper 5 is in the paper discharge side position, the paper 5 is guided to the paper discharge roller pair 76 side. Guide to pair 91 side.

  Although not shown, an image start sensor for detecting the leading edge of the paper 5 on the upstream side in the paper conveyance direction of the image forming unit 2 and an image end for detecting the trailing edge of the paper 5 on the downstream side in the paper conveyance direction are also shown. A sensor is provided.

Next, an outline of the control unit of the image forming apparatus will be described with reference to FIG. The figure is a schematic block diagram of the control unit.
The control unit 200 includes a CPU 201 that controls the entire image forming apparatus, a ROM 202 that stores programs executed by the CPU 201 and other fixed data, a RAM 203 that temporarily stores image data (print data), and the like. Non-volatile memory (NVRAM) 204 for holding data even while the power is cut off, image processing for performing various signal processing and rearrangement on image data, and other input / output signals for controlling the entire apparatus An ASIC 205 for processing and a scanner control unit 206 for performing image reading by the image reading unit 11 and data processing of the read image are provided.

  The control unit 200 also has an I / F 207 for transmitting and receiving data and signals used when receiving data from an external device, and a head drive control for driving and controlling the recording head 21 of the image forming unit 2. Section 208, head driver 209, main scanning motor 121 for main scanning of carriage 23, sub-scanning motor 131 for rotating conveying belt 32 by rotating conveying roller 32, paper feeding motor 45, and rollers for discharge conveying section 7 Motor driving units 211 to 211 including motor drivers for independently driving various motors (drive sources) such as a paper discharge motor 271 that rotates the paper and a double-sided conveyance motor 291 that rotationally drives the rollers of the duplex unit 10. 215.

  Also, a sheet feeding electromagnetic clutch for rotationally driving the sheet feeding roller 43, a branching plate solenoid for swinging and displacing the branching plate 60 between the paper discharge position and the double-sided position, and the branching plate 96 with a switchback position and a refeeding position. A clutch drive unit 216 for driving a branch plate solenoid or the like (which is referred to as a “clutch 241”), and an AC bias for applying an AC bias voltage (high voltage) to the charging roller 34. A supply unit 217 and the like are provided.

  The control unit 200 further includes an I / O 221 for capturing detection signals from the temperature / humidity sensor 300 that detects temperature and humidity, and detection signals from various sensors such as an image start sensor and an image end sensor (not shown). An operation panel 222 for inputting and displaying information necessary for the apparatus is connected.

  Here, the temperature / humidity sensor 300 for detecting temperature and humidity is provided in at least one of the locations indicated by the sensors S1 to S4 in FIG. By providing the temperature / humidity sensor 300 in the vicinity of the paper feed cassette 41 on which the paper 5 as a recording medium is loaded (the location of the sensor S1), the absolute humidity around the paper 5 to be fed is detected. The amount of moisture contained in the fed paper 5 can be obtained, and more accurate anti-curl control can be performed.

  Further, by providing the temperature / humidity sensor 300 in the vicinity of the sheet 5 that is the recording medium on which the image formation by the recording head 24 has been completed (the position of the sensor S3 of the sheet discharge conveyance unit 7), the sheet 5 after the image formation is completed. The absolute humidity of the surrounding area can be detected, the dry state of the paper 5 after the end of image formation can be obtained, and more accurate curl prevention control can be performed.

  Further, the temperature / humidity sensor 300 detects the temperature / humidity around the paper 5 fed from the paper feed cassette 41 or the like (the location of the sensor S2), and the temperature of the paper 5 re-fed in the case of duplex printing. It can also be provided at a location where humidity can be detected (location of sensor S4).

  When the original image is read by the image reading unit 2, the control unit 200 processes the read image and stores it in a buffer in the scanner control unit 206. In addition, when print data or the like is received from an external host such as an information processing apparatus such as a personal computer, an image reading apparatus such as an image scanner, or an imaging apparatus such as a digital camera via the external I / F 207, the I / F 207 Store in the included receive buffer.

  Then, the CPU 201 reads and analyzes the image data from the scanner control unit 206 and the I / F 207, performs necessary image processing, data rearrangement processing, and the like in the ASIC 205, and transfers the print image data to the head drive control unit 208. To do. The generation of dot pattern data for outputting an image based on data from the outside may be performed by storing font data in the ROM 202, for example, or the image data is converted into bitmap data by a printer driver on the external host side. The image may be developed and transferred to the image forming apparatus.

  Upon receiving image data (dot pattern data) corresponding to one line of each recording head 24, the head drive control unit 208 transfers the dot pattern data for one line to the head driver 209, and the head driver 288 performs dot printing. Based on the pattern data, a required drive waveform is selectively applied to the actuator means of the recording head 24 and driven, and droplets are ejected from the required nozzles of each recording head 24.

  In the image forming apparatus configured as described above, the sheets 5 are fed one by one from the sheet feeding unit 4 or the duplex unit 10 and are pressed against the transport belt 31 by the pressing roller 36 to change the transport direction by approximately 90 °. . Then, the sheet 5 is electrostatically attracted to the conveyance belt 31, and the sheet 5 is conveyed in the sub-scanning direction by the circular movement of the conveyance belt 31.

