Recording head control device and control method, and printing device

Abstract

To provide a recording head control device and a recording head control method which can maintain accuracy in correcting printing deviation regardless of printing resolution in a direction in which a recording head and a recording medium move relatively, and a printing device.SOLUTION: When printing resolution is set to second printing resolution which is relatively lower than first printing resolution, a second recording-start trigger signal by which a plurality of head modules is driven at a second cycle corresponding to the second printing resolution, which makes a timing of driving at least one head module delay by a delay amount, with a first cycle corresponding to the first printing resolution as a reference, is generated, and the plurality of head modules is driven based on the second recording-start trigger signal.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a control device and control method for a printhead, and a printing apparatus, and more particularly to a technique for correcting printing misalignment in a printhead in which a plurality of head modules are arranged. [Background technology]

[0002] A liquid ejection head in which a plurality of head modules are arranged is known as a recording head used in a printing device. For example, a full-line type liquid ejection head can be configured by arranging a plurality of head modules over a length corresponding to the full width of a recording medium that moves relatively.

[0003] A liquid ejection head in which multiple head modules are arranged can be subject to misalignment in the relative movement direction due to variations in the mounting positions of the head modules and variations in the manufacturing process of the head modules themselves. A known method for eliminating this misalignment is to adjust the ejection timing between the head modules according to the amount of misalignment.

[0004] For example, Patent Document 1 discloses a delay circuit that corrects print misalignment in the relative movement direction due to tilt of the recording head by shifting the print timing for each head unit. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5352951 Summary of the Invention [Problem to be solved by the invention]

[0006] On the other hand, there is known a printing device that switches the print resolution in the direction of relative movement between the print head and the print medium. However, Patent Document 1 does not mention the operation of the delay circuit when the print resolution in the direction of relative movement is switched.

[0007] The present invention has been made in consideration of the above circumstances, and aims to provide a recording head control device, control method, and printing device that maintain the accuracy of correcting print misalignment regardless of the printing resolution in the direction of relative movement between the recording head and the recording medium. [Means for solving the problem]

[0008] One aspect of a recording head control device for achieving the above object includes at least one processor, and the at least one processor acquires a recording synchronization signal of a first period corresponding to a first print resolution in the relative movement direction synchronized with the relative movement from a relative movement mechanism that moves a recording medium and a recording head having a plurality of head modules arranged thereon in a relative movement direction, and generates a first recording start trigger signal that drives the plurality of head modules at the first period, the first recording start trigger signal being the first recording start trigger signal in which the drive timing of at least one head module is delayed by an amount of delay based on the arrangement positions of the plurality of head modules with respect to the first period, and A control device for a recording head that drives multiple head modules, wherein at least one processor accepts a setting of a print resolution in a relative movement direction, the setting being a second print resolution that is relatively lower than the first print resolution, and when the second print resolution is set, generates a second recording start trigger signal that drives the multiple head modules at a second period corresponding to the second print resolution, the second recording start trigger signal being obtained by delaying the drive timing of at least one head module from the first period by an amount of delay based on the arrangement positions of the multiple head modules, and drives the multiple head modules based on the second recording start trigger signal. According to this aspect, the accuracy of correction of print misalignment can be maintained regardless of the print resolution in the relative movement direction between the recording head and the recording medium.

[0009] When the second print resolution is set, the at least one processor preferably delays the recording synchronization signal by a delay amount relative to the first period, converts the period of the delayed recording synchronization signal to a second period, and generates a second recording start trigger signal. This makes it possible to generate a second recording start trigger signal that is delayed relative to the first period corresponding to the first print resolution, even when the second print resolution is set to a lower value than the first print resolution.

[0010] Preferably, at least one processor counts the print synchronization signal for a delay amount of one pixel unit of the first print resolution, and counts a signal asynchronous with the print synchronization signal for a delay amount of less than one pixel of the first print resolution, thereby delaying the drive timing, whereby the drive timing can be delayed by the delay amount with respect to the first period.

[0011] The recording head may have a plurality of head modules arranged in a direction intersecting the direction of relative movement. Furthermore, it is preferable that at least one processor uses the head module arranged most upstream in the direction of relative movement among the plurality of head modules as a reference for the amount of delay. This makes it possible to maintain the accuracy of correction of printing misalignment for head modules other than the reference head module.

[0012] It is preferable that the printer includes an image memory for storing image data, and that at least one processor outputs control data to the plurality of head modules for controlling the driving of each head module based on the image data acquired from the image memory. This makes it possible to print an image of the image data while maintaining the accuracy of correction of printing misalignment.

[0013] One aspect of a printing device for achieving the above object is a printing device including a recording head having a plurality of head modules arranged therein, a relative movement mechanism that moves the recording head and the recording medium relative to each other in a relative movement direction and generates a recording synchronization signal of a first period that corresponds to a first printing resolution in the relative movement direction synchronized with the relative movement, and a control device for the recording head. According to this aspect, it is possible to maintain the accuracy of correction of print misalignment regardless of the printing resolution in the relative movement direction between the recording head and the recording medium.

[0014] The first print resolution is preferably the highest print resolution in the direction of relative movement in the printing device, which allows the first and second recording start trigger signals to be generated with a delay amount that is accurate to the highest print resolution.

[0015] The relative movement mechanism preferably includes a transport mechanism that transports the recording medium in the transport direction. The transport mechanism preferably includes a cylindrical transport drum that supports and transports the recording medium on its circumferential surface, and an encoder that outputs a pulse signal in response to the rotation of the transport drum, and generates a recording synchronization signal based on the pulse signal. This allows a recording synchronization signal of a first period that corresponds to a first print resolution in the transport direction synchronized with the transport.

[0016] The head module preferably includes a nozzle for ejecting the liquid, and an ejection energy generating element for ejecting the liquid from the nozzle. This aspect is applicable to a head module that ejects the liquid from the nozzle.

[0017] One aspect of a recording head control method for achieving the above object includes a resolution setting step for setting a print resolution in a relative movement direction between a recording head having a plurality of head modules arranged thereon and a recording medium, and for accepting the setting of either a first print resolution or a second print resolution that is relatively lower than the first print resolution, and when the first print resolution is set in the resolution setting step, a step for acquiring a recording synchronization signal of a first period corresponding to the first print resolution in the relative movement direction synchronized with the relative movement from a relative movement mechanism that moves the recording head and the recording medium relatively in the relative movement direction, and a step for acquiring a first recording start trigger signal that drives the plurality of head modules at the first period, and that sets the drive timing of at least one head module to a position where the plurality of head modules are arranged. and driving a plurality of head modules based on the first recording start trigger signal, and when a second print resolution is set in the resolution setting step, acquiring a recording synchronization signal from a relative movement mechanism, generating a second recording start trigger signal that drives the plurality of head modules at a second period corresponding to the second print resolution, the second recording start trigger signal being obtained by delaying the drive timing of at least one head module based on the first period by an amount of delay based on the arrangement positions of the plurality of head modules, and driving the plurality of head modules based on the second recording start trigger signal. According to this aspect, the accuracy of correction of print misalignment can be maintained regardless of the printing resolution in the direction of relative movement between the recording head and the recording medium. [Effects of the Invention]

[0018] According to the present invention, it is possible to maintain the accuracy of correcting print misalignment regardless of the print resolution in the direction of relative movement between the print head and the print medium. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic plan view of a line head in which a plurality of head modules are arranged. [Figure 2] FIG. 2 is a diagram showing a line head in which the mounting position of the head module in the Y direction is deviated from the ideal position. [Figure 3] FIG. 3 is a diagram showing the print result on the paper P when a straight line parallel to the X direction is printed by the line head shown in FIG. [Figure 4] FIG. 4 is a conceptual diagram for explaining a correction technique when the mounting position of the head module in the Y direction is deviated from the ideal position. [Figure 5] FIG. 5 is a diagram showing the print result on paper P when a straight line parallel to the X direction is printed by delaying the ejection timing of the head module by a delay time. [Figure 6] FIG. 6 is a block diagram showing the electrical configuration of a head control device for controlling the line head to perform Y-direction correction. [Figure 7] FIG. 7 is a timing chart showing the inkjet ejection synchronization signal and the piezo drive voltage waveform. [Figure 8] FIG. 8 is a timing chart showing the inkjet ejection synchronization signal and the piezo drive voltage waveform. [Figure 9] FIG. 9 is a timing chart showing the inkjet ejection synchronization signal and the piezo drive voltage waveform. [Figure 10] FIG. 10 is a timing chart showing the inkjet ejection synchronization signal and the piezo drive voltage waveform. [Figure 11] FIG. 11 is a block diagram showing the electrical configuration of the head control device according to this embodiment. [Figure 12] FIG. 12 is a timing chart showing the inkjet ejection synchronization signal and the piezo drive voltage waveform. [Figure 13] FIG. 13 is a timing chart showing the inkjet ejection synchronization signal and the piezo drive voltage waveform. [Figure 14] FIG. 14 is a flowchart showing the process of the printing method. [Figure 15]FIG. 15 is a diagram showing the overall configuration of an inkjet printing apparatus to which a head control device is applied. [Figure 16] FIG. 16 is a perspective view of the inkjet head. [Figure 17] FIG. 17 is an enlarged view of the inkjet head as seen from the nozzle surface side. [Figure 18] FIG. 18 is a plan view of the nozzle surface in the head module. [Figure 19] FIG. 19 is a cross-sectional view showing an example of the structure of one channel of droplet ejection elements, which constitute a recording element unit. [Figure 20] FIG. 20 is a block diagram showing the system configuration of the inkjet printing device. [Figure 21] FIG. 21 is a diagram showing an inkjet head according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0020] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0021] <Explanation of technical issues using concrete examples> [Line head configuration] Before describing the embodiments of the present invention, the technical problem that the invention aims to solve will be described using a specific example. Figure 1 is a schematic plan view of a line head in which a plurality of head modules are arranged.

