JP2007290399A - Inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently inhibit bleeding of ink with a small quantity of light (the total quantity of light), and thereby to realize miniturization of a light source section and to prevent head plugging. <P>SOLUTION: An inkjet recording device comprises a UV laser scanner formed near the head of the inkjet recording device which uses a UV-curable type ink. The UV laser scanner can alter arbitrarily a scanning speed or the quantity of the UV light in the width direction of the recording sheet 16. The UV laser scanner reduces the scanning speed (refer to Figure 7(B)), or enlarges the quantity of the light (refer to Figure 7(C)), and thereby irradiates the UV light intensively in the edge of a solid print section 16A where the bleeding of the ink tends to be conspicuous. Thereby, the bleeding of the ink is inhibited efficiently, and the total quantity of the light of the UV light which irradiates the recording paper 16 is reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus, and more particularly to a technique for preventing ink bleeding.

  2. Description of the Related Art Conventionally, a technique for printing on a printing object using ultraviolet curable ink, irradiating the ink after landing on the printing object with ultraviolet light, curing the ink, and preventing ink bleeding is known. (Patent Documents 1 to 10).

  In Patent Document 1, an ultraviolet (UV) light source is provided in the head traveling direction integrally with a head that ejects ink, and the ink in the recording unit recorded during the previous scan is irradiated with UV light from the UV light source. Is described.

  Patent Document 2 describes that when ink is ejected once, UV light is irradiated and cured before the next ink is ejected, thereby preventing bleeding and recording unevenness.

  Patent Document 3 describes that it is better to cure the ink before penetrating the recording medium (recording paper) (see paragraph “0104” of Patent Document 3).

  Patent Document 4 describes that a light guide for irradiating temporary curing fixing light is provided in the vicinity of an ink jet nozzle, and ink is presupposed by temporary curing fixing light from the light guide, and then finally fixed by another light source. There is.

  Patent Document 5 describes a fixed UV light source having a size that covers a range scanned by a head.

  Japanese Patent Application Laid-Open No. 2004-228688 describes that the time from ink ejection to UV irradiation is specified. There is also a description of a line type head having a length corresponding to the maximum width of the object to be printed.

  Patent Document 7 describes that various irradiation conditions including light irradiation time, irradiation intensity, irradiation area, incident angle, and the like are changed in accordance with the type of object to be printed, the type of ink, the viscosity, and the like.

  Patent Documents 8 and 9 have a description that a UV light source is provided integrally with a head.

  Patent Document 10 describes that light is guided from the outside of the head to the head portion with an optical fiber or a mirror, and irradiated with the movement of the head unit.

In the inventions described in Patent Documents 1 to 10, the UV light source for curing the ink is
1. It is fixed to the ink jet recording apparatus, and the irradiation target moves to shine light on the whole.

  2. It is fixed to the head, and light is applied to the irradiation target as the head is scanned.

  3. Light is guided from the outside of the head to the head by some means, and light is applied to the irradiation target as the head is scanned.

are categorized. In any of the inventions, the idea of irradiating light on the entire object to be printed is the same, and it is devised to irradiate more immediately after printing in order to prevent bleeding.
JP 2003-11334 A JP 2003-11343 A JP 2002-187918 A JP 2003-89198 A JP 2003-145741 A JP 2003-192943 A JP 2003-191594 A JP-A-60-132767 US Pat. No. 6,092,890 US Pat. No. 6,145,579

  The conventional ink jet recording apparatuses described in Patent Documents 1 to 10 irradiate UV light immediately after ejecting ink onto an object to be printed to prevent bleeding, but have the following problems.

  1. In order to irradiate the UV light immediately after ejecting the ink, a light source or a member that guides the UV light is required near the head. However, when the UV is irradiated to the entire printing area and the ink is further cured, High energy is required, and the light source part becomes large.

  2. When UV light is irradiated onto the object to be printed, the UV light irregularly reflected at the irradiation position reaches the periphery, but when the UV light irradiation position and the printing position are brought close to each other in order to suppress bleeding, the reflected UV light is reflected on the head. There is a risk of curing the ink before ejection and causing clogging of the head.

  3. If a laser diode with good luminous efficiency is used to save energy in an inkjet recording device, the amount of light emitted is less than that of other discharge tubes, etc., so there is not enough energy to cure the entire print width (printed object) Depending on the transport speed).

  The present invention has been made in view of such circumstances, and can effectively prevent ink bleeding with a small amount of light (total light amount), thereby reducing the size of the light source and preventing head clogging. It is another object of the present invention to provide an ink jet recording apparatus capable of detecting ink ejection and detecting ink ejected from a head using an optical system common to an optical system used for ink curing. .

  In order to achieve the object, the invention according to claim 1 performs printing by ejecting a photocurable ink onto an object to be printed, and irradiates the ink after landing on the object to be printed with light. In an ink jet recording apparatus for curing ink, a light irradiating unit disposed on the downstream side of a head for discharging the ink and irradiating light immediately after landing on the object to be printed, and a solid on the object to be printed The edge of the printing part, the edge of the line part, the isolated dot, or the part where the ink bleeding is conspicuous where the change in contrast or color is large, so that the amount of light irradiation is larger than the other part. And a control means for controlling the light irradiation means.

