Patent Grant
9956779
Field of the Invention
The present invention relates to a liquid ejection head that ejects liquids such as ink, a liquid ejecting apparatus, and a method for ejecting liquids.
Description of the Related Art
In recent years, there is an increasing demand for a consumer application, in addition thereto, a business application by higher print speeds and an industrial application in regard to the inkjet technologies that eject liquids such as ink. For improving the print speed in such a liquid ejecting apparatus, a so-called full line type liquid ejection head that is configured to cause ejection openings of a liquid ejection head to correspond to a width of a print medium is preferable. For performing ejection in high landing position density of liquid droplets by such a full line type liquid ejection head, it is desirable to increase the arrangement density of the ejection openings formed in the liquid ejection head.
Japanese patent Laid-Open No. 2009-285921 is known as the configuration of such a full line type liquid ejection head that can perform a print in high density.
However, with the arrangement of the ejection openings in the liquid ejection head disclosed in Japanese patent Laid-Open No. 2009-285921, a variation in a time difference between a landing time when a liquid droplet ejected from an ejection opening lands on a print medium and a landing time when a liquid droplet ejected from the adjacent ejection opening lands on the print medium is large. As a result, there are some cases where streaks are generated in an image printed with this arrangement. Hereinafter, the mechanism of the streak generation will be explained.
For example, in a case of printing one line in a direction crossing a conveying direction of a print medium in the ejection opening arrangement having a two-dimensional structure as shown in
The present invention provides a liquid ejection head in which ejection openings are arranged in high density, and a liquid ejecting method which can suppress generation of streaks due to a variation in a time difference of liquid droplets landing adjacent to each other on a print medium.
The present invention in its first aspect provides a liquid ejection head comprising: a first ejection opening group in which a plurality of ejection openings that eject a first kind of liquid onto a print medium are arranged in a first direction; and a second ejection opening group that is provided along the first ejection opening group to eject the first kind of liquid onto the print medium, wherein the first ejection opening group is provided upstream of the second ejection opening group in a relative moving direction between the print medium and the liquid ejection head, and the plurality of ejection openings included in the first ejection opening group are disposed in the first direction in a zigzag shape.
The present invention in its second aspect provides a liquid ejection head comprising: a plurality of liquid chambers each with an activation element for generating a droplet ejected through an ejection opening, an ejection opening plane with at least two ejection opening groups with a plurality of ejection openings ejecting droplets onto a print medium, whereby said groups are arranged in the ejection opening plane across the print medium conveying direction and wherein the ejection opening groups are arranged side by side in the ejection opening plane, the plurality of ejection openings of at least one ejection opening group are arranged in a zigzag shape, and the plurality of ejection openings of the further ejection opening groups are arranged in such a staggered manner that time lags of landing times of adjacent droplets landing on the print medium for all droplets forming a printed line across the print medium conveying direction get minimized.
The present invention in its third aspect provides a method for ejecting liquids with a liquid ejection head, comprising: a first step for preparing a liquid ejection head including a first ejection opening group in which a plurality of ejection openings that eject a first kind of liquid are arranged in a first direction in a zigzag shape, and a second ejection opening group in which a plurality of ejection openings that eject the first kind of liquid are arranged in parallel to the first ejection opening group; a second step for ejecting liquid from a first ejection opening included in the first ejection opening group to form a first dot on a print medium; a third step for ejecting liquid from a second ejection opening that is included in the first ejection opening group and is adjacent to the first ejection opening in the first direction to form a second dot in such a manner as to come in contact with the first dot on the print medium; a fourth step for ejecting liquid from a third ejection opening that is included in the first ejection opening group and is adjacent to the second ejection opening at the opposite side to the first ejection opening in the first direction to form a third dot in such a manner as to come in contact with the second dot on the print medium; and a fifth step for ejecting liquid from a fourth ejection opening included in the second ejection opening group to form a fourth dot in such a manner as to come in contact with at least one of the first dot, the second dot and the third dot on the print medium.
According to the above arrangement, it is possible to provide a liquid ejection head, and a liquid ejecting apparatus which can suppress generation of a streak by bias of the liquid due to the variation in a time difference of liquid droplets landing adjacent to each other on a print medium, and can perform a print in high density.
Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).
Hereinafter, embodiments of the present invention will be explained.
(Apparatus Configuration)
The liquid ejection head 2 is provided in a position facing a platen 6, disposing a conveying belt 5 for conveying a print medium P therebetween. The liquid ejection head 2 ascends and descends in the direction facing the platen 6 by control of a head moving unit 10. It should be noted that an operation of the head moving unit 10 is controlled by a control unit 9. In addition, as described later in
Caps 7 for executing recovery processing of the liquid ejection heads 2 are disposed in lateral sides of the liquid ejection heads 2. An operation of a cap moving unit 8 is controlled by the control unit 9 to move the cap 7 right under the liquid ejection head 2, causing the cap 7 to receive waste ink discharged from the ejection opening.
The conveying belt 5 that is a part of a conveying unit conveys the print medium P for performing a relative movement between the liquid ejection head 2 and the print medium P, and bridges over between drive rollers connected to a belt drive motor 11. An operation of the conveying belt 5 is switched by a motor driver 16. A charging device 13 is provided in the upstream side of the conveying belt 5. The charging device 13 charges the conveying belt 5 to cause the print medium P to make close contact with the conveying belt 5. Thereby the print medium is conveyed in a conveying direction X. The charging device 13 switches on/off by means of a charging device driver 13a. A pair of feeding rollers 14 supplies the print medium P onto the conveying belt 5. A feeding motor 15 rotates the pair of feeding rollers 14. The feeding motor 15 is controlled by the motor driver 16.
The above explanation is made of one example of the configuration of the liquid ejecting apparatus 1. It should be noted that the configuration of the liquid ejecting apparatus 1 shown in
The image processing unit 36 executes image processing to multi-valued image data that is input from the data input unit 31. For example, the image processing unit 36 quantizes the multi-valued image data to image data of an N-value for each pixel, and assigns a dot arrangement pattern corresponding to a gradation value “K” indicated by each quantized pixel. Specifically in a case of the multi-valued image data expressed by 256 gradations, the gradation value is converted into the K-value. It should be noted that a multi-valued error diffusion method or any intermediate gradation processing method such as an average density preserving method and a dither matrix method may be used for this processing. Thereby the image processing unit 36 produces ejection data corresponding to each ejection opening. At the time of production of this ejection data, the ink landing position onto the print medium is adjusted based upon the registration adjustment information stored in the memory unit 34. The head control unit 37 controls a print operation by the liquid ejection head 2. The above explanation is made of one example of the configuration of the control unit 9. It should be noted that the control unit 9 is not necessarily limited to this configuration. For example, a part of this configuration may be executed by causing the CPU 33 to read in programs stored in the memory unit 34 by using the RAM 35 as a work area for execution or may be executed by a hardware configuration such as an exclusive circuit.
<Configuration of Liquid Ejection Head>
Next, an explanation will made of the liquid ejection head 2 according to the present invention with reference to
As shown in
<Section Structure of Liquid Ejection Head>
Next, a sectional structure of the ejection opening area 41, which is formed in the flow passage member 4, in the vicinity region of the ejection opening 61 will be explained with reference to
The actuator unit 21 is composed of a piezoelectric sheet on an upper layer portion on which an electrode is disposed, and this layer portion is deformed in a parallel direction (pressure chamber side) to the ejection opening direction at the time electric field is impressed. Therefore a volume of the pressure chamber 53 is reduced to increase a pressure of ink, thus ejecting ink droplets from the ejection opening 61. Thereafter when the electric field is returned to the previous state, the piezoelectric sheet is back to the original shape and the volume of the pressure chamber 53 is back to the original volume. Therefore the ink is sucked in from the manifold 51. The cavity plate 22 is a metallic plate provided with many openings to oppose the pressure chambers 53. The base plate 23 is a metallic plate in which in regard to the one pressure chamber 53 of the cavity plate 22, a communication hole between the pressure chamber 53 and the aperture 55 and a communication hole from the pressure chamber 53 to the ejection opening 61 are provided.
