JP5845691B2 - Printing apparatus and printing method - Google Patents

Description

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

  2. Description of the Related Art There is known a printing apparatus that prints an image by ejecting a liquid such as ink from a head unit and landing droplets (dots) on a medium. As a printing apparatus, for example, there is an ink jet printer that ejects a photocurable ink (for example, UV ink) that is cured by irradiation with light such as ultraviolet rays (UV). A method of fixing the UV ink dots on the medium by ejecting UV ink from the nozzles onto the medium using such an ink jet printer and then curing the UV ink dots formed on the medium by irradiating with light. Is widely known. (For example, patent document 1).

JP 2000-158793 A

  In the method of Patent Document 1, the UV ink dots ejected on the medium are cured with light, so that the occurrence of bleeding (bleeding) between the UV ink dots is suppressed, and an image with good image quality is easily formed.

  However, there is a problem that unevenness occurs in glossiness in an image printed using UV ink by an inkjet printer. One possible cause of uneven glossiness is a difference in the amount of ink (also referred to as duty) per unit area ejected onto the medium. That is, a gloss difference is generated between a high gradation portion and a low gradation portion of the printed image, and this gloss difference becomes uneven. For example, when printing an image of a person's face, the gloss level may be low in a portion having a low gradation value such as skin color and a small amount of ink (low duty). On the contrary, the glossiness may increase in a portion such as a pupil where the gradation value is high and the amount of ink is large (high duty). As a result, unevenness in glossiness occurs depending on the part of the face, making it difficult to form an image with good image quality.

  In particular, in a so-called line head type printing apparatus in which the head portion is configured by a plurality of small heads arranged in the width direction of the medium, ink ejection characteristics may differ for each head that prints each line. In such a case, uneven glossiness is generated for each line, and the image quality of the printed image tends to deteriorate.

  It is an object of the present invention to reduce uneven glossiness generated for each line and form an image with good image quality when printing using UV ink in a line head type printer having a plurality of small heads. It is said.

  The main invention for achieving the above object is to arrange a first head that discharges color ink that is cured by light irradiation on a medium that is conveyed in the conveying direction, the first head and the conveying direction. A second head that discharges clear ink that is cured by light irradiation on the medium; a head unit that includes a plurality of head sets in a direction intersecting the transport direction; and an irradiation unit that irradiates the light. A printing unit that prints an image by forming dots by the color ink and dots by the clear ink in a band that is a region in which ink is ejected for each head set. The color duty, which is the amount per unit area of the color ink ejected from the first head, and the unit area of the clear ink ejected from the second head The relationship between the ink discharge amount represented by the clear duty that is the amount of the ink and the glossiness of the image printed by the discharged color ink and the clear ink is stored in the storage unit for each band, and The clear duty is determined according to the color duty for each band based on the relationship stored for each band so that the glossiness of an image printed for each band becomes a predetermined value. This is a printing apparatus.

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

It is a schematic diagram about the glossiness nonuniformity in the image printed with the inkjet printer using photocurable ink. It is a figure showing the relationship between the density of the ink on a medium, and glossiness. 1 is a block diagram illustrating an overall configuration of a printer. FIG. 2 is a schematic side view illustrating a configuration of the printer 1. FIG. 5A is a diagram illustrating the arrangement of a plurality of short heads in the color ink heads 31 to 34 and the clear ink head 35 of the head unit 30. FIG. 5B is a diagram illustrating the state of the nozzle rows arranged on the lower surface of each head. It is a figure showing an example of the relationship between color Duty and glossiness. FIG. 7 is a diagram illustrating the glossiness of an image when the color duty and the clear duty are changed in FIG. 6. It is a figure showing the flow of an inspection process. It is a figure showing an example of the test pattern printed. It is a figure showing the whole flow of the printing process of 1st Embodiment. FIG. 4 is a diagram illustrating a flow of processing performed by a printer driver in color image processing. FIG. 6 is a diagram illustrating a flow of processing performed by a printer driver in clear image processing. It is a figure explaining the method of determining clear duty with respect to color duty. It is a figure showing the whole flow of the printing process of 2nd Embodiment. It is a figure explaining the method of determining clear duty in 2nd Embodiment. It is a figure explaining the method to determine clear duty in the modification of 2nd Embodiment.

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

A first head that discharges color ink that is cured by light irradiation on a medium that is transported in the transport direction, the first head that is aligned with the first head in the transport direction, and the medium that is cured by light irradiation. A head unit having a plurality of head sets each having a second head that discharges clear ink in a direction intersecting the transport direction, an irradiation unit that irradiates the light, and a storage unit. A printing apparatus that prints an image by forming dots by the color ink and dots by the clear ink in a band that is a region where ink is ejected, and the color ejected from the first head Expressed by the color duty that is the amount per unit area of ink and the clear duty that is the amount per unit area of the clear ink ejected from the second head. The relationship between the ink discharge amount and the glossiness of the image printed by the discharged color ink and clear ink is stored in the storage unit for each band, and the gloss of the image printed for each band The printing apparatus, wherein the clear duty is determined for each band according to the color duty based on the relationship stored for each band so that the degree becomes a predetermined value.
According to such a printing apparatus, when printing is performed using UV ink in a line head type printer having a plurality of small heads, glossiness unevenness generated for each line (band) is reduced, and good image quality is achieved. Images can be formed.

In this printing apparatus, the relationship stored for each band is such that when an image having a predetermined glossiness is printed, a corresponding clear duty exists in all ranges where the color duty varies. And a second relationship in which a corresponding clear duty does not exist in a predetermined range in which the color duty varies, and the clear duty corresponding to a certain color duty is the first relationship. When there are a plurality of clear duties based on the second relation, a value based on the first relation among the plurality of clear duties is determined as a clear duty used when printing for each band. It is desirable.
According to such a printing apparatus, the difference in graininess and texture of the printed image is less noticeable, and a higher quality image can be printed.

In this printing apparatus, the relationship stored for each band is such that when an image having a predetermined glossiness is printed, a corresponding clear duty exists in all ranges where the color duty varies. And a second relationship in which a corresponding clear duty does not exist in a predetermined range in which the color duty varies, and the clear duty corresponding to a certain color duty is the first relationship. When there are a plurality of clear duties based on the second relationship, it is preferable that a minimum value among the plurality of clear duties is determined as a clear duty used when printing for each band.
According to such a printing apparatus, the amount of clear ink ejected at the time of printing can be reduced as much as possible, so that the printing cost can be reduced.

In this printing apparatus, the relationship stored for each band is such that when an image having a predetermined glossiness is printed, a corresponding clear duty exists in all ranges where the color duty varies. And a second relationship in which a corresponding clear duty does not exist in a predetermined range in which the color duty varies, and the clear duty used at the time of printing is determined based on the second relationship. In this case, in a range where there is no clear duty corresponding to the color duty, it is desirable to set the clear duty used when printing for each band to zero.
According to such a printing apparatus, it is possible to print an image in which the deterioration of the image is not noticeable while reducing the amount of the clear ink ejected at the time of printing as much as possible.

In such a printing apparatus, a test pattern having a plurality of types of patches formed for each band while changing a color duty and a clear duty using the printing apparatus was measured for each of the plurality of types of patches. It is preferable that the relationship is obtained for each band by examining a combination of the color duty and the clear duty when the glossiness reaches a predetermined magnitude based on the glossiness.
According to such a printing apparatus, the relationship between the ink discharge amount represented by the color ink duty and the clear ink duty and the glossiness is clarified, and an image having a good image quality with little uneven glossiness for each band is formed. It becomes easy to do.