[0022] In FIG. 1, the direction indicated by the white arrow (the direction from top to bottom in FIG. 1) is the paper transport direction in which paper, which is a recording medium, is transported. In this specification, the paper transport direction, which is the direction of relative movement, is referred to as the "Y direction," and the paper width direction (the horizontal direction in FIG. 1), which is perpendicular to the Y direction (an example of "intersecting"), is referred to as the "X direction." The line head 10 is configured by arranging multiple head modules 12-i (i = 1, 2, ...) along the X direction. Note that, below, when describing common content for each head module 12-i (i = 1, 2, ...), it may be written as head module 12.

[0023] 1 shows a configuration in which five head modules 12-i (i = 1, 2, ... 5) are arranged, but there is no particular limitation on the number of head modules 12 used to configure one line head 10. FIG. 1 shows an ideal line head 10 in which each head module 12-i (i = 1, 2, ... 5) is attached as designed without any attachment position error.

[0024] The head module 12 is an inkjet head module that ejects ink droplets using an inkjet method to record dots on the surface of paper. A plurality of nozzles, which are ink ejection ports (not shown), are two-dimensionally arranged on an ink ejection surface (not shown) of the head module 12. The plurality of nozzles are arranged at a density in the X direction that achieves a predetermined printing resolution.

[0025] The line head 10 achieves the same print resolution at the joints between adjacent head modules 12 in the X direction as at the other parts of the head modules 12, and achieves the desired print resolution in the X direction for the entire line head 10. The print resolution of the line head 10 in the X direction is, for example, 1200 dpi (dots per inch).

[0026] 2 is a diagram showing the line head 10 when the mounting position of the head module 12-i (i=1, 2, ... 5) in the Y direction is deviated from the ideal (design) position. When a long line head 10 is configured by arranging multiple head modules 12 in the X direction, as in the example shown in FIG. 2, variations in the positions of the head modules 12 in the Y direction may occur depending on the mounting accuracy of the head modules 12.

[0027] Fig. 3 is a diagram showing the print result on paper P when image data showing a single straight line extending in the X direction is printed by the line head 10 shown in Fig. 2. The print result 14-i (i = 1, 2, ... 5) shown in Fig. 3 is a straight line printed by each head module 12-i (i = 1, 2, ... 5). As shown in Fig. 3, the print result 14-i (i = 1, 2, ... 5) has a print misalignment caused by printing at a position shifted in the Y direction due to a shift in the mounting position of the head module 12-i (i = 1, 2, ... 5) in the Y direction.

[0028] [Y-direction correction] 4 is a conceptual diagram for explaining a technique for correcting print misalignment (referred to as "Y-direction correction") when the mounting position of head module 12-i (i = 1, 2, ... 5) in the Y direction is deviated from the ideal position. Note that mounting position misalignment can also occur in the X direction, but compensation (correction) for print quality for module mounting position misalignment in the X direction can be handled by other correction techniques such as density unevenness correction, so the following explanation deals only with mounting position misalignment in the Y direction.

[0029] The Y-direction correction corrects printing misalignment in the Y direction by delaying the ejection timing of the other head modules 12 by an amount corresponding to their mounting positions, using the head module 12 whose mounting position (an example of an "arrangement position") is located furthest upstream in the Y direction as a reference, among the multiple head modules 12 that make up the line head 10.

[0030] In the example shown in FIG. 4, of the five head modules 12-i (i = 1, 2, ... 5) lined up in the X direction, head module 12-4 is attached at the most upstream position in the Y direction. The difference in position in the Y direction between the reference position La of the most upstream head module 12-4 and the attachment position of each head module 12-i (i = 1, 2, ... 5) is defined as the Y-direction position difference Δyi (i = 1, 2, ... 5). As shown in FIG. 4, the Y-direction position difference Δyi (i = 1, 2, ... 5) is expressed as the distance in the Y direction between a specific position in the Y direction of each head module 12 (for example, the center position in the Y direction of the nozzle region) and the reference position La. The Y-direction position difference Δyi (i = 1, 2, ... 5) may be found from the printing result shown in FIG. 3.

[0031] The delay time Tdi=Δyi / v in the ejection timing of each head module 12 is calculated from the Y-direction position difference Δyi and the paper transport speed v.

[0032] The parameter representing the amount of delay in ejection timing is not limited to a numerical value expressed in units of time such as Tdi (a numerical value representing delay time), but may also be a numerical value representing a "distance (length)" equivalent to the Y-direction position difference Δyi, or a numerical value obtained by converting the distance (length) into the number of pixels corresponding to the print resolution in the Y direction. It is arbitrary which indicator to use to express the amount of delay in units of time, distance (length), or pixels, and these can be converted into each other.

[0033] 5 is a diagram showing the print result on paper P when the same image data as in FIG. 3 is printed by delaying the ejection timing of head module 12-i (i = 1, 2, ... 5) by delay time Tdi = Δyi / v. The print result 16-i (i = 1, 2, ... 5) shown in FIG. 5 is a straight line printed by each head module 12-i (i = 1, 2, ... 5). As shown in FIG. 5, the print result 16-i (i = 1, 2, ... 5) is printed at the same position in the Y direction, and as a result, it becomes similar to a single straight line extending in the X direction indicated by the image data.

[0034] In this way, with Y-direction correction, printing misalignment in the Y direction can be corrected by delaying the ejection timing of each head module 12 by an amount corresponding to its installation position, based on the position of the head module 12 most upstream in the Y direction.

[0035] [Electrical configuration of head control device] Fig. 6 is a block diagram showing the electrical configuration of a printhead control device that performs Y-direction correction by controlling the line head 10. For simplicity of illustration, Fig. 6 shows only one head module 12 as the minimum structural unit, but the actual line head 10 is made up of multiple head modules 12-i (i = 1, 2, ... 5).

[0036] Piezoelectric elements (not shown) that are ejection energy generating elements are provided in each of the multiple nozzles (not shown) of the head module 12. The head control device 20 controls the driving of the piezoelectric elements corresponding to each nozzle of the multiple head modules 12, and controls the ink ejection operation of the nozzles (whether or not to eject, and the amount of droplet ejection).

[0037] 6, the head control device 20 includes an image data memory 22, a nozzle control data output unit 24, an ejection timing correction unit 25, and a drive unit 26. The drive unit 26 includes a waveform data memory 27, a piezoelectric element drive voltage generation unit 28, and an amplifier circuit 29. The functions of the image data memory 22, the nozzle control data output unit 24, the ejection timing correction unit 25, the waveform data memory 27, and the piezoelectric element drive voltage generation unit 28 are each realized by a PLD (Programmable Logic Device). These functions may also be realized by a processor and memory.

[0038] The head control device 20 is also connected to a higher-level image data processing unit 30 and a transport unit 32 via a communication interface (not shown).

[0039] The upper image data processing unit 30 is configured by a host computer, etc. The upper image data processing unit 30 is provided with a communication interface (not shown) for communicating with the head control device 20.

[0040] The transport unit 32 is a transport mechanism (an example of a "relative movement mechanism") that transports paper (an example of a "relative movement") and generates an inkjet ejection synchronization signal (an example of a "recording synchronization signal") synchronized with the transport.

[0041] Image data memory 22 (an example of an "image memory") stores image data expanded into print image data (dot data). The image data memory 22 has a storage capacity that can hold image data for at least a pixel row equivalent to the Y-direction correction amount. The image data memory 22 outputs image data in accordance with an ejection start trigger signal, which will be described later.