The supply plate 25 is a metallic plate in which in regard to the one pressure chamber 53 of the cavity plate 22, a communication hole between the aperture 55 and a sub manifold 5a and a communication hole from the pressure chamber 53 to the ejection opening 61 are provided. The manifold plates 26, 27, 28 are metallic plates that are jointed to each other at the laminating to form holes configuring the manifold 51, and further, are respectively provided with communication holes from the pressure chamber 53 to the ejection opening 61 in regard to the one pressure chamber 53 of the cavity plate 22. The cover plate 29 is a metallic plate in which in regard to the one pressure chamber 53 of the cavity plate 22, a communication hole from the pressure chamber 53 to the ejection opening 61 is provided. The ejection opening plate 30 is a metallic plate in which in regard to the one pressure chamber 53 of the cavity plate 22, the ejection opening 61 is provided.
These nine metallic plates are aligned to each other to be laminated such that the individual ink flow passages 52 are formed. The individual ink flow passage 52 first extends from the manifold 51 to the upper side, extends horizontally in the aperture 55, then extends further to the upper side, and again extends horizontally in the pressure chamber 53. After that, the individual ink flow passage 52 extends obliquely downward in a direction away from the aperture 55 for a little while, and then vertically downward to the ejection opening 61. The actuator unit 21 is deformed in response to transmission of a signal from the liquid ejection head control unit 37 to eject ink. An ink amount capable of being ejected differs depending on a deformation amount of the actuator unit 21, and in the present embodiment, ink droplet of 5 pl, 7 pl or 12 pl can be ejected.
<Ejection Opening Arrangement>
Next, the arrangement of the ejection openings in the liquid ejection head will be in detail explained.
In the present embodiment, in a case of printing in this arrangement position of the ejection openings 61, one line in the longitudinal direction can be formed by using the ejection opening group 81 alone. That is, in a case of printing with the ejection openings 61 included in the ejection opening group 81, an ejection opening interval or an ejection amount to be ejected is set such that the adjacent liquid droplets come in contact with each other. The liquid droplets from the adjacent ejection openings in the longitudinal direction included in the ejection opening group 81 are only required to come in contact with each other, which can suppress generation of the streak as described in
Next, the arrangement of each of the ejection opening groups in the short direction (second direction) in a case of 1200 dpi will be hereinafter explained. A distance in the short direction between an ejection opening 81-1 and the adjacent ejection opening 81-2 included in the ejection opening group 81 is set such that a time taken for printing one line is a predetermined value or less. Herein the time of the predetermined value or less differs depending upon a conveying speed of a print medium, and in a case of conveying a roll-shaped print medium at a conveying speed L of (0.83 m/s), it is preferable that the maximum value T (ms) of the time of the adjacent liquid droplets is approximately 1 ms. That is, it is preferable that the maximum value T (ms) of the time of the liquid droplet=100/83×L. The adjacent ejection opening is arranged in the short direction such that the time of the liquid droplet is below that time. In a case of the conveying speed of 0.83 m/s, the adjacent ejection opening is arranged in a position away by a distance of 1 ms×0.83 m/s=0.83 mm in the short direction. As similar to the next ejection opening 81-2, the time when the adjacent ejection opening 81-3 prints one line is made to be a predetermined time or less. Therefore the ejection openings 61 included in the ejection opening group 81 are arranged in a W-letter shape (zigzag shape). In this way, it is preferable that the time difference when the liquid ejected from the adjacent ejection opening lands on the print medium is substantially equal, but a slight time difference may be permitted depending upon physical properties of ink or characteristics of a print medium. As described above, the previously landed liquid droplet starts to be contracted with time, but a later ejection is to be performed with a time difference to cause a later liquid droplet ejected from the adjacent ejection opening to come in contact with the previous liquid droplet.
Hereinafter, an explanation will be made of a second embodiment. In a case of performing drawing formation using a liquid ejection head of an inkjet method, a landing position of a liquid droplet ejected on a print medium is possibly shifted in the longitudinal direction. In general such a shift of the landing position is an inherent phenomenon of each ejection opening, and in a case of performing a sequential draw using this ejection opening, the shift of the landing position tends to be easily generated sequentially. Therefore, since the bias of the liquid is sequentially generated, the streak tends to be easily generated. Therefore, in the second embodiment, in ejection openings included in an ejection opening group 92 for ejecting later in addition to ejection openings included in an ejection opening group 91 for ejecting previously, the arrangement of ejection openings is made to be similar to that (zigzag shape) of the ejection openings in the ejection opening group 81 of the first embodiment.