  In addition, the color ink that is cured by light irradiation from the first head is discharged onto the medium transported in the transport direction, and the second head aligned with the first head in the transport direction transmits light to the medium. This is a region in which clear ink that is cured by irradiation is ejected and the light is irradiated, and ink is ejected for each head set including the first head and the second head. A printing method for printing an image by forming dots by the color ink and dots by the clear ink in a band, the amount per unit area of the color ink ejected from the first head The ink discharge amount represented by the color duty and the clear duty that is the amount per unit area of the clear ink discharged from the second head, and before the discharge Based on the relationship between the glossiness of the image formed by the color ink and the clear ink, the color duty for each band is set so that the glossiness of the image printed for each band becomes a predetermined value. The printing method is characterized by determining the clear duty accordingly.

=== Overview ===
<Glossiness of image>
First, the glossiness of a printed image will be described. The glossiness of an image depends on the state of reflected light from the medium with respect to external light. For example, if the reflected light is in a scattered state, the glossiness is low, so-called “matte”. On the contrary, if it is close to regular reflection, a high glossiness is obtained, which is a so-called “gross tone”. As described above, in the inkjet printer using the photocurable ink, unevenness occurs in the glossiness of the printed image. Schematically, the gloss level depends on the amount of ink ejected per unit area on the medium, that is, the ink droplet ejection amount. In the present specification, the amount of ink ejected per unit area is also referred to as “ink duty”.

  FIG. 1 shows a schematic diagram of uneven glossiness in an image printed by an ink jet printer using photocurable ink. For example, when a person's face is printed as an image, a part such as a cheek has a light skin color. In the light color printing region, the amount of ink droplets (ink droplets) d shot is small. Then, as shown in FIG. 1A, each ink drop d is cured by light such as ultraviolet rays (UV), so that each ink drop d on the medium S does not blur and has an independent island shape that approximates a hemisphere. It becomes a shape. That is, the density of the ink droplet d is “sparse”. For this reason, the light incident on the surface of the medium S (open arrow in the figure) is reflected in various directions on the surface of the island-shaped ink droplet d (solid arrow in the figure). That is, it becomes diffuse reflection.

  On the other hand, as shown in FIG. 1B, a dark color portion such as a pupil is expressed by solidly painting the image region. That is, in the image area, adjacent ink droplets d are arranged densely, and even if each ink droplet d is hemispherical, the state is the same as when the film-shaped ink covers the medium S. Therefore, the incident light is almost regularly reflected on the surface of the film-like ink, and the glossiness is increased. Therefore, in a human face or the like, the skin portion such as the cheek is matte tone and the pupil portion is glossy tone, and the glossiness is not uniform, resulting in an unnatural image.

  The above is the outline of the cause of occurrence of uneven glossiness. However, the mechanism of occurrence of glossiness unevenness schematically shown in FIG. 1 is a model simplified to some extent. Actually, glossiness unevenness does not simply depend only on the density of the ink droplet d. Absent. FIG. 2 shows the relationship between the density of ink on the medium S and the glossiness. This figure shows the relationship between the amount of ink (volume) per unit area on the medium S and the glossiness measured using a known glossiness meter (gross checker). When the ink amount is extremely small, the glossiness of the medium S is reflected, and when the ink amount increases, the diffuse reflection component due to the sparsely arranged ink droplets d increases and the glossiness decreases. When the ink amount per unit area exceeds a predetermined amount, the regular reflection component is relatively increased and the glossiness is increased. Further, since the glossiness of the medium S itself varies depending on the type, the relationship between the ink amount and the glossiness becomes more complicated in applications where different types of medium S are used properly.

<Outline of this embodiment>
As described above, in a printer using photocurable ink, gloss unevenness occurs due to the density of ink droplets on the medium. Moreover, since the density of ink droplets and glossiness are not in a simple proportional relationship, even if a surface-treated medium such as glossy paper or matte paper is used, the glossiness changes only uniformly over the entire image. Thus, uneven glossiness on the same medium cannot be solved. Although it is conceivable to modify the ink, it is necessary to optimize the physical properties related to the glossiness of the ink itself without impairing the original characteristics of the photocurable ink that can suppress bleeding. Furthermore, it is necessary to optimize an ink ejection method suitable for the physical properties. Therefore, much time and cost are required for the development, research and development of the ink itself and peripheral technologies such as ejection control.

  Therefore, in the present embodiment, a print image is formed using ink for printing an image (color ink) and an ink for adjusting the glossiness of the image (clear ink), and the occurrence of uneven gloss is lined up. Suppress every time. Specifically, each line on which an image is formed is formed on a medium by appropriately changing the clear ink discharge amount (clear ink duty) according to the color ink discharge amount (color ink duty). The glossiness of the image to be printed is adjusted for each line. Details of the discharge amount of each ink and the image processing method when actually printing will be described later.

=== Basic Configuration of Printing Apparatus ===
A line printer (printer 1) will be described as an example of a printing apparatus used in the present embodiment.

<Configuration of Printer 1>
The printer 1 is a printing apparatus that records an image by ejecting a liquid such as ink toward a medium such as paper, cloth, or film sheet. The printer 1 is an ink jet printer. However, the ink jet printer may be an apparatus that employs any discharge method as long as it is a printing apparatus that can print by discharging ink.

  The printer 1 prints an image on a medium by ejecting ink that is cured by irradiating light such as ultraviolet rays (hereinafter, UV), for example, ultraviolet curable ink (hereinafter, UV ink). The UV ink is an ink containing an ultraviolet curable resin, and is cured by undergoing a photopolymerization reaction in the ultraviolet curable resin when irradiated with UV. In printing using UV ink, it is easy to control the degree of curing of the ink dots formed on the medium and the shape of the ink dots by controlling the UV irradiation amount and irradiation timing. Therefore, as described above, it is possible to form an image with a good image quality by suppressing the occurrence of bleeding that occurs between UV ink dots. Further, by forming dots by curing the UV ink, it is possible to perform printing even on a medium that does not have an ink receiving layer and does not absorb ink.

  Note that the printer 1 according to the present embodiment uses four color inks of black (K), cyan (C), magenta (M), and yellow (Y) as a UV ink, and a colorless and transparent clear ink (CL ) To print the image.

  FIG. 3 is a block diagram showing the overall structure of the printer 1. The printer 1 includes a transport unit 20, a head unit 30, an irradiation unit 40, a detector group 50, and a controller 60. The controller 60 is a control unit that controls each unit such as the head unit 30 and the irradiation unit 40 based on print data received from the computer 110 that is an external device. 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.

<Computer 110>
The printer 1 is communicably connected to a computer 110 that is an external device. A printer driver is installed in the computer 110. The printer driver is a program for causing a display device to display a user interface and converting image data output from an application program into print data. This printer driver is recorded on a recording medium (computer-readable recording medium) such as a flexible disk FD or a CD-ROM. Also, the printer driver can be downloaded to the computer 110 via the Internet. In addition, this program is comprised from the code | cord | chord for implement | achieving various functions.

  The computer 110 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. The print data is data in a format that can be interpreted by the printer 1 and includes various command data and pixel data. The command data is data for instructing the printer 1 to execute a specific operation. The command data includes, for example, command data for instructing medium supply, command data indicating the transport amount of the medium, and command data for instructing medium ejection. The pixel data is data related to pixels of an image to be printed.

