Patent Publication Number: US-7722158-B2

Title: Ink-jet recording apparatus

Description:
This application is based on Japanese Patent Application No. 2005-292165 filed on Oct. 5, 2005, which is hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   The present invention relates to an ink-jet recording apparatus. 
   In the past, an ink-jet recording apparatus which ejects ink onto a recording medium, such as a sheet or a thin plastic plate, and records predetermined images, has been brought forth, and is now in practical use. Particularly, in recent years, greatly developed has been an ink-jet recording apparatus employing photo-curing type ink to record images onto an ink-non-absorbent recording medium, after which light rays irradiate the photo-curing type ink droplets deposited onto the recording medium, and forms the images. As such an ink-jet recording apparatus, developed is an ink-jet recording apparatus in which cation polymerizable photo-curing ink is used, and large amounts of light rays are irradiated at one time (for example, see Japanese Patent Application Publication Nos. 2004-203025, and 2004-255818). 
   In this ink-jet recording apparatus, for example, a single recording head for ejecting each color ink of Y (yellow), M (magenta), C (cyan) and K (black) is provided, and light irradiating sections are mounted downstream of each color recording head, with respect to conveyance direction of the recording medium. That is, after each color ink is deposited onto the recording medium, the light rays are irradiated onto each color ink from the light irradiating sections, and thereby, each ink is individually cured so that the images are recorded. 
   Further, in recent years, even when high resolution images are rapidly printed, in order to reduce a driving load of the recording head, an ink-jet recording apparatus using an interleave method has been developed, which records the images after thinned-out images are superimposed, (for example, see Japanese Patent Application Publication No. 2004-167812). 
   Meanwhile, in the ink-jet recording apparatus described in Japanese Patent Application Publication No. 2004-167812, plural recording heads for each color are provided, but as described above, due to the structure in which after each ink is deposited, the light irradiating sections irradiate light rays onto each ink, and each ink is individually cured, the problem is that each ink is separately deposited onto the recording medium, and the same colored ink droplets adjacent to each other pull at each other before curing. If such bleeding is generated, it may be impossible to obtain the desired quality images. 
   Further, since convex images are requested for the use of welfare or art, a “superposed ejection” method is used, in which the same colored ink droplets are repeatedly ejected to create the images. However, when the superposed ejection of the same color ink droplets is operated in the ink-jet recording apparatus, the deposited ink droplets expand widely, and the predetermined image quality cannot be obtained. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to offer an ink-jet recording apparatus in which bleeding is prevented and the high image quality is maintained, even when high speed printing is conducted onto the ink non-absorbent recording medium. 
   The above-described object can be attained by any one of Structures (1)-(7), described below. 
   Structure (1): An ink-jet recording apparatus including: a conveyance section to convey a recording medium; plural recording heads, aligned along a conveyance direction of the recording medium, each ejects the same type of photo-curing type ink onto the recording medium conveyed by the conveyance section; and plural light irradiating sections, aligned along the conveyance direction of the recording medium, each irradiates light rays onto the recording medium on which the photo-curing type ink has been ejected. 
   Structure (2): The ink-jet recording apparatus in Structure (1), further including: a first recording head, included in the plural recording heads, to eject the photo-curing type ink onto the recording medium conveyed by the conveyance section; a first light irradiating section, included in the plural light irradiating sections, to irradiate the light rays onto the recording medium on which the photo-curing type ink has been ejected from the first recording head; a second recording head, included in the plural recording heads, to eject the photo-curing type ink, which is the same type as the photo-curing type ink ejected from the first recording head, onto the recording medium on which the light rays have been irradiated from the first light irradiating section; and a second light irradiating section, included in the plural light irradiating sections, to irradiate the light rays onto the recording medium on which the photo-curing type ink has been ejected from the second recording head. 