[0042] The nozzle control data output unit 24 controls the transfer of nozzle selection control data for each head module 12 to each head module 12 based on the image data output from the image data memory 22. The nozzle selection control data is image data corresponding to the dot arrangement of the printing resolution, and is, for example, dot data that determines whether each nozzle is ON (ejection driven) or OFF (non-driven). The nozzle selection control data may also be dot data that indicates the droplet size for each nozzle. The nozzle control data output unit 24 transfers the nozzle selection control data to each head module 12 via a data bus.

[0043] The ejection timing correction unit 25 performs Y-direction correction by delaying the ejection timing. The higher-level image data processing unit 30 holds data on the Y-direction correction amount (delay amount) for each head module 12 according to its installation position. The ejection timing correction unit 25 acquires the Y-direction correction amount data for each head module 12, performs delay processing according to the Y-direction correction amount on the inkjet ejection synchronization signal acquired from the transport unit 32, and generates an ejection start trigger signal. In other words, the ejection start trigger signal is a signal obtained by delaying the inkjet ejection synchronization signal according to the Y-direction correction amount. The ejection start trigger signal is input to the image data memory 22 and the drive unit 26.

[0044] Digital data of a drive voltage waveform for driving the piezoelectric element is stored in the waveform data memory 27. The waveform data memory 27 outputs the digital data of the drive voltage waveform in accordance with an ejection start trigger signal.

[0045] The piezoelectric element drive voltage generation unit 28 converts the digital data of the drive voltage waveform into an analog drive voltage waveform and outputs it to the amplifier circuit 29. The amplifier circuit 29 current-amplifies the analog drive voltage waveform and supplies it to the head modules 12. Here, the drive voltage waveform data supplied to each head module 12 is the same, but different drive voltage waveform data may be used for each head module 12. In this case, using drive voltage waveform data that corresponds to the individual differences of the head modules 12 makes it possible to perform higher quality printing.

[0046] The head control device 20 configured in this manner acquires image data and the Y-direction correction amount for each head module 12 from the higher-level image data processing unit 30. The head control device 20 may acquire image data in synchronization with paper transport. The ejection timing correction unit 25 generates an ejection start trigger signal for each head module 12 by delaying the inkjet ejection synchronization signal acquired from the transport unit 32 according to the Y-direction correction amount, and outputs the signal to the image data memory 22 and the waveform data memory 27. Upon receiving the ejection start trigger signal, the image data memory 22 and the waveform data memory 27 output nozzle selection control data and piezo drive voltages to each head module 12, respectively, in units of Y-direction printing resolution. This results in selective ejection operations according to the nozzle selection control data, with the ejection timing delayed according to the Y-direction correction amount for each head module 12, thereby achieving appropriate printing.

[0047] [Processing of the ejection timing correction unit] The ejection timing correction unit 25 delays the inkjet ejection synchronization signal by the Y-direction correction amount to generate an ejection start trigger signal. The ejection timing correction unit 25 counts (an example of "counting") the inkjet ejection synchronization signal acquired from the conveyance unit 32 for each pixel of the Y-direction correction amount. Furthermore, for each pixel of the Y-direction correction amount less than one pixel, the ejection timing correction unit 25 counts (an example of "counting") the clock (an example of a "signal asynchronous to the print synchronization signal") generated by the PLD by the ratio of the correction amount to the clock count equivalent value of one theoretical cycle time of the inkjet ejection synchronization signal after completing the count for each pixel and the count for less than one pixel. The ejection timing correction unit 25 starts outputting an ejection start trigger signal after completing the count for each pixel and the count for less than one pixel. In this way, the ejection timing correction unit 25 counts the Y-direction correction amount based on the inkjet ejection synchronization signal to delay the ejection timing.

[0048] FIG. 7 is a timing chart showing the inkjet ejection synchronization signal and piezo drive voltage waveform when the ejection timing correction unit 25 does not delay the ejection timing. FIG. 7 shows the case of printing at a print resolution of 1200 dpi in the Y direction. As shown in FIG. 7, the inkjet ejection synchronization signal has a waveform including pulses consisting of rising and falling edges of the voltage. The transport unit 32 outputs one pulse as the inkjet ejection synchronization signal every time the paper is transported by 1 / 1200 inch. Note that 1 inch is 25.4 millimeters. For example, if the paper transport speed v of the transport unit 32 is 32 meters / minute, the inkjet ejection synchronization signal is output every 40 microseconds. An inkjet ejection synchronization signal with such a period is called an inkjet ejection synchronization signal with a 1200 dpi period.

[0049] Although not shown in Fig. 7, the ejection start trigger signal output from the ejection timing correction unit 25 is a signal similar to the inkjet ejection synchronization signal. This ejection start trigger signal is input to the waveform data memory 27, and as shown in Fig. 7, a piezo drive voltage waveform is output from the amplifier circuit 29 in synchronization with the rising timing of the ejection start trigger signal.

[0050] FIG. 8 is a timing chart showing the inkjet ejection synchronization signal and piezo drive voltage waveform when the ejection timing correction unit 25 delays the ejection timing by 3.5 pixels at a print resolution of 1200 dpi (an example of a "delay amount based on the first print resolution"). Similar to FIG. 7, FIG. 8 also shows a case where printing is performed in the Y direction at a print resolution of 1200 dpi. FIG. 8 also shows a count signal of a pixel unit counter (not shown) that counts the amount of correction in one pixel unit, a count signal of a sub-pixel counter (not shown) that counts the amount of correction less than one pixel, and an ejection start trigger signal output from the ejection timing correction unit 25. The count signal of the pixel unit counter, the count signal of the sub-pixel counter, and the ejection start trigger signal are processed within the PLD.

[0051] First, the pixel counter counts the inkjet ejection synchronization signal for three pixels. During this time, the sub-pixel counter is stopped. After the pixel counter has counted three pixels, the sub-pixel counter then counts 0.5 pixels. A PLD clock signal with a relatively higher frequency than the inkjet ejection synchronization signal when transporting paper at a specified transport speed is input to the sub-pixel counter. In this case, to count 0.5 pixels, the sub-pixel counter counts the number of clocks equivalent to 50% of the PLD clock count equivalent value for one theoretical cycle time of the inkjet ejection synchronization signal.

[0052] When the sub-pixel counter counts 0.5 pixels, 3.5 pixels have passed since the first inkjet ejection synchronization signal. The ejection timing correction unit 25 starts outputting an ejection start trigger signal when the sub-pixel counter finishes counting. The ejection start trigger signal is the same as the inkjet ejection synchronization signal delayed by 3.5 pixels. The amplifier circuit 29 outputs a piezo drive voltage waveform in synchronization with the rising edge of the ejection start trigger signal. As a result, as shown in Figure 8, output of the piezo drive voltage waveform starts in synchronization with the rising edge of the first pulse of the inkjet ejection synchronization signal, which is the timing of the 3.5th pixel.

[0053] In this way, the head control device 20 delays the ejection timing (an example of "recording timing") of the head module 12 by a desired delay amount.

[0054] [Switching the print resolution in the Y direction] So far, we have explained an example in which the print resolution in the Y direction is 1200 dpi, but in order to prioritize either image quality or productivity, we consider switching the print resolution in the Y direction to 1200 dpi (an example of a "first print resolution") or 600 dpi (an example of a "second print resolution that is relatively lower than the first print resolution").

[0055] 9 is a timing chart showing the inkjet ejection synchronization signal and piezo drive voltage waveform when printing at a print resolution of 600 dpi and performing a delay process equivalent to 3.5 pixels at 1200 dpi using the same delay process as described in FIG. 8. When printing at 600 dpi, the conveyance unit 32 outputs an inkjet ejection synchronization signal with a 600 dpi period. That is, the inkjet ejection synchronization signal when printing at 600 dpi has twice the period of the inkjet ejection synchronization signal when printing at 1200 dpi. Therefore, if the pixel counter counts inkjet ejection synchronization signals for three pixels, it will count six pixels at 1200 dpi. This results in a delay process that is greater than the error in the physical mounting position of the head module 12, making it impossible to perform accurate Y-direction correction.

[0056] On the other hand, since 600 dpi has half the print resolution of 1200 dpi, equivalent delay correction can be achieved by setting the Y-direction correction amount when printing at 600 dpi to half the amount when printing at 1200 dpi. Figure 10 is a timing chart showing the inkjet ejection synchronization signal and piezo drive voltage waveform when printing at a print resolution of 600 dpi and performing delay processing with a Y-direction correction amount of 1.75 pixels, which is half of 3.5 pixels at 1200 dpi. As shown in Figure 10, theoretically, the ejection timing can be delayed by 1.75 pixels at 600 dpi, or 3.5 pixels at 1200 dpi.

