JP2012101367A - Inkjet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording device capable of suppressing uneven density and uneven glossiness and thus, forming images having good image quality.SOLUTION: The inkjet recording device includes a carriage 30 including irradiation parts 34, 35 emitting ultraviolet rays and an image forming part 25 forming images by discharging ink cured by ultraviolet rays by inkjet. The carriage 30 further includes a scanning means performing bidirectional scanning along a direction approximately orthogonal to a carrying direction of a recording medium S. The irradiation parts 34, 35 include: tentative curing irradiation means 34a, 34b arranged on both sides of the image forming part 25 in the scanning direction of the carriage 30; and main curing irradiation means 35a, 35b arranged on the downstream side in the carrying direction of the recording medium S. A relationship between optical path length L1 from the tentative curing irradiation means 34a, 34b to the recording medium S and optical path length L2 from the main curing irradiation means 35a, 35b to the recording medium S is set to be L1>L2.

Description

  The present invention relates to an ink jet recording apparatus, and more particularly to an ink jet recording apparatus using ink that is cured by irradiation with ultraviolet rays.

  Conventionally, ink is ejected from an ink jet head onto a recording surface of a recording medium to form an image on the recording medium. In the field of image formation by such an ink jet recording apparatus, an ultraviolet curable ink containing a photoinitiator having a predetermined sensitivity to ultraviolet rays is used, and the ultraviolet curable ink landed on the recording medium is irradiated with ultraviolet rays. Thus, development of a recording apparatus of a type that is cured and fixed to a recording medium has been performed.

  In an ink jet recording apparatus to which ultraviolet curable ink is applied, an ink liquid immediately after landing on a medium is mounted by mounting a light source for ultraviolet irradiation on a carriage on which an ink jet head is mounted, scanning the ultraviolet light source following the ink jet head. The droplets are irradiated with ultraviolet rays to avoid displacement of the ink droplets.

  For example, Patent Document 1 below describes an ink jet recording apparatus that cures ink discharged from nozzle holes of an ink jet head with a plurality of ultraviolet light emitting diodes provided on a moving member that moves with the ink jet head. Patent Document 2 discloses a photo-curing ink jet in which photo-curable ink is ejected from a recording head and landed on the surface of a recording medium, and then light is irradiated from an irradiation device to fix the ink on the surface of the recording medium. An ink jet printer of the type is described.

JP 2005-104108 A US Pat. No. 6,457,823

  However, since the ink jet recording apparatus described in Patent Document 1 is intended to cure ink immediately after ink ejection, a plurality of irradiation apparatuses are moved in order to obtain high illuminance. It was necessary to arrange them on a member close to each other perpendicular to the scanning direction and to irradiate the recording medium surface with high illuminance almost uniformly. Further, in Patent Document 2, ink is cured by a two-stage method in which curing is performed incompletely to such an extent that the movement of ink droplets after ejection is controlled, and then completely cured. However, the method of Patent Document 2 does not describe a specific configuration for performing the first-stage curing.

  The present invention has been made in view of such circumstances, and by specifying the respective irradiation conditions when the ink is cured in two stages, it is possible to optimize the curing after droplet ejection, The purpose is to improve image quality.

  In order to achieve the above object, the present invention includes a carriage that includes an irradiation unit that irradiates ultraviolet rays, and an image forming unit that forms an image by ejecting ink that is cured by the ultraviolet rays by inkjet. The carriage includes scanning means that scans in both directions along a direction substantially perpendicular to the conveyance direction of the recording medium, and the irradiation unit is provided on both sides of the image forming unit in the scanning direction of the carriage. A temporary curing irradiation unit and a main curing irradiation unit provided on the downstream side in the conveyance direction of the recording medium, and an optical path length L1 from the temporary curing irradiation unit to the recording medium and the main curing irradiation unit. And an optical path length L2 from the recording medium to the recording medium has a relationship of L1> L2.