   Structure (3): The ink-jet recording apparatus in Structure (2), wherein the first recording head and the second recording head include plural nozzles to eject the photo-curing type ink, and wherein the photo-curing type ink ejected from the nozzles of the second recording head, are deposited at a given position on the recording medium, that position is shifted a predetermined amount in at least one of the conveyance directions of the recording medium and a nozzle alignment direction, from a position at which the photo-curing type ink is ejected from the nozzles of the first recording head. 
   Structure (4): The ink-jet recording apparatus in Structure (3), wherein the recording head is driven by a multiple-phase driven method, and wherein nozzle arrays, structured of the integer multiple number of phases to be driven, are aligned within each of the recording heads, in the conveyance direction of the recording medium. 
   Structure (5): The ink-jet recording apparatus in Structure (4), wherein the number of phases to drive the recording heads is three, and wherein the recording heads are aligned in three lines in the conveyance direction of the recording medium. 
   Structure (6): The ink-jet recording apparatus in any one of Structures (3)-(5), wherein the plural nozzles of the recording heads are aligned in a line. 
   Structure (7): An ink-jet recording apparatus, including: a conveyance section to convey a recording medium; a first group of plural recording heads to eject photo-curing type ink of a first ink type onto the recording medium conveyed by the conveyance section; a second group of plural recording heads to eject photo-curing type ink of a second ink type onto the recording medium conveyed by the conveyance section; a first group of plural light irradiating sections to irradiate light rays onto the recording medium on which the photo-curing type ink has been ejected from the first group of the plural recording heads; and a second group of plural light irradiating sections to irradiate light rays onto the recording medium on which the photo-curing type ink has been ejected from the second group of the plural recording heads. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a side view of the schematic structure of the ink-jet recording apparatus of the present embodiment. 
       FIG. 2  is a bottom surface view showing the schematic structure of the image recording unit provided in the ink-jet recording apparatus of  FIG. 1 . 
       FIG. 3  is a block diagram showing the main control structure of the ink-jet recording apparatus of  FIG. 1 . 
       FIG. 4  is a pattern diagram showing the relationship between each nozzle of the recording heads provided in the image recording unit of  FIG. 2  and positions at which ink ejected from each nozzle was deposited. 
       FIG. 5  is a timing chart showing ejection timing of each nozzle and light rays irradiation timing during an ink-ejection control. 
       FIG. 6  is a side view showing a variation of the ink-jet recording apparatus of  FIG. 1 . 
       FIG. 7  is a side view showing another variation of the ink-jet recording apparatus of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The ink-jet recording apparatus in the present embodiment will now be detailed while referring to the drawings.  FIG. 1  shows a side view of the schematic structure of the ink-jet recording apparatus. As shown in  FIG. 1 , ink-jet recording apparatus  1  includes: sheet supplying tray  2  to supply recording medium P, being an ink non-absorbent type sheet, such as a PET, conveyance section  3  to convey recording medium P stored in sheet supplying tray  2 ; image recording section  4  to record the images onto recording medium P conveyed by conveyance section  3 ; and sheet ejection tray  5  to store recording medium P, carrying the recorded images, ejected by conveyance section  3 . 
   Conveyance section  3  includes: paired conveyance rollers  31  to convey uppermost recording medium P stored in sheet supplying tray  2  into image recording section  4 ; plural paired conveyance rollers  321 ,  322  and  323  disposed on the conveyance route of recording medium P, to convey recording medium P; and paired ejection rollers  33  located on a downstream end of image recording section  4  which is positioned on the most downstream with respect to the conveyance route of recording medium P, to eject recording medium P carrying the recorded images onto sheet ejection tray  5 . 
   Image recording section  4  includes plural image recording units  40  which record superposed color images onto recording medium P, using the plural types of photo curing type ink. Plural image recording units  40  include: yellow unit  40 Y to form yellow image potions onto recording medium P using yellow (Y) photo-curing type ink, magenta unit  40 M to form magenta image portions onto recording medium P using magenta (M) photo-curing type ink, cyan unit  40 C to form cyan image portions onto recording medium P using cyan (C) photo-curing type ink, and black unit  40 K to form black image portions onto recording medium P using black (K) photo-curing type ink, wherein from the upstream end to the downstream end of the conveyance route of recording medium P, yellow unit  40 Y, magenta unit  40 M, cyan unit  40 C and black unit  40 K are aligned in that order. 