  Here, a pixel is a unit element constituting an image, and an image is formed by arranging these pixels two-dimensionally. Pixel data in the print data is data (for example, gradation values) related to dots formed on a medium (for example, paper S). The pixel data is composed of, for example, 2-bit data for each pixel. The 2-bit pixel data is data that can express one pixel with four gradations.

<Transport unit 20>
FIG. 4 is a schematic side view showing the configuration of the printer 1 of the present embodiment.
The transport unit 20 is for transporting a medium in a predetermined direction (hereinafter referred to as a transport direction). The transport unit 20 includes a transport roller 23A on the upstream side in the transport direction, a transport roller 23B on the downstream side in the transport direction, and a belt 24 (FIG. 4). When a transport motor (not shown) rotates, the upstream transport roller 23A and the downstream transport roller 23B rotate, and the belt 24 rotates. The medium supplied by a medium supply roller (not shown) is transported to a printable area (area facing a head unit 30 described later) by the belt 24. The medium that has passed through the printable area is discharged to the outside by the belt 24. Note that the medium being conveyed is electrostatically attracted or vacuum attracted to the belt 24.

<Head unit 30>
The head unit 30 is for ejecting UV ink onto a medium. The head unit 30 forms ink dots by ejecting color (KCMY) and clear (CL) inks onto the medium being conveyed, and prints an image on the medium.

  In the printer 1 shown in FIG. 4, color ink heads 31 to 34 are provided in order from the upstream side in the transport direction. The color ink head includes a first color ink head 31 (hereinafter also referred to as the first head 31), a second color ink head 32 (hereinafter also referred to as the second head 32), and a third color ink head 33 (hereinafter referred to as the first head 31). And a fourth color ink head 34 (hereinafter also referred to as a fourth head 34). In the present embodiment, black ink (K) from the first head 31, cyan ink (C) from the second head 32, magenta ink (M) from the third head 33, and yellow ink (Y from the fourth head 34). ). However, it is arbitrary which color ink each of the color ink heads 31 to 34 ejects. For example, the first head 31 ejects yellow ink (Y) and the second head 32 ejects black ink (B). You may make it discharge. In addition to the color ink heads 31 to 34, a color ink head that discharges ink of a color other than the above-described KCMY (for example, light cyan or metallic color) may be provided. Further, the first head 31 and the second head 32 may eject the same color ink. For example, both the first head 31 and the second head 32 may eject cyan ink (C).

  A clear ink head 35 for discharging colorless and transparent clear (CL) UV ink is provided on the downstream side in the transport direction of the color ink head 34. Here, the clear (CL) ink is an ink generally referred to as “clear ink” which does not contain or contains a color material. Hereinafter, the clear ink head 35 is also referred to as a fifth head 35.

  Each head is composed of a plurality of short heads, and each short head includes a plurality of nozzles that are ejection openings for ejecting UV ink.

  FIG. 5A is a diagram illustrating the arrangement of a plurality of short heads in the color ink heads 31 to 34 and the clear ink head 35 of the head unit 30. FIG. 5B is a diagram for explaining the state of the nozzle rows arranged on the lower surface of each short head. 5A and 5B are diagrams in which the nozzle is virtually seen from the upper surface.

  In the first head 31, eight short heads 31 </ b> A to 31 </ b> H are arranged in a staggered pattern along the width direction of the medium that is a direction intersecting the medium conveyance direction. Similarly, in the second head 32, eight short heads 32A to 32H are arranged in a staggered pattern along the width direction. The same applies to the third head 33, the fourth head 34, and the fifth head 35. In the example of FIG. 5A, each head is composed of eight short heads, but the number of short heads constituting each head may be more or less than eight.

  The eight short heads of each head are arranged so that their positions are aligned in the width direction of the medium. That is, the nth short head 31n of the first head, the nth short head 32n of the second head, the nth short head 33n of the third head, the nth short head 34n of the fourth head, The nth short head 35n of the fifth head is provided at the same position in the width direction. These five short heads are defined as the nth “head set”. In FIG. 5A, eight head groups A to H are formed. An image is formed in an area having a predetermined width in the medium width direction by ejecting UV ink from each head set onto the medium to form dots. This region is called a “band”. For example, an area corresponding to the head set A composed of (31A, 32A, 33A, 34A, 35A) is a band A, and KCMY color ink is ejected from the short heads 31A to 34A, respectively, and clear ink is ejected from the short head 35A. By discharging, an image is formed in the band A region. Similarly, an image is formed in the band B to band H by ejecting ink from the corresponding head group (B to H). In this way, an image to be printed (entire image) is formed by the bands A to H arranged in the medium width direction.

  A plurality of nozzle rows are formed in each short head (FIG. 5B). The nozzle row includes 180 nozzles that eject ink, and the nozzles are arranged at a constant nozzle pitch (for example, 360 dpi) from # 1 to # 180 along the width direction of the medium. In the case of FIG. 5B, two nozzle rows are arranged in parallel, and the nozzles of each nozzle row are provided at positions shifted by 720 dpi in the medium width direction. The number of nozzles in one row is not limited to 180. For example, 360 nozzles may be provided in one row, or 90 nozzles may be provided. Further, the number of nozzle rows provided in each short head is not limited to two rows.

  Each nozzle is provided with an ink chamber and a piezoelectric element (both not shown) which are piezoelectric elements. The piezo element is driven by a drive signal COM generated by the unit control circuit 64. Then, the ink chamber expands and contracts and expands by driving the piezo element, whereby the ink filled in the ink chamber is ejected from the nozzle.

  In the printer 1, a plurality of types of ink droplets having different sizes (different ink amounts) can be ejected from each nozzle depending on the magnitude of a pulse applied to the piezo element in accordance with the drive signal COM. For example, from each nozzle, there are three types of ink consisting of large ink droplets capable of forming large dots, medium ink droplets capable of forming medium dots, and small ink droplets capable of forming small dots. Can be discharged. Then, by intermittently ejecting ink droplets from each nozzle to the medium being transported, each nozzle forms a dot line (raster line) along the medium transport direction.

<Irradiation unit 40>
The irradiation unit 40 irradiates UV toward the UV ink dots landed on the medium. The dots formed on the medium are cured by receiving UV irradiation from the irradiation unit 40. The irradiation unit 40 of this embodiment includes an irradiation unit 41.

  The irradiation unit 41 is provided on the downstream side in the transport direction of the clear ink head 35 (FIG. 4), and UV for curing the UV ink dots formed on the medium by the color ink heads 31 to 34 and the clear ink head 35. Irradiate. The length of the irradiation unit 41 in the medium width direction is equal to or greater than the medium width.

  In the present embodiment, the irradiation unit 41 includes a light emitting diode (LED) as a light source for UV irradiation. The LED can easily change the irradiation energy by controlling the magnitude of the input current. Moreover, you may use light sources other than LED, such as a metal halide lamp, as the irradiation part 41. FIG. The light source of the irradiation unit 41 is isolated from the clear ink head 35 (and the color ink heads 31 to 34) by being accommodated in the irradiation unit 41. This prevents the UV light emitted from the light source from leaking to the lower surface of the clear ink head 35, so that the UV ink is cured in the vicinity of the opening of each nozzle formed on the lower surface, so that the nozzles are clogged. Is suppressed from occurring.

