JP2010284925A - Information processing apparatus, image forming apparatus, method for generating printing data, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an information processing apparatus, or the like, capable of reducing change of hue of an image printed by bidirectional printing without increasing the number of heads, taking the kind of recording medium into consideration, or decreasing printing speed. <P>SOLUTION: The information processing apparatus 400 feeds printing data to an image forming apparatus 500 which forms an image on a recording medium 12 by moving back and forth a recording head 7 having a plurality of nozzle rows for delivering liquid droplets with different colors and by delivering the liquid droplets from the nozzle rows. The information processing apparatus 400 includes: a liquid droplet data forming means 321 for forming liquid droplet data for the liquid droplets to be delivered from image data; a data detecting means 322 for detecting the liquid droplet data impacting within a specified distance from the boundary of an outgoing path and a returning path; a first impacting droplet detecting means 323 for detecting a first impacting droplet on which a later impacting droplet reaches repeatedly from the liquid droplet data impacting within a specified distance; and a liquid droplet size adjusting means 324 for decreasing the liquid droplet size of the first impacting droplet in accordance with the distance to the boundary. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image on a recording medium by moving a recording head and ejecting liquid droplets from a nozzle array, and in particular, the bidirectional color difference can be reduced between the forward path and the backward path even when the recording head is reciprocated. The present invention relates to an information processing apparatus, an image forming apparatus, a print data generation method, and a program.

  2. Related Art Inkjet printers are known that eject ink droplets of a plurality of colors based on image data to form an image on a recording medium such as paper. An ink jet printer causes ink droplets to land on a recording medium while moving a head in which a plurality of nozzles are integrated and arranged in a main scanning direction (a direction perpendicular to the transport direction). Then, the operation of conveying the recording medium by a predetermined amount, moving the head in the main scanning direction, and landing ink droplets is repeated. As inks of a plurality of colors, black (K), cyan (C), magenta (M), and yellow (Y) are known as basic colors.

  In early ink jet printers, when the head moved in the main scanning direction, ink droplets were ejected only when the head moved in the forward direction. However, in order to improve the printing speed, bidirectional ink ejection is also performed in the backward direction. Printing has become mainstream. However, since the nozzles of the respective colors are arranged in the main scanning direction in the order of KCMY, the order of ink droplets landed on the recording medium in the forward direction “KCMY” is the reverse “YMCK” order in the backward direction. . For this reason, even if ink dots of the same color should be formed due to the difference in the color order of the ink droplets landing (even if C color ink and M color ink should be ejected in the forward path and the return path, respectively), It is known that the hue may be slightly different between when discharged in the order of M and when discharged in the order of M and C on the return path.

  In order to eliminate such inconvenience, several techniques have been considered (for example, refer to Patent Documents 1 to 3). Japanese Patent Laid-Open No. 2004-151867 prevents the ejection order of each ink color from changing in the forward path and the backward path by a head mounted with nozzles in the order of C, M, Y, K and K, Y, M, C in the main scanning direction. A color recording apparatus is disclosed.

  In Patent Document 2, based on the print medium name, it is determined whether the recording medium is easy to penetrate ink (the ink that has landed first becomes dark) or difficult to penetrate (the ink that has landed later becomes dark). A printing apparatus is disclosed that determines the degree of hue change by bidirectional recording for each pixel, lowers the output density of a hue with a large hue change degree of input image data, and increases the output density of a hue with a small hue change degree. Yes.

  In Patent Document 3, a region where dots are formed by different types of ink is specified, and a recording region including at least the region is recorded by a one-way recording operation, and other recording regions are bidirectionally recorded. An ink jet recording apparatus that performs recording by operation is disclosed.

  However, as described in Patent Document 1, when the heads of the respective colors are arranged symmetrically so that the C, M, Y, and K ink ejection orders do not change between the forward pass printing and the backward pass printing, it is doubled. A number of heads are required, which increases the product cost and makes it difficult to reduce the size.

  Further, in Patent Document 2, when printing on a recording medium that is determined to be a type in which ink is likely to permeate, the total amount of color ink that is landed later is greater than the total amount of color ink that is landed first. Since the hue during bi-directional printing is reduced by converting to, the total amount of ink of the color to be landed later increases. For this reason, since the ink tends to be excessive with respect to the original total amount, problems such as ink overflow and bleeding are likely to occur. In addition, since the total amount of ink that is landed after the total amount of ink that is landed earlier is uniformly increased, there is also a problem that the color is shifted from the target color at the time of color design.

  In Cited Document 3, switching between unidirectional printing and bidirectional printing is switched depending on the output data, so image data such as full-color is always unidirectional printing, so the printing speed is extremely reduced. There is a problem that it ends up.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an information processing apparatus capable of reducing changes in the hue of an image during bidirectional printing without increasing the number of heads, considering the type of recording medium, or reducing the printing speed. It is an object to provide a forming apparatus, a print data generation method, and a program.

  In order to solve the above problems, an image forming apparatus that reciprocally moves a recording head having a plurality of nozzle rows from which droplets of different colors are ejected and ejects droplets from the nozzle rows to form an image on the recording medium. And an information processing apparatus for supplying print data, the droplet data generating means for generating droplet data of the discharged droplets from the image data, and the liquid landed within a predetermined distance from the boundary between the forward path and the backward path Data detection means for detecting droplet data, first landing detection means for detecting first landing that is landed by overlapping second landing from droplet data landed within the predetermined distance, and droplet size of the first landing And droplet size adjusting means for reducing the size according to the distance to the boundary, and supplying print data including droplet data with a reduced droplet size to the image forming apparatus.

  Information processing apparatus, image forming apparatus, print data generation method capable of reducing changes in hue of image during bidirectional printing without increasing the number of heads, considering the type of recording medium, and reducing the printing speed, and A program can be provided.

1 is an example of a side explanatory view illustrating an overall configuration of a mechanism unit of an image forming apparatus. It is an example of the plane explanatory view of the mechanism part. FIG. 3 is an example of a cross-sectional explanatory diagram along the longitudinal direction of the liquid chamber of the recording head. FIG. 4 is an example of a cross-sectional explanatory diagram of a recording head in a lateral direction of a liquid chamber (a nozzle arrangement direction). It is an example of the hardware block diagram of a control part. It is an example of a block diagram of a print control unit and a head driver. It is a figure which shows an example of the drive signal applied to a piezoelectric element. It is a figure which shows an example of the relationship between the size of a droplet and a drive signal. It is a figure which shows an example of the relationship between an ink viscosity and a drive signal. 1 is a diagram illustrating an example of an image forming system. 1 is an example of a block diagram of an image processing apparatus. It is an example of the figure which shows typically the printing result which the inkjet printer printed blue in two directions. It is an example of the figure for demonstrating a color superimposition order. FIG. 3 is an example of a diagram schematically showing first and second landing ink droplets in a forward direction and a backward direction in order to reduce a bidirectional color difference. FIG. 3 is an example of a diagram schematically illustrating control of a boundary generated by bidirectional printing and an ink adhesion amount. 3 is an example of a functional block diagram of a printer driver. FIG. FIG. 10 is an example of a flowchart illustrating a procedure for an image processing apparatus to perform color difference reduction processing during bidirectional printing. It is a figure which shows an example of the size reduction process of an ink drop. It is a figure which shows an example of the thermal type head of an edge shooter system. It is a figure which shows an example of the thermal type head of a side shooter system.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
An example of an image forming apparatus 500 that prints using print data generated by the image processing method of the present embodiment will be described with reference to FIGS. FIG. 1 shows an example of a side view for explaining the overall structure of the mechanism part of the image forming apparatus 500, and FIG. 2 shows an example of a plan view of the mechanism part.
The image forming apparatus 500 holds the carriage 3 slidably in the main scanning direction by a guide rod 1 and a guide rail 2 that are horizontally mounted on left and right side plates (not shown), and the main scanning motor 4 drives a driving pulley 6A. 2 is moved and scanned in the direction indicated by the arrow (main scanning direction) in FIG. 2 via a timing belt 5 stretched between the roller and the driven pulley 6B.
The carriage 3 includes, for example, four recording head units 7y provided with liquid ejection heads that eject ink droplets of yellow (Y), cyan (C), magenta (M), and black (K), respectively. 7c, 7m, and 7k (referred to as “recording head 7” when colors are not distinguished) are mounted. The recording head 7 has a plurality of ink ejection openings arranged in a direction crossing the main scanning direction, and the ink droplet ejection direction is directed downward in the vertical direction.

