JP2017193139A - Printing device and printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printing device which suppresses impact position deviation between forward movement and backward movement and a reduction in printing quality due to the impact position deviation.SOLUTION: A printing device 100 includes: a medium conveyance unit 20 which conveys a recording medium 95 in a conveyance direction; a discharge head 42 which discharges droplets 71 having different sizes to the recording medium 95; a head movement unit 41 which reciprocally moves the discharge head 42 in a main-scanning direction intersecting with the conveyance direction; a printer control unit 111 serving as a calculation unit which analyzes the sizes and quantity of the droplets 71 from image data to be printed on the recording medium 95, and calculates an adjustment value of discharge timing for discharging the droplets 71; and a control unit 1 which changes the discharge timing on the basis of the adjustment value.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a printing apparatus and a printing method.

  2. Description of the Related Art Conventionally, there has been an ink jet printing apparatus that forms an image or the like on a recording medium by bidirectional printing in which a discharge head that discharges droplets (ink droplets) that form dots of different sizes is reciprocated in the width direction of the recording medium. Are known. Since the droplets ejected from the ejection head have different landing positions on the recording medium depending on their size (mass), when a droplet larger or smaller than a predetermined size is ejected, the forward and backward movements Deviations in the landing positions of the liquid droplets occur with time. For example, in Patent Document 1, print images are classified into large dot images such as barcodes that are printed using the largest dot size and images other than large dot images, and landing corresponding to each image is made. A printing apparatus that performs bidirectional printing using an adjustment value that adjusts the amount of misregistration is disclosed. Accordingly, it is described that the deterioration of image quality due to the landing position deviation of the ink droplets can be prevented.

JP 2009-234071 A

  However, the printing apparatus described in Patent Document 1 adjusts the ejection timing for ejecting liquid droplets only in two categories of large dot images and images other than large dots. For this reason, the effect of correcting the landing position deviation between the liquid droplets ejected during the forward movement and the liquid droplet ejected during the backward movement and the effect of suppressing the deterioration of the print quality due to the landing position deviation were low.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 A printing apparatus according to this application example includes a medium transport unit that transports a recording medium in a transport direction, a discharge head that discharges droplets of different sizes onto the recording medium, and the discharge head in the transport direction. A head moving unit that reciprocates in the main scanning direction intersecting with the liquid crystal, and a size and quantity of the liquid droplets are analyzed from image data to be printed on the recording medium, and a calculation for calculating an adjustment value of a discharge timing for discharging the liquid droplets And a control unit that changes the ejection timing based on the adjustment value.

  According to this application example, the printing apparatus changes the ejection timing for ejecting the droplets based on the adjustment value calculated from the size and quantity of the droplets analyzed from the image data. Thereby, it is possible to suppress landing position deviation during forward movement and backward movement, and deterioration of print quality due to landing position deviation. Therefore, it is possible to provide a printing apparatus with improved print quality.

  Application Example 2 In the printing apparatus according to the application example, it is preferable that the adjustment value is calculated for each predetermined region, and the ejection timing is changed for each predetermined region.

  According to this application example, since the printing apparatus controls the ejection timing for each predetermined area based on the adjustment value calculated for each predetermined area, landing position deviation is suppressed and print quality is improved.

  Application Example 3 In the printing apparatus according to the application example described above, it is preferable that the predetermined region is a raster line in which dots formed by the droplets are arranged in the main scanning direction.

  According to this application example, since the printing apparatus changes the ejection timing of the droplets that form each raster line based on the adjustment value calculated for each raster line, the landing position deviation is further suppressed.

  Application Example 4 A printing method according to this application example includes a medium transport unit that transports a recording medium in the transport direction, a discharge head that discharges droplets of different sizes onto the recording medium, and the discharge head in the transport direction. A head moving unit that reciprocally moves in a main scanning direction that intersects with the printing apparatus, comprising: analyzing the size and quantity of the droplets from image data to be printed on the recording medium; and The method includes a step of calculating an adjustment value of a discharge timing for discharging a droplet, and a step of changing the discharge timing based on the adjustment value.

  According to this application example, the printing method of the printing apparatus includes a step of analyzing the size and quantity of droplets from image data to be printed on a recording medium, a step of calculating an adjustment value of ejection timing for ejecting droplets, And changing the droplet discharge timing based on the adjustment value. Thereby, it is possible to suppress landing position deviation during forward movement and backward movement, and deterioration of print quality due to landing position deviation. Therefore, a printing method with improved print quality can be provided.