  In other words, by intensively irradiating light to a portion where ink bleeding is conspicuous, it is possible to efficiently prevent ink bleeding and to reduce the total amount of light irradiated to the object to be printed.

  According to a second aspect of the present invention, there is provided an ink jet recording apparatus that performs printing by ejecting a photocurable ink onto an object to be printed, and irradiates the ink after landing on the object to be printed with light to cure the ink. A light irradiating means for irradiating the ink immediately after landing on the object to be printed, a light irradiating means disposed on the downstream side of the head for ejecting the ink, and a margin and a line of the solid print portion on the object to be printed Control for controlling the light irradiating means so that the amount of light irradiation is larger in the portion where the ink bleeding is conspicuous that is the edge of the portion, the isolated dot, or the portion where the contrast or the color is greatly changed than the other portion. The light irradiation means has scanning means for scanning light of a predetermined beam width in the width direction of the object to be printed, and the control means controls the scanning speed of the scanning means to be constant. And the ink It is characterized by bleeding controls the light source of the light irradiation unit so that the quantity of light irradiated to the conspicuous portion increases.

  That is, the scanning speed of light by the scanning unit is made constant, and the amount of light emitted from the light source is changed (the amount of light is changed so that the amount of light to the portion where ink bleeding is conspicuous is increased).

  3. The ink jet recording apparatus according to claim 1, wherein the light irradiating means includes a light source that emits light and a light that is emitted from the light source via the scanning mirror. And a scanning unit including an optical system for condensing on the object to be printed and a mirror driving unit for driving the scanning mirror.

  4. The ink jet recording apparatus according to claim 3, wherein the head is a line type head having a length corresponding to a maximum width of an object to be printed, and the light irradiation unit is the scanning unit. Are arranged in the longitudinal direction of the line type head.

  The number of scanning means is determined by the scannable width of each scanning means and the length of the line type head.

  5. The ink jet recording apparatus according to claim 3, wherein the light condensing unit is provided on an optical path between a light source of an optical system of the light irradiation unit and a scanning mirror, and is condensed on the object to be printed. A branching unit for branching the reflected light reflected at the point and returning from the optical system; a photosensor for detecting the reflected light branched by the branching unit; and the object to be printed based on a detection output from the photosensor. The printing apparatus further includes a print detection unit including a determination unit that determines the presence or absence of the upper ink dot.

  That is, using the optical system of the light irradiating means, the reflected light when each dot is irradiated with light is branched by the branching means on the optical system and guided to the optical sensor, and the dot output is detected by the detection output of the optical sensor. It is determined whether or not the vehicle has landed. Here, the reflected light means both specular reflection and irregular reflection.

  6. The ink jet recording apparatus according to claim 3, wherein the head and the object to be printed are first branching means provided on an optical path of an optical system of the light irradiation means. A first branching unit that divides the light so that the light passes through the gap, and irradiates ink before being ejected from the head and landing on the object to be printed, and a light source of an optical system of the light irradiating unit A second branching unit provided on an optical path between the first mirror and the scanning mirror, the second branching unit splitting the reflected light reflected by the ink before landing and returning through the optical system; An optical sensor that detects the reflected light branched by the second branching unit, and a determination unit that determines whether ink has been ejected from each nozzle of the head based on the detection output from the optical sensor. Ink discharge detection means It is characterized by comprising.

  That is, using the optical system of the light irradiating means, the first branching means provided on the optical path of the optical system branches the light so that the light passes through the gap between the head and the object to be printed. Light is applied to the ejected ink before landing. The reflected light of the light hitting the ink returns through the same optical system, is branched by the second branching means, and is guided to the optical sensor. Whether or not ink is ejected from each nozzle of the head is determined based on the detection output of the optical sensor.

  The ink jet recording apparatus according to any one of claims 1 to 6, wherein the control means for controlling the light irradiating means is a portion where the ink bleeding obtained based on the image data is conspicuous. On the other hand, the control is performed.

  According to an eighth aspect of the present invention, in the ink jet recording apparatus according to the seventh aspect, the control means calculates a portion where the ink bleeding is conspicuous by performing a filter processing calculation based on image data. .

  The ink jet recording apparatus according to any one of claims 1 to 8, wherein the light irradiating unit is disposed on a downstream side of the head from a light irradiation position on the object to be printed. It has the 2nd light irradiation means to irradiate the light which hardens the said photocurable ink with respect to the full width on a to-be-printed object.

  According to the present invention having the above-described configuration, light is intensively applied to areas where ink bleeding is conspicuous, such as the edges of solid print areas, the edges of line areas, isolated dots, or areas where contrast or color changes greatly. As a result, the total amount of light applied to the object to be printed can be reduced, and ink bleeding can be efficiently prevented. Further, by suppressing the total light quantity, it is possible to prevent the light source unit from being downsized and the head from being clogged.

