JP2013103381A - Printing apparatus and printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the rise of an image difficult to stand out by a light absorbing layer that can control light scattering of the rise part of the image and can suppress change in the hue and the glossiness feeling.SOLUTION: A printing apparatus includes: a head part that has a plurality of ejection parts for ejecting a plurality of colors of the photocurable inks cured by the irradiation of light to the printed materials by each ink color; and an irradiation part for irradiating the printed material with the light; a moving mechanism for relatively moving the head parts and printed materials; a control part for controlling the moving mechanism to make the head part and the printed materials relatively move, making a plurality of ejection parts selectively ejection a plurality of colors of photocurable inks, and making the irradiation part irradiate the photocurable inks landed in the printed materials with the light, and prints the image on the printed materials. The control part uses at least one of the plurality of ejection parts and forms the black or the gray light absorbing layer at the rise parts of the image.

Description

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

  A photo-curable liquid (for example, ultraviolet curable ink, abbreviated as “UV ink”) that is cured by irradiation with light (for example, ultraviolet violet (abbreviated as “UV”) or visible light) is ejected. For example, a printer is known as a printing apparatus that performs printing. In such a printer, UV ink is ejected from a nozzle onto a printing material such as paper, cloth, or film sheet, and then light is emitted to dots formed on the printing material. As a result, the dots are cured and fixed on the printing material (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 2005-74878

Since UV ink can be cured instantaneously by ultraviolet rays, it is possible to print on a non-absorbent medium. Compared to the case where an image is printed on an absorptive medium using permeable ink (for example, water-based ink), the printed image Are formed so as to rise from the surface of the printing material.
Furthermore, when an image is printed on a printing material using UV ink, there is a possibility that a phenomenon (thickening phenomenon) in which the vicinity of the edge of the printed image is particularly raised as compared with other portions. Due to the thickening phenomenon, when the print image is viewed with only a part of the print image being specularly reflected, the print image looks three-dimensional and the print image is thicker than it actually is. Perceived, it causes the quality of the printed image to deteriorate.

  Therefore, an object of the present invention is to make the rise of an image less noticeable.

The main invention for achieving the above object is:
A head unit having a plurality of ejection units that ejects a plurality of colors of photocurable ink that is cured by light irradiation onto a printing material for each ink color; and an irradiation unit that irradiates the printing material with the light; and the head A moving mechanism that relatively moves the printing unit and the printing material, and the moving mechanism controls the relative movement of the head unit and the printing material, so that the plurality of colors can be cured from the plurality of ejection units. A control unit that selectively ejects ink and irradiates the light curable ink landed on the printing material with the light from the irradiation unit, and prints an image on the printing material. The control unit is a printing apparatus in which a black or gray light absorption layer is formed on a rising portion of the image using at least one of the plurality of ejection units.

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

FIG. 1A is an explanatory diagram of a print image printed on a printing material using UV ink. FIG. 1B is a graph of measured values of the thickness of a region (in the vicinity of an edge) indicated by a dotted line in FIG. 1A. FIG. 2A is a top view of the print image of FIG. 1A. FIG. 2B is an explanatory diagram of a state in which light is regularly reflected in a part of the printed image in FIG. 2A. 1 is a block diagram illustrating a configuration of a printing system. 1 is a perspective view of a printer 1. FIG. FIG. 2 is a schematic view around the head of the printer 1. 6A and 6B are cross-sectional views of the printer 1. 4 is an explanatory diagram of a configuration of a head 31. FIG. 3 is an explanatory diagram of functions of a printer driver of a computer 110. FIG. It is a flowchart of a light absorption layer production | generation process. 10A to 10G are schematic explanatory diagrams illustrating an example of a state of image formation by a pass. It is the schematic of the shape of the edge part of the image printed in 1st Embodiment. It is the schematic of the shape of the edge part of the image printed by the modification 1 of 1st Embodiment. It is the schematic of the shape of the edge part of the image printed by the modification 2 of 1st Embodiment. It is explanatory drawing of a structure of the head of 2nd Embodiment. It is the schematic of the shape of the edge part of the image printed in 2nd Embodiment. It is the schematic of the shape of the edge part of the image printed in the modification 1 of 2nd Embodiment. It is the schematic of the shape of the edge part of the image printed by the modification 2 of 2nd Embodiment. It is a schematic explanatory drawing of embodiment of this invention by a line printer.

  At least the following matters will become clear from the description of the present specification and the accompanying drawings.

A head unit having a plurality of ejection units that ejects a plurality of colors of photocurable ink that is cured by light irradiation onto a printing material for each ink color; and an irradiation unit that irradiates the printing material with the light; and the head A moving mechanism that relatively moves the printing unit and the printing material, and the moving mechanism controls the relative movement of the head unit and the printing material, so that the plurality of colors can be cured from the plurality of ejection units. A control unit that selectively ejects ink and irradiates the light curable ink landed on the printing material with the light from the irradiation unit, and prints an image on the printing material. Thus, it is apparent that the control unit uses at least one of the plurality of ejection units to form a black or gray light absorption layer on the rising portion of the image.
According to such a printing apparatus, the light absorption layer can suppress light scattering at the rising portion of the image, and can suppress changes in color and gloss. Therefore, the rising part of the image can be made inconspicuous.

In this printing apparatus, it is preferable that the raised portion of the image is an end region of the edge of the image.
According to such a printing apparatus, it is possible to prevent a print image from being perceived three-dimensionally.

In this printing apparatus, the control unit forms a plurality of types of dots having different sizes on the printing material by controlling a discharge amount of the photocurable ink from each discharge unit. It is desirable to form the light absorption layer using the smallest dot among the dots.
According to such a printing apparatus, it is possible to suppress a difference in image color between a region where the light absorption layer is formed and a region where the light absorption layer is not formed.

The light absorption layer is preferably formed by discretely arranging black dots on the raised portion of the image.
According to such a printing apparatus, it is possible to suppress a difference in image color between a region where the light absorption layer is formed and a region where the light absorption layer is not formed. In addition, the rise of the image can be made less noticeable.