  Therefore, by driving the recording head 24 according to the image signal while moving the carriage 23, ink droplets are ejected onto the stopped paper 5 to record one line, and when the recording for one line is completed. Then, the paper 5 is intermittently conveyed so that the paper 5 is fed by one line and the next line is recorded, and an image is formed on the paper 5. When the recording end signal or the signal that the rear end of the paper 5 reaches the recording area is received, the recording operation is ended. Thereafter, as will be described later, after waiting processing for curling suppression, the paper 5 is sent to the paper discharge tray 8 or the duplex unit 10.

Next, an example of ink (recording liquid, hereinafter referred to as “main ink”) used in the image forming apparatus will be described.
First, an example of pigment ink will be described. As the pigment, various pigments used for inkjet can be used. In particular, the pigment surface has a hydrophilic group, the pigment is wrapped with a polymer emulsion, and the insoluble pigment is dispersed with a surfactant or a water-soluble resin. The polymer emulsion of the ink was prepared according to the production example described later.

  The wetting agent used in the ink is glycerin, 1,3-butanediol, triethylene glycol, 1,6-hexanediol, propylene glycol, 1,5-pentanediol, diethylene glycol, dipropylene glycol, trimethylolpropane. And at least one selected from trimethylolethane.

  Further, a polyol or glycol ether having 8 to 11 carbon atoms, an anionic or nonionic surfactant is added.

  Examples thereof include 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, and substances having the following structures (I) to (VII).

（Ｒ１：炭素数６〜１４の分岐してもよいアルキル基、ｍ：３〜１２、
Ｍ：アルカリ金属イオン、第４級アンモニウム、第４級ホスホニウム、アルカノールアミン）

(R1: C6-C14 alkyl group which may be branched, m: 3-12,
M: alkali metal ion, quaternary ammonium, quaternary phosphonium, alkanolamine)

（Ｒ2：炭素数５〜１６の分岐したアルキル基、
Ｍ：アルカリ金属イオン、第４級アンモニウム、第４級ホスホニウム、アルカノールアミン）

(R2: a branched alkyl group having 5 to 16 carbon atoms,
M: alkali metal ion, quaternary ammonium, quaternary phosphonium, alkanolamine)

（Ｒは分岐しても良い６〜１４の炭素鎖、ｋ：５〜２０）

(R may be branched 6-14 carbon chain, k: 5-20)

（Ｒは分岐しても良い炭素数６から１４の炭素鎖、ｎ：５〜２０）

(R is a carbon chain having 6 to 14 carbon atoms which may be branched, n: 5 to 20)

（Ｒは炭素数６から１４の炭素鎖、ｍ，ｎ：ｍ、ｎ≦２０）

(R is a carbon chain having 6 to 14 carbon atoms, m, n: m, n ≦ 20)

（Ｒは炭素数６から１４の炭素鎖、ｍ，ｎ：ｍ、ｎ≦２０）

(R is a carbon chain having 6 to 14 carbon atoms, m, n: m, n ≦ 20)

（ｐ、ｑは０〜４０）

(P and q are 0 to 40)

  By these additions, the surface tension of the ink is lowered to 40 mN / m or less. By setting the surface tension to 40 mN / m or less, it is possible to increase the penetration speed particularly into paper in a printed image. However, as a side effect, there is a point that bubbles are difficult to disappear. Further, by setting the ink viscosity at 25 ° C. to 5 mPa · sec or more, the image density can be increased.

  Moreover, various pH preparation agents and antiseptic / antifungal agents are added as necessary. In addition, it is effective to add alginic acid or the like to increase the viscosity.

Next, an example of pigment ink production will be described.
[Examples of ink production]
An ink was prepared by the following method.
Reference Example 1 Preparation of Dispersion of Phthalocyanine Pigment-Containing Polymer Fine Particle A blue polymer fine particle dispersion was obtained by reexamining Preparation Example 3 disclosed in Japanese Patent Application Laid-Open No. 2001-139849. The average particle diameter (D50%) of the fine polymer particles measured by Microtrac UPA was 93 nm.

Reference Example 2 Preparation of Dimethylquinacridone Pigment-Containing Polymer Fine Particle Dispersion A red-purple polymer fine particle dispersion was obtained in the same manner as in Reference Example 1, except that the phthalocyanine pigment of Reference Example 1 was changed to Pigment Red 122. The average particle diameter (D50%) of the polymer fine particles measured by Microtrac UPA was 127 nm.

Reference Example 3 Preparation of Monoazo Yellow Pigment-Containing Polymer Fine Particle Dispersion A yellow polymer fine particle dispersion was obtained in the same manner as in Reference Example 1 except that the phthalocyanine pigment of Reference Example 1 was changed to Pigment Yellow 74. The average particle diameter (D50%) of the polymer fine particles measured by Microtrac UPA was 76 nm.

