JP4210574B2 - Image forming apparatus and method for maintaining reliability of liquid ejection apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus and a method for maintaining the reliability of a liquid ejection apparatus.

  In various image forming apparatuses such as printers, facsimiles, copiers, plotters, printer / facsimile / copier multifunction machines, etc. equipped with a liquid droplet ejection head for ejecting the recording liquid, A mechanism for maintaining and recovering the performance of the recording head to be ejected is indispensable.

The main functions of this head performance maintenance and recovery mechanism are a cap function that covers with a highly-sealing cap member to prevent thickening and sticking of the recording liquid near the nozzle hole due to natural evaporation of ink, and a nozzle function. This is because the ejection failure due to the bubbles is recovered by discharging the recording liquid, or the ejection recovery function that sucks the recording liquid from the nozzle of the head through the cap function, and the cause that changes the flying state of the droplets attached to the nozzle surface And a wiping function for wiping off the remaining recording liquid.
JP 2002-254666 A JP-A-6-340091 Japanese Patent Laid-Open No. 11-157103 Japanese Patent No. 3216706

  In such a maintenance / recovery mechanism, as described in Patent Document 1, suction is performed in a state where the nozzle surface of the head is capped by a capping means (cap member), and then the head is urged by the wiping member. The process of wiping the nozzle surface to clean it and then capping the nozzle surface of the head again with the capping means is performed.

  By the way, in recent image forming apparatuses using ink, the use of pigment-based inks using organic pigments, carbon black or the like as colorants has been studied or put into practical use in order to enable high-quality printing on plain paper. However, unlike dyes, pigments are not soluble in water, and are usually used as water-based inks in a state where pigments are mixed with a dispersant, dispersed, and stably dispersed in water.

  Such a pigment-based ink generally has a higher viscosity than a dye-based ink, causing a problem due to the high viscosity. According to the experiments by the present inventors, in order to maintain the reliability of the head using the pigment-based ink, after performing the suction in the capping state by the suction cap and the wiping by the wiping member (wiper blade) as in the past, the operation is again performed. When capping with a suction cap, problems such as color mixing, nozzle clogging, and mist generation occurred. When these inconveniences occur, it is a matter of course that color mixing, image omission, etc. occur and image quality deteriorates.

  Therefore, the present inventors have conducted intensive research. As a result, when the nozzle surface is capped with a suction cap (nozzle suction) and then the wiping is performed and the head nozzle surface is wiped with a wiper blade, the pigment system When ink is used, when the wiper blade moves away from the nozzle surface in the wiping direction, ink adhering to the wiper blade scatters, causing color mixing, clogging due to adhesion to the nozzle, generation of mist, etc. Turned out to be caused.

  In particular, when a wiper blade that covers a range longer than the nozzle array of the head is used, a phenomenon occurs in which the adhered ink scatters and adheres to the nozzle surface of the head on the adjacent head.

  The present invention has been made on the basis of the above problems and knowledge, and an object thereof is to improve image quality in an image forming apparatus or a liquid ejection apparatus that uses a highly viscous recording liquid.

In order to solve the above-described problem, the image forming apparatus according to the present invention performs at least one wiping operation that does not wipe the nozzle surface of the head by the wiping unit after performing the suction by the suction unit, and then the head by the wiping unit. it is obtained by a configuration in which the wiping that Setsu wipe the nozzle surface. In this case, the recording liquid filled in the droplet discharge head preferably has a viscosity at 25 ° C. of 5 mPa · s to 20 mPa · s.

  The method for maintaining the reliability of the liquid ejection apparatus according to the present invention includes at least one wiping operation in which the nozzle surface of the head is capped with a suction cap and suction is performed from the nozzle of the head, and the wiping means does not wipe the nozzle surface of the head. Then, wiping is performed by wiping off the nozzle surface of the head by the wiping means. In this case, the recording liquid preferably has a viscosity at 25 ° C. of 5 mPa · s to 20 mPa · s.

  According to the reliability maintaining method of the image forming apparatus and the liquid ejection apparatus according to the present invention, wiping is performed so that the nozzle surface is not wiped off after the head suction, so that it is possible to reduce the scattering of the recording liquid adhering to the wiping member, Image quality is improved.

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a perspective explanatory view of the image forming apparatus as an example of the image forming apparatus according to the present invention, to which the reliability maintaining method for a liquid ejection apparatus according to the present invention is applied, as viewed from the front side.
The image forming apparatus includes an apparatus main body 1, a paper feed tray 2 for loading paper loaded in the apparatus main body 1, and a discharge for stocking paper on which an image is recorded (formed) mounted on the apparatus main body 1. The apparatus main body 1 further includes a cartridge loading portion 6 that protrudes forward from the front surface 4 and is lower than the upper surface 5 on one end side of the front surface 4 of the apparatus main body 1. An operation unit 7 such as operation keys and a display is arranged on the upper surface of the display. The cartridge loading unit 6 has a front cover 8 that can be opened and closed for detaching an ink cartridge 10 that is a liquid storage tank (main tank) as a liquid replenishing means.

