JP5665481B2 - Image forming apparatus, actinic ray irradiation apparatus for temporary curing, and method for changing illuminance distribution - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly, to an ink jet image forming technique using an ink that is cured by irradiation with actinic rays such as ultraviolet rays.

  Inks that are cured by irradiation with ultraviolet rays are called “ultraviolet curable inks” or “UV curable inks”, and are widely used in the field of inkjet printing (Patent Documents 1 to 6). In curing UV curable ink ejected from the print head on the recording medium (paper), the ink is partially applied immediately after the droplet ejection from the viewpoint of preventing the movement of the ink droplet after the droplet ejection and the interference with the adjacent droplet ejection. There is known a curing method in which UV irradiation is performed with a light amount sufficient to cure the ink (incompletely), and then UV irradiation is performed with a light amount sufficient to cure the ink.

  The process of partially curing the ink to such an extent as to prevent the movement and deformation of the ink droplet immediately after droplet ejection is “temporary curing”, “partial curing”, “semi-curing”, “pinning” or “setting”. (Set) ". In this specification, the term “temporary curing” is used. On the other hand, the process of further curing the ink after the preliminary curing to sufficiently cure the ink is called “main curing” or “curing”. In this specification, the term “main curing” is used. Patent Documents 1 to 5 disclose embodiments in which an ultraviolet irradiation light source for temporary curing and an ultraviolet irradiation light source for main curing are separately provided, and the two effects of temporary curing and main curing are performed by the respective light sources. .

US Pat. No. 7,800,087 US Pat. No. 6,457,823 Japanese Patent No. 4519641 US Pat. No. 7,393,095 Japanese Patent Laying-Open No. 2005-313445 US Pat. No. 7,073,901

  Wide-format inkjet printers used for business printing such as billboards and advertisements move a print head mounted on a carriage back and forth in a direction orthogonal to the paper (media) transport direction, and print images with a predetermined resolution using multiple print passes. In many cases, a multi-pass printing method is used to complete the process. In such a wide format inkjet printer, the print head nozzle group is divided by the number of passes for drawing the nozzle row to be ejected, and the paper is conveyed by the divided width so that the scanning unevenness by the print head is not noticeable. The method (called “singling drop scanning”) is common. In this case, since single-ring droplet ejection scanning and UV irradiation (temporary curing exposure) are performed simultaneously in one pass, the number of droplet ejection dots (ink droplets) with a large number of temporary curing exposures within one swath width is small. Droplet dots are mixed.

  The exposure amount for temporary curing affects the spread of ink droplets on the medium. When the ink droplet spreads, the landing dot diameter increases and the dot height decreases. Due to the difference in the total exposure amount with respect to the droplet ejection dots within one swath width, a periodic change is generated in the dot diameter, which is a cause of band-like density unevenness and gloss unevenness called “banding unevenness”.

  The present invention has been made in view of such circumstances, and actinic ray irradiation for pre-curing that can reduce the difference in the amount of irradiated light for each ink droplet that has been subjected to shingling and can improve banding unevenness. It is an object of the present invention to provide an apparatus, an image forming apparatus using the same, and a method for changing an illuminance distribution.

  In order to achieve the above object, the following invention modes are provided.

  (Invention 1): An image forming apparatus according to Invention 1 conveys an inkjet head having a plurality of nozzles that eject ink that is cured by irradiation of actinic rays, and a recording medium to which ink droplets ejected from the inkjet head are attached. Medium conveying means, scanning means for moving the inkjet head relative to the recording medium, and moving with the inkjet head by the scanning means to incompletely cure ink droplets adhering to the recording medium Provided separately from the temporary curing light source for irradiating the actinic light and the temporary curing light source, the ink droplet exposed by the temporary curing light source is subjected to additional exposure to irradiate the actinic light for main curing the ink droplet. An actinic ray irradiated from the temporary curing light source on the surface of the recording medium, Characterized in that from the upstream of the conveyance direction of the recording medium by serial medium conveying means has an illuminance distribution increasing illuminance toward the downstream.

  According to this invention, the illuminance distribution of the temporary curing light source is adjusted so that the illuminance on the downstream side is larger than the upstream side in the recording medium conveyance direction on the recording medium surface. As a result, it is possible to reduce the irradiation light amount difference (exposure amount difference) of each ink droplet within the swath width drawn by a plurality of scans. In addition, as actinic light, an ultraviolet-ray, visible light, infrared rays, or these appropriate combinations are possible.

  (Invention 2): The image forming apparatus according to Invention 2 is the image forming apparatus according to Invention 1, wherein the inkjet head has a nozzle row in which the nozzles are arranged in the recording medium conveyance direction, and the temporary curing light source is on the recording medium. And actinic rays are irradiated with a light irradiation width equal to or longer than the length of the nozzle row.

  By irradiating actinic rays with a light irradiation width equal to or greater than the length of the nozzle row (nozzle row width), it is possible to irradiate the print width all at once with respect to the print width.

  (Invention 3): In the image forming apparatus according to Invention 3, in the invention 1 or 2, the ink jet head, the temporary curing light source, and the main curing light source are integrally mounted on a carriage, and the scanning unit includes: The carriage is moved relative to the recording medium.

  It is preferably applied to a scanning type image forming apparatus in which an inkjet head on a carriage, a temporary curing light source, and a main curing light source move together.

  (Invention 4): In the image forming apparatus according to Invention 4, in any one of Inventions 1 to 3, the temporary curing light source includes at least one actinic light emitting element and light emitted from the actinic light emitting element. A transmission-type light diffusion plate that diffuses while transmitting light, and a side reflection plate that surrounds a side peripheral surface between the light diffusion plate and a wiring board on which the actinic light emitting element is mounted, and the light A light reflecting portion and a light passing portion for obtaining the illuminance distribution are formed on a light emitting surface of the diffusion plate facing the recording medium.

  According to this aspect, a necessary light irradiation width and illuminance distribution can be efficiently generated. For example, the light diffusing plate is disposed between the actinic light emitting element and the recording medium. When the light emitting surface of the light diffusing plate is directed downward and the ink droplets on the recording medium are irradiated with actinic rays from above the recording medium, the actinic light emitting element is disposed further above the light diffusing plate.

  (Invention 5): The image forming apparatus according to Invention 5 is the image forming apparatus according to Invention 4, wherein the inkjet head has a nozzle row in which the nozzles are arranged in the recording medium conveyance direction, and the temporary curing light source includes a plurality of active light sources. The light emitting element has a light emitting element row arranged in the recording medium conveyance direction, and the length of the light emitting element row is shorter than the length of the nozzle row.

  According to the present invention, a light emitting element array can be formed with a relatively small number (for example, about 2 to 4) actinic light emitting elements.

  (Invention 6) An image forming apparatus according to Invention 6 is the image forming apparatus according to any one of Inventions 1 to 5, wherein a plurality of types of temporary curing light sources or light diffusion plates having different illuminance distributions on the recording medium are prepared. Further, the present invention is characterized by comprising an attachment structure capable of exchanging the provisional curing light source or the light diffusing plate selected from the plurality of types.

  The optimum illuminance distribution of the temporary curing light source varies depending on the length of the nozzle row, the swath width determined from the number of print passes in the main scanning direction and the sub-scanning direction, the type of the recording medium, and the like. Therefore, according to the type of recording medium, the drawing mode (swath width), or a combination thereof, a plurality of types of light diffusion plates or a plurality of types of temporary curing light sources are prepared in advance and used for recording media or printing. It is preferable to change to a suitable light diffusion plate or temporary curing light source according to the time drawing mode.

  (Invention 7): In the image forming apparatus according to Invention 7, in any one of Inventions 1 to 3, the temporary curing light source is a light emitting element array in which a plurality of actinic light emitting elements are arranged in the recording medium conveyance direction. And a reflector that reflects the light emitted by each of the actinic light emitting elements toward the recording medium, and the reflector extends from the actinic light emitting element to the reflector toward the downstream side in the recording medium conveyance direction. It is characterized by being arranged with respect to the light emitting element row so that the height is lowered.

  The closer the distance from the light emitting element to the reflector (the lower the height of the reflector), the higher the illuminance of the irradiation light on the recording medium. Therefore, a distribution in which the illuminance increases from the upstream to the downstream in the recording medium conveyance direction can be formed by arranging the reflectors so that the distance between the reflectors becomes closer from upstream to downstream.

  (Invention 8): In the image forming apparatus according to Invention 8, in any one of Inventions 1 to 3, the temporary curing light source is a light emitting element array in which a plurality of actinic light emitting elements are arranged in the recording medium conveyance direction. And a light emission control means for controlling a lighting amount of the actinic light emitting element of the light emitting element array so as to obtain the illuminance distribution.

  The amount of lighting light can be adjusted by current value control, pulse width modulation (PWM) control, duty control, and the like of the actinic light emitting element.

