JP2013215886A - Inkjet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To record an image of high quality by suppressing irregularity caused by landing interference, using simple nozzle arrangement.SOLUTION: An inkjet recording device includes an inkjet head having three or more nozzle arrays for injecting curable inks cured by application of activation energy from nozzles which are arranged at a predetermined pitch in a first direction, and the three or more nozzle arrays for injecting mutually different curable inks, wherein in the three or more nozzle arrays, as for a plurality of nozzle arrays other than a first nozzle array for injecting the curable ink which is the lowest in curing sensitivity, the positions of the respective nozzles in the first direction match, and as for the first nozzle array, the positions of the respective nozzles in the first direction displace from the positions of the respective nozzles of the plurality of nozzle arrays by a predetermined amount.

Description

  The present invention relates to an ink jet recording apparatus, and more particularly to a technique for forming an image by discharging a plurality of types of inks having different curing sensitivities.

  2. Description of the Related Art There is known a serial type inkjet recording apparatus that performs recording while scanning an inkjet head that ejects a plurality of colors of ink in a direction (main scanning direction) orthogonal to a recording medium conveyance direction (sub-scanning direction). In such an ink jet recording apparatus, an arrangement in which nozzles of respective colors are arranged on the same line in the main scanning is used in order to make the droplet ejection position for each color common.

  In recent years, not only permeable media such as paper but also non-permeable (hardly permeable) media such as resin films have been used, and actinic rays are applied to the curable ink deposited on the media. An ink jet recording apparatus that is cured by irradiation is proposed.

  In the nozzle arrangement described above, since all color dots are arranged on the same line in one main scan, landing interference occurs in the main scan direction. Therefore, when curable ink is used, actinic rays are irradiated in a state where landing interference occurs in the main scanning direction, and a line-shaped surface shape is formed in the main scanning direction. As a result, there is a problem that uneven gloss in the sub-scanning direction is visually recognized due to a slight difference in shape of the unevenness of the line.

  In order to deal with such a problem, Patent Document 1 describes a technique in which the positions of the nozzles of the heads of all colors are arranged in a discrete manner. According to this technique, ink droplets of a plurality of colors are not recorded on the same line in one main scan, and landing interference can be avoided.

Japanese Patent Laid-Open No. 2003-48318

  However, the technique of Patent Document 1 has a problem that assembly and adjustment are difficult because the nozzle arrangement is complicated.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an ink jet recording apparatus that can suppress unevenness due to landing interference and record a high-quality image using a simple nozzle arrangement. And

  In order to achieve the above object, one aspect of an ink jet recording apparatus includes three or more nozzle rows that discharge curable ink that is cured by application of active energy from nozzles arranged at a predetermined pitch in a first direction. An inkjet head having three or more nozzle rows that discharge different curable inks, and an active energy applying unit that applies active energy to the ink droplets ejected from the nozzles and ejected onto the recording surface of the recording medium And a holding unit that holds the inkjet head and the active energy applying unit along a second direction orthogonal to the first direction, and relatively scans the holding unit and the recording medium in the second direction. Scanning means, a moving means for moving the holding means and the recording medium relative to each other in the first direction for each scan by the scanning means, and a holding means. Three or more nozzle rows, comprising: a control unit that forms an image on the recording surface of the recording medium while causing the ink jet head and the active energy applying unit to scan each area of the recording medium a predetermined number of times. Is the position of each nozzle in the first direction for a plurality of nozzle rows other than the first nozzle row that ejects the curable ink with the lowest curing sensitivity, and for the first nozzle row, The position of each nozzle in the first direction is shifted by a predetermined amount from the position of each nozzle in the plurality of nozzle rows.

  According to this aspect, the three or more nozzle rows that discharge different curable inks included in the inkjet head are a plurality of nozzle rows other than the first nozzle row that discharges the curable ink having the lowest curing sensitivity. The positions of the nozzles in the first direction are the same, and for the first nozzle row, the positions of the nozzles in the first direction are shifted from the positions of the nozzles in the plurality of nozzle rows by a predetermined amount. Since each of the ink droplets ejected while being scanned in the second direction by the scanning means is arranged such that the ink having the lowest curing sensitivity is shifted in the first direction, the interference in the second direction. Since the interference in the first direction can be increased, the anisotropy of the surface shape can be relaxed and the unevenness in the second direction can be improved.

  The three or more nozzle rows are four nozzle rows that discharge yellow, magenta, cyan, and black curable inks, respectively, and the curable ink having the lowest curing sensitivity may be black curable ink. This aspect can be applied to a head that discharges four color curable inks of YMCK.

  The control means deposits ink droplets onto each area of the recording medium in a predetermined droplet ejection order to form an image with a predetermined pixel pitch, and the predetermined amount is equal to the droplet ejection sequence in the first direction. It is preferable that the pitch is 1 pixel pitch or more and 2 pixel pitch or less in the traveling direction. Thereby, the nonuniformity by landing interference can be suppressed appropriately.

  It is preferable that the active energy applying unit applies the active energy to such an extent that the ink droplets deposited on the recording surface of the recording medium are incompletely cured in one scan by the scanning unit. This embodiment is particularly effective when the ink droplets that have been ejected are not immediately cured.

  You may provide the 2nd active energy provision means which carries out the main hardening of the ink droplet by further providing active energy with respect to the ink droplet to which active energy was provided by the active energy provision means. As a result, the ink droplets that have been ejected can be properly cured.

  The holding means preferably holds the second active energy applying means on the downstream side of the moving means of the inkjet head. As a result, the ink droplets that have been ejected can be properly cured.

  The holding means preferably holds the active energy applying means on both sides in the second direction of the inkjet head. Thereby, the ejected ink droplet can be appropriately temporarily cured.

  The active energy may be ultraviolet light. This embodiment can be applied to an ink jet recording apparatus using an ultraviolet curable ink.

  The control means preferably completes the image by one or two scans by the scanning means for one pixel line in the second direction. This aspect is particularly effective when the interval between ink droplets ejected by one scan is close.

  Preferably, the control unit causes the ink droplet ejection positions in the second direction by the plurality of nozzle rows to coincide with the ink droplet ejection positions in the second direction by the first nozzle row. By controlling the ink droplet ejection position in this manner, an image can be appropriately formed.

  Image processing means for correcting image data to be formed on the recording surface of the recording medium based on the displacement between the nozzle positions of the first nozzle array and the nozzle positions of a plurality of nozzle arrays other than the first nozzle array is provided. It is preferable. Thereby, it is possible to correct a color shift caused by shifting the position of the nozzle.

  According to the present invention, since the interference in the main scanning direction can be reduced and the interference in the sub scanning direction can be increased by using a simple nozzle arrangement, the anisotropy of the surface shape is reduced and unevenness in the sub scanning direction is reduced. Can be improved. Therefore, a high quality image can be recorded.