[0057] However, with such delay processing based on the 600 dpi standard, the time dependent on the count of the PLD clock that is not synchronized with the transport increases for correction times of less than one pixel, and the impact of transport unevenness becomes greater, so it is impossible to obtain the same correction accuracy as when printing at 1200 dpi, and there is a problem in that when printing at 600 dpi, there is a negative impact on the degradation of image quality at the joints of the head modules 12.

[0058] <Embodiment> [Head control device] 11 is a block diagram showing the electrical configuration of the head control device according to this embodiment. Note that parts common to those in FIG. 6 are given the same reference numerals and detailed explanations will be omitted.

[0059] 11 controls one line head 10. Furthermore, the upper image data processing unit 30 manages multiple head control devices 40. For example, in a configuration including line heads 10 for each color corresponding to four colors, cyan (C), magenta (M), yellow (Y), and black (K), a head control device 40 is provided for each line head 10 of each color, CMYK, and one upper image data processing unit 30 manages these head control devices 40 for each color.

[0060] As shown in Fig. 11, the head control device 40 includes a resolution switching control unit 42. The function of the resolution switching control unit 42 is realized by a PLD. The resolution switching control unit 42 performs switching control processing according to the set print resolution. Here, an example will be described in which the print resolution in the Y direction can be set to 1200 dpi or 600 dpi.

[0061] The ejection timing correction unit 25 includes a pixel unit counter and a sub-pixel counter (not shown). The resolution switching control unit 42 is always disposed after the processing of the ejection timing correction unit 25. That is, after the Y-direction correction is performed by the ejection timing correction unit 25, the printing resolution is switched by the resolution switching control unit 42.

[0062] In this embodiment, the transport unit 32 always outputs an inkjet ejection synchronization signal at a cycle of 1200 dpi. That is, the transport unit 32 outputs one pulse as the inkjet ejection synchronization signal every time the paper is transported by (1 / 1200) inch, regardless of the set print resolution.

[0063] [Y-direction correction] In the head control device 40, the Y direction correction when printing at a print resolution of 1200 dpi in the Y direction is the same as that of the head control device 20. Here, the case of printing at a print resolution of 600 dpi in the Y direction will be described.

[0064] 12 is a timing chart showing the inkjet ejection synchronization signal and the piezo drive voltage waveform when printing at a print resolution of 600 dpi in the Y direction and when the ejection timing is not delayed. Fig. 12 also shows the ejection start trigger signal generated by the resolution switching control unit 42.

[0065] Here, the ejection timing correction unit 25 outputs the acquired 1200 dpi inkjet ejection synchronization signal as is to the resolution switching control unit 42. The resolution switching control unit 42 thins out even-numbered pulses from the 1200 dpi inkjet ejection synchronization signal to generate a 600 dpi ejection start trigger signal consisting of only odd-numbered pulses. This 600 dpi ejection start trigger signal is input to the waveform data memory 27, and as shown in Figure 12, a 600 dpi piezo drive voltage waveform is output from the amplifier circuit 29 in synchronization with the rising timing of the ejection start trigger signal.

[0066] Fig. 13 is a timing chart showing the inkjet ejection synchronization signal and piezo drive voltage waveform when printing at a print resolution of 600 dpi in the Y direction and delaying the ejection timing by 3.5 pixels converted to 1200 dpi. Fig. 13 also shows the count signal of the pixel unit counter, the count signal of the sub-pixel counter, and the ejection start trigger signal.

[0067] Here, the ejection timing correction unit 25 counts a delay of 3.5 pixels based on the inkjet ejection synchronization signal with a 1200 dpi period. That is, as shown in FIG. 13 , the pixel unit counter first counts the inkjet ejection synchronization signal with a 1200 dpi period for three pixels, and then the sub-pixel counter counts the PLD clock signal for 0.5 pixels. When the sub-pixel counter finishes counting for 0.5 pixels, the ejection timing correction unit 25 starts outputting the inkjet ejection synchronization signal with a 1200 dpi period. That is, the inkjet ejection synchronization signal output from the ejection timing correction unit 25 is a 1200 dpi period signal delayed by 3.5 pixels in 1200 dpi conversion. This 1200 dpi period inkjet ejection synchronization signal delayed by 3.5 pixels is input to the resolution switching control unit 42.

[0068] The resolution switching control unit 42 generates an ejection start trigger signal having a period of 600 dpi, which is made up of only odd-numbered pulses, by thinning out even-numbered pulses from the input ink jet ejection synchronization signal having a period of 1200 dpi.

[0069] This ejection start trigger signal is input to the waveform data memory 27, and as shown in Fig. 13, a piezo drive voltage waveform is output from the amplifier circuit 29 in synchronization with the rising timing of the ejection start trigger signal. In other words, the piezo drive voltage waveform is a signal with a period of 600 dpi in which a delay correction of 3.5 pixels has been performed with an accuracy of 1200 dpi.

[0070] In this way, by always placing the resolution switching control unit 42 after the processing of the ejection timing correction unit 25, when the print resolution is set to 600 dpi, it is possible to perform delay correction based on the inkjet ejection synchronization signal with a 1200 dpi period (an example of "delay based on the first period") and print at a print resolution of 600 dpi.

[0071] [Printing method] FIG. 14 is a flowchart showing the processing of a printing method according to this embodiment (an example of a "recording head control method"). The printing method may be realized by a processor (not shown) included in the head control device 20 executing a printing program (an example of a "liquid ejection head control program") stored in a memory (not shown). The printing program may be provided by a computer-readable non-transitory storage medium. In this case, the head control device 20 may read the printing program from the non-transitory storage medium and store it in memory.

[0072] Step S1 (an example of a "resolution setting step") is a step in which the resolution switching control unit 42 determines the set print resolution. The print resolution is set, for example, by the user. Here, the user can select either a high-resolution mode that prioritizes image quality and prints at a print resolution of 1200 dpi in the Y direction, or a high-speed mode that prioritizes productivity and prints at a print resolution of 600 dpi in the Y direction. If the high-resolution mode is set, the process proceeds to step S2, and if the high-speed mode is set, the process proceeds to step S5.

[0073] In step S2, the ejection timing correction unit 25 acquires an inkjet ejection synchronization signal from the transport unit 32. The inkjet ejection synchronization signal is a signal with a 1200 dpi period (an example of a "first period").

[0074] In step S3, the ejection timing correction unit 25 acquires data on the Y-direction correction amount for each head module 12 from the higher-level image data processing unit 30, and performs delay processing according to the Y-direction correction amount using a pixel-unit counter and a sub-pixel counter on the inkjet ejection synchronization signal acquired from the conveying unit 32, thereby generating an ejection start trigger signal (an example of a "first recording start trigger signal") for each head module 12 with a period of 1200 dpi.

[0075] In step S4, the resolution switching control unit 42 inputs the ejection start trigger signal acquired from the ejection timing correction unit 25 to the image data memory 22 and waveform data memory 27. In synchronization with the ejection start trigger signal, the image data memory 22 and waveform data memory 27 output nozzle selection control data and piezo drive voltage, respectively, to the head module 12. As a result, in each head module 12, an ejection operation is performed in which the ejection timing (an example of "drive timing") is delayed with an accuracy of 1200 dpi in accordance with the Y-direction correction amount, and printing is performed at a print resolution of 1200 dpi.

[0076] On the other hand, in step S5, the ejection timing correction unit 25 acquires an inkjet ejection synchronization signal from the transport unit 32. The inkjet ejection synchronization signal is also a signal with a period of 1200 dpi.

[0077] In step S6, the ejection timing correction unit 25 acquires data on the Y-direction correction amount for each head module 12 from the higher-level image data processing unit 30, performs delay processing according to the Y-direction correction amount using a pixel-unit counter and a sub-pixel counter on the inkjet ejection synchronization signal acquired from the transport unit 32, and generates an ejection start trigger signal (an example of a "second recording start trigger signal") for each head module 12 with a 600 dpi cycle (an example of a "second cycle"). As described above, the ejection timing correction unit 25 can perform delay processing with an accuracy of 1200 dpi by using an inkjet ejection synchronization signal with a 1200 dpi cycle.

[0078] In step S7, the resolution switching control unit 42 inputs the ejection start trigger signal acquired from the ejection timing correction unit 25 to the image data memory 22 and waveform data memory 27. In synchronization with the ejection start trigger signal, the image data memory 22 and waveform data memory 27 output nozzle selection control data and piezo drive voltage, respectively, to the head module 12. As a result, in each head module 12, an ejection operation is performed in which the ejection timing is delayed with an accuracy of 1200 dpi in accordance with the Y-direction correction amount, and printing is performed at a print resolution of 600 dpi.