  (Invention 9): The image forming apparatus according to Invention 9 is characterized in that, in Invention 8, each of the actinic light emitting elements constituting the light emitting element array is provided with a reflector.

  In addition to controlling the amount of lighting of the actinic light emitting element, a desired illuminance distribution can be obtained by combining the form of the reflector provided in each light emitting element and the arrangement form of the light emitting element group.

  (Invention 10): In the image forming apparatus according to Invention 10, in any one of Inventions 1 to 3, the temporary curing light source has an inclined surface whose height gradually decreases toward the upstream in the recording medium conveyance direction. A first reflecting surface, a light emitting surface disposed between the first reflecting surface and the recording medium, and facing the recording medium, and a side periphery between the first reflecting surface and the light emitting surface A second reflecting surface that surrounds the surface, and a light diffusion space defined by the first reflecting surface, the light emitting surface, and the second reflecting surface, and disposed at the downstream end of the recording medium conveyance direction. And an actinic ray light emitting element.

  According to this aspect, it is possible to realize an illuminance distribution in which the illuminance increases from upstream to downstream in the media conveyance direction. A mode in which the light diffusion space is formed by a light scattering box having a hollow inside is also possible, and a mode in which the light diffusion space is formed by using a light guide is also possible.

  (Invention 11): The image forming apparatus according to Invention 11 is characterized in that, in Invention 10, a light reflection portion and a light passage portion for obtaining a desired illuminance distribution are formed on the light exit surface. And

  Various illuminance distributions are formed by combining the arrangement form in which the actinic light emitting element is arranged at the downstream end of the light diffusion space in the media conveyance direction and the pattern of the light reflecting part and light passing part formed on the light emitting surface. can do.

  (Invention 12): In the image forming apparatus according to Invention 12, in any one of Inventions 1 to 3, the temporary curing light source includes a light guide having a light exit surface facing the recording medium, and the light guide. An actinic ray emitting element disposed at the downstream end of the recording medium in the recording medium conveyance direction and a surface opposite to the light emitting surface of the light guide, and scatters light into the light guide And a scattering pattern.

  According to this aspect, it is possible to realize an illuminance distribution in which the illuminance increases from upstream to downstream in the media conveyance direction. Moreover, various illuminance distributions can be formed by the scattering pattern provided in the light guide.

  (Invention 13): The image forming apparatus according to Invention 13 is characterized in that, in any one of Inventions 1 to 12, the actinic ray is an ultraviolet ray, and the actinic ray light emitting element is an ultraviolet light emitting diode element. To do.

  For example, an ultraviolet light emitting diode (UV-LED) element is used as an ultraviolet irradiation light source for ink using a monomer that is polymerized and cured by irradiation of ultraviolet rays (so-called UV curable monomer).

  (Invention 14) The image forming apparatus according to Invention 14 is the image forming apparatus according to any one of Inventions 1 to 13, wherein the scanning direction by the scanning unit is a main scanning direction, and the recording medium conveying direction by the medium conveying unit is a sub-scanning direction. The illuminance distribution of the temporary curing light source according to at least one of the number of print passes in the main scanning direction and the sub scanning direction, the drawing mode, the drawing swath width, and the resolution in the main scanning direction and the sub scanning direction. It can be changed.

  For example, in the aspect of the invention 7, the inclination angle of the reflector is adjusted in accordance with the number of main and sub print passes, the drawing mode, and the like. Alternatively, a plurality of types of temporary curing light sources having different reflector tilt angles are prepared in advance, and the illuminance distribution is changed by changing the temporary curing light sources in accordance with the number of main and sub print passes, the drawing mode, and the like.

  In the aspects of inventions 8 and 9, the illuminance distribution can be changed by varying the control of the amount of light to be turned on according to the number of main and sub print passes, the drawing mode, and the like.

  As for the aspects of the inventions 10 and 11, a plurality of types of temporary curing light sources having different patterns of the light reflecting portion and the light passing portion provided on the light exit surface are prepared in advance, and the number of main and sub printing passes, the drawing mode, etc. Accordingly, the illumination distribution is changed by changing the temporary curing light source.

  For the aspect of the invention 12, a plurality of types of temporary curing light sources with different scattering patterns provided on the light guide are prepared in advance, and the temporary curing light sources are changed according to the number of main and sub print passes, the drawing mode, and the like. Thus, the illuminance distribution is changed.

  (Invention 15): The actinic ray irradiation apparatus for temporary curing according to Invention 15 is a method for removing ink droplets ejected from an inkjet head having a plurality of nozzles that eject ink that is cured by irradiation of actinic rays and adhered onto a recording medium. An actinic ray irradiation apparatus for temporary curing that irradiates an actinic ray that is incompletely cured, and is mounted on a carriage together with the ink jet head, on the recording medium surface, from upstream to downstream in the conveyance direction of the recording medium The illuminance distribution is adjusted so that the illuminance increases toward.

  (Invention 16): The illuminance distribution changing method according to Invention 16 is the image forming apparatus according to any one of Inventions 1 to 14, wherein the scanning direction by the scanning unit is the main scanning direction, and the recording is performed by the medium conveying unit. According to at least one of the number of print passes in the main scanning direction and the sub-scanning direction, the drawing mode, the drawing swath width, and the resolution in the main scanning direction and the sub-scanning direction when the medium transport direction is the sub-scanning direction, The illuminance distribution of the temporary curing light source is changed.

  According to the present invention, it is possible to reduce the total exposure amount difference for each droplet within one swath width, and to effectively reduce banding unevenness.

1 is an external perspective view of an ink jet recording apparatus according to an embodiment of the present invention. Explanatory drawing which shows typically the recording-medium conveyance path in an inkjet recording device Plan view showing an arrangement example of an inkjet head, a temporary curing light source, and a main curing light source disposed on a carriage The perspective view which shows the example of arrangement | positioning of an inkjet head, a temporary curing light source, and a main curing light source The perspective view which shows the structure of the temporary hardening light source which concerns on 1st Example. Sectional drawing which follows the AA line in FIG. Graph showing an example of the diffusion characteristics (Mie scattering characteristics) of a light diffusion plate 8A is a plan view of a UV-LED element mounted on a wiring board, and FIG. 8B is a plan view of a mirror formed on a light diffusion plate. The perspective view which shows the structure of the light-projection surface of a light diffusing plate Graph showing the illuminance distribution (X direction) on the media surface of ultraviolet rays irradiated from the temporary curing light source Graph showing the illuminance distribution (Y direction) on the media surface of ultraviolet rays irradiated from the temporary curing light source The perspective view which shows the principal part structure of the temporary hardening light source which concerns on 2nd Example. The perspective view which shows the structure of the temporary hardening light source which concerns on a comparative example Cross-sectional view showing a state in which ultraviolet rays are irradiated from a temporary curing light source toward a recording medium The graph which showed the illumination intensity distribution (X direction) in the media surface of the temporary curing light source which concerns on the comparison of FIG. The graph which showed the illuminance distribution (Y direction) in the media surface of the temporary hardening light source which concerns on the comparison of FIG. The graph which showed the illumination distribution (X direction) in the media surface of the temporary hardening light source which concerns on 2nd Example. The graph which showed the illuminance distribution (Y direction) in the media surface of the temporary hardening light source which concerns on 2nd Example. The top view which shows the principal part structure of the temporary hardening light source which concerns on 3rd Example. The perspective view which showed the relationship between the LED element row | line | column and media surface which comprise the temporary curing light source of FIG. The graph which showed the illumination distribution (X direction) in the media surface of the temporary hardening light source which concerns on 3rd Example. The graph which showed the illuminance distribution (Y direction) in the media surface of the temporary hardening light source which concerns on 3rd Example. The perspective view which shows the principal part structure of the temporary hardening light source which concerns on 4th Example. The perspective view which shows the mode of the light emission side of the temporary hardening light source shown in FIG. The top view which looked at the temporary hardening light source shown in FIG. 23 from the light-projection side The graph which showed the illuminance distribution (X direction) in the media surface of the temporary hardening light source which concerns on 4th Example. The graph which showed the illumination intensity distribution (Y direction) in the media surface of the temporary hardening light source which concerns on 4th Example. The perspective view which shows the principal part structure of the temporary hardening light source which concerns on 5th Example. The figure which shows the example of the pattern mask provided in a light-projection surface The graph which showed the illuminance distribution (X direction) in the media surface of the temporary hardening light source which concerns on 5th Example The graph which showed the illumination intensity distribution (Y direction) in the media surface of the temporary hardening light source which concerns on 5th Example The perspective view which shows the principal part structure of the temporary hardening light source which concerns on 6th Example. The graph which showed the illumination distribution (X direction) in the media surface of the temporary hardening light source which concerns on 6th Example The graph which showed the illuminance distribution (Y direction) in the media surface of the temporary hardening light source which concerns on 6th Example. FIG. 35A is a graph showing the density distribution in the media conveyance direction for the drawing result to which the present invention is applied, and FIG. 35B is a graph showing the density distribution in the medium conveyance direction of the drawing result by the conventional apparatus. Block diagram showing the configuration of an ink supply system of an ink jet recording apparatus Block diagram showing the main configuration of an inkjet recording apparatus

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

<Overall configuration of inkjet recording apparatus>
FIG. 1 is an external perspective view of an ink jet recording apparatus according to an embodiment of the present invention. 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 a device suitable for recording a wide drawing range such as a large poster or a commercial wall advertisement. Here, those corresponding to A3 Nobi or higher are 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 inkjet head 24 that ejects ink toward the recording medium (medium) 12, a platen 26 that supports the recording medium 12, and a guide mechanism as a head moving unit (scanning unit). 28 and a carriage 30 are 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. The reciprocating direction (Y direction) of the carriage 30 is referred to as “main scanning direction”, and the recording medium 12 conveyance direction (X direction). ) May be referred to as “sub-scanning direction”.