  According to the first aspect, provisional curing irradiation means and main curing irradiation means are provided, and the optical path length L1 to the temporary curing irradiation means and the recording medium and the optical path length L2 to the main curing irradiation means and the recording medium are L1> It is provided so as to have a relationship of L2. By shortening the illuminance by increasing the optical path length L1, the temporary curing irradiation means does not completely harden, but it is possible to perform curing at a level where the fluidity of the ink is suppressed. Further, by shortening the optical path length L2 and increasing the illuminance, the main curing irradiation means can completely cure. By separating the function of curing with the temporary curing irradiation means and the main curing irradiation means, interference control, gloss control, etc. can be controlled independently, improving image quality, suppressing landing interference, controlling glossiness, The substrate adhesion can be improved and the tack-free property can be controlled.

  A second aspect is characterized in that, in the first aspect, the optical path length L1 is not less than 15 mm and not more than 45 mm, and the optical path length L2 is not less than 1 mm and not more than 14 mm.

  According to claim 2, by setting the optical path lengths L1 and L2 in the above range, the illuminance of curing can be controlled.

  A third aspect of the present invention according to the first or second aspect is characterized in that the temporary curing irradiation unit is provided so as to irradiate the entire width direction of the image forming unit with respect to the scanning direction of the carriage. .

  According to the third aspect, since the temporary curing irradiation unit is provided so as to irradiate the entire area in the width direction of the image forming unit, the ink ejected from the image forming unit can be cured by the temporary curing irradiation unit. it can.

  A fourth aspect of the present invention is characterized in that, in any one of the first to third aspects, an irradiation angle of light irradiated from the temporary curing irradiation unit is 90 ° or more and 130 ° or less.

  According to claim 4, by setting the irradiation angle from the pre-curing irradiation means within the above range, the optical path length L1 of the pre-curing irradiation means is longer than the optical path length L2 of the main curing irradiation means, so that the irradiation area is widened. be able to.

  A fifth aspect of the present invention is characterized in that, in any one of the first to fourth aspects, a frame for adjusting an irradiation region is provided at a tip of the temporary curing irradiation unit.

  According to the fifth aspect, by providing the frame at the tip of the pre-curing irradiation means, it is possible to irradiate the recording medium uniformly by adjusting the irradiation area. Therefore, the curing by the irradiation by the temporary curing irradiation unit can be made constant, and the unevenness of the image quality can be suppressed.

  A sixth aspect of the present invention is characterized in that, in any one of the first to fifth aspects, the main curing irradiation means is provided only on the downstream side of the temporary curing irradiation means.

  According to the sixth aspect of the present invention, the main curing irradiation unit is provided only on the downstream side of the temporary curing irradiation unit with respect to the conveyance direction of the recording medium. That is, the main curing irradiation unit is not provided on the downstream side of the image forming unit. Therefore, it is possible to prevent the ink before ejection of the image forming unit and the ink immediately after ejection from being cured.

  A seventh aspect of the present invention is characterized in that, in any one of the first to sixth aspects, the temporary curing irradiation unit and the main curing irradiation unit use the same irradiation device.

  According to the present invention, since the illuminance is controlled by the difference in optical path length between the temporary curing irradiation means and the main curing irradiation means, the same irradiation apparatus can be used.

  An eighth aspect of the present invention is characterized in that, in any one of the first to seventh aspects, the temporary curing irradiation means and the main curing irradiation means are LED elements.

  According to claim 8, an LED element can be preferably used as the irradiation means. By using a light emitting diode (LED), it is possible to extend the life and reduce the weight of the apparatus.

  A ninth aspect is characterized in that, in the eighth aspect, the provisional curing irradiation means irradiates the entire region in the width direction with one LED element.

  According to the present invention, the temporary curing irradiation unit may have a low illuminance, and thus the optical path length L1 of the temporary curing irradiation unit can be increased. Therefore, since the image forming area can be irradiated with one LED element, the cost can be reduced.

  A tenth aspect of the present invention is characterized in that, in any one of the first to ninth aspects, the main curing irradiation means is provided with a plurality of LED elements along a scanning direction of the carriage.

  According to the tenth aspect, the main curing irradiation means can completely cure the ink by providing a plurality of LED elements along the scanning direction of the carriage. Further, since the carriage on which the LED element is mounted can be downsized in the recording medium conveyance direction, the apparatus can be downsized.

