JP2013075367A - Liquid ejection device and inkjet head driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid ejection device and an inkjet head driving method which prevent curing of liquid adhering to a liquid ejection surface or liquid in nozzles even if an actinic ray is irradiated to the liquid ejection surface or the nozzles in liquid ejection where liquid cured through the irradiation of the actinic ray is used.SOLUTION: The driving method is for driving an inkjet head 24 which includes a nozzle plate where an opening part of the nozzle 70 for ejecting making the ink cured through the irradiation of UV ray ejected to the recording medium, and that has the ink ejection surface 70D having ink lyophilic property, and which includes a piezoelectric element for pressurizing the ink in a pressure chamber communicating with the nozzle. Moreover, the inkjet head 24 is used while the ink ejection surface is covered with the ink. In the driving method, non-ejection driving voltage is supplied to the piezoelectric element corresponding to a non-ejection nozzle, the ink is overflowed from the non-ejection nozzle to the ink ejection surface to flow the ink covering the ink ejection surface.

Description

  The present invention relates to a liquid ejection apparatus and an inkjet head driving method, and more particularly to an inkjet head maintenance technique in an inkjet recording apparatus using ultraviolet curable ink.

  2. Related Art An ink jet recording apparatus that forms an image using an ultraviolet curable ink that is cured by irradiation with ultraviolet rays is known. In such an ink jet recording apparatus, a light source for ultraviolet irradiation is mounted on a carriage on which an ink jet head is mounted, the ultraviolet light source is scanned following the ink jet head, and the ink droplet immediately after landing on the medium is irradiated with ultraviolet light. In addition, misalignment of ink droplets and landing interference are avoided.

  In an ink jet recording apparatus to which an ultraviolet irradiation type ink is applied, there is a case where the ultraviolet light irradiated to the recording medium from the ultraviolet light source is irradiated to the ink discharge surface or the nozzle opening due to reflection or the like.

  As a result, the ink mist adhering to the ink ejection surface and the ink in the nozzle are cured by being irradiated with ultraviolet rays, which may greatly affect the ejection performance of the inkjet head.

  Patent Document 1 discloses an ink jet recording apparatus using ink that is cured by irradiation with active energy (ultraviolet rays). The ink jet recording apparatus disclosed in Patent Document 1 is provided with active energy irradiation means for each color head, and the active energy irradiation means for each head is arranged on the downstream side in the transport direction of the recording medium S of each head. Such an ink jet recording apparatus includes a vertical mechanism that raises and lowers the actinic ray irradiation means so that the actinic ray irradiation means is positioned below the head, and the actinic ray is irradiated downward from the actinic ray irradiation means, Light that travels downward does not reach stray light due to reflection or diffraction to reach the upper head.

JP 2007-210244 A

  However, as in the ink jet recording apparatus disclosed in Patent Document 1, if a configuration is adopted in which a web, which is a recording medium, is conveyed while being moved up and down, ink is ejected upward, and light is irradiated downward, the recording medium is raised. A configuration for conveying the recording medium in the direction and the downward direction is required, and the configuration for conveying the recording medium becomes complicated.

  In addition, since the recording medium has to be moved from the upper position where the head is located to the lower position where the actinic ray irradiation means is located after the ink has landed on the recording medium, the ink has landed. Then, before the light is irradiated, landing interference and ink movement may occur. Then, it becomes difficult to obtain a high-quality image.

  The present invention has been made in view of such circumstances, and in liquid discharge using a liquid that is cured by irradiation of active light, even if active light strays and is applied to the liquid discharge surface or nozzle, the liquid discharge surface An object of the present invention is to provide a liquid ejecting apparatus and an ink jet head driving method for preventing the liquid adhering to the liquid and the liquid in the nozzle from hardening.

  In order to achieve the above object, a liquid ejection apparatus according to the present invention has a liquid ejection surface in which an opening of a nozzle that ejects a liquid that is cured by irradiation of actinic rays to a medium is formed and exhibits lyophilicity with respect to the liquid. An ink jet head having a nozzle plate and pressurizing means for pressurizing a liquid in a liquid chamber communicating with the nozzle, and being used in a state where the liquid ejection surface is covered with the liquid; Drive voltage supply means for supplying a non-ejection drive voltage that does not cause the liquid to be ejected to the pressurizing means corresponding to the ejection nozzle, and actinic light radiation means for irradiating the medium with the liquid ejected from the inkjet head attached thereto A non-ejection driving voltage is supplied to the pressurizing means corresponding to the non-ejection nozzle by the driving voltage supply means, The liquid of the inner by overflowing into the liquid ejection surface with vibrate, thereby flowing the liquid covering the liquid ejection surface.

  According to the present invention, in a liquid discharge recording apparatus including an ink jet head that includes a liquid discharge surface having lyophilicity and is used in a state where the liquid discharge surface is covered with liquid, the liquid is not discharged from the nozzle. By supplying the ejection drive voltage to the pressurizing means, the liquid in the nozzle is vibrated and overflowed to the liquid ejection surface, and the liquid covering the liquid ejection surface is caused to flow, so that the active light beam is irradiated onto the liquid ejection surface. Also, the liquid is prevented from being cured on the liquid discharge surface.

1 is an external perspective view of an ink jet recording apparatus according to a first embodiment of the present invention. Explanatory drawing which shows typically the paper conveyance path of the inkjet recording device shown in FIG. Plane perspective view showing the arrangement configuration of the inkjet head and ultraviolet irradiation section shown in FIG. 3 is a perspective view. Plan view of ink ejection surface showing nozzle arrangement of inkjet head Sectional view showing the three-dimensional structure of the inkjet head FIG. 1 is a block diagram showing the main configuration of a control system of the ink jet recording apparatus shown in FIG. The block diagram which shows the further detailed structure of the control system shown in FIG. It is explanatory drawing which illustrated typically the behavior of the ink during supply of the non-ejection drive voltage. a: explanatory diagram of the ink flow on the ink ejection surface, b: explanatory diagram of the ink flow from the inside of the nozzle to the ink ejection surface Explanatory diagram schematically showing the behavior of ink after the supply of non-ejection drive voltage is stopped, a: explanatory diagram of the ink flow on the ink ejection surface, b: explanation of the ink flow from the inside of the nozzle to the ink ejection surface Figure Explanatory drawing of the effect of 1st Embodiment of this invention Waveform diagram showing an example of non-ejection drive voltage 2 is a flowchart showing a control flow of the inkjet head driving method according to the first embodiment of the invention. Explanatory drawing of the inkjet recording device (inkjet head drive method) which concerns on 2nd Embodiment of this invention. Explanatory drawing of the effect of 2nd Embodiment of this invention The wave form diagram which shows an example of the non-ejection drive voltage applied to 2nd Embodiment of this invention FIG. 3 is a block diagram showing the configuration of a control system of an ink jet recording apparatus according to a second embodiment of the present invention. 7 is a flowchart showing a control flow of an inkjet head driving method according to the second embodiment of the present invention. Explanatory drawing of the inkjet recording device (inkjet head drive method) which concerns on 3rd Embodiment of this invention. Explanatory drawing of the effect of 3rd Embodiment of this invention