In this printing apparatus, the plurality of ejection units include a first ejection unit that ejects the photocurable ink for forming a main image, and the light for forming an auxiliary image that assists the main image. A second discharge section that discharges curable ink, and the control section controls the discharge of the photocurable ink from the first discharge section and the second discharge section, respectively. It is desirable that the image and the auxiliary image are formed to overlap each other, and the light absorption layer is formed on the rising portion of the main image and the auxiliary image.
According to such a printing apparatus, the swelled portion due to the main image and the auxiliary image becomes large, so that the swell can be suppressed more effectively.

  A head unit including a plurality of ejection units that eject a plurality of colors of photocurable ink that is cured by light irradiation onto a printing material for each ink color; and an irradiation unit that irradiates the printing material with the light. A printing method for printing an image on the printing material by a printing apparatus, wherein the head unit and the printing material are moved relative to each other, and the relative movement step moves relative to the printing material. An image forming step of selectively ejecting the photocurable inks of the plurality of colors from a plurality of ejection units, and irradiating the light curable ink landed on the printing material from the irradiation unit; A black or gray light absorption layer is formed on the raised portion of the image using at least one of the plurality of ejection portions that move relative to the material, and the light from the irradiation unit is formed on the light absorption layer. A light absorption layer forming step of irradiating Printing method characterized by having become apparent.

  In the following embodiments, an ink jet printer (hereinafter also referred to as printer 1) will be described as an example.

=== Overview ===
<About thickening phenomenon and feeling of thickening>
Since a printing material such as a plastic film has a property that it is difficult to absorb ink, UV ink may be used as a photocurable ink when printing on such a printing material by an inkjet method. The UV ink is an ink containing an ultraviolet curable resin, and has a property of curing when irradiated with ultraviolet rays (UV). By curing the UV ink to form dots, printing can be performed on a printing material that does not have an ink receiving layer and does not absorb ink. Examples of the printing material that does not have the ink receiving layer include films (specifically, vinyl chloride film, polyethylene terephthalate (PET) film, etc.).

  However, since the dots formed with the UV ink are raised on the surface of the printing material, when the printed image is formed on the printing material using the UV ink, the surface of the printing material is uneven. When the print image is a filled image, the print image has a thickness.

FIG. 1A is an explanatory diagram of a print image printed on a printing material using UV ink.
Since UV ink can be instantly cured by ultraviolet rays (UV), when an image is printed using UV ink, dots are raised and formed without depending on the ink absorbability of the printing material. When the filled image is printed, the dots formed with the UV ink fill up a predetermined area, and thus a thick print image G is formed on the printing material S. For example, when printing characters on the printing material S, a thick character image (filled image) is formed on the printing material S. The thickness of the print image G printed using the UV ink is about several μm.

  FIG. 1B is a graph of measured values of the thickness of a region T (near the edge) indicated by a dotted line in FIG. 1A. The horizontal axis of the graph indicates the position of the printing material S, and the vertical axis indicates the height of the dots (the thickness of the print image G). The print image G is an image in which dots are formed with an ink weight of 10 ng and are filled with a print resolution of 720 × 720 dpi. The thickness of the printed image G was measured using a non-stop CNC (Computer Numerical Control) image measuring device Quick Vision Stream plus manufactured by Mitutoyo Corporation. As shown in the figure, the printed image G has a thickness of about 5 μm.

  A position X in the graph indicates the outermost position of the print image G. In other words, the position X indicates the position of the end (edge) of the print image G. A position A in the graph indicates the thickest position (the highest position) in the vicinity of the edge of the printed image. In other words, the position A indicates the position of the protruding portion in the vicinity of the edge of the print image G.

  The position A is located about 200 μm inside from the position X. In the region from the position X to the position A (region B in the graph), the ink is thicker toward the inner side of the print image. At position A, the thickness is maximum (about 6 μm). In the region from the position A to the position D (region C in the graph), the print image G (ink layer) becomes thinner toward the inside (right side of the drawing). At the position D, the thickness reaches about 5 μm, and on the inner side, the thickness is almost uniform.

  In the present specification, a phenomenon in which the vicinity of the edge is particularly raised as compared with other portions, such as the position A in the graph, is referred to as a “thickening phenomenon”. This thickening phenomenon is a unique phenomenon that occurs when an image is printed by an inkjet method using UV ink. Further, in this specification, the thickness of the image is measured from the edge of the image (for example, the position X in FIG. 1B) in the vicinity of the edge, specifically, in the region where the print image is formed (hereinafter also referred to as image formation region). A region obtained by combining the region B and the region C up to a uniform position (for example, the position D in FIG. 1B) is referred to as an end region E. In the case of FIG. 1B, the end region E is a region whose distance from the end of the image is about 580 μm or less. In FIG. 1B, the part indicated by the symbol F is an image forming area.

  FIG. 2A is a view of the print image G of FIG. 1A as viewed from above. FIG. 2B is an explanatory diagram of a state in which light is regularly reflected in a part of the printed image in FIG. 2A. In FIG. 2B, the part which is shined and visually recognized inside the printed image is shown in white.

  Since the thickness is substantially uniform at the center of the printed image, uniform glossiness can be obtained. However, since the thickness is not uniform in the vicinity of the edge (edge region E) of the printed image, uniform color and glossiness cannot be obtained.

  In the vicinity of the edge, due to the thickening phenomenon, the printed image does not have a uniform thickness, and a protruding portion along the edge is formed inside the edge of the printed image. As a result, depending on the reflection angle of light, as shown in FIG. 2B, a part (Ge) of the printed image G may be lit along the edge and viewed. Depending on the positional relationship / angle of the observer's eyes, the light source, and the printed image, the light regularly reflected in the inclined region of FIG. 1B enters the observer's eyes, and the printed image G is visually recognized as shown in FIG. 2B.

  As shown in FIG. 2B, when a part (Ge) of the print image G appears to shine along the edge, the entire print image is perceived in three dimensions. In other words, when a 3D object is displayed as a two-dimensional image on a display as a two-dimensional image on a computer graphic (for example, when a three-dimensional object is displayed as a two-dimensional image by ray tracing) The print image is perceived three-dimensionally. As a result, even though the thickness is actually about 5 μm, the observer of the printed image G perceives it thicker than that.

