JP2008284708A - Inkjet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain a high image quality while an installation number of light sources is suppressed. <P>SOLUTION: The inkjet recorder includes a plurality of line type recording heads arranged along a conveyance route 68 for ejecting the ink towards a recording medium 2 conveyed by a conveying part 63, and two light sources 19 and 20 which cast ultraviolet rays on the ink hit against the recording medium 2. The plurality of line type recording heads includes a recording head for black 16 which ejects the black ink of a higher surface tension than that of the color ink, and recording heads for color 13-15 which eject the color ink. The recording head for black 16 is disposed downstream of the conveyance route 68 of the recording heads for color 13-15. One light source 19 of the two light sources 19 and 20 is disposed between the recording head for color 15 and the recording head for black 16, and the other light source 20 is disposed downstream of the conveyance route 68 of the recording head for black 16. A resolution of the recording head for black 16 is set higher than resolutions of the recording heads for color 13-15. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus, and more particularly to an ultraviolet curable ink jet recording apparatus.

2. Description of the Related Art Conventionally, there is known an ultraviolet curable ink jet recording apparatus that can record images on various recording media without requiring ink jet dedicated paper. In the ultraviolet curable ink jet recording apparatus, the ink can be cured by irradiating ultraviolet rays after the ink is ejected, so that an image can be recorded even on a recording medium having no ink absorbability. Here, if the ink droplets spread too much before the ink is cured, the image quality is adversely affected. In recent years, a technique for improving the image quality by defining the surface tension of the ink has been developed. (For example, refer to Patent Documents 1 and 2).
JP 2004-244624 A Japanese Patent Laid-Open No. 2004-243761

  By the way, the ultraviolet curable ink jet recording apparatus has a serial type in which the recording head ejects ink while scanning in a direction perpendicular to the conveyance direction of the recording medium, and a fixed arrangement above the conveyance path of the recording medium. There is a line type in which the recording head discharges ink as the recording medium is conveyed.

  In the line type ink jet recording apparatus, the recording heads for each color are arranged above the transport path, but only one light source is arranged at the most downstream side with the light source arranged so as to be paired with each recording head. There is something you did. In the former case, not only the manufacturing cost increases because a plurality of expensive light sources are installed, but also the heat of the plurality of light sources may adversely affect the recording medium. On the other hand, in the latter case, even if the surface tension of the ink is defined as described above, it takes time until the ultraviolet rays are irradiated. For this reason, ink mixes before curing, resulting in a reduction in image quality.

  Accordingly, an object of the present invention is to improve the image quality while suppressing the number of installed light sources.

An ink jet recording apparatus according to the invention of claim 1
A transport unit for transporting the recording medium;
A plurality of line-type recording heads arranged along a conveyance path of the recording medium by the conveyance unit in order to eject ink toward the recording medium conveyed by the conveyance unit;
Two light sources for irradiating ultraviolet rays toward ink landed on the recording medium,
The plurality of line-type recording heads include a black recording head that discharges black ink having a surface tension higher than that of color ink, and a color recording head that discharges the color ink. The black recording head is disposed downstream of the transport path,
Of the two light sources, one light source is disposed between the color recording head and the black recording head, and the other light source is disposed downstream of the conveyance path of the black recording head. ,
The black recording head has a resolution set higher than that of the color recording head.

The invention described in claim 2 is the ink jet recording apparatus according to claim 1,
The color ink has a surface tension of 20 dyn / cm or more and 40 dyn / cm or less.

The invention described in claim 3 is the ink jet recording apparatus according to claim 1 or 2,
The difference in surface tension between the color inks ejected by the plurality of color ink recording heads is 2 dyn / cm or less.

Invention of Claim 4 is an inkjet recording device as described in any one of Claims 1-3,
The illuminance of the one light source is higher than the illuminance of the other light source.

Invention of Claim 5 is an inkjet recording device as described in any one of Claims 1-4,
The plurality of line type recording heads are multi-drop type recording heads in which the amount of ejected droplets can be freely changed.

