JP4720497B2 - Image recording apparatus and image recording system - Google Patents

Description

  The present invention relates to an image recording apparatus and an image recording system, and more particularly to an inkjet image recording apparatus and an image recording system.

  2. Description of the Related Art Conventionally, a technique using an ultraviolet curable ink has been developed in an inkjet image recording apparatus that is compatible with various recording media. For example, in the image recording apparatus described in Patent Document 1, an ink droplet landed on a recording medium by ejecting an ultraviolet curable ink containing a photoinitiator having a predetermined sensitivity to light such as ultraviolet rays. An image is recorded on a recording medium by irradiating the film with ultraviolet rays.

In addition, when performing image recording with colored ink, it is possible to improve glossiness of the entire recorded image uniformly by discharging together with transparent ink (see Patent Document 2 and Patent Document 3). .
In particular, when image recording is performed using an ultraviolet curable transparent ink on an area gradation image formed by an image forming unit of a charge copying method such as a color laser, not only the glossiness of the area gradation image is obtained. It is known that the graininess is also improved. Such improvement in graininess is due to the fact that the reflected light component changes due to the formation of the ink layer on the area gradation image, and the dye component contained in the halftone dots of the area gradation image is the ink before curing. This is due to elution into droplets. In particular, it is known that the graininess is remarkably improved in a low gradation region composed of halftone dots with a small amount of pigment component.
JP 2001-310454 A WO02 / 87886 JP 2004-284147 A

  However, when recording an image using an ultraviolet curable ink on an area gradation image, if the dye component of the halftone dot near the edge of the area gradation image elutes too much into the ink droplet, the mesh near the edge There is a possibility that the point is deformed and the sharpness of the area gradation image is deteriorated. In particular, there is a problem that the higher the area gradation image, the higher the accuracy of the position and shape of the halftone dot near the edge, and the greater the influence of the elution of the dye component on the ink.

  The present invention has been made in view of these points, and improves graininess without losing sharpness when recording an image using an active energy ray-curable ink on an area gradation image. An object of the present invention is to provide an image recording apparatus that can be used.

In order to solve the above-mentioned problem, the invention according to claim 1 is an image recording apparatus,
A recording head that discharges an active energy ray-curable ink to a recording medium on which an area gradation image is formed by a charge copying method ;
An active energy ray irradiation device for irradiating active energy rays toward the ink landed on the recording medium;
A transport mechanism for transporting the recording medium to the recording head and the active energy ray irradiation device;
A detection mechanism for detecting an edge portion of the area gradation image in the recording medium;
When the number of lines of the area gradation image is a [lpi], the dot diameter of the ink ejected toward the edge portion is smaller than 1 / (2 × a) [inch] and the edge portion A control unit that controls the recording head so that the dot diameter of the ink ejected toward a region other than 1 / (2 × a) [inch] is equal to or greater than 2 / a [inch]. ,
It is characterized by providing.

According to the first aspect of the invention, when the active energy ray-curable ink is ejected to the recording medium on which the area gradation image is formed, the edge portion of the area gradation image is detected . If the number of lines of the area gradation image is a [lpi], the dot diameter of the ink ejected toward the edge portion is smaller than 1 / (2 × a) [inch]. Is smaller than ½ of the halftone dot interval, and after landing , the ink droplets land and harden over a plurality of adjacent halftone dots in the area gradation image . On the other hand, the dot diameter of the ink ejected toward the non-edge portion is within the range of 1 / (2 × a) to 2 / a [inch], and is 1/2 of the halftone dot interval of the area gradation image. Large, ink droplets are landed and hardened so as to easily straddle adjacent halftone dots in the non-edge part of the area gradation image after landing , and image recording is performed on the recording medium on which the area gradation image is formed. Is done.

The invention according to claim 2 is the image recording apparatus according to claim 1,
When recording an image by repeating the ejection of ink by the recording head and the irradiation of active energy rays by the active energy ray irradiation device,
The amount of ink discharged for the first time toward the edge portion is 1 to 25% of the amount of ink used for recording a solid image on the edge portion.