Schematic top view of the ink jet recording apparatus 100 Magnified schematic diagram of a conventional inkjet head Diagram for explaining the interlace method Diagram for explaining conventional dot formation Magnified schematic diagram of ink jet head of this embodiment The figure for demonstrating dot formation in the case of d <p The figure for demonstrating dot formation in case of d> 2p The figure for demonstrating dot formation in the case of p <= d <= 2p The figure which shows the droplet ejection order which concerns on an Example, and an evaluation result External perspective view of an inkjet recording apparatus according to another embodiment Explanatory drawing schematically showing the recording medium conveyance path Plane perspective view showing an example of the arrangement of the temporary curing light source and the main curing light source Block diagram showing the configuration of an ink supply system of an ink jet recording apparatus Block diagram showing the configuration of an inkjet recording apparatus

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[Generation of uneven luster due to conventional technology]
FIG. 1 is a schematic top view of the ink jet recording apparatus 100. The ink jet recording apparatus 100 is configured to be able to scan the ink jet head 110, a curing light source 116, a carriage 118 (an example of a holding unit) on which the ink jet head 110 and the curing light source 116 are mounted, and the carriage 118 in the Y direction (main scanning direction). A carriage scanning mechanism (not shown, an example of scanning means), and a recording medium transport mechanism (not shown, an example of moving means) configured to move the recording medium 120 in the X direction (sub-scanning direction).

  FIG. 2 is an enlarged schematic diagram of the inkjet head 110. The inkjet head 110 includes four heads 112K, 112C, 112M, and 112Y (an example of three or more nozzle rows). The four heads 112K, 112C, 112M, and 112Y are ultraviolet curable ink (UV curable ink, an example of curable ink that is cured by application of active energy), black ink (black ink), cyan ink, magenta ink, and yellow. A plurality of nozzles 114K, 114C, 114M, and 114Y for ejecting ink are provided.

  Here, among the four colors of black ink, cyan ink, magenta ink, and yellow ink, the black ink has the lowest curing sensitivity with respect to the wavelength of the ultraviolet rays emitted from the curing light sources 116R and 116L. Here, the curing sensitivity refers to the amount of energy required for complete curing when the ink droplets are cured by irradiating ultraviolet rays, and the lowest curing sensitivity is required for complete curing. It means that the amount of energy is the largest.

  The plurality of nozzles 114K of the head 112K are arranged in a line at equal intervals along the sub-scanning direction. Similarly, the plurality of nozzles 114C of the head 112C, the plurality of nozzles 114M of the head 112M, and the plurality of nozzles 114Y of the head 112Y are arranged in a line at equal intervals along the sub-scanning direction. Here, the pitch of the nozzles 114 of each color head 112 is 100 dpi.

  The nozzles 114K, 114C, 114M, and 114Y are arranged on the same straight line parallel to the main scanning direction.

  The inkjet head 110 is scanned in the main scanning direction by scanning of the carriage 118, and ejects ink from the nozzles 114 of the respective color heads 112 according to the control of the ejection control means (not shown), whereby the recording surface of the recording medium 120 is ejected. Ink droplets of each color ink are formed (droplet ejection).

  The recording medium 120 is conveyed (scanned) by a predetermined amount in the sub-scanning direction by the recording medium conveying mechanism each time the inkjet head 110 is reciprocated in the main scanning direction.

  The curing light source 116 (an example of an active energy application unit) includes a plurality of UV-LEDs. In this UV-LED, the ink droplets of the respective color inks ejected from the respective color heads 112 onto the recording medium 120 are irradiated with ultraviolet rays to be incompletely cured (semi-cured).

  The ink droplets ejected onto the recording medium 120 are not completely cured by a single UV irradiation by the curing light source 116, but are in a semi-cured state. Here, the semi-cured state refers to a cured state from when the ink starts to be cured until it reaches the main cured state. The ink droplets in the semi-cured state are then irradiated with ultraviolet rays from a main curing light source (not shown) to be in a main cured state, and an image is recorded on the recording surface of the recording medium 120. Note that the fully cured state refers to a state where ink droplets are cured to such an extent that the image does not deteriorate even when the recording medium 120 is handled. That is, the main curing does not necessarily mean that the curing reaction has been completed.

  In addition, you may comprise so that it may harden | cure by multiple irradiation of the curing light source 116, without providing a main curing light source.

  FIG. 3 is a diagram for explaining an interlacing method (method of ejecting ink droplets in a predetermined region with a plurality of passes), which is a drawing method of the inkjet recording apparatus 100. The inkjet recording apparatus 100 can perform interlaced drawing by controlling a carriage scanning mechanism, a recording medium transport mechanism, a discharge control unit, and a light source control unit by a control unit (not shown). Here, a description will be given using an example in which printing is executed in a total of 6 passes, ie, 2 passes in the main scanning direction and 3 passes in the sub-scanning direction.

  3 indicates a recording position (pixel group) where ink droplets on the recording surface of the recording medium 120 are to be ejected, and the number of each pixel is the number of passes (in which ink droplets are ejected on that pixel). The order of droplet ejection). Here, the pixel interval (pixel pitch) of the image to be drawn is p.

  In order to perform drawing in this droplet ejection order (an example of a predetermined droplet ejection order), the inkjet head 110 is first scanned in the main scanning direction (first pass). At this time, ink is ejected from each nozzle 114 of each color head 112 (not shown in FIG. 3), and ink droplets of each color are landed on the position “1” of the pixel group 122. That is, in the first pass, droplets are ejected to the even-numbered columns of the sub-scanning columns in the pixel group 122.

  4A is an enlarged schematic view of the heads 112K, 112C, 112M, and 112Y. FIG. 4B is an ink droplet ejected from the nozzle 114 of each color head 112 onto the recording medium 120 in the first pass. It is a schematic diagram which shows 130K, 130C, 130M, 130Y. In FIG. 4B, the ink droplets of the respective colors are shown separately, but in reality, the inks are combined for each pixel to form a combined ink droplet (ink group) 132. Then, the combined ink droplets 132 adjacent in the main scanning direction are connected by landing interference, so that an ink row parallel to the main scanning direction is formed. The landing interference refers to a phenomenon in which the ink droplet shape is deformed and the ink droplet shape collapses due to the combination of adjacent ink droplets on the recording medium immediately after landing.

  The combined ink droplets 132 formed in this way are irradiated with ultraviolet rays by the curing light source 116L. As a result, the combined ink droplets 132 are in a semi-cured state.

  When the first-pass main scanning is completed, the inkjet head 110 is scanned in the reverse direction of the main scanning direction, and the recording medium 120 is conveyed by a predetermined amount in the sub-scanning direction. In FIG. 3, for convenience of explanation, the inkjet head 110 is illustrated by moving a predetermined amount upward in FIG. 3.

  Next, the inkjet head 110 is scanned again in the main scanning direction (second pass). At this time, ink is ejected from each nozzle 114 of each color head 112, and ink droplets of each color are landed on the position “2” of the pixel group 122. That is, in the second pass, each sub-scan column is an even number column, and is adjacent to one pixel (in the sub-scan direction) of the main scan row of the pixel (the position of “1” in the pixel group 122) ejected in the first pass. A droplet is ejected at a position separated by p.

  FIG. 4C is a schematic diagram showing ink droplets 130K, 130C, 130M, and 130Y ejected from the nozzle 114 of each color head 112 onto the recording medium 120 in the second pass. In FIG. 4C, the ink droplets of each color are shown separately, but in the same way as the coalesced ink droplets 132, the inks are actually coalesced for each pixel to form a coalesced ink droplet 134. . The coalesced ink droplets 134 adjacent in the main scanning direction are connected by landing interference, thereby forming an ink row parallel to the main scanning direction.

  The combined ink droplets 134 formed in this way are irradiated with ultraviolet rays from the curing light source 116R. As a result, the combined ink droplets 134 are in a semi-cured state. At the same time, the combined ink droplets 132 are also irradiated with ultraviolet rays to promote curing.