Reference Example 4 Carbon black dispersion 1 treated with a diazo compound
100 g of carbon black having a surface area of 230 m ² / g and DBP oil absorption of 70 ml / 100 g and 34 g of p-amino-N-benzoic acid are mixed and dispersed in 750 g of water, and 16 g of nitric acid is added dropwise thereto and stirred at 70 ° C. did. After 5 minutes, a solution of 11 g of sodium nitrite dissolved in 50 g of water was added, and the mixture was further stirred for 1 hour. The resulting slurry was diluted 10 times and centrifuged to remove coarse particles, the pH was adjusted with diethanolamine to pH 8-9, desalted and concentrated with an ultrafiltration membrane, and a carbon black dispersion having a pigment concentration of 15%. did. This was made into carbon black dispersion 1 with a polypropylene 0.5 μm filter. The average particle size (D50%) measured by Microtrac UPA was 99 nm.

  Examples of pigment ink sets are shown below, but the present invention is not limited to these examples. In addition, the amount (%) of each component described in the examples is based on weight.

(Pigment ink set example 1)
[Cyan ink]
An ink composition having the following formulation was prepared and adjusted with a 10% aqueous solution of lithium hydroxide so that the pH was 9. Then, it filtered with the membrane filter with an average hole diameter of 0.8 micrometer, and obtained the ink composition.
Polymer fine particles containing phthalocyanine pigment of Reference Example 10.0 wt%
(As solids)
1,3-butanediol 25.0 wt%
Glycerol 8.5wt%
_{CH 3 (CH 2) 12 O} (CH 2 CH 2 O) 3 CH 2 COOH
Active agent 2.0wt%
2-ethyl-1,3-hexanediol 1.8wt%
Proxel LV (preservative) 0.1wt%
Defoamer 0.05wt%
Ion exchange water

[Magenta ink]
An ink composition was prepared in the same manner as the cyan ink except that the following composition was used, and the pH was adjusted to 9 with sodium hydroxide.
Dimethylquinacridone pigment-containing polymer fine particles of Reference Example 0.5 wt%
(As solids)
1,3-butanediol 22.0 wt%
Glycerol 7.0wt%
Polyoxyalkylene derivative Dispanol TOC 2.0wt%
2-ethyl-1,3-hexanediol 2.0wt%
Proxel LV (preservative) 0.05wt%
Antifoaming agent 0.1wt%
Ion exchange water

[Yellow ink]
An ink composition was prepared in the same manner as the cyan ink except that the following composition was used, and the pH was adjusted to 9 with lithium hydroxide.
Monoazo yellow pigment-containing polymer fine particles of Reference Example 10.0 wt%
(As solids)
1,3-butanediol 23.5 wt%
Glycerol 7.5wt%
Polyoxyalkylene derivative Dispanol TOC 2.0wt%
2-ethyl-1,3-hexanediol 2.0wt%
Proxel LV (preservative) 0.05wt%
Antifoam KM72F 0.1wt%
Ion exchange water

[Black ink]
An ink composition was prepared in the same manner as the cyan ink except that the following composition was used, and the pH was adjusted to 9 with sodium hydroxide.
Carbon black dispersion 1 treated with the diazo compound of Reference Example 1 10.0 wt%
(As solids)
1,3-butanediol 22.5 wt%
Glycerol 7.5wt%
N-methyl-2-pyrrolidone 2.0wt%
_{CH 3 (CH 2) 12 O} (CH 2 CH 2 O) 3 CH 2 COOH 2.0wt%
2-ethyl-1,3-hexanediol 2.0wt%
Proxel LV (preservative) 0.2wt%
Defoamer 0.1wt%
Ion exchange water

  Table 1 shows the ink physical properties of each ink of Example 1 of the pigment ink set.

(Pigment ink set example 2)
[Cyan ink]
An ink composition having the following formulation was prepared and adjusted with a 10% aqueous solution of lithium hydroxide so that the pH was 9. Then, it filtered with the membrane filter with an average hole diameter of 0.8 micrometer, and obtained the ink composition.
Polymer fine particles containing phthalocyanine pigment of Reference Example 1 8.0 wt%
(As solids)
Triethylene glycol 22.5wt%
Glycerol 7.5wt%
2-pyrrolidone 5.0wt%
_{CH 3 (CH 2) 12 O} (CH 2 CH 2 O) 3 CH 2 COOH 1.6wt%
2-ethyl-1,3-hexanediol 1.8wt%
Proxel LV (preservative) 0.2wt%
Defoamer 0.1wt%
Ion exchange water

[Magenta ink]
An ink composition was prepared in the same manner as the cyan ink except that the following composition was used, and the pH was adjusted to 9 with sodium hydroxide.
Polymer fine particles containing dimethylquinacridone pigment of Reference Example 8.0 wt%
(As solids)
Propylene glycol 30.0wt%
Glycerol 10.0wt%
N-methyl-2-pyrrolidone 2.0wt%
CH ₃ (CH ₂ ) ₁₂ O (CH ₂ CH ₂ O) ₄ CH ₂ COOH 1.7 wt%
2,2,4-Trimethyl-1,3-pentanediol 1.8wt%
Proxel LV (preservative) 0.2wt%
Defoamer 0.1wt%
Ion exchange water