According to the second aspect of the present invention, the amount of ink ejected to the edge portion for the first time is as small as 1 to 25% of the ink amount used for recording a solid image on the edge portion, It is possible to effectively prevent the ink droplets adjacent to each other from coming into contact with each other.

The invention according to claim 3 is the image recording apparatus according to claim 1 or 2 ,
The ink ejected by the recording head is a transparent ink.

According to the third aspect of the present invention, since the active energy ray-curable ink ejected by the recording head is a transparent ink, it can be ejected onto the area gradation image to give gloss. It is.

The invention according to claim 4
Image forming means for forming the charging copying scheme the area coverage modulation image in the charging copying system,
The image recording apparatus according to any one of claims 1 to 3 ,
With
The area gradation image is formed on the recording medium by the image forming unit, and then the image recording is performed on the area gradation image by the image recording apparatus.

According to the fourth aspect of the present invention, the active energy ray-curable ink is ejected even on the area gradation image recorded by the charge copying method, so that the graininess and gloss can be obtained without impairing the sharpness. It is possible to improve the performance.

According to the first aspect of the present invention, the ink droplets ejected toward the edge portion of the area gradation image land without straddling a plurality of adjacent halftone dots . For this reason, at the edge portion of the area gradation image, the dye component contained in the plurality of halftone dots is prevented from being eluted and mixed into the ink, and the sharpness of the edge portion of the area gradation image is reduced. And high-definition image recording can be performed. Further, the ink ejected toward the non-edge portion of the area gradation image easily spans a plurality of adjacent halftone dots after landing. Since the non-edge part of the area gradation image consists of halftone dots containing the same pigment component, the pigment component contained in these halftone dots elutes into the ink and mixes to improve the granularity of the area gradation image Can be made. Accordingly, when an image is formed by ejecting active energy ray-curable ink onto a recording medium, the graininess can be improved without impairing the sharpness of the area gradation image.

According to the second aspect of the present invention, the ink droplets ejected for the first time toward the edge portion are prevented from coming into contact with each other, and are thus cured in an independent state. Therefore, even when an active energy ray-curable ink is ejected onto an area gradation image, the ink droplets contact each other and move from the landing position regardless of the wettability between the area gradation image and the ink. Therefore, image recording can be performed with high accuracy.

According to the third aspect of the present invention, it is possible to improve graininess and glossiness without deteriorating sharpness by discharging transparent ink on the area gradation image.

According to the fourth aspect of the present invention, the active energy ray-curable ink is also ejected onto the area gradation image recorded by the charge copying method, so that the graininess and glossiness can be obtained without impairing the sharpness. It is possible to improve.

  Hereinafter, an embodiment of an image recording apparatus according to the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

  As shown in FIG. 1, the image recording apparatus 1 according to the present embodiment includes a cylindrical drum 2 that is rotatable while holding a recording medium. The drum 2 is connected to a rotation mechanism 3 that rotates the drum 2 at a predetermined rotation speed during image recording. As shown in FIG. 2, the drum 2 is provided with a holding mechanism 4 that holds the recording medium in a state of being wound around the peripheral surface. The holding mechanism 4 is provided on each of the inner surfaces of the drum 2 and corresponding to both ends in the recording medium conveyance direction. The holding mechanism 4 is not particularly limited, and the recording medium may be attracted by generating static electricity on the peripheral surface of the drum 2.

  A guide roller 5 that sequentially guides the recording medium to the peripheral surface of the drum 2 is rotatably provided at a position facing the drum 2. A discharge tray (not shown) for discharging the recording medium released from the holding mechanism 4 is provided below the drum 2.

  Two sets of guide rails (not shown) extending in parallel with the rotation axis direction of the drum 2 are provided above the peripheral surface of the drum 2. A head unit 6 including a recording head 7 to be described later is supported on the guide rail on the upstream side in the transport direction so as to be able to reciprocate in a direction along the guide rail (hereinafter, “sub-scanning direction”). A maintenance unit 6 a that performs maintenance of the recording head 7 and the like is provided on the side of the drum 2 and at a position facing the lower surface of the head unit 6.