1 is a schematic diagram illustrating a schematic overall configuration of a printing apparatus according to an embodiment. Sectional drawing which shows the internal structure of a discharge head. FIG. 3 is an electrical block diagram illustrating an electrical configuration of the printing apparatus. The figure explaining the image processing for printing an image. The figure explaining the landing position of the droplet which forms a middle dot. The figure explaining the landing position of the droplet which forms a large dot. The figure explaining the landing position of the droplet which forms a small dot. The flowchart figure explaining a printing method. The figure explaining the analysis method of a dot.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the scale of each layer and each member is different from the actual scale so that each layer and each member can be recognized.
1, 2, 5 to 7, and 9, for convenience of explanation, the X axis, the Y axis, and the Z axis are illustrated as three axes orthogonal to each other, and the arrow directions illustrating the axial directions are illustrated. The distal end side is the “+ side” and the proximal end side is the “− side”. Hereinafter, a direction parallel to the X axis is referred to as an “X axis direction”, a direction parallel to the Y axis is referred to as a “Y axis direction”, and a direction parallel to the Z axis is referred to as a “Z axis direction”.

(Embodiment)
<Schematic configuration of printing device>
FIG. 1 is a schematic diagram illustrating a schematic overall configuration of a printing apparatus according to an embodiment. First, a schematic configuration of the printing apparatus 100 according to the present embodiment will be described with reference to FIG. In the present embodiment, an ink jet printing apparatus 100 that performs printing on the recording medium 95 by forming an image or the like on the recording medium 95 will be described as an example.

  As illustrated in FIG. 1, the printing apparatus 100 includes a medium transport unit 20, a medium contact unit 60, a printing unit 40, a drying unit 27, a cleaning unit 50, and the like. And it has the control part 1 which controls each of these parts. Each unit of the printing apparatus 100 is attached to the frame unit 90. Further, the printing apparatus 100 includes an image processing apparatus 110 (see FIG. 3) described later.

  The medium transport unit 20 transports the recording medium 95 in the transport direction (+ Y axis direction in the printing unit 40). The medium conveyance unit 20 includes a medium supply unit 10, conveyance rollers 21 and 22, a conveyance belt 23, a belt rotation roller 24, a belt driving roller 25, conveyance rollers 26 and 28, and a medium recovery unit 30. First, the conveyance path of the recording medium 95 from the medium supply unit 10 to the medium recovery unit 30 will be described.

  The medium supply unit 10 supplies a recording medium 95 for forming an image to the printing unit 40 side. As the recording medium 95, for example, a cloth such as cotton, wool, or polyester is used. The medium supply unit 10 includes a supply shaft portion 11 and a bearing portion 12. The supply shaft portion 11 is formed in a cylindrical shape or a columnar shape, and is provided to be rotatable in the circumferential direction. A belt-like recording medium 95 is wound around the supply shaft portion 11 in a roll shape. The supply shaft portion 11 is detachably attached to the bearing portion 12. As a result, the recording medium 95 wound around the supply shaft portion 11 in advance can be attached to the bearing portion 12 together with the supply shaft portion 11. Note that the winding direction and the rotation direction of the recording medium 95 held by the medium supply unit 10 shown in FIG. 1 are merely examples, and the present invention is not limited thereto. The supply shaft portion 11 may be rotated in the reverse direction, and the recording medium 95 may be supplied from a roll having the recording surface wound inside.

  The bearing portion 12 rotatably supports both ends of the supply shaft portion 11 in the axial direction. The medium supply unit 10 includes a rotation drive unit (not shown) that rotates the supply shaft unit 11. The rotation drive unit rotates the supply shaft unit 11 in the direction in which the recording medium 95 is sent out. The operation of the rotation drive unit is controlled by the control unit 1. The conveyance rollers 21 and 22 relay the recording medium 95 from the medium supply unit 10 to the conveyance belt 23.

  The conveyance belt 23 conveys the recording medium 95 in the conveyance direction (+ Y-axis direction). Specifically, the conveying belt 23 is formed in an endless shape by connecting both ends of a belt-like belt, and is hung on the belt rotating roller 24 and the belt driving roller 25. The conveyor belt 23 is held in a state where a predetermined tension is applied so that a portion between the belt rotating roller 24 and the belt driving roller 25 is parallel to the floor surface 99. An adhesive layer 29 that adheres the recording medium 95 is provided on the surface (support surface) 23 a of the conveyance belt 23. The conveyance belt 23 supports (holds) a recording medium 95 that is supplied from the conveyance roller 22 and is in close contact with the adhesive layer 29 by a medium contact portion 60 described later. Thereby, a stretchable fabric or the like can be handled as the recording medium 95.

  The belt rotation roller 24 and the belt drive roller 25 support the inner peripheral surface 23 b of the transport belt 23. A configuration in which a support portion that supports the conveyance belt 23 is provided between the belt rotation roller 24 and the belt driving roller 25 may be adopted.

  The belt drive roller 25 has a motor (not shown) that drives the belt drive roller 25 to rotate. When the belt driving roller 25 is rotationally driven, the conveyor belt 23 rotates with the rotation of the belt driving roller 25, and the belt rotating roller 24 rotates with the rotation of the conveyor belt 23. The recording medium 95 supported by the conveying belt 23 is conveyed in a predetermined conveying direction (+ Y-axis direction) by the rotation of the conveying belt 23, and an image is formed on the recording medium 95 by the printing unit 40 described later.