  In FIG. 4, the irradiation unit 40 includes only one irradiation unit 41 on the most downstream side in the transport direction. However, the irradiation unit 41 may be provided downstream of each color ink head. At that time, the irradiation unit 42 (not shown) is further provided on the most downstream side in the transport direction, and the UV ink dots are cured in two steps by irradiating UV from the irradiation unit 41 and the irradiation unit 42. It may be. For example, UV is irradiated from the irradiation unit 41 with energy sufficient to cure (temporarily cure) the surface of the UV ink dots, and the entire UV ink dots are cured (completely cured) from the irradiation unit 42 at the final stage of medium conveyance. Irradiate with UV energy. As a result, the degree of cure of the UV ink dots is adjusted, and when the UV ink dots are ejected from each head, there is a problem that the landing positions of the dots are shifted due to the repelling of the UV ink dots having a high degree of cure. It can also be difficult.

<Detector group>
The detector group 50 includes a rotary encoder (not shown), a medium detection sensor (not shown), and the like. The rotary encoder detects the rotation amount of the upstream side conveyance roller 23A and the downstream side conveyance roller 23B. The transport amount of the medium can be detected based on the detection result of the rotary encoder. The medium detection sensor detects the position of the front end of the medium being supplied.

<Controller>
The controller 60 is a control unit (control unit) for controlling the printer. The controller 60 includes an interface unit 61, a CPU 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 device for performing overall control of the 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 is configured by a storage element such as a RAM or an EEPROM. Then, the CPU 62 controls each unit such as the transport unit 20 via the unit control circuit 64 in accordance with a program stored in the memory 63.

<Image printing operation>
An image printing operation by the printer 1 will be briefly described.
When the printer 1 receives print data from the computer 110, the controller 60 first rotates a medium supply roller (not shown) by the transport unit 20 and sends the medium to be printed onto the belt 24. The medium is conveyed on the belt 24 without stopping at a constant speed, and passes under the head unit 30 and the irradiation unit 40.

In the meantime, the color ink (KCMY) is intermittently ejected for each head group of the color ink heads 31 to 34, thereby forming characters and images composed of color ink dots for each band on the medium. Further, the clear ink (CL) is intermittently ejected for each head set of the clear ink head 35 to form clear ink dots at predetermined pixels in each band. Then, the color ink dots and the clear ink dots are cured by irradiating UV from the irradiation unit 41 of the irradiation unit 40. Thereby, an image along the medium conveyance direction is printed for each band, and the entire image is printed by arranging the images (images printed for each band) in the medium width direction.
Finally, the controller 60 discharges the medium on which image printing has been completed.

=== Relationship between Ink Duty and Glossiness ===
<Relationship between color duty and clear duty>
According to the relationship between the discharge amount per unit area of color ink that forms an image (hereinafter also referred to as color duty) and the discharge amount per unit area of clear ink that adjusts glossiness (hereinafter also referred to as clear duty), How the glossiness of the image changes will be described.

  FIG. 6 is a diagram illustrating an example of the relationship between the color duty and the glossiness. The horizontal axis of the figure represents the discharge amount (color duty) per unit area of the color ink, and the vertical axis of the figure represents the magnitude of the glossiness of the image formed by the color ink (and clear ink).

First, a line drawn by a thick solid line in FIG. 6 is obtained when an image is printed while changing an ejection amount (color duty) per unit area using only ink for forming an image (here, color ink). Represents the glossiness of the image. In FIG. 6, when the size of the color duty is (X), the glossiness of the print image is represented by G (X). When printing is performed using only color ink, the relationship between the color duty and the glossiness of the image is the same as that described with reference to FIG. For example, when X = 0% (color duty is zero), the gloss value of the medium itself is indicated as G (0) = 55. Then, will gradually glossiness G with an increase in color Duty (X) (X) is small, glossiness G _{(X O)} is minimum when predetermined color Duty value = the _{X O%.} Thereafter, the glossiness G (X) gradually increases as the color duty (X) increases. When only color ink is used in this way, the magnitude of the glossiness G (X) of the part is determined by the color duty value (= X%) in a part of the image. In other words, since the glossiness is determined by the color gradation value in the portion (pixel) constituting the image, a difference in the glossiness is generated for each portion having a different gradation in the formed image.

  Therefore, the glossiness of the entire image is adjusted by further discharging a predetermined amount of clear ink in addition to the color ink for each region (portion) of the image. It is assumed that the glossiness of the print image is represented by G (X, Y) where the size of the clear duty is (Y) and the size of the color duty is (X).

  For example, the glossiness of the image when X = 0 is G (0) = 55, but the glossiness can be changed by discharging clear ink. In FIG. 6, by changing the clear duty (Y) in the range of 0 to 100%, the glossiness G (0, Y) of the image can be changed in the range of 30 to 85. Similarly, the glossiness G (X, Y) of the image can be changed within a predetermined range by changing the clear duty (Y) for the color duty (X) having a predetermined size.

  In FIG. 6, a colored region surrounded by a broken line represents a range of the magnitude of the glossiness measured from an image formed with color ink and clear ink. The broken line on the upper side of the drawing represents the upper limit Gmax (X, Y) of glossiness that can be reproduced by changing the clear duty value (Y) with respect to a predetermined color duty value (X). A broken line on the lower side of the figure represents a lower limit Gmin (X, Y) of glossiness that can be reproduced by changing the clear duty value (Y) with respect to a predetermined color duty value (X). That is, by appropriately adjusting the values of color duty (X) and clear duty (Y), the glossiness of the image can be freely adjusted within the colored region of FIG. In the case of FIG. 6, regardless of the value of the color duty (X), by adjusting the size of the clear duty (Y), an image can be formed in the glossy range of 30 to 70. Can do.

  FIG. 7 is a diagram illustrating the glossiness of an image when the color duty and the clear duty are changed in FIG. In the figure, the vertical axis represents the clear duty, and the horizontal axis represents the color duty. The curves drawn like contour lines in the figure represent the magnitude of glossiness. That is, FIG. 7 shows the relationship between the color ink discharge amount per unit area and the clear ink discharge amount per unit area (total amount of ink duty) and the glossiness of the image formed thereby. Represents. For example, when the color ink is ejected so that the color duty is (X1) when printing the image, the clear duty is (Y1) or (Y Clear ink may be ejected so that Y2). Conversely, when the clear duty is (Y1), the color duty necessary for printing an image with a glossiness level of 30 is (X1) or (X2).

  If the relationship as shown in FIG. 7 is clear, an image having a desired glossiness can be printed by appropriately selecting the size of the clear duty (Y) with respect to the color duty (X).

=== First Embodiment ===
In the present embodiment, two processes of an inspection process and a printing process are performed, and an image is printed while adjusting the size of the clear duty with respect to the color duty for each band. First, in the inspection process, the relationship corresponding to FIG. 7 is obtained for each head set and stored in the printer 1. In other words, the relationship between the total amount of the color duty and the clear duty and the glossiness of the image is obtained and stored for each band. Then, based on the relationship obtained in the inspection process, color image processing and clear image processing are performed so that the desired glossiness is obtained in the printing process, and the image is printed while adjusting the discharge amount of the clear ink with respect to the color ink. . Details of each step will be described below.

<Inspection process>
In the inspection process, a test pattern having a plurality of types of patches formed by changing the color duty and the clear duty (that is, changing the gradation value) is printed for each head set using the printer 1. That is, a test pattern is printed for each band. Then, the glossiness of each of the plurality of test patterns is measured for each patch, and the combination of the color duty and the clear duty when the glossiness becomes a predetermined magnitude is examined. Thus, the relationship between the color duty and the clear duty for forming an image having a certain glossiness is obtained for each band, and the relationship is stored in a storage medium such as the memory 63. FIG. 8 shows a flow chart of the inspection process. The inspection process is performed by executing the processes of S101 to S104.

  Since the same operation (S101 to S104) is performed for each band in the inspection process, only a certain band (for example, band A in FIG. 5A) will be described in this specification.