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

[First Embodiment]
(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, the one corresponding to A3 Nobi or higher is called “wide format”.

  The ink jet recording apparatus 10 includes an apparatus main body 20 and support legs 22 that support the apparatus main body 20. The apparatus main body 20 includes a drop-on-demand type 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 (pinning light sources) 32A and 32B for irradiating the ink on the recording medium 12 with ultraviolet rays and main curing light sources (curing light sources) 34A and 34B are provided. It is installed.

  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 ink irradiated with the ultraviolet rays from the temporary curing light sources 32A and 32B is temporarily cured to such an extent that the dots are developed (can be sufficiently spread), while avoiding landing interference.

  The main curing light sources 34 </ b> A and 34 </ b> B are light sources that irradiate ultraviolet rays for performing additional exposure after temporary curing and finally completely curing (main curing) the ink. The main curing light sources 34A and 34B perform additional exposure after irradiating the ink on the recording medium 12 with ultraviolet rays from the temporary curing light sources 32A and 32B, and finally use ultraviolet rays for completely curing (main curing) the ink. A light source for irradiation.

  The ink jet 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 arranged on the carriage 30 move integrally with the carriage 30 along the guide mechanism 28. The reciprocating direction (Y direction) of the carriage 30 corresponds to the “main scanning direction”, and the transport direction (X direction) of the recording medium 12 corresponds to the “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 adhering to 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 transport 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 its upper surface serves as a support surface (medium support surface) of the recording medium 12. 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.

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

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

(Configuration of image forming unit)
FIG. 3 is a perspective plan view showing an example of an arrangement form of the inkjet head 24, the temporary curing light sources 32A and 32B, and the main curing light sources 34A and 34B arranged on the carriage 30. FIG.

  The inkjet head 24 includes yellow (Y), magenta (M), cyan (C), black (K), light cyan (LC), light magenta (LM), clear (transparent) ink (CL), and white (white). Nozzle arrays 61Y, 61M, 61C, 61K, 61LC, 61LM, 61CL, and 61W are provided for each color of ink (W) to eject ink of the respective colors. 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 mode in which the LC and LM nozzle rows are omitted, a mode in which one of the CL and W nozzle rows is omitted, a mode in which a metal ink nozzle row is added, a metal ink nozzle row in place of the W nozzle row It is possible to adopt a form in which a nozzle row for discharging special color ink is added. Further, the arrangement order of the nozzle rows for each color is not particularly limited. However, a configuration in which an ink having a low curing sensitivity to ultraviolet light among a plurality of ink types is disposed on the side closer to the temporary curing light source 32A or the temporary curing light source 32B is preferable.

  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, and It is also possible to arrange them at equal intervals so as to be aligned along the reciprocating direction of the carriage 30 (main scanning direction, Y direction). The module group (head group) of the head modules 24Y, 24M, 24C, 24K, 24LC, and 24LM for each color may be interpreted as an “inkjet head”, or each module may be interpreted as an “inkjet head”. It is. 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 line (linearly) along the recording medium conveyance direction (sub-scanning direction, X direction) at regular intervals. In the inkjet head 24 of this example, the arrangement pitch (nozzle pitch) of nozzles constituting each nozzle row 61 is 254 μm (100 dpi), the number of nozzles constituting one row of nozzle rows 61 is 256 nozzles, and the total length L of the nozzle rows 61 _w (the total length of the nozzle row) is about 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 (picoliter), 20 pl, and 30 pl can be distinguished by changing the drive waveform.

(About drawing mode)
In the inkjet recording apparatus 10 shown in this example, multipass drawing control is applied, and the print resolution (recording 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 that fills the gap between the nozzle pitches by four-pass printing (four scans). The main scanning speed of the carriage 30 in the high production mode is 1270 mm / sec.

  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 executed at a resolution of 1200 × 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.

(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 shingling 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 main scanning direction passes and the number of sub-scanning direction passes.

（本硬化光源の構成例について）
図４に示したように、本硬化光源３４Ａ，３４Ｂは、それぞれ複数個のＵＶ‐ＬＥＤ素子３５が並べられた構造を有している。２つの本硬化光源３４Ａ，３４Ｂは、共通の構成である。本例では、本硬化光源３４Ａ，３４Ｂとして、Ｙ方向に６個、Ｘ方向に２個のＵＶ‐ＬＥＤ素子３５がマトリクス状に配置されたＬＥＤ素子配列（６×２）を例示したが、ＬＥＤ素子数及びその配列形態はこの例に限定されない。例えば、複数個のＬＥＤ素子をＹ方向に沿って一列に並べた構成も可能である。

(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.

(Temporary curing light source)
As the temporary curing light sources 32A and 32B, a UV-LED element or a UV lamp can be used. In addition, when using a plurality of UV-LED elements, it is not limited to the mode in which LEDs are arranged along the nozzle row direction, but the end surfaces (upstream end surfaces or downstream end surfaces of the temporary curing light sources 32A and 32B, or There may be a form in which the LED elements are arranged on both end faces.