In the present embodiment, a distance between the adjacent ejection openings in the short direction in the arrangement of the ejection openings in the ejection opening group 92 which performs ejection later (later timing) for printing a same line is made to be similar to that in the ejection opening group 91 such that a time taken for printing one line is a predetermined time or less. The ejection openings groups 91 and the ejection openings groups 92 are arranged such that the ejection opening of the first landing in each of the ejection opening groups 91, 92, that is, the ejection opening positioned in a top in the lower side on a wave shape arrangement, is shifted by a constant amount in the longitudinal direction. The constant amount in the present embodiment is preferably approximately ¼ of a cycle of the wave shape, but an interval in the longitudinal direction between the tops is only required to be “d” or more. Since a cycle of the arrangement of the ejection opening in the present embodiment is 16×600 dpi (42.33 μm)=677 μm, the shift amount is 169 μm that is ¼ of that cycle. That is, the arrangement of the ejection openings in the present embodiment has a substantially same cycle and amplitude in the zigzag arrangement of the ejection opening line and is shifted by ¼ in the longitudinal direction between the ejection opening group 91 and the ejection opening group 92.
In the present embodiment, the top of the wave shape is arranged to be shifted therebetween, but is not necessarily shifted. However, according to the previous review, it is found out that when the liquid ejection head of the same structure is used, the liquid droplet landing shift tends to be easily generated at the similar position. Therefore the arrangement of the ejection openings 61 in which a position of the top in the wave shape is shifted is preferable.
In this way, the present embodiment has the ejection opening arrangement in which even if the shift of the liquid droplet landing position in the longitudinal direction is generated due to the printing of the ejection opening 61 included in the first ejection opening group 91, the streak is not visible and it is possible to suppress the streak due to the bias of the liquid by the time difference between the adjacent liquid droplets.
Hereinafter, an explanation will be made of a third embodiment. In the present embodiment, an arrangement of ejection openings included in an ejection opening group 102 (
In this way, according to the present embodiment, even if the shift of the liquid droplet landing position in the longitudinal direction is generated by the ejection opening, the streak is not visible and it is possible to suppress the streak due to the bias of the liquid by the time difference between the adjacent liquid droplets.
Hereinafter, an explanation will be made of a fourth embodiment. The present embodiment is so configured that each of the ejection opening groups is provided with five common liquid flow passages 42 as shown in
As shown in
The liquid ejection head 2 is provided with 16 ejection opening lines in a direction perpendicular to the longitudinal direction, each ejection opening line provided with ejection openings 61 in a line in the longitudinal direction. In the present embodiment, each of the ejection opening groups is provided with the ejection openings 61 arranged at 300 dpi in the longitudinal direction, and it is possible to form an image at a resolution of 1200 dpi as a whole. That is, an interval “d” between the respective ejection openings of the ejection opening groups in the present embodiment is 21.1 μm. In the present embodiment, the interval “d” alone is shifted, but the shift is not necessarily required, and the printing may be performed at an interval of 300 dpi.