  When the second-pass main scanning is completed, the inkjet head 110 is scanned in the reverse direction of the main scanning direction, and the recording medium 120 is conveyed by a predetermined amount in the sub-scanning direction.

  Further, the inkjet head 110 is scanned in the main scanning direction (third pass). At this time, ink is ejected from each nozzle 114 of each color head 112 and ejected to the position “3” of the pixel group 122. That is, in the third pass, droplets are ejected next to one pixel in the main scanning column, which is an even-numbered column in the sub-scanning column and the pixel deposited in the second pass (position “2” in the pixel group 122). The ink droplets ejected here form a unified ink droplet as before, and are irradiated with ultraviolet rays from the curing light source 116L to be in a semi-cured state.

  Thereafter, similarly, the sub-scanning and the main scanning are repeated, and droplets are sequentially ejected to the positions “4”, “5”, and “6” of the pixel group 122. That is, droplets are ejected in order on the odd-numbered rows of each sub-scanning row.

  Here, a filling direction when a certain region is filled with ink droplets having a certain number of passes by the interlace method is referred to as a traveling direction of the droplet ejection order.

  For example, the ink droplet ejection position for the second pass is downstream in the transport direction (X direction) of the recording medium 120 at the ink ejection position for the first pass. Further, the droplet ejection position in the third pass is the downstream side in the transport direction of the recording medium 120 at the droplet ejection position in the second pass. Similarly, the droplet ejection position of the fifth pass is the downstream side in the transport direction of the recording medium 120 at the droplet ejection position of the fourth pass, and the droplet ejection position of the sixth pass is the recording medium of the droplet ejection position of the fifth pass. 120 on the downstream side in the transport direction.

  Therefore, in the present embodiment, the ink droplet ejection order in the X direction is opposite to the conveyance direction of the recording medium 120.

  In this way, ink droplets are ejected to all pixels of the first swath in 1 to 6 passes. Similarly, ink droplets are ejected to all pixels of the second swath in 2 to 7 passes, and ink droplets are ejected to all pixels of the third swath in 3 to 8 passes.

  FIG. 4D is a schematic diagram showing the surface shape of the recording surface of the recording medium 120 after the completion of the main curing. As shown in the figure, a line shape parallel to the main scanning direction is formed.

  As a result of intensive studies, the inventor of the present application has found that uneven glossiness in the sub-scanning direction can be easily recognized by a slight difference in shape of the line-shaped unevenness.

[Configuration of Inkjet Head According to this Embodiment]
The ink jet recording apparatus according to the present embodiment has the same configuration as that of the ink jet recording apparatus 100 shown in FIG. 1, and a detailed description thereof will be omitted.

  FIG. 5 is an enlarged schematic view of the inkjet head 111 according to the present embodiment. The ink jet head 111 includes four heads 112K, 112C, 112M, and 112Y. The four heads 112K, 112C, 112M, and 112Y have a plurality of nozzles 114K, 114C, 114M, and 114Y for ejecting black ink, cyan ink, magenta ink, and yellow ink, which are UV curable inks, respectively. .

  The plurality of nozzles 114K of the head 112K are arranged in a line at equal intervals along the sub-scanning direction. Similarly, the plurality of nozzles 114C of the head 112C, the plurality of nozzles 114M of the head 112M, and the plurality of nozzles 114Y of the head 112Y are arranged in a line at equal intervals along the sub-scanning direction. The pitch of the nozzles 114 of each color head 112 is 100 dpi.

  Each nozzle 114C, 114M, 114Y is arranged on the same straight line parallel to the main scanning direction. In addition, the nozzles 114K (corresponding to the first nozzle row) that discharge black ink having the lowest curing sensitivity correspond to the nozzles 114C, 114M, and 114Y (corresponding to a plurality of nozzle rows other than the first nozzle row). They are arranged so as to be shifted by a distance d in the traveling direction of the droplet ejection order. You may comprise so that a user can change the distance d suitably.

  The arrangement order of the heads 112K, 112C, 112M, and 112Y is not particularly limited.

  The effect of improving gloss unevenness when printing is performed by the interlace drawing method shown in FIG. 3 using the ink jet head 111 configured as described above, depending on the relationship between the shift amount d and the pixel pitch p. I will explain.

[If d <p]
First, a case where the shift amount d is smaller than the pixel pitch p will be described.

  First, the inkjet head 111 is scanned in the main scanning direction (first pass). At this time, ink is ejected from each nozzle 114 of each color head 112, and ink droplets of each color are landed on the position “1” of the pixel group 122. That is, in the first pass, droplets are ejected to the even-numbered columns of the sub-scanning columns in the pixel group 122. The nozzle 114M of the head 112K is displaced by a distance d in the traveling direction in the droplet ejection order, but ejects droplets by treating the nozzle group 122 as having no displacement with respect to the position “1” of the pixel group 122.

  6A is an enlarged schematic diagram of the heads 112K, 112C, 112M, and 112Y. FIG. 6B is an ink droplet ejected from the nozzle 114 of each color head 112 onto the recording medium 120 in the first pass. It is a schematic diagram which shows 130K, 130C, 130M, 130Y.

  Since the ink droplets 130 </ b> C, 130 </ b> M, and 130 </ b> Y of one pixel are ejected at the same position, the inks are combined to form a combined ink droplet 136.

  Further, since the ink droplet 130K is ejected at a position shifted by the distance d in the traveling direction in the droplet ejection order with respect to the other ink droplets 130C, 130M, and 130Y in the same pixel, the ink droplets 130C, 130M, and 130Y The combined ink droplet 136 is not completely combined, and the ink droplet 130K and the combined ink droplet 136 are connected.

  The combined ink droplet 136 and the ink droplet 130K formed in this way are irradiated with ultraviolet rays by the curing light source 116L. As a result, the combined ink droplet 136 and the ink droplet 130K are in a semi-cured state. Since the ink droplet 130K has a lower curing sensitivity than the coalesced ink droplet 136, the ink droplet 130K is in a semi-cured state with more fluidity.

  When the first-pass main scanning is completed, the inkjet head 111 is scanned in the reverse direction of the main scanning direction, and the recording medium 120 is conveyed by a predetermined amount in the sub-scanning direction.

  Next, the inkjet head 111 is scanned again in the main scanning direction (second pass). At this time, ink is ejected from each nozzle 114 of each color head 112, and ink droplets of each color are landed on the position “2” of the pixel group 122. That is, in the second pass, even in each sub-scan row, adjacent to one pixel (sub-scan) in the main scan row of the dot (dot at the position “1” in the pixel group 122) that was ejected in the first pass. A droplet is ejected at a position separated by p in the direction).

  FIG. 6C is a schematic diagram showing ink droplets 130K, 130C, 130M, and 130Y ejected from the nozzle 114 of each color head 112 onto the recording medium 120 in the second pass.

  Since the ink droplets 130 </ b> C, 130 </ b> M, and 130 </ b> Y of one pixel are ejected at the same position, the inks are combined to form a combined ink droplet 138.

  Further, since the ink droplet 130K is ejected at a position shifted by the distance d with respect to the other ink droplets 130C, 130M, and 130Y in the same pixel, what is the combined ink droplet 136 of the ink droplets 130C, 130M, and 130Y? The ink droplets 130K and the coalesced ink droplets 136 are connected to each other without being completely united.

  The combined ink droplet 138 and the ink droplet 130K formed in this way are irradiated with ultraviolet rays by the curing light source 116L.