  In the present specification, the fact that the printed image is perceived to be thicker than actual due to this embossing phenomenon is referred to as “thickness”. The problem of “thickness” is a peculiar problem that occurs when an image is printed by an inkjet method using UV ink.

  Note that a printed image by normal plate-making printing (flexographic printing, offset printing, etc.) has almost no thickness compared to a printed image using UV ink. For this reason, in the printed image by normal plate-making printing, the “thickness phenomenon” does not occur, and the problem of “thickness feeling” does not occur. Also, a printed image printed by infiltrating ink into the printing material S has almost no thickness. For this reason, even in a printed image printed by infiltrating the printing material S with ink, the “thickening phenomenon” does not occur, and the problem of “thickness feeling” does not occur. As described above, the build-up phenomenon and the build-up feeling are peculiar phenomena / problems that occur when an image is printed by an inkjet method using UV ink.

  Therefore, in the embodiment described below, the feeling of thickening of the swelled portion of the image (specifically, the end region E) is suppressed.

=== First Embodiment ===
≪Configuration of printing system≫
A basic configuration of the printing apparatus according to the first embodiment will be described with reference to the drawings. FIG. 3 is a block diagram showing the configuration of the printing system. FIG. 4 is a perspective view of the printer 1. FIG. 5 is a schematic view around the head of the printer 1. 6A and 6B are cross-sectional views of the printer 1. 6A corresponds to the AA cross section of FIG. 5, and FIG. 6B corresponds to the BB cross section of FIG.

  In the present embodiment, an apparatus (system) including a printer 1 described below and a computer 110 in which a printer driver is installed corresponds to a printing apparatus. The controller 60 and the computer 110 of the printer 1 constitute a control unit for controlling the printing apparatus. However, the present invention is not limited to this. For example, the control unit may be configured by only the computer 110 or the controller 60.

<About computers>
As shown in FIG. 3, the computer 110 is communicably connected to the printer 1, and outputs print data corresponding to the image to be printed to the printer 1 in order to cause the printer 1 to print an image. A printer driver is installed in the computer 110. The printer driver is a program for converting image data output from an application program into print data. The printer driver is recorded on a recording medium (computer-readable recording medium) such as a CD-ROM (Compact Disc Read Only Memory). The printer driver can also be downloaded to the computer 110 via the Internet.

<About the printer>
The printer 1 prints an image on the printing material S by discharging UV ink that is cured by irradiation with ultraviolet rays (UV), which is a kind of light, toward the printing material S such as paper, cloth, and film sheet. It is a device to do. The UV ink is an ink containing an ultraviolet curable resin as described above, and is cured by a photopolymerization reaction occurring in the ultraviolet curable resin when irradiated with UV.

  As illustrated in FIG. 3, the printer 1 includes a transport unit 10, a carriage unit 20, a head unit 30, an irradiation unit 40, a detector group 50, and a controller 60. The printer 1 that has received print data from the computer 110 that is an external device controls each unit (the transport unit 10, the carriage unit 20, the head unit 30, and the irradiation unit 40) by the controller 60. The controller 60 controls each unit based on the print data received from the computer 110 and prints an image on the printing material S. The situation in the printer 1 is monitored by the detector group 50, and the detector group 50 outputs the detection result to the controller 60. The controller 60 controls each unit based on the detection result output from the detector group 50.

  The conveyance unit 10 is for conveying the printing material S (for example, a vinyl chloride film) in a relative conveyance direction (hereinafter also simply referred to as a conveyance direction). The transport unit 10 includes a paper feed roller 11, a transport motor (not shown), a transport roller 13, a platen 14, and a paper discharge roller 15 (see FIGS. 6A and 6B). The paper feed roller 11 is a roller for feeding the printing material S inserted into the paper insertion slot into the printer. The transport roller 13 is a roller that transports the printing material S fed by the paper feed roller 11 to a printable region, and is driven by a transport motor. The platen 14 supports the printing material S being printed. The paper discharge roller 15 is a roller for discharging the printing material S to the outside of the printer, and is provided on the downstream side in the transport direction with respect to the printable region.

  The carriage unit 20 (corresponding to a moving mechanism) is for moving a head or the like in a direction intersecting with the transport direction of the printing material S (hereinafter also referred to as a moving direction). Note that the intersecting direction is generally an orthogonal direction. The carriage unit 20 includes a carriage 21 and a carriage motor 22 (see FIG. 4). The carriage 21 detachably holds an ink cartridge that stores UV ink. The carriage 21 is mounted with a head 31 and irradiation units 42a and 42b, which will be described later, and is reciprocated along the guide shaft 24 by the carriage motor 22 while being supported by the guide shaft 24 intersecting the transport direction. .

The head unit 30 is for ejecting liquid (UV ink in the present embodiment) to the printing material S. The head unit 30 includes a head 31 having a plurality of nozzles (see FIG. 5). Since the head 31 is provided on the carriage 21, when the carriage 21 moves in the movement direction, the head 31 also moves in the movement direction. Then, while the head 31 is moving in the moving direction, UV ink is intermittently ejected from the nozzles, so that dot lines (raster lines) along the moving direction are formed on the printing material S. In the following description, a path that moves from one end side to the other end side in the moving direction is called a forward path, and a path that moves from the other end side to one end side is called a return path. In the embodiment of the present invention, UV ink is ejected during both the forward pass and the return pass. That is, the printer 1 performs bidirectional printing.
The configuration of the head 31 will be described later.

  The irradiation unit 40 irradiates UV toward the UV ink landed on the printing material. The dots formed on the printing material are cured by receiving UV irradiation from the irradiation unit 40. The irradiation unit 40 includes irradiation units 42a and 42b. The irradiation units 42 a and 42 b are provided on the carriage 21. For this reason, when the carriage 21 moves in the movement direction, the irradiation units 42a and 42b also move in the movement direction.