  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. 2), and after printing, is wound by a winding roller (not shown in FIG. 1, reference numeral 44 in FIG. 2) on the front side of the apparatus. . 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. 1, an attachment portion 38 for an ink cartridge 36 is provided on the left front surface 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. 2 is an explanatory diagram schematically showing a recording medium conveyance path in the inkjet recording apparatus 10. As shown in FIG. 2, 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 recording medium conveyance direction (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 roller 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. 3 is a perspective plan view showing an example of the arrangement of the inkjet head 24, temporary curing light sources 32A and 32B, and main curing light sources 34A and 34B arranged on the carriage 30, and FIG. 4 is a perspective view thereof.

  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 are provided for ejecting the respective color inks. In FIG. 3, the nozzle rows are illustrated by dotted lines, and individual illustrations of the nozzles are 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 is also possible in which the carriages 30 are arranged at equal intervals so as to be aligned along the reciprocating direction (main scanning direction) of the carriage 30. 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.

  In each nozzle row 61, a plurality of nozzles are arranged in a row (linearly) along the recording medium conveyance direction (sub-scanning 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). 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.

  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). However, since the ultraviolet curable ink generally has a higher viscosity than the solvent ink, when using the ultraviolet curable ink, it is preferable to adopt a piezo jet method having a relatively large ejection force.

<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. In the first scan (the forward path of the carriage 30), dots are formed with a resolution of 300 dpi. In the second scan (return pass), dots are formed so as to interpolate at 300 dpi between the dots formed in the first scan (forward pass), 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 the standard mode, printing is performed at a resolution of 600 dpi × 800 dpi, and a resolution of 600 dpi × 800 dpi is obtained by 2-pass printing in the main scanning direction and 8-pass printing in the sub-scanning direction.

  In the high image quality mode, printing is performed at a resolution of 1200 dpi × 1200 dpi, and a resolution of 1200 dpi × 1200 dpi is obtained with 4 passes in the main scanning direction and 12 passes in the sub-scanning direction. The main scanning speed of the carriage 30 is 1270 mm / sec in each mode.

<About swath width by single ring scanning>
In the drawing mode of the wide format machine, drawing conditions for single ring (interlace) are determined for each resolution setting. Specifically, since the inkjet head discharge nozzle row width Lw (nozzle row length) is divided by the number of passes (number of scan repetitions) to produce a single ring, the nozzle row width of the inkjet head and the main scan The swath width differs depending on the number of passes in the direction and the sub-scanning direction (the number of divisions to be interlaced). Details of the single-pass drawing by the multi-pass method are described in, for example, Japanese Patent Application Laid-Open No. 2004-306617.

  As an example, the relationship between the number of passes and the swath width by the single ring drawing when a QS-10 head (100 dpi, 256 nozzles) manufactured by FUJIFILM Dimatix is used is as shown in the following table (Table 1). The swath width assumed by the drawing is a value obtained by dividing the nozzle row width to be used by the product of the number of passes in the main scanning direction and the number of passes in the sub scanning direction.

<About the arrangement of the UV irradiation device>
As shown in FIGS. 3 and 4, provisional curing light sources 32 </ b> A and 32 </ b> B are disposed 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 correspond to “actinic ray irradiation apparatus for temporary curing”.

  The two pre-curing light sources 32A and 32B may be turned on simultaneously during the printing operation by the inkjet head 24, but the life of the light source is extended by turning on only the pre-curing light source on the rear side during carriage movement in the main scanning direction. You may try to do that. In addition, the main curing light sources 34 </ b> A and 34 </ b> B are turned on simultaneously during the printing operation of the inkjet recording apparatus 10. In the drawing mode with a slow scanning speed, one of the light sources can be turned off, and the light emission start timings of the temporary curing light sources 32A and 32B and the main curing light sources 34A and 34B may be the same or different.

<About the configuration example of the main curing light source>
As shown in FIG. 4, 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 number of elements and the arrangement form thereof are not limited to this example. For example, a configuration in which a plurality of LED elements are arranged in a line along the Y direction is also possible.

  Further, the light source of the main curing light sources 34A and 34B is not limited to the UV-LED element 35, and a UV lamp or the like can also be used.

<About temporary curing light source>
Next, a configuration example of the temporary curing light sources 32A and 32B will be described. As already described, in the case of a printing method in which ultraviolet rays are exposed while droplets are ejected from a nozzle row by single scanning, there are ink droplets with a large number of integrated exposures and ink droplets with a small number of integrated exposures within one swath. From the viewpoint of improving the variation in total exposure due to the difference in the number of exposures, improve the illuminance distribution of the temporary curing light source, and attach an illuminance distribution that increases the illuminance toward the downstream side of the nozzle row in the media transport direction. Is preferred.

  Hereinafter, a method for realizing such illuminance distribution will be described.

(Example 1: Use of a light diffusion plate)
FIG. 5 is a perspective view showing the configuration of the temporary curing light source 210 according to the first embodiment. FIG. 6 is an end view taken along line AA of FIG. As shown in FIG. 5, the temporary curing light source 210 of this example has a substantially rectangular parallelepiped box shape. The temporary curing light source 210 includes an aluminum light emitting diode (UV-LED) element 214 housed in an aluminum housing (enclosure) 212, and a transmissive light diffusing plate 216 disposed on the bottom surface of the housing 212. It has a structure. The wiring board 220 on which the UV-LED element 214 is mounted is in a state where the LED mounting surface 221 faces the light diffusion plate 216 (in FIG. 6, the light-emitting surface of the UV-LED element 214 faces downward). In the upper part of the housing 212.

  The number of UV-LED elements 214 mounted on the wiring board 220 is preferably as small as possible from the viewpoint of the necessary UV irradiation width and cost. In this example, two UV-LED elements 214 are arranged on the wiring board 220. In order to obtain a UV irradiation width capable of performing UV irradiation at a time with respect to the nozzle row width Lw along the recording medium conveyance direction (X direction) of the inkjet head 24 described in FIG. 3, two UV-LEDs The elements 214 are arranged side by side in the recording medium conveyance direction (see FIGS. 5 and 6).

  The length (LED element array width) Lu of the LED element array in which the plurality (two in this case) of UV-LED elements 214 are arranged in the X direction is shorter than the nozzle array width Lw of the inkjet head 24. (Lu <Lw).

  A metal substrate with enhanced heat dissipation and heat resistance is used as the wiring substrate 220. Although a detailed structure of the metal substrate is not shown, an insulating layer is formed on a metal plate such as aluminum or copper, and a UV-LED element 214 and a wiring circuit for driving the LED (anode wiring, cathode) are formed on the insulating layer. Wiring) and the like are formed. Note that a metal base substrate in which a circuit is formed on a base metal may be used, or a metal core substrate in which a metal plate is embedded inside the substrate may be used.

  In addition, the periphery of the UV-LED element 214 on the LED mounting surface 221 of the wiring board 220 is subjected to a UV resisting and high reflectance white resist treatment. By this white resist layer (not shown), ultraviolet rays can be reflected and scattered on the surface of the wiring board 220, and the light generated by the UV-LED elements 214 can be efficiently used for UV irradiation for temporary curing. .

  The light diffusing plate 216 is a milky white plate formed of an optical material that diffuses light emitted from the UV-LED element 214 while transmitting it. For example, the light diffusion plate 216 is a white acrylic plate in which a white pigment (light diffusion material) is dispersed. Not only the white acrylic plate but also an optical member formed by dispersing and diffusing fine particles for light diffusion in a transparent material such as glass can be used. By changing the content of light diffusing substances (white pigments, etc.) and the average particle diameter, light diffusing plates having different transmittances and diffusing characteristics can be obtained. As an example of a preferable diffusion characteristic of the light diffusion plate 216 of this example, a UV transparent acrylic (Sumitomo Chemical Co., Ltd., trade name “Sumipex 010”), a plate thickness of 3 mm, a transmittance of 94% at a wavelength of 385 nm, a radius of 1 μm FIG. 7 shows a relative reflection intensity distribution with respect to incident light when about 200,000 silica powders are dispersed per cubic mm. The desired scattering characteristics can be designed by selecting the ratio of silica powder and the average particle size.