(Inkjet head structure)
FIG. 5A is a plan perspective view showing the nozzle arrangement of the inkjet head 24, and the nozzle row 61 for one color is shown. As shown in the figure, the nozzle row 61 for one color has nozzles 70 arranged in a row along the sub-scanning direction (X direction shown in FIG. 1). Each nozzle 70 communicates with a pressure chamber 72 (illustrated by a broken line) that stores ink to be ejected. In addition, as shown in FIG.5 (b), the aspect which arrange | positions the nozzle 70 in two rows zigzag is also possible.

  FIG. 6 is a cross-sectional view showing the three-dimensional structure of the inkjet head 24, and shows the structure of one nozzle (one discharge element). As an ink discharge method of the inkjet head 24 applied to this example, a method (piezo jet method) in which ink droplets are ejected by deformation of a piezoelectric element (piezo actuator) is employed. Since the ultraviolet curable ink generally has a higher viscosity than the solvent ink, the piezo jet method having a relatively large ejection force is advantageous.

  As shown in FIG. 6, the nozzle 70 communicates with the pressure chamber 72 via the nozzle flow path 71. The nozzle 70 includes an opening 70B formed on the ink ejection surface 70D of the nozzle plate 70A and a tapered portion 70C having a tapered shape (substantially conical shape).

  The pressure chamber 72 communicates with the nozzle 70 via the nozzle channel 71 and also communicates with the common channel 76 via the supply port (supply throttle) 74. The common flow path 76 communicates with the pressure chamber 72 corresponding to each of the nozzles 70 constituting the nozzle row 61 (see FIG. 5) for one color, and supplies ink to each pressure chamber 72.

  The diaphragm 78 constituting the ceiling surface of the pressure chamber 72 is provided with a piezoelectric element 80 at a position corresponding to the pressure chamber 72 on the outer surface of the pressure chamber 72. The piezoelectric element 80 has a structure in which a piezoelectric body is sandwiched between the upper electrode 82 and the lower electrode 84, and is deformed when a driving voltage is supplied between the upper electrode 82 and the lower electrode 84. And the diaphragm 78 is deformed.

  That is, when a drive voltage is supplied to the piezoelectric element 80 according to the image data, the diaphragm 78 is deformed to contract the volume of the pressure chamber 72, and an amount of ink corresponding to the volume decrease of the pressure chamber 72 is ejected from the nozzle 70. Is done. When the supply of the driving voltage to the piezoelectric element 80 is stopped, the strain deformation of the piezoelectric element 80 is restored and the pressure chamber 72 is restored to the original shape, and the pressure chamber 72 is supplied from the common flow path 76 via the supply port 74. The ink is filled.

  In the inkjet head 24, the ink discharge surface 70D of the nozzle plate 70A has lyophilic properties. The contact angle of the ink ejection surface 70D with respect to the ink is 40 degrees or less, and is equal to or greater than the contact angle with respect to the ink inside the nozzle 70 (for example, the tapered portion 70C). Specific examples of the lyophilic treatment of the ink discharge surface 70D include forming an oxide film by subjecting the ink discharge surface 70D to an oxidation process, or forming a metal film by a sputtering method or the like.

  As shown in FIG. 6, a liquid layer (ink layer) 88 made of ink is formed on the ink discharge surface 70D, and the ink discharge surface 70D is used while being covered with ink. When the meniscus (not shown) in the nozzle 70 is stable (static state), the ink covering the ink ejection surface 70D and the ink in the nozzle 70 are separated.

  By providing the ink discharge surface 70D having such a lyophilic property, the following effects can be obtained. First, when the ink discharge surface 70D has liquid repellency, ink mist accumulates, causing undischarge or bending. On the other hand, when the ink discharge surface 70D has lyophilic properties, the ink mist is absorbed by the ink layer of the ink discharge surface 70D, so that bending or non-discharge due to the ink mist does not occur.

  Further, since the nozzle plate is easily maintained, that is, wet wiping is performed by the ink layer on the ink discharge surface 70D, it can be said that durability against wiping is strong.

(Control system configuration)
FIG. 7 is a block diagram illustrating a main configuration of a control system 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 accordance with the reciprocating scanning (movement of the printing path) in the main scanning direction by the inkjet head 24.

  The carriage drive control unit 106 shown in FIG. 7 controls the 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 of the temporary curing light sources 32A and 32B via the LED drive circuit 118, and the UV-LED element of the main curing light sources 34A and 34B via the LED drive circuit 119. Control means for controlling light emission.

  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 (synonymous with “drawing format”), input printing conditions, input / edit attached information, and the like. Various types of information can be confirmed through the display on the display device 122.

  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 the halftone process, it corresponds to the dot size type (for example, three types such as large dot, medium dot, and 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 discharge control unit 112 generates a discharge 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 (shown with reference numeral 140 in FIG. 8). The drive waveform generation unit is means for generating a voltage waveform of a drive voltage for driving an ejection energy generating element (in this example, a piezo element) corresponding to each nozzle of the inkjet head 24. The drive waveform data is stored in advance in the information storage unit 124, and drive waveform data used as necessary is output. The 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 is applied to each ejection energy generating element of the inkjet head 24 via the head driving circuit 128, and switching elements (connected to individual electrodes 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 includes resolution setting information corresponding to the drawing mode, the number of passes (the number of scan repetitions), feed amount information necessary for controlling the sub-scan feed amount, the temporary curing light sources 32A and 32B, and the main curing light source 34A. 34B control information and the like are stored.

  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. Note that the configuration illustrated in FIG. 7 can be changed, added, and deleted as appropriate.

(Detailed description of inkjet head drive control)
Next, drive control of the inkjet head will be described in detail. FIG. 8 is a block diagram showing a more detailed configuration of the control system shown in FIG. 7, and shows a configuration for setting either a discharge waveform or a non-discharge waveform for each nozzle 70.

  As shown in FIG. 8, the information storage unit 124 includes a discharge waveform storage unit 125A that stores a discharge waveform and a non-discharge waveform storage unit 125B that stores a non-discharge waveform. The ejection waveform and the non-ejection waveform are generated in advance by a drive waveform generation unit (not shown).

  The waveform setting unit 140 shown in FIG. 8 sets a waveform for setting whether each nozzle 70 is a discharge nozzle that discharges ink based on image data or a non-discharge nozzle that does not discharge ink at each discharge timing. Generate a setting signal. The waveform setting signal is sent to the head drive circuit 128.