Next, the arrangement of each of the ejection opening groups in the short direction in a case of a resolution of 1200 dpi will be hereinafter explained. A distance between an ejection opening 111-1 and the adjacent ejection opening 111-2 in the ejection opening group 111 in the short direction is set such that a time taken for printing one line is a predetermined value or less. Herein the time of the predetermined value or less differs depending upon a conveying speed of a print medium, but in a case of conveying a roll-shaped print medium at a conveying speed L of (0.83 m/s), it is preferable that the maximum value T (ms) of the time of the adjacent liquid droplet is short. However, there are some cases where such a maximum value T (ms) cannot be structurally made short due to presence of the flow passage or the like, and it is preferably approximately 1 ms. That is, it is preferable that the maximum value T (ms) of the time of the liquid droplet=100/83×L. The adjacent ejection opening is arranged in the short direction such that the maximum value T is below that time. In a case of the conveying speed of 0.83 m/s, the adjacent ejection opening is arranged in a position away by a distance of 1 ms×0.83 m/s=0.83 mm in the short direction. Similarly in regard to the next ejection opening 111-2, a distance between the ejection opening 111-2 and the adjacent ejection opening 111-3 is set such that the time taken when the adjacent ejection opening 111-3 prints one line is a predetermined value or less. This arrangement is resultantly formed such that the ejection opening groups 111, 112 are together used to connect the ejection openings therebetween. By thus arranging the ejection openings, before one ink comes in contact with the other ink to begin to be contracted, the opposite ink comes in contact with the one ink, and the contraction force of the one ink is cancelled out to reduce the bias of the ink.
A distance between the adjacent ejection openings in the short direction in the arrangement of the ejection openings in each of the ejection opening groups 113, 114 for ejecting later is, as similar to that in each of the ejection opening groups 111, 112, set such that a time taken for printing one line is a predetermined time or less. The ejection opening groups 111 and 112, and the ejection opening groups 113 and 114 are arranged such that the ejection opening of the first liquid droplet landing in each of the ejection opening groups, that is, the ejection opening positioned in a top in the lower side on a wave line is shifted from each other by a constant amount in the longitudinal direction. The constant amount in the present embodiment is preferably approximately ¼ of a cycle of a wave, but an interval in the longitudinal direction between the tops is only required to be “d” or more. Since a cycle of the arrangement of the ejection openings in the present embodiment is 16×600 dpi (42.33 μm)=677 μm, the shift amount is 169 μm that is ¼ of that cycle.
The configuration that the arrangement of the ejection opening group in the later part of the printing is similar to that of the ejection opening group in the former part of the printing is the same as in the second embodiment. In addition, also in the present embodiment, the ejection opening in the top of the wave line is arranged to be shifted, but is not necessarily shifted. However, according to the previous review, it is found out that when the liquid ejection head of the same structure is used, the liquid droplet landing shift tends to be easily generated at the similar position. Therefore the arrangement of the ejection opening in which the position of the top in the wave line is shifted is preferable. Since the liquid flow passage comprises a plurality of liquid flow passages in the present embodiment, supply characteristics of the liquid ejection head improve to simplify the design. Further, even if the shift of the liquid droplet landing position in the longitudinal direction is generated by the ejection opening, the streak is not visible and it is possible to suppress the streak due to the bias of the liquid by the time difference between the adjacent liquid droplets.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2014-258886, filed Dec. 22, 2014, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-258886 | Dec 2014 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4194210 | Krause | Mar 1980 | A |
| 6779871 | Seto et al. | Aug 2004 | B1 |
| 20010026307 | Akahira | Oct 2001 | A1 |
| 20040041881 | Okuda et al. | Mar 2004 | A1 |
| 20050219287 | Tatsumi | Oct 2005 | A1 |
| 20050219296 | Hirakawa | Oct 2005 | A1 |
| 20050219312 | Oishi | Oct 2005 | A1 |
| 20070046735 | Kodama | Mar 2007 | A1 |
| 20070091139 | Takatsuka | Apr 2007 | A1 |
| 20100194801 | Hibi | Aug 2010 | A1 |
| 20120162318 | Muraoka et al. | Jun 2012 | A1 |
| 20130063522 | Arai et al. | Mar 2013 | A1 |
| 20130083110 | Sumiyoshi | Apr 2013 | A1 |
| Number | Date | Country |
|---|---|---|
| 0 807 522 | Nov 1997 | EP |
| 2 346 154 | Oct 1977 | FR |
| 2009-285921 | Dec 2009 | JP |
| 2010010804 | Jan 2010 | WO |
| Entry |
|---|
| Extended European Search Report dated Jun. 15, 2016, in European Patent Application No. 15201492.4. |
| Extended European Search Report dated Apr. 27, 2017, in European Patent Application No. 16204220.4. |
| Number | Date | Country | |
|---|---|---|---|
| 20160176188 A1 | Jun 2016 | US |