  First, a test pattern is printed (S101). The test pattern is formed by printing a plurality of patches using color ink (KCMY) and clear ink (CL). FIG. 9 shows an example of a test pattern to be printed. The test pattern has a plurality of types of rectangular patches that are formed while changing the size of the clear duty while keeping the color duty constant by each head set. For example, in FIG. 9, when the color duty is set to 1%, the heads in charge of the bands A to H are changed while the clear duty is changed to 6 levels of 1%, 20%, 40%, 60%, 80%, and 100%. Six types of patches are formed for each group. Next, the same test pattern is printed for the color duty = 20%, and the same test pattern is printed while changing the color duty = 40%, 60%, 80%, and 100%. In the example of FIG. 9, since the color duty value is changed in six stages, six types of test patterns are printed. Note that the numbers given to the patches in FIG. 9 are for convenience, and it is not necessary to actually print such numbers, and the arrangement and shape of the patches are not limited to the example of FIG. Further, the number of test patterns and the number of patches are arbitrary, and the more the patches are formed by narrowing the change width of each ink duty, the more accurately the relationship between the ink duty and the glossiness can be obtained.

  Since the glossiness of the printed image is affected by the glossiness of the medium itself, the test pattern is printed on the same medium as that used for actual printing. When printing on a plurality of types of media, the inspection process operation (S101 to A104) is performed for each medium used for printing.

  In this embodiment, printing is performed using four color inks of KCMY. Therefore, when the tone values of all the colors of KCMY are 255 in the area (pixel) where the color ink is ejected, the color duty = 100%. It is converted so that

  In FIG. 9, the test patterns are formed by simultaneously discharging the four color inks of KCMY and the clear ink. However, the test patterns may be formed for the respective colors of KCMY. That is, a test pattern as shown in FIG. 9 may be formed separately for each color of KCMY. In that case, the discharge amount of the clear ink is individually adjusted with respect to the discharge amount of each color ink of KCMY in the printing process described later. For example, the duty of the clear ink (CL) corresponding to the duty of the black ink (K) is determined for each predetermined area in the image, and the duty of the clear ink (CL) corresponding to the duty of the cyan ink (C) is separately set. Determined.

  After the test pattern is printed, the glossiness of each patch is measured using the above-described glossmeter (S102). Based on the measurement result of each patch, the relationship between the magnitude of glossiness and the color duty and clear duty is obtained (S103). That is, when printing on a certain medium using the printer 1, the sizes of the color duty and the clear duty for forming an image having a predetermined glossiness are checked. As a result, the relationship between the ink ejection amount represented by the color duty and the clear duty and the glossiness of the image printed by the ejected color ink and clear ink becomes clear for each band.

  For example, assume that the glossiness of the fifth patch is measured as 50 in band A in FIG. In this case, it means that the glossiness of an image printed using the head set A with color duty = 1% and clear duty = 80% is 50. For other test patterns, the glossiness is measured in the same way. In band A, when the color duty is 20%, the clear duty is 60%, and when the color duty is 40%, the clear duty is 20%. Suppose the glossiness is measured as 50. Thus, by measuring the glossiness of the patch for each band, the combination of the color duty and the clear duty for forming an image with a glossiness of 50 using the head set corresponding to the band becomes clear. 9 is a diagram (a diagram corresponding to FIG. 7) showing the relationship between the ink discharge amount represented by the color duty and the clear duty and the glossiness of the image from all the data measured for each patch in FIG. It is obtained for the band (S103). The obtained relationship is stored in the memory 63 of the printer 1 (S104).

  The inspection process reveals the relationship between the color duty and the clear duty for printing an image having a target glossiness for each band when printing an image on a certain medium.

<Printing process>
Processing that is actually performed in the printer 1 when executing printing will be described.
In the printing process, an image is printed using the printer 1 under the user so as to achieve a desired gloss level (so that gloss unevenness is reduced). The print image is formed by ejecting color ink for each predetermined region for each band. Then, the amount of clear ink discharged based on the relationship obtained in the inspection process is discharged with respect to the discharge amount (color duty) per unit area of the color ink. Adjusted.

  FIG. 10 shows the overall flow of the printing process of this embodiment. The printing step includes a glossiness setting step (S200) for setting the glossiness of an image to be printed, a color image processing step (S210) for performing processing for printing an image by discharging color ink, and the color From the clear image processing step (S250) for determining the discharge amount of the clear ink for each region according to the ink discharge amount, and the image formation processing step (S280) for actually discharging the color ink and the clear ink to form an image. Become.

(S200: Glossiness setting)
First, the user sets the gloss level (target gloss level) of an image to be printed (S200). For example, on the user interface (not shown), items such as matte tone (glossiness: about 30), semi-glossy tone (glossiness: about 50), and glossy tone (glossiness: about 70) can be displayed and selected. Keep it. Further, the gloss level may be input as a numerical value. The glossiness setting (S200) is performed for the entire printed image, but the glossiness may be set separately for each band as necessary. The glossiness may be set after color image processing (S210) described later.

(S210: Color image 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 1. 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. FIG. 11 is a diagram showing a flow of processing performed by the printer driver in color image processing.

  First, processing (resolution conversion processing) for converting image data (text data, image data, etc.) output from the application program into a resolution (printing resolution) for printing on a medium is performed (S211). 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 each gradation (for example, 256 gradations) represented by the RGB color space.

  Next, color conversion processing for converting RGB data into data in the CMYK color space is performed (S212). The image data in the CMYK color space is data corresponding to the ink color of the printer. 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 data are associated with each other.

  The pixel data after the color conversion processing is 8-bit CMYK data with 256 gradations represented by the CMYK color space. Since the data is also used in the clear image processing (S250) described later, it is copied and temporarily stored in the memory 63 or the like.

  Next, halftone processing is performed to convert the high gradation number data into the gradation number data that can be formed by the printer (S213). For example, data representing 256 gradations is converted into 1-bit data representing 2 gradations or 2-bit data representing 4 gradations by halftone processing. In the halftone process, a dither method, a γ correction, an error diffusion method, or the like is used. The data subjected to the halftone process has a resolution equivalent to the print resolution (for example, 720 × 720 dpi). The image data after halftone processing corresponds to 1-bit or 2-bit pixel data for each pixel, and this pixel data is data indicating the dot formation status (presence / absence of dot, dot size) in each pixel. Become.

  Thereafter, rasterization processing is performed in which the pixel data arranged in a matrix is rearranged for each pixel data in the order of data to be transferred to the printer 1 (S214). For example, the pixel data is rearranged according to the arrangement order of the nozzles in each nozzle row.

  Command addition processing for adding command data corresponding to the printing method to the rasterized data is performed (S215). The command data includes, for example, conveyance data indicating the medium conveyance speed.

(S250: Clear image processing)
Subsequently, clear image processing for discharging clear ink for adjusting the glossiness of the image is performed for each band. FIG. 12 is a diagram illustrating a flow of processing performed by the printer driver in clear image processing.

  First, the printer driver copies the color image print data after the color conversion process (S212) in the color image processing step, and obtains it as data for clear image processing (S251). In the clear image processing, data for ejecting clear ink is generated based on the data.

  Next, using the acquired color image data, a gradation value of clear ink is set for each region (pixel) for forming an image (S252). In other words, by setting a clear gradation value for each predetermined area in the image, the amount of clear ink (clear duty) discharged to the area is determined. Here, for the sake of explanation, the unit area is assumed to be one pixel.

