JP6056834B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to an image forming apparatus and an image forming method using an ink head that ejects droplets of photocurable ink toward a recording medium.

2. Description of the Related Art Conventionally, as an image forming apparatus such as an ink jet printer, an apparatus using a photocurable ink is known. The image forming apparatus includes an ink head unit including a plurality of ink heads that ejects photocurable ink, and a light irradiation mechanism that is disposed adjacent to the ink head unit. Each of the ink heads ejects a photocurable ink having a different hue.
In such an image forming apparatus, photocurable inks having different hues are ejected from the respective ink heads toward the recording medium. Thereby, ink dots are formed by the landed photocurable ink on the recording medium. Thereafter, the light irradiating mechanism irradiates light to the ink curable ink that has landed on the ink dot, that is, the recording medium. As a result, the ink dots are cured and fixed on the recording medium.

  The image forming apparatus using such a photocurable ink has the following problems. In other words, in the case where droplets of photocurable ink of a plurality of colors are landed on the recording medium, bleeding occurs between the ink dots when the ink dots are formed on the recording medium in contact with each other. . As a result, color mixing of photocurable inks having different hues occurs on the recording medium. As a result, there is a problem that the color reproducibility of the obtained image is lowered or the image quality is lowered.

As means for solving such a problem, Patent Document 1 discloses an image forming apparatus that controls the diameter of ink dots so that ink dots formed on a recording medium do not contact each other.
In Patent Document 2, the ink head and the temporary curing light source are alternately arranged, and the photo-curable ink ejected from the ink head and landed on the recording medium is temporarily cured adjacent to the ink head. An image forming apparatus that is temporarily cured by light from a general light source is disclosed.

JP 2005-119291 A JP 2012-45908 A

However, these image forming apparatuses have the following problems.
In the image forming apparatus described above, droplets of the photocurable ink ejected from the ink head are landed on the recording medium while the ink head is moved relative to the recording medium. For this reason, due to the directivity of the ejection direction in the ink head and the influence of disturbance, the photocurable ink droplet cannot be landed on the recording medium with high accuracy, and the position of the obtained ink dot Deviation occurs.
In the image forming apparatus described in Japanese Patent Application Laid-Open No. 2005-228561, the ink dots are displaced due to the positional deviation of the ink dots, and eventually blur occurs between the ink dots.
Further, in the image forming apparatus described in Patent Document 2, even if the ink dots are in contact with each other, the photocurable ink constituting one of the ink dots is temporarily cured, so that bleeding occurs between the ink dots. It is possible to suppress this. However, since the photocurable ink constituting the other ink dot is in an uncured state, that is, in a liquid state, the other ink is used after the photocurable ink is landed on the recording medium and temporarily cured. The photocurable ink constituting the dot is attracted to one ink dot. As a result, fine color shading is generated in the obtained image, and it is difficult to form an image with good color reproducibility and high image quality.
Such a phenomenon becomes conspicuous when an image with high resolution is formed, that is, when an image with fine ink dots and a small pitch is formed.

  Accordingly, an object of the present invention is to prevent or suppress the occurrence of bleeding between ink dots formed on a recording medium, and to form an image with good color reproducibility and high image quality. An object of the present invention is to provide an image forming apparatus and an image forming method.

An image forming apparatus of the present invention is an image forming apparatus provided with an ink head for ejecting droplets of photocurable ink toward a recording medium,
A pre-curing light irradiation mechanism for pre-curing the curable ink by irradiating the curable ink with light, and applying an energy smaller than a reference energy necessary for sufficiently curing the curable ink. Prepared
The preliminary curing light irradiation mechanism is arranged so that light from the preliminary curing light irradiation mechanism is irradiated to an ink droplet flying space between the ink head and the recording medium,
The preliminary curing light irradiation mechanism is configured to prevent the ink droplets from being reflected toward the ink head by intermittently emitting light from the preliminary curing light irradiation mechanism. The light emission timing is controlled so that the surface on the recording medium side of the photocurable ink droplets flying in the flying space is irradiated.