  In the inkjet recording apparatus 10 shown in this example, a non-ejection driving voltage generated based on a non-ejection waveform is applied to a non-ejection nozzle, and an ejection driving voltage generated based on the ejection waveform is applied to the ejection nozzle. Applied.

  FIG. 9 is an explanatory diagram schematically showing the behavior of ink during supply of a non-ejection drive voltage (shown with reference numerals 200 and 210 in FIG. 12). 9A illustrates the flow of ink on the ink discharge surface 70D, and FIG. 9B illustrates the flow of ink from the inside of the nozzle 70 to the ink discharge surface 70D.

  As shown in FIG. 9A, when non-ejection drive voltages having the same voltage and the same frequency are supplied to the piezoelectric elements 80 (see FIG. 6) corresponding to the plurality of nozzles 70 arranged in a row, The meniscus of the nozzle 70 corresponding to the piezoelectric element 80 is shaken, and as a result, ink overflows from the nozzle 70 to the ink ejection surface 70D.

  Immediately after the non-ejection drive voltage is supplied, the ink on the ink ejection surface 70D moves from the nozzle 70 toward the edge of the ink ejection surface. In FIGS. 9A and 9B, the flow of ink from the nozzle 70 toward the edge of the ink ejection surface 70D is illustrated by an arrow line denoted by reference numeral 88A.

  When attention is focused on one nozzle 70, the ink overflows radially from the nozzle 70, but the ink overflowing from each nozzle 70 collides with the ink overflowing from the adjacent nozzle 70, and as a result, the ink flow is This occurs from the nozzle 70 toward the edge of the ink ejection surface 70 </ b> D in a direction orthogonal to the arrangement direction of the nozzle 70.

  FIG. 10 is an explanatory diagram schematically illustrating the behavior of ink after the supply of the non-ejection drive voltage is stopped. 10A illustrates the flow of ink on the ink discharge surface 70D, and FIG. 10B illustrates the flow of ink from the inside of the nozzle 70 to the ink discharge surface 70D.

  When a predetermined time (about several μsec) has passed since the supply of the non-ejection drive voltage is stopped, the ink on the ink ejection surface 70D moves from the edge of the ink ejection surface 70D toward the center of the nozzle 70. In FIGS. 10A and 10B, the flow of ink from the edge of the ink ejection surface 70D toward the nozzle 70 is illustrated by an arrow line denoted by reference numeral 88B.

  That is, the piezoelectric element 80 to which the non-ejection drive voltage is supplied does not eject ink from the corresponding nozzle 70, but causes the corresponding pressure chamber 72 to ooze out from the nozzle 70 to the ink ejection surface 70D. Pressurize. When the supply of the non-ejection driving voltage is stopped, the deformation of the piezoelectric element 80 is restored, and the ink that has oozed out to the ink ejection surface 70 </ b> D is collected inside the nozzle 70.

  In this way, ink is oozed from the nozzle 70 to the ink ejection surface 70D, and the ink oozed to the ink ejection surface 70D is collected inside the nozzle 70, thereby forming the ink ejection surface 70D. Since the ink layer 88 flows, it is possible to prevent the ink from being cured at the ink discharge surface 70D and the opening 70B of the nozzle 70 even if the ink discharge surface 70D is irradiated with UV light.

  When the ink discharge surface 70D does not have a predetermined lyophilic property with respect to the ink to be used, even if a non-discharge drive voltage is applied to the non-discharge nozzle, the ink overflows from the non-discharge nozzle. No ink flow can be formed on the ink ejection surface 70D.

  FIG. 11 is an explanatory diagram of the effect of the ink jet recording apparatus (ink jet head driving method) according to the first embodiment of the present invention, from the timing when the UV irradiation of the recording medium 12 (see FIG. 1) is started. The number of non-ejection nozzles generated with respect to the elapsed time (minutes) is shown.

  A solid line denoted by reference numeral 90 in FIG. 11 is an evaluation result when a non-ejection driving voltage is applied to the non-ejection nozzles to generate ink flow on the ink ejection surface 70D, and reference numeral 92 in FIG. The broken line with is an evaluation result when the non-ejection driving voltage is not applied to the non-ejection nozzle.

  As shown in FIG. 11, although two to three non-ejection nozzles are generated even when a non-ejection driving voltage is applied, the number of non-ejection nozzles increases after about 20 minutes from the start of supply of the non-ejection driving voltage. Not done. On the other hand, when the non-ejection drive voltage is not applied, the number of non-ejection nozzles tends to increase as the pause time increases.

  In addition, the conditions of the evaluation experiment which obtained the result shown in FIG. 11 are as follows. The total number of nozzles of the inkjet head is 256 nozzles, and the non-ejection driving voltage is applied to all the nozzles. Further, as the non-ejection driving voltage, the non-ejection driving voltage 200 illustrated in FIG. 12A and the non-ejection driving voltage 210 illustrated in FIG. 12B are used.

  The non-ejection drive voltage 200 shown in FIG. 12A includes a rising portion 202 that rises from the reference potential (zero volts) to the maximum voltage, a maximum voltage portion (constant voltage portion) 204, and a falling that falls from the maximum voltage to the reference voltage. A trapezoidal shape including a portion 206.

  The maximum amplitude (potential difference) of the non-ejection drive voltage 200 is 25 V, and the time from the start timing of the rising portion 202 to the start timing of the falling portion 206 is 5 μsec.

  In the non-ejection drive voltage (group) 210 shown in FIG. 12B, the non-ejection drive voltage 200 shown in FIG. 12A is continuous in a predetermined cycle, and the cycle is about 66.7 μsec. . When this period is converted into a frequency, it becomes 15 kHz, which coincides with the ejection frequency (frequency of the ejection drive voltage).

  The non-ejection drive voltage 210 shown in FIG. 12B is a mode in which only one non-ejection drive voltage 200 is included in one ejection cycle. That is, if at least one non-ejection drive voltage 200 is supplied within one ejection cycle, the occurrence of non-ejection nozzles can be avoided.