  Hereinafter, preferred embodiments of an ink jet recording apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

  First, an outline of the ink jet recording apparatus according to the present invention will be described. FIG. 1 is an overall configuration diagram of an ink jet recording apparatus according to the present invention. As shown in the figure, the inkjet recording apparatus 10 includes a printing unit 12 having a plurality of inkjet heads (hereinafter simply referred to as “heads”) 12K, 12C, 12M, and 12Y provided for each color of ink. An ink storage / loading unit 14 that stores ink to be supplied to each of the heads 12K, 12C, 12M, and 12Y, a paper feeding unit 18 that supplies the recording paper 16, and a decurling unit 20 that removes curl from the recording paper 16. A suction belt conveyance unit 22 that is disposed opposite to the nozzle surface (ink ejection surface) of the printing unit 12 and conveys the recording paper 16 while maintaining the flatness of the recording paper 16, and a printing result by the printing unit 12 And a paper discharge unit 26 that discharges printed recording paper (printed matter) to the outside.

  The recording paper 16 delivered from the paper supply unit 18 retains curl due to having been loaded in the magazine. In order to remove this curl, heat is applied to the recording paper 16 by the heating drum 30 in the direction opposite to the curl direction of the magazine in the decurling unit 20.

In the case of an apparatus configuration that uses roll paper, as shown in FIG. 1, a cutter (first cutter) 28 is provided, and the roll paper is cut into a desired size by the cutter 28. The cutter 28 includes a fixed blade 28A having a length equal to or greater than the conveyance path width of the recording paper 16, and a round blade 28B that moves along the fixed blade 28A. The fixed blade 28A is provided on the back side of the print. The round blade 28B is disposed on the printing surface side with the conveyance path interposed therebetween. Note that the cutter 28 is not necessary when cut paper is used.

  After the decurling process, the cut recording paper 16 is sent to the suction belt conveyance unit 22. The suction belt conveyance unit 22 has a structure in which an endless belt 33 is wound between rollers 31 and 32, and at least portions facing the nozzle surface of the printing unit 12 and the sensor surface of the printing detection unit 24 are horizontal ( Flat surface).

  The belt 33 has a width that is wider than the width of the recording paper 16, and a plurality of suction holes (not shown) are formed on the belt surface. As shown in FIG. 1, a suction chamber 34 is provided at a position facing the nozzle surface of the print unit 12 and the sensor surface of the print detection unit 24 inside the belt 33 spanned between the rollers 31 and 32. Then, the suction chamber 34 is sucked by the fan 35 to be a negative pressure, whereby the recording paper 16 on the belt 33 is sucked and held.

  The power of a motor (not shown) is transmitted to at least one of the rollers 31 and 32 around which the belt 33 is wound, so that the belt 33 is driven in the clockwise direction in FIG. The recording paper 16 is conveyed from left to right in FIG.

  Since ink adheres to the belt 33 when a borderless print or the like is printed, the belt cleaning unit 36 is provided at a predetermined position outside the belt 33 (an appropriate position other than the print area).

  A heating fan 40 is provided on the upstream side of the printing unit 12 on the paper conveyance path formed by the suction belt conveyance unit 22. The heating fan 40 blows heated air on the recording paper 16 before printing to heat the recording paper 16. Heating the recording paper 16 immediately before printing makes it easier for the ink to dry after landing.

  The printing unit 12 is a so-called full line type head in which line type heads having a length corresponding to the maximum paper width are arranged in a direction (main scanning direction) orthogonal to the paper feed direction. Each of the heads 12K, 12C, 12M, and 12Y is composed of a line-type head in which a plurality of ink discharge ports (nozzles) are arranged over a length exceeding at least one side of the maximum size recording paper 16 targeted by the inkjet recording apparatus 10. Has been.

  A head 12K corresponding to each color ink in the order of black (K), cyan (C), magenta (M), and yellow (Y) from the upstream side along the feeding direction of the recording paper 16 (hereinafter referred to as the paper transport direction). 12C, 12M, and 12Y are arranged. A color image can be formed on the recording paper 16 by ejecting the color inks from the heads 12K, 12C, 12M, and 12Y while conveying the recording paper 16, respectively.

  The print detection unit 24 includes a line sensor for imaging the droplet ejection result of the print unit 12, and functions as means for checking nozzle clogging and other ejection defects from the droplet ejection image read by the line sensor.

  A post-drying unit 42 is provided following the print detection unit 24. The post-drying unit 42 is means for drying the printed image surface, and for example, a heating fan is used. Since it is preferable to avoid contact with the printing surface until the ink after printing is dried, a method of blowing hot air is preferred.

A heating / pressurizing unit 44 is provided following the post-drying unit 42. The heating / pressurizing unit 44 is a means for controlling the glossiness of the image surface, and pressurizes with a pressure roller 45 having a predetermined surface uneven shape while heating the image surface to transfer the uneven shape to the image surface. To do.

  The printed matter generated in this manner is cut into a predetermined size by the cutter 28 and then discharged from the paper discharge unit 26. It is preferable that the original image to be printed (printed target image) and the test print are discharged separately. The ink jet recording apparatus 10 is provided with a sorting means (not shown) that switches the paper discharge path so as to select the print product of the main image and the print product of the test print and send them to the discharge units 26A and 26B. Yes. Note that when the main image and the test print are simultaneously formed in parallel on a large sheet, the test print portion is separated by a cutter (second cutter) 48.