In the image forming apparatus according to the aspect of the invention, it is preferable that the preliminary curing light irradiation mechanism includes a preliminary curing light source including a laser.
In such an image forming apparatus, it is preferable that the preliminary curing light irradiation mechanism has means for scanning light from the preliminary curing light source in the ink droplet flying space.

  In the image forming apparatus of the present invention, a plurality of ink heads are arranged in one direction, and a plurality of preliminary curing light irradiation mechanisms are provided corresponding to each of the ink heads. preferable.

The image forming method of the present invention includes an ink ejection process in which droplets of photocurable ink are ejected from an ink head toward a recording medium, and light is applied to the photocurable ink that has landed on the recording medium. An image forming method including an ink curing treatment step of curing the photocurable ink by applying an energy higher than a reference energy necessary for sufficiently curing the ink,
In the ink ejection step, the reference energy is applied to the droplets of the curable ink that fly in the ink droplet flying space by irradiating light to the ink droplet flying space between the ink head and the recording medium. Pre-curing the curable ink droplets by applying a small amount of energy,
The recording medium side of the droplets of the photocurable ink flying in the ink droplet flying space so that the light is intermittently emitted and the light is prevented from being reflected toward the ink head. The light emission timing is controlled so that the surface of the light is irradiated.

In the image forming method of the present invention, it is preferable that the light applied to the ink droplet flying space is laser light in the ink ejection step.
In such an image forming method, it is preferable that in the ink ejection step, the light irradiated to the ink droplet flying space is scanned in the ink droplet flying space.

According to the present invention, the photocurable ink droplets emitted from the ink head are pre-cured before landing on the recording medium. Therefore, even if the ink dots come into contact with each other on the recording medium, it is possible to prevent or suppress bleeding between the ink dots or the other ink dot being attracted to one ink todd. Therefore, it is possible to form an image with good color reproducibility and high image quality.
In addition, in order to control the timing of light emission so that light is emitted intermittently so that the surface of the photocurable ink droplet on the recording medium side is irradiated, Since the irradiated light is reflected toward the recording medium, reflection toward the ink head is avoided. As a result, the photocurable ink attached to the nozzles of the ink head can be prevented or suppressed from being cured.

1 is a perspective view illustrating a configuration of a main part in an example of an image forming apparatus of the present invention. FIG. 2 is a plan view of the image forming apparatus illustrated in FIG. 1. FIG. 4 is an explanatory diagram illustrating a surface facing each recording medium in each ink head. It is explanatory drawing which shows the internal structure in an example of the light irradiation mechanism for main curing. It is explanatory drawing which shows the internal structure in an example of the light irradiation mechanism for pre-curing. It is explanatory drawing which shows the positional relationship of an ink head and the preliminary curing light irradiation mechanism. It is explanatory drawing which shows the position where the light in the droplet of photocurable ink is irradiated. It is explanatory drawing which shows the structure of the principal part in the other example of the image forming apparatus of this invention. It is explanatory drawing which shows the structure of the principal part in the further another example of the image forming apparatus of this invention. It is explanatory drawing which shows the structure in the other example of the light irradiation mechanism for pre-curing. It is explanatory drawing which shows the structure in the further another example of the light irradiation mechanism for pre-curing.

Embodiments of the present invention will be described below.
FIG. 1 is a perspective view showing a configuration of a main part in an example of an image forming apparatus of the present invention. FIG. 2 is a plan view of the image forming apparatus shown in FIG. In these drawings, an x direction, a y direction, and a z direction indicated by arrows are three directions orthogonal to each other. The image forming apparatus shown in FIG. 1 is configured as an ink jet printer, for example.