  The irradiation units 42 a and 42 b are provided on one end side and the other end side in the moving direction on the carriage 21 so as to sandwich the head 31. Further, the length of the irradiation units 42a and 42b in the transport direction is substantially the same as or longer than the length of the nozzle row of the head 31. In other words, the irradiation units 42a and 42b are provided at positions aligned with the nozzle rows of the head 31 in the moving direction. The irradiation units 42a and 42b move together with the head 31 and irradiate UV to a range where the nozzle row of the head 31 forms dots. Note that a metal halide lamp, an ultraviolet light emitting diode (LED), or the like is used as a light source for UV irradiation of the irradiation units 42a and 42b. When the light source is an LED, it is possible to easily change the UV irradiation energy by controlling the magnitude of the input current.

  The detector group 50 includes a linear encoder 51, a rotary encoder (not shown), a paper detection sensor 53, an optical sensor 54, and the like. A linear encoder 51 (corresponding to a detection unit) detects the position of the carriage 21 in the moving direction. The rotary encoder detects the rotation amount of the transport roller 13. The paper detection sensor 53 detects the position of the tip of the printing material S being fed. The optical sensor 54 detects the presence or absence of the printing material S by the light emitting unit and the light receiving unit attached to the carriage 21. The optical sensor 54 can detect the position of the end of the printing material S while being moved by the carriage 21 and can detect the width of the printing material S. The optical sensor 54 also has a leading end (an end on the downstream side in the transport direction, also referred to as an upper end) and a rear end (an end on the upstream side in the transport direction, also referred to as a lower end) depending on the situation. ) Can also be detected.

  The controller 60 is a control unit (control unit) for controlling the printer 1. As shown in FIG. 3, the controller 60 includes an interface unit 61, a CPU (Central Processing Unit) 62, a memory 63, and a unit control circuit 64. The interface unit 61 transmits and receives data between the computer 110 that is an external device and the printer 1. The CPU 62 is an arithmetic processing unit for controlling the entire printer 1. The memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like, and includes storage elements such as a RAM (Random Access Memory) and an EEPROM (Electrically Erasable Programmable Read-Only Memory). The CPU 62 controls each unit via the unit control circuit 64 in accordance with a program stored in the memory 63.

  When performing printing, the controller 60 repeats a dot forming operation for ejecting UV ink from the head 31 while moving the carriage 21 in the moving direction, and a transporting operation for transporting the printing material S in the transport direction. Is printed on the printing material S. In the following description, scanning in which the carriage 21 is moved (relatively) in a predetermined direction (left or right in the drawing) with respect to the printing material to perform dot formation operation or UV irradiation is referred to as “pass”. . During the pass, the head 31 and the irradiation units 42a and 42b move relative to the printing material S. At this time, as will be described later, UV irradiation by the irradiation units 42a and 42b is also performed.

<About the configuration of the head 31>
FIG. 7 is an explanatory diagram of an example of the configuration of the head 31. FIG. 7 is a view of the head 31 as viewed from below (from the platen 14 side). As shown in FIG. 7, a black ink nozzle row Nk, a cyan ink nozzle row Nc, a magenta ink nozzle row Nm, and a yellow ink nozzle row Ny are formed on the lower surface of the head 31. Each nozzle row is provided with a plurality (180 in this embodiment) of nozzles (corresponding to ejection units) that are ejection ports for ejecting the UV ink of each color. In the following description, black ink (black ink), cyan ink, magenta ink, and yellow ink are also referred to as color inks, and an image formed with the color inks is also referred to as a color image.

  The plurality of nozzles in each nozzle row are aligned at regular intervals (nozzle pitch: D) along the transport direction.

  The nozzles in each nozzle row are assigned a lower number toward the downstream side in the transport direction. Each nozzle is provided with a piezo element (not shown) as a drive element for discharging UV ink from each nozzle. By driving this piezo element with a drive signal, droplet-like UV ink is ejected from each nozzle. The discharged UV ink lands on the printing material S to form dots.

≪About printer driver processing≫
When the user of the printer 1 instructs printing of an image drawn on the application program, the printer driver of the computer 110 is activated. The printer driver receives image data from the application program, converts it into print data in a format that can be interpreted by the printer 1, and outputs the print data to the printer. When converting image data from an application program into print data, the printer driver performs resolution conversion processing, color conversion processing, halftone processing, and the like. The printer driver also performs light absorption layer generation processing for generating data for forming the light absorption layer.

FIG. 8 is an explanatory diagram of the function of the printer driver of the computer 110.
The resolution conversion process is a process of converting image data (text data, image data, etc.) output from an application program into a resolution (printing resolution) for printing on a printing material. For example, when the print resolution is specified as 720 × 720 dpi, the vector format image data received from the application program 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 RGB data of multiple gradations (for example, 256 gradations) represented by the RGB color space.

  The color conversion process is a process for converting RGB data into CMYK data represented by a CMYK color space. The CMYK data is data corresponding to the ink color of the printer. This color conversion process is performed based on a table (color conversion lookup table LUT) in which gradation values of RGB data and CMYK data are associated with each other. Note that the pixel data after the color conversion processing is CMYK data of 256 gradations represented by a CMYK color space.

  The halftone process is a process for converting high gradation number data into gradation number data that can be formed by a printer. For example, data indicating 256 gradations is converted into 2-bit data indicating 4 gradations by halftone processing. In the image data after the halftone process, 2-bit pixel data corresponds to each pixel. The 2-bit pixel data is data indicating the presence / absence of dots and the size of the dots. For example, in the case of pixel data [00], there is no dot (no dot formation), in the case of pixel data [01], the formation of small dots, in the case of pixel data [10], the formation of medium dots, and in the case of pixel data [11]. The data is large dot formation. The pixel data may be 1-bit data (2 gradations), and the pixel data may indicate only the presence or absence of dots. In any case, the pixel data after the halftone process is data indicating dots to be formed on the printing material.