Next, the mechanism of the image forming apparatus will be described with reference to FIGS. FIG. 2 is a schematic configuration diagram for explaining the overall configuration of the mechanism unit, and FIG. 3 is a plan view for explaining a main part of the mechanism unit.
A carriage 13 is slidably held in the main scanning direction by guide rods 11 and stays 12 which are horizontally mounted on left and right side plates (not shown), and moved and scanned in the direction of the arrow in FIG. 3 by a main scanning motor (not shown). To do.

  The carriage 13 has a recording head 14 composed of four ink jet heads for ejecting ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk). They are arranged in a direction crossing the main scanning direction, and are mounted with the ink droplet ejection direction facing downward.

  As the ink-jet head constituting the recording head 14, a piezoelectric actuator such as a piezoelectric element, a thermal actuator that utilizes a phase change caused by film boiling of a liquid using an electrothermal transducer such as a heating resistor, and a metal phase change caused by a temperature change. Although a shape memory alloy actuator to be used, an electrostatic actuator using an electrostatic force, or the like provided as energy generating means for ejecting ink can be used. Here, a head using a piezoelectric actuator (piezoelectric element) as energy generating means It is equipped with. Further, the recording head 14 can be constituted by a single inkjet head having a plurality of nozzle rows for ejecting droplets of each color.

  Further, the carriage 13 is equipped with a sub tank 15 which is a liquid container of each color for supplying ink of each color to the recording head 14. Ink is supplied to the sub tank 15 from the main tank (ink cartridge) 10 for each color through the ink supply tube 16. Here, the main tank 10 stores ink of each color of yellow (Y), cyan (C), magenta (M), and black (Bk) corresponding to each color, but the main tank 10 stores black ink. The tank 10 has a larger ink storage capacity than the main tank 10 that stores other color inks.

  On the other hand, as a paper feeding unit for feeding the paper 22 stacked on the paper stacking unit (pressure plate) 21 of the paper feeding tray 3, a half-moon roller (feeding) that separates and feeds the paper 22 from the paper stacking unit 21 one by one. A separation pad 24 made of a material having a large friction coefficient is provided opposite to the sheet roller 23 and the sheet feeding roller 23, and the separation pad 24 is biased toward the sheet feeding roller 23 side.

  As a transport unit for transporting the paper 22 fed from the paper feed unit on the lower side of the recording head 14, a transport belt 31 for transporting the paper 22 by electrostatic adsorption, and a paper feed unit The counter roller 32 for transporting the paper 22 fed through the guide 25 while sandwiching it between the transport belt 31 and the paper 22 fed substantially vertically upward are turned approximately 90 ° and copied onto the transport belt 31. A conveying guide 33 for adjusting the pressure and a tip pressing roller 35 urged toward the conveying belt 31 by a pressing member 34. In addition, a charging roller 36 that is a charging unit for charging the surface of the transport belt 31 is provided.

  Here, the conveyance belt 31 is an endless belt, and is configured to be looped around the conveyance roller 37 and the tension roller 38 in the belt conveyance direction of FIG. The charging roller 36 is disposed so as to contact the surface layer of the conveyor belt 31 and rotate following the rotation of the conveyor belt 31, and applies 2.5 N to both ends of the shaft as a pressing force.

  In addition, a guide member 41 is disposed on the back side of the conveyance belt 31 so as to correspond to a printing area by the recording head 14. The upper surface of the guide member 41 protrudes toward the recording head 14 from the tangent line of the two rollers (the conveyance roller 37 and the tension roller 38) that support the conveyance belt 31. As a result, the conveyance belt 31 is pushed up and guided by the upper surface of the guide member 41 in the printing region, so that highly accurate flatness is maintained.

  Further, as a paper discharge unit for discharging the paper 22 recorded by the recording head 14, a separation claw 51 for separating the paper 22 from the conveyance belt 31, a paper discharge roller 52, and a paper discharge roller 53 are provided. The paper discharge tray 3 is provided below the paper discharge roller 52. Here, the height from between the paper discharge roller 52 and the paper discharge roller 53 to the paper discharge tray 3 is increased to some extent in order to increase the amount that can be stored in the paper discharge tray 3.

  A double-sided paper feeding unit 61 is detachably mounted on the back surface of the apparatus body 1. The double-sided paper feeding unit 61 takes in the paper 22 returned by the reverse rotation of the transport belt 31, reverses it, and feeds it again between the counter roller 32 and the transport belt 11. A manual paper feed unit 62 is provided on the upper surface of the double-sided paper feed unit 61.

  Further, as shown in FIG. 3, in one non-printing area of the carriage 13 in the scanning direction, a maintenance recovery mechanism (hereinafter referred to as “reliability maintaining means for maintaining and recovering the state of the nozzles of the recording head 14”). 71) is disposed, and an empty discharge receiving member 81 is disposed in the other non-printing area.