  According to the inkjet recording apparatus of the present invention, since the curing is performed by independently controlling each of the temporary curing irradiation unit and the main curing irradiation unit, the image quality can be improved.

1 is an external perspective view of an ink jet recording apparatus according to an embodiment of the present invention. It is explanatory drawing which shows typically the paper conveyance path of an inkjet recording device. It is a plane perspective view which shows the structural example of an inkjet head. It is a side view which shows the structural example of an inkjet head. FIG. 3 is a block diagram illustrating a configuration of an ink supply system of the ink jet recording apparatus. It is a block diagram which shows the structure of an inkjet recording device.

  Hereinafter, preferred 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 inkjet recording apparatus 100 is a wide format printer that records a wide drawing range, such as a large poster or a commercial wall advertisement, and includes an apparatus main body 21 and support legs 23 that support the apparatus main body 21. In addition, here, what corresponds to A3 Nobi or more is called a “wide format”.

  The apparatus main body 21 includes a multi-channel type inkjet head 25 and a fixed platen 27. The ink jet head 25 is mounted on a carriage 30 that is reciprocated in a scanning direction Y perpendicular to the recording medium conveyance direction X along a guide mechanism 29 that is a head moving means (scanning means). As the recording medium S, 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 whether they are permeable media or non-permeable media. it can.

  The platen 27 shown in FIG. 1 is formed in an inverted bowl shape, and the upper surface serves as a support surface of the recording medium S. A pair of scanning conveyance rollers (not shown in FIG. 1, not shown in FIG. 1 and indicated by reference numeral 43 in FIG. 2) is disposed upstream of the platen 27 in the recording medium conveyance direction X as recording medium conveyance means. The scanning conveyance roller pair moves the recording medium S on the platen 27 in the recording medium conveyance direction X. The scanning conveyance roller pair holds only the end portion in the width direction of the recording medium, and reduces the diameter of the central portion of the recording medium S, thereby preventing interference with the open / close lid of the platen 27. The inkjet head 25 is moved by a guide mechanism 29 in a scanning direction Y that is orthogonal to the recording medium conveyance direction X and parallel to the support surface of the platen 27.

  An ink cartridge mounting portion for mounting a replaceable cartridge 33 for storing ink is provided on the left front surface of the apparatus main body 21. The cartridge 33 is provided corresponding to each color ink used in the ink jet recording apparatus 100 of this example. Each cartridge 33 is connected to the inkjet head 25 by an ink supply path (not shown) formed independently, and the cartridge 33 is replaced when the remaining amount of ink of each color decreases.

  The ink jet recording apparatus 100 of this example can use either ultraviolet curable ink (UV ink) or solvent ink, and the type of ink can be changed by replacing the cartridge 33. .

  Although not shown, a maintenance unit for the inkjet head 25 is provided on the right side of the apparatus main body 21 as viewed from the front. The maintenance unit is provided with a cap for keeping the ink-jet head 25 moisturized during non-printing and a wiping member (blade, web, etc.) for cleaning the nozzle surface (ink discharge surface) of the ink-jet head 25. The cap for capping the nozzle surface of the inkjet head 25 is provided with an ink receiver for receiving ink droplets ejected from the nozzle for maintenance.

  The ink jet recording apparatus 100 includes elevating means such as a screw mechanism that elevates the ink jet head 25 up and down with respect to the platen 27, and the ink jet head according to the thickness of the recording medium S mounted on the platen 27. 25 can be moved up and down with respect to the platen 27.

[Description of paper transport path]
FIG. 2 is an explanatory diagram schematically showing a sheet conveyance path in the inkjet recording apparatus 100 shown in FIG. As shown in FIG. 2, the recording medium S fed from the feeding supply roll 41a is fed by a pair of scanning conveyance rollers 43 provided at the entrance of the printing unit (upstream in the recording medium conveyance direction X of the platen 27). It is intermittently conveyed along the recording medium conveyance direction X indicated by the arrow line. The recording medium S that has reached the printing unit immediately below the ink jet head 25 is printed by the ink jet head 25, and is taken up by the take-up roll 41b after printing. A guide 45 for the recording medium S is provided downstream of the printing unit in the recording medium conveyance direction X.