   Further, each image recording unit  40  includes: platens  45 Y,  45 M,  45 C and  45 K to support recording medium P from below which was conveyed by conveyance section  3 ; and heaters  46 Y,  46 M,  46 C and  46 K located under platens  45 Y,  45 M,  45 C and  45 K, to heat recording medium P on platens  45 Y,  45 M,  45 C and  45 K. 
   Additionally, in the following description, image recording unit  40  will be explained in a case of yellow unit  40 Y, and explanation for magenta unit  45 M, cyan unit  45 C and black unit  45 K will be omitted, while the symbols of each color about the structural elements are shown after each numeral designation. 
   Above platen  45 Y of yellow unit  40 Y, recording heads  6 Y, being a line method and multiple-phase drive type, are aligned perpendicular to the conveyance direction, and are themselves aligned in parallel. In detail, recording head  6 Y is activated by a three-phase drive method, and the number of provided recording heads  6 Y is an integer multiple of the number of the phases of recording heads  6 Y, and in this case, as one multiple of the number of the phase, three recording heads  61 Y,  62 Y and  63 Y are aligned in parallel, to which the yellow photo-curing type ink of the same ink type is supplied from an ink tank, which is not illustrated. Recording head  61 Y is the first recording head relating to the present invention, while other recording heads  62 Y and  63 Y are the second recording heads relating to the present invention. Further, three recording head groups  6 Y are the first recording heads groups relating to the present invention, while the other recording head groups  6 M,  6 C and  6 K are the second recording head groups. Additionally, in the present embodiment, it is assumed that the ink as the same type is supplied from the same tank of ink, but a structure is also possible so that the same color ink is supplied to each recording head from the individual ink tanks. Further, it is also possible that the composition of color ink supplied from each ink tank is different each other, so that additives, pigments and solvent can be changed in each color ink. 
   Next,  FIG. 2  is a bottom view showing the schematic structure of yellow unit  40 Y, and as shown in  FIG. 2 , plural nozzles  601 Y,  602 Y and  603 Y to eject the photo-curing type ink are aligned on jetting surfaces of recording heads  61 Y,  62 Y and  63 Y, perpendicular to the sheet conveyance direction. Nozzles  601 Y,  602 Y and  603 Y assembled in recording heads  61 Y,  62 Y and  63 Y are aligned along the direction in which recording heads  61 Y,  62 Y and  63 Y are located, that is, they are aligned in the direction (arrow Y) perpendicular to the conveyance direction (arrow X) of recording medium P. Further, the position of nozzle  601 Y aligned in recording head  61 Y, the position of nozzles  602 Y aligned in recording head  62 Y and the position of nozzles  603 Y aligned in recording head  63 Y coincide with each other with respect to the sheet conveyance direction. 
   Yet further, plural light irradiating sections  7 Y are provided immediately downstream of each recording head  6 Y with respect to the conveyance direction in yellow unit  40 Y, and irradiate ultraviolet rays to the photo-curing type ink deposited on recording medium P to cure it. In detail, light irradiating section  71 Y is located immediately downstream of the most upstream recording head  61 Y, and further, light irradiating section  72 Y is located immediately downstream of recording head  62 Y, and similarly light irradiating section  73 Y is located immediately downstream of most downstream recording head  63 Y. That is, light irradiating section  71  is the first light irradiating section of the present invention, while other light irradiating sections  72 Y and  73 Y are the second light irradiating sections relating to the present invention. 
     FIG. 3  is a block diagram showing a main control structure of ink-jet recording apparatus  1 . As shown in  FIG. 3 , ink-jet recording apparatus  1  includes control section  8  to control each driving section. Memory section  9  memorizes a specific control program and the respective image data, to control recording head groups  6 Y,  6 M,  6 C and  6 K of each recording unit  40 , light irradiating sections  7 Y,  7 M,  7 C and  7 K, and heaters  46 Y,  46 M,  46 C and  46 K, all of which are electrically connected to control section  8 . Control section  8  reads out the control program and the image data from memory section  9 , and executes them so that all driving sections are controlled. 