  The subsystem 71 includes cap members 72a, 72b, 72c, and 72d that are capping means for capping the nozzle surface of the recording head 14, and a wiper blade 73 that is a wiping means for wiping the nozzle surface. Yes.

  In the image forming apparatus configured as described above, the sheets 22 are separated and fed one by one from the sheet feeding tray 2, and the sheets 22 fed substantially vertically upward are guided by the guide 25, and the conveying belt 31 and the counter roller 32, and the tip is guided by the transport guide 33 and pressed against the transport belt 31 by the tip pressure roller 35, and the transport direction is changed by approximately 90 °.

  At this time, a positive output and a negative output are alternately repeated from the high voltage power source to the charging roller 36 by a control circuit (not shown), that is, an alternating voltage is applied, and a charging voltage pattern in which the conveying belt 31 is alternating, that is, In the sub-scanning direction, which is the circumferential direction, plus and minus are alternately charged in a band shape with a predetermined width. When the sheet 22 is fed onto the conveyance belt 31 that is alternately charged with plus and minus, the sheet 22 is electrostatically attracted to the conveyance belt 31, and the sheet 22 is moved in the sub scanning direction by the circular movement of the conveyance belt 31. Be transported.

  Therefore, by driving the recording head 14 according to the image signal while moving the carriage 13, ink droplets are ejected onto the stopped paper 22 to record one line, and after the paper 22 is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal that the trailing edge of the paper 22 has reached the recording area, the recording operation is finished and the paper 22 is discharged onto the paper discharge tray 3.

  During printing (recording) standby, the carriage 13 is moved to the subsystem 37 side, the recording head 14 is capped by the caps 72a to 72d, and the nozzles are kept in a wet state to prevent ejection failure due to ink drying. In addition, a recovery operation for discharging ink not related to recording is performed before starting recording or in the middle of recording to maintain stable discharging performance.

Next, the configuration of the subsystem 71 will be described with reference to FIGS. 4 is an explanatory plan view of the system, FIG. 5 is an explanatory schematic sectional view of the suction cap of the system, and FIG. 6 is a schematic schematic configuration diagram of the system.
In the frame 211, two cap holders 212A and 212B, an idle discharge receptacle 213, a wiper blade 73 which is a wiping member including an elastic body as a cleaning means, and a carriage lock 215 are held so as to be able to move up and down. Yes.

  The cap holders 212A and 212B (hereinafter collectively referred to as “cap holder 212”) include two caps 72a, 72b, 72c and 72d (hereinafter referred to as “caps”) that cap the nozzle surfaces of the two recording heads 14, respectively. 72 ”).

  Here, a tube pump (suction pump) 220 as a suction means is connected to the cap 72a held by the cap holder 212A closest to the printing area via a tube 219, and the other caps 72b, 72c and 72d are tubes. Pump 220 is not connected. That is, only the cap 72a is a suction and moisturizing cap (hereinafter simply referred to as “suction cap”), and the other caps 72b, 72c and 72d are all merely a moisturizing cap. Therefore, when performing the recovery operation of the recording head 14, the head 14 that performs the recovery operation is selectively moved to a position where it can be capped by the suction cap 72a.

  A cam shaft 221 is rotatably disposed below the cap holders 212A and 212B. The cam shaft 221 includes cap cams 222A and 222B for moving the cap holders 212A and 212B up and down, and a wiper blade 73. A wiper cam 224 for raising and lowering the carriage and a carriage lock cam 225 for raising and lowering the carriage lock 215 via the carriage lock arm 217 are provided.

  Further, a wiper cleaner 218 for cleaning the wiper blade 73 can be swung in the direction indicated by an arrow on the print area side of the wiper blade 73 and is urged in a direction away from the wiper blade 73 by a spring (not shown). The camshaft 221 is provided with a wiper cleaner cam 228 for swinging the wiper cleaner 218. As shown in FIG. 5, the wiper blade 73 has a width L1 that is longer than the length L2 of the nozzle array NA composed of the nozzles Na of the recording head 14, and wipes the entire nozzle surface 14a of the recording head 14 ( Can be wiped).

  Here, the cap 72 is moved up and down by the cap cams 222A and 222B. The wiper blade 73 is moved up and down by the wiper cam 224. When the wiper cleaner 218 is moved downward, the wiper cleaner 218 moves forward and descends while being sandwiched between the wiper cleaner 218 and the empty discharge receiver 213, so that the ink attached to the wiper blade 214 is empty. It is scraped off by the discharge receptacle 213.

  The carriage lock 215 is urged upward (in the lock direction) by a compression spring (not shown) and is moved up and down by the carriage lock arm 217.

  In order to rotationally drive the tube pump 220 and the cam shaft 221, the rotation of the motor 231 is meshed with the motor gear 232 provided on the motor shaft 231 a and the pump gear 233 provided on the pump shaft 220 a of the tube pump 220 is further engaged. An intermediate gear 234 with a one-way clutch 237 is engaged with an intermediate gear 234 integrated with the intermediate gear 233, and the intermediate gear 238 coaxial with the intermediate gear 236 is fixed to the camshaft 221 via the intermediate gear 239. The cam gear 240 is engaged.