  In the head unit 6, a plurality of recording heads 7, which record an image by ejecting ink toward the recording medium, are arranged in a staggered manner. As shown in FIG. 3, the recording head 7 ejects process color inks (yellow (Y), magenta (M), cyan (C), black (K)) as actual image inks. A non-process color ink (white (W), clear) is ejected as background ink. The recording head 7 is formed in a substantially rectangular parallelepiped shape, and is arranged such that its longitudinal direction is along the sub-scanning direction. A plurality of nozzles (not shown) for discharging ink droplets are disposed on the surface of the recording head 7 facing the recording medium. The arrangement pattern of the recording heads 7 in the head unit 6 is not particularly limited and can be changed as appropriate.

  An ultraviolet irradiation device 8 that irradiates ultraviolet rays toward a recording medium conveyed below the guide rail on the downstream side in the conveyance direction is supported so as to be reciprocally movable in the sub-scanning direction. The ultraviolet irradiation device 8 is provided with a light source 9 for irradiating ultraviolet rays for curing ink droplets. In the present embodiment, the light source 9 irradiates ultraviolet rays, but those that irradiate active energy rays such as electron beams, X-rays, visible light, and infrared light can be applied according to the ink used.

  Here, the image recording apparatus 1 of the present embodiment performs image recording using an active energy ray-curable ink on an area gradation image formed on a recording medium. The area gradation image is expressed by gradation according to the size of a halftone dot, and is formed by an image forming means such as a color laser. The area gradation image mainly includes a dot-type screen in which halftone dots are arranged in a dot shape as shown in FIG. 4 and a line-type screen in which halftone dots are arranged in a line shape as shown in FIG. In the area gradation image, the number of halftone dots arranged in a 1-inch width is called a line number (unit: lpi (line per inch)). When the number of lines is a [lpi], the halftone dot interval of the area gradation image is represented by 1 / a [inch].

  The image recording apparatus 1 includes a detection mechanism 10 that detects an edge portion of an area gradation image formed on a recording medium so as to face the area gradation image forming surface of the recording medium. An edge extraction method by the detection mechanism 10 is not particularly limited, but a method of performing edge extraction by directly obtaining image data from an image forming unit that forms an area gradation image is preferable. As another edge extraction method, when the recording medium is conveyed and opposed to each other, it moves in the sub-scanning direction, analyzes the image data of the area gradation image, and binarizes it by applying a Laplacian filter or the like. And the edge extraction method by pattern matching using an area gradation image. Further, the detection mechanism 10 detects, as an edge portion, an area corresponding to at least four times the dot diameter of ink ejected by the recording head 7 to be described later with the edge of the extracted area gradation image as the center. Yes. Further, the detection mechanism 10 outputs data relating to the detected position and shape of the edge portion to the control unit 13 as a detection result.

Here, “ink” used in the present embodiment will be described.
The ink used in the present embodiment is cured by being irradiated with active energy rays. Specifically, it is an ultraviolet curable ink that is cured by irradiation with ultraviolet rays as active energy rays, and contains at least a polymerizable compound (including a known polymerizable compound) and a photoinitiator as main components. Is. Such UV curable inks are roughly classified into radical polymerization inks containing radical polymerizable compounds as polymerizable compounds and cationic polymerization inks containing cationic polymerizable compounds. Each ink can be applied as an ink used in the embodiment, and a hybrid ink in which a radical polymerization ink and a cation polymerization ink are combined may be applied as an ink used in this embodiment. However, it is particularly preferable to use a cationic polymerization ink because a cationic polymerization ink that has little or no inhibitory action on the polymerization reaction due to oxygen is superior in functionality and versatility.

  Further, the ink used in the present embodiment may be a transparent ink without adding a coloring material to the main component. In particular, when a special ink in which various additives are added to the ink discharged from the recording head 7 is used, the special ink can be discharged onto the area gradation image previously formed on the recording medium to perform post-processing. preferable. As an example of post-processing, image protection by ejecting highly durable ink, gloss imparting by ejecting glossy ink onto the recording medium, and ejecting special ink readable by a special method onto the recording medium Information addition, etc.