  Thereafter, similarly, the sub-scanning and the main scanning are repeated, and droplets are sequentially ejected to the positions “3”, “4”, “5”, and “6” of the pixel group 122.

  Thus, when d <p, the first-pass ink droplet 130K is disposed at a position between the first-pass unified ink droplet 136 and the second-pass unified ink droplet 138. Become. Therefore, there is little interference between the first-pass ink droplet 130K and the second-pass ink droplet 130K. The same applies to the second pass, the third pass, the fourth pass, the fifth pass, the fifth pass, and the sixth pass. As a result, the interference in the main scanning direction remains strong and the gloss unevenness is improved, but the effect is low.

[When d> 2p]
Next, a case where the shift amount d is larger than twice the pixel pitch p (2p) will be described.

  7A is an enlarged schematic diagram of the heads 112K, 112C, 112M, and 112Y. FIG. 7B is an ink droplet ejected from the nozzle 114 of each color head 112 onto the recording medium 120 in the first pass. It is a schematic diagram which shows 130K, 130C, 130M, 130Y.

  Since the ink droplets 130 </ b> C, 130 </ b> M, and 130 </ b> Y of one pixel are ejected at the same position, the inks are combined to form a combined ink droplet 136.

  Further, since the ink droplet 130K is ejected at a position shifted by the distance d in the traveling direction in the droplet ejection order with respect to the other ink droplets 130C, 130M, and 130Y in the same pixel, the ink droplets 130C, 130M, and 130Y It becomes an independent state at a position away from the combined ink droplet 136.

  The combined ink droplet 136 and the ink droplet 130K formed in this way are irradiated with ultraviolet rays by the curing light source 116L. As a result, the combined ink droplet 136 and the ink droplet 130K are in a semi-cured state.

  FIG. 7C is a schematic diagram showing ink droplets 130K, 130C, 130M, and 130Y ejected from the nozzle 114 of each color head 112 onto the recording medium 120 in the second pass.

  Since the ink droplets 130 </ b> C, 130 </ b> M, and 130 </ b> Y of one pixel are ejected at the same position, the inks are combined to form a combined ink droplet 138.

  Further, the ink droplet 130K is in an independent state at a position apart from the combined ink droplets 138 of the ink droplets 130C, 130M, and 130Y.

  The combined ink droplet 138 and the ink droplet 130K formed in this way are irradiated with ultraviolet rays by the curing light source 116L.

  Thus, when d> 2p, the interference pattern is formed independently at the initial stage of image formation (first pass to second pass). Therefore, although uneven gloss is improved, a pattern that easily interferes with the main scanning direction of the ink droplets 130C, 130M, and 130Y (unified ink droplets) remains slightly, and the effect of improving uneven gloss is reduced.

[When p ≦ d ≦ 2p]
Next, a case where the shift amount d is greater than or equal to the pixel pitch p and less than or equal to twice the pixel pitch p (p ≦ d ≦ 2p) will be described.

  8A is an enlarged schematic diagram of the heads 112K, 112C, 112M, and 112Y. FIG. 8B is an ink droplet ejected from the nozzle 114 of each color head 112 onto the recording medium 120 in the first pass. It is a schematic diagram which shows 130K, 130C, 130M, 130Y.

  Since the ink droplets 130 </ b> C, 130 </ b> M, and 130 </ b> Y of one pixel are ejected at the same position, the inks are combined to form a combined ink droplet 136.

  Further, the ink droplet 130K is ejected at a position shifted by a distance d in the traveling direction in the droplet ejection order with respect to the other ink droplets 130C, 130M, and 130Y in the same pixel. Due to the dot diameter of the ink droplet 130K and the dot diameter of the coalesced ink droplet 136, the ink droplet 130K does not completely merge with the coalesced ink droplet 136, and the ink droplet 130K and the coalesced ink droplet 136 are connected. It becomes a state or becomes an independent state at a position away from the united ink droplet 136.

  The combined ink droplet 136 and the ink droplet 130K formed in this way are irradiated with ultraviolet rays by the curing light source 116L. As a result, the combined ink droplet 136 and the ink droplet 130K are in a semi-cured state.

  FIG. 8C is a schematic diagram showing ink droplets 130K, 130C, 130M, and 130Y ejected from the nozzle 114 of each color head 112 to the recording medium 120 in the second pass.

  Since the ink droplets 130 </ b> C, 130 </ b> M, and 130 </ b> Y of one pixel are ejected at the same position, the inks are combined to form a combined ink droplet 138.

  The ink droplet 130K is connected to the combined ink droplets 138 of the ink droplets 130C, 130M, and 130Y, or is in an independent state at a distant position.

  The combined ink droplet 138 and the ink droplet 130K formed in this way are irradiated with ultraviolet rays by the curing light source 116L.

  Thus, in the case of p ≦ d ≦ 2p, the second-pass unified ink droplet 136 is disposed at a position between the first-pass ink droplet 130K and the first-pass unified ink droplet 136. It will be. The same applies to the second pass, the third pass, the fourth pass, the fifth pass, the fifth pass, and the sixth pass. Accordingly, interference in the sub-scanning direction between the ink droplets 130K is induced, and a droplet ejection surface is formed in a state where the ink droplets 130K and the ink droplets 130C, 130M, and 130Y (unified ink droplets) are connected. Interference in the main scanning direction of the ink droplets 130C, 130M, and 130Y is reduced, and the effect of improving gloss unevenness is high.

  For example, in the interlaced drawing method shown in FIG. 3, when the diameter of each ink droplet 130K, 130C, 130M, and 130Y is 80 μm, the gloss is obtained when the shift amount d in the traveling direction in the droplet ejection order is d = 30 to 100 μm. It was confirmed that unevenness was improved satisfactorily.

  When the nozzle arrangement of the inkjet head 111 shown in FIG. 5 is used, the image shift between colors can be corrected by the RIP software or the droplet ejection software on the printer side in units of the pixel pitch p. Only a shift amount (d−p) causes a color shift. However, if the pixel pitch p is sufficiently small, there is no problem in terms of image because it can be suppressed to a shift that cannot be visually recognized.

  In the inkjet head 111 shown in FIG. 5, the nozzles 114K (first nozzle row) that discharge the ink with the lowest curing sensitivity are set to the nozzles 114C, 114M, and 114Y (herein referred to as second nozzle rows). They were arranged by being shifted by a distance d in the traveling direction of the droplet ejection order. Thus, it is desirable that the shifting direction of the first nozzle row coincides with the traveling direction of the droplet ejection order in the nozzle arrangement direction.

  When patterning with a curable ink, the shape of the ink that has been ejected first (downward) strongly affects the final shape of the recording surface. This is because the liquid ink that has been ejected later follows the shape of the ink that has been previously ejected and cured or semi-cured.

  The ink ejected from the first nozzle array is more independent than the ink ejected from the other nozzle arrays, can induce longitudinal interference rather than lateral interference, and forms a longitudinal interference pattern. be able to.

  When the shifting direction of the nozzle row coincides with the traveling direction of the droplet ejection order in the nozzle arrangement direction, the ink droplets ejected from the first nozzle row first form a vertical interference pattern, Since the ink droplets from the second nozzle row are deposited thereon, the influence of the interference pattern in the vertical direction becomes strong, and the vertical and horizontal interference patterns are balanced.