  In the present embodiment, the recording medium 95 is supported on the side (+ Z axis side) where the surface 23 a of the conveyance belt 23 faces the printing unit 40, and the recording medium 95 together with the conveyance belt 23 from the belt rotation roller 24 side to the belt driving roller 25. It is conveyed to the side (+ Y-axis direction). On the side (−Z axis side) where the surface 23 a of the conveyor belt 23 faces the cleaning unit 50, only the conveyor belt 23 moves from the belt driving roller 25 side to the belt rotation roller 24 side (−Y axis direction). . The transport belt 23 has been described as including the adhesive layer 29 that closely contacts the recording medium 95, but the present invention is not limited to this. For example, the conveyance belt may be an electrostatic adsorption type conveyance belt that adsorbs a medium to the belt with static electricity.

  The conveyance roller 26 peels the recording medium 95 on which the image is formed from the adhesive layer 29 of the conveyance belt 23. The conveyance rollers 26 and 28 relay the recording medium 95 from the conveyance belt 23 to the medium recovery unit 30.

  The medium collection unit 30 collects the recording medium 95 conveyed by the medium conveyance unit 20. The medium recovery unit 30 includes a winding shaft portion 31 and a bearing portion 32. The winding shaft portion 31 is formed in a cylindrical shape or a columnar shape, and is provided to be rotatable in the circumferential direction. A belt-like recording medium 95 is wound around the winding shaft portion 31 in a roll shape. The winding shaft portion 31 is detachably attached to the bearing portion 32. Thereby, the recording medium 95 in the state of being wound around the winding shaft portion 31 can be removed together with the winding shaft portion 31.

  The bearing portion 32 rotatably supports both ends of the winding shaft portion 31 in the axial direction. The medium recovery unit 30 includes a rotation driving unit (not shown) that drives the winding shaft unit 31 to rotate. The rotation drive unit rotates the take-up shaft part 31 in the direction in which the recording medium 95 is taken up. The operation of the rotation drive unit is controlled by the control unit 1. The winding direction and the rotation direction of the recording medium 95 held in the medium recovery unit 30 shown in FIG. 1 are examples, and the present invention is not limited to this. The configuration may be such that the winding shaft portion 31 rotates in the reverse direction and the recording surface of the recording medium 95 is wound inward.

Next, each unit provided along the medium transport unit 20 will be described.
The medium contact portion 60 is for bringing the recording medium 95 into close contact with the transport belt 23. The medium contact portion 60 is provided on the upstream side (−Y axis side) from the printing portion 40. The medium contact portion 60 includes a pressing roller 61, a pressing roller driving unit 62, and a roller support unit 63. The pressing roller 61 is formed in a cylindrical shape or a columnar shape, and is provided to be rotatable in the circumferential direction. The pressing roller 61 is disposed so that the axial direction intersects the transport direction so as to rotate in a direction along the transport direction. The roller support part 63 is provided on the inner peripheral surface 23 b side of the conveyor belt 23 that faces the pressing roller 61 with the conveyor belt 23 interposed therebetween.

  The pressing roller driving unit 62 presses the pressing roller 61 in the transport direction (+ Y axis direction) and in the direction opposite to the transport direction (−Y axis direction) while pressing the pressing roller 61 downward in the vertical direction (−Z axis side). The roller 61 is moved. The recording medium 95 superimposed on the conveyance belt 23 is pressed against the conveyance belt 23 between the pressing roller 61 and the roller support portion 63. Thereby, the recording medium 95 can be reliably adhered to the adhesive layer 29 provided on the surface 23 a of the conveyance belt 23, and the occurrence of the floating of the recording medium 95 on the conveyance belt 23 can be prevented.

  The printing unit 40 is arranged above (+ Z axis side) with respect to the arrangement position of the conveyance belt 23. The printing unit 40 includes an ejection head 42 that ejects ink onto a recording medium 95 placed on the conveyance belt 23, a carriage 43 on which the ejection head 42 is mounted, a head moving unit 41 that moves the carriage 43, and the like. . The ejection head 42 is provided with a nozzle plate 44 in which a plurality of nozzle rows 45 are formed. For example, four nozzle rows 45 are formed on the nozzle plate 44, and different color inks (for example, cyan: C, magenta: M, yellow: Y, black: K) are ejected for each nozzle row 45. It has become. The nozzle plate 44 faces the recording medium 95 that is transported by the transport belt 23.

  The head moving unit 41 reciprocates the ejection head 42 (carriage 43) in the main scanning direction (the width direction of the recording medium 95 (X-axis direction)) that intersects the conveyance direction of the recording medium 95. The carriage 43 is supported by guide rails (not shown) arranged along the X-axis direction, and is configured to be reciprocally movable in the ± X-axis directions by the head moving unit 41. As a mechanism of the head moving unit 41, for example, a mechanism combining a ball screw and a ball nut, a linear guide mechanism, or the like can be employed. Further, the head moving unit 41 is provided with a motor (not shown) as a power source for moving the carriage 43 along the X-axis direction. When the motor is driven by the control of the control unit 1, the ejection head 42 reciprocates along the X axis direction together with the carriage 43. The printing unit 40 includes a linear encoder 91 (see FIG. 3) that detects a position of the carriage 43 along the main scanning direction.