[0079] [Inkjet printing device] FIG. 15 is an overall configuration diagram showing an inkjet printing apparatus to which the head control device 40 is applied. The inkjet printing apparatus 100 shown in FIG. 15 includes a paper feed unit 112, a treatment liquid deposition unit 114, an imaging unit 116, a drying unit 118, a fixing unit 120, and a paper discharge unit 122. The inkjet printing apparatus 100 is a single-pass image forming apparatus that forms a desired color image by ejecting droplets of ink of multiple colors from inkjet heads 172M, 172K, 172C, and 172Y onto paper 124 (an example of a "recording medium") held on an imaging drum 170 of the imaging unit 116. The inkjet printing apparatus 100 is an on-demand image forming apparatus that applies a two-liquid reaction (aggregation) method in which a treatment liquid (here, an aggregation treatment liquid) is applied onto the paper 124 before the ink droplets are ejected, and the treatment liquid and the ink liquid are reacted to form an image on the paper 124.

[0080] (Paper feed section) Sheets of paper 124 are stacked in the paper feed unit 112. The sheets of paper 124 are fed one by one from a paper feed tray 150 of the paper feed unit 112 to the treatment liquid deposition unit 114. In this embodiment, sheets of paper (cut paper) are used as the paper 124, but sheets of paper may also be cut to the required size from continuous paper (roll paper) and fed.

[0081] (Processing liquid application section) The treatment liquid application unit 114 applies treatment liquid to the recording surface of the paper 124. The treatment liquid contains a colorant aggregating agent that aggregates the colorant (e.g., pigment) in the ink applied by the drawing unit 116. Contact between this treatment liquid and the ink promotes separation of the colorant and solvent in the ink.

[0082] The treatment liquid deposition section 114 includes a paper feed cylinder 152, a treatment liquid drum 154, and a treatment liquid application device 156. The treatment liquid drum 154 is a drum that holds the paper 124 and rotates and transports it. The treatment liquid drum 154 has a cylindrical shape and is provided with grippers 155, which are claw-shaped holding means, on its outer circumferential surface. The leading edge of the paper 124 can be held by pinching the paper 124 between the claws of the gripper 155 and the circumferential surface of the treatment liquid drum 154. The treatment liquid drum 154 may be provided with suction holes on its outer circumferential surface, and suction means that draws suction through the suction holes may be connected. This allows the paper 124 to be held in close contact with the circumferential surface of the treatment liquid drum 154.

[0083] A treatment liquid application device 156 is provided outside the treatment liquid drum 154, facing its circumferential surface. The treatment liquid application device 156 is composed of a treatment liquid container in which treatment liquid is stored, an anilox roller (metering roller) that is partially immersed in the treatment liquid in the treatment liquid container, and a rubber roller that is pressed against the anilox roller and the paper 124 on the treatment liquid drum 154 to transfer the metered treatment liquid to the paper 124. This treatment liquid application device 156 allows the treatment liquid to be applied to the paper 124 while being measured.

[0084] In this embodiment, a configuration in which a roller application method is used has been exemplified, but the present invention is not limited to this, and various methods such as a spray method and an inkjet method can also be used.

[0085] The paper 124 to which the treatment liquid has been applied in the treatment liquid application unit 114 is transferred from the treatment liquid drum 154 to the imaging drum 170 of the imaging unit 116 via the intermediate conveyance unit 126 .

[0086] (Drawing section) The drawing unit 116 includes a drawing drum 170, a paper pressure roller 174, and inkjet heads 172M, 172K, 172C, and 172Y. The inkjet heads 172M, 172K, 172C, and 172Y of each color and their control devices have the same configuration as the line head 10 and head control device 40 described above.

[0087] The imaging drum 170 (an example of a "transport drum") has a cylindrical shape, similar to the treatment liquid drum 154, and is provided on its outer circumferential surface with claw-shaped holding means (grippers) 171. The paper 124 fixed to the imaging drum 170 is transported with the recording surface facing outward, and ink is applied to this recording surface from inkjet heads 172M, 172K, 172C, and 172Y.

[0088] Inkjet heads 172M, 172K, 172C, and 172Y are full-line inkjet recording heads each having a length corresponding to the maximum width of the image forming area on paper 124, and each has a nozzle row (two-dimensionally arranged nozzles) in which multiple ink ejection nozzles are arranged across the entire width of the image forming area on its ink ejection surface. Each of inkjet heads 172M, 172K, 172C, and 172Y is installed so as to extend in a direction perpendicular to the transport direction of paper 124 (the rotation direction of imaging drum 170).

[0089] A cassette of the corresponding color ink is attached to each of the inkjet heads 172M, 172K, 172C, and 172Y. Ink droplets are ejected from the inkjet heads 172M, 172K, 172C, and 172Y toward the recording surface of the paper 124 held on the outer circumferential surface of the image forming drum 170.

[0090] As a result, the ink comes into contact with the treatment liquid that has been applied to the recording surface in advance, causing the colorant (pigment) dispersed in the ink to aggregate, forming a colorant aggregate. As an example of the reaction between the ink and the treatment liquid, in this embodiment, an acid is added to the treatment liquid to lower the pH, destroying the pigment dispersion and causing it to aggregate, thereby avoiding colorant bleeding, color mixing between ink colors, and droplet interference due to liquid merging when ink droplets land. In this way, colorant flow and other problems on the paper 124 are prevented, and an image is formed on the recording surface of the paper 124.

[0091] An encoder 173 is attached to a rotation shaft (not shown) of the imaging drum 170. The encoder 173 may be attached to a drive mechanism connected to the rotation shaft. A rotary encoder that outputs a pulse signal having a specified number of pulses per rotation of the imaging drum 170 can be used as the encoder 173. The encoder 173 outputs a detection signal synchronized with the rotation of the imaging drum 170. The imaging drum 170 outputs an inkjet ejection synchronization signal based on the detection signal of the encoder 173. The imaging drum 170 may output an inkjet ejection synchronization signal obtained by correcting the detection signal of the encoder 173 based on the radius of the imaging drum 170 and the thickness of the paper 124.

[0092] The image forming unit 116 may include a maintenance mechanism for performing maintenance such as cleaning the nozzle surfaces of the inkjet heads 172M, 172K, 172C, and 172Y and discharging thickened ink.

[0093] In this embodiment, a configuration using the standard colors (four colors) of CMYK is illustrated, but the combination of ink colors and the number of colors is not limited to this. Light inks, dark inks, and special color inks may be added as needed. For example, a configuration is also possible in which inkjet heads that eject light-colored inks such as light cyan and light magenta are added, and the arrangement order of the color heads is not particularly limited.

[0094] The paper 124 on which the image has been formed in the imaging unit 116 is transferred from the imaging drum 170 to the drying drum 176 of the drying unit 118 via the intermediate conveyance unit 128 .

[0095] (Drying section) The drying unit 118 is a mechanism that dries the water contained in the solvent that has been separated by the colorant aggregation action. The drying unit 118 is equipped with a drying drum 176 and a solvent drying device 178. Similar to the treatment liquid drum 154, the drying drum 176 is equipped with a gripper 177, which is a claw-shaped holding means, on its outer circumferential surface. The leading edge of the paper 124 can be held by this gripper 177.

[0096] The solvent drying device 178 is disposed opposite the outer peripheral surface of the drying drum 176, and is composed of multiple halogen heaters 180 and hot air blowing nozzles 182 disposed between each of the halogen heaters 180. By appropriately adjusting the temperature and volume of the hot air blown from each hot air blowing nozzle 182 toward the paper 124, and the temperature of each halogen heater 180, various drying conditions can be achieved.

[0097] The paper 124 is held on the outer peripheral surface of the drying drum 176 with the recording surface of the paper 124 facing outward, and is dried while being rotated and transported, thereby preventing the paper 124 from wrinkling and lifting, and reliably preventing uneven drying caused by these.

[0098] The sheet 124 that has been dried in the drying section 118 is transferred from the drying drum 176 to the fixing drum 184 of the fixing section 120 via the intermediate conveyance section 130 .

[0099] (fixing part) The fixing unit 120 includes a fixing drum 184, a halogen heater 186, a fixing roller 188, and an in-line sensor 190. Similar to the treatment liquid drum 154, the fixing drum 184 includes a gripper 185, which is a claw-shaped holding means, on its outer circumferential surface, and the leading edge of the paper 124 can be held by this gripper 185.

[0100] The paper 124 is transported with the recording surface facing outward by the rotation of the fixing drum 184. Then, the recording surface of the paper 124 is preheated by a halogen heater 186, fixed by a fixing roller 188, and inspected by an in-line sensor 190.