  On the other hand, when the shifting direction of the first nozzle row is opposite to the traveling direction of the droplet ejection order in the nozzle arrangement direction, the ink ejected from the second nozzle row first forms a horizontal interference pattern, Since the ink droplets from the first nozzle row are deposited thereon, the interference pattern in the horizontal direction remains strong, and the unevenness improvement effect is reduced.

  As described above, the positions of the nozzles that discharge ink other than the ink with the lowest curing sensitivity are arranged to coincide with each other, and the positions of the nozzles that eject the ink with the lowest curing sensitivity are set in the sub-scanning direction. By disposing the nozzles of other inks by a predetermined amount in the traveling direction of the droplet ejection order, even when ink droplets ejected in one main scan are connected by droplet ejection interference, It is possible to suppress interference and induce interference in the sub-scanning direction. Thereby, the anisotropy of the surface shape can be relaxed and the uneven gloss can be improved.

〔Example〕
Using the inkjet recording apparatus 100, the relationship between the shift amount d in the advancing direction of the droplet ejection order of the nozzle 114K and the gloss unevenness was evaluated. Here, using the inkjet head 110 in which the nozzle interval is 254 μm (100 dpi) and the diameter of the ejected ink droplet is 80 μm, the droplet ejection order (2 passes in the main scanning direction, 8 passes in the sub scanning direction) is shown in FIG. The image of 900 × 800 dpi (sub-scanning pixel pitch p is 32 μm) was recorded with a total of 16 passes, and uneven gloss was evaluated.

  FIG. 9B is a diagram showing the evaluation results at d = 0, 30, 50, and 70 μm. “A” indicates that the gloss unevenness cannot be visually recognized, and “B” indicates that the gloss unevenness is slightly visible. And “C” were evaluated.

  When d = 0 μm, that is, when the nozzle 114K, the nozzles 114C, 114M, and 114Y are arranged so as to coincide with the traveling direction of the droplet ejection order, the uneven gloss is clearly recognized.

  When d = 30 μm (corresponding to the case of d <p), that is, when the nozzle 114K is shifted from the nozzles 114C, 114M, 114Y by 30 μm in the traveling direction of the droplet ejection order, this is improved. Although there was a slight gloss unevenness.

  When d = 50 μm (corresponding to the case of p ≦ d ≦ 2p), uneven gloss was not visible.

  When d = 70 μm (corresponding to the case of d> 2p), although it was improved, a slight gloss unevenness was visually recognized.

  As described above, the gloss unevenness can be improved by providing the shift amount d. Further, when p ≦ d ≦ 2p, the interference in the main scanning direction is most reduced, and the effect of improving the uneven gloss is high. Proven.

[Other Embodiments]
<Overall configuration of inkjet recording apparatus>
FIG. 10 is an external perspective view of an ink jet recording apparatus according to another embodiment. The ink jet recording apparatus 10 is a wide format printer that forms a color image on a recording medium 12 using ultraviolet curable ink (UV curable ink). A wide format printer is an apparatus suitable for recording a wide drawing range, such as a large poster or a commercial wall advertisement. Here, the one corresponding to A3 Nobi or higher is called “wide format”.

  The ink jet recording apparatus 10 includes an apparatus main body 20 and support legs 22 that support the apparatus main body 20. The apparatus main body 20 includes a drop-on-demand type ink jet head 24 that ejects ink toward a recording medium (medium) 12, a platen 26 that supports the recording medium 12, a guide mechanism 28 as a head moving unit, and a carriage 30. (An example of scanning means) is provided.

  The guide mechanism 28 is disposed above the platen 26 so as to extend along a scanning direction (Y direction) perpendicular to the conveyance direction (X direction) of the recording medium 12 and parallel to the medium support surface of the platen 26. ing. The carriage 30 is supported so as to reciprocate in the Y direction along the guide mechanism 28. An ink jet head 24 is mounted on the carriage 30, and temporary curing light sources 32 </ b> A and 32 </ b> B that irradiate ink on the recording medium 12 with ultraviolet rays and main curing light sources 34 </ b> A and 34 </ b> B are mounted.

  The temporary curing light sources 32A and 32B are light sources that irradiate ultraviolet rays for temporarily curing the ink so that the adjacent droplets do not coalesce after the ink droplets ejected from the inkjet head 24 have landed on the recording medium 12. is there. The main curing light sources 34 </ b> A and 34 </ b> B are light sources that irradiate with ultraviolet rays for performing additional exposure after temporary curing and finally completely curing (main curing) the ink.

  The inkjet head 24, the temporary curing light sources 32 </ b> A and 32 </ b> B, and the main curing light sources 34 </ b> A and 34 </ b> B disposed on the carriage 30 move integrally with the carriage 30 along the guide mechanism 28.

  As the recording medium 12, various media such as paper, non-woven fabric, vinyl chloride, synthetic chemical fiber, polyethylene, polyester, and tarpaulin can be used regardless of the material, regardless of permeable medium or non-permeable medium. it can. The recording medium 12 is fed from the back side of the apparatus in a roll paper state (see FIG. 11), and after printing, is wound up by a winding roller (not shown in FIG. 10, reference numeral 44 in FIG. 11) on the front side of the apparatus. (Example of moving means). Ink droplets are ejected from the inkjet head 24 to the recording medium 12 conveyed on the platen 26, and the temporary curing light sources 32A and 32B and the main curing light sources 34A and 34B are applied to the ink droplets attached on the recording medium 12. Ultraviolet rays are irradiated.

  In FIG. 10, a mounting portion 38 for the ink cartridge 36 is provided on the front surface on the left side of the apparatus main body 20. The ink cartridge 36 is a replaceable ink supply source (ink tank) that stores ultraviolet curable ink. The ink cartridge 36 is provided corresponding to each color ink used in the inkjet recording apparatus 10 of this example. Each color-specific ink cartridge 36 is connected to the inkjet head 24 by an ink supply path (not shown) formed independently. When the remaining amount of ink for each color is low, the ink cartridge 36 is replaced.

  Although not shown, a maintenance unit for the inkjet head 24 is provided on the right side of the apparatus main body 20 toward the front. The maintenance unit is provided with a cap for keeping the ink-jet head 24 moisturized during non-printing and a wiping member (blade, web, etc.) for cleaning the nozzle surface (ink ejection surface) of the ink-jet head 24. The cap for capping the nozzle surface of the inkjet head 24 is provided with an ink receiver for receiving ink droplets ejected from the nozzle for maintenance.

<Description of recording medium conveyance path>
FIG. 11 is an explanatory diagram schematically showing a recording medium conveyance path in the inkjet recording apparatus 10. As shown in FIG. 11, the platen 26 is formed in an inverted bowl shape, and the upper surface thereof serves as a support surface of the recording medium 12 (referred to as “medium support surface”). A pair of nip rollers 40 that are recording medium conveying means for intermittently conveying the recording medium 12 are disposed on the upstream side in the recording medium conveying direction (X direction) in the vicinity of the platen 26. The nip roller 40 moves the recording medium 12 on the platen 26 in the X direction.

  The recording medium 12 sent out from a supply-side roll (referred to as a “feed-out supply roll”) 42 that constitutes a roll-to-roll type medium conveying means is fed to the entrance of the printing unit (upstream of the platen 26 in the recording medium conveying direction). Are intermittently conveyed in the X direction by a pair of nip rollers 40 provided on the side). The recording medium 12 that has reached the printing unit immediately below the ink jet head 24 is printed by the ink jet head 24 and is taken up by the take-up roll 44 after printing. A guide 46 for the recording medium 12 is provided on the downstream side of the printing unit in the recording medium conveyance direction.