According to the present invention, only one light source is disposed between the color recording head and the black recording head, and one light source is disposed downstream of the conveyance path of the black recording head. Color inks that require color mixing with other inks are irradiated with ultraviolet rays after color mixing, and black inks that do not require color mixing with other inks are cured after landing on the cured color ink. Will be. Thereby, curing according to the curing condition of each ink can be realized with only two light sources, and the number of installed light sources can be suppressed.
By the way, since black ink often reproduces characters, it requires finer expression than color ink. Further, in order to obtain graininess, it is necessary to reduce the dot diameter. For this reason, the dot diameter after landing is reduced by using black ink with a higher surface tension than color ink. However, if the dot diameter is reduced, the black ink is completely coated with black ink. There is a risk that streaks will occur without being painted. For this reason, when the resolution of the black recording head is made higher than that of the color recording head as in the present invention, the solid-coated region with black ink has a finer resolution and the occurrence of streaks can be suppressed. As a result, high image quality can be achieved while suppressing the number of installed light sources.

Hereinafter, the ink jet recording apparatus according to the present embodiment will be described with reference to the drawings.
FIG. 1 shows an embodiment of an ink jet recording apparatus according to the present invention. A storage tray 61 for storing a plurality of recording media 2 in a stacked manner is provided below the inside of the ink jet recording apparatus 1. Yes. A take-out device 62 for taking out the recording medium 2 on which an image is to be recorded from the accommodation tray 61 one by one is provided above one end of the accommodation tray 61. As the recording medium 2, a cut sheet-shaped recording medium 2 made of various papers such as plain paper, recycled paper, glossy paper, various fabrics, various non-woven fabrics, resin, metal, glass and the like is applicable.

  A transport unit 63 that transports the recording medium 2 is provided above the storage tray 61. An annular conveyance belt 64 that supports the recording medium 2 in a planar shape and conveys the recording medium 2 in the horizontal direction is stretched around the conveyance section 63 by a plurality of tension rollers 65. In addition, the conveyance unit 63 is rotatably provided with a pressing roller 66 that presses the conveyance belt 64 in order to convey the recording medium 2 in a planar shape at a position where the conveyance belt 64 and the recording medium 2 start to contact each other. ing.

  Here, the surface of the conveyor belt 64 is made of, for example, an insulating layer such as polyamide, and the surface is charged by injecting charges from a power supply device (not shown) provided to apply a voltage to the surface of the conveyor belt 64. It is supposed to be. The transport belt 64 whose surface is charged in this way electrostatically attracts the recording medium introduced by the pressing roller 66 and transports the recording medium.

A discharge tray 67 for discharging the recording medium 2 on which an image is recorded is provided on the side of the inkjet recording apparatus 1.
Inside the inkjet recording apparatus 1, the recording medium 2 supplied from the storage tray 61 is transported to the transport belt 64, and after the recording medium 2 is transported by the transport belt 64, the recording medium 2 is discharged from the transport belt 64 to the discharge tray 67. A conveyance path 68 is provided. A plurality of pairs of transport rollers 69, 69... For transporting the recording medium 2 in the transport direction P are provided at predetermined positions on the transport path 68.

Further, in the vicinity of the upper portion of the conveyance belt 64, inks of each color of cyan (C), magenta (M), yellow (Y), and black (Bk: black) are sequentially applied to the recording medium 2 along the conveyance direction P. The recording heads 13, 14, 15, 16 for discharging are provided over the entire width of the conveyor belt 64. As the recording heads 13, 14, 15, and 16, a multi-drop type line recording head that can freely change the amount of ejected ink droplets is preferably used. And are arranged so as to face each other. As a result, the recording medium 2 supported by the conveyance belt 64 and the ejection surfaces of the recording heads 13, 14, 15, 16 are opposed to each other.
Hereinafter, among the recording heads 13, 14, 15, 16, the recording head 16 that discharges black ink is referred to as a black recording head 16, and color inks other than the black recording head 16 (cyan ink, magenta ink, yellow). The recording heads 13, 14, and 15 that eject ink) are referred to as color recording heads 13, 14, and 15.