  The cam shaft 221 is provided with a home position sensor cam 241 for detecting the home position. When the cap 72 comes to the lowest end by a home position sensor (not shown) provided in the subsystem 71, a home position lever is provided. (Not shown) is activated, and the sensor is opened to detect the home position of the motor 231 (other than the pump 220). When the power is turned on, the position moves up and down regardless of the position of the cap 72 (cap holder 212), the position is not detected until the movement starts, and the position is determined after detecting the home position of the cap 72 (in the middle of rising). To the bottom end. Thereafter, the carriage moves left and right, returns to the cap position after position detection, and the recording head 14 is capped.

  In this subsystem 71, when the motor 231 rotates forward, the motor gear 232, the intermediate gear 233, the pump gear 234, the intermediate gears 235 and 236 rotate, and the shaft 220a of the tube pump 220 rotates, whereby the tube pump 220 is Operates to suck the inside of the suction cap 72a. Since the other gears 238 and thereafter are blocked by the one-way clutch 237, they do not rotate (activate).

  Since the one-way clutch 237 is connected by the reverse rotation of the motor 231, the rotation of the motor 231 is transmitted to the cam gear 240 through the motor gear 232, the intermediate gear 233, the pump gear 234, the intermediate gears 235, 236, 238 and 239. The cam shaft 221 rotates. At this time, the tube pump 220 has a structure that does not rotate by the reverse rotation of the pump shaft 220a.

  Here, with the recording head 14 performing the maintenance recovery operation at the position of the suction cap 72a, the motor 231 is reversely rotated to rotate the cam shaft 221 to raise the suction cap 72a, thereby capping the nozzle surface of the recording head 14. Then, suction (nozzle suction) can be performed from the nozzles of the recording head 14 by rotating the motor 231 in the forward direction and operating the tube pump 220.

  From this state, the cam shaft 221 is rotated by reversing the motor 231, whereby the suction cap 72 a can be separated from the nozzle surface of the recording head 14. Thereafter, the wiper blade 73 rises to the wiping position (position where it comes into contact with the nozzle surface), and the carriage 13 is moved in this state, whereby the nozzle surface of the recording head 14 is wiped (wiped) with the wiper blade 73. The wiper blade 73 can then be lowered. Note that the ink in the suction cap 72a can be sucked by operating the tube pump 220 thereafter.

  The ink sucked by the suction pump 220 by the maintenance and recovery operation of the subsystem 71 or the ink that adheres to the wiper blade 73 and is removed from the wiper blade 73 by the wiper cleaner 218 becomes waste ink and is not shown. It is discharged to the waste liquid storage tank.

Next, an outline of the control unit of the image forming apparatus will be described with reference to FIG. This figure is an overall block diagram of the control unit.
The control unit 280 includes a CPU 281 that controls the entire apparatus, a ROM 282 that stores programs executed by the CPU 281 and other fixed data, a RAM 283 that temporarily stores image data, and the like, while the apparatus is powered off. And a non-volatile memory (NVRAM) 284 for holding data, an image processing for performing various signal processing and rearrangement on image data, and an ASIC 285 for processing input / output signals for controlling the entire apparatus. Yes.

  The control unit includes an I / F 286 for transmitting and receiving data and signals to and from the host side, a head drive control unit 287 and a head driver 288 for driving and controlling the recording head 14, and a main scanning motor 290. A main scanning motor driving unit 291 for driving, a sub-scanning motor driving unit 293 for driving the sub-scanning motor 292, a subsystem driving unit 294 for driving the motor 231 of the subsystem 71, and various sensors (not shown) I / O 296 and the like for inputting a detection signal from. The control unit 280 is connected to an operation panel 297 (operation unit 7) for inputting and displaying information necessary for the apparatus.

  The control unit 280 receives print data and the like from the host side such as an information processing apparatus such as a personal computer, an image reading apparatus such as an image scanner, and an imaging apparatus such as a digital camera, via the cable or the network by the I / F 286.

  The CPU 281 reads and analyzes the print data in the reception buffer included in the I / F 286, performs necessary image processing, data rearrangement processing, and the like in the ASIC 285, and transfers the image data to the head drive control unit 287. To do. The generation of dot pattern data for image output may be performed by storing font data in the ROM 282, for example, or image data is developed into bitmap data by a host-side printer driver and transferred to this apparatus. You may do it.

  When the head drive control unit 287 receives image data (dot pattern data) corresponding to one line of the recording head 14, the dot pattern data for one line is serialized to the head driver 288 in synchronization with the clock signal. Data is transmitted, and a latch signal is transmitted to the head driver 288 at a predetermined timing.

  The head drive control unit 287 includes a ROM (which can also be configured by a ROM 282) storing pattern data of a drive waveform (drive signal), and a D / A converter for D / A conversion of drive waveform data read from the ROM. A waveform generation circuit including an A converter and a drive waveform generation circuit including an amplifier and the like are included.