[Yellow ink]
An ink composition was prepared in the same manner as the cyan ink except that the following composition was used, and the pH was adjusted to 9 with lithium hydroxide.
Monoazo yellow pigment-containing polymer fine particles of Reference Example 8.0 wt%
(As solids)
1,3-butanediol 22.5 wt%
Glycerol 7.5wt%
2-pyrrolidone 5.0wt%
CH ₃ (CH ₂ ) ₁₂ O (CH ₂ CH ₂ O) ₆ CH ₂ COOH 2.0 wt%
2,2,4-Trimethyl-1,3-pentanediol 1.8wt%
Proxel LV (preservative) 0.2wt%
Defoamer 0.1wt%
Ion exchange water

[Black ink]
An ink composition was prepared in the same manner as in cyan except that the following composition was used, and the pH was adjusted to 9 with sodium hydroxide.
Carbon black-containing polymer fine particles of Reference Example 8.0 wt%
(As solids)
Dipropylene glycol 20.0wt%
Glycerol 10.0wt%
N-hydroxyethyl-2-pyrrolidone 5.0wt%
CH ₃ (CH ₂ ) ₁₂ O (CH ₂ CH ₂ O) ₄ CH ₂ COOH 1.7 wt%
2-ethyl-1,3-hexanediol 1.5 wt%
Proxel LV (preservative) 0.2wt%
Defoamer KS531 (Shin-Etsu Chemical) 0.1wt%
Ion exchange water

  The ink physical properties of each ink of this pigment ink set Example 2 are shown in Table 2.

(Pigment ink set Example 3)
[Cyan ink]
An ink composition having the following formulation was prepared, and the pH was adjusted with an organic pH adjuster.
Then, it filtered with the membrane filter with an average hole diameter of 0.8 micrometer, and obtained the ink composition.
(Reference Example 1) phthalocyanine pigment-containing polymer fine particles 10.0 wt%
(As solids)
Triethylene glycol 25.0wt%
Glycerol 9.0wt%
Surfactant _{CH 3 (CH 2) 12 O} (CH 2 CH 2 O) 3 CH 2 COOH 2.0wt%
2,2,4-Trimethyl-1,3-pentanediol 2.0wt%
Benzisothiazoline preservative 0.2wt%
Silicone antifoaming agent SAG30 (Nihon Unicar) 0.03wt%
Ion exchange water

[Magenta ink]
The pH was adjusted with sodium hydroxide in the same manner as the cyan ink except that the following composition was used.
Dimethylquinacridone pigment-containing polymer fine particles (Reference Example 2) 10.0 wt%
(As solids)
Triethylene glycol 22.0wt%
Glycerol 7.3wt%
Nonionic surfactant Softanol EP5035 1.0wt%
Alginic acid 1.0%
2-ethyl-1,3-hexanediol 2.0wt%
Benzisothiazoline preservative 0.07wt%
Silicone defoamer KS531 (Shin-Etsu Chemical) 0.02wt%
Ion exchange water

[Yellow ink]
The pH was adjusted with sodium hydroxide in the same manner as the cyan ink except that the following composition was used.
(Reference Example 3) monoazo yellow pigment-containing polymer fine particles 11.0 wt%
(As solids)
Triethylene glycol 22.0wt%
Glycerol 7.3wt%
Nonionic surfactant Softanol EP5035 1.0wt%
Alginic acid 1.0%
2-ethyl-1,3-hexanediol 1.8wt%
Preservative 0.05wt%
Silicone defoamer 0.1wt%
Ion exchange water

[Black ink]
An ink composition was prepared with an organic pH adjuster in the same manner as the cyan ink except that the following composition was used.
The carbon black dispersion 1 treated with the diazo compound of Reference Example 4 10.0 wt%
(As solids)
Triethylene glycol 22.0wt%
Glycerol 7.3wt%
Surfactant Softanol EP5035 2wt%
2-ethyl-1,3-hexanediol 2.1 wt%
Antiseptic and fungicide 0.2wt%
Silicone defoamer KS531 (Shin-Etsu Chemical) 0.1wt%
Ion exchange water

  The ink physical properties of each ink of this pigment ink set Example 3 are shown in Table 3.

The curl suppression standby process according to the first embodiment of the present invention in the image forming apparatus configured as described above will be described with reference to FIG.
When printing is started, as shown in FIG. 6, the paper feed motor 45 is driven to separate the paper 5 from the paper feed cassette 41 one by one and fed from the paper feed unit 4 to the sub-scanning transport unit 2. At this time, for example, a detection signal from a temperature / humidity sensor 300 provided at the location of the sensor S1 in FIG. 1 is read to detect absolute humidity.