  As described above, the image data after the color conversion process is 8-bit CMYK data represented by 256 gradations of each color 0 to 255 for each pixel. The printer driver selects a certain pixel A of the target band in the image and calculates the color duty at the pixel A. The color duty is calculated from the total value of the gradation values of the four KCMY colors. For example, when the gradation value of K is 128, the gradation value of C is 64, the gradation value of M is 128, and the gradation value of Y is 64 for the pixel A, the color duty is (128 + 64 + 128 + 64) / (255 + 255 + 255 + 255) × It is calculated that 100 = 37.6%.

  Here, although the tone value and the actual ink discharge amount are strictly different amounts, the tone value and the ink duty are handled in correspondence with each other in view of the following points. That is, in the above-described halftone process, the gradation value of 256 gradations is converted into the gradation value of 4 gradations (or 2 gradations) for each color, and ink is ejected based on the data of 4 gradations. become. At this time, if the gradation value before the halftone process is large (for example, the gradation value is 255), the gradation value after the halftone process is likely to be large (for example, the gradation value is 3), and the ink discharge amount may be large. High nature. Conversely, if the gradation value before halftone processing is small (for example, the gradation value is 1), the gradation value after halftone processing tends to be small (for example, the gradation value is 0), and the ink ejection amount can be small. High nature. Therefore, the amount of color ink ejected per unit area (color duty) can be considered as corresponding to the gradation value of 256 gradations.

  As described above, when the relationship between the color duty and the clear duty (relationship corresponding to FIG. 7) is obtained for each color of KCMY in the inspection process, the color duty is calculated for each color of KCMY.

  Then, the relationship between the color duty and the clear duty for each band stored in the memory 63 in the inspection process is read, and the clear in pixel A is set so that the glossiness set in the glossiness setting process (S200) is obtained. Determine the duty. Thereby, a clear gradation value (discharge amount) in the pixel A is determined. It is assumed that the clear gradation value is 255 when the clear duty = 100%.

  FIG. 13 is a diagram for specifically explaining a method of determining a clear duty for a color duty. The relationship shown in FIG. 13 corresponds to the relationship described in FIG.

  In the inspection process, the relationship between each ink duty and glossiness as shown in FIG. 13 is obtained. For example, the target glossiness is set to 30, and the color duty for a certain pixel A is calculated to be 37.6%. Suppose that In this case, from FIG. 13, the clear duty = 62.0% corresponding to the color duty = 37.6% on the curve (contour line) of glossiness 30 is determined as the clear duty value for the pixel A. When the glossiness is set to 40 or the like, the clear duty value obtained from the curve of glossiness 30 and the clear duty value obtained from the curve of glossiness 50 for the color duty = 37.6%. By performing the interpolation, a clear duty value used at the time of printing is calculated.

  In the above description, the clear duty is determined for each pixel, but the clear duty is determined for each region formed by a plurality of pixels during actual printing. For example, the color duty in the area is calculated from the average of the color gradation values in the area of 10 × 10 pixels, and the clear duty corresponding to the calculated color duty is determined. Then, according to the determined clear duty, the clear ink is ejected to the area (10 × 10 pixel area). Thereby, the processing speed of the clear image processing can be increased as compared with the processing for each individual pixel.

  Thereafter, as in the case of color image processing, halftone processing (S253), rasterization processing (S254), and command addition processing (S255) are executed. Clear image processing ends.

(S280: Image formation processing)
According to the print data of the color image and the clear image generated by the above-described processes, each color ink is actually ejected for each head set. That is, a color image is formed by ejecting color ink onto a medium according to print data of a color image. Then, according to the set clear duty, an image with less uneven glossiness can be printed by discharging a predetermined amount of clear ink for each unit region over the color image.

<Summary of First Embodiment>
In the first embodiment, the relationship between the ink ejection amount expressed by the color ink duty and the clear ink duty and the glossiness of the image formed by the ejected color ink and clear ink is obtained for each band. Then, based on the obtained relationship, a clear duty corresponding to the color duty is determined so as to form an image having a desired glossiness, and ink (color ink and clear ink) is ejected from each head set.
Thereby, when printing using UV ink, it is possible to form an image with good image quality with little uneven glossiness over the entire printed image.

=== Second Embodiment ===
In the second embodiment, the discharge amount (clear duty) per unit area of the clear ink is determined in consideration of other factors while adjusting the unevenness of the glossiness of the printed image. Specifically, the clear duty for the color duty is determined for each band in the printing process in consideration of the image quality and the amount of ejected ink in addition to the glossiness of the print image.

  The operation for obtaining the relationship between the color duty, clear duty, and glossiness for each band in the inspection process is the same as that in the first embodiment. In this embodiment, the relationship corresponding to FIG. The description will be made assuming that The configuration of the printing apparatus itself is the same as that of the printing apparatus 1 described in the first embodiment. Hereinafter, a description will be given focusing on differences from the first embodiment.

<Printing process of the second embodiment>
FIG. 14 shows the overall flow of the printing process of the second embodiment. In the present embodiment, after the glossiness setting step (S200), the printing mode is set (S205).

  The print mode can be selected from, for example, an image quality priority mode (first mode) that prioritizes image quality improvement of the printed image, and an ink amount saving mode (second mode) that reduces the amount of ejected ink as much as possible. Each mode is selected by the user. The mode is selected through a user interface (not shown). Note that the order of setting the gloss level (S200) and the setting of the print mode (S205) may be switched.

  Subsequently, color image processing (S210), clear image processing (S250), and image formation processing (S280) are performed. The color image processing in the second embodiment is the same as that in the first embodiment (see FIG. 11). On the other hand, in the clear image processing (see FIG. 12) for generating data for ejecting a predetermined amount of clear ink to a predetermined area, the clear duty determination method (S252) is different from that of the first embodiment. Details of the clear duty determination method will be described later. After the clear duty is determined for each region in S252, the same processing as in the first embodiment is performed (S253 to S255), and finally color ink and clear ink are ejected to form an image.

<Determination of clear duty>
In the determination of the clear duty in the second embodiment (S252), an optimal clear duty value is determined according to the mode set in S205. That is, a different clear duty value may be determined depending on the selected mode.

  FIG. 15 is a diagram for explaining points to be considered when determining the clear duty. In the figure, the vertical axis represents the size of the clear duty, and the horizontal axis represents the size of the color duty (unit is%). The curve in the figure represents the relationship between color duty and clear duty when printing an image with glossiness L. The curve has two curves, an upper curve Lu and a lower curve Ld. The upper curve Lu is drawn continuously without interruption between 0% and 100% of the color duty value. That is, the relationship is such that a clear duty value corresponding to the color duty value exists in the entire range (0% to 100%) in which the color duty value varies (this is the first relationship).

  On the other hand, the lower curve Ld has a discontinuous portion in which the color duty value is interrupted in the interval from B% to D%. That is, the relationship is such that there is no clear duty value corresponding to the color duty value in a predetermined range (B% to D%) in which the color duty value varies (a second relationship).

  In FIG. 15, when the color duty is A%, the clear duty corresponding to the color duty (A%) for printing an image with a glossiness L is A1% (point on the curve Lu) or A2% (curve There are two types of possibilities (points on Ld). In other words, there are a plurality of clear duties corresponding to the color duty. On the other hand, when the color duty is C% belonging to the discontinuous portion of the curve Ld in order to form an image with glossiness L, the corresponding clear duty is only C1% (a point on the curve Lu). . In other words, there is only one clear duty corresponding to the color duty.