  The liquid discharge head constituting the recording head 7 includes a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses a phase change caused by liquid film boiling using an electrothermal transducer such as a heating resistor, and a metal phase change caused by a temperature change. For example, a shape memory alloy actuator using an electrostatic force, an electrostatic actuator using an electrostatic force, or the like provided with pressure generating means for generating a pressure for ejecting ink droplets can be used. In addition, the configuration is not limited to an independent head for each color, and may be configured by one or a plurality of liquid ejection heads having a nozzle row composed of a plurality of nozzles that eject ink droplets of a plurality of colors.

The carriage 3 is also equipped with sub-tanks 8 for each color for supplying ink of each color to the recording head 7. Ink is supplied to the sub tank 8 from a main tank (ink cartridge) (not shown) via an ink supply tube 9.
On the other hand, as a paper feeding unit for feeding paper 12 stacked on a paper stacking unit (pressure plate) 11 such as a paper feeding cassette 10, a half-moon roller (for separating and feeding the paper 12 one by one from the paper stacking unit 11) A separation pad 14 made of a material having a large friction coefficient is provided opposite to the sheet feeding roller 13 and the sheet feeding roller 13, and the separation pad 14 is urged toward the sheet feeding roller 13 side.
In order to transport the paper 12 fed from the paper stacking unit 11 below the recording head 7, a transport belt 21 for electrostatically attracting and transporting the paper 12 and a guide 15 from the paper stacking unit 11 are provided. A counter roller 22 for transporting the paper 12 fed through the conveyor belt 21 and the paper 12 fed substantially vertically upward to change the direction of the paper 12 by approximately 90 ° to follow the transport belt 21. And a pressing roller 25 urged toward the conveying belt 21 by the pressing member 24. A charging roller 26 that is a charging unit for charging the surface of the conveyor belt 21 is disposed around the conveyor belt 21.

Here, the conveyance belt 21 is an endless belt, is stretched between the conveyance roller 27 and the tension roller 28, and the conveyance roller 27 rotates from the sub-scanning motor 31 via the timing belt 32 and the timing roller 33. By doing so, it is configured to circulate in the belt conveyance direction (sub-scanning direction) of FIG. A guide member 29 is disposed on the back side of the conveying belt 21 corresponding to the image forming area by the recording head 7. The charging roller 26 is disposed so as to come into contact with the surface layer of the transport belt 21 and rotate following the rotation of the transport belt 21.
As shown in FIG. 2, a slit disk 34 is coaxially attached to the shaft of the conveying roller 27, and an encoder sensor 35 that detects the slit of the slit disk 34 is provided. A rotary encoder 36 that detects the rotation amount of the transport roller 27 is realized by the slit disk 34 and the encoder sensor 35.
In addition, as a paper discharge unit for discharging the paper 12 on which ink droplets have landed by the recording head 7, the image forming apparatus 500 includes a separation claw 51 for separating the paper 12 from the conveyance belt 21 and a paper discharge roller 52. And a paper discharge roller 53 and a paper discharge tray 54 for stocking the paper 12 to be discharged.
A double-sided paper feeding unit 61 is detachably attached to the back of the image forming apparatus 500. The double-sided paper feeding unit 61 takes in the paper 12 returned by the reverse rotation of the transport belt 21, reverses it, and feeds it again between the counter roller 22 and the transport belt 21.
As shown in FIG. 2, a maintenance / recovery mechanism 56 for maintaining and recovering the state of the nozzles of the recording head 7 is disposed in the non-printing area on one side of the carriage 3 in the scanning direction. The maintenance / recovery machine 56 discharges the thickened recording liquid, a cap 57 of each color for capping each nozzle surface of the recording head 7, a wiper blade 58 which is a blade member for wiping the nozzle surface. An empty discharge receiver 59 for receiving ink droplets when performing an empty discharge for discharging ink droplets that do not contribute to recording is provided.

  In the image forming apparatus 500 configured as described above, the sheets 12 are separated and fed one by one from the sheet stacking unit 11, and the sheet 12 fed substantially vertically upward is guided by the guide 15, and the conveyance belt 21 and the counter roller 22, and the tip is guided by the conveyance guide 23 and pressed against the conveyance belt 21 by the pressing roller 25, and the conveyance direction is changed by approximately 90 °.

  At this time, the AC bias supply unit applies an alternating voltage that alternately repeats positive and negative to the charging roller 26 by a control unit (not shown), and the charging roller 26 alternates the conveying belt 21 with an alternating charging voltage pattern, that is, a loop. In the sub-scanning direction that is the direction, charging is performed with a pattern in which plus and minus are alternately repeated with a predetermined width.

When the paper 12 is fed onto the charged transport belt 21, the paper 12 is attracted to the transport belt 21 by electrostatic force, and the paper 12 is transported in the sub-scanning direction by the circular movement of the transport belt 21.
At that position, the recording head 7 is driven according to the image signal while moving the carriage 3 in the forward and backward directions, thereby ejecting ink droplets onto the stopped paper 12 to record one line. After a predetermined amount of 12 is conveyed, the next line is recorded. Upon receiving a recording end signal or a signal indicating that the trailing edge of the paper 12 has reached the recording area, the control unit ends the recording operation and discharges the paper 12 to the paper discharge tray 54.
In the case of double-sided printing, when recording on the front surface (surface to be printed first) is completed, the recording belt 12 is fed into the double-sided paper feeding unit 61 by rotating the conveyor belt 21 in the reverse direction. The paper 12 is reversed (with the back surface being the printing surface), fed again between the counter roller 22 and the transport belt 21, controlled in timing, and transported onto the transport belt 21 as described above. Then, after recording on the back surface, the paper is discharged onto the paper discharge tray 54.