  The light absorption layer generation process is a process for generating data for forming the light absorption layer in the swelled portion of the image (in the case of the present embodiment, the edge region of the print image). In the case of this embodiment, the light absorption layer is formed by discretely arranging black small dots of black ink in the end region. Therefore, the data generated by this light absorption layer generation process is data for discharging black ink from the black ink nozzle row Nk.

FIG. 9 is a flowchart of the light absorption layer generation process of FIG.
First, the printer driver performs edge extraction processing on the image data after the halftone processing, and extracts edge pixels located at the end (edge) of the print image (S001).

  Next, the printer driver determines a region (end region) having a predetermined distance (for example, 0.5 μm) from the edge pixel (S002). Thereby, an end region having a width of, for example, 0.5 μm is defined along the edge of the printed image.

  Then, the printer driver sets the pixel data “01” at a certain ratio (for example, about 5%) for a plurality of pixels included in the end region, and sets the pixel data of other pixels to “00”. (S003) is generated (hereinafter also referred to as light absorption layer data). This light absorption layer data is data in which dots (small black dots) are formed with a low duty in the end region, and dots are not formed in regions other than the end region. The duty is the ratio of the number of dots actually formed to the number of pixels constituting the unit area. For example, when the duty is 10%, dots are formed in one pixel per 10 pixels.

  In this way, the printer driver uses the black ink nozzle row Nk to form the light absorption layer data separately from the image data for discharging the color image UV ink (color ink). Is generated.

  The computer 110 generates print data by adding control data to image data and light absorption layer data composed of pixel data of four gradations, and transmits the print data to the printer 1 (see FIG. 8). The controller 60 of the printer 1 that has received the print data controls each unit in accordance with the control data included in the print data, and selectively ejects UV ink from each nozzle of the head 31 in accordance with the image data. Print an image on the material. Further, the printer 1 forms a light absorption layer by discharging black ink from the nozzles of the black ink nozzle row Nk of the head 31 according to the light absorption layer data.

≪Overview of printing operation≫
As described above, the controller 60 repeatedly executes the path for ejecting ink from the nozzles of the head 31 while moving the carriage 21 in the movement direction based on the print data and the conveyance operation for conveying the printing material S in the conveyance direction. Thus, dots are formed in the image forming area of the printing material S. Further, during the pass, the controller 60 irradiates UV from the irradiation unit upstream of the irradiation units 42 a and 42 b with respect to the movement direction of the carriage 21. As a result, the UV ink (dots) landed on the printing material S can be immediately irradiated with UV. Further, the controller 60 transports the printing material S in the transport direction between passes (transport operation).

  10A to 10G are schematic explanatory diagrams illustrating an example of a state of image formation by a pass. In addition, in the figure, the irradiation part which irradiates UV is shown with the oblique line.

  The controller 60 receives print data (including image data and light absorption layer data) from the computer 110, and repeatedly performs a pass and a transport operation based on these data.

  First, in the forward path, as shown in FIG. 10A, the controller 60 moves the carriage 21 from the standby position on one end side in the movement direction (hereinafter also referred to as home position) toward the other end side in the movement direction. When the carriage 21 reaches the image forming area, as shown in FIG. 10B, based on the image data, ink is selectively ejected from the nozzles of the moving head 31 to the printing material S, and the moving direction. UV is irradiated from the irradiation part 42a on the upstream side. The UV ink (color ink) landed on the printing material S is cured immediately upon receiving the UV irradiation from the irradiation unit 42a.

  The controller 60 stops the ejection of ink from the head 31 when the carriage 21 passes through the image forming area, and stops the irradiation of UV from the irradiation unit 42a. Then, as shown in FIG. 10C, when the carriage 21 reaches the end (the other end) of the movement range, the carriage 21 is stopped. By this pass, an image (color image) using color ink is printed on the printing material S. As described above, this color image is formed by raising the edge (end region E) of the image.

  Subsequently, the controller 60 reverses the moving direction of the carriage 21 and executes a return path. In the return pass, the controller 60 performs dot formation (dot formation using the black ink nozzle row Nk) based on the light absorption layer data.

  As shown in FIG. 10D, when the carriage 21 reaches the end region E (that is, the rising portion of the image) on the other end side in the moving direction, the controller 60 performs black discharge from each nozzle of the black ink nozzle row K with a low duty. Ink is ejected to form dots (black small dots). Moreover, the controller 60 irradiates UV from the irradiation part 42b located in the upstream of a movement direction in the path | pass of a return path. Thus, a light absorption layer is formed on the end region E of the color image.

  As shown in FIG. 10E, when the carriage 21 passes through the end region E on the other end side in the moving direction, the controller 60 stops the discharge of the black ink from the black ink nozzle row Nk, and the UV from the irradiation unit 42b. Only irradiation is performed. In addition, when the dot (color image) is completely cured in the forward path, UV irradiation may not be performed.

  Then, as shown in FIG. 10F, when the carriage 21 reaches the end region E on the one end side in the moving direction, the controller again ejects black ink from each nozzle of the black ink nozzle row Nk with a low duty to perform dot printing. (Small black dots) are formed.

  Thereafter, when the carriage 21 passes through the end region E, the controller 60 stops the ejection of ink from the black ink nozzle row Nk and the UV irradiation from the irradiation unit 42b. Then, as shown in FIG. 10G, when the carriage 21 reaches the end (home position) of the movement range, the movement of the carriage 21 is stopped.

  Thereafter, the controller 60 transports the printing material S in the transport direction by the length of the nozzle row (transport operation). As a result, the printing material S (dot-formed portion) located in the printing area is conveyed to the downstream side in the conveyance direction of the printing area, and the unprinted portion of the printing material S is conveyed to the printing area. Is done.

  In the same manner, the controller 60 repeatedly executes the path (the forward path and the return path) and the transport operation. Thereby, an image is printed on the printing material S.

≪About print image≫
FIG. 11 is a schematic diagram of the shape of the edge portion of the image printed in the first embodiment. Due to the above-described thickening phenomenon, the color image formed by the UV ink is raised at the edge (edge region E) of the image. In the present embodiment, as shown in FIG. 11, a black light absorbing layer is formed by discharging black ink to the end region E. Thus, by providing a black light absorption layer in the raised portion of the image, light scattering can be suppressed, and changes in color and gloss can be suppressed. For this reason, it is possible to make the swelled portion of the image less noticeable visually. As a result, it is possible to suppress the feeling of image thickness. In addition, by suppressing the thick feeling of the end region E, it is possible to prevent the print image from being perceived three-dimensionally.