  That is, when an image having a predetermined glossiness is printed, there are a case where only one clear duty value used at the time of printing is determined for a certain color duty value and a case where a plurality of clear duty values can be selected. Even when images having the same glossiness are printed, the image quality of the print image and the amount of ejected ink change greatly due to the difference in the clear duty value.

  For example, when the color duty in two areas in the print image is A% and C%, respectively, the clear duty is determined based on the first relationship (curve Lu in FIG. 15). . That is, the clear duty corresponding to the color duty = A% is A1%, and the clear duty corresponding to the color duty = C% is C1%. In this case, the variation range of the clear duty between the two regions is along the curve Lu, which is a relatively gradual variation (C1-A1).

  Next, when trying to determine the clear duty based on the above-described second relationship (curve Ld in FIG. 15), the clear duty corresponding to the color duty = A% is A2%. On the other hand, since the clear duty corresponding to the color duty = C% does not exist on the curve Ld, the curve Lu is inevitably referred to and the clear duty = C1% is set. In this case, the variation range of the clear duty between the two regions becomes large (C1-A2).

  As described above, when the clear duty value is greatly different in each region in the image, a difference in image quality may occur in each place.

<When priority is given to image quality improvement>
First, a description will be given of a case where it is desired to improve the image quality of a printed image for each band while suppressing occurrence of uneven glossiness (when the first mode is selected).

  As described above, when the fluctuation range of the clear duty increases between the two areas, a difference appears in the image quality of the printed image. Here, the image quality refers to graininess or texture on the surface of the printed image. The graininess represents the degree of roughness of the entire image. For example, if the ink dots (particles) formed on the medium are too large, the individual particles stand out and give the impression that the image is rough. Therefore, if the fluctuation range of the clear duty in the two regions is large, the difference in the size of the clear ink dot between the two regions tends to be noticeable, and the graininess may appear different. Also, the texture of the image is a feeling that is received due to the difference in the properties of the ink material. For example, the properties of clear ink and color ink differ depending on the presence or absence of pigments or color materials (coloring materials), and therefore the texture may look different at portions where the color duty and clear duty are extremely different on the printed image surface. . Therefore, if the variation range of the clear duty in the two regions is large, the amount of clear ink dots formed between the two regions is also different, so that the difference in texture becomes conspicuous and the image quality is deteriorated.

  Therefore, in the first mode, the clear duty corresponding to the color duty is determined for each band so that the unevenness of the graininess and the texture is less likely to occur while suppressing the uneven glossiness of the image, thereby improving the quality of the printed image. Plan.

  Specifically, based on the first relation (a relation corresponding to the curve Lu in FIG. 15) that can set the corresponding clear duty in the entire range of the color duty, the clear duty used in actual printing. Is determined. For example, in the case of printing an image with the target glossiness L in FIG. 15, in a color duty = C% area (area Q), a clear duty value = C1% is selected and a color duty = A% area ( In the area P), the clear duty value = A1% is selected.

  If A2% (see FIG. 15) is selected as the clear duty value in the region P, the variation in the clear duty between the region Q and the image quality is likely to be noticeable. However, by selecting Clear Duty = A1% in the area P, it is possible to print with higher image quality while minimizing the variation of the clear duty between the two areas as much as possible and suppressing uneven gloss (unified glossiness L). realizable.

  According to this method, the discharge amount of the clear ink tends to increase, and the printing cost may increase. However, in the first mode, priority is given to improving the image quality, so that the variation in the clear duty is set to be small regardless of the amount of clear ink discharged.

<To save ink amount>
Next, a case where the glossiness of the entire image is adjusted and the discharge amount of clear ink is desired to be reduced for each band (when the second mode is selected) will be described.

  As described with reference to FIG. 15, when there is a possibility that a plurality (two in FIG. 15) of clear duty values for realizing the target glossiness for a certain color duty value may be set, the second mode Then, a clear duty is set for each band so that the discharge amount of the clear ink is reduced. That is, the smallest value among the plurality of clear duties is determined as the clear duty used in actual printing. For example, when an image is printed with the target glossiness L in FIG. 15, when the color duty in a certain area in the image is A%, the clear duty is set to A2% instead of A1% (A1> A2 ).

  According to this method, the variation of the clear duty becomes large, and the image quality of the printed image may be deteriorated. However, in the second mode, the amount of clear ink that is ejected can be reduced, so that the printing cost can be reduced.

<Summary of Second Embodiment>
In the second embodiment, the first mode in which clear ink is ejected so as to achieve an excellent image quality while forming an image with less uneven glossiness for each band, and the image is ejected while forming an image with less uneven glossiness. The second mode that saves the amount of clear ink to be used is selected for printing.
Thereby, it is possible to print a user-preferred image according to the printing application.

<Modification of Second Embodiment>
In the example described above, the first mode and the second mode have been described, but other modes may be selected. In the first mode, the image quality of the printed image can be improved while the ink discharge amount is increased. In the second mode, the ink discharge amount can be saved, while the image quality of the printed image may be deteriorated. Therefore, as a modified example of the second embodiment, a mode (third mode) that improves image quality and saves clear ink discharge amount while minimizing the uneven glossiness of each band as much as possible will be described.

  FIG. 16 is a diagram illustrating a clear duty determination method according to a modification of the second embodiment. FIG. 16 is basically the same as FIG. 15, and the upper curve Lu represents the first relationship described above, and the lower curve Ld represents the second relationship described above. Accordingly, the clear duty value corresponding to the same color duty value is lower in the second relationship (curve Ld) than in the first relationship (curve Lu).

  When printing an image with the target gloss level set to L, in the third mode, printing is basically performed based on the second relationship (curve Ld) in which the clear duty value is low in order to save the discharged clear ink. The clear duty value used at times is determined. For example, in FIG. 16, when the color duty is A%, the clear duty is determined as A2% from the curve Ld. However, when the clear duty is to be determined based on the second relationship, there is no corresponding clear duty when the color duty is in the range of B% to D%, so the clear duty value used for printing may be determined. Can not. Therefore, the CPU 62 sets the clear duty value to zero in the range of the color duty value (B% to D%).

That is, the clear duty value of the curve Ld is regarded as zero in the discontinuous portion of the curve Ld (the color duty is in the range of B% to D%).

  This means that a clear duty value that does not fall on the glossiness L curve (curve Ld) is set, and an image with glossiness L cannot be formed in that area. That is, the glossiness is different between the area P where the color duty = A% and the area Q where the color duty = C%, which may cause uneven glossiness. However, if the difference in glossiness is equal to or less than a predetermined magnitude (for example, 20), the gloss unevenness is hardly recognized when the image is visually recognized by the human naked eye, so that it is difficult to look as if the image quality has deteriorated. That is, in the third mode, by allowing uneven glossiness within a range where the gloss difference for each image area is inconspicuous, an image in which the deterioration in image quality is not noticeable while saving the clear ink discharge amount is saved. Can be printed.

=== Other Embodiments ===
Although the printer 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 printing devices>
In each of the above-described embodiments, a printer has been described as an example of a printing apparatus, but the present invention is not limited to this. For example, color filter manufacturing apparatus, dyeing apparatus, fine processing apparatus, semiconductor manufacturing apparatus, surface processing apparatus, three-dimensional molding machine, liquid vaporizer, organic EL manufacturing apparatus (especially polymer EL manufacturing apparatus), display manufacturing apparatus, film formation The same technology as that of the present embodiment may be applied to various printing apparatuses to which inkjet technology such as a device and a DNA chip manufacturing apparatus is applied.