During printing (recording) standby, the carriage 3 is moved to the maintenance / recovery mechanism 56 side, the nozzle surface of the recording head 7 is capped by the cap 57, and the nozzles are kept in a wet state. To prevent. In addition, the recording liquid is sucked from the nozzle in a state where the recording head 7 is capped by the cap 57, and a recovery operation is performed to discharge the thickened recording liquid and bubbles, and the ink adhered to the nozzle surface of the recording head 7 by this recovery operation. Wiping is performed with a wiper blade 58 in order to remove the cleaning. In addition, an idle ejection operation for ejecting ink not related to recording is performed before the start of recording or during recording. Thereby, the ejection performance of the recording head 7 is maintained.
[Liquid discharge head]
An example of the liquid discharge head constituting the recording head 7 will be described with reference to FIGS. 3 is an example of a cross-sectional explanatory view along the longitudinal direction of the liquid chamber of the recording head 7, and FIG. 4 is an example of an explanatory cross-sectional view of the recording head 7 in the lateral direction of the liquid chamber (nozzle arrangement direction).
The liquid discharge head includes, for example, a flow path plate 101 formed by anisotropic etching of a single crystal silicon substrate, a vibration plate 102 formed by, for example, nickel electroforming bonded to the lower surface of the flow path plate 101, and a flow path plate. A nozzle plate 103 bonded to the upper surface of 101 is bonded and stacked, and thereby, a nozzle communication path 105 that is a flow path for communicating with a nozzle 104 that discharges droplets (ink droplets) and a liquid chamber 106 that is a pressure generation chamber. An ink supply port 109 communicating with a common liquid chamber 108 for supplying ink to the liquid chamber 106 through a fluid resistance portion (supply path) 107 is formed.
In addition, two rows (only one row is shown in FIG. 3) of stacked piezoelectric elements as electromechanical conversion elements that are pressure generating means (actuator means) for pressurizing the ink in the liquid chamber 106 by deforming the diaphragm 102. An element 121 and a base substrate 122 to which the multilayer piezoelectric element 121 is bonded and fixed are provided. Note that a column portion 123 is provided between the stacked piezoelectric elements 121. This support portion 123 is a portion that is formed at the same time as the laminated piezoelectric element 121 by dividing and processing the piezoelectric element member. However, since the drive voltage is not applied, it becomes a simple support.
Further, an FPC cable 126 equipped with a drive circuit (drive IC) (not shown) is connected to the multilayer piezoelectric element 121.
Then, the peripheral edge of the diaphragm 102 is joined to a frame member 130, and the frame member 130 has a through-hole 131 that houses an actuator unit composed of the laminated piezoelectric element 121 and the base substrate 122, and the common liquid chamber 108. The ink supply hole 132 for supplying ink from outside to the common liquid chamber 108 is formed. The frame member 130 is formed by injection molding with a thermosetting resin such as an epoxy resin or polyphenylene sulfite, for example.
The channel plate 101 is formed by, for example, subjecting a single crystal silicon substrate having a crystal plane orientation (110) to anisotropic etching using an alkaline etching solution such as an aqueous potassium hydroxide solution (KOH), so that a nozzle communication path 105 and a liquid chamber 106 are obtained. However, the present invention is not limited to a single crystal silicon substrate, and other stainless steel substrates or photosensitive resins can be used.
The vibration plate 102 is formed from a nickel metal plate, and is manufactured by, for example, an electroforming method (electroforming method). Alternatively, a metal plate or a joining member between a metal and a resin plate may be used. it can. The laminated piezoelectric element 121 and the support post 123 are bonded to the diaphragm 102 with an adhesive, and the frame member 130 is further bonded with an adhesive.

The nozzle plate 103 forms a nozzle 104 having a diameter of 10 to 30 μm corresponding to each liquid chamber 106 and is bonded to the flow path plate 101 with an adhesive. The nozzle plate 103 is formed by forming a water repellent layer on the outermost surface of a nozzle forming member made of a metal member via a required layer.
The laminated piezoelectric element 121 is a laminated piezoelectric element (here, PZT) in which piezoelectric materials 151 and internal electrodes 152 are alternately laminated. An individual electrode 153 and a common electrode 154 are connected to each internal electrode 152 drawn out to different end faces of the laminated piezoelectric element 121. In this embodiment, the ink in the liquid chamber 106 is pressurized using the displacement in the d33 direction as the piezoelectric direction of the multilayer piezoelectric element 121. However, the displacement in the d31 direction as the piezoelectric direction of the multilayer piezoelectric element 121 is used. It is also possible to use a configuration in which the ink in the liquid chamber 106 is pressurized. Alternatively, a structure in which one row of stacked piezoelectric elements 121 is provided on one base substrate 122 may be employed.
In the liquid discharge head configured as described above, for example, by lowering the voltage applied to the multilayer piezoelectric element 121 from the reference potential, the multilayer piezoelectric element 121 contracts, and the diaphragm 102 descends to reduce the volume of the liquid chamber 106. By expanding, the ink flows into the liquid chamber 106, and then the voltage applied to the multilayer piezoelectric element 121 is increased to extend the multilayer piezoelectric element 121 in the stacking direction, and the diaphragm 102 is deformed in the nozzle 104 direction. By contracting the volume / volume of the liquid chamber 106, the recording liquid in the liquid chamber 106 is pressurized, and droplets of the recording liquid are ejected (jetted) from the nozzle 104.
Then, by returning the voltage applied to the multilayer piezoelectric element 121 to the reference potential, the diaphragm 102 is restored to the initial position, and the liquid chamber 106 expands to generate a negative pressure. The recording liquid is filled in the liquid chamber 106. Therefore, after the vibration of the meniscus surface of the nozzle 104 is attenuated and stabilized, the operation proceeds to the next ink droplet ejection.
The driving method of the liquid discharge head is not limited to the above example (drawing-pushing), and it is also possible to perform striking or pushing according to the direction to which the drive signal is given.
(Control part)
An overview of the control unit 200 of the image forming apparatus 500 will be described with reference to FIG. FIG. 5 shows an example of a hardware block diagram of the control unit 200. The control unit 200 includes a CPU 201 that controls the entire image forming apparatus 500, a ROM 202 that stores programs executed by the CPU 201 and other fixed data (such as parameters), a RAM 203 that temporarily stores print data, image data, and the like. A rewritable non-volatile memory (NVRAM) 204 for holding data while the apparatus is powered off, image processing for performing various signal processing and rearrangement on print data and image data, and other overall apparatus And an ASIC 205 for processing input / output signals for control.
The control unit 200 generates a host I / F 206 for transmitting and receiving data and signals to and from the host side, a data transfer unit (data transfer unit 302) for driving and controlling the recording head 7, and a drive signal. A print control unit 207 including a drive waveform generation unit (drive waveform generation unit 301), a head driver (driver IC) 208 for driving the recording head 7 provided on the carriage 3 side, the main scanning motor 4 and the sub scanning motor. Motor drive unit 210 for driving 31, AC bias supply unit 212 for supplying AC bias to charging roller 26, detection signals from encoder sensors 43 and 35, temperature sensor 215 for detecting environmental temperature, and the like. An I / O 213 for inputting a detection signal from the sensor is provided. The control unit 200 is connected to an operation panel 214 for inputting and displaying information necessary for the image forming apparatus 500.
The control unit 200 receives print data from a host side such as an information processing apparatus (an image processing apparatus 400 described later) such as a personal computer, an image reading apparatus such as an image scanner, and an imaging apparatus such as a digital camera via a cable or a network. And received by the host I / F 206.
Then, the CPU 201 of the control unit 200 reads and analyzes the print data in the reception buffer included in the host I / F 206, performs necessary image processing, print data rearrangement processing, and the like in the ASIC 205. The data is transferred from the print control unit 207 to the head driver 208. A dot pattern for outputting an image is generated by a printer driver on the host side as will be described later.
The print control unit 207 transfers the print data described above to the head driver 208 as serial data, and transmits a transfer clock, a latch signal, a droplet control signal (mask signal), and the like necessary for transfer of the print data and confirmation of the transfer. Output to the head driver 208. In addition to this, the print control unit 207 includes a drive waveform generation unit and head configured by a D / A converter, a voltage amplifier, a current amplifier, and the like that perform D / A conversion on drive signal pattern data stored in the ROM 202. A drive waveform selection means to be supplied to the driver 208 is included, and a drive signal composed of one drive pulse (drive signal) or a plurality of drive pulses (drive signal) is generated and output to the head driver 208.
The head driver 208 selectively selects a drive signal (for example, the above-described drive signal) constituting a drive waveform supplied from the print control unit 207 based on print data corresponding to one line of the recording head 7 input serially. The recording head 7 is driven by applying to the piezoelectric element. At this time, by selecting a drive pulse constituting the drive signal, for example, dots having different sizes such as a large droplet (large dot), a medium droplet (medium dot), and a small droplet (small dot) can be distinguished. it can.
In addition, the CPU 201 detects a speed detection value and a position detection value obtained by sampling a detection pulse from the encoder sensor 43 constituting the linear encoder, and a speed target value and a position target value obtained from a previously stored speed / position profile. Based on the above, a drive output value (control value) for the main scanning motor 4 is calculated. When this control value is output to the motor drive unit 210, the motor drive unit 210 drives the main scanning motor 4. Similarly, the CPU 201 detects a speed detection value and a position detection value obtained by sampling a detection pulse from the encoder sensor 35 constituting the rotary encoder 36, and a speed target value and a position target obtained from a previously stored speed / position profile. A drive output value (control value) for the sub-scanning motor 31 is calculated based on the value. When this control value is output to the motor drive unit 210, the motor drive unit 210 drives the sub-scanning motor 31 via the motor driver.