  In addition, as a transmission type light diffusing plate, means for diffusing light is not limited to means for dispersing silica powder in this acrylic resin, and the surface of a substrate made of fused silica is subjected to frost treatment, frosted glass treatment, and ground glass treatment. Can be easily realized.

  Such a transmissive light diffusing plate 216 is disposed below the housing 212 so as to face the LED mounting surface 221 of the wiring board 220. In FIG. 6, a lower surface (reference numeral 217) of the light diffusing plate 216 is a light emitting surface facing a recording medium (not shown). The light diffused by the light diffusion plate 216 is irradiated from the light emitting surface 217 onto the recording medium with a light irradiation width equal to or greater than the nozzle row width Lw of the inkjet head 24.

  In FIG. 6, the upper surface (reference numeral 218) of the light diffusing plate 216, that is, the surface opposite to the light emitting surface 217 of the light diffusing plate 216 (the surface facing the UV-LED element 214). This is the light incident surface. The light incident surface 218 of the light diffusing plate 216 is coated with a disk-like mirror 232 (reflecting part) for reflecting and scattering the direct light of the UV-LED element 214 at a position facing the UV-LED element 214. Yes.

  FIG. 8A is a schematic plan view of the UV-LED element 214 mounted on the wiring board 220, and FIG. 8B is a plan view of the mirror 232 formed on the light diffusion plate 216. As shown in these drawings, the UV-LED element 214 and the mirror 232 are arranged in a corresponding positional relationship so as to face each other in the housing 212 (see FIG. 5).

  The housing 212 of the temporary curing light source 210 is made of an aluminum sheet metal (no treatment), and the inner peripheral surface 213 of the housing 212 (see FIG. 6) functions as a side reflector. Note that the inner peripheral surface 213 of the housing 212 may be subjected to a polishing process (mirror finish) for increasing reflectivity, white coating, or the like.

  FIG. 9 is a perspective view showing the configuration of the light emitting surface 217 of the light diffusing plate 216. In FIG. 8, the housing 212 is omitted. On the light emitting surface 217 of the light diffusing plate 216, a band-shaped (stripe-shaped) reflecting portion (reflecting mirror) 252 is formed by mirror coating. The bands of the reflection mirrors 252 are arranged in such a distribution that the illuminance increases toward the downstream side in the media conveyance direction. That is, the band of the reflection mirror 252 has a wider width (width in the X direction) toward the upstream side in the media conveyance direction, and gradually becomes narrower toward the downstream side. The portion of the reflection mirror 252 does not transmit light, and light is irradiated from the portion without the reflection mirror 252 (reference numeral 254).

  That is, of the light reaching the light emitting surface 217 of the light diffusing plate 216, the light reaching the reflecting mirror 252 is reflected by the reflecting mirror 252 and returns into the light diffusing plate 216. On the other hand, of the light reaching the light exit surface 217 of the light diffusion plate 216, the light reaching the portion where the reflection mirror 252 is not present (the light passage portion 254 between the bands of the reflection mirror 252) is the light passage portion. The light diffuser 216 comes out of the light diffuser 254. The band of the reflection mirror 252 on the light exit surface 217 of the light diffusing plate 216 is designed to change the band width based on a certain polynomial so that a desired illuminance distribution can be obtained. The width (X direction width) of the light passage portion 254 that is not coated with the reflection mirror 252 is wider toward the downstream side in the media transport direction, and an illuminance distribution in which the illuminance increases toward the downstream side is realized.

  According to the provisional curing light source 210 having the above-described configuration, the light emitted from the UV-LED element 214 is reflected and scattered by the mirror 232 of the light diffusion plate 216, and the inner peripheral surface 213 (side surface) of the mirror 232 and the housing 212. The light diffuser 216 enters the light diffusing plate 216 while being reflected and scattered by the white resist layer of the wiring board 220 and the like. Light that has entered from the light incident surface 218 of the light diffusing plate 216 is diffused through the light diffusing plate 216 and irradiated onto the recording medium through the light passing portion 254 of the light emitting surface 217.

  10 and 11 are graphs showing the illuminance distribution on the media surface of the ultraviolet rays irradiated from the temporary curing light source 210. FIG. FIG. 10 shows an illuminance distribution cross section in the media transport direction (X direction), and FIG. 11 shows an illuminance distribution cross section in the Y direction. These show the distribution on the center line (Y direction center line, X direction center line) of the irradiation area on the media surface.

  As shown in FIG. 10, the illuminance increases toward the downstream side in the media transport direction. Ideally, a distribution in which the illuminance changes stepwise according to the number of passes is preferable.

  Conventionally, when ultraviolet exposure is performed while droplets are ejected from a nozzle row by single ring scanning, a difference occurs in the integrated light amount exposed by temporary curing light for the droplet ejection ink within one swath depending on the drawing mode, which causes banding. However, as in the embodiment of the present invention, by using a temporary curing light source with a devised illuminance distribution, it is possible to reduce the total exposure amount difference for each droplet in one swath and to reduce the banding phenomenon. It became. As a result, the banding unevenness is small and inconspicuous. Further, the adhesion and gloss of the ink to the recording medium can be improved.

  In addition, according to the temporary curing light source 210 of this example, light having a length equal to or larger than the nozzle row width Lw is obtained with a configuration (Lu <Lw) using a small number (two in this case) of UV-LED elements 214. The irradiation width is realized.

  According to the present embodiment, it is possible to efficiently generate an illuminance distribution having a light irradiation width equal to or larger than a nozzle row width suitable for temporary curing, using a small number of UV-LED elements.

<About the form which changes the light quantity and illumination distribution of a temporary hardening light source>
When the amount of temporary curing irradiated immediately after droplet ejection is insufficient, or when the difference in exposure amount for each ink droplet in the swath is large, it is due to coalescence of adjacent ink droplets on the recording medium. The dot center of gravity will move. In order to solve such problems, it is desirable to adjust the amount of irradiation light for temporary curing as necessary.

  Since the temporary curing light amount for preventing ink droplets from moving for each recording medium differs depending on the type of recording medium used, it is preferable that only the temporary curing light amount can be adjusted according to the type of recording medium. Furthermore, since the optimal illuminance distribution of the ultraviolet rays emitted from the temporary curing light source varies depending on the number of main and sub print passes, it is preferable that the illuminance distribution can be changed according to the number of main and sub print passes.

  In order to enable such light amount adjustment and illuminance distribution adjustment of the temporary curing light source, the light diffusion plate 216 of the temporary curing light source is configured to be replaceable. A plurality of types of light diffusing plates 216 with different diffusion transmittances and different distributions of the reflecting mirrors 252 on the light emitting surface 217 are prepared in advance, and the light diffusing plate 216 is replaced according to the recording medium to be used and the drawing mode.

  For example, a light diffusion plate having a lower transmittance is used as the recording medium used has a higher surface reflectance. In addition, a light diffusing plate with a distribution of reflecting mirrors 252 that realizes an appropriate illuminance distribution is prepared in advance for each drawing mode, and an operator (printer operator) can respond according to the drawing mode at the time of printing. Replace the light diffusing plate.

  In order to facilitate the work of replacing the light diffusion plate 216, an attachment structure for detachably attaching the light diffusion plate 216 to the lower portion of the housing 212 is provided. Specifically, for example, a groove for supporting the edge of the light diffusing plate 216 is formed in the light diffusing plate mounting portion of the housing 212, and the light diffusing plate 216 is inserted along the groove to form the light diffusing plate. Set 216. When replacing the light diffusion plate 216, the set light diffusion plate 216 is pulled out and another light diffusion plate is reinserted. Not only such an insertion / removal attachment structure but also various attachment structures such as a structure for attaching / detaching using the engagement of the claws and a structure for attaching / detaching using the fitting of the unevenness can be adopted.

  Moreover, it can replace with the structure which replaces only a light diffusing plate, and the structure replaced with the temporary hardening light source containing a light diffusing plate is also possible. In this case, multiple types of temporary curing light sources corresponding to the recording medium to be used and the drawing mode are prepared in advance, and the operator (printer operator) can respond according to the type of recording medium to be used and the drawing mode at the time of printing. Work to replace the temporary curing light source.

  By replacing the light diffusing plate or the provisional curing light source including the light diffusing plate, it is possible to adjust the distribution of the amount of provisional curing light and reduce unevenness due to droplet ejection interference.