  FIG. 2 is a principal block diagram showing the system configuration of the inkjet recording apparatus 10.

  The inkjet recording apparatus 10 includes an ultraviolet (UV) laser scanner 60, a communication interface 70, a system controller 72, an image memory 74, a motor driver 76, a heater driver 78, a print control unit 80, an image buffer memory 82, a head driver 84, and the like. ing.

  The UV laser scanner 60 irradiates the ink dots ejected onto the recording paper with UV light in order to prevent ink bleeding, and cures the UV curable ink. Details of the UV laser scanner 60 will be described later.

  The communication interface 70 is an interface unit that receives image data sent from the host computer 86. As the communication interface 70, a serial interface such as USB, IEEE 1394, Ethernet, and wireless network, or a parallel interface such as Centronics can be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted. Image data sent from the host computer 86 is taken into the inkjet recording apparatus 10 via the communication interface 70 and temporarily stored in the image memory 74. The image memory 74 is a storage unit that temporarily stores an image input via the communication interface 70, and data is read and written through the system controller 72. The image memory 74 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The system controller 72 is a control unit that controls each unit such as the communication interface 70, the image memory 74, the motor driver 76, and the heater driver 78. The system controller 72 includes a central processing unit (CPU) and its peripheral circuits, and performs communication control with the host computer 86, read / write control of the image memory 74, and the like, as well as a transport system motor 88 and heater 89. A control signal for controlling is generated.

  The motor driver 76 is a driver (drive circuit) that drives the motor 88 in accordance with an instruction from the system controller 72. The heater driver 78 is a driver that drives the heater 89 such as the post-drying unit 42 in accordance with an instruction from the system controller 72.

  The print control unit 80 has a signal processing function for performing various processing and correction processing for generating a print control signal from the image data in the image memory 74 according to the control of the system controller 72, and the generated print A control unit that supplies a control signal (print data) to the head driver 84. Necessary signal processing is performed in the print control unit 80, and the ejection amount and ejection timing of the ink droplets of the printing unit 12 are controlled via the head driver 84 based on the image data. Thereby, a desired dot size and dot arrangement are realized.

The print controller 80 controls the UV laser scanner 60 to prevent ink bleeding as described later, and has a function of detecting printing and ink ejection based on a detection signal input from the UV laser scanner 60.

  The print control unit 80 includes an image buffer memory 82, and image data, parameters, and other data are temporarily stored in the image buffer memory 82 when image data is processed in the print control unit 80.

  In FIG. 2, the image buffer memory 82 is shown in a mode associated with the print control unit 80, but it can also be used as the image memory 74. Also possible is an aspect in which the print controller 80 and the system controller 72 are integrated and configured with a single processor.

  The head driver 84 drives the actuators of the print heads 12K, 12C, 12M, and 12Y for each color based on the print data given from the print control unit 80. The head driver 84 may include a feedback control system for keeping the head driving conditions constant.

  As described with reference to FIG. 1, the print detection unit 24 is a block including a line sensor. The print detection unit 24 reads an image printed on the recording paper 16, performs necessary signal processing, and the like to perform a print status (whether ejection is performed, whether droplet ejection is performed). Variation), and the detection result is provided to the print controller 80. The print control unit 80 performs various corrections on the print unit 12 based on information obtained from the print detection unit 24 as necessary.

  Next, the UV laser scanner 60 will be described.

  First, as the ink of each color of black (K), cyan (C), magenta (M), and yellow (Y) in the ink storage / loading unit 14, a UV curable ink that is cured by UV light is used. A UV laser scanner 60 is disposed in each of the heads 12K, 12C, 12M, and 12Y that discharge the inks of these colors.

  FIG. 3 is a perspective view of the head 12K and the UV laser scanner 60 provided integrally with the head 12K.

  As shown in the figure, the UV laser scanner 60 includes three scanners 60A, 60B, and 60C. The number of scanners constituting the UV laser scanner 60 provided in each head is not limited to three, and can be determined by the head width and the scanning width of one scanner.

  The recording paper (printed object) 16 has a maximum width that can be printed by the head 12, and the UV laser scanner 60 can scan the entire width of the recording paper 16 with UV light. .

  In FIG. 3, 13A is a flexible wiring board for driving and controlling the actuator for each nozzle of the head 12K, and 13B is a pipe for supplying black (K) ink to the head 12K. 15A, 15B, and 15C are flexible wiring boards for outputting signals for operating and controlling the scanners 60A, 60B, and 60C to the scanners and inputting detection signals from optical sensors (to be described later) in the scanners. It is. Reference numeral 17 denotes a UV lamp that is fixedly provided at a predetermined position downstream of the recording paper 16 fed in the direction of arrow A and can simultaneously irradiate UV light over the entire width of the recording paper 16.