  Also, if the light absorbing layer is formed with large black dots or formed with a high duty, the region where the light absorbing layer is formed (end region E) and the region where the light absorbing layer is not formed There is a possibility that the color of the image with (the region adjacent to the end region E) may change. On the other hand, in this embodiment, small black dots are discretely arranged to form a (black) light absorption layer. Therefore, it is possible to suppress the occurrence of a difference in image color between the region where the light absorption layer is formed (end region E) and the region where the light absorption layer is not formed (region adjacent to the end region E).

<Variation 1 of the first embodiment>
FIG. 12 is a schematic diagram of the shape of the edge portion of the image printed in the first modification of the first embodiment. The configurations of the printer 1 and the computer 110 are the same as those in the first embodiment.

  Compared to the first embodiment described above, the position of the light absorption layer is different. Specifically, in FIG. 12, a light absorption layer is formed under the color image (between the color image and the printing material S).

In the first modification of the first embodiment, the controller 60 first discharges only black ink onto the swelled portion (edge region E) of the image based on the light absorption layer data during the forward pass. An absorption layer is formed. In the return pass, color ink is ejected based on the image data to form a color image on the printing material S. As described above, the order of forming the light absorption layer and the color image is different from that in the first embodiment.
Since other operations are the same as those in the first embodiment, description thereof is omitted.

  As described above, even when the light absorption layer is formed between the color image and the printing material S, it is possible to make the rise of the image in the end region around the printed image inconspicuous. As a result, it is possible to suppress the feeling of thick image.

<Modification 2 of the first embodiment>
FIG. 13 is a schematic diagram of the shape of the edge portion of the image printed in the second modification of the first embodiment. In Modification 2 of the first embodiment, a light absorption layer is formed in the end region in the color image. That is, the controller 60 ejects ink from each color ink nozzle row based on the image data during the pass, and forms a light absorption layer from the black ink nozzle row Nk based on the light absorption layer data. Black ink is ejected. As a result, a print image in which the light absorption layer is formed in the edge region of the color image is formed by one pass. In the second modification of the first embodiment, the carriage 21 may be returned to the home position without performing ink ejection (dot formation), and the carrying operation may be performed after the forward pass. And then dot formation may be performed by a return pass.

  Also in the second modification of the first embodiment, light scattering can be suppressed by the light absorption layer in the end region, and the rising of the edge of the image can be made inconspicuous visually. As a result, a thick feeling can be suppressed.

  However, in the second modification of the first embodiment, the color tone of the image in the end region may change from the color tone of the image in the region adjacent to the end region. Therefore, it is more desirable to print an image in the first embodiment described above or the first modification of the first embodiment.

  As described above, according to the embodiment of the present invention, the black light absorption layer in which the small black dots are discretely arranged on the rising portion of the printed image is formed. By forming this light absorption layer, scattering of light due to the rising of the image can be suppressed, and changes in color and gloss can be suppressed. Therefore, the swell of the image can be made inconspicuous visually, and as a result, it is possible to suppress the thick feeling of the swell of the printed image.

=== Second Embodiment ===
In the second embodiment, not only CMYK color inks but also colorless and transparent clear inks are used.

The clear ink is a colorless and transparent ink, and is used for surface coating (surface coating) and color ink adhesion to the printing material S (anchor coating). In the second embodiment, clear ink is used for forming a surface coat of a color image. The surface coat is an auxiliary image for assisting a color image (corresponding to the main image). Thus, when the clear ink is applied to the surface of the image, the color image can be protected or gloss can be enhanced. . However, when surface coating is performed with clear ink, there is a risk that the feeling of thickening in the edge region of the image is further increased.
Therefore, in the second embodiment, a light absorption layer is formed as in the first embodiment.

  FIG. 14 is an explanatory diagram of the configuration of the head according to the second embodiment. Compared to the first embodiment (FIG. 7), the head 31 ′ of the second embodiment has a clear ink nozzle row Ncl in addition to the nozzle rows (Nc, Nm, Ny, Nk) that discharge color ink. Is provided. The plurality of nozzles (corresponding to the second ejection unit) of the clear ink nozzle array Ncl are aligned at a constant interval (nozzle pitch: D) along the transport direction, similarly to the color ink nozzle array. The configuration other than the head 31 ′ and the light absorption layer data generation process are the same as those in the first embodiment.

  Next, an image forming operation in the second embodiment will be briefly described. First, in the forward path, the controller 60 ejects ink from each nozzle of the color ink nozzle row of the head 31 and irradiates UV from the irradiation unit 42a on the upstream side in the movement direction among the irradiation units 42a and 42b. In this way, a color image is formed on the printing material S.

  In the next pass (return pass), the controller 60 ejects (applies) clear ink from the clear ink nozzle row Ncl of the head 31 to the entire surface of the color image. Further, during this pass, UV is irradiated from the irradiation unit 42b (upstream side in the moving direction) to cure dots formed by clear ink (hereinafter referred to as clear dots).

  Further, in the next pass (outward pass), the controller 60 discharges black ink from each nozzle of the black ink nozzle row Nk based on the light absorption layer data. As a result, a printed image in which a black light absorption layer is formed on the clear dots in the edge region E of the image is formed. Moreover, the controller 60 irradiates UV from the irradiation part 42a on the upstream side in the movement direction during this pass.

  Thereafter, the controller 60 moves the carriage 21 in the backward direction, and returns the carriage 21 to the home position. At this time, UV irradiation may or may not be performed. As described above, in the second embodiment, the carriage is reciprocated twice in the movement direction to form an image in the printing region of the printing material S.

  Then, the controller 60 transports the printing material S in the transport direction by the transport amount of the nozzle row length (transport operation). Thereafter, the same operation is repeated.