In this image forming apparatus, a plurality of (four in the illustrated example) ejecting photocurable ink droplets (hereinafter also referred to as “ink droplets”) P in the z-direction toward the sheet-like recording medium M. ) Ink head unit 10 is provided. Here, as the photocurable ink, those that are cured by ultraviolet rays can be suitably used. For the main curing, the light curable ink is cured by irradiating the light curable ink landed on the recording medium M with light L1 at positions adjacent to both ends in the y direction of the ink head unit 10. A light irradiation mechanism 20 is disposed. Each of the ink head unit 10 and the main curing light irradiation mechanism 20 is supported by a moving mechanism (not shown) that moves them along the y direction.
A plurality of (four in the illustrated example) pre-curing light irradiation mechanisms 30 for pre-curing the ink droplets P are provided at one side position in the y direction of the ink head unit 10. Each of the preliminary curing light irradiation mechanisms 30 is arranged so that the light L2 from the preliminary curing light irradiation mechanism 30 is irradiated to the ink droplet flying space S between the ink head 11 and the recording medium M. Yes.
Further, the image forming apparatus is provided with a transport mechanism (not shown) for transporting the recording medium M in the x direction in a region facing the ink head unit 10.

  In the ink head unit 10, four rectangular parallelepiped ink heads 11 that eject ink droplets P of different hues, specifically blue, yellow, magenta, and black, are arranged in the y direction. Has been placed. As shown in FIG. 3, a plurality of nozzles 12 for ejecting ink droplets P in the z direction (direction perpendicular to the paper surface in FIG. 3) are provided on the surface of each ink head 11 facing the recording medium M. They are arranged in the x direction.

FIG. 4 is an explanatory diagram showing an internal configuration in an example of the main curing light irradiation mechanism 20. In the main curing light irradiation mechanism 20, a long light source unit 22 extending in the x direction (a direction perpendicular to the paper surface in FIG. 4) is provided inside the housing 21. In the light source unit 22, a long rectangular substrate 23 is arranged in a posture extending in the x direction along a plane extending in the x direction and the y direction. On the surface of the substrate 23 (the lower surface in FIG. 4), a plurality of main curing light sources 25 each made of a rectangular plate-like light emitting diode are arranged along the surface of the substrate 23 in the x direction. Yes. Each of the main curing light sources 25 is provided with a hemispherical sealing lens 26 that covers the light emitting surface of the main curing light source 25 so as to protrude from the surface of the substrate 23.
A columnar lens 24 extending along the light source unit 22 is provided at a position facing the light emitting surface of the main curing light source 25 in the light source unit 22. A holding member 27 that holds the columnar lens 24 is provided in the opening of the housing 21. A heat sink 28 made of, for example, aluminum is provided on the back surface (upper surface in FIG. 4) of the substrate 23 in the light source unit 22. A cooling fan 29 for cooling the heat sink 28 is provided above the heat sink 28.

  The main curing light irradiation mechanism 20 irradiates the light curable ink that has landed on the recording medium M with the light L1 so as to sufficiently exceed the reference energy necessary for sufficiently curing the light curable ink. Energy is applied. Here, the reference energy can be experimentally obtained using a photocurable ink that is actually used.

  FIG. 5 is an explanatory diagram showing a configuration in an example of the pre-curing light irradiation mechanism 30. The preliminary curing light irradiation mechanism 30 is configured to receive a preliminary curing light source 31 formed of a laser diode, a polygon mirror 32 for scanning the light L2 from the preliminary curing light source 31, and the light L2 from the preliminary curing light source 31. The light transmitting window member 33 to be emitted, the first light reflecting member 34 for reflecting the light L2 from the preliminary curing light source 31 toward the polygon mirror 32, and the light L2 from the polygon mirror 32 to the light transmitting window member 33. And a second light reflecting member 35 that reflects the light.

  In the image forming apparatus of this example, a plurality of preliminary curing light irradiation mechanisms 30 are provided corresponding to each of the ink heads 11 in the ink head unit 10. As shown in FIG. 6, each of the preliminary curing light irradiation mechanisms 30 is along a plane in which the light L2 from the preliminary curing light irradiation mechanism 30 extends in the x direction and the y direction across the ink droplet flying space S. The light L2 is irradiated in a direction crossing the y direction. Then, the polygon mirror 32 is driven to rotate, and the light L2 from the preliminary curing light irradiation mechanism 30 is scanned in the ink droplet flight space S. Thereby, the light L2 is irradiated over the entire area of the ink droplet flying space S along the plane extending in the x direction and the y direction across the ink droplet flying space S. Therefore, it is possible to irradiate the ink droplets P emitted from all the nozzles 12 of the ink head 11 with the light L2.