FIG. 4 is a diagram showing an internal configuration of each of the scanners 60A, 60B, and 60C of the UV laser scanner 60, and shows the scanner 60A.

  As shown in the figure, the scanner 60 </ b> A mainly includes a UV laser light source (UV laser diode) 61, a collimator lens 62, a cylindrical lens 63, a scanning mirror 67, and a condenser mirror 69. A half mirror (or polarization mirror) 64 is disposed on the optical path between the cylindrical lens 63 and the scanning mirror 67, and a condenser lens 65 that condenses the light branched by the half mirror 64; An optical sensor 66 such as a photodiode for detecting the light condensed by the condenser lens 65 is provided.

  5A and 5B are diagrams schematically showing the optical system of the scanner 60A on the xz plane and the yz plane, respectively. As shown in FIG. 4, the x direction indicates the longitudinal direction of the head 12K (scanning direction of UV light), the z direction indicates the optical axis direction of the optical system of the scanner 60A, and the y direction indicates the x and z directions. Each orthogonal direction is shown.

  The UV light emitted from the UV laser light source 61 is converted into parallel light by the collimator lens 62 and enters the cylindrical lens 63. The parallel light incident on the cylindrical lens 63 is condensed in the y direction here, is incident on the half mirror 64, the scanning mirror 67, and the condensing mirror 69, and the UV laser light incident on the condensing mirror 69 is here. It is condensed in the x and y directions. Then, the UV light emitted from the UV laser light source 61 is condensed on the recording paper 16 as UV light having a predetermined size by the optical system. Due to the optical system of the scanner 60A, the light emission point of the UV laser light source 61 and the light condensing point on the recording paper 16 have a conjugate relationship.

  Note that the size of the UV light condensed on the recording paper 16 needs to be at least larger than the size of printing of one dot of ink (for example, φ25 μm). Depending on the characteristics of the ink and the object to be printed. In other words, it is desirable to irradiate UV light more broadly in the combination of the ink and the object to be printed which are very likely to bleed. If the physical properties are about the same as that of commonly used plain paper and ink, it is about 0.1 mm to 0.5 mm. What is necessary is just to irradiate UV light of width. Further, the condensing mirror 69 may or may not have fθ property or sinθ property, and the scanning line may not be a straight line.

  As shown in FIG. 4, the scanning mirror 67 is provided so as to be rotatable about the y-direction axis, and is driven at an arbitrary angle by a mirror driving source 68 driven by electrostatic force, electromagnetic force, or the like. By controlling the angle of the scanning mirror 67 according to a command from the print control unit 80, the UV light condensed on the recording paper 16 can be scanned in the x direction (the width direction of the recording paper 16). At this time, since an image is not drawn, high-accuracy (positional accuracy) scanning as in a general laser printer is not necessary, and the size of the UV light to be irradiated, the conveyance speed of the object to be printed, and one scanning are required. From the amount of movement of the object to be printed obtained from the time, it is sufficient to have an accuracy that does not cause the omission of the ink dots to be irradiated.

  Next, a method for preventing ink bleeding in the present invention will be described.

  FIG. 6 shows the recording paper 16 after being irradiated with UV light by the UV laser scanner 60, and the thick line portion in FIG. 6 shows the portion irradiated with UV light.

  That is, according to the present invention, the UV laser scanner 60 immediately after printing on the portion of the recording paper 16 where ink bleeding is conspicuous (that is, the edge of the solid print portion 16A, the edge of the line portion 16B, and the isolated dot 16C). The UV light is concentrated and irradiated, and then the ink is cured by irradiating the entire area of the recording paper 16 with the UV lamp 17 as shown in FIG.

Next, a method for concentrating and irradiating UV light on the recording paper 16 where ink bleeding is conspicuous will be described.

  As shown in FIG. 7A, when UV light is concentrated and irradiated to the edge of the solid printing portion 16A during printing by the UV laser scanner 60, as shown in FIG. The scanning speed in the direction (the width direction of the recording paper 16) is changed according to the scanning position, and the scanning speed is lowered only when scanning the edge of the solid print portion 16A. At this time, the amount of UV light emitted from the UV laser light source 61 is constant.

  Further, as shown in FIG. 7C, the light amount of the UV light emitted from the UV laser light source 61 is made variable to maximize the light amount when scanning the edge of the solid print portion 16A, and during other scans. Reduce the light intensity to about the bias. Note that the scanning speed of the UV laser scanner 60 at this time is constant. Further, in this embodiment, the light amount is reduced to the level of bias except for the edge, but it may be extinguished.

  The scanner 60A shown in FIG. 4 performs one-dimensional scanning with UV light. However, the scanning mirror 67 may be configured to be able to rotate in the direction around the x-direction axis so as to perform two-dimensional scanning.

  Next, a UV light scanning method using a scanner capable of two-dimensional scanning will be described.

  As shown in FIG. 8A, the printing parts 16D and 16E printed on the recording paper 16 have long edges in the direction orthogonal to the x direction, and the printing part 16F is the same as the x direction. Has a long edge in the direction.