  The drying unit 27 is provided between the transport roller 26 and the transport roller 28. The drying unit 27 dries the ink discharged onto the recording medium 95. The drying unit 27 includes, for example, an IR heater, and is discharged onto the recording medium 95 by driving the IR heater. The ink can be dried in a short time. Thereby, the strip-shaped recording medium 95 on which an image or the like is formed can be wound around the winding shaft portion 31.

  The cleaning unit 50 is disposed between the belt rotating roller 24 and the belt driving roller 25 in the Y-axis direction. The cleaning unit 50 includes a cleaning unit 51, a pressing unit 52, and a moving unit 53. The moving unit 53 integrally moves the cleaning unit 50 along the floor surface 99 and fixes it to a predetermined position.

  The pressing part 52 is, for example, an elevating device constituted by an air cylinder 56 and a ball bush 57, and makes the cleaning part 51 provided on the upper part abut on the surface 23a of the conveyor belt 23. The cleaning unit 51 is hung in a state where a predetermined tension is applied between the belt rotation roller 24 and the belt driving roller 25, and the surface of the transport belt 23 (support) that moves from the belt driving roller 25 toward the belt rotation roller 24. Surface) 23a is washed from below (−Z-axis direction).

  The cleaning unit 51 includes a cleaning tank 54, a cleaning roller 58, and a blade 55. The cleaning tank 54 is a tank for storing a cleaning liquid used for cleaning ink and foreign matters attached to the surface 23 a of the conveyor belt 23, and the cleaning roller 58 and the blade 55 are provided inside the cleaning tank 54. As the cleaning liquid, for example, water or a water-soluble solvent (alcohol aqueous solution or the like) can be used, and a surfactant or an antifoaming agent may be added as necessary.

  When the cleaning roller 58 rotates, the cleaning liquid is supplied to the surface 23a of the transport belt 23, and the cleaning roller 58 and the transport belt 23 slide. As a result, ink adhering to the conveyance belt 23, fabric fibers as the recording medium 95, and the like are removed by the cleaning roller 58.

  The blade 55 can be formed of a flexible material such as silicon rubber, for example. The blade 55 is provided downstream of the cleaning roller 58 in the conveyance direction of the conveyance belt 23. As the conveying belt 23 and the blade 55 slide, the cleaning liquid remaining on the surface 23a of the conveying belt 23 is removed.

<Discharge head>
FIG. 2 is a cross-sectional view showing the internal configuration of the ejection head. Next, the configuration of the ejection head 42 will be described with reference to FIG.

  As shown in FIG. 2, the ejection head 42 includes a nozzle plate 44, and a nozzle 46 is formed on the nozzle plate 44. A cavity 47 communicating with the nozzle 46 is formed at a position on the upper side (+ Z axis side) of the nozzle plate 44 and facing the nozzle 46. Then, ink stored in an ink supply unit (not shown) is supplied to the cavity 47 of the nozzle 46. On the upper side (+ Z axis side) of the cavity 47, a vibration plate 48 that vibrates in the vertical direction (± Z axis direction) and expands and contracts the volume in the cavity 47, and a vibration plate that expands and contracts in the vertical direction. A piezoelectric element 49 that vibrates 48 is disposed.

  The piezoelectric element 49 expands and contracts in the vertical direction to vibrate the diaphragm 48, and the diaphragm 47 pressurizes the cavity 47 by expanding and reducing the volume in the cavity 47. As a result, the pressure in the cavity 47 fluctuates, and the ink supplied into the cavity 47 is ejected through the nozzle 46. When the ejection head 42 receives a drive signal for controlling and driving the piezoelectric element 49 from the control unit 1 described later, the piezoelectric element 49 expands and the diaphragm 48 reduces the volume in the cavity 47. As a result, a reduced volume of ink is ejected as droplets 71 from the nozzles 46, and dots are formed on the recording medium 95. The ejection head 42 of the present embodiment ejects droplets 71 of different sizes (large droplets 71a, medium droplets 71b, and small droplets 71c described later).

  In the present embodiment, the pressurizing means using the longitudinal vibration type piezoelectric element 49 is exemplified, but the present invention is not limited to this. For example, a bending deformation type piezoelectric element in which a lower electrode, a piezoelectric layer, and an upper electrode are laminated may be used. Further, as the pressure generating means, a so-called electrostatic actuator that generates static electricity between the diaphragm and the electrode, deforms the diaphragm by electrostatic force, and discharges a droplet from the nozzle may be used. Furthermore, a head having a configuration in which bubbles are generated in the nozzle using a heating element and ink is ejected as droplets by the bubbles may be used.

<Electrical configuration>
FIG. 3 is an electrical block diagram illustrating an electrical configuration of the printing apparatus. Next, the electrical configuration of the printing apparatus 100 will be described with reference to FIG.