  A temperature adjusting unit 50 for adjusting the temperature of the recording medium 12 during printing is provided on the back surface (the surface opposite to the surface supporting the recording medium 12) of the platen 26 at a position facing the inkjet head 24 in the printing unit. Is provided. When the recording medium 12 at the time of printing is adjusted to a predetermined temperature, the physical properties such as the viscosity of the ink droplets that have landed on the recording medium 12 and the surface tension become the desired values, and the desired dot diameter is set. Can be obtained. In addition, as needed, the pre temperature control part 52 may be provided in the upstream of the temperature control part 50, and the after temperature control part 54 may be provided in the downstream of the temperature control part 50.

<Description of inkjet head>
FIG. 12 is a plan perspective view showing an example of an arrangement form of the inkjet head 24 arranged on the carriage 30, the temporary curing light sources 32A and 32B, and the main curing light sources 34A and 34B.

  The inkjet head 24 has yellow (Y), magenta (M), cyan (C), black (K), light cyan (LC), light magenta (LM), transparent ink (CL), and white (W) colors. For each ink, nozzle rows 61Y, 61M, 61C, 61K, 61LC, 61LM, 61CL, and 61W (an example of three or more nozzle rows) are provided for ejecting each color ink. In FIG. 12, the nozzle row is illustrated by dotted lines, and individual illustration of the nozzles is omitted. In the following description, the nozzle rows 61Y, 61M, 61C, 61K, 61LC, 61LM, 61CL, and 61W may be collectively referred to by the reference numeral 61 to represent the nozzle rows.

  The ink color type (number of colors) and the color combination are not limited to the present embodiment. For example, a form in which the LC and LM nozzle arrays are omitted, a form in which the CL and W nozzle arrays are omitted, and a form in which a nozzle array for ejecting special color ink is added are possible. Further, the arrangement order of the nozzle rows for each color is not particularly limited.

  By forming a head module for each color nozzle row 61 and arranging them, it is possible to form an inkjet head 24 capable of color drawing. For example, a head module 24Y having a nozzle row 61Y that discharges yellow ink, a head module 24M having a nozzle row 61M that discharges magenta ink, a head module 24C having a nozzle row 61C that discharges cyan ink, and black ink A head module 24K having a nozzle row 61K for discharging, and head modules 24LC, 24LM, 24CL, 24W having nozzle rows 61LC, 61LM, 61CL, 61W for discharging ink of each color of LC, LM, CL, W, respectively. A mode in which the carriages 30 are arranged at equal intervals so as to be aligned along the Y direction of the carriage 30 is also possible. The color-specific head modules 24Y, 24M, 24C, 24K, 24LC, and 24LM may be interpreted as “inkjet heads”, respectively. Alternatively, a configuration in which an ink flow path is separately formed for each color within one inkjet head 24 and a nozzle row that ejects a plurality of colors of ink with one head is also possible.

  Each nozzle row 61 has a plurality of nozzles arranged in a line (linearly) along the X direction at regular intervals. In the inkjet head 24 of this example, the arrangement pitch (nozzle pitch) of the nozzles constituting each nozzle row 61 is 254 μm (100 dpi), the number of nozzles constituting one nozzle row 61 is 256 nozzles, and the total length of the nozzle row 61 Lw (corresponding to “nozzle row length”, sometimes referred to as “nozzle row width”) is approximately 65 mm (254 μm × 255 = 64.8 mm).

  Of the nozzle rows 61Y, 61M, 61C, 61K, 61LC, 61LM, 61CL, 61, the nozzle rows other than the nozzle row 61K that discharges the black ink having the lowest curing sensitivity are the same in which each nozzle is parallel to the Y direction. It is arranged on a straight line. Further, each nozzle of the nozzle row 61K that discharges the black ink having the lowest curing sensitivity is arranged so as to be shifted from the position of each nozzle of the other nozzle row by a distance d in the traveling direction of the droplet ejection order (FIG. 5).

  Of the nozzle arrays 61Y, 61M, 61C, 61K, 61LC, and 61LM that discharge color inks (yellow, magenta, cyan, black, light cyan, and light magenta ink) that form the color of each pixel, the most curing sensitivity is obtained. The nozzles in the nozzle row other than the nozzle row that ejects low ink are arranged on the same straight line parallel to the Y direction, and the nozzles in the nozzle row that ejects the ink with the lowest curing sensitivity are shifted in the traveling direction of the droplet ejection order. It only has to be done. That is, the nozzle position of the transparent ink that does not include the color material and the white ink used for the base is not particularly limited.

  Further, the discharge frequency is 15 kHz, and three types of discharge droplet amounts of 10 pl, 20 pl, and 30 pl can be distinguished by changing the drive waveform. That is, it is possible to form three sizes of dots, small dots, medium dots, and large dots.

  As an ink ejection method of the inkjet head 24, a method (piezo jet method) in which ink droplets are ejected by deformation of a piezoelectric element (piezo actuator) is employed. In addition to a configuration using an electrostatic actuator (electrostatic actuator method) as a discharge energy generating element, a heating element (heating element) such as a heater is used to heat ink to generate bubbles and to eject ink droplets with that pressure. It is also possible to adopt a form (thermal jet system).

<About the arrangement of the UV irradiation device>
As shown in FIG. 12, provisional curing light sources 32 </ b> A and 32 </ b> B are arranged on the left and right sides in the scanning direction (Y direction) of the inkjet head 24. Further, main curing light sources 34 </ b> A and 34 </ b> B are arranged on the downstream side of the inkjet head 24 in the recording medium conveyance direction (X direction).

  The ink droplets ejected from the nozzles of the ink jet head 24 and landed on the recording medium 12 are immediately irradiated with ultraviolet rays for temporary curing by the temporary curing light source 32A (or 32B) passing thereover. Further, the ink droplets on the recording medium 12 that have passed through the printing area of the inkjet head 24 as the recording medium 12 is intermittently conveyed are irradiated with ultraviolet rays for main curing by the main curing light sources 34A and 34B.

  The temporary curing light sources 32 </ b> A and 32 </ b> B and the main curing light sources 34 </ b> A and 34 </ b> B are always turned on during the printing operation of the inkjet recording apparatus 10.

<Example of the configuration of the temporary curing light source>
As shown in FIG. 12, each of the temporary curing light sources 32A and 32B has a structure in which a plurality of UV-LED elements 33 are arranged. The two temporary curing light sources 32A and 32B have a common configuration. In this example, as the temporary curing light sources 32A and 32B, the LED element array in which six UV-LED elements 33 are arranged in a line along the X direction is illustrated, but the number of LED elements and the array form thereof are shown in this example. It is not limited. For example, a configuration in which a plurality of LED elements are arranged in a matrix in the X / Y direction is also possible.

  The six UV-LED elements 33 are arranged so that UV irradiation can be performed at once on a region having the same width as the nozzle row width Lw of the inkjet head 24.

<About the configuration example of the main curing light source>
As shown in FIG. 12, each of the main curing light sources 34A and 34B has a structure in which a plurality of UV-LED elements 35 are arranged. The two main curing light sources 34A and 34B have a common configuration. In this example, as the main curing light sources 34A and 34B, an LED element array (6 × 2) in which six UV-LED elements 35 in the Y direction and two in the X direction are arranged in a matrix is illustrated.