  Here, as shown in FIG. 2, when the nozzle interval Rk of the black recording head 16 is compared with the nozzle interval Rc of the color recording heads 13, 14, 15, the nozzle interval Rk of the black recording head 16 is greater. Is set narrow, and the number of nozzles is also set large. As a result, the resolution of the black recording head 16 is set higher than the resolution of the color recording heads 13, 14, and 15.

  Further, two light sources 19 and 20 for irradiating ultraviolet rays toward the ink landed on the recording medium 2 are provided in the vicinity of the upper portion of the conveyance belt 64. Of the two light sources 19, 20, one light source 19 is disposed between the color recording heads 13, 14, 15 and the black recording head 16, and the other light source 20 is the transport path of the black recording head 16. 68 is disposed downstream. The illuminance of one light source 19 is set higher than the illuminance of the other light source 20. Accordingly, one light source 19 completely cures the color ink ejected from the color recording heads 13, 14, 15 and landed on the recording medium 2, and the other light source 20 is supplied from the black recording head 16. The color ink discharged and cured or the black ink landed on the recording medium 2 is cured.

  Here, the ink used in the inkjet recording apparatus 1 is set so that the black ink has a higher surface tension than the color ink. Specifically, the surface tension of the color ink is 20 dyn / cm or more and 40 dyn / cm or less, and the surface tension of the black ink is set to a surface tension larger than 40 dyn / cm. Note that the difference in surface tension between the color inks cyan ink, magenta ink, and yellow ink is set to 2 dyn / cm or less.

  FIG. 3 shows a control device for controlling the ink jet recording apparatus 1 according to the present embodiment. This control device includes, for example, a CPU, a ROM, and a RAM (all not shown), and records in the ROM. A control unit 7 is provided for developing the processed program in the RAM and executing the processed program by the CPU.

  The control unit 7 is electrically connected to the transport unit 63, the color recording heads 13, 14, and 15, the black recording head 16, and the light sources 19 and 20, and these units are connected to the processing program described above. Based on the control.

Next, the operation of this embodiment will be described.
When image information is sent to the ink jet recording apparatus 1, the control unit 7 controls the transport unit 63 to take out the uppermost recording medium 2 stored in the storage tray 61 and rotate the transport roller 69 to take out the recording medium. The recorded recording medium 2 is conveyed.

  When the recording medium 2 reaches the pressing roller 66, the control unit 7 controls the conveying unit 63 to operate the pressing roller 66 to press the recording medium 2 from the front end portion thereof onto the surface of the conveying belt 64. The recording medium 2 is attracted to the conveyance belt 64. When the recording medium 2 is sent to the position of the recording head 13 along with the conveying operation of the conveying belt, the control unit 7 controls the color recording head 13 to discharge cyan ink onto the recording medium 2. Similarly, the control unit 7 controls the color recording heads 14 and 15 to discharge magenta ink and yellow ink onto the recording medium 2. Then, the control unit 7 controls one light source 19 to irradiate the recording medium 2 with ultraviolet rays to cure the color ink on the recording medium 2.

  Thereafter, the control unit 7 controls the black recording head 16 to discharge black ink onto the recording medium 2. Then, the control unit 7 controls the other light source 20 to irradiate the recording medium 2 with ultraviolet rays so as to cure the black ink on the recording medium 2.

  The recording medium 2 in which the ink is completely cured by the light irradiation is conveyed by the conveying roller 69 and is discharged from the discharge tray 67 to the outside.