  In order to adjust the temperature of the recording medium S during printing on the back surface (the surface opposite to the surface supporting the recording medium S) of the platen 27 that supports the recording medium S in the printing unit. The temperature control unit 47 is provided. When the recording medium S at the time of printing is adjusted so as to have a predetermined temperature, the physical properties such as the viscosity of the ink droplets that have landed on the recording medium S and the surface tension become the desired values, and the desired dot diameter is set. Can be obtained. If necessary, the pre-temperature control unit 49 may be provided on the upstream side of the temperature control unit 47, or the after-temperature control unit 51 may be provided on the downstream side of the temperature control unit 47.

[Description of inkjet head]
FIG. 3 is a plan perspective view showing a configuration example of the inkjet head 25.

  An ink jet head 25 is mounted on the carriage 30 that reciprocates in the scanning direction Y. Temporary curing light sources 34a and 34b for irradiating the ink on the recording medium S with ultraviolet rays and main curing light sources 35a and 35b are mounted. The inkjet head 25 includes a plurality of nozzles in the recording medium conveyance direction X corresponding to each color of cyan (C), magenta (M), yellow (Y), black (K), transparent (CL), and white (W). Are arranged at equal intervals, nozzle rows 61C, 61M, 61Y, 61K, 61CL, 61W are provided.

  In FIG. 3, the nozzle rows are indicated by broken lines, and individual illustrations of the nozzles are omitted. In the following description, the nozzle rows 61C, 61M, 61Y, 61K, 61CL, and 61W may be collectively referred to as a reference numeral 37 to represent the nozzle rows.

  In the inkjet head 25 shown in this example, the arrangement pitch (nozzle pitch) of the nozzles constituting the nozzle row 61 is 254 μm (100 dpi), and the number of nozzles constituting the nozzle row 61 is 256 nozzles. The total length L3 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, 20 pl, and 30 pl can be distinguished by changing the drive waveform.

  In addition, the aspect which comprises the separate inkjet head for every color is also possible. For example, an inkjet head 25C having a nozzle row 61C, an inkjet head 25M having a nozzle row 61M, an inkjet head 25Y having a nozzle row 61Y, an inkjet head 25K having a nozzle row 61K, and an inkjet head 25CL having a nozzle row 61CL In addition, an aspect in which the inkjet heads 25W having the nozzle rows 61W are arranged at equal intervals so as to be aligned in the main scanning direction is also possible.

  Further, a nozzle row (inkjet head) corresponding to LC (light cyan) and LM (light magenta) may be added to the configuration shown in FIG. 3, or a nozzle row (inkjet head) and W corresponding to CL may be added. Instead of the nozzle row (inkjet head), nozzle rows corresponding to LC and LM may be used.

  As the ink ejection method of the inkjet head 25, a method in which ink droplets are ejected by deformation of an actuator represented by a piezo element (piezoelectric element) (piezo jet method), and a bubble is generated by heating ink with a heating element such as a heater. Any of the thermal jet methods that eject ink droplets at that pressure can be employed. However, when UV ink is used, it is preferable to employ a piezo jet method. In this embodiment, a piezo jet method is employed.

  The inkjet head 25 having such a structure is applied with multi-pass drawing control, and can change the printing resolution by changing the number of passes. In the high production mode, printing is performed at a resolution of 600 dpi × 400 dpi. In the main scanning direction, a resolution of 600 dpi is realized by two passes (two scans), dots are formed at a resolution of 300 dpi in the first scan (outward pass), and the second scan (return pass) is the first scan. Dots are formed so that the middle of the formed dots is interpolated at 300 dpi. Further, in the sub-scanning direction, dots are formed at a resolution of 100 dpi by one scan, so that a resolution of 400 dpi is realized by four passes (four scans).

  In the standard mode, printing is executed at a resolution of 600 dpi × 800 dpi, and a resolution of 600 dpi × 800 dpi is obtained by two passes in the main scanning direction and eight passes in the sub-scanning. 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. The main scanning speed of the carriage is 1270 mm / sec in each mode.