  Note that the non-ejection driving voltage 200 illustrated in FIG. 12A and the non-ejection driving voltage 210 illustrated in FIG. 12B are merely examples, and ink is not ejected from the nozzle 70 (inside the nozzle 70). It suffices if the ink can ooze from the nozzle 70 to the ink ejection surface 70D without being separated from the ink.

  For example, a rectangular wave or a triangular wave may be applied to the non-ejection drive voltage 200, and a mode in which a plurality of non-ejection drive voltages 200 are included in one ejection cycle is also possible. In other words, the “non-ejection drive voltage” is a drive applied to the piezoelectric element 80 corresponding to the nozzle 70 when the ink inside the nozzle 70 exudes to the ink ejection surface 70D without ejecting ink from the nozzle 70. For example, there is an aspect having an amplitude of 10 percent or more and 50 percent or less with respect to the amplitude of the ejection drive voltage.

  That is, by setting the amplitude of the non-ejection drive voltage to 10% or more of the amplitude of the ejection drive voltage, the ink inside the nozzle 70 can be vibrated and overflowed to the ink ejection surface 70D.

  Further, by setting the amplitude of the non-ejection drive voltage to 50% or more of the amplitude of the ejection drive voltage, it is possible to prevent ink from being accidentally ejected from the nozzle 70.

  The frequency of the non-ejection drive voltage 210 is determined by the volume of ink overflowing from the non-ejection nozzle and the volume of ink sucked (recovered) into the nozzle 70 when the non-ejection drive voltage 200 is stopped (end of supply). Determined to be uniform.

(Control flow)
FIG. 13 is a flowchart showing a control flow of the inkjet head driving method according to the first embodiment of the present invention.

  When driving of the inkjet head 24 is started (step S10), whether all the nozzles are ejection nozzles or non-ejection nozzles is set based on the image data (step S12). For the nozzle set as a non-ejection nozzle in step S12 (Yes determination), a non-ejection waveform is set (step S14), and the frequency of the non-ejection waveform (non-ejection drive voltage) is set (step S16).

  Then, the supply of the non-ejection drive voltage is started to the piezoelectric element 80 corresponding to the non-ejection nozzle (step S18), and then the supply of the non-ejection drive voltage is stopped (step S20). Next, it is monitored whether or not a predetermined time from the stop of the supply of the non-ejection drive voltage (time until the ink exuded on the ink ejection surface 70D is collected in the nozzle 70) has elapsed (step). S22).

  In step S22, if it is determined that the predetermined time has not elapsed (No determination), monitoring of the elapsed time from the stop of supply of the non-ejection drive voltage is continued, and if it is determined that the predetermined time has elapsed (Yes). (Determination), the process proceeds to step S24.

  In step S24, it is determined whether or not the next ejection timing data exists. If the next ejection timing data exists (No determination), the process proceeds to step S12, and the processes from step S12 are repeatedly executed. The On the other hand, when there is no next ejection timing data (Yes in step S24), the driving of the inkjet head is terminated (step S32).

  In step S12, the nozzle set as the discharge nozzle (No determination), the discharge waveform is set (step S26), and the discharge drive voltage is supplied to the piezoelectric element 80 corresponding to the nozzle (step S28). When the supply of the ejection drive voltage is completed (step S30), the process proceeds to step S24.

  In the inkjet head driving method shown in this example, during printing (during image formation based on image data), the non-ejection driving voltage is always applied to at least a part of the non-ejection nozzles. Is reliably prevented.

(effect)
According to the ink jet recording apparatus and the ink jet head driving method configured as described above, in the ink jet head having an ink ejection surface having lyophilicity with respect to the ultraviolet curable ink, the piezoelectric element 80 corresponding to the non-ejection nozzle is not in the non-ejection nozzle. Even if UV light is applied to the ink ejection surface 70D by supplying ejection drive voltage, causing ink to ooze from the non-ejection nozzle to the ink ejection surface 70D and moving the ink within the ink ejection surface 70D. The ink does not harden on the surface 70D, and the occurrence of abnormal ejection nozzles can be prevented.

  Further, by moving the ink in the direction from the nozzle 70 toward the edge of the ink ejection surface 70D and the direction from the ink ejection surface 70D toward the nozzle 70, an ink flow is also generated inside the nozzle 70. Even when UV light hits the vicinity of the opening 70B, the ink inside the nozzle 70 can be prevented from curing.

  In this example, the mode in which the non-ejection driving voltage is supplied to all of the piezoelectric elements 80 corresponding to the non-ejection nozzles is illustrated, but it is sufficient that the ink flows so that the ink on the ink ejection surface 70D is not cured. A mode in which the non-ejection driving voltage is selectively supplied to the piezoelectric element 80 corresponding to a part of the nozzle is also possible.

[Second Embodiment]
(Overview)
Next, a second embodiment of the present invention will be described. In the following description, the same or similar parts as those of the first embodiment described above are denoted by the same reference numerals, and the description thereof is omitted. FIG. 14 is an explanatory diagram of an inkjet head driving method applied to the inkjet recording apparatus according to the second embodiment of the present invention.

  In the inkjet head driving method shown in this example, the frequency of the non-ejection driving voltage (group) is changed for a part of the non-ejection nozzles, and the non-ejection driving voltage group having the same frequency is applied to all the non-ejection nozzles. The flow of ink on the ink discharge surface 70D becomes faster than the case, and in particular, the ink is prevented from being cured in the vicinity of the nozzle 70.

  When a high-frequency non-ejection drive voltage is applied to the upper half nozzle group 73A shown in FIG. 14 and a low-frequency non-ejection drive voltage is applied to the lower half nozzle group 73B, reference numeral F is given. The flow of ink along the arrangement direction of the nozzles 70 as shown by the arrows (the nozzle group 73B to which the low frequency non-ejection drive voltage is applied from the nozzle group 73A to which the high frequency non-ejection drive voltage is applied). Sideward flow).

  On the other hand, when a low-frequency non-ejection drive voltage is applied to the upper half nozzle group 73A shown in FIG. As indicated by the arrow lines shown, the flow of ink along the arrangement direction of the nozzles 70 (the nozzles to which the low frequency non-ejection driving voltage is applied from the nozzle group 73B side to which the high frequency non-ejection driving voltage is applied). Flow toward the group 73A side) occurs.