  FIG. 15 is a schematic diagram of the shape of the edge of the image printed in the second embodiment. As shown in the figure, a color image is formed on the printing material S, and clear ink is applied on the color image (surface coating). Further, a light absorbing layer is formed on the clear ink in the raised portion (edge region E) of the image.

  As described above, when a surface coat of clear ink is formed on a color image, there is a possibility that the feeling of thickness of the image is further increased. Therefore, also in this case, as shown in the figure, by forming the black light absorption layer in the swelled portion (end region E), it is possible to suppress the feeling of thickening in the swelled portion of the image.

<Modification Example 1 of Second Embodiment>
FIG. 16 is a schematic diagram of the shape of the edge of the image printed in the first modification of the second embodiment.
In Modification 1 of the second embodiment, a light absorption layer is provided between the color image and the surface coat with clear ink. That is, in the forward pass, a color image is formed as in the second embodiment, the light absorption layer is formed in the return pass, and the clear ink is applied to the entire surface in the next forward pass. Thus, even if a light absorption layer is provided between the color image and the surface coat, it is possible to suppress the thick feeling of the image.

<Modification 2 of the second embodiment>
FIG. 17 is a schematic diagram of the shape of the edge of the image printed in the second modification of the second embodiment. In Modification 2 of the second embodiment, a black light absorption layer is formed in the surface coat. That is, the color image is formed in the forward pass, and the clear ink is discharged from the clear ink nozzle row Ncl to the entire image in the return pass, and the black ink from the black ink nozzle row Nk based on the light absorption layer data. Discharging. Thus, even if the light absorption layer is provided between the surface coats, it is possible to suppress the thick feeling of the image.
In the second modification, the light absorption layer is provided only in the end region of the surface coat. However, the light absorption layer may be provided also in the end region E of the color image (see FIG. 13).

=== Other Embodiments ===
Although a printer or the like as one embodiment has been described, the above embodiment is for facilitating the understanding of the present invention, and is not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<About the printer>
In the above-described embodiment, the printer (so-called serial printer) that repeats the ejection operation for ejecting ink from the head moving in the movement direction and the conveyance operation for conveying the printing material in the conveyance direction is described as an example. Absent. For example, the present invention may be applied to a line printer.

FIG. 18 is a schematic explanatory diagram of an embodiment of the present invention using a line printer.
In the line printer shown in FIG. 18, the color image forming head 311, the UV irradiation unit 421, the light absorption layer forming head 312, and the UV irradiation unit 422 are arranged upstream in the transport direction on the transport path of the printing material S. It is provided in order from the side.

  In the head 311, nozzle rows that discharge UV ink are arranged in a line (in the line direction in the drawing) in the relative transport direction (hereinafter also simply referred to as the transport direction) for each ink color. For example, a cyan ink nozzle row (denoted as “Cyan” in the drawing) that discharges cyan ink is provided on the most upstream side of the head 311 in the transport direction. A magenta ink nozzle row (denoted as “Magenta” in the drawing) for sequentially ejecting magenta ink and a yellow ink nozzle row (denoted as “Yellow” in the drawing) for ejecting yellow ink are provided on the downstream side in the transport direction. A black ink nozzle row (denoted as “Black” in the drawing) for discharging black ink is provided on the most downstream side in the transport direction of the head 311.

  The arrangement direction (line direction) of the nozzle rows of the respective color inks is a direction that intersects the relative conveyance direction of the printing material S. The “cross direction” is usually an orthogonal direction. The length (width in the line direction) of the nozzle row of each ink is formed to be approximately equal to or longer than the width in the line direction of the image forming region F. When the image forming area F extends to both edges of the printing material S in the line direction, the image forming area F extends to both edges of the printing material S (the width of the image forming area F in FIG. It becomes the same as the width of the printing material S).

  The head 312 is provided with a black ink nozzle row (denoted as “Black” in the drawing) for discharging black ink for forming the light absorption layer in the same manner as each nozzle row of the head 311.

  The irradiation unit 421 is provided in a direction intersecting with the relative conveyance direction of the printing material S on the downstream side of the head 311 in the conveyance direction. The “cross direction” is usually an orthogonal direction. That is, the irradiation unit 421 is provided along the nozzle arrangement direction (line direction). The irradiation unit 421 is formed to be approximately the same as or longer than the length of the nozzle row of each ink. Since the ink discharged on the printing material S is irradiated with UV and cured, if it is longer than the nozzle row of each ink, irradiation leakage hardly occurs.

  In addition, the irradiation unit 421 is provided with a number of LEDs 421A for UV irradiation along the line direction (nozzle arrangement direction), and by controlling the input current to each LED 421A, the UV is changed according to the position in the line direction. The irradiation intensity can be changed.

  The irradiation unit 422 is provided along the nozzle arrangement direction (line direction) on the downstream side of the head 312 in the transport direction. The configuration of the irradiation unit 422 is the same as the configuration of the irradiation unit 411, and a number of LEDs 422A for UV irradiation are provided along the in direction (nozzle arrangement direction).

  In the above configuration, UV ink is ejected from the nozzles of each nozzle row of the head 311 while the printing material S is conveyed in the conveyance direction, and the UV ink that has landed on the printing material S is irradiated with UV from the irradiation unit 421. . In this way, a color image is printed on the printing material S.

  Further, black ink is ejected from the black ink nozzle row of the head 312 on the edge region E of the color image to form a light absorption layer, and UV is applied from the LED 422 of the irradiation unit 422 to the formation region of the light absorption layer. Irradiate to cure the light absorbing layer. By doing so, a light absorption layer can be formed on the edge region E of the color image (see FIG. 11). If the head 312 and the irradiation unit 422 are provided on the upstream side of the head 311 in the transport direction, a light absorption layer can be formed under the edge region E of the color image (see FIG. 12).