[Print control unit 207, head driver 208]
An example of the print control unit 207 and the head driver 208 will be described with reference to FIG. FIG. 6 shows an example of a block diagram of the print control unit 207 and the head driver 208. As described above, the print control unit 207 generates the drive signal (common drive signal) composed of a plurality of drive pulses (drive signals) within one print cycle, and outputs the print signal. And a data transfer unit 302 for outputting a clock signal, a latch signal (LAT), and droplet control signals M0 to M3.
The droplet control signal is a 2-bit signal that instructs each droplet to open and close an analog switch 315, which will be described later, of the head driver 208, and has a waveform to be selected according to the printing cycle of the common drive signal (H level ( State transition to ON), and state transition to L level (OFF) when not selected.

The head driver 208 receives a transfer clock (shift clock) and print data (gradation data: 2 bits / CH) from the data transfer unit 302, and latches each register value of the shift register 311 with a latch signal. A latch circuit 312, a decoder 313 that decodes gradation data and droplet control signals M0 to M3 and outputs the result, and a logic level voltage signal of the decoder 313 is converted to a level at which the analog switch 315 can operate. Level shifter 314, and an analog switch 315 that is turned on / off (opened / closed) by the output of the decoder 313 provided via the level shifter 314.
The analog switch 315 is connected to a selection electrode (individual electrode) 153 of each stacked piezoelectric element 121, and receives a common drive signal from the drive waveform generator 301. Therefore, when the analog switch 315 is turned on in accordance with the result of decoding the serially transferred print data (gradation data) and the control signals MN0 to MN3 by the decoder 313, a required drive signal constituting the common drive signal is obtained. Passing (selected) is applied to the stacked piezoelectric element 121.
[Drive signal]
With reference to FIG. 7 and FIG. 8, an example of a drive signal preferable when using ink will be described. FIG. 7 shows an example of the drive signal applied to the multilayer piezoelectric element 121, and FIG. 8 shows an example of the relationship between the ink droplet size and the drive signal.

  As shown in FIG. 7, the drive waveform generation unit 301 includes a waveform element that falls from the reference potential Ve and a waveform element that rises from the state after the fall, as shown in FIG. A drive signal (drive waveform) composed of the drive pulses P1 to P8 is generated and output.

On the other hand, the analog switch 315 selects a driving pulse to be used by the droplet control signals M0 to M3 from the data transfer unit 302. Here, the waveform element in which the potential V of the drive pulse falls from the reference potential Ve is a drawing waveform element in which the stacked piezoelectric element 121 contracts and the volume of the liquid chamber 106 expands. Further, the waveform element that rises from the state after the fall is a pressurizing waveform element that causes the stacked piezoelectric element 121 to expand and the volume of the liquid chamber 106 to contract.
Then, the analog switch 315 selects the driving pulse P1 as shown in FIG. 8A when forming a small droplet (small dot) by the droplet control signals M0 to M3 from the data transfer unit 302, and selects the medium droplet ( When forming medium dots), the driving pulses P4 to P6 are selected as shown in FIG. 8B, and when forming large drops (large dots), the driving pulses P2 to P8 are selected as shown in FIG. 8C. When fine driving is performed (when the meniscus is vibrated without droplet ejection), a fine driving pulse P2 is selected as shown in FIG. 8D and applied to the stacked piezoelectric elements 121 of the recording head 7 respectively. Like that.
When forming a medium droplet, the first droplet is ejected by the drive pulse P4, the second droplet is ejected by the drive pulse P5, and the third droplet is ejected by the drive pulse P6. At this time, if the natural vibration period of the pressure chamber (liquid chamber 106) is Tc, the interval between the ejection timings of the drive pulses P4 and P5 is preferably 2Tc ± 0.5 μs. Since the drive pulses P4 and P5 are configured by simple strike waveform elements, if the drive pulse P6 is also set to the same simple strike waveform element, the ink droplet velocity becomes too large, and the landing positions of other droplet types are affected. There is a risk of shifting. Therefore, the drive pulse P6 reduces the pull-in voltage (decreasing the falling potential) to reduce the meniscus pull-in and suppress the ink drop speed of the third drop. However, the startup voltage is not reduced in order to increase the necessary ink droplet volume.
That is, in the drawing waveform element of the final drive pulse among the plurality of drive pulses, by reducing the drawing voltage relatively, the droplet discharge speed by the final drive pulse is relatively reduced, and the landing position is set to other droplets. It can be combined with the seed as much as possible.
The fine drive pulse P2 is a drive signal that vibrates the meniscus without ejecting ink droplets in order to prevent drying of the meniscus of the nozzle. This fine driving pulse P2 is applied to the recording head 7 in the non-printing area. Further, by using the drive pulse P2 which is the fine drive signal as one of the drive pulses constituting the large droplet, it is possible to shorten the drive cycle (speed up).
Furthermore, by setting the interval between the ejection timings of the fine drive pulse P2 and the drive pulse P3 within the range of the natural vibration period Tc ± 0.5 μs, the volume of ink droplets ejected by the drive pulse P3 can be increased. In other words, the droplet volume of the droplet that can be ejected by the drive pulse P3 by superimposing the expansion of the pressurized liquid chamber 6 by the drive pulse P3 on the pressure vibration of the liquid chamber 106 by the vibration cycle generated by the fine drive pulse P2 is the drive pulse P3 alone. It can be made larger than in the case of applying by.