  Then, as described above, the image forming (printing) process for forming a required image on the sheet 5 is performed by the main scanning of the recording head 24 and the sub-scanning of the sheet 5, and when the printing process is completed, Sometimes, the amount of recording liquid ejected from the recording head 24 (ejection droplet amount) is read out. In this image forming apparatus, since the number of droplets ejected from the recording head 24 is counted in this image forming apparatus, the number of ejected droplets is calculated using the count value of the number of droplets. And

  Thereafter, it is determined whether or not it is necessary to wait for the paper 5 on which image formation has been completed based on the absolute humidity and the amount of ejected droplets (either one of which is sufficient) until curl is less likely to occur (curling suppression standby). Determine. The curl suppression standby time for waiting until curl is less likely to occur on the paper is stored in advance in a table such as the absolute humidity, the amount of ejected droplets, and the curl suppression standby time in the ROM 202 or the like. It is possible to determine whether or not the curl suppression standby is necessary (whether or not the curl suppression standby time is not “0”).

  At this time, if curling suppression standby is necessary, the drive of the paper discharge motor 271 is stopped (if the paper discharge motor 271 is not driven at the time of image formation, the stopped state is maintained), and the recording head 24 is operated. The state of retreating to the maintenance / recovery mechanism 121 side is set.

  As a result, as shown in FIGS. 4 and 7, the sheet 5 on which image formation has been completed is stopped on the lower guide plate 170A of the paper discharge transport unit 7, and the transport rollers 71, 171-173 and the spurs facing this are stopped. 72, 174 to 176 are restrained from above and below, and the paper 5 is not easily curled (the curl is about to be generated but restrained from above and below, resulting in a state where it cannot be curled). . That is, as described in Patent Document 1, curling of the paper 5 cannot be suppressed only by stopping the paper 5 placed on the paper discharge belt. Since a part is restrained from above and below, the occurrence of curling can be suppressed. After waiting until the recording medium is less likely to curl,

  In this case, as shown in FIG. 7, the rear end of the sheet 5 is within the scanning area of the recording head 24, and the nozzle 24nf that discharges the droplets of the recording head 24 is more downstream than the nozzle 24nf on the most downstream side in the sheet conveying direction. By stopping and waiting the sheet 5 at the position facing the downstream side, the length of the conveyance path for waiting the sheet 5 is shortened.

  When the curl suppression standby time elapses, that is, when the curling of the paper 5 is less likely to occur, the paper discharge motor 271 is driven to rotate the rollers of the paper discharge transport unit 7. In the case of single-sided printing, processing for discharging the paper 5 to the paper discharge tray 8 is performed as it is. In the case of duplex printing, the sheet 5 is fed into the duplex unit 10. Further, in the case of duplex printing, the printing speed can be improved by discharging the paper without performing such curling suppression standby when printing on the back surface.

  In this way, there is provided means for performing a paper discharge operation after waiting until the recording medium is less likely to curl in a state where at least a part of the recording medium on which image formation by the recording head has been completed is restrained from above and below. By providing, curling can be suppressed as much as possible, and generation of defective printed matter and jam can be prevented. In particular, when a pigment-based ink having a viscosity at 25 ° C. of 5 mPa · s or more is used as the recording liquid, curling is likely to occur, and it is effective to apply the present invention.

  In this case, the curl suppression standby is set by setting whether or not to perform the curl suppression standby based on the absolute humidity and the ejection droplet amount (the amount of the recording liquid adhered to the paper), and the standby time for performing the curl suppression standby. There is no need to wait until it is not necessary, and the overall printing speed can be improved.

  When waiting for curl suppression, if the next page is to be printed, the next sheet can be fed and printing can be performed until the leading edge does not interfere with the sheet during standby. That is, the drive means (paper feed motor 45, sub-scan motor 131) for feeding the paper 5 to the image forming area by the recording head 24 and performing sub-scanning and the paper discharge motor 271 of the paper discharge transport unit 7 are different. By using the driving means, it becomes possible to feed the next sheet during the curl suppression standby, and the printing speed of continuous printing can be improved.

  Further, in the above-described embodiment, when the paper is made to stand by in order to suppress curling, the paper is kept in a stopped state, but the paper is transported and waited while being restrained from above and below by rollers (including spurs) in the duplex unit 10. It can also be set as the structure to make.

  Next, curl suppression standby processing in the second and subsequent embodiments of the image forming apparatus according to the present invention will be described with reference to FIG. The description of the same parts as those in the first embodiment will be omitted.

First, with reference to FIGS. 8 to 10, second to fourth embodiments in which parameters relating to variable setting of the standby time are different will be described.
In the second embodiment shown in FIG. 8, the moisture content of the recording medium is detected, and the standby time is variably set based on the detection result of the moisture content of the recording medium. As described above, the time until it becomes difficult to curl can be set more appropriately by directly detecting the water content of the recording medium.

  In the third embodiment shown in FIG. 9, the standby time is variably set based on the type (paper type) of the recording medium. In this case, information regarding the type of the recording medium may be input by a user using the image forming apparatus from the operation panel of the image forming apparatus or by a printer driver on the host side. Further, the type of recording medium may be automatically detected. For example, in the case of a paper type that easily curls (for example, thin paper), the standby time is set long.

  In the fourth embodiment shown in FIG. 10, the waiting time is variably set based on the type (paper type) of the recording mode (printing mode (high-quality printing mode, high-speed printing mode)). For example, in the high image quality printing mode, since the time remaining in the apparatus after printing is long for overwriting (there is a substantial waiting time), the waiting time is set short.