[Explanation of UV irradiation unit]
The temporary curing light sources 34a and 34b shown in FIG. 3 are used to temporarily cure the ink droplets ejected from the inkjet head 25 to the extent that the adjacent ink droplets do not coalesce after landing on the recording medium S. An LED element is provided as a light source (pinning light source). Further, the main curing light sources 35a and 35b include a plurality of LED elements as light sources (cure light sources) for finally curing ink droplets completely.

  That is, provisional curing light sources 34a and 34b, which are active energy irradiation means, are arranged on the left and right sides of the scanning direction Y of the inkjet head 25. Further, the main curing light source 35a is disposed downstream of the inkjet head 25 in the recording medium conveyance direction X. , 35b are arranged. The temporary curing light sources 34 a and 34 b can be moved together with the inkjet head 25 by the reciprocating movement of the carriage 30. When ultraviolet curable ink (UV ink) is used, the ink droplets ejected from the nozzles and landed on the recording medium S immediately after the ultraviolet rays of one of the temporary curing light sources 34a and 34b passing above. The irradiation unit irradiates ultraviolet rays for temporary curing.

  The ink droplets on the recording medium S that have passed through the printing area of the inkjet head 25 are irradiated with ultraviolet rays for main curing by the main curing light sources 35a and 35b. The color ink on the recording medium S that has passed through the drawing area of the inkjet head 25 is used for main curing from the main curing light sources 35a and 35b when the main curing light sources 35a and 35b pass through the upper part by the reciprocating motion of the carriage 30. Ultraviolet rays are irradiated.

  FIG. 4 is a side view showing a configuration example of the ink jet head shown in FIG.

  Temporary curing performed by the temporary curing light sources 34a and 34b does not completely cure in order to suppress interference and movement coalescence between droplets in order to make the image quality a certain level or more, but the fluidity of the ink is suppressed. The modification is performed by a weak exposure to a certain extent. Therefore, the temporary curing light sources 34a and 34b need to be applied to the droplet ejection from each nozzle before the next scanning is performed and the next droplet ejection is performed at the same position or an adjacent position. is there. Moreover, it is preferable that the irradiation distribution of the temporary curing light sources 34a and 34b is constant in the irradiation region S1. By making the irradiation distribution constant, it is possible to uniformly irradiate the ejected ink, so that image formation can be performed without unevenness. That is, the temporary curing light sources 34a and 34b are desired to uniformly irradiate the entire irradiation range with weak irradiation.

  The amount of exposure for temporary curing affects the spread of ink droplets on the recording medium. As 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 droplet ejection dots within one swath width, a periodic change is generated in the dot diameter, which causes band-like density unevenness and gloss unevenness.

  The main curing light sources 35a and 35b are preferably arranged so as to avoid the track 36 of the nozzle row 61 in the scanning direction of the carriage 30 in order to avoid the influence of the number of overwriting in the n-degree writing mode of the printer. In FIG. 3, the recording medium S is provided at a position downstream of the conveyance direction of the recording medium S and not in the downstream portion of the temporary curing light sources 34 a and 34 b in the carriage 30.

This curing light sources 35a, 35b is preferably set to 300mJ ^/ cm ² ~600mJ ^/ cm 2 approximately by irradiation of several times irradiation light amount. Therefore, it is preferable to provide 8 to 24 LED elements. Further, when the irradiation area S2 to the recording medium S becomes large, it is considered that ink before ejection is solidified by reflected light from the recording medium S and nozzle clogging occurs, and light leakage countermeasures for reflected light are taken over a wide range. Need arises. Therefore, also from this point, it is preferable to reduce the irradiation area by the main curing light sources 35a and 35b.

  Accordingly, the temporary curing light sources 34a and 34b are intended to irradiate light with low illuminance to the entire width direction of the nozzle row 61 in the scanning direction of the carriage 30, that is, the entire length L3 of the nozzle row 61, whereas the main curing light sources 35a and 35b. It is preferable to irradiate the light of a plurality of LED elements with a strong illuminance while narrowing the irradiation range of each LED element.