  The arrangement of the UV-LED elements 35 in the X direction is related to the swath width described later, and has a width corresponding to 1 / n (n is a positive integer) of the nozzle row width Lw in one scan of the carriage 30. It is determined so that UV irradiation can be performed at once. In the example of FIG. 12, the UV-LED elements 35 are arranged so that a region having a width of 1/2 (n = 2) of the nozzle row width Lw can be irradiated at once.

  In addition, the number of LED elements of the main curing light source and the arrangement form thereof are not limited to the example of FIG. Further, the light sources of the temporary curing light sources 32A and 32B and the main curing light sources 34A and 34B are not limited to the UV-LED elements 33 and 35, and a UV lamp or the like can also be used.

<About drawing mode>
The inkjet recording apparatus 10 configured as described above is applied with multi-pass drawing control, and the print resolution can be changed by changing the number of print passes. For example, three types of drawing modes, a high production mode, a standard mode, and a high image quality mode, are prepared, and the printing resolution is different in each mode. The drawing mode can be selected according to the printing purpose and application.

  In the high production mode, printing is executed with a resolution of 600 dpi (main scanning direction) × 400 dpi (sub-scanning direction). In the high production mode, a resolution of 600 dpi is realized by two passes (two scans) in the main scanning direction. First, dots are formed with a resolution of 300 dpi in the first scan (the forward path of the carriage 30). In the second scan (return pass), dots are formed such that the middle of the dots formed in the first scan (forward pass) is interpolated at 300 dpi, and a resolution of 600 dpi is obtained in the main scan direction.

  On the other hand, in the sub-scanning direction, the nozzle pitch is 100 dpi, and dots are formed at a resolution of 100 dpi in the sub-scanning direction by one main scanning (one pass). Therefore, a resolution of 400 dpi is realized by performing interpolation printing by four-pass printing (four scans).

  In this specification, the product of the number of passes in the main scanning direction and the number of passes in the sub-scanning direction is referred to as the number of passes in the drawing mode. Therefore, the number of passes in the high production mode is main scanning 2-pass printing × sub-scanning 4-pass printing = 8 passes.

  In the standard mode, printing is performed with a resolution of 600 dpi × 800 dpi. This resolution can be obtained by 2-pass printing in the main scanning direction and 8-pass printing in the sub-scanning direction. That is, the number of passes in the standard mode is main scanning 2-pass printing × sub-scanning 8-pass printing = 16 passes.

  In the high image quality mode, printing is executed at a resolution of 1200 × 1200 dpi, and this resolution is obtained by 4 passes in the main scanning direction and 12 passes in the sub-scanning direction. That is, the number of passes in the high image quality mode is main scanning 4 pass printing × sub scanning 12 pass printing = 48 passes.

  Note that, when printing in four passes in the main scanning direction, landing interference in the main scanning direction does not occur in one pass of droplet ejection, so each nozzle of the nozzle row 61K that discharges black ink with the lowest curing sensitivity. Need not be shifted by a distance d in the traveling direction of the droplet ejection order with respect to the other nozzle rows. Therefore, the shift amount of the nozzle row 61K may be configured to be changeable according to the number of passes in the main scanning direction of the drawing mode. That is, the head module 24K is configured to be movable in the X direction by a driving means such as an actuator, and the amount of movement is controlled according to the set drawing mode, thereby suppressing the occurrence of uneven glossiness according to the drawing mode. Can do.

<Description of ink supply system>
FIG. 13 is a block diagram showing the configuration of the ink supply system of the inkjet recording apparatus 10. As shown in the figure, the ink stored in the ink cartridge 36 is sucked by the supply pump 70 and sent to the inkjet head 24 via the sub tank 72. The sub tank 72 is provided with a pressure adjusting unit 74 for adjusting the pressure of the ink inside.

  The pressure adjusting unit 74 includes a pressure increasing / decreasing pump 77 communicating with the sub tank 72 via the valve 76, and a pressure gauge 78 provided between the valve 76 and the pressure increasing / decreasing pump 77.

  During normal printing, the pressure increasing / decreasing pump 77 operates in the direction of sucking ink in the sub tank 72, and the internal pressure of the sub tank 72 and the internal pressure of the inkjet head 24 are maintained at negative pressure. On the other hand, at the time of maintenance of the ink jet head 24, the pressure increasing / decreasing pump 77 operates to pressurize the ink in the sub tank 72, and the inside of the sub tank 72 and the inside of the ink jet head 24 are forcibly pressurized. The ink inside is discharged through the nozzle. The ink forcibly discharged from the inkjet head 24 is accommodated in the ink receiver of the cap (not shown) described above.

<Description of Control System of Inkjet Recording Apparatus>
FIG. 14 is a block diagram illustrating a configuration of the inkjet recording apparatus 10. As shown in the figure, the inkjet recording apparatus 10 is provided with a control device 202 as control means. As the control device 202, for example, a computer having a central processing unit (CPU) can be used. The control device 202 functions as a control device that controls the entire inkjet recording apparatus 10 according to a predetermined program, and also functions as a calculation device that performs various calculations. The control device 202 includes a recording medium conveyance control unit 204, a carriage drive control unit 206, a light source control unit 208, an image processing unit 210, and an ejection control unit 212. Each of these units is realized by a hardware circuit or software, or a combination thereof.

  The recording medium conveyance control unit 204 controls the conveyance driving unit 214 for conveying the recording medium 12 (see FIG. 10). The transport driving unit 214 includes a driving motor that drives the nip roller 40 shown in FIG. The recording medium 12 conveyed on the platen 26 (see FIG. 10) is intermittently fed in the sub-scanning direction in units of swath widths in accordance with the reciprocating scanning (movement of the printing pass) in the main scanning direction by the inkjet head 24.

  A carriage drive control unit 206 shown in FIG. 14 controls a main scanning drive unit 216 for moving the carriage 30 (see FIG. 10) in the main scanning direction. The main scanning drive unit 216 includes a drive motor connected to the moving mechanism of the carriage 30 and its control circuit.

  The light source control unit 208 adjusts the amount of light emitted from the UV-LED elements 33 of the temporary curing light sources 32A and 32B via the LED drive circuit 218, and the UV-LEDs of the main curing light sources 34A and 34B via the LED drive circuit 219. It is a control means for adjusting the light emission amount of the element 35.

  The LED driving circuit 218 adjusts the light emission amount of the UV-LED element 33 by outputting a voltage having a voltage value corresponding to a command from the light source control unit 208. In addition, the LED drive circuit 219 adjusts the light emission amount of the UV-LED element 35 by outputting a voltage having a voltage value corresponding to a command from the light source control unit 208. The LED light emission amount may be adjusted by changing the duty ratio of the drive waveform using PWM (Pulse Width Modulation) instead of changing the voltage, or changing both the voltage value and the duty ratio. May be.

The control device 202 is connected to an input device 220 such as an operation panel and a display device 222.

  The input device 220 is means for inputting a manual external operation signal to the control device 202. For example, various forms such as a keyboard, a mouse, a touch panel, and operation buttons can be adopted. Various forms such as a liquid crystal display, an organic EL display, and a CRT can be adopted for the display device 222. By operating the input device 220, the operator can select a drawing mode, input printing conditions, and input / edit attached information. Various information such as input contents and search results are displayed on the display device 222. It can be confirmed through the display.

  Further, the ink jet recording apparatus 10 is provided with an information storage unit 224 that stores various types of information and an image input interface 226 for capturing image data for printing. As the image input interface, a serial interface or a parallel interface may be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted.