Next, a fifth embodiment in which the standby process is different from the above embodiments will be described with reference to FIG.
In the fifth embodiment shown in FIG. 11, a waiting time determination process is performed after image formation is completed (after the final printing operation is completed). If waiting is required, the drive of the paper discharge motor 271 is stopped and the recording head 24 is moved. After the state is retracted to the maintenance / recovery mechanism 121 side, the recording head 24 is capped by the moisture retention cap 122 of the maintenance / recovery mechanism 121. Thereafter, the system waits for the elapse of the standby time, and waits for the control (maintenance operation impossible) in which the maintenance operation (maintenance recovery operation) by the maintenance / recovery mechanism 121 is not performed until the standby time elapses.

  That is, a maintenance operation may be performed to maintain the state of the nozzles of the recording head 24 during a stop after printing, and recording is performed by the maintenance operation when the standby paper (recording medium) is swollen by a cock ring. If the head 24 moves (for example, due to nozzle suction or wiping), the recording head 24 may rub the paper on standby, resulting in an abnormal image. Therefore, the maintenance operation by the maintenance / recovery mechanism 121 cannot be performed during standby. To prevent abnormal images from occurring.

  In addition, if the recording head 24 is left as it is, the ink in the nozzles may be dried and cause nozzle clogging depending on the length of the waiting time. Capping the surface prevents drying and prevents abnormal images due to missing nozzles.

Next, a sixth embodiment in which the stop position of the recording medium is different from the above embodiments will be described with reference to FIG.
In the sixth embodiment shown in FIG. 12, a waiting time determination process after image formation is completed, and if waiting is required, the recording medium (paper) is conveyed until the trailing edge is outside the scanning area of the carriage 23. After that, the drive of the paper discharge motor 271 is stopped and waits. Then, after the recording head 24 is retracted to the maintenance / recovery mechanism 121 side, the recording head 24 is capped with the moisture retention cap 122 of the maintenance / recovery mechanism 121. Then, the waiting time elapses.

  That is, in the case of the first to fifth embodiments in which the recording medium is stopped and waited in a state where the rear end portion of the recording medium after the image formation is within the scanning area of the carriage 23, the fifth embodiment described above will be described. As described above, a maintenance operation may be performed to maintain the state of the nozzles of the recording head 24 during a stop after printing, and a maintenance operation is performed when a standby paper (recording medium) is swollen by cockling. If the recording head 24 moves (for example, due to nozzle suction or wiping), there is a possibility that the recording head 24 rubs the waiting paper and forms an abnormal image.

  Here, when the maintenance operation is not performed as in the fifth embodiment, an abnormal image may be generated due to nozzle omission (discharge failure) due to drying of the nozzle, and the recording head is covered with a moisture retention cap. In the case of capping, the capping operation may delay the print start timing of the next page and reduce the productivity. Therefore, in this embodiment, the recording medium after the end of image formation is transported until the rear end of the recording medium is outside the scanning area of the carriage 23 and then stopped and waited, so that the occurrence of these abnormal images and the start timing of the next page are detected. It tries to eliminate the risk of delay.

Next, seventh to tenth embodiments in which the stop position of the recording medium can be variably set will be described with reference to FIGS.
In the seventh embodiment shown in FIG. 13, when a standby is necessary, the stop position of the recording medium (paper) is determined based on the maintenance operation, and the stop (stop or transport as it is) is determined at the determined paper stop position. Stop) and wait until the end of the standby. For example, when the maintenance operation does not enter during standby, the operation stops and waits on the spot, and when the maintenance operation enters, the conveyance is stopped until the rear end of the sheet is out of the carriage scanning area.

  In the eighth embodiment shown in FIG. 14, when standby is required, the stop position of the recording medium (paper) is determined based on the amount of droplets ejected onto the paper, and stopped at the determined paper stop position ( The system waits (stops as it is or stops after being conveyed) and waits until the end of the waiting. For example, when it is determined that the curl amount is small from the amount of droplets ejected onto the paper, the process is stopped as it is, and when it is determined that the curl amount is large, it is conveyed and stopped.

  In the ninth embodiment shown in FIG. 15, when standby is required, the stop position of the recording medium (paper) is determined based on the image data given from the host side or the image reading device 11, and the determined stop position of the paper And stops (stops as it is or stops after being conveyed) and waits until the end of the standby. For example, when it is determined from the image data that there are few droplets that have been ejected onto the paper and the curl amount is small, the process is stopped as it is. When it is determined that the curl amount is large, the sheet is conveyed and stopped.

  The tenth embodiment shown in FIG. 16 is provided with a curl detecting means for detecting the curl amount of the paper after the completion of printing. When waiting is required, the recording medium (paper) of the recording medium (paper) is determined based on the detection result of the curl amount detecting means. A stop position is determined, the sheet is stopped at the determined sheet stop position (stopped as it is or transported and stopped), and a standby process corresponding to the sheet stop position is performed until the end of standby. For example, if the curl amount is small, it stops as it is, and if it is large, it is conveyed and stopped.