  The upper half nozzle group 73A shown in FIG. 14 may include discharge nozzles, and the lower half nozzle group 73B shown in FIG. 14 may also include discharge nozzles. That is, the nozzle to which the non-ejection driving voltage is applied is selected from some or all of the non-ejection nozzles excluding the ejection nozzle among the nozzle group 73A and the nozzle group 73B, and the nozzle group 73A and the nozzle group 73B are selected. On the one hand, a non-ejection driving voltage with a high frequency (for example, 30 kHz, twice the ejection frequency) is applied, and on the other hand, a non-ejection driving voltage with a low frequency (for example, 3 kHz, one fifth of the ejection frequency) is applied. .

  FIG. 15 is an explanatory diagram of the effect of the inkjet head driving method according to the second embodiment, and the non-ejection nozzle with respect to the elapsed time (minutes) from the timing at which the UV irradiation of the recording medium 12 (see FIG. 1) is started. The number of occurrences is shown.

  A solid line denoted by reference numeral 94 in FIG. 15 is an evaluation result when the driving method shown in this example is applied, and a broken line denoted by reference numeral 90 in FIG. 15 has the same frequency for all nozzles. It is an evaluation result (evaluation result illustrated by a solid line in FIG. 11) when a non-ejection drive voltage is applied.

  As shown in FIG. 15, when the driving method shown in this example is applied, the generation of non-ejection nozzles is further prevented as compared with the case where a non-ejection driving voltage having the same frequency is applied to all nozzles. I understand that The conditions of the evaluation experiment that obtained the result shown in FIG. 15 are the same as the evaluation experiment that showed the evaluation result in FIG.

(Non-ejection drive voltage)
FIG. 16 is a waveform diagram showing an example of the high frequency non-ejection drive voltage 210A and the low frequency non-ejection drive voltage 210B. FIG. 16A shows the high frequency non-ejection drive voltage 210A, and FIG. ) Shows a low-frequency non-ejection drive voltage 210B.

  A high-frequency non-ejection drive voltage 210A shown in FIG. 16A has a frequency of 30 kHz (a frequency twice the ejection drive voltage), and a low-frequency non-ejection drive voltage 210B shown in FIG. It has a frequency of 15 kHz (the same frequency as the ejection drive voltage). The high frequency non-ejection drive voltage 210A has a frequency twice that of the low frequency non-ejection drive voltage 210B.

  The high-frequency non-ejection drive voltage only needs to have a frequency that is at least half of the maximum ejection frequency. Further, the low frequency non-ejection drive voltage may be less than or equal to one half of the maximum ejection frequency and less than the frequency of the high frequency non-ejection waveform.

(Control system configuration)
FIG. 17 is a block diagram illustrating a configuration of a control system in the ink jet recording apparatus according to the second embodiment. In FIG. 17, parts that are the same as or similar to those in FIG. 8 are given the same reference numerals, and descriptions thereof are omitted.

  The discharge control unit 112 shown in FIG. 17 includes a frequency setting unit 142 and a switching cycle setting unit 144 in addition to the waveform setting unit 140 shown in FIG. The frequency setting unit 142 generates a frequency setting signal representing frequency information for setting the frequency of the non-ejection driving voltage, and sends the frequency setting signal to the head driving circuit 128.

  The switching cycle setting unit 144 generates a switching cycle signal representing switching cycle information between the high frequency non-ejection driving voltage 210 </ b> A and the low frequency non-ejection driving voltage 210 </ b> B, and sends the switching cycle signal to the head driving circuit 128. The head drive circuit 128 sets the frequency of the non-ejection drive voltage for each ejection timing and for each nozzle based on the frequency setting signal, and for each ejection timing and for each nozzle based on the switching period setting signal. A switching cycle between the high frequency non-ejection drive voltage and the low frequency non-ejection drive voltage is set.

(Control flow)
FIG. 18 is a flowchart showing a control flow of the inkjet head driving method according to the second embodiment. In FIG. 18, parts that are the same as or similar to those in FIG. 13 are given the same reference numerals, and descriptions thereof are omitted.

  In the flowchart shown in FIG. 18, step S16 (frequency setting step) in FIG. 13 is changed, and step S17 (switching cycle setting step) is added. In the frequency setting step (step S <b> 16 ′) illustrated in FIG. 18, a high frequency or a low frequency is set for the nozzle to which the non-ejection driving voltage is applied. In the switching cycle step (step S17), a cycle for switching between the low frequency and the high frequency is set.

  The switching cycle can be set to about 1 to 10 seconds (for example, 3 seconds), and is appropriately determined depending on the driving conditions and environmental conditions of the inkjet head 24.

(effect)
According to the inkjet recording apparatus (inkjet head driving method) according to the second embodiment described above, the low-frequency non-ejection drive voltage is applied to some of the nozzles to which the non-ejection drive voltage is applied. 210B is applied, and the high frequency non-ejection drive voltage 210A is applied to some of the other nozzles. Therefore, on the ink ejection surface 70D, the low frequency is applied from the nozzle side to which the high frequency non-ejection drive voltage 210A is applied. A faster ink flow is generated toward the nozzle side to which the non-ejection driving voltage 210B is applied, and ink curing near the opening 70B of the nozzle 70 is prevented.

  In this example, all nozzles 70 are divided into two regions (nozzle groups 73A and 73B), and a mode in which a non-ejection driving voltage having a different frequency is applied to each of the nozzles 70 is illustrated. You may divide | segment into the above area | regions and you may apply the non-ejection drive voltage which has a 3 or more types of frequency with respect to three or more area | regions.

[Third Embodiment]
(Overview)
Next, a third embodiment of the present invention will be described. FIG. 19 is an explanatory diagram of an inkjet head driving method according to the third embodiment. In FIG. 19, parts that are the same as or similar to FIG. 14 are given the same reference numerals, and descriptions thereof are omitted.

  In the ink jet head driving method shown in FIG. 19, a nozzle to which a non-ejection driving voltage is selectively applied is set from non-ejection nozzles to generate an arbitrary ink flow on the ink ejection surface 70D.