  Therefore, in the present invention, as shown in FIG. 4, the optical path length L1 from the temporary curing light sources 34a and 34b to the recording medium S and the optical path length L2 from the main curing light sources 35a and 35b to the recording medium S are expressed as L1. The arrangement of the temporary curing light sources 34a and 34b and the main curing light sources 35a and 35b is determined so that> L2. By providing a difference in the optical path length in this way, it is possible to weaken the irradiation intensity from the temporary curing light sources 34a and 34b and increase the irradiation intensity from the main curing light sources 35a and 35b. Specifically, the optical path length L1 is preferably 15 mm to 45 mm, and the optical path length L2 is preferably 1 mm to 14 mm.

  Since the temporary curing light sources 34a and 34b can weaken the irradiation intensity, it is preferable to widen the irradiation area S1 on the recording medium S and reduce the number of LED elements installed. Costs can be reduced by reducing the number of LED elements installed. Further, since the intensity of illuminance can be increased or decreased by adjusting the lengths of the optical path lengths L1 and L2, the same ultraviolet irradiation light source can be used for the temporary curing light sources 34a and 34b and the main curing light sources 35a and 35b. .

  In order to widen the irradiation region S1 of the temporary curing light sources 34a and 34b, it is preferable that the irradiation angle of the temporary curing light sources 34a and 34b is 90 ° or more and 130 ° or less. Since the optical path length L1 from the temporary curing light sources 34a and 34b to the recording medium S is set to be longer than the optical path length L2 from the main curing light sources 35a and 35b to the recording medium S, the irradiation angle should be widened. Thus, the irradiation area S1 can be made wider. The irradiation region S <b> 1 is preferably designed so as to irradiate the entire width direction of the nozzle row 61 in the scanning direction of the carriage 30.

  For example, the optical path length L1 and the irradiation angle can be determined as follows. When the recording medium S is irradiated with light from the pre-curing light sources 34a and 34b perpendicularly, if the irradiation angle is α, the distance x from the irradiation region to the end from the optical axis is x = L1 × tan (α / 2). It becomes. Therefore, it is preferable that the distance x be arranged so that the entire region in the width direction of the orbit of the nozzle row 61 can be irradiated and that the nozzle row 61 is not exposed to light.

  The optical path lengths L1 and L2 and the irradiation angle are preferably determined so as to satisfy the following conditions within the above range. The illuminance by the LED element is assumed to be a Gaussian distribution and is determined by the half width and the quarter width. In the temporary curing light source, the illuminance at the nozzle row end is ½ or more of the illuminance peak, and further from the nozzle row end, the illuminance at ½ of the nozzle length is ¼ or less of the illuminance peak. To be determined. The main curing light source is determined so that the illuminance at a position 1/3 of the nozzle row length from the optical axis is 1/2 or less, more preferably 1/4 or less of the illuminance peak. Further, it is preferable that the optical path length L <b> 2 does not become less than the distance between the recording medium S and the inkjet head 25. The representative value is preferably 1 mm or more.

  Therefore, in order to widen the irradiation region S1, it is necessary to increase the number of LED elements when the optical path length L1 is increased and the illuminance is lower than that for performing temporary curing. As described above, it is preferable that the temporary curing light sources 34a and 34b perform temporary curing under optimum conditions by appropriately setting the optical path length L1, the irradiation angle, and the number of LED elements. In the provisional curing light sources 34a and 34b, when a plurality of LED elements are provided, a plurality of LED elements can be arranged in a line along the sub-scanning direction. Further, in addition to the structure that reduces the number of LED elements, it is possible to perform temporary curing by selecting an LED element that performs irradiation as necessary from among a plurality of LED elements provided.

  Moreover, it is preferable to provide provisional curing light sources 34a and 34b so that the irradiation area S1 of the provisional curing light sources 34a and 34b does not overlap the ejection range of the ink from the inkjet head 25. When the irradiation area S1 of the temporary curing light sources 34a and 34b is wider than a desired area, a frame is provided at the tip of the temporary curing light sources 34a and 34b to adjust the shape of the irradiation area S1. It is also possible. When the irradiation area is longer in the vertical direction than the width direction of the carriage 30 in the scanning direction, a frame may be provided so that the irradiation area does not overlap the ink ejection area.