  The head driver 288 also receives a clock signal from the head drive controller 287 and serial data as image data, and a latch circuit that latches the register value of the shift register with a latch signal from the head drive controller 287. A level conversion circuit (level shifter) that changes the output value of the latch circuit, an analog switch array (switch means) that is controlled to be turned on / off by the level shifter, and the like, and controls on / off of the analog switch array. In this way, a required drive waveform included in the drive waveform is selectively applied to the actuator means of the recording head 14 to drive the head.

Next, an example of the reliability maintenance / recovery operation (which is also the reliability maintenance method of the liquid ejection apparatus according to the present invention) in this image forming apparatus will be described with reference to FIG.
First, as described above, with the recording head 14 performing the maintenance recovery operation at the position of the suction cap 72a, the motor 231 is reversely rotated to raise the suction cap 72a to cap the nozzle surface of the recording head 14, and the motor By performing normal rotation of 231 and operating the tube pump 220, suction (nozzle suction) is performed from the nozzles of the recording head 14. From this state, the motor 231 is reversed to separate the suction cap 72 a from the nozzle surface of the recording head 14.

  Thereafter, the wiper blade 73 rises to the wiping position (position where it comes into contact with the nozzle surface), and the carriage 13 is moved in this state, and the wiper blade 73 is stopped at a position not exceeding the end face in the wiping direction of the recording head 14 (actually The carriage 13 is stopped), and the nozzle surface of the recording head 14 is wiped in a range where it is not wiped off by the wiper blade 73. After the wiping is performed, the wiper blade 73 is lowered at that position. Separate from the nozzle surface. In the case of a head provided with a nozzle cover that covers the peripheral edge of the nozzle surface, the “nozzle surface” includes the surface of the nozzle cover.

  Then, the wiper blade 73 is moved relative to the wiping start position again and then raised to the wiping position. In this state, the carriage 13 is moved, and the wiper blade 73 is stopped at a position beyond the end face in the wiping direction of the recording head 14 ( In practice, the carriage 13 is stopped) to wipe the nozzle surface of the recording head 14 with the wiper blade 73, and then the wiper blade 73 is lowered.

  Thereafter, after the suction in the suction cap 72a is performed, the suction cap 72a is raised and the nozzle surface of the recording head 14 is capped.

  The wiping process in this operation will be described with reference to FIG. First, the wiper blade 73 is raised to a position where it can come into contact with the nozzle surface 14a of the recording head 14, and is moved relative to the nozzle surface 14a of the recording head 14, as shown in FIG. In addition, the wiper blade 73 wipes the nozzle surface 14a while moving in the arrow direction C in the state shown in the phantom line. The position shown in the phantom line is shown as the position where the wiper blade 73 starts to contact the nozzle surface 14a, and does not necessarily indicate the initial state when the wiper blade 73 is raised.

  At this time, the wiper blade 73 is stopped at a position indicated by a solid line not exceeding the end face 14b of the recording head 14 in the wiping direction (arrow C direction). Accordingly, in this wiping step, the wiper blade 73 stops at a position where the nozzle surface 14a of the recording head 14 is not wiped off.

  Then, as shown in FIG. 5B, when the wiper blade 73 is lowered in the direction indicated by the arrow D from the position where it is not wiped away and separated from the nozzle surface 14a, the wiper blade 73 is deformed into a square shape. The distal end 73A gradually becomes I-shaped and then leaves the nozzle surface 14a. As a result, rapid restoration deformation of the distal end portion 73A is suppressed, so that the ink adhering to the distal end portion 73A due to wiping is reduced or eliminated.

  On the other hand, when the wiper blade 73 is moved to a position beyond the end face 14b in the wiping direction (arrow C direction) of the recording head 14 in the wiping step, the tip end portion 73A that has been deformed into a square shape is formed. In the shape of a square, it leaves the nozzle surface 14a and suddenly returns to an I-shape, and the ink adhering to the distal end portion 73A is scattered when the distal end portion 73A is restored and deformed.

  Then, as shown in FIG. 9B, by lowering the wiper blade 73, the ink adhering to the wiper blade 73 is scraped off by the wiper cleaner 218 and cleaned.

  Therefore, as shown in FIG. 9C, the wiper blade 73 is raised again to a position where it can come into contact with the nozzle surface 14a of the recording head 14, and moves relative to the nozzle surface 14a of the recording head 14. By doing so, the wiper blade 73 wipes the nozzle surface 14a while moving in the arrow direction C in the state shown in the phantom line.

  At this time, the wiper blade 73 is moved to the position indicated by the broken line beyond the nozzle surface 14 of the recording head 13 so that the nozzle surface 14 is wiped off. At this stage, since the amount of ink adhering to the wiper blade 73 is reduced, the amount of ink that is scattered when the distal end portion 73A of the wiper blade 73 is restored and deformed is reduced even if wiping is performed to wipe off the nozzle surface 14a. Or disappear.