  Further, when the print resolutions in the main scanning direction and the sub-scanning direction are different, that is, when the image forming pixel grid is rectangular, gaps and streaks may be generated due to coalescence of the landing inks. Even in such a case, it is effective to adjust the amount of provisional curing light.

<Adhesion of ink to recording medium>
The adhesion varies depending on the interaction between the ink and the recording medium (medium), and the longer the uncured time, the greater the adhesion of the ink to the medium. Since the tendency varies depending on the type of the recording medium, it is desirable to change the temporary curing light amount for each medium.

  As a method of changing the temporary curing light amount for each medium, a method of PWM controlling the drive waveform of the UV-LED element, a method of controlling the duty of the lighting drive waveform, a method of reducing the operating current, and the like can be considered. However, in comparison with such drive control, the method in which the operator replaces the light diffusing plate or the temporary curing light source including the light diffusion plate prevents the setting error for the operator by performing the replacing operation at the same time as replacing the media. There is an advantage that you can.

(Example 2: Formation of illuminance distribution by inclination (rotation) of reflector)
Next, a second embodiment suitable as a temporary curing light source will be described. FIG. 12 is a perspective view showing the main configuration of the temporary curing light source 260 according to the second embodiment. The temporary curing light source 260 includes an LED element array in which a plurality of UV-LED elements 264 are arranged in a line along the X direction (media transport direction), and a substantially semi-cylindrical reflector 266. The Here, an LED element array in which 11 UV-LED elements 264 are arranged is illustrated, but the number of UV-LED elements 264 is not particularly limited.

  The reflector 266 has a length (width) equal to or greater than the length (Lu) of the LED element array, and the reflector 266 covers the side surface portion on one side of the LED element array and the upper part of the LED element array. The light emitted from each UV-LED element 264 is reflected by the reflector 266, and ultraviolet rays are irradiated from the opening (light exit) of the reflector 266 toward the Z direction in FIG. The Z direction is a direction toward a recording medium (not shown in FIG. 12).

  The reflector 266 is arranged so that the distance (height of the reflector 266) between the UV-LED element 264 and the reflector 266 differs between the upstream side and the downstream side in the media transport direction (X direction). In other words, the longitudinal axis of the reflector 266 is inclined at a rotation angle of the angle θ with respect to the arrangement direction (X direction) of the UV-LED elements 264 so that the height of the reflector 266 becomes lower toward the downstream side in the media transport direction. In the state, the reflector 266 is arranged.

  For comparison, FIG. 13 shows an example of a temporary curing light source in which the height of the reflector 266 is configured to be constant. 13, elements that are the same as or similar to those shown in FIG. 12 are given the same reference numerals, and descriptions thereof are omitted. The provisional curing light source 260 ′ shown in FIG. 13 includes a second reflector 268 opposite to the substantially cylindrical reflector 266 (referred to as “first reflector”). A portion of a gap between the first reflector 266 and the second reflector 268 becomes a light emission port 270. In FIG. 12, the second reflector 268 is omitted for convenience of illustration, but the temporary curing light source 260 of FIG. 12 also includes the second reflector 268 as in FIG. 13. The second reflector 268 is fixed to the substrate on which the UV-LED element 264 is mounted, and even when the first reflector 266 is rotated, the second reflector 268 is not rotated.

  As shown in FIG. 14, the light exit 270 formed by the first reflector 266 and the second reflector 268 is directed downward, and ultraviolet rays are irradiated from the light exit 270 toward the recording medium 12 below. Is done.

  15 and 16 are graphs showing the illuminance distribution on the media surface of the temporary curing light source 260 'according to the comparison. FIG. 15 shows an illuminance distribution cross section in the media transport direction (X direction), and FIG. 16 shows an illuminance distribution cross section in the main scanning direction (Y direction). These show the distribution on the center line (Y direction center line, X direction center line) of the irradiation area on the media surface.

  17 and 18 are graphs showing the illuminance distribution on the media surface of the temporary curing light source 260 according to the embodiment described in FIG. FIG. 17 shows an illuminance distribution cross section in the media transport direction (X direction), and FIG. 18 shows an illuminance distribution cross section in the Y direction. These show the distribution on the center line (Y direction center line, X direction center line) of the irradiation area on the media surface.

  In FIG. 15, the distribution is generally uniform in the media conveyance direction, whereas in FIG. 17, an illuminance distribution is formed such that the illuminance increases from upstream to downstream in the media conveyance direction.

  As described with reference to FIG. 12, by adjusting the inclination (rotation) angle θ of the reflector 266, the illuminance distribution in the media transport direction can be adjusted, and a desired illuminance distribution can be obtained.

  An angle adjustment mechanism capable of adjusting the inclination (rotation) angle θ of the reflector 266 may be provided, or a plurality of types of temporary curing light sources having different angles θ of the reflector 266 may be prepared in advance. The angle θ of the reflector 266 is changed according to the type of the recording medium 12 to be used, the drawing mode, the number of main / sub passes, the drawing swath width, etc. Replace.

(Example 3: Formation of illuminance distribution by light emission control of LED element array)
Next, a third embodiment suitable as a temporary curing light source will be described. FIG. 19 is a plan view showing the main configuration of the temporary curing light source 280 according to the third embodiment. The temporary curing light source 280 includes an LED element array in which a plurality of UV-LED elements 264 are arranged in a line along the X direction (media transport direction).

  These UV-LED elements 264 are individually or in units of blocks divided into a plurality of blocks along the X direction to control the amount of light (radiance), and the illuminance decreases toward the downstream side in the media transport direction. Form a high illuminance distribution.

  FIG. 20 is a perspective view showing the relationship between the LED element array constituting the temporary curing light source 280 and the media surface. FIGS. 21 and 22 are graphs showing the illuminance distribution on the media surface 290 of the temporary curing light source 280. FIG. 21 shows an illuminance distribution cross section in the media transport direction (X direction), and FIG. 22 shows an illuminance distribution cross section in the Y direction. These show the distribution on the center line (Y direction center line, X direction center line) of the irradiation area on the media surface.

  As shown in FIG. 21, an illuminance distribution in which the illuminance increases from the upstream side to the downstream side in the X direction on the media surface is obtained. By using the temporary curing light source 280 having such an illuminance distribution, it was possible to reduce the difference in the exposure amount of the droplets in the swath. Although FIG. 19 shows an example in which the packages of eight UV-LED elements 264 are linearly arranged in a line, the number of UV-LED elements 264 arranged and the arrangement form thereof are not particularly limited. For example, a form in which a plurality of UV-LED element arrays are arranged is also possible.

  Further, the method for controlling the lighting light amount is not limited to the current value control, and each lighting light amount can be changed by pulse width modulation (PWM) control or duty (Duty) control.

  Radiation brightness of each UV-LED element 264 in accordance with a change in swath width that changes depending on the print mode, the number of main and sub print passes, the print swath width determined from the nozzle row width and the main and sub print pass numbers, and the output resolution setting Is preferably controlled.

(Example 4: Formation of illumination distribution by combination of light emission control of LED element array and reflector)
FIG. 23 is a perspective view showing a main configuration of the temporary curing light source 300 according to the fourth embodiment. In this temporary curing light source 300, a plurality of (here, six) UV-LED elements 304 are arranged in a constant interval along the X direction. The LED element group which comprises. Each UV-LED element 304 is provided with a substantially parabolic reflector 306. FIG. 23 shows an example in which packages of 12 UV-LED elements 304 are arranged in 6 × 2 rows, but the number and arrangement form of the UV-LED elements 304 are not particularly limited.

  24 is a perspective view showing a state of the light emission side of the configuration shown in FIG. 23, and FIG. 25 is a plan view of the configuration of FIG. 23 viewed from the light emission side. As shown in FIGS. 23 to 25, the light generated from the light emitting unit 305 of each UV-LED element 304 is transmitted from the opening (light emitting port) 308 of each reflector 306 to the recording medium (in FIGS. 23 to 25). Irradiated toward (not shown).

  In the fourth embodiment, similarly to the third embodiment, the current value control is performed by individually controlling the UV-LED elements 304 or in units of blocks divided into a plurality of blocks along the X direction. (Radiance) is controlled, and an illuminance distribution with higher illuminance is formed on the downstream side in the media conveyance direction.

  26 and 27 are graphs showing the illuminance distribution on the media surface of the temporary curing light source 300. FIG. 26 shows an illuminance distribution cross section in the media transport direction (X direction), and FIG. 27 shows an illuminance distribution cross section in the Y direction. These show the distribution on the center line (Y direction center line, X direction center line) of the irradiation area on the media surface. As shown in FIG. 26, an illuminance distribution in which the illuminance increases from upstream to downstream in the X direction is obtained.