  Further, the main curing light sources 35a and 35b have a structure in which a plurality of LED elements are arranged along the main scanning direction. In FIG. 3, the LED elements are arranged in a line for the sake of simplicity, but two or more lines can be arranged in the sub-scanning direction. The LED elements of the main curing light source 35a are arranged in the direction opposite to the nozzle row 61C, and the LED elements of the main curing light source 35b are arranged in the direction opposite to the nozzle row 61W. With this structure, it is possible to prevent the ultraviolet rays irradiated from the main curing light sources 35a and 35b from reaching the nozzle rows 61C, 61M, 61Y, 61K, 61CL, and 61W and curing the ink inside the nozzles.

  By providing a plurality of LED elements of the main curing light sources 35 a and 35 b along the scanning direction of the carriage 30, the carriage 30 can be downsized in the recording medium conveyance direction, and the depth length of the platen 27 facing the carriage 30. Can be shortened. Therefore, the apparatus can be made compact.

  In addition, when PET (polyethylene terephthalate) is used as a recording medium, an image is formed so that an image can be observed from the back side of the recording medium. In some cases, a layer is ejected and the whole is composed of two or three layers. At this time, in order to cure the white ink layer, there is a case where it is desired to perform the main curing only in an area within a fraction of the head length. By providing a plurality of LED elements in the scanning direction of the carriage 30, the nozzle longitudinal component of the irradiation region of the main curing light source can be shortened. Specifically, the nozzle longitudinal component of the irradiation region is preferably 1/2 to 1/3 or less of the nozzle length, more preferably 1 / n or less with respect to the number n of layers. .

[Description of ink supply system]
FIG. 5 is a block diagram showing the configuration of the ink supply system of the inkjet recording apparatus 100 shown in FIG. As shown in the figure, the ink stored in the cartridge 33 is sucked by the supply pump 71 and sent to the inkjet head 25 via the sub tank 73. The sub tank 73 is provided with a pressure adjusting unit 75 for adjusting the pressure of the ink inside.

  The pressure adjusting unit 75 includes a pressure increasing / decreasing pump 79 that communicates with the sub tank 73 via a valve 77, and a pressure gauge 81 provided between the valve 77 and the pressure increasing / decreasing pump 79.

  During normal printing, the pressure increasing / decreasing pump 79 operates in the direction of sucking ink in the sub tank 73, and the internal pressure of the sub tank 73 and the internal pressure of the inkjet head 25 are maintained at negative pressure. On the other hand, at the time of maintenance of the ink jet head 25, the pressure increasing / decreasing pump 79 operates in a direction to pressurize the ink in the sub tank 73, and the inside of the sub tank 73 and the inside of the ink jet head 25 are forcibly pressurized. The ink inside is discharged through the nozzle. The ink forcibly discharged from the inkjet head 25 is stored in the ink receiver of the cap described above.

[Explanation of Block Diagram of Inkjet Recording Apparatus]
FIG. 6 is a block diagram showing a configuration of the inkjet recording apparatus 100 according to the embodiment of the present invention. As shown in the figure, the ink jet recording apparatus 100 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 100 according to a predetermined program, and also functions as an arithmetic 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 S (see FIG. 1). The transport drive unit 114 includes a drive motor that drives the scanning transport roller pair 43 shown in FIG. 2 and a drive circuit thereof. The recording medium S conveyed on the platen 27 (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 X by the inkjet head 25. .

  The carriage drive control unit 106 shown in FIG. 6 controls the main scanning drive unit 116 for moving the carriage 30 (see FIG. 1) in the main scanning direction X. 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 is a control unit that controls light emission of the ultraviolet irradiation light sources (LED elements) 34 and 35 via the LED drive circuit 118.

  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. The operator can input printing conditions and input / edit attached information by operating the input device 120, and various information such as input contents and search results can be confirmed through the display on the display device 122. it can.

  In addition, the ink jet recording apparatus 100 is provided with an information storage unit 124 that stores various types of information and an image input interface 126 for capturing image data for printing. As the image input interface, a serial interface or a parallel interface may be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted.