[0101] The fixing roller 188 is a roller member that applies heat and pressure to the dried ink to fuse the self-dispersing polymer particles in the ink and turn the ink into a film. The fixing roller 188 applies heat and pressure to the paper 124.

[0102] The inline sensor 190 is a reading means for measuring the ejection failure check pattern, image density, image defects, etc. of an image (including test patterns, etc.) recorded on the paper 124, and a CCD (Charge Coupled Device) line sensor, etc. is used.

[0103] Instead of ink containing a high-boiling point solvent and polymer particles (thermoplastic resin particles), ink may contain a monomer component that can be polymerized and cured by exposure to ultraviolet (UV) light. In this case, the inkjet printing apparatus 100 includes a UV exposure unit that exposes the ink on the paper 124 to UV light, instead of a heat and pressure fixing unit (fixing roller 188) using a heat roller. When using ink containing an actinic ray-curable resin such as a UV-curable resin, a means for irradiating actinic ray, such as a UV lamp or an ultraviolet laser diode array, is provided instead of the heat fixing fixing roller 188.

[0104] (Paper ejection section) A paper discharge unit 122 is provided following the fixing unit 120. The paper discharge unit 122 is equipped with a discharge tray 192, and a transfer cylinder 194, a conveyor belt 196, and a tension roller 198 are provided between the discharge tray 192 and the fixing drum 184 of the fixing unit 120 so as to be in contact with them. After printing, the leading edge of the paper 124 is held by a gripper on a bar (not shown) that is stretched across the endless conveyor belt 196, and the paper 124 is carried above the discharge tray 192 by the rotation of the conveyor belt 196 and discharged onto the discharge tray 192.

[0105] [Example of inkjet head configuration] Next, the structure of the inkjet heads will be described. Since the inkjet heads 172M, 172K, 172C, and 172Y corresponding to the respective colors have a common structure, they will be hereinafter described as inkjet head 172 as a representative.

[0106] Fig. 16 is a perspective view of the inkjet head used in this embodiment. Fig. 16 shows the nozzle surface viewed from below (diagonally downward) of the head. As shown in Fig. 16, the inkjet head 172 is a full-line type line head (a page-wide head using a single-pass printing method). The inkjet head 172 is formed by connecting a plurality of (n) head modules 172-i (i = 1, 2, ... n) aligned in one direction and fixed to a housing 310. A flexible substrate 312 is connected to each head module 172-i.

[0107] FIG. 16 shows an example in which 17 head modules 172-i are joined together, but the configuration of the modules, the number of modules and the arrangement are not limited to the example shown in the figure.

[0108] 17 is an enlarged view of the inkjet head 172 viewed from the nozzle surface 172A side. Each head module 172-i is supported by head module support members 172B on both sides in the shorter direction of the inkjet head 172. In addition, both ends of the inkjet head 172 in the longer direction are supported by head protection members 172D.

[0109] Each head module 172-i (n-th head module 172-n) has a structure in which a plurality of nozzles are arranged in a matrix. In the nozzle row 351A shown in Figure 17, a plurality of nozzles arranged in a row are indicated by solid lines.

[0110] The head modules 172-i that make up the inkjet head 172 can be replaced on a module-by-module basis.

[0111] FIG. 18 is a plan view (viewed from the ejection side) of the nozzle surface 172A of the head module 172-i. Although the number of nozzles is omitted in FIG. 18, the ink ejection surface of one head module 172-i has, for example, 32 × 64 nozzles 350 arranged two-dimensionally. In FIG. 18, the Y direction is the transport direction of the paper 124, and the X direction is the width direction of the paper 124. This head module 172-i has a parallelogram-like planar shape with long-side end faces aligned in the v direction and inclined at an angle γ with respect to the X direction, and short-side end faces aligned in the w direction and inclined at an angle α with respect to the Y direction. By connecting multiple such head modules 172-i in the X direction (see FIG. 17), a nozzle array that covers the entire drawing range across the paper width is formed, and a full-line head capable of image printing at a predetermined printing resolution (e.g., 1200 dpi) in a single scan is configured.

[0112] In addition, a full-line print head for single-pass printing is not limited to cases where the entire surface of the paper 124 is used as the drawing range, and in cases where only a portion of the surface of the paper 124 is used as the drawing area (for example, when a non-drawing area (margin) is provided around the paper), it is sufficient to form the nozzle array necessary for drawing within the specified drawing area.

[0113] In the case of an inkjet head (matrix head) with a two-dimensional nozzle array, the projected nozzle array, in which each nozzle in the two-dimensional nozzle array is projected (orthogonally projected) so that it is aligned in a direction perpendicular to the paper transport direction (corresponding to the "main scanning direction"), can be considered equivalent to a single nozzle array in which nozzles are aligned at approximately equal intervals in the main scanning direction (media width direction) at a nozzle density that achieves the recording resolution. "Approximately equal intervals" means that the nozzles are substantially evenly spaced as droplets that can be recorded by an inkjet printing system. For example, the concept of "equal intervals" also includes cases in which the intervals are slightly different to account for manufacturing errors and droplet movement on the medium due to impact interference. When considering the projected nozzle array (also called the "effective nozzle array"), the nozzle positions (nozzle numbers) can be associated with the order in which the projected nozzles are aligned in the main scanning direction.

[0114] When implementing the present invention, the arrangement of the nozzles 350 in the head module 172-i is not limited to the example shown in Fig. 18, and various nozzle arrangement structures can be applied. For example, instead of the matrix arrangement described in Fig. 18, a linear array, a V-shaped nozzle array, a broken line nozzle array such as a zigzag (W-shaped, etc.) with V-shaped arrays as repeating units, etc. are also possible.

[0115] [Example of the internal structure of the head] 19 is a cross-sectional view showing an example of the structure of one channel of droplet ejection elements, which constitute a recording element unit (ejection element unit) in an inkjet head. As shown in Fig. 19, the inkjet head 172 has nozzles 350, which are ink ejection ports, and a plurality of ink chamber units (droplet ejection elements) 253, each of which has a pressure chamber 252 corresponding to each nozzle 350, arranged two-dimensionally.

[0116] The inkjet head 172 includes a nozzle plate 251A in which nozzles 350 are formed, and a flow path plate 252P in which flow paths such as pressure chambers 252 and a common flow path 255 are formed. The nozzle plate 251A and the flow path plate 252P are laminated and bonded together. The nozzle plate 251A constitutes the nozzle surface (ink ejection surface) 250A of the head 250, and has a plurality of nozzles 350 formed therein, each of which communicates with one of the pressure chambers 252.

[0117] The flow path plate 252P is a flow path forming member that constitutes the sidewall portion of the pressure chamber 252 and also forms the supply port 254 as a throttle portion (most narrowed portion) of the individual supply path that guides ink from the common flow path 255 to the pressure chamber 252. For ease of explanation, the flow path plate 252P is simply illustrated in Figure 19, but has a structure in which one or more substrates are stacked. The nozzle plate 251A and the flow path plate 252P can be made of silicon and processed into the required shape by a semiconductor manufacturing process.

[0118] The common flow channel 255 communicates with an ink tank (not shown) that is an ink supply source, and ink supplied from the ink tank is supplied to each pressure chamber 252 via the common flow channel 255 .

[0119] Piezoelectric actuators 258 each having an individual electrode 257 are bonded to a diaphragm 256 that constitutes part of the surface of the pressure chamber 252 (the top surface in FIG. 19). The diaphragm 256 in this example is made of silicon (Si) with a nickel (Ni) conductive layer that functions as a common electrode 259 corresponding to the lower electrode of the piezoelectric actuator 258, and also serves as the common electrode for the piezoelectric actuators 258 that are arranged corresponding to each pressure chamber 252. Note that a mode in which the diaphragm is formed from a non-conductive material such as resin is also possible, in which case a common electrode layer made of a conductive material such as metal is formed on the surface of the diaphragm member. Alternatively, a diaphragm that also serves as the common electrode may be made of a metal (conductive material) such as stainless steel (SUS).

[0120] Applying a drive voltage to the individual electrode 257 deforms the piezo actuator 258, changing the volume of the pressure chamber 252, and the resulting change in pressure causes ink to be ejected from the nozzle 350. After the ink is ejected, when the piezo actuator 258 returns to its original state, new ink is refilled into the pressure chamber 252 from the common flow path 255 through the supply port 254.

[0121] The means for generating the ejection pressure (ejection energy) for ejecting droplets from each nozzle in the inkjet head is not limited to a piezoelectric actuator (piezoelectric element), but various pressure-generating elements (ejection energy-generating elements) can be applied, such as a heater (heating element) in a thermal system (a system in which ink is ejected by utilizing the pressure of film boiling caused by heating by a heater), or various actuators using other systems. Depending on the ejection system of the head, an appropriate energy-generating element is provided in the flow path structure.