Since the required drive signal differs depending on the viscosity of the ink, in this image forming apparatus 500, as shown in FIG. 9, when the ink viscosity is 5 mPa · s, similarly, when the viscosity is 10 mPa · s. Drive signal at 20 mPa · s is prepared, and the viscosity of the ink is determined from the temperature detected by the temperature sensor, and the drive signal to be used is selected.
That is, when the ink viscosity is small, the voltage of the drive pulse is relatively small, and when the ink viscosity is large, the voltage of the drive pulse is relatively large. The volume can be discharged substantially constant. Further, the driving pulse P2 can vibrate the meniscus without ejecting ink droplets by selecting the crest value according to the ink viscosity.
By using a drive signal composed of such drive pulses, the time until each large, medium, and small droplet lands on the paper can be controlled, and the ejection start time differs for each large, medium, and small droplet. In addition, each drop can be landed at substantially the same position.

[Program for realizing image forming method and computer for executing program]
An example of the image forming system will be described with reference to FIG. The image forming system in FIG. 10 includes the above-described ink jet printer that is the image forming apparatus 500 and the image processing apparatus 400. Since the image forming method of the present embodiment is executed by a personal computer (PC), the image processing apparatus 400 is a computer.

  The image forming system is configured by connecting one or a plurality of image processing apparatuses 400 such as PCs and an inkjet printer 500 via a predetermined interface or network.

FIG. 11 shows an example of a block diagram of the image processing apparatus 400. As shown in FIG. 11, in the image processing apparatus 400, a CPU 401 and various ROMs 402 and RAM 403, which are memory means, are connected by a bus line. A storage device 406 using a magnetic storage device such as a hard disk, an input device 404 such as a mouse or a keyboard, a monitor 405 such as an LCD or CRT, and a storage such as an optical disk are connected to this bus line via a predetermined interface. A storage medium reading device 408 for reading the medium 409 is connected, and a predetermined interface (external I / F) 407 for communicating with a network such as the Internet or an external device such as a USB is connected.
An image processing program 410 including a program for providing the image forming method of the present embodiment is stored in the storage device 406 of the image processing apparatus 400. The image processing program 410 is installed in the storage device 406 by being read from the storage medium 409 by the storage medium reading device 408 or downloaded from a network such as the Internet. By the installation, the image processing apparatus 400 becomes operable to perform the following image processing. The image processing program 410 that performs image processing is, for example, a printer driver, and may run on a predetermined OS. Further, it may be a part of specific application software.

  The image processing method of the present embodiment can also be performed on the ink jet printer 500 side. However, in the present embodiment, the ink jet printer 500 side actually records an image drawing or character print command in the apparatus. An example that does not have a function of generating a dot pattern to be described will be described. That is, a print command from application software or the like executed by the image processing apparatus 400 serving as a host is an image processing program 410 (printer driver) according to the present embodiment incorporated as software in the image processing apparatus 400 (host computer). Is subjected to image processing.

  The image processing program 410 rasterizes the image data requested to be printed by the application software, generates multi-value dot pattern print data that can be output by the ink jet printer 500, and transfers the print data to the ink jet printer 500. The inkjet printer 500 prints out the print data. This will be described based on this series of procedures.

Specifically, in the image processing apparatus 400, an image drawing or character recording command (for example, a description of the position, thickness, and shape of a line to be recorded, or the like transmitted from application software or an operating system is recorded. The character font, size, position, etc.) are temporarily stored in the drawing data memory. These instructions are written in a specific print language.
The command stored in the drawing data memory is interpreted by the rasterizer, and if it is a line recording command, it is converted into a dot pattern according to the designated position and thickness, etc. For example, the outline information of the corresponding character is called out from the font outline data stored in the image processing apparatus (host computer) 400 and converted into a dot pattern according to the designated position and size. Converted to a dot pattern.
Thereafter, the printer driver performs image processing on these dot patterns and stores them in the raster data memory. At this time, the image processing apparatus 400 rasterizes the print data of the dot pattern using the orthogonal lattice as the basic recording position. Examples of the image processing include color management processing (CMM) for adjusting colors, γ correction processing, halftone processing such as dithering and error diffusion, further background removal processing, and total ink amount regulation processing. Then, the dot pattern (print data) stored in the raster data memory is transferred to the inkjet recording apparatus 500 via the interface.

  In the present embodiment, as a recording method, so-called one-pass printing in which an image is formed on the recording medium by one main scanning may be used, or the same nozzle group or different nozzles may be applied to the same area of the recording medium. So-called multi-pass printing, in which an image is formed by performing main scanning a plurality of times depending on the group, may be used. Further, the recording heads 7 may be arranged in the main scanning direction, and the same area may be divided by different nozzles. These recording methods can be used in appropriate combination.

  In this embodiment, in order to print the one-pass printing at a higher speed, bidirectional printing is performed in which an image is formed in either the forward direction or the backward direction when the recording head 7 slides in the main scanning direction. .

  As described in the background art, when bidirectional printing is performed by the inkjet printer 500 in which the ink for forming an image is sequentially arranged for each color, the color superposition order during forward printing and the backward printing are performed. In this case, the color superposition order is reversed, and a bi-directional color difference that causes a color difference depending on the scanning direction of the recording head 7 may occur.

  In the present embodiment, this problem is solved by controlling the amount of ink adhering to the first landing color in each of the forward printing and the backward printing so as to decrease toward the connecting portion in the reciprocating direction. .

[Image processing method of this embodiment]
FIG. 12 is an example of a diagram schematically showing a printing result in which the inkjet printer 500 prints blue in both directions. In FIG. 12, blue is printed bidirectionally. Blue is formed by landing M (magenta) and C (cyan) at approximately the same position. The ink jet printer 400 is landed in the order of magenta → cyan during forward printing, and landed in the order of cyan → magenta during backward printing. In FIG. 12, a print area 611 for forward printing, a print area 612 for backward printing, and a print area 613 for forward printing are shown in the sub-scanning direction. As schematically shown in FIG. 12, a bidirectional color difference occurs when the color superposition order is reversed.

  FIG. 13 is an example of a diagram for explaining the color superposition order. FIG. 13A shows a case where magenta is landed first, and FIG. 13B is a schematic diagram when cyan is landed first. The ink droplet that has landed first is fixed near the surface of the paper. Therefore, the next ink droplet landed so as to overlap penetrates from the periphery of the previously landed ink droplet downward in the drawing. As a result, the appearance of the printed result is dominated by the ink droplets that have landed first, so the order of M and C ink droplets is the same for both backward and forward printing, but the stacking order is different. Depending on the color will be different. For example, magenta M is dominant in FIG. 13A, and cyan C is dominant in FIG. 13B.

  FIG. 14 is an example of a diagram schematically showing first and second landing ink droplets in the forward direction and the backward direction in order to reduce the bidirectional color difference. The first landing is, for example, magenta M, and the second landing is, for example, cyan C. For the sake of explanation, in FIG. 14, the positions of the first landing and the second landing are shifted, but they are landed at substantially the same position.