  Further, not only the current value control but also the respective lighting amounts can be changed by pulse width modulation (PWM) control or duty (Duty) control. Furthermore, it is possible to change the radiance of each UV-LED element 304 in accordance with the change in swath width depending on the output resolution in accordance with the drawing mode.

(Example 5: Configuration in which an LED package is disposed at the end of a light diffusion box)
FIG. 28 is a perspective view showing the configuration of the temporary curing light source 330 according to the fifth embodiment. The temporary curing light source 330 has a configuration in which a package of the UV-LED element 334 is disposed on an end surface portion of a light diffusion box 332 having a hollow inside. The light diffusion box 332 is made of an aluminum plate whose inner peripheral surface is specularly reflected. The ceiling surface of the light diffusion box 332 has an inclined surface 340 whose height gradually decreases toward the upstream in the X direction. A cover glass (not shown) is disposed at the bottom of the light diffusion box 332. The surface of the cover glass that faces the media surface 350 (the bottom surface of the light diffusion box 332) is the light exit surface. The side plate 346 of the light diffusion box 332 functions as a side reflector that surrounds the side peripheral surface between a ceiling surface having an inclined reflecting surface (inclined surface 340) and a bottom surface that functions as a light emitting surface.

  The package of the UV-LED element 334 is arranged on the end surface portion of the light diffusion box 332 on the downstream side in the X direction with the light emitting surface facing the upstream side. The light emitted from the UV-LED element 334 is reflected and scattered inside the light diffusion box 332 and irradiated from the light exit surface toward the recording medium below. According to such a configuration, the illuminance distribution on the media surface 350 can be formed so that the illuminance distribution is higher toward the downstream in the media transport direction. In FIG. 28, only one UV-LED element 334 is arranged on the end face. However, when it is necessary to increase the amount of light, the light diffusion box 332 is enlarged and the UV-LED elements 334 are arranged vertically and horizontally. Is possible.

  Further, it is possible to coat the cover glass provided facing the media surface with a reflection mirror and adjust the illuminance distribution by the pattern. FIG. 29 is a diagram showing an example of a pattern mask formed on the light emitting surface. FIG. 29 shows an example in which a cover glass is coated with a striped reflection mirror 348. A portion (reference numeral 349) where the reflection mirror 348 is not coated becomes a light passage portion.

  30 and 31 are graphs showing the illuminance distribution on the media surface of the temporary curing light source 300. FIG. 30 shows an illuminance distribution cross section in the media transport direction (X direction), and FIG. 31 shows an illuminance distribution cross section in the Y direction. These show the distribution on the center line (Y direction center line, X direction center line) of the irradiation area on the media surface. As shown in FIG. 30, an illuminance distribution in which the illuminance increases from upstream to downstream in the media conveyance direction is obtained.

  The space inside the light diffusion box 332 in this example corresponds to the “light diffusion space”, the ceiling surface of the light diffusion box 332 corresponds to the “first reflection surface”, and the side reflection by the side plate 346 is “first”. It corresponds to “2 reflecting surfaces”.

(Example 6: Formation of illuminance distribution by light guide)
FIG. 32 is a perspective view showing the configuration of the temporary curing light source 370 according to the sixth embodiment. This temporary curing light source 370 has a configuration in which a package of UV-LED elements 374 is disposed on an end surface portion of a rectangular parallelepiped light guide 372 that is long in the medium conveyance direction (X direction).

  The light guide 372 is made of a transparent optical material. A white scattering pattern 376 is formed on the upper surface (surface opposite to the light emitting surface) of the light guide 372 with a paint in which titanium oxide powder is dispersed. The white scattering pattern 376 is obtained by distributing a large number of circular scattering portions in a predetermined arrangement form (for example, a staggered arrangement or a square lattice arrangement). The coverage per unit area can be changed by changing the size (diameter) of the circular scattering portion depending on the position on the light guide 372. The distribution of irradiation light emitted from the lower surface (light emission surface) of the light guide 372 can be adjusted by the pattern shape of the white scattering pattern 376 provided on the upper surface of the light guide 372.

  The package of the UV-LED element 374 is disposed with the light emitting surface facing the upstream in the X direction and the light emitting surface facing the upstream in the X direction at the end surface portion of the light guide 372 on the downstream side in the X direction. Usually, light incident from one end surface 378 of the light guide 372 propagates through the light guide 372 and reaches the opposite surface (the other end surface) while being totally reflected at the boundary surface of the light guide 372. . When the incident angle with respect to the boundary surface of the light guide 372 is larger than the critical angle, the light is totally reflected at the boundary surface, and when the incident angle is smaller than the critical angle, the light passes outside the light guide.

  By providing the white scattering pattern 376 on the upper portion of the light guide 372, light can be scattered on the upper surface of the light guide 372 and the amount of light totally reflected can be adjusted. Depending on the distribution of the white scattering pattern 376, the distribution of the ultraviolet rays irradiated below the light guide 372 can be arbitrarily designed, and a desired illuminance distribution can be obtained.

  For example, in the case of a configuration in which light is incident from one end surface 378 of the light guide 372, the white scattering pattern 376 increases the total reflection component closer to the UV-LED element 374 (downward in the X direction) and farther away. As the total reflection component is reduced, the amount of light that diffuses downward increases as the amount of light decreases, and provisional curing irradiation with a uniform illuminance distribution in the X direction can be realized.

  The configuration in which the UV-LED element 374 is arranged on the end surface on the downstream side in the X direction of the light guide 372 and the distribution of the white scattering pattern 376 provided on the upper surface of the light guide 372 are combined to irradiate the upstream side in the X direction. A desired distribution in which the UV light becomes small (that is, a distribution in which the UV light increases toward the downstream side) can be obtained.

  33 and 34 are graphs showing the illuminance distribution on the media surface of the temporary curing light source 370. FIG. 33 shows an illuminance distribution cross section in the media conveyance direction (X direction), and FIG. 34 shows an illuminance distribution cross section in the Y direction. These show the distribution on the center line (Y direction center line, X direction center line) of the irradiation area on the media surface.

  In addition, as a base material of the light guide 372, it is also possible to use a material in which silica powder is dispersed in the acrylic resin described in the first embodiment. Such an aspect is effective for uniformly tilting the illuminance distribution with respect to the X direction.

  Further, a plurality of types of temporary curing light sources having different illuminance distributions may be prepared in advance according to the configurations of the fifth and sixth embodiments. It is preferable to change the temporary curing light source so as to obtain an optimum illuminance distribution according to the type of the recording medium 12 to be used, the drawing mode, the number of main / sub passes, the drawing swath width, and the like.

<About LED arrangement density of temporary curing light source>
In any of the configurations of Examples 1 to 6 described above, various designs are possible for the number of UV-LED elements used in the temporary curing light source, the arrangement form, and the arrangement density. However, the arrangement density of the LED elements when the temporary curing light source is configured using a plurality of UV-LED elements is smaller than the arrangement density of the UV-LED elements 35 constituting the main curing light sources 34A and 34B. It is preferable. For example, when the provisional curing light sources 32A and 32B and the main curing light sources 34A and 34B are configured by using a plurality of UV-LED elements having the same specification, between the UV-LED elements in the LED arrangement constituting the provisional curing light sources 32A and 32B. Is made larger than the distance (arrangement interval) between the UV-LED elements in the LED arrangement constituting the main curing light sources 34A and 34B.

  In addition, the temporary curing light sources 32A and 32B can be configured using LED elements having specifications (light emission performance and light emission characteristics) different from those of the UV-LED elements used for the main curing light sources 34A and 34B. Also in this case, it is preferable to make the LED arrangement density of the temporary curing light source smaller (sparsely arranged) than the LED arrangement density of the main curing light source.

<Effect of preventing banding according to the embodiment of the present invention>
A uniform density image (solid image) with a certain gradation was drawn on the recording medium 12 using the inkjet recording apparatus 10 according to the embodiment of the present invention. The drawing result is read by a scanner, and the pixel values of the square area of 256 pixels in the main scanning direction (carriage scanning direction) × 256 pixels in the sub-scanning direction (media transport direction) are added in the vertical direction (Y direction) to obtain 4 in the X direction. The graph which calculated | required the moving average for every pixel is shown to Fig.35 (a).

  FIG. 35B is a graph in which a similar experiment was performed using a conventional inkjet recording apparatus for comparison. In the upper part of each graph of FIGS. 35A and 35B, a line schematically showing the result of each moving average is shown. In FIG. 35 (a), the value of the graph is substantially constant, and there is no density step due to banding. On the other hand, in FIG. 35B, there is a density step due to banding at the center.

<Description of ink supply system>
FIG. 36 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. 37 is a block diagram showing the configuration of the inkjet recording apparatus 10. As shown in the figure, the ink jet recording apparatus 10 is provided with a control device 102 as control means. As the control device 102, for example, a computer having a central processing unit (CPU) can be used. The control device 102 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 102 includes a recording medium conveyance control unit 104, a carriage drive control unit 106, a light source control unit 108, an image processing unit 110, and an ejection control unit 112. Each of these units is realized by a hardware circuit or software, or a combination thereof.