  As described above, the wiping process for wiping the nozzle surface after performing the wiping process for wiping the nozzle surface at least once after the nozzle suction may reduce or eliminate the scattering of the ink attached to the wiping means. If the ink splatters, color mixing occurs, or the splattered ink enters the nozzle and thickens as a result, resulting in nozzle clogging. Scattering and the like are reduced, and the image quality is improved.

  According to the experiments by the present inventors, if the viscosity of the recording liquid to be used at 25 ° C. is less than 5 mPa · s, even if wiping is performed by wiping from the beginning, the viscosity is low, so that the ink is scattered from the wiper blade. However, when the viscosity at 25 ° C. of the ink that is the recording liquid to be used is 5 mPa · s or more, wiping was performed to wipe off from the beginning as the viscosity was particularly high (viscosity at 25 ° C. was 7 mPa · s or more). In this case, it was confirmed that the ink adhering to the blade was scattered.

  Therefore, the present invention is particularly effective when the recording liquid used in the recording head is a recording liquid having a viscosity at 25 ° C. of 5 mPa · s or more. The recording liquid that can be ejected as droplets had a viscosity at 25 ° C. of 20 mPa · s.

  Here, the wiping step that is not wiped off is performed once, but the wiping step of wiping off after performing two or more times may be performed.

Next, an example of ink that is a liquid used in the image forming apparatus will be described, but the present invention is not limited thereto.
First, the ink preferably has a static surface tension γ at 25 ° C. of γ ≧ 20. Thereby, discharge stability can be ensured. That is, if the static surface tension γ at 25 ° C. is γ ≧ 20, the droplets are formed normally, and a clear image can be formed. On the other hand, when 20> γ, the ink is completely wetted with the nozzle surface or exhibits a lower contact angle, so that the ink overflows in the vicinity of the nozzle. In this state, normal meniscus is not formed on the nozzle, so droplets are not formed normally, the discharge direction is bent, unnecessary droplets (satellite droplets) are generated, mist is generated, In such a case, a problem such as a droplet not being ejected occurs. In such a state, the target pixel cannot be formed, and thus an image defect may occur.

  The ink contains a color material. The coloring material may be contained in a dissolved state or may be contained in a dispersed state. In this case, a dye is preferable as the coloring material used in a dissolved state. Examples of the color material used in a dispersed state include pigments and dyes having low solubility in solvents. By using a pigment, high light resistance and water resistance can be obtained.

  In these, it is preferable to contain a coloring material in the disperse | distributed state. In other words, when the coloring material is contained in a dispersed state, the pH change occurs at the moment of landing on the recording medium (paper) and the dispersion of the coloring material is destroyed and the coloring material aggregates, or the coloring material is a fiber of the recording medium. The phenomenon of being caught in the eyes and not flowing far away occurs. As a result of such a phenomenon, feathering and color bleeding can be suppressed, and a clear image can be obtained.

  On the contrary, if the coloring material is contained in a dissolved state, the dissolved coloring material does not easily precipitate even if a pH change occurs at the moment of landing on the recording medium, so that the coloring material does not aggregate. Further, in a state where the color material is dissolved, when the ink permeates the recording medium, the ink flows out far without being caught in the eyes of the fibers. As a result of such a phenomenon, feathering or color bleeding may occur, resulting in an unclear image.

  Examples of the dye that can be used include dyes that are classified into acid dyes, direct dyes, reactive dyes, and food dyes in the color index, and that have excellent water resistance and light resistance. These dyes may be used as a mixture of a plurality of types, or may be used as a mixture with other dyes such as pigments. These are added as long as the effect is not inhibited.

If these dyes are specifically mentioned, as acid dyes and food dyes,
C. I. Acid Yellow 17, 23, 42, 44, 79, 142,
C. I. Acid Red 1, 8, 13, 14, 18, 26, 27, 35, 37, 42, 52, 82, 87, 89, 92, 97, 106, 111, 114, 115, 134, 186, 249, 254, 289,
C. I. Acid Blue 9, 29, 45, 92, 249
C. I. Acid Black 1, 2
And so on.

As a direct dye,
C. I. Direct Yellow 1, 12, 24, 26, 33, 44, 50, 86, 120, 132, 142, 144,
C. I. Direct Red 1, 4, 9, 13, 17, 20, 28, 31, 39, 80, 81, 83, 89, 225, 227,
C. I. Direct Orange 26, 29, 62, 102,
C. I. Direct Blue 1, 2, 6, 15, 22, 25, 71, 76, 79, 86, 87, 90, 98, 163, 165, 199, 202,
C. I. Direct black 19, 22, 32, 38, 51, 56, 71, 74, 75, 77, 154, 168, 171
And so on.

As reactive dyes,
C. I. Reactive Black 3, 4, 7, 11, 12, 17,
C. I. Reactive Yellow 1, 5, 11, 13, 14, 20, 21, 22, 25, 40, 47, 51, 55, 65, 67,
C. I. Reactive Red 1, 14, 17, 25, 26, 32, 37, 44, 46, 55, 60, 66, 74, 79, 96, 97,
C. I. Reactive Blue 1, 2, 7, 14, 15, 23, 32, 35, 38, 41, 63, 80, 95
And so on.