  For example, the forward and backward colors are compared in advance, and landed first toward the joint between the reciprocating direction and the backward direction (hereinafter referred to as the boundary) so that the forward and backward colors are close to each other. The amount of ink attached to the color to be controlled is controlled to be small. By doing so, it is possible to reduce the adjacent (bidirectional) color difference between the forward direction and the backward direction and make it difficult to visually recognize the bidirectional color difference.

  This is because the adjacent color difference feels the color difference most from the viewpoint of visual characteristics. If the bidirectional color difference at the boundary is reduced, it is difficult to visually recognize the bidirectional color difference.

  As shown in FIG. 14, the two ink droplets closest to the boundary in the forward direction land in the order of M → C. However, since the ink droplets of the first landing M are small, M is not dominant, and C and M The degree of dominance can be controlled appropriately. Similarly, the two ink droplets that are closest to the boundary in the backward direction land in the order of C → M, but since the ink droplets of the first landing C are small, C is not dominant, and the degree of control of C and M Can be controlled appropriately. In this way, the bidirectional color difference between the forward direction and the backward direction can be reduced.

  Further, by controlling the ink adhesion amount so that the bidirectional color difference is reduced in the vicinity of the boundary, the target color at the time of color design can be prevented from being lost as much as possible. In other words, reducing the amount of ink attached to the ink droplets that have landed first in the entire region regardless of the position of the boundary has the adverse effect of narrowing the color gamut, but the bidirectional color difference only in the vicinity of the boundary. By controlling the ink adhesion amount so as to be small, it is possible to prevent the color reproduction range from becoming narrow.

In bidirectional printing, the forward direction → the backward direction → the forward direction →... Are alternately performed, but this situation can be considered as a configuration sandwiched between two recording heads 7.
FIG. 15 is an example of a diagram schematically illustrating control of the boundary and ink adhesion amount generated by bidirectional printing. As shown, the backward direction is sandwiched between the previous forward direction and the subsequent forward direction. The forward direction is sandwiched between the previous backward direction and the subsequent backward direction. Therefore, a boundary sandwiched between the forward direction and the backward direction and a boundary sandwiched between the backward direction and the forward direction occur alternately. For this reason, for example, the ink adhering amount of the first landing color is gradually reduced toward the nearest boundary at half (1/2) of the head length in the sub-scanning direction. For example, in the return path A, the ink droplets ejected from the upper half nozzles of the recording head 7 are gradually reduced toward the boundary a1, and the ink droplets ejected from the lower half nozzles of the recording head 7 are directed toward the boundary a2. And gradually make it smaller. This length does not need to be ½ of the recording head 7 and can be smaller than ½, for example, within a predetermined distance from the boundary (for example, an area corresponding to 8 dots). The smaller the area for controlling the ink adhesion amount, the more the load on the PC can be reduced.

  Further, the distance within a predetermined distance from the boundary may be changed depending on the color. For example, blue is 1/2 of the head length, green is 1/3 of the head length, and the like. This is because the bidirectional color difference visible to the naked eye differs depending on the color, and is preferably variable for each color.

  In addition, it is optimal that the change in the ink adhesion amount is changed continuously, but the ink adhesion amount may be changed stepwise in a minute step shape. Since the amount of change is small, the density jump is not visually recognized as banding.

  Thus, in order to reduce the bidirectional color difference in the vicinity of the boundary, in what range the ink adhesion amount is reduced with respect to the head length in the sub-scanning direction, and the ink adhesion amount per unit length in the sub-scanning direction Can be defined as a parameter.

  Even if the bidirectional color difference near the boundary is small, the ink adhesion amount may be controlled, or the ink adhesion amount may not be controlled according to the bidirectional color difference (when the color difference is small). good. For example, if ΔE (color difference) is 0.8 or less (a level at which no color difference is felt in the adjacent comparison), it is possible not to control the ink adhesion amount.

  FIG. 16 shows an example of a functional block diagram of the printer driver. The printer driver includes an image processing unit 321, an end data detection unit 322, a first landing determination unit 323, and a droplet size reduction unit 324. These are realized by the CPU executing the program.

  The image processing unit 321 performs known image processing such as CMM (Color Management Module) processing, gamma correction / halftone processing, and the like on the image data. Multi-level dot data (print data) is obtained by halftone processing. The end data detection unit 322 determines whether the dot data is included within a predetermined distance from the boundary between the forward path and the return path described with reference to FIG. Since the dot data has a one-to-one correspondence with each nozzle in each nozzle row for each color, it is easy to determine whether the dot data is included within a predetermined distance from the boundary (that is, from the end of the recording head 7). Can be judged.

  The first landing determination unit 323 determines whether there is a second landing for dot data included within a predetermined distance from the boundary. In the forward path, whether there is C, M, Y dot data landing at the same landing position as the K dot data, or whether there is M, Y dot data landing at the same landing position as the C dot data. Alternatively, the first landing determination unit 323 determines whether there is Y dot data landing at the same landing position as the M dot data. In the return path, whether there is M, C, K dot data landing at the same landing position as the Y dot data, or there is C, K dot data landing at the same landing position as the M dot data. The first landing determination unit 323 determines whether or not there is K dot data landing at the same landing position as the C dot data.

  Then, the droplet size reduction unit 324 reduces the first landing with subsequent landing. Since the dot data already obtained by the image processing unit 321 is an ink droplet having a size corresponding to M0 to M3, the dot data is reduced. For example, when reducing the amount of dot data with half the head length from the boundary, the distance with half the head length is further divided into four. Ink droplets in the area closest to the boundary are set to the original dot data × 1/4, the ink droplets in the area close to the boundary are set to the original dot data × 1/3, and the third is set as the boundary. The ink droplets in the near area are set to the size of the original dot data × ½, and the ink drops in the area closest to the boundary are set to the same size as the original dot data.

  Further, the size of the ink droplet may be adjusted regardless of the size of the original dot data. Count the ink droplets in the area closest to the boundary to the smallest size, then count the ink droplets in the area closest to the boundary from the smallest to the second size, and the ink droplets in the third closest area to the smaller one. The ink droplets in the region closest to the boundary are counted as the fourth size from the smaller one. Note that it is preferable that the number that divides the distance of ½ of the head length is larger, because the change in the amount of ink adhesion becomes continuous.

  In addition, the size of the first landing ink droplet does not necessarily decrease toward the boundary, and the size of the first landing ink droplet is uniform or random at a distance of ½ the head length from the boundary, for example. Alternatively, it may be made smaller.

  The image processing apparatus 400 is configured such that a printer driver as a program causes the computer to execute the image processing method. However, the image forming apparatus 500 itself may include means for executing the above-described image processing method. Further, an application specific integrated circuit (ASIC) that executes the image processing method may be mounted on the image forming apparatus 500. In other words, the image processing method of the present embodiment can be suitably implemented in either the printer driver or the image forming apparatus 500.

[Operation procedure]
FIG. 17 is an example of a flowchart illustrating a procedure in which the image processing apparatus 400 performs color difference reduction processing during bidirectional printing. In the following description, it is assumed that processing is performed uniformly regardless of whether or not the printer is in the bidirectional printing mode and the type of input data.