  When irradiating UV light concentrated on the edges of these printing parts 16D, 16E, 16F, when irradiating UV light to the edges intersecting the x direction of the printing parts 16D, 16E, FIG. As shown in (B), the scanning speed is lowered.

  On the other hand, when the UV light is irradiated to the edge parallel to the x direction of the printing unit 16F, the scanning speed of the UV light is increased. In the example shown in FIG. 8B, scanning is performed so as to be slower than the maximum scanning speed and higher than the speed during the low-speed scanning, but may be the maximum scanning speed.

  Moreover, although the UV light with a high scanning speed is irradiated to the edge parallel to the x direction of the printing unit 16F as described above, the UV light is irradiated a plurality of times by a plurality of scans. The recording paper 16 is conveyed and moved during a plurality of scanning periods, but the irradiation direction of the UV light is changed according to the movement of the recording paper 16 (that is, the angle of the scanning mirror 67 in the x-axis direction is changed). ), UV light is irradiated to the same edge.

  Accordingly, UV light can be intensively applied to the edge parallel to the x direction, and one scan in the x direction is required even when UV light is irradiated to a long edge parallel to the x direction. Time can be prevented from becoming longer.

  As described above, the UV laser scanner can efficiently irradiate UV light to a portion where bleeding is more noticeable when two-dimensional scanning is performed.

  By the way, at the edge of the printing portion where ink bleeding is conspicuous, it is necessary to surely cure in units of one dot of ink landed on the recording paper. Detailed description.

FIG. 9A is a diagram showing the arrangement of dots based on image data. In the example shown in FIG. 9, the dot interval is 2400 dots / inch (dpi). In addition, the dot interval of 2400dpi is 10.6μ
m.

  FIG. 9B shows a state where ink dots are arranged (droplet ejection) on the dots shown in FIG. This ink dot diameter is φ25 μm, which is larger than a dot without a gap based on image data, and adjacent ink dots partially overlap.

  FIG. 9C shows an irradiation region of UV light necessary for curing the ink dots shown in FIG.

  FIG. 9D shows the scanning speed in the case where UV light is intensively applied to the irradiation region shown in FIG.

  That is, as shown in FIG. 9D, the scanning speed of the UV light is reduced at the timing immediately before entering the irradiation area, and the scanning speed of the UV light is increased at the timing of exiting the irradiation area. As a result, the ink dots at the edge of the print portion can be reliably cured.

  In the scanner 60A shown in FIG. 4, the number of UV laser light sources 61 is one. However, a plurality of UV laser light sources may be used, and a plurality of UV lights may be scanned by one scanner. Further, the optical axis of the scanner may be incident perpendicular to the recording paper, or may be inclined and incident. In the vertical case, a larger amount of light (signal) can be obtained in the case of print detection described later. When tilting, if the optical axis is tilted away from the head so that the reflected (diffuse reflection) light to the head is weakened, trouble due to ink curing at the head can be further reduced.

  Next, a print detection method using the scanning optical system of the scanner shown in FIGS. 4 and 5 will be described.

  As described above, UV light for curing the ink dots is applied to the ink dots ejected onto the recording paper 16, and this UV light is reflected (diffusely reflected) at the condensing point on the recording paper 16. The reflected light returns to the opposite direction to that during irradiation through the optical system of the scanner.

  The half mirror 64 shown in FIG. 4 and FIG. 5 branches the reflected light that has returned through the scanning optical system of the scanner and makes it incident on the condenser lens 65. The condensing lens 65 condenses incident reflected light on the light receiving surface of the optical sensor 66.

  The optical sensor 66 outputs an electrical signal (detection signal) corresponding to the amount of incident light to the print control unit 80. Since the reflectance of the surface of the recording paper 16 and the surface of the ink dots printed on the recording paper 16 are different, the reflected light when the UV light irradiates the ink dots and the reflected light when the ink dots are not irradiated The amount of light is different, and as a result, the signal level of the detection signal detected by the optical sensor 66 is also different.

  As a result, the print control unit 80 can detect the presence or absence of ink dots based on the detection signal obtained from the optical sensor 66, and in particular, captures the detection signal from the optical sensor 66 in synchronization with the scanning position of the UV light. Thus, it is possible to detect the ink droplet ejection result in the full width direction of the recording paper 16.

  The ink jet recording apparatus 10 of this embodiment includes a print detection unit 24 including a line sensor. Instead of the print detection unit 24, a print detection unit using the scanning optical system of the scanner is used. can do.

  Next, an ink ejection detection method using the scanning optical system of the scanner shown in FIGS. 4 and 5 will be described.

  FIG. 10 is a side view of the vicinity of the head. In order to realize this ink ejection detection method, a half mirror (or polarization mirror) 71 is disposed on the optical path between the condensing mirror 69 of the scanner 60A and the condensing point on the recording paper 16.

  The UV light transmitted through the half mirror 71 irradiates the ink landed on the recording paper 16, and the UV light reflected by the half mirror 71 is bent so as to be parallel to the recording paper 16, and is ejected from the head 12K. The ink 73 before landing on the recording paper 16 can be irradiated.