  For example, the effect of preventing the ink from being cured on the ink discharge surface 70D is enhanced by increasing the flow of ink in the portion where the UV light easily hits the ink discharge surface 70D. In the inkjet head driving method shown in FIG. 19, a non-ejection driving voltage is applied to the nozzle group 73C in the region including the central portion of the ink ejection surface 70D, and the nozzle group 73D in the region not including the central portion of the ink ejection surface 70D. No non-ejection drive voltage is applied.

Then, the flow of ink from the nozzle group 73C side to the nozzle group 73D side, that is, the reference numeral R ₁ , R ₂ , F ₁ , F ₂ is attached to the longitudinal direction of the inkjet head 24 from the approximate center of the illustrated ink discharge surface 70D. A flow toward both ends of the direction occurs.

  According to the ink jet head driving method shown in FIG. 19, when UV light is likely to hit the vicinity of the central portion including the central portion of the ink discharge surface 70D, the effect of ink in the region where the UV light is likely to hit is efficiently prevented. Can do.

  The inkjet head driving method according to the second embodiment described above can be combined with the inkjet head driving method according to the third embodiment. For example, a high frequency non-ejection driving voltage is applied to the central nozzle group 73C in FIG. 19, and a low frequency non-ejection driving voltage is applied to the nozzle group 73D at both ends, so that both ends from the central portion of the ink ejection surface 70D are applied. A faster ink flow to the part may be generated, or a high-frequency non-ejection drive voltage and a low-frequency non-ejection drive voltage may be switched at a predetermined switching timing.

(effect)
FIG. 20 is an explanatory diagram of the effect of the inkjet head driving method according to the third embodiment. The solid line in FIG. 20 is a case where the driving method of the inkjet head of this example is applied, and the broken line in FIG. 20 is a case where a non-ejection driving voltage having the same frequency is applied to all the non-ejection nozzles. (Same as the solid line in FIG. 11).

  As shown in FIG. 20, according to the ink jet head driving method according to the third embodiment, the occurrence of non-ejection nozzles is effectively prevented.

  In the first to third embodiments, an ink jet recording apparatus that forms a color image on a recording medium using color ink has been exemplified. However, the application range of the present invention is to discharge liquid onto the medium by an ink jet method. It can be applied to a liquid ejection device. In this example, a serial type ink jet recording apparatus has been described as an example. However, the present invention can be applied to a configuration including a full line type ink jet head.

  As described above, the ink jet recording apparatus and the ink jet head driving method applied to the present invention have been described in detail, but can be appropriately changed without departing from the spirit of the present invention.

[Appendix]
As can be understood from the description of the embodiment described in detail above, the present specification includes disclosure of various technical ideas including the invention described below.

  (First aspect): An opening of a nozzle that discharges a liquid that is cured by irradiation with actinic rays to a medium is formed, and includes a nozzle plate having a liquid discharge surface that exhibits lyophilicity to the liquid, and communicates with the nozzle. A pressurizing unit that pressurizes a liquid in a liquid chamber, the inkjet head used in a state where the liquid ejection surface is covered with the liquid, and a pressurizing unit corresponding to a non-ejection nozzle that does not eject the liquid Drive voltage supply means for supplying a non-ejection drive voltage that does not discharge liquid; and actinic light irradiation means for irradiating actinic light to a medium to which the liquid discharged from the inkjet head is attached, and the drive voltage supply means A non-ejection driving voltage is supplied to the pressurizing means corresponding to the non-ejection nozzle to vibrate the liquid in the non-ejection nozzle and to discharge the liquid. By overflowing to the surface, and to flow the liquid covering the liquid ejection surface.

  According to this aspect, in the liquid discharge recording apparatus that includes the liquid discharge surface having the lyophilic property and includes the ink jet head that is used in a state where the liquid discharge surface is covered with the liquid, the liquid is not discharged from the nozzle. By supplying the ejection drive voltage to the pressurizing means, the liquid in the nozzle is vibrated and overflowed to the liquid ejection surface, and the liquid covering the liquid ejection surface is caused to flow, so that the active light beam is irradiated onto the liquid ejection surface. Also, the liquid is prevented from being cured on the liquid discharge surface.

  (Second Mode): The inkjet head includes a plurality of nozzles, and the driving voltage supply unit corresponds to other non-ejection nozzles with respect to the pressurizing unit corresponding to a part of the non-ejection nozzles. A non-ejection drive voltage having a frequency relatively higher than the frequency of the non-ejection drive voltage supplied to the pressurizing means is supplied.

  According to this aspect, the liquid flow on the liquid discharge surface becomes faster and the liquid is hardened in the vicinity of the nozzle as compared with the case where the non-discharge driving voltage having the same frequency is applied to all the non-discharge nozzles. Is prevented.

  Further, the liquid adhering to the liquid ejection surface in a direction from the nozzle to which the non-ejection driving voltage having a relatively high frequency is applied toward the nozzle to which the non-ejection driving voltage having a relatively low frequency is applied. Can be made to flow.

  (Third aspect): Pressurizing means to which the non-ejection drive voltage having a relatively high frequency is supplied by the drive voltage supply means, and addition to which the non-ejection drive voltage having a relatively low frequency is supplied. Frequency switching means for switching between the pressure means and the pressure means is provided.

  According to this aspect, the flow direction of the liquid adhering to the liquid discharge surface can be switched, and the liquid can be more effectively prevented from curing.

  (4th aspect): It has the switching period setting means which sets the switching period of the said non-ejection drive voltage by the said frequency switching means.

  According to such an aspect, the flow direction of the liquid adhering to the liquid ejection surface can be switched at a constant cycle, and the curing of the liquid can be prevented more effectively.

  (Fifth aspect): The inkjet head includes a plurality of nozzles, and the driving voltage supply means does not supply a non-ejection driving voltage to a pressurizing means corresponding to a part of the plurality of non-ejection nozzles. .

  According to this aspect, the flow of the liquid at the position of the non-ejection nozzle to which the non-ejection driving voltage is applied becomes faster, and the liquid is prevented from being cured at the non-ejection nozzle position and its vicinity.

  (Sixth aspect): The drive voltage supply means includes supply switching means for selectively switching between a pressurizing means for supplying a non-ejection drive voltage and a pressurizing means for not supplying a non-ejection drive voltage.