  The recording medium conveyance control unit 104 controls the conveyance driving unit 114 for conveying the recording medium 12 (see FIG. 1). The conveyance drive unit 114 includes a drive motor that drives the nip roller 40 shown in FIG. 2 and a drive circuit thereof. The recording medium 12 conveyed on the platen 26 (see FIG. 1) 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 106 shown in FIG. 37 controls a main scanning drive unit 116 for moving the carriage 30 (see FIG. 1) in the main scanning direction. The main scanning drive unit 116 includes a drive motor connected to a moving mechanism of the carriage 30 and a control circuit thereof. The light source control unit 108 controls the light emission of the UV-LED elements (214, 264, 304, 334, 374) of the temporary curing light sources 32A, 32B via the LED drive circuit 118 and the main light source via the LED drive circuit 119. This is a control means for controlling the light emission of the UV-LED elements 35 of the curing light sources 34A and 34B.

  The control device 102 is connected to an input device 120 such as an operation panel and a display device 122. The input device 120 is means for inputting a manual external operation signal to the control device 102. 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 as the display device 122. By operating the input device 120, 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 stored on the display device 122. It can be confirmed through the display.

  Further, the ink jet recording apparatus 10 is provided with an information storage unit 124 for storing various types of information and an image input interface 126 for taking in 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 126 is converted into print data (dot data) by the image processing unit 110. The dot data is generally generated by performing color conversion processing and halftone processing on multi-tone image data. The color conversion process is a process of converting image data expressed in sRGB or the like (for example, 8-bit image data for each RGB color) into color data for each ink color used in the inkjet recording apparatus 10.

  The halftone process is a process for converting the color data of each color generated by the color conversion process into dot data of each color by a process such as an error diffusion method or a threshold matrix. 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 112 generates an ejection control signal for the head drive circuit 128 based on the dot data generated by the image processing unit 110. Further, the discharge control unit 112 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 generation element (in this example, a piezo element) corresponding to each nozzle of the inkjet head 24. The waveform data of the drive voltage signal is stored in advance in the information storage unit 124, 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 128. 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 24 via the head driving circuit 128, 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 124 stores programs executed by the CPU of the control device 102, various data necessary for control, and the like. The information storage unit 124 stores resolution setting information according to the drawing mode, the number of passes (the number of scan repetitions), control information for the temporary curing light sources 32A and 32B, and the main curing light sources 34A and 34B.

  The encoder 130 is attached to the drive motor of the main scanning drive unit 116 and the drive motor of the transport drive unit 114, and outputs a pulse signal corresponding to the rotation amount and rotation speed of the drive motor. Is sent to the controller 102. Based on the pulse signal output from the encoder 130, the position of the carriage 30 and the position of the recording medium 12 (see FIG. 1) are grasped.

  The sensor 132 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 132.

<Operational Effect of Inkjet Recording Apparatus of this Embodiment>
(1) By completely separating the functions of the temporary curing light source and the main curing light source, it is possible to simply change only the amount of temporary curing corresponding to the media to be used. Thereby, it is possible to appropriately adjust the degree of interaction between the ink and the medium.

  (2) By giving a distribution to the illuminance of irradiation light for pre-curing, it is possible to reduce the exposure amount difference in the swath, and it is possible to create a print with high uniformity of dot diameter and gloss uniformity. .

  (3) It is possible to easily change the illuminance distribution and the light amount of the temporary curing light source according to the drawing mode, the number of main and sub print passes, the drawing swath width, the type of media, the type of ink, and the like.

  (4) By creating an appropriate illuminance distribution of temporary curing light according to the drawing mode, the number of main and sub printing passes, drawing swath width, media type, ink type, etc., the integrated light amount by single ring drawing and exposure This makes it possible to minimize the difference between the dots and the dot diameter and dot height of the droplet ejection dots. As a result, the banding phenomenon in which the swath width is conspicuous in a band shape can be reduced, and a highly durable print with improved adhesion can be created.

<Modification 1>
In the above embodiment, an example in which the drawing head unit (inkjet head 24) has one nozzle row for each color has been described, but the nozzle arrangement is not limited to this example. For example, for each color, a two-row zigzag arrangement, or a multi-row matrix arrangement or other two-dimensional arrangement may be used.

<Modification 2>
In the inkjet head 24 of FIG. 3, the nozzle rows 61 for each color are arranged in a plurality of rows (the same number of ink colors) at a constant nozzle row pitch along the main scanning direction (Y direction). The interval between the nozzle rows in the direction is not necessarily constant.

<Modification 3>
In the above embodiment, the temporary curing light sources 32A and 32B and the main curing light sources 34A and 34B are symmetrically arranged on both sides of the inkjet head 24 in the main scanning direction (arranged symmetrically with respect to the center line), and reciprocating scanning (both sides). Although an example in which droplet ejection and UV exposure are performed is described above, a mode in which a temporary curing light source and a main curing light source are disposed only on one side of the inkjet head 24 and drawing is performed during one-way scanning is also possible.

<Device application example>
In the above-described embodiment, the wide format ink jet recording apparatus is exemplified, but the scope of application of the present invention is not limited to this. Application to inkjet recording apparatuses other than the wide format is also possible. In addition, the present invention is not limited to graphic printing applications, electronic circuit board wiring drawing apparatuses, various device manufacturing apparatuses, resist printing apparatuses that use a resin liquid as a functional liquid for ejection (corresponding to “ink”), The present invention can be applied to various image forming apparatuses that can form various image patterns such as a fine structure forming apparatus.

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 12 ... Recording medium, 24 ... Inkjet head, 26 ... Platen, 28 ... Guide mechanism, 30 ... Carriage, 32A, 32B ... Temporary curing light source, 34A, 34B ... Main curing light source, 36 ... Ink cartridge, DESCRIPTION OF SYMBOLS 210 ... Temporary curing light source, 212 ... Housing, 214 ... Ultraviolet light emitting diode (UV-LED) element, 216 ... Light diffusing plate, 217 ... Light emission surface, 220 ... Wiring board, 221 ... LED mounting surface, 232 ... Mirror, 252 ... reflective mirror, 254 ... light passage part, 260, 280, 300, 330, 370 ... preliminary curing light source, 264, 304, 334, 374 ... ultraviolet light emitting diode (UV-LED) element, 266,268 ... reflector, 290, 350 ... Media surface, 306 ... Reflector, 332 ... Light diffusion box, 340 ... Inclined surface, 34 8: reflection mirror, 372: light guide, 376: white scattering pattern

Claims (15)