  In particular, acid dyes and direct dyes can be preferably used.

  Specific examples of the pigment that can be used include the following. In this case, these pigments may be used by mixing a plurality of types, or may be used by mixing with other pigments such as dyes.

  Examples of organic pigments include azo, phthalocyanine, anthraquinone, dioxazine, indico, thioindico, perylene, isoindolenone, aniline black, azomethine, rhodamine B lake pigment, and carbon black.

  The pigment is preferably used in the form of particles having a particle diameter of 0.01 to 0.15 μm.

  Examples of inorganic pigments include iron oxide, titanium oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, bitumen, cadmium red, chrome yellow, and metal powder. Examples of organic pigments include azo, phthalocyanine, anthraquinone, quinacridone, dioxazine, indigo, thioindigo, perylene, isoindolenone, aniline black, azomethine, rhodamine B lake pigment, and carbon black. It is done.

  Further, the particle diameter of these pigments is preferably 0.01 to 0.15 μm. If it is 0.01 μm or less, the hiding power is lowered, the density is low, the light resistance is lowered, and the light resistance of the ink when mixed with the polymer dye system becomes equivalent to that of the conventional dye system. On the other hand, if the thickness is 0.15 μm or more, clogging of the head or clogging with a filter may occur, and it may not be possible to obtain ejection stability.

  Ink is used for the purpose of making the ink have the desired physical properties, preventing drying of the ink by preventing discharge failure, and improving the dissolution stability and dispersion stability of the coloring material. It is preferable to use a water-soluble organic solvent.

  That is, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,5-pentanediol, 1,5-hexanediol, glycerol, 1,2,6-hexanetriol, 1,2,4-butanetriol Polyhydric alcohols such as 1,2,3-butanetriol and petriol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene Polyhydric alcohol alkyl ethers such as glycol monoethyl ether, ethylene glycol monophenyl ether Ter, polyhydric alcohol aryl ethers such as ethylene glycol monobenzyl ether, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-capro Nitrogen-containing heterocyclic compounds such as lactam, amides such as formamide, N-methylformamide, N, N-dimethylformamide, amines such as monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, triethylamine, dimethyl sulfoxide Sulfur-containing compounds such as sulfolane and thiodiethanol, propylene carbonate, ethylene carbonate, and γ-butyrolactone. These solvents are used alone or in combination with water.

  Of these, diethylene glycol, thiodiethanol, polyethylene glycol 200 to 600, triethylene glycol, glycerol, 1,2,6-hexanetriol, 1,2,4-butanetriol, petriol, 1,5 are particularly preferable. -Pentanediol, N-methyl-2-pyrrolidone, N-hydroxyethylpyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidinone. By using these, an excellent effect can be obtained for preventing poor jetting characteristics due to high solubility or high dispersibility of the coloring material and water evaporation.

The ink preferably contains a penetrant.
The penetrant is added for the purpose of improving the wettability between the ink and the recording medium and adjusting the penetrating speed. As the penetrant, those represented by the following formulas (I) to (IV) are preferable. That is, a polyoxyethylene alkylphenyl ether surfactant of the following formula (I), an acetylene glycol surfactant of the formula (II), a polyoxyethylene alkyl ether surfactant of the following formula (III) and the formula (IV The polyoxyethylene polyoxypropylene alkyl ether-based surfactant (1) can reduce the surface tension of the liquid, so that the wettability can be improved and the penetration rate can be increased.

（Ｒは分岐していても良い炭素数６〜１４の炭化水素鎖、ｋ：５〜２０）

(R is an optionally branched hydrocarbon chain having 6 to 14 carbon atoms, k: 5 to 20)

（ｍ、ｎ≦２０，０＜ｍ＋ｎ≦４０）

(M, n ≦ 20, 0 <m + n ≦ 40)

（Ｒは分岐してもよい炭素数６〜１４の炭化水素鎖、ｎは５〜２０）

(R is a C6-C14 hydrocarbon chain which may be branched, n is 5-20)

（Ｒは炭素数６〜１４の炭化水素鎖、ｍ、ｎは２０以下の数）

(R is a hydrocarbon chain having 6 to 14 carbon atoms, m and n are numbers of 20 or less)

  Other than the compounds of the above formulas (I) to (IV), for example, diethylene glycol monophenyl ether, ethylene glycol monophenyl ether, ethylene glycol monoallyl ether, diethylene glycol monophenyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, tetraethylene glycol chlorophenyl Use alkyl and aryl ethers of polyhydric alcohols such as ethers, nonionic surfactants such as polyoxyethylene polyoxypropylene block copolymers, fluorine-based surfactants, lower alcohols such as ethanol and 2-propanol However, diethylene glycol monobutyl ether is particularly preferable.