   Next, referring to  FIG. 4 , the control of ink-jetting of the present embodiment will be detailed, while using yellow unit  40 Y for the explanation.  FIG. 4  is a pattern diagram showing the relationship between each nozzle  601 Y,  602 Y and  603 Y of recording heads  61 Y,  62 Y and  63 Y and the positions at which ink ejected from each nozzle  601 Y,  602 Y and  603 Y is deposited, relating to the present embodiment, which is an example of the control conducted by control section  8 . In addition, the positions at which the ink ejected from each nozzle  601 Y,  602 Y and  603 Y is deposited are controlled by ink-jet timing from each nozzle  601 Y,  602 Y and  603 Y. Further, ink-ejection timing is adjusted based on the positional intervals of each recording head  61 Y,  62 Y and  63 Y, as well as the conveyance rate of recording medium P. 
   In three-phase drive recording heads  61 Y,  62 Y and  63 Y of the present embodiment, since nozzles  601 Y,  602 Y and  603 Y are grouped in one group, from right to left in  FIG. 4 , “a”, “b” and “c” are added at the end of the numerals, for convenience of this explanation. Nozzles  601   a ,  602   a  and  603   a  of recording heads  61 Y,  62 Y and  63 Y are controlled to eject the ink during the first phase, and further, nozzles  601   b ,  602   b  and  603   b  are controlled to eject the ink during the second phase, and nozzles  601   c ,  602   c  and  603   c  are controlled to eject the ink during the third phase. That is, three adjacent nozzles (for example, nozzles  601   a ,  601   b  and  601   c ) always eject ink at different times. Additionally, since the present embodiment shows the three-phase drive, three-phase group G 1  is explained, while the other groups G 2  and G 3  are omitted for this explanation, because groups G 2  and G 3  are synchronized with group G 1 . 
   In the present embodiment, nozzles  601 Y,  602 Y and  603 Y are controlled to start ink-ejection at a position which is shifted in the conveyance direction by the width of a picture element (which is one picture element) for each phase. That is, in the present embodiment, the ink droplets ejected from nozzles  601   a ,  602   b  and  603   c  are deposited approximately at position L 1  in conveyance direction X, while the ink droplets ejected from nozzles  601   b ,  602   c  and  603   a  are deposited at position L 2 , and the ink droplets ejected from nozzles  601   c ,  602   a  and  603   b  are deposited at position L 3 . In this way, in recording head  61 Y, the phase is changed by rotation for nozzles  601   a ,  601   b  and  601   c  and direction Y, and thereby, recording is conducted for each phase from adjacent picture elements in conveyance direction X. 
   That is, recording heads  61 Y,  62 Y and  63 Y form the images which are reduced by one third in direction Y by control section  8 , and after all of these reduced images are formed, a complete yellow image is formed. Due to this structure, the working frequencies of recording heads  61 Y,  62 Y and  63 Y become one third of one-phase drive recording head, which makes it possible to rapidly form the high resolution images. In addition, for ejecting the ink at the same position, the ink droplets ejected from nozzles  601   a ,  602   a  and  603   a  are controlled to be deposited at the same position (for example, B 1  in  FIG. 4 ). 
   Next, the function of ink-jet recording apparatus  1  of the present embodiment will be detailed below. 
   When image recording is started, control section  8  controls conveyance section  3  to rotate paired conveyance rollers  31  and conveyance rollers  321 ,  322  and  323 , so that recording medium P is conveyed from sheet supplying tray  2 . At the same time, control section  8  controls heaters  46 Y,  46 M and  46 C to heat recording medium P which is fed onto platens  45 Y,  45 M,  45 C and  45 K. 