  The printing apparatus 100 includes an image processing apparatus 110 and a control unit 1 that controls each unit of the printing apparatus 100. As the image processing apparatus 110, a personal computer or the like can be used. The image processing apparatus 110 (hereinafter also referred to as PC 110) may be provided separately from the printing apparatus 100.

The PC 110 includes a printer control unit 111, an input unit 112, a display unit 113, a storage unit 114, and the like, and controls a print job that causes the printing apparatus 100 to perform printing.
The software that operates the PC 110 includes general image processing application software (hereinafter referred to as an application) that handles image data to be printed, and printer driver software (hereinafter referred to as a printer) that generates print data for causing the control unit 1 to execute printing. Driver)).

The printer control unit 111 includes a CPU (Central Processing Unit) 115, an ASIC (Application Specific Integrated Circuit) 116, a DSP (Digital Signal Processor) 117, a memory 118, an interface unit (I / F) 119, and the like. The interface unit (I / F) 119 is used for data transmission / reception between the PC 110 and the control unit 1.
The input unit 112 is information input means as a human interface. Specifically, for example, a port to which a keyboard or an information input device is connected.
The display unit 113 is an information display unit (display) as a human interface, and is related to information input from the input unit 112, an image to be printed on the printing apparatus 100, and a print job under the control of the printer control unit 111. Information to be displayed.
The storage unit 114 is a rewritable storage medium such as a hard disk drive (HDD) or a memory card. The storage unit 114 is software that operates the PC 110 (a program that operates on the printer control unit 111), information to be printed, and information related to a print job. Etc. are memorized.
The memory 118 is a storage medium that secures an area for storing a program in which the CPU 115 operates and a work area in which the CPU 115 operates. The

The control unit 1 includes a control circuit 4, an interface unit (I / F) 2, a CPU 3, a memory 5, a drive signal generation unit 6, and the like. The interface unit 2 is for transmitting and receiving data between the PC 110 that handles input signals and images and the control unit 1. The CPU 3 is an arithmetic processing device for performing various input signal processing and controlling the printing operation of the printing apparatus 100.
The memory 5 is a storage medium for securing an area for storing a program of the CPU 3, a work area, and the like, and includes storage elements such as a RAM and an EEPROM.
The drive signal generation unit 6 generates a drive signal for driving the piezoelectric element 49 that discharges ink from the nozzles 46 to the droplets 71.

  The control unit 1 controls the driving of various motors provided in the medium transport unit 20 by a control signal output from the control circuit 4 to move the recording medium 95 in the transport direction (+ Y axis direction). The control unit 1 controls the drive of the motor provided in the head moving unit 41 by a control signal output from the control circuit 4 so as to move the carriage 43 on which the ejection head 42 is mounted in the width direction (X axis) of the recording medium 95. Direction). The control unit 1 controls the drive of the ejection head 42 by the control signal output from the control circuit 4 and the drive signal output from the drive signal generation unit 6 to eject ink toward the recording medium 95. The control unit 1 controls each device (not shown). The control unit 1 controls the discharge operation (discharge timing) of the droplet 71 based on the signal output from the linear encoder 91.

  The control unit 1 controls the head moving unit 41 and the ejection head 42 to perform main scanning in which the carriage 43 (ejection head 42) is moved while ejecting ink from the nozzles 46 of the ejection head 42. A raster line in which dots are arranged is formed. Then, by repeating this main scanning and sub-scanning in which the control unit 1 controls the medium conveying unit 20 to convey the recording medium 95 in the conveying direction, raster lines are arranged in the conveying direction, and an image or the like is displayed on the recording medium 95. Is formed.

<Image processing>
FIG. 4 is a diagram for explaining image processing for printing an image. Next, print data generation processing will be described with reference to FIG. Printing on the recording medium 95 is started when print data is transmitted from the PC 110 to the control unit 1. The print data is generated by the printer driver.

  The printer driver receives image data (for example, text data, full-color image data, etc.) from the application, converts the print data into a format that can be interpreted by the control unit 1, and outputs the print data to the control unit 1. When converting image data from an application into print data, the printer driver performs resolution conversion processing, color conversion processing, halftone processing, rasterization processing, command addition processing, and the like.

The resolution conversion process is a process for converting the image data output from the application into a resolution (printing resolution) when printing on the recording medium 95. For example, when the print resolution is specified as 720 × 720 dpi, the vector format image data received from the application is converted into bitmap format image data with a resolution of 720 × 720 dpi. Each pixel data of the image data after the resolution conversion process is composed of pixels arranged in a matrix. Each pixel has a gradation value of, for example, 256 gradations in the RGB color space. That is, the pixel data after resolution conversion indicates the gradation value of the corresponding pixel.
Pixel data corresponding to one column of pixels arranged in a predetermined direction among pixels arranged in a matrix is called raster data. The predetermined direction in which the pixels corresponding to the raster data are arranged corresponds to the moving direction (main scanning direction) of the ejection head 42 when printing an image.