An inkjet head having a plurality of nozzles for discharging ink that is cured by irradiation with actinic rays;
Medium conveying means for conveying a recording medium to which ink droplets ejected from the inkjet head are attached;
Scanning means for moving the inkjet head relative to the recording medium;
A temporary curing light source that irradiates with an actinic ray that is moved together with the inkjet head by the scanning means and incompletely cures ink droplets attached on the recording medium;
A main curing light source that is provided separately from the temporary curing light source, performs additional exposure on the ink droplets exposed by the temporary curing light source, and irradiates actinic rays for main curing the ink droplets;
With
The inkjet head, the temporary curing light source, and the main curing light source are integrally mounted on a carriage, and the scanning unit moves the carriage relative to the recording medium.
The actinic ray emitted from the temporary curing light source has an illuminance distribution on the surface of the recording medium where the illuminance increases from upstream to downstream in the recording medium conveying direction by the medium conveying means ,
The temporary curing light source is
At least one active light emitting device;
A transmissive light diffusing plate for diffusing while transmitting light emitted from the actinic light emitting element;
A side reflector that surrounds a side peripheral surface between the wiring board on which the actinic light emitting element is mounted and the light diffusion plate; and
An image forming apparatus , wherein a light reflecting portion and a light passing portion for obtaining the illuminance distribution are formed on a light emitting surface of the light diffusing plate facing the recording medium . The inkjet head has a nozzle row in which the nozzles are arranged in the recording medium conveyance direction,
The temporary curing light source has a light emitting element array in which a plurality of actinic light emitting elements are arranged in the recording medium conveyance direction, and the length of the light emitting element array is shorter than the length of the nozzle array. The image forming apparatus according to claim 1 . Plural types of the temporary curing light source or light diffusing plate having different illuminance distributions on the recording medium are prepared, and the temporary curing light source or the light diffusing plate selected from the plurality of types can be attached interchangeably. the image forming apparatus according to claim 1 or 2, characterized in that it comprises a mounting structure. An inkjet head having a plurality of nozzles for discharging ink that is cured by irradiation with actinic rays;
Medium conveying means for conveying a recording medium to which ink droplets ejected from the inkjet head are attached;
Scanning means for moving the inkjet head relative to the recording medium;
A temporary curing light source that irradiates with an actinic ray that is moved together with the inkjet head by the scanning means and incompletely cures ink droplets attached on the recording medium;
A main curing light source that is provided separately from the temporary curing light source, performs additional exposure on the ink droplets exposed by the temporary curing light source, and irradiates actinic rays for main curing the ink droplets;
With
The inkjet head, the temporary curing light source, and the main curing light source are integrally mounted on a carriage, and the scanning unit moves the carriage relative to the recording medium.
The actinic ray emitted from the temporary curing light source has an illuminance distribution on the surface of the recording medium where the illuminance increases from upstream to downstream in the recording medium conveying direction by the medium conveying means,
The temporary curing light source is
A light emitting element array in which a plurality of actinic light emitting elements are arranged in the recording medium conveying direction;
A reflector that reflects the light emitted by each active light emitting element toward the recording medium,
The reflector, toward the downstream side of the recording medium conveyance direction, wherein as the height from the active light emitting element to the reflector is reduced, characterized in that it is arranged relative to the light emitting element array image Image forming apparatus. An inkjet head having a plurality of nozzles for discharging ink that is cured by irradiation with actinic rays;
Medium conveying means for conveying a recording medium to which ink droplets ejected from the inkjet head are attached;
Scanning means for moving the inkjet head relative to the recording medium;
A temporary curing light source that irradiates with an actinic ray that is moved together with the inkjet head by the scanning means and incompletely cures ink droplets attached on the recording medium;
A main curing light source that is provided separately from the temporary curing light source, performs additional exposure on the ink droplets exposed by the temporary curing light source, and irradiates actinic rays for main curing the ink droplets;
With
The inkjet head, the temporary curing light source, and the main curing light source are integrally mounted on a carriage, and the scanning unit moves the carriage relative to the recording medium.
The actinic ray emitted from the temporary curing light source has an illuminance distribution on the surface of the recording medium where the illuminance increases from upstream to downstream in the recording medium conveying direction by the medium conveying means,
The temporary curing light source is
A first reflecting surface having an inclined surface whose height gradually decreases toward the upstream in the recording medium conveyance direction;
A light emitting surface disposed between the first reflecting surface and the recording medium and facing the recording medium;
A second reflecting surface surrounding a side peripheral surface between the first reflecting surface and the light emitting surface;
An actinic light emitting element disposed at an end of the light diffusion space defined by the first reflecting surface, the light emitting surface, and the second reflecting surface on the downstream side in the recording medium conveyance direction;
Images forming device you comprising: a. 6. The image forming apparatus according to claim 5 , wherein a light reflecting portion and a light passing portion for obtaining the desired illuminance distribution are formed on the light emitting surface. An inkjet head having a plurality of nozzles for discharging ink that is cured by irradiation with actinic rays;
Medium conveying means for conveying a recording medium to which ink droplets ejected from the inkjet head are attached;
Scanning means for moving the inkjet head relative to the recording medium;
A temporary curing light source that irradiates with an actinic ray that is moved together with the inkjet head by the scanning means and incompletely cures ink droplets attached on the recording medium;
A main curing light source that is provided separately from the temporary curing light source, performs additional exposure on the ink droplets exposed by the temporary curing light source, and irradiates actinic rays for main curing the ink droplets;
With
The inkjet head, the temporary curing light source, and the main curing light source are integrally mounted on a carriage, and the scanning unit moves the carriage relative to the recording medium.
The actinic ray emitted from the temporary curing light source has an illuminance distribution on the surface of the recording medium where the illuminance increases from upstream to downstream in the recording medium conveying direction by the medium conveying means,
The temporary curing light source is
A light guide having a light exit surface facing the recording medium;
An actinic light emitting element disposed at the downstream end of the light guide in the recording medium conveyance direction;
A scattering pattern that is provided on a surface opposite to the light exit surface of the light guide, and scatters light into the light guide;
Images forming device you comprising: a. The inkjet head has a nozzle row in which the nozzles are arranged in the recording medium conveyance direction,
The temporary curing light source, an image forming apparatus according to any one of claims 1 to 7, characterized in that irradiation with actinic rays in length or more light irradiation width of the nozzle array on the recording medium. The actinic rays are ultraviolet rays;
The active light emitting element used in the provisional curing light source, an image forming apparatus according to any one of claims 1 to 8, characterized in that an ultraviolet light emitting diode element. The number of printing passes in the main scanning direction and the sub-scanning direction, the drawing mode, the drawing swath width, and the main scanning direction when the scanning direction by the scanning unit is the main scanning direction and the recording medium conveyance direction by the medium conveying unit is the sub-scanning direction. and among the sub-scanning direction resolution, in response to at least one image forming apparatus according to any one of claims 1 to 9, characterized in that it is possible to change the illuminance distribution of the temporary curing light source . Actinic ray irradiation for temporary curing, which is emitted from an inkjet head having a plurality of nozzles that eject ink that is cured by irradiation of actinic rays and irradiates the actinic rays to the extent that ink droplets attached on the recording medium are incompletely cured A device,
It is mounted on a carriage together with the inkjet head,
On the surface of the recording medium, the illuminance distribution is adjusted so that the illuminance increases from upstream to downstream in the conveyance direction of the recording medium ,
At least one active light emitting device;
A transmissive light diffusing plate for diffusing while transmitting light emitted from the actinic light emitting element;
A side reflector that surrounds a side peripheral surface between the wiring board on which the actinic light emitting element is mounted and the light diffusion plate; and
An actinic ray irradiating apparatus for temporary curing , wherein a light reflecting portion and a light passing portion for obtaining the illuminance distribution are formed on a light emitting surface of the light diffusing plate facing the recording medium .   Actinic ray irradiation for temporary curing, which is emitted from an inkjet head having a plurality of nozzles that eject ink that is cured by irradiation of actinic rays and irradiates the actinic rays to the extent that ink droplets attached on the recording medium are incompletely cured A device,
  It is mounted on a carriage together with the inkjet head,
  On the surface of the recording medium, the illuminance distribution is adjusted so that the illuminance increases from upstream to downstream in the conveyance direction of the recording medium,
A light emitting element array in which a plurality of actinic light emitting elements are arranged in the transport direction of the recording medium;
  A reflector that reflects the light emitted by each active light emitting element toward the recording medium,
  The temporary reflector is disposed with respect to the light emitting element row so that the height from the actinic light emitting element to the reflector becomes lower toward the downstream side in the conveyance direction of the recording medium. Actinic ray irradiation device for curing.   Actinic ray irradiation for temporary curing, which is emitted from an inkjet head having a plurality of nozzles that eject ink that is cured by irradiation of actinic rays and irradiates the actinic rays to the extent that ink droplets attached on the recording medium are incompletely cured A device,
  It is mounted on a carriage together with the inkjet head,
  On the surface of the recording medium, the illuminance distribution is adjusted so that the illuminance increases from upstream to downstream in the conveyance direction of the recording medium,
A first reflecting surface having an inclined surface whose height gradually decreases toward the upstream in the conveying direction of the recording medium;
  A light emitting surface disposed between the first reflecting surface and the recording medium and facing the recording medium;
  A second reflecting surface surrounding a side peripheral surface between the first reflecting surface and the light emitting surface;
  An actinic light emitting element disposed at an end of the light diffusion space defined by the first reflecting surface, the light emitting surface, and the second reflecting surface on the downstream side in the conveyance direction of the recording medium;
  An actinic ray irradiation apparatus for temporary curing, comprising:   Actinic ray irradiation for temporary curing, which is emitted from an inkjet head having a plurality of nozzles that eject ink that is cured by irradiation of actinic rays and irradiates the actinic rays to the extent that ink droplets attached on the recording medium are incompletely cured A device,
  It is mounted on a carriage together with the inkjet head,
  On the surface of the recording medium, the illuminance distribution is adjusted so that the illuminance increases from upstream to downstream in the conveyance direction of the recording medium,
A light guide having a light exit surface facing the recording medium;
  An actinic light emitting element disposed at the downstream end of the light guide in the conveyance direction of the recording medium;
  A scattering pattern that is provided on a surface opposite to the light exit surface of the light guide, and scatters light into the light guide;
  An actinic ray irradiation apparatus for temporary curing, comprising: The image forming apparatus according to any one of claims 1 to 10, a scanning direction by the scanning means the main scanning direction, the main scanning direction and when the recording medium conveying direction and the sub scanning direction by the medium conveying means The illumination distribution of the temporary curing light source is changed according to at least one of the number of printing passes in the sub-scanning direction, the drawing mode, the drawing swath width, the resolution in the main scanning direction and the sub-scanning direction. How to change the illuminance distribution.

Images