   Further, control section  8  controls conveyance section  3  to rotate conveyance roller  321  to convey recording medium P, and based on the image data, control section  8  also controls recording head  61 Y which is the most upstream in yellow unit  40 Y, so that the yellow photo-curing type ink is ejected from one nozzle every three nozzles in the alignment direction of the nozzles. Yet further, control section  8  controls light irradiating section  71 Y, which is the most upstream, to activate light irradiating section  71 Y. Due to this, the yellow photo-curing type ink deposited by recording head  61 Y which is the most upstream is cured. 
   Yet further, based on the image data, control section  8  controls recording head  62 Y which is at the midstream of yellow unit  40 Y, so that the yellow photo-curing type ink is ejected to the position shifted by one image element from recording head  61 Y, but at the same position in the conveyance direction, from one nozzle every three nozzles in the alignment direction of the nozzles, and thereby, the yellow photo-curing type ink is ejected to the position to which no yellow photo-curing type ink is ejected from recording head  61 Y which is the most upstream. Yet further, control section  8  controls light irradiating section  72 Y, which is the midstream, to activate light irradiating section  72 Y. Accordingly, the yellow photo-curing type ink deposited by recording head  62 Y, which is the midstream, is cured. 
   After which, based on the image data, control section  8  controls recording head  63 Y which is the most downstream in yellow unit  40 Y, so that the yellow photo-curing type ink is ejected to the position shifted by two image elements from recording head  61 Y, but at the same position in the conveyance direction, from one nozzle every three nozzles on the alignment direction of the nozzles, and thereby, the yellow photo-curing type ink is ejected to the positions at which no yellow photo-curing type ink is ejected from recording heads  61 Y and  62 Y which are the most upstream and the midstream, respectively. Yet further, control section  8  controls light irradiating section  73 Y, which is the most downstream, to activate light irradiating section  73 Y. Accordingly, the yellow photo-curing type ink deposited by recording head  63 Y, which is the most downstream, is cured. 
     FIG. 5  is a timing chart showing the ejection timing of each nozzle and the light-ray irradiation timing in the above procedure. As shown in  FIG. 5 , after top row dots (being L 1  in  FIG. 4 ) in conveyance direction X are formed by nozzle  601   a  of recording head  61 Y (at t 1 ), light irradiating section  71 Y, which is located immediately downstream of recording head  61 Y, emits light rays (at t 2 ). Next, after top row dots L 1  in conveyance direction X are formed by nozzle  602   b  of recording head  62 Y (at t 3 ), light irradiating section  72 Y, which is located immediately downstream of recording head  62 Y, emits light rays (at t 4 ). Further, after the top row dots L 1  in conveyance direction X are formed by nozzle  603   c  of recording head  63 Y (at t 5 ), light irradiating section  73 Y, which is located immediately downstream of recording head  63 Y, emits light rays (at t 6 ). 
   Yet further, after end row of dots in conveyance direction X are formed by nozzles  601   c ,  602   c  and  603   c  of recording heads  61 Y,  62 Y and  63 Y (at t 7 , t 8 , and t 9 ), light irradiating sections  71 Y,  72 Y and  73 Y are de-activated (at t 10 , t 11  and t 12 ). 
   After the yellow image recording portions of the yellow photo-curing type ink are completed, control section  8  controls recording head  6  and light irradiating section  7  of image recording units  40  (which are magenta unit  40 M, cyan unit  40 C and black unit  40 K) to operate in the same way as above-described yellow  40 Y, and thereby, full color images are recorded on recording medium P by yellow, magenta, cyan and black photo-curing type inks. 
   After that, control section  8  controls conveyance section  3  to rotate paired conveyance rollers  33  to eject recording medium P carrying the full color recorded images to sheet ejection tray  5 . 
   As described above, based on ink-jet recording apparatus  1  of the present embodiment, after the photo-curing type inks are deposited onto recording medium P, light rays are irradiated onto recording medium P onto which photo-curing type inks have been ejected from the recording heads of plural recording head groups  6 Y,  6 M,  6 C and  6 K which jet the same types of photo-curing type ink, that is, in the condition that the photo-curing type ink deposited on recording medium P has been cured, the same type of the photo-curing type ink is ejected onto recording medium P from the other recording heads. Accordingly, those inks are not mixed and prevented from bleeding, which result in extremely high quality images. 