The pre-curing light irradiation mechanism 30 irradiates the ink droplet flying space S between the ink head unit 10 and the recording medium M with the light L2, thereby causing the ink droplet P to fly in the ink droplet flying space S. On the other hand, energy smaller than the reference energy required to sufficiently cure the photocurable ink is applied.
A specific means for applying energy smaller than the reference energy to the ink droplet P is not particularly limited, but as the pre-curing light source 31, the peak wavelength of the emitted light has a light absorption peak in the photo-curable ink. Means using a different wavelength, means for controlling the output of the light L2 emitted from the preliminary curing irradiation mechanism 30, and the like can be used.

  In the image forming apparatus described above, the recording medium M is intermittently conveyed in the x direction in a region facing the ink head unit 10 by a conveyance mechanism (not shown). Then, while moving the ink head unit 10 in the y direction, ink droplets P are ejected from the ink head 11 of the ink head unit 10 toward the conveyed recording medium M. At this time, the ink droplet P flying in the ink droplet flying space S between the ink head 11 and the recording medium M is irradiated with the light L2 from the pre-curing light irradiation mechanism 30. Thereby, energy smaller than the reference energy is applied to the flying ink droplet P, and as a result, the ink droplet P is pre-cured. Then, when ink droplets P that have been pre-cured land on the recording medium M, ink dots are formed on the recording medium M. Thereafter, the ink dots formed on the recording medium M are irradiated with the light L <b> 1 by the main curing light irradiation mechanism 20, so that the ink dots are cured and fixed on the recording medium M.

  In the above, the preliminary curing light irradiation mechanism 30 records the light L2 in the ink droplet P by intermittently emitting the light L2 from the preliminary curing light irradiation mechanism 30 as shown in FIG. It is preferable to control the emission timing of the light L2 so that the surface on the medium M side is irradiated. As a result, the light L2 applied to the ink droplet P is reflected toward the recording medium M, so that reflection toward the ink head 11 is avoided. As a result, the photocurable ink attached to the nozzles 12 of the ink head 11 can be prevented or suppressed from being cured.

According to such an image forming apparatus, the ink droplets P emitted from the ink head 11 are pre-cured before landing on the recording medium M. For this reason, even if the ink dots come into contact with each other on the recording medium M, it is possible to prevent or suppress bleeding between the ink dots or the other ink dot being attracted to one ink todd. Therefore, it is possible to form an image with good color reproducibility and high image quality.
In addition, by using laser light that has high condensing property and can be emitted with high output, in a short time with respect to the ink droplet P flying at high speed in the ink droplet flying space S that is a narrow region. Necessary energy can be made to act reliably.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and the following various modifications can be added.
(1) As shown in FIG. 8, a plurality of spares corresponding to each of the ink heads 11 in the ink head unit 10 are provided at both one side position in the y direction and the other side position in the ink head unit 10. A curing light irradiation mechanism 30 may be provided.
(2) As shown in FIG. 9, a single preliminary curing light irradiation mechanism 30 may be disposed adjacent to one main curing light irradiation mechanism 20. In such a configuration, it is preferable to control the preliminary curing light irradiation mechanism 30 so that the light L2 is intermittently emitted in accordance with the timing at which the ink droplets P are emitted from the ink head 11.

(3) The pre-curing light source mechanism 30 may have a configuration other than that shown in FIG.
FIG. 10 is an explanatory view showing a configuration in another example of the pre-curing light source mechanism 30. This pre-curing light source mechanism 30 is close to the nozzle 12 in the y direction (left and right direction in the figure) on the surface (hereinafter referred to as “emission surface”) facing the recording medium (not shown) in the ink head 11. A plurality of preliminary curing light sources 31, a light reflecting member 36 that reflects light L <b> 2 from the preliminary curing light source 31 disposed along both side edges of the emission surface of the ink head 11, and the nozzle 12. And a light-blocking member 37 disposed between the pre-curing light source 31 and blocking the light from the pre-curing light source 31 toward the nozzle 12. In the preliminary curing light source mechanism 30 having such a configuration, a light emitting diode can be used as the preliminary curing light source 31 in addition to the laser diode.