  Image data input via the image input interface 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 100.

  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). Multi-level quantization can also be performed.

  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 generating element (in this example, a piezo element) corresponding to each nozzle of the inkjet head 25. The waveform data of the drive voltage signal is stored in advance in the information storage unit 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 drive voltage signal is applied to each ejection energy generation element of the inkjet head 25 via the head drive circuit 128, and the switch element is connected to the individual electrode of each energy generation 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 print mode, the number of passes (the number of scan repetitions), control information for the ultraviolet irradiation light sources 34 and 35, and the like.

  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 S (see FIG. 1) are grasped.

  The sensor 132 is attached to the carriage 30, and the width of the recording medium S is grasped based on the sensor signal obtained from the sensor 132.

  DESCRIPTION OF SYMBOLS 21 ... Apparatus main body, 23 ... Support leg, 25 ... Inkjet head, 27 ... Platen, 29 ... Guide mechanism, 30 ... Carriage, 33 ... Cartridge, 34 ... Temporary curing light source, 35 ... Main curing light source, 36 ... Orbit of nozzle row 43 ... Scanning roller pair 47 ... Temperature adjustment unit 49 ... Pre temperature adjustment unit 51 ... After temperature adjustment unit 61 ... Nozzle row 71 ... Supply pump 73 ... Sub tank 75 ... Pressure adjustment unit 77 ... Valve: 79 ... Pump for pressure increase / decrease, 81 ... Pressure gauge, 100 ... Inkjet recording device, 102 ... Control device, 104 ... Recording medium conveyance control unit, 106 ... Carriage drive control unit, 108 ... Light source control unit, 110 ... Image processing 112: Discharge control unit 114 ... Conveyance drive unit 116 ... Main scan drive unit 118 ... LED drive circuit 120 ... Input device 122 ... Display device 124 ... Information Storage unit, 126 ... image input interface, 128 ... head driving circuit, 130 ... encoder, 132 ... sensor 132, L1, L2 ... optical path length, L3 ... overall length of the nozzle row, S1, S2 ... irradiated region

Claims (10)

A carriage including an irradiation unit that irradiates ultraviolet rays, and an image forming unit that discharges the ink cured by the ultraviolet rays by inkjet to form an image;
The carriage has scanning means that scans in both directions along a direction substantially perpendicular to the conveyance direction of the recording medium,
The irradiation unit includes a temporary curing irradiation unit provided on both sides of the image forming unit in the scanning direction of the carriage, and a main curing irradiation unit provided on the downstream side in the conveyance direction of the recording medium,
An ink jet recording apparatus, wherein an optical path length L1 from the temporary curing irradiation unit to the recording medium and an optical path length L2 from the main curing irradiation unit to the recording medium have a relationship of L1> L2.   2. The ink jet recording apparatus according to claim 1, wherein the optical path length L1 is 15 mm or more and 45 mm or less, and the optical path length L2 is 1 mm or more and 14 mm or less.   3. The ink jet recording apparatus according to claim 1, wherein the temporary curing irradiation unit is provided so as to irradiate an entire region in a width direction of the image forming unit with respect to a scanning direction of the carriage. .   The inkjet recording apparatus according to any one of claims 1 to 3, wherein an irradiation angle of light irradiated from the temporary curing irradiation unit is 90 ° or more and 130 ° or less.   The inkjet recording apparatus according to claim 1, further comprising a frame for adjusting an irradiation area at a tip of the temporary curing irradiation unit.   The inkjet recording apparatus according to claim 1, wherein the main curing irradiation unit is provided only on a downstream side of the temporary curing irradiation unit.   The ink jet recording apparatus according to claim 1, wherein the temporary curing irradiation unit and the main curing irradiation unit use the same irradiation device.   The ink jet recording apparatus according to claim 1, wherein the temporary curing irradiation unit and the main curing irradiation unit are LED elements.   The inkjet recording apparatus according to claim 8, wherein the temporary curing irradiation unit irradiates the entire region in the width direction with one LED element.   The inkjet recording apparatus according to claim 1, wherein the main curing irradiation unit includes a plurality of LED elements along a scanning direction of the carriage.

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