As described above, according to the present embodiment, one light source 19 is provided between the color recording heads 13, 14, 15 and the black recording head 16, and one light source 20 is provided downstream of the conveyance path 68 of the black recording head 16. In addition, since only two light sources 19 and 20 in total are arranged, the color ink that needs to be mixed with other inks is irradiated with ultraviolet rays after mixing, and black that does not need to be mixed with other inks. The ink is cured after landing on the cured color ink. Thereby, the hardening according to the hardening conditions of each ink can be implement | achieved only with the two light sources 19 and 20, and the installation number of the light sources 19 and 20 can be suppressed.
By the way, since black ink often reproduces characters, it requires finer expression than color ink. Further, in order to obtain graininess, it is necessary to reduce the dot diameter. For this reason, the dot diameter after landing is reduced by using black ink with a higher surface tension than color ink. However, if the dot diameter is reduced, the black ink is completely coated with black ink. There is a risk that streaks will occur without being painted. For this reason, as described above, when the resolution of the black recording head 16 is made higher than that of the color recording heads 13, 14, 15, the solid area with black ink has a finer resolution, and the generation of streaks can be suppressed. it can. As a result, it is possible to improve the image quality while suppressing the number of installed light sources 19 and 20.

  In addition, since the surface tension of the color ink is set to 30 dyn / cm or more and 40 dyn / cm or less and the difference in surface tension between the color inks is 2 dyn / cm or less, the color inks are smoothly mixed. Become.

  Since the illuminance of one light source 19 is set higher than the illuminance of the other light source 20, the color ink can be reliably cured before the black ink is ejected.

Of course, the present invention is not limited to the above-described embodiment and can be modified as appropriate.
For example, when an image is recorded on a recording medium having a high surface tension of 50 dyn / cm or more and 100 dyn / cm or less, even if black ink is easily applied to the recording medium, the resolution of the black recording head 16 is increased. Can be made equivalent to the color recording heads 13, 14, 15.

  In this embodiment, the nozzle interval Rk of the black recording head 16 is made smaller than the nozzle interval Rc of the color recording heads 13, 14, 15, and the number of nozzles is set to increase the black recording head. Although the case where the resolution of 16 is set higher than the resolution of the color recording heads 13, 14, and 15 has been described as an example, the resolution of the black recording head 16 is controlled by the control unit 7. , 14, 15 may be set higher than the resolution.

1 is a side sectional view showing a schematic configuration of an ink jet recording apparatus according to an embodiment. FIG. 2 is an explanatory diagram for comparing nozzle intervals between a black recording head and a color recording head provided in the ink jet recording apparatus of FIG. 1. FIG. 2 is a block diagram illustrating a main control configuration of the ink jet recording apparatus of FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 2 Recording medium 7 Control part 13, 14, 15 Color recording head (recording head)
16 Black recording head (recording head)
19, 20 Light source 63 Transport unit 68 Transport path

Claims (5)

A transport unit for transporting the recording medium;
A plurality of line-type recording heads arranged along a conveyance path of the recording medium by the conveyance unit in order to eject ink toward the recording medium conveyed by the conveyance unit;
Two light sources for irradiating ultraviolet rays toward ink landed on the recording medium,
The plurality of line-type recording heads include a black recording head that discharges black ink having a surface tension higher than that of color ink, and a color recording head that discharges the color ink. The black recording head is disposed downstream of the transport path,
Of the two light sources, one light source is disposed between the color recording head and the black recording head, and the other light source is disposed downstream of the conveyance path of the black recording head. ,
An inkjet recording apparatus, wherein the black recording head has a resolution set higher than a resolution of the color recording head. The inkjet recording apparatus according to claim 1, wherein
An ink jet recording apparatus, wherein the color ink has a surface tension of 20 dyn / cm or more and 40 dyn / cm or less. The inkjet recording apparatus according to claim 1 or 2,
An ink jet recording apparatus, wherein a difference in surface tension between the color inks ejected by the plurality of color ink recording heads is 2 dyn / cm or less. In the ink jet recording apparatus according to any one of claims 1 to 3,
The inkjet recording apparatus, wherein the illuminance of the one light source is higher than the illuminance of the other light source. In the ink jet recording apparatus according to any one of claims 1 to 4,
The inkjet recording apparatus, wherein the plurality of line type recording heads are multi-drop type recording heads capable of changing the amount of ejected droplets.

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