[0122] [Inkjet Printing Device Control System] Figure 20 is a block diagram of essential parts showing the system configuration of the inkjet printing apparatus 100. As shown in Figure 20, the inkjet printing apparatus 100 includes a communication interface 270, a system controller 272, a print control unit 274, a head driver 278, a motor driver 280, a heater driver 282, a treatment liquid deposition control unit 284, a drying control unit 286, a fixing control unit 288, a memory 290, and a ROM (Read Only Memory) 292.

[0123] The communication interface 270 is an interface unit that receives image data sent from the host computer 380. The communication interface 270 can be a serial interface such as USB (Universal Serial Bus), IEEE (Institute of Electrical and Electronics Engineers) 1394, Ethernet (registered trademark), or a wireless network, or a parallel interface such as Centronics. This unit may be equipped with a buffer memory (not shown) to speed up communication. The image data sent from the host computer 380 is imported into the inkjet printing apparatus 100 via the communication interface 270 and stored in memory 290.

[0124] The memory 290 is a storage means for temporarily storing images input via the communication interface 270, and data is read and written via the system controller 272. The memory 290 is not limited to a memory made of semiconductor elements, and may also use a magnetic medium such as a hard disk.

[0125] The ROM 292 stores programs executed by the system controller 272 and various data necessary for control. The ROM 292 may be a non-rewritable storage means or a rewritable storage means. The memory 290 is used as a temporary storage area for image data, as well as a development area for programs that are instructions to be executed by the processor, and as a calculation work area.

[0126] The system controller 272 is composed of a processor and its peripheral circuits, etc. The processor executes instructions stored in memory 290 and ROM 292. The hardware structure of the processor is various processors as shown below. The various processors include a CPU (Central Processing Unit), which is a general-purpose processor that executes software (programs) and functions as various functional units, a GPU (Graphics Processing Unit), which is a processor specialized for image processing, a PLD (Programmable Logic Device), which is a processor whose circuit configuration can be changed after manufacturing such as an FPGA (Field Programmable Gate Array), and a dedicated electrical circuit, such as an ASIC (Application Specific Integrated Circuit), which is a processor with a circuit configuration designed specifically for executing specific processing.

[0127] A single processing unit may be configured with one of these various processors, or may be configured with two or more processors of the same or different types (e.g., multiple FPGAs, a combination of a CPU and an FPGA, or a combination of a CPU and a GPU). Also, multiple functional units may be configured with a single processor. Examples of multiple functional units configured with a single processor include, first, a configuration in which a single processor is configured with a combination of one or more CPUs and software, as typified by a client or server computer, and this processor operates as multiple functional units. Second, a configuration in which a processor is used to realize the functions of an entire system including multiple functional units on a single IC (Integrated Circuit) chip, as typified by an SoC (System On Chip). In this way, the various functional units are configured with one or more of the above-mentioned various processors as a hardware structure.

[0128] Furthermore, the hardware structure of these various processors is, more specifically, an electric circuit made up of a combination of circuit elements such as semiconductor elements.

[0129] The system controller 272 functions as a control device that controls the entire inkjet printing apparatus 100 by executing software using various programs and parameters, including the printing program, and also functions as a calculation device that performs various calculations. That is, the system controller 272 controls each part, such as the communication interface 270, print control unit 274, motor driver 280, heater driver 282, and treatment liquid deposition control unit 284, and performs communication control with the host computer 380, read / write control of the memory 290, and generates control signals that control the motor 296 and heater 298.

[0130] The motor driver 280 is a driver that drives the motor 296 in accordance with instructions from the system controller 272. The motor 296 includes motors that drive the rotation of the paper feed drum 152, treatment liquid drum 154, imaging drum 170, drying drum 176, fixing drum 184, transfer drum 194, etc. shown in FIG. 15 , a drive motor for a pump that draws negative pressure through the suction holes of the imaging drum 170, and a motor for a retraction mechanism that moves the head units of the inkjet heads 172M, 172K, 172C, and 172Y to a maintenance area outside the imaging drum 170.

[0131] The heater driver 282 is a driver that drives the heater 298 in accordance with instructions from the system controller 272. The heater 298 includes a preheater (not shown) for preheating the paper 124 in the paper feed unit 112 to an appropriate temperature.

[0132] The print control unit 274 is a control unit that has a signal processing function that performs various processes, corrections, etc. to generate signals for print control from image data in the memory 290 in accordance with the control of the system controller 272, and supplies the generated print data (dot data) to the head driver 278.

[0133] Dot data is generally generated by performing color conversion and halftone processing on multi-tone image data. Color conversion is a process of converting image data expressed in sRGB or the like (e.g., 8-bit image data for each RGB color) into color data for each color of ink used in the inkjet printing device 100 (e.g., KCMY color data).

[0134] Halftone processing is a process in which the color data of each color generated by the color conversion process is converted into dot data of each color (for example, KCMY dot data) using an error diffusion method or threshold matrix processing.

[0135] The print control unit 274 performs the required signal processing, and based on the obtained dot data, the amount and timing of ink droplet ejection from the head 250 are controlled via a head driver 278. This achieves the desired dot size and dot arrangement. The dot data here corresponds to "nozzle selection control data."

[0136] The print control unit 274 is provided with an image buffer memory (not shown), and image data and data such as parameters are temporarily stored in the image buffer memory when image data is processed in the print control unit 274. It is also possible to configure the print control unit 274 and the system controller 272 as a single integrated processor.

[0137] To outline the process flow from image input to print output, image data to be printed is input from an external device via the communications interface 270 and stored in the memory 290. At this stage, for example, RGB image data is stored in the memory 290. The inkjet printing device 100 creates a pseudo-continuous tone image as seen by the human eye by varying the droplet density and dot size of fine ink (colorant) dots. Therefore, the input digital image must be converted into an even dot pattern that faithfully reproduces the gradation (shade) of the image as much as possible. Therefore, the original image (RGB) data stored in the memory 290 is sent to the print control unit 274 via the system controller 272, where it is converted into dot data for each ink color by halftoning using a threshold matrix or error diffusion method. That is, the print control unit 274 converts the input RGB image data into dot data for the four colors K, C, M, and Y. The dot data generated by the print control unit 274 is then stored in the image buffer memory.

[0138] Based on the print data (i.e., dot data stored in the image buffer memory) provided by the print control unit 274, the head driver 278 outputs drive signals for driving actuators corresponding to each nozzle of the inkjet head 172. The head driver 278 may include a feedback control system for maintaining constant head drive conditions.

[0139] When a drive signal output from the head driver 278 is applied to the head 250, ink is ejected from the corresponding nozzle. An image is formed on the paper 124 by controlling the ink ejection from the head 250 while transporting the paper 124 at a predetermined speed. Note that the inkjet printing device 100 shown in this example employs a drive method in which a common drive power waveform signal is applied on a module-by-module basis to the piezo actuators 258 corresponding to the nozzles 350 of each head module 172-i (i = 1, 2, ... n) that make up the inkjet head 172, and ink is ejected from the nozzles 350 corresponding to each piezo actuator 258 by switching on / off switch elements (not shown) connected to individual electrodes of each piezo actuator 258 in accordance with the ejection timing of each piezo actuator 258.

[0140] The head driver 278 and print control section 274 correspond to the head control device 40 shown in Fig. 11. The system controller 272 corresponds to the higher-level image data processing section 30 shown in Fig. 11.

[0141] The treatment liquid application control unit 284 controls the operation of the treatment liquid application device 156 (see FIG. 15) in accordance with instructions from the system controller 272. The drying control unit 286 controls the operation of the solvent drying device 178 (see FIG. 15) in accordance with instructions from the system controller 272.

[0142] The fixing control unit 288 follows instructions from the system controller 272 to control the operation of the halogen heater 186 of the fixing unit 120 and a fixing pressure unit 299 including the fixing roller 188 (see FIG. 15).

[0143] 15, the inline sensor 190 is a block that includes an image sensor. The inline sensor 190 reads the image printed on the paper 124, performs the required signal processing, etc. to detect the printing status (presence or absence of ejection, variation in droplet ejection, optical density, etc.), and provides the detection results to the system controller 272 and the print control unit 274.

[0144] The print control unit 274 performs various corrections (non-ejection correction, density correction, etc.) for the head 250 based on information obtained from the inline sensor 190, and also controls the execution of cleaning operations (nozzle recovery operations) such as preliminary ejection, suction, and wiping as necessary.