  FIG. 11 is an explanatory diagram showing a configuration of still another example of the pre-curing light source mechanism 30. The preliminary curing light source mechanism 30 includes a plurality of preliminary curing light sources 31 disposed behind the ink head 11 (upper position in FIG. 11) and a plurality of light condensing light from the preliminary curing light sources 31. The condenser lens 38 and a plurality of optical fibers 39 for guiding the light collected by the condenser lenses 38 are configured. The optical fiber 39 is arranged so that the light emitting end face thereof faces the ink droplet flying space S. In the preliminary curing light source mechanism 30 having such a configuration, a light emitting diode can be used as the preliminary curing light source 31 in addition to the laser diode.

DESCRIPTION OF SYMBOLS 10 Ink head unit 11 Ink head 12 Nozzle 20 Main curing light irradiation mechanism 21 Case 22 Light source part 23 Substrate 24 Columnar lens 25 Main curing light source 26 Sealing lens 27 Holding member 28 Heat sink 29 Cooling fan 30 Pre-curing light irradiation Mechanism 31 Precuring light source 32 Polygon mirror 33 Light transmitting window member 34 First light reflecting member 35 Second light reflecting member 36 Light reflecting member 37 Light blocking member 38 Condensing lens 39 Optical fiber L1, L2 Light M Recording medium P Ink Droplet S Ink droplet flight space

Claims (7)

An image forming apparatus including an ink head that ejects droplets of photocurable ink toward a recording medium,
A pre-curing light irradiation mechanism for pre-curing the curable ink by irradiating the curable ink with light, and applying an energy smaller than a reference energy necessary for sufficiently curing the curable ink. Prepared
The preliminary curing light irradiation mechanism is arranged so that light from the preliminary curing light irradiation mechanism is irradiated to an ink droplet flying space between the ink head and the recording medium,
The preliminary curing light irradiation mechanism is configured to prevent the ink droplets from being reflected toward the ink head by intermittently emitting light from the preliminary curing light irradiation mechanism. An image forming apparatus for controlling the timing of light emission so that the surface of a recording medium side of the droplets of the photocurable ink flying in a flying space is irradiated.   The image forming apparatus according to claim 1, wherein the preliminary curing light irradiation mechanism includes a preliminary curing light source including a laser.   The image forming apparatus according to claim 2, wherein the preliminary curing light irradiation mechanism includes a unit that scans light from the preliminary curing light source in the ink droplet flying space.   The plurality of ink heads are arranged so as to be aligned in one direction, and a plurality of preliminary curing light irradiation mechanisms are provided corresponding to each of the ink heads. The image forming apparatus according to any one of the above. Ink ejection process for ejecting light-curable ink droplets from the ink head toward the recording medium, and for sufficiently curing the curable ink by irradiating the light-curable ink that has landed on the recording medium with light. An image forming method comprising: an ink curing process that cures the photocurable ink by applying an energy that is greater than a necessary reference energy, wherein in the ink ejection process, the ink head and the recording medium By irradiating light between the ink droplet flying space between the ink, the curable ink droplet flying in the ink droplet flying space acts on the droplet of the curable ink by applying energy smaller than the reference energy. Pre-cured,
The recording medium side of the droplets of the photocurable ink flying in the ink droplet flying space so that the light is intermittently emitted and the light is prevented from being reflected toward the ink head. An image forming method, wherein the timing of light emission is controlled so as to irradiate the surface of the image.   6. The image forming method according to claim 5, wherein, in the ink ejection step, the light irradiated to the ink droplet flight space is a laser beam.   The image forming method according to claim 6, wherein, in the ink ejection step, the light irradiated to the ink droplet flying space is scanned in the ink droplet flying space.

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