  When ink is ejected from the nozzles of the head 12K and the flying ink 73 is irradiated with UV light, the reflected light reflected by the ink 73 is opposite to that during irradiation through the half mirror 71 and the optical system of the scanner. Go back in the direction.

  The reflected light from the ink 73 that has returned through the scanning optical system of the scanner can be detected by the optical sensor 66 in the same manner as the print detection described above, and the print control unit 80 detects the detection signal from the optical sensor 66. Based on this, it is possible to detect for each nozzle whether ink has been ejected from each nozzle of the head.

  According to this ink discharge detection method, it is possible to check for clogging of nozzles and the like without performing printing on the recording paper.

  In this embodiment, the ink jet recording apparatus having a line type head has been described. However, the present invention is not limited to this, and the present invention is not limited to this. The shuttle type head in which the head reciprocates in a direction orthogonal to the recording paper feeding direction is used. The present invention can also be applied to an inkjet recording apparatus.

  FIG. 11 shows a UV laser scanner 92 provided integrally with a shuttle-type head 90.

  The irradiation position of the UV light emitted from the UV laser scanner 92 moves in conjunction with the movement of the head 90. However, when UV light is intensively applied to the edge of the printing portion where ink bleeding is conspicuous. 11A to 11C, the irradiation position of the UV light emitted from the UV laser scanner 92 is changed with the movement of the head 90, and the UV light is temporarily stopped or moved at the edge of the printing portion. Reduce the speed (scanning speed). The UV laser scanner 92 can be configured in the same manner as that shown in FIG. Further, when the shuttle type head has a plurality of nozzles, it may be configured to scan the UV light two-dimensionally so as to cover the discharge position of each nozzle.

  In this embodiment, the UV curing ink is irradiated with UV light to cure the ink. However, the present invention is not limited to this, and light other than UV light (for example, infrared light or visible light) is used. When using a curing ink, it is necessary to irradiate light that cures the ink.

  Further, the portion where the ink bleeding is conspicuous is not limited to the edge of the solid printing portion 16A, the edge of the line portion 16B, and the isolated dot 16C, but also includes a portion where the contrast or the color changes greatly.

As used herein, the portion having a large contrast or color change is generally used for images such as R, G, B data, C, M, Y, K data, or L *, a *, b * data. This is expressed as two-dimensional data using the color display method, and then this two-dimensional data is multiplied by one of the edge detection matrices such as Prewitt, Sobel, and Roberts matrix, and the filter processing is performed. A portion having a large value is an edge portion, and a portion having a large change in contrast or color.

  In particular, when focusing on contrast, it is desirable to use L * data, and when focusing on color, it is desirable to use a * and b * data. May be used.

  In addition to the method of using a matrix for edge detection, absolute values of density difference and color difference with adjacent pixels may be obtained, and a portion where this value is larger may be a portion where contrast or color change is greater. For example, the absolute value of the difference between the L * data at each point may be used for the density difference between the two points, and the sum of the squares of the differences between the a * and b * data at each point may be used for the two color differences. A square root may be used.

  In addition, it is the pixels at this edge that irradiate the ink after landing in a concentrated manner, and the image density, for example, L * is obtained from the ease of bleeding determined by the characteristics of the ink and the recording medium. It is a pixel of a darker part than the threshold which is easy to spread, and its adjacent pixel.

  That is, the above-described filter processing is performed on the pixels in the range where light is applied to the ink after landing in one scan, the filter processing value for each pixel is obtained, and the histogram of this value is further obtained. By using this histogram, pixels having a larger filter processing value from the maximum value of the filter processing value of each pixel to the number of pixels that can be irradiated in one scan and the image density of the ink and the recording medium A pixel having a density equal to or higher than the threshold value determined from the ease of bleeding determined by the characteristics is set as a target pixel, and light is intensively applied to the ink after landing on the pixel and the adjacent pixel portion.

  Furthermore, more simply, the above-described filter processing is performed on the pixels in the range where light is applied to the ink after landing in one scan, the filter processing value for each pixel is obtained, and the histogram of this value is further obtained. Using this histogram, the pixel value of the filter processing value from the maximum value of the filter processing value of each pixel to the number of pixels that can be irradiated in one scan and the ink after landing of the adjacent pixels are concentrated. You may make it irradiate light.

  The definition of “L * a * b *” is, for example, as follows.

Japanese Standards Association JIS Handbook "Optics"
Color display method-L * a * b * display system and L * u * v * display system Standard number JIS Z8729: 1994
FIGS. 12A to 12C show Prewitt, Sobel, and Roberts matrices, respectively. Edges in the vertical direction and the horizontal direction are detected by the matrix shown in the figure and a matrix obtained by rotating these matrices by 90 degrees.

  The actual calculation is the same as a general image processing matrix calculation, but the absolute value of the sum of the products of the pixel of interest and its surrounding pixels and the corresponding component of any of the matrixes to be used is obtained, The larger value of the horizontal calculation result may be adopted as the filter processing value of the target pixel.