  When the printer driver serving as the image processing program 410 is activated, the image processing unit 321 performs CMM processing on the image data requested to be printed by the application software (S10). The CMM process is a process of converting from a color space of image data to a color space for a recording apparatus (image forming apparatus 500) (RGB color system → CMY color system).

  Next, the printer driver determines whether the print data is monochrome (S20). Single color means that the print data can be printed with any one of CMYK. For print data that can be reproduced in a single color, there is no inconvenience that the landing order is different in the forward direction and the backward direction, so there is no need to perform bidirectional color difference reduction processing. For this reason, in the case of a single color (Yes in S20), the image processing unit 321 performs gamma correction / halftone processing for single-color image data (S30).

  An image processing unit 321 performs halftone processing including a γ correction that performs input / output correction reflecting the characteristics of the apparatus and user's preference, and a multi-value / low-value matrix that is replaced with a dot pattern arrangement for ejecting print data. Apply to data.

  If it is not a single color (No in S20), the image processing unit 321 performs gamma correction / halftone processing for multicolor image data (S40). Thereby, a dot pattern is obtained.

  Next, the edge data detector 322 determines whether or not each ink droplet corresponds to the edge area of the recording head 7 (S50). In the present embodiment, in order to shorten the processing time, for example, the inside of 8 dots from the end is defined as the end area. Furthermore, since processing over a wider area is more effective in reducing bidirectional color differences, the end area need not be limited to 8 dots. Dots that are determined not to be edge regions are output as they are.

  For the ink droplets determined to be the end region, the first landing determination unit 323 determines whether or not the dots are ejected in the forward direction (S60). Then, the first landing determination unit 323 determines whether or not the dot is landed first (S70).

  Further, the first landing determination unit 323 determines whether or not the ink droplet ejected in the backward direction is the ink droplet that has landed first (S80).

  Then, in the forward direction or the backward direction, the droplet size reduction unit 324 performs a droplet size reduction process on the ink droplets that have landed first (S90). For example, the droplet size reduction unit 324 converts an ink droplet within 8 dots from the end portion into a smaller ink droplet as it approaches the boundary.

  Since a certain amount of area is necessary for visually recognizing the bidirectional color difference, the bidirectional color difference is difficult to be visually recognized because the area where the bidirectional color difference is generated is small in a fine line (one dot line) or a small size character. For this reason, it is possible to prevent the bidirectional color difference reduction measure from being applied to fine lines (one dot line) or small-size characters.

[Another example of color difference reduction processing]
In the present embodiment, as a method for controlling the ink adhesion amount, the ink ejection amount from the nozzle is changed or the ink ejection amount is changed to a different size, but as a method for changing the ejection amount, There is a method of controlling the amount of ejected droplets by controlling the voltage of the drive signal.

  In addition, the target color is changed by changing the reference position of the color conversion profile in the CMM process, and the ink adhesion amount is controlled by controlling the ink deposition amount per unit area in the halftone process. There are ways to control.

  As a method for obtaining the discharge amount from the nozzle that is the basis for controlling the ink adhesion amount, a method for obtaining the discharge amount from the nozzle based on the head characteristic information set for each head, and the measurement result of the dot diameter on the recording medium There is a method for obtaining the discharge amount based on the above, and a method for obtaining the discharge amount from the measured value of the reflection density on the recording medium.However, the method for actually measuring the discharge amount from the nozzle is the method with the most accurate control. is there.

  There is also a method in which a bidirectional color difference between scans is measured using an optical colorimeter, and the ink adhesion amount is controlled based on the measured value.

  It is also effective to detect the type of the recording medium and apply a correction value depending on the recording medium.

  FIG. 18 is a diagram illustrating an example of ink droplet size down processing. The input image data is blue. FIG. 18 shows a comparison between a recording head 7 that ejects ink droplets of a plurality of sizes that can be used to separate large, medium, and small droplets, and a recording head 7 that ejects single-size ink droplets.

  As described above, when large, medium, and small droplets can be sorted, a drop size reduction process is performed on cyan that landed first in the forward direction and magenta that landed first in the backward direction. The recording head 7 controls the adhesion amount by converting a large dot in the original image data toward the boundary into medium and small. As shown in the figure, the closer to the boundary between the forward path and the backward path, the smaller the ink droplet, and the dot that does not eject the ink droplet appears.

  On the other hand, when ejecting ink droplets of a single size, the recording head 7 controls the adhesion amount by converting the presence of droplets to the absence of droplets toward the end. In both the forward direction and the backward direction, the first and second rows from the boundary have three no-drops, the third and fourth rows from the boundary have two no-drops, and the fifth row from the boundary. The sixth row has one drip free. By increasing the proportion of ink droplets that are not ejected closer to the boundary in this way, the bidirectional color difference can be reduced as in the case of ejecting ink droplets of multiple sizes.

  In FIG. 18, the control of the adhesion amount is the same in the forward direction and the backward direction (in the forward direction and the backward direction, the first and third rows, the second and fifth rows, the first and third rows, respectively). In the first, second and fourth rows, the first and sixth rows, and the second and fourth rows are free of droplets), the amount of adhesion may be controlled differently in the forward direction and the backward direction. In this way, colors can be dispersed.

[Another example of the recording head 7]
In the image forming apparatus 500 of the present embodiment, the recording head 7 using a piezoelectric element has been described. However, as described above, a thermal head that discharges droplets by film boiling using an electrothermal conversion element may be used. As described above, the piezoelectric head can eject ink droplets having different sizes depending on the drive signal, so that it is easy to form a gradation image.

On the other hand, the thermal type head is advantageous in printing an image with high resolution at a high speed because it is easy to highly integrate nozzles. A thermal head will be described with reference to FIGS.
The recording head 7 shown in FIG. 19 is an edge shooter type thermal head, and includes an ejection energy generator 501 (electrodes for applying an ejection signal to the generator and a protective layer provided on the generator as necessary). The substrate 502 having the structure (not shown) is laminated by laminating a side wall of the flow path 503 and a wall material 505 constituting the nozzle 504 and a top plate 506 constituting the cover of the flow path 503. In the recording head 7, the ink travels straight from the flow path 503 toward the nozzle 504 as indicated by a one-dot chain line 507.
In this thermal head, when a recording signal is applied to the ejection energy generator 501 via an electrode (not shown) in a state where the ink is filled in the flow path 503 from a liquid chamber (not shown) in which ink is stored, the generation occurs. The ejection energy generated from the body 501 acts on the ink in the flow path 503 above the ejection energy generation body 501 (ejection energy operation unit), and as a result, the ink is ejected from the nozzle 504 as ink droplets.
Such an edge shooter type thermal head has the advantage that it is very easy to miniaturize each part with high precision, make the nozzles multi-sized or downsize, and has high productivity. On the other hand, there is a limit to the response frequency and droplet flying speed during droplet ejection. In addition, bubbles are generated in the ink due to the heat generated by the electrothermal conversion element. The bubbles contract due to a decrease in temperature, and the discharge energy generator 501 is gradually destroyed by an impact when the bubbles disappear in the vicinity of the discharge energy generator 501. The so-called cavitation phenomenon occurs, and there is a disadvantage that the lifetime is relatively short.