The color conversion process is a process for converting RGB data into data in the CMYK color system space. The CMYK colors are cyan (C), magenta (M), yellow (Y), and black (K), and the image data in the CMYK color system space is data corresponding to the ink color that the printing apparatus 100 has. . Therefore, for example, when the printing apparatus 100 uses four types of CMYK color inks, the printer driver generates image data in a CMYK color four-dimensional space based on the RGB data.
This color conversion processing is performed based on a table (color conversion lookup table LUT) in which gradation values of RGB data and gradation values of CMYK color system data are associated with each other. Note that the pixel data after the color conversion processing is, for example, CMYK color system data of 256 gradations represented by the CMYK color system space.

The halftone process is a process of converting data having a high number of gradations (256 gradations) into data having a number of gradations that can be formed by the control unit 1. By this halftone processing, data indicating 256 gradations is 1 bit data indicating 2 gradations (with or without dots) or 2 bits indicating 4 gradations (without dots, small dots, medium dots, large dots). Converted to data. Specifically, from the dot generation rate table corresponding to the gradation value (0 to 255) and the dot generation rate, the dot generation rate corresponding to the gradation value (for example, in the case of 4 gradations, no dot, small Pixel data is created so that dots are formed in a dispersed manner using the dither method, error diffusion method, etc. at the obtained generation rate. The
That is, pixel data after halftone processing is 1-bit or 2-bit data, and this pixel data is data indicating dot formation (the presence or absence of dots, the size of dots) in each pixel. For example, in the case of 2 bits (4 gradations), a dot gradation value [00] corresponding to no dot, a dot gradation value [01] corresponding to the formation of a small dot, and a dot gradation corresponding to the formation of a medium dot A value [10] and a dot gradation value [11] corresponding to the formation of a large dot are converted into four levels.

  The rasterizing process is a process of rearranging pixel data (for example, 2-bit data) arranged in a matrix according to the dot formation order at the time of printing. The rasterizing process includes a path allocation process in which image data composed of pixel data after halftone processing is allocated to each main scan that ejects droplets while the ejection head 42 reciprocates. When the pass assignment is completed, the actual nozzles forming each raster line constituting the print image are assigned.

The command addition process is a process for adding command data corresponding to the printing method to the rasterized data. The command data includes, for example, transport data related to the transport specifications of the medium (the amount of movement in the transport direction, the speed, etc.).
The print data transmission process is a process for transmitting the generated print data to the control unit 1 via the interface unit 119.
These processes by the printer driver are performed by the ASIC 116 and the DSP 117 under the control of the CPU 115 (see FIG. 3).

<Discharge timing>
FIG. 5 is a diagram for explaining the landing positions of droplets for forming medium dots. FIG. 6 is a diagram for explaining the landing positions of droplets for forming large dots. FIG. 7 is a diagram illustrating the landing positions of droplets for forming small dots. 5 to 7, the ejection head 42 a moving forward and the ejection head 42 b moving backward along the main scanning direction (X-axis direction) on the recording medium 95 are shown on the same drawing. . Next, the ejection timing for ejecting the droplet 71 and the landing position of the droplet 71 will be described.

  As shown in FIG. 5, the ejection head 42 a that moves at a constant speed (forward movement) in the + X-axis direction and the ejection head 42 b that moves at a constant speed (return movement) in the −X-axis direction include a medium dot 72 b on the recording medium 95. Droplets (hereinafter referred to as medium droplets 71b) are formed. The medium droplet 71b is ejected from the nozzle 46 at a point in front of the predetermined landing position A by a distance L in the X-axis direction, and reaches the same landing position A during forward movement and during backward movement. In other words, in the printing apparatus 100, the discharge timing for discharging the droplet 71 is the distance L so that the landing positions of the medium droplet 71b discharged during the forward movement and the medium droplet 71b discharged during the backward movement match. Is initially set.

  As shown in FIG. 6, the ejection head 42 a that moves at a constant speed (forward movement) in the + X-axis direction and the ejection head 42 b that moves at a constant speed (return movement) in the −X-axis direction are large dots 72 a on the recording medium 95. Droplets (hereinafter referred to as large droplets 71a) are formed. When the large droplet 71a is ejected at the ejection timing of the same distance L as the middle droplet 71b in the X-axis direction, the large droplet 71a has a larger mass than the middle droplet 71b, and the speed reduction after ejection is small. Then, it reaches the recording medium 95 earlier than the medium droplet 71b, and lands on a point before the predetermined landing position A by a distance M. That is, the landing position is deviated between forward movement and backward movement. This landing position deviation is suppressed by adjusting the discharge timing in a direction that delays the discharge timing by the distance M from the distance L. The distance M is also an adjustment value when ejecting the large droplet 71a. The adjustment value of the large droplet 71 a is “−M” and is stored in the memory 118. The adjustment value “−” (minus) sign means that the discharge timing for discharging the droplet 71 is shorter than the distance L.