Next, the “recording medium” used in the present embodiment will be described.
As for the recording medium used in the present embodiment, various papers such as plain paper, recycled paper, and glossy paper that are applied to ordinary inkjet printers, various fabrics, various non-woven fabrics, resins, metals, glass, and the like are used. Is applicable. The form of the recording medium is not particularly limited, and for example, a roll shape, a cut sheet shape, or a plate shape can be used according to the holding mechanism 4. In this embodiment, since the holding mechanism 4 that holds both ends in the conveyance direction of the recording medium is used, a cut sheet-like one is used.

Next, the control configuration of the image recording apparatus 1 according to the present embodiment will be described.
As shown in FIG. 6, the image recording apparatus 1 includes a detection mechanism 10, a recording head 7, an ultraviolet irradiation device 8, a sub-scanning mechanism 11, a drum 2 rotation mechanism 3, a recording medium transport mechanism 12, a holding mechanism 4, and the like. A control unit 13 is provided which is electrically connected to and controls these. The control unit 13 includes, for example, a CPU, a ROM, and a RAM (all not shown), and develops a processing program recorded in the ROM on the RAM and executes the processing program by the CPU.

  During image recording, the control unit 13 controls the rotation mechanism 3 so that the drum 2 rotates at a predetermined rotation speed, and moves the recording medium in the conveyance direction by the conveyance mechanism 12 according to the rotation speed of the drum 2. It is controlled so that it is conveyed sequentially. Further, the control unit 13 controls the holding mechanism 4 so that the recording medium guided by the guide roller is held by the drum 2 in accordance with the conveyance of the recording medium. Further, the control unit 13 is configured to release the holding of the recording medium by the holding mechanism 4 when the image recording of the recording medium held on the drum 2 is completed.

  When the image is recorded, the control unit 13 causes the detection mechanism 10 to detect the edge portion of the area gradation image formed on the recording medium held by the drum 2. The detection mechanism 10 extracts an edge of the area gradation image, detects a region having a predetermined width around the edge as an edge portion, and outputs the detection result to the control unit 13.

When recording an image, the control unit 13 controls the sub-scanning mechanism 11 so that the head unit 6 and the ultraviolet irradiation device 8 move in the sub-scanning direction in accordance with the rotation speed of the drum 2. At that time, the control unit 13 controls the recording head 7 to eject ink in accordance with the movement of the head unit 6 in the sub-scanning direction, and turns on the light source 9 while the ultraviolet irradiation device 8 moves in the sub-scanning direction. You are in control. When the recording head 7 ejects ink, the control unit 13 performs control so that the dot diameter ejected toward the edge portion of the area gradation image is smaller than the dot diameter ejected toward the non-edge portion. ing. The dot diameter of the ink droplets ejected toward the edge portion is 1 / (2 × a) [inch] which is half of the halftone interval of the area gradation image so that it does not extend over a plurality of halftone dots after landing. It is preferable to discharge so as to be small. On the other hand, the dot diameter of the ink droplets ejected toward the non-edge portion is 1 / (2 × a so as not to reach the halftone dots of the edge portion while straddling a plurality of halftone dots of the non-edge portion after landing. ) To 2 / a [inch].
The width of the edge portion is preferably set according to the dot diameter of the ink droplet ejected toward the edge portion, and the control unit 13 detects the dot diameter of the ink droplet ejected toward the edge portion. It outputs to the mechanism 10.

  Here, in the present embodiment, the control unit 13 rotates the drum 2 a plurality of times, and performs a recording process in which the ink ejection by the recording head 7 and the ultraviolet irradiation by the ultraviolet irradiation device 8 are sequentially performed a plurality of times. The image is recorded repeatedly. When the controller 13 records an image close to a solid image in the area on the edge portion, the amount of ink used for recording the solid image in the area on the edge portion is recorded in the first recording process. 1 to 25% is controlled to be ejected from the recording head 7. Here, an image close to a solid image means an image that requires an ink amount of 85% or more, assuming that the ink amount used for recording a solid image is 100%.