  In this way, by variably setting the stop position of the recording medium, the recording medium can be made to wait at a more appropriate standby position, and unnecessary operations can be omitted.

Next, still another embodiment in which the curl suppression standby process is performed or not performed will be described.
In the eleventh embodiment shown in FIG. 17, after printing is completed, it is determined whether or not standby for curl suppression is necessary based on the amount of droplets ejected on the entire sheet (recording medium). If it is necessary, after performing a standby process for stopping the paper discharge operation for a predetermined time, if the standby is not necessary, the paper is directly discharged to the paper discharge tray 8 or the duplex unit 10 (double-sided tray). To do.

  Even in this case, when the curling of the recording medium occurs, the recording medium after the image formation by the recording head is made to stand by until the curling hardly occurs, and then the paper discharge operation is performed. The curling can be suppressed as much as possible, and the occurrence of defective printed matter and jamming can be prevented.

  In the twelfth embodiment shown in FIG. 18, it is determined whether or not a curl suppression standby is necessary based on the amount of liquid droplets shot on the rear end of the paper (recording medium) after the printing is completed. As a result, if standby is required, after performing a standby process for stopping the paper discharge operation for a predetermined time, if the standby is not required, the paper is directly discharged to the paper discharge tray 8 or the duplex unit 10 (double-sided tray). The paper is processed.

  In other words, the time until the paper discharge after printing is relatively short at the rear edge of the paper, and when the printing area is concentrated on the rear edge of the paper (if the printing rate increases, it adheres When the amount of droplets is increased), the necessity of standby is determined based on the droplet amount (average number of droplets per sheet = printing rate) with respect to the entire sheet as in the eleventh embodiment. There is a possibility that the trailing edge curl of the paper cannot be correctly identified and the stack becomes defective. Therefore, stack failure can be prevented by determining whether or not curling suppression standby is necessary based on the amount of droplets that are ejected to the rear end of the paper (recording medium).

  In the thirteenth embodiment shown in FIG. 19, after printing is completed, it is determined whether or not the curl suppression standby is necessary based on the entire sheet (recording medium) and the amount of liquid droplets struck on the rear end. As a result of the determination, if standby is required, a standby process for stopping the paper discharge operation for a predetermined time is performed. If standby is not required, the paper is directly output from the paper discharge tray 8 or the duplex unit 10 (double-sided tray). The paper is discharged.

  Here, the average droplet number AVE1 per unit area of the entire sheet from the droplet amount of the entire sheet, and the average per unit area of the sheet rear end part from the droplet amount of the sheet rear end part (for example, the area of the rear end 50 mm). The droplet number AVE2 is obtained, and the larger one of the average droplet number AVE1 and the average droplet number AVE2 is regarded as the printing rate for the sheet, and based on this, it is determined whether or not the curl suppression standby is necessary.

  By doing in this way, the necessity determination can be performed with higher accuracy than in the case where the necessity determination of standby is performed for either the number of drops for the entire sheet or the number of drops for the rear end of the sheet.

  In the fourteenth embodiment shown in FIG. 20, is it necessary to wait for curl suppression based on image data to be printed, which is transferred from the host side or read by the image reading device 11 before the printing operation after paper feeding? If it is necessary to wait for a predetermined time after printing is completed, the standby process for stopping the paper discharge operation for a predetermined time is performed. A process of discharging paper to the unit 10 (double-sided tray) is performed. Here, the necessity of curling suppression standby based on the image data can be determined, for example, by determining the print area and the print distribution.

  As described above, if the necessity for standby for curl suppression is determined based on the image data, it is possible to determine the necessity for standby even before the droplet is actually placed on the paper.

Next, an embodiment including two transport modes, a standby transport mode for performing curl suppression standby and a normal transport mode for not performing curl suppression standby, will be described with reference to FIG.
In the fifteenth embodiment shown in FIG. 21, the conveyance mode of the recording medium is set to either the standby conveyance mode in which the curl suppression standby is performed or the normal conveyance mode in which the curl suppression standby is not performed based on the absolute humidity. In the transport mode, the recording medium is transported, printed (image forming apparatus), and then discharged.

  The sixteenth embodiment shown in FIG. 22 is a standby transport mode in which the recording medium is transported in a standby mode and a normal transport mode in which no curl suppression standby is performed, based on the type (paper type) of the recording medium. Set to any of these, the recording medium is conveyed in the set conveyance mode, printed (image forming apparatus), and then discharged. Note that the paper type can be specified from the operation panel of the image forming apparatus as described above, or can be specified by the printer driver on the host side.

  In the seventeenth embodiment shown in FIG. 23, a standby conveyance mode and a curl that perform a waiting state for a recording medium conveyance mode based on image data transferred from the host side or supplied from the document reading device 11 are used. It is set to one of the normal transport modes in which the suppression standby is not performed, the recording medium is transported in the set transport mode, printing (image forming apparatus) is performed, and the paper is discharged.