  In the case of this line printer, each nozzle row of the head 311, the black ink nozzle row of the head 312, and the irradiation unit 421 and the irradiation unit 422 correspond to the head unit. In this example, UV ink is ejected (dot formation) and UV irradiation is performed while the printing material S is conveyed in the conveyance direction. However, the ink is applied to the printing material S while the head portion is moved in the conveyance direction. You may make it perform discharge and UV irradiation. That is, by moving the head portion and the printing material S relative to each other in the transport direction (crossing direction) and performing UV ink ejection and UV irradiation, a dot row in which dots are arranged in the line direction (nozzle arrangement direction) is formed. What is necessary is just to form at once.

  After the color image is formed by the head 311 and the irradiation unit 421, the printing material S is reversely conveyed, the printing material S is conveyed again downstream in the conveyance direction, and black ink is ejected from the black ink nozzle row of the head 311. The light absorbing layer may be formed on the color image by discharging and irradiating UV from the irradiation unit 421. In this case, the head 312 and the irradiation unit 422 need not be provided.

  In addition, for example, an operation of ejecting ink and irradiating UV while moving the head and the irradiation unit in the medium conveyance direction with respect to continuous paper (or cut sheet) conveyed to the printing area, and the head and irradiation unit It is also possible to use a printer that repeatedly forms an image by moving in the medium width direction intersecting the transport direction, and then transports the medium portion that has not yet been printed to the print area.

  Even in the case of these printers, an end area of the image forming area may be determined based on the print data, and a light absorption layer may be formed in the end area. Thereby, like the embodiment mentioned above, the visual feeling of thickening can be suppressed.

<About nozzle>
In the above-described embodiment, ink is ejected using a piezoelectric element (piezo element). However, the method for discharging the liquid is not limited to this. For example, other methods such as a method of generating bubbles in the nozzle by heat may be used.

<About processing of computer 110>
The computer 110 described above performs resolution conversion processing, color conversion processing, halftone processing, light absorption layer generation processing, and the like. However, some or all of these processes may be performed on the printer 1 side. When the light absorption layer generation process performed by the computer 110 is performed instead on the printer side, the printer 1 can print the image subjected to the light absorption layer generation process alone on the medium. This corresponds to “printing device”. In this case, the controller 60 corresponds to a control unit.

<About light absorption layer>
In the above-described embodiment, the light absorption layer is formed with black dots of black ink, but the present invention is not limited to this. For example, the light absorbing layer may be formed of a composite black using cyan ink, magenta ink, and yellow ink. However, the black color of the black ink absorbs light more than the black color of the composite. Therefore, the use of the black ink as in the above-described embodiment further suppresses the feeling of thickening (making the swell less noticeable). Can do.

  In the above-described embodiment, the light absorption layer is formed in black. However, the present invention is not limited to this, and any color that absorbs light may be used. For example, the light absorption layer may be formed in gray using gray ink. Even in this case, a feeling of thickness can be suppressed.

  In the above-described embodiment, the light absorption layer is formed in the edge region of the image. However, the formation location of the light absorption layer is not limited to the edge region. For example, when a specific position (center, etc.) of an image is raised depending on the shape of the printing material, a light absorption layer may be formed on the raised portion. By doing so, it is possible to suppress the thick feeling of the swelled portion.

1 printer,
10 transport unit, 11 paper feed roller, 13 transport roller,
14 platen, 15 paper discharge roller,
20 carriage unit, 21 carriage,
22 Carriage motor, 24 guide shaft,
30 head units, 31 heads,
40 irradiation unit, 42a, 42b irradiation unit,
50 detector groups, 51 linear encoders,
53 Paper detection sensor, 54 Optical sensor,
60 controller, 61 interface, 62 CPU,
63 memory, 64 unit control circuit 110 computer

Claims (6)

A head unit having a plurality of ejection units that eject a plurality of colors of photocurable ink that is cured by irradiation of light onto a printing material for each ink color, and an irradiation unit that irradiates the printing material with the light;
A moving mechanism for relatively moving the head unit and the printing material;
The movement mechanism is controlled to move the head unit and the printing material relative to each other, selectively eject the plurality of colors of the photocurable ink from the plurality of ejection units, and land on the printing material. A control unit for irradiating the light curable ink with the light from the irradiation unit;
A printing apparatus for printing an image on the printing material,
The control unit forms a black or gray light absorption layer on a rising portion of the image by using at least one of the plurality of ejection units. The printing apparatus according to claim 1,
The printing apparatus according to claim 1, wherein the raised portion of the image is an edge region of the edge of the image. The printing apparatus according to claim 1 or 2,
The controller is
By controlling the discharge amount of the photocurable ink from each discharge portion, a plurality of types of dots having different sizes are formed on the printing material,
Forming the light absorbing layer using the smallest dot of the plurality of types of dots;
A printing apparatus characterized by that. The printing apparatus according to any one of claims 1 to 3,
The printing apparatus according to claim 1, wherein the light absorbing layer is formed by discretely arranging black dots on the raised portion of the image. The printing apparatus according to any one of claims 1 to 4,
The plurality of ejection units eject a first ejection unit that ejects the photocurable ink for forming a main image, and a first ejection unit that ejects the photocurable ink for forming an auxiliary image that assists the main image. 2 discharge parts,
The control unit controls the ejection of the photocurable ink from the first ejection unit and the second ejection unit to form the main image and the auxiliary image so as to overlap each other on the printing material, The printing apparatus is characterized in that the light absorption layer is formed on the rising portions of the main image and the auxiliary image. Printing provided with a head unit having a plurality of ejection units that eject a plurality of color curable inks that are cured by light irradiation onto a printing material for each ink color, and an irradiation unit that irradiates the printing material with the light A printing method for printing an image on the printing material by an apparatus,
A relative movement step of relatively moving the head portion and the printing material;
The plurality of colors of the photocurable ink is selectively discharged from the plurality of discharge units that move relative to the printing material, and the light is applied from the irradiation unit to the photocurable ink that has landed on the printing material. An image forming process of irradiating
Using at least one of the plurality of ejection portions that move relative to the printing material, a black or gray light absorbing layer is formed on the raised portion of the image, and the light absorbing layer is irradiated with the light from the irradiation unit. A light absorption layer forming step of irradiating light;
A printing method characterized by comprising:

Images