1 is an overall configuration diagram of an inkjet recording apparatus according to the present invention. Main block diagram showing the system configuration of the inkjet recording apparatus The perspective view of the printing part in which the UV laser scanner was integrally provided The figure which shows the internal structure of UV laser scanner Schematic representation of the optical system of the UV laser scanner The figure used in order to explain the irradiation part of UV light The figure used in order to explain the method of concentrating and irradiating UV light to the portion where ink bleeding is conspicuous on the recording paper The figure used for demonstrating the other method which concentrates and irradiates UV light to the part on which ink bleeding is conspicuous on a recording paper The figure used in order to explain the detail of the timing which switches the scanning speed of UV light Side view of the vicinity of the head used to explain the method of detecting ink ejection using the scanning optical system of the UV laser scanner The figure which shows the UV laser scanner integrally provided in the shuttle type head Diagram showing Prewitt, Sobel, and Roberts edge detection matrices

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 12 ... Printing part, 12K, 12C, 12M, 12Y, 90 ... Head, 16 ... Recording paper, 16A ... Solid printing part, 16B line part, 16C ... Isolated dot, 16D, 16E, 16F ... Printing , 17 ... UV lamp, 60, 92 ... UV laser scanner, 60A, 60B, 60C ... scanner, 61 ... UV laser light source (UV laser diode), 62 ... collimator lens, 63 ... cylindrical lens, 64, 71 ... half mirror 65 ... Condensing lens, 66 ... Optical sensor, 67 ... Scanning mirror, 68 ... Mirror drive source, 69 ... Condensing mirror, 72 ... System controller, 80 ... Print controller

Claims (9)

In an ink jet recording apparatus that performs printing by discharging photocurable ink onto an object to be printed, and irradiates the ink after landing on the object to be printed with light to cure the ink.
A light irradiating means disposed on the downstream side of the head for ejecting the ink and irradiating the ink immediately after landing on the object to be printed;
On the object to be printed, the edge of the solid print part, the edge of the line part, the isolated dot, or the part where the ink bleeding that is a part where contrast or color change is large is more conspicuous than the other part. Control means for controlling the light irradiation means so as to increase the irradiation amount;
An ink jet recording apparatus comprising: In an ink jet recording apparatus that performs printing by discharging photocurable ink onto an object to be printed, and irradiates the ink after landing on the object to be printed with light to cure the ink.
A light irradiating means disposed on the downstream side of the head for ejecting the ink and irradiating the ink immediately after landing on the object to be printed;
On the object to be printed, the edge of the solid print part, the edge of the line part, the isolated dot, or the part where the ink bleeding that is a part where contrast or color change is large is more conspicuous than the other part. Control means for controlling the light irradiation means so as to increase the irradiation amount,
The light irradiation means has scanning means for scanning light having a predetermined beam width in the width direction of the object to be printed,
The control unit controls the scanning speed of the scanning unit to be constant, and controls the light source of the light irradiation unit so that the amount of light applied to a portion where the ink bleeding is conspicuous is increased. Recording device.   The light irradiation means includes a light source that emits light, an optical system that includes a scanning mirror and condenses the light emitted from the light source on the object to be printed via the scanning mirror, and a mirror that drives the scanning mirror. The inkjet recording apparatus according to claim 1, further comprising a scanning unit including a driving unit.   The head is a line-type head having a length corresponding to the maximum width of the object to be printed, and the light irradiation means includes a plurality of scanning means arranged in the longitudinal direction of the line-type head. The inkjet recording apparatus according to claim 3.   A branching unit that is provided on an optical path between a light source of the optical system of the light irradiation unit and a scanning mirror, and that splits reflected light that has been reflected at a condensing point on the object to be printed and returned from the optical system; A print detecting means further comprising: an optical sensor for detecting reflected light branched by the branching means; and a determining means for determining the presence or absence of ink dots on the object to be printed based on a detection output from the optical sensor. The ink jet recording apparatus according to claim 3, wherein the ink jet recording apparatus is provided.   A first branching unit provided on an optical path of an optical system of the light irradiating unit, for branching the light so that the light passes through a gap between the head and the object to be printed, and discharging from the head; A first branching unit that irradiates the ink before landing on the object to be printed, and a second branching unit provided on an optical path between a light source of an optical system of the light irradiation unit and a scanning mirror. A second branching unit for branching the reflected light reflected by the ink before landing and returning through the optical system; and an optical sensor for detecting the reflected light branched by the second branching unit; 5. The ink discharge detection unit according to claim 3, further comprising: a determination unit configured to determine whether ink is discharged from each nozzle of the head based on a detection output from the optical sensor. The ink jet recording apparatus described.   The ink jet according to any one of claims 1 to 6, wherein the control means for controlling the light irradiation means performs the control on a portion where the bleeding of the ink obtained based on the image data is conspicuous. Recording device.   The ink jet recording apparatus according to claim 7, wherein the control unit calculates a filter process calculation based on image data to calculate a portion where the ink bleeding is easily noticeable.   A second light irradiation unit is disposed on the downstream side of the head from the light irradiation position on the object to be printed, and irradiates light for curing the photocurable ink over the entire width on the object to be printed. 9. The ink jet recording apparatus according to claim 1, further comprising a light irradiation unit.

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