  Next, an image recording method as an operation of the image recording apparatus 1 according to the present embodiment will be described. Here, the image recording apparatus 1 records an image on a recording medium on which an area gradation image is formed, and records an image close to a solid image in an area on an edge portion of the area gradation image. And

  First, when predetermined image information is sent to the image recording apparatus 1, the rotation mechanism 3 starts rotating the drum 2 and accelerates it until a predetermined rotation speed is reached. When the rotational speed of the drum 2 reaches a predetermined value, the transport mechanism 12 transports the recording medium such that the surface of the recording medium on which the area gradation image is not formed is in contact with the peripheral surface of the drum 2 and wound. To do. Then, the holding mechanism 4 first holds the leading end of the recording medium, and winds the recording medium around the circumferential surface of the drum 2 as the drum 2 rotates. The holding mechanism 4 sandwiches the rear end portion of the recording medium, and the recording medium is held by the drum 2.

  Next, the detection mechanism 10 detects an edge portion in the area gradation image of the recording medium held on the drum 2. The detection mechanism 10 reads the image data of the area gradation image when it faces the recording medium, extracts an edge, and detects an edge portion having a predetermined width centered on the edge. The detection mechanism 10 outputs the detection result of the edge portion to the control unit 13, and the control unit 13 ejects ink from the recording head 7 so that the dot diameter is smaller in the edge portion of the area gradation image than in the non-edge portion. Have the image recorded.

  The first recording process is performed by the recording head 7 and the ultraviolet irradiation device 8 during one rotation of the drum 2 after the start of image recording. Specifically, the head unit 6 is moved in the sub scanning direction along the guide rail by the sub scanning mechanism 11. Along with this, the recording head 7 also moves in the sub-scanning direction, and ink is ejected onto the edge portion so that the dot diameter after landing is smaller than the non-edge portion. Then, when the ink droplets landed on the recording medium face the ultraviolet irradiation device 8 as the drum 2 rotates, the ink droplets are irradiated with ultraviolet rays from the light source 9 and cured. Here, the amount of ink ejected in the first recording process is as small as 1 to 25% of the amount of ink used for recording a solid image, and the recording head 7 does not contact each other after ink droplets have landed. Thus, the ink droplets are cured in an independent state (see FIG. 7A). In this way, the first recording process is completed.

  Subsequently, the control unit 13 causes the second and subsequent recording steps to be completed and completes image recording on the recording medium. When the image recording is completed, the holding mechanism 4 releases the holding of the recording medium, and the recording medium is discharged to a discharge tray provided below the drum 2.

  As described above, according to the image recording apparatus 1 of the present embodiment, the ink droplets land on the edge portion of the area gradation image without straddling a large number of halftone dots. It is possible to prevent the components from eluting and the mixture of the dye components having a large number of halftone dots. Therefore, it is possible to prevent the sharpness of the edge portion of the area gradation image from being deteriorated and perform high-definition image recording. Further, in the non-edge portion of the area gradation image, an ink droplet having a large dot diameter lands on a halftone dot, and a pigment component contained in the halftone dot is eluted, thereby improving graininess. Therefore, the active energy ray-curable ink is ejected onto the recording medium, and the graininess can be improved without impairing the sharpness of the area gradation image.

  Further, since the recording head 7 ejects ink on the edge portion so that the dot diameter after landing is smaller than 1 / (2 × a) [inch], it is directed toward the edge portion of the area gradation image. The ejected ink droplets do not straddle multiple adjacent halftone dots, preventing the color components contained in the multiple halftone dots from eluting into the ink and mixing together, and reducing the sharpness of the area gradation image. It can be surely prevented.

  Further, since the recording head 7 ejects ink on the non-edge portion so that the dot diameter after landing is 1 / (2 × a) to 2 / a [inch], the non-area grayscale image is not displayed. The ink droplets ejected toward the edge portion straddle a plurality of adjacent halftone dots after landing. Since the non-edge portion is composed of halftone dots containing the same pigment component, the graininess can be improved by eluting the pigment component into the ink extending over a plurality of halftone dots.