   Further, since light irradiating sections  7 Y,  7 M,  7 C and  7 K are located immediately downstream of recording head groups  6 Y,  6 M,  6 C and  6 K with respect to the conveyance direction, the photo-curing type inks ejected from each recording head can be individually and immediately cured. 
   In addition, the recording head is driven by the multiple-phase drive method, and since the recording heads are provided which are structured of the integer multiples of the number of the drive phase, when recording medium P passes each recording head for a single time, image recording of the total picture elements can be conducted. 
   Yet further, since the recording heads are driven by the multi-phase drive method, and which are mounted as the multiple number of the drive phase, after recording medium P passes each recording head only once, a complete image element can be recorded. 
   In addition, it is a matter of course that the present invention is not limited to the above-description, and is possible to be changed. In the following explanation, concerning the sections which are the same as the sections of the present embodiment, the same symbol is used and its explanation is omitted. 
   For example, in the present embodiment, the case is explained in which light irradiating sections  7 Y,  7 M,  7 C and  7 K are mounted immediately downstream of each recording head  6 Y,  6 M,  6 C and  6 K, however as shown in  FIG. 6 , irradiating section  7  can be mounted at only the position which is immediately downstream of recording heads  6 Y,  6 M,  6 C and  6 K, each arranged in one group. To specifically explain, in ink-jet recording apparatus  1 A shown in  FIG. 6 , three groups of linear type recording heads  6 Y,  6 M,  6 C and  6 K are aligned in the recording medium conveyance direction, wherein each line type recording head includes yellow, magenta, cyan and black photo-curing type inks, so that each color is ejected onto the recording medium P in three steps to form the images. Even in the above linear position of recording heads  6 Y,  6 M,  6 C and  6 K, the photo-curing type ink of each group are simultaneously cured after each ink is ejected. 
   Accordingly, plural types of photo-curing type ink are grouped, and each ink of the group is ejected “n” times to form the images on the recording medium P, that is, it is possible to form the images by superposing the same type of ejected photo-curing type ink for “n” layers. Further, since plural light irradiating sections  7  are provided to cure the plural types of photo-curing type ink for each group, ink for each layer can be cured individually, and ink is prevented from blending. In other words, even when the images are superposed of the same type of ink for plural layers, the ink can be cured, while an even thickness of ink of each layer is assured. 
   Yet further, in the present embodiment, the case in which the recording heads of each color are driven by three-phase drive method, and three recording heads are provided, is an example for the explanation, however, the number of the drive phases of the recording heads is not limited to three, that is, as long as the number of the recording heads is the integer multiples of the number of the drive phase, any number can be used. In addition, the ejecting steps are also not limited to three, and any plural number can be employed. 
   Yet further, in the present embodiment, the case in which the images are recorded on cut sheets of recording medium P has been explained, however, it is also possible to form the images on rolled recording medium P. For example, ink-jet recording apparatus  1 B shown in  FIG. 7 , includes: supporting section  10  to provide continuous recording medium P 1 , and to control conveyance device  3  to take up recording medium P 1 , mounted in the upstream of conveyance device  3  with respect to the conveyance direction; and take-up section  11  to take up rolled recording medium P 1  at the downstream end of conveyance device  3 . Rolled recording medium P 1  carrying the full color images is taken up by take-up section  11 . 
   According to the present embodiment, after the photo-curing type inks are deposited onto the recording medium, light rays are irradiated onto the recording medium onto which photo-curing type inks have been ejected from the recording heads which eject the same types of photo-curing type ink, and thereby, under the condition that the photo-curing type ink deposited on the recording medium has been cured, the same type of the photo-curing type ink is ejected onto the recording medium from the other recording heads. Thus, those ink are not mixed and prevented from bleeding, resulting in extremely high quality images.