  According to this aspect, it is possible to apply the non-ejection driving voltage to the non-ejection nozzles at positions where actinic rays are likely to hit.

  (Seventh aspect): The supply switching means supplies the non-ejection driving voltage only to the pressurizing means corresponding to the central part of the liquid ejection surface and the non-ejection nozzles in the vicinity of the central part.

  According to this aspect, it is possible to more effectively prevent the liquid from being cured in the central portion of the ink ejection surface where the active light beam is relatively easy to hit and in the vicinity of the central portion.

  (8th aspect): The said drive voltage supply means supplies a non-ejection drive voltage with respect to the pressurization means corresponding to the said non-ejection nozzle during the liquid ejection based on ejection data.

  According to this aspect, it is possible to prevent the liquid from being cured on the liquid ejection surface during the liquid ejection based on the ejection data.

  (Ninth aspect): The drive voltage supply means supplies the next non-ejection drive voltage after a predetermined time has elapsed since the supply of the non-ejection drive voltage was stopped.

  According to this aspect, since the liquid that has oozed out of the nozzle is collected to the nozzle, the flow of the liquid toward the nozzle can be generated.

  (Tenth aspect): An opening of a nozzle that discharges a liquid that is cured by irradiation with actinic rays to a medium is formed, and includes a nozzle plate having a liquid discharge surface that exhibits lyophilicity with respect to the liquid, and communicates with the nozzle. A method of driving an ink jet head that includes a pressurizing unit that pressurizes a liquid in a liquid chamber and is used in a state where the liquid discharge surface is covered with the liquid, and is an additive corresponding to a non-discharge nozzle that does not discharge liquid. A non-ejection driving voltage that does not cause the liquid to be ejected is supplied to the pressure unit, and the liquid in the non-ejection nozzle is vibrated and overflows to the liquid ejection surface, thereby flowing the liquid covering the liquid ejection surface. I am letting.

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 12 ... Recording medium, 24, 24Y, 24M, 24C, 24K, ... Inkjet head, 32A, 32B ... Temporary curing light source, 34A, 34B ... Curing light source, 70 ... Nozzle, 70A ... Nozzle plate, 70B DESCRIPTION OF SYMBOLS ... Opening part, 70D ... Ink discharge surface, 72 ... Pressure chamber, 73A, 73B, 73C, D ... Nozzle group, 80 ... Piezoelectric element, 102 ... Control apparatus, 112 ... Discharge control part, 128 ... Head drive circuit, 140 ... Waveform setting unit, 142 ... frequency setting unit, 144 ... switching cycle setting unit, 200, 210 ... non-ejection drive voltage

Claims (10)

An opening of a nozzle that discharges a liquid that is cured by irradiation of actinic rays to a medium is formed, and includes a nozzle plate that has a liquid discharge surface that exhibits lyophilicity with respect to the liquid. An ink-jet head comprising a pressurizing means for pressing, and used in a state where the liquid discharge surface is covered with the liquid;
Drive voltage supply means for supplying a non-ejection drive voltage that does not eject liquid to a pressurizing means corresponding to a non-ejection nozzle that does not eject liquid;
Actinic ray irradiating means for irradiating actinic rays to the medium to which the liquid discharged from the inkjet head is attached;
With
The drive voltage supply means supplies a non-ejection drive voltage to the pressurizing means corresponding to the non-ejection nozzle, vibrates the liquid in the non-ejection nozzle, and overflows the liquid ejection surface, so that the liquid A liquid discharge apparatus for causing the liquid covering the discharge surface to flow. The inkjet head includes a plurality of nozzles,
The drive voltage supply means is relative to the pressurization means corresponding to a part of the non-ejection nozzles relative to the frequency of the non-ejection drive voltage supplied to the pressurization means corresponding to other non-ejection nozzles. The liquid ejection apparatus according to claim 1, wherein a non-ejection driving voltage having a high frequency is supplied.   Switching between the pressurizing means to which the non-ejection drive voltage having a relatively high frequency is supplied by the drive voltage supply means and the pressurizing means to which the non-ejection drive voltage having a relatively low frequency is supplied. The liquid ejection apparatus according to claim 2, further comprising a frequency switching unit.   The liquid ejection apparatus according to claim 3, further comprising a switching cycle setting unit that sets a switching cycle of the non-ejection driving voltage by the frequency switching unit. The inkjet head includes a plurality of nozzles,
The liquid ejection apparatus according to claim 1, wherein the driving voltage supply unit supplies a non-ejection driving voltage only to a pressurizing unit corresponding to a part of the plurality of non-ejection nozzles.   The liquid ejection apparatus according to claim 5, wherein the drive voltage supply unit includes a supply switching unit that selectively switches between a pressurization unit that supplies a non-ejection drive voltage and a pressurization unit that does not supply a non-ejection drive voltage.   The liquid discharge according to claim 6, wherein the supply switching unit supplies the non-discharge driving voltage only to the pressurizing unit corresponding to a central portion of the liquid discharge surface and a non-discharge nozzle near the central portion. apparatus.   The liquid according to claim 1, wherein the drive voltage supply unit supplies a non-ejection drive voltage to a pressurizing unit corresponding to the non-ejection nozzle during liquid ejection based on ejection data. Discharge device.   9. The liquid ejection apparatus according to claim 1, wherein the drive voltage supply unit supplies the next non-ejection drive voltage after a predetermined time has elapsed since the supply of the non-ejection drive voltage was stopped. . An opening of a nozzle that discharges a liquid that is cured by irradiation of actinic rays to a medium is formed, and includes a nozzle plate that has a liquid discharge surface that exhibits lyophilicity with respect to the liquid, and adds liquid in a liquid chamber that communicates with the nozzle. A method of driving an inkjet head, comprising a pressurizing means for pressing, wherein the liquid discharge surface is covered with the liquid,
Supplying a non-ejecting drive voltage that does not eject liquid to a pressurizing unit corresponding to a non-ejecting nozzle that does not eject liquid, causing the liquid in the non-ejecting nozzle to vibrate and overflowing to the liquid ejection surface, An ink jet head driving method for causing the liquid covering the liquid discharge surface to flow.

Images