Further, since the ink droplets ejected for the first time by the recording head 7 toward the edge portion are cured without being in contact with each other, the ink droplets ejected from the second time onward are already in the first time. Can be spread evenly in contact with the ink droplets discharged (see FIG. 7B). In addition, even when an image close to a solid image is recorded, regardless of the wettability between the area gradation image or the recording medium and the ink, there is a problem that the ink droplets come into contact with each other and move from the landing position. Therefore, it is possible to perform image recording with high accuracy.
Here, when the first recording process is performed, the ink may be ejected from the recording head 7 so that the resolution after landing of the ink droplet is 2 to 6 times that in the second and subsequent recording processes. good. By increasing the resolution after landing of the first ink droplet that is ejected, the ink droplet becomes smaller, so that ink droplets that do not form the same pixel do not contact each other after landing and are independent. It is possible to maintain the state efficiently.

  Further, there is no particular limitation on the image forming means for forming the area gradation image, and the active energy ray-curable ink is ejected onto the area gradation image recorded by the charge copying method, thereby impairing the sharpness. It is also possible to improve the graininess and glossiness. Further, as shown in FIG. 8, an image forming unit is connected to the image recording apparatus 1, and the formation of the area gradation image and the image recording with the active energy ray curable ink are continuously performed by one image recording system. It is also good.

  Note that the width of the edge portion can be appropriately changed. When a high sharpness image is required, the width of the edge portion is increased so that the dye component contained in the halftone dots is not eluted and mixed into the ink. Is preferable.

1 is a perspective view showing an image recording apparatus according to the present invention. 1 is a side view showing an image recording apparatus according to the present invention. FIG. 3 is a plan view showing the arrangement of recording heads according to the present invention. It is explanatory drawing which shows the image recording method which concerns on this invention, and the state in which the ink was discharged by the recording head toward each of the edge part and the non-edge part of the area gradation image formed by arranging the dot in the dot form It is explanatory drawing which shows. It is explanatory drawing which shows the image recording method which concerns on this invention, and the state by which the ink was discharged by the recording head toward each of an edge part and a non-edge part of the area gradation image formed by arranging the halftone dots in the line form It is explanatory drawing which shows. It is a block diagram which shows the control structure of the image recording apparatus which concerns on this invention. It is explanatory drawing which shows the image recording method in the case of recording an image close | similar to a solid image in the area | region above an edge part, (a) is a side view of the recording medium after the 1st recording process, (b) is It is a side view of the recording medium after the second and subsequent recording steps. It is explanatory drawing which shows the image recording system which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image recording device 2 Drum 3 Rotating mechanism 4 Holding mechanism 6 Head unit 7 Recording head 8 Ultraviolet irradiation device 9 Light source 10 Detection mechanism 11 Sub-scanning mechanism 12 Conveyance mechanism 13 Control part

Claims (4)

A recording head that discharges an active energy ray-curable ink to a recording medium on which an area gradation image is formed by a charge copying method ;
An active energy ray irradiation device for irradiating active energy rays toward the ink landed on the recording medium;
A transport mechanism for transporting the recording medium to the recording head and the active energy ray irradiation device;
A detection mechanism for detecting an edge portion of the area gradation image in the recording medium;
When the number of lines of the area gradation image is a [lpi], the dot diameter of the ink ejected toward the edge portion is smaller than 1 / (2 × a) [inch] and the edge portion A control unit that controls the recording head so that the dot diameter of the ink ejected toward a region other than 1 / (2 × a) [inch] is equal to or greater than 2 / a [inch]. ,
An image recording apparatus comprising: When recording an image by repeating the ejection of ink by the recording head and the irradiation of active energy rays by the active energy ray irradiation device,
The amount of ink discharged for the first time toward the edge portion is 1 to 25% of the amount of ink used for recording a solid image on the edge portion. Image recording device.   The image recording apparatus according to claim 1, wherein the ink ejected by the recording head is a transparent ink. Image forming means for forming the charging copying scheme the area coverage modulation image in the charging copying system,
The image recording apparatus according to any one of claims 1 to 3 ,
With
An image recording system in which the area gradation image is formed on the recording medium by the image forming unit, and then the image recording is performed on the area gradation image by the image recording apparatus.

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