[0145] The inkjet printing device 100 has a high-resolution mode in which printing is performed at a printing resolution of 1200 dpi in the transport direction of the paper 124, and a high-speed mode in which printing is performed at a printing resolution of 600 dpi. 1200 dpi is the highest printing resolution in the transport direction of the paper 124 in the inkjet printing device 100. The user can set either the high-resolution mode or the high-speed mode via the host computer 380.

[0146] <Modification> The form of the line head composed of multiple head modules is not limited to the form of the line head 10 and the inkjet head 172. For example, as shown in Fig. 21, the present invention can also be applied to a line head 410 having a structure in which multiple head modules 412-i are arranged in a zigzag pattern.

[0147] Furthermore, in the above embodiment, an inkjet recording device that forms an image by ejecting ink droplets directly onto paper 124 (direct recording method) has been described, but the scope of application of the present invention is not limited to this, and the present invention can also be applied to an intermediate transfer type inkjet recording device that first forms an image (primary image) on an intermediate transfer body and then transfers that image to recording paper in a transfer section to form the final image.

[0148] In the above embodiment, the application of the present invention to an inkjet recording apparatus for graphic printing has been described as an example, but the scope of application of the present invention is not limited to this example. For example, the present invention can be widely applied to inkjet-type image forming apparatuses that draw various shapes and patterns using liquid functional materials, such as wiring drawing apparatuses that draw wiring patterns of electronic circuits, manufacturing apparatuses for various devices, resist printing apparatuses that use resin liquid as a functional liquid to be discharged, color filter manufacturing apparatuses, and microstructure forming apparatuses that form microstructures using materials for material deposition.

[0149] <Other> In the above embodiment, an inkjet printing device has been described as an example of a printing device, but the scope of application of the present invention is not limited to this. In addition to the inkjet method, the present invention can also be applied to various types of printing devices, such as a thermal transfer recording device with a line head (a device that uses thermal elements as recording elements), an LED (Light Emitting Diode) electrophotographic printer, and a silver halide photographic printer with an LED line exposure head (a device that uses LED elements as recording elements).

[0150] The technical scope of the present invention is not limited to the scope described in the above embodiments. The configurations and the like in each embodiment can be appropriately combined with each other within the scope that does not deviate from the spirit of the present invention. [Explanation of symbols]

[0151] 10...Line head 12...Head module 12-i...Head module 14-i...Printing results 16-i...Printing result 20...Head control device 22...Image data memory 24...Nozzle control data output section 25...Ejection timing correction unit 26...Drive unit 27...Waveform data memory 28...Piezo element drive voltage generation unit 29...Amplifier circuit 30...High-order image data processing unit 32...Transport unit 40...Head control device 42...Resolution switching control section 100...Inkjet printing device 112…Paper feed section 114... Processing liquid application unit 116...Drawing section 118...Drying section 120...Fixing part 122...Paper ejection section 124...Paper 126...Intermediate conveying section 128...Intermediate conveying section 130...Intermediate conveying section 150...Paper tray 152…Paper feed cylinder 154...Processing liquid drum 155...Gripper 156... Processing liquid application device 170...Drawing drum 171...Holding means (gripper) 172...Inkjet head 172A...Nozzle surface 172B...Head module support member 172C...inkjet head 172D...Head protection member 172-i...head module 172K...inkjet head 172M...inkjet head 172-n...Head module 172Y...inkjet head 173...Encoder 174...Laura 176...Drying drum 177...Gripper 178...Solvent drying device 180...Halogen heater 182...Nozzle 184...Fixing drum 185...Gripper 186...Halogen heater 188...Fuser roller 190...Inline sensor 192...Outlet tray 194...torso 196...Conveyor belt 198...Tension roller 250...head 250A...Nozzle surface (ink ejection surface) 251A...Nozzle plate 252...Pressure chamber 252P...Flow path plate 253...ink chamber unit (droplet ejection element) 254...supply port 255...Common flow path 256…Diaphragm 257…Individual electrode 258...Piezoelectric actuator 259…Common electrode 270...Communication interface 272...System Controller 274...Print control unit 278...Head driver 280...Motor driver 282...Heater driver 284... Treatment liquid application control unit 286... Drying control unit 288...Fuser control unit 290…Memory 296...Motor 298...Heater 299... Fixing pressure unit 310…Housing 312...Flexible substrate 350...Nozzle 351A...Nozzle row 380...host computer 410...Line head 412-i...head module La…Reference position P…Paper S1~S7...Printing method steps

Claims

1. at least one processor; The at least one processor a recording synchronization signal having a first period and corresponding to a first print resolution in the relative movement direction, synchronized with the relative movement, is obtained from a relative movement mechanism that moves the recording medium and the recording head, in which a plurality of head modules are arranged, in the relative movement direction; generating a first recording start trigger signal that drives the plurality of head modules at the first period, the first recording start trigger signal being obtained by delaying the drive timing of at least one head module by a delay amount based on arrangement positions of the plurality of head modules with respect to the first period; driving the plurality of head modules based on the first recording start trigger signal; A control device for a recording head, The at least one processor receiving a setting of a second print resolution in the relative movement direction, the second print resolution being relatively lower than the first print resolution; When the second print resolution is set, generating a second recording start trigger signal that drives the plurality of head modules at a second cycle corresponding to a second print resolution, the second recording start trigger signal being obtained by delaying the drive timing of at least one head module by an amount of delay based on the arrangement positions of the plurality of head modules with respect to the first cycle; driving the plurality of head modules based on the second recording start trigger signal; A control device for a recording head.

2. The at least one processor When the second print resolution is set, delaying the recording synchronization signal by the delay amount; converting the period of the delayed recording synchronization signal into the second period to generate the second recording start trigger signal; The control device for a recording head according to claim 1 .

3. The at least one processor counting the recording synchronization signal for one pixel unit of the first print resolution in the delay amount; and delaying the drive timing by counting a signal asynchronous with the recording synchronization signal for an amount of delay less than one pixel of the first printing resolution.

3. The control device for a recording head according to claim 1 or 2.

4. the recording head has the plurality of head modules arranged in a direction intersecting the direction of the relative movement; The control device for a recording head according to any one of claims 1 to 3.

5. The at least one processor the delay amount is based on the head module arranged most upstream in the relative movement direction among the plurality of head modules. The control device for a recording head according to any one of claims 1 to 4.

6. An image memory for storing image data, The at least one processor outputting control data for controlling driving of each of the plurality of head modules based on the image data acquired from the image memory; The control device for a recording head according to any one of claims 1 to 5.

7. a recording head in which a plurality of head modules are arranged; a relative movement mechanism that moves the recording head and the recording medium relative to each other in a relative movement direction and generates a recording synchronization signal of a first period that corresponds to a first print resolution in the relative movement direction and is synchronized with the relative movement; a control device for a recording head according to any one of claims 1 to 6; A printing device comprising:

8. the first printing resolution is the highest printing resolution in the direction of relative movement in the printing device; The printing device according to claim 7.

9. the relative movement mechanism includes a transport mechanism that transports the recording medium in a transport direction; 9. The printing device according to claim 7 or 8.

10. The transport mechanism includes: a conveying drum having a cylindrical shape and supporting and conveying the recording medium on its circumferential surface; an encoder that outputs a pulse signal corresponding to the rotation of the conveying drum; Equipped with generating the recording synchronization signal based on the pulse signal; The printing device according to claim 9.

11. The head module includes: a nozzle from which the liquid is discharged; an ejection energy generating element for ejecting the liquid from the nozzle; Equipped with The printing device according to any one of claims 7 to 10.

12. a resolution setting step for setting a print resolution in a relative movement direction between a recording medium and a recording head having a plurality of head modules arranged thereon, the resolution setting step receiving a setting of either a first print resolution or a second print resolution that is relatively lower than the first print resolution; When the first print resolution is set in the resolution setting step, acquiring, from a relative movement mechanism that moves the recording head and the recording medium in a relative movement direction, a recording synchronization signal of a first period that is synchronized with the relative movement and corresponds to a first print resolution in the relative movement direction; generating a first recording start trigger signal that drives the plurality of head modules at the first period, the first recording start trigger signal being obtained by delaying the drive timing of at least one head module by a delay amount based on the arrangement positions of the plurality of head modules with respect to the first period; driving the plurality of head modules based on the first recording start trigger signal; and When the second print resolution is set in the resolution setting step, acquiring the recording synchronization signal from the relative movement mechanism; generating a second recording start trigger signal that drives the plurality of head modules at a second cycle corresponding to a second print resolution, the second recording start trigger signal being obtained by delaying the drive timing of at least one head module from the first cycle by an amount of delay based on the arrangement positions of the plurality of head modules; driving the plurality of head modules based on the second recording start trigger signal; To carry out A method for controlling a recording head.

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