  As shown in FIG. 7, the ejection head 42 a that moves at a constant speed (forward movement) in the + X-axis direction and the ejection head 42 b that moves at a constant speed (return movement) in the −X-axis direction include small dots 72 c on the recording medium 95. Droplets (hereinafter referred to as small droplets 71c) are formed. When the small droplet 71c is ejected at the ejection timing of the same distance L as the middle droplet 71b in the X-axis direction, the small droplet 71c has a smaller mass than the middle droplet 71b and has a large decrease in speed after ejection. Then, it reaches the recording medium 95 later than the medium droplet 71b and lands on a point ahead of the predetermined landing position A by a distance P. That is, the landing position is deviated between forward movement and backward movement. This landing position deviation is suppressed by adjusting the ejection timing in a direction to make the ejection timing earlier than the distance L by the distance P. The distance P is also an adjustment value when the small droplet 71c is ejected. The adjustment value of the small droplet 71 c is “+ P” and is stored in the memory 118. The adjustment value “+” (plus) sign means that the discharge timing for discharging the droplet 71 is longer than the distance L.

<Printing method>
FIG. 8 is a flowchart for explaining the printing method. FIG. 9 is a diagram for explaining a dot analysis method. Next, the printing method of the present embodiment will be described with reference to FIGS. In the present embodiment, it is assumed that each dot 72 forming an image is formed by the ejection head 42 having four nozzles 46 for the sake of simplicity of explanation.

Step S1 is a step of receiving image data to be formed on the recording medium 95.
Step S2 is a step of performing image processing. The printing apparatus 100 generates pixel data 81 (see FIG. 9) in which dots are expanded by the above-described halftone process.

  Step S3 is a step for analyzing dots. The printer control unit 111 analyzes the size and quantity of the droplets 71 for each predetermined area from the image data to be printed on the recording medium 95. Note that the printer control unit 111 of this embodiment sets a raster line in which dots 72 formed by the droplets 71 are arranged in the main scanning direction as a predetermined region.

  FIG. 9 shows an example of pixel data 81 expanded from image data and dot analysis data 82. Note that the raster line numbers (L1 to L8) corresponding to the raster lines formed by the dot rows arranged in the main scanning direction and the position of the ejection head 42 in the sub-scanning direction are attached to the side of the pixel data 81. . Each raster line L1 to L8 also corresponds to a row of analysis data 82. In addition, nozzle numbers (# 1 to # 4) corresponding to the respective nozzles 46 are attached to the sides of the ejection head 42.

The dots 72 of the raster lines L1 to L4 are formed by the main scanning performed by the ejection head 42 in the + X-axis direction. The dots 72 in the raster lines L5 to L8 are mainly formed by the ejection head 42 moving backward in the −X axis direction after the recording medium 95 (see FIG. 1) is transported by 4 nozzles in the transport direction (+ Y axis direction). It is formed by scanning.
The pixel data 81 shows a large dot 72a, a medium dot 72b, and a small dot 72c that are formed in each pixel by two main scans of forward and backward movements. In the analysis data 82, the numbers of large dots 72a, medium dots 72b, and small dots 72c forming the raster lines L1 to L8 are shown for each raster line L1 to L8. In the analysis data 82, the large dot 72a is represented as “L”, the medium dot 72b as “M”, and the small dot 72c as “S”.

  The printer control unit 111 sets S dots as “−1”, M dots as “0”, and L dots as “+1”, and the average dot size for forming the raster lines L1 to L8 is within a range of −1 to +1. Digitize. For example, since the raster line L2 is formed by three medium dots 72b and seven large dots 72a, the average dot size is (3 × 0 + 7 × (+1)) / 10 = + 0.7. Since the raster line L6 is formed by five small dots 72c and five medium dots 72b, the average dot size is (5 × (−1) + 5 × 0) /10=−0.5. Become. This dot size corresponds to the size of the droplet 71 ejected from each nozzle 46 forming each raster line L1 to L8. For example, the average droplet size ejected from nozzle # 2 in forward main scanning is “+0.7”. Further, the average droplet size ejected from the nozzle # 2 in the backward main scanning is “−0.5”. Steps S2 and S3 correspond to steps for analyzing the size and quantity of the droplets 71 from the image data to be printed on the recording medium 95.

Step S4 is a step of calculating an adjustment value of the discharge timing for discharging the droplet. The printer control unit 111 as the calculation unit calculates an adjustment value of the ejection timing for ejecting the droplet 71 based on the average droplet size obtained in step S3. As an example, calculation of the adjustment value of nozzle # 2 will be described.
The average droplet size during the forward movement of the nozzle # 2 is “+0.7”. The printer control unit 111 adds the adjustment value “−M” and the numerical value “0.7” of the large droplet 71a stored in the memory 118 from the “+” (plus) sign, and the nozzle at the time of forward movement The adjustment value of # 2 is set to “−0.7M”.
The average droplet size at the time of the backward movement of the nozzle # 2 is “−0.5”. The printer control unit 111 adds the adjustment value “+ P” and the numerical value “0.5” of the small droplet 71c stored in the memory 118 from the “−” (minus) sign, and the nozzle # at the time of backward movement The adjustment value of 2 is “+0.5 P”.