  In addition, it is preferable to add a pH adjusting agent or a rust preventive agent to the ink for the purpose of preventing elution and corrosion of the member in contact with the ink. As the pH adjuster, any substance can be used as long as the pH can be adjusted to 6 or more without adversely affecting the prepared ink. For example, amines such as diethanolamine and triethanolamine, hydroxides of alkali metal elements such as lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonium hydroxide, quaternary ammonium hydroxide, quaternary phosphonium hydroxide Products, alkali metal carbonates such as lithium carbonate, sodium carbonate and potassium carbonate. Examples of the rust inhibitor include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

  Further, it is preferable to add an antiseptic / antifungal agent to the ink for the purpose of antiseptic / antifungal. As the antiseptic / antifungal agent, sodium dehydroacetate, sodium sorbate, 2-pyridinethiol-1-oxide sodium, isothiazoline-based compound, sodium benzoate, sodium pentachlorophenol and the like can be used.

  Furthermore, it is preferable to add an antifoaming agent to the ink in order to suppress unnecessary foaming. As the antifoaming agent, a silicon-based antifoaming agent is preferably used. In general, there are oil type, compound type, self-emulsification type, emulsion type, etc. for silicone antifoaming agent, but considering the use in water system, use of self-emulsification type or emulsion type ensures reliability. This is preferable. Further, modified silicon-based antifoaming agents such as amino-modified, carbinol-modified, methacryl-modified, polyether-modified, alkyl-modified, higher fatty acid ester-modified, alkylene oxide-modified, etc. may be used.

  Examples of commercially available silicone antifoaming agents include silicone antifoaming agents from Shin-Etsu Chemical Co., Ltd. (KS508, KS531, KM72, KM85, etc., trade names), silicones from Toray Dow Corning Co., Ltd. Defoamers (Q2-3183A, SH5510, etc .: trade names), Silicone defoamers (SAG30, etc .: trade names) from Nippon Unicar Co., Ltd., Defoamers from Asahi Denka Kogyo Co., Ltd. (Adecanol series: Trade names) ) And the like.

  Then, the recording liquid is prepared by adjusting the viscosity at 25 ° C. so as to be 5 mPa · s or more, and is used for the image forming apparatus of the above-described embodiment to maintain the reliability of the recording head 14 by the subsystem 71. A recovery action was performed. As a result, when the wiping is performed from the beginning, the recording liquid adhering to the wiper blade 73 may scatter and affect the image quality. As a result, almost no scattering of the recording liquid adhering to the wiper blade 73 was confirmed or disappeared, and a desired image quality was obtained.

  The present invention can be applied to an image forming apparatus such as a printer, a facsimile machine, a copying machine, a printer / fax / copier multifunction machine, or an image forming apparatus using a recording liquid which is a liquid other than ink. Can also be applied.

1 is a perspective view illustrating an example of an image forming apparatus according to the present invention as viewed from the front side. 2 is a configuration diagram illustrating an outline of a mechanism unit of the image forming apparatus. FIG. It is principal part plane explanatory drawing of the mechanism part. FIG. 2 is an explanatory plan view of a subsystem of the image forming apparatus. It is explanatory drawing with which it uses for description of the braid | blade of the same subsystem. It is a schematic block diagram of the system. FIG. 2 is a schematic block explanatory diagram of a control unit of the image forming apparatus. It is a flowchart with which it uses for description of an example of reliability maintenance recovery operation | movement. It is explanatory drawing with which it uses for the concrete description of the reliability maintenance recovery operation | movement.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Ink cartridge 13 ... Carriage 14 ... Recording head 15 ... Sub tank 71 ... Sub system 72a-72d ... Cap 73 ... Wiper blade 220 ... Suction pump 231 ... Motor

Claims (4)

A reliability maintaining unit including a suction unit for capping a nozzle surface of a droplet discharge head for discharging a droplet with a suction cap and suctioning from the nozzle of the head, and a wiping unit for wiping the nozzle surface of the head; In the image forming apparatus provided, the reliability maintaining unit performs at least one wiping that does not wipe the nozzle surface of the head by the wiping unit after performing suction by the suction unit, and then performs the wiping unit by the wiping unit. image forming apparatus and performing wiping that Setsu wipe the nozzle surface of the head.   The image forming apparatus according to claim 1, wherein the recording liquid filled in the droplet discharge head has a viscosity at 25 ° C. of 5 mPa · s to 20 mPa · s.   In a reliability maintaining method for maintaining the reliability of a liquid ejection apparatus including a liquid droplet ejection head for ejecting recording liquid droplets, the nozzle surface of the head is capped with a suction cap, and suction is performed from the nozzle of the head. A method of maintaining the reliability of the liquid ejecting apparatus, comprising: performing wiping of wiping off the nozzle surface of the head by the wiping unit after performing wiping not wiping the nozzle surface of the head by the wiping unit at least once. .   4. The method for maintaining the reliability of a liquid discharge apparatus according to claim 3, wherein the recording liquid has a viscosity at 25 ° C. of 5 mPa · s to 20 mPa · s.

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