  In the eighteenth embodiment shown in FIG. 24, the standby conveyance mode in which the conveyance mode of the recording medium is set to standby and the curl suppression standby is not performed on the basis of the amount of droplets that have been ejected onto the recording medium after completion of printing. Set to one of the transport modes, the recording medium is transported in the set transport mode, printed (image forming apparatus), and then discharged.

  The nineteenth embodiment shown in FIG. 25 detects the curling amount of the recording medium after printing, and sets the recording medium conveyance mode in a standby conveyance mode for waiting for curl suppression based on the detected curling amount. The normal conveyance mode in which the curl suppression standby is not performed is set, and the recording medium is conveyed in the set conveyance mode to perform printing (image forming apparatus), and then discharged.

Next, a description will be given of a twentieth embodiment in which the normal transport mode is preferentially printed when image data for a plurality of pages can be held, with reference to FIG.
In this embodiment, there is provided storage means capable of storing a plurality of pages of image data read by the image reading device 11 or a plurality of pages of image data transferred from the host side. Then, out of the image data stored in the storage means, the image data of the page that can be transported and printed in the normal transport mode is read out and preferentially printed, and then the image data of the page that needs the standby transport mode Is read and transported in the standby transport mode for printing.

1 is a schematic configuration diagram illustrating an overall configuration of an image forming apparatus according to the present invention. FIG. 2 is an explanatory plan view of an image forming unit and a sub-scanning conveyance unit of the apparatus. It is a side explanatory view similarly. FIG. 6 is an explanatory view of the main part of the paper discharge conveyance unit. FIG. 2 is a block explanatory diagram for explaining a control unit of the image forming apparatus. It is a flowchart with which it uses for description of the curl suppression standby process which concerns on 1st Embodiment of this invention which the control part performs. FIG. 6 is an explanatory diagram for explaining a relationship between a waiting sheet and a recording head. It is a flowchart with which it uses for description of the curl suppression standby process which concerns on 2nd Embodiment of this invention. It is a flowchart with which it uses for description of the curl suppression standby process which concerns on 3rd Embodiment of this invention. It is a flowchart with which it uses for description of the curl suppression standby process which concerns on 4th Embodiment of this invention. It is a flowchart with which it uses for description of the curl suppression standby process which concerns on 5th Embodiment of this invention. It is a flowchart with which it uses for description of the curl suppression standby process which concerns on 6th Embodiment of this invention. It is a flowchart with which it uses for description of the curl suppression standby process which concerns on 7th Embodiment of this invention. It is a flowchart with which it uses for description of the curl suppression standby process which concerns on 8th Embodiment of this invention. It is a flowchart with which it uses for description of the curl suppression standby process which concerns on 9th Embodiment of this invention. It is a flowchart with which it uses for description of the curl suppression standby process which concerns on 10th Embodiment of this invention. It is a flowchart with which it uses for description of the curl suppression standby process which concerns on 11th Embodiment of this invention. It is a flowchart with which it uses for description of the curl suppression standby process which concerns on 12th Embodiment of this invention. It is a flowchart with which it uses for description of the curl suppression standby process which concerns on 13th Embodiment of this invention. It is a flowchart with which it uses for description of the curl suppression standby process which concerns on 14th Embodiment of this invention. It is a flowchart with which it uses for description of the curl suppression standby process which concerns on 15th Embodiment of this invention. It is a flowchart with which it uses for description of the curl suppression standby process which concerns on 16th Embodiment of this invention. It is a flowchart with which it uses for description of the process which concerns on 17th Embodiment of this invention. It is a flowchart with which it uses for description of the process which concerns on 18th Embodiment of this invention. It is a flowchart with which it uses for description of the process which concerns on 19th Embodiment of this invention. It is a flowchart with which it uses for description of the process which concerns on 20th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Apparatus main body 2 ... Image formation part 3 ... Sub-scanning conveyance part 4 ... Paper feed part 5 ... Paper (recording medium)
DESCRIPTION OF SYMBOLS 7 ... Paper discharge conveyance part 8 ... Paper discharge tray 11 ... Image reading part 23 ... Carriage 24 ... Recording head 31 ... Conveyance belt 32 ... Conveyance roller 34 ... Charging roller

Claims (2)

A recording head for discharging droplets of recording liquid ;
In the apparatus main body, one surface of the recording medium on which image formation by the recording head has been completed is held by a guide plate, and the recording medium is conveyed from both sides of the recording medium with a roller and a spur constrained respectively. Conveying means for
Control means for controlling the recording medium that has been subjected to the image formation to be stopped in a state in which the recording medium is restrained by the conveying means and to wait .
The control means includes
During the curl suppression waiting time until curling due to the droplets landing on the recording medium is less likely to occur, the recording medium is made to wait in the restrained state,
An image forming apparatus, comprising: means for changing the curl suppression standby time according to at least one of an amount of droplets that have been ejected onto the recording medium and an absolute humidity within the apparatus main body . Said means for changing the claims and changes in response to at least one of the type in the recording medium of the absolute humidity of the curl suppressing amount of droplets waiting time implanted into the recording medium and the apparatus main body Item 2. The image forming apparatus according to Item 1.

Images