Step S5 is a step of executing printing by changing the ejection timing based on the adjustment value. The printer control unit 111 transmits print data to which the adjustment value is added to the control unit 1. Then, the control unit 1 changes the ejection timing based on the adjustment value and executes printing.
For example, the control unit 1 changes the discharge timing of the nozzle # 2 from the distance L, which is the discharge timing of the medium droplet 71b, to the distance L-0.7M, and executes main scanning by forward movement. The controller 1 then transports the recording medium 95 by four nozzles in the transport direction (+ Y-axis direction), and then changes the discharge timing of the nozzle # 2 from the distance L, which is the discharge timing of the medium droplet 71b, to a distance L + 0.5P. The main scan by the backward movement is executed. Although detailed description is omitted, the control unit 1 also changes the discharge timings of the nozzles # 1, # 3, and # 4 based on the adjustment values obtained in the same manner as the nozzle # 2. The control unit 1 precisely corrects the ejection timing of the droplet 71 ejected during the forward movement and the ejection timing of the droplet 71 ejected during the backward movement for each nozzle 46 (each raster line). Landing position deviation at the time of movement and deterioration of print quality due to landing position deviation can be suppressed.

  In the present embodiment, the dot forming the raster line is defined as the predetermined area, and the adjustment value is obtained for each predetermined area (for each raster line) to change the ejection timing. However, the present invention is not limited to this. . For example, the dots formed by one main scan (one pass) may be set as the predetermined area. In the case of image data including a plurality of thumbnail images, the dots forming each thumbnail image may be set as the predetermined area. Good.

As described above, according to the printing apparatus 100 according to the present embodiment, the following effects can be obtained.
The printer control unit 111 of the printing apparatus 100 analyzes the size and quantity of the droplets 71 for each predetermined region from the image data to be printed on the recording medium 95 using the raster line as the predetermined region, and generates the droplets 71 that form the predetermined region. An adjustment value of the discharge timing to be discharged is calculated. Then, the control unit 1 changes the ejection timing based on the adjustment value and executes printing. Thereby, it is possible to suppress landing position deviation during forward movement and backward movement, and deterioration of print quality due to landing position deviation. Therefore, it is possible to provide a printing apparatus with improved print quality.

  The printing method of the printing apparatus 100 includes a step of analyzing the size and quantity of the droplets 71 for each predetermined region from image data to be printed on the recording medium 95 using a raster line as a predetermined region, and the droplets 71 forming the predetermined region. The method includes a step of calculating an adjustment value of discharge timing to be discharged, and a step of executing printing by changing the discharge timing based on the adjustment value. Thereby, it is possible to suppress landing position deviation during forward movement and backward movement, and deterioration of print quality due to landing position deviation. Therefore, a printing method with improved print quality can be provided.

  DESCRIPTION OF SYMBOLS 1 ... Control part, 2 ... Interface part, 3 ... CPU, 4 ... Control circuit, 5 ... Memory, 6 ... Drive signal generation part, 10 ... Medium supply part, 20 ... Medium conveyance part, 23 ... Conveyance belt, 24 ... Belt Rotating roller, 25 ... belt driving roller, 27 ... drying unit, 30 ... medium recovery unit, 40 ... printing unit, 41 ... head moving unit, 42, 42a, 42b ... discharge head, 43 ... carriage, 45 ... nozzle row, 46 ... Nozzle, 49 ... piezoelectric element, 50 ... cleaning unit, 60 ... medium contact portion, 71 ... droplet, 71a ... large droplet, 71b ... medium droplet, 71c ... small droplet, 72 ... dot, 72a ... large dot 72b ... medium dots, 72c ... small dots, 81 ... pixel data, 82 ... analytical data, 91 ... linear encoder, 95 ... recording medium, 100 ... printing device, 110 ... image processing device, 111 ... Centers controller (calculating unit) 112 ... input unit, 113 ... display unit, 114 ... storage unit, 115 ... CPU, 116 ... ASIC, 117 ... DSP, 118 ... memory, 119 ... interface unit.

Claims (4)

A medium transport unit for transporting the recording medium in the transport direction;
An ejection head that ejects droplets of different sizes onto the recording medium;
A head moving unit that reciprocally moves the ejection head in a main scanning direction intersecting the transport direction;
A calculation unit that analyzes the size and quantity of the droplets from image data to be printed on the recording medium, and calculates an adjustment value of a discharge timing for discharging the droplets;
And a controller that changes the ejection timing based on the adjustment value. The adjustment value is calculated for each predetermined area,
The printing apparatus according to claim 1, wherein the ejection timing is changed for each predetermined area.   The printing apparatus according to claim 2, wherein the predetermined area is a raster line in which dots formed by the droplets are arranged in a main scanning direction. A medium transport unit that transports the recording medium in the transport direction, an ejection head that ejects droplets of different sizes onto the recording medium, and a head moving unit that reciprocates the ejection head in the main scanning direction intersecting the transport direction; A printing method for a printing apparatus comprising:
Analyzing the size and quantity of the droplets from image data to be printed on the recording medium;
Calculating a discharge timing adjustment value for discharging the droplet;
And a step of changing the ejection timing based on the adjustment value.

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