  Image data input via the image input interface 226 is converted into print data (dot data) by the image processing unit 210. This dot data is generally generated by performing color conversion processing and halftone processing on multi-tone image data.

  Note that each nozzle in the nozzle row 61K is arranged with a distance d shifted from the position of each nozzle in the other nozzle row in the advancing direction in the droplet ejection order, so that the image shift between the colors is corrected. There is a need. The image data that has been subjected to the correction processing may be captured from the image input interface 226, or the image processing unit 210 may perform the correction processing.

  Various known means such as an error diffusion method, a dither method, a threshold matrix method, and a density pattern method can be applied as the halftone processing means. The halftone process generally converts gradation image data having an M value (M ≧ 3) into gradation image data having an N value (N <M). In the simplest example, it is converted into binary (dot on / off) dot image data, but in halftone processing, it corresponds to the dot size type (for example, three types such as large dot, medium dot, small dot). It is also possible to perform multi-level quantization.

  The binary or multi-valued image data (dot data) obtained in this way controls the drive (on) / non-drive (off) of each nozzle, and in the case of multiple values, controls the droplet amount (dot size). Used as ink ejection data (droplet ejection control data).

  The ejection control unit 212 generates an ejection control signal for the head drive circuit 228 based on the dot data generated by the image processing unit 210. Further, the discharge control unit 212 includes a drive waveform generation unit (not shown). The drive waveform generation unit is a means for generating a drive voltage signal for driving an ejection energy generating element (in this example, a piezo element) corresponding to each nozzle of the inkjet head 25.

  The waveform data of the drive voltage signal is stored in advance in the information storage unit 224, and waveform data to be used is output as necessary. The signal (drive waveform) output from the drive waveform generation unit is supplied to the head drive circuit 228. Note that the signal output from the drive waveform generation unit may be digital waveform data or an analog voltage signal.

  A common driving voltage signal is applied to each ejection energy generating element of the inkjet head 25 via the head driving circuit 228, and the switching element is connected to the individual electrode of each energy generating element according to the ejection timing of each nozzle. By switching on / off (not shown), ink is ejected from the corresponding nozzle.

  The information storage unit 224 stores programs executed by the CPU of the control device 202, various data necessary for control, and the like. The information storage unit 224 stores resolution setting information according to the drawing mode, the number of passes (the number of scan repetitions), light emission amount information of the temporary curing light sources 32A and 32B, and the main curing light sources 34A and 34B.

  The encoder 230 is attached to the drive motor of the main scanning drive unit 216 and the drive motor of the transport drive unit 214, and outputs a pulse signal corresponding to the rotation amount and rotation speed of the drive motor. Is sent to the controller 202. Based on the pulse signal output from the encoder 230, the position of the carriage 30 and the position of the recording medium 12 (see FIG. 10) are grasped.

  The sensor 232 is attached to the carriage 30, and the width of the recording medium 12 is grasped based on the sensor signal obtained from the sensor 232.

  According to the ink jet recording apparatus 10 configured as described above, the nozzles for ejecting ink other than the ink with the lowest curing sensitivity are arranged in the same position in the sub-scanning direction, and the ink with the lowest curing sensitivity is ejected. Since the nozzle to be moved is shifted from the other ink nozzles by a predetermined amount in the traveling direction of the droplet ejection order, even when ink droplets ejected in one main scan are connected by droplet ejection interference, The anisotropy of the surface shape can be relaxed, and the uneven brightness can be improved.

  In the above embodiment, an example in which an image is formed using UV ink has been described. However, the present invention can be applied to the case where a curable ink that is cured by applying active energy is used. For example, an ink that is cured by X-ray, molecular beam, ion beam, or the like can be used.

  The technical scope of the present invention is not limited to the scope described in the above embodiment. The configurations and the like in the respective embodiments can be appropriately combined among the respective embodiments without departing from the spirit of the present invention.

  DESCRIPTION OF SYMBOLS 10,100 ... Inkjet recording device 12,120 ... Recording medium, 24, 110 ... Inkjet head, 32A, 32B ... Temporary curing light source, 34A, 34B ... Main curing light source, 30, 118 ... Carriage, 112 ... Head, 114 ... Nozzle, 116L, 116R ... curing light source, 122 ... pixel group, 130 ... ink droplet, 132, 134, 136, 138 ... united ink droplet

Claims (11)

Three or more nozzle rows that discharge curable ink that is cured by application of active energy from nozzles that are arranged at a predetermined pitch in the first direction, and that each eject three different curable inks An inkjet head having a row;
Active energy applying means for applying the active energy to ink droplets ejected from the nozzles and ejected onto the recording surface of a recording medium;
Holding means for arranging and holding the ink jet head and the active energy applying means along a second direction orthogonal to the first direction;
Scanning means for relatively scanning the holding means and the recording medium in the second direction;
Moving means for relatively moving the holding means and the recording medium in the first direction for each scanning by the scanning means;
Control means for forming an image on the recording surface of the recording medium while causing the inkjet head and the active energy applying means held by the holding means to scan each area of the recording medium a predetermined number of times. ,
With
The three or more nozzle rows have the same nozzle position in the first direction for a plurality of nozzle rows other than the first nozzle row that discharges the curable ink having the lowest curing sensitivity. As for the first nozzle row, an ink jet recording apparatus in which the position of each nozzle in the first direction is deviated from the position of each nozzle in the plurality of nozzle rows by a predetermined amount. The three or more nozzle rows are four nozzle rows that discharge curable inks of yellow, magenta, cyan, and black, respectively.
The inkjet recording apparatus according to claim 1, wherein the curable ink having the lowest curing sensitivity is the black curable ink. The control means deposits ink droplets on each area of the recording medium in a predetermined droplet ejection order to form an image with a predetermined pixel pitch,
3. The inkjet recording apparatus according to claim 1, wherein the predetermined amount is not less than 1 pixel pitch and not more than 2 pixel pitch in the traveling direction of the droplet ejection order in the first direction.   4. The active energy applying unit applies the active energy to the extent that ink droplets deposited on the recording surface of the recording medium are incompletely cured in one scan by the scanning unit. The ink jet recording apparatus according to any one of the above.   5. The inkjet according to claim 4, further comprising a second active energy applying unit that performs main curing of the ink droplet by further applying active energy to the ink droplet to which the active energy is applied by the active energy applying unit. Recording device.   The inkjet recording apparatus according to claim 5, wherein the holding unit holds the second active energy applying unit on a downstream side of the moving unit of the inkjet head.   The inkjet recording apparatus according to claim 1, wherein the holding unit holds the active energy applying unit on both sides of the inkjet head in the second direction.   The inkjet recording apparatus according to claim 1, wherein the active energy is ultraviolet light.   9. The inkjet recording apparatus according to claim 1, wherein the control unit completes an image by one or two scans by the scanning unit with respect to one pixel line in the second direction. 10.   The control unit causes ink droplet ejection positions in the second direction by the plurality of nozzle arrays to coincide with ink droplet ejection positions in the second direction by the first nozzle arrays. The ink jet recording apparatus according to claim 1.   Image processing for correcting data of an image formed on the recording surface of the recording medium based on a displacement between the nozzle positions of the first nozzle array and the nozzle positions of a plurality of nozzle arrays other than the first nozzle array The ink jet recording apparatus according to claim 1, comprising means.

Images