<Nozzle trains>
In the above-described embodiment, an example in which an image is formed using four colors of KCMY and clear ink has been described. However, the present invention is not limited to this. For example, an image may be recorded using inks of colors other than KCMY and CL, such as light cyan, light magenta, and white.
The order of arrangement of the nozzle rows in the head portion is also arbitrary. For example, the order of the nozzle rows for K and C may be switched, or the number of nozzle rows for K ink may be greater than the number of nozzle rows for other inks.

<About piezo elements>
In each of the above-described embodiments, the piezo element PZT is exemplified as an element that performs an operation for discharging a liquid. However, other elements may be used. For example, a heating element or an electrostatic actuator may be used.

1 Printer 1, 20 Transport unit,
23A upstream conveyance roller, 23B downstream conveyance roller,
24 belts, 30 head units,
31-34 Color ink head, 35 Clear ink head,
40 irradiation units, 41 irradiation units, 50 detector groups,
60 controller, 61 interface, 62 CPU,
63 memory, 64 unit control circuit,
110 computer

Claims (10)

A first head that discharges color ink that is cured by light irradiation on a medium that is transported in the transport direction, the first head that is aligned with the first head in the transport direction, and the medium that is cured by light irradiation. A head unit having a plurality of head sets each having a second head that ejects clear ink in a direction intersecting the transport direction;
An irradiation unit for irradiating the light;
A storage unit,
A printing apparatus for printing an image by forming dots by the color ink and dots by the clear ink in a band which is a region where ink is ejected for each head set;
Ink represented by a color duty that is an amount per unit area of the color ink ejected from the first head and a clear duty that is an amount per unit area of the clear ink ejected from the second head Storing the relationship between the ejection amount and the glossiness of an image printed with the ejected color ink and clear ink in the storage unit for each band;
In order that the glossiness of the image printed for each band becomes a predetermined value,
The printing apparatus, wherein the clear duty is determined according to the color duty for each band based on the relationship stored for each band. The printing apparatus according to claim 1,
Among the relationships stored for each band, the ink discharge amount represented by the color duty and the clear duty is the entire range in which the color duty varies when an image having a predetermined glossiness is printed. In the first relationship in which the corresponding clear duty exists and the clear duty corresponding in the predetermined range does not exist in all the ranges in which the color duty fluctuates, and the corresponding clear duty in the range other than the predetermined range. A second relationship in which
When there are a plurality of clear duties corresponding to a color duty of a certain size based on the first relation and the second relation,
A printing apparatus, wherein a value based on the first relationship among a plurality of the clear duties is determined as a clear duty used when printing for each band. The printing apparatus according to claim 1,
Among the relationships stored for each band, the ink discharge amount represented by the color duty and the clear duty is the entire range in which the color duty varies when an image having a predetermined glossiness is printed. In the first relationship in which the corresponding clear duty exists and the clear duty corresponding in the predetermined range does not exist in all the ranges in which the color duty fluctuates, and the corresponding clear duty in the range other than the predetermined range. A second relationship in which
When there are a plurality of clear duties corresponding to a color duty of a certain size based on the first relation and the second relation,
A printing apparatus, wherein a minimum value among the plurality of clear duties is determined as a clear duty used when printing for each band. The printing apparatus according to claim 1,
Among the relationships stored for each band, the ink discharge amount represented by the color duty and the clear duty is the entire range in which the color duty varies when an image having a predetermined glossiness is printed. In the first relationship in which the corresponding clear duty exists and the clear duty corresponding in the predetermined range does not exist in all the ranges in which the color duty fluctuates, and the corresponding clear duty in the range other than the predetermined range. A second relationship in which
When the clear duty used at the time of printing is determined based on the second relationship,
In the predetermined range where there is no clear duty corresponding to the color duty, the clear duty used when printing for each band is set to zero. The printing apparatus according to claim 1, wherein
About a test pattern having a plurality of types of patches formed for each band while changing the color duty and clear duty using the printing apparatus,
Based on the glossiness measured for each of the plurality of types of patches,
By examining the combination of the color duty and the clear duty when the glossiness becomes a predetermined size,
The printing apparatus is characterized in that the relationship is obtained for each band. Discharging a color ink that is cured by light irradiation from a first head onto a medium transported in a transport direction;
Discharging clear ink that is cured by light irradiation to the medium from the first head and the second head aligned in the transport direction;
Irradiating the light, and
Printing that prints an image by forming dots by the color ink and dots by the clear ink in a band that is a region where ink is ejected by a head set having the first head and the second head A method,
Ink represented by a color duty that is an amount per unit area of the color ink ejected from the first head and a clear duty that is an amount per unit area of the clear ink ejected from the second head Based on the relationship between the ejection amount and the glossiness of the image formed by the ejected color ink and the clear ink,
The way glossiness of images printed bands becomes a predetermined value, the printing method characterized by determining the clear Duty in accordance with the prior SL color Duty.   A first head that discharges color ink that is cured by light irradiation on a medium that is transported in the transport direction, the first head that is aligned with the first head in the transport direction, and the medium is cured by light irradiation. A second head that ejects clear ink;
  An irradiation unit for irradiating the light;
  A storage unit,
  Printing that prints an image by forming dots by the color ink and dots by the clear ink in a band that is a region where ink is ejected by a head set including the first head and the second head A device,
  Ink represented by a color duty that is an amount per unit area of the color ink ejected from the first head and a clear duty that is an amount per unit area of the clear ink ejected from the second head Storing the relationship between the ejection amount and the glossiness of an image printed by the ejected color ink and the clear ink in the storage unit;
  The clear duty is determined according to the color duty based on the relationship stored in the storage unit so that the glossiness of an image printed on the band becomes a predetermined value. Printing device to do.   The printing apparatus according to claim 7, wherein
  Among the relationships stored in the storage unit, the ink discharge amount represented by the color duty and the clear duty is the entire range in which the color duty varies when an image having a predetermined glossiness is printed. In the first relationship in which the corresponding clear duty exists and the clear duty corresponding in the predetermined range does not exist in all the ranges in which the color duty fluctuates, and the corresponding clear duty in the range other than the predetermined range. A second relationship in which
  When there are a plurality of clear duties corresponding to a color duty of a certain size based on the first relation and the second relation,
  A printing apparatus, wherein a value based on the first relationship among a plurality of the clear duties is determined as a clear duty used when printing the band.   The printing apparatus according to claim 7, wherein
  Among the relationships stored in the storage unit, the ink discharge amount represented by the color duty and the clear duty is the entire range in which the color duty varies when an image having a predetermined glossiness is printed. In the first relationship in which the corresponding clear duty exists and the clear duty corresponding in the predetermined range does not exist in all the ranges in which the color duty fluctuates, and the corresponding clear duty in the range other than the predetermined range. A second relationship in which
  When there are a plurality of clear duties corresponding to a color duty of a certain size based on the first relation and the second relation,
  The printing apparatus, wherein a minimum value among the plurality of clear duties is determined as a clear duty used when printing the band.   The printing apparatus according to claim 7, wherein
  Among the relationships stored in the storage unit, the ink discharge amount represented by the color duty and the clear duty is the entire range in which the color duty varies when an image having a predetermined glossiness is printed. In the first relationship in which the corresponding clear duty exists and the clear duty corresponding in the predetermined range does not exist in all the ranges in which the color duty fluctuates, and the corresponding clear duty in the range other than the predetermined range. A second relationship in which
  When the clear duty used at the time of printing is determined based on the second relationship,
  In the predetermined range where there is no clear duty corresponding to the color duty, the clear duty used when printing the band is set to zero.