The thermal type head shown in FIG. 20 is a side shooter type recording head 7 and includes an ejection energy generator 511 (an electrode for applying an ejection signal to the generator and a protective layer provided on the generator as necessary). A flow path forming member 515 that forms the side wall of the flow path 513 is stacked on a substrate 512 having a structure (not shown), and a nozzle plate 516 having a nozzle 514 formed thereon is stacked on the flow path forming member 515. ing. In this recording head 7, as indicated by a one-dot chain line 517, the direction of ink flow to the ejection energy operating portion in the flow path 513 is perpendicular to the opening center axis of the nozzle 514.
With such a configuration, the energy from the ejection energy generator 511 can be more efficiently converted into the formation of ink droplets and the kinetic energy of the flight, and the meniscus can be quickly restored by supplying ink. This is advantageous and is particularly effective when a heating element is used as the discharge energy generator 511. In addition, a so-called cavitation phenomenon in which the discharge energy generating body is gradually destroyed by the impact when bubbles that are a problem in the edge shooter disappear can be avoided by the side shooter method. In other words, in the side shooter method, when the bubbles grow and the bubbles reach the nozzle, the bubbles are communicated with the atmosphere, and the bubbles do not contract due to a decrease in temperature. Therefore, the life of the recording head 7 becomes relatively long. .

  As described above, the image processing apparatus 400 according to the present embodiment can change the hue of an image during bidirectional printing without increasing the number of heads, considering the type of recording medium, or reducing the printing speed. Can be reduced.

[Appendix]
(1) The ink adhesion amount change amount of the first landing color may be controlled based on a bidirectional color difference generated at the boundary between forward printing and backward printing.
(2) a range in which the ink adhesion amount is changed by a bidirectional color difference generated at the boundary between forward printing and backward printing when controlling the ink deposition amount of the first landing color toward the end portion; The amount of change may be controlled.
(3) In order to reduce the bidirectional color difference that occurs at the boundary between forward printing and backward printing, the amount of ink that is landed first may be continuously changed toward the edge. .
(4) In order to reduce the bidirectional color difference that occurs at the boundary between forward printing and backward printing, the amount of ink that is landed first may be changed stepwise toward the edge. .
(5) The amount of adhesion may be controlled by changing the reference position of the color conversion profile by controlling the range and amount of change in the amount of ink adhesion in the color conversion unit.
(6) The halftone parameter may be converted so as to change the ink adhesion amount in the halftone processing unit, and the range and change amount of the ink adhesion amount may be controlled.
(7) The amount of adhesion may be controlled by converting the droplet data of each pixel unit after conversion into output data based on the range and amount of change in the amount of ink adhesion.
(8) The range and amount of change of the ink adhesion amount may be controlled based on the head characteristic information.
(9) The range and amount of change of the ink adhesion amount may be controlled based on the measured value of the ejection amount from the recording head 7.
(10) The ejection amount from the recording head 7 may be calculated from the measured value of the dot diameter on the recording medium, and the range and amount of change of the ink adhesion amount may be controlled based on the dot diameter.
(11) Even if the bidirectional color difference generated at the boundary between forward printing and backward printing is calculated from the measured value of the optical colorimeter, the range and amount of change of the ink adhesion amount are controlled. Good.
(12) The range and amount of change of the ink adhesion amount may be controlled by the recording medium used for printing.
(13) In the case of being sandwiched between two recording heads as in the forward path / return path / return path, the range and amount of change of the ink adhesion amount may be controlled within 1/2 of the print head length. .

7 Recording head 10 Paper cassette 11 Paper stacking unit 12 Paper (recording medium)
DESCRIPTION OF SYMBOLS 13 Paper feed roller 21 Conveyance belt 22 Counter roller 23 Conveyance guide 24 Holding member 25 Holding roller 26 Charging roller 27 Conveyance roller 200 Control part 207 Print control part 208 Head driver 400 Image processing apparatus 500 Image forming apparatus

Japanese Patent Laid-Open No. 08-295034 JP 2003-025613 A JP 2004-050705 A

Claims (8)

Print data is supplied to an image forming apparatus that reciprocally moves a recording head having a plurality of nozzle rows from which droplets of different colors are ejected and ejects droplets from the nozzle rows to form an image on the recording medium. An information processing apparatus,
Droplet data generation means for generating droplet data of discharged droplets from image data;
Data detection means for detecting droplet data landed within a predetermined distance from the boundary between the forward path and the return path;
First landing detection means for detecting first landing that is landed by overlapping second landing from droplet data landed within the predetermined distance;
Droplet size adjustment means for reducing the droplet size of the first landing according to the distance to the boundary,
Supplying print data including droplet data with a reduced droplet size to the image forming apparatus;
An information processing apparatus characterized by that. The droplet size adjusting means reduces the droplet size as the first landing closer to the boundary,
The information processing apparatus according to claim 1. The droplet size adjusting means increases the ratio of not discharging the first landing as it is closer to the boundary.
The information processing apparatus according to claim 1. The region within the predetermined distance is a region closer to the end of the nozzle row than the center in the longitudinal direction of the nozzle row,
The information processing apparatus according to any one of claims 1 to 3. In an image forming apparatus for reciprocating a recording head having a plurality of nozzle rows from which droplets of different colors are ejected and ejecting droplets from the nozzle rows to form an image on the recording medium,
Droplet data generation means for generating droplet data of droplets discharged from image data;
Data detection means for detecting droplet data landed within a predetermined distance from the boundary between the forward path and the return path;
First landing detection means for detecting first landing that is landed by overlapping second landing from droplet data landed within a predetermined distance;
An adhesion amount reducing means for reducing the adhesion amount of the first landing material adhering to the recording medium than the adhesion amount determined from image data;
An image forming apparatus comprising: The adhesion amount reducing means reduces the adhesion amount by changing the discharge amount from the nozzle.
6. The image forming apparatus according to claim 5, wherein the image forming apparatus is controlled. Print data supplied to an image forming apparatus that reciprocally moves a recording head having a plurality of nozzle rows from which droplets of different colors are ejected and ejects droplets from the nozzle rows to form an image on the recording medium. A generation method of
A step of generating droplet data of droplets to be ejected from image data by a droplet data generation means;
A step of detecting data of droplets landed within a predetermined distance from the boundary between the forward path and the return path;
First landing detection means detects from the droplet data landed within a predetermined distance the first landing landed with the second landing,
A droplet size adjusting means, reducing the droplet size of the first landing according to the distance from the boundary,
Supplying print data including droplet data with a reduced droplet size to the image forming apparatus;
A method for generating print data. Print data supplied to an image forming apparatus that reciprocally moves a recording head having a plurality of nozzle rows from which droplets of different colors are ejected and ejects droplets from the nozzle rows to form an image on the recording medium. Is a program that causes a computer to generate
On the computer,
A droplet data generation step for generating droplet data of droplets discharged from the image data;
A data detection step for detecting droplet data landed within a predetermined distance from the boundary between the forward path and the return path;
A first landing detection step for detecting first landing that is landed by overlapping second landing from droplet data landed within a predetermined distance;
A droplet size adjusting step for reducing the droplet size of the first landing according to the distance from the boundary;
Supplying print data including droplet data with a reduced droplet size to the image forming apparatus;
A program that executes

Images